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Copper nanoparticles (CuNPs) are of great interest due to their extraordinary properties such as high surface-to-volume ratio, high yield strength, ductility, hardness, flexibility, and rigidity. CuNPs show catalytic, antibacterial, antioxidant, and antifungal activities along with cytotoxicity and anticancer properties in many different applications. Many physical and chemical methods have been used to synthesize nanoparticles including laser ablation, microwave-assisted process, sol-gel, co-precipitation, pulsed wire discharge, vacuum vapor deposition, high-energy irradiation, lithography, mechanical milling, photochemical reduction, electrochemistry, electrospray synthesis, hydrothermal reaction, microemulsion, and chemical reduction. Phytosynthesis of nanoparticles has been suggested as a valuable alternative to physical and chemical methods due to low cytotoxicity, economic prospects, environment-friendly, enhanced biocompatibility, and high antioxidant and antimicrobial activities. The review explains characterization techniques, their main role, limitations, and sensitivity used in the preparation of CuNPs. An overview of techniques used in the synthesis of CuNPs, synthesis procedure, reaction parameters which affect the properties of synthesized CuNPs, and a screening analysis which is used to identify phytochemicals in different plants is presented from the recent published literature which has been reviewed and summarized. Hypothetical mechanisms of reduction of the copper ion by quercetin, stabilization of copper nanoparticles by santin, antimicrobial activity, and reduction of 4-nitrophenol with diagrammatic illustrations are given. The main purpose of this review was to summarize the data of plants used for the synthesis of CuNPs and open a new pathway for researchers to investigate those plants which have not been used in the past. Graphical abstractProposed Mechanism for Antibacterial activity of copper nanoparticles.

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Employing natural or arti cial sunscreens is essential to protect the skin from ultraviolet radiations that cause premature aging and develop melanoma and other forms of skin cancer. The 2-Phenylbenzimidazole-5-sulfonic acid, commonly known as ensulizole is a water-soluble arti cial sunscreen that absorbs mostly UV-B (280 nm − 315 nm) radiations and protects the skin against the harmful effects of these radiations. Steady-state absorption indicates a strong absorption feature at 303 nm and a weak at 316 nm that have been identi ed as π → π* and n → π* transitions, respectively. The photoluminescence (PL) spectra indicate that the PL of ensulizole is less Stokes-shifted in polar solvents and more Stokes-shifted in non-polar solvents. The average PL lifetime of ensulizole is longer in non-polar solvents as compared to polar solvents and it exhibits the shortest PL lifetime in aqueous medium that signi es its e ciency in water. This suggests in non-polar solvents intersystem crossing is the dominant mode of relaxation of the excited ππ* state. Furthermore, an increase of pH of ensulizole solution decreases the PL intensity and the lifetime.Stern-Volmer equation is employed to evaluate bimolecular quenching rate constant k q that suggests the diffusional dynamic mode of PL quenching is operative.

There are only scarce reports on using lanthanum cerates in water electrocatalysis. The electrocatalytic facility in water-splitting is manifested in two of the electrochemical output parameters: the lower onset potential and the higher peak current response. The robustness of the envisioned scheme of using lanthanum cerates perovskite (LaCeO 3 ; LCO) in combination with doped compositions provides better electrochemical results for water-splitting when comparing to the use of costly metallic or alloy nanomaterials. Lanthanum cerates were researched for the B-site doping effect on the resulting chemistry for the water electrocatalysis. Series of LaCe 1-x M x O 3+δ (LCMO; M = Fe 3+ , Cr 3+ , Cu 2+ , Zn 2+ ; x = 0.02─0.10) nanopowders were synthesized and tested electrochemically by using cyclic voltammetry and impedance analysis for water-splitting in alkaline methanol at ambient conditions. The oxygen evolution reaction (OER) was evidenced by the multifold water-splitting current with perovskite powders coated on to the glassy carbon (GC) electrode. An obvious correspondence was detected between the electrocatalytic activity and the morphological, structural properties of perovskite ceramic powders.