First-principles investigation of aluminum intercalation and diffusion in TiO2 materials: Anatase versus rutile

Aluminum-ion batteries, emerging as a promising post-lithium battery solution, have been a subject of increasing research interest. Yet, most existing aluminum-ion research has focused on electrode materials development and synthesis. There has been a lack of fundamental understanding of the electrode processes and thus theoretical guidelines for electrode materials selection and design. In this study, by using density functional theory, we for the first time report a first-principles investigation on the thermodynamic and kinetic properties of aluminum intercalation into two common TiO 2 polymorphs, i.e., anatase and rutile. After examining the aluminum intercalation sites, intercalation voltages, storage capacities and aluminum diffusion paths in both cases, we demonstrate that the stable aluminum intercalation site locates at the center of the O 6 octahedral for TiO 2 rutile and off center for TiO 2 anatase. The maximum achievable Al/Ti ratios for rutile and anatase are 0.34375 and 0.36111, respectively. Although rutile is found to have an aluminum storage capacity slightly higher than anatase, the theoretical specific energy of rutile can reach 20.90 Wh kg −1 , nearly twice as high as anatase (9.84 Wh kg −1 ). Moreover, the diffusion coefficient of aluminum ions in rutile is 10 −9 cm 2 s −1 , significantly higher than that in anatase (10 −20 cm 2 s −1 ). In this regard, TiO 2 rutile appears to be a better candidate than anatase as an electrode material for aluminum-ion batteries

Adsorption and diffusion of CO₂ and CH₄ in covalent organic frameworks: an MC/MD simulation study

<p>Covalent organic frameworks (COFs) are a promising gas separation material which have been developed recently. In this work, we have used grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations to investigate the adsorption and diffusion properties of CO₂ and CH₄ in five recent synthesised COF materials. We have also considered the properties of amino-modified COFs by adding –NH₂ group to the five COFs. The adsorption isotherm, adsorption/diffusion selectivity, self/transport diffusion coefficients have been examined and discussed. All of the five COFs exhibit promising adsorption selectivity which is higher than common nanoporous materials. An S-shaped adsorption isotherm can be found for CO₂ instead of CH₄ adsorption. The introduction of –NH₂ group is effective at low pressure region (<200 kPa). The diffusion coefficients are similar for TS-COFs but increase with the pore size for PI-COFs, and the diffusion coefficients seem less dependent on the –NH₂ groups.</p

Refining Toroidal Assemblies from Cross-Linked Triblock Copolymer Micelles

Constructing uniform and tunable toroidal assemblies remains a significant challenge. Here, we proposed a strategy to construct toroids from the self-assembly of cross-linked ABC triblock copolymer micelles. The work demonstrated that these cross-linked micelles are effective building units for forming toroidal assemblies in a vast parameter space of A and C blocks. The toroid size is precisely determined by the asymmetry of A and C patches in the cross-linked ABC triblock copolymer micelles, which can be tailored by adjusting the relative lengths and cross-linking degrees of A and C blocks. The formation of toroids follows a step-growth manner, leading to tritoroids and tetra-toroids since the length before toroid formation mismatches the toroid perimeter. We also found that reducing the copolymer concentration and increasing the incompatibility between A and C blocks can improve the uniformity of toroids. Our work provides a promising route to prepare uniform toroidal nanostructures and bridges the gap between the stepwise assembly of polymers and that of nanoparticles

Photocontrollable Intermittent Release of Doxorubicin Hydrochloride from Liposomes Embedded by Azobenzene-Contained Glycolipid

