Physisorption of amino acids on TiO₂: Changes in the nonlinear optical properties

Issue title: V Congress of Theoretical and Computational Physical Chemistry, 8-10 of December of 2014, Altos de Pipe, Caracas, Venezuela

Guest editors: Fernando Ruette, Anibal Sierralta, Morella Sánchez and Ney Luiggi

Article type: Research Article

Authors: Marcano, Emildo^{a; *} | Cisneros, José Gregorio^a | Alayón, Johana^a | Murgich, Juan^b

Affiliations: [a] Universidad Pedagógica Experimental Libertador, Instituto Pedagógico de Caracas, Centro de Investigaciones en Ciencias Naturales (CICNAT), Laboratorio de Química Computacional, Caracas, Venezuela | [b] Centro de Química, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas, Venezuela

Correspondence: [*] Corresponding author: Emildo Marcano, Universidad Pedagógica Experimental Libertador, Instituto Pedagógico de Caracas, Centro de Investigaciones en Ciencias Naturales (CICNAT), Laboratorio de Química Computacional, Apartado 47102, Caracas 1020-A, Venezuela. E-mail:jedi148@gmail.com

Abstract: Calculations at HF, DFT (CAM-B3LYP) level were carried out with the 6-31+G(d,p) basis set for estimate the polarizability (α), the first hyperpolarizability (β) and the second hyperpolarizability (γ) for aromatic amino acids: tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe), before and after of the physisorption on an anatase nanoparticle model. The results show that, the values for < α >, β total and < γ > increases as different indole, phenol, or benzene moieties were substituted, according to the sequences Phe < Tyr < Trp. Therefore, these properties enhance when the electronic delocalization is increased due to the substitution of aromatic systems. Moreover, the increase in the value of the polarizability, were accompanied by a decrease in the adsorption energy for the amino acid-anatase interaction, suggesting an increment in the stability for the complex linking by a weak attractive dispersion force to be induced between them. In relation to the adsorption energy, the negative Eads indicated that the amino acid adsorption is exothermic for the structures studied and thus the adsorption system is energetically stable. Indole, phenol, and benzene substitution on amino acid structure had a low impact on the Eads values, and the order for physisorption stability was Tyr > Phe > Trp. For β total, the values showed a much higher sensitivity to the physisorption effect. We propose that amino acid studied can be used as target system in the study of interaction amino acid-anatase with nonlinear optical microscopy techniques.

Keywords: Polarizability, hyperpolarizability, reorganization energy, 4,5-dicyanoimidazole, DFT, MP2

DOI: 10.3233/JCM-160668

Journal: Journal of Computational Methods in Sciences and Engineering, vol. 17, no. 1, pp. 127-137, 2017