Efficient hole transport materials based on naphthyridine core designed for application in perovskite solar photovoltaics.

Naphthyridine-based compounds with a donor-acceptor-donor (D-A-D) skeleton were considered as hole transport materials (HTMs) for perovskite solar cells (PSCs). The optical characteristics, stability, solubility, Hirshfeld surface analysis, crystal structure, and hole transport properties of the HTMs were studied systematically. The HOMO energies of all HTMs were higher than valence band of CH3NH3PbI3 (MAPbI3) perovskite signifying naphthyridine-based HTMs had appropriate energy alignments for usage in PSCs. The LUMO level of designed HTMs were higher than MAPbI3 conduction band ensuring prevention of backward electronic movement from MAPbI3 to the cathode. The λabsmax amounts of all HTMs were close 400 nm, which showed their competition with perovskite was impossible. The 18NP and 26NP HTMs had higher hole mobilities compared to that of the Spiro-OMeTAD. Considering aligned HOMO energies, suitable hole mobilities, satisfactory stability and solubility, 18NP (1,8-Naphthyridine) and 26NP (2,6-Naphthyridine) were introduced as the best HTM materials for PSCs which could replace Spiro-OMeTAD.

Revealing the role of different nitrogen functionalities in the drug delivery performance of graphene quantum dots: a combined density functional theory and molecular dynamics approach.

The amount and type of nitrogen (N) functionalities in graphene quantum dots can be controlled by tuning the synthesis conditions, which gives rise to their diverse applications. Nitrogen-doped graphene quantum dots (N-GQDs) are highly biocompatible and their properties can be easily tuned. In this work, the role of different N-functionalities in the drug delivery performance of N-GQDs was investigated via molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The results indicated that the magnitude of binding energy between the gemcitabine (GC) drug and the central N-GQDs, i.e., graphitic, pyridinic and amido, was greater than that of pristine GQDs and edge N-GQDs. The quantum molecular descriptors revealed that adsorption of GC drug on the nanocarriers enhanced the chemical reactivity. The adsorption of the GC drug on the nanocarriers was spontaneously proceeded. However, the Gibbs free energy values for adsorption of the GC drug on the center N-GQDs were greater than those of pristine GQDs and edge N-GQDs. Also, the nature of the intermolecular interactions between the GC drug and nanocarriers was further investigated through quantum theory of atoms in molecules (QTAIM) and noncovalent interaction index (NCI). The simulation results demonstrated that the GC drug was loaded on the surface of all nanocarriers, while favorable drug release could occur only from the center N-GQDs in acidic environments of cancer tissues. Finally, the mechanism for the penetration of the drug-loaded nanocarriers across the cell membrane was studied and discussed via steered molecular dynamics (SMD). The results indicated that the force required to pull the drug-loaded nanocarriers was the smallest when the nanocarriers were penetrated perpendicularly rather than parallelly or obliquely into the membrane plane. Overall, the results suggested that the center N-GQDs had better performance in drug delivery than pristine GQDs and edge N-GQDs. Our findings offer insightful information on efficient utilization of N-GQDs as drug delivery systems.

Hexagonal boron nitride nanosheet as novel drug delivery system for anticancer drugs: Insights from DFT calculations and molecular dynamics simulations.

Density functional theory (DFT) calculations and molecular dynamic (MD) simulations were accomplished to comprehend the nature of the interactions between 5-fluorouracil (FU)/6-mercaptopurine (MP)/6-thioguanine (TG) anticancer drugs and hexagonal boron nitride (BN) nanosheet as a drug delivery system. It is found from the calculations that the adsorption process of drug molecules on the BN nanosheet is exothermic and occurs spontaneously. The polarity for the drug loaded complexes, offers the possibility of improving the condition of solubility, which is favorable for drug delivery in biological media. Orbital energy and density of state (DOS) calculations show that HOMO-LUMO energy gap of BN nanosheet decreases upon the adsorption of drug molecules. The quantum molecular descriptors show that the absorption of drugs on BN nanosheet increases the chemical reactivity. The results of the energy decomposition analysis (EDA) indicated that the dispersion interaction plays a predominant role in the stabilization of the drug-BN complexes. The intermolecular interactions were also investigated by the noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. The MD results showed that the average of the interaction energy values in acidic conditions are lower (absolute values) than corresponding values obtained at neutral pH, which indicated the drug could be released within the target cancer cells. These findings contribute to the development of drug delivery systems based on BN nanosheet for delivery of anticancer drugs.

π-Hydrogen bonding and aromaticity: a systematic interplay study.

Quantum DFT calculations, corrected for long-range interactions, have been carried out on complex models formed between HF as a proton donor and 2-methylene-2H-indene derivatives as proton acceptors. Using various exocyclic X substitutions, mutual effects of the aromaticity and the strength of the resulting π-hydrogen bond (after its evaluation by AIM methodology) have been investigated. The results show that the aromaticity of 6-membered rings and the hydrogen bond strength increase upon increasing the electron-donating character of the X-substituents. Based on some aromaticity indices (HOMA, FLU, SA and NICS(1)zz), it has been shown that the formation of a π-hydrogen bond causes an increase of aromaticity of the 6-membered ring. Also, the strength of the resulting π-hydrogen bond (with an energy of about 4.0 to 7.0 kcal mol-1) depends on the aromaticity of the 6-membered ring and increases with an increase in the aromaticity. In addition, a linear relationship was found between the most negative value of the molecular electrostatic potential (Vmin) and the HOMA, which confirms that the Vmin in the region of the studied ring could be used as a new index to estimate the amount of aromaticity. The electronic properties of the complexes have also been evaluated by means of the molecular electrostatic potential (MEP), the atoms in molecules (AIM) and the natural bond orbital (NBO) analyses.

Ultrasonic-assisted synthesis of ZrO2 nanoparticles and their application to improve the chemical stability of Nafion membrane in proton exchange membrane (PEM) fuel cells.

Zirconium dioxide (ZrO2) nanoparticles were fabricated successfully via ultrasonic-assisted method using ZrO(NO3)2·H2O, ethylenediamine and hydrazine as precursors in aqueous solution. Morphology, structure and composition of the obtained products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance spectroscopy (DRS). Then, the synthesized nanoparticles were used to prepare Nafion/ZrO2 nanocomposite membranes. The properties of the membranes were studied by ion exchange capacity (IEC) proton conductivity (σ), thermal stability and water uptake measurements. The ex-situ Fenton's test was used to investigate the chemical stability of the membranes. From our results, compared with Nafion membrane, the nanocomposite membrane exhibited lower fluoride release and weight loss. Therefore, it can concluded that Nafion/ZrO2 nanocomposite exhibit more chemical stability than the pure Nafion membrane. ATR-FTIR spectra and SEM surface images of membranes also confirm these results.