In situ growth of gold and silver nanoparticles onto phyto-functionalized boron nitride nanosheets: Catalytic, peroxidase mimicking, and antimicrobial activity

This is the first report on a green and sustainable approach for the in situ growth of gold (Au) and silver (Ag) nanoparticles onto h-boron nitride nanosheets (BNNs) surface, through the use of gallnut extract (GNE) as a natural and potential reducing agent instead of chemical reductants, commonly reported for their harmful effects on the environment and human health. BNNs were synthesized by ultrasonic exfoliation of boron nitride using GNE. GNE functional groups on BNNs surface were able to act as reducing sites for metal salts enabling the in situ growth of either Au or Ag nanoparticles on their surface. The synthesized Au-BNNs and Ag-BNNs nanohybrids were characterized in terms of transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray photoelectron spectroscopy (EDS), X-ray diffraction (XRD), UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) techniques. UV–visible spectroscopy confirmed the formation of Au and Ag nanoparticles at 517 and 391 nm. The size of Au and Ag nanoparticles grown on BNNs surface was approximately 4 and 7 nm, respectively. XRD and XPS also confirmed the formation of nanoparticles onto BNNs. FTIR analysis revealed that most of the GNE functional groups present on BNNs were not observed in Au-BNNs and Ag-BNNs spectra, confirming the reduction of metal ions by polyphenols present on BNNs. The produced Au-BNNs and Ag-BNNs nanohybrids displayed a 4-nitrophenol reduction of 88.7 and 76.5%, respectively, with a greater peroxidase mimicking activity compared to either nanoparticles or BNNs alone. The antimicrobial activity of the synthesized nanocomposites was evaluated against Escherichia coli and Staphylococcus aureus. Regardless of the bacterial strain, Ag-BNNs nanohybrids showed higher antimicrobial potential in inhibiting bacterial growth compared to the pristine Ag nanoparticles, with a higher antibacterial effect against Gram-positive than Gram-negative bacteria. Our results present new elements regarding BNNs-based nanohybrids which may help expand their applications in various fields such as catalyst, antimicrobial, biomedical, biosensor, and fillers in polymer matrix.