Spontaneous formation of cadmium hydroxide nanostrands in water

Cadmium hydroxide nanostrands with a diameter of 1.9 nm were spontaneously formed by raising the pH of a dilute Cd(NO3)2 solution. The length reaches a few micrometers and the aspect ratio exceeds 1000. The crystallographic structure was successfully elucidated by high-resolution electron microscopy. The surface of the nanostrands was remarkably positively charged and adsorbed an astonishing number of negatively charged dye molecules.     

Bundle-like assemblies of cadmium hydroxide nanostrands and anionic dyes

Molecularly flat and extremely long bundle-like assemblies were prepared from cadmium hydroxide nanostrands and polysulfonated dyes. The dye molecules were regularly aligned along with the nanostrands, as confirmed by electron microscopies and UV-vis absorption spectroscopy. Strong electrostatic interaction between the two components was useful to control the fibrous morphologies and optical properties of these organic/inorganic nanocomposites.     

Time-dependent growth of zinc hydroxide nanostrands and their crystal structure

Positively-charged crystalline zinc hydroxide nanostrands with a diameter of 2 nm and a length of a few micrometres rapidly grew in dilute aqueous solution of zinc nitrate and aminoethanol. The nanostrands were composed of hexagonal clusters of [Zn(61)(OH)(116)(H(2)O)(n)](6+).     

The preparation of CdO nanowires from solid-state transformation of a layered metal-organic framework

A new coordination polymer formulated as [C₈H₁₀CdO₇]_n·4H₂O has been prepared via a hydrothermal procedure by using 1,4-benzenedicarboxylic (p-BDC) and Cd^II salt as starting materials. The structure was determined by single-crystal X-ray diffraction and the result shows that the complex crystallizes in orthorhombic system, space group Pcca, with M_r=402.62, a=7.293(2) Å, b=9.980(3) Å, c=19.889(6) Å, V=1447.6(8) Å³, Z=4, D_c=1.847 g/cm³, F(000)=808, μ(MoKα)=1.559 mm⁻¹, R=0.0478, wR=0.1150, GOF=1.199. It displays a neutral layered framework along ab plane constructed by hydrogen-bonding interaction through infinite zigzag chains. Its thermal decomposition and solid-state transformation course between 30 and 550 °C was recorded by TG curve and XRD pattern, respectively. Interestingly, it is found that at higher temperature the crystal material was converted to uniform CdO nanowires, suggesting an effective and reasonable complex-precursor procedure for preparing one-dimensional crystalline nanomaterials.     

Single-walled carbon nanotube-based coaxial nanowires: synthesis, characterization, and electrical properties

We report herein the template-directed synthesis, characterization, and electric properties of single-walled carbon nanotube- (SWNT-) based coaxial nanowires, that is, core (SWNT)-shell (conducting polypyrrole and polyaniline) nanowires. The SWNTs were first dispersed in aqueous solutions containing cationic surfactant cetyltrimethylammonium bromide (CTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonyl phenyl ether (O pi-10). Each individual nanotube (or small bundle) was then encased in its own micellelike envelope with hydrophobic surfactant groups orientated toward the nanotube and hydrophilic groups orientated toward the solution. And thus a hydrophobic region within the micelle/SWNT (called a micelle/SWNT hybrid template) was formed. Insertion and growth of pyrrole or aniline monomers in this hybrid template, upon removal of the surfactant, produce coaxial structures with a SWNT center and conducting polypyrrole or polyaniline coating. Raman and Fourier transform infrared (FTIR) spectroscopy and scanning (SEM) and transmission (TEM) electron microscopy were used to characterize the composition and the structures of these coaxial nanowires. The results revealed that the micellar molecules used could affect the surface morphologies of the resulting coaxial nanowires but not the molecular structures of the corresponding conducting polymers. Electric properties testing indicated that the SWNTs played the key roles in the conducting polymer/SWNT composites during electron transfer in the temperature range 77 K to room temperature. Compared with the SWNT network embedded in the conducting polymers, the composites within which SWNTs were coated perfectly by the identical conducting polymers exhibited higher barrier heights during electron transfer.     

Rare-Earth-compound nanowires, nanotubes, and fullerene-like nanoparticles: synthesis, characterization, and properties

Various low-dimensional nanostructures, such as nanowires, nanotubes, nanosheets, and fullerene-like nanoparticles have been selectively synthesized from rare-earth compounds (hydroxides, fluorides) based on a facile hydrothermal method. The subsequent dehydration, sulfidation, and fluoridation processes lead to the formation of rare-earth oxide, oxysulfide, and oxyhalide nanostructures, which can be functionalized further by doping with other rare-earth ions or by coating with metal nanoparticles. Owing to the interesting combination of novel nanostructures and functional compounds, these nanostructures can be expected to bring new opportunities in the vast research areas of and application in biology, catalysts, and optoelectronic devices.     

