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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]

In organic photovoltaic technology, tailoring the acceptor or donor unit to enhance intramolecular charge transfer is a well-known approach, however, the effect of modifying conjugated bridge units is an underdeveloped phenomenon. In this study, this approach has been focused, where a series of conjugated bridges including, a) electron-excessive heterocycles, b) electron-deficient heterocycles, and c) short-chain unsaturated hydrocarbons have been substituted from thiophene bridge-containing D-π-A; N-methyl-4,5-diazacarbazole (donor) and bay-annulated indigo (acceptor) molecule. This quantum chemical study aims to investigate the effect of various types of π-conjugated bridges on the electronic structure and solar cell activity of already reported material. The selected π-conjugated bridges include electron-excessive (furan, pyrrole, & thiophene) and electro-deficient (diazine, tetrazine, & pyridine) heterocycles, and short-chain hydrocarbons (ethylene & ethyne). The optimized structural parameters e.g., dihedral angles (θ), distortion energies (E dis), & bond distances (d), and electronic behaviour i.e., Frontier Molecular Orbitals (FMO), Electrostatic Potentials (ESP), Density of States (DOS) spectra, dipole moments (μ), and absorption spectra of the hypothetically designed molecules are estimated using density functional theory calculations. The solar cell proficiency is investigated with transition dipole moment (μ T), reorganization energy (RE), Transition density matrix (TDM), exciton binding energy (E b), and open circuit voltage (Voc). Our finding encompassed that our designed D-π-A molecules show significant improvement in their electronic behaviour, especially when the thiophene bridge of the reference molecule is substituted with the excess electron heterocycles, especially pyrrole. The HOMO-LUMO gap of this particular molecule (MPy) is reduced to 2.07 eV, resulting in the significant charge transfer between donor and acceptor units (0.15 e-). Moreover, the results of RE, TDM, E b , and V oc also support the high solar cell efficiency of pyrrole-containing molecules. [Display omitted] • Photovoltaic properties enhancement through variation of conjugated bridge between donor- π-acceptor groups. • B3LYP-(BJ)D3/6–31+G(d, p) level of DFT was adopted. • The significant reduction of HOMO-LUMO gap (up to 2.07 eV) was observed. • RE, TDM, E b , and V oc analyses supported the high solar cell efficiency. [ABSTRACT FROM AUTHOR]

Though the gas sensing applications of graphdiyne have widely reported; however, the biosensing utility of graphdiyne needs to be explored. This study deals with the sensitivity of graphdiyne nanoflake (GDY) towards the uric acid (UA) within the density functional framework. The uric acid is allowed to interact with graphdiyne nanoflake from all the possible orientations. Based on these interacting geometries, the complexes are differentiated with naming, i.e., UA1@GDY, UA2@GDY, UA3@GDY, and UA4@GDY (Fig. 1). The essence of interface interactions of UA on GDY is derived by computing geometric, energetic, electronic, and optical properties. The adsorbing affinity of complexes is evaluated at ωB97XD/6–31 + G(d, p) level of theory. The stabilities of the complexes are quantified through the interaction energies (Eint) with reasonable accuracy. The calculated Eint of the UA1@GDY, UA2@GDY, UA3@GDY, and UA4@GDY complexes are − 31.13, − 25.87, − 20.59, and − 16.54 kcal/mol, respectively. In comparison with geometries, it is revealed that the higher stability of complexes is facilitated by π-π stacking. Other energetic analyses including symmetry adopted perturbation theory (SAPT), noncovalent interaction index (NCI), and quantum theory of atoms in molecule (QTAIM) provide the evidence of dominating dispersion energy in stabilizing the resultant complexes. The HOMO–LUMO energies, NBO charge transfer, and UV–vis analysis justify the higher electronic transition in UA1@GDY, plays a role of higher sensitivity of GDY towards the π-stacked geometries over all other possible interaction orientations. The present findings bestow the higher sensitivity of GDY towards uric acid via π-stacking interactions. [ABSTRACT FROM AUTHOR]

