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This study investigates the intermolecular interactions between 6-mercaptopurine (MP) and 6-thioguanine (TG) drugs with Fe- and Ni-layered single hydroxides (LSH) using DFT calculations. Hydrogenated Fe and Ni LSH show the best performance as drug agents with suitable adsorption energies and moderate interactions with the drugs. Computational analyses, including Natural Bond Orbital (NBO), Non-Covalent Interaction (NCI) surfaces, optical properties, and electronic structure evaluations, elucidate the impact of drug loading on these materials. NCI surface analyses reveal strong attractive interactions within LSH carriers, crucial for their stability, while weaker van der Waals interactions with MP/TG drugs suggest the potential for controlled drug release. Optical and electronic property shifts underscore notable optical and electronic changes upon drug loading, essential for detecting the adsorption process. These characteristics demonstrate LSH’s robustness and effectiveness in designing effective drug delivery systems. more...

Two-dimensional (2D) heterostructures open the door toward novel applications, such as multiterminal transistors, by integrating the properties of the participant materials. Here we construct 2D heterostars from zigzag-triangular graphene (ZTG) and group-III nitrides. They are investigated using density functional theory and non-equilibrium Green’s function approaches. These heterostars are ferromagnetically spin-ordered devices that originate and distribute on ZTG. Further control over the net spin can be achieved by forming bilayer heterostars where spin can be increased, decreased, or removed. Single-layer heterostars are wide energy gap semiconductors of ∼3.5 eV that decrease to ∼1 eV in bilayers or are kept unchanged in other bilayers. Quantum transport calculations show that different spintronic devices can be constructed by connecting the source/drain voltage to different terminals of the nanostars. These devices are characterized by a low tunneling current through the potential barrier of group-III nitrides that significantly increased by applying gate voltage. A spin filter based on graphene-AlN nanostar with efficient separation of spin-up current is demonstrated. Also, a significant improvement in both the spin-up and spin-down currents can be achieved in the same nanostar but using other terminals. 2D heterostars are then potential candidates for building multi-terminal spintronic devices. more...

In this study, we delve into the structural and electronic intricacies of 2D aluminum nitride quantum dots (AlN-QDs) and their derivatives. Through detailed analysis, we uncover notable variations in bond lengths upon passivation with elements such as fluorine (F) and hydroxyl (OH) groups, with the latter exhibiting a particularly intriguing stability profile with a binding energy of 5.171 eV. Our investigation reveals a substantial energy gap of ∼5 eV in AlN-QDs, indicating enhanced electron confinement and optimal conditions for semiconductor applications. Furthermore, we elucidate the electron donation properties of nitrogen atoms and electron acceptance tendencies of aluminum atoms within AlN-QDs, shedding light on their unique electronic structure. Quantum stability assessments unveil charge distribution asymmetries and variations in electronegativity, contributing to a deeper understanding of AlN-QDs' robustness. We also demonstrate a significant enhancement in electrical conductivity, notably with AlN-QDs-surf-2CO exhibiting remarkable performance. Additionally, our study showcases AlN-QDs-OH's exceptional adsorption capabilities, evidenced by significantly higher adsorption energies for small organic compounds, highlighting their potential as highly effective sensors. Optical investigations further reinforce these findings, revealing distinct shifts in absorption spectra upon adsorption, which underscore the substantial impact of adsorbates on AlN-QDs' optical properties more...

New nanobelts and nanoribbons are built from zigzag-hexagonal graphene quantum dots. Their stability, electronic, optical, and sensing properties are studied using density functional theory calculations. The infrared spectra's real vibrational frequencies and positive binding energy prove the stability of the constructed structures. The thermal stability at 600 K is also confirmed by molecular dynamics simulations. The nanobelts have a significantly low energy gap compared to the planer single quantum dots or the extended nanoribbons based on these nanodots. This is a result of the wrapping of the graphene nanodots which raises the π-overlapping between adjacent rings that decreases the energy gap. Interactive electronic states localized at the zigzag edges characterize both nanobelts and nanoribbons. Thus these systems are promising candidates for sensing and catalytic applications. Their sensing capability is tested by studying the adsorption of selected volatile organic compounds such as chloromethane and trichloroethylene. The findings indicate that these gases are effectively adsorbed with moderate adsorption energy and charge transfer, opening the door toward gas sensor applications. more...

