Colorimetric optical nanosensors for trace explosive detection using metal nanoparticles: advances, pitfalls, and future perspective

Abstract

Warfare threats and acts of terror are challenging situations encountered by defense agencies across the globe and are of growing concern to the general public, and security-minded policy makers. Detecting ultra-low quantities of explosive compounds in remote locations or under harsh conditions for anti-terror purposes as well as the environmental monitoring of residual or discarded explosives in soil, remains a major challenge. The use of metal nanoparticles (NPs) for trace explosive detection has drawn considerable interest in recent years. For nano-based explosive sensor devices to meet real-life operational demands, analytical parameters such as, long-shelf life, stability under harsh conditions, ease-of-use, high sensitivity, excellent selectivity, and rapid signal response must be met. Generally, the analytical performance of colorimetric-based nanosensor systems is strongly dependent on the surface properties of the nanomaterial used in the colorimetric assay. The size and shape properties of metal NPs, surface functionalisation efficiency, and assay fabrication methods, are factors that influence the efficacy of colorimetric explosive nanosensor systems. This review reports on the design and analytical performances of colorimetric explosive sensor systems using metal NPs as optical signal transducers. The challenges of trace explosive detection, advances in metal NP colorimetric explosive design, limitations of each methods, and possible strategies to mitigate the problems are discussed.

Small Electron-Rich Isomeric Solid-State Emitters with Variation in Coplanarity and Molecular Packings: Rapid and Ultralow Recognition of TNT

“…However, these polymeric/oligomeric molecules are associated with pitfalls such as expensive/multistep synthesis, lack of purity, reproducibility, selectivity, and, most importantly, ill-defined molecular structures. Moreover, the detection sensitivity is also not promising compared to this report. , Few other strategies are identified for ppq level detection, but they need expensive metal nanoparticles and the complex high-cost instrumental arrangement. , Especially, the use of metal nanoparticles in trace explosive detection looks promising . Still, the synthetic difficulties/reproducibility, lack of understanding of molecular structure, emission tuning (intensity and wavelength), stability, and limited scope of utility in solution state are the potential drawbacks compared to solid-state emitters .…”

“…Moreover, the detection sensitivity is also not promising compared to this report. , Few other strategies are identified for ppq level detection, but they need expensive metal nanoparticles and the complex high-cost instrumental arrangement. , Especially, the use of metal nanoparticles in trace explosive detection looks promising . Still, the synthetic difficulties/reproducibility, lack of understanding of molecular structure, emission tuning (intensity and wavelength), stability, and limited scope of utility in solution state are the potential drawbacks compared to solid-state emitters . Hence, solid-state emitting small molecules would be preferred to achieve on-the-spot detection of TNT.…”

“…14,15 Especially, the use of metal nanoparticles in trace explosive detection looks promising. 16 Still, the synthetic difficulties/reproducibility, lack of understanding of molecular structure, emission tuning (intensity and wavelength), stability, and limited scope of utility in solution state are the potential drawbacks compared to solid-state emitters. 16 Hence, solid-state emitting small molecules would be preferred to achieve on-the-spot detection of TNT.…”

“…16 Still, the synthetic difficulties/reproducibility, lack of understanding of molecular structure, emission tuning (intensity and wavelength), stability, and limited scope of utility in solution state are the potential drawbacks compared to solid-state emitters. 16 Hence, solid-state emitting small molecules would be preferred to achieve on-the-spot detection of TNT. Notably, the detection of picric acid (another typical explosive) is well-explored with solid-state emitters due to its lower LUMO (lowest unoccupied molecular orbital) value, favorable energy transfer, and the presence of phenolic−OH functionality.…”

Rapid and selective on-site detection of triacetone triperoxide based on visual colorimetric method

“…Colorimetry is another simple technique for the rapid, qualitative, and selective on-site detection of peroxide explosives. [27][28][29][30][31][32][33][34][35][36][37] Colorimetric methods mainly include traditional colorimetric methods, colorimetric sensors, and colorimetric sensor arrays. Traditional colorimetry mainly uses various chemical reagents to detect the TATP.…”