Formation Of Colloidal Particles Research Articles

Self-organization of C60 fullerene molecules in xylene/ethanol mixtures

Fullerene molecules have been intensively studied over the past few decades due to their unique chemical and physical properties, which have great potential in a wide range of applications. In this article, the formation and aging of C60 colloids in the xylene/ethanol system is considered. The peculiarities of these processes are studied by the methods of refractometry, optical absorption, Raman spectroscopy and dynamic light scattering (DLS). It has been experimentally established that the formation of colloidal particles in a C60/xylene/ethanol mixture depends on the volume content of the components and the storage time of the solution. The time required to achieve stability of self-organization of solute molecules in a C60/xylene/ethanol mixture is discussed.

Functional-Group-Induced Single Quantum Well Dion-Jacobson 2D Perovskite for Efficient and Stable Inverted Perovskite Solar Cells.

In two-dimensional/three-dimensional (2D/3D) perovskite heterostructure, randomly distributed multiple quantum wells (QW) 2D perovskites are frequently generated, which are detrimental to carrier transport and structural stability. Here, the high quality 2D/3D perovskite heterostructure is constructed by fabricating functional-group-induced single QW Dion-Jacobson (DJ) 2D perovskites. The utilization of ─OCH3 in the precursor solution facilitates the formation of colloidal particles with uniform size, resulting in the production of a pure 2D DJ perovskite with an n value of 3. This strategy facilitates the improvement of 3D structural stability and expedites carrier transport. The resultant devices accomplish a power conversion efficiency of 25.26% (certified 25.04%) and 23.56% at a larger area (1 cm2 ) with negligible hysteresis. The devices maintain >96% and >89% of their initial efficiency after continuous maximum power point tracking under simulated AM1.5 illumination for 1300h and under damp-heat conditions (85°C and 85% RH) for 1010h, respectively.

Colloidally Stable Polypyrrole Nanoparticles Synthesized by Surfactant-Free Coupling Polymerization.

Surfactant-free polypyrrole (PPy) nanoparticles, which were colloidally stable in aqueous medium, were successfully synthesized by coupling polymerization of pyrrole using Fe(NO3)3 solids in the absence of any colloidal stabilizer. The pyrrole monomers were gradually supplied from the vapor phase, and the coupling reaction of the monomers could proceed to generate PPy in a water medium. The resulting PPy nanoparticles were extensively characterized in terms of diameter, bulk chemical composition, surface chemistry, and colloidal stability by dynamic light scattering, electron microscopy, elemental microanalysis, Fourier transform infrared spectroscopy, Raman spectroscopy, electrophoresis, and X-ray photoelectron spectroscopy. The characterization results indicated that the PPy nanoparticles can be colloidally stable based on the electrostatic stabilization mechanism due to cationic charges generated on the PPy molecules by doping during the polymerization. General chemical oxidative polymerization in aqueous medium using the Fe(NO3)3 oxidant without a colloidal stabilizer as a control experiment resulted in generation of atypical PPy aggregates with over a micrometer size, indicating that the polymerization at low ionic strength is essential for colloidal particle formation. Finally, it was demonstrated that the PPy nanoparticles worked as a surfactant-free black-colored particulate emulsifier by adsorption at the oil-water interface to stabilize Pickering-type oil-in-water emulsions.

Photoluminescence of float glass surface doped with copper nanoparticles

In this study we have investigated the effect of ion-exchange introduced copper ions on the photoluminescence properties of the modified float glass. Copper nanoparticles were formed, directly without reducing agents on the float glass by treating in vapour or melts of copper chloride containing salt due to the presence of tin in the glass surface layer. An absorption peak at 560 nm was observed in the UV–VIS spectra of treated samples, proving the formation of copper colloidal particles. A photoluminescence (PL) emission (around 520 nm) and excitation (between 260 and 300 nm) spectra were obtained, which are typical for the presence of Cu+ ions. It was established that the emergence and displacement of emission spectra is strongly dependant on temperature, processing time, additional treatment and Cu+ concentration. Moreover, X-ray diffraction analysis (XRD) was performed in order to determine the formed crystalline phases in the amorphous glass surface. Morphological features were investigated by scanning electron microscopy (SEM).

