WO2013063064A1

WO2013063064A1 - Nanostructure and artificial photosynthesis

Info

Publication number: WO2013063064A1
Application number: PCT/US2012/061616
Authority: WO
Inventors: Mengyan Shen; Cong Wang; Yeshaya Koblick
Original assignee: Mengyan Shen; Cong Wang; Yeshaya Koblick
Priority date: 2011-10-25
Filing date: 2012-10-24
Publication date: 2013-05-02

Abstract

Nanostructured arrays having a metal catalyst (e.g., cobalt) are irradiated with light to initiate the an artificial photosynthetic reaction resulting in the formation of carbon- containing molecules, for example, long chained hydrocarbons or amino acids. A nanostructure having one or more structural elements having a high aspect ratio can formed over a substrate and are placed in contact with water and a carbon-containing source (e.g., carbon dioxide, bicarbonate, methane). When the nanostructure is exposed to light, the water and the carbon-containing source can react to form a molecule having at least two carbon atoms chained together. Structural elements may include a number of metal layers arranged in a patterned configuration so that, upon light irradiation, a greater amount of light energy is concentrated in close proximity to the region where the reaction is catalyzed than for the case without the patterned configuration. Structural elements may also include a number of sub- structural elements disposed on the surface of the structural elements. The sub- structural elements may include a catalyst for initiating reactions that lead to the formation of long chain molecules containing carbon.

Description

NANOSTRUCTURE AND ARTIFICIAL PHOTOSYNTHESIS

BACKGROUND

1. Field of Invention

Aspects described herein relate to methods and apparatuses for producing carbon- containing molecules via artificial photosynthesis which can be used as a source of renewable energy. In some instances, a nano structured apparatus may serve to initiate a reaction in the presence of water and a carbon-containing source to generate carbon molecule chains.

2. Related Art

Sunlight is a renewable and environmentally friendly energy source that many have looked to harness as a solution to global energy. If able to effectively convert and store solar energy on a large scale and at low cost, solar energy can be a viable source of alternative energy. There has been a significant amount of interest in replicating the natural process of photosynthesis. Researchers have endeavored to split water into hydrogen and oxygen to store solar energy by the photovoltaic effect and electrolysis. Researchers have also sought to convert carbon dioxide and water to carbohydrate and hydrocarbon compounds through charge transfer using photoexcited semiconductors for many years. Previously, an electric current has been run through Ti0₂ nanotubes mixed with water and carbon dioxide to produce methane gas.

SUMMARY

The inventors have recognized and appreciated that, under appropriate conditions, a nano structured apparatus may be used to initiate a reaction involving water and a carbon- containing source resulting in the production of long-chained carbon molecules (e.g., hydrocarbons, amino acids, polymers), much akin to photosynthesis. As a result, the products generated by methods and apparatuses contemplated by the inventors may be a source of renewable energy which may further allow for more efficient utilization and conservation of existing energy resources. Essentially, fuel in the form of carbon-containing molecules having at least two carbon atoms chained together may be produced from exposing a suitable nanostructure to water, a carbon-containing source such as carbon dioxide and light (e.g., sunlight). In some embodiments, when a nano structured apparatus fabricated in accordance with manufacturing techniques discussed herein is exposed to light radiation in the presence of water and a carbon-containing source (e.g., carbon dioxide, methane, bicarbonate), a reaction takes place producing molecules having at least two carbon atoms chained together. Such a reaction may be catalyzed by the nanostructured apparatus where the only source of energy for driving the reaction is from the light radiation. In some cases, the nanostructured apparatus includes an array of structural elements having a high aspect ratio (e.g., nanospikes, nanoflakes) and incorporating a catalyzing material (e.g., cobalt, iron) that effectively lowers the free energy of reaction for single carbon molecules to chemically bond with other molecules under suitable conditions. Appropriate light energy for driving the artificial photosynthesis reaction may be provided from, for example, ambient light, sunlight, artificially generated light, or any other suitable source of electromagnetic radiation.

Accordingly, methods of producing chained carbon molecules and the products themselves may be useful as a source of renewable energy.

A nanostructure may be fabricated and placed in conditions such that the

nanostructure comes into contact with water and a carbon-containing source and, upon light irradiation, catalyzes a reaction between the water and the carbon-containing source. The reaction between the water and the carbon-containing source may involve chemical bonding of carbon atoms with other carbon atoms or other non-carbon atoms (e.g., nitrogen, oxygen) to form organic chains that can be used as sources of energy (e.g., combustible compounds). The nanostructure may include a number of structural elements attached to a substrate and having a high aspect ratio. In some embodiments, the structural elements may include one or more metal catalysts. In some embodiments, the structural elements may include multiple metal catalysts in a patterned configuration, such as for example, in a periodic arrangement of alternating layers that are horizontally aligned.

In an illustrative embodiment, an apparatus for producing carbon-containing molecules is provided. The apparatus includes a nanostructure adapted to catalyze a light- initiated reaction between water and a carbon-containing source that results in a molecule having at least two carbon atoms chained together.

In another illustrative embodiment, a method of forming a carbon-containing molecule is provided. The method includes contacting a nanostructure with water and a carbon-containing source; and exposing the nanostructure to light to initiate a reaction between the water and the carbon-containing source to form a molecule having at least two carbon atoms chained together. In a further illustrative embodiment, a method of manufacturing an apparatus for producing a carbon-containing molecule is provided. The method includes forming a nanostructure bonded to a substrate, the nanostructure adapted to catalyze a light-initiated reaction between water and a carbon-containing source that results in a molecule having at least two carbon atoms chained together.

In another illustrative embodiment, a system for producing long chain molecules is provided. The system includes a chamber containing water and a carbon-containing source; and a nanostructure disposed within the chamber and in contact with the water and the carbon-containing source, the nanostructure adapted to catalyze a light-initiated reaction between the water and carbon-containing source in the chamber to result in a molecule having at least two carbon atoms chained together.

The foregoing is a non-limiting summary of the invention, which is defined by the attached claims. Other aspects, embodiments, features will become apparent from the following description.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like descriptor. For purposes of clarity, not every component may be labeled in every drawing.

The advantages and features of this invention will be more clearly appreciated from the following detailed description, when taken in conjunction with the accompanying drawings.

Figs. 1A-1C show electron micrographs of nanostructures in accordance with various embodiments;

Fig. 2A illustrates a section view schematic of a nanostructure in accordance with some embodiments;

Fig. 2B depicts a section view schematic of the nanostructure of Fig. 2A exposed to radiation;

Fig. 3A illustrates a section view schematic of another nanostructure in accordance with some embodiments;

Fig. 3B depicts a section view schematic of the nanostructure of Fig. 3A exposed to radiation; Fig. 4 depicts a schematic and an optical micrograph of a system having a

nanostructure according to an illustrative embodiment;

Fig. 5A shows a schematic of a system having a nanostructure subject to irradiation in accordance with some embodiments;

Fig. 5B shows a schematic of another system having a nanostructure subject to irradiation in accordance with some embodiments;

Fig. 6 illustrates a schematic section view of a nanostructure in accordance with some embodiments;

Fig. 7 illustrates a schematic section view of two layers of a nanostructure in accordance with some embodiments;

Fig. 8 depicts a graph showing resonance wavelengths corresponding to different layers of a nanostructure and in accordance with some embodiments;

Figs. 9A-9G illustrate a process for forming a nanostructure in accordance with some embodiments;

Figs. 10A-10H depict another process for forming a nanostructure in accordance with some embodiments;

Fig. 11 show an electron micrograph of a nanostructure in accordance with some embodiments;

Figs. 12A-12B show measured results of an example process for forming carbon- containing molecules;

Fig. 13 depicts measured results of an example process for forming carbon-containing molecules;

Figs. 14A-14C show measured results of another example process for forming carbon-containing molecules; and

Fig. 15 depicts cross-sections of different embodiments of a nanostructure in accordance with some embodiments.

DETAILED DESCRIPTION

Aspects discussed herein relate to the use of an apparatus having nano structural features for producing long chain carbon-containing molecules (e.g., hydrocarbons, amino acids, polymers) from water and a carbon-containing source typically having a single carbon atom (e.g., carbon dioxide, bicarbonate, methane). In some embodiments, a nanostructure having one or more structural elements is bound to a substrate and is placed in contact with water and a suitable carbon-containing source. When the nanostructure is irradiated with light, a reaction between the water and carbon-containing source is catalyzed by the nanostructure and a molecule having at least two carbon atoms chained together is formed. In an embodiment, nitrogen is in contact with the nanostructure along with water and the carbon-containing source such that when the nanostructure is irradiated with light, amino acids are formed.

Accordingly, nanostructures and methods for their use may allow for the ability to produce renewable energy in the form of carbon-containing molecules having at least two carbon atoms chained together (e.g., long chained hydrocarbons). Because such sources of energy is so easily renewed, existing energy resources (e.g., fossil fuels, coal, nuclear energy, etc.) may be more efficient utilized and conserved.

In some embodiments, a suitable nanostructure is fabricated using methods involving a femtosecond laser where the focused laser beam causes formation of an array of nano-spike structures from a metal precursor, the method being discussed further below. The

combination of the structure and the metal of the nanostructure serves as a catalyzing agent that allows for long chained carbon-containing molecules to be formed in the presence of light energy, water and the carbon-containing source. The inventors have appreciated that such a reaction, given the reactants and products, is similar to that which occurs in photosynthesis, which is a chemical process that uses light energy to convert carbon dioxide, as a carbon-containing source, into organic compounds typically having several carbon atoms chained together. As such, methods and apparatuses described herein are contemplated to be useful as a form of artificial photosynthesis and in providing a valuable source of renewable energy.

A single nano structural apparatus may be used to perform photosynthesis efficiently and effectively, serving to initiate catalytic processes including photodissociation. For example, water, carbon dioxide and nitrogen molecules can be photodissociated around and in proximity to nano structural surfaces of a suitable nanostructure. In some embodiments, nanostructures have one or more structural elements that each have a tip with a diameter on the order of a few nanometers. The tip of each structural element in the nanostructure is able to focus light shined on to the nanostructure as a light concentrator in the region where the tip is located. For example, upon exposure to light radiation, a nano structured metal surface may enhance the irradiated light to an intensity of more than 10,000 times that of initial incidence. Such focused light may function to dissociate molecules through single photon and/or multiple-photon processes. As discussed further below, structural elements of a nanostructure may have other features that assist in focusing exposed light so as to enhance the process of artificial photosynthesis.

