Potential of hybrid gold nanoparticles/graphene oxide (AuNPs/GO) coated single mode fiber (SMF) sensor by exploiting localized surface plasmon resonance (LSPR) effect for Musta’mal water identification was studied. Three structure shapes of fiber optics such as straightshape, loop-shape and u-shape had been prepared. Three layers of AuNPs with 50 nm in diameter were drop-casted onto the partially unclad polished single mode fiber (SMF) to observe the maximum sensitivity of LSPR. To enhance the LSPR effect, one layer of GO was deposited on top of the AuNPs layer. Two optical light sources with least attenuation (1310 nm and 1550 nm) were employed to study the optical power output as the sensor immersed in different type of water samples. The u-shape SMF portrayed the maximum output power about 24.2 dBm at 1550 nm wavelength. According to the analysis, the deployment of 1550 nm laser wavelength resulted in better sensitivity with 23.2% improvement compared to 1310 nm wavelength. Apparently, the LSPR phenomenon created by AuNPs/GO able to enhance the plasmonic signal up to 51.9% than the uncoated SMF. The thinnest diameter of SMF’s cladding, d=0.1195 mm with U-shape structure exhibited the highest power different of 1.10 dBm, in which suggested the best sensing performance. In conclusion, the optimization of AuNPs/GO u-shape polished SMF resulted in the maximum sensitivity with value of S=72.7 dBm/RIU for Musta'mal water identification.

This work is carried out to study the effect of noble metal thicknesses, namely gold and silver on the SPR characteristics for smart food packaging technology applications. A Kretschmann prism coupling was introduced to excite surface plasmon polaritons (SPP). The optical refractive indices values of gold and silver were set as Rgold=0.1759+3.4104i and Rsilver=0.0585+4.2665i respectively. The thicknesses of noble metal thin films were varied between t=25nm and 95nm with the increment of 10nm for each reading. SPR signal analyses were performed by studying the characteristics of SPR peaks such as Q-factor and FWHM. Both analyses demonstrated an outstanding optical properties of silver at t=55nm in comparison with gold due to its low FWHM and high Q-factor values which proves its ability to generate excellent amount of SPP. The employment of silver witnessed the enhancement of Q-factor value up to 7.09% and the decrement of FWHM about 76.58%, relatively with gold. The introduction of silver able to convert 87.20% SPP, whilst the usage of gold only capable to excite 81.4% SPP. In conclusion, application of silver noble metal at t=55nm able to generate maximum SPR. This excellent criterion placed silver as a spectacular candidate in the development of low cost and high sensitive SPR sensor for food quality assessment applications.

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