Promising sensor applications of graphdiyne for various gases and toxic molecules have extensively been studied; however, similar studies for the detection of chemical warfare agents (CWA) are not reported. Here, we report the adsorption of Lewisites (L1, L2, and L3), on graphdiyne nanoflake (GDY) using density functional theory (DFT) ωB97XD/6‐31+G (d,p) method. Our results show that Lewisite molecules are preferably physiosorbed at the triangular portion of GDY nanoflake. In particular, the binding of L3 (3‐chlorovinyl arsine) on GDY nanoflake is thermodynamically favorable than L1 (1‐chlorovinylarsonous dichloride) and L2 (2‐chlorovinylarsonous chloride). Symmetry adopted perturbation theory (SAPT0) analysis reveals that the least contribution of repulsive exchange component is present in case of L2@GDY complex. Further, the smallest HOMO‐LUMO energy gap, appreciable charge transfer (NBO), and largest red shift in ultraviolet‐visible (UV‐Vis) spectrum are also in accord with the higher %sensitivity of graphdiyne toward L2. Quantum theory of atom in molecule (QTAIM) analysis is performed to get insight into the noncovalent interactions. Therefore, it is predicted that the sensitivity of GDY nanoflake is potentially high for Lewisite especially for L2. [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]

Excess electron generation through doping with alkali and superalkali metals is well known to enhance NLO responses. On the contrary, superhalogen doping is an unexplored dimension. Herein, we report the first ever examples where superhalogen doping alone is introduced as a new and effective approach to impart large NLO responses. Density functional theory (DFT) calculations illustrate that superhalogen (BeF3 and BeCl3)-doped cyclic oligofurans (nCF) possess exceptionally high NLO responses (first hyperpolarizability (β0), hyper-Rayleigh scattering coefficient (βHRS), electro-optical Pockels effect (EOPE), second harmonic generation (SHG), and nonlinear refractive index (n2)), which are not trivial for organic compounds. Upon doping with superhalogens, the first hyperpolarizability (β0) of nCF increases to 3 × 105 a.u. in the BeF3@6CF complex, whereas the β0 values of the BeF3@5CF, BeCl3@5CF and BeCl3@6CF complexes are 6 × 104, 3 × 104 and 4 × 104 a.u., respectively. An enormously large third order nonlinear optical response coefficient with an electric field-induced second harmonic generation (ESHG) value of 2.1 × 109 a.u. is observed for the BeCl3@6CF complex. The remarkable NLO responses of the superhalogen-doped cyclic oligofuran complexes are due to the electron withdrawing nature of the halogen atoms, which are responsible for withdrawing electrons from the oxygen atoms of nCF to create poles. The significant hyperpolarizability (β0) of the BeF3@6CF complex is due to the most electronegative nature of fluorine. Furthermore, these results are rationalized through a two-level model. Bvec values are calculated for these complexes because they give more meaningful numbers from an experimental point of view. The stability of the complexes is judged through interaction energies, whereas electronic properties are calculated by chemical reactivity descriptors, the HOMO–LUMO gaps (Eg) and NBO charge transfer analysis. TD-DFT calculations reveal that the maximum absorbance for the BeF3@6CF complex is shifted to the longest wavelength. [ABSTRACT FROM AUTHOR]

[Display omitted] • The chiral recognition ability of CBPQT4+ is systematically studied using DFT simulations. • Chirodiastalic energy (E chir) indicates the L -enantiomer complexes are more stable than D -complexes. • The quantitative analyses of noncovalent interaction indicate the structures are stabilized by the dispersion forces. • The electronic properties analyses illustrate the high chiral response of CBPQT4+ towards small molecular amino acids. • Overall findings reveal that the CBPQT4+ macrocycle has an excellent ability to differentiate between L - and D -enantiomers. Two enantiomeric forms of amino acids in a chiral medium behave quite differently because of the different orientation of their functional groups in space. Thus, the phenomenon of chiral recognition is crucial with the focus on applications in molecular sensing and enantioselective separations. The present research work is focused on the illustration of the potential chiral recognition of a porous CBPQT4+ macrocycle for sulfur-containing amino acids, which is elucidated by the conformational energies landscape with quantitative non-covalent analysis and their electronic behaviour. Herein, we report the chiral recognition of sulfur-containing amino acids e.g., cysteine (CY), homocysteine (HCY), and methionine (MT), by tetra-protonated (4+) CBPQT macrocycle via density functional theory (DFT) calculations. Geometry optimization, thermodynamic stability, noncovalent interaction analysis, symmetry-adapted perturbation (SAPT), and electronic properties analyses are employed to characterize the chiral response of the complexes formed by CBPQT4+ with D - and L -isomers of selected amino acids. The interactive conformations of complexes indicate physisorption of amino acids through the central cavity of the macrocycle. The maximum chiral discrimination is observed in the case of D - and L -cysteine isomers, which is 3.56 kcal/mol. It is revealed that the complex; D -CY@CBPQT4+ is energetically more stable than the L -CY analogue, whereas, L -HCY and L -MT show higher stability as compared to D -type counterparts, probably due to the interaction of the thiol groups with π-electrons of macrocycle in respective stable complexes. Non-covalent interaction (NCI) analyses including, reduced density gradient-based NCI index and SAPT reveal that the methionine-based complexes show the highest attractive components e.g., electrostatic, dispersion, and induction with the lowest repulsive exchange contribution, which is followed by homocysteine and cysteine. Overall, results show that the CBPQT4+ macrocycle has an excellent ability to differentiate between L - and D -amino acids, the difference is more pronounced when the structure of amino acid is small and rigid. [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]

