Sunlight assisted degradation of methylene blue dye by zinc oxide nanoparticles green synthesized using Vitex negundo plant leaf extract

Zinc oxide nanoparticles (ZnO NPs) were formed through a simple green synthesis route using Vitex negundo (V. negundo) leaf extract as reducing and capping source. Morphological, structural, chemical and optical features of the prepared ZnO NPs were examined by field emission SEM, XRD, EDAX, PL, FTIR and UV–vis DRS, respectively. FESEM images precisely visualized morphology of the ZnO NPs as spherical with particles size ranges between 5 and 35 nm having a mean diameter of ∼ 19 nm. XRD pattern revealed formation of hexagonal wurtzite structured ZnO NPs with high crystallinity. Further, the observed asymmetric stretching vibration of Zn-O bond confirmed the formation of hexagonal wurtzite structured ZnO NPs. Photocatalytic activity of the ZnO NPs was assessed against methylene blue (MB) dye degradation under natural sunlight illumination. Results of the photocatalytic experiment disclosed an impressive MB dye degradation efficiency of 98.50 % at 60 min. Moreover, green synthesized ZnO NPs exhibited a maximum mineralization (TOC removal) efficiency of 92.34 % at 5 h of sunlight illumination

Cow dung extract as a low-cost and natural sensitizer for zinc oxide nanoparticles photoanode based dye-sensitized solar cell: A novel initiative for waste to energy conversion

Cow dung extracts are prepared using ethanol and methanol as solvents. Electronic absorption spectra of cow dung extracts have exhibited wide absorption in the UV and visible region between 300 and 730 nm. The absorption of cow dung extracts showed variations in intensity and absorption peaks at different wavelengths, which can be attributed to presence of diverse photosynthetic pigments corresponding to polarity of applied solvents. The observed pigments of chlorophyll a, chlorophyll b and carotenoids in the cow dung extracts can be ascribed to the feeding behavior of the cow. The FTIR and UV–vis absorption results have disclosed that the sensitization of zinc oxide nanoparticles (ZnO NPs) photoanode is mainly due to the chlorophylls present in the cow dung extract. The methyl group in the chlorophyll molecules from ideal bond with ZnO NPs that enables transfer of electrons from chlorophyll molecules to conduction band of ZnO NPs. The solar cells sensitized with cow dung extract in methanol has delivered highest energy conversion efficiency of 0.102%, which can be ascribed to presence of relatively a greater number of photosynthetic pigments

Ultra-small Ni@NiFe2O4/TiO2 magnetic nanocomposites activated peroxymonosulphate for solar light-driven photocatalytic mineralization of Simazine

In the heterogeneous photocatalytic degradation of environmental contaminants the recovery, reuse of employed nanocatalyst was crucial and it is essentially required for the scale up applications. Besides, designing a magnetic material with heterojunction that can effectively oxidize the toxic organic contaminants to non-toxic substance under different reaction conditions including direct solar light irradiation remains a challenge. Considering the above facts, herein, we tailored heterojunction between the magnetic materials and non-magnetic materials with ultra-small Ni nanoparticles modified NiFe2O4/TiO2 nanostructures (Ni@NiFe2O4/TiO2 magnetic nanocomposites) through a simple sonochemical route. The Raman phonons at ∼ 540 cm−1 consistent to nickel metal nanoparticles and the spinel ferrites crystal structure confirmed the formation of Ni@NiFe2O4/TiO2 magnetic nanocomposites. The reduced optical bandgap of the resulting nanocomposites indicated the effective absorption of direct solar light irradiation when compared to the bare TiO2. Thus in-turn, enhanced the photocatalytic efficiency of simazine degradation in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k´= 11.0 × 10–4 s−1) and augmented the activation of peroxymonosulphate (PMS) in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k´= 32.5 × 10–4 s−1). Ni@NiFe2O4/TiO2 +PMS exhibited 3 folds enhanced efficiency in the presence of sunlight. The as-prepared NiFe2O4/TiO2 magnetic nanocatalysts were more stable and the efficiency of simazine oxidation was approximately same for the continuous five cycles at the optimized experimental conditions. The Ni@NiFe2O4/TiO2 magnetic nanocomposites preparation and the activation of PMS may promise the applications in an efficient wastewater treatment