CAJ | 학술논문

获得了不同浓度下哑甲基蓝(methylene blue,MB)溶液在银溶胶中的表面增强拉曼光谱.结果表明:亚甲基蓝分子与银纳米粒子高浓度下物理吸附为主,低浓度下化学吸附为主;不同浓度下存在不同的吸附取向,即高浓度下为"直立"取向,低浓度为"平躺"取向.通过观察低浓度下MB在银胶中吸附时间对谱图的影响,得知低浓度下吸附取向不随时间发生变化.应用密度泛函(DFT)方法在B3LYP/6-31+G~*和LANL2DZ基组水平上对亚甲基蓝阳离子(MB~+)及MB~+与Ag原子形成的不同构型体系进行了结构优化和频率计算.实验与理论计算结果表明,MB~+有可能通过N-Ag和S-Ag与Ag原子形成两种较强的吸附构型.电荷布居分析表明,与S原子相比,芳香环上的N原子更易与Ag发生相互作用.还对实验观察到的部分谱峰及它们的振动模式作出了初步归属和讨论.
획득료불동농도하아갑기람(methylene blue,MB)용액재은용효중적표면증강랍만광보.결과표명:아갑기람분자여은납미입자고농도하물리흡부위주,저농도하화학흡부위주;불동농도하존재불동적흡부취향,즉고농도하위"직립"취향,저농도위"평당"취향.통과관찰저농도하MB재은효중흡부시간대보도적영향,득지저농도하흡부취향불수시간발생변화.응용밀도범함(DFT)방법재B3LYP/6-31+G~*화LANL2DZ기조수평상대아갑기람양리자(MB~+)급MB~+여Ag원자형성적불동구형체계진행료결구우화화빈솔계산.실험여이론계산결과표명,MB~+유가능통과N-Ag화S-Ag여Ag원자형성량충교강적흡부구형.전하포거분석표명,여S원자상비,방향배상적N원자경역여Ag발생상호작용.환대실험관찰도적부분보봉급타문적진동모식작출료초보귀속화토론.
Surface-enhanced Raman spectra of methylene blue (MB) at different concentrations in silver colloid were obtained. The results indicate that the physical adsorption is dominant at high concentration while the chemical adsorption is the main fashion at relatively low concentration; there are different adsorption orientations at different concentration: MB~+ molecule is perpendicular to the surface of silver nanoparticle at high concentration and adopts a parallel orientation on the surface of nanoparticle at low concentration. The effect of adsorbing time of MB molecule in Ag colloid was investigated and the adsorption dynamics study shows that the parallel orientation at low concentration does not change with the adsorbing time increasing. Density functional theory (DFT) calculations at the level of B3LYP/6-311+G * (for C, S, N, H)/LANL2DZ (for Ag) were employed to optimize the structures and predict Raman frequencies of MB~+ and various MB~+ -Ag complexes. The results of experiments and calculations suggest that the silver atom prefers to be bound to N and S atoms in the aromatic ring, and thus two different complexes are formed, i. e. conformer N-Ag and conformer S-Ag. Moreover, the Mulliken charge population analysis indicates that N atom in the aromatic ring prefers to interact with Ag than S atom does. Finally, the Raman frequencies observed in the experiments and their vibrational modes were tentatively assigned and discussed.