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Hydrogen peroxide assisted sol–gel coating of core-shell microcapsules of phase change materials (PCMs) is reported. A doubly coated paraffin core with an inner poly(melamine-formaldehyde) shell and an outer coating of peroxostannate, peroxoantimonate, their mixture or the respective metal oxides are reported. Triple coating of the paraffin core with a poly(melamine-formaldehyde) inner shell, tin oxide middle layer and graphene oxide outer coating is also achieved by hydrogen peroxide sol–gel processing. The latent heats of the microencapsulated PCMs ranged between 122 and 192 J g−1. The sol–gel process involves stabilization of the peroxostannate or peroxoantimonate sol in basic aqueous hydrogen peroxide and subsequent destabilization and deposition of the sol by addition of an antisolvent. Transformation to the metal oxide coating is conducted by chemical reduction with sodium sulfite or by mild heat treatment without leakage of the paraffin core.

Microencapsulation of a carbon nanotube (CNT)-loaded paraffin phase change material, PCM in a poly(melamine-formaldehyde) shell, and the respective CNT-PCM gypsum composites is explored. Although a very low level (0.001-0.1 wt %) of intramicrocapsule loading of CNT dopant does not change the thermal conductivity of the solid, it increases the measured effusivity and thermal buffering performance during phase transition. The observed effusivity of 0.05 wt % CNT-doped PCM reaches 4000 W s

We introduce a green synthesis approach for high-performance sodium-ion battery anodes that does not involve hydrothermal treatment or excessive energy use. Wet chemistry involving ammonium peroxostannate intermediate coating of reduced graphene oxide can be done at low temperature without excessive use of solvents. The process is practically waste-free and does not involve acid waste. Thermal treatment is required only for the solid material. The electrode exhibited very high stability and the charging capacity was reduced from 320 to 310 mA h g–1 after 2000 cycles at 3 A g–1. Moreover, the synthesis protocol demonstrated here is highly versatile with different, alternative pathways that provide many degrees of freedom in the process sheet design and in material composition.

Formation of vanadium oxide nanofilm-coated graphene oxide (GO) is achieved by thermally induced explosive disintegration of a microcrystalline ammonium peroxovanadate-GO composite. GO sheets isolate the microcrystalline grains and capture and contain the microexplosion products, resulting in the deposition of the nanoscale products on the GO. Thermal treatment of the supported nanofilm yields a sequence of nanocrystalline phases of vanadium oxide (V3O7, VO2) as a function of temperature. This is the first demonstration of microexplosive disintegration of a crystalline peroxo compound to yield a nanocoating. The large number of recently reported peroxide-rich crystalline materials suggests that the process can be a useful general route for nanofilm formation. The V3O7@GO composite product was tested as a sodium ion battery anode and showed high charge capacity at high rate charge-discharge cycling (150 mAh g-1 at 3000 mA g-1 vs 300 mAh g-1 at 100 mA g-1) due to the nanomorphology of the vanadium oxide. NRF (Natl Research Foundation, S’pore)

Nitroguanidine, a widely used nitramine explosive, is an environmental contaminant that is refractory, persistent, highly mobile in soils and aquifers, and yet under-researched. Nitroguanidine determination in water and soil poses an analytical challenge due its high hydrophilicity, low volatility, charge neutrality over a wide pH range, and low proton affinity which results in low electrospray interface (ESI)-MS sensitivity. A sensitive method for the determination of nitroguanidine in aqueous and soil matrices was developed. The method is based on reduction by zinc in acidic solution, hydrophobization by derivatization, preconcentration on C18 cartridge, and LC-MS quantification. The demonstrated limit of detection (LOD) reaches 5 ng/L and 22 ng/g in water and soil, respectively. Analysis of a contaminated site demonstrates that it is possible to map a contamination plume that extends over 1 km from the source of the contamination.

