Study on the monolayer arrangement and optical properties of single-dispersed metallic particles on solid surfaces

1.在正常辐射入射下，对从乙醇-水混合溶液沉积到硅（111）衬底上的胶体银颗粒（直径约30 nm）上的十八烷硫醇（ODT）进行了红外吸收光谱测量。光谱作为银质量厚度和ODT浓度的函数。表明，与没有银粒子存在的情况相比，ODT的吸收带强度增强。研究还发现，无论ODT浓度如何，每个吸收带的强度在粒子的特定质量厚度处达到最大值，这表明吸收增强与粒子聚集之间存在密切关系。这确实得到了颗粒的FE-SEM形态学检查的支持。基于紫外-可见透射和红外衰减全反射（ATR）实验，研究了ODT分子在纯溶胶中的化学吸附对银胶体颗粒的聚集作用。制备的银溶胶由于粒子的等离子体共振，呈现出以395 nm为中心的单一吸收峰。在溶胶中加入溶解了ODT的乙醇后，等离子体共振峰出现了红移并随之变宽，这表明溶液中的粒子通过ODT吸附而聚集。通过红外ATR光谱分析发现，在溶液中加入odt溶解乙醇后，溶液中的颗粒聚集在锗ATR棱镜的基面上。在适度的ODT浓度下，通过ODT吸附在棱镜表面发生强烈的聚集，从而有可能观察到ODT吸收带。利用氦氖激光（632.8 nm）对跌落在硅衬底上的胶体颗粒进行拉曼散射，以更清楚地阐明制备银溶胶过程中产生的离子种类对颗粒跌落在硅衬底上后聚集的影响。观察到硝酸盐离子引起的拉曼带。将沉积的硅衬底浸泡在纯水中1小时后，该条带几乎消失。然而;将基质浸泡在水中5小时后，硝酸盐条带更加强烈。拉曼散射强度的增加可以解释为，假设环境中的硝酸盐离子被稀释或被吸附的硝酸盐离子或多或少地被水解吸，从而使银胶体粒子聚集，导致所谓的SERS活性位点增加。实际上，当沉积的硅衬底随后浸入ODT溶解的乙醇中时，没有观察到由于ODT引起的拉曼带，这可能是因为假设SERS活性位点被硝酸盐离子占据了。少

1.Infrared absorption spectral measurements have been performed at normal incidence of radiation on octadecanethiol (ODT) deposited from ethanol-water mixed solutions onto colloidal silver particles (ca. 30 nm in diameter) on Si(111) substrates. The spectra taken as a function of silver mass thickness and ODT concentration. indicate that the absorption bands of ODT are enhanced in intensity in comparison to the case in which no silver particles are present. It is also found that regardless of ODT concentration each absorption band reaches a maximum in intensity at a particular mass thickness of the particles, suggesting an intimate relationship between the absorption enhancement and the aggregation of the particles. This indeed was supported by FE-SEM morphological inspection of the particles.2.Aggregation of silver colloidal particles in the hydrosol through chemisorption of ODT molecules has been investigated on the basis of UV-visible transmission and infrared attenuated total refle … More ction (ATR) experiments. As-prepared silver sol showed a single absorption peak centered at 395 nm due to plasma resonance of the particles. Upon addition of ODT-dissolved ethanol to the sol, the plasma resonance peak showed a redshift accompanying a broadening, an indication of the aggregation of the particles in the solution by ODT adsorption. By use of infrared ATR spectroscopy, it was found that the particles in the solution aggregate on the base plane of a germanium ATR prism upon addition of ODT-dissolved ethanol to the solution. At moderate ODT concentrations, intense aggregation via ODT adsorption takes place on the prism surface, thus making it possible to observe ODT absorption bands.3.Raman scattering from the adsorbed species on the colloidal particles after dropping on Si substrates has been taken using a He-Ne laser (632.8 nm) in order to more clarify the influence of ionic species produced during preparation of the colloidal silver sol upon aggregation of the particles after dropping the particles on the silicon substrate. A Raman band due to nitrate ion was observed. This band almost disappeared by immersing the deposited silicon substrate into pure water far 1 hour. However ; the nitrate band was observed more strongly after immersion of the substrate into the water for 5 hours. This increase of Raman scattering intensity can be explained by assuming that the environmental nitrate ions were diluted or adsorbed nitrate ions were desorbed more or less by the water and thereby aggregation of the silver colloid particles proceeded, leading to an increase of the so-called SERS active sites. Actually, no Raman bands due to ODT could be observed when the deposited silicon substrate was subsequently immersed into ODT-dissolved ethanol This maybe explained by assuming that the SERS active sites were occupied by nitrate ions. Less