Electron Density Difference Research Articles

AIEE active novel chalcone based fluorescent probe for sensitive detection of drotaverine in solid state and real samples through fluorescence enhancement

A novel chalcone based probe OBP with exquisite aggregation induced emission enhancement (AIEE) has been rationally synthesized through simple two-step process. Owing to remarkable emission characteristics, probe OBP has been employed for selective and sensitive detection of drotaverine (DV) in solution and solid state. Significant fluorometric and colorimetric enhancement in fluorescence emission was displayed by probe OBP at λmax 455 nm after exposure to DV. Photo induced electron transfer (PET) process is responsible for detection of DV through OBP down to nanomolar level. OBP-DV interaction was elucidated through fluorescence and UV–Vis. spectroscopy along with 1H NMR titration experiments. Moreover, density functional theory (DFT) calculations were performed to analyze thermodynamic stability, density of states (DOS), frontier molecular orbitals (FMO), non-covalent interactions (NCI), quantum theory of atom in molecule (QTAIM), electron density difference (EDD) and natural bond orbital (NBO). Additionally, OBP was investigated for DV detection in blood samples as well as in solid state.

Investigating the sensing efficiency of C6O6Li6 for detecting lung cancer-related volatile organic compounds: A computational density functional theory approach

Volatile organic compounds (VOCs), such as acetone (AC), isoprene (IS), 1-hexene (HX), and benzene (BN), are important biomarkers in the exhaled breath of lung cancer patients. This research evaluates the potential of C6O6Li6 as a sensor for detecting these VOCs in the early stages of lung cancer. The adsorption of VOCs on C6O6Li6 was explored using Density Functional Theory (DFT) calculations at ωB97X-D3/def2-TZVP level of theory. Interaction energies for the most stable complexes were observed as −18.08 kcal/mol for AC@C6O6Li6, −14.06 kcal/mol for HX@C6O6Li6, −9.12 kcal/mol for IS@C6O6Li6, and −8.31 kcal/mol for BN@C6O6Li6. These values indicate the physiosorption of VOCs on C6O6Li6. Noncovalent interactions between the VOCs and C6O6Li6 were studied through Quantum Theory of Atom in Molecule (QTAIM) and Non-Covalent Interaction (NCI) analyses. The electronic properties were evaluated through Frontier Molecular Orbital (FMO), Natural Bond Orbital (NBO), Electron Density Difference (EDD), and Density of States (DOS) analyses. FMO analysis shows an increase in the HOMO-LUMO energy gap upon interaction of these VOCs with the C6O6Li6 surface, while NBO analysis indicates charge transfer from the surface to the VOCs. This study significantly enhances our understanding of C6O6Li6′s potential as a sensor material for early lung cancer detection using breath biomarkers.

Fluoromethane and chloromethane adsorption studies on hydrogenated C8 nanosheets – A first-principles study

We studied the structural stability of hydrogenated C8 (H-C8) sheets which exhibit body-centered tetragonal (BCT) structure and found to be stable in its structure. The energy gap of H-C8 sheets is observed to be 3.517 eV. The structural firmness of H-C8 is verified with formation energy, which is recorded as −5.947 eV/atom. Besides, fluoromethane and chloromethane, two predominant halomethanes are adsorbed on H-C8 nanosheets. The effectiveness of the H-C8 sheets for the detection of fluoromethane and chloromethane is explored in the current work with the help of density functional theory (DFT) calculations. In addition, the electronic properties and adsorption attributes of fluoromethane and chloromethane on H-C8 sheets were investigated through the band structure, DOS spectrum, and electron density difference diagrams. Moreover, the charge transfer and adsorption energy calculations were also determined to ascertain halomethane adsorption. The results show that halomethanes are physisorbed (-0.429 eV to −0.823 eV) as well as chemisorbed (-1.574 eV) on H-C8 sheets. Thus, H-C8 nanosheets can be used as a sensing element towards fluoromethane and chloromethane molecules.

