Volume Average Diameter Research Articles

New Porous Silicon-Containing Organic Polymers: Synthesis and Carbon Dioxide Uptake

The design and synthesis of new multifunctional organic porous polymers has attracted significant attention over the years due to their favorable properties, which make them suitable for carbon dioxide storage. In this study, 2-, 3-, and 4-hydroxybenzaldehyde reacted with phenyltrichlorosilane in the presence of a base, affording the corresponding organosilicons 1–3, which further reacted with benzidine in the presence of glacial acetic acid, yielding the organic polymers 4–6. The synthesized polymers exhibited microporous structures with a surface area of 8.174–18.012 m2 g−1, while their pore volume and total average pore diameter ranged from 0.015–0.035 cm3 g−1 and 1.947–1.952 nm, respectively. In addition, among the synthesized organic polymers, the one with the meta-arrangement structure 5 showed the highest carbon dioxide adsorption capacity at 323 K and 40 bar due to its relatively high surface area and pore volume.

Encapsulation of a Ru(II) Polypyridyl Complex into Polylactide Nanoparticles for Antimicrobial Photodynamic Therapy.

Antimicrobial photodynamic therapy (aPDT) also known as photodynamic inactivation (PDI) is a promising strategy to eradicate pathogenic microorganisms such as Gram-positive and Gram-negative bacteria. This therapy relies on the use of a molecule called photosensitizer capable of generating, from molecular oxygen, reactive oxygen species including singlet oxygen under light irradiation to induce bacteria inactivation. Ru(II) polypyridyl complexes can be considered as potential photosensitizers for aPDT/PDI. However, to allow efficient treatment, they must be able to penetrate bacteria. This can be promoted by using nanoparticles. In this work, ruthenium-polylactide (RuPLA) nanoconjugates with different tacticities and molecular weights were prepared from a Ru(II) polypyridyl complex, RuOH. Narrowly-dispersed nanoparticles with high ruthenium loadings (up to 53%) and an intensity-average diameter < 300 nm were obtained by nanoprecipitation, as characterized by dynamic light scattering (DLS). Their phototoxicity effect was evaluated on four bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa) and compared to the parent compound RuOH. RuOH and the nanoparticles were found to be non-active towards Gram-negative bacterial strains. However, depending on the tacticity and molecular weight of the RuPLA nanoconjugates, differences in photobactericidal activity on Gram-positive bacterial strains have been evidenced whereas RuOH remained non active.

One-step extrusion of concentrated lidocaine lipid nanocarrier (LNC) dispersions.

Lipid nanocarriers (LNCs) have been successfully produced by many methods including high pressure homogenization, sonication and microemulsification, but it remains very difficult to produce dispersions with greater than 30% LNCs, volume average particle diameter less than 150nm, and concentration of drugs useful for topical products. This research is the first to propose and demonstrate extrusion to manufacture highly concentrated drug containing LNC dispersions continuously and economically in a single step. By treating crude emulsions in a twin-screw extruder which has sections for homogenizing, mixing and fast-cooling inside the extruder, lidocaine-loaded LNC dispersions were successfully generated with lipid concentration up to 60% and particle diameters less than 50nm. Electrical conductivity and birefringence measurements indicate that in the lidocaine system, lamellar microemulsions are intermediate structures and compositions with low lipid concentrations that do not present evidence of lamellar structures fail to give nanoparticles when processed. This paper also presents a new method for measuring kinetics of drug release from nanoparticles based on pH stat titration. Sufficiently precise data from pH stat titration allows determination of rate laws for release occurring on a time scale of minutes versus hours or days. The release rate of lidocaine from extruded 35% lipid nanoparticles was constant (zero order release kinetics) through the first hour (40% of drug release), a valuable property for drug delivery.

Preparation of Nano/Submicron Ganoderma Tsugae and Its Stability

The preparation and stability of nano/submicrometer-sized Ganoderma tsugae (G. tsugae) was explored. The fruit body of G. tsugae was treated by homogenization and media-milling. Three sizes (0.8, 0.3, and 0.2 mm) of media were employed for consecutive milling. The final product was obtained by centrifugation (10,000 g, 10 min). Particle sizes were determined by using a laser-light particle size analyzer and further examined by using transmission electron microscopy. The removal of large particles resulted in better stability. After being stored at25°C for 21 days, the volume-average diameter of supernatant III increased from 0.105 to 0.137 μm. Freeze-drying resulted in particle aggregation and an increase in particle size. Twenty percent of the particles in the freeze-dried supernatant III were smaller than 100 nm, with an average diameter greater than 1 μm. Nevertheless, autoclaving did not result in severe instability of supernatant III. After being stored at 25°C for 12 months, about 40% of the particles were smaller than 100 nm, with an average diameter of 373 nm. In addition, the contents of bioactive compounds such as β-(1,3)-D-glucans, crude triterpenoids, total dietary fiber and chitin in media-milled products were much greater than those present in the hot-water extract.

