2H2O Single Crystals Research Articles

Temperature-Induced Reversible Photoluminescence Switching and Ultraviolet-Pumped Light-Emitting Diode Applications of a Perovskite (C6H10N2)2MnCl6·2H2O Crystal.

Zero-dimensional (0D) organic-inorganic hybrid halides present many fascinating photophysical properties for promising optoelectronic applications such as light-emitting diodes (LEDs), X-ray imaging, photodetectors, and anticounterfeiting. Herein, a centimeter-sized single crystal (C6H10N2)2MnCl6·2H2O with a 0D perovskite structure was obtained via a solvent evaporation method. A bright red emission at 618 nm with a larger Stokes shift of more than 300 nm and a long fluorescence lifetime of 6.21 ms were measured. Notably, a reversible PL switching from red emission to nonluminescence has been presented in the cycles of heating-cooling processes from RT to 100 °C. Furthermore, the temperature-induced luminescence shows a quick recovery after 20 conversion cycles, exhibiting excellent stability and temperature sensing. According to the structural and theoretical analyses, the temperature-induced luminescence is primarily due to hydrogen-bonding interactions between (MnCl6)4- and H2O molecules. Particularly, a temperature anticounterfeiting application has been designed based on its reversible temperature-dependent PL switching. Importantly, the ultraviolet-pumped LEDs fabricated by (C6H10N2)2MnCl6·2H2O single crystals are perfectly achieved. Anyway, this work clearly demonstrates that 0D Mn-based perovskite with temperature-dependent PL switching greatly extends its potential applications in electro-optical display, temperature sensing, and anticounterfeiting devices.

Giant Rotational Magnetocaloric Effect in Ni(en)(H2O)4·2H2O: Experiment and Theory

An experimental study of the rotational magnetocaloric effect in Ni(en)(H2O)4SO4∙2H2O (en = ethylenediamine) single crystal is presented. The study was carried out at temperatures above 2 K and was associated with adiabatic crystal rotation between the easy plane and hard axis in magnetic fields up to 7 T. The magnetocaloric properties of the studied system were investigated by isothermal magnetization measurement. The experimental observations were completed with ab initio calculations of the anisotropy parameters. A large rotational magnetic entropy change ≈12 Jkg−1K−1 and ≈16.9 Jkg−1K−1 was achieved in 5 T and 7 T, respectively. The present study suggests a possible application of this material in low-temperature refrigeration since the adiabatic rotation of the single crystal in 7 T led to a cooldown of the sample from the initial temperature of 4.2 K down to 0.34 K. Finally, theoretical calculations show that S = 1 Ni(II)-based systems with easy-plane anisotropy can have better rotational magnetocaloric properties than costly materials containing rare-earth elements in their chemical structures.

Chiral Hybrid Copper(I) Iodide Single Crystals Enable Highly Selective Ultraviolet-Pumped Circularly Polarized Luminescence Applications.

Light-emitting diodes (LEDs) with the circularly polarized luminescence features have attracted attention to the promising applications ranging from solid-state lighting and displays to bioencoding and anticounterfeiting. The prerequisite of circularly polarized luminescence is highly emissive chiral materials. Here, we demonstrated that (R/S-MBA)4Cu4I8·2H2O (MBA = α-methylbenzylaminium) and acentric Gua6Cu4I10 (Gua = guanidinium) single crystals were grown on the basis of Gua3Cu2I5 by the slow evaporation method. (R/S-MBA)4Cu4I8·2H2O single crystals exhibited excellent circularly polarized luminescence (CPL) characteristics. More importantly, ultraviolet-pumped LEDs (UV-LEDs) based on (R/S-MBA)4Cu4I8·2H2O and Gua6Cu4I10 single crystals exhibit a higher optical selectivity when exposed to right-handed and left-handed circular polarization (RCP and LCP) conditions. (S-MBA)4Cu4I8·2H2O single crystals and Gua6Cu4I10 single crystals induced by the (R)-MBA cation exhibit the different polarized light intensities at PL peak positions in different λ/4 waveplate polarizer angle directions, which provides new possibilities for the further applications from 3D displays to spintronics, as well as anticounterfeiting.

