Detection of Trace-Level Nitroaromatic Explosives by 1-Pyreneiodide-Ligated Luminescent Gold Nanostructures and Their Forensic Applications

Abstract

By attaching the1-pyreneiodide ancillary ligand to the surface of polyvinylpyrrolidone-stabilized gold (Au:PVP) cluster or the cetyltrimethyl ammonium bromide-stabilized gold (Au:CTAB) nanorod, a new class of luminescent mixed ligand-stabilized gold nanostructures is synthesized. This postsynthetic surface modification method followed by us is a comparatively easier and hassle-free technique to acquire surface-active luminescent “functional nanomaterials”. Careful analyses of transmission electron microscopy images revealed that the sizes of these Au-clusters or Au-nanorods remain unchanged without any noticeable aggregation in the medium. Owing to the formation of an excimer within the neighboring pyrenes mounted on the surface of core nanostructures (i.e., Au:PVP nanocluster and Au:CTAB nanorod), the resulting pyrene-grafted nanocomposites exhibit strong emission characteristics. The strong excimer emission is significantly quenched in the presence of electron-deficient chemical inputs, and this phenomenon can be used for analytical purposes. Using these luminescent Au-nanomaterials, we demonstrate a selective detection and sensing of trace-level nitroaromatic explosives (e.g., trinitrotoluene, trinitrophenol (TNP), dinitrotoluene, 4-nitrotoluene, etc.). It was observed that the Py-Au:PVP nanocluster is equally effective for explosive detection in both solution and solid phases with the limit of detection up to 10 nanomolar. A high Stern–Volmer constant of up to 3.88 × 106 M–1 was seen in the case of TNP in anhydrous methanol at 298 K. The deactivation pathway operating within the Py-Au:PVP nanocluster and the analytes is thought to be a result of a predominating static quenching process, where a nonfluorescent D–A supramolecular adduct is formed in the medium. Py-Au:PVP has also been successfully used to develop latent fingerprints from nonporous surfaces under an exposure of 365 nm UV light. The results suggest that these new composite materials could behave as potential “functional nanomaterials”, which might be a promising alternative for on-the-spot detection of explosive traces as well as for easy visualization of latent fingerprints.

Synthesis of Orange-Red Emissive Au-SG and AuAg-SG Nanoclusters and Their Turn-OFF vs. Turn-ON Metal Ion Sensing

“…To understand the sensing mechanism we have measured the hydrodynamic diameter (D h ) and excited state life times (τ) of the both clusters during gradual addition of some selected metal salts. In general the luminescence quenching phenomenon occurs through photo-induced electron transfer (PET) process via static or dynamic interaction between probe and the analyte [40][41][42][43][44][45][46][47][48]. However, the turn-on sensing is uncommon and the underlying mechanism may be very distinct for different probes [49][50][51].…”

“…Trace level detection of various analytes including metal ions, explosives, speci c biomolecules, toxic molecules and food contaminants by luminescent noble metal clusters is a promising approach [38][39][40][41][42][43].…”

Photoluminescent MoS2 and MoSe2 Quantum Dots for the Detection of Nitro-Organic Explosives

“…The calorimetric and fluorescence-based explosive sensing is cost-effective, easy to use with fast response time, and hence ideal for on-the-spot testing of analytes. Various light emissive materials such as organic small molecules and polymers, , metal–organic frameworks, metal nanoclusters, − nanoassemblies, ,, and semiconductor nanoparticles (QDs) , have been synthesized and demonstrated as fluorescence sensors for explosive detection. Considering the high emission quantum yield, tunable band gap energy in the UV–vis region, and availability of hustle-free surface functionalization strategies, the use of QD-based fluorescence sensors is gaining more importance. , At the same time, to avoid toxic materials (e.g., Cd, Pb), heavy metal-free QDs for various sensing and optoelectronic applications have been a research priority in recent times. − Transition metal dichalcogenide-based QDs (MoX 2 , WX 2 , where X = S/Se) are very promising materials with size- and dimension-specific optical, photoluminescence, and electronic properties, ,− especially MoS 2 /Se 2 QDs are found to have inherent strong emission properties, high chemical stability, low toxicity, and easy surface functionalization procedures. , In the bulk phase of MoS 2 , two sulfur (S) atoms in two hexagonal planes are separated by an atomic plane of a molybdenum atom with excellent chemical and thermal stability.…”