Surface properties-dependent antifungal efficiency of Ag/SiO2 nanocomposites

The production of silver nanoparticles (Ag NPs) is important for antibacterial and antifungal applications. Many studies utilized natural resources (e.g., biopolymers and rice husk silica) for Ag NPs' synthesis and stabilization, but few of them reported the effect of surface charge on the products' antifungal performance. This study uses biopolymers (i.e., chitosan (CTS) and carboxymethyl cellulose (CMC)) to synthesize Ag NPs and investigate their impact on Ag NPs morphologies, surface charge, and antifungal properties. Two functional nanocomposites (NCs) based on Ag NPs were developed via a chemical method using either (i) CTS or CMC as a stabilizing agent and (ii) rice husk silica as a supported material. Both stabilizers produce well-dispersed Ag NPs on the silica surface, with CTS-stabilized NCs showing a positive surface charge (51.1 mV) and CMC-stabilized NCs exhibiting a negative surface charge (- 64.1 mV). Antifungal experiments revealed that both NCs effectively inhibited the mycelial growth of P. palmivora and P. oryzae. The positively charged NC exhibited the strongest activity against P. palmivora, whereas the negatively charged NC was the most effective against P. oryzae. These results emphasize the benefit of using stabilizing agents to boost the antifungal performance of Ag NPs.