The electronic and optical properties and hydrogen storage capacity of doped two-dimensional TiO2 quantum dots are studied using density functional theory computations. The considered dopants are C, S, N, Fe, Ni, and Zn. Temperature stability is confirmed at 500 K according to ab initio molecular dynamics simulations. Doping and vacancy formation increase the energy gap due to the relaxation of Ti-atoms by additional electrons from the dopants or surface reconstruction after removing O or Ti atoms. The UV–Vis absorption spectra imply that the dominant absorption peak experiences a blue shift after doping and vacancies. The pristine TiO2 is promising for hydrogen storage with suitable adsorption energy that can be enhanced by doping. We obtained a gravimetric adsorption capacity of 6.23 wt% which is higher than the 6.0 wt% issued by the US Department of Energy. Therefore, the high adsorption capacity/energy and thermal stability render TiO2 nanodots promising for efficient H2-storage devices. more...

Clean air is essential for a sustainable and healthy human settlement. Hazardous gases produced by industry ruin the air quality, thus it is crucial to find efficient treatment methods. The capability of ultrathin TiO2 quantum dots to adsorb different gases, namely CO, CO2, SO2, H2S, NO2, NH3, and O3, are investigated using DFT calculations. Based on electronic properties and molecular electrostatic potential, edge Ti-atoms are highly interactive and are suitable active sites for gas adsorption. Adsorption energy, charge transfer, and atom in molecule analysis confirm that all the considered gases are successfully absorbed. The UV–Vis spectrum experience redshift /blueshift after adsorption of (CO, CO2, H2S, NH3)/(H2S, O3) and thus can be used to test the adsorption process. These favorable adsorption properties and the calculated quick recovery time make the two-dimensional TiO2 quantum dots potential candidates for efficient and reusable gas sensors. more...

Porphyrin derivatives are known singlet oxygen sensitizers in photodynamic therapy (PDT). Energy transfer from a class of diolefinic laser dyes (DOLDs) as energy donors to the sodium salt of meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) as the accepter of energy would extend the range of photon harvesting down to the UV-region. Energy transfer was substantially enhanced in the presence of metallic silver nanoparticles (AgNPs), as revealed by steady-state emission spectroscopy, lifetimes, and quantum mechanics. DOLDs under investigation are 2,5-distyrylpyrazine (DSP), 1,4-bis (β-pyridyl-2 vinyl) benzene (P2VB), and 1,4 bis (2-methylstyryl) benzene (MSB) as efficient donors of intense absorption in the UV-region. AgNPs enhance the rate of energy transfer from DOLDs to TPPS via bringing donor and acceptor into close- proximity with a concomitant increase in dipole–dipole interaction between excited state donor and ground-state acceptor. The DOLDs molecular structures were optimized using the DFT/CAM-B3LYP/6-311G++ (d, p) level of theory. The calculated electronic absorption spectra for the studied DOLDs in the gaseous phase and methanol solvent were studied using the time-dependent density functional theory (TD-DFT) at M06-2X/6-311G++ (2d,2p) level. The calculated absorption/emission spectra for DSP laser dye in methanol are obtained at the TD/ M06-2X/6-311G++(2d, 2p) method. Notably, all theoretical results of the molecular structures under study highly agreed with the practical optical results. Energy transfer rate constants (kET) amid energy donor/acceptor pairs were determined by Stern-Volmer constants (KSV) and donors' lifetime measurements. The KSV values indicate an enhanced Fluorescence Resonance Energy Transfer (FRET) efficiencies in the presence of negatively charged AgNPs. The critical transfer distances Ro were determined from the spectral overlap between the emission spectrum of donor and absorption spectrum of TTPS. These outcomes propose the application of designed metal-enhanced FRET for energy-transfer-based assays and photodynamic therapy (PDT) applications. more...