Unimodal Particle Size Distribution Research Articles

Mannose-Decorated Solid-Lipid Nanoparticles for Alveolar Macrophage Targeted Delivery of Rifampicin.

Alveolar macrophages play a vital role in a variety of lung diseases, including tuberculosis. Thus, alveolar macrophage targeted anti-tubercular drug delivery through nanocarriers could improve its therapeutic response against tuberculosis. The current study aimed at exploring the efficacy of glyceryl monostearate (GMS)-based solid-lipid nanoparticles (SLNs) and their mannose functionalized forms on the alveolar macrophage targeting ability of an anti-tubercular model drug, rifampicin (Rif). Rif-loaded SLNs were accomplished by the solvent diffusion method. These carriers with unimodal particle size distribution (~170 nm) were further surface-modified with mannose via Schiff-base reaction, leading to slight enhancement of particle diameter and a decline of drug loading capacity. The encapsulated Rif, which was molecularly dispersed within the matrices as indicated by their XRD patterns, was eluted in a sustained manner with an initial burst release effect. The uptake efficiency of mannose-modified SLNs was remarkably higher than that of corresponding native forms on murine macrophage Raw 264.7 cells and human lung adenocarcinoma A549 cells. Eventually, the mannose-modified SLNs showed a greater cytotoxicity on Raw 264.7 and A549 cells relative to their unmodified forms. Overall, our study demonstrated that mannose modification of SLNs had an influence on their uptake by alveolar macrophages, which could provide guidance for the future development of alveolar macrophage targeted nanoformulations.

Development of rapidly soluble mebendazole nanosuspension for colorectal cancer

Mebendazole (MBZ) has been proven as a repurposing molecule against colorectal cancer. Unfortunately, its clinical application is constrained by its extremely poor solubility and bioavailability. The aim of the current work was to augment the dissolution rate at colonic pH and the anticancer efficacy by formulating MBZ nanosuspension (NS). A robust MBZ NS was developed using a combination of Sodium Lauryl Sulphate (SLS) and Hydroxy Propyl Methyl Cellulose E5 (HPMC) as stabilizers through the dual centrifugation method. The prepared MBZ NS exhibited the smallest particle size (362.6 ± 12.3 nm) with unimodal particle size distribution and excellent short-term stability. DSC and FT-IR studies confirmed the crystallinity and the absence of interactions with the stabilizers used. The developed MBZ NS demonstrated ∼20 folds higher dissolution than MBZ alone in colonic pH. Cell experiments showed that HPMC E5 and SLS were safe on HT-29 and HT-116 cell lines. In addition, IC50 of MBZ-NS was found to be 1.028 ± 0.030 μM and 0.884 ± 0.050 μM in HT-29 and HT-116 cell lines, respectively. Furthermore, 1.5 folds and 1.8 folds reduction in 3D tumor spheroids after treatment with MBZ-NS was observed compared to the control and MBZ physical mixture. From the In Vitro Live/Dead Cell Assay higher amount of red fluorescence in treatment groups confirmed a large number of dead cells compared to the control. In a nutshell, the produced MBZ NS could be employed as a promising formulation to achieve a higher dissolution rate and anticancer efficacy against colorectal cancer of repurposing drug MBZ.

Evolutionary mechanism and particle characterization analysis of dust produced by wet-mix shotcrete in tunnels

Wet-mix shotcrete, an essential form of concrete support, has been widely applied in underground constructions such as tunnels and mines. This study analyzed the gas jet structure and particle velocity differential equations in the wet-mix shotcrete process and physicochemically characterized collected dust samples. Based on field measurements and laboratory analyses, we established an experimental platform and a numerical simulation model for wet-mix shotcrete to investigate dust generation characteristics. The results showed the following: 1) The particles generated during wet-mix shotcrete primarily consisted of cement particles, exhibiting a spherical and blocky shape with a relatively regular morphology. However, their surfaces possessed numerous burrs and pores, resulting in poor wettability. 2) Suspended aerosol particles mainly comprised particles below 10 µm, exhibiting a unimodal particle size distribution. Smaller particles showed a higher abundance, with particles below 2 µm accounting for over 95% of the total particles. 3) The dust generation during wet-mix shotcrete was significantly influenced by the compressed gas flow rate and material viscosity. An increase in the gas flow rate or material viscosity led to higher production of fine particles. This study elaborated the mechanisms underlying particle generation during wet-mix shotcrete, providing valuable insights for wet-mix shotcrete dust control techniques.

