We have used k-resolved inverse photoemission spectroscopy to measure the temperature-dependent intensity of radiative transitions into unoccupied electronic states of Ni(110) along its ΓY¯ high-symmetry line in the surface Brillouin zone. Our measurements yield a strong temperature dependence of a transition into an unoccupied crystal-derived surface state. This temperature dependence weakens as the position of the state moves away from the Y¯ high-symmetry point. We use a Debye–Waller model to interpret the intensity attenuation of the direct transitions with increasing temperature. From our results of a transition into the sp-derived bulk state observed at ∼ 1 eV above the Fermi level, we estimate the effective surface Debye temperature of Ni(110) to be 240 ± 20 K.
Indoor air quality in archival environments is critically threatened by hazardous gases such as HCHO, C6H6, and Rn, which originate from collection materials and building structures remain largely undetected. Using first-principles theory, this study investigates the structural stability, electronic properties, and gas adsorption performance of noble metal (Ru and Nb)-doped Janus PtSSe monolayers as potential resistive sensing materials for three target gases. The results reveal that both Ru and Nb dopants preferentially substitute at the Se site, and Nb-doping enhances the electron-donating capability of the substrate, leading to stronger adsorption energies and greater charge transfer compared to Ru-doping. Band structure analysis shows that Nb-PtSSe exhibits larger bandgap modulations with somewhat higher sensing response. Specifically, HCHO and C6H6 are chemisorbed behaving chemiresistive detection, while Rn, as noble gas with low chemical reactivity, behave weak physisorption and polarization-induced charge redistribution that achieves a tiny response. Recovery time analysis reveals that Nb-PtSSe suffers from long desorption times, while Ru-PtSSe achieves significantly faster recovery at 398 K. Thus, Ru-PtSSe emerges as a practically viable candidate for fast-recovery applications. This work not only provides a theoretical foundation for developing PtSSe-based gas sensors but also highlights the critical role of dopant selection in tailoring sensing performance for cultural heritage preservation applications.
Based on first-principles calculations, we systematically investigate the gas sensing behavior of pristine and Ni/Pd/Pt-doped Janus HfSSe monolayers toward H2, CO2, and CH4. Pristine HfSSe exhibits weak physisorption with negligible work-function variation and sensing response. Transition metal doping introduces localized d-orbital states near the Fermi level, which significantly enhance charge transfer and work-function modulation, giving rise to distinct electronic responses for different gas molecules. Specifically, Ni@HfSSe exhibits high sensitivity to CO2, Pd@HfSSe achieves balanced sensitivity and favorable reversibility for CH4, and Pt@HfSSe shows strong H2 response but suffers from poor recovery. Our findings demonstrate that transition metal doping combined with strain engineering provides an effective strategy for tunable and selective gas sensing in Janus two-dimensional materials.
Volatile organic compounds (VOCs) generated by industrial production, fossil fuel utilization and vehicular emissions pose substantial threats to public health and environmental quality. Therefore, it is highly desirable to design a high‐performance VOCs sensing device with both rapid response and superior sensitivity. In this work, density functional theory (DFT) calculations were performed to elucidate the adsorption characteristics of different VOCs (C6H6, C2H4, CH3Cl, CH3OH, and H2CO) on two‐dimensional heteronuclear bimetallic phthalocyanine monolayers (TiCoPc and VCoPc). Calculations reveal that the TiCoPc and VCoPc monolayers show strong chemisorption (|Eads| > 0.80 eV) toward H2CO, C2H4, CH3Cl and CH3OH, but only weak physisorption toward C6H6. The underlying adsorption mechanisms were revealed by analyzing the density of states, charge transfer and electron localization function. Interestingly, TiCoPc and VCoPc show excellent selectivity for H2CO, CH3OH or C2H4 when exposed to conventional background gases such as H2O, CH4 and CO2. Notably, adsorption of H2CO and CH3OH induces pronounced modulation in band-gap, magnetic moment and work function. Finally, recovery time analysis reveals the strong potential of the TiCoPc monolayer as a reusable sensor for C2H4, C6H6 and CH3Cl, whereas the VCoPc monolayer is an excellent sensing material for C6H6, CH3Cl and CH3OH. These results give theoretical justification for designing and optimizing advanced phthalocyanine‐based VOCs sensors.
