Monodisperse Polystyrene Latex Research Articles

Statistical Analysis for Quality Control of Monodispersed Polystyrene Particles Certified Reference Materials

Monodispersed polystyrene latex (PSL) particles serve as certified reference materials (CRMs) for ensuring quality, method validation, and calibration of particle size measuring instruments. They were produced in compliance with ISO 17034:2016 standards. However, limitations arise in the quality control of CRM characteristics due to challenges in synthesizing particles of consistent size across multiple batches. It is widely recognized that variations in particle size homogeneity between batches can occur in the particle manufacturing process even when conducted under identical conditions and ingredients. This paper aims to explain and demonstrate statistical analyses conforming to ISO Guide 35:2017 used for quality control and certifying reference values for monodispersed polystyrene particles. The procedure can be divided into three steps: 1) preliminary check by using dynamic light scattering (DLS), 2) preliminary check by using transmission electron microscopy (TEM), and 3) final homogeneity testing, along with short-term and long-term stability assessment and characterization. The described protocol can control the quality of particles from multiple batch productions by establishing criteria at each step to ensure particle size consistency. The certified value of a 100 nm diameter monodispersed polystyrene particle produced by the National Institute of Metrology, Thailand (NIMT) is 105.5 ± 4.6 nm, acceptable for measurement traceability for testing and calibration services. Keywords: Quality control, polystyrene particles, certified reference materials

In chamber calibration and performance evaluation of air quality low-cost sensors

Assessing individual exposure to PM2.5 (particulate matter of aerodynamic diameter lesser than 2.5 μm) requires precise monitoring of PM2.5 concentrations at specific geographical and temporal scales. This demand is met globally by low-cost particulate matter sensors, although calibrating them is difficult. In this study, four low-cost PM sensors, Sharp GP2Y1010AU0F, Honeywell HPMA115S0-XXX, Plantower PMSA003-A, and Sensirion SPS30, were calibrated and tested using various aerosols. The calibration method has three steps: individual (considering each sensor independently to a single aerosol type; n = 1), combined (all sensors for a specific model together for a specific aerosol type; n = 4), and generic (all sensors for a given model together to all aerosols; n = 16). Sensor responses are processed using linear, quadratic, power-law, and artificial neural network (ANN) algorithms in each calibration stage. Performance metrics, including coefficient of determination (R2), mean absolute percentage error (MAPE), root mean square error (RMSE), and percentage coefficient of variation (% CV), were utilized for assessment. Amongst all the four tested sensors, the Sensirion SPS30 sensors gave the best performance with a minimum R2 value of 0.911 when calibrated with a generic ANN calibration algorithm. Also, the MAPE was less than 10 %, and the RMSE was less than 7 % when exposed to different particles. Sensirion SPS30 showed the lowest inter-sensor variability with % CV less than 6 %. Sensors identified monodisperse polystyrene latex (PSL) particle size in the investigation. Regardless of exposure to 0.3, 0.46, 0.60, or 1.0 μm PSL, the reported number size distribution for the PMSA003 sensor remained consistent and did not align with the results from Grimm. As the PSL size rose, the SPS30 size distribution changed towards larger particle sizes, although it did not always match Grimm data. As the PSL size increased, the sensor's PM1, PM2.5, and PM10 mass proportions altered.

Prediction models for the flux decay profile and initial flux of microfiltration for therapeutic proteins.

Microfiltration (MF) is an essential step during biopharmaceutical manufacturing. However, unexpected flux decay can occur. Although the flux decay profile and initial flux are important factors determining MF filterability, predicting them accurately is challenging, as the root cause of unexpected flux decay remains elusive. In this study, the methodology for developing a prediction model of flux decay profiles was established. First, the filtration profiles of different monodisperse polystyrene latex and silica beads of various sizes were evaluated. These results revealed that the size and surface electrostatic properties of the beads affect the flux decay profile. Taking the size and surface electrostatic properties of protein aggregates into account, we constructed a predictive model using model bead filtration profiles. We showed that this methodology was applicable to two different MF filters to predict the flux decay profile of therapeutic proteins. Because our proposed prediction model is based on normalized flux, the initial flux is required to predict the overall filtration profile. Then, we applied the Hagen-Poiseuille equation using sample viscosity values to estimate the initial flux. The developed prediction models can be used for effective MF scale-up assessment during the early stages of process development.

