Temperature dependent surface enhanced Raman spectroscopy of piperidine in AgBr sol

Abstract

The temperature dependent surface enhanced Raman (SER) spectra of piperidine in AgBr sols are presented with emphasis on the study of the intensity variation as the temperature increases. Most of the SER intensities decrease as the temperature increases. This is interpreted as due to the increase of the adsorption distance from the sol particle surface. It is also inferred from the various slopes of the decrease in intensity of various modes that there is variation of the SER effect in the dimension of a single bond, i.e. in 1.5 Å. Moreover, from the temperature dependent SER spectra, it is concluded that due to thermal agitation, both axial and equatorial piperidine molecules are adsorbed on the sol particle surface as the temperature increases. The energy difference between these two forms are calculated to be around 20 kcal/mol which is believed to be larger than that in solution due to the adsorption effect. Besides, two peaks at 1390 and 1231 cm −1 show an anomalous positive thermal effect which could be due to the very complicated SERS mechanism. Finally, it is discussed that the temperature dependent SERS study possesses potentiality in revealing the chemical structure near the sol particle and noble metal electrode surfaces.