Molecular\nSurface Doping of Cellulose Nanocrystals:\nA High-Throughput Computational Study

Cellulose, a linear polymer of glucose residues, is the\nmost abundant\nbiopolymer on Earth. However, its inability to conduct electricity\nlimits its applications in flexible electronics and energy storage\ndevices. Here, we performed high-throughput first-principles computational\nscreening to identify promising molecules for surface doping of cellulose\nnanocrystals (CNCs). We examined over 1600 molecules, including those\nfrom the TABS database, to find candidates for p-type and n-type doping.\nOur results identified several p-type dopants, such as hexacyano-trimethylene-cyclopropane\n(CN6-CP) and octacyanoquinodimethane (OCNQ). However, no suitable\nn-type dopants were found due to the low electron affinity of cellulose.\nWe constructed atomic models of CNCs of cellulose Iα and Iβ\ncrystals, showing how their electronic band structures depend on surface\nhydrogen bond reconstructions. We propose a novel mechanism for photocurrent\ngeneration in CNC Iα surfaces by manipulating the hydrogen bond\nnetwork at the surfaces. The selection of potential p-type dopants\nwas further refined through the first-principles calculations of the\nCNC models with molecular dopants adsorbed on the surface. Finally,\nwe demonstrate that suitable surface functionalization can enhance\nthe electron affinity of CNCs, partially overcoming the challenges\nof n-type doping.