Computational insights on the adsorption of glycine, methionine, tyrosine and phenylalanine on the zinc oxide nanocluster Zn12O12

The current work investigated the interaction of ZnO nanoparticles (NPs) with glycine, tyrosine, methionine and phenylalanine. (ZnO)₁₂ cage-like cluster was modeled using the density functional theory to determine the adsorption energy, the preferred sites for adsorption of amino acids, and the electronic structure of the formed complexes. The findings suggest that pure amino acids interact with (ZnO)₁₂ via a chemisorption process. The thermodynamic parameters computed showed that the complexation is an exothermic process and enthalpy-driven. The oxygen atoms in the carboxyl groups of the four studied amino acids are involved in the adsorption process. PHE_Zn₁₂O₁₂ exhibits the highest adsorption energy (− 207.50 kJ/mol) due to its interaction with the Zn₁₂O₁₂ nanocluster through two different adsorption sites. The electronic and sensing properties were examined by analyzing the HOMO and LUMO energies and the HOMO–LUMO energy gap (|ΔEg|). The sensitivity of Zn₁₂O₁₂ nanocluster toward the studied amino acids was examined by comparing the percentage variation of the gap after the adsorption, which can reach the value of 38%, suggesting the potential of Zn₁₂O₁₂ nanocluster as a promising sensor for the detection of amino acids. Interaction region indicator (IRI) analysis was performed for a visual understanding of the different interactions occurring between the amino acids and the Zn₁₂O₁₂ nanocluster. The results of this study can shed some light on the possible application of ZnO-based nanobiosensors for detecting protein tyrosine/tryptophan nitration as an early symptom of several serious chronic diseases.