Polypyrrole is experimentally reported as an excellent sensor for biological molecules including urea and uric acid. DFT calculations at M05-2X/6–31++G(d,p) are performed to gain theoretical insight into the sensing mechanism of polypyrrole for urea, uric acid, acetamide and sulfonamide. Geometry optimization and electronic property calculations have been performed on a series of oligopyrrole (1, 3, 5, 7 and 9) complexes, and the properties are extrapolated to infinite polymer through 2nd degree polynomial fit. Energy decomposition analyses (SAPT0) have been performed to demonstrate the contribution of electrostatic, induction, exchange and dispersion. The trend of SAPT0 interaction energies is very much comparable to that of binding energies. The noncovalent components of SAPT0 regularly increase with oligomer chain length; however, these components become almost constant after trimer for urea, acetamide, and sulfonamide. The increase in interaction and SAPT0 energies illustrate an increase in sensitivity of polypyrrole. Charge transfer and electronic properties also illustrate the high sensitivity of polypyrrole for uric acid. Energy difference between HOMO and LUMO orbitals of polypyrrole decreases upon doping with analytes. The decrease in the HOMO-LUMO gap shows an increase in the conductivity of polypyrrole. Our results indicate that polypyrrole has the highest sensing ability for uric acid, consistent with the experimental observations. [ABSTRACT FROM AUTHOR]

An accurate comparison of the interaction of furan, pyrrole, and thiophene with different gaseous analytes is vital not only for understanding the sensing mechanism of corresponding polymers but also for rational design of new materials. In the present study, DFT calculations at (M05-2X/Aug-cc-PVDZ) have been performed to investigate the interaction behavior of furan, pyrrole, and thiophene (as models for their corresponding polymers) with different analytes (NH, CO, CO, NH, HCN, HO, HS, CH, CHOH, SO, SO, HO). The interaction of heterocycles with analytes is illustrated by changes in geometric, energetic, and electronic properties. SAPT calculations were performed for energy decomposition analysis to study the contribution of non-covalent components of the total interaction energy for each complex. Analysis of energetic and electronic properties reveals that all heterocycles are highly sensitive to SO. The results suggest that sensing ability of polypyrrole is higher than polyfuran and polythiophene for all analytes. [ABSTRACT FROM AUTHOR]

In this study, oxygenated triarylmethyl (oxTAM) is investigated by DFT calculations as a drug carrier framework for Nitrosourea (NU) and Fluorouracil (FU) drugs. Based on the adsorption analysis i.e. , energies and distances between interacting atoms, it is found that oxTAM exhibits excellent carrier abilities for the delivery of FU (−1.53 eV & 2.00 Å) and NU (−1.33 eV & 2.12 Å) drugs. NCI and QTAIM results indicate the presence of hydrogen bonding in drug-carrier complexes. The values of dipole moment and global chemical descriptors show the significant reactivity of oxTAM for NU and FU drugs. Based on electronic property analysis, FU@oxTAM has a higher adsorption trend for complexation with oxTAM as compared to NU@oxTAM. Moreover, FU can easily release from the carrier due to the decreasing adsorption stability after protonation under an acidic environment as well as a short recovery time observed for the oxTAM carrier surface. Keeping in view all the above parameters, we inferred that oxTAM can serve as a potential drug delivery system for anticancer drugs including, Nitrosourea and Fluorouracil drugs. [ABSTRACT FROM AUTHOR]