Starfruit-shaped gold nanorods and nanowires: synthesis and SERS characterization

Recently, branched and star-shaped gold nanoparticles have received significant attention for their unique optical and electronic properties, but most examples of such nanoparticles have a zero-dimensional shape with varying numbers of branches coming from a quasi-spherical core. This report details the first examples of higher-order penta-branched gold particles including rod-, wire-, and platelike particles which contain a uniquely periodic starfruitlike morphology. These nanoparticles are synthesized in the presence of silver ions by a seed-mediated approach based on utilizing highly purified pentahedrally twinned gold nanorods and nanowires as seed particles. The extent of the growth can be varied, leading to shifts in the plasmon resonances of the particles. In addition, the application of the starfruit rods for surface-enhanced Raman spectroscopy (SERS) is demonstrated.     

Layered hydroxide nickel benzoates: Hydrothermal synthesis, structure characterization, and exfoliation reaction

Mussel adhesive proteins have received considerable attention due to their ability to bind strongly to many surfaces under water. Key structural features of these proteins include a large number of 3,4-dihydroxyphenyl-L-ALANIN (DOPA) and positively charged lysine residues. We elucidate the effects of solution pH, in the pH range 3-9, on adsorption kinetics, adsorbed amount, and layer structure on silicon oxynitride by employing Dual Polarization Interferometry. As a comparison, the cationic globular protein lysozyme was also investigated. The zeta-potential of the silicon oxynitride substrate was determined as a function of pH, and the isoelectric point was found to be below pH 3. Mefp-1 is positively charged at pH<10, and thus, the protein is expected to have an electrostatic attraction for the surface at all pH values investigated. The adsorbed amount and the initial adsorption rate were found to increase with solution pH, and no significant desorption occurred due to rinsing with pure water. The layer thickness after rinsing was 3-4 nm, except at pH 3, where the adsorption was limited to a small amount. Covalent cross-linking of the Mefp-1 layer with NaIO(4) resulted in a small but significant compaction and increase in refractive index of the layer. The results are discussed in terms of the role of DOPA and electrostatic interactions for the adsorption of Mefp-1 to silicon oxynitride.     

A cadmium hydroxide complex of a N3S-donor ligand containing two hydrogen bond donors: synthesis, characterization, and CO2 reactivity

Treatment of the ebnpa (N-2-(ethylthio)ethyl-N,N-bis((6-neopentylamino-2-pyridyl)methyl)amine) ligand with a molar equivalent amount of Cd(ClO(4))(2).5H(2)O in CH(3)CN followed by the addition of [Me(4)N]OH.5H(2)O yielded the cadmium hydroxide complex [(ebnpaCd)(2)(mu-OH)(2)](ClO(4))(2) (1). Complex 1 has a binuclear cation in the solid-state with secondary hydrogen-bonding and CH/pi interactions involving the ebnpa ligand. In acetonitrile, 1 forms a binuclear/mononuclear equilibrium mixture. The formation of a mononuclear species has been confirmed by conductance measurements of 1 at low concentrations. Variable temperature studies of the binuclear/mononuclear equilibrium provided the standard enthalpy and entropy associated with the formation of the monomer as DeltaH degrees = +31(2) kJ mol(-1) and DeltaS degrees = +108(8) J mol(-1) K(-1), respectively. Enhanced secondary hydrogen-bonding interactions involving the terminal Cd-OH moiety may help to stabilize the mononuclear complex. Treatment of 1 with CO(2) in acetonitrile results in the formation of a binuclear cadmium carbonate complex, [(ebnpaCd)(2)(mu-CO(3))](ClO(4))(2) (2).     

Disubstituted diphenyldithiophosphates of cadmium: synthesis,characterization, and single-crystal X-ray structure

A series of new disubstituted diphenyldithiophosphate complexes of cadmium [{(ArO)₂PS₂}₂Cd] (9–12) have been isolated in aqueous media while their donor stabilized adducts [{(ArO)₂PS₂}₂Cd·2C₅H₅N] (13–16) [(Ar = 2,4-(CH₃)₂C₆H₃, 2,5-(CH₃)₂C₆H₃, 3,4-(CH₃)₂C₆H₃ and 3,5-(CH₃)₂C₆H₃)] have been isolated in chloroform. These newly synthesized complexes were characterized by elemental analyses, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic analyses. The dithiophosphate ligands are coordinated bidentate to the cadmium ion via the two thiolate sulfurs. The compounds [{(3,5-CH₃)₂C₆H₃O}₂PS₂HNEt₃] (4) and [{(3,5-CH₃)₂C₆H₃O}₂PS₂]₂Cd(NC₅H₅)₂ (16) crystallize in the monoclinic system with space group P2₁/c. Single-crystal X-ray analysis of 4 reveals that phosphorus of the anion is tetrahedrally bonded to two S and two O atoms. The structure is stabilized by cation–anion N–H?S intermolecular hydrogen bond interactions. In 16, two diphenyldithiophosphate ions are bidentate with both sulfurs coordinated to cadmium. Each forms a four-membered chelate ring in the equatorial plane. Two pyridines are axially coordinated to cadmium leading to octahedral geometry. The thermal properties of this complex have also been examined by combined DTA/DTG thermal analyses.     

