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.