Small-rotation-angle moiré structures of 2H TaSe monolayers on Au(111).

Direct synthesis of two-dimensional (2D) materials with moiré patterns can provide 2D moiré structures with a clean interface and be useful for future electronics applications. However, the synthesis of moiré structures with small rotation angles is challenging since such structures possess the tendency to untwist during high temperature synthesis. Here, we study the moiré structures formed by epitaxially grown 2H TaSe monolayers on Au(111).

Transition metals of Pt and Pd on the surface of topological insulator Bi2Se3.

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material.

Drug Release from Surfactant-Containing Amorphous Solid Dispersions: Mechanism and Role of Surfactant in Release Enhancement.

Purpose: To understand how surfactants affect drug release from ternary amorphous solid dispersions (ASDs), and to investigate different mechanisms of release enhancement.

Methods: Ternary ASDs containing ritonavir (RTV), polyvinylpyrrolidone/vinyl acetate (PVPVA) and a surfactant (sodium dodecyl sulfate (SDS), Tween 80, Span 20 or Span 85) were prepared with rotary evaporation. Release profiles of ternary ASDs were measured with surface normalized dissolution.

Release Mechanisms of Amorphous Solid Dispersions: Role of Drug-Polymer Phase Separation and Morphology.

Formulating poorly soluble molecules as amorphous solid dispersions (ASDs) is an effective strategy to improve drug release. However, drug release rate and extent tend to rapidly diminish with increasing drug loading (DL). The poor release at high DLs has been postulated to be linked to the process of amorphous-amorphous phase separation (AAPS), although the exact connection between phase separation and release properties remains somewhat unclear.

Improved Aerosolization Stability of Inhalable Tobramycin Powder Formulation by Co-Spray Drying with Colistin.

Purpose: Tobramycin shows synergistic antibacterial activity with colistin and can reduce the toxic effects of colistin. The purpose of this study is to prepare pulmonary powder formulations containing both colistin and tobramycin and to assess their in vitro aerosol performance and storage stability.

Methods: The dry powder formulations were manufactured using a lab-scale spray dryer.

Balancing Solid-State Stability and Dissolution Performance of Lumefantrine Amorphous Solid Dispersions: The Role of Polymer Choice and Drug-Polymer Interactions.

Amorphous solid dispersions (ASDs) are of great interest due to their ability to enhance the delivery of poorly soluble drugs. Recent studies have shown that, in addition to acting as a crystallization inhibitor, the polymer in an ASD plays a role in controlling the rate of drug release, notably in congruently releasing formulations, where both the drug and polymer have similar normalized release rates. The aim of this study was to compare the solid-state stability and release performance of ASDs when formulated with neutral and enteric polymers.

Effect of Storage Humidity on Physical Stability of Spray-Dried Naproxen Amorphous Solid Dispersions with Polyvinylpyrrolidone: Two Fluid Nozzle vs. Three Fluid Nozzle.

In a spray drying operation, a two-fluid nozzle (2FN) with a single channel is commonly used for atomizing the feed solution. However, the less commonly used three-fluid nozzle (3FN) has two separate channels, which allow spray drying of materials in two incompatible solution systems. Although amorphous solid dispersions (ASDs) prepared using a 3FN have been reported to deliver comparable drug dissolution performance relative to those prepared using a 2FN, few studies have systematically examined the effect of 3FN on the physical stability.

Structural and Chemical Transformations of Zinc Oxide Ultrathin Films on Pd(111) Surfaces.

Structural and chemical transformations of ultrathin oxide films on transition metals lie at the heart of many complex phenomena in heterogeneous catalysis, such as the strong metal-support interaction (SMSI). However, there is limited atomic-scale understanding of these transformations, especially for irreducible oxides such as ZnO. Here, by combining density functional theory calculations and surface science techniques, including scanning tunneling microscopy, X-ray photoelectron spectroscopy, high-resolution electron energy loss spectroscopy, and low-energy electron diffraction, we investigated the interfacial interaction of well-defined ultrathin ZnOH films on Pd(111) under varying gas-phase conditions [ultrahigh vacuum (UHV), 5 × 10 mbar of O, and a D/O mixture] to shed light on the SMSI effect of irreducible oxides.

Stabilizing Hybrid Electrochromic Devices through Pairing Electrochromic Polymers with Minimally Color-Changing Ion-Storage Materials Having Closely Matched Electroactive Voltage Windows.

Conjugated electrochromic polymers hold great promises for next-generation color-changing windows and displays. One of the major roadblocks in their solid-state electrochromic devices is the relatively poor cycling stability. Finding ion-storage materials as a charge-balancing component is critical in improving their electrochemical cycling stability.

Physical Stability and Dissolution of Lumefantrine Amorphous Solid Dispersions Produced by Spray Anti-Solvent Precipitation.

This study aims to develop amorphous solid dispersion (ASD) of lumefantrine with a cost-effective approach of spray anti-solvent precipitation. Four acidic polymers, hydroxypropylmethylcellulose phthalate (HPMCP), hydroxypropylmethylcellulose acetate succinate (HPMCAS), poly(methacrylic acid-ethyl acrylate) (EL100) and cellulose acetate phthalate (CAP) were studied as excipients at various drug-polymer ratios. Of the studied polymers, satisfactory physical stability was demonstrated for HPMCP- and HPMCAS-based ASDs with no observed powder X-ray diffraction peaks for up to 3 months of storage at 40 °C/75% RH.

