The adsorption of bromomethane onto the exterior surface of aluminum nitride, boron nitride, carbon, and silicon carbide nanotubes: A PBC-DFT, NBO, and QTAIM study

Design of C24 fullerene-based sensors for gamma-butyrolactone detection as advanced tools for biomedical and pharmaceutical applications

The detection of gamma-butyrolactone (GBL) is crucial in medicinal chemistry due to its role as a precursor to gamma-hydroxybutyrate (GHB) and its potential for misuse. This study presents a sensor for GBL detection based on fullerene C24 and its beryllium-, calcium-, and magnesium-doped derivatives. Using density functional theory (DFT) and time-dependent DFT (TD-DFT), we optimized the structures and analyzed their electronic, optical, and quantum properties. Key parameters such as energy gaps, chemical reactivity, dipole moments, and adsorption energies were evaluated. Among the studied systems, magnesium-doped C24 (MgC23) exhibited the highest reactivity, a pronounced red shift in UV absorption upon GBL complexation, and an optimal balance of adsorption energy and recovery time. These results highlight MgC23 as a promising candidate for sensitive and efficient GBL detection in pharmaceutical and forensic applications.

Interaction of CO, CO2, CSO, H2O, N2O, NO, NO2, O2, ONH, and SO2 gases onto BNNT(m,n)_x, (m = 3, 5, 7; n = 0, 3, 5, 7; x = 3-9)

CONTEXT

This research investigates two critical areas, providing valuable insights into the properties and interactions of boron nitride nanotubes (BNNTs). Initially, a variety of BNNT structures (BNNT(m,n)_x, where m = 3, 5, 7; n = 0, 3, 5, 7; x = 3-9) with different lengths and diameters are explored to understand their electronic properties. The study then examines the interactions between these nanotubes and several gases (CO, CO2, CSO, H2O, N2O, NO, NO2, O2, ONH, and SO2) to identify the most stable molecular configurations using the bee colony algorithm for global optimization. The primary findings highlight the impact of nanotube diameter on these properties. It was observed that smaller diameters result in a larger energy gap due to increased quantum confinement. Significant charge transfer, especially with CO, was detected, affecting the electronic structure of the nanotubes. The study highlighted that BNNTs exhibit the strongest adsorption tendencies for NO₂, O₂, and SO₂. These findings underscore the critical roles of nanotube diameter and charge transfer in sensor applications and demonstrate the comprehensive utility of various analytical methods in understanding BNNT-gas interaction mechanisms.

METHODS

The research employs a comprehensive computational framework based on density functional theory (DFT). Various DFT methods, such as PBE0, B3LYP(GD3BJ), CAM-B3LYP, HSE06i, M06-2X, and ωB97XD functionals, are utilized along with the Def2tzvp basis set for the calculations. Structural optimizations are performed to ensure accuracy, and modifications to the energy gaps are analyzed using conceptual DFT. Additionally, Total Density of States (TDOS) analyses are conducted. Charge transfer mechanisms are investigated through Natural Bond Orbital (NBO) analysis. The interactions between gases and nanotubes are characterized at critical points using the Quantum Theory of Atoms in Molecules (QTAIM) framework.

Mechanism insights and experimental feasibility of using boron nitride nanocones for rapid adsorption and degradation of SF6 decomposition compounds

