Antisolvent Effect Research Articles

Investigation of antisolvent effect on gold nanoparticles during postsynthesis purification

Gold nanoparticles (Au NPs) were synthesized by reducing HAuCl4 using borane tert-butylamine complex in the presence of alkylamine (dodecylamine, hexadecylamine, and octadecylamine) and didodecyldimethylammonium bromide. Ethanol was used as an antisolvent for the postsynthesis purification of Au NPs. Au NPs had uniform size distribution after first wash with ethanol and the aggregation and growth of Au NPs happened after second wash with ethanol. The Au NPs were characterized by TEM, SEM, XRD, 1H NMR, UV–vis absorption and FTIR spectroscopy. The aggregated mechanism after the second wash with ethanol was proposed. Au NPs still retained their monodispersity after second wash compared with after first wash using the antisolvents, such as acetonitrile, dimethyl sulfoxide and acetone. The presented results suggest that the good choice of antisolvent is critical for the postsynthesis purification of Au NPs.

Improvement of polymer:fullerene bulk heterojunction morphology via temperature and anti-solvent effect

Morphology of polymer:fullerene bulk heterojunctions (BHJ) displays beside suitable energy level alignment between donor and acceptor as well as a sufficient absorption one of the most crucial impacts on organic photovoltaic device efficiency and stability. In particular, the structural order of the polymer phase impacts the charge separation efficiency and transport. In this work we present a comprehensive study on the control of the polymeric order initiated already in solution by using fractions of anti-solvent isopropanol (IPA), and via adjusting the processing temperature for common solutions of an anthracene-containing poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) bearing statistically either linear (octyloxy) or branched (2-ethylhexyloxy) side-chains (AnE-PVstat) and phenyl-C61-butyric acid methyl ester (PCBM). Detailed analysis of photophysical data, absorption, and photoluminescence (PL) spectra, of deposited AnE-PVstat:PCBM thin films suggest the formation of J-aggregates for the copolymer to be in strong correlation with the processing formulation (presence of non-solvent IPA) and post-treatment parameters (annealing temperature). The findings for our system indicate that the addition of IPA increases the intermolecular interaction between the polymer chains, consistent with enhanced charge carrier (hole) mobility (μh) in the final film reaching values as high as 10−3 cm2 V−1 s−1. The subtle control of polymer aggregation led to an overall variation in the solar cell device efficiency by about 50%, with optimal processing settings of IPA additive and a solution temperature of 15 °C.

Polymorphism in Pharmaceutical Drugs by Supercritical CO2 Processing: Clarifying the Role of the Antisolvent Effect and Atomization Enhancement

Supercritical carbon dioxide (scCO2) induces polymorphism in pharmaceutical drugs. However, it is unclear whether polymorphism is induced by the CO2 antisolvent effect or simply by the spray-drying step involved in the scCO2 antisolvent processes. Herein, this effect is clarified by using supercritical enhanced atomization techniques assisted with scCO2 and scN2 and three drugs (indomethacin (IND), carbamazepine (CBZ), and theophylline (TPL)) that have already exhibited polymorphism when processed by classical supercritical antisolvent (SAS) processing. Polymorphs were obtained by supercritical enhanced atomization (SEA) using either CO2 or N2 revealing that polymorphism was induced by atomization in all cases except for TPL, which was very sensitive to the CO2 antisolvent action. The TPL polymorph was produced by the atomization of supercritical antisolvent induced suspensions (ASAIS) process, which enables SAS to be performed in standard (atmospheric pressure) spray dryers. A computational fluid dynamic...

Cellulose Solubility in Ionic Liquid Mixtures: Temperature, Cosolvent, and Antisolvent Effects.

Select ionic liquids (ILs) dissolve significant quantities of cellulose through disruption and solvation of inter- and intramolecular hydrogen bonds. In this study, thermodynamic solid-liquid equilibrium was measured with microcrystalline cellulose in a model IL, 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIm][DEP]) and mixtures with protic antisolvents and aprotic cosolvents between 40 and 120 °C. The solubility of cellulose in pure [EMIm][DEP] exhibits an asymptotic maximum of approximately 20 mass % above 100 °C. Solubility studies conducted on antisolvent mixtures with [EMIm][DEP] and [BMIm][Cl] indicate that protic solvents, ethanol, methanol, and water, significantly reduce the cellulose capacity of IL mixtures by 38-100% even at small antisolvent loadings (<5 mass %). Alternatively, IL-aprotic cosolvent (dimethyl sulfoxide, dimethylformamide, and 1,3-dimethyl-2-imidazolidinone) mixtures at mass ratios up to 1:1 enhance cellulose dissolution by 20-60% compared to pure [EMIm][DEP] at select temperatures. Interactions between the IL and molecular solvents were investigated by Kamlet-Taft solvatochromic analysis, FTIR, and NMR spectroscopy. The results indicate that preferential solvation of the IL cation and anion by co- and antisolvents impact the ability of IL ions to interact with cellulose thus affecting the cellulose dissolution capacity of IL-solvent mixtures.