Lane formation of colloidal particles driven in parallel by gravity.

We investigate the lane formation in nonequilibrium systems of colloidal particles moving in parallel that are driven by the force of gravity. For this setup, an experimental implementation of a channel on a slope can be conceptualized. We employ the Brownian dynamics algorithm and confine the repulsive particles with hard walls based on the solution of the Smoluchowski equationin the half space. A difference of the driving force acting on the colloids could be achieved by using two spherical particle types with differing diameters but equal mass density. First, we investigate how a difference in the channel slope affects the lane formation of the systems, after which we analyze the lanes that formed. We find that the large particles push the small particles to the walls, resulting in exclusively small particle lanes at the walls. This contrasts the equilibrium state, where depletion forces push the larger particles to the walls. Additionally, we have a closer look at the mechanisms by which the lanes form. Finally, we find system parameter values that foster lane formation to lay the foundation for an experimental realization of our proposed setup. To round this off, we give an exemplary calculation of the slope angle needed to get the experimental system into a state of lane order. With the examination of lane order in systems that are driven in parallel, we hope to deepen our understanding of nonequilibrium order phenomena.

Environmental impact of solution pH on the formation and migration of iron colloids in deep subsurface energy systems

Deep subsurface stimulation processes often promote fluid-rock interactions that can lead to the formation of small colloidal particles that are suspected to migrate through the rock matrix, partially or fully clog pores and microfractures, and promote the mobilization of contaminants. Thus, the goal of this work is to understand the geochemical changes of the host rock in response to reservoir stimulation that promote the formation and migration of colloids. Two different carbonate-rich shales were exposed to different solution pHs (pH = 2 and 7). Iron and other mineral transformations at the shale-fluid interface were first characterized by synchrotron-based XRF mapping. Then, colloids that were able to migrate from the shale into the bulk fluid were characterized by synchrotron-based extended X-ray absorption structure (EXAFS), scanning electron microscopy (SEM), and single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-icpTOF-MS). When exposed to the pH = 2 solution, extensive mineral dissolution and secondary precipitation was observed; iron-(oxyhydr)oxide colloids colocated with silicates were observed by SEM at the fluid-shale interfaces, and the mobilization of chromium and nickel with these iron colloids into the bulk fluid was detected by sp-icpTOF-MS. Iron EXAFS spectra of the solution at the shale-fluid interface suggests the rapid (within minutes) formation of ferrihydrite-like nanoparticles. Thus, we demonstrate that the pH neutralization promotes the mobilization of existing silicate minerals and the rapid formation of new iron colloids. These Fe colloids have the potential to migrate through the shale matrix and mobilize other heavy metals (such as Cr and Ni, in this study) and impacting groundwater quality, as well produced waters from these hydraulic fracturing operations.

Biomimetic mineral layer over layer-by-layer assemblies: Growth mechanism directed by collagen fibrils

In this study, we describe a promising biomimetic method for growing a hybrid calcium phosphate (CaP) – collagen coating designed following the same principles that govern biomineralization of hard tissues. For this purpose, we explore the versatility of layer-by-layer (LbL) method to incorporate type I collagen and alkaline phosphatase (ALP), while controlling their supramolecular organization and bioactivity. This provides a way to generate in situ CaP ion precursors in the vicinity of collagen proteins, which are self-assembled into fibrils at the solid/liquid interface and further crosslinked. The catalytic properties of ALP, including initial activity and operational stability, is evaluated when the enzymes are embedded within the LbL film. Moreover, a systematic study of the intermediate states of the mineralization is performed by means of atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Results show that the presence of collagen fibrils within the LbL film plays a pivotal role in the growth mechanism of the biomimetic mineral layer. The main findings support that the role of fibrils consists in favoring the adsorption of enzymes and providing a suitable environment for CaP nucleation and growth. Interestingly, early-stage AFM observations reveal the preferential formation of colloidal particles of CaP onto the collagen fibrils, followed by a significant increase of their surface coverage, yielding particles onto and in-between the fibrils. Further mineralization leads to a coating fully covering the support and mainly exhibiting flat and continuous layer covered with a dense network of mineralized collagen fibrils. The approach described in this work provides a straightforward way for the design of biomimetic hybrid coatings with the perspective of tuning cell-material interaction in biomedical applications dealing with hard mineralized tissues.

