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Chitosan-coated Fe3O4 nanoparticles were prepared by coprecipitation followed by reaction with chitosan and different volumes of glutaraldehyde. Coating was modified by varying the volume of glutaraldehyde and reaction time. XRD pattern shows maxima compatible Fe3O4 structure. FTIR spectroscopia confirms the presence of chitosan, more evident in samples with higher chitosan content, as denoted by TGA. TEM images of samples with low glutaraldehyde content reveal particles coated with a homogeneous chitosan shell. Meanwhile, those prepared with high glutaraldehyde volume show nanoparticles dispersed in an organic matrix. Samples present almost superparamagnetic behavior with magnetization saturation values that are reduced as the content of organic matter increases. Regarding the stability of these samples in solution, the presence of a homogeneous coating improves the initial suspension, although it does not prevent its subsequent aggregation over time. However, this aggregation process is reduced for sample synthesized with 1 mL of glutaraldehyde after 6 h of reaction.

Filter cake is critical to maintaining the stability of the excavation face of an underwater shield tunnel in a high-permeability stratum. In a high-permeability formation, generating an effective filter cake on the excavation face is difficult with a pure bentonite slurry, which penetrates the ground and may not achieve the required suspension pressure. Determining how to efficiently and quickly form a thin and low-permeability filter cake on the tunnel working face has become a key engineering problem in the construction of slurry shield tunnels in high-permeability strata. In this study, the relationship between slurry viscosity and the slurry pressure gradient of pure bentonite was established by performing slurry permeability experiments. The influence of slurry viscosity on the formation of the filter cake in a high-permeability formation was studied under different pressure gradients. In addition, the effect of additive particle size on the slurry filter cake formation was analyzed by introducing additives with different particle sizes to pure bentonite slurries with different viscosities. The test results indicate that (1) for the pure bentonite slurry, the critical initial pressure gradient can be used as a rough indicator of the formation of the filter cake, and the relationship between the critical maximum pore diameter and the average pore diameter of the formation can be compared to establish and analyze the formation law of the slurry filter cake; (2) adding particles to the slurry can enhance the effect of the pure bentonite slurry; and (3) adding coarse-grained materials can effectively improve the film-forming effect. The slurry is more compact when the particle size is close to the average pore size of the formation.

Particle size distribution (PSD) analysis for nanoparticle is important for quality management of CMP slurry, that used in chemical mechanical polishing (CMP) process. CMP slurry contains poly-dispersed particles, which consist of size-different primary particles and secondary particles in suspension. It is difficult to measure PSD for poly-dispersed particle using Dynamic Light Scattering, which is one of a typical method to evaluate PSD for mono-dispersed particles. The image analysis is also employed for PSD analysis. For image analysis, it needs to transfer the particles from suspension to a substrate before measurement. In this procedure, some particles aggregate with surrounding particles. It causes the difference between the PSD for dispersed particles in suspension and the PSD for observed particle using image analysis. In addition, concentration measurement is important for quality management of CMP slurry. Mass concentration is used in concentration evaluation for CMP slurry. However, it is difficult to identify the molar concentration for multi-modal particles, respectively. In this study, we suggested a method to define molar concentration spectra to express both a modal diameter and molar concentration for multi-modal nanoparticles to evaluate the CMP slurry. In order to measure the molar concentration spectra, we suggested a novel particle sizing method using nanoparticle chip (NPC) to measure number-weighted mean particle diameter, a variance of diameters, and molar concentration for every spectrum. Nanoparticles grid on a substrate to maintain the poly-dispersed condition in suspension to process NPC. NPC can assist the image analysis process to measure the PSD of particles in suspension. The number of particles, that aligned on the substrate, can be counted to measure the molar concentration. In this paper, a fundamental experiment was performed to investigate the feasibility of molar concentration spectra measurement. It is confirmed the molar concentration spectra for poly-dispersed particles can be measured by using NPC and it is considered that PSD with molar concentration spectra can give detail information of abrasive grain in suspension for quality management of CMP slurry.

An extensive literature review shows a lack of comprehensive research work regarding the distribution of poly-disperse solids in Newtonian and non-Newtonian fluids. In this investigation, the efficiency of a coaxial reactor (a high rotational speed central axial-flow impeller and a low speed wall-scrapping anchor impeller) in distributing the poly-disperse particles in water (Newtonian) and carboxymethyl cellulose (CMC) solutions (non-Newtonian) was assessed employing a flow-visualization methodology (electrical resistance tomography). The solids hold-up profiles were measured by making use of the tomograms. The critical rotational speed of a central stirrer in achieving the just suspension state for various operating conditions was determined via measuring the particle bed height. The extent of axial distribution of poly-disperse particles was characterized utilizing the data from tomography measurement. The effects of some key variables such as poly-disperse ratio, impeller rotational mode, and CMC loading on the distribution of poly-disperse particles in coaxial agitated systems were extensively analyzed. The capability of the coaxial impellers in distributing the poly-disperse solids in water and CMC solutions was compared to that with a traditional single agitator. Overall, an improved level of distribution of poly-disperse particles in water and CMC solutions was obtained at lower power usage employing the coaxial impellers.

This study examines the electrophoretic deposition of Yb2Si2O7 particles on SiC substrates to produce Environmental Barrier Coatings. To prepare crack-free and homogeneous green coatings, the effect of the solvent, dispersant concentration, and pH were investigated. Ethanol provided a well-dispersed suspension and crack-free coating which was shown by sedimentation tests and microstructure analysis. The effect of the dispersant concentration was investigated with zeta potential measurement and microstructure analysis with a concentration above 0.5 g/L resulting in higher ionic strength and producing cracked and uneven coatings. The ionic strength was also associated with the powder packing density with larger indentation impressions measured for loosely packed coatings. The deposition rate depended on the suspension properties influenced coating integrity with delamination evidenced by analysing the current density drop during deposition. Sintering of the green coatings having different densities and microstructure showed their importance in the preparation of uniform and dense sintered coatings.

Hypothesis Flow curve measurement is commonly used to characterize the flow behavior of concentrated suspensions. However, dynamic changes in the suspension inner microstructures under highly sheared conditions have not been correctly understood even though they strongly affect the measured shear stress. We hypothesize that the real particle dynamics during shearing could be effectively revealed by a systematic investigation that combines macroscopic flow curve measurements with operando microstructural observation employing an optical coherent tomography (OCT) apparatus and surface interaction measurements with the colloidal probe atomic force microscopy (AFM) method. Experiments The model system was spherical SiO2/toluene suspensions stabilized by polyethyleneimine (PEI) partially complexed with different fatty acids. Inner structures of the suspensions during flow curve measurements were observed by the OCT technique. The surface-surface interactions in toluene were analyzed using the colloidal probe AFM method. Findings Operando OCT observations revealed that during flow curve measurements, the suspensions can have completely different microscopic flow modes depending on the fatty acid species complexed to PEI and the solid concentrations. These microscopic flow modes could not be recognized using the typical flow curve measurements alone. The different flow modes can be explained by surface interactions measured by the colloidal probe AFM method.

