Thammika Srisamana and Anyarat Watthanaphanita,b*
a Material Science and Engineering Program, Faculty of Science, Mahidol University, Nakhon Pathom, 73170, Thailand
b Department of Chemistry, Faculty of Science, Mahidol University, Nakhon Pathom, 73170, Thailand

This research focuses on developing a method for synthesizing hybrid nanoparticles composed of gold nanoparticles (AuNPs) and nitrogen-doped carbon dots (CDs). These materials have potential applications in nanotechnology, sensing, and biomedical fields. The synthesis involves a two-step process. First, we used a hydrothermal method to prepare CDs from mangosteen peel extract, a natural source that is both sustainable and environmentally friendly. These CDs emit green light, making them suitable for optical applications. In the second step, we synthesized AuNPs/CDs hybrid colloids by applying plasma to a solution containing CDs and a gold precursor, specifically gold(III) chloride trihydrate. We systematically investigated key factors influencing the synthesis, including the concentration of CDs, the presence of sodium alginate as a stabilizer, and the duration of plasma discharge. These parameters significantly affected the size, stability, and optical properties of the resulting nanoparticles. Notably, incorporating gold into the CDs led to a blue shift in their luminescence, meaning that the emission color changed from green to a shorter wavelength, indicating modifications in electronic properties. This study provides valuable insights into controlling the synthesis of hybrid AuNPs/CDs for various advanced applications. The findings emphasize the importance of precise experimental conditions in tailoring nanoparticle properties for future use in nanotechnology, materials science, and medical diagnostics.