Synthesis and Characterization of Dried Leaves Derived Carbon Quantum Dots and g-C₃N₄ Composite

In this work, carbon quantum dots (CDs) was successfully synthesized by hydrothermal treatment using dried leaves as green precursor. Graphitic carbon nitride (g-C₃N₄) was combined with CDs to prepare CDs/g-C₃N₄ composites with three different weight percentage at 0.6, 0.8 and 1.0 wt%, respectively. The morphological structure, optical properties and chemical compositions of CDs and composites were characterized using various spectroscopic techniques. CDs solution portrayed a significant fluorescence property that bright blue-green fluorescence can be observed by naked eye under ultraviolet (UV) light irradiation. The highest fluorescence emission was recorded at 320 nm with the optimal excitation wavelength of 423 nm. Ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS) results displayed red-shifted adsorption spectra of CDs/g-C₃N₄ composites from 500 nm to 800 nm. No upconversion photoluminescence (UCPL) was detected in CDs based on the photoluminescence (PL) study. The loading of CDs on g-C₃N₄ reduced the band gap from 2.7 eV to 2.59 eV.