Narrow Particle Size Distribution Research Articles

One-step spray solution combustion synthesis of nanostructured spherical Ca3Co4O9: The fuel effect

In the research, a one-step method for the rapid preparation of spherical nanostructured particles of Ca3Co4O9, involving the combustion of reactive aerosol drops containing calcium and cobalt nitrates as the metal precursors and hexamethylenetetramine as the fuel, is reported. The results of thermodynamic analysis and study of crystalline structure of obtained materials suggest that the reaction in the investigated system proceeds with heat release, which indicates its self-sustaining nature. Applying hexamethylenetetramine fuel at φ range of 0.4 – 0.6 and ambient temperature of 900 ℃ resulted in formation of Ca3Co4O9 powders with narrow particle size distribution of 0.2 – 1 µm. Microstructural studies revealed that the Ca3Co4O9 particles are hollow with nanometer-scale wall thicknesses and their surface consists of lamellar grains with sizes ranging from 14 to 100 nm.

Synthesis of uniform sized ZnS quantum dots using hydrodynamic cavitation and their characterization

Abstract As representative non-toxic cadmium-free quantum dots (QDs), ZnS QDs with high quantum efficiency, super stability and excellent biocompatibility had attracted wide attention in the fields of photocatalysis, solar cells and biomedicine. In this study, hydrodynamic cavitation (HC) technology was applied to the preparation of ZnS QDs. By adjusting HC device parameters, water soluble ZnS QDs with small particle size, narrow particle size distribution range, high absorbance, high luminous efficiency and high quantum yield were prepared. The morphology, size distribution, element composition and optical properties of ZnS QDs were studied by various characterization methods. ZnS QDs with average particle size of 1.48 nm, fluorescence quantum yield of 34.07% and Stokes shift of 112 nm were obtained. In addition, the mechanism of preparation of ZnS QDs by using HC method was also studied. It is hoped that this HC technology can provide a new idea for large-scale preparation of ZnS QDs with excellent properties.

Enhanced Visible-Light Photocatalytic Activity of Bismuth Ferrite Hollow Spheres Synthesized via Evaporation-Induced Self-Assembly

Semiconductor hollow spheres have garnered significant attention in recent years due to their unique structural properties and enhanced surface area, which are advantageous for various applications in catalysis, energy storage, and sensing. The present study explores the surfactant-assisted synthesis of bismuth ferrite (BiFeO3) hollow spheres, emphasizing their enhanced visible-light photocatalytic activity. Utilizing a novel, facile, two-step evaporation-induced self-assembly (EISA) approach, monodisperse BiFeO3 hollow spheres were synthesized with a narrow particle size distribution. The synthesis involved Bi/Fe citrate complexes as precursors and the triblock copolymer Pluronic P123 as a soft template. The BiFeO3 hollow spheres demonstrated outstanding photocatalytic performance in degrading the emerging pollutants Rhodamine B and metronidazole under visible-light irradiation (100% degradation of Rhodamine B in <140 min and of metronidazole in 240 min). The active species in the photocatalytic process were identified through trapping experiments, providing crucial insights into the mechanisms and efficiency of semiconductor hollow spheres. The findings suggest that the unique structural features of BiFeO3 hollow spheres, combined with their excellent optical properties, make them promising candidates for photocatalytic applications.

Encapsulated inorganic pigments in epoxy composite microspheres using emulsion synthesis

Inorganic pigments are a commonly used colorant with various applications and promising prospects. However, the implement of organic pigments is hindered by poor dispersion stability in coatings due to non-uniform morphology and size. Herein, encapsulated pigments of Cobalt Chrome Green CoCr2O4 (PG 26), Cobalt Blue CoAl2O4 (PB 28), Titanium Chrome Yellow TiCrSbO6 (PB 24) in epoxy microspheres are obtained via an oil-in-water emulsion polymerization. The morphology, particle size, thermal properties, glass transition temperature (Tg) and color performance of the composite microspheres were characterized by different analytical techniques. The average particle size varied with pigments types and loadings. When the content of CoCr2O4 and CoAl2O4 is in the range of 15 wt%-30 wt%, and TiCrSbO6 content is between 15 wt%-25 wt%, the composite microspheres exhibit a narrow particle size distribution, regular morphology, and smooth surface. The size followed the rule of CoAl2O4/epoxy (20–26 μm) > CoCr2O4/epoxy (14-16μm) > TiCrSbO6/epoxy (6–9 μm). Besides, according to the aggregation-induced emission (AIE) principle, the relationship between fluorescence intensity and reaction time was investigated, thus deducing the curing process of the epoxy groups with m-xylenol dimethylamine (MXDA). The kinds of three inorganic fillers exhibit varying effects on the diffusion process of MXDA. TiCrSbO6 promotes the progress of the epoxy-amine curing reaction. Notably, CoCr2O4 microspheres exhibited stable green value (a*) and color saturation (C*), TiCrSbO6 microspheres showed increased yellow value (b*) and saturation (C*), and CoAl2O4 microspheres enhanced blue value (b*) with minimal change in lightness (L*). Overall, this study provides a comprehensive understanding of the properties of inorganic pigment/epoxy composite microspheres and highlights their potential for improved dispersion stability in coating applications.

