Vu Nhat Pham, Si Nguyen Thanh, Tien Nguyen Thanh, Nguyen Minh Tho
Department of Chemistry, Can Tho University, Can Tho 900000, Vietnam.
Computational Chemistry Research Group, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam.
J Phys Chem A. 2021 Apr 29;125(16):3244-3256. doi: 10.1021/acs.jpca.0c11182. Epub 2021 Apr 16.
Computational approaches within the framework of density functional theory (DFT) were employed to elucidate the binding mechanism of the cysteine amino acid on silver nanoparticles using several small silver clusters Ag with = 2-10 as surface models. The long-range corrected LC-BLYP functional and correlation consistent basis sets cc-pVTZ-PP and cc-pVTZ were used to determine the structural features, energetics, and spectroscopic and electronic properties of the resulting complexes. In vacuum and highly acidic conditions, cysteine molecules prefer to adsorb on silver clusters via their amine group. In aqueous solution, the thiolate head turns out to be the most energetically favorable binding site. The cysteine affinity of silver clusters is greatly altered in different conditions, i.e., acidic solution < vacuum < aqueous solution, and is strongly dependent on the cluster size. As compared to free clusters, the frontier orbital energy gap of the ones capped by cysteine is significantly improved, which corresponds to stronger stability, especially in aqueous solution. The analysis of frontier orbitals also reveals that both forward and backward electron donations exhibit comparable contributions to the enhancement of stabilizing interactions. As for an application, a chemical enhancement mechanism of the surface-enhanced Raman scattering (SERS) procedure of cysteine by silver clusters was also analyzed.
在密度泛函理论（DFT）框架内采用计算方法，以几个含银原子数(n = 2 - 10)的小银簇(Ag_n)作为表面模型，来阐明半胱氨酸氨基酸与银纳米颗粒的结合机制。使用长程校正的LC - BLYP泛函以及相关一致基组cc - pVTZ - PP和cc - pVTZ来确定所得配合物的结构特征、能量以及光谱和电子性质。在真空和高酸性条件下，半胱氨酸分子倾向于通过其胺基吸附在银簇上。在水溶液中，硫醇盐头部成为能量上最有利的结合位点。银簇对半胱氨酸的亲和力在不同条件下有很大变化，即酸性溶液＜真空＜水溶液，并且强烈依赖于簇的大小。与自由簇相比，被半胱氨酸封端的簇的前沿轨道能隙显著改善，这对应于更强的稳定性，尤其是在水溶液中。对前沿轨道的分析还表明，向前和向后的电子给予对稳定相互作用增强的贡献相当。至于应用方面，还分析了银簇对半胱氨酸表面增强拉曼散射（SERS）过程的化学增强机制。
