Modified supercritical antisolvent method with enhanced mass transfer to fabricate drug nanoparticles

The main aim of this study was to modify the supercritical antisolvent precipitation method to enhance the mass transfer in order to prepare smaller nanoparticles of drugs. The supercritical antisolvent apparatus was customized by introducing a titanium horn in the precipitation chamber for generation of the ultrasonic field for enhanced mass transfer and the method was called supercritical antisolvent with enhanced mass transfer (SAS-EM). The effects of flow rate, ultrasonic amplitude, drug concentration and flow time on the particle size were investigated. The results showed that increasing the flow rate, incrementing the ultrasonic power up to an optimum point, decreasing the drug concentration and reducing the flow time helped to achieve smaller quercetin particles in the range of 120–450 nm. It is also shown that there is a tradeoff between the particle size and the yield; therefore the process parameters can be selected based on the particle size requirement. DSC studies suggested that the crystallinity of SAS-EM prepared quercetin nanoparticles decreased as compared to original quercetin powder. The dissolution of SAS-EM prepared nanoparticles increased significantly in comparison with the original quercetin powder. However, there was no significant difference in the dissolution of various quercetin nanoparticles samples prepared by the SAS-EM process. The best dissolution percent achieved was 75% for the smallest size sample prepared at the flow rate of 5 ml/min, power supply of 200 W, drug concentration of 10 mg/ml, and flow time of 4 min.     

Droplet size and morphology analyses of dry liquid

Dry water is a free-flowing powder consisting of numerous solid particle-stabilized water droplets with typical sizes and volumes of 10^?6–10^?4 m and 10^?3–10³ pL, respectively. We describe the first characterization of dry water stabilized with hydrophobic silica nanoparticles, by using laser diffraction droplet size distribution analysis. The water droplet dimensions were measured to be a few tens of micrometers in air, by using the laser diffraction method. These dimensions correspond well with measurements by both laser diffraction and optical microscopy methods for a Pickering-type water-in-n-dodecane emulsion prepared by dispersing dry water in n-dodecane. Optical microscopy confirmed that the dry water consisted of flocs of non-spherical water droplets, and the flocs ranged in size from a few tens of micrometers to a few millimeters in air. On the basis of these results, the flocs of water droplets were proposed to dissociate into individual water droplets under the air blast during droplet size measurement by the laser diffraction method. It was also confirmed that pressurizing the dry water between two glass slides led to encapsulated water leaking from the silica nanoparticle shells. This on-demand pressure-sensitive water leak phenomenon shows a possible usage of the dry waters as a material delivery carrier.     

Core-shell composite nanoparticles with magnetic and temperature dual stimuli-responsive properties for removing emulsified oil

Core-shell magnetic and thermosensitive composite nanoparticles, named as M-DMEA, were prepared by grafting polyoxyalkylated N,N-dimethylethanolamine onto magnetite (Fe₃O₄) nanoparticles. A series of characterizations were performed to figure out the properties of the as-prepared M-DMEA. The results reveal that the M-DMEA is superparamagnetic and has irregular shape with a core-shell structure. The flocculation performance of M-DMEA in oily wastewater produced from flooding (OWPF) treatment was investigated for the first time. It was found that the M-DMEA could separate emulsified oil droplets from OWPF rapidly under an external magnetic field with high oil removal (92.3% at the dosage of 2.5 g/L) at 65 °C. Moreover, due to its excellent magnetic response, the M-DMEA can be collected and recycled for another 3 cycles. Factors affecting the flocculation performance were discussed in detail. It is anticipated that as-prepared M-DMEA might find its potential application in practical oily wastewater treatment.     

Synthesis of cobalt boride nanoparticles using RF thermal plasma

Nanosize cobalt boride particles were synthesized from the vapor phase using a 30 kW–4 MHz radio frequency (RF) thermal plasma. Cobalt and boron powder mixtures used as precursors in different composition and feed rate were evaporated immediately in the high temperature plasma and cobalt boride nanoparticles were produced through the quenching process. The X-ray diffractometry (XRD) patterns of cobalt boride nanoparticles prepared from the feed powder ratio of 1:2 and 1:3 for Co:B showed peaks that are associated with the Co₂B and CoB crystal phases of cobalt boride. The XRD analysis revealed that increasing the powder feed rate results in a higher mass fraction and a larger crystalline diameter of cobalt boride nanoparticles. The images obtained by field emission scanning electron microscopy (FE-SEM) revealed that cobalt boride nanoparticles have a spherical morphology. The crystallite size of the particles estimated with XRD was found to be 18–22 nm.     

