Synthesis and high proton conductivity of an indium-substituted Keggin-type quaternary heteropoly acid.

The synthesis and characterization of an indium-substituted quaternary heteropoly acid with a Keggin structure, H4[In(H2O)PW9Mo2O39]·11H2O (PMo9W2In), is reported. At 18 °C under 80% relative humidity, PMo9W2In displays protonic conductivity of 2.32 × 10-4 S cm-1 with an activation energy of 35.52 kJ mol-1, indicating that it is a potential solid protonic conductor following the vehicle mechanism. Its conductivity increases with temperature in the measured temperature range.

Enhanced Oral Delivery of Curcumin via Vitamin E TPGS Modified Nanodiamonds: a Comparative Study on the Efficacy of Non-covalent and Covalent Conjugated Strategies.

Despite that either non-covalent or covalent attachment of hydrophilic polymers or surfactants onto nanodiamonds (NDs) could overcome the shortcomings of being a drug delivery system, it is hard to draw a definite conclusion which strategy is more effective. Hence, with the purpose of comparing the influence of different coating approach of NDs on the oral delivery efficiency of water-insoluble model drug curcumin (CUR), NDs were firstly modified with D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) via non-covalent or covalent conjugation method, and then loaded with CUR (CUR@NDs-COOH/TPGS or CUR@NDs-TPGS). In comparison with the core-shell-structured CUR@NDs-COOH/TPGS, CUR@NDs-TPGS were irregular in shape with dense TPGS film, and exhibited smaller size, more negatively potential, and higher drug loading efficiency. The covalent connection group also showed higher anti-cancer activity, cellular uptake, and permeability through the Caco-2 cell monolayers, as well as favorable distribution, penetration, and retention in rat intestines. The oral bioavailability study in rats demonstrated that CUR@NDs-TPGS showed significantly greater Cmax and AUC0-t in contrast with CUR suspension and the TPGS-coated ones, respectively. The findings illustrated that covalent grafting TPGS onto the surface of NDs possesses better efficacy and biocompatibility on oral delivery of poorly soluble drug CUR than pristine and non-covalent coated nanoparticles.

A Copper Coordination Polymer with Matching Energy Level for Modifying Hole Transport Layers to Improve the Performance of Perovskite Solar Cells.

Spiro-OMeTAD is currently the most widely used hole transport material for the preparation of high-performance perovskite solar cells (PSCs), usually requiring the addition of additives to achieve the desired electronic conductivity. However, the quality of the film is degraded owing to the addition of additives. Holes and defects can be observed, and the dispersion of the additives are uneven inside. Here, a copper coordination polymer, Cu-bix, with matching energy level and fluorescent properties was screened for use as an additional additive to dope Spiro-OMeTAD. The doping of Cu-bix effectively improved the dispersion state of the additives in the hole transport layers and alleviated the aggregation of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) or/and lithium salt complexes in the film. Owing to better dispersion of the additives, Spiro-OMeTAD was more fully and uniformly oxidized whereas the possibility of charge recombination was reduced in the devices. Furthermore, the flat and tightly bonded film layer obtained by optimization of the doping amount can efficiently transfer holes from the perovskite layers to the hole transport layers. Possible interaction mechanisms between additives and the copper coordination polymer are proposed and discussed. The resulting power conversion efficiency (PCE) for Cu-bix-doped PSCs was improved from 16.52 % to 18.47 % compared to the pristine devices, and this type of PSCs also showed a long stability in air owing to the increased hydrophobicity of the Cu-bix-based hole transport layers.

Catalytic synthesis of chloroacetates with thermoregulated ionic liquids based on vanadium-substituted polyoxometalate.

A series of polyoxometalate-based ionic liquid (POM-IL) catalysts with functional sulfonic acid groups, [TEAPS]3+n PW12-n V n O40 (n = 1, 2, 3) were synthesized and characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectrophotometry (FT-IR), UV-Vis spectrophotometry (UV), potentiometric titration and thermogravimetry-differential scanning calorimetry (TG-DSC). The catalytic ability and reusability of the POM-IL catalysts were evaluated on esterification of chloroacetic acid and n-amyl alcohol. The optimum reaction conditions, 0.2 g of the catalyst amount, 10 mL of water carrier, 140 °C of reaction temperature, and 1.2/1 of the molar ratio of alcohol/acid, were obtained by an orthogonal test. [TEAPS]5PW10V2O40 was found to be the best active catalyst with an esterification rate of 98.75% and could be reused five times without significant decrease in activity. The ionic liquid acted as a temperature-responsive catalyst, forming a homogeneous mixture with the reactants at reaction temperature, and could be precipitated and separated from products when the reaction ends at ambient temperature. Therefore, an environmentally friendly and highly efficient approach for the synthesis of chloroacetates is provided.