The desirability of the high nonlinear response of two-dimensional (2D) materials for electronics and optoelectronic devices drove us to investigate the nonlinear optical (NLO) behavior of alkali metal atom (AA) doped lithiated boron-containing hexahydroxy-triphenylene (LiBHHTP). In this context, the geometric, electronic, optical, and NLO properties are investigated. The doped AA atoms including Li, Na, and K preferably interact via the oxygen atoms of the LiBHHTP surface. The stability of the doped complexes is revealed by the interaction energies (E int), which are −22.90, −16.10, and −16.52 kcal/mol for Li@LiBHHTP, Na@LiBHHTP, and K@LiBHHTP complexes, respectively. The alterations in the electronic behavior of LiBHHTP are observed upon doping with alkali atoms via Frontier Molecular Orbital (FMO), Natural Bond Orbital (NBO), and the Density of State (DOS) analyses. The FMO analysis reveals that these complexes are electride in nature with absorption transparency in the UV–Vis range. Finally, the NLO behavior of designed complexes is evaluated through static and dynamic hyperpolarizabilities. Among reported complexes, K@LiBHHTP exhibits significantly large static hyperpolarizability (βₒ), 2.24 × 105 au. The dynamic NLO response of doped LiBHHTP complexes is also high, where the values are ranged in between 3.67 × 105 and 6.04 × 108 au at 1064 nm. This article not only highlights the effects of alkali atom doping on the NLO behavior of materials but also presents the first Lithiated boron-containing triphenylene as a next-generation optoelectronic material. [Display omitted] [ABSTRACT FROM AUTHOR]

The detection of toxic molecules has gained imperial attention to protect living organisms and their environment. The broadly explored sensor behaviour of triazine-based C3N4 reveals their ultra-high sensitivity towards numerous toxic molecules e.g., chemical welfare agents. However, another potential analogue of C3N4 composed of heptazine exhibits remarkable electrical and optical properties but has not been much explored in sensor technology, especially for toxic pollutants. Keeping this in mind, the sensing performance of heptazine-based g-C3N4 is explored for the detection of toxic amides by using First Principles calculations. In this context, acryloyl amide (C2H3CONH2), acryloyl chloride (C2H3COCl), fluoroacetic acid (C2H3FCOOH), flouroaceta amide (C2H2FONH2), flouroacetyl chloride (C2H2FOCl) are selected as toxic pollutants; herein, for the ease of understanding, these molecules are represented as AAM, ACl, FAAc, FAA, & FACl, respectively. The electrochemical sensitivity of g-C3N4 is determined via geometric, energetic, and electronic properties analysis, whereas the photochemical sensitivity is explored by UV–Vis absorption analysis based on TD-DFT calculations. The interaction energies of studied molecules on C3N4 range between − 9.09 and - 23.39 kcal/mol depending upon the type of interactions e.g., hydrogen bonding or dispersion, which are explained on the basis of Symmetry Adopted Perturbation Theory, Non-Covalent Interaction Index, and Quantum Theory of Atoms in Molecules analyses. The density of State analysis, Frontier Molecular Orbitals and NBO charge transfer characterized that the electronic behaviour of g-C3N4 can be an effective sensor material with a semiconducting nature and significant charge transfer. Lastly, UV–Vis absorption analysis confirms the photosensitivity of g-C3N4 upon interaction with toxic molecules. [ABSTRACT FROM AUTHOR]

In this study, for the first time, boron oxide nanoflake is analyzed as drug carrier for favipiravir using computational studies. The thermodynamic stability of the boron oxide and favipiravir justifies the strong interaction between both species. Four orientations are investigated for the interaction between the favipiravir and the B3O3 nanoflake. The Eint of the most stable orientation is −26.98 kcal/mol, whereas the counterpoise-corrected energy is −22.59 kcal/mol. Noncovalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses are performed to obtain insights about the behavior and the types of interactions that occur between B3O3 nanoflake and favipiravir. The results indicate the presence of hydrogen bonding between the hydrogen in the favipiravir and the oxygen in the B3O3 nanoflake in the most stable complex (FAV@B3O3-C1). The electronic properties are investigated through frontier molecular orbital analysis, dipole moments and chemical reactivity descriptors. These parameters showed the significant activity of B3O3 for favipiravir. NBO charge analysis transfer illustrated the charge transfer between the two species, and UV-VIS analysis confirmed the electronic excitation. Our work suggested a suitable drug carrier system for the antiviral drug favipiravir, which can be considered by the experimentalist for better drug delivery systems. [ABSTRACT FROM AUTHOR]

