Rapid synthesis of triple-layered cylindrical ZnO@SiO₂@Ag core-shell nanostructures for photocatalytic applications

Core-shell nanocomposites are promising materials in the degradation of harmful chemicals released from industries/factories. In this work, ZnO@SiO₂@Ag triple–layered core-shell nanocomposites synthesized by a facile chemical precipitation route at 400 °C using as-prepared ZnO@SiO₂ samples as a precursor were investigated for photocatalytic application. The synthesized ZnO@SiO₂ and ZnO@SiO₂@Ag samples were characterized using XRD, SEM, TEM, XPS, and UV-Vis spectrometer. The XRD studies showed that both nanocomposites possess the hexagonal wurtzite crystalline phase of the core ZnO. Moreover, the average crystallite sizes of ZnO@SiO₂@Ag composites determined from the XRD spectra were found to be 27.98 nm and 30.56 nm for reaction times of 4 h and 12 h, respectively. The SEM and TEM analyses indicate that the morphologies of the samples were rod-shaped. The UV-Vis spectroscopy showed that the ZnO@SiO₂@Ag nanoparticles exhibited maximum absorbance peak at 363 nm with a calculated band gap energy of 3.13 eV. In addition, the photocatalytic activity and stability were analyzed by a photoreduction method using the photodegradation property of organic methylene blue under UV-Vis light irradiation. Compared with the “bare” ZnO@SiO₂ samples, the stability and photocatalytic performance of the Ag coated ZnO@SiO₂@Ag nanocomposites were highly enhanced, and the reasons for the enhancement are discussed.