Investigations on the interactions between curcumin loaded vitamin E TPGS coated nanodiamond and Caco-2 cell monolayer.

This study aimed at investigating the potential mechanism of improved transportation of the curcumin loaded D-α-tocopherol polyethylene glycol 1000 succinate coated nanodiamonds system (NDs/CUR/TPGS complexes) using an in vitro Caco-2 cell monolayer model. The core-shell structured NDs/CUR/TPGS nanocomplexes were 196.32 ±â€¯5.76 nm in size, with a high loading efficiency of 81.59 ±â€¯3.42%. Cytotoxicity results suggested that the blank NDs did not induce any serious toxicity on Caco-2 cells even after incubated for 72 h. The cell viability for all the series of CUR loaded preparations was found to follow the sequence of CUR suspension > NDs/CUR > NDs/CUR/TPGS. Confocal laser fluorescence microscopy (CLSM) and flow cytometry system (FACS) studies confirmed that the cellular uptake of NDs could be efficiently enhanced by TPGS decoration. The transport mechanism of NDs/CUR and TPGS coated ones was mainly through an energy dependent, clathrin-mediated and caveolin-mediated endocytosis, and the endocytosis of NDs/CUR was also via macropinocytosis. Furthermore, the Papp value (AP-BL) of NDs/CUR and NDs/CUR/TPGS was 2.09- and 3.86-fold higher than that of the CUR suspension. All the results demonstrated that the pharmacological activates and intestinal permeability of CUR across Caco-2 cell monolayer was greatly enhanced by NDs/CUR/TPGS nanocomplexes. Thus NDs could be a promising oral drug delivery platform for improving the intestinal permeability and oral bioavailability of poorly soluble drugs.

Synthesis and performance of solid proton conductor molybdovanadosilicic acid.

A molybdovanadosilicic acid H5SiMo11VO40·8H2O was synthesized and investigated in this work. The structure features and hydration degree of this acid were characterized by IR, UV, XRD and TG-DTA. Its proton conductivity was studied by electrochemical impedance spectroscopy (EIS). The EIS measurements demonstrated that H5SiMo11VO40·8H2O showed excellent proton conduction performance with proton conductivity reaching 5.70 × 10-3 S cm-1 at 26 °C and 70% relative humidity. So, it is a new solid high proton conductor. The conductivity enhances with the increase of temperature, and it exhibits Arrhenius behavior. The activation energy value for proton conduction is 21.4 kJ mol-1, suggesting that the proton transfer in this solid acid is dominated by Vehicle mechanism.

Synthesis and conductive performance of polyoxometalate acid salt gel electrolytes.

Two vanadium-substituted polyoxometalate acid salt gel electrolytes, [PyPS]3H4SiW9V3O40 and [PyPS]5H2SiW9V3O40, have been synthesized using a 1-(3-sulfonic group) propylpyridine (PyPS) and a Keggin vanadium-substituted heteropoly acid H7SiW9V3O40 through an ionic self-assembly method, and adjusting the ratio of cation and anion. A substitution effect of the acid salt gel electrolytes has been investigated. Interestingly, when protons of the polyoxometalate acid salt gel electrolytes are substituted, both the conductivity and the phase transformation temperature increase. The fastest conductivity of these gel electrolytes was as high as 2.57 × 10-2 S cm-1 at 110 °C.

Ex Vivo and in Vivo Evaluation of the Effect of Coating a Coumarin-6-Labeled Nanostructured Lipid Carrier with Chitosan-N-acetylcysteine on Rabbit Ocular Distribution.