In this study, for the first time, static and dynamic NLO responses of pure and superhalogen doped aromatic heterocyclic monomers have been investigated by using density functional theory (DFT) calculations. The thermal, electronic, linear, and nonlinear optical properties are computed at the ωB97XD/6-31+G(d,p) method. The thermodynamic stabilities of reported complexes are estimated based on interaction energies, which are in the range of −28.06 to −83.20 kcal/mol. The lowest interaction energies are observed for AlF 4 @X (X = C 4 H 4 NH, C 4 H 4 O, C 4 H 4 S, and C 5 H 5 N) complexes, which correspond to their higher stabilities. The appreciable decrease in the HOMO-LUMO energy gap (E gap) is an indicative of the increase in reactivity after doping with superhalogens. The decrease in E gap is further demonstrated with the help of density of state (DOS) analysis. The significant nonlinear optical responses of the superhalogen doped aromatic heterocyclic monomers are due to the strong electron-withdrawing nature of the fluorine atom. Overall, the results indicate the high NLO response for the AlF 4 @X complexes due to the presence of four electron-withdrawing fluorine atoms in AlF 4. The NLO results are further analyzed through the two-level model. • Superhalogen doping of aromatic heterocyclic monomers is investigated for enhancement of NLO response. • HOMO-LUMO gap significantly decreases upon complexation. • AlF 4 @X exhibit significant thermodynamic stability upto −83.20 kcal/mol. • AlF 4 @X showed excellent third order nonlinear response. [ABSTRACT FROM AUTHOR]

The aim of this study was the design of novel NLO materials based on superalkali doped NH 2 -GDY. Accurate analysis of the interaction stability was obtained at the ωB97XD/6–31+G(d, p) level of theory. Geometric, energetic, electronic and hyperpolarizability analyses collectively illustrate the remarkable static and dynamic NLO response of the reported complexes. [Display omitted] Keeping in mind the desirability of novel two-dimensional materials with an ultra-high nonlinear optical (NLO) response for the fabrication of optoelectronic devices, we have investigated nine complexes by doping superalkalis (M 2 X; M = Li, Na, K and X = F, Cl, Br) onto the novel aminated graphdiyne (NH 2 -GDY) quantum dots. The geometric, electronic and NLO responses (static and dynamic) of the M 2 X doped aminated graphdiyne (M 2 X@NH 2 -GDY) complexes have been systematically investigated using density functional theory (DFT) computations. All the superalkalis are preferably oriented on the triangular large porous site of NH 2 -GDY containing extensive delocalized π-conjugated electrons and interact via an intermolecular π-electron donor–acceptor (D-π-A) process. The lithium and potassium-containing superalkali doped complexes exhibit high structural stability due to their large interaction energies. The change in the electronic properties of the M 2 X doped NH 2 -GDY quantum dots is investigated by analyzing the NBO charge transfer, vertical ionization energies (VIEs), HOMO-LUMO energy gaps and density of states spectra. TD-DFT calculations show ultra-high transparency of these complexes in the ultraviolet region. The strong NLO characteristics of the designed complexes are demonstrated by their high static and dynamic hyperpolarizability values. Among all the nine complexes, the K 2 F@NH 2 -GDY, K 2 Cl@NH 2 -GDY and K 2 Br@NH 2 -GDY complexes possess exceptionally high β o values: 1.16 × 104, 1.06 × 104 and 1.02 × 104 au, respectively, owing to the large atomic radius and high atomic number of the potassium metal atoms. The frequency-dependent NLO responses, Electro-Optical Pockels Effects (EOPE) and Second Harmonic Generation (SHG) are analyzed to investigate the dynamic NLO response. It is revealed that the K 2 X@NH 2 -GDY complexes also exhibit exceptionally high dynamic NLO responses (107 or 108 au) at 1064 nm wavelength. Our present research not only highlights the significance of superalkali doping on aminated graphdiyne quantum dots but also indicates that the K 2 X@NH 2 -GDY complexes are potentially important for next-generation optoelectronic devices. [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]

