Colloidal Dispersions Research Articles

Solution-Processable Route for Large-Area Uniform 2D Semiconductor Nanofilms.

The semiconductor thin film engineering technique plays a key role in the development of advanced electronics. Printing uniform nanofilms on freeform surfaces with high efficiency and low cost is significant for actual industrialization in electronics. Herein, a high-throughput colloidal printing (HTCP) strategy is reported for fabricating large-area and uniform semiconductor nanofilms on freeform surfaces. High-throughput and uniform printing rely on the balance of atomization and evaporation, as well as the introduced thermal Marangoni flows of colloidal dispersion, that suppresses outward capillary flows. Colloidal printing with in situ heating enables the fast fabrication of large-area semiconductor nanofilms on freeform surfaces, such as SiO2/Si, Al2O3, quartz glass, poly(ethylene terephthalate) (PET), Al foil, plastic tube, and Ni foam, expanding their technological applications where substrates are essential. The printed SnS2 nanofilms are integrated into thin-film semiconductor gas sensors with one of the fastest responses (8 s) while maintaining the highest sensitivity (Rg/Ra = 21) (toward 10ppm NO2), as well as an ultralow limit of detection (LOD) of 46 ppt. The ability to print uniform semiconductor nanofilms on freeform surfaces with high-throughput promises the development of next-generation electronics with low cost and high efficiency.

Dynamical arrest transition of a bidisperse two-patchy colloidal dispersion: A dynamic Monte Carlo study.

During the last few years, patchy colloidal dispersions have emerged as ideal candidates of glass-formers of systems composed of particles that interact with non-isotropic potentials. However, from the computational point of view, the characterization of their dynamical properties close to the glass transition via any kind of molecular dynamics simulation technique can be very difficult due to the slowing down of both the rotational and translational dynamics. Although a plethora of dynamical techniques have been developed to account for the dynamics of patchy colloids, new and complementary simulation techniques are required to explore, much faster and more efficiently, the dynamical arrest transition of patchy colloidal dispersions when computer simulation consists of a large number of particles and, due to the slow particle dynamics at the glass transition, an extended time window is explicitly required. Then, in this contribution, by means of the so-called dynamic-Monte Carlo method, we report on the dynamical arrest transition, both rotational and translational, of a bidisperse patchy colloidal dispersion, following three different paths along the density-temperature plane, including high densities and low temperatures. Although this method has not been extensively tested at extreme thermodynamic conditions, we show that even at the dynamical arrest transition, it allows us to extract good dynamical data from a complex system. Therefore, it turns out to be a promising technique to explore the onset of vitrification of anisotropic colloidal particles.

Physicochemical, structural, and emulsifying properties of stable blended whey and soy protein colloidal dispersion prepared by pH‐shifting and ultrasound

This study investigated physiochemical, structural, and emulsifying properties of whey and soy protein blends (4%, w/v), which were combined at various proportions by pH‐shifting and ultrasound. The mixed dispersions exhibited small particle sizes (below 200 nm), with the smallest value observed at a sample with WPC to SPI ratio of 50:50. Reducing whey protein gave the blend lower surface hydrophobicity and higher α‐helix structure. More soy protein resulted in larger droplet size, lower surface charge, and greater flocculation of fabricated emulsions. Emulsions with soy protein lower than 50% were acceptable due to the nano‐scale size and small flocculation index.

Hyperreflective photonic crystals created by shearing colloidal dispersions at ultrahigh volume fraction

Colloidal crystallization serves as one of the most economic and scalable production methods for photonic crystals. However, insufficient optical performance, nonuniformity and low reproducibility remain challenges for advanced high-value applications. In this study, we optimally formulate a photocurable dispersion of silica particles and apply shear flow to unify the orientation of the colloidal crystals, ensuring high optical performance and uniformity. The silica particles experience strong repulsion at ultrahigh volume fractions of 50% but demonstrate low mobility, leading to polycrystalline structures. Applying shear flow to the dispersions allows the silica particles to rearrange into larger crystalline domains with a unidirectional orientation along the flow. This shear-induced structural change produces absolute reflectivity at the stopband as high as 90% and a high transparency of 90% at off-resonant wavelengths with minimal diffusive scattering. Furthermore, the strong interparticle repulsion ensures a uniform volume fraction of particles throughout the dispersion, reducing deviations in the optical properties. We intricately micropattern the photocurable dispersions using photolithography. Additionally, the photonic films and patterns can be stacked to form multiple layers, displaying mixed structural colors and multiple reflectance peaks without sacrificing reflectivity. These superior photonic materials hold promise for various optical applications, including optical components and anticounterfeiting patches.

