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The interaction of crystal violet (CV) with halide, halate ions, and pyridine and the interaction of CV with colloidal silver surface have been studied by surface-enhanced Raman spectroscopy (SERS) with near-infrared (NIR) excitation. Cl -, Br -, I -, and BrO 3 - ions as well as pyridine give rise to a large enhancement of the Raman modes of CV, while no Raman bands of CV could be observed in the presence of ClO 3 - and IO 3 - ions. The adsorbability of the complexes CV/BrO 3 - and CV/pyridine is higher than that of ClO 3 - and IO 3 - ions, while the latter is higher than that of the complexes CV/ClO 3 - and CV/IO 3 - . CV interacts with the silver surface quite possibly through the lone pair electrons on the N atoms. Halide and halate ions account not only for part of the surface enhancement from the surface plasmon excitation resonance but also for the chemical enhancement in the NIR-SERS. The chemical enhancement factors caused by Cl -, Br -, I -, and BrO 3 - ions are estimated to be about 49, 77, 15, and 36, respectively.
Liang et al. (Wed,) studied this question.