The effect of modification of TiO 2 with different palladium concentrations on its characteristics and photocatalytic efficiency was studied. Photo catalysts were prepared by the sol-gel method and were characterized by different techniques. A uniform distribution of palladium through the TiO 2 matrix was observed. The X-ray diffraction patterns of the pure and palladium doped TiO 2 were found to be quiet similar and the average particle size was not significantly changed. As a result of palladium doping, the UV-Vis analysis showed a red shift in the onset of wavelength of absorbance and the band gap was changed from 3.39 to 3.06 eV for the 0.3 wt% Pd/TiO 2 sample. Photo catalytic removal study of formic acid showed that the 0.3 wt% palladium doped photocatalyst exhibits the highest efficiency among the different palladium doped photocatalysts using sun light as the radiation source.

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Molybdenum (VI) oxide nanoparticles (α-MoO3 NPs) were green synthesised using buckthorn leaf extract as the reducing and capping agents. The α-MoO3 NPs were characterised by thermogravimetric analysis, fourier transforms infrared spectroscopy, X-ray diffraction, field emission scanning, and transmission electron microscopy, energy-dispersive x-ray spectroscopy, and Brunauer–Emmett–Teller surface area analysis. The analyses showed the formation of spherical-shaped α-MoO3 NPs with ∼50 nm mean crystallite size, 3.825 m2 g-1 surface area, and 0.005 cm3 g-1 total pore volume. The synthesised α-MoO3 was then applied for adsorption of Cd (II) from aqueous solutions. Optimisation of various adsorption parameters resulted in complete Cd (II) removal under the conditions: 0.1 g α-MoO3 dose, 60 min contact time, 50 mg l-1 initial Cd (II) concentration, pH 7 and 298 K. The experimental results were further assessed using different kinetic, isotherm and thermodynamic models. The data were best described by pseudo-second-order (R2 = 0.992) and Langmuir (R2 = 0.98) models with a maximum adsorption capacity of 57.5 mg g-1 at optimum conditions. Thermodynamic results indicated that the adsorption process is feasible, spontaneous, and endothermic in nature. Moreover, upon regeneration and interference results, α-MoO3 is stable and selective for Cd (II) adsorption in presence of other cations. Upon these results, the biosynthesised α-MoO3 NPs can be used as a selective adsorbent for the efficient removal of Cd (II) from aqueous media.

Copper (II) oxide nanoparticles (CuONPs) were green synthesized using Ocimum basilicum leaves aqueous extract in which polyphenols act as reducing and stabilizing agents. The synthesized CuONPs were characterized using X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, selected area electron diffraction, and Brunauer–Emmett–Teller (BET) surface area analysis. The analyses indicated the formation of crystalline rod-like monoclinic pure CuONPs with a mean grain size of 15 nm, a surface area of 396 m2 g−1, and a total pore volume of 0.71 cm3 g−1. A glassy carbon electrode (GCE) was modified using the synthesized CuONPs and electropolymerized poly(methyl orange) (PMO). The modified PMO/CuONPs/GCE electrode was electrochemically characterized and applied for the estimation of folic acid (FA) by cyclic voltammetry, chronoamperometry, linear sweep voltammetry, and differential pulse voltammetry techniques. The influence of pH (7), scan rate (50 mV/s), supporting electrolyte (0.1 M KCl) and FA concentration has been optimized. FA is precisely determined in the range from 0.01 to 1.5 µΜ with a low detection limit (0.002 µΜ), a low quantitation limit (0.068 µΜ), high reproducibility (RSD 0.37, 10 measurements), and high stability (98% activity after 50 days). FA in food samples was determined by the new sensor with high recoveries from 93 to 108.8%. Graphical Abstract

Zinc oxide nanoparticles (ZnO NPs) were biosynthesized. According to GC/MS analysis, chalcone; the main phytochemical; is probably complexed with Zn ions that are then oxidized to ZnO NPs by atmospheric O2 during heating. The ZnO NPs were characterized by TG, FTIR, XRD, FESEM, TEM, eEDAX, and BET surface area analysis. Sphere-like ZnO NPs were formed with 11 nm mean crystallite size, 5.2 m2 g−1 surface area, and 0.02 cm3 g−1 total pore volume. The synthesized ZnO showed excellent photocatalytic degradation (96.5±0.24% in 1 hour at 25 °C) of malachite green (MG) in aqueous solutions under UV light at optimum conditions; pH 10, MG initial concentration of 20 mg L−1, and ZnO dose of 1.5 g L−1. Also, ZnO showed very good reusability (92.9± 0.2% after 5 runs). The experimental data obeyed pseudo-first-order kinetics (R2=0.92). The photocatalysis process is dependent on the following species in the order: OH. > electron/positive hole pairs > O2.−. Moreover, photodegradation efficiency decreased in the presence of CO32−, HCO3−, and Cl−, but increased in the presence of NO3−, and SO42− ions. Thus, the green synthesized ZnO NPs can be applied as an efficient photocatalyst for the removal of MG from aqueous media.