Solid-state Powders Research Articles

Unraveling the Ultrasonic-Assisted Synthesis of Green-Emitting CsPbBr3@Cs4PbBr6: Reaction Process, Luminescence Property, and Display Application.

The pursuit of stable and highly emissive perovskite materials has garnered increasing attention in optoelectronic applications. Green-emitting CsPbBr3@Cs4PbBr6, as a green-emissive material in the solid-state form, has great potential as a color conversion material for full-color displays. However, it is a challenge to achieve mass preparation under ambient conditions. Meanwhile, the formation mechanism is ambiguous. This study reports a ligand-free and rapid mass synthesis of nanomicrosized CsPbBr3@Cs4PbBr6 solid via an ultrasonic-assisted method. The synthesized CsPbBr3@Cs4PbBr6 solids exhibit uniform morphology, high stability, and solid-state quantum efficiency of approximately 55%. Moreover, the transformation mechanism from Pb-Br complexes in the synthesis process is fully investigated by monitoring the phase and spectral evolution. By employing it as a green emitter, the obtained white light-emitting diode (LED) device shows high performance with a correlation color temperature of 7635 K and a wide color gamut of 123% NTSC. This study offers a low-cost and simple operation mass production method for solid-state perovskite powders with excellent chemical stability. Additionally, it provides new insights into the formation mechanism of highly efficient perovskite materials and promotes their practical applications.

Scattering Elimination in 2D IR Immune from Detector Artifacts.

Highly scattering samples, such as polymer droplets or solid-state powders, are difficult to study via coherent two-dimensional infrared (2D IR) spectroscopy. Previously, researchers have employed (quasi-) phase cycling, local-oscillator chopping, and polarization control to reduce scattering, but the latter method poses a limit on polarization-dependent measurements. Here, we present a method for Scattering Elimination Immune from Detector Artifacts (SEIFDA) in pump-probe 2D IR experiments. Our method extends the negative probe delay method of removing scattering from pump-probe spectroscopy to 2D experiments. SEIFDA works well for all polarizations when combined with the optimized noise reduction scheme to remove additive and multiplicative noise. We demonstrate that our method can be employed with any polarization scheme and reliably lowers the scattering at parallel polarization to comparable levels to the conventional 8-frame phase cycling with probe chopping (8FPCPC) at perpendicular polarization. Our system can acquire artifact free spectra in parallel polarization when the signal intensity is as little as 5% of the intensity of the interference between the pump pulses scattered into the detector. It reduces the time required to characterize the scattering term by at least 50% over 8FPCPC. Through detailed analysis of detector nonlinearity, we show that the performance of 8FPCPC can be improved by incorporating nonlinear correction factors, but it is still worse than that of SEIFDA. Application of SEIFDA to study the encapsulation of Nile red in polymer droplets demonstrates that this method will be very useful for probing highly scattering systems.

Solid-state production of uniform metal powders for additive manufacturing by ultrasonic vibration machining

This work presents a new technique to generate uniform and micron-sized metal powders for additive manufacturing. By collecting discrete chips resulting from ultrasonic vibration machining, we demonstrate the feasibility of all solid-state production consistent powders with tight dimensional tolerance, the ability to control powder geometry, and good efficiency. The technique offers a new route for sustainable and low-cost manufacturing of high-quality metal powders. The powder generation mechanism is analyzed with a special tool path design to ensure consistent dimensions over multiple cuts. An analytical model to predict the dimensions of produced powders under different cutting parameters is introduced. Aluminum and brass powders of different dimensions are produced, and the overall shear ratio that governs the deformation during the machining process is calibrated with the experimental results. The morphology consistency of produced powders is investigated over multiple hours of production, illuminating the role of tool wear on final powder shape. A high-efficiency powder collection system and a scalable solution for parallel production are proposed for the introduced technique. Additive manufacturing experiments (laser powder bed fusion) are conducted using produced A356 aluminum powders, demonstrating the printability of produced powders in additive manufacturing. The microhardness of the printed parts for five different process parameters is measured to be 45% higher than the raw material on average.

