Narrow Particle Size Distribution Research Articles

A comparative study on the production of Ni1/3Co1/3Mn1/3C2O4 cathode precursor material for lithium-ion batteries using batch and slug-flow reactors

The intermittent nature of the renewable energy sources drifts research interest towards various electrochemical energy storage devices, such as the lithium ion battery, which offers consistent power supply. The manufacturing cost and electrochemical performance of a battery pack largely depends on the quality of the cathode material, which further depends on the production method and its parameters. However, the traditional stirred tank-based co-precipitation manufacturing process for precursors of lithium nickel manganese cobalt oxide (NCM111) cathode suffers from inhomogeneity in the reaction environment, which leads to non-uniform morphology and particle size distribution (PSD). In this work, slug-flow-based manufacturing platform, which offers a homogeneous reaction environment, is used for the continuous production of NCM111 oxalate precursors. One of the novel features of this work is the comparative study between the quality of batch and slug-flow-derived products. The slug-flow-derived product is found to be better in terms of having bigger particle size, narrower PSD and higher tap density. The study on the single and dual-element precipitation in similar conditions to understand the co-precipitation behavior in the slug-flow manufacturing platform is also a unique feature of this work. Furthermore, the effect of NH4OH concentration and residence time (RT) on the electrochemical performance of cathode were also studied and it is found that the cathode precursors synthesized at a NH4OH concentration of 0.08 M and a RT of 2 minutes followed by lithiation shows a better electrochemical performance of 128 mAh g−1 at 0.1 C with cycling stability of more than 80% both at 0.5 C and 1 C.

Dual targeting total saponins of Pulsatilla of natural polymer crosslinked gel beads with multiple therapeutic effects for ulcerative colitis

Oral colon targeted drug delivery system (OCTDDS) is desirable for the treatment of ulcerative colitis (UC). In this study, we designed a partially oxidized sodium alginate-chitosan crosslinked microsphere for UC treatment. Dissipative particle dynamics (DPD) was used to study the formation and enzyme response of gel beads from a molecular perspective. The formed gel beads have a narrow particle size distribution, a compact structure, low cytotoxicity and great colon targeting in vitro and in vivo. Animal experiments demonstrated that gel beads promoted colonic epithelial barrier integrity, decreased the level of pro-inflammatory factors, accelerated the recovery of intestinal microbial homeostasis in UC rats and restored the intestinal metabolic disorders. In conclusion, our gel bead is a promising approach for the treatment of UC and significant for the researches on the pathogenesis and treatment mechanism of UC.

Fluorinated polymer-derived microporous carbon spheres for CFx cathodes with high energy density

Fluorinated carbon (CFx) compounds have extensive applications in lithium primary battery cathodes owing to their high energy density. In this investigation, a novel CFx compound offering superior electrochemical properties was synthesized via a low-temperature fluorination process, utilizing Pluronic F127 as a template agent and microporous carbon spheres produced through soft template-assisted high-temperature carbonization and chemical activation as precursors, and by regulating the amount of soft template F127 added. The reduction in microsphere size, narrower particle size distribution, and introduction of defects contribute to augmenting the molar ratio of F to C (F/C) of CFx while preserving the electrochemical activity of C-F bonds. The specific capacity of fluorinated polymer-derived microporous carbon spheres (FPMCSs) with a high fluorination degree rivals that of commercial fluorinated graphite (FG). The microsphere morphology and microporous structure not only furnish abundant sites for fluorination reactions in electrode processes but also facilitate Li+ diffusion, ensuring ample rate capability. The synthesized FPMCSs exhibited a peak specific capacity of 1079 mAh g–1 and a maximum energy density of 2679 Wh kg–1 (substantially surpassing the 2180 Wh kg–1 of commercial FG). Hence, the prepared FPMCSs underscore the significance of selecting suitable carbonaceous materials and designing structures deliberately, showing promising potential for achieving high energy density in CFx cathodes in the future, employing readily available and cost-effective raw materials.