This study is focused on further understanding the characteristics of chitosan-N-acetylcysteine surface-modified nanostructured lipid carriers (CS-NAC-NLCs) in their interaction with ocular mucosa. Coumarin-6 (C6)-labeled NLCs, including uncoated NLCs, chitosan hydrochloride (CH)-, and CS-NAC-coated NLCs, were developed using a melt-emulsification technique and subsequently decorated with different types or portions of chitosan derivatives. Mucoadhesion was evaluated ex vivo using a flow-through process with fluorescence detection. The results demonstrated that the presence of CS-NAC on the C6-NLC surface provided the most obvious enhancement in adhesion due to the formation of both noncovalent (ionic) and covalent (disulfide bridges) interactions with mucus chains. Meanwhile, the concentration of CS-NAC in the formulation positively influenced the viscosity of the nanoparticles and hence prolonged their retention in the ocular tissue. Transcorneal penetration studies revealed that CS-NAC-NLC particles were able to penetrate through the entire corneal epithelium primarily via a transcellular route. The transport depth and velocity strongly relied on the modification material and the particle size. Ex vivo fluorescence imaging and in vivo ocular distribution investigations showed that C6 was broadly distributed in rabbit eye tissues and absorbed by aqueous humor after CS-NAC-NLC instillation. In relation to C6 eye drops, CS-NAC-NLCs achieved considerably higher Cmax (4.01-fold), MRT0-∞ (1.87-fold), and AUC0-∞ (16.29-fold) in the aqueous humor. Moreover, the increase in drug absorption was greater in the cornea than in the conjunctiva. Thereby, it is possible to draw a conclusion that CS-NAC-NLCs presented great potential for drug application to the front portion of the eye.

Thermoresponsive Polyoxometalate/Ionic Liquid Supramolecular Gel Electrolytes for Supercapacitors: Fabrication, Structure, and Heteropolyanion Structure Effect.

We report the fabrication, structure, and heteropolyanion structure effect of polyoxometalate (POM)/ionic liquid (IL) supramolecular gels. These supramolecular gels exhibit ordered structures, as a result of their excellent reversible self-assembly, and they show various physicochemical properties, determined by the heteropolyanion structure effect of POM anions. Specifically, the formation of POM/IL supramolecular gels results in a highly ordered layer-shape structure, which has been calculated using X-ray powder diffraction patterns and proven by transmission electron microscopy images for the first time. When these POM/IL supramolecular gels are heated, they become viscous liquid sols, with melting isotropic drops and even flowerlike structures on microscopic scales, while it undergoes a reversible gel-sol phase transformation from gel to sol. The heteropolyanion structure effect in these two IL gels, [TBTP]5PW10V2O40 and [TBTP]8P2W16V2O62, on their physicochemical properties is demonstrated. The POM structures have a strong structure effect on the physicochemical properties. As the size of heteropolyanions increases, there is a significant improvement in the conductivity, thermal performance, and oxidizability, with a lower phase inversion temperature, which means that the Dawson-type compound, [TBTP]8P2W16V2O62, has a higher conductivity, lower melting point, stronger oxidizability, and better thermal performance than the Keggin-type compound, [TBTP]5PW10V2O40, under the same conditions.

Synthesis and high proton conductive performance of a quaternary vanadomolybdotungstosilicic heteropoly acid.

A new vanadium and molybdenum-substituted quaternary silicon-containing heteropoly acid H6SiW9MoV2O40·15H2O has been synthesized in this paper by the stepwise acidification and the stepwise addition of elemental solutions. The structural feature and hydration of this product were characterized by IR, UV, XRD and TG-DTA, and its proton conductivity was measured by electrochemical impedance spectroscopy (EIS). The result of EIS shows that H6SiW9MoV2O40·15H2O is a solid high-proton conductor with a conductivity of 6.01 × 10(-3) S cm(-1) at 22 °C and 80% relative humidity, which increases at higher temperatures. Its conductive activation energy is 27.5 kJ mol(-1), which suggests that the mechanism of proton conduction is dominated by the vehicle mechanism.

Substitution effect in reversible gel-liquid phase transformation polyoxometalate ionic liquid compounds.

The substitution effect in a series of POM-type reversible gel-liquid phase transformation ionic liquid compounds, [MIMPS]8P2W16V2O62, [MIMPS]6H2P2W16V2O62 and [MIMPS]4H4P2W16V2O62, has been investigated. Interestingly, there is an obvious substitution effect on the physicochemical properties of these compounds. When protons are substituted in place of ammonium, both the conductivity and the thermo-stability of the compounds can be increased a lot, and more protons can enhance this tendency.

