Selective detection of diethanolamine utilizing an LMR/LSPR-based optical fiber sensor

Abstract

Diethanolamine (DEA) is used for amine wash to remove toxic gases such as hydrogen sulphide (H₂S) while processing crude oil and in other pharmaceutical products. The detection of diethanolamine is of prime importance to avoid its harmful impact. In this study, we have designed a lossy mode resonance (LMR)-based optical fiber sensor for the detection of DEA. An optical fiber probe was fabricated by coating a bulk layer of titanium dioxide (TiO₂) on the core of the optical fiber (probe-1). To extend this study, we prepared biosynthesised gold nanoparticles and coated them on to the top of the TiO₂-layer-coated probe (probe-2). The surface structure was confirmed using characterization techniques such as FESEM, HRTEM and UV-visible spectroscopy. Further, a comparative study among probe-1 and probe-2 has been carried out in terms of their performance parameters such as sensitivity, figure of merit, limit of detection, repeatability and response time. The sensitivity of the TiO₂ bulk layer/AuNP bilayer-coated optical fiber probe (probe-2) was observed to be 16 079.63 nm RIU⁻¹ (0.074 nm mM⁻¹), which was approximately double the sensitivity of the TiO₂ bulk layer-coated optical fiber probe (probe-1). Selectivity experiments were also performed to confirm the high sensitivity of the sensor towards DEA.