Synthesis,crystal structure,infrared spectrum and thermal behaviourof α-BaHPO4

The phosphate α-BaHPO₄ was synthesised as a single-phase crystalline powder starting from an aqueous solution of barium hydroxide and phosphorus pentoxide at 373 K. α-BaHPO₄ crystallises in a new structure type in which the Ba²⁺ ions form a distorted body-centred arrangement with the HPO₄^? anions in the quasi-octahedral voids (BaHPO₄, Aem2, Z = 16, a = 459.96(9), b = 22.809(5), c = 14.081(3) pm, wR₂ = 0.077, R₁ = 0.069, 1995 reflections, 102 parameters). The crystal structures of α-BaHPO₄ and β-BaHPO₄ are compared. The infrared spectrum and a thermal and thermogravimetric analysis of α-BaHPO₄ are also reported.     

Fixed-bed study for adsorptive removal of furfural by activated carbon

In our previous study [A.K. Sahu, V.C. Srivastava, I.D. Mall, D.H. Latye, Sep. Sci. Technol. 43 (5) (2008) 1239], commercial grade activated carbon (ACC) was used for adsorptive removal of furfural from aqueous solution using batch studies. In the present study, continuous fixed-bed adsorption was carried out in ACC packed bed for the removal of furfural from aqueous solution. The effects of important factors namely bed height (Z = 15–60 cm), influent concentration of furfural (C_o = 50–200 mg/l), the flow rate (Q = 0.02–0.04 l/min) and column diameter (D = 2–4 cm) were studied. Capacity of the bed to adsorb furfural was found to increase with an increase in the value of Z, C_o and D; and with decrease in the value of Q. Adams–Bohart, Bed-Depth Service-Time, Thomas, Yoon–Nelson, Clark and Wolborska models were applied to the experimental data for the prediction of the breakthrough point, and to determine the characteristic parameters of the column. Error analysis showed that the Yoon–Nelson model best described the experimental breakthrough curve, while Wolborska model showed good prediction of breakthrough curve for the relative concentration region up to 0.5.     

Oxidative homo-coupling of potassium aryltrifluoroborates catalyzed by gold nanocluster under aerobic conditions

Gold(0) nanoclusters, stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP-n), catalyzed the oxidative homo-coupling reaction of potassium aryltrifluoroborate in water under air. Catalytic activity was dependent on the size of clusters. The smallest cluster Au:PVP-1 (d_av = 1.3 ± 0.3 nm) gave the highest activity, while Au:PVP-7 (d_av = 9.5 ± 1.0 nm) did not catalyze the homo-coupling. The catalyst was reusable for several times. Positively charged surface on the Au cluster, generated by the adsorption of molecular oxygen, would be the active site of the catalysis.     

Photochemistry of 1,3,5-trithianes in solution: Steady-state and laser flash photolysis studies

In this work, we characterized the direct photochemistry of a set of five structurally-related 1,3,5-trithianes. The compounds were 1,3,5-trithiane, the α- and β-isomers of the 2,4,6-trimethyl derivatives, and the α- and β-isomers of the 2,4,6-triphenyl derivatives. Under steady-state, 254-nm irradiation of acetonitrile solutions of all five trithianes, dithioesters of the form RC( = S)SCH(R)SCH₂R were identified and shown to be primary photoproducts (R = H, CH₃, or C₆H₅). Shorter dithioesters, RC( = S)SCH₂R, were also identified and shown to be secondary products. The presence of the dithioesters could be monitored by their strong absorption bands in the region of 310 nm. This same band was evident following the laser flash photolysis of the five trithianes. The laser-induced transient spectra showed another absorbing species (I) in all five trithianes. This species was not stable and showed a complementary decay that matched the growth of the stable photoproducts at 310 nm. This suggested that the intermediates (I) are the precursors of the corresponding dithioesters, RC( = S)SCH(R)SCH₂R. These correlated processes were related to monophotonic events. However, in the laser flash photolysis experiments in the triphenyl derivatives, there was an additional pathway for the formation of the dithioesters, and this was biphotonic. When the biphotonic formation of products was compensated for, RC( = S)SCH(R)SCH₂R formation quantum yields from steady-state and laser flash photolysis matched within experimental error. The absorption band of (I) varied systematically with substituents, 320 nm in 1,3,5-trithiane, 340 nm in the 2,4,6-trimethyl derivatives, and 420 nm in the 2,4,6-triphenyl derivatives. The nature of these intermediates (I) were discussed as resulting from CS bond cleavage, probably heterolytic.     