Gas-insulated switchgear (GIS) employs sulfur hexafluoride (SF6) as an insulating medium to shield electrical gadget. However, SF6 can decompose under sure situations, generating dangerous sulfur-based totally compounds which include SO2, SOF2, and SO2F2. These byproducts pose enormous dangers to both protection and environmental integrity. Efficiently adsorbing and disposing of those compounds is critical for ensuring operational reliability and reducing environmental dangers. This study investigates the adsorption and degradation mechanisms of SF₆ decomposition compounds (SO₂, SOF₂, and SO₂F₂) on boron nitride nanocones (BNNCs) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Our comprehensive analysis covers five distinct systems, exploring individual and combined adsorption scenarios. The findings reveal that the apex of BNNCs plays a crucial role in the adsorption process, showing high efficiency in adsorbing SO₂ (adsorption energy - 1.22 eV) and facilitating the catalytic breakdown of SOF₂ (adsorption energy - 1.57 eV). The positively charged potential at the nanocone's apex significantly influences the dissociation and subsequent adsorption of fluorine atoms, with an energy barrier for F dissociation at the apex (1.8 kcal/mol) much lower than at the sidewall (5.3 kcal/mol). In gas mixtures, SO₂ preferentially binds to the apex region of BNNCs, with a bond length of approximately 1.38 Å. BNNCs demonstrate superior adsorption capabilities for SO₂ and SOF₂ compared to other boron nitride nanostructures, with adsorption energies up to 89% higher. The electron transfer analysis reveals that BNNC complexes act as potent electron donors, particularly in the case of BNNC@3SO₂F₂. Additionally, BNNCs show significant potential as sensors for detecting SO₂F₂, with a rapid recovery time of 4.67 ps and a notable decrease in the Fermi level energy to -4.97 eV upon adsorption. The study also provides insights into the angular distribution and charge density difference profiles, offering a detailed understanding of the adsorption mechanisms. These findings have important implications for improving the safety and efficiency of gas-insulated switchgear (GIS) and contribute to the development of more effective environmental protection solutions in electrical power systems.

Investigating the electronic properties and reactivity of polyaniline emeraldine base functionalized with metal oxides

Due to its appealing qualities, such as its miniature size and the ability to modify physical properties through chemical synthesis and molecular design, polymer material offers considerable advantages over traditional inorganic material-based electronics. Conjugate polymers are particularly interesting because of their molecular design capabilities, which enable the synthesis of conducting polymers with a variety of ionization potentials and electron affinities (EA), and their ability to control the energy gap and electronegativity (χ). Accordingly, density functional theory (DFT) at the B3LYP/SDD model was used to present possible interactions between polyaniline (PANi) and both alkali and heavy metal oxides. Total dipole moment (TDM), HOMO-LUMO band gap energy (ΔE), ionization energy (IE), EA, chemical hardness (η), chemical potential (μ), electrophilicity index (ω), chemical softness (S), and χ are calculated. TDM of PANi increased while ΔE decreased due to functionalization. The distribution of electronic charge density in molecular electrostatic potential (MESP) maps together with the results of ω reflected the electrophilic nature. The obtained results confirmed that the addition of metal oxides significantly improves the TDM, ΔE, and reactivity descriptors. A strong correlation between the experimental and calculated IR spectra was observed. Additionally, PANi-2MgO and PANi-2MnO model molecules exhibited the highest reactivity. Accordingly, PANi functionalized with MgO and MnO are promising candidates for energy storage devices.

Incrimination and impact on recovery times and effects of BN nanostructures on antineoplastic drug-electronic density study

CONTEXT

By delivering the drug to the intended cell location, the use of nanomaterials in the drug delivery system may influence how the patient receives the medication and may assist in mitigating severe side effects. Density functional theory was used to assess the use of boron carbon nitride nanocages (BNCNCs), boron nitride (BNNSs), and boron carbon nitride nanosheets (BNCNSs) as melphalan (Mln) drug carriers in both the gaseous and fluid phases. We systematically examined the dipole moment, density of states, frontier molecular orbital, and optimal adsorption energy to understand the targeted drug delivery potential of these nanostructures. Adsorption energy analysis revealed that in both gas and water media, Mln drug adsorption takes place spontaneously on all the conjugated structures. The occurrence of adsorption energy as physisorbed energy suggests that the process is reversible, and desorption can take place with a much lower energy input. This physical contact is appropriate for the unquestionable unloading of Mln medications to the intended location. The reactivity is higher in BNNSs and BNCNSs, while the stability is higher in BNCNCs. The recovery time shows a shorter time for BNNSs and BNCNSs, while BNCNC shows a potential desorption time in higher temperature. These conclusions are corroborated by the results of the quantum theory of atoms in molecules (QTAIM). After the interaction analysis, it was observed that the BNCNCs can act as potential carriers for the melphalan. From dipole moment analysis, all three nanostructures show a high hydrophilic nature but quite higher in BNCNCs after doping in both media. Overall, all the structures show the potential carrier for melphalan drug.

