Synthesis of copper nanoparticles with controllable crystallinity and their photothermal property

Synthesis of copper (Cu) nanoparticles in aqueous solution is of great challenge due to their tendency to oxidization upon exposure to air. In this work, well crystallized Cu nanoparticles with diameters of about 80 nm were successfully prepared in aqueous solution via simply reducing copper salts by sodium hypophosphite at presence of hydrochloric acid, and with polyacrylamide (PAM) as the capping agent. Experimental results showed that the presence of H+ facilitated formation of Cu nanoparticles and the crystallinity of the nanoparticles is highly dependent on Cl- concentration. Meanwhile, the size and morphology of the resulted nanoparticles could be controlled by concentration of PAM. The obtained Cu nanoparticles were further uniformly distributed in polyvinyl alcohol, forming a Cu-PVA hydrogel, which showed a significant photothermal conversion efficiency as high as 23.9% upon laser illumination. Continuous cycling test confirmed the long-term photothermal performance of the Cu-PVA hydrogel, and a bacterial killing efficiency of more than 99% could be realized after incubating it with E. coli under laser irradiation for 10 min. Besides, the prepared Cu nanoparticles may find practical applications in electronic and catalytic areas where the properties are closely related to nanoparticles crystallinity.