Ring-like residual deposits are often observed after drying suspension droplets on surfaces. That introduces a crucial defect in practical applications, such as ink-jet printing that requires a uniform deposit. In this study, depositions after drying sessile/pendant droplets with silica/polystyrene particles were examined to identify the effect of gravitational sedimentation of particles on self-pinning and deposition pattern. The suspension droplet with larger polystyrene (or silica) particles would trigger the self-pinning at larger (or smaller) particle concentrations. The deposition pattern of pendant drops with silica particles is hill-like. This is due to the large density difference between silica and water to induce high sedimentation velocity, and the particles would precipitate and aggregate along the air–liquid interface to form a hollow shell deposit. The depositions for suspensions with bi-dispersed particles, the larger silica particles would accumulate at the bottom of the deposit due to the higher sedimentation velocity, in contrast to the well-mixed in the deposits for bi-dispersed polystyrene particles. The sedimentation and capillary flow velocities were calculated and discussed. These new findings reveal that the particle density (gravity effect) can be used to adjust the sedimentation velocity to control the deposition morphology and particle size distribution even to suppress the coffee-ring effect.

This paper proposes a comparative study of two techniques of granulation of a submicronic alumina powder with high binder content slurries, by spray drying and freeze granulation for the preparation of mixed granules. First, the viscosity and flow index of the suspensions are given as a function of dispersant, solid and binder contents versus alumina content, and the data are analysed in order to give a predictive model in a wide range. Suspensions with varying viscosities (7–208 mPa.s), densities (1.31–1.76) and surface tensions (23–40 mN/m) were then granulated. The first observations reveal the importance of the content and the molar mass of the binder: when they are too high, the freeze granulation fails and filaments are produced instead of granules due to extensive stretching of the molecular chains of the binder during spraying. Then through a theoretical analysis of the phenomena leading to granulation, an original dimensionless number is proposed to describe the evolution of the granule size as a function of suspension formulation. This number is related to the Reynolds and Weber number and is able to predict the granule size over a wide range (20–500 μm for freeze granulation, and 5–30 μm for spray drying). Spray drying leads to smaller granules with various shapes, from full shape to hollow or donut-like, whereas freeze granulation leads to bigger but spherical granules with a microporosity, and a size easier to predict as no drying shrinkage is observed.

Present work deals with the study of rheological aspects related with finer particles of Fly Ash (FA) slurry suspension. The effect of sodium sulfate as an additive has been studied with three different proportions in basic slurry suspension. Throughout the investigation the shear rate varies from 50 to 200 s−1. In this study, additive shows a promising trend in order to improve the rheology of fine particles slurry suspension. The high viscosity reduction associated with the suspension of FA slurry is characterized by high concentration (CW) of additives. However, reduction rate was more dominating in the case of 0.4 (% by weight) of the additives. Results reveals that additive of above manner provides a suitable and alternate arrangement for transportation of fine particles slurry suspension through pipeline at higher concentration.

Alternating crossflow filtration is an emerging technology to mitigate fouling in crossflow microfiltration of cell-protein mixtures by periodically reversing the direction of flow. So far, it is understood that the anti-fouling effects are mostly related to the pressure fluctuations upon changing from forward to reversed flow direction and to a smaller extent to the flow reversal along the membrane as such. However, it is not yet clear how pressure fluctuations and flow reversal influence the axial distribution of fouling and the prevailing types of fouling. We conducted alternating crossflow filtrations of a model suspension containing yeast cells (4.2% dry matter) and bovine serum albumin (0.8 g l−1), where the duration and crossflow velocity of the forward and the backwards phase were varied independently. We found that the material, which deposits in the forward phase, can be better removed or loosened during the backwards phase, and vice versa, if forward and backwards flow conditions are equal in terms of time, crossflow velocity and overall transmembrane pressure. This leads to a detectable overall lower resistance due to deposit layer formation. Despite the positive effects of alternating crossflow filtration on filtration resistance, flux, and solute transmission, the less compact deposit layer also allows for an easier penetration of solutes and small particles into the membrane pores, which was detectable in terms of an increased ratio of irreversible fouling resistance.

The influence of particle size and functional group as one of the pivots for particle interaction that enhances electrorheological performance were studied by varying the particles to micron and nanometer-sized polyacrylonitrile (PAN) spheres for rheological comparability analysis. Emulsion polymerization and catalytic amination with diethylene triamine (DETA) were used to successfully synthesize ER particle samples and then dispersed in silicon oil for suspension analysis. Micron-sized particles presented a large surface electron density for high conversion of nitrile groups with DETA than in nano. Polar groups from DETA improved particle polarization which enhanced ER effect by increasing yield strength by more than 10 folds on raw PANs. However, small sized nano particle exhibited relatively reduced ER effect owing to aggregation by Brownian motion pronouncing aminated micro PAN with the best ER activity followed by the aminated nano PAN, micro PAN and nano PAN as follows.

Purpose This study tests the feasibility of using a submersible spectrophotometer as a novel method to trace and apportion suspended sediment sources in situ and at high temporal frequency. Methods Laboratory experiments were designed to identify how absorbance at different wavelengths can be used to un-mix artificial mixtures of soil samples (i.e. sediment sources). The experiment consists of a tank containing 40 L of water, to which the soil samples and soil mixtures of known proportions were added in suspension. Absorbance measurements made using the submersible spectrophotometer were used to elucidate: (i) the effects of concentrations on absorbance, (ii) the relationship between absorbance and particle size and (iii) the linear additivity of absorbance as a prerequisite for un-mixing. Results The observed relationships between soil sample concentrations and absorbance in the ultraviolet visible (UV–VIS) wavelength range (200–730 nm) indicated that differences in absorbance patterns are caused by soil-specific properties and particle size. Absorbance was found to be linearly additive and could be used to predict the known soil sample proportions in mixtures using the MixSIAR Bayesian tracer mixing model. Model results indicate that dominant contributions to mixtures containing two and three soil samples could be predicted well, whilst accuracy for four-soil sample mixtures was lower (with respective mean absolute errors of 15.4%, 12.9% and 17.0%). Conclusion The results demonstrate the potential for using in situ submersible spectrophotometer sensors to trace suspended sediment sources at high temporal frequency.

