nH 2O Research Articles

Structural properties of K xV 2O 5. nH 2O nanocrystalline films

X-ray diffraction (XRD), transmission electron microscope (TEM), atomic force microscope (AFM), Fourier transform infrared (FTIR) spectra and differential scanning calorimetry (DSC) were used to investigate the structure of K x V 2O 5. nH 2O xerogel films (with 0.0 ≤ x < 0.0091 mol). These films were produced by the sol–gel technique. XRD as well as TEM showed that K x V 2O 5. nH 2O thin films are highly oriented nanocrystals. The particle size as obtained is on the average 12 nm. AFM revealed that the grain shape of the present samples is a rod-like shape. DSC showed an endothermic peak with a minimum ranging between 102 °C and 172 °C due to the intercalation of K + ions.

Effect of alkali metal ion and hydrogen bonds on thermal stability of M[VO(O 2) 2bpy]· nH 2O (M = Li +–Rb +) and Cs[VO(O 2) 2bpy]·H 2O 2 complexes

The compounds M[VO(O 2) 2bpy]· nH 2O (M = Li +–Rb +) and Cs[VO(O 2) 2bpy]·H 2O 2 were characterized by thermogravimetry (TG). In the course of TG experiments, performed from 25 up to 550 °C, three main stages of decomposition were observed: (i) dehydration, (ii) releasing of the oxygen molecules and (iii) decomposition of bpy. The final product of decomposition is MVO 3, with small amounts of paramagnetic vanadium(IV) species. Volatile products were detected on-line using mass spectrometer. Mechanism of the decomposition is discussed on the basis of crystal structures of complexes. The main role is played by hydrogen bonds involving peroxo ligands and polarising power of alkali metal ions.

Application of Ce(IV) in industrial wastewater treatment

At present, rare earth application in wastewater treatment has become more and more widely, according to the fact that the Ce(IV) has the strong oxidation ability under acid condition, we have studied the application of Ce(IV) in industrial wastewater treatment originally. Results showed that oxidation-reduction reaction occurred between Ce(IV) and the organic compounds or other reducing substances in industrial wastewater, thereby the colority and CODcr reduced effectively. Ce(IV) formed [Ce(OH) x·nH 2O] (4- x)+ after hydrolyzation and Ce(III) obtained after Ce(IV) reduction formed [Ce(OH) x·nH 2O] (3- x)+ after hydrolyzation, these hydrate had big specific surface area, could adsorb the suspension substances and removed toxic or harmful ions in industrial wastewater. After treatment by Ce(IV), the analytical results of industrial wastewater are as follows: The CODcr became 58 mg/L from 1646 mg/L, the total COD removal efficiency was more than 95.0%. Turbidity reduced to no more than 10NTU from 87NTU. The chroma became 6 degree from 26 degree, suspension substances content decreased to no more than 2 mg/L from 36 mg/L, and total arsenic and fluorion became <0.05 mg/L and <0.10 mg/L from 0.60 and 15.3 mg/L. Total cadmium reduced to 0.01 mg/L from the 0.58 mg/L. These all indicated that Ce(IV) was one kind of latent good water treatment chemical.

Cation–anion interactions involving hydrogen bonds: Syntheses and crystal structures study of hexafluorotitanate(IV) salts with pyridine and methyl substituted pyridines

Fluorotitanates (LH) 2[TiF 6]· nH 2O ( 1: R = pyridine, n = 1, 2: R = 2-picoline, n = 2, 3: R = 2,6-lutidine, n = 0, 4: R = 2,4,6-collidine, n = 0) and (LH)[TiF 5(H 2O)] ( 3a: L = 2,6-lutidine) have been synthesized by the reaction of pyridine or corresponding methyl substituted pyridines and titanium dioxide dissolved in hydrofluoric acid. The crystal structures of ionic compounds 1, 2, 3, 3a and 4 have been determined by single-crystal X-ray diffraction analysis. The hydrogen bonding led to the formation of discrete (LH) 2[TiF 6] units ( 4), chains ( 1– 3), and layers ( 3a). The additional π– π interactions present in 1, 2, and 4 results in chain structures of 1 and 4 and in a layer structure of 2. The [TiF 6] 2− and [TiF 5(H 2O)] − anions were observed by 19F NMR spectroscopy in aqueous solutions of 1, 2, 3, 3a and 4.