A novel approach to the synthesis of semiorganic ammonium hydrogen oxalate oxalic acid dihydrate single crystal and its characterization

A different approach used in the synthesis of ammonium hydrogen oxalate oxalic acid dihydrate (NH4H3(C4O8)·2H2O) single crystals is presented. The crystals are synthesized using solvent evaporation technique. The analysis of the synthesized NH4H3(C4O8)·2H2O single crystals has been carried out through measurements such as single-crystal X-ray diffraction (SCXRD), powder XRD, UV–Vis and photoluminescence spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis (TG–DTA), Vickers microhardness measurements and current versus voltage (I–V) characteristics. The evaluation of the molecular structure of the crystals using SCXRD shows that they belong to the triclinic crystal system with space group P-1. The structural properties of the crystals are also evaluated using powder XRD measurements on their finely crushed powder. These measurements corroborate the results of SCXRD and confirm the triclinic system of the crystals. The optical properties like absorbance and emission of these crystals are determined using UV–Vis and photoluminescence spectroscopy, respectively. These measurements show that the crystals exhibit substantial emission in the blue region. The thermal stability and the decomposition mechanism of the crystals is studied using TG–DTA analysis. The mechanical strength of the crystals is determined using Vickers microhardness technique. The photoresponse of the NH4H3(C4O8)·2H2O crystals is analyzed from light-dependent I–V characteristics, and it is observed that the crystals exhibit photoresistive behavior.

A fluorescence quenching sensor for Fe3+ detection using (C6H5NH3)2Pb3I8·2H2O hybrid perovskite

A new organic-inorganic hybrid perovskite (C6H5NH3)2Pb3I8·2H2O single crystal has been synthesized through a facile solution method. In this perovskite, there exists a 1D infinite lead iodide chains constituted by Pb3I8 groups, which is surrounded by anilines. As an active fluorescence quenching sensor material, this perovskite shows excellent performance for Fe3+ detection in N, N-dimethylformamide (DMF) solution with a detection limit of 1.0 × 10−7 mol/L, including short response time, high sensitivity and high selectivity. The sensitivity and selectivity towards Fe3+ is much higher than that towards other metal cations, which provides a facile way for detecting Fe3+ cations in solution. Electron paramagnetic resonance (EPR) confirms that the mechanism of fluorescence quenching can be attributed to Fe3+ inhibition to the radiative electron-hole recombination via capturing electrons.

Growth, Properties, and Structure of Cadmium Sulfamate Cd(NH2SO3)2 · 2H2O

The temperature dependence of the solubility of Cd(NH2SO3)2 compound in the range from 25 to 80°C has been determined. It is found that Cd(NH2SO3)2 · 2H2O and Cd(NH2SO3)2 are crystallized from aqueous solution below and above 40°C, respectively. Cd(NH2SO3)2 · 2H2O single crystals are obtained, their structure is solved, and some physicochemical properties are investigated.

Proton conductivity and spectral data of Cs2HPO4 · 2H2O

The Cs2HPO4 · 2H2O single crystals synthesized from an aqueous solution containing equimolar amounts of H3PO4 and Cs2CO3 were studied by impedance and IR spectroscopy, X-ray diffraction analysis, and differential scanning calorimetry (DSC). The IR spectra were analyzed in accordance with the structural data, and the absorption bands were assigned. The proton conductivity was studied at temperatures in the range 20–250°C. The conductivity of dehydrated Cs2HPO4 was low, ~10–5–10–9 S cm–1 at 90–250°C with an activation energy of conductivity E a = 1.1 eV at 130–250°C. The processes determining the character of the temperature dependence of conductivity were consistent with the DSC and thermogravimetry data. According to these data, dehydration of the crystalline hydrate Cs2HPO4 · 2H2O starts at 60°C and occurs in three stages, forming Cs2HPO4 · 1.5H2O below 100°C; anhydrous Cs2HPO4 at t > 160°C, which is stable up to 300°C; and Cs4P2O7 above 330°C.

