Fabrication and evaluation of ZnO nanorods by liquid-phase deposition

The ZnO nanorod growth mechanism during liquid-phase deposition (LPD) has been investigated, with results considered in the context of phase stabilization, LPD chemical processes, and Gibbs free energy and entropy. Zinc oxide (ZnO) possesses unique optical and electronic properties, and obtaining ZnO species with high specific surface area is important in ZnO applications. Highly c-axis-oriented ZnO films are expected to be utilized in future optical and electrical devices. ZnO nanorods were synthesized using an aqueous solution deposition technique on a glass substrate with a free-standing ZnO nanoparticle layer. ZnO nanorod growth was easily controlled on the nanoscale by adjustment of the immersion time (15-210 min). X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), and film thickness measurements were used to characterize the crystalline phase, orientation, morphology, microstructure, and growth mechanism of the ZnO nanorods. FE-SEM images were analyzed by image processing software, which revealed details of the of ZnO nanorod growth mechanism.     

Nanoporosity of an interpenetrated NbO-type molecular framework studied by single crystal X-ray diffraction

The molecular framework [Fe(NCS)(2)(tmbpz)(2)](tmbpz = 3,3',5,5'-tetramethyl-4,4'-bipyrazolyl) consists of a robust doubly interpenetrated NbO-type network that remains stable on the removal of solvent guest molecules.     

Phase transition sequence in ferroelectric Aurivillius compounds investigated by single crystal X-ray diffraction

The investigation of the phase transition sequence in SrBi₂Ta₂O₉ (SBT) and SrBi₂Nb₂O₉ (SBN) is reported using single-crystal X-ray diffraction. By monitoring specific reflections as a function of temperature, sensitive either to the superstructure formation or to polar displacements, it was possible to check the existence or not of an intermediate phase. This latter was confirmed in SBT, but within experimental accuracy could not be detected in SBN.     

Synthesis and X-ray single crystal structure of a bivalent glycocluster

The crystal structure of a bivalent glycocluster containing aromatic amides reveals that alkylation of secondary amides alters amide configuration and thus carbohydrate presentation. This also facilitates non covalent interactions (azide-azide, carbonyl-pyranose and aromatic-pyranose) and thus carbohydrate-carbohydrate stacking.     

Synthesis and single crystal X-ray analysis of two griseofulvin metabolites

The two phenols, 6-O-desmethyl griseofulvin and 4-O-desmethyl griseofulvin are metabolites of the antifungal drug griseofulvin. Herein, we present an improved synthesis of the 6-phenol derivative, and an unequivocal proof of both structures by single-crystal X-ray analysis.     

Preparation of ZnS nanorods by a liquid crystal template

ZnS nanorods were synthesized in lamellar liquid crystals of C(12)E(4) by mixing zinc ions and thioacetamide (TAA) solution. The effects of the reactant concentration and the surfactant/water molar ratio in the liquid crystal system on the morphology and size of the ZnS particles were investigated. The prepared ZnS particles are regular nanorods having a width of about 60 nm and a length of about 80-380 nm, with a largest aspect ratio of about 6.3. A lamellar liquid crystal templating mechanism has been proposed to interpret the experimental results.     

Fabrication of TiN nanorods by electrospinning and their electrochemical properties

TiN nanorods were synthesized using electrospinning technique followed by thermolysis in different atmospheres. A dimethyl formamide-ethanol solution of poly-(vinyl pyrrolidone) and Ti (IV)-isopropoxide was used as the electrospinning precursor solution and as-spun nanofibers were calcined at 500 °C in air to generate TiO₂ nanofibers. Subsequently, a conversion from TiO₂ nanofibers to TiN nanorods was employed by the nitridation treatment at 600∼1400 °C in ammonia atmosphere. A typical characteristic of the final products was that the pristine nanofibers were cut into nanorods. The conversion from TiO₂ to TiN was realized when the nitridation temperature was above 800 °C. As-prepared nanorods were composed of TiN nano-crystallites and the average crystallite size gradually increased with the increase of the nitridation temperature. Electrochemical properties of TiN nanorods showed strong dependence on the nitridation temperature. The maximum value of the specific capacitance was obtained from the TiN nanorods prepared at 800 °C.     