An in-depth in situ IR study of the thermal decomposition of barium trifluoroacetate hydrate

The pyrolysis of Ba(CF 3COO) 2· nH 2O at temperatures up to 1000 °C, under flowing pure Ar, O 2 and O 2 saturated with water vapour, was extensively analysed. The existence of a :CF 2 diradical is inferred and the formation of HF is observed directly for the first time during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic two-stage decomposition of the anhydrate salt occurs between 282 and 325 °C, forming BaF 2 via an unstable CF 3COOBaF intermediate. Fourier transform infrared spectroscopy revealed the influence of water on the reactions of the liberated gaseous products, identifying CF 3COOH, HF, CHF 3 and CO 2 as the principal volatile species, with C 2F 4, C 2F 6, CO and SiF 4 also detected. The decomposition temperature is significantly lower than previously reported, which has implications for sol–gel processing.

Synthesis of Ru 0.58In 0.42O y⋅ nH 2O nanoparticles dispersed onto poly(sodium-4-styrene sulfonate)-functionalized multi-walled carbon nanotubes and their application for electrochemical capacitors

In this work, poly(sodium-4-styrene sulfonate) (PSS)-functionalized multi-walled carbon nanotubes (FMWCNTs) were first synthesized via a polymer-assisted technique. Then, Ru 0.58In 0.42O y ⋅ nH 2O nanoparticles (NPs) were mono-dispersed onto the FMWCNTs surfaces under mild hydrothermal condition. Here, PSS with negative charge serves as a bifunctional molecule both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru 3+ and In 3+ to facilitate the good dispersion of Ru 1− x In x O y ⋅ nH 2O NPs onto their surfaces. The good dispersion of Ru 0.58In 0.42O y ⋅ nH 2O NPs onto FMWCNTs makes OH − ions and electrons easily contact these NPs with abundant electroactive sites, which results in a large specific capacitance (SC) of 319 F g −1 for the naocomposites. Moreover, a symmetric electrochemical capacitor (EC) is constructed by using the nanocomposites as electrodes and delivers large specific energy density of 18.1 Wh kg −1, desirable power property of 1302 W kg −1, high electrochemical reversibility and good SC retention of 84.7%.

Nanosecond study of spin state transition induced by a single nanosecond laser shot on [Fe(NH 2trz) 3] compounds inside and outside their thermal hysteresis loops

We show that the combination of a free running 80 MHz femtosecond Ti–sapphire oscillator with a nanosecond Nd:YAG laser makes it possible to record in real time, with a nanosecond time resolution, reversible or irreversible phase transitions photo-induced by a single laser pulse. This set-up is used to study the spin state transition photo-induced inside and outside the thermal hysteresis loops of a series of [Fe(NH 2trz) 3]X 2· nH 2O compounds (with X = NO 3 and Br). Original dynamics are presented and discussed. The results indicate that at room temperature, it is the laser induced heating that drives the recorded photo-induced phase transition.

A vanadium-based conversion coating as chromate replacement for electrogalvanized steel substrates

The vanadium conversion coating as chromate replacement was prepared on electrogalvanized steel (EG) plates previously treated in a solution mainly composed of vanadate. Corrosion behavior of these EG plates in contact with 3.5% NaCl solution was investigated using potentio-dynamic measurement and electrochemical impedance spectroscopy (EIS) measurement. The morphology and composition of the vanadium conversion coating were studied using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) in conjunction with argon-ion sputtering. According to the results, the V-treated EG plate shows the best corrosion protection property compared with the untreated and Cr-treated EG plates. The vanadium-rich coating is composed of the closely packed particles. The coating mainly consists of vanadium and oxygen, which mainly exist as V 2O 5, VO 2, and its hydrates such as V 2O 5· nH 2O, VO(OH) 2.

Growth kinetics of vanadium pentoxide nanostructures under hydrothermal conditions

The work reported here involved a study of the growth kinetics of V 2O 5 nH 2O nanostructures under hydrothermal conditions. The coarsening process of V 2O 5 nH 2O nanoribbons was followed by subjecting the as-prepared suspensions to hydrothermal treatments at 80 °C for periods ranging from 0 to 7200 min. X-ray diffraction (XRD) confirms that the hydrothermal treatments at 80 °C caused no significant modification of the long-range order structure of samples subjected to different periods of hydrothermal treatment. Field emission scanning transmission electron microscope (FE-STEM) was used to analyze the morphology and width distribution of the nanostructures. The results indicated that the crystal growth mechanism in the [1 0 0] direction of vanadium pentoxide 1D nanostructure under hydrothermal conditions is well described by the oriented attachment (OA) mechanism. This evidence was supported by HRTEM images showing the existence of defects at the interface between nanostructures, which is characteristic of the oriented attachment (OA) mechanism.