A DSC and XPS characterization of core–shell morphology of block copolymer nanoparticles

Self-assembly of amphiphilic block copolymer chains is known to produce core–shell nanoparticles, but imaging techniques have generally failed to provide clear evidence about the multiphase structure. We report herein the advantages and limitations of modulated temperature differential scanning calorimetry (MDSC) and X-ray photoelectron spectroscopy (XPS) for the morphology study of spherical poly(hydroxyethyl acrylate)-b-polystyrene diblock copolymer nanoparticles with an intensity-average diameter of 40 nm. Using lyophilized particles, MDSC is more informative than XPS since it allows the three morphological features of composite latex particles to be distinguished: polystyrene core, poly(hydroxyethyl acrylate) shell, and interface. In MDSC, phase separation is evidenced by two distinct increments of heat capacity (ΔCp) in the glass transition regions of the two blocks. By measuring ΔCp values, an interface weight fraction of 70% is measured that gradually decreases to 50% with annealing time (150 °C, 2 h), indicating a higher extent of phase separation.

Simple and immediate quantitative evaluation of dispersive mixing

A dimensionless mixing number is developed to quantify dispersive mixing in a simple and immediate way. This takes into account number-average diameter, volume-average diameter and interfacial area simultaneously. It is an experimentally determined number, meaning the calculations are performed using microscopy images. This parameter was validated using various polymer blends (droplet morphology) and composite systems and can be used to compare various technologies on the basis of dispersive mixing efficiency.

How Do Charged End-Groups on the Steric Stabilizer Block Influence the Formation and Long-Term Stability of Pickering Nanoemulsions Prepared Using Sterically Stabilized Diblock Copolymer Nanoparticles?

Reversible addition-fragmentation chain transfer (RAFT) solution polymerization is used to prepare well-defined poly(glycerol monomethacrylate) (PGMA) chains bearing carboxylic acid, tertiary amine, or neutral end-groups. Each of these PGMA precursors was then chain-extended in turn via RAFT aqueous emulsion polymerization of 2,2,2-trifluoroethyl methacrylate to form spherical nanoparticles as confirmed by transmission electron microscopy (TEM) analysis. Dynamic light scattering studies indicated an intensity-average diameter of approximately 25 nm. Aqueous electrophoresis measurements confirmed that the amine-functional nanoparticles became cationic at low pH owing to end-group protonation. In contrast, carboxylic acid-functional nanoparticles became appreciably anionic at pH 10 owing to end-group ionization. Finally, nanoparticles bearing neutral end-groups exhibited zeta potentials close to zero over a range of solution pH. High-shear homogenization of n-dodecane in the presence of such sterically stabilized nanoparticles led to the formation of oil-in-water Pickering macroemulsions with volume-average diameters of 20-30 μm. High-pressure microfluidization was then used to prepare the three corresponding Pickering nanoemulsions. Each Pickering nanoemulsion was characterized by analytical centrifugation and TEM studies of the dried nanoemulsion droplets confirmed their original nanoparticle superstructure. The nanoparticle adsorption efficiency at the oil-water interface was assessed by gel permeation chromatography (using a UV detector) for each nanoparticle type at both pH 3 and 7. Nanoparticles with charged end-groups exhibited relatively low adsorption efficiency, whereas up to 90% of the neutral nanoparticles were adsorbed onto the oil droplets. This observation was supported by small-angle X-ray scattering experiments, which indicated that the packing efficiency of neutral nanoparticles around oil droplets was higher than that of nanoparticles bearing charged end-groups. Analytical centrifugation was used to evaluate the colloidal stability of the aged Pickering nanoemulsions. Pickering nanoemulsions stabilized with nanoparticles bearing charged end-groups proved to be significantly less stable than those prepared using neutral end-groups.