Effects of cage topology on ethylene adsorption mechanism in silver exchanged CHA and RHO zeolites: An Inelastic Neutron Scattering and Density Functional study

Zeolite-based adsorbents have been successfully used for many challenging separations due to their tunable properties. A particularly notable application involves the separation of light olefins from paraffins, wherein the molecular sieving properties of zeolites play a pivotal role. Additionally, the selective interaction of alkenes with transition metal cations, positioned within the channels and cavities of microporous zeolites, further enhances separation capabilities.This study aims to comprehensively characterize the interactions between ethylene and Ag+ exchanged zeolites, employing a multidisciplinary approach, combining Inelastic Neutron Scattering (INS), Infrared (IR) spectroscopy, Nuclear Magnetic Resonance (NMR), UV–Vis and Density Functional Theory (DFT) calculations. CHA and RHO, zeolites largely applied in gas separation processes, were chosen due to their similar small pore sizes and pore volume, but different cavity shapes and flexibilities.The interpretation of derived DFT Electron Density Difference, experimentally supported by 13C Solid State NMR results, provide an understanding of each framework’s role during the charge transfer mechanisms between ethylene and transition metal species. Specific deformations in the flexible framework of zeolite RHO explain a blueshift of the band at 400 cm−1 in the librational region of INS spectra compared to CHA. This structural change in RHO, represented by the conic shape of the cage 8-ring side pockets, increases steric effects over the adsorbate while rendering the metallic adsorption center less exposed within the zeolite’s cavity, finally leading to a weaker adsorption energy. The redshift of C=C stretching frequencies observed by IR spectroscopy and DFT calculations, as well as C=C and C-H bond lengthening of ethylene confirm the formation of π-complexes on silver in both zeolites and allowed a further evaluation of the effects of the different frameworks cages on the aforementioned interaction.

Mechanistic insights and DFT analysis of bimetal doped styrofoam-like LaFeO3 perovskites with in-built dual redox couples for enhanced Photo-Fenton degradation of Tetracycline

The rising number of contaminants released into the environment and the inadequacies of traditional wastewater treatment techniques have led to the demand for enhanced oxidation technologies like photo-Fenton. In this study, bimetal co-doped lanthanum orthoferrite (BixLa1-xCuyFe1-yO3 (x = 0, 0.01, 0.05, 0.1; y = 0, 0.01, 0.05, 0.1, 0.15)) based photo-Fenton catalysts with the in-built redox couples Fe3+/Fe2+, Cu2+/Cu+ and oxygen vacancies have been successfully synthesised via a facile one-pot solution combustion route. Systematic studies show that the Bi0.05La0.95Cu0.1Fe0.9O3 (LFOBC) exhibits an optimal photo-Fenton degradation rate of 0.0497/min for Tetracycline (TC) removal, being ∼ 1.8 and ∼ 6.2 times greater than Bi0.05La0.95FeO3 (LFOB) and pristine LaFeO3 (LFO) respectively. DFT analysis confirmed the better adsorption and dissociation of H2O2 on a bimetal co-doped catalyst and identified the electron density difference in LFOBC, which can induce the H2O2 dissociation. A detailed investigation of various influencing reaction parameters is explored. The degradation pathway for the LFOBC catalyst with the toxicological characteristics of each intermediate is analysed. This study presents the Bi0.05La0.95Cu0.1Fe0.9O3 as a potential photocatalyst for enhanced photo-Fenton degradation with excellent efficiency observed for the degradation of various harmful pollutants for environmental remediation.

Constructing asymmetric dual active sites through symbiotic effect for achieving efficient and selective photoreduction of CO2 to C2H4

Asymmetric dual active sites are constructed through symbiotic effect. Owing to the differences in electron density, adsorption capacity and dipole–dipole repulsion, the energy barriers are reduced, leading to selective C2H4 production.

DFT study on adsorption properties of TM(Ni, Co)Nx -doped graphene for high-temperature sensing of SF6 decomposed gases

Gas sensing is the key to online monitoring SF6 decomposition gases in gas-insulated switchgear (GIS) fault diagnosis. However, the gas sensors for high-temperature sensing of SF6 decomposed gases are still lacking. In this paper, the adsorption performance of TM(Co, Ni)Nx-doped graphene as gas-sensing materials for the SF6 decomposed gases of SO2, SOF2, and SO2F2 were studied by DFT calculations, especially for the case at high temperatures. The adsorption energy (Eads), adsorption distance (D), transferred charge (Qt), and molecular dynamics simulations were performed to study the gas adsorption ability of TMN2-doped graphene. The electronic structures were clarified by analysis of the density of states (DOS), the partial density of states (PDOS), electron density difference, and molecular orbitals. The molecular dynamics simulations at 873 K indicated the high thermodynamic stability of TM(Co, Ni)Nx-doped graphene, which promised their superior gas sensing performance to detect SF6 decomposed gases at high temperatures.

