Detection Of Nerve Agent Simulants Research Articles

UiO-66-NH2 initiated cascade reaction: Constructing a ratiometric fluorescence sensor for ultrasensitive detection of nerve agent simulant

BackgroundHighly toxic organophosphorus nerve agents often exist in the form of gas in the environment and can damage human neuroregulatory system by inhibiting the activity of acetylcholinesterase (AChE). However, fluorescent probes based on small organic molecules bring a secondary burden to environment, and their sensitivity and specificity for sarin simulant diethyl chlorophosphate (DCP) detection are unsatisfactory. Nanozyme cascade systems with signal amplification can be used for highly sensitive identification of analytes, but are rarely used in ratiometric analysis of DCP. Combination of enzyme cascades and ratiometric fluorescence ensures the accuracy and sensitivity of the output signal. ResultsWe prepared a self-assembled nanohybrid (Ag–AuNCs@UiO-66-NH2) by metal-organic framework material and gold nanoclusters. On the one hand, UiO-66-NH2 with enzyme-like activity was used to hydrolyze DCP into diethyl phosphate (DEP) and chloridion (Cl−). Cl− hindered aggregation-induced enhanced emission (AIEE) of AuNCs by binding with Ag+ and decreased the fluorescence of AuNCs. On the other hand, ligand metal charge transfer effect (LMCT) of UiO-66-NH2 was blocked by DCP to enhance the fluorescence of UiO-66-NH2. Combining ratiometric analysis and nanozyme cascade reaction, an ultra-sensitive fluorescence sensor for detecting DCP was constructed, and ensured the accuracy of experimental results. In addition, Ag–AuNCs@UiO-66-NH2 was embedded into the agarose hydrogel substrate, the resulting agarose hydrogel film allowed quantitative assessment of DCP vapor and high sensitivity was demonstrated (detection limit as low as 1.02 ppb). SignificanceA strategy combining enzyme cascade with ratiometric fluorescence was proposed, which improved the accuracy and sensitivity of the analysis results. The soft-solid platform based on agarose hydrogel film was constructed to realize the quantitative monitoring of sarin simulant gas. The LOD value obtained in this work is much lower than the immediately life-threatening or health threatening concentration of sarin.

Cu2+-functionalized Zr-MOF triggers O-phenylendiamine oxidation for ultrasensitive ratiometric fluorescence detection of nerve agent simulant

Developing a fluorescence sensor capable of precisely identifying highly toxic nerve agents has become a focus of research, given that they are easily available and can be used by terrorists to threaten the security of the world. In this work, we designed a ratiometric fluorescence sensing platform with Cu2+-modified UiO-66-NH2 (Cu2+@UiO-66-NH2) and o-phenenediamine (OPD) as signal indicators and successfully used for the liquid and gas detection of the nerve agent simulant diethyl chlorophosphate (DCP). UiO-66-NH2 obtained oxidase activity by simple Cu2+ modification, which catalyzed the oxidation of OPD to give a yellow fluorescent product 2, 3-diaminophenazine (DAP). In this detection system, the fluorescence of UiO-66-NH2 was greatly enhanced by blocking the ligand metal charge transfer (LMCT) process inside the framework by DCP. At the same time, the amino group of DAP was phosphorylated by DCP, and the attenuation of DAP fluorescence was observed by the static quenching effect. In addition, the Cu2+@UiO-66-NH2/OPD loaded agarose hydrogel device can be used to detect DCP vapor with naked eyes and showed satisfactory detection result (LOD: 6.65 ppb).

Dual-State Fluorescent Probe for Ultrafast and Sensitive Detection of Nerve Agent Simulants in Solution and Vapor.

The development of fluorescent probes for detecting nerve agents has been the main concern focus of research because of their lethal toxicity for humans. Herein, a probe (PQSP) based on the quinoxalinone unit and the styrene pyridine group was synthesized and could visually detect a sarin simulant diethyl chlorophosphate (DCP) with excellent sensing properties in solution and solid states. Interestingly, PQSP showed an apparent intramolecular charge-transfer process by catalytic protonation after reacting with DCP in methanol, accompanied with the aggregation recombination effect. The sensing process was also verified by nuclear magnetic resonance spectra, scanning electron microscopy, and theoretical calculations. In addition, the papered test strips of loading probe PQSP exhibited an ultrafast response time within 3 s and high sensitivity with a limit of detection of 3 ppb for the detection of DCP vapor. Therefore, this research provides a designed strategy for developing the probes with dual-state emission fluorescence in solution and solid states for detecting DCP sensitively and rapidly, which can be fabricated as chemosensors to visually detect nerve agents in practice.

