Fiber-optic evanescent-wave absorption copper(II) sensor based on sol-gel-derived organofunctionalized silica cladding

A fiber-optic evanescent-wave absorption sensor was constructed on the basis of an organofunctionalized silica cladding. The cladding material was prepared by the sot-gel processing of an organofunctional silicon alkoxide, which contains a propyl-ethylenediamine triacetate (PEDTA) group. The PEDTA group can chelate with a Cu(II) ion to form a colored complex. Because of the large formation constant of the complexation reaction, a kinetic approach was used to quantify the Cu(II) content in samples. The sensor has a dynamic range of 0.5-100 ppm and a detection limit of 56 ppb. The measurement of the Cu(II) content in a scattering medium has also been demonstrated.