Synthesis and electrocatalytic evaluation of PtNi catalyst supported on SBA-15 modified carbon

Maximizing catalyst activity and stability while minimizing costs remains a formidable challenge. In this study, we employed the straightforward and easily executed ethylene glycol reduction method to synthesize highly active and stable Pt-Ni alloy catalysts, utilizing SBA15-modified carbon as the supporting material. Subsequent meticulous examinations delved into their physicochemical properties and electrocatalytic activities.Transmission electron microscopy (TEM) analyses unveiled a uniform distribution of PtNi particles on the support, showcasing a narrow particle size distribution centered around approximately 1.91 nm with minimal aggregation. Electrochemical assessments demonstrated that Pt3Ni/SBA15-C outperforms Pt/C, exhibiting 56 and 167 mV higher half-wave potentials (E1/2) and onset potential (Eonset), respectively. Furthermore, our meticulously prepared Pt3Ni/SBA15-C, featuring a cage structure, displayed remarkable stability while sustaining superior catalytic durability under an applied potential of +0.7 V. These findings underscore the effectiveness of the cage structure catalyst, comprising porous nanoparticles, in ensuring both catalytic activity and stability. The results collectively contribute to advancing our understanding of catalyst design and performance optimization in electrochemical applications.

Powder Synthesis and Characterization of Al0.5CoCrFeNi High-Entropy Alloy for Additive Manufacturing Prepared by the Plasma Rotating Electrode Process.

The Al0.5CoCrFeNi high-entropy alloy powder was produced by using a plasma rotating electrode process. The morphology, microstructure, and physical properties of the powder were characterized. The powder exhibited a smooth surface and a narrow particle size distribution with a single peak. The relationships between particle size and secondary dendrite arm space as well as cooling rate were evaluated as follows: λ = 0.0105d + 0.062 and vc = 4.34 × 10-5d-2 + 2.62 × 10-2d-3/2, respectively. The Al0.5CoCrFeNi powder mainly consisted of fcc + bcc phases. As the powder particle size decreased, the microstructure of the powder changed from dendritic to columnar or equiaxed, along with a decrease in the fcc content and an increase in the bcc content. The tap density (4.76 g cm-3), flowability (15.01 s × 50 g-1), oxygen content (<300 ppm), and sphericity (>94%) of the powder indicated suitability for additive manufacturing.

Extraction of lignin-containing nanocellulose fibrils from date palm waste using a green solvent

Lignin-containing nanocellulose (LNC) is a compelling alternative to traditional nanocellulose (NC), it offers enhanced yields and a reduction in the demand for toxic chemicals. This research involves the isolation of LNC from date palm waste using a green hydrolysis process and its subsequent characterization. The potential of using ionic liquids (ILs) as green solvents to isolate LNC has not yet been explored. Our findings suggest that 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) can hydrolyze partially delignified and unbleached lignocellulose, achieving LNC synthesis. The obtained LNC showed a higher yield than its NC counterpart and exhibited rod-shaped fibers with nanoscale diameters and micrometer lengths, indicating a high aspect ratio. Dynamic Light Scattering (DLS) results indicate average particle sizes of 143.20 nm for NC and 282.30 nm for LNC, with a narrow particle size distribution conforming their monodisperse behavior. Thermogravimetric analysis and differential scanning calorimetry revealed high thermal stability (initial degradation temperature = 222.50 °C and glass transition temperature = 84.45°C) of LNC. Moreover, the obtained LNC fibers were crystalline (crystallinity index = 52.76 %). Their activation energy (124.95 kJ/mol) was determined using the Coats–Redfern method by employing eight solid-state diffusion models. Overall, this study motivates the use of ILs as green solvents to produce lignocellulose derivatives that are suitable for various applications.

Fabrication of PVDF/TiO2@CQDs photocatalytic films by ink-jet printing for dye degradation under visible light

PVDF/TiO2@CQDs hybrid photocatalytic thin films were prepared by ink-jet printing. The printing ink was prepared with the TiO2, TiO2(s)@CQDs (surface composite), and TiO2(i)@CQDs (situ doping) nanoparticles as precursors, respectively. Compared to TiO2(s)@CQDs, TiO2(i)@CQDs has a smaller particle size (about 10.01 nm) and a narrower particle size distribution (6∼14 nm), which can improve the photocatalytic effect while avoiding nozzle clogging. The PVDF/TiO2(i)@CQDs hybrid film exhibited a high degradation efficiency (η) of 93.71 % for Rhodamine B (RhB) within 150 min under visible light with a catalyst load of only 0.49 wt%. The reaction rate constant (ks) of the PVDF/TiO2(i)@CQDs film was about 4.3 times higher than that of the PVDF/TiO2(s)@CQDs film. The small particle size of this S-scheme TiO2(i)@CQDs heterostructure nanoparticle and the more effective contact interface formed between TiO2 and carbon quantum dots (CQDs) further facilitated electron transfer and enhanced photoactivity. The firmly immobilized catalysts on the Polyvinylidene fluoride (PVDF) film substrate through Ti-F coordination bonds ensured the reusability and stability of the photocatalytic film (the η of RhB still reached 88.05 % after 10 consecutive cycles). This work provides a new strategy for the application of ink-jet printing technology in photocatalysis.