The Relationship between Serum Zonulin and Innate Immunity in Patients with Inflammatory Bowel Disease

The aim of the study was to investigate the relationship between the serum zonulin and the cellular immunity in patients with ulcerative colitis (UC) and Crohn’s disease (CD). The study included 97 patients, 13 (13.4%) patients with CD and 84 (86.6%) patients with UC. The concentration of zonulin in the serum was studied using the ELISA kits. The investigation of the circulated leukocyte subpopulation was carried out through flow cytometry. The functional activity of the circulating neutrophils was studied using the absorption capacity of the monodisperse polystyrene latex particles and indicators of oxygen-dependent metabolism in the nitroblue tetrazolium test. The serum zonulin concentration in CD patients was significantly higher compared with UC patients (p = 0.003). The zonulin concentration directly correlated with the functional activity of the circulating neutrophils. Patients with a zonulin concentration > 472.4 pg/mL had a significantly higher number of band neutrophils (p = 0.0104), CD3+CD8+ cells (p = 0.0212), NK cells (p = 0.0161), and lower–CD19+ cells (p = 0.0034). Among the IBD patients, zonulin was associated with IBD severity. An increase in the serum concentration of zonulin was associated with an increase in the functional activity of circulating neutrophils and an increase in the number of CD3+CD8+ cells, NK cells, and a decrease in the number of CD19+ cells.

Concept, absolute calibration, and validation of a new benchtop laser imaging polar nephelometer

Abstract. Polar nephelometers provide in situ measurements of aerosol angular light scattering and play an essential role in validating numerically calculated phase functions or inversion algorithms used in space-borne and land-based aerosol remote sensing. In this study, we present a prototype of a new polar nephelometer called uNeph. The instrument is designed to measure the phase function, F11, and polarized phase function, -F12/F11, over the scattering range of around 5 to 175∘, with an angular resolution of 1∘ at a wavelength of 532 nm. In this work, we present details of the data processing procedures and instrument calibration approaches. uNeph was validated in a laboratory setting using monodisperse polystyrene latex (PSL) and di-ethyl-hexyl-sebacate (DEHS) aerosol particles over a variety of sizes ranging from 200 to 800 nm. An error model was developed, and the level of agreement between the uNeph measurements and Mie theory was found to be consistent within the uncertainties in the measurements and the uncertainties in the input parameters for the theoretical calculations. The estimated measurement errors were between 5 % and 10 % (relative) for F11 and smaller than ∼ 0.1 (absolute) for -F12/F11. Additionally, by applying the Generalized Retrieval of Aerosol and Surface Properties (GRASP) inversion algorithm to the measurements conducted with broad unimodal DEHS aerosol particles, the volume concentration, size distribution, and refractive index of the ensemble of aerosol particles were accurately retrieved. This paper demonstrates that the uNeph prototype can be used to conduct accurate measurements of aerosol phase function and polarized phase function and to retrieve aerosol properties through inversion algorithms.

Development and performance evaluation of a two-stage cascade impactor equipped with gelatin filter substrates for the collection of multi-sized particulate matter

