Mixed-flow design for microfluidic printing of two-component polymer semiconductor systems.

The rational creation of two-component conjugated polymer systems with high levels of phase purity in each component is challenging but crucial for realizing printed soft-matter electronics. Here, we report a mixed-flow microfluidic printing (MFMP) approach for two-component π-polymer systems that significantly elevates phase purity in bulk-heterojunction solar cells and thin-film transistors. MFMP integrates laminar and extensional flows using a specially microstructured shear blade, designed with fluid flow simulation tools to tune the flow patterns and induce shear, stretch, and pushout effects. This optimizes polymer conformation and semiconducting blend order as assessed by atomic force microscopy (AFM), transmission electron microscopy (TEM), grazing incidence wide-angle X-ray scattering (GIWAXS), resonant soft X-ray scattering (R-SoXS), photovoltaic response, and field effect mobility. For printed all-polymer (poly[(5,6-difluoro-2-octyl-2H-benzotriazole-4,7-diyl)-2,5-thiophenediyl[4,8-bis[5-(2-hexyldecyl)-2-thienyl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl]) [J51]:(poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}) [N2200]) solar cells, this approach enhances short-circuit currents and fill factors, with power conversion efficiency increasing from 5.20% for conventional blade coating to 7.80% for MFMP. Moreover, the performance of mixed polymer ambipolar [poly(3-hexylthiophene-2,5-diyl) (P3HT):N2200] and semiconducting:insulating polymer unipolar (N2200:polystyrene) transistors is similarly enhanced, underscoring versatility for two-component π-polymer systems. Mixed-flow designs offer modalities for achieving high-performance organic optoelectronics via innovative printing methodologies.

A Low-Temperature Approach for the Phase-Pure Synthesis of MIL-140 Structured Metal-Organic Frameworks.

In a systematic investigation, the synthesis of metal-organic frameworks (MOFs) with MIL-140 structure was studied. The precursors of this family of MOFs are the same as for the formation of the well-known UiO-type MOFs although the synthesis temperature for MIL-140 is significantly higher. This study is focused on the formation of Zr-based MIL-140 MOFs with terephthalic acid (H2 bdc), biphenyl-4,4'-dicarboxylic acid (H2 bpdc), and 4,4'-stilbenedicarboxylic acid (H2 sdc) and the introduction of synthesis field diagrams to discover parameters for phase-pure products. In this context, a MIL-140 network with H2 sdc as linker molecule is first reported. Additionally, an important aspect is the reduction of the synthesis temperature to make MIL-140 MOFs more accessible even though linkers with a more delicate nature are used. The solvothermal syntheses were conducted in highly concentrated reaction mixtures whereby a targeted synthesis to yield the MIL-140 phase is possible. Furthermore, the effect of the often-used modulator approach is examined for these systems. Finally, the characteristics of the synthesized MOFs are compared with physisorption measurements, thermogravimetric analyses, and scanning electron microscopy.

The Origin of MoS2 Significantly Influences Its Performance for the Hydrogen Evolution Reaction due to Differences in Phase Purity.

Molybdenum disulfide (MoS2 ) is at the forefront of materials research. It shows great promise for electrochemical applications, especially for hydrogen evolution reaction (HER) catalysis. There is a significant discrepancy in the literature on the reported catalytic activity for HER catalysis on MoS2 . Here we test the electrochemical performance of MoS2 obtained from seven sources and we show that these sources provide MoS2 of various phase purity (2H and 3R, and their mixtures) and composition, which is responsible for their different electrochemical properties. The overpotentials for HER at -10 mA cm-2 for MoS2 from seven different sources range from -0.59 V to -0.78 V vs. reversible hydrogen electrode (RHE). This is of very high importance as with much interest in 2D-MoS2 , the use of the top-down approach would usually involve the application of commercially available MoS2 . These commercially available MoS2 are rarely characterized for composition and phase purity. These key parameters are responsible for large variance of reported catalytic properties of MoS2 .

Exploring the preparation of YbBa2Cu3O7-y superconductor in flowing oxygen atmosphere.