Cobalt-doped todorokites prepared by refluxing at atmospheric pressure as cathode materials for Li batteries

Cobalt-doped todorokites were synthesized by refluxing process at atmospheric pressure from the transformation of birnessites. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), scanning electron microscope (SEM) and chemical composition analysis were used to characterize the crystal structures, surface morphologies and chemical compositions of synthesized products. Results showed that all refluxing products were todorokites with 3 × 3 tunnel structure and the chemical compositions were denoted as Mg x Co y MnO z · nH 2O, where 0.18 ≤ x ≤ 0.22, 0 ≤ y ≤ 0.31, 2.01 ≤ z ≤ 2.52 and 0.35 ≤ n ≤ 0.73. Cobalt-doped todorokites were investigated as cathode materials of lithium rechargeable batteries for charge/discharge characteristics. Discharge capacity of the undoped todorokite was about 211 mAh g −1 at first cycle, and then decreased to 37 mAh g −1 after 30 cycles. The cyclic capacities of todorokite could be improved remarkably by substitution of cobalt for manganese. Todorokites with Co content of 10–15% displayed better discharge performance. Mg 0.18Co 0.12MnO 2.19·0.45H 2O with Co content about 10% showed a high initial discharge capacity of 219 mAh g −1 and cycling capacity of 102 mAh g −1 after 100 cycles. The effect of doping cobalt on electrochemical performance of todorokite was further proved with cyclic voltammetry by using powder microelectrode.

Controllable synthesis and photoluminescence of LaPO 4:Eu 3+ nanomaterials

Hexagonal LaPO 4· nH 2O:Eu 3+ nano-wires and dual-phase LaPO 4:Eu 3+ nano-wires with hexagonal and monoclinic structures were synthesized by hydrothermal reaction at 150 and 220 °C, respectively. The effects of high temperature treatment on the structure, morphology and photoluminescence of the specimens were also investigated with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectrophotometer (FL). The results indicated the phase transformation for LaPO 4:Eu 3+ from the hexagonal structure to the monoclinic structure occurred, after the specimens were calcined at 900 °C for 12 h in the air. The wire-like structures of LaPO 4:Eu 3+ were destroyed and transformed into particle-like structures at high temperature. The mechanism of transformation from nano-wires to particles was introduced briefly. The photoluminescence properties of as-prepared and annealed specimens were also discussed in detail.

Simulation of the Raman spectra of zwitterionic glycine + nH 2O ( n = 1, 2, …, 5) by means of DFT calculations and comparison to the experimentally observed Raman spectra of glycine in aqueous medium

Raman spectra of an aqueous solution of glycine (Gly) have been recorded in the range of 400–2000 cm −1. In aqueous solution, glycine molecules exist in their zwitterionic form, having two opposite charged poles, COO − and NH 3 +. The zwitterionic structure of glycine (ZGly) is stabilized by the hydrogen bond interaction of water (W) molecules. In the present report, we have optimized the ground state geometries of different hydrogen bonded complexes of [ZGly + (W) n=1–5 ] in aqueous medium using DFT calculations at the B3LYP/6-311++G(d) level of theory. A comparative discussion on the structural details and binding energies (BEs) of each conformer has been also done. The theoretical Raman spectra were calculated corresponding to the most stable [ZGly + (W) n=1–5 ] conformers. The theoretically simulated Raman spectra of each stable conformer were compared with experimentally observed Raman spectra to explore the number of water molecules needed for stabilizing the structure of ZGly. The theoretically simulated Raman spectra corresponding to the most stable conformer of [ZGly + (W) 5] having a BE of −22.8 kcal/mol, are matching nicely with the experimentally observed Raman spectra. Thus, on the basis of the above observations, we conclude that the conformer, [ZGly + (W) 5] is the most probable conformer in the aqueous medium. We also believe that in the conformer, [ZGly + (W) 5] the five water molecules are arranged around the ZGly in such a way that the effect of steric hindrance is less compared to the other conformers. The dipole–dipole interaction potential (DDP) is also calculated corresponding to the strongest hydrogen bond for each [ZGly + (W) n=1–5 ] conformer.

