A photocatalysis system based on composite nanostructures of controlable peptide nanotubes and graphene

Self-assembly is the way that is used by Mother Nature to create complex materials of hierarchical shapes and diverse functionalities. The photosynthesis apparatus of plant is an example of such complex materials that can direct convert the sunlight energy into chemical energy. Inspired by this, many artificial photosynthesis systems have been successfully engineered. However, most of these systems were based on only one type of simple nanostructure, such as nanosphere or nanotube. The charge separation and exciton transfer in such systems may be further improved by combining multiple nano-structures. Here, we report a novel photo catalysis system based on composite nanostructures of controllable peptide nanotubes and graphene. We use the mixture of diphenylalanine (FF) and carboxyl graphene for the photo catalysis because they are stable under different solvent conditions and highly conductive, which can provide more paths for exciton transfer. Moreover, the diameters of the peptide nanotubes become thinner in the preflence of carboxyl graphene, leading to a more uniformly distributed system than simply using the peptide nanotubes alone. The FF peptide nanotubes can connect with the carbonyl graphene (CG) to form the composite nanostructures because of the π-π stacking interaction between benzene rings of FF and conjugated πup bond of CG. The composite nanostructures of controllable peptide nanotubes and graphene provide more transmission channels for the excitions since they can travel on the nanotubes, CG or the compound of the both. We also demonstrate that when the photo-harvesting ruthenium complex and catalytic platinum nanoparticles are deposited on the system, the nicotinamide adenine dinucleotide (NADP+) can reduce to NADPH. The catalytic efficiency and rate are much higher than thaose of other artificial photosynthesis systems reported in the literature. Surprisingly, we find that the catalytic efficiency of the combined system is better than the sum of separated systems with only FF nanotubes or carboxyl graphene. The high turnover frequency, high reaction rate, and low toxicity of this artificial photosynthesis system will make the combined system attractive for large-scale applications, including optoelectronic industry, energy industry, etc.