Ferroptosis boosted oral cancer photodynamic therapy by carrier-free Sorafenib-Ce6 self-assembly nanoparticles

Oral cancer is a disease with high morbidity and mortality worldwide and greatly impacts the quality of life, especially in patients with advanced stages. Photodynamic therapy (PDT) is one of the most effective clinical treatments for oral cancers. However, most clinically applied photosensitizers have several deficiencies, including oxygen dependence, poor aqueous solubility, and a lack of tumor-targeting ability. Herein, the carrier-free multifunctional Sorafenib (Sor), chlorin e6 (Ce6), and Fe3+ self-assembly co-delivery nanoparticles (Sor-Ce6 NPs) were constructed via combining a ferroptosis inducer Sor and a photosensitizer Ce6 for synergetic therapy. The as-synthesized Sor-Ce6 NPs presented excellent colloidal stability and water dispersity with good in vivo tumor-targeting ability. More significantly, the low dose of Sor-Ce6 NPs had little dark toxicity but produced significantly enhanced ROS and supplied O2 sustainably to increase phototoxicity through ferroptosis pathway. Notably, the Sor-Ce6 NPs showed significantly higher in vitro and in vivo anti-tumor efficacy than the Sor/Ce6 mixture due to the improvement of cellular uptake and the incorporation of foreign Fe ions in the system, which also confer the T1 magnetic resonance-guided imaging ability to the formed Sor-Ce6 NPs. Our study demonstrates a promising self-assembled strategy for overcoming hypoxia-related PDT resistance for oral cancer treatment.

Weak Alignment Liquid Crystal Media from Colloidal Dispersion and Self-assembled Oligopeptide for Anisotropic NMR

Weak Alignment Liquid Crystal Media from Colloidal Dispersion and Self-assembled Oligopeptide for Anisotropic NMR

Synthesis of a water‐soluble chain transfer agent and its application in gel dispersions

AbstractPre‐crosslinked gel particles, colloidal dispersion gels, and polymer microspheres are often used as profile‐controlling and flooding agents to displace residual crude oil from formations. The preparation process of these profile‐controlling and flooding agents is complicated. In order to simplify the preparation steps, a water‐soluble chain transfer (RAFT) agent, S,S′‐bis(2‐propionic acid) trithiocarbonate (PATTC), was synthesized, and then, hydrogel dispersions were prepared by one‐pot RAFT polymerization. The structure of PATTC was confirmed by infrared spectroscopy and nuclear magnetic resonance. The effects of reaction conditions on the viscosity and viscosity‐average molecular weight of hydrogel dispersions were explored, the rheology, viscoelasticity, particle size, temperature responsiveness, and salinity responsiveness of hydrogel dispersions were measured, and the seepage properties of hydrogel dispersions in porous medium were analyzed. The results show that at higher shear rates, the polyacrylamide gel dispersions exhibited Newtonian fluid characteristics. Viscoelasticity tests further confirmed that the polyacrylamide gel dispersions were successfully synthesized. The particle size of the hydrogel dispersions is 1–75 μm, its viscosity is less affected by temperature and salinity, and its residual resistance coefficient is higher than that of the polyacrylamide solution under similar apparent viscosity.

