Abstract
The present invention relates to a device for heterogeneous plasmonic photocatalysis. The device comprises a crystalline or quasi-crystalline superstructure of plasmonic nanoparticles attached to a substrate, and a plurality of catalytically active nanoparticles embedded into the superstructure of plasmonic nanoparticles. Further, the invention relates to a method of manufacturing the device for heterogeneous plasmonic photocatalysis.
Claims
1. A device for heterogeneous plasmonic photocatalysis, comprising a substrate; a superstructure of plasmonic nanoparticles attached to the substrate; and a plurality of catalytically active nanoparticles embedded into the superstructure of plasmonic nanoparticles.
2. The device according to claim 1, wherein a diameter of the plasmonic nanoparticles and a diameter of the catalytically active nanoparticles is in the range of 1 to 100 nm.
3. The device according to claim 2, wherein the diameter of the plasmonic nanoparticles is larger than 20 nm and/or wherein the diameter of the catalytically active nanoparticles is smaller than 10 nm.
4. The device according to claim 1, wherein the superstructure of plasmonic nanoparticles is a crystalline or a quasi-crystalline superstructure.
5. The device according to claim 1, wherein the superstructure of plasmonic nanoparticles has a two-dimensional hexagonal order, or a face-centered cubic or hexagonal close-packed three-dimensional order.
6. The device according to claim 5, wherein the superstructure of plasmonic nanoparticles consists of a monolayer or of a multilayer of plasmonic nanoparticles.
7. The device according to claim 1, wherein the plurality of catalytically active nanoparticles is intercalated in interspaces of the superstructure of plasmonic nanoparticles in between the plasmonic nanoparticles.
8. The device according to claim 7, wherein each of the plurality of catalytically active nanoparticles is positioned essentially in the center between three adjacent plasmonic nanoparticles.
9. The device according to claim 1, wherein the plurality of catalytically active nanoparticles is attached to a surface of the plasmonic nanoparticles, thereby generating bimetallic nanoparticles comprising a plasmonic metal core and a catalytically active metal coating.
10. The device according to claim 1, further comprising a porous layer of silica coated onto the superstructure of plasmonic nanoparticles.
11. The device according to claim 1, wherein the substrate is made of glass or silicon, or is a conductive substrate like indium tin oxide coated glass.
12. The device according to claim 1, wherein the plasmonic nanoparticles are made of gold, silver, copper, or aluminum, and/or wherein the catalytically active nanoparticles are made of a catalytically active metal like platinum, palladium, ruthenium, or rhodium.
13. The device according to claim 1, wherein the device is configured for photocatalytic hydrogen evolution.
14. A method of manufacturing a device for heterogeneous plasmonic photocatalysis comprising a substrate, a superstructure of plasmonic nanoparticles attached to the substrate, and a plurality of catalytically active nanoparticles embedded into the superstructure of plasmonic nanoparticles, the method comprising the steps of: providing a plurality of nanoparticles, wherein the plurality of nanoparticles comprises a plurality of plasmonic nanoparticles and a plurality of catalytically active nanoparticles, or wherein the plurality of nanoparticles comprises a plurality of bimetallic nanoparticles comprising a plasmonic metal core and a catalytically active metal coating; functionalizing the plurality of nanoparticles with polystyrene-based ligands and providing the nanoparticles with the polystyrene-based ligands in an organic solvent; applying the nanoparticles with the polystyrene-based ligands in the organic solvent onto a polar liquid subphase; causing self-assembly of the nanoparticles to a film of a crystalline or quasi-crystalline superstructure of plasmonic nanoparticles by drying the organic solvent; and transferring the film of the superstructure of plasmonic nanoparticles from the polar liquid subphase to a substrate.
15. The method according to claim 14, further comprising the step of coating the film of the superstructure of plasmonic nanoparticles with a porous layer of silica.
16. The method according to claim 14, wherein a diameter of the plasmonic nanoparticles and a diameter of the catalytically active nanoparticles is in the range of 1 to 100 nm.
