Surface‐enhanced Raman scattering of pyridine in silver colloids excited in the near‐infrared region

Abstract

A scanning Raman spectrometer and an Nd:YAG laser operating at 1.06 p n were used to observe the surfaceenhanced Raman scattering (SERS) of pyridine in yellow silver colloids. Enhancement factors for the triangle ring breathing vibration mode at 1006 cm-' and for the totally symmetric breathing mode at 1036 cm-' are about 16.5 and 21 times larger, respectively, than those found for excitation at 514.5 nm. The large enhancement factors for excitation in the near-infrared region suggest that further refinement of the theories currently proposed to explain the SERS effect is necessary.

Bifunctional Fe3O4/Ag nanoparticles obtained by two-step laser ablation in pure water

“…The SERS activity by excitation at 785 nm may be due to the presence of coadsorbed chloride ions that activate both electromagnetic and chemical enhancement even in the NIR region [40][41][42]. This activation could be related to the formation of large metal aggregates in the deposited dry film, as shown in Fig.…”

Acid with visible and near-infrared excitations

“…On the other hand, AgÈCl clusters are referred to as SERS active sites for molecules adsorbed via ÈOH, which includes a lone electron pair of the oxygen atom, analogous to that of the nitrogen atom in pyridine. 1,13,21 This implies that the unusual SERS e †ect in the NIR region is not only related to the excitation wavelength, but also depends on the adsorption behavior of the remaining adsorbed PHBA molecules.…”

“…AgÈCl clusters are usually considered to be the SERS active sites on which the charge-transfer (CT) transition between the silver surface and adsorbed molecules occurred. 13,14,18,21 has shown that for some molecules, such as salicylic acid and benzoic acid, their SERS signals excited in the visible region decrease rapidly and some are even entirely quenched upon adding a very small amount of chloro ions. This indicates that AgÈCl clusters, usually known as SERS active sites, do not show SERS activity for the above-mentioned molecules when excited in the visible region.…”

Adsorption of pyridine, ?-picoline and isonicotinonitrile on Ag colloidal particles studied by surface-enhanced Raman scattering spectroscopy

“…Their theory gave an enhancement of the Raman band of 10 orders of magnitude for pyridine adsorbed on Ag particles. Liang et al 5 measured the SERS spectrum of pyridine in Ag colloid with excitation at 1.06 µm and observed that the spectrum showed a well resolved fine structure compared with the spectra observed by previous workers. Muniz-Miranda 6 observed a new band at 1025 cm 1 in the SERS spectrum of pyridine in aged Ag colloid.…”