Detection of trace amounts of chromium(VI) using hydrogel coated Fiber Bragg grating

The present article investigates a hydrogel Coated Fiber Bragg grating (FBG) based sensor capable of detecting trace amounts of carcinogenic chromium(VI) metal ion. A stimulus responsive hydrogel encompassed with tetraalkylammonium salts which is specifically sensitive to Cr(VI) ion, is synthesized and coated on FBG. When the proposed sensor system is exposed to various concentrations of Cr(VI) ion solutions, FBG peak is shifted due to the mechanical strain induced by the stimulus swelling property of the hydrogel. The peak shift is correlated with the concentration of the Cr(VI) metal ion. Thus a Chemo-mechanical-optical sensing approach for the detection of Cr(VI) is studied. Trace amounts of chromium(VI) ion as low as 10 ppb can be estimated by the method. The resolution of the sensor system is found to be 0.83 ppb. The sensor has shown good sensitivity, selectivity, and repeatability.