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The reactions of Ln2O3 (Ln = La Lu) with ReO2 were examined in high temperature hydrothermal water (650 °C). In all cases the rhenium oxide was added in a three-fold excess. No external mineralizer was needed and the rhenate itself acted as a sufficient mineralizer to form high quality single crystals of several crystalline products. These form in good yield with compositions varying as a function of the size of the rare earth ion. The largest sesquioxide, La2O3, forms the well-known La4Re6O19 phase, but when Ln = Nd or Pr, a new product, Ln2Re2O7(OH), is isolated. Reactions with Ln = Sm Tb form Ln4Re2O11, and those with Dy Lu form Ln2ReO5. The new Ln2Re2O7(OH) series was characterized as a new structure type by single crystal X-ray diffraction. This structure features a tetrameric Re4O16 cluster embedded in a lanthanide oxide framework. Additional detailed structural data is also provided for Tb4Re2O11 and Eu4Re2O11, which were not previously reported for the Ln4Re2O11 family. In Ln2Re2O7(OH), no direct Re Re bond (Re Re = 2.60 A) is observed while Ln4Re2O11 appears to possess a rhenium-rhenium double bond with a Re Re distance of 2.42 A. Single crystal Raman data supports both of these characterizations. Magnetic data is reported for Ln2Re2O7(OH) and Tb4Re2O11, and their behavior appears to be dominated by the f-element magnetic moments. At low temperatures Tb4Re2O11 displays possible canted antiferromagnetic coupling.

Two new structural types of BaREGeO4(OH) and BaRE10(GeO4)4O8 (RE = Ho3+,Er3+) single crystals were synthesized via high-temperature and high-pressure hydrothermal synthesis. The BaREGeO4(OH) compounds were found to crystallize in the orthorhombic space group Pbca. BaHoGeO4(OH) is used as a representative of the family with cell parameters of a = 5.7175(2) A, b = 10.1556(5) A, c = 10.6189(9) A and V = 964.97(8) A3. The BaREGeO4(OH) structure contains a one-dimensional chain of rare-earth polyhedra linked through edge sharing of oxygen atoms. High density BaRE10(GeO4)4O8 crystals crystallize in the monoclinic space group C2/m and feature a sheet like arrangement of rare-earth oxide polyhedra with Keggin-like features. BaHo10(GeO4)4O8 is used as a representative of this structure type with cell parameters of a = 12.4533(8) A, b = 7.2008(5) A, c = 12.0034(8) A, β = 100.183(2)⁰ and V = 1059.43(12) A3. Barium polyhedra and isolated GeO4 units aid in connecting the rare earth oxide framework to extend it in three-dimensional (3-D) space. Characterization by single crystal X-ray diffraction and Raman and photoluminescence spectroscopies is reported.

The growth of large high quality single crystals of three lithium silicates and germanates Li 2 SiO 3 , Li 2 SiO 5 , and Li 2 GeO 3 is described. The crystals are all grown using hydrothermal fluids at 650 °C and 1 kbar using simple oxide feedstock and 3–6 M LiOH serving as both the lithium ion source and mineralizer. The crystals could be grown by spontaneous transport without any specific seeding, and grew between 2 and 10 mm/edge and without evidence of cracking, physical twinning or multiple domain structures. The crystals were characterized by single crystal diffraction, UV–vis spectroscopy and Raman spectroscopy. All the crystals are acentric and polar. Preliminary nonlinear optical properties were investigated using the Kurtz method and indicate that the crystals exhibit Type-1 phase matching ability, and Li 2 SiO 3 demonstrates a significant nonlinear optical conversion efficiency, making it of potential interest as a UV NLO crystal.

Two new halide-containing cesium manganese vanadates have been synthesized by a high-temperature (580 °C) hydrothermal synthetic method from aqueous brine solutions. One compound, Cs3Mn(VO3)4Cl, (1) was prepared using a mixed cesium hydroxide/chloride mineralizer, and crystallizes in the polar noncentrosymmetric space group Cmm2, with a = 16.7820(8) A, b = 8.4765(4) A, c = 5.7867(3) A. This structure is built from sinusoidal zig-zag (VO3)n chains that run along the b-axis and are coordinated to Mn2+ containing (MnO4Cl) square-pyramidal units that are linked together to form layers. The cesium cations reside between the layers, but also coordinate to the chloride ion, forming a cesium chloride chain that also propagates along the b-axis. The other compound, Cs2Mn(VO3)3F, (2) crystallizes in space group Pbca with a = 7.4286(2) A, b = 15.0175(5) A, c = 19.6957(7) A, and was prepared using a cesium fluoride mineralizer. The structure is comprised of corner sharing octahedral Mn2+ chains, with trans fluoride ligands acting as bridging units, whose ends are capped by (VO3)n vanadate chains to form slabs. The cesium atoms reside between the manganese vanadate layers, and also play an integral part in the structure, forming a cesium fluoride chain that runs along the b-axis. Both compounds were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and single-crystal Raman spectroscopy. Additionally, the magnetic properties of 2 were investigated. Above 50 K, it displays behavior typical of a low dimensional system with antiferromagnetic interactions, as to be expected for linear chains of manganese(ii) within the crystal structure.