Damping and mechanical properties of SiC particles reinforced aluminium matrix composites prepared by colloidal dispersion and suction filtration method

In order to uniformly distribute SiCp in the aluminium matrix and prepare SiCp/Al composites with high mechanical and damping properties, a preparation method of colloidal dispersion and suction filtration was developed. It was observed from the microstructure of the composites that the SiCp/Al composites prepared by colloidal dispersion and suction filtration method had good interfacial structures, and the interfacial reaction between SiCp and aluminium matrix was effectively inhibited. Tensile mechanical properties at room temperature and damping properties in the temperature range of 25 °C to 300 °C were tested for the SiCp/Al composites with volume fractions of 5% to 10%. The results showed that SiCp/Al composites have excellent mechanical and damping properties when the volume fraction of SiCp was 7%. This is because SiCp were uniformly distributed in the aluminium matrix, and formed a good interfacial bond with the aluminium matrix, which benefitted both the interfacial slip loss and the strengthening effect of SiCp.

Preparation of stable colloidal dispersion of surface modified Fe3O4 nanoparticles for magnetic heating applications

The effect of surface modification on enhancing the magnetic heating behavior of magnetic nano fluids were investigated, for this purpose Fe3O4 nanoparticles were synthesized using co-precipitation method and surface modification was done using citric acid, ascorbic acid, tetraethyl orthosilicate (TEOS), polyvinyl alcohol (PVA) and polyethylene glycol (PEG). Experimental heating tests using AC magnetic field were done in the frequency of 100 kHz and different magnetic field (H) intensities. Theoretically the specific absorption rate (SAR) in magnetic nano fluids is independent of nanoparticles concentration but the experimental results showed different behavior. The theoretical SAR value @ H = 12kA.m–1 for Nano fluids containing bare Fe3O4 nanoparticles was 11.5 W/g but in experimental tests the obtained value was 9.72 W/g for nano fluid containing 20,000 ppm of dispersed nanoparticles. The experimental SAR calculation was repeated for sample containing 10,000 ppm of nanoparticles and the results showed increase in experimental SAR that is an evidence of nanoparticles agglomeration in higher concentrations. The surface modification has improved the dispersion ability of the nanoparticles. The Ratio of SAR, experimental, 20000ppm to SAR, experimental, 10000ppm was 0.85 for bare Fe3O4 nanoparticles dispersion but in case of surface modified nanoparticles this ratio has increased up to 0.98 that shows lower agglomeration of nanoparticles as a result of surface modification, although on the other hand the surface modification agents were magnetically passive and so it is expected that in constant concentration the SAR for bare Fe3O4 nanoparticles to be higher than this variable for surface modified nanoparticles. At lower concentrations the dispersions containing bare Fe3O4 nanoparticles showed higher SAR values but at higher concentrations the surface modified Fe3O4 nanoparticles showed better results although the active agent amount was lower at them. Finally, it should be noted that the nanoparticles that were surface modified using polymeric agents showed the highest decrease in experimental SAR amounts comparing theoretical results that was because of the large molecules of polymers comparing other implemented surface modification agents.

Unlocking cementitious performance: nano‐lubrication via polycarboxylate superplasticizers

AbstractPolycarboxylate (PCE) superplasticizers are the most important additive in concrete, which can effectively improve the workability of cement slurry. Different from the traditional regarding of PCEs as dispersants, here, we understand the PCEs as nano‐lubricants. By employing the molecular dynamics simulation, a sophisticated model was used to evaluate the interfacial friction between the C–S–H particles. The results reveal that the PCEs can reduce the interfacial friction between the C–S–H particles, and thus increase the fluidity of cement slurry. Further analyses infer the role of PCE segments in lubrication. The carboxylates on PCEs ensure the anchoring and hinder the separation of Ca ions. The side chains are used to lubricate the C–S–H surface, due to the weak adsorption between the side chains and the C–S–H surface. Predictably, this study not only provides a method to directly evaluate the performance of PCEs but also suggests new insights into the colloid dispersion of the low‐water content system.

Molecularly Confined Topochemical Transformation of MXene Enables Ultrathin Amorphous Metal-Oxide Nanosheets.