17. The method according to claim 14, wherein the superstructure of plasmonic nanoparticles is a crystalline or a quasi-crystalline superstructure.
18. The method according to claim 14, wherein the superstructure of plasmonic nanoparticles has a two-dimensional hexagonal order, or a face-centered cubic or hexagonal close-packed three-dimensional order.
19. The method according to claim 18, wherein the superstructure of plasmonic nanoparticles consists of a monolayer or of a multilayer of plasmonic nanoparticles.
20. The method according to claim 14, wherein the plurality of catalytically active nanoparticles is intercalated in interspaces of the superstructure of plasmonic nanoparticles in between the plasmonic nanoparticles.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 shows a schematic setup of a device for heterogeneous plasmonic photocatalysis according to an embodiment of the invention.
[0045] FIGS. 2A and 2B show transmission electron microscopy photographs of a device for heterogeneous plasmonic photocatalysis in two different magnifications according to another embodiment of the invention.
[0046] FIG. 3 shows a transmission electron microscopy photograph of a device for heterogeneous plasmonic photocatalysis with a bilayer according to another embodiment of the invention.
[0047] FIGS. 4, 5, and 6 show transmission electron microscopy photographs of a device for heterogeneous plasmonic photocatalysis with tuned geometry according to another embodiment of the invention.
[0048] FIG. 7 shows a transmission electron microscopy photograph of a device for heterogeneous plasmonic photocatalysis with bimetallic nanoparticles according to another embodiment of the invention.
[0049] FIG. 8 shows photocatalytic performances of both an Au supercrystal and an Au-Pt supercrystal on the formic acid decomposition.
[0050] FIG. 9 shows a block diagram of a method of manufacturing a device for heterogeneous plasmonic photocatalysis according to an embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0051] FIG. 1 shows a schematic setup of a device 100 for heterogeneous plasmonic photocatalysis according to an embodiment of the invention. A plurality of plasmonic nanoparticles 130 is arranged to a superstructure 120. This superstructure 120 is attached to a substrate 110. In the interspaces in between the plasmonic nanoparticles, a plurality of catalytically active nanoparticles 140 is embedded.
[0052] FIGS. 2A and 2B show transmission electron microscopy photographs of a device 100 for heterogeneous plasmonic photocatalysis in two different magnifications according to another embodiment of the invention. This thin film of an exemplary nanoparticle superstructure comprises gold nanoparticles as plasmonic nanoparticles 130 which are about 39 nm in diameter, and intercalated catalytic active platinum nanoparticles 140 with a diameter of about 3 nm. The interparticle gaps between the plasmonic gold nanoparticles are about 5 nm. Both, FIG. 2A and FIG. 2B, show a monolayer of plasmonic nanoparticles with a 2-D hexagonal quasicrystalline order. The scale bar is 100 nm for FIG. 2A and 500 nm for FIG. 2B.
[0053] FIG. 3 shows a transmission electron microscopy photograph of a device 100 for heterogeneous plasmonic photocatalysis with a bilayer of the superstructure 120 of plasmonic nanoparticles 130 according to another embodiment of the invention. The particle size and interparticle gaps correspond to the superstructure shown in FIGS. 2A and 2B. The thin films exhibit a defined layered structure with thicknesses ranging from mono- to multilayers.
[0054] FIGS. 4, 5, and 6 show transmission electron microscopy photographs of a device 100 for heterogeneous plasmonic photocatalysis with tuned geometry according to another embodiment of the invention. With the variation of the size of the plasmonic nanoparticles and the interparticle spacing, the tuning of the geometry can be demonstrated. Geometry, interparticle spacing and loading with platinum nanoparticles can be tuned via the molecular weight of the polystyrene coating ligand, the diameter of the gold nanoparticles, and the ratio of gold nanoparticles to platinum nanoparticles. In FIG. 4, the diameter of the gold nanoparticles is 39 nm, and the gaps between the gold nanoparticles have a width of about 5.5 nm. In FIG. 5, the diameter of the gold nanoparticles is 35 nm, and the gaps between the gold nanoparticles have a width of about 2.5 nm. And in FIG. 6, the diameter of the gold nanoparticles is 22 nm, and the gaps between the gold nanoparticles have a width of about 3.5 nm. In all samples, the diameter of the platinum nanoparticles is about 3 nm. It is noted that the platinum nanoparticles as catalytically active nanoparticles in FIGS. 5 and 6 are located preferably in the center of three adjacent nanoparticles, whereas FIG. 4 shows an essentially homogeneous distribution of the platinum nanoparticles along the interparticle gap.