Screen-Printing of NiO-ScSZ on YSZ Substrate Using Solid-State Reaction and Glycine-Nitrate Process Precursors for Solid Oxide Electrochemical Cells

Solid oxide electrochemical cells (SOCs) consisting of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are widely studied for the development of high-efficiency energy generation and storage devices. To investigate the effect of precursor particle size on the microstructural and morphological properties of the electrode, glycine nitrate process and solid-state reaction ball-milling were utilized as synthesis methods for Nickel oxide-scandia stabilized zirconia (NiO-ScSZ) powders. The synthesized powders were then screen-printed on commercial YSZ solid electrolyte substrates. The structure and morphology of the sintered electrodes were investigated. Particle size analysis (PSA) revealed that NiO-ScSZ precursor powders obtained from GNP ball-milled had a smaller average particle size than solid-state reaction ball-milled powders. For the sintered NiO-ScSZ films, cubic structures of both NiO and ScSZ have been observed from the X-ray diffraction (XRD) patterns. A better porous morphology with less agglomeration and better dispersion of NiO and ScSZ phases was revealed by the scanning electron microscopy (SEM) micrographs and elemental mapping for the GNP-ball-milled synthesized powders.

Circularly polarized luminescence enlargement from crystals to oriented films of enantiopure 2D hybrid perovskites.

Chiral 2D organic-inorganic hybrid perovskites (C-2D-OIHPs) with circularly polarized luminescence (CPL) have important promising applications in optical, electronic, and chiroptoelectronic devices. Herein, we report enantiomeric crystals of R/S-FMBA)2PbBr4. (FMBA = 4-fluorophenethylamine), which demonstrated bright room-temperature CPL emission. For the first time, the oriented films along the c-axis of this pair of C-2D-OIHPs exhibited a 16-fold increase in the asymmetry factors of absorbance (gCD) and a 5-fold rise in the asymmetry factors of CPL (glum), reaching up to ± 1 × 10-2.

One-step large-scale fabricating aggregation-induced emission carbon dots with strong solid-state fluorescence emission

Carbon dots (CDs) possessing favorable stability and optical properties have attracted extensive attention for their potential application in solid-state light-emitting devices. However, due to the stacking of π–π conjugated systems, solid-state CDs often suffer aggregation-caused quenching effect, resulting in fluorescence quenching. There are few reports on solid-state fluorescent CDs fabricated without using other solid matrices. In this work, we report a facile approach for one-step synthesis of yellow-green solid-state CDs without using matrix. The synthesized CDs show an independent excitation and emission in various organic solvents. Importantly, the prepared CDs show solvatochromism and aggregation-induced emission redshift effect. By simply drying the colloidal solution of CDs, yellow-green solid-state fluorescent CD powders with a photoluminescence quantum yield of 25.5% can be obtained. High-performance white light-emitting diodes with Commission Internationale de L'Eclairage coordinates at (0.35, 0.37) are prepared by employing the yellow-green solid-state CD powders. The corresponding color temperature and color rendering index are 4691 K and 91.5 under ultraviolet excitation of 365 nm, respectively. The facile synthesis method of solid-state fluorescent CDs with unique optical features offers promising future for CDs-based optoelectronic devices.

Spectro-temporal behavior of dye-based solid-state random lasers under picosecond pumping regime.

In this work, the spectral and temporal properties of the random laser emission from dye-doped solid state powders are investigated in picosecond pumping regime. Ultrafast time-resolved spectroscopy achieved with a streak-camera has been used to perform a detailed study of the temporal evolution of the spectrum of their single pulses. Under conditions of low population inversion density, it is observed that the detected radiation occurs as isolated peaks with a very narrow spectro-temporally spread (ΔωΔt≅1). This behavior remains under conditions of high population inversion density, suggesting that the underlying physical mechanism that produces the emission is the same whatever the pumping conditions. Measurements carried out by varying the numerical aperture of the detection system show that each detected peak within a single pulse is associated with a photon pack emitted in a random direction and wavelength. The relationship between the distribution of paths lengths done by photons inside the active medium, and the gain explains the observed behavior.