In some cases, suitable structural elements of nanostructures are able to focus light in a manner that functions as a nano-optical lens having photodissociation possessing properties. Such properties may also be useful for surface enhanced Raman spectroscopy (SERS) involving enhanced Raman scattering by molecules adsorbed on rough metal surfaces.

In some embodiments, nanostructures may be formed as an array of high aspect ratio structural elements. In some instances, as shown in Fig. 1A-1C, nanostructures take on a nanoforest, nanograss and/or nanoflake configuration. Figs. 1A-1C depict scanning electron microscope images of an illustrative embodiment of a nanostructure having structural elements of cobalt microparticles disposed on an iron substrate. Fig. 1A shows the formation of cobalt nanoflakes after a femtosecond laser irradiation of cobalt powder in water at a fluence of 5 kJ/m per pulse. Fig. IB depicts the formation of cobalt nanograss fabricated with the same femtosecond laser system at a fluence of 1 kJ/m per pulse. Fig. 1C illustrates the formation of a cobalt nanoforest on an iron substrate fabricated using a femtosecond laser at a fluence of 5 kJ/m per pulse.

Nanostructures described and the structural elements that make up the nanostructures may have any suitable geometry and dimensions. For example, structural elements of a nanostructure may have a spike or grass-like geometry. Or, structural elements of

nanostructures may have a flake-like geometry having a relatively thin thickness. In some embodiments, structural elements of nanostructures bound on a substrate have an average height of less than 5 microns, or less than 3 microns. In some embodiments, structural elements of nanostructures bound on a substrate have an average height of greater than 100 nm, greater than 500 nm, or greater than 1 micron. Structural elements of nanostructures may have any suitable thickness, for example, less than 1 micron, less than 500 nm, less than 200 nm, or less than 100 nm in thickness.

As discussed previously, structural elements of suitable nanostructures may have a relatively high aspect ratio (i.e., height to thickness ratio), as some structural elements may be formed as nano-spikes, nano-flakes or nano-needles. In some embodiments, the aspect ratio of a structural element may be between about 1 and about 20, between about 1 and about 10, or between about 2 and about 8.

As discussed, nanostructures having one or more structural elements may be bound to a substrate. Accordingly, structural elements of nanostructures are generally not aggregated together, but rather, pack in an orderly fashion. Fig. 1C depicts an example of a packing arrangement where structural elements of the nano structure are arranged in an orderly configuration without aggregation.

In some embodiments, flakes and grass-like nanostructures are thinner than 100 nm, resulting in a generally large the surface area of the nano structured apparatus. In some cases, nano structured surfaces formed with high intensity femtosecond laser irradiation are able to tolerate high photodissociation light intensities around the nanostructures without incurring damage to the structural elements or the substrate.

Structural elements of nanostructures described may have any suitable composition. In some embodiments, nanostructures include one or more metals. Suitable metals incorporated in a nanostructure may include, but are not limited to, Co, Fe, Ni, Ti, stainless steel, and/or alloys thereof. In some embodiments, a nanostructure having suitable characteristics and dimensions in accordance with the present disclosure may be formed of a polymeric material (e.g., polyimide, PTFE, polyester, polyethylene, polypropylene, polystyrene, polyacrylonitrile, etc.). Where a nanostructure includes a metal and a polymer, in some cases, structural elements made up of the polymer are coated with a metallic material. Or alternatively, structural elements made up of a metal may be coated with the polymer. In some embodiments, a metal oxide (e.g., cobalt oxide, iron oxide, nickel oxide, titanium oxide, etc.) is incorporated in structural elements of the nanostructure and may be provided as a coating to a metal portion. In some cases, neither a metal nor a metal oxide are incorporated in a nanostructure and the structural elements that make up the nanostructure.

In various embodiments, a structural element may be formed in a manner that exposes a suitable metal so as to result in effective catalysis of reactions for producing carbon-carbon bonds and the formation of long chain carbon-containing molecules. For example, cobalt and iron are contemplated as non-limiting materials for use in structural elements of

nanostructures that are able to catalyze reactions such as hydrocarbon synthesis from carbon monoxide and hydrogen. Accordingly, structural elements of appropriate nanostructures may include cobalt, iron or any other suitable material that provides a catalyzing agent for artificial photosynthetic reactions when water and a carbon-containing source are irradiated with light under suitable conditions.

Nanostructures of the present disclosure having one or more structural elements may be formed by any suitable method. In some embodiments, a suitable nanostructure is formed by the application of a pulsed femtosecond laser for inducing self-assembly of the

nanostructure. For example, cobalt or iron nanostructures may be formed by applying femtosecond laser irradiations to the surfaces of a cobalt or iron pre-cursor. Pulsed laser- assisted etching may be a useful method for fabricating small regular structural features directly on a solid surface. In some instances, such a fabrication method can be orders of magnitude faster than chemical or ion beam etchings. For example, a Ti: sapphire

femtosecond laser may be suitable for fabricating nanostructures and respective structural elements. Laser irradiations for forming nanostructures discussed herein may exhibit energy levels of between about 1 kJ/m 2 and about 5 kJ/m 2 , though are not limited as such. For example, suitable nanostructures may be formed with laser irradiations having different energy levels, or without laser irradiation at all. As such, suitable nanostructures in accordance with the present disclosure are not required to be formed by laser irradiation. Indeed, suitable nanostructures may be formed by any appropriate method, such as for example, chemical etching and/or electroplating.

In some embodiments, a femtosecond laser may be applied to irradiate a metal powder dispersion in a solvent, for example, cobalt or iron microparticles dispersed in water. In some cases, the femtosecond laser may be applied to emit a beam having a wavelength between about 500 nm and about 1 micron (e.g., 800 nm). In some embodiments, during irradiation, the femtosecond laser may exhibit a pulse duration of between about 50 femtoseconds and about 200 femtoseconds (e.g., 100 femtoseconds). Due to the femtosecond irradiation, the metal powder dispersion may self-assemble into an organized array of high aspect ratio nano structural elements. For example, in an embodiment, a femtosecond laser is applied at a wavelength of 800 nm with a pulse duration of about 100 femtoseconds to irradiate cobalt microparticle powders dispersed in water. Such a laser irradiation results in a transformation of the surfaces of the cobalt microparticles into nanometer- sized flakes or nanometer- sized grasses. Examples of nanostructures formed via application of a

femtosecond laser are shown in Figs. 1A and IB.

As discussed above, for some embodiments, forming a nanostructure that is used to catalyze reactions for producing a long chained molecule (e.g., hydrocarbon, amino acid, etc.) may include initially providing a metal powder as a pre-cursor (e.g., metal microparticles dispersed in a solvent) to the nanostructure. In some cases, such a metal powder may have an average width (e.g., diameter) of between about 10 microns and about 500 microns, between about 50 microns and about 200 microns (e.g., about 100 microns). In some embodiments, a metal may be provided as a pre-cursor in a form other than a powder, such as a network or solution.

Any suitable metal may be used as a pre-cursor to the nanostructure, such as Co, Ag, Cu, Fe, Ni, Ti, stainless steel and/or a combination thereof. Pre-cursors having multiple metals may be provided as a mixture or an alloy. In some cases, Co mixed with one or more metals may serve to augment catalysis and ultimately enhance the process of photosynthesis. For instance, appropriately applied radiation from a femtosecond laser may interact with Fe, Cu, Ti, Ni, or Ag metals mixed with Co to form a suitable nanostructure. Other catalyzing materials may be used in forming the nanostructure. In some embodiments, the nanostructure does not require the incorporation of cobalt to function as a suitable catalyst.

In forming nano structures that enable initiation of reactions leading to the production of long chained molecules, for some embodiments, metal pre-cursors (e.g., metal powders) are melted into a semi-liquid state prior to formation of the nanostructures. For instance, irradiation by the femtosecond laser may cause a metal pre-cursor to coalesce into a semi- liquid state. The semi-liquid metal may subsequently self- assemble into high aspect ratio nano structural elements.

An appropriate nanostructure may be included in an apparatus to suitably catalyze reactions that lead to the formation of organic molecules. Such an apparatus may include, at least, a suitable nanostructure, water, a carbon-containing source and a source of light irradiation. In some embodiments, the apparatus includes a chamber that contains the nanostructure, water and the carbon-containing source.

Any suitable carbon-containing source may be used in a reaction with water catalyzed by the nanostructure to form larger organic molecules. In some embodiments, the carbon- containing source may be carbon dioxide. In some embodiments, the carbon-containing source may be bicarbonate and/or methane. The carbon-containing source may be a mixture of carbon dioxide, bicarbonate, and methane or may include a molecule other than carbon dioxide, bicarbonate, or methane. In some embodiments, carbon dioxide, bicarbonate, and methane are absent from the carbon-containing source. In cases where methane is provided in the carbon-containing source, in some instances, the methane is transferred to a liquid fuel, greatly decreasing the overall cost of methane gas transportation. Further, any suitable concentration of bicarbonate may be used.

In some embodiments, the apparatus includes nitrogen as a reactant along with the water and the carbon-containing source. Accordingly, light irradiation on a suitable nanostructure may initiate a reaction that produces nitrogen-containing molecules, such as amino acids.

Long chained organic molecules can be formed by any suitable method. In some embodiments, an appropriate nanostructure having a number of structural elements (e.g., array of nano structured spikes) is disposed in a chamber and in contact with water and a carbon-containing source such as carbon dioxide. The nanostructure and the starting materials (e.g., water and carbon dioxide) are irradiated to initiate a reaction between the starting materials to form an organic molecule having at least two carbon atoms chained together. Irradiation may include any appropriate energy derived from electromagnetic waves. For example, the nanostructure may be irradiated by shining natural light into the chamber. Artificially generated light may also be sufficient to initiate a suitable reaction. In some embodiments, appropriate radiation (e.g., electromagnetic light, visible light) involves focusing the light waves on to portions of the nanostructure disposed within the chamber. For example, the light may be focused on to certain regions of structural elements (e.g., nano- needle tips) where the light can be further concentrated so as to enhance carbon-carbon bonding.