Synthesis, crystal structures and spectroscopic studies of praseodymium(III) malonate complexes

Reactions of malonic acid (H 2mal) with PrCl 3·6H 2O afforded the known complex [Pr 2(mal) 3(H 2O) 6] n ( 1), and compounds [Pr 2(mal) 3(H 2O) 6] n ·2 nH 2O ( 2·2 nH 2O), [PrCl(mal)(H 2O) 3] n ·0.5 nH 2O ( 3·0.5 nH 2O) and [Pr(mal)(Hmal)(H 2O) 3] n · nH 2O ( 4· nH 2O) using various reaction ratios, reaction media (H 2O, MeOH) and pH values. Analogous reactions with CeCl 3·7H 2O afforded compounds [Ce 2(mal) 3(H 2O) 6] n ( 5), [CeCl(mal)(H 2O) 3] n · nH 2O ( 6· nH 2O) and [Ce(mal)(Hmal)(H 2O) 3] n · nH 2O ( 7· nH 2O). Compounds 2·2 nH 2O and 3·0.5 nH 2O were characterized by X-ray crystallography, and 4– 7 by microanalytical and spectroscopic data. The malonate(-2) ligand adopts three different coordination modes in the structures of 1– 3, i.e., the μ 2-κ O:κ O′:κ O″ and the μ 4-κ 2 O:κ O′:κ 2 O″:κ O‴ in 1 and 2 leading to a 3D network structure, and the μ 3-κ 2 O:κ O′:κ 2 O″:κ O‴ in 3 promoting an 1D structure. The thermal decomposition of 1 and 3·0.5 nH 2O was monitored by TG/DTA and TG/DTG measurements. The structural features of 1– 3 are discussed in terms of known malonato(-2) Ln III and Ca II complexes. The bioinorganic chemistry relevance of our results is discussed.

Optical properties of Zn 3(OH) 2V 2O 7· nH 2O nanosheets

Strong green photoluminescence (PL) was observed for hydrothermal synthesized Zn 3(OH) 2V 2O 7· nH 2O nanosheets. The energy band structure of the material was theoretically computed using first principle method and experimentally obtained by linear extrapolating from UV–vis reflection spectrum. It is shown that the material is an indirect bandgap semiconductor with a direct bandgap of 3.03 eV at Γ and an indirect gap of 2.8 eV from R to Γ. UV–vis reflection spectrum changes regularly along with doping of cobalt, showing clearly reflection peaks of Co 2+. The bandgap of Zn 3(OH) 2V 2O 7· nH 2O decreases significantly along with doping of cobalt, indicating the substitution of Co 2+ with Zn 2+. The intensity of the PL spectrum of Zn 3(OH) 2V 2O 7· nH 2O that annealed in vacuum remains almost unchanged, whereas it distinctly decreases with doping of cobalt. The results indicate that it is zinc vacancies that cause the green emitting, which is in accordance with Zn deficiency that deduced from energy dispersion spectroscopy characterization.

Influence of sulfate ions on properties of co-precipitated Y 3Al 5O 12:Nd 3+ nanopowders

A new precursor of yttrium aluminum garnet with an approximate composition of NH 4AlY 0.6(CO 3) x (OH) y (SO 4) z · nH 2O has been synthesized via a reverse strike co-precipitation method with ammonium hydrogen carbonate as the precipitant and ammonium aluminum sulfate as the sulfate ions source. The evolution of phase, chemical composition and morphology of the precursor during calcination has been studied by means of XRD, XPS, DTA–TG, BET methods and FT-IR spectroscopy. The loosely agglomerated powders with narrow size distribution, spherical shapes and diameter of 50–60 nm have been obtained by calcination of the sulfate-containing precursor at 1100 °C for 2 h. The doping by sulfate ions enhances densification of Y 3Al 5O 12:Nd 3+ nanopowders compared to undoped ones. This leads to improved microstructure and optical transmittance of vacuum sintered ceramics prepared from sulfate-doped nanopowders.