La-doped ZnO nanoparticles: Simple solution-combusting preparation and applications in the wastewater treatment

La-doped ZnO nanoparticles have been successfully synthesized by a simple solution combustion method via employing a mixture of ethanol and ethyleneglycol (v/v = 60/40) as the solvent. Zinc acetate and oxygen gas in the atmosphere were used as zinc and oxygen sources, and La(NO₃)₃ as the doping reagent. The as-obtained product was characterized by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. Experiments showed that La-doped ZnO nanoparticles exhibited the higher capacities for the removal of Pb²⁺ and Cu²⁺ ions in water resource than undoped ZnO nanoparticles.     

Sintering behavior of spherical aggregated nanoparticles prepared by spraying colloidal precursor in a heated flow

The sintering behavior of spherical aggregated nanoparticles prepared by spraying colloidal precursor into a heated flow was investigated both experimentally and theoretically. Spherical micrometer-sized particles consisting of compactly aggregated nanoparticles were formed, due to solvent evaporation and the drying process of the colloidal precursor. The degree of sintering of aggregated nanoparticles depended on the furnace temperature profile, residence time and primary particle size of the aggregated nanoparticles. Spherical monodispersed colloidal silica, in sizes ranging from 22 to 100 nm was selected as the primary particles. The sintering rate increased with temperature and residence time, and decreased with increasing primary particle size. The aggregated nanoparticles sintered completely, resulting in particles with smooth surfaces that were synthesized at 1400 °C, residence time 31.7 s that was obtained by using a carrier gas flow rate of 1.5 L/min and 0.1 M colloidal silica nanoparticles 100 nm in size. An appropriate model of sintering in the system was proposed to explain the shrinkage and the neck growth of the aggregated nanoparticles. The sintering analysis suggested that solid-state volume diffusion suitably described the sintering mechanism of spherical aggregated silica nanoparticles in a heated flow.     

Compressive strength and drying shrinkage of fly ash-bottom ash-silica fume multi-blended cement mortars

This paper studies the physical properties, compressive strength and drying shrinkage of multi-blended cement under different curing methods. Fly ash, ground bottom ash and undensified silica fume were used to replace part of cement up to 50% by weight. Specimens were cured in air at ambient temperature, water at 25, 40 and 60 °C, sealed with plastic sheeting for 28 days. The results show that absorption and volume of permeable pore space (voids) of blended cement mortars at 28 day under all curing methods tend to increase with increasing silica fume replacement. The compressive strength of blended cement with fly ash and bottom ash was lower than that of Portland cement control at all curing condition while blended cement with silica fume shows higher compressive strength. In addition, the compressive strength of specimens cured with water increased with increasing curing temperature. The drying shrinkage of all blended cement mortar cured in air was lower than that of Portland cement control while the drying shrinkage of blended cement mortar containing silica fume, cured with plastic sealed and water at 25 °C was higher than Portland cement control due to pore refinement and high autogenous shrinkage. However, the drying shrinkage of blended cement mortar containing SF cured with water at 60 °C was lower than that of Portland cement control due to lower autogenous shrinkage and the reduced microporosity of C–S–H.     

Characteristics and release property of polylactic acid/sodium monofluorophosphate microcapsules prepared by spray drying

Microcapsules composed of polylactic acid (PLA)/corrosion inhibitor sodium monofluorophosphate (MFP) were prepared by spray drying, and the effects of processing parameters on the morphology and encapsulation efficiency of the microcapsules were investigated. The results showed that low viscous PLA solution only resulted in porous microcapsules with low encapsulation efficiency, whereas filamentous substances were produced instead of microcapsules once PLA solution content exceeded 5%. When spray pressure exceeded 0.4 MPa, the microcapsule surface was wrinkled due to high evaporation rate of the atomized droplets. The spray pressure less than 0.3 MPa created larger atomized droplets and yielded the adhesive microcapsules with lower encapsulation efficiency. The optimal emulsion parameters were as follows: PLA concentration, 5%; water-oil ratio, 1:9; inlet air temperature, 50 °C; and spray pressure, 0.4 MPa. The resulting microcapsules exhibited a good sustained-release behavior in a simulated concrete pore solution.     

