Sustainable green synthesis of Gulbakawali (GB) leaf extract-based GB-LaAgO2 and GB-LaCoO3 nanoparticles was studied for enhanced catalytic and antifungal applications. Primarily, the formation of lanthanum-based metal oxide nanoparticles (LaMNPs, where M = Ag, Co) was detected by UV-visible spectroscopy via changing the color of the solutions from cream white to reddish and unchanged light cream white during reaction and showing new surface resonance plasmon (SRP) bands at 261, 580 nm for AgNPs and 254, 329 nm for CoNPs, respectively. Phytochemical analysis supports that the Gulbakawali plant extracts containing flavonoids, alkaloids, terpenoids etc. are responsible for the reduction and oxidation of Ag+1 to Ag0 and Co+2 to Co+3 during the reaction without adding any capping agent. Synthesized GB-LaMNPs were characterized by different spectroscopy analyses. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses revealed that the average crystallite and particle sizes were 16.08 ± 1 and 14.8 ± 1 nm for GB-LaAgO2 and 15.53±1 and 42.3 ± 1 nm for GB-LaCoO3, respectively. XPS study reveals that lanthanum, silver, and cobalt were present in +3, +1, and +3 oxidation states with satisfied valences of the metal ions and supported the composition formula of GB-LaAgO2 and GB-LaCoO3. The band gap energies for the GB-LaAgO2 and GB-LaCoO3 nanoparticles were found to be 5.24 and 5.21 eV, respectively. The catalytic reduction of 2,4,6-trinitrophenol (picric acid) to 2,4,6-triaminophenol is better in the presence of GB-LaAgO2 compared to GB-LaCoO3, and its rate constant (k) is 6.47 x 10−3 s−1. Similarly, the antifungal activity of GB-LaAgO2 shows better result compared to GB-LaCoO3 against Alternaria alternata and Fusarium oxysporium phytopathogenic fungi microbes. In the presence of GB-LaAgO2, the radial mycelial growth of A. alternata was reduced to 78.39 ± 3.08% at 0.5 mg/mL, 81.40 ± 0.90% at 1 mg/mL, and 85.42±2.34% at 1.5 mg/mL concentrations respectively. For F. oxysporium, GB-LaAgO2 showed 62.94 ± 2.58, 70.04 ± 1.67, and 81.02±0.93% inhibitions at the same concentration, demonstrating a clear dose-dependent antifungal effect.
Satpute et al. (Mon,) studied this question.