Adsorption Of Sarin Research Articles

Renewable adsorption/desorption of sarin on TM-doped CNTs: First principle calculations

Sarin, isopropyl methylphosphonofluoridate (C4H10O2FP), is a highly toxic nerve agent that can paralyze the central nervous system of human. The use of advanced materials with high adsorption capacity and easy regeneration for adsorbing sarin is an effective strategy to remove sarin. In the present work, we investigate sarin adsorption on TM-doped CNT(TM-CNT) by using DFT method (TM=Co, Cu, Cr, Fe, Mn, Ni, Zr). It is found that TM-CNT has a strong adsorption capacity for sarin molecule with the adsorption energy ranging from -1.55 to 2.11 eV. More important, the interaction between sarin molecule and adsorbent can be changed by applying an external electric field. When the added electric field is -0.005 a.u, adsorption energy became positive and sarin can release from the substrate easily. In addition, the adsorption of sarin changes the optical properties of the substrate obviously, which makes TM-CNT a promising candidate to detect sarin in the environment.

Closer Look at Adsorption of Sarin and Simulants on Metal–Organic Frameworks

The development of effective protection against exposure to chemical warfare agents (CWAs), such as sarin, relies on studies of its adsorption on the capturing materials and seeking candidates capable of adsorbing large amounts of sarin gas. Many metal-organic frameworks (MOFs) are promising materials for the effective capture and degradation of sarin and simulant substances. Among the simulants capable of mimicking thermodynamic properties of the agent, not all of them have been investigated on the ability to act similarly in the adsorption process, in particular, whether the agent and a simulant have similar mechanisms of binding to the MOF surface. Molecular simulation studies not only provide a safe way to investigate the aforementioned processes but can also help reveal the mechanisms of interactions between the adsorbents and the adsorbing compounds at the molecular level. We performed Monte Carlo simulations of the adsorption of sarin and three simulants, dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), and diisopropyl fluorophosphate (DIFP), on selected MOFs that have previously shown strong capabilities to adsorb sarin. On the basis of the calculated adsorption isotherms, enthalpy of adsorption, and radial distribution functions, we revealed common mechanisms among the particularly efficient adsorbents as well as the ability of simulants to mimic them. The findings can help in selecting a suitable simulant compound to study CWA adsorption on MOFs and guide further synthesis of efficient MOFs for the capture of organophosphorus compounds.

Impact of intrinsic framework flexibility for selective adsorption of sarin in non-aqueous solvents using metal–organic frameworks

Molecular modeling of mixture adsorption in nanoporous materials can provide insight into the molecular-level details that underlie adsorptive separations. Modeling of adsorption often employs a rigid framework approximation for computational convenience. All real materials, however, have intrinsic flexibility due to thermal vibrations of their atoms. In this article, we examine quantitative predictions of the adsorption selectivity for a dilute concentration of a chemical warfare agent, sarin, from bulk mixtures with aqueous and non-aqueous (methanol, isopropyl alcohol) solvents using metal-organic frameworks (MOFs). These predictions were made in MOFs approximated as rigid and also in MOFs allowed to have intrinsic flexibility. Including framework flexibility appears to have important consequences for quantitative predictions of adsorption selectivity, particularly for sarin/water mixtures. Our observations suggest the intrinsic flexibility of MOFs can have a nontrivial impact on adsorption modeling of molecular mixtures, especially for mixtures containing polar species and molecules of different sizes.

Theoretical study of sarin adsorption on (12,0) boron nitride nanotube doped with silicon atoms

Sarin gas is one of the most lethal nerve agent used in chemical warfare, which its detection is import to prevent a chemical attack and to identify a contamination area. Herein, density functional theory was used to investigate the (12,0) boron nitride nanotube (BNNT) and Si–doped BNNT as possible candidates to sarin detection. The Si-atoms doped improve the electronic properties of nanotubes by altering the electrostatic potential, HOMO and LUMO energies. Based in the adsorption energies and the conductivity increased to ~33 and 350%, respectively, for Si- and 2Si-BNNT imply that they can be used for sarin detection.

Sarin Decomposition on Pristine and Hydroxylated ZnO: Quantum-Chemical Modeling

An atomistic understanding of interactions between chemical warfare agents (CWAs) and filter materials is crucial for discovery and design of new materials suitable for chemical protection. The high toxicity of CWAs is a major barrier for experimental studies and significantly impedes the development of improved filter materials. Our recent studies show that density functional theory-based modeling serves as a powerful companion to experimental studies and assists in interpretation of experiments performed on surface-enhanced degradation of CWA simulant compounds. A strong synergy between theory and experiment enables predictive modeling of interactions of toxic CWAs with filter materials. Here, we present a comprehensive study of sarin adsorption and decomposition on pristine and hydroxylated ZnO(1010) surfaces performed by means of quantum-chemical calculations. We found that both simulated ZnO surfaces (an idealized pristine surface and hydroxylated surface, a more realistic and relevant form of ZnO a...

Spectroscopically Resolved Binding Sites for the Adsorption of Sarin Gas in a Metal-Organic Framework: Insights beyond Lewis Acidity.

