New Study Highlights Hybrid Nanocomposites as a Dual Solution for Microbial Resistance and Pollution

By Dr. Noopur JainReviewed by Bethan DaviesFeb 21 2025

A recent study published in Scientific Reports explores the dual functionality of silica-based nanocomposites in antimicrobial and photocatalytic applications.

The researchers investigated how these hybrid materials could address microbial resistance while simultaneously combating environmental contamination, demonstrating their potential to enhance the efficacy and safety of existing treatments. The study focused on synthesizing and characterizing crystalline silica (C-SiO₂), silver-silica (Ag-SiO₂), and zinc oxide-silica (ZnO-SiO₂) using environmentally friendly methods.

Background

Antimicrobial resistance is an escalating public health challenge, with conventional therapies often proving ineffective against resistant bacterial strains. At the same time, rapid industrialization and urbanization contribute to increasing environmental pollution, highlighting the need for materials that can both eliminate pathogens and degrade pollutants efficiently. While photocatalytic materials show promise in antimicrobial applications, they face limitations such as low efficacy under visible light, potential toxicity, and economic feasibility. This underscores the demand for advanced nanocomposites that offer enhanced efficiency in microbial treatment while supporting environmental remediation.

Hybrid nanocomposites like C-SiO₂, ZnO-SiO₂, and Ag-SiO₂ combine the advantageous properties of metal oxides, semiconductors, and silica, making them particularly effective for antimicrobial and photocatalytic functions. Their antibacterial effects primarily stem from reactive oxygen species (ROS) generation, metal ion release, and electrostatic interactions. However, the precise mechanisms remain partially understood, necessitating further investigation into their comparative performance and multifunctionality.

The Current Study

To develop these nanocomposites, the researchers utilized green synthesis techniques with natural precursors. Rice husk served as the raw material for C-SiO₂ nanoparticles, undergoing cleaning, air-drying, and combustion at high temperatures in a controlled environment to produce rice husk ash. Green tea and aloe vera extracts acted as reducing and stabilizing agents in the synthesis of Ag-SiO₂ and ZnO-SiO₂ nanocomposites.

Various analytical techniques were employed to characterize the synthesized materials. UV-visible spectroscopy measured light absorption characteristics, X-ray diffraction (XRD) identified crystalline phases, and Fourier transform infrared spectroscopy (FTIR) confirmed the presence of functional groups, indicating successful material formation. Scanning electron microscopy (SEM) provided insights into particle morphology and size.

To assess antimicrobial efficacy, the researchers conducted disc diffusion tests against pathogenic bacteria, including Gram-positive and Gram-negative strains. This involved preparing bacterial suspensions, plating them on nutrient agar, and applying nanocomposite-infused discs to measure inhibition zones.

Results and Discussion

UV-visible spectroscopy revealed distinct absorption peaks for C-SiO₂ nanoparticles in the 200–300 nm range, confirming the successful synthesis of high-purity SiO₂-based materials. The absence of significant peaks in the visible spectrum indicated minimal impurities, reinforcing sample integrity. Optical properties were further analyzed using Tauc's plots to determine the optical bandgap, a crucial factor in photocatalytic applications.

FTIR analysis validated the formation of nanocomposites through characteristic functional groups, while XRD profiles aligned with standard JCPDS cards, confirming their crystalline nature.

In antimicrobial testing, Ag-SiO₂ and ZnO-SiO₂ nanocomposites exhibited strong inhibition against E. coli and Staphylococcus aureus, with inhibition rates of approximately 80 % and 88 %, respectively. The photocatalytic efficiency of these materials was assessed through the degradation of synthetic dyes, with the ZnO-SiO₂ composite achieving a 75 % degradation rate for p-nitroaniline, highlighting its effectiveness in pollutant remediation. These results suggest that integrating silver and zinc oxide into silica matrices significantly enhances both antibacterial and photocatalytic performance.

Despite these promising findings, the study identified certain challenges. Long-term stability remains a concern, as prolonged exposure to light and ROS could affect structural integrity and effectiveness. Additionally, scalability and maintaining uniform particle sizes in large-scale production require further refinement.

Conclusion

This study underscores the multifunctional potential of C-SiO₂, Ag-SiO₂, and ZnO-SiO₂ nanocomposites, synthesized using sustainable green methods. Their strong antimicrobial and photocatalytic properties position them as viable alternatives to conventional treatments, addressing both microbial resistance and environmental pollution. With promising reusability and antioxidant activity, these hybrid materials hold significant potential for environmental remediation and biomedical applications.

Future research should focus on enhancing the stability and scalability of these nanocomposites, optimizing their properties for broader applications in global health and environmental sustainability.

Journal Reference

Ali A., Ali S.R., et al. (2025). Comparative study of silica and silica-decorated ZnO and ag nanocomposites for antimicrobial and photocatalytic applications. Scientific Reports 15, 5010. DOI: 10.1038/s41598-025-89812-5, https://www.nature.com/articles/s41598-025-89812-5