Instrument-based detection methods for adulteration in spice and spice products – A review <s> Surface Enhanced Raman Spectroscopy Principle <s> The nature of "hot spots" in surface-enhanced Raman scattering (SERS) and the novel fabrication of Ag thin films for efficient SERS measurements are the main focus of this review. By using 4-aminobenzenthiol or 1,4-phenylenediisocyanide molecules we can characterize the nanogap formed by a metal nanoparticle and a flat metal substrate, or the gap between two spherical metal nanoparticles. These nanogaps are indeed SERS-active sites and the apparent size of "hot spots" is found to be very limited. To use SERS for routine chemical identifications, the substrates should be stable, reproducibly prepared, inexpensive, and easy to make. We introduce a method for the facile fabrication of Ag thin films, simply by soaking glass substrates in ethanolic solutions of AgNO(3) and butylamine, and their application as efficient SERS substrates. Ag-coated glass capillary and Ag deposited magnetic nanoparticles can be used for the microanalysis of bio- and hazardous chemicals. <s> BIB001 </s> Instrument-based detection methods for adulteration in spice and spice products – A review <s> Surface Enhanced Raman Spectroscopy Principle <s> p-Aminobenzenethiol (ABT) is a popular molecule for surface-enhanced Raman scattering experiments (SERS), providing large signal enhancements on a range of metal surfaces. However, SERS intensities vary very much according to experimental conditions, and the interplay between ABT protonation, polymer state, and electronic structure/Raman cross section is still not completely clear. To understand main factors affecting Raman intensities, density functional theory (DFT) and matrix polarization theory (MPT) models were used to generate the spectra and compare to the experiment. The simulations showed that ABT protonation as well as its binding to the metal surface shift the absorption threshold, which invokes resonance or preresonance conditions favorable to the signal enhancement. The MPT approximation enabled modeling of the effect of the metal bulk and orientation of the dye on the metal surface on the enhancement and relative band intensities. The simulations can be done relatively easily and reveal chem... <s> BIB002
Surface enhanced Raman spectroscopy (SERS) works on a surface phenomenon that enhances the Raman scattering intensity by molecules in the vicinity of nano-structured metal surfaces (such as Au, Ag and Cu) when excited by electromagnetic radiation BIB002 . The enhancement of Raman scattering is due to surface plasmon resonance, photon driven electron transfer, surface chemistry of nanoparticles being employed, and interaction between radiation and the material (Ding et al. 2014) . The enhancement factor can be as high as 10 14 , facilitating observation to single molecule level BIB001 .