A peroxogermanate thin film was deposited in high yield at room temperature on graphene oxide (GO) from peroxogermanate sols. The deposition of the peroxo-precursor onto GO and the transformations to amorphous GeO2, crystalline tetragonal GeO2, and then to cubic elemental germanium were followed by electron microscopy, XRD, and XPS. All of these transformations are influenced by the GO support. The initial deposition is explained in view of the sol composition and the presence of GO, and the different thermal transformations are explained by reactions with the graphene support acting as a reducing agent. As a test case, the evaluation of the different materials as lithium ion battery anodes was carried out revealing that the best performance is obtained by amorphous germanium oxide@GO with >1000 mAh g–1 at 250 mA g–1 (between 0 and 2.5 V vs Li/Li+ cathode), despite the fact that the material contained only 51 wt % germanium. This is the first demonstration of the peroxide route to produce peroxogermanate ...

Manganese mud (MnM) is a manganese oxide petal-like nanostructured precipitate that accumulates on the inner surface of pipes transferring reclaimed effluent from the Shafdan soil aquifer t...

A peroxogermanate thin film was deposited in high yield at room temperature on graphene oxide (GO) from peroxogermanate sols. The deposition of the peroxo-precursor onto GO and the transformations to amorphous GeO

A way to benefit from the favorable attributes of both organic microencapsulation, including the hermetic sealing of the organic PCM core, and inorganic microencapsulation, including dispersibility in aqueous and polar solvents and improved thermal conductivity, is outlined. The approach is demonstrated by uniformly coating organic polymer encapsulated PCMs with zinc oxide, which allows thermal percolation through the interconnected inorganic shells. We demonstrate that hydrogen peroxide sol-gel processing can be used to form such uniform zinc peroxide coatings which are then converted by chemical treatment to zinc oxide shells. The way to overcome different challenges associated with the synthesis of thin film coatings of organic PCMs by zinc oxide are addressed, and the favorable attributes of the new doubly coated PCM capsules are demonstrated. National Research Foundation (NRF) Accepted version This research is supported by a grant from the National Research Foundation, Prime Minister Office, Singapore under its Campus of Research Excellence and Technological Enterprise (CREATE) programme. The financial support of the Ministry of Science is thankfully acknowledged. We thank the Harvey M. Krueger Family Centre for Nanoscience and Nanotechnology of the Hebrew University of Jerusalem and the Israel Science Foundation. The zinc peroxide deposition was supported by the Russian Science Foundation (№17-73-10482). CHNS-analysis was performed at the User Facilities Center of IGIC RAS within the State Assignment on Fundamental Research to the Kurnakov Institute of General and Inorganic Chemistry.

Crystalline acenes are promising organic p-type semiconductors for future electronics. However, despite their importance to emerging and future electronics and in distinct contrast to the large technological care that is devoted to control the impurity levels in inorganic semiconductors, organic impurities in crystalline organic electronic components were left largely unexplored. The impurities in commercially available crystalline anthracene, tetracene and pentacene were analyzed and compared to crystalline organics that were obtained by two methods: solution (flux) growth, where the solvent was naphthalene, solid at room temperature but liquid in the crystal growth temperature range and by physical vapor transport. The impurities were identified by different methodologies: GC–EI–MS, a gas chromatograph GC equipped with an electron ionization ion source and a single quadrupole mass analyzer; GC–SMB–EI–QQQ–MS, a GC equipped with a low temperature electron ionization ion source (supersonic molecular beam, SMB), and a triple quadruple mass analyzer; high resolution MALDI–TOF–TOF–MS, matrix assisted laser desorption with two time of flight analyzers in series; and ESI–Q–TOF–MS, electrospray ionization mass spectrometers equipped with a quadruple mass analyzer and time of flight analyzers. Regular GC–EI–MS exhibited poor impurity identification power. The other three techniques provided complementary pictures of the various impurities present in these semiconductors with a significant overlap between identified impurities by the three instrumental approaches. GC–SMB–EI–QQQ–MS was the most revealing instrumental technique especially when combined with ChromatoProbe™ thermal desorption injector since the latter helped minimize degradation of pentacene during sample preparation. In all three organic semiconductors (OSs), the analyses clearly revealed a significant cleansing of the impurities by the physical vapor transport technique. The naphthalene flux crystallization method introduced a significant amount of naphthalene and benzothiofuran impurities, the latter being a known naphthalene impurity.