Pulverization is a potentially powerful solution for the resource management of surplus- and non-standard agricultural products, maintaining their nutritional values for long and ensuring their homogeneity, whereas their original textures could disappear to narrow the application ranges. Therefore, new technologies should be developed for reconstructing the powders to provide them with new physical characteristics. Herein, we developed a novel food material, nata puree (NP), by nata de coco (bacterial cellulose gel) disintegration with a water-soluble polysaccharide using a household blender. The process worked well with (1,3)(1,4)-β-glucan (BGL) as the polysaccharide, which could be substituted with barley extract. Lichenase treatment of the NP dramatically modified its physical properties, suggesting the importance of the BGL polymeric forms. NP exhibited distinct potato powder and starch binding activities, which would be attributed to its interactions with the cell wall components and a physical capture of powders by the NP network, respectively. NP supplementation into the potato paste improved its firmness and enabled its printable range shift for 3D food printing to a lower powder-concentration. NP also promoted the dispersion of powders in its suspension, and designed gelation could also be successfully performed by the laser irradiation of an NP suspension containing dispersed curdlan and turmeric powders. Therefore, NP could be applied as a powder modifier to a wide range of products in both conventional cooking, food manufacturing, and next generation processes such as 3D food printing.

Cellulose nanocrystals are renewable plant-based colloidal particles capable of forming photonic films by solvent-evaporation-driven self-assembly. So far, the cellulose nanocrystal self-assembly process has been studied only at a small scale, neglecting the limitations and challenges posed by the continuous deposition processes that are required to exploit this sustainable material in an industrial context. Here, we addressed these limitations by using roll-to-roll deposition to produce large-area photonic films, which required optimization of the formulation of the cellulose nanocrystal suspension and the deposition and drying conditions. Furthermore, we showed how metre-long structurally coloured films can be processed into effect pigments and glitters that are dispersible, even in water-based formulations. These promising effect pigments are an industrially relevant cellulose-based alternative to current products that are either micro-polluting (for example, non-biodegradable microplastic glitters) or based on carcinogenic, unsustainable or unethically sourced compounds (for example, titania or mica).

Separation of microalgae of various sizes and shapes is an important process that enables subsequent production of useful compounds. Herein, the separation of microalgae was accomplished using a magnetite-containing gel (42 μm) packed into a column. An algal suspension was injected into the top of the gel bed, after which water was passed through the column. The pressure generated during the process caused the lower domain of the gel bed to deform, resulting in narrowed gaps between the gel beads. When a suspension of Nannochloropsis sp. (0.0069-0.69 g L-1) was loaded and water was passed through the column at an applied pressure of 0.01-0.10 MPa, the majority of microalgae were captured within the upper domain of the gel bed, while only 20% were captured within the lower domain. The amount of Nannochloropsis sp. captured was expressed by an ordinary differential equation to determine the capture coefficient, K, and the maximum capture amount, Qmax. As pressure increased, gel gaps narrowed, K increased, and Qmax decreased because of a reduction in the number of effective capture sites upon compaction of the gel. When a mixed suspension of Anabaena sp., Monoraphidium sp., and Desmodesmus sp. (0.069 g L-1 each) was injected into the gel bed at an applied pressure of 0.01 MPa, only Anabaena sp. was captured at the bottom of the gel bed. This device can be applied for the separation of microalgae in rivers and the sea.

Transfer of SARS-CoV-2 from solids to fingers is one step in infection via contaminated solids, and the possibility of infection from this route has driven calls for increased frequency of handwashing during the COVID-19 pandemic. To analyze this route of infection, we measured the percentage of SARS-CoV-2 that was transferred from a solid to an artificial finger. A droplet of SARS-CoV-2 suspension (1 µL) was placed on a solid, and then artificial skin was briefly pressed against the solid with a light force (3 N). Transfer from a variety of solids was detected, and transfer from the non-porous solids, glass, stainless steel, and Teflon, was substantial when the droplet was still wet. The viral titer for the finger was 13–16% or 0.8–0.9 log less than for the input droplet. Transfer still occurred after the droplet evaporated, but was smaller, 3–9%. We found a lower level of transfer from porous solids but did not find a significant effect of solid wettability for non-porous solids.

We prepared single-walled carbon nanotube (SWNT) suspensions in phosphate buffer solutions containing 1% of a coconut-based natural detergent (COCO) or 1% of sodium dodecyl sulfate (SDS). The suspensions exhibited strong photoluminescence (PL) in the near-infrared region, suggesting that the SWNTs, such as those with (9, 4) and (7, 6) chiralities, were monodispersed. Upon diluting the suspensions with a detergent-free phosphate buffer solution, the PL intensity of the SDS-containing SWNT suspension was significantly lower than that of the COCO-containing SWNT suspension. The COCO-containing SWNT suspension was more stable than the SDS-containing SWNT suspension. The SWNT concentration of the suspensions prepared via bath-type sonication was lower than that of the suspensions prepared via probe-type sonication. However, near-infrared (NIR) PL intensity of the SWNT suspensions prepared via bath-type sonication was much higher than that of the SWNT suspensions prepared via probe-type sonication regardless of the detergent. This suggested that the fraction of monodispersed SWNTs of the suspensions prepared via bath-type sonication was larger than that of the suspensions prepared via probe-type sonication, although the SWNT concentration was low. Our results indicated that COCO favored the fabrication of SWNT suspensions with stable and strong NIR PL, which are useful for various biological applications.

Marble and limestone have been extensively used as building materials in historical monuments. Environmental, physical, chemical and biological factors contribute to stone deterioration. The rehabilitation of stone damage and the delay of further deterioration is of utmost importance. Inorganic nanoparticles having chemical and crystallographic affinity with building materials is very important for the formation of protective coatings or overlayers. In the present work, we have tested the possibility of treating calcitic materials with suspensions of amorphous calcium carbonate (am-CaCO3, ACC) and amorphous silica (AmSiO2). Pentelic marble (PM) was selected as the test material to validate the efficiency of the nanoparticle suspension treatment towards dissolution in undersaturated solutions and slightly acidic pH (6.50). Suspensions of ACC and AnSiO2 nanoparticles were prepared by spontaneous precipitation from supersaturated solutions and by tetraethyl orthosilicate (TEOS) hydrolysis, respectively. The suspensions were quite stable (nine days for ACC and months for AmSiO2). ACC and Am SiO2 particles were deposited on the surface of powdered PM. The rates of dissolution of PM were measured in solutions undersaturated with respect to calcite at a constant pH of 6.50. For specimens treated with ACC and AmSiO2 suspensions, the measured dissolution rates were significantly lower. The extent of the rate of dissolution reduction was higher for AmSiO2 particles on PM. Moreover, application of the nanoparticles on the substrate during their precipitation was most efficient method.

