A portable and miniaturized lab-on-fiber sensor based on a responsive Fabry-Perot resonance cavity for the detection of thiocyanate.

Thiocyanate (SCN^-) detection is highly significant because of the toxicity of SCN^-. Herein, a portable and miniaturized lab-on-fiber (LOF) sensor is reported for the detection of SCN^- through integrating a Fabry-Perot (F-P) optical resonance cavity based on anionic-responsive metal-insulator-metal (MIM) onto an optical fiber tip. The responsive MIM optical resonance cavity is constructed with an intermediate cationic polymer brush layer (poly[2-(methacryloyloxy)ethyl] trimethylammonium chloride, PMETAC) and two silver layers <i>via</i> a facile <i>in situ</i> "layer-by-layer" construction method. When the fabricated LOF sensor was immersed in SCN^- solutions, an obvious reflection dip shift can be observed, which is feasible for the quantitative detection of SCN^-. What's more, the fabricated LOF sensor exhibits outstanding selectivity and anti-interference against other interfering anions. Furthermore, the fabricated LOF sensor also displays other excellent advantages endowed by the polymer brush film, such as a fast response rate and outstanding reproducibility. Therefore, it is believed that the fabricated miniaturized LOF sensor would show great potential as a portable sensor in future applications, such as environmental monitoring and clinical diagnosis.