The effects of nontoxic bio-based substances (egg white) on the performance and passivation of ZnO nanorods arrays-based light emitting devices.

An innovative approach is proposed to passivate the existing defects from metal oxide semiconductors by functionalizing nontoxic bio-based substances. As a demonstration, we synthesized zinc oxide nanorods (ZnO NRs) using a hydrothermal method and incorporated chicken egg white (albumen) as a passivator to the defects. X-ray diffraction analysis of ZnO NRs shows enhanced quality and crystallinity features after incorporating albumen. XPS measurements were performed not only to introduce the chemical bonding between the albumen and the bare ZnO NRs but also specifically provide evidence of successful capping and defect passivation to the surface layer of ZnO NRs. It was observed that when the albumen was annealed, it formed sulfhydryl groups and disulfide bonds (which created disulfide bridges) from the chemical reaction in irreversible thermal denaturation. Steady-state photoluminescence of ZnO NRs showed two emission bands, i.e. near band-edge emission (NBE) and deep-level emission (DL). The NBE is significantly improved as compared to DL emission after capping and annealing the albumen, while the quenching of DL emission confirmed the reduced defects arising from the surface of ZnO NRs. The advantages and enhanced characteristics of the albumen-capped ZnO NRs led to fabricating a stable and highly efficient light-emitting device. This work opens the great potential of utilizing nontoxic and low-cost biomaterials in passivating the defects of metal oxide nanomaterials for the development of bio-inspired and stable optoelectronic devices.