C 4 N is a novel porous two-dimensional material with fascinating electronic and chemical properties. Thereby, the sensing ability of C 4 N is the most aspect topic of research nowadays. In this study, potential application of C 4 N nanoflake as a chemical sensor for the toxic pesticides has been investigated using density functional theory calculations. The sensing ability of C 4 N for pesticides is evaluated through the interaction energy, noncovalent interaction index (NCI), quantum theory of atoms in molecule (QTAIM), molecular orbitals and CHELPG charge transfer analyses. The first principle calculations on ωB97XD/6-31G(d, p) level of DFT show that the C 4 N is selectively sensitive to Dichlorodiphenyltrichloroethane (DDT), Fenitrothion (FNT), Dimethoxy (DMDT), Ronnel (RN) and Fenthion (FT). The interaction of pesticides leads to the significant changes in the electronic structure of C 4 N. The observed sequence of interaction energy of our reported complexes is DDT@C 4 N > FNT@C 4 N > DMDT@C 4 N > RN@C 4 N > FT@C 4 N. The electronic structure changes can be demonstrated from two aspects: the strong interaction between pesticide molecule and C 4 N, the variation in HOMO-LUMO orbital energies and charge transfer from C 4 N to pesticide. The charges distribution between analytes and C 4 N nanoflake on interaction is analyzed by the electron density differences (EDD) and charge decomposition analysis (CDA). Our results reveal the potential application of C 4 N in electronic and sensor devices especially for the detection of toxic chemicals. [Display omitted] • The sensing of C 4 N nanoflake toward pesticides is investigated theoretically. • The results are based on the geometric, energetic, and electronic analyses. • ωB97XD and M052X-D3/6-31G (d,p) levels of DFT are implemented to measure the sensing affinity of C 4 N. • The thermodynamic stability is in the order of DDT@C 4 N > FNT@C 4 N > DMDT@C 4 N > RN@C 4 N > FT@C 4 N. [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]

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]

The chemical warfare agents (CWAs) are highly toxic for living systems and environment. These diverse effects of CWAs, especially blistering agents, need the development of highly selective sensors for their rapid and effective detection. Herein, by using density functional theory calculations, we explained the adsorption of nitrogen (NM) and sulphur mustard (SM) blistering agents on graphdiyne (GDY) sheet. The calculated adsorption energies illustrate the physisorption of blistering (SM & NM) agents on the graphdiyne surface. The symmetry adopted perturbation theory (SAPT) analysis predicts that the dispersion is a dominating component of interaction energy. Reduced density gradient (RDG) and quantum theory of atoms in molecules (QTAIM) analyses are performed to justify the nature of interactions. Based on QTAIM analysis, the interaction energies between graphdiyne and blistering agents are noncovalent in nature. Furthermore, RDG results reveals that the van der Waals interactions i.e., dispersion forces dominate in the complexes. The %sensitivity and average energy gap variations are illustrated by HOMO-LUMO gaps. The detection ability of graphdiyne is further studied using UV–Vis analysis, NBO charge transfer and density of state analysis. These properties depict the appreciable sensitivity of graphdiyne towards blistering agents (SM and NM). We believe that the results of this study are fruitful for experimentalist to design highly sensitive CWAs sensors using graphdiyne sheet. Unlabelled Image • The adsorption of blistering agents on GDY is studied by ωB97XD/6-31+G(d,p) method of DFT. • Adsorption behaviour is elucidated by SAPT, RDG and QTAIM analyses. • The dispersion forces dominate between BA-GDY complexes. • This study shows that GDY sheet has high sensitivity towards blistering agents. [ABSTRACT FROM AUTHOR]

Although, the sensor applications of straight chain conducting polymers are well explored, but, the cyclic analogues are not much explored in this regard. The density functional theory calculations are performed to study the interaction behaviour of tetracyclic oligomers such as tetrapyrrole (4CP), tetrafuran (4CF) and tetrathiophene (4CT) for the detection of harmful gases like, phosgene, thiophosgene and formaldehyde. The most stable interaction configurations, interaction energies (E int), interaction distance (D int), SAPT0 energies, NCI, NBO charge transfer, HOMO-LUMO gaps and maximum absorbance are evaluated to understand the sensitivity and selectivity of these cyclic analogues toward poisonous gases. The results of all these properties illustrate that 4CP exhibits the highest sensitivity towards analytes with the sequence of formaldehyde > phosgene > thiophosgene. The interaction energies are −10.91, −9.03 and −7.58 kcal mol−1 for fd@4CP, ph@4CP and tph@4CP complexes, respectively. SAPT0 results depict that the electrostatic forces have strong influence in these complexes which indicate the presence of strong hydrogen bond between 4CP and analytes. However, this is not the case in other oligomer-analyte complexes especially in 4CT based complexes. The highest sensitivity of 4CP enables it to act as promising sensing material for formaldehyde, phosgene and thiophosgene as compared to 4CF and 4CT. Image 1 • Sensing affinities tetracyclic analogues have been investigated. • Toxic chemicals namely phosgene, thiophosgene and formaldehyde are investigated. • ωB97XD/6-31 + G (d, p) method of DFT has implemented. • Tetracyclic pyrrole has high sensitivity over furan and thiophene analogues. [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]