The rheological behaviors of highly concentrated fine particle suspensions (clay-silt-water mixtures) and coarse particle suspensions (coarse particles within a fine particle suspension) were investigated in this study. Experimental results demonstrated that the Bingham Fluid Model with two rheological parameters, Bingham yield stress and viscosity, well characterized the rheological behavior of fine particle suspensions at shear rates between 4 and 20 s−1. The inclusion of coarse particles within a fine particle suspension induced an enhancement to the rheological parameters. The rheological parameters of a coarse particle suspension not only depend on its total particle fraction but also on its relative fine/coarse particle fractions. Empirical equations of these two parameters were proposed, quantitatively related to both fine and coarse particle fractions. Results indicated that the Bingham yield stress and viscosity are much more (an order larger) sensitive to changes in fine particle fraction than to changes in coarse particle fraction.

Research on bulk nanobubbles with various applications has been widely reported in the literature. However, the majority of studies are still limited to small scales with non-continuous generation processes, thus, the results may be difficult to apply on large-scale applications. In this work, a nanobubble generator was developed based on hydrodynamic cavitation using a two-chamber swirling flow nozzle that efficiently produced nanobubbles and had the potential to be applied to continuous flow systems and processes. The bulk nanobubble characteristics were evaluated according to the hydrodynamic diameter, zeta potential, and dissolved oxygen (DO) concentration based on the influence of the gas flow rate ratio (Ql/Qg), generation time, gas type, pH value, and NaCl concentration on the generated nanobubbles. The results show that oxygen and air nanobubbles smaller than 200 nm were successfully generated in pure water. The oxygen and air nanobubbles were negatively charged in pure water. The effects of pH and salt addition were similar to those during nanobubble generation using ultrasonic cavitation. In alkaline medium, nanobubbles were smaller and more stable than in acidic medium. The addition of salt to the nanobubble suspension reduced the repulsive electrostatic forces between the nanobubbles by increasing their size and decreasing their negative zeta potential. The resulting oxygen and air nanobubbles in pure water were verified to be stable for up to 10 and 5 months, respectively, without any significant changes in size or zeta potential. These results corresponded to predictions by the ionic repulsion model based on microbubble shrinkage.

Suspended solids, such as silica particles and cellulose fibers, were added to a sucrose aqueous solution, and ice crystals were coarsened at −10 °C. From the radius of the ice crystals, the coarsening rate constant was obtained using the Lifshitz–Wagner equation and the impact of the suspended solid on the coarsening of ice was evaluated. The results showed that the addition of the silica particle suppressed coarsening, but this behavior was not dependent on particle size. It was also shown that cellulose fibers suppressed coarsening more than silica particles. In order to clarify these causes, the present study investigated the correlation between Lw–Lmea and the coarsening rate constants obtained from different suspensions. Lw is the latent heat of fusion (calculated value) corresponding to the water content of the suspension, while Lmea is the latent heat of fusion (measured value) obtained by thermal analysis. A correlation was observed between Lw–Lmea and the logarithm of the coarsening rate constant. Lw–Lmea represents the volume of water that did not form ice crystals on the addition of the suspended solid (volume of unfrozen water at −10 °C), with a larger Lw–Lmea associated with greater inhibition of coarsening. The present findings suggest that suspended solids inhibit coarsening by promoting ice crystal melting.

The evaporation of a nano-suspension droplet on a substrate has gained extensive attention recently due to its potential application in the rising industry of functional coating. In this paper, we reported that the droplet evaporation behavior can be controlled by the nanoparticles' concentration and the functional group on the surface of nanoparticles. Experimental results indicated that the suspension of nanoparticles notably enhanced the evaporation rate of droplets and decreased the duration time of the continuous-contact-radius (CCR) stage. This effect was more obvious when the nanoparticles were modified by the perfluorodecyltrimethoxysilane (PDTS), which made the particles more hydrophobic. Besides, the modified nanoparticles can effectively inhibit the formation of coffee rings during evaporation. These results may have important applications for the energy-efficient enhancement of the water evaporation rate.

Objective of this work was to develop a novel method for characterizing real 3D shapes of particles smaller than 20 μm by X-ray microtomography (X-RMT). Multidimensional separation of heterogenous solids through agglomeration in suspension will improve recycling processes as the particle shape and the agglomerate size are used for shape-selective separation. In the present paper we discuss the fundamentals of X-ray tomography and the experimental setup for selective spherical agglomeration in suspension. A specific preparation method of the particulate sample for X-RMT followed by 3D image processing, are essential for the shape analysis expressed as sphericity. We also discuss the limitation of this method due to the so-called Partial Volume Effect and particle clusters in the order of magnitude of X-RMT resolution. As proof of concept, we used a mixture of graphite platelets and spheronized graphite particles for a shape selective-agglomeration in suspension. The remaining fines were analyzed and showed more platelets than in the mixture. This indicates that spheronized particles are preferably bound in the agglomerates. These findings show that, based on the discussed sample preparation and a 3D image analysis in connection with X-RMT, particle shapes of micronized particles can be discriminated.

Turbidimeters are low-cost devices, which are widely used for suspended sediment monitoring (SSM). The specific turbidity is typically relative to 1/d (d is the diameter of particles) regarding the suspensions with mono-sized sphere-shaped particles. As the production of the dispersed suspension of TiO2-NPs is vital for their photocatalysis applications, turbidity provides a test to measure the dispersion of TiO2-NPs. In the present paper, the performance of a self-manufactured turbidimeter device has been investigated using the suspensions of TiO2-NPs in different alcoholic media. The results showed that over time, the intensity of light passing through the upper part of the test tube containing TiO2-NPs suspension increased, suggesting the settlement of TiO2 nanoparticles. In the middle part of the test tube; however, an almost stable trend was observed, which was more evident in the case of isopropanol with higher viscosity. The results also illustrated that there was no relation between the concentration of suspension and the value of transmitted light for concentration below 0.08 g/l; however, for concentrations above that, the intensity of transmitted light decreased with the increase of suspension concentration.