Transfer of Metals under Hydrothermal Conditions in the Form of Colloidal Particles and Supersaturated True Solutions

Colloids of metals have been studied much more poorly in hydrothermal solutions than in surface and underground waters. Nevertheless, literature data indicate that colloidal particles containing metals are present in hydrothermal minerals, in geogas, in groundwaters above orebodies, in fluid inclusions of minerals, and in geothermal solutions. These particles are usually thought to be formed at nucleation in supersaturated solution, which is generated in conversion reactions of minerals or when fluids boil. Published experimental data confirm that colloidal particles can be formed and preserved in hydrothermal conditions. Experimental data on the filtration of supersaturated and colloidal solutions in porous media at elevated temperatures are still too scarce to enable a comprehensive and reasonably accurate assessment of the mobility of colloidal particles under these conditions. The involvement of colloids in the hydrothermal ore-forming process is most clearly manifested at formation of rich epithermal Au deposits. The example of a quartz geothermometer is employed to demonstrate that metals can be transferred in true supersaturated solution, and this mechanism may be even more efficient than colloidal transfer. Metals can thus be transferred in the hydrothermal process in significantly higher concentrations than it follows from the traditional approach based on equilibrium thermodynamics.

Size-Dependent Photobleaching Mechanism and Kinetics Induced by Nanosecond Laser Pulses in Colloidal Semiconductor Quantum Dots.

An experimental-theoretical approach is proposed to investigate the size-dependent photobleaching of colloidal semiconductor quantum dots (QDs) excited by a nanosecond pulsed laser. In the experimental background, the ground-state absorption and photoluminescence (PL) spectra of chemically prepared QDs are monitored over an excitation time at distinct laser irradiances. The magnitude of photobleaching in the QD solution is quantified by the decay rate of the PL signal as a function of the excitation time and the laser power. A theoretical spectroscopy model is then used to estimate the particle size distribution (PSD) in colloidal solution from the absorption data generated at different laser powers. The resulting evolution of the PSD of the QD ensemble under irradiation is analyzed in terms of classical crystallization theories dealing with the formation, growth, and dissolution of colloidal particles in a supersaturated medium. The QD response to laser irradiation is also interpreted by a simple mechanical model that correlates the photoinduced hydrostatic strain at the solid/liquid interface and the predicted variation of the mean particle size. The reported experimental and theoretical methods are used to completely elucidate the basic physico-chemical processes responsible for the laser-induced photobleaching kinetics of glutathione-capped CdTe aqueous QDs with very small mean sizes. For this purpose, we synthesized a series of colloidal QD samples with mean particle diameters ranging from 1.95 to 2.68 nm. Our results indicate that a faster photobleaching rate occurs in QD samples with smaller sizes in which particle dissolution under laser irradiation is predominant. On the other hand, the photobleaching rate becomes slower in samples with larger dot sizes, possibly due to the formation of core/shell structures in solution via thermal degradation of thiol ligands either during the chemical synthesis or as a consequence of the subsequent interaction with the excitation laser.