Growth and Characterization of a Nonlinear Optical Single Crystal: Bis(4-nitrobenzoate) Tetraaquamanganese (II) Dihydrate (BNMD)

Semiorganic optically transparent Bis(4-nitrobenzoate) tetraaquamanganese (II) dihydrate [Mn (p-NO2C6H4COO)2 (H2O)4]·2H2O (BNMD) single crystals were grown by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis was carried out to determine the lattice parameters of the crystal. Powder X-ray diffraction pattern was recorded and indexed for the structural confirmation. The crystalline quality was confirmed by HRXRD. The presence of functional group in the compound has been confirmed by FTIR analysis. UV-Visible transmission spectrum has been recorded to determine the cut-off wavelength region of the crystal. The Second Harmonic Generation of BNMD crystal was confirmed by Kurtz-Perry powder method using Nd:YAG laser and found to be 0.59 times that of KDP. The dielectric response of the crystal was also investigated and reported. The microhardness study reveals that the hardness number (Hv) increases with load. From the values of work hardening coefficients, it was concluded that BNMD crystal belong to the category of soft materials. Thermal studies were performed using differential thermal analysis (DTA).

Growth and characterization of neodymium and ytterbium doped barium chloride dihydrate single crystals

Pure, Nd doped and Nd:Yb co-doped barium chloride dihydrate (BaCl2·2H2O) single crystals were grown and analyzed with various characterization techniques. The measured unit cell parameters show that the grown crystals belong to monoclinic system. Powder X-ray diffraction spectra indicates that the dopants enhance (2 1 0) orientation of BaCl2·2H2O crystal. X-ray rocking curves have been recorded to analyze the crystallinity of the grown single crystals. Optical absorption spectra of the grown crystals contain strong absorption bands in infrared region. Spectral overlap of absorption bands of Yb3+ and Nd3+ ion around 850 nm–1060 nm in Nd:Yb co-doped single crystal indicates the prospect of energy transfer between them. A significant enhancement has been observed in the photoluminescence spectrum of Nd:Yb co-doped single crystal recorded with 244 nm laser excitation. Photon upconversion ability of the crystals was tested using Nd:YAG laser of wavelength 1064 nm. An unusual upconverted green emission from pure centrosymmetric BaCl2·2H2O single crystal has been observed. The energy of upconverted green light of Nd:Yb co-doped barium chloride dihydrate single crystal is higher which may be due to energy transfer occurred between Yb3+ and Nd3+ ions. FTIR and FT-Raman spectral analyses were carried out to study the vibrational modes of pure, Nd doped and Nd:Yb co-doped BaCl2·2H2O single crystals.

Experimental investigation of the EPR parameters and molecular orbital bonding coefficients for VO2+ ion in NaH2PO4·2H2O single crystals

Electron paramagnetic resonance (EPR) spectra of VO2+ ions in NaH2PO4·2H2O single crystal have been studied. The spin-Hamiltonian parameters and molecular orbital bonding coefficients were calculated. The angular variation of the EPR spectra shows two different VO2+ complexes. These are located in different chemical environment and each environment contains four magnetically inequivalent VO2+ sites. The crystal field around VO2+ ion is approximately axially symmetric since a strong V=O bond distorts the crystal lattice. Spin Hamiltonian parameters and molecular orbital bonding coefficients were calculated from the EPR data and the nature of bonding in the complex was discussed together.