The modeling of the fluidization or sedimentation velocity of a suspension of solid particles is revisited by examining experiments conducted in either a liquid or a gas. A general expression is found in the case of negligible fluid inertia, i.e. at low Reynolds or Archimedes number. It is built as the product of the velocity of an isolated particle by three non-dimensional corrections that each takes into account a specific physical mechanism. The first correction reflects the variation of the buoyancy with the particle concentration. The second correction describes how the drag force increases with the concentration in case of negligible particle inertia. The third one accounts for the further increase of the drag when the particle inertia is increased. Remarkably, each correction only relies on a single of the three independent non-dimensional groups that control the problem: (1) the particle volume fraction Φs; (2) the ratio Φs/Φpack where Φpack is the bed packing concentration; (3) the Stokes number S t 0 , which characterizes the inertia of the particles and controls their agitation. Moreover, the onset of the instability that separates the homogeneous regime from the heterogeneous one is found to be controlled similarly by the Stokes number. Empirical expressions of the corrections are given, which provide a reliable tool to predict fluidization and sedimentation velocities for all values of the three non-dimensional numbers. The present results emphasize the crucial role of particle inertia, which is often disregarded in previous modeling approaches, such as that of Richardson and Zaki.

Zinc oxide is a versatile semiconductor material, widely used for its electronic and photocatalytic properties. In this work, we report a response-surface investigation of a simple technique for the immobilization of nanosized ZnO powder onto 5.0-mm glass beads. The nanoparticles are suspended in ultrapure water, and the glass beads are immersed in this suspension under vigorous stirring. The beads are removed from the suspension and calcined, after which a ZnO layer is formed on their surface. Using a modified response-surface methodology (modified Doehlert design), we investigated the effect of the nominal ZnO suspension concentration, the annealing temperature and the number of coating rounds on the amount of ZnO fixed onto the substrates and on the photocatalytic performance of the resulting films under visible light. Our results show that the coated beads have good photocatalytic activity, being able to remove up to 50% of a load of acetaminophen (used as a model contaminant) from a 5.0 ppm solution under simulated solar irradiation. We present and discuss the effects of temperature and precursor concentration, shown to be statistically significant only to a certain extent; limited to the number of coating rounds.

Silymarin, is a therapeutically important flavonoid act as a hepatoprotective agent. However, has a positive effect on metabolism act as a hydrophobic drug but has a very low bioavailability. The aim of the present study was to prepare appropriate formulations of Silymarin in order to enhance its bioavailability. The natural suspending agents like (Xanthan gum, Tragacanth gum, Acacia gum and Iranian gum) were used for the formulation of suspensions, while emulsions were prepared with the combination of surfactant, co-surfactant and oil. The formulations were evaluated for their physical stability, pH, refractive index and conductivity. Among different formulations and suspensions prepared with xanthan gum as a green stabilizing agents were most stable. Emulsions formulated with tween 80 as a surfactant, polyethylene glycol as co-surfactant and olive oil were clear and stable for more than six months. The refractive index, pH and conductivity of the most stable suspension and emulsions were 1.347, 6.9 and 0.18 s/m and 1.43, 6.9, 0.01 s/m respectively. It was concluded that xanthan gum and tween 80 with polyethylene glycol has a good potential to enhance the therapeutic efficiency and stability of silymarin suspension and emulsion.

Kraft lignin is an underutilized material mainly combusted in the pulping industry. Its conversion to value-added products for further end-use applications is limited due to its insolubility in water. In this work, the modification of kraft lignin (KL) was conducted through oxidation and carboxymethylation to generate anionic water-soluble lignin (OKL, and CMKL, respectively). The results indicated that these biopolymers acted as effective dispersants in an aluminum oxide suspension. Subsequently, generated biomaterials were polymerized with acrylamide monomer to generate flocculants (i.e., OKL-AM and CMKL-AM) for the aluminum oxide suspension. The properties of polymers were characterized extensively, and the polymerization of OKL and CMKL with acrylamide increased the molecular weight (Mw) of the biomaterials from 16 × 103 and 28 × 103 to 684 × 103 and 387 × 103 g/mol, respectively. Flocculation studies under stirring revealed that the chord length of aluminum oxide particles increased substantially by treating the suspension with the OKL-AM polymer. The reflocculation analysis provided further insight into the reversibility and high strength of formed flocs. Our results confirmed that by following a one-step reaction, a lignin-based dispersant could be generated, and further polymerizing the biomaterials (i.e., dispersants) would make it a valuable flocculant. This investigation confirms a versatile and environmentally friendly pathway to convert a waste material (i.e., lignin) to a green dispersant and flocculant.

Introduction. At the current stage of hygienic evaluation, the substantiation of at least approximate safe concentrations in the ambient air of populated areas for nanoparticles is an up-to-date challenge. Its persistence dissolves the guidelines for risk management and divests the supervisory bodies of legal support. A comparative toxicological evaluation of the studied substance and its chemical analogue is one of the guidelines for the academic substantiation of the hygienic standards for the permissible content of hazardous substances in the air. It already has previously defined exposure standards. Materials and methods. To investigate the cytotoxicity of the studied particles, a shift of the cellular composition of the bronchoalveolar lavage fluid (BALF) was used. Also, some biochemical measurements of the BALF supernatant were investigated. Outbred female rats were instilled with a suspension of particles in the volume of 1 ml of various concentrations in the form of an intratracheal suspension. Distilled water was used as a solvent. Statistical analysis of the data obtained was performed using the Student’s t-test. Results. The comparative assessment of the cytotoxicity of an original industrial aerosol containing 72% amorphous silica with an average particle size of 90 nm (SiO 2 IA) was performed. It also included engineered particles of amorphous silica with an average size of 43 nm (SiO 2 NPs), a commercial, an industrial sample of 100% amorphous silica with a particle size of 5 to 60 nm (amorphous SiO 2 ), and a reference sample of standard quartz DQ 12 in a volume of 1 ml of water suspension. Under the findings of changes in the cellular composition of the bronchoalveolar lavage fluid 24 hours after the intratracheal instillation of these particles, it was revealed that the biological power (in terms of the NL/AM ratio) of both SiO 2 NPs and amorphous SiO 2 is statistically much higher than the industrial aerosol under study. It is also higher than the standard quartz dust DQ 12 . In this regard, the cytotoxicity of SiO 2 IA may be explained by the predominant content of amorphous silica nanoparticles in it. Conclusion. Under the obtained results, the appropriateness of using indicative safe exposure levels (ISEL) of 0.02 mg/m 3 for amorphous silica needs to be reviewed. The safe reference level of impact guideline does not contain data concerning the particle size and the percentage of amorphous SiO 2 in the aerosol. Nevertheless, it is impossible to pollute the ambient air with an aerosol containing only this substance. Contribution: Solovyеva S.N. — collection and processing of material; Sutunkova M.P. — the concept and design of the study, writing; Kuzmin S.V. — the concept and design of the study; Privalova L.I. — the concept and design of the study, editing; Gurvich V.B. — the concept and design of the study; Katsnelson B.A. — concept and design of the study. All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version. Conflict of interest. The authors declare no conflict of interest. Acknowledgement. The study had no sponsorship.