アルコール添加による高出力マイクロ波照射粒子生成プロセス

Microwave has been often used for nano-particle synthesis because rapid growth and mono-dispersed particle size are obtained. However, superheat behavior causes larger bubble size and disorders temperature distribution when higher power of microwave is irradiated. Accordingly, superheat must be prevented for stable operation of nano-particle process. In previous study, we found that bubble formation happened during particle formation at the same time when FeCl3 aqueous solution is heated by microwave. According to the results through in-situ particle size measurement during the irradiation, superheat behavior occurred at the condition of the higher power and lower suspension density. In this study, ethylene glycol with lower electric constant was added to promote particle nucleation and to enlarge particle number density. Moreover, the solute is not dissolved in ethylene glycol as anti-solvent although ethylene glycol is dissolved in water. The results showed that bubble size during the irradiation and particle size after the irradiation became smaller by the ethylene glycol addition. As a result, operation by higher power became possible, and higher particle number density was obtained as synergy effect of anti-solvent effect and quick thermal response by microwave. Finally, addition of alcohol became good method for nano-particle formation process to prevent superheat behavior during higher power irradiation.

Effects of solid poly (ethylene glycols) addition to the solutions of aniline or N,N-dimethylaniline with water: Experimental measurements and modeling

In this work, the liquid - liquid and solid - liquid phase behaviour of ten aqueous pseudo-binary and three binary systems containing polyethylene glycol 2050, polyethylene glycol 35000, aniline, N,N-dimethylaniline and water, in the temperature range T = (298.15 to 350.15) K and at ambient pressure of 0.1 MPa, was studied. The obtained temperature-composition phase diagrams showed that the only functional co-solvent was PEG2050 for aniline in water, while PEG35000 even showed a clear anti-solvent effect in the N,N-dimethylaniline aqueous system. The experimental SLE data have been correlated by the Non-Random Two-Liquid (NRTL) model, and the correlation results are in accordance with the experimental results.

Anti-solvent crystallization of a ternary Lennard–Jones mixture performed by molecular dynamics

Anti-solvent crystallization from a ternary mixture was examined by an NpT ensemble molecular dynamics simulation. The co-solvent and anti-solvent effects were represented by the Lennard–Jones interaction energy parameter, εij. The homogeneous binary solution of the solute and solvent was achieved at a constant temperature and pressure. Anti-solvent crystallization was introduced by changing some co-solvent molecules to anti-solvent molecules, immediately. The configuration of solute molecules was investigated by using the radial distribution function, g(r), and the local composition, xL. The value of εij affected the configuration of the solute molecules significantly; the decrease in εij provided the localization and crystallization of the solute molecules. The composition of the anti-solvent molecules in the solution also affected the configuration of the solute molecules; the increase in the anti-solvent composition produced the crystal structure of the solute molecules more rapidly. These qualitative results corresponded well to anti-solvent crystallization. The radial distribution function represented the crystal structure for solute molecules, and the local composition of the solute was increased from the bulk composition as the effect of the anti-solvent increased. We proposed that the time variation of the local composition of the solute represents the temporal development of the crystal structure and the time to crystallization well.

입체 장애 알카놀아민 혼합 수용액에서 중탄산칼륨 결정의 냉각 반용매 결정화

absorption processes have a good potential for large scale capture of but a large amount of absorbing solution has to be regenerated, undesirably increasing the consumption of energy such as sensible heat and latent heat of vaporization. In this study, a cooling crystallization process which would separate the -rich potassium bicarbonate crystals from -lean water was developed to reduce the energy penalty. Sterically hindered alkanolamine additives were used to enhance the removal efficiency and their antisolvent effect on the crystallization was found in a continuous cooling crystallizer. The production yields of crystals were increased in the sequence of 2-amino-2-methyl-1-propanol (AMP) nuclear magnetic resonance, the additives favored the formation of bicarbonate ions by steric hindrance effect and increased the supersaturation of . It is shown that the additives increase the mean size of crystals and crystal growth rate by increasing supersaturation. The additives are promising for enhancing the removal efficiency and reducing the regeneration energy cost of absorbing solution by promoting crystallization.

