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In this article, an efficient synthesis of histidinecapped ZnO nanoparticles was carried out in absolute ethanol by using solvothermal technique. The synthesized nanoparticles were further characterized by using different techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transfer infrared (FTIR), UV-visible spectroscopy, thermal analysis (TG/DTG/DTA) and photoluminescence spectroscopy. The XRD measurement reveals that the prepared nanoparticles have hexagonal wurtzite structure. From XRD data, the average crystalline size is calculated to be 22 nm according to half width of (1 0 1) diffraction peak using Debye-Scherrer formula. Moreover, the antibacterial activities of nanoparticles sample have been performed under standard method. The antibacterial activities of histidine-capped zinc oxide nanoparticles are tested against human bacterial pathogen such as Staphylococcus aureus, Escherichia coli, Klebsiella sp., Enterococcus faecalis and Pseudomonas aeruginosa by using agar well diffusion method. Besides, antibacterial activities of ZnO nanoparticles (20 to 60 μg) are compared with four well-known antibiotics viz., Amikacin (30 mcg), Ciprofloxacin (5 mcg), Gentamicin (5 mcg) and Norfloxacin (10 mcg). From antibacterial studies, it has been concluded that if the concentration of histidine-capped ZnO nanoparticles increases, then the antibacterial activities also increase.

In this study, copper nanoparticles (Cu NPs) were synthesised by using diethylenetriamine as a protective agent in chemical reduction method. The obtained nanoparticles were characterised by various spectroscopic techniques like powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), UVÀvisible spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal analysis (TG/DTA). The structure and composition were estimated by PXRD, FTIR, EDS, UVÀvisible and TG/DTA techniques, while particles size and morphology behaviours were investigated by SEM and TEM instrumentation. A noteworthy, average particle size of nanoparticles was found around 40 nm with spherical shapes. Furthermore, the applications part of NPs were studied as a catalyst for one-pot solvent-free green synthesis of 3,4-dihydropyrano[c] chromenes from different aromatic aldehydes, malonitrile and 4-hydroxycoumarin by stirring at 80 C. Moreover, the antibacterial properties of NPs were assessed in vitro against human bacterial pathogen such as Staphylococcus aureus, Escherichia coli, Klebsiella sp. and Pseudomonas aruginosa using agar well diffusion method. Gram positive bacteria S. aureus (18 mm) exhibited a maximum zone of inhibition at 60 mg/ml of Cu NPs. Nonetheless, antibacterial activities of Cu NPs (10À100 mg) were compared with four wellknown antibiotics likes amikacin (30 mcg), ciprofloxacin (5 mcg), gentamicin (5 mcg) and norfloxacin (10 mcg). This study indicates that Cu NPs exhibited a strong antibacterial activity against all the test pathogens even at lower concentration.

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Copper nanoparticles (Cu NPs) were found to be an extremely efficient and effective catalyst for synthesis of 2,4,5-trisubstituted imidazole via three-component reactions of benzil, aldehydes, and ammonium acetate at room temperature. The products obtained were followed by thin-layer chromatography. After completion of the reaction, the reaction mixture was diluted with water (20 mL). The solid imidazole product was washed with water and recrystallized from ethanol to remove nanocopper to afford the pure imidazole compounds. The method provides several advantages such as simple operation, short reaction time, clean reaction profile, lower catalyst loading and high yield. The used catalyst in the reaction could be recovered conveniently and reused for several times. The high yields of reactions are attributed to the effect of Cu NPs due to high surface-to-volume ratio. Due to simple workup procedures, very short times and excellent product yields make this method an interesting alternative to other methodologies.