Synthesis of gold nanoparticles embedded graphene oxide for fibre optic gas sensor applications / Mohd Rafal Sahudin

In this work, graphene oxide (GO) was successfully synthesized with the optimization formulation obtained using 1g of graphite, 3g of potassium permanganate (KMnO4), 25 mL of sulfuric acid (H2SO4), 5 mL of hydrogen peroxide (H2O2) with 20°C of reaction temperatures and 3 hours of reaction time. The AuNPs were successfully synthesized with the optimum condition using 0.254 mM of gold chloride (HAuCl4) and 40 mM of trisodium citrate (NaCt). The composite structure of AuNPs embedded to GO (GOAuNPs) was performed by direct mixing of GO solution to AuNPs solution at various volume ratios (1:05, 1:1, 1:2.5, 1:5, 1:7.5, 1:10 and 1:15). Then, fabrication of GO, AuNPs, and composite GO-AuNPs (at various volume ratios) encapsulated optical fibre probes was performed via dipping process for 24 hours with the aid of vortex mixing. The detection using indoor air exposed the highest light intensity signal on the fibre optic sensor generated from the GO-AuNPs-based sensor at a volume ratio of 1:5 and 1:10. For spectral analysis, the highest CO2 detection was detected by fibre optic sensors with GO-AuNPs (1:5) as a coating material with 62.7% signal improvement from uncoated sensor probe, 26.4% higher than the signal from GO-coated and 33.9% better than AuNPs-coated sensor. The highest N2 detection was obtained by the sensor fabricated of GO-AuNPs (1:10) with the signal enhancement of 59.8% from uncoated probe sensors.