REBCO has been used extensively as coated conductors applied to superconducting magnets due to its exceptional superconducting properties. As a REBCO superconductor, YbBa2Cu3O7-y (Yb123) has a low melting temperature, making it suitable for use as an intermediate medium connector while preparing the superconducting joint. However, there is still uncertainty about the formation mechanism of Yb123 and the synthesis of this superconductor has not been fully understood. Therefore, this study systematically investigated the phase transformation process of Yb123 during heat treatment in flowing oxygen. The results indicated that Yb123 sample with the highest phase purity could be obtained by annealing at 927 °C or 937 °C but not in between, respectively. Furthermore, a quantitative phase analysis revealed that the sample annealed at 937 °C had a phase purity greater than 80 wt%. Additionally, a strong c-axis texture was observed in the bulk Yb123 superconductor prepared at 937 °C. Meanwhile, the superconducting results revealed that the bulk sample's Tc was 89.9 K, and its self-field critical current densities at 4.2 K and 77 K were 1.3 × 105 A/cm2 and 5.0 × 103 A/cm2, respectively. Based on the results mentioned above, the phase transformation process and formation mechanism of Yb123 in flowing oxygen were elaborated.

Bilayer 2D-3D Perovskite Heterostructures for Efficient and Stable Solar Cells.

With a stacking-layered architecture, the bilayer two-dimensional-three-dimensional (2D-3D) perovskite heterostructure (PHS) not only eliminates surface defects but also protects the 3D perovskite matrix from external stimuli. However, these bilayer 2D-3D PHSs suffer from impaired interfacial charge carrier transport due to the relatively insulating 2D perovskite fragments with a random phase distribution. Over the past decade, substantial efforts have been devoted to pioneering molecular and structural designs of the 2D perovskite interlayers for improving their charge carrier mobility, which enables state-of-the-art perovskite solar cells with high power conversion efficiency and exceptional operational stability. Herein, this review offers a comprehensive and up-to-date overview on the recent progress of bilayer 2D-3D PHSs, encompassing advancements on spacer cation engineering, interfacial charge carrier modification, advanced deposition protocols, and characterization techniques. Then, the evolutionary trajectory of bilayer 2D-3D PHSs is outlined by summarizing its mainstream development trends, followed by a perspective discussion about its future research opportunities toward efficient and durable perovskite solar cells.

Solid-state versatility in tranexamic acid drug: structural and thermal behavior of new salts and cocrystals.

Tranexamic acid (TNA) is an anti-fibrinolytic hemostatic drug widely used in various medical treatments. Six new salts and five cocrystals of TNA are reported here and the crystal structures of the obtained multicomponent compounds were determined using single-crystal X-ray diffraction (SC-XRD) techniques. TNA formed salts with coformers maleic acid (MEA), nicotinic acid, DL-mandelic acid and saccharin. Salt formation with MEA resulted in three different solid forms, namely TNA-MEA (1:1), TNA-MEA (2:1) and TNA-MEA-H2O (1:1:1). All synthesized TNA salt structures were crystallized as anhydrous except for TNA-MEA-H2O (1:1:1). TNA formed cocrystals with phenolic coformers such as catechol (CAT), resorcinol, hydroquinone, pyrogallol (PRG) and phloroglucinol. All cocrystal structures crystallized as hydrates except for TNA-PRG (1:1). The detailed structural investigation using SC-XRD revealed the presence of robust N-H...O and O-H...O hydrogen bonds in TNA salts and cocrystals. In TNA cocrystals, except for TNA-CAT-H2O (1:1:1), the coformer molecules interact with TNA molecules via bridged water molecules. In all the salt structures, TNA exists as cations, in which both carboxylic and amino groups are protonated (-COOH and -NH3+), while in cocrystals TNA exists as zwitterions with total charge zero. All synthesized multicomponent compounds were further characterized by differential scanning calorimetric, thermogravimetric and Fourier transform infrared analyses, and the formation of new multicomponent compounds were assessed based on the melting temperatures, percentage weight loss and stretching frequencies, respectively, corresponding to TNA/coformer molecules. A powder X-ray diffraction study confirmed the bulk purity of the synthesized crystalline multicomponent compounds.