Azobenzene-contained glycolipids GlyAzoC<i>n</i>s, newly structured azobenzene derivatives, which have an azobenzene moiety between the galactosyl and carbon chains of various sizes, have been synthesized. The GlyAzoC<i>n</i>s undergo reversible photoinduced isomerization in both ethanol solution (free state) and liposomal bilayer (restricted state) upon irradiation with UV and vis light alternately. The drug release of Liposome@Gly induced by isomerization was found to be an instantaneous behavior. The photoinduced control of DOX release from liposome was investigated in various modes. The Liposome@Glys have been found to keep the entrapped DOX stably in the dark with less than 10% leakage in 10 h but release nearly 100% of cargos instantaneously with UV irradiation. The molecular structure of GlyAzoC<i>n</i>s and the property of the liposomal bilayer were considered as important factors influencing drug release. Among the synthesized GlyAzoC<i>n</i>s, GlyAzoC7 was shown to be the most efficient photosensitive actuator for controlling drug release. A lower proportion of cholesterol in Liposome@Glys was conducive to promote the release amount. Results indicated that the synthesized GlyAzoC<i>n</i>s could act as a role of smart actuators in the liposome bilayer and control the drug to release temporarily and quantitatively

Influence of C2–H of Imidazolium-Based Ionic Liquids on the Interaction and Vapor–Liquid Equilibrium of Ethyl Acetate + Ethanol System: [Bmim]BF₄ vs [Bmmim]BF₄

The effect of C2–H of alkylimidazolium tetrafluoroborate ionic liquids on the interaction and vapor–liquid equilibrium (VLE) of the ethyl acetate + ethanol mixture was studied using spectroscopy and the COSMO-RS method. Concentration-dependent ¹H NMR chemical shifts of ethyl acetate + ethanol + [Bmim]­BF₄ or [Bmmim]­BF₄ (<i>x</i>_IL = 0.1 and 0.3) systems show that the interaction between [Bmim]­BF₄ and ethanol is much stronger than that between [Bmmim]­BF₄ and ethanol. Moreover, the experimental and predicted VLE demonstrate that the improvement of relative volatility of ethyl acetate to ethanol by [Bmim]­BF₄ is better than that by [Bmmim]­BF₄. Also, σ-profile obtained from COSMO-RS method indicates that the hydrogen bonding donator ability of [Bmim]⁺ is greater than that of [Bmmim]⁺. Therefore, it can be deduced that the acidic C2–H plays an important role in the interaction differentiation of the ionic liquids and their effect on the VLE of the ethyl acetate + ethanol system, resulting from the interaction of the acidic C2–H with the ethanol that is much stronger than with the ethyl acetate

Dual Thermoresponsive Aggregation of Schizophrenic PDMAEMA‑<i>b</i>‑PSBMA Copolymer with an Unrepeatable pH Response and a Recycled CO₂/N₂ Response

A dual thermoresponsive block copolymer of poly­[2-(dimethylamino)­ethyl methacrylate]-<i>block</i>-poly­(sulfobetaine methacrylate) (PDMAEMA-<i>b</i>-PSBMA) exhibited reversible schizophrenic aggregation behavior in water because of the upper critical solution temperature (UCST) of the PSBMA block and the lower critical solution temperature (LCST) of the PDMAEMA block. Both the UCST and LCST shifted to lower values with increasing DMAEMA/SBMA block ratios, which was ascribed to the hydrophobic/hydrophilic balance of both blocks. Because of the salt-sensitive PSBMA and pH-responsive PDMAEMA, the UCST and LCST values of PDMAEMA-<i>b</i>-PSBMA were codetermined by varying the salt concentrations and pH. Specifically, increasing the salt concentration resulted in a notable decrease in the UCST and a slight increase in the LCST due to the salt-induced screening of the electrostatic attractions of the PSBMA and salt-enhanced solubility of the PSBMA blocks, respectively. The LCST decreased with increasing pH because of the deprotonation of PDMAEMA, and the UCST first increased and then decreased with increasing pH. Besides, the copolymer with larger PDMAEMA content was more sensitive to pH. For the repetitive adjustment to thermoresponsive aggregation, repeated addition of acids and bases induced salt accumulation and diminished the switchability of pH, whereas repeated switching cycles were achieved by CO₂/N₂ bubbling without introducing salt enrichment. The difference in HCl/NaOH titration and CO₂/N₂ bubbling also existed in the switching cycles when PDMAEMA-<i>b</i>-PSBMA served as a stimulus-responsive emulsifier