Tailoring grain growth and densification toward a high-performance solid-state electrolyte membrane

The synthesis of dense and uniform solid-state electrolyte membranes for Li batteries is challenging due to the lack of fine control over the grain growth by conventional sintering methods. Using such techniques, abnormal grain growth can often occur, with associated contaminants and voids, often resulting in electrolyte membranes that suffer from high resistivity, poor stability, and the risk of Li dendrite penetration. Herein, we report a new high-temperature (1500 K) and rapid sintering (30 s) process by Joule heating that tailors the grain growth and densification toward high-quality, high-performance solid-state electrolyte membranes. The high temperature contributes to the rapid removal of impurities, leading to a dense and uniform microstructure in seconds. The short sintering time provides controlled grain growth, with nearly unchanged grain size and distribution compared to the solid-state electrolyte powders prior to sintering. Using calcined Ta-doped Li7La3Zr2O12 (LLZTO) garnet powders, we show that the grain size distribution before and after the rapid sintering are nearly identical (∼4 μm for both), while defects (e.g., voids and gaps) and impurities are effectively eliminated. The resulting high-quality membrane features good ionic conductivity (6.4 × 10−4 S cm−1 at room temperature) and excellent stability during lithium striping/plating (>300 h under 0.2 mA cm−2), making it suitable for Li battery applications. This high-temperature rapid sintering approach can be further extended to a variety of ceramic Li+ conductors toward the future development of solid-state batteries.

High reliable non-reducible ultra-fine BaTiO3-based ceramics fabricated via solid-state method

The ultra-thin multilayer ceramics capacitors (MLCCs) with layer thickness less than 1 μm are in urgent demand due to the rapid development of modern electronic industries. However, the preparation of the dielectric materials with the desirable grain size <150 nm is a huge challenge. In this work, the ultra-fine BaTiO3 (BT) powders (<120 nm) prepared via solid-state reaction method, hydrothermal method and hydrothermal method following a heat treatment (850 °C) are selected to prepare the nano-crystalline non-reducible BT-based ceramics, respectively. The effect of the synthesis methods on the microstructure, electric performance and the reliability of the BT-based ceramics are studied. The results of the Raman, XPS and FT-IR spectroscopy demonstrate that a large number of internal stresses and point defects (hydroxyl/proton defects, Ba vacancies) are existed in the hydrothermal powders and can be eliminated to some extent by a proper heat treatment. Unfortunately, plenty of nano-pores (10–20 nm) are observed in the hydrothermal powders, which cannot be eliminated via the heat treatment or sintering process totally. As a result, the BT-based ceramic prepared by the solid-state powders has an absolute advantage in accelerating aging failure performance, compared to that prepared hydrothermal powders. The TSDC results indicate that the ceramic prepared by the solid-state powders has a lower oxygen vacancy concentration and a higher activation energy. Furthermore, a scaling analysis based on a RC equivalent model identifies the longer oxygen vacancy diffusion time for the ceramic prepared by the solid-state powders. All these features demonstrate that the solid-state ultra-fine BT powders are a promising candidate for the fabrication of the ultra-thin layer MLCCs.