Solvent-driven micro/nanostructures of squaraine and croconaine dyes based on quinoxalinone for visual detection of nerve agent simulants

The detection of nerve agents has been the focus of research due to their extreme threat for human health and safety. In this paper, the quinoxalinone-based squaraine (NESQ) and croconaine (NECR) dyes are synthesized and used as chemosensors to investigate the sensing properties with diethyl chlorophosphate (DCP) in solvents. They exhibit a huge absorption spectra red-shift from visible region to near-infrared region due to the transformation of anionic basic form and zwitterionic acidic form, which is verified by experiments and theoretical calculations. The self-assembly micro/nanostructures transformation of NESQ and NECR can be driven by adding different solvents, which is characterized by SEM and AFM technology. Upon adding DCP, the absorption wavelength of NESQ and NECR in DMF respectively exhibits 186 nm and 281 nm red-shifts from visible region to near-infrared region with obvious color change, which is larger than the previously reported. The proposed sensing mechnism was verified by 1H NMR spectra and SEM technology. Compared to NECR, NESQ exhibits a lower limit of detection and a faster responsive time for sensing DCP. The characteristics of these dyes would provide a new design strategy of chromogenic chemsensors with large wavelength shift and self-assembly morphologies transformation for the visual detection of nerve agents.

Selective and rapid detection of nerve agent simulants by polymer fibers with a fluorescent chemosensor in gas phase

Nerve agents (NAs) are the most feared and unpredictable chemical warfare agents (CWAs) on the battlefield and in the hands of terrorists. To cope with chemical terrorism or chemical warfare, it is urgent to establish a rapid and reliable detection method for NAs. In this work, we have developed two 6-aminoquinolin-2-yl-methanols (AQmol-1 and AQmol-2), which can selectively detect two nerve agent simulants, diisopropylfluorophosphate (DFP) and diethylchlorophosphate (DCP), over other organophosphate compunds. In this sensing reaction, the hydroxy group of two sensors is phosphorylated by DFP/DCP and simulanutaus protonation of nitrigen of the quinoline to form a stronger electron donor-acceptor (DA) molecule over the sensor molecule, giving corresponding fluorescence response. Therein, AQmol-2 diplays ratiometirc fluorescence response towards DFP/DCP with a lower limit of detection (LOD) 0.18 μM or 0.16 μM, respectively. Furthermore, two AQmol-2 embedded solid polymers, membrane and fibers (the diameter <1 μm), were fabricated for detection of DFP/DCP vapor. Both AQmol-2-embedded solid-state polymers can detect DFP/DCP vapor more rapidly over those (about 30 min) in solutions. The polymer fibers from an electrospaning technology give more rapid response toward DCP (within 20 s) over that (3 min) of the membrane. Therefore, AQmol-2-embedded polymer nanofibrosis is promissing way for selective and rapid detection of nerve agents in gas phase.

Challenges in Fluorescence Detection of Chemical Warfare Agent Vapors Using Solid-State Films.

Organophosphorus (OP)-based nerve agents are extremely toxic and potent acetylcholinesterase inhibitors and recent attacks involving nerve agents highlight the need for fast detection and intervention. Fluorescence-based detection, where the sensing material undergoes a chemical reaction with the agent causing a measurable change in the luminescence, is one method for sensing and identifying nerve agents. Most studies use the simulants diethylchlorophosphate and di-iso-propylfluorophosphate to evaluate the performance of sensors due to their reduced toxicity relative to OP nerve agents. While detection of nerve agent simulants in solution is relatively widely reported, there are fewer reports on vapor detection using solid-state sensors. Herein, progress in organic semiconductor sensing materials developed for solid-state detection of OP-based nerve agent vapors is reviewed. The effect of acid impurities arising from the hydrolysis of simulants and nerve agents on the efficacy and selectivity of the reported sensing materials is also discussed. Indeed, in some cases it is unclear whether it is the simulant that is detected or the acid hydrolysis products. Finally, it is highlighted that while analyte diffusion into the sensing film is critical in the design of fast, responsive sensing systems, it is an area that is currently not well studied.

