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We proved that ice crystallized from water molecules within as-synthesized graphene oxide (GO) can be used as a spacer among individual GO sheets to form an expanded GO aerogel with a three-dimensional porous network structure. This designed specific structure can be retained during further processes to form graphene paper. Due to the fact that the as-fabricated graphene paper contains carbon defects and space in its infrastructure, this creates more electroactive surfaces and interfaces to significantly increase the Faradaic reaction efficiency. With the introduction of redox-electrolyte K3Fe(CN)6 into a KOH electrolyte, we can obtain a 95-fold increase in the specific capacitance compared with the value obtained in the traditional KOH electrolyte. The ice-crystallization formed graphene paper electrode showed high electroactivity because the specific porous structure can favor the fast transfer of electrolyte ions, such as Fe(CN)63- ions. The presented results prove that ice-crystallization formed GO can serve as a chemically tunable platform for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]

Amongst the most popular methods for the production of metal oxide nanostructures is hydrothermal synthesis. For producing ZnO nanostructures, a nitrate-based precursor reaction with equimolar amounts of hexamethylenetetramine (HMTA) is commonly used. In these reactions, zinc nitrate provides the source of Zn2+ ions, and HMTA produces the desired amount of OH− ions. The growth process occurs due to a dissolution-secondary precipitation mechanism. ZnO nanostructures are characterized by anisotropic growth with different growth rates of the individual faces, where (v(0001) > v(101¯0) > v(101¯1¯) > v(101¯1) > v(0001¯)). Therefore, considering the principle of energy minimization, the most favorable is vertical growth perpendicular to the (0001) plane, which ensures the formation of characteristic rod-like nanostruchtures of ZnO. The mentioned process takes place when chemical reactions are in equilibrium. Shifting from the equilibrium conditions by varying the parameters of reaction, or using capping agents, makes it possible to change the growth rate of individual crystallographic planes and, as result, affect the morphology of the obtained nanostructure. In this paper the influence of concentration and composition of the reagents, growth time and temperature, pH of the solution, and the presence of different capping agents on the growth process of nanostructured ZnO were investigated. Optimal synthesis parameters for obtaining nine independent ZnO morphologies have been determined. The distinctive feature of these experiments is the fact that the samples were obtained as durable, homogeneous, epitaxial coatings on hard surfaces. This can be especially interesting for the development of sensors and other fields where surface area is crucial, and it opens up more possibilities than use of the nanostructured ZnO powders. [ABSTRACT FROM AUTHOR]

The exposure of the crystallographic facets of CeO2 nanocrystals may alter their surface structure and composition, leading to significant discrepancies in their reactivity with respect to catalyzing different reactions. In this paper, a facile strategy of etching hollow CeO2 spheres (@CeO2) with a fluorine-containing ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), under hydrothermal conditions was developed to achieve surface-fluorinated @CeO2 nanoparticles with exposed active high-energy facets, which were further assembled in situ into @CeO2 nanoparticle assemblies. The IL, [Bmim][BF4], is believed to play an important role in determining the formation of CeO2 nanoparticles, and the mild release of fluorine species from [Bmim][BF4] may account for the surface-fluorination and the exposure of active high-energy facets of CeO2. The CeO2 nanoparticle assemblies are ideal model materials for studying crystal facet-dependent catalytic behavior. By loading well-dispersed Au nanoparticles via a sol-impregnation method, @CeO2/Au nanoparticle assemblies were achieved, which showed an enhanced catalytic performance for benzyl alcohol aerobic oxidation. In comparison with @CeO2/Au nanoparticle assemblies obtained by etching @CeO2 spheres with other fluorine-containing agents, NH4BF4, NaBF4, and NH4F, under identical reaction conditions, @CeO2/Au nanoparticle assemblies achieved by etching with [Bmim][BF4] exhibited the highest catalytic activity for benzyl alcohol aerobic oxidation. The surface-fluorination and the exposure of active high-energy facets of CeO2 nanoparticles are believed to be responsible for the enhancement of their catalytic activity. This methodology provides a robust strategy to create CeO2 materials with the active high-energy facets exposed and afford model materials for investigating crystal facet-dependent catalytic behavior, which currently represents an exciting issue in the nanocatalysis community. [ABSTRACT FROM AUTHOR]

This paper reports on a facile hydrothermal route that has been developed to synthesize a precursor Gd(OH)2.14F0.86 and a novel phosphor host Gd6O5F8. The morphology of the micro-sized Gd(OH)2.14F0.86/Gd6O5F8 can be easily tuned in a controlled manner by altering the fluorine sources, alkali solutions, reaction time and the pH values of the initial solution. Under ultraviolet (UV) light, vacuum ultraviolet (VUV) light and low-voltage electron beam excitation, the Gd(OH)2.14F0.86/Gd6O5F8:Ln3+ (Eu, Tb and Tm) samples show the characteristic f–f transitions of the Ln3+ ions and give bright red, green and blue emissions, respectively. The results prove that the as-synthesized Gd6O5F8 are excellent host lattices for rare earth luminescence, which may find potential applications in solid-state light, field emission displays (FEDs). [ABSTRACT FROM AUTHOR]