Three new strontium manganese vanadates, Sr 2 Mn 2 (V 3 O 10 )(VO 4 ) ( I ), Sr 3 Mn(V 2 O 7 ) 2 ( II ), and Sr 2 Mn(VO 4 ) 2 (OH) ( III ), were prepared using a high temperature (580 °C) hydrothermal method with various chloride salts as the mineralizer. Minor differences in the chloride stoichiometry led to significant differences in product. Compound I crystallizes in the monoclinic space group P 2 1 / c ( a = 6.8773(12) A, b = 15.061(3) A, c = 11.609(2) A, β = 96.745(8)°), and consists of edge-shared octahedral manganese(II) dimers coordinated by trimeric [V 3 O 10 ] and monomeric [VO 4 ] groups. Compound II crystallizes in the tetragonal crystal system, P 4 3 2 1 2 ( a = 6.9951(2) A, c = 25.4390(7) A), and is built from monomeric manganese(II) octahedra chelated by two pyrovanadate [V 2 O 7 ] groups and linked to each other by additional pyrovanadates to form layers. Compound III is a noncentrosymmetric variation on the brackebuschite structure type, crystallizing in the monoclinic space group P 2 1 ( a = 7.6316(3) A, b = 6.1204(3) A, c = 8.6893(3) A, β = 111.3940(10)°). The structure is composed of octahedral manganese(III) edge-sharing chains coordinated to corner-sharing monomeric [VO 4 ] groups, thereby forming a manganese vanadate chain. All compounds were characterized by single-crystal X-Ray diffraction, powder X-Ray diffraction, infrared spectroscopy and single-crystal Raman spectroscopy. Density functional theory calculations were employed to investigate the relative stability of compound III .

Carbon nanofibers of 1–2 nm height and micrometer length were synthesized via a hydrothermal conversion of cellulose nanocrystals at 240 °C. The fibers were characterized by atomic force microscopy, transmission electron microscopy, powder X-ray diffraction and Raman spectroscopy. In the hypothesized mechanism, the self-assembly of cellulose nanocrystals prior to their carbonisation provides a template for the nanofiber formation.

Two terbium germanates have been synthesized via high-temperature and high-pressure hydrothermal synthesis with 20 M KOH as a mineralizer using Tb4O7 as a starting material. Tb13(GeO4)6O7(OH) crystallizes in trigonal space group R3, is built up of isolated GeO4 units, and contains a complex arrangement of terbium oxide polyhedra. K2TbGe2O7 is a terbium(4+) pyrogermanate that is isostructural with K2ZrGe2O7 and displays a rare stable Tb4+ oxidation state in the solid state.

Despite noteworthy progress in the fabrication of large-area graphene sheetlike nanomaterials, the vapor-based processing still requires sophisticated equipment and a multistage handling of the material. An alternative approach to manufacturing functional graphene-based films includes the employment of graphene oxide (GO) micrometer-scale sheets as precursors. However, search for a scalable manufacturing technique for the production of high-quality GO nanoscale films with high uniformity and high electrical conductivity is still continuing. Here we show that conventional dip-coating technique can offer fabrication of high quality mono- and bilayered films made of GO sheets. The method is based on our recent discovery that encapsulating individual GO sheets in a nanometer thick molecular brush copolymer layer allows for the nearly perfect formation of the GO layers via dip coating from water. By thermal reduction the bilayers (cemented by a carbon-forming polymer linker) are converted into highly conductive and transparent reduced GO films with a high conductivity up to 104 S/cm and optical transparency on the level of 90%. The value is the highest electrical conductivity reported for thermally reduced nanoscale GO films and is close to the conductivity of indium tin oxide currently in use for transparent electronic devices, thus making these layers intriguing candidates for replacement of ITO films.

Three new barium manganese vanadates, all containing hexagonal barium chloride layers interpenetrated by [V2O7]4– groups, were synthesized using a high-temperature (580 °C) hydrothermal method. Two of the compounds were prepared from a mixed BaCl2/Ba(OH)2 mineralizer, and the third compound was prepared from BaCl2 mineralizer. An interesting structural similarity exists between two of the compounds, Ba2Mn(V2O7)(OH)Cl and Ba4Mn2(V2O7)(VO4)2O(OH)Cl. These two compounds crystallize in the orthorhombic space group Pnma, Z = 4, and are structurally related by a nearly doubled a axis. The first structure, Ba2Mn(V2O7)(OH)Cl (I) (a = 15.097(3) A, b = 6.1087(12) A, c = 9.5599(19) A), consists of octahedral manganese(II) edge-sharing chains linked by pyrovanadate [V2O7] groups, generating a three-dimensional structure. Compound II, Ba4Mn2(V2O7)(VO4)2O(OH)Cl (a = 29.0814(11) A, b = 6.2089(2) A, c = 9.5219(4) A), is composed of manganese(III) edge-sharing chains that are coordinated to one another through pyrovanadat...

We describe a simple technique to alter the shape of silver nanoparticles (AgNPs) by rolling a glass tube over them to mechanically compress them. The resulting shape change in turn induces a red-shift in the localized surface plasmon resonance (LSPR) scattering spectrum and exposes new surface area. The flattened particles were characterized by optical and electron microscopy, single nanoparticle scattering spectroscopy, and surface enhanced Raman spectroscopy (SERS). AFM and SEM images show that the AgNPs deform into discs; increasing the applied load from 0 to 100 N increases the AgNP diameter and decreases the height. This deformation caused a dramatic red shift in the nanoparticle scattering spectrum and also generated new surface area to which thiolated molecules could attach as evident from SERS measurements. The simple technique employed here requires no lithographic templates and has potential for rapid, reproducible, inexpensive and scalable tuning of nanoparticle shape, surface area, and resonance while preserving particle volume.