In cases where long chain hydrocarbons are produced, reactions for forming hydrocarbons may involve dissociating carbon dioxide into carbon monoxide and oxygen, dissociating water into hydrogen and oxygen, and then synthesizing hydrocarbons from the hydrogen and carbon monoxide. Such photodissociation processes are shown by equations (1) and (2) below:

H₂0 + photons— > H₂ + 1/2 0₂, (1)

C0₂ + photons— > CO + 1/2 0₂. (2)

In an embodiment, water and nano structured Co microparticles are sealed in a glass chamber and, to induce photodissociation, the chamber is irradiated with sunlight. For example, an artificial light source may be used to simulate sunlight at air mass (AM) 1.5 100 mW/cm" to irradiate the nano structured Co microparticles in the sealed chamber while in a room temperature environment. Such irradiation may give rise to the formation of hydrogen and carbon monoxide in the chamber. In some embodiments, no thermal or electrolysis effects are involved in the reaction, as no electric circuit elements are provided on or in close proximity to the nanostructures.

A metal nanostructure surface (e.g., Co nanostructure) may enhance photodissociation for the synthesis of hydrocarbons. In some instances, hydrogen atoms and the carbon monoxide molecules formed in the photodissociation process coexist around the metal surface. Accordingly, the hydrogen atoms and carbon monoxide molecules may form various hydrocarbons on the metal catalytic surfaces.

In an example, hydrocarbon synthesis using Co nanostructures is described. A dispersion of nano structured Co microparticle powder and distilled water is placed on the bottom of a glass chamber. After removing the air in the chamber, the chamber is filled with carbon dioxide and the chamber is sealed. A light source is used to simulate sunlight at AM 1.5 100 mW/cm to irradiate the nano structured Co microparticles in the sealed chamber while in a room temperature environment. After several hours of irradiation, the water becomes brown and turbid, and a layer of an oil or a wax-like substance accumulates on the surface of the water. After irradiation, alcohol compounds may be present in the water. In addition, after irradiation, various kinds of hydrocarbons and carbohydrates may be synthesized and found accumulated in the oil or wax-like layer, including alkanes, olefins, carbon ringed structures, alcohols and branched paraffins.

In some embodiments, liquid and solid hydrocarbons are produced at a rate of about

50 mlV(gh) on the nano structured cobalt microparticles. It should be appreciated that the rate of long chain molecule formation is not limited to particular rates described herein.

Figs. 2A-2B depict a schematic of an illustrative embodiment of an artificial photosynthesis process. A nanostructure 10 (e.g., cobalt nanostructure) includes a structural element 12 (e.g., nano-spike) having a high aspect ratio attached to an underlying substrate 14. As illustrated in Fig. 2B, light 200 that is incident on the nanostructure focuses in such a manner that the light becomes concentrated around and in the immediate vicinity 202 of the nanostructure. Water and carbon dioxide molecules are photodissociated on the surface of the structural element 14. After the light irradiation ceases, the photodissociated molecules remain on the surface of the structural element and efficiently form hydrocarbon molecules. In some embodiments, surface-enhanced photodissociated molecules are predominantly located at the surface of the nano structured surface and, hence, are able to form longer chain molecules than, for example, water and carbon dioxide having been dissociated through the photovoltaic effect and electrolysis which may not result in dissociated molecules located in a high concentration at a catalytic surface. While not expressly shown in Figs. 2A-2B, it can be appreciated that nanostructure 10 may include more than one structural element 12.

In some embodiments, a thin oxide layer covers the structural element of the nanostructure. For example, upon suitable formation of a high aspect ratio metal

nanostructure with a femtosecond laser, a metal oxide layer (e.g., cobalt oxide) is also formed over the underlying metal nanostructure. Fig. 3A shows a nanostructure 10 where a high aspect ratio structural element 12 is formed on a substrate 14. During the course of formation of the nano structured system, a metal oxide layer 16 is formed over the high aspect ratio structural element 12. The metal oxide layer may have any suitable thickness. In some embodiments, the metal oxide layer has a thickness of less than about 10 nm, less than about 5 nm, or in some cases, between about 1 nm and about 2 nm.

As shown in Fig. 3B, when light 200 is incident on the nano structured system 10, in some cases, the incident light may become intensified in the vicinity 202 around the high aspect ratio structural elements and the thin layer of metal oxide, reaching a relatively high local temperature. In some cases, the oxide (e.g., metal oxide) layer may serve as a protective layer for the high aspect ratio structural element. In some cases, the oxide may act as a photosensitizer and/or a catalyst. In an embodiment, molecules of water and the carbon- containing source (e.g., carbon dioxide) are photo-dissociated on to the nano structured surface, remaining on or in close proximity to the nano structured surface so as to form hydrocarbon molecules. Nanostructure 10 may include one or more structural elements 12.

Fig. 4 illustrates a schematic embodiment of an experimental setup for initiating an artificial photosynthesis reaction. Light 200 is irradiated to nano structured cobalt microparticles dispersed in 10 inches of water 20 and carbon dioxide while sealed in a glass chamber. On the surface of the water forms a thin layer of oil-like or a wax-like substance. An optical microscopic image of the oil-like or wax-like substance is shown on the right side of Fig. 4. Results of an experiment where a cobalt nanostructure was exposed to continuous and intermittent sunlight are presented below in the examples section.

In some embodiments, the efficiency of storing light energy in products arising from the artificial photosynthesis processes described herein is between about 5% and about 20% (e.g., about 10%). However, any suitable efficiency may be achieved using systems and methods described herein. Efficiency may be determined by comparing the energy stored in the molecules produced with the energy from the level of irradiation exposure. In some cases, liquid and solid hydrocarbon compounds are synthesized from carbon dioxide, water and sunlight at a production rate of more than 5,000 ulV(gh), more than 10,000 uL/(gh), or more than 20,000 uL/(gh). Since conditions for artificial photosynthesis are relatively straight-forward to provide (e.g., sunlight, atmospheric temperature and pressure, metal nanostructure), surface-enhanced photo-disassociation and synthesis processes described herein may enable methods for large-scale production and applications of artificial photosynthesis to arise. In some embodiments, the mass production of hydrocarbons is about 10³ to about 10⁶ times greater than that of previous works.

Nanostructures produced can be stable and functional even after a substantial amount of time. For example, Co nanostructures may be stable and still functional after two months or more of repeated use. A chamber within which a nano structure and appropriate reactants may be contained may include characteristics that facilitate reaction of the materials to form long chained organic molecules. In some embodiments, the chamber may be constructed so that reactants are easily recycled. For example, as water evaporates during a reaction, the chamber may have a structure that facilitates condensation of the water on to walls of the chamber and further enabling the water to flow back toward nanostructure so as to be used for reaction(s) in forming organic molecules. In some embodiments, a chamber has a curved shape (e.g., round, oval) so as to easily permit the flow of dew from water and hydrocarbons back toward the nanostructure. The chamber may be made from any suitable material, such as for example, glass.

In a representative embodiment, Fig. 5 A depicts a round hemispherical shaped chamber 100 surrounding a nanostructured array 110 disposed at the base of the chamber. In another representative embodiment, Fig. 5B illustrates an round half-oval shaped chamber 100 where a nanostructured array 110 is disposed at the base of the chamber. In both embodiments, the nanostructured array 110 is covered in water 120 having a depth d, for example, about 2 mm. Further, the chamber may have any suitable height h. Upon exposure to radiation 200, photodissociation reactions may be suitably catalyzed to bring about hydrocarbon production. In various embodiments, water and hydrocarbons may evaporate and condense on the surface of the chamber 100, forming droplets of dew 130. The dew 130, upon condensation, flows readily back down toward the base where the nanostructured array 110 is located. It should be appreciated that the chamber 100 should not be limited to particular shapes described, as any suitable shape may facilitate water and/or hydrocarbon condensation on a surface and flow of the water and/or hydrocarbon dew back down toward the base of the chamber.

In some embodiments, the water may be placed in contact with the nanostructure to form a film having a suitable depth within a chamber. For example, the water has a depth of approximately 2 mm, or less than 2 mm within the chamber. In some cases, the water has a depth of greater than 2 mm.

The carbon-containing source may include a gas having a suitable pressure within the chamber. In some embodiments, the carbon-containing source includes carbon dioxide gas having a pressure of between about 1 atm and about 5 atm within the chamber. In some embodiments, a gas of the carbon-containing source may have a pressure within the chamber that is less than 1 atm or greater than 5 atm. Other gases may be possible besides carbon dioxide, for example, carbon monoxide or methane. In some embodiments, a system that suitably induces reactions that lead to the formation of organic molecules, includes methods for concentrating light intensity. For example, a system may include a lens to focus light irradiated on to the nano structure. In some cases, a system includes reflectors for reflecting light back toward the nano structure.

In some embodiments, the apparatus includes a filtration system for removing oxygen from the chamber. As oxygen is produced, the effect of its accumulation is that excess oxygen may result in a reduction of the reaction rate of water and the carbon-containing source for forming long chained organic molecules. Accordingly, it may be beneficial to provide a method for removing the oxygen as it is produced. In some embodiments, a filter or membrane system is provided (not shown in the figures) which functions to extract excess oxygen from the system.

The apparatus may also include a system for removing oils containing long chained organic molecules (e.g., alkanes, polyolefins, molecules having at least two carbons chained together, amino acids, benzene, etc.) from the base of the chamber. As oils containing long chained carbon molecules accumulate around the nano structural elements, another filtration system may be provided for extracting this substance without affecting the remaining contents that are disposed within the chamber.

In some embodiments, the apparatus may be configured to maintain a continual supply of water or the carbon-containing source (e.g., carbon dioxide) within the chamber. As the reactions progress, not only will the long chained organic products accumulate, but the reactants will also be used up. For example, a separate system and attachment may be provided to the chamber (not shown in the figures) where the levels of water and carbon dioxide within the chamber are monitored and automatically maintained within certain pressure levels (e.g., carbon dioxide pressure of between 1-5 atm, water depth of about 2 mm). Accordingly, the system can be configured to run continuously as reaction products are removed and reactants are replenished.

