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Graphyne (GYN) has received immense attention in gas adsorption applications due to its large surface area. The adsorption of toxic ammonia and nitrogen halides gaseous molecules on graphyne has been theoretically studied at ωB97XD/6–31 + G(d, p) level of DFT. The counterpoise corrected interaction energies of NH3, NF3, NCl3, and NBr3 molecules with GYN are − 4.73, − 2.27, − 5.22, and − 7.19 kcal mol−1, respectively. Symmetry-adapted perturbation theory (SAPT0) and noncovalent interaction index (NCI) reveal that the noncovalent interaction between analytes and GYN is dominated by dispersion forces. The significant change in electronic behavior, i.e., energies of HOMO and LUMO orbitals and NBO charge transfer correspond to the pronounced sensitivity of GYN towards considered analytes, especially NBr3. Finally, TD-DFT calculation reveals a decrease in electronic transition energies and shifting of adsorption to a longer wavelength. The recovery time for NX3@GYN is observed in nanoseconds, which is many orders of magnitude smaller than the reported systems. The recovery time is further decreased with increasing temperature, indicating that the GYN benefits from a short recovery time as a chemical sensor. [ABSTRACT FROM AUTHOR]

Chemical warfare agents (CWAs) are highly poisonous and their presence may cause diverse effects not only on living organisms but also on environment. Therefore, their detection and removal in a short time span is very important. In this regard, here the utility of graphdiyne (GDY) nanoflake is studied theoretically as an electrochemical sensor material for the hazardous CWAs including A-230, A-232, and A-234. Herein, we explain the phenomenon of adsorption of A-series CWAs on GDY nanoflake within the density functional theory (DFT) framework. The characterisation of adsorption is based on optimised geometries, BSSE-corrected energies, SAPT0, RDG, FMO, CHELPG charge transfer, QTAIM and UV-Vis analyses. The calculated counterpoise adsorption energies for reported complexes range from − 13.70 to − 17.19 kcal mol−1. These adsorption energies show that analytes are physiosorbed onto GDY which usually takes place through noncovalent interactions. The noncovalent adsorption of CWAs on GDY is also attributed by the SAPT0, RDG and QTAIM analyses. These properties also reveal that dispersion factors dominate in the complexes among many noncovalent components (exchange, induction, electrostatic, steric and repulsion). In order to estimate the sensitivity of GDY, the %sensitivity and average energy gap variations are quantitatively measured by energies of HOMO and LUMO orbitals. In terms of adsorption affinity of GDY, UV-Vis analysis, CHELPG charge transfer and DOS analyses depict an appreciable response towards these toxic CWAs. [ABSTRACT FROM AUTHOR]

Cyclic oligofurans containing five and six furan rings (5CF & 6CF) doped with superalkalis are presented here as a new type of NLO material. The OLi3@nCF, ONa3@nCF and OK3@nCF (n = 5 & 6) complexes are optimized at the M05-2X/6-31+G(d,p) level of theory. In these complexes, the superalkalis maintain their identity, and interact through the cavity of the cyclic oligofurans (nCF). Nonlinear optical properties are obtained through first hyperpolarizability (βo) of the complexes. The NLO response is rationalized on the basis of dipole moment (μo), energies of crucial excitation states (Eex) and vertical ionization energies (VIE). The highest hyperpolarizabilities (βo = 5 × 107 a.u. and βvec = 3 × 107 a.u.) are observed for OK3@nCF complexes along with the lowest EH–L, prominent NBO charge transfer, the highest dipole moment, and pronounced polarizability. The remarkable NLO response is attributed to the generation of excess electrons by superalkali doping. UV-Vis spectra are calculated to realize the transparency of these complexes in the UV-Vis region. The results suggest that higher NLO response is obtained when superalkalis are doped in higher oligofurans. [ABSTRACT FROM AUTHOR]