This study presents the development and evaluation of a high flow rate gelatin cascade impactor (GCI) to collect different PM particle sizes on water-soluble gelatin substrates. The GCI operates at a flow rate of 100 lpm, and consists of two impaction stages, followed by a filter holder to separate particles in the following diameter ranges: >2.5 μm, 0.2–2.5 μm, and <0.2 μm. Laboratory characterization of the GCI performance was conducted using monodisperse polystyrene latex (PSL) particles as well as polydisperse ammonium sulfate, sodium chloride, and ammonium nitrate aerosols to obtain the particle collection efficiency curves for both impaction stages. In addition to the laboratory characterization, we performed concurrent field experiments to collect PM2.5 employing both GCI equipped with gelatin filter and personal cascade impactor sampler (PCIS) equipped with PTFE filter for further toxicological analysis using macrophage-based reactive oxygen species (ROS) and dithiothreitol consumption (DTT) assays. Our results showed that the experimentally determined cut-point diameters for the first and second impaction stages were 2.4 μm and 0.21 μm, respectively, which agreed with the theoretical predictions. Although the GCI has been developed primarily to collect particles on gelatin filters, the use of a different type of substrate (i.e., quartz) led to similar particle separation characteristics. The findings of the field tests demonstrated the advantage of using the GCI in toxicological studies due to its ability to collect considerable PM-toxic constituents, as corroborated by the DTT and ROS values for the GCI-collected particles which were 26.44 nmol/min/mg PM and 8813.2 μg Zymosan Units/mg PM, respectively. These redox activity values were more than twice those of particles collected concurrently on PTFE filter using the PCIS. This high-flow-rate impactor can collect considerable amounts of size-fractionated PM on water-soluble filters (i.e., gelatin), which can completely dissolve in water allowing for the extraction of soluble and insoluble PM species for further toxicological analysis.

A single-parameter hygroscopicity model for functionalized insoluble aerosol surfaces

Abstract. The impact of molecular level surface chemistry for aerosol water-uptake and droplet growth is not well understood. In this work, spherical, nonporous, monodisperse polystyrene latex (PSL) particles treated with different surface functional groups are exploited to isolate the effects of aerosol surface chemistry for droplet activation. PSL is effectively water insoluble and changes in the particle surface may be considered a critical factor in the initial water uptake of water-insoluble material. The droplet growth of two surface modified types of PSL (PSL-NH2 and PSL-COOH) along with plain PSL was measured in a supersaturated environment with a Cloud Condensation Nuclei Counter (CCNC). Three droplet growth models – traditional Köhler (TK), Flory–Huggins Köhler (FHK) and the Frenkel–Halsey–Hill adsorption theory (FHH-AT) were compared with experimental data. The experimentally determined single hygroscopicity parameter, κ, was found within the range from 0.002 to 0.04. The traditional Köhler prediction assumes Raoult's law solute dissolution and underestimates the water-uptake ability of the PSL particles. FHK can be applied to polymeric aerosol; however, FHK assumes that the polymer is soluble and hydrophilic. Thus, the FHK model generates a negative result for hydrophobic PSL and predicts non-activation behavior that disagrees with the experimental observation. The FHH-AT model assumes that a particle is water insoluble and can be fit with two empirical parameters (AFHH and BFHH). The FHH-AT prediction agrees with the experimental data and can differentiate the water uptake behavior of the particles owing to surface modification of PSL surface. PSL-NH2 exhibits slightly higher hygroscopicity than the PSL-COOH, whereas plain PSL is the least hygroscopic among the three. This result is consistent with the polarity of surface functional groups and their affinity to water molecules. Thus, changes in AFHH and BFHH can be quantified when surface modification is isolated for the study of water-uptake. The fitted AFHH for PSL-NH2, PSL-COOH, and plain PSL is 0.23, 0.21, and 0.18 when BFHH is unity. To simplify the use of FHH-AT for use in cloud activation models, we also present and test a new single parameter framework for insoluble compounds, κFHH. κFHH is within 5 % agreement of the experimental data and can be applied to describe a single-parameter hygroscopicity for water-insoluble aerosol with surface modified properties.

