Tetrabutylammonium Hydroxide Solution Research Articles

Highly Efficient Liquid-Phase Exfoliation of Layered Perovskite-like Titanates HLnTiO4 and H2Ln2Ti3O10 (Ln = La, Nd) into Nanosheets

Nanosheets of layered perovskite-like oxides attract researchers as building blocks for the creation of a wide range of demanded nanomaterials. However, Ruddlesden–Popper phases are difficult to separate into nanosheets quantitatively via the conventional liquid-phase exfoliation procedure in aqueous solutions of bulky organic bases. The present study has considered systematically a relatively novel and efficient approach to a high-yield preparation of concentrated suspensions of perovskite nanosheets. For this, the Ruddlesden–Popper titanates HLnTiO4 and H2Ln2Ti3O10 (Ln = La, Nd) have been intercalated by n-alkylamines with various chain lengths, exposed to sonication in aqueous tetrabutylammonium hydroxide (TBAOH) and centrifuged to separate the nanosheet-containing supernatant. The experiments included variations of a wide range of conditions, which allowed for the achievement of impressive nanosheet concentrations in suspensions up to 2.1 g/L and yields up to 95%. The latter were found to strongly depend on the length of intercalated n-alkylamines. Despite the less expanded interlayer space, the titanates modified with short-chain amines demonstrated a much higher completeness of liquid-phase exfoliation as compared to those with long-chain ones. It was also shown that the exfoliation efficiency depends more on the sample stirring time in the TBAOH solution than on the sonication duration. Analysis of the titanate nanosheets obtained by means of dynamic light scattering, electron and atomic force microscopy revealed their lateral sizes of 30–250 nm and thickness of 2–4 nm. The investigated exfoliation strategy appears to be convenient for the high-yield production of perovskite nanosheet-based materials for photocatalytic hydrogen production, environmental remediation and other applications.

Effect of 2D Alpha-Zirconium Phosphate Nanosheets in Interfacial Tension Reduction and Wettability Alteration: Implications for Enhanced Oil Recovery

Summary α-Zirconium phosphate (α-ZrP) nanocrystals were synthesized by refluxing method and subsequently exfoliated into extremely thin 2D nanosheets by tetrabutylammonium hydroxide (TBAOH) solution. Dynamic light scattering, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the size distribution and morphology of α-ZrP nanosheets. Interfacial tension (IFT) and contact angle measurement were conducted by different concentrations of α-ZrP nanosheets solutions. The results displayed that the wettability of porous media surface was altered from oleophilic to hydrophilic and the IFT decreased with the increasing of α-ZrP nanosheets concentrations. A new method was proposed to calculate the Hamaker constant for 2D α-ZrP nanosheets. The calculated results displayed that α-ZrP nanosheets were not easy to agglomerate under experimental environment and when the interaction energy barrier increased, the transport amount of α-ZrP nanosheets also increased. Coreflooding tests were also performed with various concentrations and the oil recovery efficiency increased from 33.59 to 51.26% when α-ZrP nanosheets concentrations increased from 50 to 1,000 ppm.

Simultaneous enrichment of inorganic and organic species of lead and mercury in pg L−1 levels by solid phase extraction online combined with high performance liquid chromatography and inductively coupled plasma mass spectrometry

