Graphene- and Multi-Walled Carbon Nanotubes-Coated Tapered Plastic Optical Fiber for Detection of Lard Adulteration in Olive Oil

A rapid and high-performance sensor for lard adulterant in edible oil was developed using the tapered plastic optical fiber (POF) coated with graphene and multi-walled carbon nanotubes. The coating material was deposited onto a tapered POF with a taper waist diameter and a taper length of 0.45 mm and 1 cm, respectively. The addition of the coating material was used to increase the sensitivity and selectivity coefficient of the tapered POF toward the lard substance. The sensing mechanism is based on a simultaneous interaction of lard substance and an evanescent wave of tapered POF with the coating layers. The results showed that graphene coating on the tapered POF increased the selectivity coefficient of the tapered POF towards lard substance from 33.54 to 324.19, and it gave a sensitivity of 0.427 dBm/%. In comparison, multi-walled carbon nanotubes coating increased the selectivity coefficient to 71.65 and increased its sensitivity to 1.189dBm/%. Thus, the proposed configuration of the tapered POF with the coating material offered a simple configuration for a rapid, high sensitivity and selectivity detection of lard adulterant in edible oils.