Sensors based on surface plasmon resonance in a plastic optical fiber for the detection of trinitrotoluene

Abstract

The objective of this study is to present an optical chemical sensor based on surface plasmon resonance (SPR) in a plastic optical fiber (POF) for the selective detection and analysis of trinitrotoluene (TNT) in aqueous solution.The fabricated optical chemical sensor was realized removing the cladding of a plastic optical fiber along half the circumference, spin coating on the exposed core a buffer of Microposit S1813 photoresist, and finally sputtering a thin gold film. A molecularly imprinted polymer (MIP) film was, then, deposited on the thin gold film to allow the selective detection of TNT. The film was a methacrylic acid-divinyl benzene copolymer obtained by radicalic polymerization at high temperature.The experimental results show that the use of MIP layer is suitable for highly selective detection of TNT, down to about 50μM (i.e. ∼11μg/ml). This shows that the direct detection of a low molecular mass substance is possible by SPR transduction, even at low concentration. Furthermore, the proposed sensing head is low cost and relatively easy to realize, and may be very attractive for the detection and analysis of trinitrotoluene (TNT), in particular considering that it does not involve the use of any electrical devices and it can be used for remote/online monitoring exploiting, f.i., a fiber optic link.