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In this paper, we report a simple sol–gel method for the synthesis of a composite containing reduced graphene oxide (R-GO) embedded within nano LiFePO 4 particles for a lithium-ion battery cathode. This composite has an effective electron pathway and a highly meso-porous structure as compared to conventional LiFePO 4 . Highly conductive R-GO, together with the meso-porosity results in a material that has good electronic conductivity and high electrolyte permeability. Electrodes fabricated from the composite exhibited excellent performance when evaluated as lithium-ion battery cathodes, including compared to pristine LiFePO 4 . The electrode of the R-GO composite exhibits excellent rate capabilities of 125 mAh g −1 at 10 C, whereas pristine LiFePO 4 could deliver only 81.5 mAh g −1 at the same condition. It also achieves an improved cyclability with capacity retention ratios of 92.48% after 200 cycles at 10 C, as well.

Incorporation of thermally reduced graphene oxide (RG-O) into the metal oxide semiconductor BiVO4 improves its photoactivity by about three times for sulfite oxidation. The enhancement of photoactivity is attributed to reduced electron–hole recombination of BiVO4 using the RG-O as a conductive matrix in the composite photocatalyst. Photoelectrochemical behavior of the BiVO4 and RG-O/BiVO4 composite electrodes were simulated using finite element analysis to obtain the carrier mobility and its lifetime in the photoelectrodes. In contrast with sulfite oxidation, the improvement of photocurrent for water oxidation of RG-O/BiVO4 composite electrode was not significant because of the slower kinetics for water oxidation. To address the kinetic limitations, platinum (Pt) as an effective electrocatalyst was photodeposited on the RG-O/BiVO4 electrode. Addition of the Pt significantly improved water oxidation photocurrent of the Pt/RG-O/BiVO4 electrode. RG-O/W–Mo-doped BiVO4 composite electrodes were also prepared to investigate a further enhancement of photoactivity of W–Mo-doped BiVO4. The behavior obtained from RG-O/W–Mo-BiVO4 and RG-O/BiVO4 electrodes provides a valuable insight into the role of RG-O as a conducting additive and the role of W and Mo as dopants into BiVO4.

Chemical doping can decrease sheet resistance of graphene while maintaining its high transparency. We report a new method to simultaneously transfer and dope chemical vapor deposition grown graphene onto a target substrate using a fluoropolymer as both the supporting and doping layer. Solvent was used to remove a significant fraction of the supporting fluoropolymer, but residual polymer remained that doped the graphene significantly. This contrasts with a more widely used supporting layer, polymethylmethacrylate, which does not induce significant doping during transfer. The fluoropolymer doping mechanism can be explained by the rearrangement of fluorine atoms on the graphene basal plane caused by either thermal annealing or soaking in solvent, which induces ordered dipole moments near the graphene surface. This simultaneous transfer and doping of the graphene with a fluoropolymer increases the carrier density significantly, and the resulting monolayer graphene film exhibits a sheet resistance of ∼320 Ω/sq. Finally, the method presented here was used to fabricate flexible and a transparent graphene electrode on a plastic substrate.

The nitrate-form of Ca–Fe-layered double hydroxide (Ca–Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca–Fe-LDH–NO3− compound and its H2PO4−-intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO42− caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca–Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO42− and H2PO4−. Under acidic conditions, phosphate ions were slowly released from the Ca–Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca–Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

The cobalt-substituted tin dioxide nanocrystals were synthesized by the one-pot hydrothermal method. According to the powder X-ray diffraction and elemental analyses, the cobalt ions were successfully substituted into the rutile lattice of the SnO2 phase, which consequently resulted in an increase in the volume of the unit cell. Electron microscopy revealed that with an increase in the content of the substituted cobalt ions, the particle size of the SnO2 nanocrystals becomes smaller. In addition, the X-ray absorption spectroscopy clearly demonstrated that the substituent cobalt ions were stabilized in a divalent oxidation state in a distorted octahedral symmetry, while the tin ions were in a tetravalent oxidation state. The electrochemical measurements revealed that the substitution of Sn with Co significantly enhanced the negative electrode performance of tin dioxide nanocrystals at optimal Co content. The present study clearly demonstrated that a partial substitution of cobalt in the SnO2 phase can provide an effective way of optimizing the electrochemical properties of the tin dioxide nanocrystals.