In more embodiments, a structural element of a nanostructure for use in accordance with the present disclosure may include a number of layers formed in a patterned

arrangement (e.g., periodic). Fig. 6 illustrates a schematic of a nanostructure 300 attached to a substrate 310 and a structural element 320 (e.g., having a high aspect ratio such as in accordance with nano-needles, nano-flakes, nano-grass, etc.). The structural element 320 includes a number of metal layers formed in a patterned arrangement. In an embodiment, the layers of the nano structural element are formed in a periodic arrangement of alternating radiation-focusing metal layers and catalyzing metal layers. In some embodiments, the radiation-focusing metal layer may contain one or more metals from the group including Au, Al, Ag, Cu, or combinations thereof. In some cases, certain metals such as Al may be more inexpensive than other metals, such as Au or Ag. In some embodiments, the catalyzing metal layer may contain one or more metals from the group including Co, Ag, Cu, Fe, Ni, Ti, or combinations thereof. Metal layers (e.g., radiation-focusing and catalyzing) provided in the nano structured element may be metal alloys or mixtures. Combinations described herein may also include mixtures or alloys.

Radiation-focusing and catalyzing metal layers may alternate in a periodic

configuration. In an embodiment, for instance, a first radiation-focusing metal layer 322a includes any one of Au, Al, Ag, Cu, or a combination thereof. A first catalyzing metal layer 326a including any one of Co, Ag, Cu, Fe, Ni, Ti, or a combination thereof is formed immediately adjacent to the first radiation-focusing metal layer 322a. A second radiation- focusing metal layer 322b is disposed adjacent to the first catalyzing metal layer 326a and may include any one of Au, Al, Ag, Cu, or a combination thereof. Similarly, a second catalyzing metal layer 326b may be disposed adjacent to the second radiation-focusing metal layer 322b. Such a progression may be repeated in alternating fashion along the length of the structural element. In various embodiments, radiation-focusing metal layers and catalyzing layers may be disposed in contact with one another or, alternatively, an additional layer may be disposed between a radiation-focusing metal layer and a catalyzing layer (e.g., another metal, polymer, adhesive).

Layered structural elements may provide a number of benefits. In some

embodiments, the radiation-focusing metal layer of Au, Al, Ag or Cu may serve to focus or concentrate incident light around the edges of the layer adjacent to the neighboring catalyzing metal layers. This increased level of light energy may help to augment the rate and amount of reaction of water and carbon-containing source molecules (e.g., carbon dioxide, bicarbonate, methane). Accordingly, the catalyzing metal layer functions to initiate the artificial photosynthesis reaction based on the enhanced level of energy provided by neighboring radiation-focusing metal layers. For instance, Au has a plasmon resonant wavelength that focuses light radiation so as to be concentrated in its vicinity to a much greater degree than Co. Thus, the light concentrated by the Au allows for the level of reaction catalysis by Co to be enhanced. In Fig. 6, radiation-focusing metal layers 322a, 322b, 322c, 322d are arranged in an alternating configuration with catalyzing metal layers 326a, 326b, 326c. When the nanostructure is irradiated, radiation is focused in concentration regions 324a, 324b, 324c, 324d corresponding to each of the radiation-focusing metal layers 322a, 322b, 322c, 322d. When more light energy is provided in regions proximate to catalyzing metal layers 322a, 322b, 322c, 322d, reactions for producing carbon-containing molecules are augmented.

Such layered features of the nano structural element may also reduce the general amount of oxidation that occurs in the system. For example, Au is generally resistant to oxidation and may serve as a protective material that prevents oxidation reactions from occurring in its vicinity. Accordingly, a catalyzing metal layer may be protected from oxidation by neighboring radiation-focusing metal layers. In some instances, the presence of radiation-focusing metal layers in the layered structure significantly reduces, or in some cases prevents, oxidation in the nanostructure altogether.

Various layers (e.g., radiation-focusing and catalyzing) of a structural element of the overall nanostructure may have suitable dimensions such as average width w and thickness t. For example, metal layers of structural elements may be formed as nano-disks having appropriate average width and thickness dimensions. Fig. 7 depicts two layers 322, 326 of a structural element of a nanostructure having an average width w and a thickness t. In some embodiments, the thickness of a layer of a structural element may be less than about 100 nm, or less than about 50 nm (e.g., having a thickness of 20 nm). In some embodiments, the average width of a layer of a structural element may be between about 5 nm and about 200 nm, or between about 10 nm and about 100 nm (e.g., having a diameter of about 10 nm or about 100 nm). In some instances, the average width w may be a diameter of a cross-section having a generally arcuate shape (e.g., having a circular or oval cross- section).

In some cases, the level at which certain wavelengths of light is absorbed may depend on the material and the dimensions of each layer. For instance, a relatively large radiation- focusing metal layer may serve to concentrate longer wavelengths of light as compared with a relatively small radiation-focusing metal layer. As an example, a radiation-focusing metal layer having a diameter of about 100 nm and a thickness greater than 20 nm may have a resonant peak at wavelengths corresponding to red or infrared radiation. That is, a larger volume radiation-focusing metal layer may have a tendency to give rise to concentrated light having a wavelength in the red or infrared regime at a greater degree than light having wavelength in the blue or ultraviolet regime.

As different sizes of structural elements of a nanostructure may correspond to different resonant wavelength peaks (e.g., plasmon resonant wavelengths), structural elements may be constructed in a configuration so as to exhibit a substantial degree of photosynthesis efficiency across a significant portion of the electromagnetic wavelength spectrum. In some embodiments, a periodic arrangement of alternating radiation-focusing metal layers and catalyzing metal layers may be suitable to concentrate light energy in proximity to and around the structural elements, resulting in efficient production of long chain carbon-containing molecules. Accordingly, the efficiency of energy production embodied in the carbon-containing molecules formed may increase due to the patterned configuration of the structural elements in the nanostructure. Such nanostructures may give rise to a photosynthesis process that is generally stable and may also exhibit longevity. It can be appreciated that other patterned arrangements of structural elements in a nanostructure may be possible. For example, while not shown, rather than having horizontally aligned layers of alternating radiation-focusing layers and catalyzing layers, a structural element of a nanostructure may exhibit vertically aligned layers of radiation-focusing layers and catalyzing layers. In another embodiment, radiation-focusing materials and catalyzing materials are not required to be formed as layers, but could simply be formed within particular regions of structural elements within a nanostructure.

Fig. 8 illustrates depicts a graph showing resonance wavelengths corresponding to different layers. Each of the radiation-focusing metal layers is constructed with a material having a set of dimensions that result in a unique resonant peak wavelength. The curves 502, 504, 506, 508, 510, 512, 514, 516, 518, 520 each illustrate the resonant peak of a

corresponding radiation-focusing metal layer. Accordingly, as shown in Fig. 8, resonant peaks are present for the spectrum of light from a wavelength of 61 nm to 492 nm generally resulting in radiation having various wavelengths in this spectrum to be well absorbed. That is, the nanostructure may be configured to concentrate almost every wavelength of light in close proximity to respective catalyzing layers so as to readily initiate artificial

photosynthesis reactions described herein.

Figs. 9A-9G depict an illustrative embodiment of a lithographic process for fabricating a nanostructure having structural elements where each structural element includes metal layers arranged in a periodic configuration. In this embodiment, a nanostructure is fabricated via femtosecond laser processes described herein, a reverse mold is made of the nanostructure, and appropriate layers of metal are subsequently deposited in the reverse mold. Accordingly, a nanostructure is formed having different layers of materials making up each of the structural elements.

As shown in Fig. 9A, a nanostructure having a first plurality of structural features 304 is formed on a substrate 302, for example, using a suitable method involving femtosecond laser irradiation as described above. For instance, the nanostructure may be formed by appropriately subjecting a dispersed mixture of metal powder (e.g., cobalt microparticles) to a femtosecond laser, giving rise to the first plurality of structural features 304 having a high aspect ratio. The shape of the nanostructure may then be duplicated with any appropriate material that can be provided via a suitable deposition processes. Fig. 9B illustrates the substrate 302 and the first plurality of structural elements 304 covered with a suitable overmold 306. Any suitable method or material for providing the overmold 306 may be used, such as through an appropriate polymerization process (e.g., application of a photoresist material).

Once the overmold is provided on the nanostructure, as illustrated in Fig. 9C, the underlying nanostructure with the first plurality of structural features 304 and the substrate 302 are removed. The structural features may be removed by any suitable method, for example, by a solvent (organic or inorganic) that dissolves the structural features, yet permits the overmold to remain without any resulting damage. As shown, a plurality of recessed structures 308 are provided in place of the plurality of structural features. Any appropriate material may be suitably deposited within the recessed structures 308. Fig. 9D depicts a stage in the initial deposition process where the overmold 306 is inverted and metal layers 322a, 326a are deposited into the recessed structures. As illustrated, a radiation-focusing metal layer 322a is deposited into a recessed structure and a catalyzing metal layer 326a is deposited on the radiation-focusing metal layer.

Figs. 9E and 9F illustrate steps where the recessed structures are filled with appropriate layers of material and a substrate is provided so as to hole the structural elements together. Fig. 9E depicts metal layers 322a, 326a, 322b, 326b, 322c, 326c, 322d disposed in the recessed structure in successive fashion. In this embodiment, alternating radiation- focusing metal layers 322a, 322b, 322c, 322d and catalyzing metal layers 326a, 326b, 326c are arranged in a periodic configuration. As a result, upon exposure of light radiation to the nanostructure, light may be suitably focused at particular regions in a manner where reactions between water and the carbon-containing source may be enhanced. As shown in Fig. 9F, a substrate 310 is provided so as to hold the plurality of structural elements together once the overmold 306 is removed. The substrate may be any suitable material, for example, a metal that is able to form a suitable attachment with the structural elements.

Layers (e.g., metal layers) of structural elements in a nanostructure may be formed by any suitable method. In some embodiments, metal layers are provided through thin layer deposition of one layer after another, such as through evaporation, sputtering, or another appropriate method of deposition. In other embodiments, metal layers are formed within the recessed structures via a suitable chemical plating method so as to fabricate structural elements. The aspect ratio of structural elements may be increased even more than that provided by the overmold template of the initial nanostructure formed by application of the femtosecond laser. For instance, while not shown in the figures, openings may be drilled into the ends of the recessed structures, forming an even deeper recess. In some embodiments, an electron beam may be employed to increase the depth of the recessed structures where a suitable pattern of metal layers can be subsequently formed within the recessed structures.

The overmold 306 may be removed by any suitable method. In some embodiments, the overmold is a photoresist that is removed through radiation of an appropriate wavelength and intensity of light. In other embodiments, the overmold may be removed by a suitable solvent that dissolves the material of the overmold while allowing the second plurality of structural elements 320 to remain. Fig. 9G illustrates the nanostructure 300 including the second plurality of structural elements 320 where the second plurality of structural elements are disposed over the substrate 310. In some embodiments, the second plurality of structural elements are attached to the substrate via a suitable bond or adhesive. The nanostructure with structural elements and substrate may then be placed in a suitable chamber under conditions that give rise to artificial photosynthesis. For example, the nanostructure may be placed in contact with water and a carbon-containing source and exposed to light in a manner such that a reaction between the water and the carbon-containing source is initiated resulting in long chain carbon-containing molecules.