Two-dimensional (2D) amorphous nanosheets with ultrathin thicknesses have properties that differ from their crystalline counterparts. However, conventional methods for growing 2D materials often produce either crystalline flakes or amorphous nanosheets with an uncontrollable thickness. Here, we report that ultrathin amorphous metal-oxide nanosheets featuring superior flatness can be realized through the molecularly confined topochemical transformation of MXene. Using MXene Ti2CTx as an example, we show that surface modification of Ti2CTx nanosheets with molecular ligands, such as oleylamine (OAm) and oleic acid (OA), not only imparts notable colloidal dispersity to Ti2CTx nanosheets in nonpolar organic solvents but also confines their subsequent oxidation to in-plane configurations. We demonstrate that unlike the drastic oxidation conventionally observed for pristine MXene, hydrophobizing MXene with OAm and OA ligands enables individual Ti2CTx nanosheets to undergo independent oxidation in a nondestructive manner, resulting in amorphous titanium oxide (am-TiO2) nanosheets that faithfully retain the dimension and flatness of pristine MXene. These am-TiO2 nanosheets exhibit exceptional activity as substrates for surface-enhanced Raman scattering. Importantly, this molecular confinement strategy can be extended to other MXene materials, providing a versatile approach for synthesizing ultrathin amorphous metal-oxide nanosheets with tailored compositions and functionalities.

Dual-mode colorimetric and photothermal aptasensor for detection of kanamycin using flocculent platinum nanoparticles

Chitosan (CS)-stabilized platinum nanoparticles (CS/PtNPs) were employed to develop a novel aptamer-based dual-mode colorimetric and photothermal biosensor for selective detection of kanamycin (KAN). As a peroxidase-like catalyst, the CS/PtNPs showed outstanding catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). As a stabilizing agent, CS excelled at fixing the KAN binding aptamer on the surface of the CS/PtNPs, amplifying their catalytic activity and enhancing colloidal dispersion and stability. The oxidized TMB (TMBox) functioned as a signal for the colorimetric, photothermal aptasensor because of its observable absorbance of light in the visible and near-infrared (NIR) regions. When light from a NIR laser was absorbed by the TMBox in the reaction solution, heat was generated in inverse proportion to the KAN concentration. The developed colorimetric and photothermal modes of the aptasensor showed a linear detection range of 0.1–50 and 0.5–50 μM, with a limit of detection (LOD) of 0.04 and 0.41 μM, respectively. Moreover, the aptasensor successfully determined KAN concentrations in spiked milk samples, verifying the reliability and reproducibility in practical applications. The dual-mode aptasensor based on CS/PtNPs for KAN detection, utilizing both color change and heat generation signals through a single probe (TMBox), demonstrates rapid response, simplicity in operation, cost-effectiveness, and high sensitivity. In addition, unlike typical immunoassays, this aptamer-based peroxidase-like nanozyme activation and inhibition strategy required no washing process, which was very effective in terms of reducing the time required for an assay and sustaining a high sensitivity.

Preparation and characterization of stable methyl myristate−in−water nanoemulsions as advanced working fluids for cooling systems

Phase change material emulsions (PCME) have gained increasing scientific interest due to their potential to enhance the storage capability of thermal facilities. Herein we present the design and characterization of oil−in−water (O/W) nanoemulsions by employing a dispersed phase mixture (2–12 wt%) enriched in methyl myristate as phase change material. The emulsifier and dispersed phase compositions were optimized based on dynamic light scattering and calorimetric analyses. A two−surfactant formulation composed of sodium dodecyl sulfate and BrijTM S2 (20:49 in weight) was selected to produce stable colloidal dispersions of a methyl stearate:n–hexadecane:methyl myristate mixture (at a mass proportion of 1:3:36) in water. No phase separation or significant growth in emulsified droplet size was detected under storage conditions or when the slurries were subjected to different heating−cooling cycles. The melting/crystallization transitions, rheological behavior, thermal conductivity and density of optimized nanoemulsions were experimentally investigated in order to further understand how the concentration and physical state of suspended droplets may influence those thermal and physical properties. According to differential scanning calorimetry studies, slurries showed moderate subcooling degrees (∼3 °C), even though their solid−liquid transitions extended over a slightly wider range of temperatures than the same mixture used as the dispersed phase but in bulk−form. The shear−thinning character observed for developed nanoemulsions at low temperatures disappeared with the melting of suspended droplets. Considering an operating temperature interval of 15 °C around melting−crystallization phase changes, the 12 wt% optimized suspension presented a storage capacity 18 % higher than that of water under the same conditions. Furthermore, thermal reliability tests verified that phase change characteristics did not significantly changed after 8 months of storage and throughout 500 thermal cycles.