Organoiridium(III) Complexes as Luminescence Color Switching Probes for Selective Detection of Nerve Agent Simulant in Solution and Vapor Phase.

In this work, cationic organoiridium(III) complex based photoluminescent (PL) probes have been developed to selectively detect the chemical warfare nerve agent mimic, diethyl chlorophosphate(DCP) at nanomolar range by distinct bright green to orange-red luminescence color switching (on-off-on) in solution as well as in the vapor phase. Interference of other chemical warfare agents (CWAs) and their mimics was not observed either by PL spectroscopy or with the naked-eye in solution and gas phase. The detection was attained via a simultaneous nucleophilic attack of two -OH groups of the 4,7-dihydroxy-1,10-phenanthroline ligand with DCP by forming bulkier phosphotriester. The detailed reaction mechanism was established through extensive 1H NMR titration, 31P NMR, and ESI-MS analysis. Finally, a test paper strip and solid poly(ethylene oxide) (PEO) film with iridium(III) complex 1[PF6] were fabricated for the vapor-phase detection of DCP. The solution and vapor-phase detection properties of these luminescent Ir(III) complexes can offer a worthy approach into the design of new metal complex based PL switching probes for chemical warfare agents.

Acetylcholinesterase-based inhibition screening through in situ synthesis of gold nanoparticles: Application for detection of nerve agent simulant

We report a novel, simple, and sensitive colorimetric assay by the in situ formation of gold nanoparticles in the presence of acetylcholinesterase and acetylthiocholine for the detection of chemical warfare agent simulant, 1,5-bis(4-allyldimethylammoniumphenyl)pentan-3-one dibromide (BW284c51). In this method, we used a low concentration (7mM) of sodium borohydride to produce stable gold nanoparticles by the enzymatic hydrolysis of acetylcholinesterase (AChE). The product of enzymatic reaction thiocholine acts as a stabilizing agent. UV–visible spectra and transmission electron microscopy confirmed that the formation of stable gold nanoparticles in the presence of enzymatically produced thiol molecule. The in situ formation of gold nanoparticles was hindered by the addition of AChE inhibitor, BW284c51, which irreversibly blocked the active sites and decreased the production of thiol molecule. This, in turn, caused a decrease in the absorption peak of the nanoparticles at 520nm. The proposed method achieved a limit of detection of 0.77×10−9M. The probe was also successfully used for determination of chemical warfare agent simulant, BW284c51 in spiked real water samples.

Determination of the chemical warfare agents Sarin, Soman and Tabun in natural waters employing fluorescent hybrid silica materials

A novel mesoporous silica material containing boron–dipyrromethene (BODIPY) moieties (I) is employed for the detection of nerve agent simulants (NASs) and the organophosphate nerve or chemical warfare agents (CWAs) Sarin (GB), Soman (GD), and Tabun (GA) in aqueous environments. The reactive BODIPY dye with an optimum positioned hydroxyl group undergoes acylation reactions with phosph(on)ate substrates, yielding a bicyclic ring. Due to aggregation of the dyes in water, the sensitivity of the free dye in solution is very low. Only after immobilization of the BODIPY moieties into the silica substrates is aggregation inhibited and a sensitive determination of the NASs diethyl cyanophosphonate (DCNP), diethyl chlorophosphate (DCP) and diisopropyl fluorophosphate (DFP) possible. The signaling mode is a strong quenching of the fluorescence, reaching LODs in the pM range. The best performing hybrid material was singled out from a library of hybrid silicas varying in morphology and surface functionalization. The response to actual CWAs such as GB, GD, and GA has also been tested, offering similar behavior as for the simulants. The proposed reaction mechanism has been verified by investigation of other model materials, containing for instance BODIPY moieties without an optimum hydroxyl group (III) or a BODIPY dye with an all-aliphatic counterpart (IV). The latter can only form a monocyclic reaction product, showing much less reactivity as I. Assays with other possible competitors have been additionally carried out, showing favorably low cross-reactivities. Finally, the determination of NASs in several natural waters has been demonstrated.

