Photoluminescence of bis(8-hydroxyquinoline) zinc (Znq2) and magnesium (Mgq2)

Absorption and photoluminescence (PL) spectra, PL quantum efficiency, and PL lifetime have been investigated on bis(8-hydroxyquinoline) zinc (Znq₂) and magnesium (Mgq₂) in solutions and powder. Znq₂ and Mgq₂ have the lowest-energy absorption band at 376 and 396 nm in acetonitrile solution, respectively, and emission band with peak at 555 and 480 nm. The PL quantum efficiency is 0.03 and 0.45 for Znq₂ and Mgq₂ in the solution, respectively, while 0.45 and 0.36 in powder. Unlike the case of powders, two PL lifetimes are obtained in solutions. The longer lifetime is attributed to molecule having interaction with its neighboring molecule, while the shorter one to the isolated single molecule.     

Cation mobility and structural changes on the water removal in zeolite-like zinc hexacyanometallates (II)

The cation (A⁺) mobility and structural changes on the water molecules removal in zeolite-like zinc hexacyanometallates series, Zn₃A₂[Fe(CN)₆]₂·xH₂O with A=Na, K, Rb and Cs, were studied from X-ray diffraction data recorded for hydrated and anhydrous samples at room temperature and at 77 K. The crystal structure for the anhydrous phases were solved and refined and then compared with those corresponding to their hydrated form. On the water molecules removal the charge balancing cation (A⁺) migrates to favor a stronger interaction with the N ends of the CN bridges where the framework negative charge is located. This cation-framework interaction model is supported by the recorded IR spectra for both hydrated and anhydrous samples. The new cation position induces distortion for both the cavity shape and their windows and also leads to cavity volume reduction. This is relevant for the properties of this family of solids as porous materials and their behavior in adsorption and separation processes, among them for hydrogen storage.     

Zinc-8-hydroxyquinoline intercalated in calcium bentonite: A promising DO sensor

Zn(II) and 8-hydroxyquinoline were made to react in an in situ solid−solid reaction in the interlayer space of Ca-bentonite from Thailand, resulting in [Zn(8-hydroxyquinoline)₂]²⁺, the well known -Znq₂. X-ray diffraction patterns showed that the interlayer space of the bentonite increased from 1.56 to 1.67 nm on going from Zn(II)-bentonite to Znq₂-bentonite, which confirmed the intercalation of Znq₂ in bentonite. The intercalated Znq₂-bentonite compound was mixed with a solution of polystyrene in toluene and coated as a film on a polystyrene sheet. The fluorescence intensity of Znq₂-bentonite film was measured in the presence of dissolved oxygen (DO). It was found that the fluorescence intensity of the film decreased as dissolved oxygen increased, which is a promising result for developing an optical dissolved oxygen sensor (DO sensor). The fluorescence quenching by oxygen followed the Stern-Volmer plot.     

Synthesis,crystal growth,and characterization of piperazinediium bis (4-aminobenzoate) dihydrate - An efficient third-order nonlinear optical single crystal for opto-electronic applications

Organic compound of protonated Piperazinediium bis (4-aminobenzoate) dihydrate C₄H₁₂N₂²⁺2(C₇H₆NO₂⁻).2(H₂O) (PZ4AB) was synthesized and crystal was grown by slow evaporation solution growth technique. Powder X-ray diffraction and High resolution X-ray diffraction studies affirmed the crystalline perfection of the grown crystal. Fourier transform infrared spectral analysis ascertained the frequencies of various functional groups present in PZ4AB crystal. Optical transmittance and optical band gap estimation explored the optical phenomena of PZ4AB crystal. The laser-induced surface damage threshold value of PZ4AB crystal was measured to be 1.0615 GW/cm² for the 1064 nm Nd:YAG laser radiation. From Thermogravimetric and differential scanning calorimetric studies, the stability of PZ4AB crystal was ascertained. The dielectric manner was endowed as a function of frequency and temperature. The mechanically soft nature of the crystal was assessed by Vickers hardness measurement which exhibited the reverse indentation size effect. The nonlinear refractive index, absorption coefficient and the third-order nonlinear susceptibility of crystal were divulged by Z-scan technique.     

Optical absorption spectrum of diammonium nickel bis(tetrafluoroberyllate) hexahydrate

The optical absorption spectrum of diammonium nickel bis (tetrafluoroberyllate) hexahydrate (NH₄)₂Ni(BeF₄)₂.6H₂O has been investigated at the laboratory and liquid nitrogen temperatures. The spectrum is characteristic of the Ni²⁺ ion in an octahedral crystal field. Splitting of one of the bands at the liquid nitrogen temperature are attributed to the spin-orbit interaction.     

