Photo-catalytic degradation of Rhodamine 6G under visible lamp using citrate stabilized ZnO nanoparticles

Abstract

This study reports on the synthesis of citrate-stabilized zinc oxide (ZnO) nanoparticles (NPs) for the photocatalytic degradation of Rhodamine 6G (R6G) dye using visible irradiation at neutral pH. The ZnO nanoparticles (ZnO NPs) were characterized by Zeta sizer, FTIR, XRD, UV/Vis and TEM for molecular structure, crystallinity, absorbance (bandgap) and morphology respectively. The IR spectrum showed a stretching band at ≈650 cm −1 due to the Zn O bond and another vibrating band of Zn O at 875 cm −1 , and a broad peak at 2925 cm −1 for the OH (Acid) group, and 1600 cm −1 for unsaturated (C=C). XRD showed a hexagonal wurtzite structures with particle sizes between 5 and 10 nm across the planes. The average crystalline size, calculated from the most intense diffraction peaks corresponding to the crystal lattice planes (100), (002), and (101) was found to be 7.29 nm. The TEM analyses showed a size distribution of 30–40 nm (TEM) with the average crystalline size of 42 nm showing a narrow size distribution, proven by a lognormal standard deviation of 0.32. UV–Vis spectroscopy confirmed nanoparticle formation with a band gap of 3.82 eV. BET analysis revealed that ZnO NPs have a mesoporous structure (pore size ≈17 nm) and a surface area of 8.87 m 2 /g. Zeta potential measurements showed a value of +40.9 mV, indicating excellent colloidal stability; the BJH plot consolidated this fact with a pore diameter of 17 nm. The photocatalytic efficiency of ZnO NPs was tested against Rhodamine 6G (R6G) under visible light. Up to 53.7 % degradation was achieved for 10 ppm R6G, 20.9 % for 20 ppm R6G and 11.0 % for 30 ppm R6G after 150 min, with a blue shift in absorbance confirming dye breakdown. These results demonstrate the potential application of citrate-stabilized ZnO NPs in solar-driven photocatalytic degradation of organic dyes. • Citrate stabilized ZnO to enhance dispersion, stability and crystalline structure. • XRD and TEM confirmed hexagonal wurtzite structure with particle sizes below 100 nm. • Citrate-stabilized ZnO nanoparticles are mesoporous with a pore size of ~17 nm and introduced ZnO surface defects. • Excellent colloidal stability and low aggregation tendency. • Improved photocatalytic efficiency of citrate-stabilized ZnO NPs under visible light.