Nyangiwe N N, Ouma C N M
Natural Resources and the Environment, Council for Scientific and Industrial Research (CSIR), P O BOX 395, Pretoria, 0001, South Africa; University of Pretoria, Department of Chemical Engineering, Private Bag X 20, Hatfield, 0028, South Africa.
Natural Resources and the Environment, Council for Scientific and Industrial Research (CSIR), P O BOX 395, Pretoria, 0001, South Africa; HySA-Infrastructure, North-West University, Faculty of Engineering, Private Bag X6001, Potchefstroom, 2520, South Africa.
J Mol Graph Model. 2019 Nov;92:313-319. doi: 10.1016/j.jmgm.2019.08.013. Epub 2019 Aug 16.
Understanding the nature of the interactions between natural organic matter (NOM) and engineered nanoparticles (ENPs) is of crucial importance in understanding the fate and behaviour of engineered nanoparticles in the environment. In the present study, dispersion-corrected density functional theory (DFT-D) has been used to elucidate the molecule-surface interactions of higher molecular weight (HMW) NOM ambiguously present in the aquatic systems, namely: humic acid (HA), fulvic acid (FA) and protein Cryptochrome (Cry) on Ag (111) surface. Investigations were done in the gas phase and to mimic real biological environment, water has been used as a solvent within the conductor-like screening model (COSMO) framework. The calculated adsorption energies for HA, FA and Cry on Ag (111) surface were -27.90 (-18.45) kcal/mol, -38.28 (-18.68) kcal/mol and -143.89 (-150.82) kcal/mol respectively in the gas (solvent) phase and the equilibrium distances between the surface and HA, FA and Cry molecules were 1.87 (2.18) Å, 2.31(2.31) Å and 1.91 (1.70) Å respectively in the gas (solvent) phase. In both gas and water phase Cry showed stronger adsorption which means it has a stronger interaction with Ag (111) surface compared to HA and FA. The results for adsorption energy, solvation energy, isosurface of charge deformation difference, total density of state and partial density of states indicated that indeed these chosen adsorbates do interact with the surface and are favourable on Ag (111) surface. In terms of charge transfer, one of many calculated descriptors in this study, electrophilicity (ω) concur that charge transfer will take place from the adsorbates to Ag (111) surface.
了解天然有机物（NOM）与工程纳米颗粒（ENPs）之间相互作用的本质对于理解工程纳米颗粒在环境中的归宿和行为至关重要。在本研究中，采用色散校正密度泛函理论（DFT-D）来阐明水生系统中存在的高分子量（HMW）NOM的分子-表面相互作用，即：腐殖酸（HA）、富里酸（FA）和蛋白质隐花色素（Cry）在Ag(111)表面的相互作用。研究在气相中进行，为模拟真实生物环境，在类导体屏蔽模型（COSMO）框架内将水用作溶剂。在气相（溶剂相）中，HA、FA和Cry在Ag(111)表面的计算吸附能分别为-27.90（-18.45）kcal/mol、-38.28（-18.68）kcal/mol和-143.89（-150.82）kcal/mol，表面与HA、FA和Cry分子之间的平衡距离在气相（溶剂相）中分别为1.87（2.18）Å、2.31(2.31) Å和1.91（1.70）Å。在气相和水相中，Cry均表现出更强的吸附，这意味着与HA和FA相比，它与Ag(111)表面的相互作用更强。吸附能、溶剂化能、电荷变形差等值面、总态密度和分态密度的结果表明，这些选定的吸附质确实与表面相互作用，并且在Ag(111)表面是有利的。就电荷转移而言，本研究中计算的众多描述符之一亲电性（ω）表明电荷将从吸附质转移到Ag(111)表面。
