乙基麦芽酚分子的密度泛函理论计算及表面增强拉曼光谱分析

Calculation of Ethyl Maltol Molecules Using Density Functional Theory and analysis of its Surface-enhanced Raman Scattering Spectra

乙基麦芽酚是一种常见的食品添加剂。该分子可能以"平面"或"立体"两种分子构型存在。应用密度泛函理论,分别对两种可能存在的构型进行了分子模拟计算,其中"平面"构型分子的理论计算拉曼光谱与实验值高度吻合,而"立体"构型分子的理论计算拉曼光谱与实验值差异显著。表明乙基麦芽酚分子是以"平面"分子构型存在。分别通过"银胶法"和"纳米银阵列法"制备了两种用于表面增强拉曼光谱的基底。采用10-3 mol/L的乙基麦芽酚溶液进行了拉曼增强实验,其中"纳米银阵列法"制备的基底增强效果明显优于"银胶法"制备的基底。通过比较乙基麦芽酚分子原始固体光谱与增强光谱的差异发现:造成1400至1600波数段内特征振动峰发生显著频移的原因,是由于纳米银增强基底的加入导致乙基麦芽酚分子中酮基基团中碳氧双键之间的电荷密度改变而造成的,该结论确定了乙基麦芽酚分子的吸附取向。

Ethyl maltol is a common food additive.The molecules may be ＂flat＂ or ＂stereo＂ two molecular structure.Application of density functional theory,the two possible molecular structure all had been calculated.The theory calculation result of ＂flat＂ molecular structure was highly similar with the experimental Raman spectra,but the theory calculation result of ＂stereo＂ molecular structure was significant difference with the experimental data.It shows that the ethyl maltol molecules is ＂flat＂ structure.Two kinds of Surface-enhanced Raman substrates were prepared separately by ＂Silver Colloids method＂ and ＂Nano-silver array method＂.10-3 mol/L ethyl maltol solution was used in the Raman enhanced experiment.The enhanced effect of the substrates which were prepared by ＂Nano-silver array method＂ was better than the other one.Through comparing the original solid Raman spectra and the SERS spectra of ethyl maltol molecules we found that： The reason of the frequency shift between 1400 to 1600 wavenumber is due to the change of charge density between the Nano-silver enhanced substrates and Carbon oxygen double bond.The adsorption orientation of ethyl maltol molecules was determined according to this conclusion.