Particle morphology of alkali metal chloride salts in induction heating based pulsed spray drier: Experimental analysis and ANN prediction

Hygroscopic nature of alkali metal chloride salts makes attaining mono-sized dried particles from their aqueous precursor solution an engineering challenge for conventional co-current or counter-current spray driers. Conventional spray driers offer better thermal utilization in either the spray zone or dried particle zone depending on their configuration viz. co-current or counter-current, respectively. In this work, an alternative prototype named induction heating based pulsed spray drier (IH-PSD) is proposed to obtain dry alkali metal chloride salt powders with narrow particle size distribution. Laser diffraction analysis is carried out for initial droplet size distribution whereas scanning electron microscopy and sieve shaker analysis is carried out for studying the particle morphology and particle size distribution of dried powder for all the selected salts. The resultant particle properties emphasized in the present work are the dried particle to initial droplet diameter ratio and the wet basis moisture content. It has been observed that the ratio of mean volume diameter of dried particle to sauter mean diameter of initial droplet lies in the range of 0.4–3.6 meanwhile the wet basis moisture content of dried powder lies in the range of 1.4–3.6 for the selected salts. Artificial neural network (ANN) model is applied for inferring the influence of IHPSD process parameters on the above mentioned dried particle properties and satisfactory convergence with experimental values has been achieved.

Reflectivity and Angular Anisotropy of Liquid Crystal Microcapsules with Different Particle Sizes by Complex Coalescence.

Cholesteric liquid crystal microcapsules (CLCMs) are used to improve the stability of liquid crystals while ensuring their stimulus response performance and versatility, with representative applications such as sensing, anticounterfeiting, and smart fabrics. However, the reflectivity and angular anisotropy decrease because of the anchoring effect of the polymer shell matrix, and the influence of particle size on this has not been thoroughly studied. In this study, the effect of synthesis technology on microcapsule particle size was investigated using a complex coalescence method, and the effect of particle size on the reflectivity and angular anisotropy of CLCMs was investigated in detail. A particle size of approximately 66 µm with polyvinyl alcohol (PVA, 1:1) exhibited a relative reflectivity of 16.6% and a bandwidth of 20 nm, as well as a narrow particle size distribution of 22 µm. The thermosetting of microcapsules coated with PVA was adjusted and systematically investigated by controlling the mass ratio. The optimized mass ratio of microcapsules (66 µm) to PVA was 2:1, increasing the relative reflectivity from 16.6% (1:1) to 32.0% (2:1) because of both the higher CLCM content and the matching between the birefringence of the gelatin-arabic shell system and PVA. Furthermore, color based on Bragg reflections was observed in the CLCM-coated ortho-axis and blue-shifted off-axis, and this change was correlated with the CLCM particle size. Such materials are promising for anticounterfeiting and color-based applications with bright colors and angular anisotropy in reflection.

Factors, Mechanisms, and Kinetics of Spontaneous Emulsification for Heavy Oil-in-Water Emulsions.

In challenging reservoirs where thermal recovery falls short, cold or chemical oil recovery methods are crucial. Spontaneous emulsification (SE), triggered by gentle disturbance, significantly enhances oil recovery. In elucidating SE mechanisms and kinetics, SE processes via direct contact between oil and aqueous phases without stirring were conducted. The effects of temperature, emulsifier concentration, pH, NaCl concentration, and the oil-to-water ratio on SE were investigated through droplet size analysis and turbidity measurements. Furthermore, the emulsification mechanism and derived emulsification kinetics based on turbidity data were obtained. The results underscore the feasibility of SE for oil-water systems, reducing viscous and capillary resistances without agitation. The emulsified oil mass increased with the temperature, pH, and aqueous-to-oil phase volume ratio while decreasing with the NaCl concentration. In this study, for GD-2 crude oil, the optimal emulsified oil amount occurred at a betaine surfactant (BetS-2) emulsifier concentration of 0.45%. Microscopic photo analysis indicated narrow particle size distributions and small droplets, which remained stable over time under various experimental conditions. A combined SE mechanism involving ultralow interfacial tension, interfacial turbulence due to Marangoni effects, and "diffusion and stranding" due to in situ emulsifier hydrophilicity, was speculated. Additionally, an analogous second-order kinetic equation for SE was proposed, indicating exceptional correlation with calculated and experimentally measured values. This study offers theoretical insight for enhancing oil recovery in chemical and cold production of heavy oil in oilfields.