Biomaterial-associated infections caused by pathogenic bacteria have important implications on human health. This study presents the design and preparation of a smart surface with pH-responsive wettability. The smart surface exhibited synergistic antibacterial function, with high liquid repellency against bacterial adhesion and highly effective bactericidal activity. The wettability of the surface can switch reversibly between superhydrophobicity and hydrophobicity in response to pH; this controls bacterial adhesion and release. Besides, the deposited silver nanoparticles of the surface were also responsible for bacterial inhibition. Benefiting from the excellent liquid repellency, the surface could highly resist bacterial adhesion after immersing in a bacterial suspension for 10 s (85%) and 1 h (71%). Adhered bacteria can be easily eliminated using deposited silver nanoparticles during the subsequent treatment of alkaline bacterial suspension, and the ratio of deactivated bacteria was above 75%. After the pH returned to neutral, the deactivated bacteria can be easily released from the surface. This antibacterial surface showed an improved bacterial removal efficiency of about 99%. The results shed light on future antibacterial applications of the smart surface combining both bactericidal and adhesion-resistant functionalities.

A continuous-flow strategy based on the microreaction system is developed for the synthesis of monodispersed polymethylsilsesquioxane (PMSQ) spheres via one-step sol-gel method. Methyltrimethoxysilane (MTMS) and ammonium hydroxide (NH4OH) were used as silicon source and catalyst, respectively. The microreaction system includes three parts: a microdispersion device for the rapid hydrolysis of MTMS, a tubular reactor for subsequent condensation and fast growth of the particles, and a stirring reactor for final aging process. The effects of synthesis parameters on the particle size and size distribution were explored, mainly including the flow rates of ammonia solution and MTMS, concentration of NH4OH, solvent composition, and collection time of the reaction suspension. The particle size could be tuned from several hundred nanometers to a few microns with narrow particle size distribution. In addition, the operational stability of the continuous-flow microreaction system was also investigated. The continuous-flow process presents a high level of controllability, stability, and robustness, while enabling fast and reproducible scaling of laboratory results into large-scale production.

The increasing energy demand has prompted engineers to explore deeper wells where rich oil and gas reserves exist. However, the high-temperature and high-salt conditions have impeded the further application of traditional water-based fracturing fluids in such reservoirs. Therefore, it is urgent to develop fracturing fluids that are suitable for such geographic characteristics. In this study, for the first time, a novel synthetic polymer, poly-(acrylamide-co-acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid) (P3A), was investigated as a rheological modifier for water-based fracturing fluids in high-temperature and high-salt conditions and compared with a guar gum system. Results showed that the apparent viscosity increased with increasing P3A and guar gum concentrations, and the thickening ability of P3A was much better than that of guar gum. Despite the better shear and temperature resistance and proppant suspension ability of guar gum fluids in high-temperature and saturated salt conditions, plentiful solid residues after gel-breaking have prevented their progress in the petroleum industry. P3A fluids have no residues, but the unsatisfying proppant suspension capability and high dosage encourage us to promote their rheological performance via interaction with an organic zirconium crosslinker. Infrared spectroscopy and scanning electron microscopy were applied to guarantee the successful reaction of P3A with the crosslinker. The subsequent investigation indicated that the transformed fracturing fluid exhibited remarkably improved thickening capability and satisfying rheological performance in terms of temperature and shear resistance and proppant-carrying ability as well as gel-breaking results in a high-temperature and saturated salt environment. All of the above results suggest the potential application of crosslinked P3A in hydraulic fracturing for the reservoirs with hostile conditions, and this article also provides a new orientation for synthetic polymers utilized in the oil and gas industry.

The Stokes equation used in the measurement of particle size distribution is based on the assumption that there are no interactions between settling soil particles. This requirement is fulfilled by using a low-concentration suspension. Therefore a highly precise determination of the suspension density is needed and makes that the measurement is sensitive to temperature changes and other random factors. In the presented paper, we attempted to overcome this problem by using increased initial suspension concentrations and at the same time taking into account the mutual interactions of sedimenting particles. The Batchelor equation was used to calculate the hindered settling velocity of the particles. The problem of mutual dependence among the concentration of particles and measurement times for individual fractions was solved by applying a simple iterative procedure. Application of the procedure caused the results obtained with the use of various initial suspension concentrations to become more similar than without it.

Nanocellulose is a renewable material with excellent properties. At present, nanocellulose powder is mainly prepared by high-cost spray drying, which severely limits its output and quality. In this paper, we propose an innovative method to prepare dispersible nanocellulose powder by simple precipitation and conventional evaporation. Potassium acetate was added to CNC (a kind of nanocellulose) suspension to precipitate and purify CNC. The added potassium acetate was dissolved in ethanol and removed. Then dispersible nanocellulose powder can be obtained by simple evaporation. In CNC purification, we discussed the combination of different electrolytes and CNCs. It was found that although the monovalent electrolytes lead to weak aggregation with CNC, the resulting dry CNC powder had the best dispersion. In CNC drying, we discussed the effects of different dispersants and different drying methods on the forming of dry CNC powder. It is revealed that ethanol is the best dispersant tested in this paper because it can only form a single hydrogen bond with CNC and is easy to evaporate. In the evaporation of CNC and ethanol mixture, it will not lead to the aggregation of CNC fibers. It is hopeful that the new method may greatly reduce the cost of the preparation of nanocellulose powder.

Inhibiting particles aggregation plays a crucial role in maintaining the stability of nanofluids. In this work, applying a rod electrode was developed to reduce particles aggregation and sedimentat...

Highly dispersed micrometric mica particles with a uniform size and flake-like morphology were crystallized from an initial gel composed of Al2O3-K2O-ZnO-SiO2-H2O-EtOH (1.0: 24.0: 3.9: 5.3: 1050: 43.2) using Ludox AS-40 colloidal silica (40 wt.% suspension in water) as a silica source and a suitable amount of EtOH as an additive. Micrometric mica was used to prepare Co2+-exchanged catalyst by a common ion-exchange procedure. The catalyst was first successfully applied in aerobic epoxidation of styrene. Freshly prepared catalyst provided 92.1 mol.% conversion of styrene and selectivity to epoxide of 84.6%. Recycling studies showed feasibility of catalyst regeneration and the possibility of the repeated use of Co2+-exchanged mica as a heterogeneous catalyst.

