Development of polysilazane-based coatings embedding AgNPs-decorated silica nanospheres for further antimicrobial applications

Amid global concerns regarding the proliferation of superbugs and viruses, new antimicrobial coatings have been explored to devise innovative solutions. In this context, this work presents a novel approach not previously reported in the literature, involving the synthesis of a composite coating composed of a polymeric ceramic precursor and silica nanoparticles decorated with silver nanoparticles. These nanoparticles are produced through a sol-gel synthesis process; subsequently, they are incorporated into a polymeric matrix to introduce silver as the antibacterial agent. The resulting coating is manually applied onto soda lime substrates. The characterization process unfolds in two phases. Firstly, the silver-decorated silica nanospheres undergo examination via field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis to confirm the synthesis of silver nanoparticles onto silica nanospheres and to evaluate their morphology, structure, and concentration. The antibacterial effectiveness of the synthesized filler is then demonstrated through a zone of inhibition test using Staphylococcus epidermidis. Subsequently, the coating, comprising a polysilazane as a ceramic precursor (commercially known as Durazane 1800) and the filler, was characterized in the same way, evaluating its morphology, composition, and structure. Additionally, the antibacterial efficacy is verified by means of the zone of inhibition test. After incorporation into the polymeric matrix, the resulting composite coatings were homogeneous and dense. Structural characterization by X-ray diffraction confirmed the presence of metallic silver in the coatings, while scanning electron microscopy showed that the nanospheres were evenly dispersed within the polysilazane matrix but mostly encapsulated. Antibacterial tests on the coatings did not show an inhibition zone, likely due to the limited exposure of the silver nanoparticles caused by the dense and non-porous nature of the matrix. These findings highlight the importance of optimizing matrix porosity and surface accessibility in future studies to enhance the antibacterial performance of such hybrid coatings.