An environmentally benign l-cysteine functionalized ZnO/TiO2 nanohybrid decorated on cellulose nanofibers for effective photo degradation of organic hydrocarbons

Abstract

Efficient L-cysteine (LC) functionalized ZnO–TiO₂ nanohybrids in different ratios were fabricated using a facile approach with a phytoextract of the Mirabilis jalapa plant as a reducing agent. The fabricated nanohybrids were characterized by different spectroscopic and microscopic techniques. The photocatalytic activity of these nanohybrids was studied in the presence of natural sunlight in different aqueous solutions of benzene, toluene and phenol. The presence of LC on the surface of the nanohybrid functions as the co-catalytic centre inhibiting the electron–hole recombination rate. It was observed that maximum degradation was achieved when the optimal molar ratio of ZnO to TiO₂ was 1 : 1 with a rate constant as high as 0.011 min⁻¹. The fabricated nanohybrid also exhibited a good degradation pattern for toluene despite its symmetric structure with methyl-benzene conjugation. This enhancement of the photocatalytic property of the nanohybrid could be accredited to the reduced band gap and enhanced surface properties that decreased the rate of recombination of electron–hole pairs. The nanohybrid with 1 : 1 ratio was further utilized to decorate cellulose nanofibers obtained from the stems of the same plant and cast in the form of a paper. The paper was cut into small strips and utilized for the photodegradation study of industrial waste water. The nanohybrid decorated nanocomposite paper exhibited good photodegradation efficiency in the presence of NOM, heavy metals and variable pH (5.5–10), which can be attributed to the further lower recombination rates of electron–hole pairs for efficient degradation.