Linear conducting polymers are extensively studied as sensors for various analytes, whereas studies on cyclic analogues are limited. In this study, sensor applications of cyclic oligothiophenes (nCTs) have been explored by means of DFT (density functional theory) calculations. Three models, namely, five (5CT)-, six (6CT)- and seven (7CT)-membered cyclic oligothiophenes are evaluated against twelve different gaseous analytes. For optimization of geometries and interaction energies, the B3LYP method including Grimme's dispersion correction (B3LYP-D3) was applied with the 6-31++G(d,p) basis set. Chemical interactions of nCTs with NH3, CO, CO2, N2H4, HCN, H2O2, H2S, CH4, CH3OH, SO2, SO3 and H2O analytes are analyzed via interaction energies, Gibbs free energies, electronic properties and UV-Vis analysis. The interaction energies are quantitatively correlated with the volume of the cyclic oligothiophene (nCT). The electronic properties are calculated at the widely accepted B3LYP/6-31G(d) level of theory; however, the TD-B3LYP/6-31G(d) method is used for the UV-Vis analysis. Symmetry-adapted perturbation theory reveals that the 5CT system is highly sensitive towards analytes as compared to the 6CT and 7CT systems. This assumption is also strengthened by the HOMO–LUMO gaps and excited state properties. ESAPT, HOMO–LUMO gaps, NCI, and NBO charge transfer suggest that nCTs are highly sensitive towards SO3 followed by SO2. The density of state spectra shows the reasonable variation in the peaks of nCTs upon interaction with SO2 and SO3 analytes. The findings of this study suggest that cyclic oligothiophenes can effectively be used for the rational design of atmospheric sensors, which are superior to the conventional sensors. [ABSTRACT FROM AUTHOR]

The sensing affinity of C 4 N is the most fascinating topic of research due to its excellent chemical and electronic properties. Moreover, owing to the highly active porous cavity, C 4 N can easily accommodate foreign molecules. Herein, we studied the adsorption properties of carbamate insecticides (CMs) namely, Dimetalin (DMT), Carbanolate (CBT), Isolan (ISO) and Propoxur (PRO) using density functional theory calculations. All the results are calculated at widely accepted ωB97XD functional along with 6-31G(d, p) basis set. The calculated counterpoise corrected interaction energy of the reported complexes ranges between −20.05 and −27.04 kcal/mol, however, the interaction distances are found to be higher than 2.00 Å. The values of interacting parameters depict that the carbamate molecules are physisorbed via noncovalent interactions that can easily be reversible. Moreover, the binding of selected insecticides notably changes the electronic structure of C 4 N. The electronic changes are characterized by the energies of HOMO & LUMO, their energy gaps and CHELPG charge transfer. The charge density difference between C 4 N surface and carbamate pesticides are characterized by EDD and CDA analysis. Moreover, the ab initio molecular dynamic study reveals that the complexes are stable even at 500 K. The photochemical sensing properties of C 4 N are estimated by time dependent UV–Vis calculations. The high sensitivity of C 4 N towards considered analytes enable it to act as a promising sensor for toxic pesticides. [Display omitted] • The sensing of C 4 N towards carbamate insecticides is investigated within the framework of DFT. • The results are characterized by the geometric, energetic, electronic, and optical analyses. • All the results are computed at ωB97XD/6-31G (d,p) level of DFT. • The trend of thermodynamic stability of complexes is as follow; DMT@C4N > CBT@C4N > ISO@C4N > PRO@C4N. [ABSTRACT FROM AUTHOR]