CO2 capturing by self-assembled belt[14]pyridine encapsulated ionic liquid complexes: a DFT study.

In the current study, CO2 capturing ability of encapsulated ionic liquids (ENILs) i.e., tetramethylammonium chloride (TMACl), 1,3-dimethylimidazolium chloride (MIMCl), and methylpyridinium hexafluorophosphate (MPHP) encapsulated in self assembled belt[14]pyridine (BP) has been studied. The results show that strong van der Waals forces are involved in capturing of CO2 by these encapsulated ionic liquids. Strong attractive forces arise from synergistic effect of ionic liquid (encapsulated) and atoms of belt. The interaction energies (E int) ranging from -12.54 to -18.64 kcal mol-1 reveal the capturing of CO2 by these systems as thermodynamically feasible process. The type and strength of interactions between CO2 and encapsulated ionic liquids is studied through QTAIM and NCI analyses. NCI analysis clearly shows that capturing of CO2 is assisted by van der Waals forces between CO2 and encapsulated ionic liquid complexes. The same feature is confirmed through QTAIM analysis as well. Natural bond orbital (NBO) analysis' results show the charge transfer between the fragments (encapsulated ionic liquids and CO2) which is validated further through electron density differences (EDD) analysis. Overall, transfer of charge towards CO2 from encapsulated ionic liquids is proved through the charge accumulation over CO2 (i.e., blue isosurfaces on CO2 molecules) through EDD analysis. The FMO analyses show the decrease in H-L gaps of encapsulated ionic liquids after CO2 capturing. The successful charge transfer and reduction in H-L gap indicate better interaction in the designed systems thus revealing these systems as a potential candidates for CO2 capturing. Overall, the best results for CO2 capture i.e., the highest interaction energy, the lowest H-L gap, and the strongest forces of interactions are shown by methylpyridinium hexafluorophosphate (MPHP) encapsulated belt[14]pyridine (BP-MPHP) system. This is due to the larger anion of methylpyridinium hexafluorophosphate as compared to the other two encapsulated ionic liquids with Cl- as anion which enables it to develop strong interactions with CO2. The designed belt[14]pyridine based encapsulated ionic liquid systems are promising prospects with better CO2 capture performance and represent a new entrant in the CO2 capturing systems.

Systematic surface bowing in 2D III-nitride monolayers.

In this article we report novel composite materials of bucky ball (C60 fullerene) and III-nitrides (BN, AlN, GaN, InN). The experimental feasibility of the novel composite materials is confirmed through negative binding energies and molecular dynamics simulations performed at 500 K. The structural properties of the novel composites are explored through density functional theory. An unusual phenomenon of surface bowing is observed in the 2D structure of the III-nitride monolayers due to the C60 sticking. This surface bowing systematically increases as one proceeds from BN → AlN → GaN → InN. The electron density difference and Hirshfeld charge density analysis show smaller charge transfer during the complexation, which is probably due to weak van der Waal's forces. The presence of van der Waal's forces is also confirmed by the Atom in Molecule analysis, Reduced Density Gradient Technique and Non-covalent Interaction analysis. This work provides a foundation for further theoretical and experimental studies of the novel phenomenon of systematic bowing in the 2D structure of III-nitride monolayers.

Intramolecular charge transfer enhanced optical limiting in novel hydrazone derivatives with a D1-D-Ai-π-A structure.

The present paper investigates one of the hydrazone derivatives (BTH with a D-π-A structure) based on density functional theory. With the computation results of ground state absorption (GSA), excited-state absorption (ESA) and multi-photon absorption (MPA), the optical limiting effect observed in the experiment for the BTH molecule can be well predicted and elucidated by the MPA-ESA mechanism. The analysis of the hole-electron and the electron density differences between two transition states reveal that the main transitions involved in the GSA and ESA of BTH could be recognized as local excitation. Based on these observations, four novel hydrazone derivatives based on the BTH unit with a D1-D-Ai-π-A structure were designed to promote intramolecular charge transfer (ICT). It shows that the ICT effect is well improved by adding the D1 and Ai units. Compared with the original BTH molecule, the main bands of GSA and ESA of D1-D-Ai-π-A molecules are both red-shifted. In addition, GSA, ESA and MPA probabilities are all improved because the obvious charge transfer character results in the transition dipole moment change from localized to delocalized. Accordingly, the optical limiting effect in these hydrazone derivatives is well enhanced. These observations provide guidance for designing novel optical limiting materials based on the hydrazone derivatives.