Particle Size Distributions and Extinction Coefficients of Aerosol Particles in Land Battlefield Environments

In land battlefield environments, aerosol particles can cause laser beams to undergo attenuation, thus deteriorating the operational performance of military laser devices. The particle size distribution (PSD) and extinction coefficient are key optical properties for assessing the attenuation characteristics of laser beams caused by aerosol particles. In this study, we employed the laser diffraction method to measure the PSDs of graphite smoke screen, copper powder smoke screen, iron powder smoke screen, ground dust, and soil explosion dust. We evaluated the goodness of fit of six common unimodal PSD functions and a bimodal lognormal PSD function employed for fitting these aerosol particles using the root mean square error (RMSE) and adjusted R2, and selected the optimal PSD function to evaluate their extinction coefficients in the laser wavelength range of 0.249~12 μm. The results showed that smoke screens, ground dust, and soil explosion dust exhibited particle size ranges of 0.7~50 µm, 1~400 µm, and 1.7~800 μm, respectively. The lognormal distribution had the best goodness of fit for fitting the PSDs of these aerosol particles in the six unimodal PSD functions, followed by the gamma and Rosin–Rammler distributions. For the bimodal aerosol particles with a lower span, the bimodal lognormal PSD functions exhibited the best goodness of fit. The graphite smoke screen exhibited the highest extinction coefficient, followed by the copper and iron powder smoke screens. In contrast, the ground dust and soil explosion dust exhibited the lowest extinction coefficients, reaching their minimum values at a wavelength of approximately 8.2 μm. This study provides a basis for analyzing and improving the detection and recognition performance of lasers in land battlefield environments.

Goat milk powders enriched with grape pomace seed extract: Physical and techno-functional properties

This study aimed to evaluate the physical (particle size and ζ-potential) and techno-functional properties (emulsifying and foaming) of goat milk powders enriched with grape pomace seed extract (TME), as promising food ingredients in the formulation of functional food. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Raman spectroscopies, along with advanced chemometric tools were employed as well as Scanning Electron Microscopy (SEM) for analyzing TME powders. All powders exhibited a unimodal particle size distribution and ζ-potential values more negative than −36 mV. ATR-FTIR and Raman spectroscopies combined with principal component analysis (PCA) demonstrated distinct separation among skimmed goat milk (M), thermally treated skimmed goat milk (TM), and TME powders in different spectral regions (amide I, II, III, and fingerprint region). This separation resulted from the applied thermal treatment, the presence of phenolic compounds and their complexes with goat milk proteins, and the formation of Maillard reaction products. SEM analysis confirmed the different morphology and shapes of M, TM and TME powders. The 0.1% solutions of M, TM and TME exhibited good emulsifying properties (emulsion activity index and emulsion stability index) but showed poor foaming properties, except for the M sample. Solution concentrations higher than 0.1% for all samples (0.5% and 1.0%) displayed poor techno-functional properties. In summary, a schematic representation of the arrangement of casein micelles in 0.1% M, TM and TME samples, on oil/water and air/water surfaces was provided. The production of TME powders represents an innovative strategy for waste recovery in the production of functional food ingredients with good emulsifying properties.

