SURFACE-ENHANCED RAMAN SPECTROSCOPY SUBSTRATE FOR ARSENIC SENSING IN GROUNDWATER

• US 20090225310A1
• Filed: 02/17/2009
• Published: 09/10/2009
• Est. Priority Date: 07/28/2003
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Arnold, John, Tao, Andrea R., Sinsermsuksakul, Prasert, Mulvihill, Martin, Yang, Peidong
• Granted Patent: US 9,057,705 B2
• Time in Patent Office: Days
• US Class Current: 356/301
• CPC Class Codes: G01N 21/658 enhancement Raman, e.g. surface plasmons
• CPC Class Codes: H01L 21/0245 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 29/0676 oriented perpendicular or at an angle to a substrate
• CPC Class Codes: H01L 29/518 the insulating material containing nitrogen, e.g. nitride, oxynitride, nitrogen-doped material
• CPC Class Codes: H01L 29/775 with one dimensional charge carrier gas channel, e.g. quantum wire FET

Abstract

A surface-enhanced Raman spectroscopy (SERS) substrate formed from a plurality of monolayers of polyhedral silver nanocrystals, wherein at least one of the monolayers has polyvinypyrrolidone (PVP) on its surface, and thereby configured for sensing arsenic is described. Highly active SERS substrates are formed by assembling high density monolayers of differently shaped silver nanocrystals onto a solid support. SERS detection is performed directly on this substrate by placing a droplet of the analyte solution onto the nanocrystal monolayer. Adsorbed polymer, polyvinypyrrolidone (PVP), on the surface of the nanoparticles facilitates the binding of both arsenate and arsenite near the silver surface, allowing for highly accurate and sensitive detection capabilities.

Claims

1. A sensor, comprising:

a substrate;

the substrate comprising at least one high-density monolayer of polyhedral silver nanocrystals;

wherein each of the nanocrystals comprise a layer of polyvinypyrrolidone (PVP) on its surface.

2. A sensor as recited in claim 1, wherein the nanocrystals comprise octahedra.

3. A sensor as recited in claim 1, wherein the nanocrystals have a shape selected from the group consisting of truncated cubes, cuboctahedra, truncated octahedral, and octahedra.

4. A sensor as recited in claim 1, wherein the substrate comprises a plurality of close-packed monolayers of polyhedral silver nanocrystals.

5. A sensor as recited in claim 1, wherein said nanocrystals are shape-controlled using Langmuir-Blodgett compression.

6. A sensor as recited in claim 1, wherein said PVP is grafted onto the silver surface by polyhedral nanocrystal synthesis.

7. A sensor as recited in claim 1, wherein the substrate comprises a surface-enhanced Raman spectroscopy (SERS) substrate.

8. A sensor as recited in claim 6:

wherein prior to synthesis, the nanocrystals of the nanocrystal monolayer comprise an exposed silver surface;

wherein an analyte solution of polyvinypyrrolidone (PVP) is deposited on the exposed silver surface of the nanocrystal monolayer; and

wherein said analyte solution facilitates the binding of both arsenate and arsenite near the exposed silver surface.

9. A sensor as recited in claim 6, wherein incident electromagnetic radiation is localized on said silver surface.

10. An apparatus for sensing arsenic, comprising:

a surface-enhanced Raman spectroscopy substrate;

the substrate comprising at least one high density monolayers of differently shaped polyhedral silver nanocrystals;

wherein each of the nanocrystals comprise a layer of polyvinypyrrolidone (PVP) on its surface.

11. An apparatus as recited in claim 10, wherein the nanocrystals comprise octahedra.

12. An apparatus as recited in claim 10, wherein the nanocrystals have a shape selected from the group consisting of truncated cubes, cuboctahedra, truncated octahedral, and octahedra.

13. An apparatus as recited in claim 10, wherein the substrate comprises a plurality of close-packed monolayers of polyhedral silver nanocrystals.

14. An apparatus as recited in claim 10, wherein said nanocrystals are shape-controlled using Langmuir-Blodgett compression.

15. An apparatus as recited in claim 10, wherein said PVP is grafted onto the silver surface by polyhedral nanocrystal synthesis.

16. An apparatus as recited in claim 15:

wherein prior to synthesis, the nanocrystals of the nanocrystal monolayer comprise an exposed silver surface;

wherein an analyte solution of polyvinypyrrolidone (PVP) is deposited on the exposed silver surface of the nanocrystal monolayer; and

wherein said analyte solution facilitates the binding of both arsenate and arsenite near the exposed silver surface.

17. An apparatus as recited in claim 16, wherein incident electromagnetic radiation is localized on said silver surface.

18. A sensor for sensing arsenic prepared by a process comprising the steps of:

providing a substrate;

forming at least one layer of polyhedral silver nanocrystals on the substrate;

at least one said layer comprising a nanocrystal monolayer having an exposed silver surface; and

exposing the silver surface of the nanocrystal layer to an analyte solution of polyvinypyrrolidone (PVP);

wherein said analyte solution facilitates the binding of both arsenate and arsenite near the exposed silver surface.

19. The sensor as recited in claim 18, wherein forming at least one layer comprises:

preparing colloidal solutions of polyhedral shapes;

carrying out Langmuir-Blodgett assembly to form nanocrystal monolayers;

transferring the nanocrystal monolayers to silicon supports;

exposing the nanocrystal layer to analyte molecules by incubation and subsequent Raman detection in solution.

20. The sensor as recited in claim 18, wherein the nanocrystals comprise octahedra.

21. A sensor as recited in claim 18, wherein the nanocrystals have a shape selected from the group consisting of truncated cubes, cuboctahedra, truncated octahedral, and octahedra.

22. A sensor as recited in claim 18, wherein the at least one layer comprises a plurality of high-density, close-packed monolayers of polyhedral silver nanocrystals.