Quantification of ultra-trace inorganic and organic species of lead and mercury in unpolluted environmental water is crucial to estimate the mobility, toxicity and bioavailability and interactions. Simultaneous pre-concentration of Pb and Hg species in pg L−1 levels followed by multi-elemental speciation analysis makes great sense to a large set of unstable samples because of time advantages. Herein simultaneous enrichment and speciation analysis of ultra-trace lead and mercury in water was developed by online solid-phase extraction coupled with high performance liquid chromatography and inductively coupled plasma mass spectrometry (SPE-HPLC-ICP-MS) for this aim. Pb(II), trimethyl lead (TML), triethyl lead (TEL), Hg(II), methylmercury (MeHg) and ethylmercury (EtHg) were baseline separated in 11 min under gradient elution using 5 mM l-cysteine (Cys) at pH 2.5 in the 0–1 and 4–15 min and 5 mM Cys + 0.5 mM tetrabutyl ammonium hydroxide solution at pH 2.5 in the 1–4 min. Lead and mercury species in 10 mL intact water samples were adsorbed on a 1 cm C18 enrichment column pre-conditioned with 10 mL of 1 mM 2-mercaptoethanol at 10 mL min−1, and then directly desorbed by the mobile phases. High enrichment factors (459 for Pb(II), 1248 for TML, 1627 for TEL, 2485 for Hg(II), 1984 for MeHg and 1866 for EtHg) were obtained with good relative standard deviations (<5%), leading to low LODs (0.001–0.011 ng L−1) and LOQs (0.004–0.036 ng L−1). Good accuracy of this method was validated by two certified reference materials of total lead in water (GBW08601) and total mercury in water (GBW08603) along with spiked recoveries (89–93%). The method was applied to analyze trace lead and mercury species in river, lake, tap and rain water, and purified and mineral water. Inorganic lead of 13–68 ng L−1 and inorganic mercury of 21–49 ng L−1 were measured in the nine water samples whereas TML, TEL and MeHg were not detected with 2–5 ng L−1 EtHg presented only in one river water and tap water.

Enhancement of Enzymatic Hydrolysis of Lignocellulose by Tetrabutylammonium Hydroxide (TBAOH) and Tetramethylammonium Hydroxide (TMAOH) Aqueous Solution Pretreatment

AbstractBACKGROUNDLignocellulose is usually pretreated as a raw material, and then it undergoes hydrolysis, fermentation, and other processes to produce biofuels, which is conducive to improving the utilization of agricultural and forestry wastes. However, most pretreatments, such as acid–base, CO2 explosion, and microbial degradation, could enhance the yield of enzymatically hydrolyzed (EH) sugars, but the conditions are relatively harsh, environmentally unfriendly, and economically unfeasible. Ionic liquids, in view of their excellent physical and chemical properties and strong solubility, have been proven to be an effective green solvent for pretreating lignocellulose. The aim of this study was to exploit tetrabutylammonium hydroxide (TBAOH) and tetramethylammonium hydroxide (TMAOH) aqueous solutions to pretreat corn cob under relatively mild conditions.RESULTSThe optimal pretreatment conditions for the two solutions were 30 °C, TBAOH concentration of 20 wt%, 60 min, 5 wt/wt, and 20 °C, TMAOH concentration of 10 wt%, 60 min, 5 wt/wt, and the corresponding sugar yields were 88.9% and 92.2%, respectively. Compared with the unpretreated corn cob, the yield of EH sugar increased by about 2.7–2.8 times. Characterization results confirmed that hemicelluloses and lignin were removed from the raw material during the pretreatment process, and that the cellulose was purified. Furthermore, after 5 cycles of reuse of the TBAOH and TMAOH aqueous solutions, the pretreated corn cob could still achieve a sugar yield higher than 70%.CONCLUSIONThe pretreatment with TBAOH and TMAOH aqueous solutions significantly enhanced the enzymatic hydrolysis, which provided a green, simple, and economical new approach for the pretreatment of agricultural waste biomass. © 2021 Society of Chemical Industry

Exfoliation of surfactant swollen layered MWW zeolites into two-dimensional zeolite nanosheets using telechelic liquid polybutadiene

