Surface-enhanced spectroscopy-active sandwich nanoparticles
Surface-enhanced Raman spectroscopy (SERS) uses nanoscale metal particles (SERS-active particles) or surface roughness to enhance the Raman signal of Raman-active analytes contacting the surface. SERS sandwich particles contain SERS-active particles sandwiching a Raman-active substance and serve as optical tags. Preferably, the particles are rod-shaped, with each layer (SERS-active and Raman-active) formed as a distinct stripe of the particle. These freestanding particles can be derivatized with surface ligands capable of associating with analytes of interest in, for example, a biological sample. The acquired Raman spectrum of the particle encodes the identity of the ligand. Because of the simplicity and intensity of Raman spectra, highly multiplexed assays are capable using SERS particles with different Raman-active species.
1 . A collection of distinguishable particles, each particle comprising:
at least two surface-enhanced spectroscopy-active outer regions;
a spectroscopy-active analyte positioned between said outer regions; and
an encapsulant at least partially surrounding said outer regions and said analyte,
wherein the particle has a maximum length of at most 300 nm, and wherein said particles have distinguishable SES spectra.
2 . The collection of claim 1 , wherein a plurality of said particles comprises a particle comprising an outer region comprising a metal selected from the group consisting of Au, Ag, Cu, Na, Al, Li and Cr.
3 . The collection of claim 2 , wherein a plurality of said particles comprises a particle comprising an outer region comprising Au.
4 . The collection of claim 2 , wherein a plurality of said particles comprises a particle comprising an outer region comprising Ag.
5 . The collection of claim 1 , wherein a plurality of said particles comprises a particle comprising an outer region having a diameter less than about 200 nm.
6 . The collection of claim 5 , wherein a plurality of said particles comprises a particle comprising an outer region having a diameter less than about 150 nm.
7 . The collection of claim 6 , wherein a plurality of said particles comprises a particle comprising an outer region having a diameter less than about 100 nm.
8 . The collection of claim 1 , wherein a plurality of said particles comprises an encapsulant having a thickness less than about 1 micron.
9 . The collection of claim 8 , wherein a plurality of said particles comprises an encapsulant having a thickness between about 0.5 nm and about 100 nm.
10 . The collection of claim 1 , wherein a plurality of said particles comprises an outer region comprising an alloy of metals selected from the group consisting of Au, Ag, Cu, Na, Al, Li and Cr.
11 . The collection of claim 1 , wherein a plurality of said particles comprises a submonolayer coating of said spectroscopy-active analyte formed on said outer region.
12 . The collection of claim 1 , wherein a plurality of said particles comprises a monolayer coating of said spectroscopy-active analyte formed on said outer region.
13 . The collection of claim 1 , wherein a plurality of said particles comprises a multilayer coating of said spectroscopy-active analyte formed on said outer region.
14 . The collection of claim 1 , wherein a plurality of said particles comprises an encapsulant comprising a material selected from the group consisting of glass, polymers, metals, metal oxides, and metal sulfides.
15 . The collection of claim 1 , wherein a plurality of said particles comprise an encapsulant comprising a plurality of materials selected from the group consisting of glass, polymers, metals, metal oxides and metal sulfides.
16 . The collection of claim 1 , wherein a plurality of said particles comprises an encapsulant comprising glass oxide (SiO x ).
17 . The collection of claim 1 , wherein a plurality of said particles comprises an encapsulant comprising TiO x .
18 . The collection of claim 1 , wherein said distinguishable spectra are obtained by a method selected from the group consisting of SERS, SERRS, SEHRRS and SEIRA.
19 . The collection of claim 1 , wherein a plurality of said particles comprises an spectroscopy-active analyte that is an aromatic analyte.
20 . The collection of claim 1 , wherein said particles encode information that is recorded or stored.
21 . A dispersion comprising a solvent and a plurality of particles, each of said particles comprising: at least two surface-enhanced spectroscopy-active outer regions;
a spectroscopy-active analyte positioned between said outer regions; and
an encapsulant at least partially surrounding said outer regions and said analyte,
wherein the particle has a maximum length of at most 300 nm, and wherein said particles have distinguishable SES spectra