Alloying In2O3 and Ga2O3 on AlN templates for deep-ultraviolet transparent conductive films by mist chemical vapor deposition

We studied the phase diagram of (In x Ga1−x )2O3 thin films with a composition of x = 0 to 1 on Aluminum Nitride (AlN) templates grown using mist chemical vapor deposition. From X-ray diffraction results, we observed that the (In x Ga1−x )2O3 thin films exhibited three different single-phase crystal structures depending on the value of x: orthorhombic (κ)-(In x Ga1−x )2O3 for x ≤ 0.186, hexagonal (hex)-(In x Ga1−x )2O3 for 0.409 ≤ x ≤ 0.634, and body-centered cubic (bcc)-(In x Ga1−x )2O3 for x ≥ 0.772. The optical bandgap of (In x Ga1−x )2O3 was tuned from 3.27 eV (bcc-In2O3) and 4.17 eV (hex-InGaO3) to 5.00 eV (κ-Ga2O3). Moreover, hex-(In x Ga1−x )2O3 exhibited a wide bandgap (4.30 eV) and a low resistivity (7.4×10‒1 Ω·cm). Furthermore, hex-(In x Ga1−x )2O3 thin films were successfully grown on GaN and AlGaN/GaN templates. Therefore, hex-(In x Ga1−x )2O3 can be used in transparent conductive films for deep-ultraviolet LEDs.

Microemulsion-Based Solid Lipid Nanoparticles As Emulsion Stabilisers

The preparation and properties of water-in-oil (W/O) emulsions stabilised solely by adsorbed surface-active solid lipid nanoparticles (SLNs) at the oil-water interface were studied. Monostearin-based SLNs were prepared using food-grade micoremulsions as nanoscle 'reactors'. Hot oil-in-water (O/W) microemulsions (70°C) consisting of monostearin, Tween 20, ethanol and water were crash-cooled to 4°C to promote the liquid-solid transition of the monostearin and thus develop sub-micron solid lipid particles. SLNs obtained from the cooled microemulsions were partially stabilised with addition to lecithin (0.5% w/w) to the microemulsion system. With 2% (w/w) added monstearin, the W/O emulsion was stable for the 14 days of study. The microstructure of the emulsions revealed the presence of two stabilisation mechanisms, namely Pickering-type and continuous phase crystal network stabilisation, which both contributed to slowing dispersed droplet coalescence. Overall, this study demonstrated that surface-active SLNs developed using a microemulsion technique could effectively kinetically stabilise model W/O emulsions.

Microemulsion-Based Solid Lipid Nanoparticles As Emulsion Stabilisers

The preparation and properties of water-in-oil (W/O) emulsions stabilised solely by adsorbed surface-active solid lipid nanoparticles (SLNs) at the oil-water interface were studied. Monostearin-based SLNs were prepared using food-grade micoremulsions as nanoscle 'reactors'. Hot oil-in-water (O/W) microemulsions (70°C) consisting of monostearin, Tween 20, ethanol and water were crash-cooled to 4°C to promote the liquid-solid transition of the monostearin and thus develop sub-micron solid lipid particles. SLNs obtained from the cooled microemulsions were partially stabilised with addition to lecithin (0.5% w/w) to the microemulsion system. With 2% (w/w) added monstearin, the W/O emulsion was stable for the 14 days of study. The microstructure of the emulsions revealed the presence of two stabilisation mechanisms, namely Pickering-type and continuous phase crystal network stabilisation, which both contributed to slowing dispersed droplet coalescence. Overall, this study demonstrated that surface-active SLNs developed using a microemulsion technique could effectively kinetically stabilise model W/O emulsions.

Novel Flexible PVDF-TrFE and PVDF-TrFE/ZnO Pressure Sensor: Fabrication, Characterization and Investigation