Two-dimensional (2D) zeolites have the potential to enhance mass transport by reducing diffusion lengths and thus find applications in catalysis and separation. High aspect ratio 2D zeolite nanosheets are required for fabrication of thin, high-flux zeolite membranes. Preparation of 2D zeolite nanosheets can be achieved by exfoliation of layered zeolite precursors, which usually requires multiple steps including swelling with cationic surfactants, exfoliation by applying a mechanical force such as shearing or sonication, purification and removal of the surfactants. The exfoliation of surfactant swollen layered zeolite precursors has been studied using molten polystyrene and telechelic liquid polybutadiene, but still requires extensive shearing force. Recently, a novel one-step exfoliation method has been developed for non-swollen MWW zeolite precursors using tetrabutylammonium hydroxide (TBAOH) solution. In this work, we study the exfoliation of surfactant swollen MWW layered precursors (with and without aluminum) in commercially available liquid hydroxyl-terminated polybutadiene (HTPB) with the aim to provide fundamental understanding of the interaction between the liquid polybutadiene and the surfactant swollen layered zeolite precursors. It was found that surfactant swollen ITQ-1, (ITQ-1(S)), a pure silica layered precursor with MWW framework after being swollen with a cationic surfactant, can be exfoliated in liquid HTPB at room temperature without applying any additional shearing force. The aluminum containing surfactant swollen MWW precursors can be also exfoliated in HTPB at room temperature, but require additional shearing forces. The exfoliation process was monitored using rheology experiments and studied by tuning the composition of the zeolite precursors. The interaction between the layered zeolite precursor and the hydroxyl group of the liquid polybutadiene allows the polymer to intercalate the precursor and exfoliate it into nanosheets. The presence of framework aluminum and the nature of the organic structure directing agents (OSDAs) are key parameters affecting the exfoliation process. Framework Al is unfavorable for the exfoliation possibly due to the surface charges introduced by the aluminum. Bulky OSDA, trimethyladamantammonium (TMAda + ), in the interlayer spacing may facilitate the exfoliation. • Swollen ITQ-1 can self-disassemble in liquid hydroxyl-terminated polybutadiene. • Interaction between zeolite and hydroxyl group of the polybutadiene is crucial. • The presence of Al in the framework is unfavorable for the exfoliation. • Presence of a bulky OSDA in the interlayer spacing promotes the exfoliation.

Cellulose hydrogel skeleton by extrusion 3D printing of solution

Abstract Cellulose is the most abundant natural polymer on earth, which has obtained increasing interest in the field of functional materials development for its renewable, high mechanical performance and environmental benign. In this study, the traditional processing method (wet spinning and film production) of cellulose-based materials was applied by using cellulose solution for 3D printing, which can directly build complex 3D patterns. Herein, a natural cellulose is dissolved in an effective mixed aqueous solution of dimethyl sulfoxide (DMSO) and tetrabutylammonium hydroxide (TBAH). The cellulose solution extrusion was controlled by a modified fused deposition modeling (FDM) 3D printer. During the controlled extrusion 3D printing process, the viscous cellulose solution will gelifies and further solidifies into a predetermined 3D pattern at room temperature in air. Subsequently, a cellulose hydrogel skeleton was obtained, when the 3D pattern was solvent-exchanged with deionized water. Finally, the mechanical and swelling performance of the cellulose hydrogel scaffold was improved by a cross-linking agent treatment method. With treatment of the 3D printed scaffolds in 0.8 wt% cross-linking agent solution, the obtained cellulose hydrogel could absorb 28 g/g water, and the compression strength was 96 kPa. This work provided an efficient way to prepare natural cellulose hydrogel by 3D printing under room temperature.

Fabrication of enhanced epoxy composite by embedded hierarchical porous lignocellulosic foam

Plant biomass exhibits great potential in developing eco-friendly polymer composites. However, their complex composition hinders their utilization in high-performance materials. Herein, rice straw was pretreated by a steam explosion (SERS) and converted into lignocellulosic foam (LCF), which proved to be an efficient enhancement in fabricating epoxy composite. The SERS was dissolved in tetrabutylammonium hydroxide and dimethyl sulphoxide aqueous solution (TBAH/DMSO/H2O) to form a gel, and then freeze-dried to obtain the lignocellulosic foam. By introducing 4 wt% lignocellulosic foam, the compressive strength of the prepared composites (LCF/EP) reached 221.4 MPa, with a density of 1.22 g/cm3. The polarization microscope (POM) combined with a scanning electron microscope (SEM) analysis proved the lignocellulosic foam powder was homogeneously dispersed in the epoxy matrix. The differential scanning calorimetry (DSC) and the structural characterization by infrared spectroscopy (FTIR) show good interaction of straw-based foam with epoxy. The glass transition temperature (Tg) increased to 142.4 °C with 4 wt% content of LCF. The thermogravimetric analysis (TGA) showed an increased onset decomposition temperature of 372.8 °C with the same content of LCF. This work provides a new approach for the development of new lightweight and high-strength composite from biomass polymer.