Design of a Re-Dispersible High Drug Load Amorphous Formulation

Amorphous solid dispersions (ASD) are a commonly used enabling formulation technology to drive oral absorption of poorly soluble drugs. To ensure adequate solid-state stability and dissolution characteristics, the ASD formulation design typically has ≤ 25% drug loading. Exposed to aqueous media, ASD formulations can produce drug-rich colloidal dispersion with particle size < 500 nm. This in situ formation of colloidal particles requires incorporation of excess excipients in the formulation. The concept of using engineered drug-rich particles having comparable size as those generated by ASDs in aqueous media is explored with the goal of increasing drug loading in the solid dosage form. Utilizing ABT-530 as model compound, a controlled solvent-antisolvent precipitation method resulted in a dilute suspension that contained drug-rich (90% (w/w)) amorphous nanoparticles (ANP). The precipitation process was optimized to yield a suspension containing < 300 nm ANP. A systematic evaluation of formulation properties and process variables resulted in the generation of dry powders composed of 1–8 µm agglomerates of nanoparticles which in contact with water regenerated the colloidal suspension having particle size comparable to primary particles. Thus, this work demonstrates an approach to designing a re-dispersible ANP based powder containing ≥90% w/w ABT-530 that could be used in preparation of a high drug load solid dosage form.

Ultrafiltration to characterize PM2.5 water-soluble iron and its sources in an urban environment

Soluble forms of transition metals in airborne particles are linked to adverse health impacts. Iron (Fe) is often the most abundant transition metal in ambient PM2.5. In Atlanta, the water-soluble fraction of Fe had a stronger association with adverse cardiovascular outcomes than PM2.5 mass and total Fe. Water solubility is operationally defined. One determining factor is the pore size in the liquid filtration (0.45 μm in this study) used to isolate water-soluble species, implying colloidal particles smaller than the pore size may be included in the water-soluble group. Here, we characterize the properties of PM2.5 water-soluble iron (WS Fe) utilizing ultrafiltration and investigate sources of the various isolated fractions based on one-year of samples collected in urban Atlanta (N = 355). Annual average Fe solubility (WS Fe divided by total Fe) was 12%, with the highest solubility in the warm season (May–Sept.) when aerosol acidity (pH of 1.8–2.7) and oxalate concentrations were highest. Ultrafiltration showed that 84% of WS Fe (extract that passed through 0.45 μm pore filter) was smaller than nominally 4 nm, with 61% of the soluble iron was smaller than nominally 2 nm. A correlation analysis, experiments involving addition of oxalate to sample extract and a pH cycling experiment with selected Fe species were consistent with the oxalate-Fe ligand being mainly found in the smallest ultrafiltrate size (< nominally 2 nm), whereas pH cycling could lead to the formation of colloidal particles with sizes between nominally 2–4 nm. Magnetite, a solid Fe nanoparticle (smaller than 0.1 μm) detected in human organs in previous studies, was undetectable in the PM2.5 WS Fe in urban Atlanta. These data show that most WS Fe is composed of soluble species or very small colloidal particles (roughly <4 nm), making them highly bioavailable.

STUDY OF THE EFFECT OF ASPHALTENE-RESINOUS COMPOUNDS ON THE SEPARATION OF OIL EMULSIONS

The separation of oil emulsions is an important step in the purification of crude oil from water, mineral salts, and various associated contaminants, asphaltene-resinous substances, and paraffin contained in the oil. In the formation and stabilization of oil emulsions in the form of colloidal particles in the oil, insoluble dispersed solids also have a high effect. Examples of such substances are microcrystals of solid paraffins, asphaltenes, ferrous sulfides, and other mechanical mixtures. These substances form a strong mechanical barrier on small water droplets distributed in the oil phase, which prevents the separation of water. In this work, the effect of various compounds in the oil on the separation of oil emulsions was studied in detail, a suitable model was proposed, and information was provided on promising methods for the separation of oil emulsions

Different colloidal particle formation process between conjugated polymer and unmodified C60 in preparation of suspension for electrophoretic deposition by reprecipitation method

Electrophoretic deposition provides material-efficient film formation on large area electrodes. In this study, it has been found that there is a significant difference in the colloidal particle formation process between a thiophene-based copolymer poly(3-octylthiophene- 2,5-diyl-co-3-decyloxythiophene-2,5-diyl) (POT-co-DOT) and C60 in preparation of suspension for electrophoretic deposition by reprecipitation method. This difference is attributed to the difference between low molecular weight materials with specific molecular weight and polymers with molecular weight distribution. The composition of POT-co-DOT:C60 composite film by electrophoretic deposition has also been estimated.