In further embodiments described herein, a nanostructure suitable for catalyzing a reaction for producing long chained carbon-containing molecules may include a number of structural elements having a high aspect ratio disposed on a substrate and a plurality of sub- structural elements disposed on surfaces of each of the structural elements. In an

embodiment, nanoflake structures are substantially evenly distributed along a surface of a high aspect ratio structural element (e.g., nanospike). Each of the nanoflake structures may exhibit a curved shape and an edge that is oriented in a direction that faces away from the structural element. In some cases, such nanostructures may be arranged and configured in a manner that resembles a flower-type shape.

Nanostructures having a number of sub-structural elements disposed on the surface of a high aspect ratio structural element may be fabricated by electroplating the structural element under appropriate conditions. For example, the structural element may have a conductive layer formed thereon and then be subject to an electroplating process in a suitable metal ion solution. In some embodiments, a structural element having a high aspect ratio may be formed out of a curable polymeric material using methods described herein. Once the structural element is formed, a conductive layer may subsequently be deposited on the structural element. The high aspect ratio structural element, having the conductive layer formed thereon, is then subject to suitable electroplating conditions such that a metal catalyst layer is formed on the conductive layer of the high aspect ratio structural element. Under certain conditions, the metal catalyst layer formed by electroplating on the structural element includes sub- structural elements having substantially smaller dimensions (e.g., height, width) than the structural element itself. Figs. 10A-10H depict an illustrative embodiment of a process employing lithographic techniques for fabricating a nanostructure having high aspect ratio structural elements and sub-structural elements formed on the structural elements so as to resemble a nano-flower conformation.

Figs. 1 OA- IOC illustrate steps that are similar to those shown in Figs. 9A-9C where a lithographic process is used to fabricate an overmold. The overmold is then used to create a suitable nanostructure having high aspect ratio structural elements. In this embodiment, a suitable method, such as those described above, involving femtosecond laser irradiation is used to form a nano structured precursor having a plurality of structural elements 404 characterized by having a high aspect ratio and disposed on a substrate 402. For example, a femtosecond laser may be employed to irradiate a dispersed mixture of metal powder (e.g., cobalt, iron, nickel microparticles) on a suitable substrate (e.g., silicon) to form the structural elements of the nano structured precursor. In some cases, a femtosecond laser is utilized to scan a silicon surface to form arrays of nano- spike structures.

In a non-limiting embodiment, the structural elements of the nano structured precursor are generally one-dimensional in accordance with structural elements of nanostructures described above which are useful for catalyzing light- initiated reactions for forming long chain molecules that include carbon. For example, structural elements of the nano structured precursor may have a height h_p of approximately 500 nm (or, e.g., between about 100 nm and about 1000 nm, between about 200 nm and about 400 nm) and having an average width w_p measured at the midpoint of the height of approximately 50 nm (or, e.g., between about 10 nm and about 100 nm, approximately 20 nm). The structural elements are spaced apart from one another an average distance s of about 100-200 nm (or, e.g., between about 100 nm and about 500 nm) along the surface of the substrate.

As shown in Fig. 10B, the substrate 402 and the first plurality of structural elements 404 that make up the nanostructured precursor are covered with a suitable overmold 406 so as to create an inverse shaped nano structure. The overmold 406 may be formed according to any suitable technique and may include a suitable polymer (e.g., polymethylmethacrylate (PMMA)), photoresist material or other appropriate material. In some embodiments, the material used to create the overmold is deposited over the nano structured precursor 404 so as to conform to an suitable inverse shape. The overmold is then heated or irradiated for a suitable period of time (e.g., 70 C for 4 hours), allowing for the overmold material to fully set. It can be appreciated that overmolds which remain intact after the nano structure fabrication process is completed may be reused, allowing for appropriate nanostructures in accordance with the present disclosure to be mass-reproducible.

The underlying nano structured precursor with the first plurality of structural elements

404 and the substrate 402 may be suitably removed, yielding a plurality of recessed structures 408 in place of the structural elements. The nanostructured precursor may be removed by any suitable technique, such as but not limited to an appropriate etch step or mechanical removal. Fig. IOC depicts the overmold 406 having the inverse shaped nanostructure provided by the recessed structures 408.

In Fig. 10D, a curable material (e.g., polyurethane) is deposited into the plurality of recessed structures 408. The curable material may be any appropriate substance, such as a suitable polymer or other material that may be altered from a deformable state to a substantially rigid state. The curable material may be hardened (e.g., polymerized), such as for example, using an appropriate level of heat and/or irradiation (e.g., ultraviolet light) and is not so limited in this regard. In an example, a polyurethane (PU) gel is deposited into the recessed structures 408 of the overmold 406 and is subsequently irradiated with an amount of UV light sufficient for the PU to be cured into a solid. Once the curable material hardens into a solid, the overmold 406 may be removed by any suitable method (e.g., etch step, mechanical removal), resulting in a plurality of structural elements 412 on a substrate 410, as shown in Fig. 10E.

As illustrated in Fig. 10F, a conductive layer 414 may be coated on to the cured material so as to yield a plurality of structural elements 412 having a conductive surface. Accordingly, once coated, the structural elements 412 include the conductive layer 414. In some embodiments, the conductive layer 414 may be deposited via thermal evaporation, sputtering, painting, or any other suitable method. The conductive layer may have a suitable thickness, such as between about 1 nm and about 100 nm (e.g., between 20-50 nm, approximately 20 nm). The conductive layer may also include any suitable material, such as but not limited to Au, Al, Ag, Cu, Co, Fe, Ni, Ti, stainless steel, or combinations thereof. In some embodiments, depositing a conductive layer 414 on to the structural elements 412 makes the structural elements more suitable to undergo electroplating, which will be discussed next.

The plurality of structural elements 412 and the conductive layer 414 may then be subject to electroplating. An exemplary electroplating apparatus is shown in Fig.lOG where a solid metal electrode 440 and the nano structured apparatus 400, acting as an electrode, are immersed in a solution 430 containing ions. An electrical current is applied to the solid metal electrode 440 and the nano structured apparatus 400 via a closed circuit 450. The electrical current drives a number of electrochemical redox reactions that occur at the electrodes where atoms from the solid metal 440 are released as ions into the solution 430 and ions from the solution come together to form a metal layer on the nano structured apparatus 400.

In an example, a nano structured apparatus 400 having a number of high aspect ratio structural elements and a cobalt electrode 440 are immersed in a cobalt solution (e.g., C0SO₄) having a suitable concentration (e.g., between 1% and about 50% mol, approximately 10% mol) and the circuit 450 is operated to run a current of between about 0.1 amperes and about 2 amperes (e.g., about 1 ampere). The electroplating process of a metal layer on the nano structured apparatus may run for a suitable period of time, for example, between about 1 minute and about 15 minutes (e.g., between about 2 minutes and about 10 minutes, approximately 5 minutes). A metal layer is accordingly deposited on the surface of the structural elements 412.

As a result, the high aspect ratio structural elements 412 now include a metal layer 416 disposed on the conductive layer 414 which is disposed, in turn, on the underlying cured material (e.g, polyurethane). The metal layer 416 may have any suitable thickness, such as between about 1 nm and about 1000 nm (e.g., between about 300 nm and about 800 nm, approximately 200 nm). The metal layer may include any suitable material, such as but not limited to Au, Al, Ag, Cu, Co, Fe, Ni, Ti, stainless steel, or combinations thereof. In some embodiments, the metal layer 416 includes a number of sub-structural elements 418, as shown in Fig. 10H. In some instances, the sub-structural elements 418 self-assemble into nano-flake and/or nano-spike shapes so that the sub-structural elements disposed on the surface of a structural element resemble a nano-flower conformation.

Because electroplating typically results in the formation of a relatively flat film, the inventors did not expect the occurrence of sub-structural elements to be distributed on the larger structural elements and were surprised at the overall shape that resulted in the nano structured apparatus from the fabrication method. In some embodiments, sub-structural elements may arise due to the electrical field distribution around the structural element upon which the sub- structural elements are formed. In some embodiments, sub- structural elements may arise due to the presence of cracks in the underlying structural element. For example, a crack on a structural element, when subject to electroplating may serve to nucleate and/or increase the growth of a sub- structural element at the location of the crack. Cracks in the underlying structural element may be present, for example, in the cured material (e.g., polyurethane) and/or the conductive layer coated on the cured material.

The metal layer 416 including sub-structural elements 418 disposed thereon may serve as a catalyst for reactions (e.g., artificial photosynthesis) where a reactant that includes hydrogen and a reactant that includes carbon are exposed to light (artificial or natural) such that long chain molecules that include carbon are produced. In some embodiments, the sub- structural elements provide for an increase in photo synthetic efficiency. The sub-structural elements may have points (one-dimensional) or edges (two-dimensional) that are oriented in a manner that faces in a direction away from the structural element upon which the sub- structural element is disposed. Such edges may serve to concentrate light to a greater degree than that which would otherwise occur absent the sub-structural elements. The sub- structural elements also provide additional surface area which may also serve to enhance efficiency in the catalyzed reactions.

Fig. 11 depicts an SEM micrograph of the nanostructured apparatus 400 including structural elements 412 that include a number of conductive layers and several sub-structural elements 418 disposed thereon. The sub-structural elements 418 are substantially evenly distributed along the exterior surface of the structural element. The sub -structural elements are shaped and arranged as two-dimensional nano-flakes where each of the nano-flake structures has a curved shape and an edge that is oriented in a direction that faces away from the structural element. In some embodiments, sub-structural elements are interconnected on the surface of the structural element. In some embodiments, sub- structural elements are separately formed on the surface of the structural element without interconnection between one another.

As shown , an average width of the sub- structural elements is generally less than a width of the structural element upon which the sub- structural elements are disposed. In addition, an average length of the sub-structural elements is less than a length (or height) of the structural element upon which the sub- structural elements are disposed. In some embodiments, the average length of the sub- structural elements is between about 100 nm and about 1000 nm. In some embodiments, the average width of the sub-structural elements is between about 1 nm and about 100 nm.