International audience; Cellulose paper degradation products forming in the “tideline” area at the wet-dry interface of pure cellulose paper were analyzed using gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) and high-resolution electrospray ionization-mass spectrometry (ESI-MS, LTQ Orbitrap) techniques. Different extraction protocols were employed in order to solubilize the products of oxidative cellulose decomposition, i.e., a direct solvent extraction or a more laborious chromophore release and identification (CRI) technique aiming to reveal products responsible for paper discoloration in the tideline area. Several groups of low molecular weight compounds were identified, suggesting a complex pathway of cellulose decomposition in the tidelines formed at the cellulose-water-oxygen interface. Our findings, namely the appearance of a wide range of linear saturated carboxylic acids (from formic to nonanoic), support the oxidative autocatalytic mechanism of decomposition. In addition, the identification of several furanic compounds (which can be, in part, responsible for paper discoloration) plus anhydro carbohydrate derivatives sheds more light on the pathways of cellulose decomposition. Most notably, the mechanisms of tideline formation in the presence of molecular oxygen appear surprisingly similar to pathways of pyrolytic cellulose degradation. More complex chromophore compounds were not detected in this study, thereby revealing a difference between this short-term tideline experiment and longer-term cellulose aging.

We describe a method for conformal coating of reduced graphene oxide (rGO) by stibnite nanocrystallites. First, graphene oxide (GO) supported amorphous hydroperoxoantimonate was produced using the recently introduced hydrogen peroxide synthesis route. Sulfurization of the amorphous antimonate yielded supported antimony(V) oxide nanoparticles and sulfur, which were then converted by high temperature vacuum treatment to 15–20 nm rGO supported stibnite. The usefulness of the new material and synthesis approach are demonstrated by highly efficient and stable lithium battery anodes. Since both sulfur lithiation and antimony–lithium alloying are reversible, they both contribute to the charge capacity, which exceeded 720 mA h g–1 after 50 cycles at a current density of 250 mA g–1. The very small crystallite size of the stibnite provides a minimum diffusion pathway and allows for excellent capacity retention at a high rate (>480 mA h g–1 at 2000 mA g–1 was observed). The nanoscale dimensions of the crystallites minimize lithiation-induced deformations and the associated capacity fading upon repeated charge–discharge cycles. The flexibility and conductivity of the rGO ensure minimal ohmic drop and prevent crack formation upon repeated cycles.

The ultrathin peroxoantimonate coating of graphene oxide from hydrogen peroxide-rich solutions of hydroxoantimonate is demonstrated. An amorphous 1–2 nm Sb (V) oxide film is formed and can be further crystallized by exposure to an electron beam to give a 2–5 nm thick supported Sb 6 O 13 particulate coating. Heat treatment of the peroxoantimonate yielded different crystalline oxides, whereas in the presence of the graphene support only trigonal Sb (0) was produced by heat treatment in vacuum or an argon atmosphere. The graphene oxide support is essential for the formation of the Sb (0) phase and even in air a substantial elemental antimony was obtained. Whereas heat treatment of uncoated graphene oxide in an inert atmosphere produces reduced graphene oxide, the antimony oxide coated graphene oxide is not reduced by the heat treatment. Only after the supported antimony oxide is reduced to give the trigonal Sb (0) phase the graphene oxide was reduced by the heat treatment. The phases before and after the different heat treatments are characterized by electron and X-ray diffraction, thermal analysis, XPS studies, electron microscopy and wet chemistry.