Engineering artesunate-loaded micelles using spray drying for pulmonary drug delivery

Novel d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) micelles containing the anti-cancer drug artesunate (ART) were developed in a dry powder form for inhalation for the treatment of lung cancer. Targeted delivery to the lungs via inhalation is a challenge and the current study involved the development, characterization, and cytotoxicity determination of the dry powder formulations. TPGS micelles encapsulating ART were successfully prepared using thin-film hydration method followed by the preparation of dry powder formulation by spray-drying that included lactose and leucine as carrier molecules. Characterization of the dry powder formulation using Sympatec laser diffraction particle size analyzer and next generation impactor showed a unimodal particle size distribution with a mean particle size of 3.27 μm and a fine particle fraction of 31%, respectively. Artesunate loaded micelle dry powder formulation demonstrated higher cytotoxicity towards the A549 adenocarcinomic human alveolar basal epithelial cell line when compared to currently used cancer therapies docetaxel and doxorubicin. In general, this study demonstrates that spray-dried micelles containing artesunate can potentially be used as a dry powder formulation for inhalation for the treatment of lung cancer.

Comparative Studies of the Uptake and Internalization Pathways of Different Lipid Nano-Systems Intended for Brain Delivery.

Lipid nano-systems were prepared and characterized in a series of well-established in vitro tests that could assess their interactions with the hCMEC/D3 and SH-SY5Y cell lines as a model for the blood-brain barrier and neuronal function, accordingly. The prepared formulations of nanoliposomes and nanostructured lipid carriers were characterized by z-average diameters of ~120 nm and ~105 nm, respectively, following a unimodal particle size distribution (PDI < 0.3) and negative Z-potential (-24.30 mV to -31.20 mV). Stability studies implied that the nano-systems were stable in a physiologically relevant medium as well as human plasma, except nanoliposomes containing poloxamer on their surface, where there was an increase in particle size of ~26%. The presence of stealth polymer tends to decrease the amount of adsorbed proteins onto a particle's surface, according to protein adsorption studies. Both formulations of nanoliposomes were characterized by a low cytotoxicity, while their cell viability was reduced when incubated with the highest concentration (100 μg/mL) of nanostructured lipid formulations, which could have been associated with the consumption of cellular energy, thus resulting in a reduction in metabolic active cells. The uptake of all the nano-systems in the hCMEC/D3 and SH-SY5Y cell lines was successful, most likely following ATP-dependent internalization, as well as transport via passive diffusion.

A study of biochar physiochemistry and particle size distribution influencing the properties of water-based slurry fuels

Biochar-based slurry is a fossil-free-liquid fuel derived from a renewable source, biomass. This study aims to examine the properties of this fuel as an alternative to coal-water slurries. The slurries were produced by suspending 40 wt% biochar in a solution made of water and a surfactant. Two biochar types from chemically treated and untreated rice straw (RS) were utilized to assess the impact of particle-particle interactions and biochar physicochemical composition on slurry properties, including stability, rheology, and heating value. Additionally, three particle size distributions (PSD), two unimodal and a bimodal, were used to analyze the effect of PSD on the abovementioned properties.All slurries had an average energy content of 7.32 ± 0.27 MJ/kg. The stability of the slurry was higher for fine particles from treated RS with unimodal PSD (Dv50 8.8 ± 0.68 μm). However, slurries containing fine and coarse particles with bimodal PSD (Dv50 15.8 ± 0.64 μm) had relatively lower apparent viscosities of 342.1 and 336.55 mPa.s at a shear rate of 100 s−1 for slurries made of biochar from treated and untreated RS, respectively. Slurries containing coarse particles from treated and untreated RS with unimodal PSD (Dv50 18.6 ± 0.32 μm) led to higher viscosities and particle settling rates. Biochar morphology and chemical surface constitution significantly influenced slurry stability, while PSD greatly impacted rheological results.