Although citric acid (CA) has antioxidant, antibacterial, and acidulating properties, chronic ingestion of CA can cause urolithiasis, hypocalcemia, and duodenal cancer, emphasizing the need for early detection. There are very few documented electrochemical-based sensing methods for CA detection due to the challenging behavior of electrode fouling caused by reactive oxidation products. In this study, a novel, non-enzymatic, and economical electrochemical sensor based on cobalt oxide nanoparticles (CoO x NPs) is successfully reported for detection CA. The CoO x NPs were synthesized through a simple thermal decomposition method and characterized by SEM, FT-IR, EDX, and XRD techniques. The proposed sensing platform was optimized by various parameters, including pH (7.0), time (15 min), and concentration of nanoparticles (100 mM) etc. In a linear range of 0.05–2500 μM, a low detection limit (LOD) of 0.13 μM was achieved. Theoretical calculations (ΔRT), confirmed hydrogen bonding and electrostatic interactions between CoO x NPs and CA. The detection method exhibited high selectivity in real media like food and biological samples, with good recovery values when compared favorably to the HPLC method. To facilitate effective on-site investigation, such a sensing platform can be assembled into a portable device. [Display omitted] • Novel Cobalt oxide electrochemical sensing platform for citric acid detection. • Insight mechanistic with Density functional theory studies has been investigated. • Achieving a low detection limit of 0.13 μM within a linear range of 0.05–2500 μM. • Effective integration of real samples for use in clinical and food industries. • Great potential of fabricating a device for on-site measurements. [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]

Research is actively being carried out to design new materials with exceptional nonlinear optical (NLO) responses. In this context, a systematic investigation of designing novel hypothetical materials e.g., superalkalides based on stacked Janus dimer, all- cis -1,2,3,4,5,6-hexafluorocyclohexane (C 6 H 6 F 6) 2 has been reported using high-level density functional simulations. The superalkalides are designed here by doping alkali metals on the fluorine face and superalkalis on the hydrogen face of Janus dimer. The thermodynamic stability of newly designed complexes is demonstrated by the interaction energies (E int), ranging between −13.64 and −33.12 kcal/mol. Moreover, the superalkalide nature of these complexes is proved by negative charge and HOMO on superalkalis in natural bond orbitals (NBO) and frontier molecular orbitals (FMO) analyses, respectively. Energy gaps (E g) between HOMO and LUMO orbitals of the designed complexes lie in the range of 0.63–0.83 eV. UV–Vis analysis is performed to gain idea about the transparent region of electromagnetic spectrum for nonlinear activity. The nonlinear activity of the designed superalkalide(s) is studied by static first hyperpolarizability β 0 , dynamic first hyperpolarizability β (ω) and dynamic second hyperpolarizability γ(2- ω ; ω , ω). The highest β 0 , β (ω), and γ(2- ω ; ω , ω) ranges up to 1.1 × 107, 2.9 × 106 and 2.9 × 1012 au, respectively for designed complexes. A comprehensive examination of these superalkalides based on stacked Janus dimers with exceptionally high NLO response highlights their potential for use in nonlinear optical materials. [Display omitted] • Nonlinear optical response of Stacked Janus dimer based superalkalides is investigated. • Doping of alkali metals and superalkalis on the dimer serve to reduce the energy gap of the complexes significantly. • All the designed superalkalide complexes are transparent in deep UV region. • The highest β o value of 2.9 × 107 au is observed for K-2-K 2 F complex. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) switchable materials play a crucial role in the fields of electronics and optoelectronics. The selection of an appropriate switching approach is vital in designing such materials to enhance their NLO response. Among various approaches, thermos-switching materials have shown a 4-fold increase in NLO response compared to other photo-switching materials. In this study, we computationally investigated the geometric, electronic, and nonlinear optical properties of reversible lactone-based thermochromic compounds using the ωB97XD/6-311+G (d,p) level of theory. Molecular orbital studies are employed to analyze the electronic properties of the close and open isomers of these compounds, while time-dependent density functional theory (TD-DFT) analysis is utilized to evaluate their molecular absorption. Our findings reveal that the π-electronic conjugation-induced delocalization significantly influences the ON-OFF switchable nonlinear optical response of the lactone-based thermochromic compounds. Notably, among all compounds, the open isomer of lactone 2 exhibits the highest hyperpolarizability value (6596.69 au). Furthermore, we extended our analysis to investigate the frequency-dependent second and third-order hyperpolarizabilities. The most pronounced frequency-dependent NLO response is observed at 532 nm. Additionally, we calculated the refractive index of these thermochromic compounds to further assess their nonlinear optical response. The open isomer of lactone 1 demonstrates the highest refractive index value (3.99 × 10−14 cm2/W). Overall, our study highlights the excellent potential of reversible thermochromic compounds as NLO molecular thermos-switches for future applications. [Display omitted] • NLO response of lactone based thermochromic compounds is studied. • The open isomer of lactone exhibits higher static first hyperpolarizability than the close isomer. • Frequency dependent NLO increases with increasing frequency. • The open isomer of lactone 1 has the highest refractive index value of 3.99 × 10−14 cm2/W. [ABSTRACT FROM AUTHOR]