Surface Composition and Aerosolization Stability of an Inhalable Combinational Powder Formulation Spray Dried Using a Three-Fluid Nozzle.

Purpose: This study aims to understand the impact of spray drying nozzles on particle surface composition and aerosol stability.

Methods: The combination formulations of colistin and azithromycin were formulated by 2-fluid nozzle (2 N) or 3-fluid (3 N) spray drying in a molar ratio of 1:1. A 3-factor, 2-level (2) factorial design was selected to investigate effects of flow rate, inlet temperature and feed concentration on yield of spray drying and the performance of the spray dried formulations for the 3 N.

Water-Induced Phase Separation of Spray-Dried Amorphous Solid Dispersions.

Spray drying is widely used in the manufacturing of amorphous solid dispersion (ASD) systems due to its fast drying rate, enabling kinetic trapping of the drug in amorphous form. Spray-drying conditions, such as solvent composition, can have a profound impact on the properties of spray-dried dispersions. In this study, the phase behavior of spray-dried dispersions from methanol and methanol-water mixtures was assessed using ritonavir and copovidone [poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA)] as dispersion components.

Physical stability and release properties of lumefantrine amorphous solid dispersion granules prepared by a simple solvent evaporation approach.

Amorphous solid dispersions (ASDs) of lumefantrine, which has low aqueous solubility, have been shown to improve bioavailability relative to crystalline formulations. Herein, the crystallization tendency and release properties of a variety of lumefantrine ASD granules, formed on a blend of microcrystalline cellulose and anhydrous lactose, prepared using a simple solvent evaporation method, were evaluated. Several polymers, a majority of which contained acidic moieties, and different drug loadings were assessed.

Comparison of Drug Release and Adsorption under Supersaturating Conditions for Ordered Mesoporous Silica with Indomethacin or Indomethacin Methyl Ester.

Incomplete drug release from mesoporous silica systems has been observed in several studies. This work aims to increase the understanding of this phenomenon by investigating the mechanism of drug-silica interactions and adsorption behavior from supersaturated aqueous solutions of two similar drug molecules with different hydrogen bonding capabilities. Drug-silica interactions between indomethacin or its methyl ester and SBA-15 were investigated using spectroscopic techniques (infrared, fluorescence and X-ray photoelectron) and adsorption experiments.

Surface Composition and Formulation Heterogeneity of Protein Solids Produced by Spray Drying.

Purpose: The aim of this study is to determine the effects of saccharide-containing excipients on the surface composition of spray-dried protein formulations and their matrix heterogeneity.

Methods: Spray-dried formulations of myoglobin or bovine serum albumin (BSA) were prepared without excipient or with sucrose, trehalose, or dextrans. Samples were characterized by solid-state Fourier-transform infrared spectroscopy (ssFTIR), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and scanning electron microscopy (SEM).

Silica-supported, narrowly distributed, subnanometric Pt-Zn particles from single sites with high propane dehydrogenation performance.

The development of highly productive, selective and stable propane dehydrogenation catalysts for propene production is strategic due to the increasing need for propene and the availability of shale gas, an abundant source of light alkanes. In that context, the combination of surface organometallic chemistry (SOMC) and a thermolytic molecular precursor (TMP) approach is used to prepare bimetallic subnanometric and narrowly distributed Pt-Zn alloyed particles supported on silica grafting of a Pt precursor on surface OH groups present in a Zn single-site containing material followed by a H reduction treatment. This material, that exhibits a Zn to Pt molar ratio of 3 : 2 in the form of alloyed Pt-Zn particles with a 0.

Solar-Blind UV Photodetector Based on Atomic Layer-Deposited CuO and Nanomembrane β-GaO pn Oxide Heterojunction.

Herein, we present a solar-blind ultraviolet photodetector realized using atomic layer-deposited p-type cuprous oxide (CuO) underneath a mechanically exfoliated n-type β-gallium oxide (β-GaO) nanomembrane. The atomic layer deposition process of the CuO film applies bis(,'-di-secbutylacetamidinato)dicopper(I) [Cu(Bu-Me-amd)] as a novel Cu precursor and water vapor as an oxidant. The exfoliated β-GaO nanomembrane was transferred to the top of the CuO layer surface to realize a unique oxide pn heterojunction, which is not easy to realize by conventional oxide epitaxy techniques.

Competitive heavy metal adsorption onto new and aged polyethylene under various drinking water conditions.

The study goal was to identify factors that influence copper (Cu), iron (Fe), lead (Pb), manganese (Mn), and zinc (Zn) loading on new and aged low-density polyethylene (LDPE) under various drinking water conditions. The applied aging procedure increased LDPE surface area, hydrophilicity and the number of oxygen containing functional groups. Aged LDPE adsorbed up to a 5 fold greater metals than the new LDPE: Cu > Pb, Zn > Mn.