The phytogenic synthesis method to highly active, recoverable and recyclable heterogeneous copper oxide nanocatalyst and encapsulated within biomaterial that acts as a nontoxic and renewable source of reducing and stabilizing agent. The biosynthesized CuO NPs were characterized using UV–Vis absorption spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and thermo gravimetric analysis-differential scanning calorimetry (TGA–DSC), techniques. The formation of CuO NPs with the size 20–45 nm range is shown in TEM image. Significantly, in aqueous phase CuO NPs have high catalytic activity for the reduction of Congo red (CR), methylene blue (MB) and 4-nitrophenol (4-NP) in the presence of the sodium borohydride (NaBH4) at room temperature. In addition, CuO NPs catalyst can be easily recovered by centrifugation and reused for 6 cycles with more than 90% conversion efficiency. CuO nanocatalyst, leaching after catalytic application was investigated by ICPAES (Inductively coupled plasma atomic emission spectroscopy). CuO NPs possess great prospects in reduction of pernicious dyes and nitro organic pollutants in water

To investigate molecular aspects of the antibacterial effect of size-dependent core-shell intrinsic defects of nanocrystalline ZnO synthesized through high energy ball milling technique. Mechanically synthesized and characterized 7, 10 and 15 h milled ZnO nanoparticles were evaluated for antibacterial activity with molecular investigation by computational molecular docking. Synthesized ZnO nanoparticles displayed shrinkage of core and increase of shell with reduction in size of bulk ZnO particles from 250 to 80, 40 and 20 nm and increase in zeta potential up to -19 mV in 7, 10 and 15 h nano ZnO. Antibacterial activity was found increased with decrease in size due to increased reactive oxygen species and membrane damage in bacteria. Synthesized nano ZnO exhibit size-dependent antibacterial action as consequences of interactions with cell membrane proteins via hydrogen bond interaction with amino acid residues followed by internalization, membrane depolarization and induction of reactive oxygen species generation.