Cantilever-based aptasensor for trace level detection of nerve agent simulant in aqueous matrices

In this paper, sensitive and specific detections on dimethyl methylphosphonate (DMMP), a representative simulant of sarin and organophosphorus pesticides, are demonstrated by a piezoresistive cantilever-based aptasensor in neutral electrolytic solution. By improving the design and fabrication processes of the cantilever-based sensor, a Hooge factor of 4.8×10−6 and a surface stress sensitivity of 1.47×10−3 (N/m)−1 have been obtained, and the output fluctuation has been minimized to 1μV at a 3V bias voltage. For selective and specific molecular capturing, the sensing cantilevers was functionalized by 78-mer 5′-biotinylated aptamers in a biotin-streptavidin system. The aptasensor was experimentally demonstrated to have a linear behavior in detecting DMMP within the concentrations of 50nM–1.0μM. Attributed to the low electrical noise and high sensitivity of the piezoresistive cantilever, a limit of detection of 50nM for DMMP was well obtained in phosphate buffered saline at neutral pH value. Besides, the aptasensors were also exposed to apple juice with DMMP added, whose detecting results indicate that the existence of biomacromolecular polysaccharides and the regional desorption of mercapto self-assembled layer from the gold film on the sensing cantilevers could result in a decrease of the detecting sensitivity slightly. The proposed cantilevers are promising for low cost, trace level and on-site biological/chemical detections.

Towards metal-organic framework based field effect chemical sensors: UiO-66-NH2 for nerve agent detection.

We present a highly sensitive gas detection approach for the infamous 'nerve agent' group of alkyl phosphonate compounds. Signal transduction is achieved by monitoring the work function shift of metal-organic framework UiO-66-NH2 coated electrodes upon exposure to ppb-level concentrations of a target simulant. Using the Kelvin probe technique, we demonstrate the potential of electrically insulating MOFs for integration in field effect devices such as ChemFETs: a three orders of magnitude improvement over previous work function-based detection of nerve agent simulants. Moreover, the signal is fully reversible both in dry and humid conditions, down to low ppb concentrations. Comprehensive investigation of the interactions that lead towards this high sensitivity points towards a series of confined interactions between the analyte and the pore interior of UiO-66-NH2.

Triarylcarbinol functionalized gold nanoparticles for the colorimetric detection of nerve agent simulants

Gold nanoparticles functionalized with a triarylcarbinol derivative have been used as colorimetric molecular probes for the naked-eye detection of the nerve agent simulants DCNP and DFP. The detection process is based on the compensation of charges at the surface of the nanoparticles which triggers their aggregation in solution with the resulting change in their plasmon band.

Polynorbornene derived 8-hydroxyquinoline paper strips for ultrasensitive chemical nerve agent surrogate sensing.

The detection of nerve agent simulants is achieved by the photoinduced electron transfer (PET) mechanism. A "turn-on" fluorescence response upon phosphorylation at 8-hydroxyquinoline of norbornene-based triazolyl functionalized 8-hydroxyquinoline () followed by intramolecular rearrangement provides very intense green emission. The detection limit of polymer () coated paper strips is 25 ppb with instantaneous response.

Functionalized Gold Nanoparticles as an Approach to the Direct Colorimetric Detection of DCNP Nerve Agent Simulant

AbstractNew functionalized gold nanoparticles have been synthesized and their ability to act as colorimetric molecular probes for the naked‐eye detection of nerve agent simulant DCNP has been studied. The detection process is based on the compensation of charges at the surfaces of the functionalized AuNPs, which triggers their aggregation with the resulting change in the color of the solution.