The Formation of NaYF4 : Er3+, Yb3+ Nanocrystals Studied by In Situ X‐ray Scattering: Phase Transition and Size Focusing

Abstractβ‐NaYF4 nanocrystals are a popular class of optical materials. They can be doped with optically active lanthanide ions and shaped into core‐multi‐shell geometries with controlled dopant distributions. Here, we follow the synthesis of β‐NaYF4 nanocrystals from α‐NaYF4 precursor particles using in situ small‐angle and wide‐angle X‐ray scattering and ex situ electron microscopy. We observe an evolution from a unimodal particle size distribution to bimodal, and eventually back to unimodal. The final size distribution is narrower in absolute numbers than the initial distribution. These peculiar growth dynamics happen in large part before the α‐to‐β phase transformation. We propose that the splitting of the size distribution is caused by variations in the reactivity of α‐NaYF4 precursor particles, potentially due to inter‐particle differences in stoichiometry. Rate equation modeling confirms that a continuous distribution of reactivities can result in the observed particle growth dynamics.

Characterization of an Electronic Nicotine Delivery System (ENDS) Aerosol Generation Platform to Determine Exposure Risks

Evaluating vaping parameters that influence electronic nicotine delivery system (ENDS) emission profiles and potentially hazardous exposure levels is essential to protecting human health. We developed an automated multi-channel ENDS aerosol generation system (EAGS) for characterizing size-resolved particle emissions across pod- and mod-type devices using real-time monitoring instruments, an exposure chamber, and vaping parameters including different ventilation rates, device type and age, e-liquid formulation, and atomizer setup. Results show the ENDS device type, e-liquid flavoring, and nicotine content can affect particle emissions. In general, pod-type devices have unimodal particle size distributions and higher number emissions, while mod-type devices have bimodal size distributions and higher mass emissions. For pod-type devices, later puff fractions emit lower aerosols, which is potentially associated with the change of coil resistance and power during ageing. For a mod-type device, an atomizer with a lower resistance coil and higher power generates larger particle emissions than an atomizer with a greater resistance coil and lower power. The unventilated scenario produces higher particle emission factors, except for particle mass emission from pod-type devices. The data provided herein indicate the EAGS can produce realistic and reproducible puff profiles of pod- and mod-type ENDS devices and therefore is a suitable platform for characterizing ENDS-associated exposure risks.

RDX crystals with high sphericity prepared by resonance acoustic mixing assisted solvent etching technology

In order to obtain high-quality spherical RDX crystal particles, the RDX crystals were suspended in a mixed solvent of cyclohexanone and cyclohexane, subsequently a solvent etching study was carried out under the action of vibration/acoustic flow coupled flow field, which generated by resonance acoustic mixing. The effects of solvent ratio, temperature, acceleration and experiment time on morphology as well as particle size of RDX crystals were studied. Not only were the morphology, particle size distribution and crystal form of RDX crystals determined, but also the thermal decomposition performance and mechanical sensitivity of spherical RDX were examined and discussed. Results indicated that under the process of solvent/non-solvent volume ratio at 1:2, temperature of 40°C, acceleration of 40 g and experiment time of 4 h, α-type RDX crystal with sphericity of 0.92 can be obtained. Furthermore, the median particle size (D50) of spherical RDX crystals is 215.8 μm with a unimodal particle size distribution (size span 1.34). For one thing, the thermal decomposition peak temperature of spherical RDX is about 2.5°C higher than that of raw RDX, and apparent activation energy reaches 444.68 kJ/mol. For another thing, impact sensitivity and friction sensitivity of spherical RDX are 18.18% and 33.33% lower than that of raw RDX, respectively. It demonstrates that safety of spherical RDX under thermal, impact and friction stimuli has been improved.

Dependence of Ice Crystal Size Distributions in High Ice Water Content Conditions on Environmental Conditions: Results from the HAIC-HIWC Cayenne Campaign