On Nucleation Pathways and Particle Size Distribution Evolutions in Stratospheric Aircraft Exhaust Plumes with H2SO4 Enhancement.

Stratospheric aerosol injection (SAI) is proposed as a means of reducing global warming and climate change impacts. Similar to aerosol enhancements produced by volcanic eruptions, introducing particles into the stratosphere would reflect sunlight and reduce the level of warming. However, uncertainties remain about the roles of nucleation mechanisms, ionized molecules, impurities (unevaporated residuals of injected precursors), and ambient conditions in the generation of SAI particles optimally sized to reflect sunlight. Here, we use a kinetic ion-mediated and homogeneous nucleation model to study the formation of H2SO4 particles in aircraft exhaust plumes with direct injection of H2SO4 vapor. We find that under the conditions that produce particles of desired sizes (diameter ∼200-300 nm), nucleation occurs in the nascent (t < 0.01 s), hot (T = 360-445 K), and dry (RH = 0.01-0.1%) plume and is predominantly unary. Nucleation on chemiions occurs first, followed by neutral new particle formation, which converts most of the injected H2SO4 vapor to particles. Coagulation in the aging and diluting plumes governs the subsequent evolution to a narrow (σg = 1.3) particle size distribution. Scavenging by exhaust soot is negligible, but scavenging by acid impurities or incomplete H2SO4 evaporation in the hot exhaust plume and enhanced background aerosols can matter. This research highlights the need to obtain laboratory and/or real-world experiment data to verify the model prediction.

PH-Responsive Nanogels Generated by Polymerization-Induced Self-Assembly of a Succinate-Functional Monomer.

Colloidal nanogels formed from a pH-responsive poly(succinate)-functional core and a poly(sulfonate)-functional corona were prepared via a previously unreported reversible addition-fragmentation chain-transfer (RAFT)-mediated aqueous emulsion polymerization-induced self-assembly (PISA) route. Specifically, a poly(potassium 3-sulfopropyl methacrylate) (PKSPMA50) macromolecular chain-transfer agent (macro-CTA) was synthesized via RAFT solution polymerization followed by chain-extension with a hydrophobic, carboxylic acid-functional, 2-(methacryloyloxy) ethyl succinate (MES) monomer at pH 2. Colloidal nanoparticles with tunable diameters between 66 to 150 nm, depending on the core composition, and narrow particle size distributions were obtained at 20% w/w solids. Well-defined pH-responsive nanogels that swell on increasing the pH could be prepared even without the addition of a cross-linking comonomer, and introducing an additional cross-linker to the core led to smaller nanogels with lower swelling ratios. These nanogels could reversibly change in size on cycling the pH between acidic and basic conditions and remain colloidally stable over a wide pH range and at 70 °C.

Microbially Mediated Rubber Recycling to Facilitate the Valorization of Scrap Tires.

The recycling of scrap tire rubber requires high levels of energy, which poses challenges to its proper valorization. The application of rubber in construction requires significant mechanical and/or chemical treatment of scrap rubber to compatiblize it with the surrounding matrix. These methods are energy-consuming and costly and may lead to environmental concerns associated with chemical leachates. Furthermore, recent methods usually call for single-size rubber particles or a narrow rubber particle size distribution; this, in turn, adds to the pre-processing cost. Here, we used microbial etching (e.g., microbial metabolism) to modify the surface of rubber particles of varying sizes. Specifically, we subjected rubber particles with diameters of 1.18 mm and 0.6 mm to incubation in flask bioreactors containing a mineral medium with thiosulfate and acetate and inoculated them with a microbial culture from waste-activated sludge. The near-stoichiometric oxidation of thiosulfate to sulfate was observed in the bioreactors. Most notably, two of the most potent rubber-degrading bacteria (Gordonia and Nocardia) were found to be significantly enriched in the medium. In the absence of added thiosulfate in the medium, sulfate production, likely from the desulfurization of the rubber, was also observed. Microbial etching increased the surface polarity of rubber particles, enhancing their interactions with bitumen. This was evidenced by an 82% reduction in rubber-bitumen separation when 1.18 mm microbially etched rubber was used. The study outcomes provide supporting evidence for a rubber recycling method that is environmentally friendly and has a low cost, promoting pavement sustainability and resource conservation.