Several alkali metal hydroxoantimonates, K 2 [Sb(O)(OH) 5 ], Na[Sb(OH) 6 ], Cs[Sb(OH) 6 ] and Cs 2 [Sb 2 (μ-O) 2 (OH) 8 ] were isolated from aqueous solutions and characterized by single crystal and powder X-ray diffraction studies and by FTIR and thermal analysis. Crystal structures involving [Sb(O)(OH) 5 ] 2− were never anticipated before, and this is also the first disclosure of a dinuclear antimonate [Sb 2 (μ-O) 2 (OH) 8 ] 2− . Aqueous antimonate solutions of different pH were studied by high resolution electrospray mass spectrometry showing pH indifferent spectra and predominance of the mono and dinuclear antimonate species at pH 4–10.

The preparation of antimony doped tin oxide (ATO) conductive thin films on mica (muscovite) clays is described. ATO coating solution was prepared from ethylene glycol monomer, citric acid ligand, SbCl 3 and SnCl 2 precursors in alcohol solution. Muscovite thin film coating was prepared by gradual addition of the precursor solution to a water–muscovite clay dispersion. Under appropriate precursor concentrations and temperature, aggregation of the clays and ATO particles was prevented, and the ATO film grew exclusively on the clay substrate. Heat treatment of the coated mica resulted in semi transparent and conductive clays which could be used for composite film formation. Whereas the Pechini route is widely used for dip coating of ATO films, here we extend the approach for coating particulate matter. The films were characterized by electronic microscopy, X-ray photoelectron spectroscopy, powder diffraction, and thermal analysis and the dependence of conductivity on calcination temperature and precursor concentrations are described.

Stable amorphous potassium peroxostannate nanoparticles with controlled sizes (10–100 nm), morphology, and hydrogen peroxide percentage (19–30 wt %) were synthesized for the first time. The compounds were characterized by vibrational spectroscopy, 119Sn MAS NMR spectroscopy, powder X-ray diffraction, and thermogravimetry. These characteristics were compared to those for K2Sn(OH)6 and K2Sn(OOH)6. Potassium peroxostannate particles are mainly built of peroxo-bridged polymer chains. The particles are stable when stored in a dry state or suspended in nonaqueous solvents; in contact with water, they release hydrogen peroxide.

Stable, amorphous potassium peroxystannate nanoparticles of controlled average size—in the range 10–100 nm—and of controlled hydrogen peroxide content—in the range of 19–30 wt%—were synthesized by hydrogen peroxide induced polymerization in water–potassium hexahydroxostannate solutions. The sol phase and the precipitate were characterized by vibrational spectroscopies, 119Sn NMR, XPS and XRD using crystalline K2Sn(OH)6 and K2Sn(OOH)6 reference materials. This is the first study to show that peroxocoordination induces polymerization of a main group element. 119Sn NMR studies show that peroxotin coordination and polymerization took place already in the hydrogen peroxide–water phase. The high abundance of peroxotin bonds revealed by 119Sn MAS NMR, vibrational spectroscopy, and XPS suggests that the particles are predominantly made of peroxo bridged tin networks. Although the particles are highly stable in the dry phase as well as in alcohol solutions and do not lose hydrogen peroxide upon storage, they release their stored hydrogen peroxide content by exposure to water.

Low concentration, as low as 0.4 wt.% graphene oxide organogels is reported for different organic solvents. The gelation of organic solvents at exceedingly low concentrations opens the door for the implementation of graphene oxides based electrolytes in various electrochemical applications. Here we demonstrate the use of acetonitrile–graphene oxide (GO) gel containing iodide/triiodide as a quasi-solid electrolyte for dye sensitized solar cells (DSCs). Electrochemical impedance studies reveal that the mass transfer barrier is not adversely affected by the presence of the minute amount of GO gel former. The achieved energy conversion efficiency (η) for the device without GO and with 1% GO gel electrolytes is 6.9% and 7.5% respectively under one sun illumination. Keywords: Graphene oxide, Organogel, Dye-sensitized solar cell, Quasi-solid state electrolyte