METHODS

The quantum mechanical approach, or DFT, has been used to study the fundamental structural, electrical, thermodynamic, and other aspects of proposed structures to develop an acceptable Mln drug detector. The adsorbate and all adsorbents were optimized via the hybrid B3LYP functional and the 6-311G +  + (2d, p) basis set approach prior to the adsorption process. The Gaussian 09 package was used at 298 K as the constant temperature and 1 atm as the constant pressure. The structures are examined using the same functional models for solvation analysis-6-311 G +  + (2d, p) and B3LYP-as well as the polarized continuum model (PCM) model as the foundation set. Density of states was studied using GaussSum 3.0 software. The interaction studies QTAIM and RDG were studied using VMD and Multiwfn software.

Phographene as a new carbon allotrope for adsorption and detection of SO2, AsH3, NO2, CF3H, and CO2 air pollutant gaseous species

CONTEXT

Phographene and its family member structures are of the newly proposed semiconductors for detection of chemicals. That is, in this project, the potential of using α-phographene (α-POG) both for adsorption and detection of five types of the most important air pollutant gases containing SO2, AsH3, CF3H, NO2, and CO2 species were investigated.  The results of the time dependent density functional theory (TD-DFT) calculations indicate that during the adsorption of NO2, and SO2 by the sorbent, big redshifts occur (up to 866.2 nm, and 936.5, respectively) resulting in considerable changes in the orbitals and the electronic structures of the systems. Moreover, the results of the thermodynamic calculations reveal that α-POG could selectively adsorb SO2, NO2, and AsH3 gases (with different orders), but it could not adsorb the two other gases.Finally, the outcome of the band gap calculations shows that between all mentioned gases, α-POG could selectively detect the presence of SO2, and then NO2; while, this nanosheet could not sense the existence of AsH3, CF3H, or CO2 gases.

METHODS

All of the calculations were carried out by using the Gaussian 03 quantum chemical package. In addition, the physiochemical parameters were extracted from the output files for further calculations. Studies on all saddle points and the following calculations were performed applying the B3LYP/6-311g(d,p) level of theory.

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

Investigating the potential of monocyclic B9N9 and C18 rings for the electrochemical sensing, and adsorption of carbazole-based anti-cancer drug derivatives: DFT-based first-principle study

CONTEXT

For the first time, the use of monocyclic rings C18 and B9N9 as sensors for the sensing of carbazole-based anti-cancer drugs, such as tetrahydrocarbazole (THC), mukonal (MKN), murrayanine (MRY), and ellipticine (EPT), is described using DFT simulations and computational characterization. The geometries, electronic properties, stability studies, sensitivity, and adsorption capabilities of C18 and B9N9 counterparts towards the selected compounds confirm that the analytes interact through active cavities of the C18 and B9N9 rings of the complexes.