Exploring the stability and aromaticity of rare earth doped tin cluster MSn16- (M = Sc, Y, La).

Rare earth elements have high chemical reactivity, and doping them into semiconductor clusters can induce novel physicochemical properties. The study of the physicochemical mechanisms of interactions between rare earth and tin atoms will enhance our understanding of rare earth functional materials from a microscopic perspective. Hence, the structure, electronic characteristics, stability, and aromaticity of endohedral cages MSn16- (M = Sc, Y, La) have been investigated using a combination of the hybrid PBE0 functional, stochastic kicking, and artificial bee colony global search technology. By comparing the simulated results with experimental photoelectron spectra, it is determined that the most stable structure of these clusters is the Frank-Kasper polyhedron. The doping of atoms has a minimal influence on density of states of the pure tin system, except for causing a widening of the energy gap. Various methods such as ab initio molecular dynamics simulations, the spherical jellium model, adaptive natural density partitioning, localized orbital locator, and electron density difference are employed to analyze the stability of these clusters. The aromaticity of the clusters is examined using iso-chemical shielding surfaces and the gauge-including magnetically induced currents. This study demonstrates that the stability and aromaticity of a tin cage can be systematically adjusted through doping.

A hybrid ZnO/BaTiO3 nano-network for the enhancement of the energy harvesting

Energy-level matching and stress transfer are significant characters of heterojunction to achieve excellent carrier generation and transportation behavior for energy harvesting. Here, we proposed a novel flexible nanogenerator built by ITO/PET layers spin-coated with ZnO/BaTiO3 heterojunction composite, whose electrical output performance can be largely enhanced due to the nano-network constructed by BaTiO3 microspheres and ZnO nanorods. Under periodic stress, varying temperature field and contact-separation conditions, the energy harvesting capacity of ZnO/BaTiO3 nanogenerator is enhanced greatly compared with pure BaTiO3 one, which can be attributed to the improvements of stress and carrier transport efficiency depending on the network structure and energy band matching in ZnO/BaTiO3 heterojunction. The maximum output voltage and current are improved by 6.6 and 4.38 times to 7.2 V and 0.07 μA, respectively, after the polarization treatment by applied electric field, due to the ferroelectric domain rearrangement. While the highest output current reach to 1.0 μA and 2.0 μA for contact-separation and varying temperature modes as TENG and PyENG, respectively. A DFT theoretical result is obtained that electrons accepting/losing capacities of ZnO/BaTiO3 heterojunction are improved with increasing pressure according to the plane-averaged electron density difference. These results indicate that this simply-made multimode nanogenerator can be a promising candidate for energy harvesting under different external excitations.

Insight into properties and reutilization potential of spent polyaniline adsorbents containing transition metals through DFT calculations

Although adsorption technology is an efficient way for removing heavy metal pollutants from wastewater, its widespread application faces challenges related to the disposal and reutilization of hazardous spent adsorbents. Here, we employ density functional theory (DFT) calculations to investigate the properties and reutilization potential of spent PANI adsorbents containing transition metal ions. Bond strength analysis reveals the high stability of spent PANI adsorbents, which is crucial for their safe reutilization. The interaction region indicator (IRI), localized orbital locator (LOL), and decomposition analysis of Wiberg bond order were employed to understand the nature of the bonds between transition metals and imine N atoms. Fukui function analysis indicates that the presence of reducing groups and reductive metal ions in spent PANI adsorbents enhances their chemical stability. The atomic dipole moment corrected Hirshfeld (ADCH) charge and electron density difference (EDD) analysis reveals electron transfers between transition metals and PANI. Moreover, assessments of electrical conductivity, electronic density under electric fields, excited states, and surface charge demonstrate that spent PANI adsorbents hold significant potential for use in energy storage, electrocatalysis, photocatalysis, and environmental pollutant removal. This study provides a molecular-level understanding of the properties and reutilization potential of spent PANI adsorbents.