A Novel Cleaning Approach to Remove the Carbon Contaminant from Ru Surface of EUV Mask

The carbon contamination on extreme ultraviolet (EUV) mask surface is known to lose its reflectivity and change the critical dimension. Conventional cleaning methods such as SPM and UV/O3 cleaning are widely used for the removal of organic contaminants but can cause surface damages on EUV mask such as surface oxidation and etching of absorber pattern. In this study, we proposed to remove carbon contaminant using quaternary ammonium hydroxides and an organic solvent mixture solution. This study investigated the effect of the cleaning solution on the hydrocarbon film removal by using four kinds of quaternary ammonium hydroxides as alkaline chemical and Dimethyl Sulfoxide (DMSO) and tetrahydrofuran (THF) organic solvents as polar aprotic solvents. The hydrocarbon film was effectively removed from Ru surface in the mixture of tetrabutylammonium hydroxide (TBAH) and THF. When DMSO was used with TBAH solution, the hydrocarbon film was also completely removed at a longer process time than THF with TBAH solution.

Surface modification of TiO2 particles with the sono-assisted exfoliation method

This study reported a novel approach to optimize the photocatalytic property of anatase TiO2 particles by delaminating their outer surface into highly reactive nanosheets via the sono-assisted exfoliation method. To modify the surface, TiO2 particles were dispersed in aqueous solution of 10M sodium hydroxide (NaOH) and tetrabutylammonium hydroxide (TBAOH), followed by irradiation with high intensity ultrasonic wave (20kHz, 150W/cm2) for 60min. The intercalation and exfoliation processes were accelerated with the driving force of the extreme acoustic cavitation leading to the delamination of TiO2 nanosheets with highly reactive exposed {001} facets from the mother TiO2 crystals. The presence of TBAOH increased yield of nanosheets formation and stabilized the nanosheet structure. The unique morphology of the surface modified TiO2 particles provided benefits in increasing the specific surface area and lowering the optical band gap energy (Eg) and electron-hole recombination rate resulting in an enhancement of methylene blue dye degradation efficiency. The surface modification of TiO2 particles by the sono-assisted exfoliation method can optimize the photocatalytic activity by yielding synergetic effects of the high surface reactive sites of the nanosheets and the high degree of crystallinity of the bulk structure.

Physical-chemical Properties of Aqueous TBAOH Solution for Gas Hydrates Promotion

Gas hydrates attract the attention of many industries for various potential applications such as gas separation and storage. To industrialize the gas hydrate technology, rapid hydrate formation at mild conditions is crucial. Chemical additives such as ionic liquids were investigated for hydrate promotion. The knowledge of physical-chemical properties of ionic liquids is crucial in development of gas hydrate technology in industry as these fundamental properties determined the hydrate formation rate. This work measures the density, pH, electrical conductivity, and surface tension of aqueous tetrabutylammonium hydroxide solutions. The concentrations were chosen to cover the common hydrate promotion range of 0.001-10 wt%. The results showed high dependence of the studied properties on the concentration. pH and electrical conductivity were increased with increase of TBAOH concentration conversely to density and surface tension. The amount of CO2 consumed to form the hydrate was measured at a pressure of 35bar and a temperature 274.15. Significant increase of CO2 consumption in the presence of TBAOH solutions was observed. However, as the concentration increased, more CO2 was consumed.