Method of preparation, visualization and ultrastructural analysis of a formulation of probiotic Bacillus subtilis KATMIRA1933 produced by solid-phase fermentation

Probiotic preparations are used in medical treatment and in agricultural practice. They modulate numerous activities in eukaryotic hosts, such as: inhibition of pathogenic microbiota; stimulation of immunological responses; and production of antioxidants, anti-mutagens, and DNA protectors. Also, probiotic bacteria are used as a preventive measure to prevent bacterial diseases of the gastrointestinal tract. Solid-phase fermentation is reported as being used in the production of probiotic formulations where a solid substratum, such as soy and oil meal, is utilized for the growth of beneficial microorganisms. However, there are insufficient reports in the literature related to methodological approaches enabling evaluation of the final products of solid-phase fermentation.We suggest a novel method enabling evaluation of probiotic solid-state fermentation dry powders and observation of their morphology, ultrastructure, and elucidation of the quantitative distribution of probiotic microorganisms in solid substrates using electron microscopy.•The method is intended for ultrastructure microphotography of dry substances - for example, ultrastructure of solid-phase fermentation products.•The method allows preserving the ultrastructure of substrates that are damaged when soaking.•The method does not require additional equipment and reagents and can be used in all laboratories using electron microscopy.

Improving Correlations Between Drug Solubilization and In Vitro Lipolysis by Monitoring the Phase Partitioning of Lipolytic Species for Lipid-Based Formulations

Solution proton nuclear magnetic resonance analysis was used in conjunction with in vitro lipolysis to elucidate the time-dependent speciation and release of lipolytic products during the digestion of lipid-loaded inorganic particles, allowing correlations to be made between the phase partitioning of lipolytic products and an encapsulated poorly soluble drug. Silicon dioxide, montmorillonite, and laponite were used to encapsulate medium chain triglycerides into solid-state lipid-based formulations (LBFs), and coumarin 102 was selected as a model poorly soluble compound. The specific inorganic carrier material used to encapsulate medium chain triglycerides significantly impacted the release and partitioning of the solubilizing lipolytic products, that is, diglycerides, monoglycerides, and fatty acids. A strong linear correlation was obtained between drug solubilization and fatty acid release to the aqueous phase (R2 = 0.996), indicating fatty acids to be the most important lipid species for enabling solubilization and potential drug absorption in vivo. This method was developed to improve upon the use of pH-stat titration for characterizing LBF digestion during in vitro lipolysis studies and is demonstrated herein to provide useful insights into how the selected inorganic carrier material impacts LBF performance when solid-state LBF powders are fabricated via adsorption.

In-situ embedding of carbon dots in a trisodium citrate crystal matrix for tunable solid-state fluorescence

It is still a challenging issue to achieve efficient and tunable fluorescent carbon dot (CD) powders. Herein, we report a novel and general solvothermal strategy to in-situ embedding CDs in trisodium citrate crystal matrix, and these CDs exhibit tunable emission from green to yellow and a high quantum yield up to 21.6% in solid state, comparable to that in solution. This intriguing fluorescence phenomenon may be caused by the space confinement from trisodium citrate crystal matrix, thus enabling CDs to effectively suppress the aggregation-induced luminescence quenching. The CD powders have been employed for fabricating white light-emitting devices on blue chips with adjustable color temperature. Moreover, solid-state lighting systems like flexible fluorescent films and plates have been demonstrated by using the CD powders as the luminescent medium. This work provides a facile way to achieve tunable solid-state fluorescence CD powders, which have promising applications in CDs-based luminescence devices.

High Performance Anion-Exchange Membranes and Ionomers for Use in Alkaline Membrane Fuel Cells

