Development of an impedimetric sensor based on carbon dots and chitosan nanocomposite modified electrode for Cu(II) detection in water

Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor...     

Correlation between P chemical shift tensor and local structure in lithium cyclohexaphosphates Li6P6O18·3H2O and Li6P6O18

To understand the surprising behavior between the variations of the P′–P–P″ angles and the correlated variations of the O′–P–O″ ones, two lithium cyclohexaphosphate compounds Li₆P₆O₁₈·3H₂O and Li₆P₆O₁₈ are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P₆O₁₈]⁶⁻ ring anions but with 3m or internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of ⁷Li and ³¹P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for ⁷Li or ³¹P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the ³¹P chemical shift tensor is dependent on the deviations of the O–P–O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P′–P–P″ and the ones of the O′–P–O″ is related to the overall charge on the PO₄ group. We also find the positions of the isotropic lines for ⁷Li essentially depend on the site co-ordination of this nuclei.     

Synthesis,characterization and optical properties of ZnO nanoparticles with controlled size and morphology

Zinc oxide monodispersed nanoparticles were synthesized using a modified polyol process without any requirement to use a catalyst or calcination step at high temperature. The morphology and the size of the resulting oxide particles were adjusted by using several synthesis parameters (temperature, alkaline ratio, hydrolysis ratio, etc.). The increasing of the alkaline ratio results in a great change of the elaborated particles morphology that evolved from irregular and anisotropic forms (conical, nanorod-like and elliptical) to spherical one. A growth mechanism of these particles was proposed on the basis of zincite crystal structure and the morphology evolution as a function of the synthesis parameters. The photoluminescence spectra show UV-excitonic and visible emission bands. The strongest intensity of the visible emission was observed in nanorod-like particles, which implies an increased fraction of oxygen vacancies in this sample. The rod-like particles with 1 μm length show the dominant UV-emission, which evidences their improved stoichiometry.     

Infrared and polarized Raman spectra of a noncentrosymmetric compound "sodium samarium fluorosilicate" NaSmSiO4.0.25NaF

Chemical preparation, infrared and Raman spectra of sodium samarium fluorosilicate, NaSmSiO(4).0.25NaF are presented. The spectra are analyzed with regard to the symmetry, and the numbers of the SiO(4)(4-) internal vibrational modes observed in the Raman and infrared spectra are consistent with the predictions.     

Correlation between 31P chemical shift tensor and local structure in lithium cyclohexaphosphates Li6P6O18 x 3H2O and Li6P6O18

To understand the surprising behavior between the variations of the P'-P-P" angles and the correlated variations of the O'-P-O" ones, two lithium cyclohexaphosphate compounds Li6P6O18 x 3H2O and Li6P6O18 are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P6O18]6- ring anions but with 3m or 1 internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of 7Li and 31P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for 7Li or 31P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the 31P chemical shift tensor is dependent on the deviations of the O-P-O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P'-P-P" and the ones of the O'-P-O" is related to the overall charge on the PO4 group. We also find the positions of the isotropic lines for 7Li essentially depend on the site co-ordination of this nuclei.     

Hydrothermal Synthesis,Crystal Structures and Characterization of Two Hydrogen Phosphates Templated by 4-Amino-2,2,6,6-tetramethylpiperidine

Abstract

Chemical preparations, crystal structures, thermal analyses, and IR spectroscopic studies are given for two new hydrogen phosphates templated by 4-amino-2,2,6,6-tetramethylpiperidine: (C₉H₂₂N₂)₂·(H₂PO₄)·(HPO₄)·(F)·H₂O (I) and (C₉H₂₂N₂)·(H₂PO₄)₂(II). The structures are determined by single crystal X-ray diffraction. Both compounds crystallize in the P2₁/c (N°14) monoclinic space group with the unit cell parameters: a = 14.856 (1) Å, b = 14.092 (2) Å, c = 14.7166 (9) Å, β = 118.434 (7)°, V = 2709.2 (4) Å ³, and Z = 4 for (I) and a = 9.803 (2) Å, c = 0.466 (2) Å, c = 15.640 (8) Å, β = 94.990 (4), V = 1598.68 (7) ų, and Z = 4 for (II).

The structure of I, refined to R = 0.042 and R_w = 0.067 for 6009 reflections (I ≥ 2σ (I)), exhibits infinite inorganic chains _∞((H₂PO₄)·(HPO₄)·(F)·H₂O)^4? linked together through weak hydrogen bonds to form layers onto which the diprotonated [C₉H₂₂N₂]^{2 +} amine molecules are anchored.

The structure of II, refined to R = 0.060 and R_w = 0.086 for 1435 reflections (I ≥ 2σ (I)), consists of _∞(H₂PO₄)^? (100) layers between which [C₉H₂₂N₂]²⁺ cations are inserted. A network of hydrogen bonds connects the different components. IR spectra of I and II show the characteristic bands of amine groups and phosphate anions.     

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe M?ssbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles.     

Chemical preparation and crystal structure of 6′-butoxy-2,6-diamino-3,3′azo-dipyridine monohydrate

Chemical preparation, X-ray single crystal, and calorimetric studies of C₁₄H₁₈N₆O·H₂O are described. The compound crystallizes in the triclinic space group, P with unit cell dimensions: a = 6.2640(3), b = 10.9840(4), c = 12.2220(3) Å, = 105.03(2), = 96.96(2), = 101.6(2)°, V = 712.10(5) ų, and Z = 2. The 6-butoxy-2,6-diamino-3,3-azo-dipyridine monohydrate structure is built up from organic layers parallel to the (120) plane linked via O—H···N bond.     

Catechol derivatives-coated Fe3O4 and γ-Fe2O3 nanoparticles as potential MRI contrast agents

Superparamagnetic iron oxide nanoparticles, Fe₃O₄ and γ-Fe₂O₃, were produced by the so-called polyol process. In order to stabilize the particles in a physiological environment as potential contrast agents for Magnetic Resonance Imaging (MRI), the as-prepared particles were successfully transferred to an aqueous medium through ligand exchange chemistry of the adsorbed polyol species with the dopamine or the catechaldehyde. The ligands were able to participate in bidentate binding to the nanoparticles surface and to improve the stability of aqueous suspensions of the nanoparticles. Analysis was performed by various techniques including X-ray diffraction, transmission electron microscopy, infrared spectroscopy and thermal analysis. The results of magnetic measurements and initial in vitro magnetic resonance imaging essays are presented for the pre- and post-surface modified nanoparticles, respectively and discussed in relation with their structure and microstructure.