Simple Qualitative Modelling of Particle Size Analysis using Ray Tracing Method

Understanding particle size analysis is essential for pharmaceutical, mining, environmental, coatings, and other industries. Although there are numerous technologies that can be utilized to take particle size measurements, the results of those measurements are presented automatically and are sometimes difficult to understand. In this study, using the ray-tracing method, simple qualitative modelling of particle size analysers can be developed. The laser is positioned as the initial position of the light source in x and y directions. The cell is pictured by cuvettes with four surfaces clear, and the particle is modelled as a sphere. Reflection of a single ray of the laser beam on many spheres can be performed using single ray reflection on a single sphere consecutively until the beam leaving the observation region or arriving at a light sensor. Then with vector formulation of ray direction after reflection on many spheres system we can define with n = 1,2,3,… where . As a test of the particle size analysis model, the results are compared with measurements of the monodisperse polystyrene latex. Interesting patterns in FFT and autocorrelation function results are found. Unfortunately, this finding is still considered inconclusive, due to the pattern obtained is not completely like the experimental results.

A bilateral comparison of particle number concentration standards via calibration of an optical particle counter for number concentration up to ∼1000 cm−3

The first bilateral comparison of particle number concentration (PNC) standards via calibrating the counting efficiency (CE) of an optical particle counter (OPC) at high concentration of 1000 cm−3 is reported. An OPC (GRIMM 11-D) has been used as the transfer standard between NMC and NMIJ, with its CE being calibrated using monodisperse polystyrene latex (PSL) particles around 0.3 µm by the Faraday Cup Aerosol Electrometers (FCAE) of both metrology institutes. The CE of the OPC has been evaluated for a series of increasing concentrations to determine the highest concentration level which is free from coincidence loss. The OPC was also calibrated at 0.5 µm using an inkjet aerosol generator (IAG) and FCAE to compare its CE at different concentration levels. We have analysed the CE’s stability at decreasing concentration levels from 1228 to 0.5 cm−3 to derive the evidence for the equivalence of CE at different concentration levels. The CE values of the OPC around 0.3 and 0.5 µm measured by two institutes have agreement within 1.5% (normalizederror En < 1), which can serve as evidence of the equivalence of the PNC standards of both metrology institutes for concentrations up to 1000 cm−3. The measurement setup, comparison results and uncertainty analysis for the OPC calibration have been presented.

Combined Effects of Masking and Distance on Aerosol Exposure Potential

ObjectiveTo quantify the efficacy of masking and “social distancing” on the transmission of airborne particles from a phantom aerosol source (simulating an infected individual) to a nearby target (simulating a healthy bystander) in a well-controlled setting. MethodsAn aerosol was created using monodisperse polystyrene latex beads in place of infectious respiratory secretions. Detection was by aerodynamic particle spectrometry. Both reusable cloth masks and disposable paper masks were studied. Transmission was simulated indoors during a 3-minute interval to eliminate the effect of variable ventilation rate on aerosol exposure. The study commenced on September 16, 2020, and concluded on December 15, 2020. ResultsCompared with a baseline of 1-foot separation with no masks employed, particle count was reduced by 84% at 3 feet of separation and 97% at 6 feet. A modest decrease in particle count was observed when only the receiver was masked. The most substantial exposure reduction occurred when the aerosol source was masked (or both parties were masked). When both the source and target were masked, particle count was reduced by more than 99.5% of baseline, regardless of separation distance or which type of mask was employed. ConclusionThese results support the principle of layered protection to mitigate transmission of SARS-CoV-2, the virus causing COVID-19, and other respiratory viruses and emphasize the importance of controlling the spread of aerosol at its source. The combination of masking and distancing reduced the exposure to exhaled particulates more than any individual measure. Combined measures remain the most effective way to combat the spread of respiratory infection.

