Targeted catalytic degradation of organophosphates: pursuing sensors

Abstract

Chemical security has been a hot topic over several years, especially involving organophosphates (OP), which are related to organophosphorus chemical warfare and pesticides. The main challenges are to develop efficient ways to destroy stockpiles of these materials and also to monitor their presence in the field or food. A promising approach in this sense is the targeted design of catalysts that can react with OP and degrade them. Herein, we present a summary of some recent advances towards OP detoxification and monitoring that involves four different approaches: (i) How? Understanding the mechanism: thorough mechanistic elucidation and design of an ideal catalytic scaffold; (ii) Nanocatalysts and sensors: rational functionalization of carbon nanomaterials leading to nanocatalysts as powder and thin films. A surface-enhanced Raman scattering (SERS) sensor for OP was also obtained combining the functionalized material with silver nanoparticles; (iii) Catalysts from waste: reuse of rice husk waste as well as waste derived from the cheap gum arabic for developing biocatalysts that have high added-value and are environmentally friendly; (iv) A simple sensor: a simple, cheap and compact homemade colorimeter that can be used as a colorimetric sensor for detecting quantitatively various compounds, including pesticides.

Enhancement of organophosphate degradation by electroactive pyrrole and imidazole copolymers

“…Also, the p(Py:IMZ-50) and p(Py:IMZ-60) samples showed a 5×10 3 -fold rate increment in comparison to the spontaneous degradation [22]. This increment is higher than that provided by IMZ in homogeneous catalysis (2×10 3 -fold) [22] and similar to other results reported elsewhere [39], suggesting that the PPy-IMZ copolymer obtained by this simple method has a great potential for the degradation of OP. The rate increments obtained with the copolymers are significant considering the heterogeneous nature of the catalytic system, which can hamper the diffusion of OP to the IMZ active sites, and the low quantity of IMZ in the copolymer, which is probably lower than the content of Py.…”

Nucleophilic Neutralization of Organophosphates: Lack of Selectivity or Plenty of Versatility?

“…Such inherent chemical features justify the use of IMZ as acidic, basic or even nucleophilic catalyst, as illustrated in Figure 12, for the selective reactions at the phosphorus atom of organophosphate (the most common preferred pathway). [37][38][39][40] Indeed, the versatility of IMZ is used by nature in enzymes and proteins playing key roles in several biological processes. [40][41][42] For example, the side chain of IMZ ring present in histidine residue is responsible for the RNA transphosphorylation -an important step in protein synthesis -via preferential general acid-base catalysis.…”

“…In light of the effectiveness of IMZ promoting deacetylation reactions and the key role of histidine residue IMZ ring catalyzing dephosphorylation processes in living organisms, [39] several studies on the reactivity of isolated IMZ and monosubstituted derivatives towards various organophosphates were reported in the last decade. [37] Indeed, remarkable catalytic activity was revealed for that class of N-nucleophiles, effectively promoting neutralization processes. Interestingly, IMZ has a distinct behavior towards P=O and P=S organophosphates, attacking different electrophilic centers.…”

Innovative Technologies for Chemical Security

“…Many organophosphate pesticides, like organophosphorus nerve agents, are hazardous to human health. Professor Elisa Orth from the Federal University of Parana (Brazil) described her research on catalysts that can be used for degradation and/or sensing of these chemicals [88]. Her approach uses graphene and carbon nanotubes functionalised with multiple catalytic groups, for example metallic nanoparticles [89,90].…”