Abstract A new method that automatically determines the modality of an observed particle size distribution (PSD) and the representation of each mode as a gamma function was used to characterize data obtained during the High Altitude Ice Crystals and High Ice Water Content (HAIC-HIWC) project based out of Cayenne, French Guiana, in 2015. PSDs measured by a 2D stereo probe and a precipitation imaging probe for particles with maximum dimension (Dmax) &gt; 55 μm were used to show how the gamma parameters varied with environmental conditions, including temperature (T) and convective properties such as cloud type, mesoscale convective system (MCS) age, distance away from the nearest convective peak, and underlying surface characteristics. Four kinds of modality PSDs were observed: unimodal PSDs and three types of multimodal PSDs (Bimodal1 with breakpoints 100 ± 20 μm between modes, Bimodal2 with breakpoints 1000 ± 300 μm, and Trimodal PSDs with two breakpoints). The T and ice water content (IWC) are the most important factors influencing the modality of PSDs, with the frequency of multimodal PSDs increasing with increasing T and IWC. An ellipsoid of equally plausible solutions in (No–λ–μ) phase space is defined for each mode of the observed PSDs for different environmental conditions. The percentage overlap between ellipsoids was used to quantify the differences between overlapping ellipsoids for varying conditions. The volumes of the ellipsoid decrease with increasing IWC for most cases, and (No–λ–μ) vary with environmental conditions related to distribution of IWC. HIWC regions are dominated by small irregular ice crystals and columns. The parameters (No–λ–μ) in each mode exhibit mutual dependence.

Effect of Acyl Chain Length on Hydrophobized Cashew Gum Self-Assembling Nanoparticles: Colloidal Properties and Amphotericin B Delivery

Given its many potential applications, cashew gum hydrophobic derivatives have gained increasing attraction in recent years. We report here the effect of acyl chain length on hydrophobized cashew gum derivatives, using acetic, propionic, and butyric anhydrides on self-assembly nanoparticle properties and amphotericin B delivery. Nanoparticles with unimodal particle size distribution, highly negative zeta potential, and low PDI were produced. Butyrate cashew gum nanoparticles presented smaller size (&lt;~100 nm) than acetylated and propionate cashew gum nanoparticles and no cytotoxicity in murine fibroblast cells was observed up to 100 µg/mL for loaded and unloaded nanoparticles. As a proof of concept of the potential use of the developed nanoparticle as a drug carrier formulation, amphotericin B (AmB) was encapsulated and fully characterized in their physicochemical, AmB association and release, stability, and biological aspects. They exhibited average hydrodynamic diameter lower than ~200 nm, high AmB efficiency encapsulations (up to 94.9%), and controlled release. A decrease in AmB release with the increasing of the anhydride chain length was observed, which explains the differences in antifungal activity against Candida albicans strains. An excellent storage colloidal stability was observed for unloaded and loaded AmB without use of surfactant. Considering the AmB delivery, the acyl derivative with low chain length is shown to be the best one, as it has high drug loading and AmB release, as well as low minimum inhibitory concentration against Candida albicans strains.

Understanding the effects of process parameters and material properties on the breakage mechanisms and regimes of a milling process

Milling is an important unit operation used as a particle design process in solid drug manufacturing processes. The size reduction process, where granules break into smaller fragments, governs the operation of the mill. The breakage behavior in a mill can be described through its breakage mechanisms, which are described using the critical screen size, breakage mode, and breakage rate. Breakage mechanisms are important because they determine the output quality attributes of the mill, such as the particle size distribution (PSD) and mass throughput. This study investigates the effect of process parameters and material properties on breakage mechanisms and determines its correlation to the output quality attributes. Additionally, dynamic data was collected and analyzed to determine the effect of process parameters and material properties on the transition of regimes and the evolvement of breakage modes. The findings in this study indicate that stronger granules undergo solely impact-attrition breakage mode, whereas weaker granules first undergo impact breakage mode and then transition into impact-attrition mode. Mass throughput is observed to be higher for impact mode than impact-attrition mode. Moreover, impact mode produces a wide and unimodal PSD, while impact-attrition mode produces a bimodal distribution.