Textural characteristics of activated carbons derived from tabah bamboo manufactured by using H3PO4 chemical activation

Activated carbon utilization in a different application requires a specific characteristic. Textural characteristics such as pore volume (V P ), surface area (S A ), pore diameter (D P ) and pore size distribution (PSDs) have an important effect on the quality and utility of activated carbon. Such characteristics are attributed to the activated carbon adsorption capacity. This research is concerned to investigate the textural properties of activated carbons derived from tabah bamboo ( Gigantochloa nigrociliata ) which are chemically activated using H 3 PO 4 activating agent. Carbonization was carried out up to 800 O C for 1.5 hours. Activations were set up to 820 O C for each 50, 100 and 150 minutes. The activated carbons produced are expressed as AC-50min, AC-100min, and AC-150min each for activation during 50, 100, and 150 minutes. The results of the research show that the higher activation time produced activated carbons with higher pore volume and wider average pore diameter but no pattern was observed on the surface area. The highest surface area of 398.400 m 2 /g and the highest pore volume of 0.680 cc/g were achieved by AC-100min and AC-150min activated carbons, respectively. The highest N 2 adsorption capacity of 48.743 cc/g was achieved on the activated carbon of AC-150min. AC-50min, AC-100min, and AC-150min have average pore diameters, respectively, around of 1.258 nm, 1.750 nm, and 3.950 nm. AC-50min and AC-100min produced pores with a monomodal pore size distribution and a bimodal pore size distribution was found on AC-150min

Modelling of particle size distribution in butyl acrylate emulsion polymerisation in a batch reactor

ABSTRACT A computer model for the development of particle size distribution in a batch reactor for the emulsion polymerisation of butyl acrylate was developed, solved and validated. Population balance model was represented by partial differential equations and these equations were solved by using the method of orthogonal collocation. The model was validated against two sets of experimental data taken from literature. The model’s reliability was demonstrated by successful simulation of the experimental data for the number of variables which included the number of particles formed at different emulsifier and initiator concentrations, the variation of conversion with time at one initiator concentration and one emulsifier concentration and number average diameter, volume average diameter at different emulsifier concentrations. The model is simpler and more accurate than the reported population balance models for this system in the literature. The simplicity is brought by studying the model in different levels of details in our earlier works.

Experimental investigation of the effect of volume concentration and average diameters of nanoparticles on the contact angle of wetting between nanofluids and different substrates

The influence of different volume concentrations and average diameters of Al2O3 nanoparticles on the contact angle of wetting between nanofluids and different substrates was experimentally investigated. The concentrations of aluminium oxide nanoparticles were varied from 0.0625 vol.% to 1 vol.%. The average diameters of aluminium oxide nanoparticles were varied from 43 nm to 150 nm. Andesite, diabase, gabbro-diabase and metabasalt were chosen as the substrates. The dependences of the value of the contact angle of wetting between nanofluids and different substrates were obtained as a result of the experiments. It was shown, that the contact angle of wetting nonlinearly depended on the nanoparticles volume concentration. In addition, it was found that the wetting angle also depends on the substrate material, on which the drop lies. It was also obtained that the contact angle of wetting between different substrates and nanofluids with average and huge nanoparticles (> 75 nm) increased 1.25-1.5 times even at the smallest concentration (0.0625 vol.%) and then achieved the plateau. In contrast, the contact angle of wetting between different substrates and nanofluids with small nanoparticles (< 50 nm) reached maximum at a concentration of 0.0625 vol.% and after that slowly decreased to the values lower than those for the pure water.

Poly(3,4-ethylenedioxythiophene) Grains Synthesized by Solvent-free Chemical Oxidative Polymerization

Abstract Poly(3,4-ethylenedioxythiophene) (PEDOT) grains were synthesized by solvent-free chemical oxidative polymerization in one-step and one-pot manner. The resulting PEDOT grains had atypical shapes with a volume-average diameter of 57 ± 45 µm and showed an electrical conductivity of 1.9 × 10−3 S cm−1. Furthermore, it was clarified that the PEDOT grains showed light-to-heat photothermal property.

Design space determination and process optimization in at-scale continuous twin screw wet granulation

At-scale industrial continuous twin screw wet granulation process was analyzed and optimized via design of experiment (DoE). The Box-Behnken method was selected to investigate the influence of key process variables on granule properties and tablet properties. The effects of the key process variables were analyzed. The experimental results have demonstrated that both the granule properties and tablet properties are influenced by the throughput, the screw speed and the screw element. Particularly, the screw element type and the milling process were found having significant effects on tablet tensile strength and disintegration time. The design space (DS) based on volume average granule diameter (Y4 < 800 µm) and tablet disintegration time (Y8 < 4 min) was determined using Monte Carlo simulations. Validation experiments have shown the robustness of the DS. A case study of the DS application is presented. It was demonstrated how to select optimum working conditions of key process parameters based on the DS.

