We have investigated surface enhanced Raman scattering (SERS) stemming from pseudoisocyanine (PIC) molecules adsorbed on Ag nanoparticles by using optical trapping techniques in aqueous solution. By focusing a near-infrared (NIR) laser beam with linear polarization in addition to a visible excitation laser beam, the PIC concentration necessary to detect SERS is dramatically reduced to 10−14 M, whereas no effect is confirmed with circular polarization. This finding suggests that optical trapping by a linearly polarized laser beam induces the formation of Ag nanoaggregates that incorporate PIC molecules at a specific nanosite where the localized electromagnetic (EM) field is strongly enhanced. The optical force exerted on these Ag nanoparticles and PIC molecules is discussed on the basis of experimental results for the laser-polarization dependence of the SERS and Rayleigh scattering spectra.
Tuesday, July 28, 2009
Surface Enhanced Raman Scattering from Pseudoisocyanine on Ag Nanoaggregates Produced by Optical Trapping with a Linearly Polarized Laser Beam
Yoshito Tanaka and Hiroyuki Yoshikawa
We have investigated surface enhanced Raman scattering (SERS) stemming from pseudoisocyanine (PIC) molecules adsorbed on Ag nanoparticles by using optical trapping techniques in aqueous solution. By focusing a near-infrared (NIR) laser beam with linear polarization in addition to a visible excitation laser beam, the PIC concentration necessary to detect SERS is dramatically reduced to 10−14 M, whereas no effect is confirmed with circular polarization. This finding suggests that optical trapping by a linearly polarized laser beam induces the formation of Ag nanoaggregates that incorporate PIC molecules at a specific nanosite where the localized electromagnetic (EM) field is strongly enhanced. The optical force exerted on these Ag nanoparticles and PIC molecules is discussed on the basis of experimental results for the laser-polarization dependence of the SERS and Rayleigh scattering spectra.
We have investigated surface enhanced Raman scattering (SERS) stemming from pseudoisocyanine (PIC) molecules adsorbed on Ag nanoparticles by using optical trapping techniques in aqueous solution. By focusing a near-infrared (NIR) laser beam with linear polarization in addition to a visible excitation laser beam, the PIC concentration necessary to detect SERS is dramatically reduced to 10−14 M, whereas no effect is confirmed with circular polarization. This finding suggests that optical trapping by a linearly polarized laser beam induces the formation of Ag nanoaggregates that incorporate PIC molecules at a specific nanosite where the localized electromagnetic (EM) field is strongly enhanced. The optical force exerted on these Ag nanoparticles and PIC molecules is discussed on the basis of experimental results for the laser-polarization dependence of the SERS and Rayleigh scattering spectra.
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