Facile Synthesis of Fe-Doped Hydroxyapatite Nanoparticles from Waste Coal Ash: Fabrication of a Portable Sensor for the Sensitive and Selective Colorimetric Detection of Hydrogen Sulfide

[Image: see text] In this work, a new strategy has been reported for the portable detection of H(2)S based on Fe-doped hydroxyapatite nanoparticles (Fe-HA) using a colorimetric paper test strip integrated with a smartphone platform. Fe-HA NPs were fabricated successfully via recycling waste coal ash. The obtained probe response toward H(2)S was through a distinct visual color change. The sensing mechanism is based on the displacement reaction, in which PO(4)(3-) is replaced by S(2-). The prepared test strip shows high selectivity, and the other compounds containing thiol and sulfur anion have a negligible effect on the detection of H(2)S. The designed scheme is applied for H(2)S detection in the concentration range of 0.5–130 ppm with a limit of detection of 70 ppb. Furthermore, such a disposable sensor was used as a practical system for monitoring H(2)S in actual water samples, suggesting the promising potential of this platform for suitable analysis of H(2)S in an aqueous environment.