Ag/SiO2 colloidal nanocomposites (NCs) were prepared through the semi-continuous chemical reduction of silver ions on a silica surface; NaBH4 was used as a primary reducing agent, while carboxymethyl cellulose (CMC) served as a secondary reductant and a stabilizer at low temperature. Silver nanoparticles (AgNPs) of an average diameter of 3.89±0.18 nm were uniformly and densely dispersed on the SiO2 surface, forming 218.6-nm-sized Ag/SiO2 NCs. The zeta potential of the Ag/SiO2 NCs (−92.6 mV) was more negative than that of silica (−24 mV), indicating their high long-term stability. Furthermore, their proposed formation mechanism was confirmed via Fourier transform infrared spectroscopy. Then, the bactericidal effect of the Ag/SiO2 was evaluated based on their minimal inhibitory concentration (MIC) against Ralstonia solanacearum 15 (R. solanacearum 15); it was 62.5 ppm, much lower than that of conventional AgNPs (500 ppm). Therefore, these highly stable Ag/SiO2 colloidal NCs with more effective antibacterial activity than conventional AgNPs are a promising nanopesticide in agriculture.

Herein, the effect of reaction time in the cationic exchange method on the CdS/Ag2S structure and photocatalytic activity is investigated. A hydrothermal approach is used to produce CdS nanorods, and then a cation exchange method is applied to synthesize CdS/Ag2S composites. The heterostructure between CdS and Ag2S is determined by the X‐ray diffraction and transmission electron microscopy studies. Comparing pure CdS NRs and CdS/Ag2S by the UV–vis diffuse reflection spectra data, the introduction of Ag2S is proven to enhance the light absorption in visible region. The Brunauer–Emmett–Teller method indicates that CdS and CdS/Ag2S are mesopore materials and the specific surface areas of CdS, CdS/Ag2S‐15, CdS/Ag2S‐30, and CdS/Ag2S‐60 samples without and with a cation‐exchange reaction time of 15, 30, and 60 min are 305, 900, 187, and 52 m2 g−1, respectively. The photocatalytic activity of CdS/Ag2S is examined through the ciprofloxacin photodegradation. The ciprofloxacin degradation rate increases with the introduction of CdS and reached a maximum value of 60% within 180 min for CdS/Ag2S‐15 under simulated sunlight irradiation, which is 1.5 times greater than that of pure CdS. The ciprofloxacin degradation rate decreases as the cation‐exchange reaction time is increased to 60 min (26% after 180 min illumination).