Identification of Recycled Cooking Oil by Varying Number of Au/GO Coated Fiber Optic’s Loop Ring

This study investigates the effect gold nanoparticles (Au)/graphene oxide (GO) coated fibre optics with various number of loop ring in identifying recycled cooking oil based on their frying time. Various layers of gold nanoparticles (AuNP) suspension were deposited onto the substrate via drop casting technique. Few material characterizations were performed such as Fourier Transform Infrared (FTIR) spectroscopy, Ultraviolet Visible (UV-Vis) spectroscopy and refractometer analysis. Three macrobending structures of Au/GO coated fiber optic’s loop ring such as single, double and triple loops with diameter of 1.5cm were formed to generate large area of evanescent field around the fibre and to excite surface plasmon polaritons due to the interaction between AuNPs and analytes. Cooking oil samples with different frying time such as 14 minutes, 28 minutes and 42 minutes were prepared as analytes. The FTIR analysis revealed some changes in the transmittance percent of some bands as well as some slight shifts in the exact position of the bands due to the different of fatty acid composition. As the Au/GO coated fibre optics were immersed into the samples, the penetration depths were obtained as 142.75nm and 168.91nm at operating wavelengths of λ=1310nm and λ=1550nm, respectively. By using 1550nm operating wavelength due to its greater penetration depth than 1310nm, triple loop rings fibre optics coated with two layers of AuNP and one layer of GO exhibits a linear consistency with maximum sensitivity up to 69.17% due to the formation of large evanescent field around the loop area and intense SPP excitation.