Miscible Solvents Research Articles

Extending the Library of Light‐Dependent Protochlorophyllide Oxidoreductases and their Solvent Tolerance, Stability in Light and Cofactor Flexibility

AbstractBiocatalysis is increasingly used in combination with light to develop new and more sustainable synthetic methods. Thereby, mostly a chemical photocatalyst harvesting the light energy is combined with an established enzymatic reaction, thus the biocatalyst itself does not require the light for its specific reaction. Here we expand the library of an enzyme which requires light for its natural reaction, namely the light‐dependent protochlorophyllide oxidoreductase (LPOR). This enzyme catalyzes the NADPH‐dependent reduction of a C=C in a N‐heterocycle. Out of five LPORs identified by sequence search, four were found to be well expressible in E. coli and active. Investigating the light intensity, which is an important parameter describing energy input and subsequently may enable fast reaction, it turned out that the four LPORs can stand the maximum light intensity reachable with the equipment used (1450 μmol photons m−2 s−1). However, the natural substrate and product were degraded at these conditions, allowing only 15 % of the maximum input (211 μmol photons m−2 s−1). Furthermore, the LPORs accepted seven different water miscible solvents with a solvent content of up to 20 % v/v and were active at a pH from 6 to 10. While all LPORs known to date are exclusively NADPH dependent, two LPORs identified here were active also with NADH. The cofactor selectivity could be pinned to three amino acid residues, which interestingly do not directly bind to the cofactor.

Precipitation printing towards diverse materials, mechanical tailoring and functional devices

Additive manufacturing allows for the fabrication of complex structures which are hard to achieve through conventional machining, extrusion, injection molding or blow molding processes. Current additive manufacturing methods for polymers, such as vat photopolymerization, powder bed fusion, material extrusion and binder jetting, still have limitations on the types of polymers that can be 3D printed. Recently, a novel solution-based polymer additive manufacturing method, termed precipitation printing, is developed which is based on the solubility of the polymer being printed in two mutually miscible solvents. In this work, the precipitation printing technique is further developed to expand the range of applicable materials, towards different thermoplastics (poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA)), thermoset rubber (acrylonitrile butadiene rubber (NBR)) and polymer nanocomposites (multiwalled carbon nanotubes (MWCNTs)-PVDF). The printing process is rapid and enables the realization of large structures with complex geometries as well as printing at a higher resolution than the material extrusion method, while also allowing the fabrication of micro-scale structures with greater than 100 μm resolution. Porosity and mechanical property tailoring of the precipitation printed materials are achievable through the control of process parameters, such as solvent/non-solvent pair selection, salinity of the non-solvent and printing temperature. In addition, the successful demonstrations of a directly 3D printed NBR check valve and a MWCNTs-PVDF strain gauge indicate the great potential for precipitation printing as a promising one-step process for the production of functional devices.

Oil recovery from fractured porous media with/without initial water saturation by using 3-pentanone and its aqueous solution

This paper presents an application of 3-pentanone, a symmetric dialkyl ketone, to enhance the water imbibition in coreflooding of fractured carbonate cores. 3-Pentanone was tested in two ways: 1.1- wt% 3-pentanone solution in reservoir brine (3pRB) and pure 3-pentanone (3p) as a miscible solvent. It was presented previously that 3p is a mutual solvent for oil and water, and can rapidly change the rock wettability to strongly water-wet with its electron-rich oxygen atom through the oil and water phases. The main objective of this research is to investigate how the initial water saturation (Swi) in the matrix affects the imbibition of 3pRB or 3p from the fracture and the resulting recovery of oil from the matrix.The experimental results were analyzed in terms of material balance (mass and volume) with simplifying assumptions. This analysis enabled to estimate how much of the injected components were imbibed into the surrounding matrices from the fracture and the relative contribution of the injected components to displacing oil in the matrix. Results for the 3pRB and 3p injections indicate collectively that 3-pentanone was more effective in enhancing oil recovery when an aqueous phase was initially present in the matrix.

