An optical fiber crystal violet sensor using a porous ITO membrane coated on an optical fiber surface with UV photon-enhanced sensitivity

Abstract

Indium tin oxide (ITO) is an optically transparent semiconductor used in many optoelectronic devices. In this work, the porous properties of an ITO membrane coated on the surface of a bent optical fiber probe (BOFP) were explored in the effort to develop an optical fiber crystal violet sensor. It was discovered that the flowable electrons promoted to ITO's conduction band by UV photons enhanced the adsorption of crystal violet onto the porous ITO membrane and significantly increased the sensitivity of optical fiber evanescent wave absorption spectrometry for detecting this compound in aqueous sample solutions. Compared with a bare fiber BOFP, the sensitivity of the porous ITO-coated BOFP was 2.2 × 10⁴ times more sensitive in fiber optic EW absorption spectrometric detection of crystal violet in aqueous sample solutions. This sensor achieved a detection limit of 5.3 ng mL⁻¹, which is much lower than the detection limit of traditional UV/Vis spectrometry for detecting this compound in aqueous sample solutions. The sensor was tested for analyzing crystal violet concentration in a pharmacy product, Gentian Violet, purchased from a local pharmacy store, and the obtained analytical results agree well with those obtained using a conventional UV/vis absorption spectrometry method. A standard addition/recovery test was also performed using tap water as the sample matrix to verify the effectiveness of the sensor for the quick analysis of crystal violet in water samples, and the obtained recovery rate ranged from 98.7% to 101%.