Enhancement of Flexural Strength by Slip Casting Cordierite Ceramics with h-BN Nanoparticles

In this study, we enhanced the flexural strength of cordierite ceramics by incorporating h-BN (hexagonal boron nitride) nanoparticles, facilitated by the slip casting process. Initially, commercial cordierite powder with an average particle size of 10 mm underwent a ball-milling process to reduce the size to 2.5 mm and simultaneously achieve a narrower particle size distribution. The resulting slurry, composed of 67% solid content, exhibited improved stability during the slip casting process for both pristine cordierite and the mixture containing 1 – 2 wt% h-BN nanoparticles. After sintering, the bulk material containing 2wt% h-BN nanoparticles demonstrated a remarkable flexural strength of 174.8 MPa, a significant improvement compared to the initial 119.5 MPa obtained without the addition of h-BN. It is worth noting that the introduction of h-BN nanoparticles did not induce substantial changes in dielectric constant and thermal conductivity, indicating that the desired mechanical enhancement did not compromise other crucial material properties. This research demonstrates a successful approach to concurrently optimize the flexural strength, dielectric constants, and thermal conductivity of cordierite ceramics. This breakthrough opens up new avenues for advanced applications in a wide range of fields, from electronics to aerospace, where high-strength, thermally stable materials are in demand.

Thermosensitive polymer prodrug nanoparticles prepared by an all-aqueous nanoprecipitation process and application to combination therapy

Despite their great versatility and ease of functionalization, most polymer-based nanocarriers intended for use in drug delivery often face serious limitations that can prevent their clinical translation, such as uncontrolled drug release and off-target toxicity, which mainly originate from the burst release phenomenon. In addition, residual solvents from the formulation process can induce toxicity, alter the physico-chemical and biological properties and can strongly impair further pharmaceutical development. To address these issues, we report polymer prodrug nanoparticles, which are prepared without organic solvents via an all-aqueous formulation process, and provide sustained drug release. This was achieved by the “drug-initiated” synthesis of well-defined copolymer prodrugs exhibiting a lower critical solution temperature (LCST) and based on the anticancer drug gemcitabine (Gem). After screening for different structural parameters, prodrugs based on amphiphilic diblock copolymers were formulated into stable nanoparticles by all-aqueous nanoprecipitation, with rather narrow particle size distribution and average diameters in the 50–80 nm range. They exhibited sustained Gem release in human serum and acetate buffer, rapid cellular uptake and significant cytotoxicity on A549 and Mia PaCa-2 cancer cells. We also demonstrated the versatility of this approach by formulating Gem-based polymer prodrug nanoparticles loaded with doxorubicin (Dox) for combination therapy. The dual-drug nanoparticles exhibited sustained release of Gem in human serum and acidic release of Dox under accelerated pathophysiological conditions. Importantly, they also induced a synergistic effect on triple-negative breast cancer line MDA-MB-231, which is a relevant cell line to this combination.

Novel Phytosomal Formulation of Emblica officinalis Extracts with Its In Vivo Nootropic Potential in Rats: Optimization and Development by Box-Behnken Design

Purpose. The present study aimed to improve the aqueous solubility, permeability, bioavailability, and nootropic potential of standardized Emblica officinalis extract (EOE) by developing a novel phytosomal formulation. Method. Emblica officinalis extract-loaded phytosomes (EOPs) were prepared using solvent evaporation. The EOP was prepared at different molar ratios of extract and phospholipid. Herein, the effects of phospholipid extract ratio (A), temperature (B), and reaction time (C) were systematically investigated on entrapment efficiency using Box-Behnken design. In vitro and in vivo characterizations of the optimized formulation were performed. Results. Optimized EOP formulation (89.90 ± 0.24 μg/ml) exhibited improved aqueous solubility than plain EOE (11.85 ± 0.25 μg/ml). The optimized formulation’s particle size and Zeta potential were 198.4 ± 0.20 nm and −39.0 ± 0.40 mv. DSC and XRD studies confirmed the partial amorphization of EOE in phytosomes. Optimized formulation exhibited 69.82 ± 0.17% of EOE release at 12 h and followed zero-order release kinetics. Moreover, the phytosomal formulation of EOE exhibited its rationality with an improvement of bioavailability by 2.7 folds compared with pure EOE. Compared to EOE, EOP showed significantly (p&lt;0.05 lower escape and transfer latencies on both days in MWMT and EPMT, indicating more effective memory-enhancing activity. Furthermore, EOP-treated rats exhibited improved acetylcholine (Ach) levels than EOE. Brain tissue concentrations measured following EOP oral administration (1.06 ± 0.04 μg/ml) were substantially greater (p&lt;0.05) than those following EOE (0.32 ± 0.07 μg/ml). The brain dopamine and serotonin concentration were found to be higher (16.27 ± 1.209 and 43.28 ± 1.550 ng/ml) in the EOP-treated group as compared to the pure extract-treated group (10.40 ± 1.185 and 32.79 ± 1.738 ng/ml). Conclusion. Improvement of aqueous solubility, permeability, dissolution, bioavailability, and narrower particle size distribution could facilitate enhancement in the nootropic potential of EOE phytosomal formulation.