Tribological properties of novel palygorskite nanoplatelets used as oil-based lubricant additives

Layered palygorskite (PAL), commonly called attapulgite, is a natural inorganic clay mineral composed of magnesium silicate. In this study, an aqueous miscible organic solvent treatment method is adopted to prepare molybdenum-dotted palygorskite (Amo-PMo) nanoplatelets, which greatly improved the specific surface area of PAL and the dispersion effect in an oil-based lubricant system. Their layered structure and size were confirmed using transmission electron microscopy (TEM) and atomic force microscopy. Following a tribological test lubricated with three additives (PAL, organic molybdenum (SN-Mo), and Amo-PMo), it was found that the sample of 0.5 wt% Amo-PMo exhibited the best tribological properties with a coefficient of friction of 0.09. Moreover, the resulting wear scar diameter and wear volume of the sliding ball surface were 63% and 49.6% of those lubricated with base oil, respectively. Its excellent lubricating performance and self-repairing ability were mainly attributed to the generated MoS2 adsorbed on the contact surfaces during the tribochemical reaction, thereby effectively preventing the direct collision between asperities on sliding solid surfaces. Thus, as-prepared Amo-PMo nanoplatelets show great potential as oil-based lubricant additives, and this study enriches the existing application of PAL in industry.

Mixed Solvents to Optimize the Energy Density of Nonaqueous Vanadium Redox Flow Batteries

Nonaqueous redox flow batteries have the potential to be more energy-dense than their aqueous counterparts. The wider electrochemical stability windows of organic solvents enable higher-voltage redox reactions, which have already been demonstrated to improve molar energy density (Wh/molactives). Exceeding the theoretical maximum volumetric energy density (Wh/L) of state-of-the-art commercial active liquids (37.5 Wh/L for aqueous vanadium at 1.4 V and 2.0 M, a standard concentration [1]) requires increasing the active-species concentration past a threshold that is inversely proportional to the nonaqueous cell’s potential. Vanadium acetylacetonate (V(acac)3) is a potentially useful active species for nonaqueous flow batteries because its disproportionation delivers 2.2 V [2].As well as containing an electrochemically active species, flow-battery electrolytes must also contain a supporting salt, whose ions maintain electroneutrality during cell operation by travelling across the separator membrane. The minimum ionic strength needed in the electrolyte to maintain this charge balance up to the maximum theoretical state of charge depends on the number of charges received by the active species across all of its oxidation states. This minimum support concentration may be different from the optimal concentration of salt required to achieve sufficient conductivity.For a given nonaqueous electrolyte, optimization for a given active-species chemistry to achieve maximum volumetric energy density requires careful selection of solvent systems and supporting electrolyte, subject to the constraints of solubility limits (at all oxidation states of the active species), electroneutrality, and conductivity [3]–[5].In this work we use the well-established disproportionation chemistry of the V(acac)3 active species, with tetraethylammonium tetrafluoroborate (TEABF4) as supporting salt. The solubility limit of V(acac)3 in several solvents is determined densitometrically [4]. Promising binary mixtures of mutually miscible solvents are explored further, with the aim of choosing one solvent that preferentially solvates V(acac)3 and the other that solvates TEABF4. Optimization of the binary electrolyte identifies a solvent system of acetonitrile and dioxolane which offers a maximum V(acac)3 solubility of 0.95 M and a theoretical energy density of 29.3 Wh/L. The reversible electrochemistry of this mixture is confirmed with voltammetry, and stable cyclability is demonstrated in a benchtop flow cell [6]. Key performance metrics will be reported, including energy, voltaic, coulombic, and utilization efficiencies, electrolyte conductivity, and peak power density.While the results for the V(acac)3/ TEABF4 system are promising, this work provides a logical workflow and strategy for maximizing energy density that can be applied to other nonaqueous chemistries to achieve their true potential.[1] C. Minke and T. Turek, ‘Materials, system designs and modelling approaches in techno-economic assessment of all-vanadium redox flow batteries – A review’, J. Power Sources, vol. 376, pp. 66–81, Feb. 2018.[2] Q. Liu, A. E. S. Sleightholme, A. A. Shinkle, Y. Li, and L. T. Thompson, ‘Non-aqueous vanadium acetylacetonate electrolyte for redox flow batteries’, Electrochem. Commun., vol. 11, no. 12, pp. 2312–2315, 2009.[3] M. O. Bamgbopa, N. Pour, Y. Shao-Horn, and S. Almheiri, ‘Systematic selection of solvent mixtures for non-aqueous redox flow batteries – vanadium acetylacetonate as a model system’, Electrochimica Acta, vol. 223, pp. 115–123, 2017.[4] A. A. Shinkle, T. J. Pomaville, A. E. S. Sleightholme, L. T. Thompson, and C. W. Monroe, ‘Solvents and supporting electrolytes for vanadium acetylacetonate flow batteries’, J. Power Sources, vol. 248, no. January 2015, pp. 1299–1305, 2014.[5] T. Herr, J. Noack, P. Fischer, and J. Tübke, ‘1,3-Dioxolane, tetrahydrofuran, acetylacetone and dimethyl sulfoxide as solvents for non-aqueous vanadium acetylacetonate redox-flow-batteries’, Electrochimica Acta, vol. 113, pp. 127–133, Dec. 2013.[6] J. D. Saraidaridis and C. W. Monroe, ‘Nonaqueous vanadium disproportionation flow batteries with porous separators cycle stably and tolerate high current density’, J. Power Sources, vol. 412, pp. 384–390, Feb. 2019.

