Spectral, antimicrobial, TGA and photocatalytic degradation studies of copper neem–urea complex using synthetic, nano and doped ZnO

Abstract

ABSTRACT Present paper reports the synthesis of copper neem–urea (CNU) complex through reported methods and is characterised by elemental and spectroscopic techniques such as IR, NMR and ESR. The nanoparticles of ZnO and ZnO doped with SiO2 which was extracted from industrial ashes were synthesised by precipitation method and characterised by UV, SEM-EDX and XRD techniques. Kinetics of degradation for the synthesised complex in solid-state was studied using thermogravimetric analysis technique (TGA). For kinetic analysis, Freeman Carroll, Coats–Redfern, Horowitz–Metzger, Broido and Piloyan–Novikova equations have been used to calculate the energy of activation as well as other thermodynamic parameters, i.e. Gibbs free energy (∆G), enthalpy (∆H) and entropy (∆S). The photocatalytic degradation was carried out by irradiating the solutions of CNU containing ZnO by UV and sunlight in different solvents. Studies suggested that the use of photocatalyst may enhance the degradation rate of CNU at normal temperatures. The disappearance of copper surfactants follows a pseudo-first-order kinetics according to the Langmuir–Hinshelwood (L-H) model. A tentative mechanism has been proposed for the photodegradation of copper surfactants. The doped ZnO with SiO2 was found to be the best catalyst in comparison to nano and synthesised ZnO for photodegradation studies. Antibacterial and antifungal studies have been done to understand the biological applications of the molecule against some bacteria and fungi which may cause skin diseases. The toxicity patterns of CNU on Staphylococcus aureus, Coagulase-negative staphylococci (CoNs), Acinetobacter baumanii, Pseudomonas aeruginosa, Micrococcus bacteria and Candida tropicalis, Candida parapsilosis, Rhodotorula and Trichophytonrubrum fungi at varying concentrations using Mueller Hinton Agar plate’s technique have been studied, analysed and also been reported here.