This study demonstrates the adsorption of C2H6 and C2H4 using C18 and B9N9 in their monocyclic forms using density functional theory (DFT), illustrating that the inner cavities are the active sites for adsorbing these analytes. It is illustrated that the adsorption performance of C18 is energetically more exothermic than that of its B9N9 counterpart. The adsorption energies of analytes with C18 are approximately ∼-17.00 kcal/mol, while for B9N9, the energies are below 9.00 kcal/mol for both analytes. NCI analysis further reveals that stability arises from the dispersion contribution (H—π), which is more pronounced upon interaction with C18. The electronic fluctuations (FMO) and charge transfer (NBO) properties of monocycles are enhanced upon complexation with these organic molecules; however, the effect is comparatively higher in C18 than in B9N9. The HOMO-LUMO gaps vary from 3.05 eV to 3.51 eV in C18, while a negligible change is noticed in the case of B9N9. However, a maximum NBO charge transfer is observed for the C2H6@C18 complex, i.e., 0.015 e-. The π-electrons of C18 play a crucial role by enabling considerable charge transfer, especially for C2H6, owing to the greater number of H-π interactions. Consequently, the findings based on the isolated gas-phase complexation, rather than a realistic adsorption environment, suggest that C18 is a potential adsorbent for binding small organic molecules.
Density functional theory (DFT) calculation was used to examine the adsorption performance, thermal stability, and the electronic, magnetic and optical properties of an InAs monolayer toward toxic gas molecules (CO2, SO2, CO, SH2, NH3, and NO2). The most stable adsorption geometry was determined based on the adsorption energy calculation. CO2, CO, and SH2 have shown physisorption nature with minimal charge transfer and negligible perturbation of the electronic structure. While SO2, NH3, and NO2 undergo strong chemisorption, characterized by significant charge transfer and strong surface binding. NH3 decreases the band gap by 0.03 eV, whereas SO2 increases it by 0.14 eV. Notably, NO2 induces a spin-polarized electronic state with a net magnetic moment of 1 μB, resulting in a semiconducting spin-up channel and a metallic spin-down channel. The ab-initio molecular dynamics simulations at 300 K confirm the structural stability of all adsorption systems. Work-function analysis reveals pronounced surface modification for NH3, SO2, and NO2, indicating high sensitivity toward these gases. Recovery-time calculations further show that CO2, CO, and SH2 desorb rapidly, enabling fast and reversible sensing, whereas SO2, NH3, and NO2 exhibit longer recovery times owing to their strong adsorption. The optical analysis shows that each gas leads to unique response: NH3 enhances absorption in the visible-NIR region, while SO2 and NO2 reduce NIR absorption and increase transmittance, providing characteristic optical fingerprints for gas discrimination. These combined adsorption, electronic, magnetic, optical, and kinetic results identify the InAs monolayer as a promising multifunctional platform for toxic gas sensing, offering rapid and reversible detection of CO2, CO, and SH2, together with highly sensitive optoelectronic detection of NH3, SO2, and NO2.
As a renewable carbon source, biomass is widely employed as a precursor for activated carbon synthesis to remove environmental pollutants, owing to its abundance and cost effectiveness. In this study, microporous dominant orange peel based activated carbon (OPAC) was prepared via KOH activation using waste citrus peels. The optimal preparation conditions were determined as an activation temperature of 800 °C, activation time of 2 h, and alkali to carbon ratio of 4:1, yielding an ultrahigh specific surface area of 3383.84 m2/g and an iodine adsorption value of 2926.42 mg/g. The OPAC exhibited a maximum phenol adsorption capacity of 194.50 mg/g at 25 °C. Adsorption kinetics followed the pseudo second order model (R2 = 0.99929), suggesting the involvement of chemisorption, while the Langmuir isotherm (R2 > 0.999) confirmed monolayer adsorption. Thermodynamic analysis revealed spontaneous (ΔG0 < 0), exothermic (ΔH0 = -16.467 kJ/mol), and entropy driven (ΔS0 = -50.092 J/(mol·K)) adsorption. Density functional theory (DFT) calculations demonstrated that phenol adsorption on OPAC is primarily physisorption driven (adsorption energy -0.79 eV) with a minor chemisorption contribution, supported by electron density difference maps. The excellent performance originates from the synergistic effect of hierarchical micro and mesopores, π-π stacking, hydrogen bonding, and van der Waals interactions. This study provides a quantitative theoretical foundation for biomass valorization and coking wastewater treatment.
The excellent properties of two-dimensional (2D) materials has sparked a research boom for both theoretical studies and experimental synthesis. A series of novel 2D carbon monolayers composed of tetra, penta and hexa rings, named TPH-Cx, have been designed by defect transformation of penta-graphene. We discussed several molecular-assembly strategies as potential routes toward the experimental realization of TPH-Cx monolayers. After confirming their energetic, dynamical, and thermal stability, the TPH-Cx monolayers are predicted to exhibit semiconducting behavior, with PBE-calculated band gaps ranging from 1.83 to 2.22 eV. Under equi-biaxial tensile strain, the bandgaps of TPH-Cx are tunable. Notaby, some TPH-Cx monolayers exhibit strain-induced negative Poisson's ratios, and the magnitude of the negative Poisson's ratio generally increases with increasing strain. These results suggest their potential applications in nanoelectronic and nanomechanical devices. This study provides novel insights for the design and development of 2D novel carbon monolayers.