Depending on the active acidity of an aqueous solution, the colloidal stability of a titanium dioxide suspension in the form of anatase (food additive E171), containing nanoparticle with average sizes of ~10 and ~200 nm is studied. It is shown that the nanoparticle stability is reached in an alkali medium at pH > 9.6. A decrease in pH from 9.6 to 6.2 (neutral) results in an increase in the zeta-potential from –30 to –20 mV and is accompanied by the formation of nanoagglomerates ~20 nm in size involving small particles. In an acidic medium with pH ~2.6 (human stomach), the zeta-potential increases to +10 mV and is accompanied by small agglomerate coarsening to 50–60 nm. In this case, an increase in the average size to ~40 nm is observed even for ~2 min. The found rapid agglomeration should reduce the probability of E171 nanofraction penetration through cellular membranes in the human stomach. However, the Е171 nanofraction penetrability significantly increases in the small intestine where food intake mostly occurs, and a medium is close to neutral, pH ~ 8.

Adding pre-foamed colloidal alumina to ultrastable Al2O3-stabilised foams can be a path towards partially counteracting the firing shrinkage of these materials and producing macroporous ceramics with smaller pores. Nevertheless, this system still presents a long setting time and high sintering-induced shrinkage, which hinders the production of larger samples and reduces its porosity. In the present work, it was observed that adding calcium aluminate cement suspension (CACS) and CaCO3 (calcite) to the aforementioned system can speed up its solidification kinetics, improve its mechanical strength and reduce its shrinkage after firing, maintaining high porosity and smaller pore sizes. By using these raw materials, samples with an average pore size below 60 μm, total porosity above 70%, and a narrower pore size distribution were attained after thermal treatment at 1600 °C for 5h. Moreover, due to the in situ formation of calcium hexaluminate, their shrinkage after sintering was almost halved (from ~20% to 11%).

This study investigates the influence of synthesis conditions of iron(II) oxalate particles on the particle morphology for their utilization in smart materials known as electrorheological (ER) fluids. Particle morphology has a significant impact on the ER behavior of the particles enabling their use in many unique practical applications. In this study, fifteen various iron(II) oxalate particles differing in synthesis conditions were prepared, out of which four variations were selected for an in depth investigation due to their promising morphology. The influence of synthesis conditions on the morphology of the resulted particles was evaluated by scanning electron microscopy analysis. An X-ray diffraction analysis was employed to confirm the dominant FeC2O4 · H2O phase presented in the synthesized particles. The ER suspensions consisted of the selected four iron(II) oxalate particles dispersed in silicone oil. An optical microscope and a rheometer, both operating under external electric field, enabled a precise and accurate investigation of the structure, the ER performance. Visual observation was used to evaluate the sedimentation stability of the suspension.

Background. There are various natural excipients which have been used as suspending agents in pharmaceutical suspensions due to the presence of mucilage in their specialized cells and their capacity to form a colloidal gel in an aqueous medium. Objective. The purpose of this study was to evaluate the suspending capacity of Aloe elegans mucilage in suspension formulations. Materials and Methods. Aloe elegans mucilage (AEM) was evaluated as a suspending agent in comparison with xanthan gum (XG) in paracetamol suspensions at 1, 2, 3, 4, and 5% ( w / v ) concentrations. The resulting suspensions were evaluated for their sedimentation volume, apparent viscosity, flow rate, rate of redispersibility, pH, assay, and dissolution profile. Results. The volume of sedimentation, apparent viscosity, and redispersibility rate of the formulations were significantly increased ( p < 0.05 ), with the concentration of the suspending agents. Meanwhile, the apparent viscosity for all formulations has significantly decreased ( p < 0.05 ) with an increase in shear rates. Volume of sedimentation, apparent viscosity, and redispersibility degree of the formulations prepared with AEM were significantly ( p < 0.05 ) lower than XG-containing formulations at the same concentration. Nevertheless, the sedimentation volume of all formulations with AEM was significantly ( p < 0.05 ) higher than the suspension without any suspending agent. With regard to drug content and pH values, all formulations showed an acceptable result with the standards. All formulations showed a release of greater than 85% of drug content within 45 min. Conclusion. Aloe elegans mucilage could have a potential to be utilized as an alternative suspending agent in pharmaceutical suspensions.

Suspension reduction kinetics of hematite ore particles at 1710 K to 1785 K was described by the Johnson-Mehl-Avrami-Kolmogorov model with Avrami exponent of 1.405. The apparent activation energy is 105.5 kJ mol−1 with the rate determining step of nucleation and growth. The reduction degree of the hematite at the endpoint is a linear function of temperature and the logarithmic oxygen potential of the reacting gas. A peak function of reaction rate constant with particle size has been verified in this work, and the maximum value of the reaction rate is located at around 85 µm particle size. The influence of heat transfer on the reaction process has been evaluated. The results suggest that the heating-up process for large particles, 244 µm particles, for instance, cannot be ignored. It can retard the reaction rate compared to small particles. Normally, the reaction rate constant decreases linearly with the increase of ln[p(O2)] of the reacting gas mixture. However, 95 vol pct CO2 in the reacting gas can accelerate the reaction rate of thermal decomposition of hematite due to the emissivity of CO2 gas. It results in a higher reaction rate of 110 µm particles in 95 vol pct CO2-containing gas than that in other less CO2-containing gases.

Introduction. Kamchatka Krai is a region with low population density and poorly developed industry. However, in large cities the air quality is degraded due to economic activity. Aim. To study the concentration of airborne particulate matter (in particular, up to 1 µm and up to 10 µm) in Petropavlovsk-Kamchatsky and Yelizovo air and carry out a comparative analysis with the previously obtained results of environmental monitoring of atmospheric suspension.Materials and methods. Airborne particulate matter was studied in snow which was collected during snowfalls to avoid its secondary pollution by anthropogenic aerosols. The melted snow was analyzed on a Fritsch Analysette 22 NanoTech laser particle analyzer (Germany).Results. PM1 particles were found in five snow samples taken in Petropavlovsk-Kamchatsky. The quantity of PM₁₀ is low in all samples, and only in two of six sampled areas it reaches 12%. Compared to the results of previous studies, the concentration of PM1 is at the same level as in previous years, and the content of PM₁₀ has decreased. In samples from Yelizovo, the same trends are observed. Compared to 2018, when a high concentration of PM₁₀ particles was found in almost all samples, reaching 57.2%, there is a trend towards a decrease in the concentration of the potentially hazardous PM fraction.Conclusion. Updated data on the particle size distribution of airborne particulate matter in two cities of the Kamchatka Peninsula were obtained. In the snow samples collected in Petropavlovsk-Kamchatsky and Yelizovo, we found PM₁ and PM₁₀ particles hazardous to human health, although their concentration is generally lower than in previous years of the study.

