Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, Mexico D. F. 01000, Mexico.
Nanoscale. 2014 Mar 21;6(6):3325-34. doi: 10.1039/c3nr06202c. Epub 2014 Feb 12.
Using time-perturbed density functional theory the optical activity of metal-thiolate compounds formed by highly symmetric Ag and Au nanoparticles (NPs) and a methyl-thiol molecule is studied after performing atomic optimizations and electronic calculations upon adsorption. Many different sites and orientations of the adsorbed molecule on icosahedral Ag and Au NPs of 55 atoms are considered. Upon molecular adsorption atomic distortions on Au NPs are induced while not on Ag, which causes higher molecular adsorption energies in Au than in Ag. Structural distortions and the specific molecular adsorption site and orientation result in chiral metal-thiolate NPs. Ag and Au compounds with similar chirality, according to Hausdorff chirality measurements, show different optical activity signatures, where circular dichroism spectra of Au NPs are more intense. These dissimilarities are attributed in part to the differences in the electronic density of states, which are a consequence of relativistic effects and the atomic distortion. It is concluded that the optical activity of Ag and Au compounds is due to different mechanisms, while in Au it is mainly due to the atomic distortion of the metallic NPs induced after molecular adsorption, in Ag it is defined by the adsorption site and molecular orientation with respect to the NP symmetry.
使用时间微扰密度泛函理论，对高度对称的 Ag 和 Au 纳米粒子（NPs）与一个甲基硫醇分子形成的金属-硫醇化合物的旋光活性进行了研究，在吸附后进行了原子优化和电子计算。考虑了吸附分子在 55 个原子的二十面体 Ag 和 Au NPs 上的许多不同位置和取向。分子吸附会引起 Au NPs 的原子变形，而 Ag 则不会，这导致 Au 中的分子吸附能比 Ag 高。结构变形以及特定的分子吸附位置和取向导致手性金属-硫醇 NPs 的形成。根据 Hausdorff 手性测量，具有相似手性的 Ag 和 Au 化合物表现出不同的旋光活性特征，其中 Au NPs 的圆二色光谱更强。这些差异部分归因于电子态密度的差异，这是相对论效应和原子变形的结果。结论是，Ag 和 Au 化合物的旋光活性是由不同的机制引起的，而在 Au 中，主要是由于分子吸附后金属 NPs 的原子变形引起的，而在 Ag 中，则由吸附位置和分子取向相对于 NP 对称性决定。