Understanding how crystallographic strain orientation governs coupled structural, electronic, and thermoelectric responses of low-symmetry two-dimensional materials remains an open challenge. In particular, the strain-structure-property relationships in pentagonal transition-metal dichalcogenides have not been systematically clarified. In this work, we employ first-principles density functional theory combined with semiclassical Boltzmann transport analysis to investigate the effects of uniaxial strain applied along the in-plane x- and y-directions on PdS2 and PtS2 monolayers. Owing to their non-equivalent X-S bonding topology, strain applied along different directions activates distinct microscopic deformation pathways, with εxx accommodated predominantly through bond-length variation, whereas εyy involves a greater contribution from bond-angle rearrangement and out-of-plane structural relaxation. At equilibrium, PdS2 and PtS2 exhibit band gaps of 2.13 eV and 3.00 eV, respectively, which decrease significantly under tensile strain, with reductions of up to 66.63% and 52.0%. Strain-dependent projected density-of-states analysis further reveals orientation-dependent changes in the energetic distribution and overlap of Pd/Pt-d and S-p states near the band edges, providing an orbital-level link between directional lattice deformation and electronic reconstruction. These electronic changes are reflected in the thermoelectric response, with the Seebeck coefficient and power exhibiting pronounced dependence on both strain magnitude and loading orientation for both p-type and n-type carriers. Comparative analysis reveals that PtS2 displays a more favorable thermoelectric response, while PdS2 shows enhanced sensitivity to strain orientation demonstrating complementary thermoelectric performance and strain tunability. The dynamical and thermal stability of representative highly strained configurations were further examined by phonon and ab initio molecular dynamics simulations. Overall, the results establish crystallographic strain orientation as an additional degree of freedom, beyond strain magnitude alone, for controlling coupled structural, electronic, and thermoelectric properties in low-symmetry two-dimensional materials.
Carboxymethylation represents a promising chemical modification strategy to overcome the inherent limitations of phenolic compounds, particularly their low aqueous solubility and susceptibility to oxidative degradation. This study investigates the Williamson-type carboxymethylation of gallic acid—a model hydrolysable tannin—using monochloroacetic acid under alkaline conditions, complemented by comprehensive density functional theory (DFT) calculations at the B3LYP/6-311G(d,p) level. Experimental characterization revealed successful derivatization with a 5.4-fold enhancement in aqueous solubility (435 mg/mL) compared to native gallic acid. Thermogravimetric analysis demonstrated significantly improved thermal stability, with the carboxymethylated derivative yielding 63.1% carbonaceous residue at 700 °C versus 20.4% for the parent compound, suggesting structural complexity beyond simple substitution likely involving dimerization during alkaline activation. FTIR spectroscopy confirmed hydroxyl group substitution and ether linkage formation, while gel permeation chromatography indicated molecular weight distribution between 1000–5000 g/mol, consistent with oligomeric structures. DFT computations elucidated electronic structure modifications: the derivative exhibited a reduced HOMO-LUMO gap (4.04 eV vs. 4.80 eV), elevated dipole moment (9.10 D vs. 1.02 D), and enhanced global electrophilicity (4.80 eV), correlating with increased chemical reactivity. Monte Carlo simulations further revealed spontaneous adsorption on Fe(110) and Al(111) surfaces, though with lower affinity than native gallic acid. Rheological measurements confirmed shear-thinning behavior in aqueous solutions, positioning the derivative as a functional bio-based additive. This integrated experimental-theoretical approach validates carboxymethylation as a viable route to engineer phenolic compounds with tunable physicochemical properties for advanced applications in pharmaceuticals, functional materials, and green chemistry.
Thanks to its high specific surface area and light weight, graphene shows great promise as a supporting structure for hydrogen storage. Based on this observation, we suggest the use of Net-graphene, a newly discovered 2D-dimensional carbon nomenclature with porous structures, as an adsorbent material for hydrogen storage. In this study, we use first-principles calculations based on the density functional theory (DFT) and ab initio Molecular dynamics (AIMD) simulation techniques, focusing on the hydrogen adsorption ability and thermodynamic stability of Li-decorated Net-graphene systems. Calculations indicate that Li atoms strongly adsorb on Net-graphene with no formation of Li clusters. Theoretically, the adsorption ability with four Li atoms on each Net-graphene sheet has the potential to adsorb up to 20 H₂ molecules with an average adsorption energy per H₂ molecule at -0.20 eV, making it possible to reach a hydrogen weight percentage of 8.91%, thus far exceeding the U.S. DOE challenge with plenty of room on improvement. The desorption temperature at 205 K also indicates that hydrogen desorption will occur under moderate conditions and with high efficiency. Overall, Li-decorated Net-graphene combines high storage capacity with favorable adsorption energetics, highlighting its promise as an efficient hydrogen storage material.