On the dissolution state of cellulose in aqueous tetrabutylammonium hydroxide solutions

We have characterized the dissolution state of microcrystalline cellulose (MCC) in aqueous 40 wt% tetrabutylammonium hydroxide (TBAH) using a combination of light and small angle X-ray scattering, up to 0.1 g cm−3.

Development of a novel, fast, sensitive method for chromium speciation in wastewater based on an organic polymer as solid phase extraction material combined with HPLC–ICP-MS

Speciation analysis of inorganic chromium in wastewater is of great significance for the monitoring of environmental pollution. In this work, N,N-bis(2-aminoethyl)ethane-1,2-diamine functionalized poly(chloromethyl styrene-co-styrene) was synthesized, characterized and used as the adsorbent to preconcentrate chromium species in environmental waters by on line solid-phase extraction (SPE). The trace speciation analysis of Cr(III) and Cr(VI) in wastewater has been used by short-column high-performance liquid chromatography hyphenated to inductively coupled plasma spectrometry (HPLC–ICP-MS) after on-line SPE. Cr(III) and Cr(VI) have been adsorbed on the anion exchange column after transforming the cationic Cr(III) to an anionic [Cr(III)–EDTA]− complex devoid of re-dox reagent, and then eluted rapidly (within seconds) with a very low concentration of tetrabutylammonium hydroxide (TBAH) solution. This method provides a reliable on-line preconcentration method and detection coupled technique. Under the optimized conditions, high enrichment factors have been obtained for Cr(VI) and [Cr(III)–EDTA]− with 30mL sample solution up to 105 and 128, respectively. The low detection limits of 0.0068ngmL−1 and 0.0041ngmL−1, with the relative standard deviations (RSDs) of 4.3% and 3.6% were obtained for Cr(VI) and [Cr(III)–EDTA]−, respectively. The developed method was validated by analyzing Certified Reference Materials GSBZ50027-94, and the spike tests were also performed. At the same time, thanks to the merit of simple operation, rapid adsorption/desorption dynamics, high enrichment and low LODs, the established method was applied to analyze three wastewater samples from different discharge port.

Synthesis and Electrochemical Properties of IrO2 Nanosheets

1. Introduction IrO2 is known as one of the most highly active and stable OER catalysts. It is essential that high surface area materials are used, either by preparing porous architectures or dispersing nanoparticles on conducting supports since Ir is a precious metal. Two-dimensional nanosheets have recently attracted increased interest as building blocks for high surface area porous materials. Nanosheets with electronic conductivity, for example, RuO2 nanosheets find application in transparent conductive electrodes as well as electrochemical energy storage and conversion.1,2) IrO2 is analogous to RuO2in many aspects; both possess the rutile structure and are room-temperature metallic conductors. Here we report the successful synthesis of an ion exchangeable layered iridium oxide which can be exfoliated into elemental nanosheets and subsequently used as an electrocatalyst. 2. Experimental Layered K0.30Ir0.93O2•nH2O was prepared by solid-state reaction of a 1:2 mixture of K2CO3 and IrO2 under inert atmosphere. Proton exchange was conducted by reaction in 1 M HCl for 3 days. Chemical exfoliation was conducted by shaking H0.30Ir0.93O2•nH2O in an aqueous solution of tetrabutylammonium hydroxide for 1 week. Electrochemical properties were studied in H2SO4 and HClO4. Results and discussion The Ir0.93O2 nanosheets (typical AFM image given in Fig. 1 inset) have an average thickness of c.a. 1.5 nm. The sharp edges suggest that the nanosheets are highly crystalline. Cyclic voltammograms of the Ir0.93O2 nanosheet electrode in 0.5 M H2SO4 is shown in Fig. 1. Three distinct redox peaks are observed. The E 1/2=0.95 and 1.19 peaks are typical of IrO2 3) and assigned to the Ir3+/Ir4+ and Ir4+/Ir5+ couple. The peaks at E 1/2=0.83 is observed only for IrO2 nanosheet, and shifts in HClO4; this peak is attributed to ad/desorption of anion. The onset of OER is observed at a potential similar to IrO2 nanoparticles.4) The specific capacitance between 0.2 and 1.2 V vs RHE at 2 mV s-1 was 93 kF mol-1, or 432 F g-1, which is the highest reported value for IrO2-based materials. It also closely matches the value of 88 kF mol-1 for RuO2nanosheet. Thus, almost all of the nanosheets surface is electrochemically accessible, and thus should provide unprecedented high utilization of the precious metal. 1) W. Sugimoto, H. Iwata, Y. Yasunaga, Y. Murakami, Y. Takasu, Angew. Chem. Int. Ed., 42, 4092 (2003). 2) K. Fukuda, T. Saida, J. Sato, M. Yonezawa, Y. Takasu, W. Sugimoto, Inorg. Chem., 49, 4391 (2010). 3) H. Andreas, H. Elzanowska, I. Serebrennikova, V.J. Birss. J. Electrochem. Soc., 147, 4598 (2000). 4) Y. Lee, J. Suntivich, K.J. May, E.E. Perry, Y. Shao-Horn, J. Phys. Chem. Lett. 3, 399 (2012). Figure 1. Cyclic voltammograms of IrO2 nanosheet electrodes in 0.5 M H2SO4 at 50 mV -1 (inset shows a typical AFM image of nanosheets on Si). Figure 1