Colorimetric monitoring of humidity by opal photonic hydrogel

The present study demonstrated a new fast colorimetric humidity sensor using the opal hydrogel composite (OHC). First, a highly monodisperse polystyrene (PS) latex was synthesized by soap-free emulsion polymerization and deposited on a glass substrate in order to form a three-dimensional opal photonic crystal. Then, the homogenous hydrogel precursor was infiltrated into the interstitial space of opal by capillary forces and underwent chemical polymerization to construct an embedded PS crystalline colloidal array within a poly (acrylamide-co-acrylic acid) hydrogel network. The scanning electron microscopic images confirmed the formation of opal structures. An interesting feature of the presented OHC sensor is that the sensor is transparent in a dry state and an increase in relative humidity (RH) leads to a colorful film. In addition, UV/Vis spectroscopy was performed within an RH range of 25–95%, indicating that reflection peak height gradually develops by RH increasing and the peak position shifts from 413 to 518 nm. Further, the sensor functions extremely rapidly and changes its color by increasing RH within a few seconds (less than 3 s) and becomes transparent again quickly as humidity represents a decrease. Based on the results, repeated humidity changes revealed that the sensor has an excellent reproducibility without any reduction in response time and sensitivity or a color change. Finally, it has good adhesion to the glass substrate which makes it a suitable RH sensor in different applications, along with the rapid response time, high sensitivity, repeatability, and the visual alarm.

Interlaboratory comparison of nanoparticle size measurements between NMIJ and NIST using two different types of dynamic light scattering instruments

The question of how to relate particle sizes measured using a fixed-angle dynamic light scattering (DLS) instrument with those measured using a multi-angle DLS instrument is addressed. A series of nearly monodisperse polystyrene latex (PSL) particles with nominal diameters of 100 nm, 70 nm, 50 nm, and 30 nm were measured using two different types of DLS instruments: one owned by the National Metrology Institute of Japan (NMIJ) of the multi-angle type and the other owned by the National Institute of Standards and Technology (NIST) of the fixed-angle type. The mean particle size of the PSL particles was measured using the multi-angle-type instrument at various scattering angles and at various concentrations of particle suspension. These data were used to establish the functional dependence of the measured particle size on the scattering angle and particle concentration through the least-squares fitting method. The established function was then used to predict the mean particle sizes that would have been obtained if the same scattering angle and particle concentrations as those used at NIST had been selected at NMIJ. The mean particle sizes obtained at NIST and at NMIJ agreed quite well for all four PSL particle samples after compensating for the angle and concentration differences. The result of this study clearly demonstrates that consideration for the dependence of measured particle sizes on the scattering angle and particle concentration is crucial in intra-method comparisons of mean particle sizes obtained using DLS.

Controlled morphology of electrospun nanofibers from waste expanded polystyrene for aerosol filtration

This paper reports on the recycling of expanded polystyrene (EPS) waste to be repurposed as EPS nanofibrous mats for air filtration applications. The EPS nanofibrous mats were prepared via electrospinning technique. The EPS solutions for producing the mats were made by dissolving the EPS waste in dimethylformamide (DMF) and d-limonene solvents. The mixing ratio of DMF and d-limonene solvents were varied to obtain EPS solutions with different surface tension and viscosity. As a result, different fiber morphology (smooth fiber, wrinkled fiber, and beaded fiber) and diameter ranging from 314 nm to 3506 nm were obtained. The synthesized EPS nanofibrous mats were characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, x-ray diffraction spectroscopy, differential scanning calorimetry, mechanical strength, porosity, and water contact angle measurement apparatus. The mechanical strength measurement exhibited that the beaded fiber had the highest tensile strength and the lowest elasticity compared to wrinkled and smooth fiber. The water contact angle measurement showed that the EPS nanofibrous mats were classified as ultra-hydrophobic, which was a good criterion for air filter media. Some filtration parameters of the EPS nanofibrous mats were measured, including particle collecting efficiency, pressured drop, and quality factor. The particle collecting efficiency of each EPS nanofibrous mats was measured using monodisperse polystyrene latex (PSL) particles and PM2.5 from burning incense as the test particles. The EPS nanofibrous mats had a high collecting efficiency (up to 99.99%) and had a low pressure drop (below 70 Pa) for the face velocity of 5.4 cm s−1. The quality factor of the EPS nanofibrous mats reached 0.10 for PSL filtration and 0.16 for PM2.5 filtration. Overall, the EPS nanofibrous mats with controlled morphology were suitable to be used as air filtration media with high mechanical strength, ultra-hydrophobic surface, and high quality factor.

