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Herein, surface-enhanced Raman spectroscopy (SERS) combined with principal component analysis (PCA) has been successfully applied in the evaluation of cigarette flavoring quality using monolayer films of Au nanoparticles as substrates. With such a method, even a slight difference in the formula of the essence that cannot be directly identified by SERS can be distinguished.

A silver cluster having the composition Ag(9)(H(2)MSA)(7) (H(2)MSA = mercaptosuccinic acid) was synthesized in macroscopic quantities using a solid-state route. The clusters were purified by PAGE and characterized by UV-vis, FTIR, luminescence, and NMR spectroscopy, TEM, XPS, XRD, TG, SEM/EDAX, elemental analysis, and ESI MS. The solid-state route provides nearly pure Ag(9) clusters, and nanoparticle contamination was insignificant for routine studies. Formation of various clusters was observed by modifying the conditions. The effect of ligands on the synthesis was checked. The cluster decomposed slowly in water, and the decomposition followed first-order kinetics. However, it could be stabilized in solvent mixtures and in the solid state. Such materials may be important in cluster research because of their characteristic absorption profiles, which are similar to those of Au(25) and Au(38). The cluster showed luminescence with a quantum yield of 8 × 10(-3) at 5 °C.