Resonance local phonon mode and electron spin-lattice relaxation of formate-type free radicals studied by electron spin echo in Cd(HCOO)2·2H2O crystal

The results of X-band electron spin resonance (ESR) and electron spin echo (ESE) measurements for free radicals generated in Cd(HCOO)2·2H2O single crystal are presented. From ESR spectra analysis the radicals were identified as after x-ray irradiation and as HOCO after γ-ray irradiation. The room temperature g-factors are: g|| = 1.9969 and g⊥ = 2.0024 for and g1 = 2.0087, g2 = 2.0029 and g3 = 1.9960 for HOCO. Axial g-tensor symmetry for is due to fast reorientation of the radical molecule around the g||-axis. Assignment of HOCO is confirmed by hyperfine splitting (Amax = 0.4 mT) from a single distant proton. Spin lattice relaxation rate was determined from ESE measurements in temperature range 4–250 K. Both radicals relax via local resonance mode lying within acoustic phonon branch. The existing theories of electron spin-lattice relaxation via local resonance mode are critically reviewed and compared with experimental data. A new approximation is proposed giving local mode energy = 56 cm−1 for and = 44 cm−1 for the HOCO-radical.

ChemInform Abstract: Crystal Structure of Bis(dimethylammonium) Hexaaquanickel(II) Bis(sulfate) Dihydrate.

AbstractLarge (Me2NH2)2 [Ni(H2O)6] (SO4)2·2H2O single crystals (up to 4 mm crystal size) are grown from an aqueous solution of NiSO4, Me2NH, and H2SO4 (1:2:1) by slow solvent evaporation (room temp., 12 weeks).

Unraveling the mechanism of NO ligand photoisomerism by time-resolved infrared spectroscopy

UV–Vis- and infrared femtosecond spectroscopy makes it possible to reveal all different steps of photochemical reactions after the electronic excitation. The electronic relaxations are observed in the UV–Vis spectral range whereas the nuclear motions are monitored in the infrared spectral range. We used femtosecond time-resolved infrared spectroscopy to demonstrate the photoisomerization of the NO ligand photoinduced by a visible femtosecond pulse in a Na2[Fe(CN)5NO]·2H2O single crystal occurs in about 350fs. The analysis of data makes it possible to unravel the mechanism leading to the photoisomerization of the NO ligand.

EPR, ENDOR and DFT study of l-lysine·HCl·2H 2O single crystals X-irradiated at 66 K

Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR (EIE) results indicated at least three radicals produced in l-lysine·HCl·2H 2O crystals irradiated at 66 K. EPR from radical R1 dominated the spectra and it was identified as the carboxyl anion, (H 2OOĊ) CH (NH 3) + (CH 2) 4 (NH 3) +. Density-Functional Theory (DFT) calculations supported the assignment and indicated that the carboxyl group transformed from planar to a pyramidal configuration following electron trapping. Two small couplings detected from R1 were ascribed to protons transferred to the carboxyl group from neighboring molecules through intermolecular hydrogen bonds. Radical R2 was identified as the product of decarboxylation, ĊH (NH 3) +(CH 2) 4 (NH 3) +. Although it was not possible to obtain R2's α-coupling tensor from the experiment, EPR simulations and DFT calculations provided strong support for the identification. Radical R3 exhibited several β-couplings but could be detected only in one plane and could not be identified.

Investigations of the Phase Transition and Proton Dynamics in Rubidium Methane Phosphonate Studied by Solid-State NMR

In search of new solid acid proton conductors, we prepared the solid acid rubidium methane phosphonate (RMP). These crystals have a monoclinic structure (P2/c; a = 9.3452, b = 9.3142, and c = 7.5021 A; β = 101.12). The salt incorporates a hydrated lamellar structure. The 1H MAS NMR reveals two different types of acidic protons as well as the water protons in the lamella. The 1H VT MAS NMR of RMP·2H2O single crystal shows a structural phase transition around 320 K, and the high-temperature phase exhibits significant proton dynamics. The proton proximities are established by solid state 1H DQF NMR. The dehydration of RMP crystal leads to structural collapse, and the resultant RMP powder is extremely hygroscopic. The proton environment and dynamics are examined using 1H DQF NMR, which reveals that the dehydrated RMP powder has rigid lattice, in contrast with the hydrated form. Further the 1H VT MAS NMR shows that dehydrated RMP powder has no phase transition, and no significant proton dynamics are observed i...