Energy deposition in liquid scintillators composed of CsPbBr3 colloidal nanocrystal dispersions.

Liquid scintillation processes are commonly used for various applications involving radioactivity levels analysis, as well as experiments in the field of high energy physics, most commonly in the form of organic scintillating cocktails. In this paper, we explore the potential of halide perovskite nanocrystal colloidal dispersions as an alternative to those organic mixtures. After an optimization of the nanocrystals' mean size and surface chemistry, the scintillation yield of these composite mixtures is evaluated through Compton - Triple to Double Coincidence Ratio experiments and compared with commercial liquid scintillator. The obtained results shine a light on the energy deposition mechanisms in nanocrystals-based liquid scintillators.

Highly efficient recyclable bismuth nanocatalysts fabricated using a facile one-step aqueous method for faster reduction of azo dye contaminants.

Easily accessible robust synthesis of metallic nanoparticles (NPs) and their colloidal stabilization via successive surface functionalization with desired molecules are crucial for catalytic applications. In this research, tannic acid (TA)-functionalized bismuth (Bi)-based novel NPs were prepared via a simple in situ aqueous reduction of Bi3+ ions for the catalytic reduction of azo groups. The synthesis, morphology, and structure of Bi/TANPs were confirmed through spectroscopic, electron microscopic and X-ray diffraction analyses. The Bi/TANPs comprise Bi, carbon, oxygen and sodium as building components and possess a high negative surface charge of -58 mV, colloidal dispersity, thermal stability and crystalline structure. The Bi/TANPs are almost spherical shaped with an average diameter of 33 nm. The surface of the catalyst is mesoporous with a high specific surface area of 267 m2 g-1. The designed Bi/TANPs exhibit pH-specific affinity for azo dye molecules and reduced azo moieties in the presence of aqueous NaBH4 without requiring any hydrogen gas supply. The catalytic reduction efficiencies of Bi/TANPs against methylene blue and Congo red are almost 100%. These reduction reactions are very fast owing to the presence of TA moieties on the catalyst surface, which facilitate direct electron transfer to azo groups, and follow a pseudo-first-order kinetic model. The catalyst is mechanically recyclable, and shows a minimal loss (<3%) of its initial efficiency until the fifth cycle. This study not only developed an efficient catalyst for the remediation of azo dye-contaminated water, but also offers novel insights into the synergistic effects of TA and glycerin on the reduction mechanism of aqueous Bi3+ ions and the concomitant colloidal stabilization of Bi NPs.

Water stable colloidal PVP coated spin crossover nanoparticles.

Stable aqueous dispersions of spin-crossover (SCO) doped [FeII(Htrz)2(trz)](BF4) nanoparticles (NPs) were prepared by using water-soluble polyvinylpyrrolidone (PVP) as protecting polymer. The metal or ligand substitution percentage regulated the ultra-small size and morphology of the NPs. At the same time, the colloidal dispersions showed a complete conversion of the LS state to the HS state of the FeII ion.

Microfluidic dissolution of nanoemulsions in solvents.

We experimentally investigate the behavior of nanoemulsion and microscale emulsion jets flowing in solvents using coaxial microfluidic devices. The stability of colloidal dispersions made of oil droplets dispersed in water is significantly altered by the presence of a miscible solvent, which induces complex solutal and droplet coalescence instabilities over various timescales. We reveal intriguing microflow patterns of oil-in-water micro- and nanoemulsion threads in a continuous phase of isopropanol, including the dissolving, diffusive, gravitational, and stable thread regimes. We discuss the evolution of core-annular flow characteristics and develop scaling relationships to model thread dynamics through measurements of effective diameter as well as persistence and gravitational lengths. A microflow method based on dynamic similitude is developed to estimate the diffusion coefficients of nanoemulsions and microscale emulsions in miscible solvents. This work shows the possibility to process soft colloidal dispersions and control degradation mechanisms using microfluidic techniques.