Motivated by the excellent geometric and electronic properties of recently reported triphenylene (TP), for the first time, we studied the nonlinear optical responses of superalkalis (Li 3 O and Na 3 O) doped triphenylene and amino (HATP), hydroxy (HHTP) and thiol (HTTP) functionalized quantum dots by using density functional theory. The geometric stabilities of eight reported complexes are measured through the interaction energies at ωB97XD/6-31+G(d,p) level of theory. Our results reveal that Li 3 O@HATP and Na 3 O@HATP complexes are highly stable with the interaction energies of −60.36 and −57.26 kcal/mol, respectively. The HOMO-LUMO energy gaps of TP, HATP, HHTP and HTTP are significantly varied upon complexation with M 3 O which is evident by the strong charge transfer from excess electron donor superalkalis (M 3 O) to the surfaces. However, the π back donation is more pronounced in M 3 O@HATP complexes, revealed by the negative value of CHELPG charge transfer on M 3 O. Due to the donation and back donation of charges between M 3 O and HATP, the significantly high first static hyperpolarizability ( β o ) and its projection to dipole moment ( β vec ) are computed for M 3 O@HATP complexes. The β o of Li 3 O@HATO and Na 3 O@HATP complexes are 3 × 104 au. The β o of Na 3 O@HHTP complex is surprisingly high (1 × 105 au) which is justified by the two-level model. Moreover, the NLO responses of co-doped Li 3 O/Na 3 O and mixed functional groups TP-quantum dots are also computed. Among them, the maximum β o (5 × 104) is observed for the Na 3 O@AHTP complex. Finally, the TD-DFT calculations reveal that the reported complexes show excellent transparency in the ultraviolet region especially M 3 O@HATP and Na 3 O@HHTP complexes. [Display omitted] • The NLO response of superalkalis (M 3 O) doped TP, HATP, HHTP and HTTP are computed. • The NLO responses of these novel complexes are investigated in the framework of density functional theory (DFT) calculations. • The results are rationalized by analyzing the geometric, energetic, electronic, linear and nonlinear optical properties. • Theoretical results reveal that Na 3 O@HATP, Li 3 O@HATP and Na 3 O@HHTP complexes exhibit superior optical behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study theoretically presents the sensing affinities of cyclic tetrapyrrole (CTPy) towards toxic gaseous molecules. • The sensitivity of CTPy is measured against the toxic chemicals namely NH 3 , NF 3 , NCl 3 and NBr 3. • ωB97XD/6-31+G(d, p) level of DFT has implemented to measure the sensitivity of CTPy. • DFT results proved that CTPy is highly sensitive towards the considered analytes. Toxic gas sensors with ultrahigh sensitivity are highly desirable and those can be achieved with the help of infinite π-conjugation of cyclic conducting polymers. In this DFT study, we demonstrate the adsorption performance of tetracyclic oligopyrrole (CTPy) towards NH 3 and nitrogen halides including NF 3 , NCl 3 and NBr 3. The CTPy possesses infinite conjugation and highly active cavity which provides an excellent platform for the adsorption of upcoming gas molecules. Thermodynamically, the observed interaction energies of NH 3 , NF 3 , NCl 3 and NBr 3 analytes with CTPy at ωB97XD/6-31+G(d,p) level of theory are −13.14, −3.00, −6.00 and −7.50 kcal/mol, respectively. In addition, the molecular dynamic simulations are performed at GFN2-xTB method to confirm the stability of CTPy and respective complexes. The SAPT0 and NCI analyses reveal that dispersion forces play a significant role to stablize these complexes. Moreover, the electrostatic component also contributes in stabilizing the NH 3 @CTPy, NCl 3 @CTPy and NBr 3 @CTPy complexes. The variation in the electronic properties including HOMO-LUMO gaps of complexes along with the significant NBO charge transfer indicate the increasing conductivity of CTPy upon complexation with reported analytes. The prominent charge transfer on interaction might be due to the increasing π to π* transition, thus the λ max is shifted to longer wavelength in UV–vis spectra. [ABSTRACT FROM AUTHOR]

[Display omitted] • DFT studies are executed for hydrogen storage on Germanium (Ge 5 −2 & Ge 9 −2) and Silicon (Si92−) Zintl clusters. • The superior adsorption behavior of Zintl ions is illustrated by comparing with neutral analogues. • The adsorption behavior is investigated by using M052X/6-31+G(d,p) method. • The storage capability is explained with the help of geometric and electronic properties. Hydrogen storage is a subject of extensive research because hydrogen is a clean and eco-friendly for future applications. New strategies are being developed simultaneously for the easy and effective storage of hydrogen gas. Herein, we report the hydrogen adsorption on the Germanium and Silicon Zintl clusters within the framework of density functional theory (DFT). The excellent adsorption of hydrogen on Ge 5 2−, Ge 9 2−, Si 9 2− based Zintl clusters is achieved in terms of adsorption energies, electronic properties such as, HOMO-LUMO gaps, natural bond orbital (NBO) charge transfer, variation in dipole moment and density of state analysis (DOS). The superior adsorption affinities of these Zintl clusters are demonstrated in comparison with the adsorption capability of Ge and Si neutral clusters. In comparison, the adsorption energies of H 2 @Zintl phase complexes are higher than those of corresponding H 2 @neutral clusters. For example, the adsorption energy of b- exo -H 2 @Si 9 2− complexes is −11.13 kJ mol−1 which is far higher than −3.47 kJ mol−1 for the neutral analogue (b- exo -H 2 @Si 9 0). The effect of hydrogen adsorption on the E H-L gaps in Zintl clusters is also more pronounced, and the higher charge transfer is observed as well. Overall, results suggest the higher adsorption strength of Zintl cluster for H 2 as compared to neutral clusters. [ABSTRACT FROM AUTHOR]