On the role of hydrophobic interactions in cellulose dissolution and regeneration: Colloidal aggregates and molecular solutions

The development of strategies for dissolution and regeneration of cellulose constitutes an increasingly active research field due to the direct relevance for many production processes and applications. A wide variety of suitable solvents for cellulose are already available. However, cellulose solvents are of highly different nature reflecting the great challenges in the understanding of the subtle balance between the different interactions. Here, we report on the effect of two different solvents on the dissolution of cellulose on multiple length scales and its consequences for the characteristics of the regenerated material. While an aqueous tetrabutylammonium hydroxide solution gives rise to what appears to be dissolution down to the molecular level, a sodium hydroxide solution does not dissolve cellulose molecularly but rather leaves aggregates of high crystallinity stable in the cellulose dope. The dramatic difference between a small inorganic cation and an amphiphilic cation indicates a critical role of hydrophobic interactions between cellulose molecules and provides support for the picture that cellulose molecules have pronounced amphiphilic properties. (C) 2015 Elsevier B.V. All rights reserved. (Less)

Accordion-like swelling of layered perovskite crystals via massive permeation of aqueous solutions into 2D oxide galleries

Platelet crystals of a layered perovskite showed massive accordion-like swelling in a tetrabutylammonium hydroxide solution. The permeation of the solution induced the huge expansion of the interlayer spacing as well as the crystal thickness up to 50-fold, leading to a very high water content of >90 wt%.

Novel fluorinated gemini surfactants with γ-butyrolactone segments.

In this work, novel γ-butyrolactone-type monomeric and dimeric (gemini) surfactants with a semifluoroalkyl group [Rf- (CH2)3-; Rf = C4F9, C6F13, C8F17] as the hydrophobic group were successfully synthesized. Dimethyl malonate was dimerized or connected using Br(CH2)sBr (s = 0, 1, 2, 3) to give tetraesters, and they were bis-allylated. Radical addition of fluoroalkyl using Rf-I and an initiator, i.e., 2,2'-azobisisobutyronitrile for C4F9 or di-t-butyl peroxide for C6F13 and C8F17, was perform at high temperature, with prolonged heating, to obtain bis(semifluoroalkyl)-dilactone diesters. These dilactone diesters were hydrolyzed using KOH/EtOH followed by decarboxylation in AcOH to afford γ-butyrolactonetype gemini surfactants. Common 1 + 1 semifluoroalkyl lactone surfactants were synthesized using the same method. Their surfactant properties [critical micelle concentration (CMC), γCMC, pC20, ΓCMC, and AG] were investigated by measuring the surface tension of the γ-hydroxybutyrate form prepared in aqueous tetrabutylammonium hydroxide solution. As expected, the CMC values of the gemini surfactants were more than one order of magnitude smaller than those of the corresponding 1 + 1 surfactants. Other properties also showed the excellent ability of the gemini structure to reduce the surface tension. These surfactants were easily and quantitatively recovered by acidification. The monomeric surfactant was recovered in the γ-hydroxybutyric acid form, and the gemini surfactant as a mixture of γ-butyrolactone and γ-hydroxybutyric acid forms.