New metastable hybrid phase,Zn2(OH)2(C8H4O4), exhibiting unique oxo-penta-coordinated Zn(II) atoms

The metastable phase (phase 1) Zn(OH)₂(tp)₂ (tp = C₈H₄O₄^2?) was found to be an intermediate forming during the hydrothermal synthesis of Zn₃(OH)₄tp (phase 2). Its structure has been determined ab initio from synchrotron powder diffraction data and refined with the Rietveld method: space group P2₁/c, a = 3.48856(2) Å, b = 5.84645(2) Å, c = 22.1331(1) Å, β = 103.46(1)°, D_x = 2.488 g/cm³, R_p = 0.10, R_B = 0.095 (402 independent reflections). The structures of the two analogues were compared. Whereas a mixed coordination of the zinc atoms was found in phase 2, phase 1 exhibits only penta-coordinated Zn(II). Moreover, different optical properties were observed, Zn₂(OH)₂(tp) showing photoluminescence at 378 nm under λ_ex = 316 nm.     

The crystal structure of Rb2SeO4 at high temperature

The crystal structure of Rb₂SeO₄ in its high-temperature phase is reported for the first time. Powder diffraction data collected at T = 898 K show that it is hexagonal (a = 6.3428(1) Å, c = 8.5445(1) Å, V = 297.71(1) Å³, space group P6₃/mmc (194), Z = 2) and is isostructural to Tl₂SeO₄, thus belonging to the α-K₂SO₄ structure type. DSC measurements indicate that the phase transition occurs at T = 818 K.     

Influence of molar mass of polymer on the solvent activity for binary system of poly N-vinylcaprolactam and water

The water activity in aqueous solution of poly N-vinyl caprolactam with different molecular weights is measured by isopiestic method at T = 308.15 K. The results show that water activity and vapour pressure of poly N-vinylcaprolactam solution increases with increasing the molecular weight. The Flory-Huggins model, the modified Flory-Huggins model and Freed Flory-Huggins equation + NRTL model are used for correlation of the experimental solvent activity. It is found that the Freed Flory-Huggins + NRTL model is better than the others.     

Volumetric and isentropic compressibility behaviour of aqueous solutions of (polyvinylpyrrolidone + sodium citrate) at T = (283.15 to 308.15) K

The apparent specific volumes and isentropic compressibilities have been determined for polyvinylpyrrolidone in aqueous solutions of sodium citrate by density and sound velocity measurements at T = (283.15 to 308.15) K at atmospheric pressure. The results show a positive transfer volume of PVP from an aqueous solution to an aqueous sodium citrate solution. For low concentrations of PVP, the apparent specific volumes of PVP in water increased along with an increase in the polymer mass fraction, while in aqueous sodium citrate solutions decreased along with an increase in the polymer mass fraction. For high concentrations of PVP, the apparent specific volumes of PVP in water and in aqueous sodium citrate solutions were independent of the polymer mass fraction. The apparent specific isentropic compressibility of PVP is negative at T = (283.15 and 288.15) K, which imply that the water molecules around the PVP molecules are less compressible than the water molecules in the bulk solutions. The positive values of apparent specific isentropic compressibility at T = (298.15, 303.15, and 308.15) K imply that the water molecules around the PVP molecules are more compressible than the water molecules in the bulk solutions. Finally, it was found that the apparent specific isentropic compressibility of PVP increases as the concentration of sodium citrate increases.     

The removal of uranium (VI) from aqueous solutions onto natural sepiolite

The adsorption of uranium (VI) from aqueous solutions onto natural sepiolite has been studied using a batch adsorber. The parameters that affect the uranium (VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, and temperature, have been investigated and optimized conditions determined. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of sepiolite and experimental results showed this to be 34.61 mg · g^?1. The experimental results were correlated reasonably well by the Langmuir adsorption isotherm and the isotherm parameters (Q_o and b) were calculated. Thermodynamic parameters (ΔH° = ?126.64 kJ · mol^?1, ΔS° = ?353.84 J · mol^?1 · K^?1, ΔG° = ?21.14 kJ · mol^?1) showed the exothermic heat of adsorption and the feasibility of the process. The results suggested that sepiolite was suitable as sorbent material for recovery and adsorption of uranium (VI) ions from aqueous solutions.     