METHODS

Based on the interaction energies, the sensitivity of surfaces towards EPT, MKN, MRY, and THC analytes is observed. The interaction energy of EPT@B9N9, MKN@B9N9, MRY@B9N9, and THC@B9N9 complexes are observed - 20.40, - 19.49, - 20.07, and - 18.27 kcal/mol respectively which is more exothermic than EPT@C18, MKN@C18, MRY@C18, and THC@C18 complexes are - 16.37, - 13.97, - 13.96, and - 11.39 kcal/mol respectively. According to findings from the quantum theory of atoms in molecules (QTAIM) and the reduced density gradient (RDG), dispersion forces play a significant role in maintaining the stability of these complexes. The electronic properties including FMOs, density of states (DOS), natural bond orbitals (NBO), charge transfer, and absorption studies are carried out. In comparison of B9N9 and C18, the analyte recovery time for C18 is much shorter (9.91 × 10-11 for THC@C18) than that for B9N9 shorter recovery time value of 3.75 × 10-9 for EPT@B9N9. These results suggest that our reported sensors B9N9 and C18 make it faster to detect adsorbed molecules at room temperature. The sensor response is more prominent in B9N9 due to its fine energy gap and high adsorption energy. Consequently, it is possible to think of these monocyclic systems as a potential material for sensor applications.

Enhanced hydrogen storage of alkaline earth metal-decorated Bn (n = 3-14) nanoclusters: a DFT study

CONTEXT

Boron-based nanostructures hold significant promise for revolutionizing hydrogen storage technologies due to their exceptional properties and potential in efficiently accommodating and interacting with hydrogen molecules. In this paper, boron-based Bn (n = 3-14) nanoclusters decorated with alkaline earth metals (AEM = Ca and Be) were investigated for hydrogen storage applications based on density function theory (DFT) calculations. To evaluate H2 adsorption capability, the adsorption energies, frontier molecular orbitals (FMOs), natural bond orbital (NBO), and quantum theory of atoms in molecule (QTAIM) analysis are performed. The primary aim of this research work is to achieve targeted value of 5.5 wt% set by the US Department of Energy (DOE) for the year 2025. The results revealed that B5Ca2, B6Ca2, and B10Ca2 structures have the ability to hold up to 12H2 molecules with gravimetric capacities of 15.20, 14.21, and 8.60 wt%, respectively, when compared to other boron structures decorated with calcium. Similarly, for Be-decorated structure, B3Be2 structure can accommodate 3H2 molecules with gravimetric capacity of 10.59 wt%. The result of this study indicates that AEM-decorated Bn nanoclusters hold great promise as potential materials for hydrogen storage.

METHODS

Density functional theory (DFT) approach at ωB97XD/6-311++G(d,p) level of theory is employed to investigate the possibility of storing H2 molecules on alkaline earth metal (AEM = Ca and Be)-decorated Bn (n = 3-14) nanoclusters. All DFT computations were performed using Gaussian 09 software. To calculate frontier molecular orbitals (FMOs) and quantum theory of atoms in molecule (QTAIM) analysis, we have used GaussView and Multiwfn software, respectively.

Theoretical study on efficient HF gas sensing by functionalized, decorated, and doped nanocone strategy

Hydrogen fluoride (HF) is a highly dangerous and corrosive gas that can cause severe burns and respiratory damage. The density functional theory method (DFT) used to study the interaction between the HF gas and the surface of a carbon nanocone (CNC) doped with gallium atom as a chemical sensor. The results showed that CNC wasn't a good candidate to sense the HF gas and consequently its electrical properties are changed insignificant. To improve the properties of the CNC, several strategies were tried: functionalizing by pyridinol (Pyr) and pyridinol oxide (PyrO), decorated with metals (M = B, Al, and Ga), and doped with element of third group (M = B, Al, and Ga). The obtained data demonstrated that the promising results were obtained by doping the CNC with Ga atom. After full optimization, we achieved one stable configuration between the HF gas and CNC-Ga structure (S15 configuration) with Eads = -19.86 kcal/mol. The electronic properties of the CNC-Ga structure is sensible changed after the HF molecule is adsorbed. According to calculated the energy gap between HOMO and LUMO orbitals of S15 configuration are increased which could be applied a chemical signal. Eventually, one could propose that the CNC-Ga has the ability to act as a Φ-type sensor based on its physical adsorption energy and quick recovery time and doped with gallium atom is a promising strategy.