With the development of human healthcare devices, smart sensors, e-skins, and pressure sensors with outstanding sensitivity, flexibility, durability and biocompatibility have attracted more and more attention. In this paper, to develop a novel flexible pressure sensor with high sensitivity, different poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)-based composite membranes were fabricated, characterized and tested. To improve the β-phase crystallinity and piezoelectricity of the membranes, and for the purpose of comparison, nano ZnO particles with different concentrations (99:1, 9:1 in a weight ratio of PVDF-TrFE to ZnO) were, respectively added into PVDF-TrFE polymer acting as a nucleating agent and dielectric material. To facilitate the formation of β-phase crystal, the membranes were fabricated by electrospinning method. After the electrospinning, an annealing process was conducted to the fabricated membranes to increase the size and content of β-phase crystal. Then, the fabricated PVDF-TrFE membranes, acting as the core sensing layer, were, respectively built into multiple prototype sensors in a sandwich structure. The sensitivity of the prototype sensors was tested by an auto-clicker. The stimulation of the auto-clicker on the prototype sensors generated electrical signals, and the electrical signals were collected by a self-built testing platform powered by LabVIEW. As a result, combining the addition of ZnO nanofillers and the annealing process, a highly sensitive pressure sensor was fabricated. The optimal peak-to-peak voltage response generated from the prototype sensor was 1.788 V which shows a 75% increase compared to that of the pristine PVDF-TrFE sensor. Furthermore, a human pulse waveform was captured by a prototype sensor which exhibits tremendous prospects for application in healthcare devices.

Controllable One-Step Synthesis of Mixed-Phase TiO2 Nanocrystals with Equivalent Anatase/Rutile Ratio for Enhanced Photocatalytic Performance

In this study, the novel mixed-phase TiO2 nanocrystals (s-TiO2) with nearly equivalent anatase/rutile ratio were fabricated in the reagent of sec-butanol at the relatively low temperature of 80 °C by using a facile one-step condensing reflux method. The photocatalytic water splitting hydrogen production performance of s-TiO2 nanocrystals is close to that of commercial TiO2 (P25), and its photocatalytic degradation performance is about four times that of P25. The energy-level staggered interfaces and surface bridged hydroxyl groups significantly increased due to the anatase/rutile mixed-phase crystal structure and high specific surface area, which might generate the synergistic effect for the improvement of photocatalytic degradation.

Laves phase crystal analysis (LaCA): Atomistic identification of lattice defects in C14 and C15 topologically close-packed phases

The identification of defects in crystal structures is crucial for the analysis of atomistic simulations. Many methods to characterize defects that are based on the classification of local atomic arrangement are available for simple crystalline structures. However, there is currently no method to identify both, the crystal structures and internal defects of topologically close-packed (TCP) phases such as Laves phases. We propose a new method, Laves phase crystal analysis (LaCA), to characterize the atomic arrangement in Laves crystals by interweaving existing structural analysis algorithms. The new method can identify the polytypes C14 and C15 of Laves phases, typical crystallographic defects in these phases, and common deformation mechanisms such as synchroshear and non-basal dislocations. Defects in the C36 Laves phase are detectable through deviations from the periodic arrangement of the C14 and C15 structures that make up this phase. LaCA is robust and extendable to other TCP phases. Graphic abstract

Crystallization from the Gas Phase: Morphology Control, Co-Crystal and Salt Formation

Multicomponent crystallisation is a widely studied technique in pharmaceutical chemistry to enhance physical properties of API’s such as solubility, stability and bioavailability without chemically modifying the drug moiety itself. Methods to produce multicomponent crystals are varied with solution crystallisation being the predominant method. Crystal morphologies also influence an API’s properties with needle shaped crystals dissolving slower and possessing poor flow properties compared to a more equant block shape. In this paper, we discuss the preparation of co-crystals and co-crystal salts of two poorly soluble drugs, pyrimethamine and diflunisal. In particular, we compare production of multicomponent crystals via cosublimation with the more common methods of mechanical grinding and solution crystallisation. Samples are sublimed on a laboratory scale from both ends of standard 15 × 160 mm test tubes sealed under vacuum with two heaters were used to equalize the sublimation rates of the components. We show that a range of multicomponent pharmaceutical crystals can be prepared that are not accessible via solution crystallisation, including polymorphs and ansolvates. In addition to binary systems, ternary crystals can also be obtained via this technique. Various diflunisal co-crystals crystallise as thin needles and we describe the use of tailor-made additives to obtain unprecedented morphology control of gas phase crystal growth. Finally, we discuss the formation of co-crystal salts in the absence of solvent. Salt formation was observed to occur during gas phase crystallisations in accordance with the pKa rule of 3 and modelling studies were carried out to understand the nature of proton transfer in these crystals in the absence of a solvent.