Selective Extraction and Detection of Hg2+ in Aqueous Solution by using Rhodamine Dye-Modified Silica Gel

Novel silica gel-immobilized rhodamine (SGR) anchored by hydrazinium hydrate was synthesized. The selectivity and adsorption ability of the SGR for metal cations were investigated with fluorophotometry and atomic absorption spectrophotometery, respectively. The SGR exhibits high selectivity and adsorption capacity for Hg2+. The maximum static adsorption capacity of the SGR for Hg2+ was 25.8 μmol g−1. The linear response range covers a concentration range of Hg2+ from 20 ppb to 2000 ppb and the detection limit is 10 ppb. The determination of Hg2+ in real water samples displays satisfactory results, and the SGR can be used repeatedly by treating with a solution of tetrabutylammonium hydroxide.

Ex Situ Activation of Li-Excess Layered Cathode Materials for High-Capacity Lithium Ion Batteries

Ex situ activation of Li-excess layered cathode material (Li[Li0.2Mn0.54Ni0.13Co0.13]O2) has been carried out via proton exchange in hydrochloric acid (HCl), followed by chemical exfoliation in tetrabutylammonium hydroxide (TBA·OH) solution and post-heat treatment, in which morphologic and structural reconstructions of pristine cathode material simultaneously take place. Exquisite nanoflower-shaped derivative is achieved with significant increased surface area and uniform pore size distribution after protonation and TBA·OH exfoliation. Sintering nanoflower-structured derivative contributes to hierarchical mesoporous structure and cubic spinel phase within final converted cathode material. The chemical activation of Li-excess layered cathode material results in phase transition from original layered to refactored spinel structure. The activated cathode material in spinel phase and hierarchical porous structure shows significantly improved electrochemical performance, which reveals Coulombic efficiency of 99.93% in the initial cycle at 1C (1C=250 mA/g) and retains high specific capacity of 200.8 mAh/g after 100 cycles, in comparison with 59.16% and 58.1 mAh/g of pristine Li-excess layered cathode materials, respectively. Remarkable enhanced rate capability has also been accomplished in activated cathode, delivering initial discharge capacities of 313.6, 267.2, and 126.3 mAh/g at 0.1, 0.5, and 5C, respectively. Such considerably enhanced cycleabilitiy and rate capability can be attributed to ex situ activation of Li2MnO3 component, phase transition, and/or morphologic and structural reconstructions of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. This work opens up various routes to achieve excellent electrochemical performance from high-capacity Li-excess layered cathode materials.

All-Solid-State Thin-Film Electrochemical Capacitors Using Inorganic Nanosheets Electrolytes