Focusing of Airborne Particles Using Groove-Induced Envelope (GRIP) Flow Air-Microfluidic Concentrator

Monitoring personal exposure to airborne particulate matter (PM) necessitates the need for ubiquitous portable PM sensing systems. Most current microfluidic PM detectors will be significantly improved if the particles suspended in the air-stream are focused into a narrow stream. In this paper, we present a novel microfabricated groove-induced envelope flow (GRIP) air-microfluidic PM focusing system. In this device, the horizontal focusing is achieved by enveloping the main flow using clean sheath flow from the sides of the microchannels, while vertical focusing is achieved using grooved structures on top and bottom of the microchannels. The grooves are fabricated using a novel fabrication technique that is compatible with the DRIE fabrication process of other air-microfluidics PM sensors, making it easier to integrate these two components into small air-microfluidic circuits. The performance of this system was evaluated using the opto-gravimetric method. Mono-dispersed polystyrene latex spheres were injected into the GRIP system and subsequently collected on membrane filters attached to the outlet. Epi-fluorescent microscopy was then used to image the distribution of the particles on the filter. The experimental results confirm that the efficiency of the GRIP device for focusing particles in air-microfluidic channels, enabling increased sensitivity and elimination of wall losses in future micro-electro-mechanical-systems PM sensor.

Characterisation of particle collection and transmission in a polydimethylsiloxane based denuder sampler

Denuder sampling devices consisting of two multi-channel silicone rubber traps separated by a quartz fibre filter, have been effectively employed for the simultaneous sampling of gas and particle associated semi-volatile organic compounds. Here controlled laboratory experiments were conducted to further elucidate the fundamental operating mechanisms of this portable denuder with respect to particle transmissions. Particle collection efficiency of the quartz fibre filters as well as particle transmission efficiency through the silicone rubber traps using ambient aerosol and aqueous suspensions of monodisperse polystyrene latex (PSL) as test particles (0.3, 0.5 and 0.8 µm), were evaluated for various scenarios. Particle size and number concentration were measured with a scanning mobility particle sizer. Transmission efficiency of the denuder was determined from the ratio of particle concentration transmitted by the denuder to that of a bypass line. All sizes of PSL particles were collected with high efficiency and reproducibility by the quartz fibre filter (>98% with variation coefficients <16%). Overall transmission efficiencies for all particles >100 nm ranged from 91% to 100% (variation coefficients of 2–14%). Transmission efficiencies decreased when PDMS tubes were twisted but were not significantly different for traps made by different individuals. Ambient particles, which were studied for the first time, were collected with 88–95% collection efficiency. Losses of smaller particle size fractions in the trap portion of the denuder were likely due to diffusion and electrostatic effects. The high particle collection and transmission efficiencies of all tested particle sizes indicated that these denuders are very effective tools for aerosol measurements.

Applying Pulse Height Analysis (PHA) Technique on an Optical Particle Counter (OPC) using Commercial ADC Module

Pulse height analysis (PHA) has been designed and evaluated, which was applied to an optical particle counter (OPC, Rion KC-03), for measuring the particle size distribution. A commercial ADC module (Contec, AIO-160802AY) was employed to convert, record, and process the OPC output signal. A self-designed application processed the ADC data into distribution plot. The PHA system was calibrated using monodisperse polystyrene latex (PSL) particles with a diameter of 304, 394, and 572 nm as test particles. The PHA could obtain the particle size distribution with the measurement time interval of 10 seconds, which make it possible for the real-time application.

Field and Laboratory Evaluations of the Low-Cost Plantower Particulate Matter Sensor.