Smart Responsive Polymers: Fundamentals and Design Principles

In this review, we summarize recent theoretical and computational developments in the field of smart responsive materials, together with complementary experimental data. A material is referred to as smart responsive when a slight change in external stimulus can drastically alter its structure, function, or stability. Because of this smart responsiveness, these systems are used for the design of advanced functional materials. The most characteristic properties of smart polymers are discussed, especially polymer properties in solvent mixtures. We show how multiscale simulation approaches can shed light on the intriguing experimental observations. Special emphasis is given to two symmetric phenomena: co-non-solvency and co-solvency. The first phenomenon is associated with the collapse of polymers in two miscible good solvents, whereas the latter is associated with the swelling of polymers in poor solvent mixtures. Furthermore, we discuss when the standard Flory–Huggins-type mean-field polymer theory can (or cannot) be applied to understand these complex solution properties. We also sketch a few examples to highlight possible future directions, that is, how smart polymer properties can be used for the design principles of advanced functional materials.

Aqueous miscible organic-layered double hydroxides with improved CO2 adsorption capacity

Potassium-promoted layered double hydroxide (LDH)-derived materials are suitable elevated temperature CO2 adsorbents for pre-combustion CO2 capture. A challenge for the commercialization of LDHs as efficient CO2 adsorbents is their low capacities (ca. 0.5–0.6 mmol/g@400 °C) due to their hydrogen-bonded stacked structure. In this study, the aqueous miscible organic solvent treatment (AMOST) was used to exfoliate Mg3Al–CO3 LDH into nanosheets with a flower-like morphology, resulting in high surface areas of 287 and 212 m2/g for CC1 (washed with ethanol) and CC2 (washed with acetone), respectively. The exfoliated LDH structure exposed more interlayered CO2 active sites and promoters for alkali metal modification. Six impregnation solvents, water, acetone, ethanediol, ethanol, DMAC, and methanol were screened to optimize the CO2 uptake of 20 wt% K2CO3-promoted CC1. K2CO3/CC1(ed) using ethanediol as the impregnation solvent reached a CO2 working capacity of 1.46 mmol/g at 400 °C in the first cycle and 1.23 mmol/g after 10 cycles, twice the capacity of the commercial K2CO3/MG70. Material characterization indicated that the unexpectedly high performance of K2CO3/CC1(ed) could be attributed to the uniform K+ dispersion on the surface of K2CO3/CC1(ed) rather than bulk phase formation and the release of the residual solvent during calcination that could generate more paths for CO2 diffusion.