The use of hot‐stage microscopy and thermal micro‐Raman spectroscopy in the study of phase transformation of metoclopramide HCl monohydrate

The aim of this work was to investigate the transformation behavior of metoclopramide HCl with monohydrate (MCP HCl H₂O) using differential scanning calorimetry (DSC), thermogravimetric analysis, hot‐stage microscopy (HSM), and thermal micro‐Raman spectroscopy. The results of the present study indicate that the three‐step phase transformation of MCP HCl H₂O was clearly determined via the thermal‐dependant Raman spectral changes. These three steps of phase transformation were dehydration, recrystallization, and new crystal formation, which were markedly correlated with the endothermic and exothermic results of DSC study and the observations of HSM. The results generally evidence that MCP HCl H₂O crystals were first dehydrated to form an anhydrous sample, then recrystallized and transformed to a new crystal form of MCP HCl. Copyright © 2011 John Wiley & Sons, Ltd.     

Intercalation behavior of barium phenylphosphonate

The dependence of basal spacing and water content of BaC₆H₅PO₃·xH₂O on the relative humidity was studied. Intercalates of 1-alkylamines (C₂-C₁₀) and 1-alkanols (C₃-C₁₀) were prepared from barium phenylphosphonate dihydrate and also from anhydrous host and characterized by powder X-ray diffraction and thermogravimetric analysis. The intercalates of alkanols and alkylamines prepared from dihydrate are quite stable at ambient conditions and contain one guest molecule per formula unit. The guest molecules are probably arranged in monomolecular way and are perpendicular to the host layers in the case of amines or tilted to the host layers at an angle of about 80° in the case of alkanols. The intercalates prepared from anhydrous host are unstable and their basal spacings indicate parallel arrangement of the guests chains. Formation of mixed intercalates was not observed when barium phenylphosphonate dihydrate was contacted with a mixture of alkanols or amines.     

Characterizations of octahedral zinc oxide synthesized by sonochemical method

The ultrasonic reaction of zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (C₆H₁₂N₄) was investigated by varying the concentration of the reactants, the irradiation time, and the type of sonicator. The morphology, composition, and phase structure of the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. Octahedral zinc oxide (ZnO) micropowders were formed at low concentrations, 0.05 M, of Zn(NO₃)₂·6H₂O and C₆H₁₂N₄ in both lab-made sonicator and commercial ultrasonic bath. However, at concentrations between 0.1 and 1.0 M Zn(NO₃)₂-C₆H₁₂N₄ mainly plate-like zinc hydroxide nitrate hydrate (Zn₅(OH)₈(NO₃)₂(H₂O)₂) resulted with only a small fraction of ZnO, irrespective of the irradiation time employed, highlighting the sensitivity of the system to the concentration of the starting materials. Heat treatment of Zn₅(OH)₈(NO₃)₂(H₂O)₂ at 350 °C in air affords a ZnO phase of irregular morphology. Octahedral ZnO is found to exhibit slightly lower IR absorption and similar UV absorption to that of commercial prismatic hexagonal ZnO, although an extra peak due to small quantities of Zn₅(OH)₈(NO₃)₂(H₂O)₂ is observed.     

Electronic structure and optical properties of wurtzite-kesterite Cu2ZnSnS4

As promising light-absorber material for solar cells, Cu₂ZnSnS₄ was found to have another crystal structure (wurtzite-kesterite) in addition to the conventional zinc blende-kesterite structure. Structural flexibility of Cu₂ZnSnS₄ opens up an avenue to develop light-absorber material with novel exciting properties and applications. However, its electronic and optical properties have not been comprehensively studied yet. For this purpose, the method of density functional theory within hybrid functional of PBE0 was adopted to study the structural, electronic, and optical properties of wurtzite-kesterite Cu₂ZnSnS₄ in this Letter. The calculated results suggested that the energy of its band gap is about 1.372 eV and it has obvious optical anisotropy. Furthermore, its crystal structure leads local internal fields that are especially beneficial to suppress the recombination of photoexcited electron–hole pairs.     

Sonication-assisted synthesis of a new cationic zinc nitrate complex with a tetradentate Schiff base ligand: Crystal structure,Hirshfeld surface analysis and investigation of different parameters influence on morphological properties

A nanostructured cationic zinc nitrate complex with a formula of [ZnLNO₃]NO₃ (where L = (N²E,N^2′E)-N¹,N^1′-(ethane-1,2-diyl)bis(N²-((E)-3-phenylallylidene)ethane-1,2-diamine)) was prepared by sonochemical process and characterized by single crystal X-ray crystallography, scanning electron microscopy (SEM), FT-IR and NMR spectroscopy and X-ray powder diffraction (XRPD). The X-ray analysis demonstrates the formation of a cationic complex that metal center is five-coordinated by four nitrogen atom from Schiff base ligand and one oxygen atom from nitrate group. The crystal packing analysis demonstrates the essential role of the nitrate groups in the organization of supramolecular structure. The morphology and size of ultrasound-assisted synthesized zinc nitrate complex have been investigated using scanning electron microscopy (SEM) by changing parameters such as the concentration of initial reactants, the sonication power and reaction temperature. In addition the calcination of zinc nitrate complex in air atmosphere led to production of zinc oxide nanoparticles.