Towards the design of organocatalysts for nerve agents remediation: The case of the active hydrolysis of DCNP (a Tabun mimic) catalyzed by simple amine-containing derivatives

Zr(OH)4/GO Nanocomposite for the Degradation of Nerve Agent Soman (GD) in High-Humidity Environments

Zirconium hydroxide, Zr(OH)₄ is known to be highly effective for the degradation of chemical nerve agents. Due to the strong interaction force between Zr(OH)₄ and the adsorbed water, however, Zr(OH)₄ rapidly loses its activity for nerve agents under high-humidity environments, limiting real-world applications. Here, we report a nanocomposite material of Zr(OH)₄ and graphene oxide (GO) which showed enhanced stability in humid environments. Zr(OH)₄/GO nanocomposite was prepared via a dropwise method, resulting in a well-dispersed and embedded GO in Zr(OH)₄ nanocomposite. The nitrogen (N₂) isotherm analysis showed that the pore structure of Zr(OH)₄/GO nanocomposite is heterogeneous, and its meso-porosity increased from 0.050 to 0.251 cm³/g, compared with pristine Zr(OH)₄ prepared. Notably, the composite material showed a better performance for nerve agent soman (GD) degradation hydrolysis under high-humidity air conditions (80% relative humidity) and even in aqueous solution. The soman (GD) degradation by the nanocomposite follows the catalytic reaction with a first-order half-life of 60 min. Water adsorption isotherm analysis and diffuse reflectance infrared Fourier transform (DRIFT) spectra provide direct evidence that the interaction between Zr(OH)₄ and the adsorbed water is reduced in Zr(OH)₄/GO nanocomposite, indicating that the active sites of Zr(OH)₄ for the soman (GD) degradation, such as surface hydroxyl groups are almost available even in high-humidity environments.

Swell and Destroy: A Metal-Organic Framework-Containing Polymer Sponge That Immobilizes and Catalytically Degrades Nerve Agents

Organophosphorus chemical warfare agents function as potent neurotoxins. Whilst the destruction of nerve agents is most readily achieved by hydrolysis, their storage and transport are hazardous and lethal in milligram doses, with any spillage resulting in fatalities. Furthermore, current decontamination and remediation measures are limited by a need for stoichiometric reagents, solvents, and buffered solutions, complicating the process for the treatment of bulk contaminants. Herein, we report a composite polymer material capable of rendering bulk VX unusable by immobilization within a porous polymer until a metal-organic framework (MOF) catalyst fully hydrolyzes the neurotoxin. This is an all-in-one capability that minimizes the use of multiple reagents, facilitated by a porous high internal phase emulsion-based polystyrene monolith housing an active zirconia MOF catalyst (MOF-808); the porous polymer absorbs and immobilizes the liquid agents, while the MOF enables hydrolysis. The dichotomous hierarchy of porous materials facilitates the containment and rapid hydrolysis of VX (>80% degradation in 8 h) in the presence of excess H₂O. This composite can further enable the hydrolysis of neat VX with reliance on ambient humidity (>95% in 11 days). Potentially, 4.5 kg of the composite can absorb, immobilize, and degrade the contents of a standard chemical drum/barrel (208 L, 55 gal) of the chemical warfare agent (CWA). We believe that this composite is the first example of what will be the go-to approach for CWA immobilization and degradation in the future. Furthermore, we believe that this demonstration of a catalytically reusable absorbent sponge provides a signpost for the development of similar materials where immobilization of a substrate in a catalytically active environment is desirable.

Visual detection of a nerve agent simulant using chemically modified paper strips and dye-assembled inorganic nanocomposite

Chromogenic probe with oxidized bis-indolyl scaffold has been synthesized for the detection of a nerve gas mimicking agent, DCNP (diethyl cyanophosphonate) at pH 8.0 in water. The mechanism of interaction was proposed as the release of cyanide ion through the indole group mediating the hydrolysis of phosphorous-hetero atom bond and, thereafter, the Michael addition of the liberated CN^- ion to the electron deficient C[double bond, length as m-dash]C bond of the bis-indolyl moiety. The reaction featured a remarkable change in color from red to colorless at ambient condition. Then, low-cost and portable paper strips were designed for a rapid and on-site vapor phase detection of DCNP without involving any sophisticated instrument or skilled personnel. Finally, a dye assembled inorganic nanocomposite material was devised to achieve a more sensitive 'turn-on' detection of DCNP in water.

Investigation of sarin(Se) reactivity against human plasma proteins using liquid chromatography-tandem mass spectrometry

Electron ionization mass spectrum of sarin(Se) was interpreted in compare of sarin MS spectrum. Inhibition of butyrylcholinesterase of human plasma by sarin and sarin(Se) was determined spectrophotometrically using modified Ellman method. It appeared that after incubation with sarin and sarin(Se), cholinesterase inhibition were 93% and 83%, respectively. Sarin, sarin(Se), and sarin(Se)-d₇ were spiked into a vial containing human plasma, and albumin adduct metabolites were identified using liquid chromatography-tandem mass spectrometry. The experiments show that these agents are attached to tyrosine on albumin in human blood. Corresponding deuterated adducts were used to confirm the proposed mechanisms for the formation of the fragments in mass spectrometry experiments.

Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes

Four different synthetic routes were used to prepare active forms of cerium oxide that are capable of destroying toxic organophosphates: a sol-gel process (via a citrate precursor), homogeneous hydrolysis and a precipitation/calcination procedure (via carbonate and oxalate precursors). The samples prepared via homogeneous hydrolysis with urea and the samples prepared via precipitation with ammonium bicarbonate (with subsequent calcination at 500°C in both cases) exhibited the highest degradation efficiencies towards the extremely dangerous nerve agents soman (O-pinacolyl methylphosphonofluoridate) and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) and the organophosphate pesticide parathion methyl. These samples were able to destroy more than 90% of the toxic compounds in less than 10 min. The high degradation efficiency of cerium oxide is related to its complex surface chemistry (presence of surface OH groups and surface non-stoichiometry) and to its nanocrystalline nature, which promotes the formation of crystal defects on which the decomposition of organophosphates proceeds through a nucleophilic substitution mechanism that is not dissimilar to the mechanism of enzymatic hydrolysis of organic phosphates by phosphotriesterase.

An Au(iii)–amino alcohol complex for degradation of organophosphorus pesticides

A gold(iii)–amino alcohol complex induces the P–S bond cleavage in organophosphorous pesticides giving rise to less toxic compounds.