Despite the numerous publications describing the photocatalytic and electronic properties of heptazine-based C 3 N 4 , the systematic study on the sensing behavior of pure heptazine-C 3 N 4 toward harmful chemical warfare agents (CWAs) is still lacking. Herein, we performed DFT calculations to investigate the adsorption behavior of C 3 N 4 toward various harmful and toxic CWAs including formaldehyde (OCH 2), thioformaldehyde (SCH 2), phosgene (OCCl 2), and thiophosgene (SCCl 2). ωB97XD functional of DFT along with 6–31G (d, p) basis set is used for all calculations for accurate estimation of noncovalent interactions. The CWAs are physiosorbed onto the C 3 N 4 having calculated interaction energy between −16.01 and −11.00 kcal/mol. Noncovalent interactions are further analyzed by symmetry-adapted perturbation theory (SAPT0), noncovalent interaction index (NCI), and quantum theory of atoms in molecules (QTAIM) analyses. The electronic behavior is characterized by the HOMO and LUMO energies, their energy gaps, and natural bond orbital (NBO) charge transfer. The charge transportation either donation or back donation is characterized by energy density difference (EDD) and charge decomposition analysis (CDA) analyses. The results demonstrate the trend of sensitivity of C 3 N 4 for toxic gases is OCH 2 @C 3 N 4 > SCH 2 @C 3 N 4 > OCCl 2 @C 3 N 4 > SCCl 2 @C 3 N 4. This theoretical work suggests that the C 3 N 4 can act as a good electrochemical sensor for a variety of toxic gaseous molecules. [Display omitted] • The sensing abilities of C 3 N 4 towards toxic molecules have been characterized by using ωB97XD/6-31G(d, p) level of DFT. • The sensing behavior of C 3 N 4 is studied through interaction geometries, energies, and electronic properties. • Among designed structures, OCH 2 @h-g-C 3 N 4 exhibits the strongest interaction due to electrostatic interactions. • C 3 N 4 exhibits significant sensitivity towards toxic molecules. [ABSTRACT FROM AUTHOR]

The development of anode materials with an optimum cell voltage and better stability is an important challenge for high-performance Li-ion batteries. In this study, we have investigated the electrochemical potential of pristine and Li-doped C 60 fullerene through density functional theory (DFT) simulations, with a focus on their potential applications in lithium-ion batteries. Our findings reveal that exohedral doping with a more electronegative counter anion can significantly increase the cell voltage. Particularly, when lithium cations are encapsulated within C 60 fullerene with antimony hexachloride (SbC l 6 −) as the counter anion, the highest cell voltage of 2.06 V is achieved. Furthermore, we have explored the impact of substituting carbon atoms with boron, nitrogen, phosphorus, and silicon on the Gibbs free energy change and cell potential. These substitutions led to an acceptable cell voltage compared to pristine C 60 fullerenes where the most suitable cell voltage of 1.75 V is observed for SbCl 6 /Li@C 59 B. This enhancement occurs because boron increases the electron deficiency of C 60 fullerene, thereby promoting stronger interactions with electronegative counter anions. These systems with a cell voltage of 1.75 V are deemed ideal candidates in lithium-ion batteries. [Display omitted] • The electrochemical potential of C 60 fullerenes doped with counter anion is studied. • The cell potential is enhanced by substitution of carbon atom with hetero-atoms. • The most suitable cell voltage of 1.75 V is observed for SbCl 6 /Li@C 59 B. [ABSTRACT FROM AUTHOR]