1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the solid-state precursor on the electrochemical activity of these nanomaterials and to elucidate the mechanism responsible for the excellent activity of β-MnO2 nanorods as well. According to powder X-ray diffraction analyses, treating manganese oxide precursors that have an oxidation state of ≤+3 with persulfate ions under hydrothermal conditions yields manganese oxides with the β-MnO2 structure. In contrast, the use of a LiMn2O4 precursor with a higher Mn valence leads to the formation of the α-MnO2-structured manganese oxide. Electron microscopic studies clearly show a 1D nanorod-type morphology for the β-MnO2 material, whereas a 1D nanowire-type morphology with a higher aspect ratio is observed for the α-MnO2 material. The diameter of the β-MnO2 nanorods decreases as the Mn valence in the precursors becomes smaller. According to e...

The porous hierarchical assembly of lithium-rich Li1+xMnO 3-δ 2D nanoplates as well as isolated 0D nanocrystalline homologues has been synthesized via lithiation reactions of nanostructured manganese oxides under hydrothermal conditions. According to powder X-ray diffraction and electron microscopy, a hydrothermal LiOH treatment for nanostructured δ-MnO2 precursor produces a lithium-rich Li 1+xMnO3-δ phase with the nanoworm-like hierarchically assembled 2D nanoplate morphology. After the lithiation reaction under identical conditions, the 1D nanowires of the α-MnO2 precursor are transformed into the 0D nanoparticles of the Li 1+xMnO3-δ phase. The Mn K-edge X-ray absorption spectroscopic analysis for the lithiated materials clearly demonstrated that tetravalent manganese ions are stabilized in octahedral sites of a Li 2MnO3-type layered structure composed of edge-shared MnO6/LiO6 octahedra. From electrochemical measurements, it was found that the lithiated Li1+xMnO3-δ nanostructured materials show much superior electrode performance over the precursor manganese oxides and bulk lithium-rich manganate. The powder X-ray diffraction analyses for the electrochemically cycled derivatives clearly demonstrated that the improvement of electrode performance after lithiation can be attributed to the phase transformation to the Li-rich Li 1+xMnO3-δ phase with high structural stability. On the basis of the present experimental findings, we are able to conclude that the present phase transformation route provides a new method not only to synthesize nanostructured lithium-rich manganese oxides with controllable dimensionality and morphology but also to improve the electrode performance of nanostructured manganese oxides Refereed/Peer-reviewed

Mesoporous potassium-intercalated layered titanate has been synthesized through a reassembling of exfoliated titanate nanosheets and potassium cations. According to powder X-ray diffraction, electron microscopy, and N2 adsorption-desorption isotherm analyses, the intercalation of potassium ions gave rise not only to a slight basal expansion of the layered titanate but also to the formation of mesoporous assembly of the layered crystallites. In comparison with the pristine cesium titanate and its protonated derivative, the mesoporous potassium-intercalated titanate showed better photocatalytic activity for the photodegradation of organic molecules and higher adsorption capability for organic dye and CO2 molecules, as well. Refereed/Peer-reviewed

The formation mechanism and atomic arrangement of one-dimensional (1D) nanostructured titanates have been systematically investigated with combinative spectroscopic and microscopic analyses. First of all, the influence of the interlayer distances of the lepidocrocite-type titanate precursor on the formation efficiency of 1D nanobelts has been studied, clearly demonstrating that the increase of basal spacing upon the protonation does not promote the formation of 1D nanostructures. This finding did not support the previously proposed exfoliation mechanism of the layered titanate precursor. Of special interest is that the poor efficiency of the protonated titanate as a precursor could be enhanced by Fe substitution, underscoring the importance of precursor dissolution. According to time-dependent electron microscopic analyses, the hydrothermal alkali treatment initially gave rise not only to a decrease in the particle size of the precursor but also to the formation of 1D titanate nanobelts with lepidocrocite...

Mesoporous iron oxide-layered titanate nanohybrids have been synthesized through a reassembling reaction between exfoliated titanate nanosheets and iron hydroxide nanoclusters, in which an electrostatic attraction between both nanosized species could be achieved at low pH of 1.5. The formation of the layer-by-layer ordered heterostructure with the repeating unit of 1.33 nm was clearly evidenced by powder X-ray diffraction and transmission electron microscopic analysis. According to Fe K-edge X-ray absorption spectroscopy, the hybridized iron oxide crystallizes with loosely packed network of three edge-shared FeO6 octahedra units. N2 adsorption−desorption isotherm and diffuse reflectance UV−vis measurements clearly demonstrated that the present iron oxide-layered titanate nanohybrids showed greatly expanded surface areas with mesopores (∼190−230 m2g−1) and narrow bandgap energies (∼2.3 eV), which are of crucial importance in creating a visible light-active photocatalyst. The test of photocatalytic activity...

