Detection of Benzoic Acid Using Tapered Surface Plasmon Resonance Polymer Fiber

Excessive use of food additives such as benzoic acid negatively affects human health, leading to serious conditions such as liver failure, kidney failure and cancer. To detect benzoic acid in food, this project proposes the development of a surface plasmon resonance polymer optical fiber (SPR-POF) sensor. The sensor is fabricated by removing portion of the POF’s cladding and core, followed by coating it with a 5nm thick layer of gold (Au) film. The D-shaped POF structure after polishing was analyzed and examined using Field Emission Scanning Electron Microscopy (FESEM). A detectable change in the response of the sensor that occurs when it encounters different concentrations of benzoic acid, enabling the identification of its presence SPR-POF detects power loss with a discrete peak generated by a 650nm diode laser and a power meter is used to show the chemical fingerprint of benzoic acid. This allows quantitative and qualitative measurement of peak wavelength intensity, which in turn allows the detection of benzoic acid concentration. The main results show that the gold-coated and polished D-shaped optical fiber sensor has the lowest power loss of -7.6 dB at a concentration of 0.4 g/ml, with the lowest limit of detection (LoD) of 5.6 ng/mL indicating high sensitivity.