Here we report molecular level details regarding the adsorption of sarin (GB) gas in a prototypical zirconium-based metal-organic framework (MOF, UiO-66). By combining predictive modeling and experimental spectroscopic techniques, we unambiguously identify several unique bindings sites within the MOF, using the P═O stretch frequency of GB as a probe. Remarkable agreement between predicted and experimental IR spectrum is demonstrated. As previously hypothesized, the undercoordinated Lewis acid metal site is the most favorable binding site. Yet multiple sites participate in the adsorption process; specifically, the Zr-chelated hydroxyl groups form hydrogen bonds with the GB molecule, and GB weakly interacts with fully coordinated metals. Importantly, this work highlights that subtle orientational effects of bound GB are observable via shifts in characteristic vibrational modes; this finding has large implications for degradation rates and opens a new route for future materials design.

Sensing and elimination of the hazardous materials such as Sarin by metal functionalized γ-graphyne surface: A DFT study

Sarin is an organophosphorus compound, poisonous and deadly, which is used in the preparation of chemical weapons. We are looking for materials for using as sensing and capturing of Sarin, so the effect of Li, Ti, Fe and Ni single atoms on the structural and electronic properties of graphyne (GY) toward Sarin adsorption was investigated by DFT-D calculations. Seven sites of GY and different distances from GY plane were investigated to gain the best structure of M-decorated GY. Then, adsorption of Sarin on the pristine and M-decorated GY was considered. The results showed that H1 is the best site for metal decoration and Sarin adsorption. Pristine GY is a semiconductor with direct band gap about 0.431 eV. Metal intern causes to change GY character into semi-metallic and decrease GY band gap. Decoration with all metals improves adsorption energy of Sarin, extremely, e.g. up to 4.5 times for Ti-decoration. Among six examined sites of Sarin, for Ni-decoration, etheric oxygen and for others, oxygen of carbonyl group is the best site for adsorption. In all systems, charge transfer happens from Sarin and metal to GY sheet. Also, in presence of the Sarin molecule, the band gap values decrease. Adsorption energies, location of metal atoms, metal and Sarin charges, band structure and partial density of state (PDOS) diagrams were brought and discussed. Ultimately, our study shows that Li, Ti, Fe and Ni-decorated GY can be used as a promising candidate for sensing and capturing applications of CWAs such as Sarin.

Sarin chemisorbent based on cobalt-doped graphene

Ion bombardment on graphene sheets can produce atomic vacancies that can trap metal atoms. In this paper, we demonstrated that these trapped metal atoms can effectively bind other molecules with heteroatoms, making them chemisorbed to the graphene. The trapped cobalt atom can bind sarin molecule through fluorine atom with dissociation energy significantly higher than the one bonded via oxygen atom. This suggests that it can displace water molecule and therefore pledge for sarin chemisorbent in atmospheric environment. Our investigations also revealed that metallic character is enhanced upon sarin adsorption unlike the bonding of water molecule with trapped metal atom in graphene lattice which causes an opening of small (0.02 eV) band gap. Present findings can have promising application towards detecting the presence of toxic sarin molecules.

Investigation of Sarin Nerve Agent Adsorption Behavior on BN Nanostructures: DFT Study

The adsorption behavior and electronic response of BN nanosheet, nanotube, and nanocage to sarin gas, a nerve agent, were studied using density functional theory calculations. The adsorption energy is increased by increasing the BN nanostructure curvature, and it is about − 0.5, − 1.6, and − 3.4 kcal/mol for BN sheet, tube, and cage, respectively. The BN sheet and tube are insensitive to sarin gas. Although the BN cage is sensitive, it suffers from a weak interaction, and low adsorption capacity. To overcome this problem the BN cage is doped with different impurity atoms including, Sc, Al, Si, and C. The Sc and Al dopings significantly increase the reactivity of BN cage to sarin but the sensitivity is not increased sensibly. The Si and C dopings make the BN cage more reactive and sensitive to sarin gas. The C-doped BN nanocage may be a promising sensor because of its higher sensitivity, compared to the Si-doped one. After the sarin adsorption on the C-doped BN cage, its gap decreases by about 64.0% which exponentially increases the electrical conductivity, creating an electrical signal. Also, the recovery time is about 7.9 × 1015, 1.4 × 1023, 0.004, and 0.013 s for Sc, Al, Si, and C-doped BN cages, respectively.

First-Principles Calculations of Sarin Adsorption on Anatase Surfaces

We report density functional theory calculations investigating the adsorption of the organophosphate nerve agent sarin (GB) on clean (101), (001)-(1 × 4), and (001)-(1 × 1) surfaces of anatase titanium dioxide (TiO2). Our calculations show that GB chemisorbs on all three surfaces by the formation of a dative bond between the phosphoryl oxygen and a five-coordinated titanium atom in the surface. The adsorption of GB on the (001)-(1 × 4) and (001)-(1 × 1) surfaces (−45.1 and −34.8 kcal mol–1) is substantially stronger than on the (101) surface (−18.2 kcal mol–1). This could be a result of reactive surface states observed within the TiO2 band gap at the (001) surfaces but not the (101) surface. Our calculations show that the GB adsorption passivates these surface states. GB adsorption also breaks a bridging oxygen bond on both (001) surfaces, leading to a titanyl group that is also predicted to occur in adsorption of the simulant dimethyl methylphosphonate (DMMP) on anatase (001). The ordering of the three a...

