Room temperature gas sensing properties of tubular hydroxyapatite

Abstract

Tubular hydroxyapatite (HAp) was prepared by a combined method of cation exchange membrane-assisted and electrochemical deposition. For comparison, rod-like HAp was also fabricated by the hydrothermal method. The products were characterized by scanning electron microscope (SEM), X-ray diffraction analysis (XRD) and Brunauer–Emmett–Teller (BET) analysis. The gas sensing properties toward ammonia were studied particularly. The selectivity to various volatile organic compounds was also investigated, then, the response and the recovery time were determined. Results showed that the hollow mesoporous and nanocrystalline nature are the key factors that increases the sensing properties of HAp. Tubular HAp based sensors exhibit 1.35–1.65 times of response value to ammonia than the rod-like based one. At the concentration of ammonia of 2000 ppm, the response value of HAp tubes was up to 84.58%, and the response time was as short as 10 s. Even at a low concentration of 50 ppm, the response was still detectable. Furthermore, tubular HAp shows great stability and reproducibility for gas sensing. Results also indicated that tubular HAp has obvious response to various gases, but has the highest response to ammonia. The growth mechanisms of tubular HAp and the gas sensing mechanisms were proposed.