The effects of processing technique on formation temperature of calcium aluminate magnesium (CaO.2MgO.8Al2O3)

This study aims at the synthesis of a ternary phase crystal CaO.2MgO.8Al2O3 (CM2A8) in the Al-rich part of the ternary system CaO-Al2O3-MgO through two techniques: (1) sol–gel citrate and (2) solid-state reaction. Based on the measurement of particle size, density, phase analysis, nature of bounds, and microscopic observation, the effect of the processing technique on the crystal purity, crystallite size, and synthesis temperature of the as-prepared CM2A8 powder was investigated. Phases analysis (XRD patterns) showed in the sol–gel citrate combustion method almost a single-phase material (calcium aluminate magnesium phases) at relatively lower temperatures while in the solid-state method as-prepared CM2A8 powder with a small amount of spinel (MgAl2O4 = MA) and calcium hexaaluminate (CaAl12O19 = CA6) secondary phases. The generated heat through the combustion of the reaction of ammonium nitrate and citrate-based complexes decreases the synthesis temperature of nanocrystalline CM2A8, and the CM2A8 phase is formed at a temperature of 1400 °C. While growth mechanism in the solid-state reaction method adheres to the two-dimensional nucleation theory and a thick hexagonal flake known as CM2A8 is produced at a temperature of 1700 °C. In comparison with the crystals synthesized by the solid-state reaction method, the powder density of the nanocrystals synthesized by a sol–gel combustion method exhibits higher values (3.54 g.cm−3 and 3.65 g.cm−3, respectively). Peak intensities in the 400–1000 cm−1 range, according to FTIR measurements, correspond to metal–oxygen–metal (M–O–M) bonds (vibrations of Al–O stretching in Mg–O–Al and Ca–O–Al), and they grow as the temperature rises from 200 °C to 1400 °C, indicating that CM2A8 was the crystal that was formed. The morphological analysis (FESEM) revealed that most of the agglomerate particles synthesized by the sol–gel citrate combustion remained within the range of 50–83 nm, while the particles synthesized by the had particles as 1 μm. The specific surface area synthesized CM2A8 via the sol–gel method is in the range of 10–24 m2/g. The main advantages of the sol–gel citrate process are the high purity of the product, the narrow particle size distribution, and the achievement of uniform nanostructure at low temperatures.

Starch nanoparticles with predictable size prepared by alternate treatments of ball milling and ultrasonication

In this study, starch nanoparticles (SNPs) were prepared by alternate treatments of liquid nitrogen ball milling and ultrasonication. The impact, shear and friction forces produced by ball milling, and acoustic cavitation and shear effects generated by ultrasonication disrupted starch granules to prepare SNPs. The SNPs possessed narrow particle size distribution (46.91–210.52 nm) and low polydispersity index (0.28–0.45). Additionally, the SNPs exhibited the irregular fragments with good uniformity. The relative crystallinity decreased from 34.91 % (waxy corn starch, WCS) to 0–25.91 % (SNPs), and the absorbance ratios of R1047/1022 decreased from 0.81 (WCS) to 0.60–0.76 (SNPs). The SNPs had lower thermal stability than that of WCS, characterized by a decrease in Td (temperature at maximum weight loss) from 309.39 °C (WCS) to 300.39–305.75 °C (SNPs). Furthermore, the SNPs exhibited excellent swelling power (3.48–28.02 %) and solubility (0.34–0.97 g/g). Notably, oil absorption capacity of the SNPs (9.77–15.67 g/g) was rather greater than that of WCS (1.33 g/g). Furthermore, the SNPs possessed the lower storage modulus (G′), loss modulus (G″) and viscosity than that of WCS. The SNPs with predictable size and high dispersion capability prepared in this study lay a foundation for expanding the application of SNPs.

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.

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.

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.

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.

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.