This presentation will describe the latest research at the University of Surrey on the development of high-performance anion-exchange membranes (AEM) and ionomers (AEI) for use in alkaline membrane fuel cells (AEMFC). These anion-exchange polymer electrolyte matreials are produced using the peroxidation pre-irradiation grafting method (RG). Recent achievements that will be discussed in this presentation include: Synthesis of RG-AEMs with new chemistries that are more stable to alkali than those containing the benzyltrimethylammonium benchmark;The ability to produce RG-AEMs based on low density polyethylene (LDPE) as well as poly(ethylene-co-tetrafluoroethylene) (ETFE);Synthesis of thinner AEMs (< 30 μm thickness);Synthesis of an interesting class of RG-based solid-state AEI powders;AEMs with high hydroxide conductivities and high performances in hydrogen-fuelled AEMFC;Advanced use of Raman micro-spectroscopy for studying radiation-grafted anion-exchange polymer electrolytes. We will demonstrate that changes in head-group chemistry can switch off several alkali degradation mechanisms for RG-AEMs. We will also show that 2 W cm-2 peak power densities can be achieved in H2/O2 AEMFCs containing Pt cathodes and > 1 W cm-2 can be achieved with non-platinum-group-metal cathodes. The figure below shows the performance of a thin ETFE-based RG-AEM in H2/O2 and H2/air(CO2-free) AEMFCs when Ag/C cathode is used as a cathode electrocatalyst. Figure 1

Synthesis and fluorescence emission properties of D-π-D monomers based on dithieno[3,2-b:2′,3′-d]thiophene

We herein present four highly fluorescent and stable D-π-D monomers (2), which were designed and synthesized using different types of aryl substituent as the donor via a Suzuki-Miyaura coupling reaction. We have studied these four symmetrical chromophores by UV–vis absorption and fluorescence emission spectroscopy both in solution and the solid state. This research shows that the introduction of the aryl groups can effectively reduced the HOMO-LUMO gap of thiophene chromophore resulting in a shift of the wavelength of the absorption and fluorescence emission. The notable optical features of their solid-state powders also exhibited a distinct red-shift in comparison with the emissions of their dilute solutions. These results combined with the theoretical calculations (B3LYP/6–31G*) indicate that these systems are promising candidates in the fabrication of organic electroluminescence devices.

High Performance Radiation-Grafted Anion Conducting Polymer Electrolytes for Energy Applications

This presentation will describe the latest research at the University of Surrey and the development of radiation-grafted anion-exchange membranes (RG-AEM) and ionomer powders (AEI) for use in devices such as alkali membrane fuel cells. The presentation will provide an overview of the following recent achievements: Synthesis of RG-AEMs with heterocyclic chemistries that are more stable to alkali that the those containing the benzyltrimethylammonium benchmark;Synthesis protocols that require reduced radiation doses, reduced amounts of monomer and the use of water rather than organic solvents;Synthesis of thinner RG-AEMs;The ability to produce RG-AEMs based on low density polyethylene (LDPE) rather than partially fluorinated ETFE;Synthesis of an interesting class of solid-state AEI powders;AEMs with high hydroxide conductivities and high performances in H2/O2 fuel cells. For example, the graph show the beginning-of-life 60°C H2/O2 fuel cell performances achieved with Pt-based catalysts and RG-AEMs made from 25 μm ETFE (red) and 13 μm ETFE (green) with no gas back-pressurization applied.

D-π-D chromophores based on dithieno[3,2-b:2',3'-d]thiophene (DTT): Potential application in the fabrication of solar cell

In this work, four stable dithieno[3,2-b:2',3'-d]thiophene-based π-extended molecules were designed and synthesized via a Pd-catalysed Sonogashira coupling reaction. The structures of these symmetrical compounds, including dithieno[3,2-b:2',3'-d]thiophene (DTT) as the π-center and various donor (D) groups, were determined on the basis of NMR spectral data, elemental analysis, and X-ray crystallography. The photo-physical properties of the DTT-based derivatives 2 were fully investigated in both solution and the solid state. The notable optical features of their solid-state powders showed significant red-shifts in comparison with the luminescence of their dilute dichloromethane solutions. These results combined with the theoretical calculations indicate that they are promising candidates for several applications in electronic and optoelectronic devices, as well as organic dyes for solar cells.