Miscible-Solvent-Assisted Two-Phase Synthesis of Monolayer-Ligand-Protected Metal Nanoclusters with Various Sizes.

Effective yet versatile synthetic strategies for size-tunable metal nanoclusters (NCs) are scarce. This has hampered the development of this unique class of nanomaterials. Here, a general protocol is reported for the synthesis of high-quality metal NCs protected by a variety of organic ligands (e.g., selenolate, thiolate, and phosphine) based on a miscible-solvent-assisted phase transfer between water and organic solution. This method is demonstrated to be facile, rapid (≤3 h), scalable (gram-scale), and versatile. The size of the selenolated and thiolated Au NCs can be tuned from Au10 to Au61 by simply varying the miscible solvent in proportions and types. The advantages of this method, such as quick phase separation and no need for purification treatment, enable real-time monitoring of metal NC growth within the NaBH4 reduction system. The results show that the size of Au NCs gradually increases with increasing valence electron count by a stepwise 2x e- hopping mechanism (x = 0-5), i.e., 0 e- → 2 e- → 4 e- → 8 e- → 18 e- → 22 e- → 32 e- .

Bicomponent nanofibers from core–shell nozzle in gas jet spinning process

ABSTRACTThis work evaluates the use of a core–shell nozzle assembly in conjunction with gas jet spinning technique for production of bicomponent nanofibers from an immiscible polymer pair of polyvinylpyrrolidone (PVP) and poly(vinyl acetate) (PVAc) with three morphological forms—interpenetrating network (IPN), core–shell, and bilobal structurers—by varying the sets of miscible solvents offering different affinity for the polymers. Such fiber structures have strong potential in drug delivery and wound dressing applications. Solutions of PVP and PVAc in respective single solvents metered through a core–shell nozzle assembly meet at the exit of the nozzle and a liquid jet is initiated upon contact with a turbulent gas jet. The gas jet stretches the liquid jet into nanofibers. The results indicate that miscible solvent pairs with low affinity for one of the polymer component yield core–shell morphology with distinct polymer interfaces, while the miscible solvent pairs with high affinity for both polymers produce IPN morphology. Also, interchanging core and shell solutions does not alter the IPN morphology. Finally, bilobal nanofiber structures result from spinning of polymer solutions in miscible solvents with low affinity for the second polymer using a nonconcentric core–shell nozzle assembly. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48901.

Distribution of Iodine in two Miscible solvents

Nernst's distribution equation is employed when any of the solute present in the normal state in the two immiscible solvents, its distribution coefficients value can be calculated. Here it is also possible to use Nernst's distribution equation for a solute when it is present in the normal state in miscible solvents, then we can also calculate distribution constant coefficients for any case of a solute. In this paper to mentioned for iodine itself distributing between the two miscible solvents such as cyclohexane and carbon tetrachloride. if the distribution ratio precisely known for miscible solvents then it will possible to study of distribution constants of Iodine in the two miscible solvents.

Morphology control in metallosupramolecular assemblies through solvent-induced steric demand.

Controlling the supramolecular self-assembly of π-conjugated systems into defined morphologies is a prerequisite for the preparation of functional materials. In recent years, the development of sophisticated sample preparation protocols and modulation of various experimental conditions (solvent, concentration, temperature, etc.) have enabled precise control over aggregation pathways of different types of monomer units. A common method to achieve pathway control consists in the combination of two miscible solvents in defined proportions - a "poor" and "good" solvent. However, the role of solvents of opposed polarity in the self-assembly of a given building block still remains an open question. Herein, we unravel the effect of aggregation-inducing solvent systems of opposed polarity (aqueous vs. non-polar media) on the supramolecular assembly of a new bolaamphiphilic Pt(ii) complex. A number of experimental methods show a comparable molecular packing in both media driven by a synergy of solvophobic, aromatic and weak hydrogen-bonding interactions. However, morphological analysis of the respective aggregates in aqueous and non-polar media reveals a restricted aggregate growth in aqueous media into spherical nanoparticles and a non-restricted 2D-nanosheet formation in non-polar media. These findings are attributed to a considerably more efficient solvation and, in turn, increased steric demand of the hydrophilic chains in aqueous media than in nonpolar media, which can be explained by the entrapment of water molecules in the hydrophilic aggregate shell via hydrogen bonds. Our findings reveal that the different solvation of peripheral solubilizing groups in solvents of opposed polarity is an efficient method for morphology control in self-assembly.