Ab initio investigation of the competition of pnicogen, halogen, and hydrogen bonds resulting from the interactions between cyanophosphine and hypohalous acids.

The complexes formed as a result of the interactions between cyanophosphine (CP, H2PCN) and hypohalous acid molecules (HOX, X = F, Cl, Br, and I) were studied by employing ab initio computations conducted at the MP2/aug-cc-pVTZ level. Three types of complexes were acquired (I, II, and III) as a result of the (O∙∙∙P) pnicogen bond, the (N∙∙∙H) hydrogen bond, and the (N∙∙∙X) halogen bond interaction, respectively. The results of harmonic vibrational frequency calculations with no imaginary frequencies confirmed the structures as minima. In addition, given the interaction energy of the complexes, hydrogen bond complexes of structure II have the highest stability compared to other structures. In all studied complexes, the strength of the interactions depended on the electronegativity of the halogen atoms. The characteristics and nature of the whole three types of complexes were examined and evaluated with natural bond orbital (NBO), atom in molecules (AIM), molecular electrostatic potential (MEP) maps, non-covalent interaction (NCI) index, and electron density difference (EDD) analyses. The optimization of all complexes and corresponding monomers was conducted through the ab initio method, employing the MP2 level along with the aug/cc-pVTZ basis set for all atoms, except for the iodine (I) atom, for which the aug-cc-pVTZ (PP) basis set was employed. Subsequent frequency calculations were executed to ascertain the minimum energy state of the complexes at the MP2 level and the aug/cc-pVTZ basis set, utilizing Gaussian09 software. The MEP maps of the monomers were generated using the analysis-surface suite (WFA-SAS) software package. To probe the orbital interactions within the studied complexes, NBO analysis was performed employing NBO software. The assessment of bond nature, topological features, and electron density values at critical points for the studied complexes was undertaken using AIMAll software. The NCI index was derived utilizing Multiwfn software, and its three-dimensional representation was rendered using VMD software.

Influence on the mechanical properties and electronic structures of Cu-alloyed Ti5Sn3 compounds from first-principles calculations

First-principles calculations within density functional theory are performed to evaluate the mechanical properties and electronic structures of Cu-alloyed Ti5Sn3 compounds. It was confirmed that the Cu atom prefers to occupy Ti6g site with the lowest site occupation energy. The mechanical properties show that the bulk modulus of Ti5Sn3 can be reduced after Cu alloying. In addition, both the Young's modulus and Poisson's ratio increase and then decrease as the increasing of Cu atoms. The density of states and electron density differences reveal that the replacement of Cu atoms generates new chemical bonds but weakens the p-d orbital hybridization between Ti and Sn atoms, leading to a first increase and then decrease in elastic modulus and hardness.

Evaluate the potential utilisation of B3S monolayer as a novel formaldehyde gas sensor

It is crucial to identify an efficient system for the sensing of formaldehyde (FD). The feasibility of utilising a B3S monolayer (B3SML) detector of FD was evaluated by analysing the adsorption, optical properties, gas-sensing behaviour, and electronic properties of FD and other gas molecules on the B3SML under density functional theory (DFT). The pristine B3SML was found to have satisfactory sensing toward FD molecules. The analysis of the adsorption mechanisms, geometric systems, adsorption energy, electronic and optical properties, charge transfer, and electron density differences revealed that the B3SML could potentially serve as an FD detector. It can be said that the B3SML is a promising sensor for detecting FD molecules. The present study contributes to the existing knowledge of gas-surface interactions and helps develop 2D sensor structures to detect FD gas molecules.

Revealing the mechanism of manganese doping in sulphoaluminate cement clinker

The production of cement clinker from solid waste generated by industrial development is a valid way to reduce the exploitation of natural resources and protect the environment. This paper reports the doping behavior of manganese (Mn) ions in sulphoaluminate cement (SAC) clinker. Results from energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and density functional theory (DFT) simulations indicate that Mn ions enter C4AF by replacing Fe ions, and rarely incorporate into the other two minerals, C4A3S‾ and C2S. Further analysis of the partial density of states (PDOS) and electron density difference (EDD) indicates that the Mn doping mechanism can be ascribed to the comparable electronic contributions of the host and guest ions. These insights into the doping behavior of Mn ions will provide meaningful information to guide the utilization of Mn-containing solid waste as an alternative raw material for the synthesis of SAC clinker.

