Novel Optical Fiber Sensor for Explosive (Trinitrophenol) Detection

Highly selective and sensitive optical fiber nitroexplosive (2,4,6-trinitrophenol (TNP) also known as picric acid (PA)) sensor utilising the evanescent wave based intensity modulation technique is reported. The fiber sensor employs a novel polymer (PFTPA) thin sensing film as the cladding on the centrally decladded straight and uniform multimode optical fiber. Detailed experimental investigations are carried out to analyze the response characteristics of the proposed sensor. The sensor exhibits linear response in the range of 0–50 ppb TNP concentration, with a high sensitivity of 0.0032/ppb (73.31 × 10⁴ M⁻¹), and a remarkably low limit of detection of 1.06 ppb. The sensor also shows fast response and recovery time of 2 s. Further, the sensor exhibits high selectivity towards TNP. Additionally, the proposed sensor exhibits a very good degree of repeatability, reliability, stability and reversibility, which demonstrates the potential of the proposed sensor as a simple and straightforward approach for highly selective, sensitive sensor for on-site and real-time detection of TNP. Furthermore, the proposed optical fiber sensor was successfully applied to the detection of TNP in real water samples.