Potential advantages of a novel chitosan-N-acetylcysteine surface modified nanostructured lipid carrier on the performance of ophthalmic delivery of curcumin.

The transient precorneal retention time and low penetration capacity into intraocular tissues are the key obstacles that hinder the ophthalmic drug delivery of many therapeutic compounds, especially for drugs with poor solubility and permeability. To break the stalemate, N-acetyl-L-cysteine functionalized chitosan copolymer (CS-NAC), which exhibit marked bioadhesion and permeation enhancing effect, was synthesized. The curcumin encapsulated NLC (CUR-NLC) was produced and optimized followed by surface absorption of CS-NAC. After coating, changed particle size from 50.76 ± 2.21 nm to 88.64 ± 1.25 nm and reversed zeta potential from -20.38 ± 0.39 mV to 22.51 ± 0.34 mV was observed. The in vitro CUR release from NLC was slower than that of CUR-NLC and chitosan hydrochlorides (CH) coated NLC due to the inter and/or intramolecular disulfide formation of thiomers on the surface of nanocarriers. The modification also significantly enhanced transcorneal penetration compared with CH-NLC and the uncoated ones. The effect on bioadhesion and precorneal retention were evaluated by in vivo imaging technique and ocular pharmacokinetics studies revealing that the clearance of the formulations was significantly delayed in the presence of CS-NAC and the effect was positively related to the degree of thiolation. In summary, CS-NAC-NLC presented a series of notable advantages for ophthalmic drug application.

Temperature-dependent gel-type ionic liquid compounds based on vanadium-substituted polyoxometalates with Keggin structure.

A series of temperature-dependent gel-type ionic liquid compounds have been synthesized from 1-(3-sulfonic group) propyl-3-methyl imidazolium (abbreviated as MIMPS) and three vanadium-substituted heteropoly acids H5SiW11VO40, H5SiMo11VO40 and H7SiW9V3O40. The designed and synthesized gel-type polyoxometalate ionic liquids (POM-ILs) have demonstrated a tendency to exhibit a layered structure. Moreover, they can undergo a phase transformation from a viscous gel-state to a liquid-state below 100 °C, and ionic conductivity up to 10(-3) S cm(-1) was observed at 120 °C. Cyclic voltammetry was carried out to study their electrochemical properties in organic solutions, and it was found that the oxidizability of the three POM-ILs decreases in the order: [MIMPS]7SiW9V3O40 > [MIMPS]5SiMo11VO40 > [MIMPS]5SiW11VO40. This result indicates that the redox behavior can be tuned by changing the chemical composition of the heteropolyanions.

Synthesis and conductive performance of indium-substituted ternary heteropoly acids with Keggin structures.

Two new high-proton conductors, indium-substituted ternary heteropoly acids with Keggin structures, H4[In(H2O)PW11O39]·11H2O and H5[In(H2O)SiW11O39]·8H2O, have been synthesized and characterized using elemental analysis, IR, UV, XRD and TG-DTA. Their proton conductivities were measured using electrochemical impedance spectroscopy (EIS), and the results indicate that H4[In(H2O)PW11O39]·11H2O and H5[In(H2O)SiW11O39]·8H2O are solid high-proton conductors with a conductivity of 2.60 × 10(-4) S cm(-1) and 5.25 × 10(-4) S cm(-1), respectively, at 18 °C and 80% relative humidity (RH). Their activation energies are 33.40 kJ mol(-1) and 28.52 kJ mol(-1), which suggests that the mechanism of proton conduction is the vehicle mechanism. In the range of the measured temperatures, the conductivity of both heteropoly acids increases with higher temperatures.

Correction: The invertible electrochemical properties and thermal response of a series of gel-type ionic liquids based on polyoxometalates.

Correction for 'The invertible electrochemical properties and thermal response of a series of gel-type ionic liquids based on polyoxometalates' by Xuefei Wu et al., Phys. Chem. Chem. Phys., 2014, 16, 24598-24603.

Keggin-type polyoxometalate-based ionic liquid gels.