Zero-valent antimony and antimony oxide were deposited on graphene oxide by the recently introduced peroxide deposition route. The antimony@graphene oxide (GO) anode exhibits a charging capacity of 340 mAh g-1 with excellent stability at a current rate of 250 mA g-1 after 50 cycles of lithiation, which is superior to all other forms of antimony anodes that have been reported thus far. The electrode also exhibits a good rate performance, with a capacity of 230 and 180 mAh g-1 at a rate of 500 and 1000 mA g-1, respectively. We attribute the superior performance of the antimony@GO anodes to our coating protocol, which provides a thin layer of nanometric antimony coating on the graphene oxide, and to a small amount of antimony oxide that is left in the anode material after heat treatment and imparts some flexibility. The efficient charge distribution by the large surface area of reduced GO and the expansion buffering of the elastic graphene sheets also contributed to the superior stability of the anode. Published version

Sodium-ion batteries are an alternative to lithium-ion batteries for large-scale applications. However, low capacity and poor rate capability of existing anodes are the main bottlenecks to future developments. Here we report a uniform coating of antimony sulphide (stibnite) on graphene, fabricated by a solution-based synthesis technique, as the anode material for sodium-ion batteries. It gives a high capacity of 730 mAh g(-1) at 50 mA g(-1), an excellent rate capability up to 6C and a good cycle performance. The promising performance is attributed to fast sodium ion diffusion from the small nanoparticles, and good electrical transport from the intimate contact between the active material and graphene, which also provides a template for anchoring the nanoparticles. We also demonstrate a battery with the stibnite-graphene composite that is free from sodium metal, having energy density up to 80 Wh kg(-1). The energy density could exceed that of some lithium-ion batteries with further optimization.

The significant probe dilution is one of the reasons to use soluble dyes and concentrated ion solutions for studies of colloid transport in subsoils and aquifers. We studied the clay transport in sand columns with Rhodamine 6G-intercalated montmorillonite (MMT). Our MMT-R exhibited transfer properties similar to the non-dyed clays but was detectable starting from 1 ppb by fluorescence and only from 0.5 ppm by turbidity. More contaminated soil adsorbed the MMT-R better than the pure one and therefore the reduction of influent turbidity may have the unintended effect of decreasing soil adsorption capacity.

A generic method for conductive film coating of minerals and acid-sensitive materials by antimony-doped tin oxide (ATO) is introduced. The coating was performed from a hydrogen peroxide stabilized stannate and antimonate precursor solution. This is the first demonstration of ATO coating from an organic ligand-free solution. Uniform coating of different clays and other irregular configurations by monosized 5 nm ATO particles was demonstrated. The deposition mechanism and the observed preference for mineral surface coating over homogeneous agglomeration of the tin oxide particles are explained by a hydrogen peroxide capping mechanism and hydrogen bonding of the hydroperoxo nanoparticles to the H(2)O(2)-activated mineral surfaces.

The crystal structure of cesium hexahydroperoxostannate Cs2Sn(OOH)6 is presented. The compound was characterized by single crystal and by powder X-ray diffraction, FTIR, 119Sn MAS NMR, and TG-DTA. Cs2Sn(OOH)6 crystallizes in the trigonal space group P3, a = 7.5575(4), c = 5.1050(6) A, V = 252.51(4) A3, Z = 1, R1 = 0.0120 (I > 2σ(I)), wR2 = 0.0293 (all data), and comprises cesium cations and slightly distorted octahedral [Sn(OOH)6]2− anions lying on the threefold axis. The [Sn(OOH)6]2− unit forms 12 interanion hydrogen bonds resulting in anionic chains spread along the c-axis. All six hydroperoxo ligands are crystallographically equivalent; O−O distances are 1.482(2), only slightly longer than the O−O distance in hydrogen peroxide. FTIR and 119Sn MAS NMR reveal the similarity between all alkali hydroperoxostannates.