Chitosan nanoparticles generation using CO2 assisted processes

The current concerns of sustainable development make the biobased polymers the object of many studies. Chitosan is a biobased, biocompatible and biodegradable polysaccharide with antibacterial and cytocompatible properties. In this study, we aimed to generate chitosan particles with two processes using CO2 under pressure, in order to decrease the use of organic solvent and to obtain nanoparticles.The first is a supercritical anti-solvent process: CO2 acts as an anti-solvent toward an acetic acid aqueous solution of dissolved chitosan in which ethanol was added to enhance the anti-solvent effect. The reciprocal miscibility of CO2 with the solvents induces the reduction of their solvating power, leading to supersaturation at the capillary outlet and causing the crystallization of the particles.This process led to the generation of more or less agglomerated chitosan nanoparticles with an individual average size of 378nm.In the second process, the pressurized CO2 is dissolved in water to lower the pH. This in turn allows the chitosan to be dissolved and the resulting solution is sprayed, thanks to the pressurized CO2, into a hot air stream. This new process allowed the generation of dried chitosan nanoparticles with a median size of 390nm.

New thermoresistant polymorph from CO2 recrystallization of minocycline hydrochloride.

To prepare and thoroughly characterize a new polymorph of the broad-spectrum antibiotic minocycline from its hydrochloride dehydrate salts. The new minocycline hydrochloride polymorph was prepared by means of the antisolvent effect caused by carbon dioxide. Minocycline recrystallized as a red crystalline hydrochloride salt, starting from solutions or suspensions containing CO2 and ethanol under defined conditions of temperature, pressure and composition. This novel polymorph (β-minocycline) revealed characteristic PXRD and FTIR patterns and a high melting point (of 247 ºC) compared to the initial minocycline hydrochloride hydrates (α-minocycline). Upon dissolution the new polymorph showed full anti-microbial activity. Solid-state NMR and DSC studies evidenced the higher chemical stability and crystalline homogeneity of β-minocycline compared to the commercial chlorohydrate powders. Molecular structures of both minocyclines present relevant differences as shown by multinuclear solid-state NMR. This work describes a new crystalline structure of minocycline and evidences the ability of ethanol-CO2 system in removing water molecules from the crystalline structure of this API, at modest pressure, temperature and relatively short time (2h), while controlling the crystal habit. This process has therefore the potential to become a consistent alternative towards the control of the solid form of APIs.

&lt;b&gt;Solid-liquid equilibrium measurements for the ternary system PCL + chloroform + nonsolvents (n-hexane, ethanol, methanol, isopropanol) at 303.15 K&lt;/b&gt; - doi: 10.4025/actascitechnol.v36i1.16615

This work reports experimental data of polycaprolactone (PCL) polymer solubility in chloroform as solvent and n-hexane, methanol, ethanol and isopropanol as nonsolvents, at atmospheric pressure (about 1,0 bar) and temperature of 303.15 K. It was used PCL with 70000-90000 and 2000 molar mass (MM). The experiments of solubility were performed using a jacketed-cell with temperature controlled by an ultrathermostatic bath, in which a turbidity method was adopted and used. From the obtained results it should be observed that the n-hexane presented a more pronounced anti-solvent effect in the PCL solubility, where the heterogeneous region (solid phase presence) was broader than when other nonsolvent. It was also observed that the binodal curves measured with the high molar mass polymer showed similar results compared to the low molar mass one.

Cosolvent or Antisolvent? A Molecular View of the Interface between Ionic Liquids and Cellulose upon Addition of Another Molecular Solvent

Ionic liquids (ILs) are promising nonderivatizing solvents for the dissolution of cellulose and lignin in biomass pretreatment processes, which are, however, retarded by sluggish dynamics. Recent investigations showed that cosolvents such as dimethyl sulfoxide (DMSO) can accelerate the dissolution dramatically. On the other hand, water is used as a common antisolvent to regenerate cellulose from solutions. To understand the co-/antisolvent effects in dissolving cellulose by ILs, we performed molecular dynamics simulations of the interfaces between an Iβ cellulose crystal and different solvent systems, including ILs, DMSO, water, and mixed solvent systems. The density profiles and pair energy distributions (PEDs) show that the anions interact much more strongly with the cellulose surface than the cations, which is responsible for the dissolution of cellulose. It was found that the number of chloride ions in contact with cellulose does not cause the co-/antisolvent effect. In contrast, the cellulose-chloride PEDs are sensitive to the addition of molecular solvents, such as DMSO and water. Detailed analyses show that multiple hydrogen-bond (HB) patterns are formed between chloride and the hydroxyl groups of cellulose that are noticeably changed in the presence of DMSO or water. A combined analyses of both the PEDs and HB patterns can provide valuable information about the enhancement of cellulose dissolution. The simulation results in this work present useful knowledge for the design of solvent systems for dissolving cellulose or other types of biomass.