New iodate materials as potential laser matrices. Preparation and characterisation of α-M(IO3)3 (M = Y,Dy) and β-M(IO3)3 (M = Y,Ce, Pr,Nd, Eu,Gd, Tb,Dy, Ho,Er). Structural evolution as a function of the Ln3+ cationic radius

Anhydrous yttrium iodate presents polymorphism; two crystalline phases are obtained under hydrothermal conditions. α-Y(IO₃)₃ crystallises in the monoclinic space-group P2₁/c with a three-dimensional structure, whereas β-Y(IO₃)₃ crystallises in the monoclinic space-group P2₁/n with a two-dimensional structure. The lattice parameters are a = 7.038(1) Å, b = 8.466(1) Å, c = 13.317(1) Å, β = 99.65(1)°, V = 782.3(2) Å³, Z = 4 for α-Y(IO₃)₃ and a = 8.685(1) Å, b = 5.964(1) Å, c = 14.958(1) Å, β = 96.99(2)°, V = 769.0(2) Å³, Z = 4 for β-Y(IO₃)₃. The α-form is isostructural with α-Dy(IO₃)₃ studied in this work and α-Ln(IO₃)₃ (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, and Lu) already studied. The β-form is isostructural with β-Ln(IO₃)₃ (Ln = Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho and Er) studied in this work. The structural evolutions as a function of the Ln³⁺ cationic radius are studied. α-Y(IO₃)₃ and β-Y(IO₃)₃ present good thermal stability since they decompose at 600 °C. They are transparent up to 11.5 μm and they have good optical damage thresholds on powder.     

Synthesis of ktenasite,a double hydroxide of zinc and copper,and its intercalation reaction

Ktenasite was synthesized by the simple method of mixing ZnO powder with CuSO₄ solution at room temperature. The X-ray diffraction pattern of synthesized ktenasite was very similar to that of mineral ktenasite. The lattice parameters were determined as a=0.559, b=0.616, c=2.374 nm and β=95.63°, which agreed comparatively well with those for mineral ktenasite. The synthesized ktenasite consisted of thin rectangular particles ranging in size from 2 to 4 μm in length. TEM observation suggested the formation of a super lattice structure in the a-axis direction and significant crystal growth in the b-axis direction. The intercalation reaction of sodium dodecyl sulfate (NaDS) with ktenasite showed that the intercalation took place accompanied by the expansion of basal spacing from 1.17 to 2.70 nm. The reaction progressed by the SO₄²⁻/DS⁻ anion exchange mechanism with the dissolution of interlayer [Zn(H₂O)₆]SO₄ salt.     

Looking glass inhibitors: both enantiomeric N-benzyl derivatives of 1,4-dideoxy-1,4-imino-d-lyxitol [a potent competitive inhibitor of α-d-galactosidase] and of 1,4-dideoxy-1,4-imino-l-lyxitol [a weak competitive inhibitor of α-d-galactosidase] inhibit naringinase,an α-l-rhamnosidase competitively

Benzhydryl protection by diphenyldiazomethane of an alcohol in enantiomeric base-sensitive ribonolactones allows short efficient syntheses of 1,4-dideoxy-1,4-imino-d-lyxitol (DIL) and of 1,4-dideoxy-1,4-imino-l-lyxitol (LIL). DIL showed potent [K_i = 0.13 μM]—and LIL showed weak [K_i = 113 μM]—competitive inhibition of α-d-galactosidase. Both enantiomers N-benzyl-DIL [K_i = 64 μM] and N-benzyl-LIL [K_i = 13 μM] were moderate competitive inhibitors of naringinase, an α-l-rhamnosidase.     