Development of photocatalytic degradation and kinetic study for imidazolium based ionic liquids in Fe-Cu/TiO2-AC system

Ionic Liquids (ILs) are already recognized by the chemical industry as they possess a wide spectrum of physical and chemical properties (solubility, polarity, viscosity or solvent miscibility). However, a release of ILs from industrial processes into aquatic environments may lead to water pollution, because of their high solubilities in water. Due to these reasons, this work is conducted to investigate the photodegradation on ILs structure varies in alkyl chain length and anion group. The photocatalytic degradation was conducted based on fixed parameter optimized which includes pH = 6, [photocatalyst] = 1g/L, [ILo] = 0.11 mM and [H2O2] = 0.75 ml/L. The reaction for emimCl follows zero order whereas both bmimCl and bmimBF4 follow the first order reaction.

Prediction of Miscibility of HTPB Curing System and Solvents by Molecular Dynamics Simulations

In order to study on HTPB curing system and solvent’s miscibility, molecular dynamic simulations were performed to analyse curing system’s miscibility with water, ethyl alcohol, methylbenzene, acetone and tetrahydrofuran from several aspects like solubility parameter, molecular configuration and density distribution. The result shows that the computed results of the solubility parameter have high consistency with experimental values and the maximum relative error is less than 3%. The solubility parameter differences of acetone, tetrahydrofuran and curing system are relatively small with a homogeneous distribution and a relatively high miscibility. Methylbenzene’s miscibility is general while the ethyl alcohol’s and water’s miscibility are relatively poor.

Technology Focus: EOR Modeling (January 2020)

Technology Focus The bulk of the literature on enhanced oil recovery (EOR) from the past year has been devoted to an improved understanding of trends started more than a decade ago with physical and numerical modeling. A quick review of the basics will be helpful for putting these developments in perspective. The concept of displacement in an EOR method requires bringing the mobility ratio of displacing fluid to that of displaced oil under unity [Kw µ o / Ko µw less than 1; Ko, Kw being relative permeabilities of displaced oil and displacing fluid (e.g., water), respectively, and µ o, µw being their respective viscosities], and increasing sweep efficiency (Es) of the displacement process. Various established EOR methods try to accomplish this in different ways, depending on the formation and oil types, aiming to keep costs and environmental impact down while obtaining high and quick recovery. Thus, polymers or foams have been used traditionally to increase viscosity of displacing fluids (µw). To reduce Kw/Ko, surfactant; alkaline; microbes, which create in-situ surfactants; or low-salinity water, which changes wettability to water, were used. Steam or hot water have also been used to reduce both Kw and µo. Miscible gas or solvent displacements were used to attack µo. Quite frequently, a combination of these mechanisms has been applied, alkaline/surfactant/ polymer being a good example. Similarly, to address improvement in sweep, blocking agents such as polymers, microgels, or microbes, or a combination of a couple of these mechanisms, have been applied. While the underlying mechanisms remain the same, major developments in EOR in recent years center on the use of engineered water or nanoparticles to reduce Kw, on the experimental development of chemicals that are less susceptible to high-temperature and high-salinity environments, or on the use of novel computational techniques and machine learning to design and monitor the flood operations better. The literature of the last year is an important reflection of that evolution, as the selected papers reflect. Recommended additional reading at OnePetro: www.onepetro.org. SPE 195553 Investigation of Pore-Scale Mechanisms of Microbial Enhanced Oil Recovery Using Microfluidics by Calvin Gaol, Clausthal University of Technology, et al. SPE 192110 Polymers and Their Limits in Temperature, Salinity, and Hardness: Theory and Practice by Eric Delamaide, IFP Technologies Canada, et al. SPE 192651 Performance Evaluation and Field Trial of Self-Adaptive Microgel Flooding Technology by Zhe Sun, China National Offshore Oil Corporation, et al.