Introduction These days, demands of safe, inexpensive and large-capacity energy storage devices are increasing for various applications as power sources of electrical vehicles. All-solid-state thin-film electrochemical capacitors using protons as carriers can meet such demands. However, solid-state electrolytes have large electrolyte resistance and interfacial resistance between electrolytes and electrodes, which cause depression of powers and energy densities of electrochemical capacitors. In this study, we focused on extremely thin nanosheets, which are plate-like particles with thicknesses of only a few nanometers. Electrolyte resistance was reduced by applying thin-films of stacked nanosheets to electrolytes. Also, all-solid-state thin-film electrochemical capacitors were fabricated, and evaluated by electrochemical measurements. As the proton conducting nanosheet, we selected a-zirconium hydrogenphosphate monohydrate (α-Zr(HPO4)2·H2O : ZrP), composed of naturally abundant elements. Experimental ZrP powders were prepared from zirconium oxide hydrate (ZrO2·nH2O) powders through treating with phosphoric acid by hydrothermal synthesis method. A colloidal suspension of ZrP nanosheets was obtained by exfoliation of ZrP powders induced by shaking with aqueous solution of tetrabutylammonium hydroxide. ZrP films were prepared by applying concentrated colloidal suspension of ZrP nanosheets on substrates and drying them in air. Protonic conductivities of ZrP films were measured by alternating-current impedance measurement in the frequency range from 1 MHz to 100 Hz with an applied voltage of ±100 mV. All-solid-state thin-film electrochemical capacitors were fabricated with ruthenium oxide hydrate (RuO2·nH2O : RuO2) as both electrodes and ZrP films as electrolytes. Galvanostatic charge/discharge tests were carried out in the cell voltage range of 0 – 1 V at a constant current density of 100 mA g− 1. Results & Discussions Fig. 1shows protonic conductivities of the ZrP film at relative humidity (R. H.) 90% and those of the ZrP tablet at saturated vapor [1]. The thickness of the ZrP film was 700 nm. Protonic conductivity of the ZrP film increased as with increasing temperature, and reached 3.2×10−6 Scm−1 at 80oC. The activation energy of protonic conduction in the ZrP film was 0.28 eV. This value is close to the activation energy of the ZrP tablet (0.25 eV) [1], and this suggests that the mechanism of protonic conduction in ZrP films is the same to that in ZrP tablets. The thickness of the ZrP film was over one thousand times smaller than that of the ZrP tablet (1 mm), so the areal electrolyte resistance could be reduced from 1.0×105 Ωcm2 (ZrP tablet at 27oC, R. H. 90%) [2] to 1.0×102 Ωcm2 (ZrP film at 30oC, R. H. 90%). Fig. 2 shows the charge and discharge curves of the all-solid-state thin-film electrochemical capacitor (RuO2|ZrP-film|RuO2) measured at a constant current density of 100 mA g−1. No recognizable plateau regions are observed in either the charge or the discharge curves. The electrochemical capacitor exhibited a reversible capacity of 22 mAh g−1 at the 10th cycle. This capacity is much higher than that of many other proton conducting all-solid-state capacitors [3, 4], and is comparable to those of electrochemical capacitors assembled with liquid electrolytes. In addition, the cycle characteristic was good and coulombic efficiency was high (h = 93%), suggesting the influences of side reactions to be small.

Determination of Arsenic Species in Fruit Juice and Fruit Drink Products Using Ion Pair Chromatography Coupled to Inductively Coupled Plasma Mass Spectrometry

Ion-pair chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS) was evaluated and validated for the determination of arsenic species in fruit juice and fruit drink products. A Phenomenex analytical column (Prodigy 3 μ ODS (3) 4 μm × 2.0 mm × 150 mm) and a mobile phase consisting of 5 mmol l−1 malonic acid, 3 mmol l−1 of tetrabutylammonium hydroxide solution and 5 % methanol were used to achieve arsenic speciation separation. The arsenic species were detected at m/z 75 with an Agilent 7500cx ICP-MS. After demonstrating the method was sensitive, accurate and fit for purpose, and it was applied to analyze 96 fruit juice and fruit drink samples. Speciation analysis of the 96 fruit juice and fruit drink products revealed that inorganic arsenic was the major species found in the majority of juice products tested in the study. The concentration of inorganic arsenic (sum of As3+ and As5+) ranged from<limit of quantification (LOQ) to 23.9 μg l−1, with a mean value of 3.57 ± 4.42 μg l−1. Dimethylarsenate (DMA) was found in 32 of the samples, and the mean value is 0.30 ± 0.55 μg l−1. Monomethylarsenate (MMA) was found in 26 of the samples, and the mean value is 0.30 ± 0.71 μg l−1.