Ribbon- and boardlike nanostructures of nickel hydroxide: synthesis, characterization, and electrochemical properties

We report the synthesis, characterization, and electrochemistry properties of ribbon- and boardlike nanostructures of nickel hydroxide, which crystallize in different phases. The ribbonlike nanostructures (nanoribbons) of nickel hydroxide were synthesized by treating amorphous alpha-Ni(OH)2 with high concentrations of nickel sulfate. These nanoribbons crystallized in a new phase had typical widths of 5-25 nm, thicknesses of 3-9 nm, and lengths of up to a few micrometers. After further treatment in alkali at 60 degrees C, the nanoribbons converted to boardlike nanostructures (nanoboards), which crystallized in the beta-phase with the average length-width-thickness ratio of 20:6:1. The crystal structures, Raman spectra, and electrochemical properties of these nanostructures of nickel hydroxide are described in this paper. For comparison, the amorphous alpha-Ni(OH)2 has also been investigated. Moreover, the intermediate product between the nanoribbons and the nanoboards displays a unique structure, which implied an interesting transformation process. The nanoribbons with the new phase show some unique features in Raman spectra, two new peaks located at 3534 and 3592 cm(-1) in the OH stretching region, indicating the new chemical environment of the hydroxyl groups. The nanoboards exhibit the highest specific capacity, which is close to the theoretical capacity of beta-Ni(OH)2. It suggests that the boardlike nanostructure is helpful in improving the electrochemical performance of nickel hydroxide. Because of their unique structures and properties, the nanoribbons and nanoboards of nickel hydroxide may give a new perspective for applications in the areas of catalysts and rechargeable batteries.     

Water-swellable MgAl-LDH (layered double hydroxide) hybrids: synthesis, characterization, and film preparation

LDH hybrids were synthesized from Cl (-)MgAl-LDHs by anion exchange with short-chain alkyl carboxylate intercalants: C n H 2 n+1 COO (-) ( n = 0-3). Among them, LDH3 (LDH with Mg/Al = 3) hybrids containing acetate ( n = 1) and propionate ( n = 2) exhibited swelling behavior in water. The action of water on acetate-LDH3 (AcO-LDH3) and propionate-LDH3 (PrO-LDH3) led to semitransparent suspensions via a viscous gel state. From the X-ray diffraction profiles of the gels, only a broad feature was observed by the loss of the sharp reflections. The reflections reappeared for the films obtained by drying the gel, indicating the restacking of the LDH nanosheets into the original stacked structure. Observation using atomic force microscopy revealed delaminated nanosheets with a thickness of 1.1-1.5 nm with the same morphological features as the starting LDHs. XRD measurement and AFM observation supported the formation of unilamellar LDH sheets. Semitransparent self-standing LDH films were obtained by peeling off the films formed on a PE (polyethylene) substrate by drying the colloidal suspension thereon. The thickness of the obtained flexible films ranged from 10 to 25 microm, and they could be anion exchanged with inorganic and organic anions in the film state.     

Systematic synthesis and characterization of single-crystal lanthanide orthophosphate nanowires

A simple hydrothermal method has been developed for the systematic synthesis of lanthanide orthophosphate crystals with different crystalline phases and morphologies. It has been shown that pure LnPO(4) compounds change structure with decreasing Ln ionic radius: i.e., the orthophosphates from Ho to Lu as well as Y exist only in the tetragonal zircon (xenotime) structure, while the orthophosphates from La to Dy exist in the hexagonal structure under hydrothermal treatment. The obtained hexagonal structured lanthanide orthophosphate LnPO(4) (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) products have a wirelike morphology. In contrast, tetragonal LnPO(4) (Ln = Ho, Er, Tm, Yb, Lu, Y) samples prepared under the same experimental conditions consist of nanoparticles. The obtained hexagonal LnPO(4) (Ln = La --> Tb) can convert to the monoclinic monazite structured products, and their morphologies remained the same after calcination at 900 degrees C in air (Hexagonal DyPO(4) is an exceptional case, it transformed to tetragonal DyPO(4) by calcination), while the tetragonal structure for (Ho--> Lu, Y)PO(4) remains unchanged by calcination. The resulting LnPO(4) (Ln = La --> Dy) products consist almost entirely of nanowires/nanorods with diameters of 5-120 nm and lengths ranging from several hundreds of nanometers to several micrometers. Europium doped LaPO(4) nanowires were also prepared, and their photoluminescent properties were reported. The optical absorption spectrum of CePO(4) nanowires was measured and showed some differences from that of bulk CePO(4) materials. The possible growth mechanism of lanthanide phosphate nanowires was explored in detail. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, electron diffraction, infrared absorption spectra, X-ray photoelectron spectroscopy, optical absorption spectra, and photoluminescence spectra have been employed to characterize these materials.     