In some embodiments, the sub- structural elements exhibit a generally two- dimensional nano-flake or nano-plate configuration. The sub-structural elements may have a curved shaped, as shown in Fig. 11, akin to a nano-flake or, alternatively in some instances, the sub-structural elements may exhibit a relatively straight shape, more akin to a nano-plate. In some embodiments, the sub- structural elements may exhibit a generally one-dimensional nano-spike configuration similar to that shown with respect to the underlying structural elements upon which the sub- structural elements are disposed.

The sub- structural elements may exhibit a high aspect ratio, which is the ratio of the length of the sub- structural element, as measured from the surface of the structural element upon which the sub-structural element is disposed to the opposing edge of the sub- structural element, and the smaller of two widths of the sub- structural element, as measured at the midpoint of the length of the sub- structural element and substantially running parallel to the surface of the structural element upon which the sub-structural element is disposed. In some embodiments, similarly to the underlying structural element, the aspect ratio of a sub- structural element may be between about 1 and about 20, between about 1 and about 10, or between about 2 and about 8.

The nanostructure having structural elements and a number of sub-structural elements disposed on the surface of the structural elements may be placed in suitable conditions that give rise to artificial photosynthesis (e.g., within in an appropriate chamber with reactants appropriate for producing long chained molecules containing carbon). In some embodiments, the nanostructure is placed in contact with a reactant that includes hydrogen (e.g., water) and a reactant that includes carbon (e.g., C0₂, CO, methane, natural gas, etc.) and is exposed to light in a manner such that a reaction between the hydrogen-containing reactant and the carbon-containing reactant is catalyzed and proceeds in a manner that results in long chain molecules that contain carbon (e.g., hydrocarbons, amino acids, etc.).

Nano structured apparatuses in accordance with the present disclosure may be used to catalyze reactions with any suitable combination of reactants. While water is contemplated for some embodiments as a reactant that includes hydrogen which can be utilized to produce long chain carbon-containing molecules, for some embodiments involving reactions catalyzed by a suitable nano structured apparatus, water is not required, nor is a hydrogen- containing reactant. Further, any suitable reactant that includes at least one carbon atom may be used in accordance with systems and methods described, such as but not limited to, methane, C0₂, CO, ethane, propane, butane, natural gas and various components and combinations thereof. Based on the reactants provided, nano structured apparatuses fabricated according to methods described herein may produce long chain molecules that contain carbon, such as but not limited to hydrocarbons, amino acids, alcohols, polymers, fertilizers, etc.

It can be appreciated that aspects of the present disclosure are not limited solely to the specific embodiments discussed. For example, sub-structural elements may be formed on any suitable high aspect ratio structural element described herein, such as structural elements that include a curable polymer material (e.g., polyurethane) and metal (e.g., layered or non- layered structures).

As described above, any appropriate light energy may be harvested to initiate a reaction catalyzed by a nanostructured apparatus. While naturally occurring light (e.g., sunlight) may be used an energy source for carrying out the reactions, artificially generated light may also be used, such as radiation sourced from a light bulb, electronically generated radiation (e.g., via LEDs), a laser, an electro-optic source where optical properties may be modified by an electric field, an optically pumped source, or any other suitable energy source. As described above, a lens may be used to focus irradiated light energy directly toward the nanostructure so as to increase reaction throughput and efficiency. In some embodiments, light energy irradiated toward the nanostructure may be modulated (e.g., spatial, wavelength modulation, etc.) so as to potentially enhance reactions catalyzed by the nanostructure.

Benefits afforded by systems and methods described herein which use suitable nanostructures (e.g., made up of one or more metals) for producing long chain carbon- containing molecules may include: (a) efficiently storing light energy into liquid and solid compounds formed by a carbon-containing source (e.g., carbon dioxide, bicarbonate, methane, etc.) and water; (b) a spontaneous photodissociation process without the use of thermal or electrolysis effects; (c) a process suitable with water and atmospheric temperature and pressure; (d) stable and continuous functionality without the need for extra equipment; and (e) usage of sunlight as the only energy source for producing the carbon-containing molecules.

EXAMPLES

The dynamics of artificial photosynthesis was studied as related to whether continual or intermittent sunlight was applied to a cobalt nanostructure. The system used was that shown schematically in Fig. 4 where a light chopper was rotated so as to provide cyclical irradiation to the nano structured system at intervals of about 2 ms each. The nano structured system including the chopper was irradiated for the same amount of time as compared to a nano structured system where the chopper was not included. For both cases, the water became brown and turbid, and various hydrocarbons with similar compositions and production rates were obtained, including olefins, alcohols, branched paraffins and alkanes. Despite the chopper blocking off the light source during half of the irradiation time, the actual production rate was increased, when using the chopper, by about 110% [about 105 mlV(gh)]. Accordingly, for some embodiments, exposing the nanostructure to intermittent light may be effective to increase the rate of reaction of water and the carbon-containing source to produce carbon molecules having at least two carbon atoms chained together.

Figs. 12A-12B illustrate relative amounts of hydrocarbons and gas that were produced from the different nano structured systems. Fig. 12A depicts the reaction products generated from three experiments where a cobalt nano structured array is exposed to sunlight in the presence of water and carbon dioxide. Set 1 illustrates the reaction products from a system where a cobalt nanostructure is irradiated with sunlight. Set 2 depicts the reaction products from a system where a cobalt nanostructure is subject to intermittent sunlight irradiation through use of a light chopper. Set 3 illustrates the reaction products recorded from a system where an iron nanostructure is irradiated with sunlight. The "n" shown in Fig. 12A is to denote the number of carbon atoms in a molecule. Fig. 12A refers to the hydrocarbon and carbohydrate products that were detected in liquid and solid states. As shown, a combination of olefins, alcohols, branched paraffins and alkanes were detected from the light-initiated reactions catalyzed by the Co nanostructure. The amount of long chained organic molecules produced from the nano structured array where a chopper was included within the

experimental setup was observed to be greater, almost double, than that of the same system having the nanostructured array and where the chopper was not included.

Fig. 12B shows the amount of gas products detected from the reactions after sunlight irradiation, recording hydrogen, carbon monoxide and methane. Also shown in Fig. 12B, a generally low production rate of 2 mlJ(gh) of methane may occur in the gas phase.

In addition, the amount of hydrocarbons produced over time was measured comparing nanostructured systems that were exposed to intermittent sunlight (with a chopper) and nanostructured systems that were exposed to continuous sunlight (without a chopper). Fig. 13 shows an embodiment of data recording hydrocarbon production rates where, in some cases, an irradiation time threshold may exist for hydrocarbons to be formed. Such a threshold may be caused by a minimum dissociated molecule concentration for the synthesis reaction. In some embodiments, adding a chopper can lower the time threshold as compared to not having a chopper using the same light source. As shown, for the case where the nano structured array was exposed to continuous sunlight, the production of long chain carbon-containing molecules (artificial photosynthesis) began to occur at about 4.5 hours. For the case where the nano structured array was exposed to intermittent sunlight, the production of long chain carbon-containing molecules began to occur at about 2 hours. Fig. 13 also illustrates irradiation time dependencies of the formation of hydrocarbons and carbohydrates for some embodiments using cobalt nano structured arrays irradiated with continuous sunlight and intermittent sunlight.

In another example, a nano structured apparatus was fabricated in accordance with Figs. 10A-10H and as depicted in the SEM micrograph of Fig. 11. A nanostructure having polyurethane nano-spikes was formed after curing polyurethane deposited into a PMMA overmold. A layer of Au was then thermally evaporated on to the polyurethane

nanostructure, conductively coating the high aspect ratio structural elements. The conductively coated nano structured apparatus was then subject to electroplating opposite a solid cobalt electrode. Both the conductively coated nano structured apparatus and the solid cobalt electrode were immersed in a 10% mol concentration C0SO₄ solution. A 1 ampere electrical current was run through the solution and the respective electrodes for a plating period of approximately 5 minutes to form a cobalt coating on the structural elements of the nano structured apparatus. The cobalt coating includes sub- structural elements forming a nano-flake flower-type configuration with the structural elements, as shown in Fig. 11. The nano structured apparatus was placed in a chamber in contact with water and C0₂ and exposed to sunlight, catalyzing a reaction between the water and the C0₂, producing a number of long chain carbon-containing molecules.

Figs. 14A-14C depict the results of a gas chromatography mass spectrometry (GC/MS) analysis conducted on the products formed through the above catalyzed reaction involving the nano structured apparatus including the cobalt sub- structural elements disposed on the conductively coated polyurethane structural elements. Fig. 14A depicts the spectrum indicating the respective peaks that correspond to the detected products. Figs. 14B-14C show recorded results that identify the constituents corresponding to each of the peaks shown in Fig. 14A. For instance, peaks 4-8, 10 and 14-16 indicate the occurrence of relatively long- chained hydrocarbons in the products, including alkenes and alkanes having chains of between 5-20 carbon atoms. Such molecules include, but are not limited to, those products detected by the GS/MS analysis such as dodecane, tetradecane, hexadecane, n-hexadecanoic acid, pentadecanoic acid, n-hexadecanoic acid, eicosane, 7-hexyl-eicosane, heneicosane, pentadecane, 8-hexyl-pentadecane, nanodecane, octacosane, heptadecane and heptacosane. Additional Aspects

As discussed herein, in some embodiments, nanostructures may be adapted to catalyze a reaction that results in the formation of a molecule having at least two carbon atoms chained together when the nanostructures are irradiated with electromagnetic radiation e.g., light, in the presence of a carbon-containing source. Any suitable carbon-containing source may be used, such as any suitable one or more single-carbon molecule reactants (e.g., methane, carbon dioxide, carbon monoxide, bicarbonate, or natural gas) or reactants having molecules that include a plurality of carbon atoms (e.g., long chain organic molecules, olefins, alkanes, alkenes, paraffin, alcohols, ethane, ethylene, etc.). The carbon-containing source may optionally react with a hydrogen-containing source, such as water, for example, to produce molecules that include a plurality of carbon atoms and one or more hydrogen atoms, such as hydrocarbons, for example. However, in such embodiments, any suitable hydrogen-containing source may be used, not limited to water. Any of the carbon-containing molecules described herein, such as molecules including a plurality of carbon molecules, or longer chain molecules, may be formed as a product of the nanostructure-catalyzed reaction. Such products may be used for any of a variety of applications, for example, fuel, fertilizer, etc.

