Since the first use of chemical warfare agents (CWA) (1915) to the recent attacks in Syria (2017) on mankind, there have been many incidents where CWA have claimed thousands of lives and left many more contaminated. In order to provide the appropriate and immediate medical counter measure to the victims, the exact classification of these chemical agents within few minutes on the field itself using a rapid and simple detection technique is extremely important to save the lives of the effected people. This has motivated all of us to explore the novel strategies/detection systems that can be field deployable with better selectivity and greater sensitivity. In view of this, we present a novel chemosensor, 3,6-bis(dimethylamino)-9(10H)-acridine thione (1), that can detect mustard gas and its simulant by both chromogenic and fluorogenic methods. For the first time, a single probe was able to demonstrate the detection with unprecedented selectivity over most probable interferences (nerve agents and alkylating agents) including solvents, acids, and bases which are routinely present in the environment. The desired level of sensitivity by naked eyes (0.04 mg/mL), UV spectroscopy (0.02 mg/mL), and fluorescence spectroscopy (0.005 mg/mL) makes this method truly field deployable. For the spot detection on the affected areas, a handy and potable chemosensor kit was also fabricated. This paper provides a simple, highly specific, and easy to use method in "actual sense" that not only detects the agents in the solution phase but also in the contaminated samples.

A chromogenic and fluorogenic system based on a squaraine dye (SQ) was used for the highly selective and sensitive detection of the chemical warfare agent sulfur mustard.

A novel strategy using ferrocenyl dye (1) was developed for highly selective chromogenic detection of all nerve agents. The protocol was first established with nerve agent mimics (DFP, DCNP, and malaoxon) and then implemented on real agents, i.e. sarin, tabun and VX. The developed chemosensor showed no interferences from the most probable interferents such as acetyl chloride, sulfur mustard, oxygen mustard and DMMP. Real-time visual detection with a lower limit of detection (below LD) made the present protocol highly appealing and versatile.

Our approach uses squaraine (SQ) as the molecular-receptor as well as an indicator for the chromogenic and fluorogenic detection and discrimination of nerve agents Tabun and Vx. To mimic a real-life scenario, the protocols were implemented in spiked water and soil samples, on surfaces, and in the gas phase. The lower detection limit will be useful to protect human health and national security.

A series of novel thiourea based receptors (1-12) with different signaling units and spacers have been synthesized for the detection of cyanide ion. Among these receptors, 4,4'-bis-[3-(4-cyanophenyl)thiourea]diphenyl sulfide 6 and 4,4'-bis-[3-(3-cyanophenyl)thiourea]diphenyl sulfide 9 exhibited selective detection of cyanide by the naked-eye as well as by UV-Vis spectroscopy. Furthermore, the chemosensor is insensitive to the presence of other environmentally relevant anions. The chromogenic transformation permits the detection of cyanide (TBA(+) and K(+) salts) in the natural environment.

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In the present study, a chemical probe was finely tuned for the highly selective and sensitive chromogenic and fluorogenic detection of toxic anions and a nerve agent. Studies on the binding sites, signaling units and spacers led to a receptor molecule, i.e., 2,7-bis-[3-(4-cyanophenyl)thiourea] fluorene 2, which detected multiple analytes such as fluoride, cyanide, and a tabun mimic. The optical responses obtained from all the three analytes were quite distinct from one another. More importantly, we have been successful in demonstrating the highly specific chromo-fluorogenic detection of a tabun mimic over other chemical warfare agents and reactive and non-reactive electrophilic interferents. In an attempt to mimic real-life scenarios, the applicability of our protocol was further extended to demonstrate the presence of a tabun mimic on solid surfaces, in the gas phase and in a spiked soil sample.

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