Microfluidic preparation of surfactant-free ultrafine DAAF with tunable particle size for insensitive initiator explosives

High purity and ultrafine DAAF (u-DAAF) is an emerging insensitive charge in initiators. Although there are many ways to obtain u-DAAF, developing a preparation method with stable operation, accurate control, good quality consistency, equipment miniaturization, and minimum manpower is an inevitable requirement to adapt to the current social technology development trend. Here reported is the microfluidic preparation of u-DAAF with tunable particle size by a passive swirling microreactor. Under the guidance of recrystallization growth kinetics and mixing behavior of fluids in the swirling microreactor, the key parameters (liquid flow rate, explosive concentration and crystallization temperature) were screened and optimized through screening experiments. Under the condition that no surfactant is added and only experimental parameters are controlled, the particle size of recrystallized DAAF can be adjusted from 98 nm to 785 nm, and the corresponding specific surface area is 8.45 m2·g-1 to 1.33 m2·g-1. In addition, the preparation method has good batch stability, high yield (90.8% to 92.6%) and high purity (99.0% to 99.4%), indicating a high practical application potential. Electric explosion derived flyer initiation tests demonstrate that the u-DAAF shows an initiation sensitivity much lower than that of the raw DAAF, and comparable to that of the refined DAAF by conventional spraying crystallization method. This study provides an efficient method to fabricate u-DAAF with narrow particle size distribution and high reproducibility as well as a theoretical reference for fabrication of other ultrafine explosives.

Direct mechanochemical synthesis of CaMoO4 and Dy3+ doped CaMoO4 nanoparticles and their photoluminescent properties

Calcium molybdate (CaMoO4) and Dy3+ doped CaMoO4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO4 and Dy3+ doped CaMoO4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO4 samples contain absorption peaks corresponding to the MoO4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO4 and Dy3+ doped CaMoO4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F9/2 → 6H11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO4 nanoparticles can find application in different optical instruments.

Engineering Nitrogen-Doped Carbon Quantum Dots: Tailoring Optical and Chemical Properties through Selection of Nitrogen Precursors.

The process of N-doping is frequently employed to enhance the properties of carbon quantum dots. However, the precise requirements for nitrogen precursors in producing high-quality N-doped carbon quantum dots (NCQDs) remain undefined. This research systematically examines the influence of various nitrogen dopants on the morphology, optical features, and band structure of NCQDs. The dots are synthesized using an efficient, eco- friendly, and rapid continuous hydrothermal flow technique. This method offers unparalleled control over synthesis and doping, while also eliminating convention-related issues. Citric acid is used as the carbon source, and urea, trizma base, beta-alanine, L-arginine, and EDTA are used as nitrogen sources. Notably, urea and trizma produced NCQDs with excitation-independent fluorescence, high quantum yields (up to 40%), and uniform dots with narrow particle size distributions. Density functional theory (DFT) and time-dependent DFT modelling established that defects and substituents within the graphitic structure have a more significant impact on the NCQDs' electronic structure than nitrogen-containing functional groups. Importantly, for the first time, this work demonstrates that the conventional approach of modelling single-layer structures is insufficient, but two layers suffice for replicating experimental data. This study, therefore, provides essential guidance on the selection of nitrogen precursors for NCQD customization for diverse applications.