Exploiting the homogeneous expansion limit of CO2-expanded media for the synthesis of polymeric nanoparticles

This paper describes a novel method for the direct synthesis of polymeric nanoparticles based on the CO2-expanded liquid concept. This technique exploits the anti-solvent effect of dense CO2 to induce an emulsion in a polymer solution at a point known as the homogeneous expansion limit (HEL). Polymerization is carried out in the dispersed phase which consists mainly of polymer and monomer. Herein, we report on nanoparticle formation via polymerization of methyl methacrylate using a macroazoinitiator in CO2-expanded ethanol at 70°C and 10MPa. It is shown that polymerization at the HEL leads to well defined polymeric nanoparticles with diameters of around 100nm. The nanoparticles are generally smaller and more uniform in size than those obtained in the corresponding CO2-free approach (dispersion polymerization).

Antisolvent Crystallization Approach to Construction of CuI Superstructures with Defined Geometries

A facile high-yield production of cuprous iodide (CuI) superstructures is reported by antisolvent crystallization using acetonitrile/water as a solvent/antisolvent couple under ambient conditions. In the presence of trace water, the metastable water droplets act as templates to induce the precipitation of hollow spherical CuI superstructures consisting of orderly aligned building blocks after drop coating. With water in excess in the mixed solution, an instant precipitation of CuI random aggregates takes place due to rapid crystal growth via ion-by-ion attachment induced by a strong antisolvent effect. However, this uncontrolled process can be modified by adding polymer polyvinyl pyrrolidone (PVP) in water to restrict the size of initially formed CuI crystal nuclei through the effective coordination effect of PVP. As a result, CuI superstructures with a cuboid geometry are constructed by gradual self-assembly of the small CuI crystals via oriented attachment. The precipitated CuI superstructures have been used as competent adsorbents to remove organic dyes from the water due to their mesocrystal feature. Besides, the CuI superstructures have been applied either as a self-sacrificial template or only as a structuring template for the flexible design of other porous materials such as CuO and TiO2. This system provides an ideal platform to simultaneously investigate the superstructure formation enforced by antisolvent crystallization with and without organic additives.

Coordination Chemistry and Antisolvent Strategy to Rare-Earth Solid Solution Colloidal Spheres

We have devised in this work a general synthetic strategy for preparation of single- and multicomponent rare-earth coordination polymer colloidal spheres (RE-CPCSs). This strategy is based on an integration of coordination chemistry and antisolvent effect for synchronized precipitation. Highly monodisperse RE-CPCSs with homogeneous mixing of RE elements, which are not readily attainable by any existing methods, have been successfully prepared for the first time. In addition, the type and molar ratio of these colloidal spheres can be adjusted easily in accordance to the variety and dosage of precursor salts. The molar ratio of RE elements in as-prepared colloidal spheres shows a linear relationship to that of starting reactants. Furthermore, the RE-based core/shell colloidal spheres can be facilely prepared by introducing other metal salts (beyond lanthanide elements) owing to their different coordination chemistry and precipitation behavior. By adjusting concentrations of the ionic activators, luminescent properties can be tuned accordingly. Moreover, the RE-CPCSs can be transformed to monodisperse lanthanide oxide spheres via simple heat treatment. We believe that the present synthetic strategy provides a viable route to prepare other lanthanide-containing colloidal spheres that have enormous potential for future applications as optoelectronic devices, catalysts, gas sensors, and solar cells.

Experimental and Theoretical Analysis of the Operating Parameters for Precipitating Acetaminophen and Tretinoin with Solution Enhanced Dispersion by Supercritical Fluids

The aim of this work is to analyze the experimental conditions for particle production with solution enhanced dispersion by supercritical fluids. Thermodynamics, atomization process, and mass transfer are separately studied in terms of phase equilibria, disintegration regimes, and mass transfer coefficients of liquid and vapor phases. These calculations are correlated with the precipitation data of acetaminophen and tretinoin. According to experimental results, the smallest and more spherical particles (with fewer aggregates) for both solids are obtained just above the mixture critical point of the antisolvent–solvent system with a high antisolvent–solvent mass flow rate ratio. Theoretical results indicate that a high mass transfer coefficient of the liquid phase and a high degree of supersaturation are produced at those conditions. That means a great antisolvent effect because of the low liquid side mass transfer resistance and a small particle size because of the high supersaturation. Furthermore, resul...