This review provides an overview of some exciting, new as well as somewhat older, directions in sol-gel electrochemical applications of silicates and composite silicate electrodes. Rather than provide an exhaustive account of all the many papers that have been published on sol-gel electrochemistry and composite sol-gel electrodes, we prefer to illustrate the versatility of sol-gel chemistry by a few select examples which on the one hand illustrate the power entailed in sol-gel technology for electrochemical applications, and on the other hand point to hot electrochemical fields in which more research is due and exciting developments are to be expected. We start this review with a brief historical perspective. The inorganic sol-gel and silicone electrochemistry fields are both rather old though never extensively dealt with particularly when it comes to sensing applications. In contrast, the sol-gel electrochemistry of inorganic-organic hybrids is a relatively young field whose importance was recognized only in the last 30 years, and despite, or maybe even owing to the late recognition it is being very extensively studied nowadays. The use of composite electrodes for sensing and other applications is emphasized in this review, and the fast evolving electrodriven deposition techniques are reviewed.

A new form of conductive and transparent porous composite electrode is introduced. The electrode material is composed of antimony-doped, tin oxide (ATO)-coated mica platelets imbedded in sol-gel-derived silicate or methyl silicate network. The platelet clays self-align in a layered structure within the silicate film, an anisotropic construction that minimizes the ATO loading required to achieve electric percolation. Transparency and resistance as a function of clay loading is reported with typical values of 100 k Omega/square and 1.5 OD for a 20-microm-thick film. The transparency is lower as compared to sputtered ATO glasses, but this is, as far as we know, the best method for the low-temperature preparation of transparent, porous, and electrically conductive (as opposed to the amply reported ionically conductive) electrode materials. Permselectivity induced by the silicate and clay ingredients is demonstrated by permeation of positively charged methyl viologen compared to negatively charged ferricyanide. Prussian blue-modified ATO-coated platelets dispersed in sol-gel-derived silicate were used to demonstrate feasibility of a transparent and electrically conductive porous electrochromic material.

A highly stable sodium ion battery anode was prepared by deposition of hydroperoxostannate on graphene oxide from hydrogen-peroxide-rich solution followed by sulfidization and 300 °C heat treatment. The material was characterized by electron microscopy, powder X-ray diffraction and X-ray photoelectron spectroscopy which showed that the active material is mostly rhombohedral SnS2 whose (001) planes were preferentially oriented in parallel to the graphene oxide sheets. The material exhibited >610 mA h g−1 charge capacity at 50 mA g−1 (with >99.6% charging efficiency) between 0 and 2 V vs. Na/Na+ electrode, high cycling stability for over 150 cycles and very good rate performance, >320 mA h g−1 at 2000 mA g−1.

We describe a new, simple and low-temperature method for ultra-thin coating of graphene oxide (GO) by peroxostannate, tin oxide or a mixture of tin and tin oxide crystallites by different treatments. The technique is environmentally friendly and does not require complicated infrastructure, an autoclave or a microwave. The supported peroxostannate phase is partially converted after drying to crystalline tin oxide with average, 2.5 nm cassiterite crystals. Mild heat treatment yielded full coverage of the reduced graphene oxide by crystalline tin oxide. Extensive heat treatment in vacuum at >500 °C yielded a mixture of elemental tin and cassiterite tin oxide nanoparticles supported on reduced graphene oxide (rGO). The usefulness of the new approach was demonstrated by the preparation of two types of lithium ion anodes: tin oxide-rGO and a mixture of tin oxide and tin coated rGO composites (SnO(2)-Sn-rGO). The electrodes exhibited stable charge/discharge cyclability and high charging capacity due to the intimate contact between the conductive graphene and the very small tin oxide crystallites. The charging/discharging capacity of the anodes exceeded the theoretical capacity predicted based on tin lithiation. The tin oxide coated rGO exhibited higher charging capacity but somewhat lower stability upon extended charge/discharge cycling compared to SnO(2)-Sn-rGO.

Yeast displaying glucose oxidase on their surface were encapsulated in a graphene oxide hydrogel. The ability of the modified yeast to reduce graphene oxide by glucose assimilation while maintaining viability was tested with time and deemed suitable for biofuel cell applications.