Fabricating of grape seed proanthocyanidins loaded Zein-NaCas composite nanoparticles to exert effective inhibition of Q235 steel corrosion in seawater

Grape Seed Proanthocyanidins (GSP), underutilized by-products, exhibit encouraging biological activities, but their structural instability limits practical applications. A solution to this problem was found here by using GSP-loaded zein– sodium caseinate (NaCas) composite nanoparticles. Core-shell biopolymer nanoparticles were fabricated by antisolvent precipitation method to form NaCas stabilized zein core nanoparticles. The GSP-loaded zein-NaCas composite nanoparticles were self-assembled into spherical nanoparticles with homogeneous distribution (PDI around 0.2) and high negative charge (about –30 mV). FTIR analysis indicated that hydrogen bonding, hydrophobic and electrostatic attractions act as the main energy for the formation of colloidal particles. Stability test showed that the particles have stable corrosion inhibition efficiency for Q235 steel within 15 d in a wide range of ionic strength and pH value, and thus can adapt to the changes of seawater environment. Corrosion results manifested that GSP-loaded zein-NaCas composite nanoparticles display good re-dispensability and controlled release performance, whose inhibitive efficiency for Q235 steel in seawater is obviously higher than that of GSP (200 mg/L, 96.06% versus 71.89%).

Formation of colloidal micro‐nano particles and flavor characteristics of Greenland halibut bone soup

In this study, halibut bone, a byproduct of Greenland halibut processing, was prepared into a thick soup through a non-frying process. The formation of colloidal micro-nano particles and flavor characteristics in halibut bone soup was explored. The results showed that the nutrients in halibut bones migrated to the soup continuously with the cooking process and reached the highest concentration (total sugars, 38.16mg/100ml; water-soluble proteins, 25.71mg/ml; fatty acids, 2.15g/100ml; solids, 1.14g/100ml) at 150min. Taste substances such as organic acids, 5'-nucleotides and total free amino acids (TFAAs) content in halibut bone soup also reached maximum at 150min. At this time, results for particle size showed that MNPs with uniform size (725.62nm) were formed, which made the bone soup milky white, stable, and had good tasting. Headspace-gas chromatography-ion mobility spectrometry results showed that a total of 59 volatile substances were detected from the halibut bone soup. The content of volatile flavor substances in the 150min group was lower than that in the 90-120min group. Meanwhile, aldehydes and ketones gradually became esters. PRACTICAL APPLICATION: Soup is an indispensable part of the world food culture. In order to increase the added value of Greenland halibut, halibut bone soup was studied in this paper. This study found that halibut bone soup that had not been fried, formed the MNPs and has a more harmonious and pleasant flavor. Thus, non-fried halibut bone soup is a good processing method and can improve economic efficiency.

Effects of thermoultrasonic treatment on characteristics of micro-nano particles and flavor in Greenland halibut bone soup

In order to investigate the effects of thermoultrasonic treatment (TUT) on the formation of colloidal micro-nano particles (MNPs) and the quality of halibut bone soup, nutrients, particle characteristics, and flavor characteristics were analyzed. The morphology of MNPs was studied using an optical microscope. Results showed that TUT could increase the nutrient content (total sugars, 22.15 mg/100 mL; water soluble proteins, 173.24 mg/mL; fatty acids, 1779.7 mg/100 mL; solids, 3.16 g/100 mL), reduce the particle size (605.92 nm) and interfacial tension. Meanwhile, TUT make the halibut bone soup has better emulsifying characteristics and stability. The contents of flavor substances, such as esters, 5′-nucleotides, organic acids in the halibut bone soup were more abundant, while the contents of hexanal and 1-octen-3-ol and fishy off-flavor were reduced in TUT group. The overall odor and taste outline were more harmonious. Therefore, TUT can be used in the production of high quality fish bone soup, and TUT could be considered as a good deep processing technology for halibut bone and improve economic efficiency.