Rationalising the influence of solvent choice on the porosity of conjugated microporous polymers

Conjugated microporous polymers (CMPs) synthesised in different solvents give different surface areas dependent on the solvent choice. No one solvent results in a high surface area across a range of different CMP materials. Here, we present an investigation into how the porosity of CMPs is affected by solvent polarity. It is seen that the trends differ depending on the respective monomer dipole moments and whether hydrogen bonding groups are present in the monomers and are able to interact with the respective solvent via hydrogen bonding. It is believed that this methodology could be used to influence future materials design of both structure and synthesis strategy.

Separation of chloride and sulphate ions from nanofiltration rejected wastewater of steel industry

This work focused on the removal of chlorides and sulphates from nanofiltration rejected water of steel industry by the method of precipitation using miscible organic solvents such as diisopropylamine (DIIPA), isopropylamine (IPA), and ethylamine (EA) in different proportions. Solvent based precipitation showed that miscible organic solvents such as DIPA/IPA/EA is effective in precipitating salts from NF rejected water and thereby reducing the concentrations of chlorides and sulphates. Effects of solvent to water ratio, pH, temperature and mixing time was thoroughly investigated. Sulphate and chloride removal efficiency of 99.82 % and 77.50 % respectively, was observed. The treated water can be reused to the system or discharged safely to the environment. Response surface methodology (RSM) was applied to optimize the parameters for the removal of chloride and sulphate ions. Analysis of variance was used to study the incurred data, which then fitted to the second-order quadratic equation, by regression. Four important parameters namely volume of the solvent, pH, temperature and contact time were optimized using central composite design (CCD). Up to 98 % of solvent was recovered by simple distillation for further use. The precipitated salts were characterized by FESEM, XRD and FTIR analysis.

The Impact of Solvent Selection: Strategies to Guide the Manufacturing of Liposomes Using Microfluidics.

The aim of this work was to assess the impact of solvent selection on the microfluidic production of liposomes. To achieve this, liposomes were manufactured using small-scale and bench-scale microfluidics systems using three aqueous miscible solvents (methanol, ethanol or isopropanol, alone or in combination). Liposomes composed of different lipid compositions were manufactured using these different solvents and characterised to investigate the influence of solvents on liposome attributes. Our studies demonstrate that solvent selection is a key consideration during the microfluidics manufacturing process, not only when considering lipid solubility but also with regard to the resultant liposome critical quality attributes. In general, reducing the polarity of the solvent (from methanol to isopropanol) increased the liposome particle size without impacting liposome short-term stability or release characteristics. Furthermore, solvent combinations such as methanol/isopropanol mixtures can be used to modify solvent polarity and the resultant liposome particle size. However, the impact of solvent choice on the liposome product is also influenced by the liposome formulation; liposomes containing charged lipids tended to show more sensitivity to solvent selection and formulations containing increased concentrations of cholesterol or pegylated-lipids were less influenced by the choice of solvent. Indeed, incorporation of 14 wt% or more of pegylated-lipid was shown to negate the impact of solvent selection.