Exploring the promising application of Be12O12 nanocage for the abatement of paracetamol using DFT simulations

The removal of paracetamol from water is of prime concern because of its toxic nature in aquatic environment. In the present research, a detailed DFT study is carried out to remove paracetamol drug from water with the help of Be12O12 to eliminate the related issues. Three different geometries (CMP-1, CMP-2, CMP-3,) are obtained with the highest adsorption energies value (Eads) of - 31.2316 kcal/mol for CMP-3 without any prominent structural change. It is observed from the study that O atom from the carbonyl group (C=O) and H atom from O-H group successfully interact with O and Be atoms of the nanocage respectively. Natural bonding orbitals analysis reveals charge transfer to paracetamol drug from Be12O12 nanocage with maximum charge transfer of - 0.159 e for CMP-3 with bond angle of 1.65 Å confirming the stability of the CMP-3 among the optimized complexes. The quantum theory of atoms in molecule concludes that the interaction between paracetamol drug molecule and Be12O12 is purely closed-shell weak electrostatic in nature in CMP-1 and CMP-3 and shared interaction in CMP-2. The thermodynamics analysis witnesses that the process is exothermic and spontaneous. The regeneration study reveals the reversible nature of the adsorbent. The overall study presents Be12O12 nanocage as a potential adsorbent and may be used in future for the purification of water from a number of emerging pollutants.

Increasing the Photovoltaic Power of the Organic Solar Cells by Structural Modification of the R-P2F-Based Materials

CONTEXT

The present study aims to improve the performance of optoelectronics and photovoltaics by constructing an acceptor-donor-acceptor (A-D-A) molecule with a fullerene-free acceptor moiety. The study utilizes malononitrile and selenidazole derivatives to tailor the molecule for enhanced photovoltaic abilities. The study analyzes molecular properties and parameters like charge density, charge transport, UV absorption spectra, exciton binding energies, and electron density difference maps to determine the effectiveness of the tailored derivatives.

METHODS

To optimize the geometric structures, the study used four different functionals (B3LYP, CAM-B3LYP, MPW1PW91, and ɷB97XD) along with a double zeta valence basis set 6-31G(d, p) basis set. The study compared the results of the tailored derivatives with a reference molecule (R-P2F) to determine improvements in performance. The light harvesting efficiency of the molecules was analyzed by performing simulations in the gas and solvent phases (chloroform) based on the spectral overlap between the solar irradiance and the absorption spectra of the molecules. The open-circuit voltage (V_OC) of each molecule was also analyzed, representing the maximum voltage that can be obtained from the cell under illuminated conditions. The findings indicated that the M1-P2F designed derivative is a more effective, with energy gap of 2.14 eV, and suitable candidate for non-fullerene organic solar cell application, based on various analyses such as power conversion efficiency, quantum chemical reactivity parameters, and electronic features.

Gas-Phase Interaction of CO, CO2, H2S, NH3, NO, NO2, and SO2 with Zn12O12 and Zn24 Atomic Clusters

Atmospheric pollutants pose a high risk to human health, and therefore it is necessary to capture and preferably remove them from ambient air. In this work, we investigate the intermolecular interaction between the pollutants such as CO, CO₂, H₂S, NH₃, NO, NO₂, and SO₂ gases with the Zn₂₄ and Zn₁₂O₁₂ atomic clusters, using the density functional theory (DFT) at the meta-hybrid functional TPSSh and LANl2Dz basis set. The adsorption energy of these gas molecules on the outer surfaces of both types of clusters has been calculated and found to have a negative value, indicating a strong molecular-cluster interaction. The largest adsorption energy has been observed between SO₂ and the Zn₂₄ cluster. In general, the Zn₂₄ cluster appears to be more effective for adsorbing SO₂, NO₂, and NO than Zn₁₂O₁₂, whereas the latter is preferable for the adsorption of CO, CO₂, H₂S, and NH₃. Frontier molecular orbital (FMO) analysis showed that Zn₂₄ exhibits higher stability upon adsorption of NH₃, NO, NO₂, and SO₂, with the adsorption energy falling within the chemisorption range. The Zn₁₂O₁₂ cluster shows a characteristic decrease in band gap upon adsorption of CO, H₂S, NO, and NO₂, suggesting an increase in electrical conductivity. Natural bond orbital (NBO) analysis also suggests the presence of strong intermolecular interactions between atomic clusters and the gases. This interaction was recognized to be strong and noncovalent, as determined by noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. Overall, our results suggest that both Zn₂₄ and Zn₁₂O₁₂ clusters are good candidate species for promoting adsorption and, thus, can be employed in different materials and/or systems for enhancing interaction with CO, H₂S, NO, or NO₂.