Effects of Au/Fe and Fe nanoparticles on Serratia bacterial growth and production of biosurfactant

The overall objective of this study was to compare the effects of Au/Fe and Fe nanoparticles on the growth and performance of Serratia Jl0300. The nanoparticle effect was quantified not only by the bacterial growth on agar plate after 1 hour interaction with the nanoparticles, but also by its production of a biosurfactant from used vegetable oil. The nanoparticles were prepared using the foam method. The concentrations of the nanoparticles used for the bacterial interaction study were varied from 1 mg/L to 1 g/L. The test results showed that the effect of nanoparticles on the bacterial growth and biosurfactant production varied with nanoparticle type, concentrations, and interaction time with the bacteria. Au/Fe nanoparticles didn't show toxicity to Serratia after short time (1 h) exposure, while during 8 days fermentation Au/Fe nanoparticles inhibited the growth of Serratia as well as the biosurfactant production when the concentration of the nanoparticles was higher than 10 mg/L. Fe nanoparticles showed inhibition effects to bacterial growth both after short time and long time interaction with Serratia, as well as to biosurfactant production when its concentration was higher than 100 mg/L. Based on the trends observed in this study, analytical models have been developed to predict the bacterial growth and biosurfactant production with varying concentrations of nanoparticles.     

Preparation and photocatalytic activity of nanoporous zirconia electrospun fiber mats

Nanoporous zirconia electrospun fiber mats (NZEFM) have been prepared by an electrospinning process using nonionic F108 as a pore-forming agent. This nonaqueous synthesis route has been employed to fabricate a stable “building block” porous structure inside the nano-scale fibers. The mats composed of individual fibers proved to be robust after calcination at up to 450 °C or stirring in water. The photocatalytic activity of NZEFM is apparently higher than that of commercial zirconia powder for the degradation of methyl orange in aqueous solution. Moreover, amorphous NZEFM mixed with the tetragonal phase obtained at 450 °C proved to be more efficient than the monoclinic phase NZEFM obtained at 900 °C. Various dyes could be degraded by NZEFM under UV light irradiation. The highly photocatalytic activity of NZEFM could be attributed to its high specific surface area and nanoporous “building block” structure made up of stacked zirconia nanoparticles.     

Microwave-assisted synthesis of BaWO4 nanoparticles and its photoluminescence properties

Single-crystal BaWO₄ nanoparticles have been successfully synthesized under microwave irradiation. The results show that nearly monodisperse BaWO₄ nanoparticles have been successfully prepared without using surfactants. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL). The XRD results indicated that the BaWO₄ nanoparticles obtained had a tetragonal unit cell (a = 0.5612, c = 1.2706 nm). The TEM images show that the as-prepared BaWO₄ have good narrow particle-sized distributions containing a number of nanoparticles with uniform sizes. The products show a strong photoluminescence peak at 432–436 nm with the excitation at 365 nm.     

Synthesis of hydroxysodalite zeolite by alkali-activation of basalt powder rich in calc-plagioclase

Hydroxysodalite (H-SOD) microcrystalline particles were synthesized from basalt powder rich in calcic-plagioclase (anorthite) by alkali activation at 80 °C/24 h. Sodium hydroxide (NaOH) solution was used as alkaline activator. The reactivity of the natural solid precursor basalt was studied using differential scanning calorimetry (DSC), and a maximum reaction enthalpy of (?ΔH) of 170 J/g was obtained. The chemical, mineralogical, and textural properties were obtained by using X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N₂-adsorption-desorption measurements. The synthesized material has a specific BET surface area of 20.5 m² g^?1 approximately 200 times higher than raw basalt material (0.1 m² g^?1). The compressive strength of basalt based H-SOD/sand composite samples cured at 80 °C for 24 h upon using different amounts of the activator (NaOH) was evaluated under dry and saturated conditions. The dry samples with NaOH/basalt mass ratio of 0.12 have reached a compressive strength of 57 MPa. Wet samples, on the other hand, showed a compressive strength of 25 MPa after seven days of soaking in water and four episodes of wetting and drying. The present work illustrates that crystalline H-SOD could be synthesized from cheap basalt powder precursor.     

