RETRACTED ARTICLE: Comparative study of silica and silica-decorated ZnO and ag nanocomposites for antimicrobial and photocatalytic applications
Arooj Ali, Syed R. Ali, Riaz Hussain, Rashida Anjum, Qiang Liu, Mohamed S. Elshikh, Noorah A. Alkubaisi, Rashid Iqbal, Sylwester Tabor, Marek Gancarz
Abstract
The increasing threat of multi-resistant infectious agents and environmental toxins has led to a demand for new therapeutic and catalytic materials. In this study, C-SiO₂ (crystalline silica), Ag-SiO₂ (silver-silica), and ZnO-SiO₂ (zinc oxide-silica) nanocomposites (NCs) were synthesized through green methods and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). These silica-based nanomaterials were investigated as potential photocatalysts for the degradation of p-nitroanilines and their antibacterial and antioxidant properties. XRD analysis showed crystalline sizes of 14 nm for C-SiO₂ NPs, 18 nm for Ag-SiO₂, and 20 nm for ZnO-SiO₂ NCs. UV-visible spectroscopy revealed energy band gaps of 4.5 eV for C-SiO₂ NPs, 3.23 eV for Ag-SiO₂, and 2.84 eV for ZnO-SiO₂. FTIR analysis confirmed the formation of SiO₂ in all samples through the Si-O-Si absorption peak. SEM revealed distinct morphologies: C-SiO₂ NPs as agglomerated granular particles, Ag-SiO₂ NCs as flattened rods or sheets, and ZnO-SiO₂ as roughly spherical. Antimicrobial testing showed that ZnO-SiO₂ and Ag-SiO₂ NCs exhibited 80% and 88% antimicrobial activity against Escherichia coli and Pseudomonas, with Ag-SiO₂ also demonstrating strong activity against Staphylococcus. The minimum inhibitory concentration (MIC) of Ag-SiO₂ and ZnO-SiO₂ NCs was found to be 80%, outperforming C-SiO₂ NPs. Antioxidant activity assays showed scavenging efficiencies of 45%, 57.8%, and 71% for C-SiO₂, Ag-SiO₂, and ZnO-SiO₂ NCs, respectively, at 30 mg/ml. ZnO-SiO₂ NCs also achieved a 75% degradation rate for p-nitroanilines, while Ag-SiO₂ achieved 45%. This study demonstrates that ZnO-SiO₂ and Ag-SiO₂ NCs are effective materials for disinfection and pollutant degradation, offering an eco-friendly solution for environmental and health challenges.