Electronic properties of l-tryptophan adsorbed on Ti₃C₂T_x (T=O) MXenes

MXenes are the largest graphene like two-dimensional material family developed in recent years. They exhibit unique layered structures with outstanding physical and chemical properties, which can be tunable varying the surfaces terminal groups. In this article, the effect of oxygen saturation on the reactivity of Ti3C2 surfaces is evaluated by means of first-principles modeling of Ti3C2Ox=1 or 2 slabs. Both surfaces exhibit metallic character and work functions show larger reactivity in the case of superficial oxygen deficiency. To further evaluate the surface reactivity, the amino acid model l-tryptophan was studied. The stable configurations of the adsorbed molecule were obtained, and the more stable adducts were found for Ti3C2O. In the case of Ti3C2O2, physisorption occurs while in the case of Ti3C2O, dissociative bidentate chemisorption configuration is adopted. Differences in optical absorbance and work function energy were determined as a preliminary step towards the evaluation of these structures as potential sensing devices.