[0055] FIG. 7 shows a transmission electron microscopy photograph of a device 100 for heterogeneous plasmonic photocatalysis with bimetallic nanoparticles according to another embodiment of the invention. The bimetallic nanoparticles comprise plasmonic nanoparticles 130 as plasmonic core, whereas catalytically active nanoparticles 140 are attached to the surface of the plasmonic nanoparticles 130 as coating. Thus, bimetallic nanoparticles are formed, which are arranged in a superstructure 120. The superstructure is a 2-D hexagonal supercrystal of bimetallic nanoparticles with a diameter of the gold nanoparticles of about 50 nm, which are coated with a porous shell of palladium with a shell thickness of about 6 nm. The scale bars are 1 m for the large picture and 100 nm for the inset.
[0056] FIG. 8 shows photocatalytic performances of both an Au supercrystal and an Au-Pt supercrystal on the formic acid decomposition, which is a reaction producing hydrogen. Photocatalytic tests for such structures have been performed with a supercrystal comprising gold nanoparticles, which was followed by the successful fabrication of the hybrid structure through the inclusion of Pt nanoparticles to the system and thus forming an Au-Pt supercrystal. The performance of the gold-platinum supercrystal has been compared with the pristine supercrystal. The preliminary results obtained in those tests are shown in FIG. 8. It can be already realized that the inclusion of the Pt nanoparticles is beneficial for the overall activity, which presents a three-fold increase under simulated sunlight conditions of 150 mW cm.sup.2, compared to the Au supercrystal with or without illumination. These results stress how beneficial it is to mix materials of different natures to exploit the individual properties of each material to accomplish a superior photocatalyst. Therefore, these unprecedented systems set a benchmark in the design of future heterostructures with well-organized patterns.
[0057] FIG. 9 shows a block diagram of a method of manufacturing a device 100 for heterogeneous plasmonic photocatalysis according to an embodiment of the invention. The method comprises the step S210 of providing a plurality of nanoparticles, wherein the plurality of nanoparticles comprises a plurality of plasmonic nanoparticles 130 and a plurality of catalytically active nanoparticles 140, or wherein the plurality of nanoparticles comprises a plurality of bimetallic nanoparticles comprising a plasmonic metal core and a catalytically active metal coating. However, the bimetallic nanoparticle can be regarded as plasmonic nanoparticle with a plasmonic core and catalytically active nanoparticles coated to the surface of the plasmonic nanoparticle. The method comprises further the step S220 of functionalizing the plurality of nanoparticles with polystyrene-based ligands and providing the nanoparticles with the polystyrene-based ligands in an organic solvent, and the step S230 of applying the nanoparticles with the polystyrene-based ligands in the organic solvent onto a polar liquid subphase. Further, the method comprises the step S240 of causing self-assembly of the nanoparticles to a film of a crystalline or quasi-crystalline superstructure 120 of plasmonic nanoparticles 130 by drying the organic solvent, and the step S250 of transferring the film of the superstructure 120 of plasmonic nanoparticles 130 from the polar liquid subphase to a substrate 110. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.
[0058] In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
LIST OF REFERENCE SIGNS
[0059] 100 device for heterogeneous plasmonic photocatalysis [0060] 110 substrate [0061] 120 superstructure of plasmonic nanoparticles [0062] 121 interspace of the superstructure [0063] 130 plasmonic nanoparticle [0064] 140 catalytically active nanoparticles
