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摘要
The interface between the silver nanoparticles (AgNPs) obtained by the classical wet method and the red or white wines has been explored using the surface-enhanced Raman scattering technique (SERS), aiming to assess the technique capability for providing direct spectral biomarkers of wines. Regardless of the wine color, their normal Raman scattering excited with visible laser lines showed strong fluorescence signal superimposed with the main bands attributable to the alcohol and water, which drastically hamper wine component detection or wine discrimination without additional chemometrics. The observed SERS bands in red wines with the 532 nm are likely associated with the SE(R)RS effect of anthocyanin pigments which absorb this line, while the fluorescence enhancement for other flavonoids is co-existent and resulted in strong superimposed SE(R)RS background. Moreover, possessing large number of hydroxyl groups in molecular structure and being pH-sensitive in alkaline environment, flavonoids undergo molecular changes like auto-oxidation, dimerization, and polymerization. Adding small amount of wine to the AgNPs, which provides alkaline environment (pH 7.5) in a ratio of 1:50 v/v wine:AgNPs, results in instant NP aggregation associated with molecular changes in flavonoid molecular structure and adsorption on the AgNPs. The strength of this complex process is essentially dependent on the wine content, the balance between water and ethanol (which is also an intrinsic characteristic of each wine and a reason of SERS dependencies), and the pH of the wine (which defines its acidity). Thus, SERS pilot study established the optimal approach and showed great promise for extended applications aiming to fast wine monitoring, with substantial advantages over the current agreed techniques.
- 出版日期2018-3