Cr-substituted β-Mn1-xCrxO2 nanowires with nonaggregated morphology have been synthesized by the chemical oxidation of layered LiMn0.9Cr0.1O2 microcrystals under hydrothermal conditions at elevated temperature. According to powder X-ray diffraction analysis, a persulfate treatment at 200 °C gives rise to a unique transformation from a monoclinic-layered structure to a pyrolusite- (β-MnO2-) type structure. Electron microscopic analyses clearly demonstrated that the oxidized derivative consists of well-separated single-crystalline nanowires with a diameter of ∼30 nm and a length of several micrometers. Mn K-edge and Cr K-edge X-ray absorption spectroscopy and chemical analysis provide straightforward evidence for the substitution of chromium ions for the manganese sites of the pyrolusite-structured manganese oxide nanowires. Of special importance is that the present Cr-substituted β-MnO2-type nanowires show promising electrode performance for Li+ ion batteries, superior to those of pristine LiMn0.9Cr0.1O2, ...

CeO 2 -coated LiMn 2 O 4 spinel cathode was synthesized using two-step synthesis method. All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. The results of the electrochemical performances on CeO 2 -coated electrode are compared to those of electrodes based on LiMn 2 O 4 spinel without CeO 2 coating. CeO 2 -coated LiMn 2 O 4 cathode improved the cycling stability of the electrode. The capacity retention of 2 wt% CeO 2 -coated LiMn 2 O 4 was more than 82% after 150 cycles between 3.0 and 4.4 V at room temperature and 82% after 40 cycles at elevated temperature of 60 °C. The amounts of dissolved manganese-ions in CeO 2 -coated LiMn 2 O 4 significantly are smaller than pristine LiMn 2 O 4 systems especially at elevated temperatures. Surface-modified LiMn 2 O 4 can suppress the dissolution reaction of manganese-ions at elevated temperature and clearly improve the cyclability of the spinel LiMn 2 O 4 cathode materials.

LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) compounds have been synthesized by a direct molten-salt method that uses a eutectic mixture of LiNO 3 and LiOH salts. According to X-ray diffraction analysis, these materials have a well-developed layered structure (R3-m) and are an isostructure of LiNiO 2 . The LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) compounds have average particle sizes of 1–5 μm depending on the amount of Ti salt. Charge–discharge tests show that a LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) cathode prepared at 700 °C has an initial discharge capacity as high as 171 mA h g −1 and excellent capacity retention in the range 4.3–2.8 V at a current density of 0.2 mA cm −2 .

Olivine structure LiFePO 4 /C composite powders are synthesized as cathode materials for Li-ion batteries via a conventional solid-state reaction. Improvement in electrochemical performance has been achieved by using poly(vinyl alcohol) as the carbon sources for the as-prepared materials. The influence of the heat treatment on the physical and the electrochemical properties of LiFePO 4 /C materials is investigated. To examine the effect of added carbon content on the properties of materials, a one-step heat treatment has been employed with control of the PVA content in the precursor. Six samples were prepared with 0, 1, 3, 5, 10 and 30 wt.% PVA added to the raw materials. The particle size of LiFePO 4 decreases as the carbon content increases. Materials with medium carbon contents have a small charge-transfer resistance and thus exhibit superior electrochemical performance. Interestingly, for a LiFePO 4 /C composite with a low PVA content, an unusual plateau at 4.3 V is observed. It is considered that this is due to the Fe 3+ /Fe 4+ redox reaction of Fe 3+ compounds that are present as an impurity. For samples with a high PVA amount, a thicker carbon coating provides an obstacle to improve the electrochemical properties.

The dissolution of nickel oxide cathode in the electrolyte is one of the major technical obstacles to the commercialization of molten carbonate fuel cell (MCFC). To improve the MCFC cathode stability, the alternative cathode material for MCFC was prepared, which was made of Co/Ce-coated on the surface of Ni powder using a polymeric precursor based on the Pechini method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX) were employed in characterization of the alternative cathode materials. The Co/Ce-coated Ni cathode prepared by the tape-casting technique. The solubility of the Co/Ce-coated Ni cathode was about 80% lower when compare to that of pure Ni cathode under CO2:O2 (66.7:33.3%) atmosphere at 650 °C. Consequently, the fine Co/Ce-coated Ni powder could be confirmed as a new alternative cathode material for MCFC.

