ABSTRACT
V-series nerve agents are very lethal to health and cause the inactivation of acetylcholinesterase which leads to neuromuscular paralysis and, finally, death. Therefore, rapid detection and elimination of V-series nerve agents are very important. Herein, we have carried out a theoretical investigation of carbon nitride quantum dots (C2N) as an electrochemical sensor for the detection of V-series nerve agents, including VX, VS, VE, VG, and VM. Adsorption of V-series nerve agents on C2N quantum dots is explored at M05-2X/6-31++G(d,p) level of theory. The level of theory chosen is quite adequate in systems describing non-bonding interactions. The adsorption behavior of nerve agents is characterized by interaction energy, non-covalent interaction (NCI), Bader's quantum theory of atoms in molecules (QTAIM), frontier molecular orbital (FMO), electron density difference (EDD), and charge transfer analysis. The computed adsorption energies of the studied complexes are in the range of -12.93 to -17.81 kcal/mol, which indicates the nerve agents are physiosorbed onto C2N surface through non-covalent interactions. The non-covalent interactions between V-series and C2N are confirmed through NCI and QTAIM analysis. EDD analysis is carried out to understand electron density shifting, which is further validated by natural bond orbital (NBO) analysis. FMO analysis is used to estimate the changes in energy gap of C2N on complexation through HOMO-LUMO energies. These findings suggest that C2N surface is highly selective toward VX, and it might be a promising candidate for the detection of V-series nerve agents.
ABSTRACT
Permeation and selectivity of alkaline metal atoms and ions through normal and defected hexagonal boron nitride is explored in the presence and absence of water. The defects include one (VB and VN), two (VBN) and three atoms (VB(2N) and VN(2B)) vacancies. The barriers are obtained by scanning potential energy surface for the movement of alkaline earth metal atoms and ions through the nanosheet. The size and morphology of defects in h-BN sheet significantly affect the energy barrier. h-BN sheet with VN defect possess good Be/Be2+ selectivity. Permeation of Be atoms through VBN-h-BN, VB(2N)-h-BN and VN(2B)-h-BN is a barrierless process. Mostly, the permeation barriers are reduced in the presence of water molecule for Be, Ca and Ca2+. The effect of water molecule is more pronounced on the permeation of Ca atom and ion through normal and defected h-BN sheet as compared to smaller alkaline earth metal atoms and ions. The study can be extended to investigate the separation capability of porous hexagonal boron nitride nanosheet for other metal atoms and ions. HighlightsPermeability of pristine and vacancy defected h-BN nanosheet is studied for alkaline earth metal atoms and ions.Increase in pore size and applied electric field decrease the permeation barriers for alkaline earth metal atoms and ions.VN h-BN sheet possess good Be/Be2+ selectivity.Permeation of Be atoms through VBN-h-BN, VB(2N)-h-BN and VN(2B)-h-BN is a barrierless process.Permeation barriers are reduced in the presence of water molecule for Be, Ca and Ca2+.Communicated by Ramaswamy H. Sarma.
Subject(s)
Boron Compounds , Boron , Metals, Alkaline Earth , Water , MetalsABSTRACT
Finding new materials with exceptionally large nonlinear optical response is an interesting and challenging avenue for scientific research. Here, we report the alkali metal doped Zn12O12 nanocages as inorganic electrides with excellent nonlinear optical response. Density functional theory calculations have been performed for geometric, electronic and nonlinear optical response of exo- and endohedrally alkali metal doped Zn12O12 nanoclusters. For exohedral doping, all different possible doping sites are considered for decoration of alkali metal on the nanocage. The electride nature of the complexes is highly dependent on the position of alkali metal doping. All exohedral complexes except for alkali metal doping on six membered ring (r6) are electride in nature, as revealed from frontier molecular orbital analysis. Interaction energies reveal that all doped nanoclusters except endo-K@Zn12O12 are thermodynamically stable. The exothermic encapsulation of alkali metals in Zn12O12 nanocages is in marked contradiction with other inorganic fullerenes where encapsulation is an endothermic process. The barriers for boundary crossing are also evaluated in order study the interconversion of exo- and endohedral complexes. Doping of alkali metal significantly influences the properties of nanocages. HOMO-LUMO (H-L) gap is reduced significantly whereas hyperpolarizability is increased several orders of magnitude. The NLO response of exohedrally doped complexes is higher than the corresponding endohedral complexes, which is in mark contradiction with the behavior of phosphide or nitride nanocages. The highest first hyperpolarizability of 1.0 × 105 au is calculated for K@r6-Zn12O12 complex. Third order NLO response of these complexes is calculated and compared with the best systems reported in the literature at the same level of theory.