Conventional washing methods release little radioactive cesium fixed in soils. Adding a Cs+ adsorbent to a suspension of Cs-contaminated soil rapidly removes the Cs+ released to the solution, causing more Cs+ release from the soil. We investigated this method by adding a sheet embedded with mordenite powder to a suspension of 133Cs+-retaining wet/dry montmorillonite and water/0.1 mol L−1 KNO3. Adding the sheet increased Cs+ release in all cases, with the highest increase for wet montmorillonite in water. The advantages of this method are the easy removal of the sheet from the suspension and the low Cs concentration in the final solution.

Formulation of high solid load slurries is an important aspect in achieving dense, high quality ceramic green body shaping by additive manufacturing techniques. To this end, the understanding and control of interparticle interactions in non-aqueous organic slurry systems is imperative. With nanosized powders gaining increasing interest, particle stabilization by long-chain polymeric dispersants is undesirable due to the high exclusion volume associated and the subsequent decrease in the maximum solid load of the suspension. In this study, we focus on the stabilization mechanisms provided by metal cation complexes in methyl ethyl ketone and isopropanol-based spinel slurries. Special focus is given to chromium (III) 2-ethylhexanoate. Hemi-micelle formation at the powder surface in methyl ethyl ketone is suggested as a highly efficient stabilization mechanism. Complexes of metal dopant cations may open new pathways towards future advances in ceramic slurry formulation, especially in the field of additive manufacturing. Furthermore, the importance of solvation forces is discussed on the basis of the protic or aprotic character of the solvent used.

Particle size characterization for active pharmaceutical ingredients (APIs) in nasal spray suspension products presents unique challenges because both the API and excipient particles are present in the final dosage form. Currently, an established method is lacking because traditional particle sizing technologies do not distinguish the chemical identity of the particles. In this study, a non-destructive, ingredient-specific particle sizing method was developed for characterization of mometasone furoate (MF) nasal spray suspensions using Morphology Directed Raman Spectroscopy (MDRS). A five-step method development procedure was used in this study: sample preparation, particle imaging and morphology analysis, particle Raman measurements and classification, morphology filter selection, and minimum number of particles determination. Wet dispersion sample preparation method was selected to ensure that the particles were measured in their original suspended state. A training set containing over 10,000 randomly-selected particles, including both the API and excipient particles, was used to gain a comprehensive understanding of particle size, shape, and chemical ID for the nasal spray suspension. Morphology and Raman measurements were performed on each particle in the training set. The measurement results suggested that the aspect ratio and intensity mean filter combination was an appropriate morphology filter setting to selectively target API particles and exclude most of excipient particles. With further optimization of the morphology filter cutoff values and determination of minimal number of particles to be measured, the total measurement time was reduced from 90 hours to 8 hours. The morphologically screening strategy ultimately allowed us to create a time-efficient practical API-specific particle size distribution (PSD) methods for nasal spray suspensions. This study shows that MDRS is a fit for purpose analytical technique for determining ingredient-specific PSDs of the pharmaceutical formulation studied in this work.

Dynamics of colloidal particles can be controlled by the application of electric fields at micrometer-nanometer length scales. Here, an electric field-coupled microfluidic flow-focusing device is designed for investigating the effect of an externally applied alternating current (AC) electric field on the hydrodynamic assembly of cellulose nanofibrils (CNFs). We first discuss how the nanofibrils align parallel to the direction of the applied field without flow. Then, we apply an electric field during hydrodynamic assembly in the microfluidic channel and observe the effects on the mechanical properties of the assembled nanostructures. We further discuss the nanoscale orientational dynamics of the polydisperse and entangled fibrillar suspension of CNFs in the channel. It is shown that electric fields induced with the electrodes locally increase the degree of orientation. However, hydrodynamic alignment is demonstrated to be much more efficient than the electric field for aligning CNFs. The results are useful for understanding the development of the nanostructure when designing high-performance materials with microfluidics in the presence of external stimuli.

Исследовано влияние поверхностно-активных веществ (ПАВ) различной природы: твина-80, сорбитана моноолеата SPAN-80, додецилсульфата натрия, и синтанола промышленного производства ДС-10 на ресуспендируемость и седиментационную устойчивость водной суспензии ментола. The effect of surfactants of various natures (tween-80, sorbitan monooleate SPAN-80, sodium dodecyl sulfate, and industrial-grade synthanol DS-10) on the resuspendability and sedimentation stability of an aqueous menthol suspension was studied.

Nanocomposite hydrogels containing two-dimensional nanosilicates (NS) have emerged as a new technology for the prolonged delivery of biopharmaceuticals. However, little is known about the physical–chemical properties governing the interaction between NS and proteins and the release profiles of NS–protein complexes in comparison to traditional poly(ethylene glycol) (PEG) hydrogel technologies. To fill this gap in knowledge, we fabricated a nanocomposite hydrogel composed of PEG and laponite and identified simple but effective experimental conditions to obtain sustained protein release, up to 23 times slower as compared to traditional PEG hydrogels, as determined by bulk release experiments and fluorescence correlation spectroscopy. Slowed protein release was attributed to the formation of NS–protein complexes, as NS–protein complex size was inversely correlated with protein diffusivity and release rates. While protein electrostatics, protein concentration, and incubation time were important variables to control protein–NS complex formation, we found that one of the most significant and less appreciated variable to obtain a sustained release of bioactive proteins was the buffer chosen for preparing the initial suspension of NS particles. The buffer was found to control the size of nanoparticles, the absorption potential, morphology, and stiffness of hydrogels. From these studies, we conclude that the PEG–laponite composite fabricated is a promising new platform for sustained delivery of positively charged protein therapeutics.

A microparticle counter based on a metal mesh device was developed. The metal mesh device had a lattice-shaped structure with well-regulated holes of 1.8 μm. The collection percentages of differently sized microparticles using the metal mesh device were determined by flow cytometry. The cut-off point and hole size of the metal mesh device were identical. Polystyrene microparticles were detected from changes in the spectroscopic properties of the metal mesh device. When microparticles were trapped on the holes of the metal mesh device, the transmittance in the infrared spectra decreased. Microparticles smaller than the holes were not detected by the metal mesh device, whereas 2 and 3 μm microparticles were detected. Polystyrene and silica microparticles could be counted using the metal mesh device via calibration curves between the concentration of microparticles and the change level in the transmittance of the metal mesh device. The separation of microparticles from a mixture suspension using the metal mesh device was evaluated. Unlike a microfiber filter, only 2 μm microparticles were collected from coexisting 1 μm microparticles by the metal mesh device. Owing to its high separation ability, the metal mesh device selectively detected 2 μm microparticles in coexisting 10-equivalence 1 μm microparticles.