9, 10-Bis(8-Quinolinoxymethyl)Anthracene—A Fluorescent Sensor for Nanomolar Detection of Cu2+ with Unusual Acid Stability of Cu2+-Complex

In this work, the dipod 9,10-bis(8-quinolinoxymethyl)anthracene (1) and for comparison, monopod 9-(8-quinolinoxymethyl)anthracene (2) have been synthesized. The fluoroionophore 1 in pH 7.1 HEPES buffered CH₃CN:H₂O (4:1 v/v) solution shows quenching only with Cu²⁺ with lowest limit of detection 150 nM, amongst various metal ions. Fluoroionophore 1 could also be applied to sense Co²⁺ with lowest limit of detection 600 nM. By modulating the pH of the solution and concentration of Cu²⁺, 1 shows respective “On-Off-On” and “On-Off” fluorescent switching. The self-assembly of two Cu²⁺ ions and two molecules of fluoroionophore 1 to form closed structure [Cu₂(L)₂]⁴⁺ seems to be responsible for nanomolar sensitivity towards Cu²⁺. The combination of delayed second protonation of 1 (pK_a2?=?2.6) and stepwise protonation of [Cu₂ L ₂]⁴⁺ causes unusual stability of [Cu(LH)₂]⁴⁺ even at pH?<?2.

A photoemission study (XPS and UPS) of the superconductor ErBa2Cu4O8 and comparison with YBa2Cu3O7-δ(δ≈0,1)

Core level and valence band photoemission spectra of the 124 superconductor ErBa₂Cu₄O₈ are investigated using MgK , HeI, and HeII radiation and compared with photoemission spectra of orthorhombic YBa₂Cu₃O₇ and tetragonal YBa₂Cu₃O_6.2 samples. It is found that the Cu 2p _3/2 core level and the UPS valence band spectra of ErBa₂Cu₄O₈ and YBa₂Cu₃O₇ are very similar but differ significantly from those of YBa₂Cu₃O_6.2. From the resemblance between the ErBa₂Cu₄O₈ and YBa₂Cu₃O₇ spectra it follows that the electronic structures of these two compounds are closely related in spite of an additional CuO chain in the 124 phase. The differences between the YBa₂Cu₃O_6.2 spectra and the other spectra are explained by the the presence of monovalent copper at the crystallographic Cu(1) sites. The Cu 2p _3/2 lineshapes of the here studied superconductors and some Cu^II compounds are discussed.     

Level-crossing-Untersuchung der Hyperfeinstruktur des 3d 10 4p 2 P 3/2-Terms von Cu63 und Cu65

The level-crossing technic has been used to investigate the hyperfinestructur of the 3d ¹⁰ 4p ² P _3/2-term in Copper I by scattering the resonance line λ=3248 Å on an atomic beam of separated isotop Cu⁶³ respectively Cu⁶⁵ in an external magnetic field. From the level-crossing signals values for the magnetic dipol interaction constantsA and for the electric quadrupol interaction constantsB are deduced to beeA(Cu⁶³)=(194,72±0,15) Mc/secB(Cu⁶³)=?(28,8±0,6) Mc/secA(Cu⁶⁵)=(208,57±0,15) Mc/secB(Cu⁶⁵)=?(25,9±0,6) Mc/sec. With theA-value of the 3d ¹⁰ 4p²P_1/2-term from optical measurements the ratioA(² P _3/2)∶A(² P _1/2)≈0,4 is about twice greater than for an unperturbetalkali-like²P-term. From the width of the level-crossing signals a mean lifetime of the 3d¹⁰ 4p²P_3/2-term τ=(7,0±0,2) · 10^?9 sec is deduced.     

Optically induced structural transformation in disordered kesterite Cu2ZnSnS4

The kesterite-structured semiconductor Cu₂ZnSnS₄ is one of the most promising compound for earth-abundant low-cost solar cells. One of the complex problem on this way deals with its stoichiometry. In this work Raman spectra of Cu-rich Cu₂ZnSnS₄ crystals are discussed in connection with the non-stoichiometric composition and disordering within the cation sublattice of the kesterite. The shift of the main A-peak from 338 to 331 cm^?1 and its broadening are attributed here to transition from the kesterite (I $\bar 4$ symmetry) to the disordered kesterite structure (I $\bar 4$ 2m symmetry). It is shown that this transition may also be driven by an intense light, which could stimulate transformation of Cu⁺-ion to Cu²⁺-ions and facilitates generation of Cu_Zn-defects on 2d-crystalographic positions.     

Critical wetting and surface-induced continuous phase transition on Cu3Au(001)

In the bulk Cu₃Au is known to undergo adiscontinuous order-disorder phase transition atT ₀=663 K. Spin polarized low-energy-electron diffraction (SPLEED) reveals acontinuous surface-induced order-disorder phase transition-equivalent to a critical wetting transition—on the surface of Cu₃Au. The results indicate that nearT ₀ the observed singularity is related to the surface order parameter which can be described by a functional dependence of the formt ¹ with ¹=0.77±0.06.     

Investigations of EPR g Factors and Rhombic Distortion for the Rhombic Cu2+ Centers in K2Zn1?x Cu x F4 Crystals at Low Temperature

The electron paramagnetic resonance g factors g _i (i?=?x, y, z) of two rhombic Cu²⁺ centers, Cu²⁺(II) and Cu²⁺(III), in K₂Zn_1?x Cu _x F₄ crystals found at low temperature are calculated from the complete diagonalization (of energy matrix) method based on the cluster approach. The calculations show that the ground state wave function of the two rhombically compressed Cu²⁺ centers is $ | {d_{{z^{2} }} }\!\!> $ with a small admixture of $ | {d_{{x^{2} - y^{2} }} } \!\!> $ . The rhombic distortions for both Cu²⁺ centers are obtained from the calculations. The results are discussed.     