Organic–inorganic hybrid composite membranes have been prepared and evaluated for polymer electrolyte membrane fuel cells (PEMFCs) at 100–140 °C. A series of synthesized poly (fluorinated arylene ether)s was sulfonated by fuming sulfuric acid (20% SO3). The zirconium phosphate composite membrane was prepared by soaking the sulfonated poly (fluorinated arylene ether)s stepwise in 1 M zirconyl chloride solution and 1 M phosphoric acid solution. The chemical, thermal, and electrochemical properties of the composite membrane were investigated by thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and unit cell test. The cell performance of the zirconium phosphate sulfonated poly (fluorinated arylene ether)s composite membrane was superior to that of the starting membrane at intermediate temperature, 100–140 °C. And the cell performance with composite membrane indicated stable behavior during experimentation when operating temperature maintained at 120 °C, whereas sulfonated poly (fluorinated arylene ether)s membrane was irreversible degradation under the same condition.

The properties of a new cathode material of nano-sized TiO 2 -coated Ni powder for application in molten carbonate fuel cells (MCFCs) are investigated. The material is prepared by a sol–gel method. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) with energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and Raman spectroscopy are employed to characterize the cathode material. The nano-sized TiO 2 particles are homogenously coated on the surface of the Ni powder. A stable LiTi 1− x Ni x O 2 phase is formed on the surface of the Ni powder during immersion in molten carbonate at 650 °C. The solubility of the TiO 2 -coated Ni cathode is about 50% lower compare with that of a pure Ni cathode.

Submicron-sized Li(Ni1/3Co1/3Mn1/3)O2 particles were prepared by spray pyrolysis. A polymeric precursor solution containing citric acid and ethylene glycol enabled the formation of submicron-sized Li(Ni1/3Co1/3Mn1/3)O2 spherical particles with narrow-sized distribution and non-aggregation characteristics in the spray pyrolysis. The mean sizes of the particles post-treated at temperatures of 800 and 900∘C were 380 and 770 nm. On the other hand, the Li(Ni1/3Co1/3Mn1/3)O2 particles obtained from the aqueous solution had irregular morphology and broad-sized distribution. The discharge capacity of the particles prepared from polymeric precursor solution decreased from 88 mAh/g to 135 mAh/g after 50 cycles. The particles prepared from polymeric precursor solution had high discharge capacity and good cyclic properties than those of the particles prepared from the aqueous solution.

CeO2-coated LiCoO2 particles were successfully synthesized by a sol–gel coating of CeO2 on the surface of the LiCoO2 powder and subsequent heat treatment at 700 °C for 5 h. The surface-modified and pristine LiCoO2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), slow rate cyclic voltammogram (CV), and differential scanning calorimetry (DSC). Cyclic voltammetry curves suggested that the CeO2 coating suppressed the phase transitions. Unlike pristine LiCoO2, the CeO2-coated LiCoO2 cathode exhibited better capacity retention than the pristine LiCoO2 electrode in the higher cutoff voltage. Differential scanning calorimetric data revealed the higher thermal stability of the CeO2-coated LiCoO2 electrode.

Fluorine-doped nanocrystalline tin dioxide materials (F:SnO 2 ) have been successfully prepared by the sol–gel process from a single molecular precursor followed by a thermal treatment at 450–650 °C. The resulting materials were characterized by FTIR spectroscopy, powder X-ray diffraction, nitrogen adsorption porosimetry (BET) and transmission electron microscopy (TEM). The mean particle size increased from 5 to 20 nm and the specific surface area decreased from 123 to 37 m 2 /g as the temperature of heat treatment was risen from 450 to 650 °C. Fluorine-doped nanocrystalline SnO 2 exhibited capacity of 560, 502, and 702 mA h/g with 48%, 50%, and 40% capacity retention after 25 cycles between 1.2 V and 50 mV at the rate of 25 mA/g, respectively. In comparison, commercial SnO 2 showed an initial capacity of 388 mA h/g, with only 23% capacity retention after 25 cycles.