A series of reversible phase transformation ammonium- and phosphonium-based polyoxometalate ionic liquid (POM-IL) gels were synthesized and studied with a focus on the correlation between their physicochemical properties and their chemical structure. The products were successfully characterized by IR, UV, XRD and TG-DTA, and their ionic conductivities were measured. The Keggin-type heteropolyanion clusters decorated with long alkyl chains demonstrated a tendency to exhibit a gel state at room temperature, while all the gels transformed into liquids after heating and then recovered after cooling. With a decrease in the alkyl chain length, a significant improvement in the thermal stability and conductivity of the ammonium-based POM-IL gels can be achieved. Moreover, compared with the corresponding ammonium compound, phosphonium-based POM-IL gel was found to be more stable at high temperature and exhibited better conductivity.

The invertible electrochemical properties and thermal response of a series of gel-type ionic liquids based on polyoxometalates.

A series of vanadium-substituted Dawson-structure POM-type ionic liquids, [TEAPS]7P2W17VO62 and [TEAPS]9P2W15V3O62, bearing sulfo-group grafted ammonium (TEAPS) cations and Dawson-type polyoxoanions have been formed which are reversible-thermal-response type gels. These gel-type compounds exhibit a phase transition from a quasi-solid gel phase to an isotropic sol phase. What's more, this series of hybrid compounds can undergo reversible electrochemical reactions in dimethyl formamide (DMF) owing to the reduction of the vanadium in POM anions as a simple anion, which is unlikely to happen in water solution because of water protonation.

Proton conductive watery channels constructed by Anderson polyanions and lanthanide coordination cations.

A 3D inorganic-organic hybrid proton conductor, [Sm(H2O)5(CO2CH2NH3)2][Al(OH)6Mo6O18]·10H2O (), has been synthesized by using coordination cations, [Sm(H2O)5(gly)2](3+) (gly = (-)CO2CH2NH3(+)), and polyanions, [Al(OH)6Mo6O18](3-) ([AlMo6]). The polyanions ([AlMo6]) and the coordination cations ([Sm(H2O)5(gly)2](3+)) stack to form a 3D supramolecular network structure containing 1D channels along the c axis by electrostatic force and H-bonding. Significantly, the 1D channels are water-filled with a high water content (both Sm coordinated and in lattice). Dynamic adsorption measurements were implemented at 1 atm, and 95% relative humidity (RH). The water adsorption amount (6.51 wt% at 25 °C and 5.68 wt% at 80 °C) consistent with the number of lattice water molecules of suggests that the water chains were retained at elevated temperatures (80 °C) under 95% RH. Alternating-current (AC) impedance measurements of reveal an outstanding conductivity for of 4.53 × 10(-3) S cm(-1) at 80 °C under 95% RH. The activation energy of calculated from the Arrhenius plots of the proton conductivity is 1.09 eV, which indicated that the protons transfer by a vehicle mechanism.

Ammonium- and phosphonium-based temperature control-type polyoxometalate ionic liquids.

Ammonium- and phosphonium-based polyoxometalate ionic liquids (POM-ILs) have been synthesized and characterized. The results of small-angle XRD indicate that phosphonium-based POM-IL possesses a layered type structure. They are temperature control-type POM-ILs and can exhibit a phase transformation below 100 °C. Phosphonium-based POM-IL exhibits higher thermal stability and conductivity than its ammonium analogue.

Monolacunary Keggin polyoxometalates connected to ten 4d or 4f metal atoms.

The rational self-assembly of mono-lacunary Keggin clusters with 4d and 4f metal salts via a conventional method has yielded two novel polyoxometalate-based 4d-4f heterometallic compounds containing lacunary Keggin anions connected to ten metal atoms: {[Ag{Ag2(H2O)4}{Ln(H2O)6}2H ⊂ {SiW11Ln(H2O)4O39}2]·nH2O (Ln = Ce and n = 7 for 1, Ln = Pr and n = 3 for 2). Their structures were determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. A structural feature in 1 and 2 is that each [SiW11O39](8-) cluster (SiW11) is connected to ten metals (five Ag(+) and five Ln(3+) cations), representing the highest number of connected metal atoms to any mono-lacunary Keggin anion to date. This large connectivity leads to a structure with a purely inorganic 3D framework with two kinds of channels along the [100] and [010] directions. The magnetic properties of both compounds show the expected magnetic moments (0.8 and 1.6 amu K mol(-1) per Ce(3+) and Pr(3+) ion, respectively) and confirm the presence of isolated Ce(3+) and Pr(3+) ions.