Interface Interaction between MoO₃ and Carbon Dots Derived from Chitosan Promoted the Photocurrent Extraction Ability of Carriers in a Wide Range of the Light Spectrum

Due to the large number of defects at the grain boundaries of nanocomposites, defects have a significant effect on the physico-chemical properties of a material. Therefore, controlling the charging behaviour of functional nanocomposites in a non-contact manner with a light field can improve their physical and chemical properties. Chitosan-derived carbon dots were synthesised by exploiting the abundant N element in chitosan. In order to passivate the defects of chitosan-derived carbon dots, a MoO3/carbon dot nanocomposite was constructed in this study to tailor the band gap and improve the extraction ability of carriers through light induction. The results showed that the strong interfacial interaction between MoO3 and carbon dots enhanced the optical absorption and interfacial charge transfer in the visible and some near-infrared regions. The resulting MoO3/carbon dot heterostructure was coated on A4 printing paper, and electrodes were integrated in the coating film. The photocurrent signals of the thick film were investigated using 405, 532, 650, 808, 980 and 1064 nm light sources. The results indicated that the phenomenon of photocurrent switching to the visible light and some near-infrared light regions was observed. The charge carrier extraction ability of the MoO3/carbon dot nanocomposite through light triggering was much better than that of chitosan-derived carbon dots. The on/off ratio and response speed of the MoO3/carbon dot nanocomposite were significantly improved. The physical mechanism was discussed based on the ordered and disordered structures of polymer-derived carbon nanomaterials. This material could be applicable to the development of broadband flexible photosensors, artificial vision or light-utilising interdisciplinary fields.