Fabrication of soy protein nanoparticles based on metal-phenolic networks for stabilization of nano-emulsions delivery system

The use of soy protein isolate (SPI) nanoparticles as a stabilizer in nano-emulsion systems has garnered significant interest. While metal-phenolic networks (MPNs) have been explored for their multifunctional surface modification capabilities, their integration with food protein-based delivery systems remains less explored. In this study, we attempt to develop a novel strategy to encapsulate cinnamaldehyde using MPNs (EGCG-Fe3+) with self-assembling soy protein nanoparticles (SE-Fe NPs) as a stabilizer for nano-emulsions. UV, Raman, and X-ray photoelectron spectroscopy analyses demonstrated that SE-Fe NPs were generated through metal-phenolic coordination and covalent interactions. SE-Fe NPs had a narrower particle size distribution and enhanced radical scavenging (up to 3.35-fold), as well as thermal stability. Furthermore, the smaller droplet size, higher modulus, higher cinnamaldehyde encapsulation efficiency (from 63.5% to 84.2%), and improved bio-accessibility of SE-Fe NPs stabilized nano-emulsions delivery system demonstrated in this study shows promising future applications in the food industry.

Pulse Spray Drying for Bovine Skimmed Milk Powder Production.

Pulse Spray Drying (PSD) has potential as a sustainable means of skimmed milk powder (SMP) production. In this study, powders were obtained from PSD using different drying outlet temperatures (70, 80, 90 and 100 °C), and their characteristics were compared to those of traditional Spray Drying (SD). Native whey proteins were well preserved and Solubility Indexes were over 98% in all cases, despite powders obtained by PSD displaying lower solubility than the SD ones. No visual difference was observable in the powders (ΔE < 2); however, PSD powders were found to be yellower with a higher Browning Index. The drying technology did not have a significant effect on powder moisture content and bulk density. Particle size distribution and scanning electron microscopy images confirmed the presence of fine particles (<10 μm) in all samples that might have provided poor flowability and wetting behavior (overall Carr Index and Hausner ratio were 33.86 ± 3.25% and 1.52 ± 0.07, respectively). Higher amounts of agglomerated particles were found at low temperatures in the products processed with both technologies, but PSD samples showed a narrower particle size distribution and hollow particles with more wrinkles on the surface (probably due to the fast evaporation rate in PSD). Overall, PSD provided SMP with comparable physicochemical characteristics to SD and, once optimized at the industrial level, could offer significant advantages in terms of thermal efficiency without significant modification of the final product quality.

Himalayan lichen biomass for green synthesis of silver nanocolloids: growth kinetics, effect of pH and metal sensing.

Lichen is one of the most abundant non-vascular biomasses; however, a systematic study on the application of biomass in nanomaterial synthesis is very limited. In this study, an aqueous lichen extract was obtained from Hypotrachyna cirrhata, one of the most abundant Himalayan lichen biomasses, using a simple cold percolation method. The effects of extract-to-silver nitrate mixing ratio, pH and waiting time on the growth and stability of nanoparticles were systematically explored. The rate constant for bio-reduction was found to be 5.3 × 10-3 min-1. Transmission electron microscopy showed a narrow particle size distribution with a mean particle size of 11.1 ± 3.6 nm (n = 200). The X-ray diffraction and selected area electron diffraction techniques confirmed the formation of cubic crystals. The synthesized colloidal solution showed excellent response to Hg2+ and Cu2+ ions in spiked water samples. The limit of detection and calibration sensitivity for Hg2+ and Cu2+ ions were found to be 1 and 5 mg l-1 and 2.9 × 10-3 and 1.6 × 10-3 units ppm-1, respectively. These findings suggested that spherical silver nanoparticles with a narrow particle size distribution can be synthesized on a laboratory scale using an aqueous H. cirrhata lichen extract, and the colloidal solution can be used for the detection of selected heavy metals in water samples.

Explaining the green volcanic sunsets after the 1883 eruption of Krakatoa

Abstract. Volcanic sunsets are usually associated with extended and enhanced reddish colours typically complemented by purple colours at higher elevations. However, many eyewitnesses reported remarkably clear and distinct green twilight colours after the eruption of Krakatoa (Sunda Strait, Indonesia) in 1883. To the best of our knowledge, no earlier studies exist providing an explanation for this unusual phenomenon. In the current work, we employ simulations with the SCIATRAN radiative transfer model to investigate the processes leading to green volcanic sunsets. Green sunsets can be simulated based on plausible assumptions by anomalous scattering on stratospheric sulfate aerosols. We investigate the sensitivity of the twilight colours to relevant parameters such as aerosol optical depth (AOD), the parameters of the particle size distribution (PSD), and the amount of ozone. The main requirements for the occurrence of green twilights are a sufficiently large aerosol optical depth combined with particle radii of about 500–700 nm (assuming stratospheric sulfate aerosols) and a preferably narrow aerosol particle size distribution. The occurrence of green twilights after historic eruptions provides important constraints on the particle size of volcanic aerosols.