Ingredients, structure and reconstitution properties of instant powder foods and the potential for healthy product development: a comprehensive review.

Instant foods are widely presented in powder forms across different food segments, which potentially can be formulated with functional or beneficial compounds to provide health benefits. Many reconstituted instant powder foods form colloidal suspensions with complex structures. However, designing instant powder food could be challenging due to the structural complexity and high flexibility in formulation. This review proposed a new classification method for instant powder foods according to the solubility of ingredients and the structure of the reconstituted products. Instant powder foods containing insoluble ingredients are discussed. It summarised challenges and current advances in powder treatments, reconstitution improvement, and influences on food texture and structure to facilitate product design in related industries. The characteristics and incorporation of the main ingredients and ingredients with health benefits in product development were reviewed. Different products vary significantly in the ratios of macronutrients. The macronutrients have limited solubility in water. After being reconstituted by water, the insoluble components are dispersed and swell to form colloidal dispersions with complex structures and textures. Soluble components, which dissolve in the continuous phase, may facilitate the dispersing process or influence the solution environment. The structure of reconstituted products and destabilising factors are discussed. Both particle and molecular structuring strategies have been developed to improve wettability and prevent the formation of lumps and, therefore, to improve reconstitution properties. Various types of instant food have been developed based on healthy or functional ingredients and exhibit positive effects on the prevention of non-communicable diseases and overall health. Less processed materials and by-products are often chosen to enhance the contents of dietary fibre and phenolic compounds. The enrichment of phenolic compounds, dietary fibres and/or probiotics tend to be simultaneous in plant-based products. The process of the ingredients and the formulation of products must be tailored to design the desired structure and to improve the reconstitution property.

Directional drying of a colloidal dispersion: quantitative description with water potential measurements using water clusters in a poly(dimethylsiloxane) microfluidic chip.

We have developed a poly(dimethylsiloxane) (PDMS) microfluidic chip to study the directional drying of a colloidal dispersion confined in a channel. Our measurements on a dispersion of silica nanoparticles once again revealed the phenomenology commonly observed for such systems: the formation of a porous solid with linear growth in the channel at short times, slowing down at longer times as the evaporation rate decreases. The growth of the solid is also accompanied by mechanical stresses that are released by the delamination of the solid from the channel walls and the formation of cracks. In addition to these observations, we report original measurements using hydrophilic filler in the PDMS formulation used (Sylgard-184). When the PDMS matrix is in contact with water, water molecules pool around these hydrophilic sites, resulting in the formation of microscopic water clusters whose size depends on the water potential ψ. In our work, we have used these water clusters to estimate the water potential profile in the channel as the porous solid grows. Using a transport model that also takes into account solid delamination in the channel, we then linked these water potential measurements to the hydraulic permeability of the porous solid. These measurements finally enabled us to show that the slowdown in the evaporation rate is due to the invasion of the porous solid by air/water nanomenisci at a critical capillary pressure ψcap.

Few-layered graphene increases the response of nociceptive neurons to irritant stimuli.

The unique properties of few-layered graphene (FLG) make it interesting for a variety of applications, including biomedical applications, such as tissue engineering and drug delivery. Although different studies focus on applications in the central nervous system, its interaction with the peripheral nervous system has been so far overlooked. Here, we investigated the effects of exposure to colloidal dispersions of FLG on the sensory neurons of the rat dorsal root ganglia (DRG). We found that the FLG flakes were actively internalized by sensory neurons, accumulated in large intracellular vesicles, and possibly degraded over time, without major toxicological concerns, as neuronal viability, morphology, protein content, and basic electrical properties of DRG neurons were preserved. Interestingly, in our electrophysiological investigation under noxious stimuli, we observed an increased functional response upon FLG treatment of the nociceptive subpopulation of DRG neurons in response to irritants specific for chemoreceptors TRPV1 and TRPA1. The observed effects of FLG on DRG neurons may open-up novel opportunities for applications of these materials in specific disease models.