Aqueous Precipitate of Methanolic Extract of Bergenia ciliata Leaves Demonstrate Photoirradiation-Mediated Dual Property of Inhibition and Enhancement of Silver Nanoparticles Synthesis

Background: The aqueous and methanolic extracts (AE and ME) of Bergenia ciliata leaves have contradictory silver nanoparticles (AgNP) synthesis potential, influenced by photoirradiation. Method: In the current study, photoirradiation-mediated AgNP synthesis potential of two sub-extracts of ME, namely aqueous precipitated ME (PME) and aqueous dissolved ME (DME), were studied through comparison of their physicochemical properties. Results: In dark, DME demonstrated significant AgNP synthesis, whereas PME did not synthesize AgNPs. However, photoirradiation reversed the role of both the sub-extracts in nanoparticles synthesis. PME also demonstrated an inhibitory effect on AE-mediated AgNP synthesis in dark. GC-MS identified pyrogallol as the major reducing agent in both the sub-extracts. Photoirradiation significantly influenced the nanoparticle size and percent elemental composition of the AgNP. In dark, PME and DME produced AgNP of approx. 23.94 nm and 31.08 nm diameters, respectively, which significantly increased to 47.26 nm and 47.48 nm, respectively, on photoirradiation. Although no significant change in the percent silver composition was observed in PME-AgNP on photoirradiation (approx. 68%), DME demonstrated enhanced silver percent from approx. 58% to 72% on photoirradiation. Both DME- and PME-AgNPs were stable up to 15 days at 4 °C. Conclusions: PME has photoirradiation-mediated dual property of inhibition and enhancement of AgNPs synthesis.