Determination of co-crystal phase purity by mid infrared spectroscopy and multiple curve resolution.

Multivariate Curve Resolution (MCR) was used to determine the phase purity of pharmaceutical co-crystals from mid infrared spectra. An in-silico coformer screening was used to choose one of ten potential coformers. This analysis used quantum chemistry simulation to predict which coformers are thermodynamically inclined to form cocrystals with the model drug, hydrochlorothiazide. The coformer chosen was nicotinamide. An experimental solvent screening by ultrasound assisted slurry co-crystallization was performed to evaluate the capacity of the method to determine phase purity. Afterwards, slurry and slow evaporation co-crystallizations were performed at 10, 25, and 40 °C using 7 solvent systems, and two levels of agitation for the evaporation co-crystallization (on and off). Mid infrared spectroscopy (MIRS) analysis of the products of these co-crystallizations was used to develop an MCR model to determine co-crystal phase purity. The MCR results were compared with a reference co-crystal. Experimental design (DoE) was used to investigate the effect of solvents, temperature, and agitation on the purity of co-crystals produced by slurry and evaporation co-crystallization. DoE revealed that evaporation co-crystallization with agitating at 65 rpm formed co-crystals with greater phase purity. The optimal temperature varied with the solvent used.

Direct Hydrothermal Deposition of Antimony Triselenide Films for Efficient Planar Heterojunction Solar Cells.

Antimony selenide (Sb2Se3) has attracted increasing attention in photovoltaic applications due to its unique quasi-one-dimensional crystal structure, suitable optical band gap with a high extinction coefficient, and excellent stability. As a promising light-harvesting material, the available synthetic methods for the fabrication of a high-quality film have been quite limited and seriously impeded both the fundamental study and the efficiency improvement. Here, we developed a facile and low-cost hydrothermal method for in situ deposition of Sb2Se3 films for solar cell applications. In this process, we apply KSbC4H4O7 and Na2SeSO3 as the antimony and selenium sources, respectively, in which thiourea (TU) serves as an additive to suppress the formation of Sb2O3 impurities. As a result, improved phase purity and enhanced crystallinity of the Sb2Se3 film are thus obtained, along with decreased trap states. Finally, the planar heterojunction Sb2Se3 solar cell delivered a power conversion efficiency of 7.9%, which is thus far the highest reported efficiency among solution-processed Sb2Se3 solar cells. This simple procedure and efficiency achievement demonstrate the great potential of the hydrothermal deposition process for the fabrication of high-efficiency Sb2Se3 solar cells.

Curing the fundamental issue of impurity phases in two-step solution-processed CsPbBr3 perovskite films.

Inorganic lead halide perovskite CsPbBr3 offers attractive photophysical properties and phase stability for high-performance optoelectronic devices. However, CsPbBr3 films produced by the classic solution-based two-step method are always accompanied with impurity phases of CsPb2Br5 and Cs4PbBr6, which represents a major efficiency-limiting factor for future advances of CsPbBr3-based devices. The challenge lies in the complexity of the Cs-Pb-Br phase system, requiring both spatially and temporally precise control of the precursor stoichiometry during solution-phase growth of CsPbBr3 films. By adopting 2-methoxyethanol as the solution conversion medium instead of commonly applied methanol, the reaction between CsBr and PbBr2 can be finely controlled to yield single phase CsPbBr3 films within a few minutes; extending the solution-conversion step to 24 h does not alter the phase purity of resulting CsPbBr3 films. The present work paves the way to regulate the crystal growth behaviors of two-step solution-processed CsPbBr3 films by simple solvent engineering.

Controllable Growth of Centimeter-Sized 2D Perovskite Heterostructures for Highly Narrow Dual-Band Photodetectors.

