"Two-in-one" sulfur and nitrogen co-doped fluorescent silicon nanoparticles: Simultaneous as the fluorescent probe and photocatalyst for in-situ real time visual monitoring and degradation of tetracycline antibiotics.

Detection and removal of contaminants are significant for environmental monitoring and remediation. In the present study, "two-in-one" silicon nanoparticles (SiNPs) were designed and prepared to simultaneously act as the fluorescent probe and degradation catalyst to detect and remove tetracycline (TCs) antibiotics. Thiourea and 3-aminopropyltrimethoxysilane were dopant and silicon source to generate fluorescent sulfur and nitrogen co-doped SiNPs (SN-SiNPs). The blue fluorescence of SN-SiNPs was selectively quenched by TCs due to the inner filter effect, whilst accompanied by the newly appeared yellow-green fluorescence resulting from aggregation induced fluorescence emission effect. Based on this phenomenon, SN-SiNPs can be used as fluorescent colorimetric probes for detection of doxycycline, oxytetracycline and tetracycline with limits of detection of 1.8 μg/L, 3.0 μg/L and 4.2 μg/L, respectively; the semi-quantitation can even be visually achieved by naked eyes. Particularly, SN-SiNPs were capable to catalyze the degradation of the three TCs effectively, achieving the removal rates of doxycycline, oxytetracycline and tetracycline of >90 %, >80 % and > 70 % after 240 min exposure to UV light. The catalytic ability of SN-SiNPs was derived from hydroxyl radical (•OH), superoxide radical (•O) and singlet oxygen (O) produced by SN-SiNPs under UV irradiation. Moreover, integrating the fluorescent probe and photocatalyst together, the proposed SN-SiNPs simultaneously realized catalyzing the degradation of the three TCs and in-situ visually monitoring of the degradation process in real time. This study innovatively proposed an integrated probe for the detection and catalytic degradation of TCs, providing a new "two-in-one" strategy for rapid and simple detection and removal of drug pollutants.