Interaction of 5-Fluorouracil on the Surfaces of Pristine and Functionalized Ca12O12 Nanocages: An Intuition from DFT

The utilization of nanostructured materials for several biomedical applications has tremendously increased over the last few decades owing to their nanosizes, porosity, large surface area, sensitivity, and efficiency as drug delivery systems. Thus, the incorporation of functionalized and pristine nanostructures for cancer therapy offers substantial prospects to curb the persistent problems of ineffective drug administration and delivery to target sites. The potential of pristine (Ca₁₂O₁₂) and formyl (-CHO)- and amino (-NH₂)-functionalized (Ca₁₂O₁₂-CHO and Ca₁₂O₁₂-NH₂) derivatives as efficient nanocarriers for 5-fluorouracil (5FU) was studied at the B3LYP-GD3(BJ)/6-311++G(d,p) theoretical level in two electronic media (gas and solvent). To effectively account for all adsorption interactions of the drug on the investigated surfaces, electronic studies as well as topological analysis based on the quantum theory of atoms in molecules (QTAIM) and noncovalent interactions were exhaustively utilized. Interestingly, the obtained results divulged that the 5FU drug interacted favorably with both Ca₁₂O₁₂ and its functionalized derivatives. The adsorption energies of pristine and functionalized nanostructures were calculated to be -133.4, -96.9, and -175.6 kcal/mol, respectively, for Ca₁₂O₁₂, Ca₁₂O₁₂-CHO, and Ca₁₂O₁₂-NH2. Also, both topological analysis and NBO stabilization analysis revealed the presence of interactions among O₃-H₃₂, O₂₇-C₂₄, O₁₀-C₂₇, and N₂₄-H₃₂ atoms of the drug and the surface. However, 5FU@Ca₁₂O₁₂-CHO molecules portrayed the least adsorption energy due to considerable destabilization of the molecular complex as revealed by the computed deformation energy. Therefore, 5FU@Ca₁₂O₁₂ and 5FU@Ca₁₂O₁₂-NH₂ acted as better nanovehicles for 5FU.

DFT Study for Adsorbing of Bromine Monochloride onto BNNT (5,5), BNNT (7,0), BC2NNT (5,5), and BC2NNT (7,0)

The study of intermolecular interactions is of great importance. This study attempted to quantitatively examine the interactions between bromine monochloride (BrCl) with pristine boron nitride nanotube (BNNT) armchair (5,5) and zigzag (7,0) as well as armchair (5,5) BC2NNT and zigzag (7,0) BC2NNT in vacuum. Quantum mechanical studies of such systems are possible in the density functional theory (DFT) framework. For this purpose, various functionals, such as B3LYP-D3, [Formula: see text]B97XD, and M062X, have been used. One of the most suitable basis functionals for the systems studied in this research is 6-311G (d), which has been used in both optimization calculations and calculations related to wave function analyses. The main part of this work is the study of various analyses that reveal the nature of the intermolecular interactions between the two components introduced above. The results of conceptual DFT, natural bond orbital, non-covalent interactions, and quantum theory of atoms in molecules (QTAIM) were consistent and in favor of physical adsorption in all systems. Gallium had more adsorption energy than other dopants. The HOMO–LUMO energy gaps were as follows: BNNT (5,5): 10.296, BNNT (7,0): 9.015, BC2NNT (5,5): 7.022, and BC2NNT (7,0): 5.979[Formula: see text]eV at B3LYP-D3/6-311G (d) model chemistry. The strongest interaction is related to the BC2NNT (7,0)/BrCl cluster: [Formula: see text][Formula: see text]eV. The results of QTAIM and NCI analysis identified the intermolecular interactions of the type of strong van der Waals interaction for these nanotubes. The sensitivity of the adsorption increased when a gas molecule interacted with carbon-doped BNNT, and the change in the frontier orbital gap could be used to design nanosensors to detect BrCl gas.

