Two-dimensional carbon materials show great potential for gas sensing; however, the zero band gap of pristine graphene frameworks limits their response performance. In this study, B-doped Irida-graphene (IG) was investigated. The most stable configuration after double-B doping is a wavy 2B-IG structure, which transforms IG from a zero-band-gap material into a semiconductor with a direct band gap of 0.908 eV. The 2B-IG structure exhibits favorable sensing responses toward O2, NO2, SO2, NO, and NH3. Among these gases, NO2 induces the largest band-gap variation, while O2 and NO adsorption generate magnetism. NO2 and NH3 can recover rapidly at elevated temperatures, whereas the other gases exhibit fast recovery at room temperature. Charge-transfer and orbital-hybridization analyses indicate that the interaction between gas molecules and 2B-IG dominates the sensing behavior. These results demonstrate the potential of 2B-IG as a sensing material and provide theoretical guidance for the design of two-dimensional gas sensors.
Based on ReaxFF-lg reactive force field, reactive molecular dynamics simulations were conducted to investigate the high-temperature pyrolysis of pure epoxy resin (ep) matrix and aluminum/epoxy resin (Al/ep) with different aluminum mass fractions. The pyrolysis of ep exhibited significant selectivity, with the preferential cleavage of CO ether and CN amine bonds with low bond dissociation energy in the initial reaction stage. Al nanoparticles preferentially captured oxygen during pyrolysis to form AlO passivation layer, which then underwent thermal fragmentation at high temperatures, exposing more active sites. With the increase in Al content, the generation of oxygen-containing gaseous products such as CO and H2O was inhibited, while H2 yield increased continuously, indicating that Al had a prompting effect on the dehydrogenation reaction of ep. The apparent activation energy and pre-exponential factor of the products H2, H2O, and CO exhibit consistent evolution, and the product formation process conforms to the kinetic compensation effect
The ZrSSe/GaP van der Waals heterojunction is studied via first-principles calculations. The most stable configuration exhibits an indirect bandgap of 1.565 eV with type-II band alignment, forming a direct Z-scheme charge-transfer pathway. Phonon spectra and AIMD simulations confirm its stability. The GaP conduction band minimum provides Ue = 1.033 eV for the hydrogen evolution reaction (HER), reducing the barrier from 1.701 to 0.668 eV; the oxygen evolution reaction (OER) rate-limiting step (O* → OOH*) becomes downhill with an additional 2.293 V bias. A – 2% compressive strain induces an indirect-to-direct bandgap transition, while band edges remain suitable for water splitting across the −5% to +5% strain range. The heterojunction shows enhanced optical absorption (4.220 × 105 cm−1 in the visible) and achieves an exceptional solar-to‑hydrogen (STH) efficiency of 16.160%. These results highlight the ZrSSe/GaP heterojunction as a promising candidate for photocatalytic water splitting and optoelectronic devices, and provide design insights for Janus-based heterostructures.
CH4 and NO are critical pollutants, and their detection and capture are essential for environmental and human health. Using first-principles computations, we systematically investigated the adsorption behavior, electronic structure, and desorption kinetics of CH4 and NO on pristine and Li/Al/C/O-substituted inorganic biphenylene monolayers (I-BPN). Substitutional doping modulates surface charge and orbital hybridization, tuning gas adsorption strengths. Li- and Al-doped systems show low CH4 adsorption energies (−1.85 and − 1.47 eV) and high NO energies (−3.61 and − 2.90 eV), indicating strong chemisorption suitable for capture. C/O-doped systems exhibit moderate CH4 adsorption (−0.84 to −0.94 eV), ideal for sensing. Charge redistribution and orbital coupling vary with adsorption intensity, and recovery time calculations suggest reversible adsorption-desorption via thermal control. This work provides insights for designing I-BPN-based sensors and capture devices.
In this study, density functional theory (DFT) calculations were performed to investigate the adsorption of chloromethane (CH3Cl) and bromomethane (CH3Br) on pristine and nitrogen-doped TiO2 nanoparticles. The effects of N-doping at different sites (N-2f, N-3f, and doubly N-doped) on the adsorption behavior, electronic structure, and sensing performance were systematically examined. The adsorption energies indicate that the N-2f-doped surface exhibits the most negative value, representing the most energetically favorable configuration. Bader charge analysis reveals that electron transfer occurs from the molecule to the nanoparticle surface in all configurations, with CH3Br donating more charge than CH3Cl. Charge density difference maps confirm electron accumulation in the Ti-halogen region, further supporting chemical bond formation, while PDOS analysis reveals strong orbital hybridization between Ti and halogen states. Notably, the doubly N-doped (2N-doped) nanoparticle exhibits rapid recovery times (0.57–6.9 ms) at room temperature, making it promising for reusable gas sensors.
While Ih symmetry suggest uniform spherical aromaticity, the constraints of M20 dodecahedra (M = N, P, As, Sb, to Bi) cause a significant deviation from this norm. Structural and natural bond orbital analyses indicate a gradual breakdown of classical hybridization caused by internal orbital strain. Such structural strain destabilizes frontier molecular orbitals and induces progressive energetic destabilization down group 15. These consequences were magnetically evaluated by multidimensional magnetic mapping at ωB97X-D/def2-TZVP. The magnetic calculations disclosed functional-independent (ωB97X-D, B3LYP-D3, and M06-2×) and verified higher stability for def2-TZVP over def2-TZVPD for these systems. While N20-As20 cages display localized surface aromaticity with isolated paratropic cores, the increased overlap causes a magnetic crossover at Sb20 where the diatropic domains merged into a continuous magnetic field at cage cavity. Beyond this threshold, Bi20 exhibits pronounced p-orbital strain and strong scalar relativistic effects disrupt its classical bonding and force returning to a diffuse and paratropic state.