Soot particle size distributions in turbulent opposed jet flames with premixed propene–air reactants

Emissions of soot are strongly dependent on turbulence-chemistry interactions due to the relatively slow formation and oxidation processes. Studies of laminar flames have shown that both flow conditions and the chemistry of the parent fuel have a significant impact on measured particle size distributions (PSDs). The current study determines the impact of flow on the development of PSDs in premixed turbulent flames through a variation in the total rate of strain using an opposed jet configuration with fractal grid generated turbulence. The impact of fuel chemistry is investigated under such conditions through the use of propene–air flames with results compared to the corresponding ethene–air flames quantified in earlier studies. Samples were extracted using a quartz probe featuring aerodynamic quenching and dual port dilution at the probe tip and in the transfer-line. Spatially resolved PSD data is obtained along the stagnation point streamline using a scanning mobility particle sizer equipped with nano- and long-DMA columns to show the evolution through the turbulent flame brush. Results confirm that PSDs of soot in premixed turbulent flames are exceptionally sensitive to both the chemistry of the parent fuel and the flow field. The reduced residence times in the current turbulent flows lead to maximum median and mean mobility diameters below 10 nm with higher rates of strain promoting unimodal PSD shapes. It is further shown that the chemistry of the parent fuel has a strong influence on PSDs with propene causing a two order of magnitude increase in smaller particles compared to the corresponding ethene flame.

Lipid nano-carriers loaded with Cannabis sativa extract for epilepsy treatment – in vitro characterization and in vivo efficacy studies

Taking into consideration the latest reported beneficial anticolvusant effects of cannabidiol (CBD) and cannabiodiolic acid (CBDA) for clinical applications and the advantages of lipid nano-systems as carriers for targeted brain delivery, the aim of this study was set in direction of in vitro physico-chemical and biopharmaceutical characterization and in vivo evaluation of nanoliposomes and nanostructured lipid carriers loaded with Cannabis sativa extract intended for safe and efficient transport via blood-brain barrier and treatment of epilepsy. These nanoliposomes and nanostructured lipid formulations were characterized with z-average diameter <200 nm, following unimodal particle size distribution, negative values for Z-potential, high drug encapsulation efficiency and prolonged release during 24h (38.84-60.91 %). Prepared formulations showed statistically significant higher antioxidant capacity compared to the extract. The results from in vivo studies of the anticonvulsant activity demonstrated that all formulations significantly elevated the latencies for myoclonic, clonic and tonic seizures and, therefore, could be used in preventing different types of seizures. A distinction in the potential of the nano-systems was noted, which was probably anticipated by the type and the characteristics of the prepared formulations.

Dynamic light scattering inversion based on Tikhonov regularization and parameter-optimized generalized regression neural network

Neural network technology shows certain superiority in the field of dynamic light scattering (DLS) inversion. However, due to the complex problems of training sample and parameter selection, its application has certain limitations. At present, it has not been applied to the inversion of bimodal particle size distribution (PSD). Aiming at training sample generation and smoothing parameter optimization of generalized regression neural network (GRNN), a DLS inversion method combining Tikhonov regularization and parameter-optimized GRNN (Tikhonov-PGRNN) is proposed. In this method, the PSD of Tikhonov regularization inversion is used as prior information to generate the training samples, the one-dimensional search method is used to obtain the optimal smoothing parameter, and the normalized field autocorrelation function data is input into GRNN to estimate the PSD. Simulated data for narrow and broad 522 nm unimodal, 216 nm/667 nm bimodal PSDs were inverted by Tikhonov-PGRNN and Tikhonov under different noise levels. The results show that Tikhonov-PGRNN can realize the inversion of unimodal and bimodal PSDs. Compared with Tikhonov, the peak position error and the distribution error of PSDs inverted by Tikhonov-PGRNN are smaller and the method has higher anti-noise performance. The inversion results of experimental data are consistent with the conclusion of simulation data. The peak position errors of 203 nm, 555 nm unimodal and 33 nm/203 nm, 306 nm/974 nm bimodal particle systems inverted by Tikhonov-PGRNN are 1.48%, 0.39% and 3.55%/0.76%, 7.90%/1.74% respectively, which are better than the inversion results of Tikhonov. • A DLS inversion method of Tikhonov-PGRNN is proposed. • Tikhonov inversion result is used as prior information to generate training samples. • Optimal smoothing parameter is obtained by one-dimensional search method. • Tikhonov-PGRNN has higher anti-noise performance. • Tikhonov-PGRNN can obtain a high-accuracy inversion result.