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Effect of glutamic acid on the preparation and characterization of Pickering emulsions stabilized by zein

In this study, glutamic acid and zein were utilized to prepare colloidal nanoparticles as stabilizers for Pickering emulsions. The effect of the ratio of glutamic acid to zein on the stability, zeta potential, particle size, morphology, and structure of colloidal nanoparticles was studied. The results showed that zein and glutamic acid combined in the form of noncovalent bonds, which changed the characteristics of the zein. In addition, colloidal particles aggregation was induced by glutamic acid, which altered the distribution of droplets in the emulsion, and increased the adsorption of proteins on the surface of the oil droplets, as reflected by the analysis of the size, microstructure, rheological behaviours, and driving force of the Pickering emulsion. Hydrophobic interactions and electrostatic interactions were the main driving forces for the formation of colloidal particles, which was determined by driving force analysis and the change of the zeta potential.

Colloidal transport and flocculation are the cause of the hyperenrichment of gold in nature

Aqueous complexation has long been considered the only viable means of transporting gold to depositional sites in hydrothermal ore-forming systems. A major weakness of this hypothesis is that it cannot readily explain the formation of ultrahigh-grade gold veins. This is a consequence of the relatively low gold concentrations typical of ore fluids (tens of parts per billion [ppb]) and the fact that these "bonanza" veins can contain weight-percent levels of gold in some epithermal and orogenic deposits. Here, we present direct evidence for a hypothesis that could explain these veins, namely, the transport of the gold as colloidal particles and their flocculation in nanoscale calcite veinlets. These gold-bearing nanoveinlets bear a remarkable resemblance to centimeter-scale ore veins in many hydrothermal gold deposits and give unique insight into the scale invariability of colloidal flocculation in forming hyperenriched gold deposits. Using this evidence, we propose a model for the development of bonanza gold veins in high-grade deposits. We argue that gold transport in these systems is largely mechanical and is the result of exceptionally high degrees of supersaturation that preclude precipitation of gold crystals and instead lead to the formation of colloidal particles, which flocculate and form much larger masses. These flocculated masses aggregate locally, where they are seismically pumped into fractures to locally form veins composed largely of gold. This model explains how bonanza veins may form from fluids containing ppb concentrations of gold and does not require prior encapsulation of colloidal gold particles in silica gel, as proposed by previous studies.

Study on Optimization of Compound Flocculant’s Purification Process of Sugarcane Juice

Sugarcane juice contains a lot of non-sugar organic impurities, and most of the non-sugar organic impurities are suspended in the sugarcane juice in the form of colloidal particles, making the juice turbid. Flocculant is an indispensable clarification aid in the cane juice cleaning process, and its use effect will directly affect the production cost of sugar cane sugar and the quality of white granulated sugar products. This paper is based on the sulfite process of sugar production. After the sulfur smoked juice is heated, the composite flocculant is mixed with the sugarcane juice and then settled. The clear juice is taken to determine the physical and chemical indicators, and the clarification effect of the composite flocculant is investigated. The response surface method is optimized to obtain the composite The best material ratio of the flocculant is PAM 1.70ppm, CTS 1.90ppm, diatomaceous earth 2.10ppm, and the compound flocculant with the best material ratio is used for the cane juice cleaning process experiment. The orthogonal test method optimizes the cane juice cleaning process as The cleaning effect is best when the added amount of phosphoric acid is 160 ul/L, the pre-ash pH value is 6.4, and the neutralization pH value is 7.4, the obtained clear juice is clear and bright, and the color value is low.