Low-cost high-performance fiber-optic pH sensor based on thin-core fiber modal interferometer

A new fiber-optic pH sensor based on a thin-core fiber modal interferometer with electrostatic self-assembled nanocoating is presented. After inserting a segment of thin-core fiber into a standard single-mode fiber, high-order cladding modes are excited and interfere with the core mode to form an in-fiber modal interferometer. The side surface of the sensor is then deposited with poly(allylamine hydrochloride) and poly(acrylic acid) nanocoating by electrostatic self-assembly technique. A fast and linear response is obtained in either acid or alkali solution (in the pH range 2.5 to 10) with resolution of 0.013 pH unit.

A novel flocculant of Al(OH)3–polyacrylamide ionic hybrid

A novel flocculant based on hybrid Al(OH)(3)-polyacrylamide (HAPAM) has been synthesized using a redox initiation system ((NH(4))(2)S(2)O(8)-NaHSO(3)) at 40 degrees C in aqueous medium. The HAPAM was characterized by viscometry, IR spectroscopy, TEM, conductivity, and TGA. The flocculation behavior for 0.25 wt% kaolin suspension was evaluated by spectrophotometry and phase contrast microscopy. It was found that an ionic bond exists between Al(OH)(3) colloid and polyacrylamide (PAM) chains in the HAPAM and the flocculation efficiency of HAPAM is much better than that of commercial polyacrylamide (PAM) and PAM/AlCl(3) blend.