Non-covalent interactions of cysteine onto C60, C59Si, and C59Ge: a DFT study

The study of intermolecular interactions is of great importance. This study attempted to quantitatively examine the interactions between cysteine (C₃H₇NO₂S) and fullerene nanocages, C₆₀, in vacuum. As the frequent introduction of elements as impurities into the structure of nanomaterials can increase the intensity of intermolecular interactions, nanocages doped with silicon and germanium have also been studied as adsorbents, C₅₉Si and C₅₉Ge. Quantum mechanical studies of such systems are possible in the density functional theory (DFT) framework. For this purpose, various functionals, such as B3LYP-D3, ωB97XD, and M062X, have been used. One of the most suitable basis functionals for the systems studied in this research is 6-311G (d), which has been used in both optimization calculations and calculations related to wave function analyses. The main part of this work is the study of various analyses that reveal the nature of the intermolecular interactions between the two components introduced above. The results of conceptual DFT, natural bond orbital, non-covalent interactions, and quantum theory of atoms in molecules were consistent and in favor of physical adsorption in all systems. Germanium had more adsorption energy than other dopants. The HOMO-LUMO energy gaps were as follows: C₆₀: 5.996, C₅₉Si: 5.309, and C59Ge: 5.188 eV at B3LYP-D3/6-311 G (d) model chemistry. The sensitivity of the adsorption increased when an amino acid molecule interacted with doped C₆₀, and this capability could be used to design nanocarrier to carry cysteine amino acid.

Encapsulation of Pollutant Gaseous Molecules by Adsorption on Boron Nitride Nanotubes: A Quantum Chemistry Study

Based on density functional theory (DFT) and the semiempirical method PM7, we analyze the encapsulation process of polluting gases and/or their adsorption on different sites, viz., on the inner wall, the outer wall, and on the boron nitride (BN) nanotube ends, with chirality (7,7) armchair. DFT calculations are performed using the Perdew-Burke-Ernzerhof (PBE) functional and the M06-2X method through the 6-31G(d) divided valence orbitals as an atomic basis. Various geometrical configurations were optimized by minimizing the total energy for all analyzed systems, including the calculation of vibrational frequencies, which were assumed to be of a nonmagnetic nature, and where the total charge was kept neutral. Results are interpreted in terms of adsorption energy and electronic force, as well as on the analysis of quantum molecular descriptors for all systems considered. The study of six molecules, namely, CCl₄, CS₂, CO₂, CH₄, C₄H₁₀, and C₆H₁₂, in gas phase is addressed. Our results show that C₄H₁₀, C₆H₁₂, and CCl₄ are chemisorbed on the inner surfaces (encapsulation) and on the nanotube ends. In contrast, the other molecules CS₂, CO₂, and CH₄ show weak interaction with the nanotube surface, leading thereby to physisorption. Our findings thus suggest that this kind of polluting gases can be transported within nanotubes by encapsulation.