The dissociative adsorption of H2 on Pd(111) is a prototypical surface reaction where energy dependence of sticking probability is attributed to steering and trapping mechanisms; however, adsorption-site contributions are not explicitly delineated. We use ab initio molecular dynamics (AIMD) simulations to examine the site-specific reactivity of H2 molecule as it impinges with varying incident energies on a rigid Pd(111) surface. For molecules directed toward the atop site, the dissociation probability decreases between 12.5 and 100 meV before increasing and saturating in the 300–400 meV range. Conversely, molecules targeting the hollow or bridge site remain essentially unreactive below 100 meV, but display a monotonic rise in reactivity at higher energies. This site dependence suggests that the experimentally reported high-energy saturation originates from atop-like reactive pathways. Further analyses reveal how local barriers and approach geometries govern reactivity, establishing a mechanistic link between atomistic dynamics and sticking behavior in H2 dissociation on Pd(111).
Silicon carbide (SiC) and aluminum nitride (AlN) are wide-bandgap semiconductors with superior thermal and electronic properties, widely used in optoelectronics and electronic packaging. Herein, first-principles calculations are employed to systematically investigate the structural stability, electronic and optical properties of two-dimensional (001)-oriented SiC/AlN heterostructures. All constructed heterostructures are direct-bandgap semiconductors, and their bandgaps can be effectively tuned by adjusting the layer thickness ratio and interfacial bonding mode. The N-Si bonds exhibit higher covalency than C-Al bonds. Increasing SiC layers enhances optical absorption and reflectivity, while more AlN layers reduce the static refractive index. The optical properties of these materials-including their absorption and reflectivity-can be systematically controlled through precisely engineered adjustments of the SiC/AlN layer ratio, thereby demonstrating remarkable tunability. Increasing the SiC layer number enhances the optical absorption and reflection capacity, while a lower static refractive index accelerates light propagation. The results offer meaningful theoretical guidance for the optoelectronic device applications of such heterostructures.
The interaction of biologically significant molecules with nanostructured materials is of considerable interest for sensing and biomedical applications. In this study, a comprehensive density functional theory (DFT) investigation is performed to explore the adsorption behavior of glucose on Mg12O12 nanocage and its implications for surface-enhanced Raman scattering (SERS) activity. Geometry optimization and electronic structure calculations were carried out at the B3LYP-D3/6-31+G(d,p) level, incorporating solvent effects via the PCM/SMD model. The results reveal that glucose adsorption occurs preferentially through its hydroxyl oxygen atoms interacting with electropositive Mg sites, leading to stable complexes characterized by significant charge redistribution. The adsorption process is thermodynamically favorable in both vacuum and aqueous environments, with enhanced stability observed in solution. Frontier molecular orbital analysis shows a reduction in the HOMO-LUMO energy gap upon adsorption, indicating improved electronic coupling and increased chemical reactivity. Detailed reactivity analyses, including MEP, ELF, LOL, and NCI confirm that hydrogen bonding and van der Waals interactions dominate the stabilization of the complex. The adsorption also induces notable changes in dipole moment, polarizability, and density of states, suggesting enhanced sensitivity of the nanocage toward glucose. Furthermore, Raman spectral analysis demonstrates significant intensity enhancement and peak shifts, primarily governed by charge-transfer mechanisms, confirming the potential of Mg12O12 as a non-plasmonic SERS substrate. Overall, this study provides molecular-level insights into glucose-nanocage interactions and highlights Mg12O12 as a promising platform for biosensing and nanomedical applications. The findings show that glucose binds preferentially through its hydroxyl oxygen atoms to the electropositive Mg sites of the Mg12O12 nanocage, forming a stable adsorbed complex supported by charge redistribution and favorable adsorption energetics. Adsorption reduces the energy gap and alters the dipole moment, polarizability, and density of states, indicating improved electronic communication between glucose and the nanocage. The Raman response is also strongly enhanced after adsorption, mainly through charge-transfer interactions, suggesting that Mg12O12 can serve as an efficient non-plasmonic SERS platform for glucose sensing.