Seabuckthorn seed protein concentrate: a novel seed protein; emulsifying properties as affected by ultrasonication and enzymatic hydrolysis

SummaryThe study investigated the influence of ultrasonication and enzymatic hydrolysis on emulsifying properties of Seabuckthorn seed protein concentrate (SSPC). Sonication was done at 24 kHz (50% amplitude) for different time combinations (15, 45 and 75 min), and enzymatic hydrolysis of SSPC was done using pepsin, trypsin and protamex, resulting in different SSPC emulsions. All the emulsions were characterised to ascertain the particle size distribution, pH stability, temperature stability and rheology. Hydrolysed SSPC was also characterised for the respective degree of hydrolysis by pepsin, trypsin and protamex. The pepsin revealed the highest degree of hydrolysis among the proteases, followed by trypsin and protamex. The ultrasonicated SSPC and SSPC hydrolysate emulsions showed unimodal particle size distribution except for pepsin hydrolysate emulsions which showed bimodal size distribution of particles. The variation in pH from 2 to 5 increased the particle size, while at higher pH (7–10), the particle size decreased for all the emulsions. The increase in temperature from 25°C to 85 °C increased the droplet size of all the emulsions except for protamex at 75 min, which showed a relatively smaller droplet size than other proteases. All the emulsions displayed shear thinning behaviour, however, the pepsin‐treated emulsions showed the highest consistency index and K‐value. The resulting ultrasonicated and different protease‐treated SSPC emulsions can be suitable green and nontoxic alternatives to synthetic emulsifiers used in the food industry.

Sulfidization-free synthesis of well dispersed (Gd,La)2O2S:Pr3+ nanopowders and the effect of La3+ on structure and luminescence

Pr3+ activated Gd2O2S and La2O2S are finding a wide range of luminescence applications but their solid-solution form has rarely been reported in the literature. A series of [(Gd1.0-xLax)0.99Pr0.01]2O2S (x = 0.0–1.0, GLOS:Pr3+) solid-solution phosphor nanopowders were directly produced in this work by calcining their sulfated hydroxide type precursors in flowing hydrogen at 900 °C, without using any of the harmful sulfidization reagents indispensable to other technical routes. The synthesis method also has the significant advantages of fine crystallites (∼20–35 nm), high specific surface area (∼16–21 m2/g) and unimodal particle size distribution (average particle size ∼120–140 nm) of the product. Photoluminescence study indicated that La3+ doping may remarkably enhance Pr3+ luminescence under 263 nm excitation, though tends to lower the thermal stability and elongate the lifetime of the emission. Aside from phosphor application, the thus-synthesized GLOS:Pr3+ powders would be well suited for the sintering of high-quality ceramic scintillators because of their fine particle/crystallite size and unimodal/narrow size distribution.

Modeling Electrode Heterogeneity in Lithium-Ion Batteries: Unimodal and Bimodal Particle-Size Distributions

In mathematical models of lithium-ion batteries, the highly heterogeneous porous electrodes are frequently approximated as comprising spherical particles of uniform size, leading to the commonly used single-particle model (SPM) when transport in the electrolyte is assumed to be fast. Here electrode heterogeneity is modeled by extending this to a distribution of particle sizes. Unimodal and bimodal particle-size distributions (PSD) are considered. For a unimodal PSD, the effect of the spread of the distribution on the cell dynamics is investigated, and choice of effective particle radius when approximating by an SPM assessed. Asymptotic techniques are used to derive a correction to the SPM valid for narrow, but realistic, PSDs. In addition, it is shown that the heterogeneous internal states of all particles (relevant when modeling degradation, for example) can be efficiently computed after the fact. For a bimodal PSD, the results are well approximated by a double-particle model (DPM), with one size representing each mode. Results for lithium iron phosphate with a bimodal PSD show that the DPM captures an experimentally observed double plateau in the discharge curve, suggesting it is entirely due to bimodality.