The liquid volume expansion effect as a simple thermodynamic criterion in cholesterol micronization by supercritical assisted atomization

The data of the liquid volume expansion could normally be used as one of the thermodynamic criteria to decide an appropriate process of supercritical fluid based micronization techniques. The liquid volume expansion data were predicted by the vapor–liquid phase equilibrium calculation of two binary systems (CO2/acetone and CO2/ethanol) using Peng–Robinson equation of state. The results indicated that the liquid volume expansion of CO2/acetone mixtures was much larger than that of CO2/ethanol mixtures at the specified temperature and pressure. According to the thermodynamic criterion, acetone was affirmed to be a good solvent for supercritical antisolvent process (SAS) due to the higher liquid volume expansion, while ethanol was suitable for supercritical assisted atomization (SAA). This thermodynamic criterion was applied to the micronization of cholesterol and spherical particles were prepared in various organic solvents by SAA with an enhanced mixer. When the liquid volume expansion was lower than 80%, SAA could be successfully conducted and the good morphology and size distribution of the cholesterol particles were obtained. If the liquid volume expansion was higher than 140%, the solute would precipitate in the mixer before the atomization leading to the blockage of nozzle due to the antisolvent effect. In that case, the cholesterol particles in the mixer maintained the same morphology and crystalline structure as the SAS processed. This criterion is a practical and accessible tool to successfully implement the SAA process avoiding undesirable precipitation in the mixer.

Purification of Phytochemicals by Gas Antisolvent Precipitation with Carbon Dioxide

Gas antisolvent precipitation (GAP) using dense carbon dioxide (CO2) is a novel technique for the purification or enrichment of phytochemicals by selective crystallisation. It involves dissolution of sub-critical CO2 into an organic solution of the extract for selectively reducing the solubility of the solid solutes of interest by anti-solvent effect. The recovery and enrichment of three bioactive phytochemicals, such as β-carotene, α-hydroxycitric acid, and licochalcone-A have been investigated in this paper. Initially, organic solvent (Soxhlet) extraction or supercritical CO2 extraction has been carried out for the recovery of β-carotene from mango leaves, α-hydroxycitric acid from kokum, and licochalcone-A from licorice. Subsequently, purification has been performed by the GAP process using CO2 in the pressure range of 40 to 70 bar at 298 K, followed by filtration at the same pressure and temperature, and removal of the residual solvent from the product by flushing it with CO2. High performance liquid chromatography (HPLC) analysis of the phytochemicals before and after the GAP process confirms significant enrichment of the active ingredients.

A novel process for precipitation of ultra-fine particles using sub-critical CO 2

Supercritical CO 2 has been utilized as solvent, cosolvent or antisolvent in several processes for production of ultra-fine solid particles with narrow size distribution. The key to the precipitation of such particles is to produce a very large, rapid and uniform supersaturation in the solution of a solid substance. This can be achieved either by a rapid and large reduction in the temperature of solution or by drastically increasing the CO 2 solubility for imparting the antisolvent effect. Most of these CO 2 processes require high-pressure pumps, specially designed nozzles and accurate control of process parameters. In order to obviate these requirements, a simple technique of precipitation by pressure reduction over the gas-expanded liquids (PPRGEL), such as CO 2-expanded organic solutions has been utilized to impart a large, uniform and rapid reduction of temperature in the solution for instantaneous precipitation of ultra-fine particles. This process utilizes sub-critical CO 2 at relatively low pressures of 40–70 bar and near ambient temperature of 303 K for creating a temperature drop of 30–70 K in the solution within seconds, without using any specially designed nozzle or high-pressure pumps. The present paper validates the process principle for precipitation of Zinc acetate (ZnAc) nanoparticles from its organic solution in a mixed solvent of acetone and dimethyl sulfoxide (DMSO). Nanoparticles are produced with the average size of 20–250 nm (from 100 ml of solution in a high-pressure vessel of 1.09 L working volume), and vary in shapes such as long needles, rods and near spherical depending on pressure (40–70 bar at 303 K), solid concentration (0.01–0.05 g/ml) and addition of stabilizer.

Sustained release of drugs dispersed in polymer nanoparticles.

Sustained release of drugs dispersed in polymer nanoparticles.