Heterostructures consisting of 2D layered perovskites are expected to exhibit interesting physical phenomena inaccessible to the single 2D perovskites and can greatly extend their functionalities for electronic and optoelectronic applications. Herein, we develop a solution method to synthesize (C4H9NH3)2PbI4/(C4H9NH3)2(CH3NH3)Pb2I7 heterostructures with centimeter size, high phase purity, controllable thickness and junction depth, high crystalline quality, and great stability for highly narrow dual-band photodetectors. On the basis of the different lattice constant, solubility, and growth rate between (C4H9NH3)2PbI4 and (C4H9NH3)2(CH3NH3)Pb2I7, the designed synthetic method allows to first grow the (C4H9NH3)2PbI4 at the water-air interface and subsequently the (C4H9NH3)2(CH3NH3)Pb2I7 layer is formed via a diffusion process. Such a growth process provides an efficient way for us to readily obtain heterostructures with various thickness and junction depth by controlling the concentration, reaction temperature, and time. The formation of heterostructures has been verified by X-ray diffraction, cross-section photoluminescence, and reflection spectroscopy with the estimated junction width below 100 nm. Photodetectors based on such heterostructures exhibit low dark current (∼10-12 A), high on-off current ratio (∼103), and highly narrow dual-band spectral response with a full-width at half-maximum (fwhm) of 20 nm at 540 nm and 34 nm at 610 nm. The high performance can be attributed to the high crystalline quality of the heterostructures and the extremely large resistance in the out-of-plane direction. The synthetic strategy is versatile for other 2D perovskites, and the narrow dual-band spectral response with all fwhm < 40 nm can be continuously tuned from red to blue by properly changing the halide compositions.

Phase pure, high hardness, biocompatible calcium silicates with excellent anti-bacterial and biofilm inhibition efficacies for endodontic and orthopaedic applications.

Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanoparticles (CSNPs) of the α-wollastonite phase without using any surfactant or peptizer at the lowest ever reported calcination temperature of 850 °C. Further, the phase purity is confirmed by quantitative phase analysis. The nano-network like microstructure of the CSNPs is characterized by FTIR, Raman, XRD, FESEM, TEM, TGA, DSC etc. techniques to derive the structure property correlations. The performance efficacies of the CSNPs against gram-positive e.g., S. pyogenes and S. aureus (NCIM2127) and gram-negative e.g., E. coli (NCIM2065) bacterial strains are studied. The biocompatibility of the CSNPs is established by using the conventional mouse embryonic osteoblast cell line (MC3T3). In addition, the biofilm inhibition efficacies of two varieties of CSNPs e.g., CSNPs(W) and CSNPs(WC) are investigated. Further, the interconnection between ROS e.g., superoxide (O2.-) and hydroxyl radical (.OH) generation capabilities of CSNPs and their biofilm inhibition efficacies is clearly established for the very first time. Finally, the mechanical responses of the CSNPs at the microstructural length scale are investigated by nanoindentation. The results confirm that the α-wollastonite phases present in CSNPs(W) and CSNPs(WC) possess extraordinarily high nanohardness and Young's moduli values. Therefore, these materials are well suited for orthopaedic and endodontic applications.

Fabrication of Lead-Free Bi0.5Na0.5TiO3 Thin Films by Aqueous Chemical Solution Deposition.

Piezoelectric ceramics are widely used in actuator applications, and currently the vast majority of these devices are based on Pb ( Zr , Ti ) O 3 , which constitutes environmental and health hazards due to the toxicity of lead. One of the most promising lead-free material systems for actuators is based on Bi 0 . 5 Na 0 . 5 TiO 3 (BNT), and here we report on successful fabrication of BNT thin films by aqueous chemical solution deposition. The precursor solution used in the synthesis is based on bismuth citrate stabilized by ethanolamine, NaOH , and a Ti-citrate prepared from titanium tetraisopropoxide and citric acid. BNT thin films were deposited on SrTiO 3 and platinized silicon substrates by spin-coating, and the films were pyrolized and annealed by rapid thermal processing. The BNT perovskite phase formed after calcination at 500 °C in air. The deposited thin films were single phase according to X-ray diffraction, and the microstructures of the films shown by electron microscopy were homogeneous and dense. Decomposition of the gel was thoroughly investigated, and the conditions resulting in phase pure materials were identified. This new aqueous deposition route is low cost, robust, and suitable for development of BNT based thin film for actuator applications.