Due to the rapid development of low-cost air-quality sensors, a rigorous scientific evaluation has not been conducted for many available sensors. We evaluated three Plantower PMS A003 sensors when exposed to eight particulate matter (PM) sources (i.e., incense, oleic acid, NaCl, talcum powder, cooking emissions, and monodispersed polystyrene latex spheres under controlled laboratory conditions and also residential air and ambient outdoor air in Baltimore, MD). The PM2.5 sensors exhibited a high degree of precision and R2 values greater than 0.86 for all sources, but the accuracy ranged from 13 to >90% compared with reference instruments. The sensors were most accurate for PM with diameters below 1 μm, and they poorly measured PM in the 2.5-5 μm range. The accuracy of the sensors was dependent on relative humidity (RH), with decreases in accuracy at RH > 50%. The sensors were able to produce meaningful data at low and high temperatures and when in motion, as it would be if utilized for outdoor or personal monitoring applications. It was most accurate in environments with polydispersed particle sources and may not be useful in specialized environments or experiments with narrow distributions of PM or aerosols with a large proportion of coarse PM.

Fabrication and Characterization of Monodisperse Polystyrene Latex (PSL) with Various Diameters

The focus of this study was the synthesis of polystyrene latex (PSL) particles and their diameter control for the application of aerosol filtration test. Simple emulsion polymerization was used as the method to produce uniformly spherical PSL particles. The diameter of PSL particles ranging from (160 to 941) nm was obtained by controlling the reaction parameters during the polymerization process. The reaction parameters were the concentration of styrene monomer, the concentration of potassium persulphate initiator, and the solution temperature. The diameter of PSL particles was larger as the concentration of styrene monomer, and initiator concentration increased, as analyzed from their SEM images. The higher the solution temperature, the resulting particles diameter would be smaller.

Enzymatic catalyzed corn fiber gum-bovine serum albumin conjugates: Their interfacial adsorption behaviors in oil-in-water emulsions

The purpose of present study was to investigate the interfacial behaviors of the peroxidase-catalyzed intermolecular conjugates of corn fiber gum (CFG) and bovine serum albumin (BSA) (gum and protein weight ratio of 4:1). CFG-BSA conjugate stabilized emulsion remained stable with low flocculation and coalescence degree during storage in comparison to single BSA or CFG emulsion, attributing to its higher amount of adsorbed protein and polysaccharide. As shown by SDS-sulfate polyacrylamide gel electrophoresis, the adsorbed protein at the surface of oil droplets stabilized by CFG-BSA conjugate was partly crosslinked with CFG, forming an entangled emulsion network with increased apparent viscosity. Adsorbed CFG-BSA conjugates distributed loosely around the droplet interfaces as revealed by images of confocal laser scanning microscopy. Their interfacial layer thickness was estimated to be 85.1 nm using a monodisperse polystyrene latex particle model, which was not only larger than the adsorbed layer thickness of single CFG (71 nm) or BSA (6.9 nm) but also their combined layer thickness. To our knowledge, it is the first time that the interfacial properties of enzymatically-crosslinked polysaccharide and protein have been studied.

Particle Velocities near and along the Electrode during Electrophoretic Deposition: Influence of Surfactant Counter-Ions

Research into the micro-nanostructured coatings process has made a variety of new applications available. Electrophoretic deposition (EPD) is an efficient and attractive technique to produce coated materials. Therefore the understanding of the formation and growth mechanism of the coating process continues to be investigated. In this study, a home-made EPD laminar flow cell was used for in-situ investigation of the particle velocity and deposition of micronic particles on a cathode. Monodisperse polystyrene latex particles were functionalized with cationic surfactants: cetyltrimethyl ammonium bromide (CTAB) or cetyltrimethyl ammonium chloride (CTAC). The tangential velocity of the particles when they migrated to the electrode, the approach angle and the tangential velocity along the electrode were measured under a DC electric field. From the values of the velocities, the particle-electrode distance was evaluated in CTAB and CTAC solutions. The electrophoretic velocity was calculated from the electrophoretic mobility of the particles and the electric field applied to the particles. All these parameters depend on the type of surfactant counter-ions and influence the growth of the coating. Dense structures were obtained in CTAB solution while open structures were observed in CTAC solution.