In some embodiments, the reaction efficiency may be improved by appropriately shaping and/or spacing structural elements of the nanostructures disposed on the substrate. For example, structural elements of a nanostructure may be spaced apart from one another along the substrate with an inter-nano structural spacing chosen to improve the efficiency of a reaction. In some embodiments, the efficiency may be improved by spacing the structural elements of the nanostructures apart along the substrate by approximately the distance of the wavelength of the electromagnetic radiation that is used to irradiate the nanostructure during the reaction. As an example, the inter-nano structural spacing may be defined as the distance along the substrate between the center of adjacent structural elements of the nanostructures. In some embodiments, the average inter-nanostructural spacing may be equal to or approximately equal to λ, where λ is a wavelength of electromagnetic radiation for which the nanostructures are designed to catalyze a reaction. In some embodiments, the average inter- nanostructural spacing along the substrate may be between λ/2 and 2λ. If a monochromatic source of electromagnetic radiation is used to catalyze a reaction (e.g., an optically-pumped source, such as a laser), λ is the wavelength of the electromagnetic radiation produced by the monochromatic source. However, as some sources of electromagnetic radiation (e.g., sunlight) are not monochromatic, a characteristic wavelength for such a source may be used as the wavelength λ in setting the inter-nanostructural spacing. For example, for a non- monochromatic source of electromagnetic radiation, the characteristic wavelength may be chosen as the wavelength having the highest spectral irradiance, for example, which for sunlight may occur in the visible portion of the electromagnetic spectrum. However, any suitable characteristic wavelength may be selected, such as the wavelength having the mean spectral irradiance, or another wavelength characteristic of the electromagnetic radiation.

In some embodiments, structural elements of the nanostructures may be arranged in a regular pattern, such as a grid-like pattern, for example. However, nanostructures may include any suitable arrangement, such as a non-regular arrangement of structural elements.

In some embodiments, structural elements of the nanostructures may be shaped in a manner that increases the maximum energy density of the incident electromagnetic radiation. When the maximum energy density of the electromagnetic radiation is increased, the reactions described herein may proceed with higher efficiency. In some embodiments, structural elements of nanostructures having sharper tips (e.g., structural elements having a smaller tip radius) may produce a higher maximum energy density of electromagnetic radiation as compared to structural elements having tips that are less sharp (e.g., structural elements having a larger tip radius).

Fig. 15 depicts illustrative embodiments of structural elements (e.g., of

nanostructures) 612a, 612b, 612c disposed on respective substrates 610a, 610b, 610c, and may be formed of any suitable material, such as cobalt, for example. As shown, structural elements 612b, 612c have respective tip radii that are smaller (sharper) than that of structural element 612a, resulting in a greater concentration of light energy at the tip upon irradiation with sunlight. In addition to height and thickness, the structural elements may exhibit a suitable tip radius. In some embodiments, the average tip radius of the structural elements is less than 50 nm, less than 20 nm, less than 10 nm, less than 5 nm, or less than 1 nm.

Structural element 612c includes a base 614 which may have a generally pyramidal or conical shape which, in some cases, may provide added mechanical support and stability for the structural element 612c. However, base 614 may be formed of any suitable shape.

A nanostructure having structural elements with sharp tips may be created by any of a variety of suitable techniques. In some embodiments, if the nanostructure is produced using a laser, such as a femtosecond laser, an increased amount of output energy from a laser than would otherwise be used may be employed to form a structural element having a sharper tip. For example, the amount of power output from the laser used to form structural elements of the nanostructure may be increased by at least about 300 mW, such as from approximately 500 mW to approximately 1000 mW. In some embodiments, a base structure (e.g., 614) may be fabricated with the structural element through a suitable electroplating method, for example. In some cases, an additional femtosecond laser treatment may be employed to form sub- structural elements of the nanostructure.

As discussed above, the amount of electromagnetic radiation concentrated in proximity to the tip of a sharper structural element (having a smaller tip radius) may be greater than the amount of light concentrated in proximity to a tip of a structural element that is comparatively more dull (having a greater tip radius). As an example, when light irradiated on to a structural element 612a gives rise to a particular light energy density in close proximity to the tip of the structural element, for the same amount of source light irradiated on to structural elements 612b, 612c, the light energy density arising in close proximity to the tip of the structural element may increase by as much as 10 2 , 104 or more. That is, the light energy density at the tip of a structural element of a nanostructure may be greater by over two to four orders of magnitude than the light energy density for a tip that exhibits less of a degree of sharpness. In some embodiments, structural elements having a relatively sharper tip may provide for a irradiance of 99% or higher focused on the respective tips. As shown in Fig. 15, sharper tips produce a higher concentration of electromagnetic radiation at the tips of the structural elements of the nanostructures.

In some embodiments, the electromagnetic radiation irradiated toward the

nanostructures may be focused (e.g., using a lens) or modulated in any suitable manner, prior to impinging on the nanostructures. In some embodiments, characteristics of the

electromagnetic radiation may be adjusted so as to give rise to increased overall reaction efficiency. Such characteristics may include, but are not limited to, frequency, intensity, degree of focus, amplitude, etc. Any suitable source of electromagnetic radiation may be used. For example, irradiated electromagnetic radiation may be from a natural source, such as sunlight, or an artificial source, such an electro-optic source, an optically pumped source (e.g., a laser), or any other suitable source.

In some embodiments, carbon-containing molecules may be captured (e.g., sequestered) from the surrounding environment and used as the carbon-containing source. Capturing carbon-containing molecules (e.g., carbon dioxide, carbon monoxide, methane, natural gas, etc.) from the environment may provide a low-cost source of carbon-containing molecules that is readily available and may have the benefit of reducing the amount of carbon present in the environment.

In some embodiments, the carbon-containing source molecules may be captured and introduced (e.g., dissolved) into the solution used for a reaction. For example, a reactor contemplated for use with nanostructures discussed herein may be suitably arranged in conjunction with a flue gas source so that flue gas (e.g., arising from a

chemical/power/manufacturing plant, or any other suitable source) is passed over the reactant solution and carbon-containing gases are dissolved into solution. In some embodiments, an air contactor or fan may be used to direct the gas (e.g., flue gas, natural gas) toward the reactant solution so as to facilitate dissolving of a suitable amount of gas into the solution. In some embodiments, dry ice (solid carbon dioxide) may be sublimated and bubbled into the reactant solution, giving rise to a solution having carbon dioxide dissolved therein. It can be appreciated that other systems for supplying the reactant solution with one or more appropriate carbon-containing sources may be used.

When carbon dioxide from the surroundings is captured and dissolved into a reactant solution, in some cases, for an aqueous solution, the carbon dioxide may become ionized so as to form carbonate, or carbonic acid, within the aqueous solution. In some embodiments, carbon dioxide may be captured and dissolved into a basic solution such as but not limited to NaOH, resulting in a solution having a number of ions, including Na⁺¹, C0₃ ², HC0₃ ^_1, and others. For example, a solution of NaOH (e.g., 10 wt. NaOH) having a pH of -12 may be exposed to dry ice, resulting in carbon dioxide being dissolved into solution. As a result of the increased presence of carbon dioxide, the pH of the solution may decrease, for example, from -12 to -8.5. Other suitable basic solutions may be employed, for example, KOH, Ba(OH)₂, Ca(OH)₂, LiOH, etc. The solution may be suitably exposed to a nanostructure which is irradiated with electromagnetic radiation (e.g., sunlight) for a period of time. Any suitable period of time may be used (e.g., 8 hours, in one example). Due to irradiation of the nanostructure in the presence of the reactant solution with carbon dioxide dissolved therein, reactions where smaller carbon molecules (e.g., methane, carbon dioxide, carbon monoxide, etc.) may be combined to form larger carbon-containing molecules (e.g., long chain organic molecules, olefins, alkanes, alkenes, paraffin, alcohols, etc.) are catalyzed. For instance, without a sufficient amount of irradiation, the pH of the solution may remain the same (e.g., at -8.5); however, with irradiation sufficient to cause reactions forming longer chain carbon- containing molecules to occur, the pH of the solution may increase appropriately (e.g., from -8.5 to -8.8), due to carbon dioxide effectively being removed from the system. Such removal of carbon dioxide from the system may effectively regenerate the base solution or, in other words, cause the solution to become more apt to capture more surrounding carbon dioxide. In addition to having an increased pH, the regenerated base solution may

subsequently capture additional carbon dioxide, or other carbon-containing source molecules, for example, from flue gas, atmosphere, and/or a geothermal fluid stream. In some cases, due to a carbon-containing source (e.g., carbon dioxide, methane, carbon monoxide) being supplied directly to the reactant solution, the reaction rate may increase by approximately -5%, or more.

In some embodiments, a solution is used to capture carbon-containing material from the surrounding environment (e.g., by dissolving carbon dioxide into the solution). The solution having the carbon-containing material captured therein may be used as a carbon- containing source for a light-initiated reaction with the nano structure. As the light-initiated reaction proceeds, the carbon-containing material previously captured may be removed from solution, for example, by forming a molecule having at least two carbon atoms chained together. Accordingly, the solution may then be adapted to further capture carbon-containing material (e.g., from the surrounding environment). As a result, the solution and the nanostructure may provide for a cyclical system where carbon-containing material is continuously captured from the surrounding environment as light-initiated reactions forming molecules having at least two carbon atoms chained together proceed.

In some embodiments, the base solution may be pressurized from 1 to 10 atm to improve efficiency in the reactor. For example, a carbon dioxide solution may be added to the base solution so as to increase the conversion efficiency of carbon containing molecules dissolved in the base solution liquid to longer chain carbon molecules when irradiated with electromagnetic radiation (e.g., sunlight) exposure to the photo-catalyst. In some

embodiments, the carbon dioxide may be dissolved into the base solution or mixed using a batch, semi-batch, or continuous flow reactor. In some cases, the base solution may be separated from the hydrocarbon product containing one or more carbon chains by employing a membrane, column, or other appropriate method. Accordingly, the pressure range of carbon dioxide and base solution within a reaction chamber can be increased from 1 to 10 atm.