Self-aggregation of liquids from biomass in aqueous solution

Aggregation of several chemicals from biomass: furfural derived compounds (furfural, 5-methylfurfural, furfuryl alcohol and tetrahydrofurfuryl alcohol), lactate derived compounds (methyl lactate, ethyl lactate and butyl lactate), acrylate derived compound (methyl acrylate) and levulinate compounds (methyl levulinate, ethyl levulinate and butyl levulinate) in aqueous solution has been characterised at T = 298.15 K through density, ρ, speed of sound, u, and isentropic compressibilities, κ_S, measurements. In addition the standard Gibbs free energies of aggregation have been also calculated. Furthermore, in order to deepen insight the behaviour of these chemicals in aqueous solution, the solubility of these compounds has been measured at T = 298.15 K.     

Pressure effects on an organic radical ferromagnet γ-phase BBDTA · GaCl4

A radical cation salt, BBDTA (= benzo[1,2-d:4,5-d′]bis[1,3,2]dithiazole) · GaCl₄, has three polymorphs, labeled α, β and γ. The γ-phase shows a ferromagnetic ordering at 7.0 K, and this Curie temperature (T_C) is eminently high, in contrast to those of the other organic radical ferromagnets. We have investigated the pressure effects on the γ-phase of BBDTA · GaCl₄ through ac magnetic susceptibility measurements under hydrostatic pressure up to 16.2 kbar. The value of T_C increases with linear fashion against pressure and exceeds 14 K at 16.2 kbar. By applying further pressure, it may exceed 16 K of the organic ferromagnet, TDAE-C₆₀, which has the highest T_C in organic materials. However, the real component of the ac susceptibility below T_C is remarkably suppressed with increasing pressure and, at around 2 kbar, it decreases down to 3.5% of that at ambient pressure. Those pressure effects might originate from the pressure-induced structural transformation from the ferromagnetic γ-phase to the diamagnetic α- and/or β-phases and the enhancement of the intermolecular interactions in the surviving γ-phase.     

Thiazolylhydrazone dervatives as inhibitors for insect N-acetyl-β-d-hexosaminidase and chitinase

Insect chitinase and N-acetyl-β-d-hexosaminidases (Hex) are potential targets for developing new pesticides. Here, a series of thiazolylhydrazones I (with substituted group R₁ at N3) and II (with substituted group R₁ at N2) were designed, synthesised and evaluated as competitive inhibitors of OfHex1 and OfChi-h, from the agricultural pest Ostrinia furnacalis. Derivatives I-3d and II-3d, with phenoxyethyl group at R₁, demonstrated the best inhibitory activities against OfHex1 and OfChi-h. Molecular docking analysis indicated that the branched conformation compound II-3d (K_i = 1.5 μmol/L) formed more hydrogen bonds with OfHex1 than the stretched conformation compound I-3d (K_i = 5.9 μmol/L). The differences in compounds’ binding conformations with OfChi-h explained differences in inhibitory activity of compounds I-3d (K_i = 1.9 μmol/L) and II-3d (K_i = 4.1 μmol/L). This work suggests a novel scaffold for developing specific Hex and Chi-h inhibitors.     

Jahn–Teller phase transition in Cu0.50TiO(PO4): Powder structural characterization of the β-variety and thermal study

The thermal study of Cu_0.50TiO(PO₄), by X-ray diffraction and DSC, shows a phase transition α → β with a hysteresis (∼600 °C during heating; ∼300 °C during cooling). Single crystals have been obtained for the α-phase but the β-phase can only be stabilised at room temperature as a powder mixture with α. Structural characterization of the β-variety has been done with diffraction data (X-ray Cu Kα₁ and neutrons) using a powder rich in β-phase (α(20%) + β(80%)). A monoclinic cell (a = 7.1134(7) Å; b = 7.7282(7) Å; c = 7.3028(7) Å; β=119.30(1)°; V = 350.1(1) Å³) has been found for β-phase, space group P2₁/c. An “ab initio” structure determination has been done, and the Rietveld refinement leads to cR_wp = 0.150 and R_B = 0.041. The results from the X-ray data were confirmed by refinements from neutron data.Similarly to the α-phase, the structure of β-Cu_0.50TiO(PO₄) can be described as a TiOPO₄ framework constituted of chains of tilted corner-sharing [TiO₆] octahedra running parallel to the c axis and cross linked by [PO₄] tetrahedra. Ti atoms are displaced from the centres of the octahedral units, leading to long (2.27 Å) and short (1.73 Å) Ti–O(1) bonds. The [CuO₆] octahedra exhibit a typical Jahn–Teller distorted coordination with four short equatorial Cu–O bonds (2 × 1.93 Å and 2 × 2.06 Å), and two longer apical Cu–O bonds (2 × 2.33 Å). The two longer Cu–O bonds are almost parallel to the b axis.The transition from the α to the β-phase is characterized by a “rocking” of the Jahn–Teller elongation from the (a,c) plane to the b direction accompanied by a relatively strong expansion of the cell volume.     

