Electronic and optical properties of chromophores from bacterial cellulose

Abstract

We report a systematic computational investigation on the electronic and optical properties of the principal chromophores found in bacterial cellulose (BC). In particular, we focus on the three chromophoric leading structures that were isolated from aged BC (1) 2,5-dihydroxy-[1,4]benzoquinone (2) 5,8-dihydroxy-[1,4]naphthoquinone and (3) 2,5-dihydroxyacetophenone. For the isolated molecules we performed all-electrons density functional theory (DFT) and time dependent DFT calculations with a localized Gaussian basis set and the hybrid exchange correlation functional B3LYP. We quantified key molecular properties relevant as electron affinities, ionization energies, quasi-particle energy gaps, optical absorption spectra, and exciton binding energies. We address moreover the impact of the solvent on the optical properties of the above systems using starting configurations obtained after classical molecular dynamics simulations in water. Our results could be of importance to comprehend the mechanisms underlying the processes of degradation of BC, which are of fundamental relevance for cultural heritage applications.