Layered Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) have been prepared by the mixed hydroxide and molten-salt synthesis method. The individual particles of synthesized materials have a sub-microsize range of 200–500 nm, and LiNi0.475Mn0.475Zr0.05O2 has a rougher surface than that of LiNi0.5Mn0.5O2. The Li/Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) electrodes were cycled between 4.5 and 2.0 V at a current density of 15 mA/g, the discharge capacity of both cells increased during the first ten cycles. The discharge capacity of the Li/LiNi0.475Mn0.475Zr0.05O2 cell increased from 150 to 220 mAh/g, which is 50 mAh/g larger than that of the Li/LiNi0.5Mn0.5O2 cell. We found that the oxidation of oxygen and the Mn3+ ion concerned this phenomenon from the cyclic voltammetry (CV). Thermal stability of the charged Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) cathode was improved by Zr doping.

A high-performance LiNi 0.8 Co 0.2 O 2 cathode was successfully fabricated by a sol–gel coating of CeO 2 to the surface of the LiNi 0.8 Co 0.2 O 2 powder and subsequent heat treatment at 700 °C for 5 h. The surface-modified and pristine LiNi 0.8 Co 0.2 O 2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), slow rate cyclic voltammogram (CV), and differential scanning calorimetry (DSC). Unlike pristine LiNi 0.8 Co 0.2 O 2 , the CeO 2 -coated LiNi 0.8 Co 0.2 O 2 cathode exhibits no decrease in its original specific capacity of 182 mAh/g (versus lithium metal) and excellent capacity retention (95% of its initial capacity) between 4.5 and 2.8 V after 55 cycles. The results indicate that the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium ion batteries.

Thermosensitive cyclotriphosphazenes bearing alkoxy poly(ethylene glycol) and amino acid esters as side groups could be functionalized to chelate the antitumor (diamine)platinum(II) moiety through the dicarboxylate group of the amino acid substituent on the cyclic phosphazene ring. Surprisingly, like the precursor cyclotriphosphazenes, these (diamine)platinum(II)–cyclotriphosphazene conjugates were also found to exhibit variable lower critical solution temperatures (LCST) in the wide range of 12 to 92 °C. Furthermore, the present conjugates have shown outstanding in vitro and in vivo antitumor activities due to controlled release of the antitumor (diamine)platinum(II) moiety with hydrolytic degradation of the phosphazene ring. A few of these conjugates have shown LCSTs below body temperature, and it has been shown from a model animal experiment that the conjugates with a LCST below body temperature may be applied to local drug delivery by direct intratumoral injection.

Chemically activated graphene ('activated microwave expanded graphite oxide', a-MEGO) was used as a cathode material for Li-ion hybrid supercapacitors. The performance of a-MEGO was first verified with Li-ion electrolyte in a symmetrical supercapacitor cell. Hybrid supercapacitors were then constructed with a-MEGO as the cathode and with either graphite or Li(4)Ti(5)O(12) (LTO) for the anode materials. The results show that the activated graphene material works well in a symmetrical cell with the Li-ion electrolyte with specific capacitances as high as 182 F g(-1). In a full a-MEGO/graphite hybrid cell, specific capacitances as high as 266 F g(-1) for the active materials at operating potentials of 4 V yielded gravimetric energy densities for a packaged cell of 53.2 W h kg(-1).

A simple approach has been developed for the synthesis of Pt nanoparticles with uniform diameters of approximately 2.9 nm supported on reduced graphene oxide (RG-O) platelets via a modified polyol method. Compared to Johnson Matthey (JM) Pt/C (75 wt % Pt) catalyst, the Pt/RG-O (70 wt % Pt) composite showed much higher electrochemical surface area, greater catalytic activity towards the oxygen reduction reaction (ORR), and significantly better single cell polarization performance. The maximum power density of the Pt/RG-O composite was about 128 mW cm−2, an 11% greater than the JM Pt/C commercial catalyst.

Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocomposite, consisting of two metal oxides, can be synthesized by the reaction between permanganate anions and aluminum oxyhydroxide keggin cations. The as-prepared manganese oxide-aluminum oxide nanocomposite is X-ray amorphous whereas heat-treatment gives rise to the crystallization of an α-MnO2 phase at 600 °C and Mn 3O4/Mn2O3 and γ-Al 2O3 phases at 800 °C. Electron microscopy and N 2 adsorption-desorption-isotherm analysis clearly demonstrate that the as-prepared nanocomposite is composed of a porous assembly of monodisperse primary particles with a size of ∼20 nm and a surface area of >410 m 2 g-1. Of particular interest is that the small particle size of the as-prepared nanocomposite is well-maintained up to 600 °C, a result of the prevention of the growth of manganate grains through nanoscale mixing with alumina grains. The calcined nanocomposite shows very-high catalytic activity for the oxidation of cyclohexene with an extremely high conversion efficiency of >95% within 15 min. The present results show that the improvement of the crystallinity without significant crystal growth is very crucial for optimizing the catalytic activity of manganese oxide nanocrystals. Refereed/Peer-reviewed

The exfoliation of layered Li[Mn(1/3)Co(1/3)Ni(1/3)]O(2) into individual monolayers could be achieved through the intercalation of quaternary tetramethylammonium (TMA(+)) ions into protonated metal oxide. An effective exfoliation occurred when the TMA(+)/H(+) ratio was 0.5-50. Reactions outside this range produced no colloidal suspension, but all the manganese cobalt nickel oxides precipitated. Atomic force microscopy and transmission electron microscopy clearly demonstrated that exfoliated manganese cobalt nickel oxide nanosheets have a nanometer-level thickness, underscoring the formation of unilamellar nanosheets. The maintenance of the hexagonal atomic arrangement of the manganese cobalt nickel oxide layer upon the exfoliation was confirmed by selected area electron diffraction analysis. According to diffuse reflectance ultraviolet--visible spectroscopy, the exfoliated manganese cobalt nickel oxides displayed distinct absorption peaks at approximately 354 and approximately 480 nm corresponding to the d-d transitions of octahedral metal ions, which contrasted with the featureless spectrum of the pristine metal oxide. In the light of zeta potential data showing the negative surface charge of manganese cobalt nickel oxide nanosheets, a heterolayered film of manganese cobalt nickel oxide and conductive polymers could be prepared through the successive coating process with colloidal suspension and polycations. The UV--vis and X-ray diffraction studies verified the layer-by-layer ordered structure of the obtained heterolayered film, respectively.

1D nanostructured manganese oxides are prepared by oxidation reaction of precursor LiMn(2-x)Cr(x)O(4) microcrystals under hydrothermal condition. The crystal structure and morphology of the obtained manganese oxides are strongly dependent on the reaction condition and the chemical composition of the precursors. The alpha-MnO(2) nanowires are prepared by reaction at 120 degrees C, and their aspect ratios decrease with the Cr content in the precursor. Treating precursors with persulfate ions at 160-180 C yields the beta-MnO(2) nanorods for the precursors LiMn(2-x)Cr(x)O(4) with lower Cr content and the alpha-MnO(2) nanowires for the precursors with higher Cr content. The structure dependence of the products on the Cr content in the precursors is related to the high octahedral site stabilization energy of Cr(3+) ions and/or to the increase of Mn valence state upon Cr substitution. The increase of Cr content in the precursors degrades the electrode performance for the manganates prepared at 160 degrees C but improves electrode activity for those prepared at 180 degrees C. This observation can be explained by the structural variation and chromium substitution of the hydrothermally treated manganates. We conclude that the use of spinel LiMn(2-x)Cr(x)O(4) as precursors provides an effective way to synthesize 1D nanostructured manganate with tailored crystal structure and morphology. Refereed/Peer-reviewed

The nanoscale hybridization of titanium oxide with copper oxide was carried out to control the phase transformation behavior of titanium oxide and develop a new photocatalyst active in visble light. Analysis by X-ray diffraction, electron microscopy, and nitrogen adsorption-desorption isotherm to gauge pore size distribution showed that intercalative hybridization between copper oxide and titanium oxide produced a mesoporous layer-by-layer interstratified heterostructure with a repeating distance of ∼24.2 A and an average pore size of ∼52 A. X-ray absorption spectroscopy at Cu K- and Ti K-edges clearly demonstrated that divalent copper oxides were interstratified with lepidocrocite-type titanium oxide. As a result of the modification of band structure, the resulting nanohybrids showed high activity for photoinduced degradation of organic dye molecules under visible light illumination. Heat-treatment of the nanohybrids at 500 °C produced anatase TiO2 at the expense of intermediate rutile TiO2 formed in the lower temperature region (300–400 °C). This suggests a phase transition from rutile TiO2 to anatase TiO2. This phenomenon is related to the variation in the surface energy of titania caused by the redox process of hybridized copper oxide and by the phase transition of co-existing Ti-deficient titanium oxide.