Electronic properties of l-tryptophan adsorbed on Ti3C2Tx (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.

Automated summary

This article investigates the characteristics and surface reactivity of MXenes as two-dimensional materials, as well as the impact of oxygen saturation on their performance. By simulating the effects of oxygen saturation on the Ti3C2 surface, it is found that surface deoxygenation increases its reactivity. Besides, the adsorption configurations of an amino acid model on MXene surfaces were studied, revealing differences between Ti3C2O and Ti3C2O2 in terms of adsorption modes.