Tuning the interfacial charge transfer dynamics of cellulose-graphene quantum dot nanocomposites by edge functionalization

Cellulose-graphene quantum dot (GQD) nanocomposites are emergent new materials for flexible electronics. The quantum yield of photogenerated charge carriers depends on the electronic structure and dynamics of charge transfer at the interface of cellulose-GQD nanocomposites, which is unknown. In the present work, we inves-tigate the properties of cellulose-GQD nanocomposites in terms of functionalization of GQD based on density functional theory calculations with a conductor-like polarizable continuum model (CPCM). The cellulose-GQD nanocomposite has better photoelectric performance than GQD alone. A nonpolar solvent improves the charge transportation of cellulose-GQD nanocomposites. At the high edge coverage, functionalization of GQD with groups containing a C--O double bond decreases the absorption intensity and shifts the absorption maxima of the cellulose-GQD nanocomposites to longer wavelengths. On the other hand, functional groups that do not contain a C--O double bond have no effect on the absorption spectra of cellulose-GQD nanocomposites at the low edge coverage. Increasing the edge coverage of the -NO2 and -CHO groups stabilizes the highest occupied orbitals of the GQDs, leading to extraction of holes from the GQDs. Due to the increased solvent reorganization energy, structural flexibility, electronic coupling, and electron-phonon coupling, cellulose-GQD nanocomposites func-tionalized with either -NO2 or -CHO exhibit faster hole transfer compared to non-radiative electron-hole recombination.