Heat Transfer and Fluid Flow Optimization of Titanium Dioxide–Water Nanofluids in a Turbulent Flow Regime

In this study, the convection heat transfer and pressure drop of titanium dioxide–water nanofluids were modeled by applying the fuzzy C-means adaptive neuro-fuzzy inference system approach for a completely developed turbulent flow based on experimentally obtained training and test datasets. Two models were proposed based on the effective parameters; one model was developed for the Nusselt number considering the effects of the Reynolds number, Prandtl number, nanofluid volume concentration and average nanoparticle diameter. Another model was suggested for the pressure drop of the nanofluid as a function of the Reynolds number, nanofluid volume concentration, and average nanoparticle diameter. The results of these two proposed models were compared with experimental data as well as the existing correlations in the literature. The validity of the proposed models was benchmarked by statistical criteria. Moreover, a modified non-dominated sorting genetic algorithm multiobjective optimization technique was applied to obtain the optimum design points, and the final result was shown in a Pareto front.

Green synthesis and characterization of iron oxide nanoparticles using Ficus carica (common fig) dried fruit extract

Ficus carica (common fig) dried fruit extract was used to synthesize iron oxide nanoparticles in this study. Biomaterials in the common fig dried fruit extract synthesized the iron nanoparticles by reducing the iron precursor salt and then acted as capping and stabilizing agents. The nanoparticles were produced smaller than 20nm diameters and oxidized due to the high phenolic compound content in the common fig dried fruit extract. Nanoparticles were characterized by energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS). First, color change and pH reduction occurred immediately due to the iron nanoparticle synthesis. TEM images showed that the nanoparticles were at 9±4nm diameters and the metallic core-oxide shell form. The nanoparticles were in spherical shapes with a monodisperse distribution. EDX, XRD and FTIR analysis signals showed the iron oxyhydroxide/oxide formation. Absorption peaks were detected at 205nm and 291nm due to the iron metallic core hydrolysis products. The intensity-average diameter of nanoparticles was calculated at 475nm diameter by DLS analysis. Colloid stability was determined as moderate at 20.7mV.

Properties and Stability of Perilla Seed Protein-Stabilized Oil-in-Water Emulsions: Influence of Protein Concentration, pH, NaCl Concentration and Thermal Treatment.

Perilla seed protein (PSP) was extracted from defatted perilla seed meal and applied in oil-in-water (O/W) emulsions as an emulsifier. We investigated the influences of protein concentration (0.25–1.5 wt %), pH (3.0–9.0), NaCl concentration (0–350 mmol/L) and thermal treatment (70–90 °C, 30 min) on the physical characteristics of O/W emulsions, including volume-average diameter, ζ-potential, interfacial protein concentration, microstructure and so on. Results showed that increasing PSP concentration would decrease the d4,3 and a 1.0 wt % PSP concentration was sufficient to ensure the stability of emulsion. Under pH 3.0–9.0, emulsions were stable except at pH 3.0–5.0 which was proximal to the isoelectric point (pH 4.5) of PSP. At high NaCl concentrations (250–350 mmol/L), the emulsions exhibited relatively lower absolute ζ-potential values and a large number of aggregated droplets. A moderate thermal treatment temperature (e.g., 70 °C) was favorable for the emulsion against aggregation and creaming. However, when 90 °C thermal treatment was performed, a clear layer separation was observed after 2 weeks storage and the emulsion showed a poor stability. The findings of this work are of great importance for the utilization and development of PSP as an emulsifier for food emulsions.

Towards a general prediction-model for the current-induced mobilisation of objects on the sea floor

The aim of this work was to quantify the physical conditions, required for the mobilisation of unexploded ordnance devices (UXO) on the sea floor. As a basis for this, the hydrodynamic processes around UXO were measured in the wind tunnel and the flume tank in terms of conditions, especially Reynolds numbers. From these experiments, the typical shape of a sandy sea floor in the close vicinity of an object, due to current-induced burial was determined. Knowing this, the model for current-induced mobilisation of objects was developed. The model assumes a critical dimensionless Moment Factor MF=a⋅Reb, where the parameters a and b had to be investigated. This was accomplished by performing a total number of 287 numerical simulations, wind-tunnel testings and flume tank experiments at different geometric scale factors (1:10, 1:5, 1:2 and 1:1). With the parameter values so determined, the model describes the critical situation of an arbitrary shaped cylinder-like object regarding the incident flow velocity, the immersed mass and the burial depth, as well as the length and the volume-averaged diameter of the object.

