Thermal behavior, morphology and antibacterial properties study of silica/quercetin nanocomposite materials prepared by sol-gel route

The sol-gel process was used to synthesize four organic/inorganic hybrid materials by entrapping different amounts of quercetin (Q), namely 5, 10, 15 and 20 mass%, in a silica (S) matrix. A detailed characterization focused on revealing the nature of the bonds between the inorganic and organic components was performed by Fourier transform infrared (FTIR) spectroscopy. Silica/quercetin (SQ) hybrid materials showed an increase in the mass loss percentages of the first decomposition step with increasing the amount of Q, thus suggesting the incorporation of Q in the hybrid materials and a stabilization of the structure by hydrogen bonds. The morphology of the SQ hybrids investigated by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS) confirmed a regular size distribution of the particles and a homogeneous distribution of quercetin in the silica matrix in the suitable expected ratio. Furthermore, the SEM images confirmed the absence of contaminants during the sol-gel synthesis. Finally, the antibacterial properties of the SQ hybrid materials were tested using four (two Gram-positive and two Gram-negative) bacteria strains. The results demonstrated that they can be proposed as valuable antibacterial agents against Escherichia coli and Pseudomonas aeruginosa as Gram-negative bacteria and Staphylococcus aureus and Enterococcus faecalis as Gram-positive for amounts above 50 mg.