Selective Detection of Nerve Agent Simulants by Using Triarylmethanol‐Based Chromogenic Chemodosimeters

On page 4937 (2nd columm) of the original article1 the sentence “Under temperate conditions, most nerve agents have a low vapour pressure, which means they can evaporate quickly” should be replaced by “Under temperate conditions, most nerve agents have a high vapour pressure, which means they can evaporate quickly”. The Authors

Liquid–liquid–solid microextraction and detection of nerve agent simulants by on-membrane Fourier transform infrared spectroscopy

A coupling of novel liquid–liquid–solid microextraction (LLSME) technique based on porous hydrophobic membrane and Fourier-transform infrared spectroscopy has been presented for the detection, identification and quantification of markers and simulants of nerve agents. Two isomers O,O′-dihexyl methylphosphonate (DHMP) and O,O′-dipentyl isopropylphosphonate (DPIPP) were chosen as model analytes for the study. In the present technique, organic phase was immobilised within the pores of membrane after fixing it in an assembly, which was then immersed into aqueous sample of target analytes for extraction. The analytes were directly determined on the surface of membrane by FTIR spectroscopy without elution. On comparison with solid phase microextraction (SPME), LLSME was found to be much more efficient. The method was optimised and quantitative analyses were performed using calibration curves obtained via Beer's law and employing processing of spectra obtained, via a multivariate calibration technique partial least square (PLS). Relative standard deviations (RSDs) for intraday repeatability and interday reproducibility were found to be in the range of 0.20–0.50% and 0.20–0.60%, respectively. Limit of detection (LOD) was achieved up to 15ngmL−1. Applicability of the method was tested with an unknown real sample obtained in an international official proficiency test (OPT).

A rhodamine-deoxylactam based sensor for chromo-fluorogenic detection of nerve agent simulant

N-(rhodamine B)-deoxylactam-5-amino-1-pentanol (dRB-APOH) was designed and prepared as the chromo-fluorogenic sensor for detection of a nerve agent simulant via analyte triggered tandem phosphorylation and opening of the intramolecular deoxylactam. The successful detection of diethyl chlorophosphate suggests the utility of rhodamine-deoxylactams as the chromo-fluorogenic signal reporting platform for design of sensors targeting reactive chemical species via various chemistries.

Nerve agent simulant detection by using chromogenic triaryl methane cation probes

Two triaryl methane cations have been used as probes for colorimetric detection of nerve agent simulants. Buffered mixed aqueous solutions of 1 and 2 showed bathochromic shifts in the presence of DCNP (diethylcyanophosphonate) and DCP (diethylchlorophosphate). The colour modulation can be observed to the naked eye. Appropriate mechanisms for the recognition event are proposed.

Selective Detection of Nerve Agent Simulants by Using Triarylmethanol‐Based Chromogenic Chemodosimeters

AbstractA family of triarylcarbinols 1–11 has been synthesised, and the chromogenic behaviour of the members in the presence of nerve‐agent simulants diethylcyanophosphonate (DCNP) and diisopropylfluorophosphate (DFP) in acetonitrile and in buffered mixed water/acetonitrile solutions has been investigated. Hydrophobic polyethylene oxide films of these compounds have been prepared. Some of these triarylcarbinols act as OFF/ON chemodosimeters for the nerve agent simulants. The sensing mechanism includes phosphorylation of the hydroxyl group in the triarylcarbinol derivatives, followed by a dephosphatation reaction induced by the electron‐donor groups present in the structure. The existence of additional tert‐butyldimethylsilyl ether groups in compounds 2 and 3 permits these reagents to act as double probes by allowing selective signalling of DFP. The reactivity between 1 and 4–6 with DFP and DCNP in acetonitrile or water/acetonitrile solutions under pseudo first‐order kinetic conditions was studied to determine rate constants (k) and the half‐life times (t1/2) for the corresponding reactions. Films containing compound 2 were used to detect simulants both in solution and in the vapour phase. Finally, a logic device was designed that incorporated compounds 2, 14, and 15 that allowed detection of DFP (a Sarin and Soman simulant) and DCNP (a Tabun simulant), even in the presence of possible interferents such as acids.

Surface-Enhanced Raman Detection of Nerve Agent Simulant (DMMP and DIMP) Vapor on Electrochemically Prepared Silver Oxide Substrates

Surface-enhanced Raman scattering (SERS) spectra of the chemical nerve agent simulants dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP) were obtained in the vapor phase. The spectra obtained demonstrate the possibility of detecting these nerve agent species in the vapor phase using electrochemically roughened silver oxide substrates prepared from silver foil.