Biosynthesis of ZnO and Ag/ZnO nanoparticles from Chrysophyllum cainito seed, leaf and stem-bark extracts for the photocatalytic degradation of methyl orange and antimicrobial application

Green synthesis is environmentally friendly, and one-step method with a notable advantage over a host of numerous other synthetic methods. This study used three plant extracts of Chrysophyllum cainito as stabilizing and as reducing agents in green synthesis of ZnO and Ag doped ZnO nanoparticles. The synthesized nanoparticles were characterized using XRD, FTIR, TEM, SEM-EDS and UV–visible techniques. The UV–visible absorption spectra showed two distinct absorption peaks at 240 nm and 296 nm. FTIR showed intense and broad O-H vibrational mode between 3419.45 cm −1 - 3696.24 cm −1 for ZnO and AgNPs. The SEM results confirm the formation of sub-100nm sized particles while EDS revealed the presence of elemental silver in SSN, LSN and SN samples. The XRD revealed the most intense peak of (111) showing Ag and ZnO samples with face cubic centered shape. TEM micrographs showed shiny spots and quite narrow size distributions with particle sizes of 5.65 nm, 4.51 nm, 4.30 nm and 5.70 nm for SN, SSN, LSN and LDW. The photocatalytic degradation of azo dye, methyl orange was also studied with the undoped ZnONP and doped Ag/ZnO nanoparticles as catalytic agents. The results showed that methyl orange experienced faster degradation of 89% in 25 min at 25 °C with SN sample compared to undoped ZnONP under the same conditions. Antimicrobial results revealed that samples SSN and LSN showed no activity against Bacillus subtilis at 50 and 25 mg/mL, while LDW and SSN have no activity against the bacteria Klebsiella , at 50 and 25 mg/mL.