Further, the efficiency of reactions according to the present disclosure may be appropriately increased. For instance, certain reactants may be supplied to the reactor system (e.g., chamber) so as to facilitate reactions to move forward. In some embodiments, a reaction system which includes the nanostructure and the reactant mixture may be

manipulated so as to provide a continual supply of reactants (e.g., a carbon containing source, hydrogen-containing source and/or other source) to the reactant mixture while the reaction proceeds. Products may be removed from the reactor system also resulting in reactions to proceed more readily. For example, suitable reaction systems may be arranged so as to remove extraneous product (e.g., oxygen, long chain carbon molecules) from the system, facilitating the reaction to proceed.

In some embodiments, modifying the pressure and/or temperature within the system may increase reaction efficiency. For instance, increasing the temperature within the reactor system may serve to increase the rate of reaction upon irradiation of the nanostructure.

Increasing the pressure within a reactor system (e.g., above atmospheric pressure, in a range from 1 atm to 3 atm, or 1 atm to 10 atm) may allow the overall reaction efficiency of the system to increase. In some cases, an increase in pressure may produce an increase in reactant concentration (e.g., carbon-containing sources) within the reactant mixture, resulting in nanostructure-catalyzed irradiation reactions to proceed forward more readily.

In some embodiments, the reactor system may incorporate a generally continuous flow configuration. As an example, an open reactor arrangement may be used where carbon- containing gas may be introduced into a reaction solution from underneath the solution (e.g., from dry ice sublimation). This carbon-containing gas may be provided as a supply of carbon-containing source to the reaction. In some embodiments, a continuous flow reactor arrangement is provided with one or more inlets and outlets that provide flow to and from an otherwise enclosed chamber. In some cases, one or more inlets may provide a supply of at least one reactant for reactions catalyzed by nanostructures described herein. In addition, one or more outlets may serve to remove at least one composition from the reactant solution that would otherwise limit reaction efficiency. In some embodiments, reaction rates may increase as much as approximately 15 -20 , using such techniques.

A suitable inlet may provide a continuous supply of a carbon-containing source including small carbon-containing molecules (e.g., carbon dioxide, carbon monoxide, methane, etc.) to the reactor system. Inlets may optionally provide other compositions to the reactor as well, such as water, nitrogen, etc.

Suitable outlets may be used, for example, in conjunction with a suitable product recovery system. In some embodiments, one or more outlets may remove various products that may arise from light-initiated reactions catalyzed by nanostructures in accordance with the present disclosure. Such products formed from the nanostructure catalyzed reactions may include, but are not limited to, long-chain carbon-containing molecules, ringed organic molecules, alkanes, olefins, alkenes, amino acids, oxygen, nitrogen, other by-products, etc. Outlets may be constructed so as to provide a distillation and/or filtration function. In some cases, a reactor system may include a membrane or other filter device in combination with an outlet so as to selectively filter out particular compositions from the reactor facilitating overall reaction efficiency.

Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. It will be apparent that other embodiments and various modifications may be made to the present invention without departing from the scope thereof. The foregoing description of the invention is intended merely to be illustrative and not restrictive thereof. The scope of the present invention is defined by the appended claims and equivalents thereto.

What is claimed is:

Claims

1. An apparatus for producing carbon-containing molecules, the apparatus comprising: a nanostructure including at least one structural element disposed on a substrate and a plurality of sub-structural elements comprising a catalyst disposed on the at least one structural element.

2. The apparatus of claim 1, wherein the at least one structural element has a length that is disposed along a direction perpendicular to a surface of the substrate and a width that is disposed along a direction parallel to the surface of the substrate, the length of the at least one structural element being greater than the width of the at least one structural element.

3. The apparatus of claim 1, wherein the at least one structural element has an aspect ratio of greater than 1.

4. The apparatus of claim 1, wherein an average width of the plurality of sub- structural elements is less than a width of the at least one structural element.

5. The apparatus of claim 1, wherein an average height of the plurality of sub- structural elements is less than a height of the at least one structural element.

6. The apparatus of claim 1, wherein the catalyst of the plurality of sub-structural elements comprises a metal and/or metal oxide.

7. The apparatus of claim 6, wherein the metal and/or metallic oxide of the plurality of sub- structural elements comprises at least one of Au, Al, Ag, Cu, Co, Fe, Ni, Ti and stainless steel, or a combination thereof.

8. The apparatus of claim 1, wherein the plurality of sub-structural elements have an average aspect ratio of greater than 1.

9. The apparatus of claim 1, wherein the plurality of sub-structural elements comprise a plurality of nanoflake structures having a curved shape.

10. The apparatus of claim 1, wherein the plurality of sub-structural elements are substantially evenly distributed along a surface of the at least one structural element.

11. The apparatus of claim 1, wherein an average height of the plurality of sub- structural elements is between about 100 nm and about 1000 nm.

12. The apparatus of claim 1, wherein an average width of the plurality of sub- structural elements is between about 1 nm and about 100 nm.

13. The apparatus of claim 1, wherein each of the plurality of sub- structural elements has an edge that is oriented in a direction that faces away from the at least one structural element.

14. The apparatus of claim 1, wherein an average distance that each of the plurality of sub- structural elements is spaced from one another is between about 100 nm and about 200 nm.

15. The apparatus of claim 1, wherein the at least one structural element comprises a polymeric material.

16. The apparatus of claim 1, wherein the at least one structural element comprises a conductive material.

17. The apparatus of claim 16, wherein the conductive material comprises a conductive layer having a thickness of between about 10 nm and about 100 nm.

18. The apparatus of claim 1, wherein the at least one structural element has a height of between about 1 micron and about 3 microns and a thickness of less than about 500 nm.

19. The apparatus of claim 1, wherein the at least one structural element includes a metal or metal oxide comprising at least one of Au, Al, Ag, Cu, Co, Fe, Ni, Ti, stainless steel, or a combination thereof.

20. The apparatus of claim 1, wherein the nanostructure is adapted to catalyze a light- initiated reaction between a hydrogen-containing and a carbon-containing source that results in a molecule having at least two carbon atoms chained together.

21. A method of manufacturing an apparatus for producing a carbon-containing molecule, the method comprising:

forming a nanostructure including:

forming at least one structural element on a substrate; and

forming a plurality of sub-structural elements comprising a catalyst on the at least one structural element.

22. The method of claim 21, wherein forming the at least one structural element comprises forming the at least one structural element to have a length that is disposed along a direction perpendicular to a surface of the substrate and a width that is disposed along a direction parallel to the surface of the substrate, the length of the at least one structural element being greater than the width of the at least one structural element.

23. The method of claim 21, wherein forming the at least one structural element comprises forming at least one structural precursor.

24. The method of claim 23, further comprising providing an overmold for the at least one structural precursor.

25. The method of claim 24, further comprising removing the at least one structural precursor from the overmold so as to provide the overmold with at least one recessed structure.

26. The method of claim 25, further comprising filling the at least one recessed structure with a curable material.

27. The method of claim 26, further comprising curing the curable material to form the at least one structural element.

28. The method of claim 21, further comprising forming a conductive layer on the at least one structural element.

29. The method of claim 21, wherein forming a plurality of sub- structural elements comprises forming a plurality of sub- structural elements comprising metal on the at least one structural element.

30. The method of claim 21, wherein forming a plurality of sub- structural elements comprising metal on the at least one structural element comprises electroplating at least one of Au, Al, Ag, Cu, Co, Fe, Ni, Ti and stainless steel, or a combination thereof on the at least one structural element.

31. The method of claim 21, wherein forming a plurality of sub- structural elements comprising metal on the at least one structural element comprises electroplating the at least one structural element in a metal solution having a concentration of between about 1% mol and about 50% mol.

32. The method of claim 31, wherein electroplating the at least one structural element in a metal solution comprises electroplating for a time period of between about 1 minute and about 10 minutes.

33. The method of claim 31, wherein electroplating the at least one structural element in a metal solution comprises electroplating at a power of between about 0.1 amperes and about 2 amperes.

34. The method of claim 31, wherein electroplating the at least one structural element in a metal solution comprises electroplating in a C0SO₄ solution.

35. The method of claim 21, wherein forming a plurality of sub- structural elements comprises forming a plurality of nanoflake structures having a curved shape on the at least one structural element.

36. The method of claim 21, wherein forming a plurality of sub- structural elements comprises forming an even distribution of sub- structural elements along a surface of the at least one structural element.

37. The method of claim 21, wherein forming a plurality of sub- structural elements comprises forming a sharp edge that is oriented in a direction that faces away from the at least one structural element.

38. A nano structured apparatus comprising:

at least one structural element; and

a plurality of nanoflake structures substantially evenly distributed along a surface of the at least one structural element, wherein each of the plurality of nanoflake structures has a curved shape and an edge that is oriented in a direction that faces away from the at least one structural element.

39. An apparatus for producing carbon-containing molecules, the apparatus comprising: a nano structure adapted to catalyze an electromagnetic radiation initiated reaction with at least one carbon-containing source that results in a molecule having at least two carbon atoms chained together.

40. The apparatus of claim 39, wherein the nanostructure includes at least one structural element having an end with a tip radius of less than 50 nm.

41. The apparatus of claim 39, wherein the nanostructure includes at least one structural element having a pyramidal or conical base.

42. A method of forming a carbon-containing molecule, the method comprising:

contacting a nanostructure with a carbon-containing source; and

exposing the nanostructure to electromagnetic radiation to initiate a reaction with the carbon-containing source to form a molecule having at least two carbon atoms chained together.

43. The method of claim 42, further comprising capturing a carbon-containing material into a solution to form the carbon-containing source.

44. The method of claim 43, wherein capturing a carbon-containing material into the solution comprises passing the carbon-containing material over or through the solution causing the carbon-containing material to at least partially dissolve into the solution.

45. The method of claim 43, wherein after exposing the nanostructure to light to initiate a reaction with the carbon-containing source, the carbon-containing material is removed from the solution by forming the molecule having at least two carbon atoms chained together.

46. The method of claim 45, further comprising capturing an additional carbon-containing material into the solution.

47. A system for producing carbon-containing molecules, the system comprising:

a nanostructure adapted to catalyze a light-initiated reaction with at least one carbon- containing source that results in a molecule having at least two carbon atoms chained together; and

a solution adapted to capture a carbon-containing material to comprise the at least one carbon-containing source.

48. The system of claim 47, further comprising an inlet for supplying carbon-containing source to the solution.

49. The system of claim 47, further comprising an outlet for removing at least a portion of the solution from the system.

50. The system of claim 47, wherein the solution is adapted to capture the at least one carbon-containing source from a surrounding environment.