Synthesis of γ-Al2O3 nanopowders by freeze-drying

This work studies the synthesis of γ-Al₂O₃ nanopowders by a freeze-drying method. Aqueous solutions of Al₂(SO₄)₃·18H₂O were used as precursors to Al concentrations of 0.76, 1.00 and 1.40 M. Homogeneous spherical granules with diameters ranging from 1 to 100 μm have been obtained. These porous granules are constituted by soft agglomerates of nanoparticles with primary particle size lower than 20 nm. The microstructure of the agglomerates largely depends on the freezing kinetics. After drying amorphous aluminium sulphate powder is obtained that decomposes at 825 °C leading to the formation of γ-Al₂O₃. Physicochemical study of the freeze-dried powders is performed through particle size distribution and zeta potential measurements. The characterisation of the powders is evaluated considering the influence of processing parameters such as the salt concentration, the freezing rate and the thermal treatment for the synthesis and the dispersing conditions of the obtained powders. By adjusting the dispersing conditions a minimum particle size <30 nm is measured, thus confirming that granules can be easily dispersed into nanoparticles.     

Synthesis of magnetite nanoparticles by surfactant-free electrochemical method in an aqueous system

A simple surfactant-free electrochemical method is proposed for the preparation of magnetite nanoparticles using iron as the anode and plain water as the electrolyte. This study observed the effects of certain parameters on the formation of magnetite nanoparticles and their mechanism in the system, including the role of OH^? ions, the distance between electrodes and current density. We found that OH^? ions play an important role in the formation of magnetite nanoparticles. Particle size can be controlled by adjusting the current density and the distance between electrodes. Particle size increases by increasing the current density and by decreasing the distance between electrodes. Particle formation cannot be favored when the distance between electrodes is larger than a critical value. The magnetite nanoparticles produced by this method are nearly spherical with a mean size ranging from 10 to 30 nm depending on the experimental conditions. They exhibit ferromagnetic properties with a coercivity ranging from 140 to 295 Oe and a saturation magnetization ranging from 60 to 70 emu g^?1, which is lower than that of the corresponding bulk Fe₃O₄ (92 emu g^?1). This simple method appears to be promising as a synthetic route to producing magnetite nanoparticles.     

High-sensitivity humidity sensor based on SnO2 nanoparticles synthesized by microwave irradiation method

Tin oxide hexagonal-shaped nanodiscs (SnO) and spherical nanoparticles (SnO₂) have been prepared by using a simple household microwave irradiation method with an operating frequency of 2.45 GHz. This technique permits us to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystallite size was evaluated from powder X-ray diffraction (XRD) studies and was in the 20 to 25 nm range. Transmission electron microscopy (TEM) analysis showed that the as prepared SnO form as hexagonal-shaped nanodiscs and upon subsequent annealing at 500 °C for 5 h in air, the SnO gets converted to spherical-shaped nanoparticles of SnO₂. The SnO₂ sample shows good sensitivity towards the relative humidity. The calculated response and recovery time were found to be 32 s and 25 s respectively. These results indicate promising applications of SnO₂ nanoparticles in a highly sensitive environmental monitoring and humidity controlled electronic devices. The samples were further subjected to thermal analyses (TG–DTA) and UV–VIS diffusion reflectance spectroscopy (DRS) studies.     

Effect of sputtering power on the electrical and optical properties of Ca-doped ZnO thin films sputtered from nanopowders compacted target

In the present work, we have deposited calcium doped zinc oxide thin films by magnetron sputtering technique using nanocrystalline particles elaborated by sol–gel method as a target material. In the first step, the nanoparticles were synthesized by sol–gel method using supercritical drying in ethyl alcohol. The structural properties studied by X-ray diffractometry indicates that Ca doped ZnO has a polycrystalline hexagonal wurzite structure with a grain size of about 30 nm. Transmission electron microscopy (TEM) measurements have shown that the synthesized CZO is a nanosized powder. Then, thin films were deposited onto glass substrates by rf-magnetron sputtering at ambient temperature. The influence of RF sputtering power on structural, morphological, electrical, and optical properties were investigated. It has been found that all the films deposited were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (0 0 2) crystallographic direction. They have a typical columnar structure and a very smooth surface. The as-deposited films show a high transmittance in the visible range over 85% and low electrical resistivity at room temperature.     