The structure of doped ceria plays an important role in its chemical reactivity and catalytic performance. However, for the majority of the dopants studied, whether a monophasic solid solution is formed or not is typically determined only by standard X-ray diffraction (XRD). In-depth structural characterization is lacking. In this paper we have prepared Zn-doped ceria nanocrystals exhibiting twice the oxygen storage capacity (OSC) of pure ceria. X-ray photoelectron spectroscopy (XPS) shows that the material is chemically inhomogeneous with zinc enrichment in the surface layer. X-ray fluorescence (XRF) reveals significant compositional inhomogeneity of the material after annealing in air at 1300 °C for 24 h. The standard structural characterization of this material using room temperature XRD and transmission electron microscopy (TEM) fails to reveal its correct phase composition. Based on clear evidence from in situ high temperature XRD we show that, after calcination at 500 °C, the material is not monophasic: X-ray amorphous ZnO is present within the material. The amorphous ZnO crystallizes at 800 °C and undergoes second-stage incorporation at even higher temperatures. This second-stage incorporation is not complete after annealing and trace amounts of ZnO remain according to synchrotron-based XRD. Our work provides valuable insight into the incorporation mechanism of zinc into the ceria lattice, and in particular, raises some doubts on the phase compositions reported in many previous studies on doped ceria. [ABSTRACT FROM AUTHOR]

We suggest in this paper that the combinative use of bent tritopic carboxylate, linear dipyridyl and adaptable Cu2+ ion leads to a higher probability of self-penetrated polymeric networks. This assertion is supported by four structures isolated herein, among which two are self-penetrated, highlighting the potential for controlled assembly of self-penetrating networks. [ABSTRACT FROM AUTHOR]

Here we report a study on controlling the shape of particles by regulating the diffusion of chemicals. To change the diffusion rate of the reactive ions, we used a designed three-cell reactor in which the reactive ions were separated by porous membranes. We studied the reduction of hexachloroplatinate ions by sodium borohydride as an example. The experimental results show that control of the chemical diffusion led to the platinum product changing from cubic particles to dendritic particles. Further analysis indicates that the cubic particles were formed by the classic crystallization process via layer-wise deposition, while the dendritic particles were formed by the non-classic crystallization process through cluster aggregation. The control over the chemical diffusion prolongs the nucleation period and produces nuclei continuously, facilitating the aggregation of nuclei, which leads to the crystallization switching from the classic model to the non-classic model. The obtained results in this paper suggest that control over the chemical diffusion is a green and promising process to manipulate the structures of materials. [ABSTRACT FROM AUTHOR]

CuGeO3, a quasi-one-dimensional S = 1/2 antiferromagnet, is the first inorganic material to display a spin-Peierls transition (SP) in which the lattice of the S = 1/2 antiferromagnetic 1-D chain system undergoes dimerization below the transition temperature to give a singlet ground state. The sizedependent magnetic properties and SP transitions of CuGeO3 are little understood. In this paper, we report the size-controlled synthesis of CuGeO3 nanorods by a hydrothermal method via adjustment of the reaction conditions. The size-effect on their magnetic properties has been investigated. In smaller crystalline CuGeO3 nanorods (ca. <600 nm length), the SP transition is found to be quenched, demonstrating that the magnetoelastic coupling is blocked in these small nanorods. By contrast, longer CuGeO3 nanorods (∼600 nm to >2 μm length) show a weak SP transition. These findings demonstrate that size tuning is an effective tuning parameter for controlling the ground state properties of CuGeO3 and other magnetic materials where spin-lattice interactions are important. [ABSTRACT FROM AUTHOR]

A 1-D chain-like hybrid coordination polymer [(CuBr)2(bpy)]n(bpy = 2,2′-bipyridine) was first synthesized viaa hydrothermal reaction of copper(I) bromide with 2,2′-bipyridine (bpy). The most fascinating feature of [(CuBr)2(bpy)]nis the unusual six-member-(Cu3Br3)-ring motif. The skeleton of copper bromide combined with bpy in [(CuBr)2(bpy)]nhas not been reported. In addition, research on pyrolysis of [(CuBr)2(bpy)]nwas reported in this paper. Oriented growth of single crystalline Cu(111) flake, which is usually prepared through depositing onto the surface of high-quality metal films (substrates), was synthesized by simply pyrolyzing [(CuBr)2(bpy)]nby adjusting the heating procedures. No capping reagent was induced to simplify the system. Since most of the research of pyrolysis of coordination polymers focuses on the relationship between the structure of precursor and sinter, the results of this paper show how the reaction conditions affect the morphology of the product and give a simple method for the synthesis of a Cu(111) flake, which has wide application in industry. [ABSTRACT FROM AUTHOR]

In this paper, we have built up the organic-inorganic hybrid co-crystal (1) by using the derivative of ethylenediammonium cations (N,N,N′,N′-tetra-p-methoxybenzyl-ethylenediamine, L1) and [CuCl4]2−anions. The reaction was carried out by mixing MeOH solution of CuCl2·2H2O and HCl/MeOH solution of L1at room temperature. Two types of inclusion compounds can be formed when using different guest molecules. When guest molecules, such as anthracene or phenanthrene, were included, it resulted in the formation of interlayered structures: anthracene ⊂ [H2L1]2+·[CuCl4]2−(2) and phenanthrene ⊂ [H2L1]2+·[CuCl4]2−(3). When β-naphthyl phenol were included, it led to the formation of pillared-layered complexes of [1-chloride-β-naphthyl phenol]1.0·[β-naphthyl phenol]0.5·[methanol]1.0⊂ 2[H2L1]2+·2Cl−·[CuCl4]2−(4). [ABSTRACT FROM AUTHOR]