Investigations on functionalized GO as selective and efficient amino acids carrier supported by density functional calculations

Interaction of graphene oxide (GO) with proteins and peptides has grabbed a lot of attention in biomedical applications. Taking cognizance of this, the present study accentuate the interaction of pure and nitrogen doped GO (N-doped GO) with five different amino acids i.e. tryptophan (Trp), histidine (His), proline (Pro), aspartic acid (Asp) and glycine (Gly). Consequence of various experimental parameters such as pH, adsorbent dosage, contact time and initial amino acids concentration on adsorption behavior has also been studied. It is concluded that pH has most significant effect on adsorption of amino acids and maximum adsorption of amino acids on GO nanosurfaces were observed at pH 2. Fitting of experimental data with Langmuir isotherm established that adsorption is monolayer. The kinetic studies confirmed that adsorption process followed pseudo-second-order kinetics. The experimental results have been backed by quantum chemical calculations performed in the formalism of density functional theory. As the interaction between amino acids and GO surface was understood, the study was further extended to investigate if the amino acids bind selectively with the nanosurface from binary solutions of amino acids i.e. Trp/His, Trp/Pro, Trp/Asp, Trp/Gly.