An EPR study of Cu 2+ ions in [Zn(picol) 2(H 2O) 2]·2H 2O single crystals

Electron paramagnetic resonance spectra of Cu 2+-doped [Zn(picol) 2(H 2O) 2]·2H 2O (C 12H 18N 2O 8Zn) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu 2+ ions substitute for magnetically inequivalent Zn 2+ ions. Two magnetically inequivalent sites for Cu 2+ were observed. The spin Hamiltonian parameters were determined and thus, the ground state wave functions of Cu 2+ ions in two sites were constructed.

EPR and Optical Absorption Studies of VO2+ Doped KH2PO4 and KH3C4O8·2H2O Single Crystals

VO2+ doped potassium dihydrogen phosphate (KH2PO4) and potassium tetraoxalate (KH3C4O8 · 2H2O) single crystals and powders are examined by electron paramagnetic resonance and optical absorption spectroscopy. Angular variations of KH2PO4 and KH3C4O8 ·2H2O single crystals show four and two different VO2+ sites, respectively. The local symmetry of VO2+ complexes is nearly axial for both host crystals. The optical absorption spectra show three bands. Spin Hamiltonian parameters are measured and molecular orbital coefficients are calculated by correlating EPR and optical absorption data for the central vanadyl ion

Polarized IR, spontaneous and stimulated Raman spectra of Y(HCOO)3·2H2O single crystal — a new Raman laser material

Polarized Raman and IR spectra have been measured for Y(HCOO)3·2H2O single crystal at room temperature. Assignment of the observed bands to the respective internal and external vibrations was proposed on the basis of factor group approach for the orthorhombic P212121 (D24) space group and the literature data for the other metal formates. The results obtained for the spontaneous Raman scattering have been used in the discussion of the stimulated Raman spectra of the material studied. Copyright © 2006 John Wiley & Sons, Ltd.

A study on new phase transitions in Cs2CaCl4·2H2O single crystals by observation of 133Cs NMR

The 133Cs 1/2→−1/2 spin–lattice relaxation rate, T1−1, and the spin–spin relaxation rate, T2−1, for a Cs2CaCl4·2H2O single crystal have been measured in function of temperature. The dominant relaxation mechanism of this crystal over the whole temperature range investigated here proceeds via quadrupole interaction. The changes in the 133Cs spin–lattice relaxation rate near 325K (=Tc1) and 360K (=Tc2) correspond to phase transitions in the crystal. The change in the spin–lattice relaxation rate at Tc1 is small because the crystal lattice does not change very much during this phase transition. The change in T1−1 near Tc2 is due to the critical slowing down of the soft mode that typically occurs in structural phase transitions. The temperature dependence of the spin–lattice relaxation rate for this crystal has maximum values at about 240K, which is attributable to the effect of molecular motion as described by Bloembergen–Purcell–Pound theory. The phase transition temperatures Tc1 and Tc2 obtained from the temperature dependence of the relaxation rate is also clear from data obtained using differential scanning calorimetry. Therefore, we know that previously unreported phase transitions occur at 325 and 360K.

A New Hydrothermal Route to Prism-shaped CuSeO3·2H2O Single Crystals

Abstract Prism-shaped CuSeO3·2H2O single crystals, with sizes of 0.64–0.77 × 0.45–0.67 × 0.26–0.33 mm, were synthesized via a new hydrothermal reaction of CuCl2·2H2O and Se powder in aqueous ammonia at 180 °C. The double crystal X-ray diffraction rocking curve shows that the single crystals have high quality. And optimum conditions for the growth of CuSeO3·2H2O single crystals are discussed.