Carbon quantum dots-decorated nano-zirconia: A highly efficient photocatalyst

Abstract A unique and efficient composite material was synthesized by incorporating carbon quantum dots on to the surface of zirconia (ZrO 2 ) nanoparticles. ZrO 2 nanoparticles with an average diameter of 40 nm were synthesized by a sol-gel process with zirconium oxychloride as the precursor. Carbon quantum dots (CQDs) were synthesized via a facile method by calcining a solution of ammonium citrate. Synthesized CQDs suspended in absolute ethanol emitted a green glow under UV irradiation. A convenient one-step process involving mixing in absolute ethanol under sonication was adopted for the formation of CQD-decorated ZrO 2 nanoparticles (CQDZ). The dried final composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic performance of CQDZ was evaluated by quantifying the removal efficiency of methylene blue dye. CQDZ managed to remove methylene blue by 66.5%, 76.5%, 84.3% and 95.0% under UV-irradiation of 10, 20, 40 and 60 min respectively. Under the same experimental conditions, pure ZrO 2 nanoparticles managed to remove only 34% of the dye under 60 min of UV irradiation. The produced composite showed promise as a formidable contender to be used in industrial dye removal from waste water.