Reološke lastnosti gošče iz glinice za izdelavo keramičnih kalupov

This research is about the properties of ceramic slurries prepared from hydrous nano-alumina-based binder and a corundum matrix used for fabricating the prime coat of ceramic shell moulds. Solid-state alumina powders with different granulations were used. The modification of the technological properties of the prepared slurries was based on additions of a polyacrylic binder with different amounts of polymer with respect to the alumina for different powder ratios. The slurries were prepared and tested in a mechanical mixer. During the slurry preparation (within 96 h), the plate weight, Zahn cup 4# viscosity and dynamic viscosity were controlled. The morphology and chemical properties of corundum powders and polymer were characterized with SEM and powder-grain-size distribution. The obtained results of the corundum-based ceramic slurries indicate that the application of a polymeric binder with various concentrations based on nano-alumina oxides causes different properties in comparison to the other commonly used binders.

Temperature-Dependent Exciton and Trap-Related Photoluminescence of CdTe Quantum Dots Embedded in a NaCl Matrix: Implication in Thermometry.

Temperature-dependent optical studies of semiconductor quantum dots (QDs) are fundamentally important for a variety of sensing and imaging applications. The steady-state and time-resolved photoluminescence properties of CdTe QDs in the size range from 2.3 to 3.1 nm embedded into a protective matrix of NaCl are studied as a function of temperature from 80 to 360 K. The temperature coefficient is found to be strongly dependent on QD size, with the highest sensitivity obtained for the smallest size of QDs. The emission from solid-state CdTe QD-based powders is maintained with high color purity over a wide range of temperatures. Photoluminescence lifetime data suggest that temperature dependence of the intrinsic radiative lifetime in CdTe QDs is rather weak, and it is mostly the temperature-dependent nonradiative decay of CdTe QDs which is responsible for the thermal quenching of photoluminescence intensity. By virtue of the temperature-dependent photoluminescence behavior, high color purity, photostability, and high photoluminescence quantum yield (26%-37% in the solid state), CdTe QDs embedded in NaCl matrices are useful solid-state probes for thermal imaging and sensing over a wide range of temperatures within a number of detection schemes and outstanding sensitivity, such as luminescence thermochromic imaging, ratiometric luminescence, and luminescence lifetime thermal sensing.

Aggregation-induced bathochromic fluorescent enhancement for fluorenone dyes

Organic solid-state luminescence materials with aggregation-induced emission enhancement have attracted considerable interest in recent years. In this work, we develop a class of 2,7-diphenylfluorenone derivatives that exhibit prominent aggregation-induced emission properties with high solid-state quantum yields. Their solid-state powders show a ∼160 nm bathochromically shifted fluorescence and longer lifetime compared to their emission in dilute THF solution. The X-ray single structures and photophysical properties reveal that the mechanism of aggregation-induced emission in this class of fluorenone compounds is due to the formation of static excimers through hydrogen bonds in the solid state. The emission of their THF solution peaked at 380 nm and originates from the single molecule and the emission of their solid-state powder peaked at 550 nm originates from the excimers. The aggregation-induced emission properties and luminescence mechanism are further verified by the design of 2,7-diphenylfluorenone-diboronic acid adduct, which exhibited weak luminescence in high pH buffer and red-shifted strong luminescence in acidic buffer.

Preparation routes and electrical properties for Ni0.6Mn2.4O4 NTC ceramics

Ni0.6Mn2.4O4 negative temperature coefficient ceramics were prepared by using solid-state coordination reaction and traditional solid-state methods, their structures and properties were characterized by using scanning electron microscopy, powder X-ray diffractometer and temperature dependent resistivity test. For solid-state reaction powders, the calcination temperature necessary for formation of the spinel phase was 1000 °C, which is 300 °C higher than that of solid-state coordination reaction powders. Regardless of preparation routes, the ceramics were crystallized in a single cubic spinel structure when the sintering temperature was lower than or equal to 1150 °C, Mn3O4 impurity phase was detected when the sintering temperature raised to 1200 °C. Having higher densities and bigger grain sizes, the solid-state coordination reaction samples had smaller room temperature resistivities and larger B 25/50 values as compared with those of solid-state samples.