Improved photocatalytic, antimicrobial and photoelectrochemical properties of nanocrystalline Cu2+-doped ZnO nanoparticles

Abstract

Herein we present the first report on the synthesis of Cu2+-doped ZnO nanoparticles via the solution-combustion using a new fuel (Glutamine). Systematic studies were carried out to assess the influence of Cu2+-concentration on photocatalytic, antimicrobial, and photoelectrochemical characteristics through various characterizations such as XRD, SEM-EDS, FTIR, UV–Visible, photocatalytic, antimicrobial, photoelectrochemical and Photoluminescence. XRD results show the formation of single-phase nanocrystalline particles and the substitution of Cu2+ at the Zn2+ site without the occurrence of impurity phases. SEM & EDS analysis revealed almost spherical particles and nominal (measured and experimental) element compositions. The structural changes induced due to the substitution of Cu2+ into the ZnO host lattice are evident in FTIR data, which show the presence of stretched ZnO bonds. The band gap narrowing effect was observed up to 5 mol% Cu2+ and thereafter band gap widens. PL spectra exhibit multiple emission peaks related to defects present in the host ZnO induced by the Cu2+ & PL intensity increases with the increase of doping concentration up to 3 mol % of Cu2+ beyond that its decreases with increasing concentration. The prepared NPs demonstrate promising photocatalytic activity against MB dye in both the UV and visible ranges. The maximum 94% percentage degradation was recorded for 9 mol% CuZnO, which is the highest among CuZnO NPs reported to date. In addition, 3 mol% and 2 mol% CuZnO NPs have shown potential antimicrobial activity against Bacillus and Pseudomonas respectively. The possible mechanism for both photocatalytic activity and antimicrobial activity is demonstrated. Furthermore, 5 mol% CuZnO has shown the largest transient photocurrent of 1.147 mA/cm2, which is ∼12 times larger than undoped ZnO (0.096 mA/cm2) due to the band-gap narrowing, suggests the possibility of photoelectrochemical sensors.