MoS2 QDs/8-Armed Poly(Ethylene Glycol) Fluorescence Sensor for Three Nitrotoluenes (TNT) Detection

In this work, ammonia cross-linked 8-armed polyethylene glycol hydrogel material was successfully synthesized and used as a template for synthesizing nanoparticles with fluorescent properties. The 8-armed polyethylene glycol hydrogel template was used to prepare molybdenum disulfide quantum dots (MoS2 QDs). The ammonium tetrathiomolybdate functioned as a molybdenum source and hydrazine hydrate functioned as a reducing agent. The fluorescence properties of the as-prepared MoS2 QDs were investigated. The bursting of fluorescence caused by adding different concentrations of explosive TNT was studied. The study indicated that the synthesized MoS2 QDs can be used for trace TNT detection with a detection limit of 6 nmol/L and a detection range of 16–700 nmol/L. Furthermore, it indicated that the fluorescence-bursting mechanism is static bursting.

Biomimetic Sensitive Elements for 2,4,6-Trinitrotoluene Tested on Multi-Layered Sensors

In spite of technological progress, most of the current techniques for 2,4,6-trinitrotoluene (TNT) detection are time consuming due to laborious sensor preparation. Thereby, the aim of this work was to enlarge the knowledge for preparing sensitive elements for TNT with the aid of molecular imprinting; a known technique used to deliver biomimetic materials. The study first depicts the auto-assembly mechanism of (TNT) with functional diamino-silanes (i.e., N-(2-aminoethyl)-3-aminopropyl methyl dimethoxysilane), via “double” Meisenheimer complexes. This mechanism is being described herein for the first time and applied further to obtain molecularly imprinted polymer (MIP) films for TNT recognition. For testing the potential application of films as chemical sensor elements, typical rebinding assays of TNT in a liquid state and the rebinding of TNT in a vapor state, using multilayered sensor chips composed of quartz-chromium (Cr)-gold (Au)-titanium oxide (TiO2), were employed. Batch rebinding experiments have shown that thinner films were more efficient on retaining TNT molecules in the first five min, with a specificity of about 1.90. The quartz-Cr-Au-TiO2-MIP capacitive sensors, tested in vapor state, registered short response times (less than 25 s), low sensitivity to humidity and high specificity for TNT.

Interfacial effect of dual ultra-thin SiO2 core–triple shell Au@SiO2@Ag@SiO2 for ultra-sensitive trinitrotoluene (TNT) detection

The ultra-sensitive detection of trinitrotoluene (TNT) demonstrates that interfacial effect of double-layer dielectric silica achieves the LSPR enhancement effect in Au@SiO2@Ag@SiO2.

Molecularly Imprinted Sol-Gel for TNT Detection with Optical Micro-Ring Resonator Sensor Chips

A sensor for trinitrotoluene (TNT) detection was developed by using a combination of optical micro-ring technology and a receptor coating based on molecularly imprinted sol-gel layers. Two techniques for deposition of receptor layers were compared: Airbrush technology and electrospray ionization. A concentration of less than 5 ppb for TNT in the gas-phase, using electrospray deposition of the receptor layer, was detected. The cross-sensitivities to organic substances and further nitro-based explosives were compared. As a result, the sensitivity to TNT is about one order of magnitude higher in comparison to the explosives 2,4-dinitrotoluene (DNT) or 1,3-dinitrobenzene (DNB) and about four orders of magnitude higher than the organic substances phenol, ethanol, and acetone. The signal response of the sensor is fast, and the compact sensor design enables the deposition of different receptor layers on multiple optical micro-rings on one chip, which allows a more precise analysis and reduction of side effects and false alarms.

Janus-micromotor-based on–off luminescence sensor for active TNT detection

An active TNT (2,4,6-trinitrotoluene) catalytic sensor based on Janus upconverting nanoparticle (UCNP)-functionalized micromotor capsules, displaying “on–off” luminescence with a low limit of detection has been developed. The Janus capsule motors were fabricated by layer-by-layer assembly of UCNP-functionalized polyelectrolyte microcapsules, followed by sputtering of a platinum layer onto one half of the capsule. By catalytic decomposition of hydrogen peroxide to oxygen bubbles, the Janus UCNP capsule motors are rapidly propelled with a speed of up to 110 μm s−1. Moreover, the Janus motors display efficient on–off luminescent detection of TNT. Owing to the unique motion of the Janus motor with bubble generation, the likelihood of collision with TNT molecules and the reaction rate between them are increased, resulting in a limit of detection as low as 2.4 ng mL−1 TNT within 1 minute. Such bubble-propelled Janus UCNP capsule motors have great potential for contaminated water analysis.

Smart Sensor Using Cellulose-Based Material for TNT Detection

A smart sensor with cellulose-based material was developed for the detection of 2,4,6-trinitrotoluene (TNT), using potassium hydroxide/ethanol reagent adsorbed onto a cellulose cotton swab. A red color was observed immediately after exposure to TNT. The sensor allowed rapid qualitative and semi-quantitative analysis of TNT by naked-eye, observation at TNT amounts > 2 μg. To improve precision and accuracy, a smartphone was used to capture digital images of the color. A calibration curve was constructed between log TNT (μg) vs. color intensity, and was linear in the range 1-30 μg-TNT with R2= 0.9975. The limit of detection (3.3σ/slope) was 0.11 μg-TNT and percentage relative standard deviation (%RSD, n=10) was 2.30. The sensor was used to detect the TNT samples of soil and from non-porous and porous surfaces.