High Sensitivity In-Situ Copper (∏) Detection of Chitosan Based on the Knotted-Shaped Fiber

A novel fiber sensor which can detect the concentration of copper ions indirectly was proposed and demonstrated by coating the knotted-shaped fiber with chitosan. The diameter of the knotted-shaped fiber was determined to be 10 mm. The Mach-Zehnder Interference generated due to bending deformation that excited some core-modes into higher order cladding-modes and two modes interfered. Chitosan was selected as the identification material for coating the fiber. In order to enhance the chelation between chitosan and copper ions, and improve the sensitivity of copper ions, glutaraldehyde was used to chemically modify chitosan. The original fiber sensor was annealed to obtain a stable structure, and then it was immersed in the modified chitosan solution and deionized water to form an available chitosan coating on the surface of the sensor. In the detection experiment with copper ions concentration of 0-330 ppm, the results show that interference spectra uniformly red-shift with the increase of the copper ions concentration and the sensitivity of the copper ion was 24.6 pm/10ppm. At the same time, ideal spectral fluctuations were demonstrated in the stability inquiry experiments.