Ultrasensitive Surface Plasmon Resonance Detection of Trinitrotoluene by a Bis-aniline-Cross-Linked Au Nanoparticles Composite

Abstract

A bis-aniline-cross-linked Au nanoparticles (NPs) composite is electropolymerized on Au surfaces. The association of trinitrotoluene, TNT, to the bis-aniline bridging units via pi-donor-acceptor interactions allows the amplified detection of TNT by following the surface plasmon resonance (SPR) reflectance changes as a result of the coupling between the localized plasmon of the AuNPs and the surface plasmon wave associated with the gold surface. The detection limit for analyzing TNT by this method is approximately 10 pM. The electropolymerization of the bis-aniline-cross-linked AuNPs composite in the presence of picric acid results in a molecular-imprinted matrix for the enhanced binding of TNT. The imprinted AuNPs composite enabled the sensing of TNT with a detection limit that corresponded to 10 fM. Analysis of the SPR reflectance changes in the presence of different concentrations of TNT revealed a two-step calibration curve that included the ultrasensitive detection of TNT by the imprinted sites in the composite, KassI. for the association of TNT to the imprinted sites, 6.4 x 10(12) M-1, followed by a less sensitive detection of TNT by the nonimprinted pi-donor bis-aniline sites (KNIass. = 3.9 x 10(9) M-1). The imprinted AuNPs composite reveals impressive selectivity. The structural and functional features of the bis-aniline-cross-linked AuNPs composites were characterized by different methods including ellipsometry, AFM, and electrochemical means. The dielectric properties of the AuNPs composite in the presence of different concentrations of TNT were evaluated by the theoretical fitting of the respective experimental SPR curves. The ultrasensitive detection of the TNT by the AuNPs composite was attributed to the changes of the dielectric properties of the composite, as a result of the formation of the pi-donor-acceptor complexes between TNT and the bis-aniline units. These changes in the dielectric properties lead to a change in the conductivity of the AuNPs matrix.

The rational development of molecularly imprinted polymer-based sensors for protein detection

“…267 LSPR has been demonstrated for TNT imprinted gold nanoparticles, cross-linked and electropolymerized on a gold surface. 255 A detection limit of 10 fM was achieved, associated with changes in the dielectric properties of the bis-aniline polymer upon the formation of a -donor-acceptor complex with the analyte. Nanoparticle islands of gold on a glass substrate were employed for enhanced SPR, facilitated by plasmon coupling to gold nanoparticles embedded in a cholesterol-imprinted polymer film.…”

Electrospun Fluorescent Nanofibers for Explosive Detection

“…This has grabbed the attention and interest for the detection of nitroaromatic explosives in the recent years [6,7]. Following the speculation and the need, numerous methods have been devised for the detection of TNT, namely gas and liquid chromatography, mass spectrometry, surface plasmon resonance (SPR), surface enhanced Raman scattering (SERS), field-effect transistors, electrochemical methods and fluorescent and colorimetric methods [8][9][10][11][12]. These techniques, however, suppose to be time consuming, requiring bulky equipment with a tedious way of preparing the sample and usually require an expert operator.…”

Molecularly Imprinted Polymer Waveguides for Direct Optical Detection of Low‐Molecular‐Weight Analytes

“…[ 14 ] These systems were reported to be capable of direct detection of small molecular analytes at typically μM-mM concentrations; [ 3 ] however, several works reported the limit of detection at as low as pM concentrations. [ 9,15 ] Besides MIP layers, well-controlled synthesis of molecularly imprinted polymer micro-and nanoparticles (nanoMIP) was carried out by using precipitation, emulsion, or miniemulsion polymerization with a template dispersed in solution [ 16 ] or attached to particle or bead carriers. [ 17 ] NanoMIPs represent versatile materials that can be further processed and, e.g., their affi nity purifi cation allowed selecting nanoMIP fractions with dissociation affi nity constants K d as good as 10 −8 -10…”