Adsorption of 1-chloro-1,2,2,2-tetrafluoroethane on pristine, Al, Ga-doped boron nitride nanotubes: a study involving PBC-DFT, NBO analysis, and QTAIM

In the present investigation, the feasibility of detecting the 1-chloro-1,2,2,2-tetrafluoroethane gas molecule on the outer surface of pristine single-walled boron nitride nanotube, as well as its aluminium- and gallium-doped structures, was carefully evaluated. For achieving this goal, a periodic boundary condition density functional theory level of study using both HSE06 and B3LYP-D3 functionals together with a 6-311G(d) basis set has been used. Subsequently, the CAM-B3LYP, ωB97XD, and M06-2X functionals with a 6-311G(d) basis set were also employed to consider the single point energies. Natural bond orbital and quantum theory of atoms in molecules were implemented by using the HSE06/6-311G(d) method and the results were compatible with the electronic properties. In this regard, the total density of state, the Wiberg bond index, natural charge, natural electron configuration, donor–acceptor natural bond orbital interactions, and the second-order perturbation energies are performed to explore the nature of the intermolecular interactions. All of the energy calculations and population analyses show that by adsorbing of the gas molecule onto the surface of the considered nanostructures, the intermolecular interactions are of the type of strong chemical adsorption. Between the doped nanotubes, aluminium-doped nanotube has very high adsorption energy compared with gallium. Generally, it was revealed that the sensitivity of the adsorption will be increased when the gas molecule interacts with decorated nanotubes and decrease the HOMO–LUMO band gap; therefore, the change of electronic properties can be used to design suitable nanosensors.

The adsorption of chlorofluoromethane on pristine, and Al- and Ga-doped boron nitride nanosheets: a DFT, NBO, and QTAIM study

In the present investigation, the feasibility of detecting the chlorofluoromethane (CFM) gas molecule onto the outer surface of pristine single layer boron nitride nanosheet (BNNS), as well as its aluminum (Al)- and gallium (Ga)-doped structures, was carefully evaluated. For achieving this goal, a density functional theory level of study using the Perdew, Burke, and Ernzerhof exchange-correlation (PBEPBE) functional together with a 6-311G(d) basis set has been used. Subsequently, the B3LYP, CAM-B3LYP, wB97XD, and M062X functionals with a 6-311G(d) basis set were also employed to consider the single-point energies. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) were implemented by using the B3LYP-D3/6-311G(d) method, and the results were compatible with the electronic properties. In this regard, the total density of states (TDOSs), the Wiberg bond index (WBI), natural charge, natural electron configuration, donor-acceptor natural bond orbital interactions, and the second-order perturbation energies are performed to explore the nature of the intermolecular interactions. All of the energy calculations and population analyses denote that by adsorbing of the gas molecule onto the surface of the considered nanostructures, the intermolecular interactions are of the type of strong chemical adsorption. Among the doped nanosheets, Ga-doped nanosheet has very high adsorption energy compared with other elements (i.e., Ga-doped > Al-doped > pristine). Generally, it was revealed that the sensitivity of the adsorption will be increased when the gas molecule interacts with decorated nanosheets and decrease the HOMO-LUMO band gap; therefore, the change of electronic properties can be used to design suitable nanosensors to detect CFM gas. Graphical abstract.

Effect of Substitution for Insertion of CO2 into Epoxides and Aziridines: An Ab Initio Study

The insertion of CO2 into epoxides and aziridines has been studied using density functional theory (B3LYP) and ab initio (MP2) methods, and the effect of substitution for the two reactions are further explored. It is found that the reactivity of epoxides and aziridines are similar, and insertion of CO2 proceeds through a concerted mechanism. The substitutions of methyl and phenyl does not change the reaction mechanism, but the transition state for the substitution on the attacking position becomes loose with a lower free energy barrier. The substitutions of methyl and phenyl decrease the free energy barrier, with phenyl substitution having a greater affect. The results also show that the free energy barriers for the insertions of CO2 into aziridines are ~10kcalmol−1 lower than the corresponding reactions of CO2 with epoxides.