Direct bromination of nano hydroxyapatite strategy towards particle brushes via surface-initiated ATRP for highly efficient heavy metal removal

Aminated n-HAP-g-polyacrylonitrile (n-HAP-g-APAN) particle brushes were developed for highly efficient heavy metal removal based on surface-initiated ATRP (SI-ATRP) and subsequent amination. An efficient one-step method for morphology controlled synthesis of ATRP initiator immobilized n-HAP (n-HAP-Br) was realized by using 2-bromoisobutyric acid as tetherable initiator. Uniform and individually dispersed n-HAP-Br NCs were obtained with controlled morphology and particle size by adding portion of water miscible organic solvents to rational adjusting aqueous dispersion medium. Aminated n-HAP-g-APAN displayed record-high adsorption capacity of heavy meatal ions due to the combined contributions of grafted APAN providing pendent amino diethylenepentamine as chelating groups and n-HAP core towards heavy metal ions (pure n-HAP of qe = 284.4 mg/g vs n-HAP-g-APAN of qe = 944.4 mg/g). The proposed one-step direct bromination of n-HAP strategy provides the preparation of uniform n-HAP NCs ready for polymer grafting and further fabrication of n-HAP-g-polymers via SI-ATRP for various applications depending on the characteristic of grafted polymers.

Dual drug-loaded biodegradable Janus particles for simultaneous co-delivery of hydrophobic and hydrophilic compounds.

Bicompartmental Janus particles have many advantages in drug delivery, including co-delivery of two compounds with varying solubilities, differential release kinetics, and two surfaces available for targeting ligands. We present a novel strategy using the double emulsion method for the coencapsulation and staggered release of a hydrophobic and hydrophilic drug from anisotropic PLGA/PCL Janus particles, as well as a UV detection method to measure the release of two different compounds from Janus particles. Curcumin and quercetin were chosen as the model hydrophobic compounds for drug loading studies, while acetaminophen (APAP) and naproxen were chosen as the model hydrophilic–hydrophobic drug pair for encapsulation methods and drug loading. Also, a similar double emulsion method was also applied for PLGA/Preicrol® Janus particles containing Doxorubicin and Curcumin. Hydrophobic drugs were encapsulated by the single O/W emulsion technique. Hydrophilic compounds required special modifications due to their poor oil solubility and tendency to escape to the outer aqueous phase during the emulsification and solvent evaporation steps. In total, three different strategies for incorporating hydrophilic drugs were employed: (1) O/W emulsion with partially water miscible solvent, (2) O/W emulsion with co-solvent (i.e. acetone, methanol, ethanol), or (3) W/O/W double emulsion. The encapsulation efficiencies and drug loading percentages were measured using UV/Vis spectroscopy and compared for the different synthesis methods. It was found that the double emulsion method resulted in the highest encapsulation efficiency and drug loading of the hydrophilic drug.

Tuneable functionalities in layered double hydroxide catalysts for thermochemical conversion of biomass-derived glucose to fructose

Layered double hydroxides (LDHs) with varying crystallite sizes (2.6–43 nm), layer numbers (3–70), specific surface area (18–455 m2 g−1), pore volume (0.025–1.6 mL g−1), and functional groups were synthesised via conventional urea hydrolysis and co-precipitation methods and aqueous miscible organic solvent (AMOST) treatment. They were evaluated as the solid base catalysts for the thermochemical isomerisation of biomass-derived glucose to fructose with the aim of establishing the structure-performance relationships for carbon-efficient biorefinery. The results showed that the fructose yield increased with increasing crystallite size of LDHs due to the enhanced exposure of active sites. However, excessive increase in the structural accessibility could be detrimental because high hydrophilicity potentially resulted in water clusters surrounding the active sites and hindering their interaction with glucose. Nano-sized particles in small quantity that were visually indiscernible may partially account for the catalytic activity. The kinetics test suggested that the conversion of glucose to intermediates may act as the rate-determining step when the reaction temperature increased. The activation energy for the LDH-catalysed glucose conversion was estimated to be 52.8 kJ mol−1. The highest fructose yield of 25 mol% was achieved at 120 °C for 5 min in water. The recycling test suggested that the catalytic performance became stable after the second run, possibly due to the formation of a passive layer. This study elucidates the structure-controlled functionalities of the LDH catalysts to serve a base-catalysed biorefinery reaction, and provides mechanistic insights into the active components and the catalyst transformation during thermochemical biomass conversion.