DOI: https://doi.org/10.55373/mjchem.v27i5.190

Keywords: Blue graphene quantum dots; gold nanoparticles; fibre optic sensor; microwave; optical signal

Abstract

Graphene quantum dots (GQDs) and gold nanoparticles (AuNPs) are recognized as promising materials for sensing applications due to their exceptional photochemical properties. This study investigates the impact of AuNPs of sizes 30, 60, and 90 nm, when conjugated with blue-emission graphene quantum dots (b-GQDs), on the performance of a fibre optic sensor. The AuNPs were prepared using a seeding-growth method, while b-GQDs were synthesized through a microwave-assisted method. Characterization techniques, including UV-visible (UV-Vis) spectroscopy, fluorescence spectrophotometry, Zeta size analysis, and X-ray diffraction (XRD), were employed to confirm the optical properties, particle size, and crystallinity of the samples. Compared to the uncoated fibre optic probe, the 30 nm AuNPs coating alone enhanced the sensor signal by 42.5%, while the b-GQDs coating resulted in an 84.9% improvement. Remarkably, the hybrid structure of b-GQDs with 30 nm AuNPs achieved the highest signal enhancement of 143.5%, surpassing hybrids with larger AuNP sizes. These findings revealed a synergistic effect between b-GQDs and smaller-sized AuNPs, making it beneficial for the development of a highly sensitive fibre optic sensor.