Engineering functionalized Zr-MOFs as facile removal of indole: Experimental studies and first-principles modeling

Zr-based metal-organic frameworks (Zr-MOFs) are emerging as potential adsorbents for removing nitrogen contaminants in fuel and wastewater. Functionalized Zr-MOFs exhibited superior indole (IND) adsorption capacity than the original MOF, but the activity of the multiple adsorption sites has not been discussed. Through experiment measurement and Density Functional Theory (DFT) calculations, this research investigated the IND adsorption mechanism at various sites on Zr-BDC-NH2 and Zr-BDC-NO2. Based on the adsorption isotherm, the adhesion of IND with Zr-MOFs was determined via the Freundlich model. DFT results suggest that the IND adsorption occurred at highly active sites such as O-linker, μ3-O-cluster, N-amine, and O-nitro via hydrogen and π-hydrogen bonds. Furthermore, the binding energy at each adsorption site in Zr-BDC-NH2 is higher than in Zr-BDC-NO2. In addition to the hydrogen acceptor bond, the π-hydrogen bond has also been analyzed through the electron density difference.

Three‐Dimensional Ionospheric Evolution and Asymmetry of the Electron Density Depletion Generated by the 21 June 2020 Annular Solar Eclipse

AbstractThe three‐dimensional computerized ionospheric tomography (3DCIT) technique has been used to reconstruct the ionospheric response to the 21 June 2020 annular solar eclipse and the results are evaluated by constellation observing system for meteorology, ionosphere, and climate observations. The 3DCIT‐derived electron density (Ne) difference between the eclipse and quiet days showed that the Ne depletion was between 200 and 550 km and the maximum magnitude was about −3.0 × 1011 el/m3 which was at 280 km in altitude. The contributions from below 250 and 350 km altitudes to Vertical Total Electron Content (VTEC) depletion were ∼30% and ∼60%, respectively. Significant asymmetry of Ne depletion with respect to the eclipse path was captured in 3DCIT results, and the deviation conditions between the Ne depletion central line and eclipse path varied at different altitudes. Simulations with the thermosphere‐ionosphere‐electrodynamics general circulation model generally showed consistent ionospheric variations with GNSS (Global Navigation Satellite System) VTEC and 3DCIT electron density. Furthermore, term analysis on the ion continuity equation indicates that the asymmetry of Ne depletion was mainly induced by the neutral wind disturbance which converged toward the eclipse region and caused opposite transport effects on both sides of the eclipse path. The thermospheric composition was also changed by disturbed neutral wind and impacted plasma production and loss rates, contributing to the Ne depletion asymmetry.

Umpolung Isomerization in Radical Copolymerization of Benzyl Vinyl Ether with Pentafluorophenylacrylate Leading to Degradable AAB Periodic Copolymers

AbstractThis study revealed that benzyl vinyl ether (BnVE) shows a peculiar isomerization propagation in its radical copolymerization with an electron‐deficient acrylate carrying a pentafluorophenyl group (PFA). The co‐monomer pair inherently exhibits the cross‐over propagation feature due to the large difference in the electron density. However, the radical species of PFA was found to undergo a backward isomerization to the penultimate BnVE pendant giving a benzyl radical species prior to propagation with BnVE. The isomerization brings a drastic change in the character of the growing radical species from electrophilic to nucleophilic, and thus the isomerized benzyl radial species propagates with PFA. Consequently, the two monomers were consumed in the order AAB (A: PFA; B: BnVE) and the unique periodic consumption was confirmed by the pseudo‐reactivity ratios calculated by the penultimate model: r11=0.174 and r21=6600 for PFA (M1) with BnVE (M2). The pentafluorophenyl ester groups of the resulting copolymers are transformed into ester and amide groups by post‐polymerization alcoholysis and aminolysis modifications. The unique isomerization in the AAB sequence allowed the periodic introduction of a benzyl ether structure in the backbone leading to efficient degradation under acid conditions.