Comparative study by single crystal X-ray structure determinations of tetramethylaminoborane and tetramethylethene at 110 K

The single crystal structures of the two isoelectronic and isosteric compounds tetramethylaminoborane and tetramethylethene have been determined by an X-ray study at 110 K. The distances of the central bonds are refined to 140.3(1) pm (B=N) and 134.8(1) pm (C=C), the CXXC-torsion angles (XX=CC, BN) are smaller than 1° in both compounds. A bond-length-bond-order correlation for the aminoboranes [(CH₃)₂N] _n B(CH₃)_3–n withn=1, 2, and 3 give a regression coefficient of 0.9977, the same is found for the CNC-angle as a function of the CBNC-torsion angle. Also, the comparison among these aminoboranes show that the variation of CBNC-torsion angles has more influence on bond lengths at small angles.     

Fabrication and self-assembly of hydrophobic gold nanorods

Hydrophobic gold nanorods were fabricated from hydrophilic gold nanorods coated with hexadecyltrimethylammonium bromide by treating with mercaptopropyltrimethoxysilane (MPS) and subsequently octadecyltrimethoxysilane (ODS). The fabrication of the hydrophobic shell went through the process of (1) binding MPS onto the nanorods, (2) hydrolysis of methoxysilanes, and (3) immobilization of ODS by dehydration condensation. The 2- or 3-D ordered structures of hydrophobic nanorods were self-assembled by the evaporation of solvent on a substrate. The aspects of 2-D assemblies were dependent on the concentration of the nanorods, as was seen in transmission electron microscopic images. At a low concentration, the nanorods assembled parallel to the substrate, whereas they stood on the substrate at a high concentration. On the other hand, in a solid of the gold nanorods, the formation of the 3-D assembly was confirmed by small-angle X-ray scattering. The assembly consisted of hexagonal arrays of the gold nanorods and their lamellar accumulation.     

X-ray diffraction and quantum-chemical analysis of a single crystal of 2,5-dimethyl-3,4-dihydro-2h-pyran-2-carboxylic acid

The structure of synthesized 2,5-dimethyl-3,4-dihydro-2H-pyran-2-carboxylic acid was investigated by the single crystal X-ray diffraction analysis method. It was established that the molecule of the acid exists in the form of the endo isomer while the single crystal exists as a racemate of the two enantiomeric endo stereomers. Quantum-chemical calculations of a model of the macrocell of the acid by means of the semiempirical MOPAC2009 program agree well with the X-ray diffraction data.     

Chalcogenolato-di-thiocarbamato-complexes of zinc: The X-ray single crystal structures of pyridine adducts

Novel mixed complexes 2,4,6-Me₃C₆H₂SZnS₂CNEt₂ (1), 2,4,6-Me₃C₆H₂SeZnSe₂CNEt₂ (2) and their pyridine adducts ([Zn(SC₆H₂Me₃-2,4,6)₂(C₅H₅N)₂] (3), [Zn(SeC₆H₂Me₃-2,4,6)₂(C₅H₅N)₂] (4) and (Et₂CNSe₂)₂Zn.NC₅H₅ (5) and (Et₂CNS₂)₂Zn.NC₅H₅ (6) have been synthesised and characterised. The X-ray single crystal structures of (4), (5) and (6) have been determined.     

Fabrication of CoO nanorods via thermal decomposition of CoC2O4 precursor

Cobalt oxide (CoO) nanorods were synthesized by annealing CoC₂O₄ precursor. The nanorods were identified by Transmission electron microscopy (TEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and other methods. The results showed that the nanorods are composed of cubic CoO with diameter of 10–80 nm, and lengths ranging from 1 to 3 μm. The mechanism of formation of CoO nanorods was also discussed.     

Some experimental aspects of absolute configuration determination using single crystal X-ray diffraction

Students of single crystal X-ray diffraction are often give advice as to how best to collect their data when attempting absolute configuration determination. These ‘rules’ often have more grounding in gut-feeling than evidence. Thus, in an effort to provide advice and evidence that today’s crystallographers can pass onto to tomorrow’s young scientists, we present a systematic study of 1-deoxy-l-arabinitol, a straight chain sugar which crystalises well in the space group $\text{I}{4}_1$.     

