Nanoparticles in explosives detection – the state-of-the-art and future directions

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Detection of explosive markers using zeolite modified gas sensors

Detection of hidden explosive devices is a key priority for security and defence personnel around the globe. Electronic noses, based on metal oxide semiconductors (MOS), are a promising technology for creating inexpensive, portable and sensitive devices for such a purpose. An array of seven MOS gas sensors was fabricated by screen printing, based on WO3 and In2O3 inks. The sensors were tested against six gases, including four explosive markers: nitromethane, DMNB (2,3-dimetheyl-2,3-dinitrobutane), 2-ethylhexanol and ammonia. The gases were successfully detected with good sensitivity and selectivity from the array. Sensitivity was improved by overlaying or admixing the oxides with two zeolites, H-ZSM-5 and TS-1, and each showed improved responses to –NO2 and –OH moieties respectively. Admixtures in particular showed promise, with excellent sensitivity and good stability to humidity. Machine learning techniques were applied to a subset of the data and could accurately classify the gases detected, even when confounding factors were introduced

Preparation and photocatalytic activity of ZnGa2O4-β-Ga2O3 thin films

Photocatalytic zinc gallate thin films were fabricated by aerosol-assisted chemical vapor deposition (AACVD). The photocatalytic enhancement of ZnGa2O4-β-Ga2O3 compared with ZnGa2O4 thin films results from heterojunction interface facilitating charge separation

Sensitive and specific detection of explosives in solution and vapour by surface-enhanced Raman spectroscopy on silver nanocubes

Surface-enhanced Raman spectroscopy (SERS) has been widely utilised as a sensitive analytical technique for the detection of trace levels of organic molecules. The detection of organic compounds in the gas phase is particularly challenging due to the low concentration of adsorbed molecules on the surface of the SERS substrate. This is particularly the case for explosive materials, which typically have very low vapour pressures, limiting the use of SERS for their identification. In this work, silver nanocubes (AgNCs) were developed as a highly sensitive SERS substrate with very low limit-of-detection (LOD) for explosive materials down to the femtomolar (10−15 M) range. Unlike typical gold-based nanostructures, the AgNCs were found suitable for the detection of both aromatic and aliphatic explosives, enabling detection with high specificity at low concentration. SERS studies were first carried out using a model analyte, Rhodamine-6G (Rh-6G), as a probe molecule. The SERS enhancement factor was estimated as 8.71 × 1010 in this case. Further studies involved femtomolar concentrations of 2,4-dinitrotoluene (DNT) and nanomolar concentrations of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), as well as vapour phase detection of DNT

Plasmonic Gold Nanostars Incorporated into High-Efficiency Perovskite Solar Cells

Incorporating appropriate plasmonic nanostructures into photovoltaic (PV) systems is of great utility for enhancing photon absorption and thus improving device performance. Herein, the successful integration of plasmonic gold nanostars (AuNSs) into mesoporous TiO2 photoelectrodes for perovskite solar cells (PSCs) is reported. The PSCs fabricated with TiO2-AuNSs photoelectrodes exhibited a device efficiency of up to 17.72 %, whereas the control cells without AuNSs showed a maximum efficiency of 15.19 %. We attribute the origin of increased device performance to enhanced light absorption and suppressed charge recombination

Pseudohexagonal Nb2O5-Decorated Carbon Nanotubes as a High-Performance Composite Anode for Sodium Ion Batteries

Pseudohexagonal Nb2O5 (TT-Nb2O5) has been applied in sodium ion batteries (SIBs) for the first time. Lower synthesis temperatures, improved conductivity and stability were achieved by the introduction of a designed carbon framework. The TT-Nb2O5/carbon nanotube composite exhibits high specific capacity (135 mAh g−1 at 0.2 A g−1) in long cycles and good rate capability (53 mAh g−1 at high current density of 5 A g−1). The outstanding electrochemical performance is attributed to the superior electrical conductivity and connectivity, optimal mass transport conditions and the mechanical strength and durability established by the strongly linked TT-Nb2O5 and MWCNT network. This study provides a cost-effective route to the application of Nb2O5 in SIBs

Multichannel detection and differentiation of explosives with a quantum dot array

The sensing and differentiation of explosive molecules is key for both security and environmental monitoring. Single fluorophores are a widely used tool for explosives detection, but a fluorescent array is a more powerful tool for detecting and differentiating such molecules. By combining array elements into a single multichannel platform, faster results can be obtained from smaller amounts of sample. Here, five explosives are detected and differentiated using quantum dots as luminescent probes in a multichannel platform: 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), tetryl (2,4,6-trinitrophenylmethylnitramine), cyclotrimethylenetrinitramine (RDX), and pentaerythritol tetranitrate (PETN). The sharp, variable emissions of the quantum dots, from a single excitation wavelength, make them ideal for such a system. Each color quantum dot is functionalized with a different surface receptor via a facile ligation process. These receptors undergo nonspecific interactions with the explosives, inducing variable fluorescence quenching of the quantum dots. Pattern analysis of the fluorescence quenching data allows for explosive detection and identification with limits-of-detection in the ppb range