A novel sulfhydryl-modified superparamagnetic photonic crystal sensing material for the simultaneous heavy metal ions detection and adsorption treatment

Abstract

A novel superparamagnetic photonic crystal (Fe3O4@SiO2@Sulfhydryl SPC) was successfully created for simultaneous visual detection and absorption of harmful heavy metal ions. This SPC was made by combining photonic crystal and superparamagnetic nanosphere technologies. During detection, Fe3O4@SiO2@Sulfhydryl nanospheres can move in the liquid sample and fully absorb the target substances. The detection range is from 1 μg/L to 5 mg/L, which corresponds to the critical concentration range for heavy metal ions in drinking water and sewage. The detection limit is 1 μg/L. In the detection process, the signal responded rapidly and remained stable when analyzed with a fiber optic spectrometer. Notably, the signal intensity decreased significantly, with a reduction of 62.22 a.u. for Hg2+ and 124.31 a.u. for Ag+. Simultaneously, the visual results were striking. The SPC changed color from orange (PC structural color) to the original reddish-brown color of the solution with the formation of magnetic aggregates (PC structural color disappeared). This SPC exhibits excellent sensitivity, offers a clear visual display, possesses strong absorption detection capabilities, is easy to use, cost-effective, and, importantly, does not cause secondary pollution. Furthermore, the harmful heavy metal ions absorbed by the SPC can be easily removed from the water sample using an external magnetic field, overcoming challenges related to efficient separation of the adsorbent material from wastewater. As a result, this SPC holds great promise for real-time visual monitoring and practical sewage purification processes.