Adsorption of sarin on MgO nanotubes: Role of doped and defect sites

Sarin is a highly toxic organophosphorus chemical warfare agent which has been employed in various wars and terrorist attacks. Due to an urgent need of finding safe methods to decompose this toxic nerve agent, the research on decomposition of sarin gains importance. In the present work, the decomposition of sarin molecule on MgO nanotube and Ti-doped MgO nanotube has been investigated. For this purpose, the structural and electronic characteristics of nanotubes are first examined. It is seen that although doping with Ti modifies the properties of the nanotube, adsorption of sarin on both kinds of nanotubes presents similar characteristics. Adsorption is found to be more favorable at low-coordinated sites, i.e., the 3c site is preferred over 4c. Five kinds of surface defect sites have been considered i.e., O4c, O4c2−, Mg4c, Mg4c2+ and (MgO)4c. Adsorption of sarin on various defect sites produces different products. In two of the cases, the neutral oxygen defect and MgO defect, the molecule breaks completely into fragments and is destructively decomposed. Hence, our study proposes a new metal oxide system that might destructively adsorb chemical warfare agents and highlights the need for further exploration of untested metal oxide systems.

CI and DFT Studies of the Adsorption of the Nerve Agent Sarin on Surfaces

A theoretical study is presented on the adsorption of the sarin molecule, a nerve agent, on three model solid surfaces: aliphatic (graphane), aromatic (graphene), and ionic (CaO). Calculations are carried out using accurate electronic structure methods based on configuration interaction (CI) as well as complementary density functional theory (DFT) and time dependent (TD) DFT calculations. The objective is to describe surface interactions accurately in order to identify factors that affect adsorption of sarin. Potential energy curves are calculated and compared between surface types. Computed CI binding energies to graphane, graphene, and calcium oxide surfaces are 2.2, 4.5, and 13.2 kcal/mol, respectively. The corresponding DFT binding energies are 6.4, 4.8, and 18.8 kcal/mol, respectively. Excited states of free sarin as well as sarin bound to the surfaces are examined using TDDFT and CI. Low-lying excited states of the adsorption complexes involving excitations from the surface to sarin are calculated.

Adsorption of Sarin and Soman on Dickite: An ab Initio ONIOM Study

The adsorption of sarin (GB), isopropyl methylphosphonofluoridate (C4H10FO2P), and soman (GD), 3,3-dimethyl-2-butyl methylphosphonoflouridate (C7H16FO2P), on the octahedral and tetrahedral surfaces of dickite was investigated using the ONIOM(B3LYP/6-31G(d,p):PM3) and ONIOM(B3LYP/6-31G(d,p):HF/3-21G) methods and the representative cluster models. In the case of adsorption on the octahedral sheet of dickite, the location of six hydrogen atoms of the outer −OH groups and the geometry of the adsorbed molecules were optimized. In the case of adsorption on the tetrahedral side of the dickite layer, the geometry of the mineral fragment was kept frozen. The location and orientation of GB and GD on the tetrahedral and octahedral surfaces of dickite were found. The adsorption on the surface of minerals occurs because of the formation of multiple hydrogen bonds between adsorbed GB and GD and the hydroxyl groups (the octahedral side) and the basal oxygen atoms (the tetrahedral side). This type of adsorption results in the polarization and the electron density redistribution of GB and GD on the surface of the mineral. The interaction energies of sarin and soman with the octahedral and tetrahedral surfaces corrected by the BSSE energy were found. The adsorption energies obtained at the ONIOM(B3LYP/6-31G(d,p):PM3) level of theory and using large models of the mineral for the adsorption systems of GB and GD on the octahedral surface of dickite are about −16 and −15 kcal/mol, respectively. In the case of adsorption on the tetrahedral surface, the interaction energies of adsorption systems with GB and GD are about −7.0 and −9.0 kcal/mol, respectively.

Investigation and Development of Protective Ointments III : Adsorption characteristics of sarin from solutions

The adsorption of sarin from n -heptane solutions by silica gels, alumina, bentonite, and certain carbonaceous adsorbents was studied. The results obtained have been interpreted according to the Langmuir adsorption isotherm. Of the various adsorbents tested, those of a silicaceous nature were found to be superior, exhibiting very strong adsorptive tendencies toward the fluorophosphate ester. A linear relationship was found to exist between the limiting adsorptive capacity and the specific surface area of the adsorbents. The average area occupied by a sarin molecule, furthermore, was found to be approximately 80 A 2 , irrespective of the adsorbent, a value in reasonable agreement with that suggested by a molecular model. Both of these relationships indicate that sarin is adsorbed primarily as a unimolecular layer.