Rapid,high yield,solution-mediated transformation of polycrystalline selenium powder into single-crystal nanowires

Single-crystal selenium nanowires were successfully synthesized for the first time by a convenient solution-mediated transformation of polycrystalline powder, and characterized by SEM, XRD, TEM and HRTEM.     

Swallowtail porphyrins: synthesis, characterization and incorporation into porphyrin dyads

The incorporation of symmetrically branched tridecyl ("swallowtail") substituents at the meso positions of porphyrins results in highly soluble building blocks. Synthetic routes have been investigated to obtain porphyrin building blocks bearing 1-4 swallowtail groups. Porphyrin dyads have been synthesized in which the zinc or free base (Fb) porphyrins are joined by a 4,4'-diphenylethyne linker and bear swallowtail (or n-pentyl) groups at the nonlinking meso positions. The swallowtail-substituted Zn(2)- and ZnFb-dyads are readily soluble in common organic solvents. Static absorption and fluorescence spectra and electrochemical data show that the presence of the swallowtail groups slightly raises the energy level of the filled a(2u)(pi) HOMO. EPR studies of the pi-cation radicals of the swallowtail porphyrins indicate that the torsional angle between the proton on the alkyl carbon and p-orbital on the meso carbon of the porphyrin is different from that of a porphyrin bearing linear pentyl groups. Regardless, the swallowtail substituents do not significantly affect the photophysical properties of the porphyrins or the electronic interactions between the porphyrins in the dyads. In particular, time-resolved spectroscopic studies indicate that facile excited-state energy transfer occurs in the ZnFb dyad, and EPR studies of the monocation radical of the Zn(2)-dyad show that interporphyrin ground-state hole transfer is rapid.     

Exceptionally stable, hollow tubular metal-organic architectures: synthesis, characterization, and solid-state transformation study

An effective solvothermal procedure has been developed to synthesize the new three-dimensional metal-organic framework, [ZnF(AmTAZ)].solvents, using either 3-amino-1,2,4-triazole (AmTAZ) or 3-amino-1,2,4-triazole-5-carboxylic acid (AmTAZAc) and a choice of several Zn(II) salts as starting materials. The three-dimensional structure displays open-ended, hollow nanotubular channels that are formed by hexanuclear metallamacrocyclic Zn(6)F(6)(AmTAZ)(6) rings. The framework integrity is maintained to 350 degrees C, at which point most of the guest solvent molecules have been removed, as evidenced by single-crystal X-ray analyses, (1)H solid-state NMR, and TGA measurements. At higher temperatures, the framework is converted either to zinc oxide (ZnO) when heated in air or to zinc cyanamide (ZnCN(2)) when heated in an inert atmosphere. In both cases, the as-grown, rodlike crystal shape is maintained during the solid-state transformation, suggesting a possible route for preparing one-dimensional crystalline nanomaterials.     

Layered copper hydroxide n-alkylsulfonate salts: synthesis, characterization, and magnetic behaviors in relation to the basal spacing

A series of hybrid inorganic-organic copper(II) hydroxy n-alkylsulfonate with a triangular lattice, Cu(2)(OH)(3)(C(n)H(2)(n)(+1)SO(3)) (n = 6, 8, 10), are prepared by anion exchange, starting from copper hydroxy nitrate Cu(2)(OH)(3)NO(3). These compounds show a layered structure as determined by X-ray diffraction, with interlayer distances of 14.3-34.8 A in alternation with interdigitated bilayer packing. Magnetic properties have been investigated by means of dc and ac measurements. All the compounds show similar metamagnet behaviors, with a Neel temperature of about 11 K. A subtle difference in the ac magnetic susceptibility among the compounds is understood by the existence of hydrogen bonding between the sulfonate headgroup and the hydroxide anion. A detailed molecular structure of the alkyl chains incorporated to the inorganic copper hydroxide layer is also discussed from the FTIR data.