Photocatalytic behavior of TiO2 nanoparticles supported on porous aluminosilicate surface modified by cationic surfactant

In order to utilize the photocatalytic function of TiO₂ nanoparticles in materials manufactured from organic polymeric compounds, such as paper, resins, and textiles, TiO₂ nanoparticles supported on aluminosilicate, which contained 1, 5, and 10 wt% of TiO₂ were prepared by mixing commercial TiO₂ nanoparticles and porous aluminosilicate at pH 7 in a cationic surfactant aqueous solution. Most of the supported TiO₂ nanoparticles on the aluminosilicate surface were observed by TEM–EDS (energy depressive X-ray spectroscopy) analysis. TiO₂ nanoparticles supported on aluminosilicate reduced the formaldehyde concentration from 20 to 0 ppm after UV irradiation for 20 h; the reduction of formaldehyde concentration under UV irradiation was obviously different from that in the dark. Moreover, a paper mixed with 20 wt% of TiO₂ nanoparticles supported on aluminosilicate bleached the stains colored with cigarette tar after UV irradiation for 6 h. However, the paper maintained its initial tensile strength even after UV irradiation for 1 year; in contrast, the paper mixed with a simple dry mixture of TiO₂ powder and aluminosilicate lost approximately half of its initial tensile strength after a year. TiO₂ nanoparticles supported on aluminosilicate could exhibit photocatalytic activity without decomposing the organic polymeric compounds.     

Improved chemical stability of ascorbic acid and thiamine nitrate in L-HPC granules

The stability of drugs in extruded granules prepared with low substituted hydroxypropylcellulose (L-HPC) and water was investigated using ascorbic acid (AA) and thiamine nitrate (TN) as model drugs. d-Mannitol was used as the control additive for a comparison with L-HPC. The percentage of AA remaining after storage at 60 °C for 14 days in a closed glass bottle was 57% in d-mannitol granules and 89% in L-HPC granules, showing higher stability of AA in L-HPC granules. On powder X-ray diffraction measurement, AA in L-HPC and d-mannitol granules was in an amorphous state. The loss on drying (LOD) (1 g, 105 °C, 2 h) of the granules containing both AA and TN was higher in L-HPC granules (1.96%). The moisture content around AA and TN in granules was calculated. The contents were 1.36% and 4.67% in L-HPC and d-mannitol granules, respectively. Furthermore, the water activities at 25–40 °C were measured in L-HPC and d-mannitol granules, being lower in L-HPC granules at all measurement temperatures. These findings suggested that the superior storage stability of AA in granules prepared with L-HPC was due to L-HPC-induced reduction of the moisture content around AA and TN and water activity of the granules.     

Positive and negative effects of dielectric breakdown in transformer oil based magnetic fluids

The transformer oil based magnetic fluids can be considered as the next-generation insulation fluids because they offer exciting new possibilities to enhance dielectric breakdown voltage as well as heat transfer performance compared to pure transformer oils. In this study, we have investigated the dielectric breakdown strength of the fluids with the various volume concentrations of nanoparticles in accordance with IEC 156 standard and have tried to find the reason for changing the dielectric breakdown voltage of the fluids from the magnetic field analysis. It was found that the dielectric breakdown voltage of pure transformer oil is around 12 kV with the gap distance of 1.5 mm. In the case of our transformer oil-based magnetic fluids with 0.08% < Φ < 0.6% (Φ means the volume concentration of magnetic nanoparticles), the dielectric breakdown voltage shows above 40 kV, which is 3.3 times higher positively than that of pure transformer oil. Negatively in the case when the volume concentration of magnetic nanoparticles is above 0.65%, the dielectric breakdown voltage decreases reversely. From the magnetic field analysis, the reason might be considered as two situations: the positive is for the conductive nanoparticles dispersed well near the electrodes, which play an important role in converting fast electrons to slow negatively charged particles, and the negative is for the agglomeration of the particles near the electrodes, which leads to the breakdown initiation.     

Preparation,characterization and dissolution behavior of artemisinin microparticles

In the present study, a modified 4-fluid nozzle spray drier was used to prepare microparticles of a poorly water soluble drug, artemisinin with the aim of improving its solubility. We also investigated the effect of process variables on the physical properties and dissolution rate of spray dried artemisinin. A full factorial experimentally designed study was performed to investigate the following spray drying variables: inlet temperature and feed concentration. The artemisinin powder and spray dried artemisinin microparticles were characterized by scanning electron microscopy (SEM), differential scanning calorimetric (DSC), X-ray diffraction (XRD) and dissolution. SEM study suggested that the inlet temperature and feed concentration impacted on the particle size of the spray dried particles. The crystallinity of spray dried particles was slightly decreased with increasing inlet temperature and concentration. The dissolution of spray dried particles was markedly improved as compared to commercial artemisinin. A dissolution surface-response model was used to elucidate the significant and direct relationships between drug feed concentration and inlet temperature on one hand and dissolution on the other hand. The best dissolution was found to be 117.00 ± 5.15 μg/mL at the drug feed concentration of 10 g/L and inlet temperature of 140 °C.