The sensing properties of 2D carbon materials are well explored for various gaseous analytes, however, the detection of toxic chemicals e.g. , phosgene (Ph), thiophosgene (ThP) and phosogenoxime (PhO) are rarely studied. To the best of our literature survey, only a single study is found for the adsorption of phosgene on 2D carbon nanoflake (graphyne). This motivated us to explore the sensitivity of graphdiyne (GDY) nanoflake for the detection of phosgene and couple of its derivatives. Therefore, we have performed a density functional analysis to simulate the comparative interaction between phosgene, thiophosgene and phosogenoxime with graphdiyne nanoflake. The interaction behaviours are estimated by interaction energies, (symmetry adopted perturbation) SAPT0 analysis, (noncovalent interaction index) NCI analysis, molecular orbital analysis, natural bond orbital (NBO) charge transfer and UV–Vis absorption analysis. The obtained results demonstrate the trend in sensitivity of graphdiyne for analytes is PhO@GDY > ThP@GDY > Ph@GDY. The sensible justification for the particular observation is provided by the energy gaps between HOMO and LUMO orbitals in term of %sensitivity. The %sensitivity is in complete accord with the aforementioned trend. In addition, results suggest that graphdiyne based sensor for detecting phosgene and derivatives are better in sensitivity in comparison with already reported graphyne sensor. Image 1 • Adsorption of phosgene, thiophosgen and phosogenoxime molecules on graphdiyne nanoflake is studied. • ωB97XD/6-31+G (d,p) level of DFT has implied to elucidate the sensing applications. • Graphdiyne is highly sensitive toward phosgene and related derivatives. [ABSTRACT FROM AUTHOR]

This study presents a novel approach for exploring the sensitivity and selectivity of cyclic oligofuran (5/6/7CF) toward gaseous analytes and their comparison with straight chain analogues (5/6/7SF). The work is not only vital to understand the superior sensitivity but also for rational design of new sensors based on cyclic ring structures of oligofuran. Interaction of cyclic and straight chain oligofuran with NH 3 , CO, CO 2 , N 2 H 4 , HCN, H 2 O 2 , H 2 S, CH 4 , CH 3 OH, SO 2 , SO 3 and H 2 O analytes is studied via DFT calculation at B3LYP-D3/6–31++G (d, p) level of theory. The sensitivity and selectivity are illustrated by the thermodynamic parameters (E bind , SAPT0 energies, NCI analysis), electronic properties (H-L gap, percentage of average energy gap, CHELPG charge transfer, DOS spectra), and UV–Vis analysis. All these properties are simulated at B3LYP/6-31G (d) level of theory while UV–Vis is calculated at TD-DFT method. Cyclic oligofurans have high binding energies with analytes compared to 5/6/7SF which corresponds to higher sensitivity of 5/6/7CF. Furthermore, the cyclization of oligofuran significantly improves the sensitivity and selectivity of the system. Alteration in electronic properties of 5/6/7CF and 5/6/7SF is remarkably high upon complexation with SO 2 and SO 3. Further the stability of rings (5, 6 and 7 membered cyclic oligofurans) and their SO 3 complexes is also confirmed by molecular dynamics calculations. The findings of the work clearly suggest that the cyclic geometry enhances not only sensitivity but also selectivity of conducting polymers (oligofuran). Image 1 • The sensitivity and selectivity of cyclic/straight chain oligofurans is investigated for various gaseous analytes. • Grimme dispersion method is used for the correct determination of binding energies. • Theoretical analysis shows that cyclic oligofuran is a selective sensor for oxides of sulfur (SO 2 and SO 3). • All the properties are in favor of higher sensitivity and selectivity of cyclic oligofuran over straight chain counterpart. [ABSTRACT FROM AUTHOR]

Conducting organic polymers (COPs) are excellent candidates for sensor application. Polypyrrole is much superior in this regard than other COPs. A few studies indicate the potential of polypyrrole for some specific analytes; however, global picture of sensitivity and selectivity of polypyrrole sensor for various common analytes remains unclear. Here, we present first comprehensive study of polypyrrole sensors for various analytes: NH3, CO2, CO, N2H4, HCN, H2O2, H2S, CH4, CH3OH, SO2, SO3, and H2O. Geometric, thermodynamic, and electronic properties are calculated for infinite polymer to realize the sensor application of polypyrrole. The strongest interaction energy is observed for nPy‐N2H4 followed by nPy‐SO2/SO3 complexes. However, the interaction energy, charge transfer, FMO analysis, density‐of‐states, and electronic transitions envision the highest response toward SO2 and SO3. Surprisingly, the electronic properties of N2H4 complexes show quite opposite behavior than interaction energy. The uneven behavior of electronic properties for hydrazine is due to the interaction from two different sites which decreases the charge transfer. The excellent geometric and electronic properties related to the oxides of sulfur reveal that polypyrrole is highly selective toward SO2 and SO3. [ABSTRACT FROM AUTHOR]