Sensitive cadmium detection using chitosan-coated plastic optical fiber

An optical sensor based on a plastic optical fiber (POF) was developed using PVA-borate-chitosan Coating as a reagent for detecting cadmium in water. The coating is made as a hydrogel containing chitosan that varied in 10 wt% and 20 wt% as an absorber of cadmium ions and was supported by sodium tetraborate and polyvinyl alcohol (PVA) to form a hydrogel reagent matrix. This reagent is coated on an unclad Plastic Optical Fiber (POF) formed in a U-shaped configuration with variations of 1, 2, and 3 layers. The structure of the reagent is characterized by X-ray diffraction (XRD), and the homogeneity of the optical fiber is observed using an Optical Microscope (MO). Sensor testing is carried out using an optoelectronic device based on Autonics BF5, which shows the best performance results are obtained by using a chitosan concentration of 10 wt% and three layers due to the weakening of the layer due to the formation of the U configuration. Photoluminescence and Scanning Electron Microscopy Energy Dispersive X-ray spectroscopy (SEM-EDX) results show that cadmium ions have been bound to the reagent layer to form non-radioactive recombination and chelate complexes. The cadmium solution is characterized using Ultraviolet-Visible Spectroscopics (UV-Vis), indicating that some dissolved elements in the solution so that the sensor was not compatible with repeated use. However, the Atomic Absorption Spectroscopy (AAS) results of the cadmium solution showed a reduction in cadmium levels of 33.82 % after testing. The reductions indicate that the sensor can bind and detect Cadmium with high sensitivity and low resolution of 88.69 dB/ppm and 1.13 × 10 −4 ppm, respectively. This PVA-borate-chitosan coating-based fiber optic sensor has great potential in developing cadmium detection devices in water that have high sensitivity, high selectivity to heavy metal ions, flexibility, low cost, and are environmentally friendly.