Exploring the structural, electronic, and hydrogen storage properties of hexagonal boron nitride and carbon nanotubes: insights from single-walled to doped double-walled configurations.

This study investigates the structural intricacies and properties of single-walled nanotubes (SWNT) and double-walled nanotubes (DWNT) composed of hexagonal boron nitride (BN) and carbon (C). Doping with various atoms including light elements (B, N, O) and heavy metals (Fe, Co, Cu) is taken into account. The optimized configurations of SWNT and DWNT, along with dopant positions, are explored, with a focus on DWNT-BN-C. The stability analysis, employing binding energies, affirms the favorable formation of nanotube structures, with DWNT-C emerging as the most stable compound. Quantum stability assessments reveal significant intramolecular charge transfer in specific configurations. Electronic properties, including charge distribution, electronegativity, and electrical conductivity, are examined, showcasing the impact of doping. Energy gap values highlight the diverse electronic characteristics of the nanotubes. PDOS analysis provides insights into the contribution of atoms to molecular orbitals. UV-Vis absorption spectra unravel the optical transitions, showcasing the influence of nanotube size, dopant type, and location. Hydrogen storage capabilities are explored, with suitable adsorption energies indicating favorable hydrogen adsorption. The desorption temperatures for hydrogen release vary across configurations, with notable enhancements in specific doped DWNT-C variants, suggesting potential applications in high-temperature hydrogen release. Overall, this comprehensive investigation provides valuable insights into the structural, electronic, optical, and hydrogen storage properties of BN and C nanotubes, laying the foundation for tailored applications in electronics and energy storage.

Promising sensors for pharmaceutical pollutant adsorption using Clar's goblet-based 2D membranes.

This study focuses on the design of new 2D membranes from connected Clar's Goblet as a potential sensor for pharmaceutical pollutants, specifically the painkiller drugs aspirin, paracetamol, ibuprofen, and diclofenac. The electronic, optical, and interaction properties are investigated using density functional theory calculations. The Clar's Goblet membranes (CGMs) that were chosen are semiconductors with an energy gap of around 1.5 eV, according to energy gap calculations and density of states. Molecular electrostatic potential (ESP) analysis shows that CGMs have electrophilic and nucleophilic sites, suggesting their suitability for interacting with pharmaceutical pollutants. The adsorption energies confirm the chemical adsorption of pharmaceutical pollutants with diclofenac showing the strongest adsorption. The UV-Vis absorption spectra of CGMs-drug complexes are analyzed, revealing a redshift compared to the absorption spectrum of CGMs alone, confirming the adsorption of these drugs. Further analysis using hole/electron examinations indicates that the type of excitation is local excitation rather than charge transfer excitation. This study quantitatively characterized hole and electron distribution in excited states using various indices. The analysis revealed local excitation transitions and significant charge transfer between the CGMs molecule and pharmaceutical pollutants. Additionally, non-covalent interaction analysis indicates the presence of van der Waals interactions, highlighting the adsorption behavior of the drugs. These results demonstrate the potential of CGMs as a highly sensitive sensor for pharmaceutical pollutants.

Exploring the Potential of Chemically Modified Graphyne Nanodots as an Efficient Adsorbent and Sensitive Detector of Environmental Contaminants: A First Principles Study.

In this study, we investigated the reactivity of γ-graphyne (Gp) and its derivatives, Gp-CH3, Gp-COOH, Gp-CN, Gp-NO2, and Gp-SOH, for the removal of toxic heavy metal ions (Hg+ 2, Pb+ 2, and Cd+ 2) from wastewater. From the analysis of the optimized structures, it was observed that all the compounds exhibited planar geometry. The dihedral angles (C9-C2-C1-C6 and C9-C2-C1-C6) were approximately 180.00°, indicating planarity in all molecular arrangements. To understand the electronic properties of the compounds, the HOMO (EH) and LUMO (EL) energies were calculated, and their energy gaps (Eg) were determined. The EH and EL values ranged between - 6.502 and - 8.192 eV and - 1.864 and - 3.773 eV, respectively, for all the compounds. Comparing the EH values, Gp-NO2 exhibited the most stable HOMO, while Gp-CH3 had the least stable structure. In terms of EL values, Gp-NO2 had the most stable LUMO, while Gp-CH3 was the least stable. The Eg values followed the order: Gp-NO2 < Gp-COOH < Gp-CN < Gp-SOH < Gp-CH3 < Gp, with Gp-NO2 (4.41 eV) having the smallest energy gap. The density of states (DOS) analysis showed that the shape and functional group modifications affected the energy levels. Functionalization with electron-withdrawing (CN, NO2, COOH, SOH) or electron-donating (CH3) groups reduced the energy gap. To specifically target the removal of heavy metal ions, the Gp-NO2 ligand was selected for its high binding energy. Complexes of Gp-NO2-Cd, Gp-NO2-Hg, and Gp-NO2-Pb were optimized, and their properties were analyzed. The complexes were found to be planar, with metal-ligand bond distances within the range of 2.092→3.442 Å. The Gp-NO2-Pb complex exhibited the shortest bond length, indicating a stronger interaction due to the smaller size of Pb+ 2. The computed adsorption energy values (Eads) indicated the stability of the complexes, with values ranging from - 0.035 to -4.199 eV. Non-covalent interaction (NCI) analysis was employed to investigate intermolecular interactions in Gp-NO2 complexes. The analysis revealed distinct patterns of attractive and repulsive interactions, providing valuable insights into the binding preferences and steric effects of heavy metals.