Synthesis, characterization, oxidative degradation, antibacterial activity and acetylcholinesterase/butyrylcholinesterase inhibitory effects of some new phosphorus(V) hydrazides

Some new phosphorus(V) hydrazides 1a– 12a were synthesized and characterized by 1H, 13C, 31P NMR, IR spectroscopy and elemental analysis. Moreover, the interaction of Cu(M) 2· nH 2O with 1a, 3a and 7a gave 4,4′-bis(morpholine)diazene ( 1b). In fact, in these reactions, copper(II) ions acted as oxidizing agent. The results supported the proposed mechanism. The structures of compounds 1a, 1b and 1c were further determined by X-ray crystallography. Compounds 1a– 12a were screened for their antibacterial activities. Also, the acetyl- and butyrylcholinesterase inhibitory activity of 1a, 3a, 7a, 11a and 12a was measured using Ellman’s method. It is interesting that these compounds were more potent inhibitors of BChE than of AChE. Also, using Lineweaver–Burk plots, it was indicated these compounds are mixed inhibitors.

Synthesis and characterisation of novel ruthenium multi-substituted polyoxometalates: α,β-[SiW 9O 37Ru 4(H 2O) 3Cl 3] 7−

Novel ruthenium multi-substituted polyoxometalate compounds of general formulae K 6Na[SiW 9O 37Ru III 4(H 2O) 3Cl 3]· nH 2O (α- and β-SiW 9O 34 isomers) were synthesised via the reactions of the trilacunary Keggin α- and β-[SiW 9O 34] 10 − anions with RuCl 3 in aqueous solution. Characterisation was performed by analytical, spectroscopic, magnetic, and electrochemical techniques. The results are in accordance with the new polyoxometalates having the trivacant Keggin anion (α or β isomer) linked to a cubane-type Ru 4O 4 cluster. The co-ordination sphere of ruthenium is completed with water molecules and chloride anions. Magnetic measurements showed that the majority of the molecules have the Ru ions cluster in a compensated configuration constrained to an antiferromagnetic alignment at very low temperature and following a Curie-Weiss like behaviour. For both isomers, cyclic voltammetry revealed quasi-reversible redox processes at the ruthenium centres, namely Ru IV/III and Ru III/II, which were found to be pH dependent. The novel polyoxotungstates incorporate the highest content of ruthenium (W:Ru = 2.25:1) ever reported for Keggin-, Dawson or sandwich-type transition metal-substituted polyoxometalates and may find promising applications as oxidative catalysts.

Surface modification of silica-coated zirconia by chemical treatments

Zirconia surface modification by various chemical treatments after silica coating by sandblasting was investigated in this study. The surface of silica-coated dental zirconia was hydroxylated by treatment with different acids at room temperature for 4 h, rinsed with deionized water and air-dried. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Shifts in binding energies for Zr 3d 5/2 and Si 2p peaks were observed after treatment with acids, thereby showing a change in the chemical states of zirconium and silicon on the surface layer of silica-coated zirconia. The XPS analysis revealed that the silica-coated zirconia (SiO 2–ZrO 2) surfaces had changed to hydrous silica-coated zirconia (SiO 2–ZrO 2· nH 2O). One-way ANOVA analysis revealed there was significant difference in both surface roughness parameters of silica-coated zirconia after chemical treatments and the surface topography varied depending on the acid treatment.

Facile synthesis of [1]benzothieno[3,2- b]benzothiophene from o-dihalostilbenes

A convenient one-pot synthesis of [1]benzothieno[3,2- b]benzothiophene from readily available o-dihalostilbenes using combined reagents of sodium sulfide nonahydrate (Na 2S·9H 2O) or sodium hydrosulfide hydrate (NaSH· nH 2O) and sulfur is described along with plausible reaction paths in this intriguing reaction.

The key factor determining the anodic deposition of vanadium oxides

This work demonstrates that anodic deposition of vanadium oxide (denoted as VO x · nH 2O) can be considered as the chemical co-precipitation of V 5+ and V 4+ oxy-/hydroxyl species and the accumulation of V 5+ species at the vicinity of electrode surface is the key factor for the successful anodic deposition of VO x · nH 2O at a potential much more negative than the equilibrium potential of the oxygen evolution reaction (OER). The results of in situ UV–vis spectra show that the V 4+/V 5+ ratio near the electrode surface can be controlled by varying the applied potential, leading to different, three-dimensional (3D) nanostructures of VO x · nH 2O. The accumulation of V 5+ species due to V 4+ oxidation at potentials ≥0.4 V (vs. Ag/AgCl) has been found to be very similar to the phenomenon by adding H 2O 2 in the deposition solution. The X-ray photoelectron spectroscopic (XPS) results show that all VO x · nH 2O deposits can be considered as aggregates consisting of mixed V 5+ and V 4+ oxy-/hydroxyl species with the mean oxidation state significantly increasing with the applied electrode potential.