Mössbauer and single crystal X-ray studies of polymeric dimethylchlorotin acetate

The solid state structure of dimethylchlorotin acetate has been investigated by Mössbauer spectroscopy and single crystal X-ray analysis. Tin-119 Mössbauer spectra have been recorded at 80 K and 300 K, and the measured isomer shift and quadrupole splitting parameters have been correlated with the crystallographic data. The crystal structure has been determined using heavy-atom methods in conjunction with least-squares refinement of data measured on a two-circle X-ray diffractometer. Crystals are orthorhombic, space group Pna2₁, with four formula weights in a cell having the dimensions a = 9.315(3), b = 11.061(3), c = 7.656(2) Å and U = 788.78 ų. The observed and calculated densities are 2.07 and 2.05 mg m^?3, respectively. The structure was refined using 842 observed reflections to give conventional discrepancy factors of R = 0.040 and R' = 0.044. The crystal structure is composed of Me₂ClSn units bridged by acetate ligands giving rise to polymeric chains which run along the a direction. The tin atom is in a distorted trigonal bipyramidal environment consisting of two axial oxygen atoms distanced 2.165(6) and 2,392(7) Å from the metal, and equatorial positions occupied by two methyl groups and a chlorine atom. Distortions within the coordination polyhedron may be attributed to a further weak but apparently significant tin-oxygen interaction (Sn-O 2.782(7) Å), resulting in the tin atom becoming six-coordinate.     

Chemical enhancement by nanomaterials under X-ray irradiation

We report here a new phenomenon of dynamic enhancement of chemical reactions by nanomaterials under hard X-ray irradiation. The nanomaterials were gold and platinum nanoparticles, and the chemical reaction employed was the hydroxylation of coumarin carboxylic acid. The reaction yield was enhanced 2000 times over that predicted on the basis of the absorption of X-rays only by the nanoparticles, and the enhancement was found for the first time to depend on the X-ray dose rate. The maximum turnover frequency was measured at 1 × 10(-4) s(-1) Gy(-1). We call this process chemical enhancement, which is defined as the increased yield of a chemical reaction due to the chemical properties of the added materials. The chemical enhancement described here is believed to be ubiquitous and may significantly alter the outcome of chemical reactions under X-ray irradiation with the assistance of nanomaterials.     

Cyclooctene epoxidation with H2O2 and single crystal X-ray determined crystal structures of new molybdenum and tungsten catalysts bearing the hydrophilic ligand hydroxymethyldiphenylphosphine oxide

The dioxo molybdenum and tungsten complexes MoO₂Cl₂(OPPh₂CH₂OH)₂ and WO₂Cl₂(OPPh₂CH₂OH)₂ have been synthesized and characterized by FT-IR, ¹H and ³¹P NMR. Their structures, as determined by single crystal X-ray diffraction analysis, reveal distorted octahedral geometries with cis terminal oxygen atoms, trans Cl ligands and that the hydroxymethyldiphenylphosphine oxide ligands coordinate through the oxygen atom bonded to the P atom. Both of the compounds are studied as catalysts for the epoxidation of cis-cyclooctene in the presence of hydrogen peroxide as a source of oxygen. Both complexes showed good activity and very high selectivity for the formation of cyclooctene oxide.     

Effects of gamma irradiation on the single crystal ergosterol: An EPR study

Single crystals of ergosterol were investigated by Electron Paramagnetic Resonance (EPR) technique, with γ irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 380 K, and the spectra were found to be slightly dependent on temperature. Because of the importance of ergosterol it is important to determine the irradiation effects on this molecule.Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal ergosterol, we found that two paramagnetic species which were labeled as radical A, CH_2αH_β, and radical B, CH_αH_βH_γH_σ, were produced in the host crystal. The EPR parameters; spectroscopic splitting factor, g, and hyperfine coupling constant, a, were determined for each radical.