Affinity between Metal–Organic Frameworks and Polyimides in Asymmetric Mixed Matrix Membranes for Gas Separations

A series of flat-sheet asymmetric mixed matrix membranes (MMMs) have been fabricated with MOF-5, Cu₃(BTC)₂, and MIL-53­(Al) as fillers and PI polymer as a matrix through the dry–wet phase inversion method. After the surface modification by coating a PAA solution (15% wt) on the top of the obtained membrane, a thin defect-free selective skin in the MMM is obtained. The permeance of various gases such as H₂, He, CH₄, N₂, and CO₂ and their gas pair selectivity have been investigated, respectively. The results show that Cu₃(BTC)₂/PI MMM possesses the best gas separation performance with H₂ permeance of 0.44 GPU and H₂/CH₄ selectivity of 100. In addition, the mechanism of MOF fillers in MMMs has been further revealed by the interaction analysis between MOF fillers and PI chains

Interplay between Halogen and Hydrogen Bonds in 2D Self-Assembly on the Gold Surface: A First-Principles Investigation

The interplay between halogen bonding and hydrogen bonding has caused recent interest in the formation of 2D self-assembled molecular arrays on solid surfaces. Herein we present a first-principles density functional theory study of the self-assemblies of two brominated anthraquione molecules on Au(111) and Au(110). The possible binding sites of these two compounds on the facets were first explored, and then various self-assembled patterns involving different halogen and hydrogen bonds were examined both in the gas phase and on the gold surface. To visually investigate the nature of lateral adsorbate–adsorbate and vertical adsorbate–substrate interactions, the atoms in molecules, noncovalent interaction index, and electron density difference analyses were undertaken. The molecules tend to be self-assembled by means of triangular binding motifs with simultaneous halogen and hydrogen bonds. Upon the formation of the dimers in the gas phase as well as on the gold surface, significant band shifts around the Fermi energy take place, due to intermolecular orbital hybridization. The simulated scan tunneling microscopy images via the Tersoff–Hamann approach are in good agreement with those determined experimentally. The results reported in this work should be of fundamental importance in the simultaneous application of these two parallel noncovalent interactions in molecular self-assembly on surfaces

Theoretical Exploration of Halogen Bonding Interactions in the Complexes of Novel Nitroxide Radical Probes and Comparison with Hydrogen Bonds

In this work, halogen bonding interactions in the complexes of two new nitroxide radicals, which contain both a halogen-bond-donor group and an electron-spin-resonance-active radical unit, were investigated using density functional theory calculations. For comparison, the corresponding hydrogen-bonded complexes were also examined. Halogen bonds in these systems are predicted to be linear and much stronger than hydrogen bonds. To further understand the nature of these interactions, many theoretical methods, such as atoms in molecules, noncovalent interaction index, localized orbital locator, energy decomposition analysis, electron density difference, and electron spin densities, were employed. Compared with hydrogen bonds, halogen bonds have more open shell and covalent interaction components. Particularly, the formation of halogen bonds changes the ratio of different conformations, leading to spin density shift on certain atoms. The results reported herein will assist in the design of new functional probes for the detection of halogen bonding

Halogen-Bond-Based Molecular Self-Assembly on Graphene Surface: A First-Principles Study

The formation of halogen-bond-based 2D supramolecular assemblies on solid surfaces has become a hot research topic in recent years. Herein, we report a theoretical study of the halogen-bonded network formation of pyridine derivatives and aryl–halide molecules on graphene surface using first-principles density functional theory (DFT) calculations. To unravel the characteristics of molecule–molecule and molecule–substrate interactions, the noncovalent interaction index (NCI), electron density difference (EDD), density of state (DOS), and topographical scan tunneling microscopy (STM) image analyses were undertaken. The N···I interactions between terminal pyridyl groups and iodoperfluorobenzenes are predicted to be somewhat stronger than the molecule–surface stacking interactions and appear to be the primary interactions in the self-assembled networks, with geometries in good agreement with the experimental STM images. The results reported in this work should be of great importance in the applications of these interactions in molecular self-assembly on surfaces