甲基橙-银胶体系pH和氯离子效应的光谱研究

研究了甲基橙-银胶体系的光吸收和光致发光信号随pH值和加入氯离子的变化规律.实验发现随着pH值的增加, 分子的荧光发射峰与银胶的光吸收峰的重叠增大, 引起体系中能量转移效率的增加, 即428 nm分子荧光峰的淬灭和560 nm聚集体的特征光致发光峰增强现象的加剧.另外, 不同pH值下氯离子的加入都会使染料分子更加密集的吸附在胶体银颗粒表面, 形成分子吸附更加紧密的聚集体, 造成体系中受表面吸附分子影响的光致发光峰获得了极大的增强.同时, 因聚集体表面吸附层染料分子对入射光的大量吸收, 导致到达内核银表面的入射光强度减弱, 致使体系能量转移通道在一定程度上受阻, 表现为428 nm荧光峰的淬灭幅度减小.参照分子聚集体的形成理论, 接合体系光谱的变化, 从pH值的改变和Cl^-的加入对分子结构及加剧聚集体的形成等方面的影响来解释发光和光吸收的显著变化.

Spectroscopy studies of methyl orange on silver colloids: pH and Cl- effects

The UV-Vis absorption and photoluminescence spectral signals of silver colloids and methyl orange (MO) in different pH systems before and after adding Cl^- were studied. It was found that the energy transfer efficiency changes with the pH value, i.e., the fluorescence quenching at 428 nm and photoluminescence enhancement at 560 nm was greatly strenthened with the increase of pH of the system. After adding Cl^-, dense adsorption layer was formed, leading to stronger spectral signals associated with surface enhancement. On the other hand, because of the decrease of incident light to the inside of Ag-MO complex, energy transfer channel may be suffocated to some extent, the quenching amplitude of 428 nm fluorescence band decreased. Compared with these notable phenomena and discussed with correlative theoretic analysis, it's clear that different molecular structures and adsorption models of MO onto Ag surfaces exist with the changing of pH and the adding of Cl^-, which give rise to the different phenomena observed.