Green synthesis of silica-coated gold nanoparticles employing femtosecond laser, solid targets, and water.

Gold nanoparticles are widely used in biomedical applications due to their unique properties. However, traditional synthesis methods generate contaminants that cause cytotoxicity and compromise the biocompatibility of the nanomaterials. Therefore, green synthesis methods are essential to produce pure and biocompatible nanoparticles, ensuring their effectiveness in biomedical applications. This study introduces a novel approach for synthesizing silica-coated gold nanoparticles (AuNP@SiO₂) using femtosecond laser ablation in water, eliminating the need for chemical reagents. The process involves three key laser-based steps: Si ablation, SiNP@SiO₂ fragmentation, and Au ablation, all conducted in a liquid environment. The resulting AuNP@SiO₂ were characterized using transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), and zeta potential measurements. The results demonstrated that the AuNP@SiO₂ nanoparticles exhibit high colloidal stability, with a notably negative zeta potential of (-72.0 ± 0.3) mV, effectively preventing particle aggregation. TEM analysis confirmed predominantly spherical nanoparticles with an average diameter of (15.87 ± 0.70) nm, encapsulated by a SiO₂ layer ranging from 1 to 3 nm in thickness. The synthesis approach produced nanoparticles with an average size distribution below 35 nm. This green synthesis method not only produces stable and well-characterized AuNP@SiO₂ nanoparticles but also represents a significant step towards more sustainable nanomaterial production, with promising implications for biomedical applications.