Surface functionalization of twisted graphene C32H15 and C104H52 derivatives with alkalis and superalkalis for NLO response; a DFT study

Abstract

Herein, we present the detailed comparative study on geometric, electronic, optical and non-linear optical response of alkalis and superalkalis doped twisted graphene. The results illustrate that alkali metals and superalkalis interact with the central ring of the twisted graphene through non-covalent interactions which demonstrate the stability of the resultant complexes. NBO charges indicate the transfer of electrons from dopant (alkali metal atoms and superalkalis) towards twisted graphene sheet. Superalkalis doped twisted graphene complexes exhibit higher first hyperpolarizability values compared to alkali metals analogues. Among superalkalis doped complexes, K3O@C104H52 shows the highest βo value of 1.68 × 105 au. In frequency dependent first hyperpolarizability analysis, strong second harmonic generation (SHG) response of K3O@C32H15 complex is observed at both selected resonance frequency values (532 nm and1064 nm) whereas EOPE value of K3O@C32H15 complex shows higher induced response at 1064 nm wavelength. The static hyperpolarizability (βo) further increases under the influence of applied electric field. Among all complexes, Li3O@C32H15 graphene complex has the highest βo value (1.40 × 105 au) under applied electric field along x axis when sheet is in y-z plane. This analysis will be an important guideline for future studies on twisted graphene based NLO materials.