Crystal structure of single crystals of nonlinear optical l-histidinium trichloroacetate

Single crystals of a new histidinium salt: l-histidinium trichloroacetate {abbreviated as LHTCA; [(C₃N₂H₄) CH₂CH (NH₃) (CO₂)]⁺ CCl₃COO⁻} were grown by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in a non-centrosymmetric space group P2₁ of monoclinic system with cell parameters a = 5.4505(18) Å, b = 25.769(8) Å, c = 9.210(2) Å and β = 99.98(2)° with Z = 4. The structure has been refined to an R-value of 0.05 for 2539 observed reflections using three-dimensional X-ray diffraction data. The vibrational structure of the compound confirms the presence of various functional groups in the molecule. The UV–Vis–NIR spectrum shows a good transparency in the whole of the region from ultraviolet to near IR. The Kurtz–Perry powder SHG measurement confirms the frequency doubling of the crystal and its powder SHG efficiency was measured as d_eff = 0.33 d_eff (KDP).     

Surface-enhanced Raman studies of bradykinin using colloidal gold

In this paper, bradykinin (BK), an endogenous peptide hormone, which is involved in a number of physiological and pathophysiological processes was deposited onto the colloidal Au nanoparticles. The surface-enhanced Raman spectroscopy (SERS) was used to determine the adsorption mode of BK under different environmental conditions, including: excitation wavelengths (514.5 nm and 785.0 nm), pH of aqueous sol solutions (from pH = 3 to pH = 11), and size of the colloidal nanoparticles (10, 20, and 50 nm). The metal surface plasmon of the colloidal suspended Au nanoparticles was examined by ultraviolet-visible (UV–vis) spectroscopy. The results showed that the C-terminal part of BK plays a crucial role in the adsorption process onto the colloidal suspended Au particles. The Phe^5/8 and Arg⁹ residues of BK mainly participate in the interactions with the colloidal Au nanoparticles. At acidic pH of the solution (pH = 3), the BK COO⁻ terminal group through the both oxygen atoms strongly binds to the Au nanoparticles. The Phe⁵/Phe⁸ rings adopt tilted orientation with respect to the colloidal Au nanoparticles with diameters of 10 and 20 nm. As the particle size increases to 50 nm, the flat orientation of the Phe ring(s) with respect to the Au nanoparticles is observed.     

Electrochemical properties of Li(Li(1−x)/3CoxMn(2−2x)/3)O2 (0 ⩽ x ⩽ 1) solid solutions prepared by poly-vinyl alcohol (PVA) method

The whole range of solid solutions Li(Li_(1−x)/3Co_xMn_(2−2x)/3)O₂ (0 ⩽ x ⩽ 1) was firstly synthesized by an aqueous solution method using poly-vinyl alcohol as a synthetic agent to investigate their structure and electrochemical properties. X-ray diffraction results indicated that the synthesized solid solutions showed a single phase without any detectable impurity phase and have a hexagonal structure with some additional peaks caused by monoclinic distortion, especially in the solid solutions with a low Co amount. In the electrochemical examination, the solid solutions in the range between 0.2 ⩽ x ⩽ 0.9 showed higher discharge capacity and better cyclability than LiCoO₂ (x = 1) on cycling between 2.0 and 4.6 V with 100 mA g⁻¹ at 25 °C. For example, Li(Li_0.2Co_0.4Mn_0.4)O₂ (x = 0.4) exhibited a high discharge capacity of 180 mA h g⁻¹ at the 50th cycle. By synthesizing the solid solution between Li₂MnO₃ and LiCoO₂, the electrochemical properties of the end members were improved.