Electronic and optical properties of chemically modified 2D GaAs nanoribbons.

We employed density functional theory calculations to investigate the electronic and optical characteristics of finite GaAs nanoribbons (NRs). Our study encompasses chemical alterations including doping, functionalization, and complete passivation, aimed at tailoring NR properties. The structural stability of these NRs was affirmed by detecting real vibrational frequencies in infrared spectra, indicating dynamical stability. Positive binding energies further corroborated the robust formation of NRs. Analysis of doped GaAs nanoribbons revealed a diverse range of energy gaps (approximately 2.672 to 5.132 eV). The introduction of F atoms through passivation extended the gap to 5.132 eV, while Cu atoms introduced via edge doping reduced it to 2.672 eV. A density of states analysis indicated that As atom orbitals primarily contributed to occupied molecular orbitals, while Ga atom orbitals significantly influenced unoccupied states. This suggested As atoms as electron donors and Ga atoms as electron acceptors in potential interactions. We investigated excited-state electron-hole interactions through various indices, including electron-hole overlap and charge-transfer length. These insights enriched our understanding of these interactions. Notably, UV-Vis absorption spectra exhibited intriguing phenomena. Doping with Te, Cu, W, and Mo induced redshifts, while functionalization induced red/blue shifts in GaAs-34NR spectra. Passivation, functionalization, and doping collectively enhanced electrical conductivity, highlighting the potential for improving material properties. Among the compounds studied, GaAs-34NR-edg-Cu demonstrated the highest electrical conductivity, while GaAs-34NR displayed the lowest. In summary, our comprehensive investigation offers valuable insights into customizing GaAs nanoribbon characteristics, with promising implications for nanoelectronics and optoelectronics applications.

Chemically modified covalent organic frameworks for a healthy and sustainable environment: First-principles study.

Pure water is a key element for a sustainable and healthy environment of human inhabitation. Since major sources of water contamination are industrially generated heavy metal cations there is great demand for efficient methods of their treatment. Here, using density functional theory, we investigate the covalent organic framework's electronic and optical properties and their interaction with the most dangerous heavy metal pollutants, namely Hg+2, Pb+2, and Cd+2. We consider biphenyl boroxine covalent organic frameworks before and after chemical modification with CN, COOH, NH2, and NO2 groups. In addition to the molecular geometries, such parameters as the dipole moment, chemical potential, electronegativity, chemical hardness, and binding energy are calculated. It is found that CN, COOH, and NO2 functional groups are favorable for intermolecular bonding with harmful transition metals. The functionalization with the mentioned groups reduces the band gap of the pristine covalent organic frameworks and increases their reactivity. As a result, strong complexes with Cd+2, Hg+2, and Pb+2 can form, which, as follows from our calculations, can be detected by the red shift in their optical absorption spectra.

Enhanced photocatalytic and antimicrobial performance of a multifunctional Cu-loaded nanocomposite under UV light: theoretical and experimental study.

Due to modern industrialization and population growth, access to clean water has become a global challenge. In this study, a metal-semiconductor heterojunction was constructed between Cu NPs and the Co0.5Ni0.5Fe2O4/SiO2/TiO2 composite matrix for the photodegradation of potassium permanganate, hexavalent chromium Cr(VI) and p-nitroaniline (pNA) under UV light. In addition, the electronic and adsorption properties after Cu loading were evaluated using density functional theory (DFT) calculations. Moreover, the antimicrobial properties of the prepared samples toward pathogenic bacteria and unicellular fungi were investigated. Photocatalytic measurements show the outstanding efficiency of the Cu-loaded nanocomposite compared to that of bare Cu NPs and the composite matrix. Degradation efficiencies of 44% after 80 min, 100% after 60 min, and 65% after 90 min were obtained against potassium permanganate, Cr(VI), and pNA, respectively. Similarly, the antimicrobial evaluation showed high ZOI, lower MIC, higher protein leakage amount, and cell lysis of nearly all microbes treated with the Cu-loaded nanocomposite.

Two-dimensional quantum dots for highly efficient heterojunction solar cells.

The electronic and optical properties of finite silicene, graphene, and arsenene heterostructures are investigated using first principles calculations. The optoelectronic properties of these structures are precisely controlled, by chemical functionalization, shape, and size, to produce suitable donor energy gap and minimal conduction band offset that enable the construction of efficient heterojunction solar cells. Heterojunctions with only Van der Waals interactions between layers have been achieved in functionalized silicene/graphene and arsenene/graphene. The distribution of the highest occupied/lowest unoccupied molecular orbital on donor/acceptor layer in addition to the contribution of each layer into the total electronic density of states insure that the only interlayer interaction is the van der Waals one and charge separation is attained. The heterojunctions have donors' energy gaps ranging from 1.2 to 1.8 eV which in conjunction with the very low conduction band offset ∼ 0.002 eV enable the building of type-II solar cells with extremely high power conversion efficiency up to 23.34%. The prominent low energy optical excitations are mainly contributed by a transition from donor molecular orbitals to acceptor ones. Therefore, functionalized 2D heterojunctions are excellent candidates for building ultrathin, stable, and low-cost efficient solar cells.