Global structural searches and quantum-chemical calculations identify planar B7Se2− isomer 1 (D2h, 1Ag) as the global minimum. It contains two peripheral BSeB bridging units and a delocalized B7 framework, whereas boronyl-like isomer 2 (Cs, 3A′), featuring terminal BSe multiple bonds, lies 20.35 kcal mol−1 higher at the CCSD(T) level. CMO and AdNDP analyses reveal a 6σ-aromatic and formally 4π-antiaromatic bonding framework in isomer 1, together with Se → B π back-donation that electronically stabilizes its planar structure. In contrast, localized terminal BSe multiple bonding in isomer 2 disrupts the delocalized B7 framework and produces an elongated geometry. These results demonstrate that cooperative delocalized bonding can outweigh localized terminal BSe multiple bonding in boron-rich selenium clusters.
Global energy demand is continuously surging due to population growth and growth of industrialization in this prospective, solar energy is one of the emerging solution. In the current investigation, D-π-A organic dyes (1–9) were designed by tuning the π-spacer and evaluated as sensitizers for dye-sensitized solar cells (DSSCs). Molecular orbital analysis confirmed that the optimal energy alignment for efficient electron transfer while absorption on TiO2 study reveal that the performance for dyes with larger π-spacers particularly those containing sulphur and selenium were enhance the photo physical properties. Further, density of state (DOS), partial density of state (PDOS), natural bond orbital (NBO) and molecular electrostatic potential (MEP) analyses were providing deeper insight into electronic behaviour of the designed molecules. The calculated results infer that the designed dye–semiconductor were exhibited stable adsorption modes and favourable interactions. Impressively, the predicted power conversion efficiencies (PCE) reached up to 28.28% that demonstrate the potential of these engineered dyes molecules for high-performance DSSCs.
AbstractThis computational study determines aqueous pKa values of caffeic acid (CA), caffeic acid phenethyl ester (CAPE), and its pyridine analogue (PEHA). Using DFT (PW6B95/Def2-TZVP for conformers; M06-2X/6–31++G(2df,p) for pKa) and SMD solvation, we benchmarked three thermodynamic cycles with explicit water monomers (n = 0–6) or clusters. Cycle 1 with appropriate water numbers, Cycles 2(a)/(b) provided the most reliable estimates for carboxylic, phenolic, and phenolate acidities; Cycle 3 was moderately suitable for carboxylic sites but unsuitable for phenolates. Isodesmic calibration against 11 phenols yielded r = 0.980 (MAE = 0.17); target compounds gave MAE = 0.75. CAPE and PEHA exhibit nearly identical acidities (pKa1 ∼ 7.7, pKa2 ∼ 11.5); CA shows distinct acidity (pKa1 = 4.8, pKa2 = 8.6, pKa3 = 11.2). Cycle 2(a) is unsuitable for pyridinium pKaH; Cycle 1 (n = 4–5) or Cycle 2(b) (n = 5) is recommended for basic nitrogen centers.
Polyoxometalates are discrete metal oxo clusters built from linked metal oxygen coordination units. Here, we use assembly modelling and density functional theory to examine two polyoxoselenitoaurate families, [AuSeO4]nn− and [Au3Se2O8]nn+, with n=2 to 6. Both families are constructed from {AuO4} square planar and {SeO3} trigonal pyramidal building units, allowing cyclic and prismatic architectures to be compared directly. The results show that stability is governed by how well each nuclearity accommodates the local geometry of these units. The cyclic tetramer best preserves the Au–O geometry, whereas the pentagonal prismatic cage is lowest in energy among the prismatic structures, closely followed by the cubic tetramer. Alternative selenite orientations are destabilised by short nonbonding O⋯O contacts and geometric congestion. Both families are closed shell and show HOMO–LUMO gaps of about 3.2 to 3.9 eV. The calculated trends rationalise the experimentally observed nuclearities and identify local geometric strain as a design principle for polyoxoaurate synthesis.
Fulleride crystals (M3C60) are materials whose electrical transport properties are influenced by the distinct structural environments of their tetrahedral and octahedral interstitial doping sites. In this work, the chemical bond overlap model (OP/TOP), the quantum theory of atoms in molecules (QTAIM), and molecular descriptors were utilized to investigate M⋯C60 interactions. Representative clusters modeling isolated tetrahedral M(C60)4 and octahedral M(C60)6 environments (M=Li, Na, K, Rb, Cs) were investigated using density functional theory at the ωB97X-D3/def2-SVP level. Molecular descriptors reveal that alkali-metal doping decrease the HOMO-LUMO gap (ΔEHL), and both the ionization potential (IP) and chemical hardness (η). For all metals except Rb, the octahedral models exhibited lower HOMO-LUMO gaps and IP than the corresponding tetrahedral models. QTAIM and OP/TOP descriptors indicate that the M-C bonds within the tetrahedral sites exhibit ionic behavior characterized by interatomic charge depletion (∇2ρBCP>0, HBCP>0) and highly concentrated overlap density (∇2ρOCP≪0). In contrast, the octahedral sites feature delocalized electron overlap profiles. The combined QTAIM and OP/TOP analyses indicate distinct electronic structure for the two interstitial environments: tetrahedral sites are associated with stronger charge-transfer characteristics, whereas octahedral sites display more spatially distributed electron density.