Effect of heavy tempering on microstructure and yield strength of 28CrMo48VTiB martensitic steel

The 28CrMo48VTiB martensitic steel for sulfide stress cracking (SSC) resistance oil country tubular goods (OCTG) of C110 grade was thermally processed through quenching at 890 °C and tempering at 600 °C–720 °C for 30–90 min. The microstructures of all samples were characterized using field emission scanning electron microscopy (FESEM), electron backscattering diffraction (EBSD), transmission electron microscopy (TEM) and x-ray diffractometry (XRD). Also, the tensile properties were measured. The results indicated that the yield strength (YS) decreased as both the tempering temperature and duration increased, due to the coarsening of martensitic packet/block/lath structures, the reduction of dislocation density, as well as the increase of both the volume fraction and average diameter of the precipitates. The martensitic lath width was the key microstructural parameter controlling the YS of this heavily-tempered martensitic steel, whereas the corresponding relationship was in accordance with the Langford-Cohen model. Furthermore, the martensitic structure boundary and the solid solution strengthening were the two most significant factors dominating the YS, in comparison with the dislocation and precipitation strengthening.

Assessment of spatial heterogeneity in continuous twin screw wet granulation process using three-compartmental population balance model

In this study, a novel three-compartmental population balance model (PBM) for a continuous twin screw wet granulation process is developed, combining the techniques of PBM and regression process modeling. The developed model links screw configuration, screw speed, and blend throughput with granule properties to predict the granule size distribution (GSD) and volume-average granule diameter. The granulator screw barrel was divided into three compartments along barrel length: wetting compartment, mixing compartment, and steady growth compartment. Different granulation mechanisms are assumed in each compartment. The proposed model therefore considers spatial heterogeneity, improving model prediction accuracy. An industrial data set containing 14 experiments is applied for model development. Three validation experiments show that the three-compartmental PBM can accurately predict granule diameter and size distribution at randomly selected operating conditions. Sixteen combinations of aggregation and breakage kernels are investigated in predicting the experimental GSD to best judge the granulation mechanism. The three-compartmental model is compared with a one-compartmental model in predicting granule diameter at different experimental conditions to demonstrate its advantage. The influence of the screw configuration, screw speed and blend throughput on the volume-average granule diameter is analyzed based on the developed model.

Aqueous Superparamagnetic Magnetite Dispersions with Ultrahigh Initial Magnetic Susceptibilities

Superparamagnetic nanoparticles with a high initial magnetic susceptibility χo are of great interest in a wide variety of chemical, biomedical, electronic, and subsurface energy applications. In order to achieve the theoretically predicted increase in χo with the cube of the magnetic diameter, new synthetic techniques are needed to control the crystal structure, particularly for magnetite nanoparticles larger than 10 nm. Aqueous magnetite dispersions (Fe3O4) with a χo of 3.3 (dimensionless SI units) at 1.9 vol %, over 3- to 5-fold greater than those reported previously, were produced in a one-pot synthesis at 210 °C and ambient pressure via thermal decomposition of Fe(II) acetate in triethylene glycol (TEG). The rapid nucleation and focused growth with an unusually high precursor-to-solvent molar ratio of 1:12 led to primary particles with a volume average diameter of 16 nm and low polydispersity according to TEM. The morphology was a mixture of stoichiometric and substoichiometric magnetite according to X-ray diffraction (XRD) and Mössbauer spectroscopy. The increase in χo with the cube of magnetic diameter as well as a saturation magnetization approaching the theoretical limit may be attributed to the highly crystalline structure and very small nonmagnetic layer (∼1 nm) with disordered spin orientation on the surface.

A process optimization strategy of a pulsed-spray fluidized bed granulation process based on predictive three-stage population balance model

In this work, a three-stage population balance model (TSPBM) was developed for a pulsed top-spray fluidized bed granulation (FBG) process. The batch top-spray FBG process was divided into three stages based on the analysis of granule properties evolution and different granulation mechanisms were considered in each stage of the TSPBM. In each stage, population balance model (PBM) describes the evolution of granule size distribution (GSD), and partial least square (PLS) regressions describes the relationship between the operating variables and kernel parameters in PBM. By fitting coefficients of PLS regressions using experimental data, the developed TSPBM establishes a predictive relationship between the manipulated binder spray parameters of pulsed frequency, binder flow rate and atomization pressure and granule critical quality attributes (CQAs). A model-based multi-stage optimization strategy was proposed to improve the granule quality of the pulsed-spray FBG. The optimization strategy reduced the process error caused by mismatch between developed model and actual system. In the optimization strategy, volume average granule diameter is only measured online at the end of each stage. Based on the online measurement, the optimization strategy adjusts process operating variables to remedy any drift between measured and predicted GSD. Validation experiments and simulation tests were carried out to validate the effectiveness of the proposed TSPBM and optimization strategy. The developed TSPBM is shown to accurately predict experimental GSD and shows high accuracy comparing to the one-stage PBM. The proposed optimization strategy can improve the prediction capability by >50% compared to an offline optimization.