Growth, EPR and optical absorption spectra of l-threonine single crystals doped with Cu ions

We investigated the crystal growth, electron paramagnetic resonance (EPR) and optical absorption spectra of l-threonine doped with Cu²⁺. The quality, size and habit of the single crystals grown from aqueous solution by the slow solvent evaporation and by the cooling methods vary when the impurities are introduced during the growth process. The variations with the magnetic field orientation of the EPR spectra of single-crystal samples at room temperature and 9.77 GHz in three crystal planes (ab, bc and ac) show the presence of copper impurities in four symmetry-related sites of the unit cell. These spectra display well resolved hyperfine couplings of the of Cu²⁺ with the I_Cu= of the copper nuclei. Additional hyperfine splittings, well-resolved only for specific orientations of the magnetic field, indicate that the copper impurity ions in the interstitial sites have two N ligands with similar hyperfine couplings. The principal values of the g and A_Cu tensors calculated from the EPR data are g₁=2.051(1), g₂=2.062(2), g₃=2.260(2), A_Cu,1=16.9(5)×10⁻⁴ cm⁻¹, A_Cu,2=21.8(6)×10⁻⁴ cm⁻¹, A_Cu,3=180.0(5)×10⁻⁴ cm⁻¹. The principal directions corresponding to g₃ and to A_Cu,3 are coincident within the experimental errors, reflecting the orientation of the bonding planes of the copper ions in the crystal. The values of the crystal field energies are evaluated from the optical absorption spectrum, and the crystal field and bonding parameters of the Cu impurities in the crystal are calculated and analyzed. The EPR and optical absorption results are discussed in terms of the crystal structure of l-threonine and the electronic structure of the Cu²⁺ ions, and compared with data reported for other systems. The effects of the impurities in the growth and habit of the crystals are also discussed.     

On theg≃2 ESR resonance in YBa2Cu3O7-y high-T c superconductor

Various samples of single-phase YBa₂Cu₃O_7–y have been examined by X-band ESR in theg2 region forTT _c .The observed spectra are attributed to oxygen coordinated Cu²⁺ ions with a large delocalization of the unpaired spins. These are probably due, in part, to the inclusion of some impurity phase. However, an analysis of the intensity as a function of the temperature in different samples indicates that a possible intrinsic contribution to the ESR signal of Cu²⁺ ions from the superconducting phase is due, at most, to 1% of the total copper in the formula. This small quantity of isolated Cu²⁺ ions may be due to the presence of low symmetry Cu³⁺ ions or, equivalently, non-magnetic centers such as Cu²⁺–O^– pairs in the chains.CISM (M.P.I.) and GNSM (C.N.R.)     

Hyperfine field of156Gd in Tb(Zn1−xCux) with x=0, 0.36, 0.46

Time-integral - perturbed angular correlation measurements have been made on¹⁵⁶Gd nuclei in TbZn_1–xCu_x using two Ge(Li) detectors. The hyperfine fields at¹⁵⁶Gd nuclei in TbZn_1–xCu_x at 77 K are found to be –177±26, –104±24 and –27±38 kOe for TbZn, TbZn_0.64Cu_0.36 and TbZn_0.54Cu_0.46, respectively. These values indicate that the transferred hyperfine fields at Gd nuclei are positive due to the exchange interaction of s-f type.     

On the structure of non-superconducting YBa2Cu3O6+ɛ

The crystal structure of non-superconducting, tetragonal YBa₂Cu₃O₆₊ ( close to 0) (s.g.P4/mmm) was studied at room temperature by means of single crystal X-ray diffraction, electron microscopy and electron diffraction. Crystals may easily be obtained by heating YBa₂Cu₃O₇ samples under vacuum. For 0, the tetragonal single crystals are chemically and crystallographically homogeneous — without any twin domains. The only defects immediately apparent are stacking faults alongc. The structure is very closely related to that of the high-T _c superconductor YBa₂Cu₃O₇. The most important difference is, that the oxygen on theb-axis (O(1)), which together with Cu(1) forms Cu–O–Cu–O-chains alongb in YBa₂Cu₃O₇, is vacant in YBa₂Cu₃O₆. Some crystals show a superstructure with superstructure reflections which are sharp in thea ^*–a ^*-plane but form diffuse streaks alongc ^*. We propose a model which relates these superstructure reflections to a 2-dimensional ordering of residual oxygen atoms on the O(1) site (corresponding to >0 in the chemical formula YBa₂Cu₃O₆₊).     

Biharmonic pumping in dye lasers with distributed feedback

Conclusions We have shown that biharmonic pumping can effectively excite traveling population gratings in an active medium when m <(W_o/2 +1/T₁), and temperature gratings if m <(₀x_m)^–1. As the order m increases the population-grating excitation efficiency decreases, while that of the temperature gratings may either increase or decrease. The times taken for the thermal and resonance processes which form the gratings to build up are given by the expressions t=₀x_m, t =T₁/(1 +W₀T₁/2), respectively. In this case distributed feedback is formed by a thermal mechanism if (14) is satisfied, and by resonance mechanism if the opposite inequality is satisfied. The self-excitation threshold over a wide range of parameters depends logarithmically on the amplitude of the grating forming the distributed feedback. Hence, for a comparatively small excess of the threshold, self-excitation of a laser with distributed feedback is possible over a wide spectrum. Thus, for double excess of the self-excitation threshold and T₁ =10^–9 sec, =1, and H =8 lasing over a wide spectrum of 10 cm^–1 is possible.Translated from Zhurnal Prikladnoi Spektroskipii, Vol. 40, No. 2, pp. 195–202, February, 1984.We wish to thank A. A. Afanasev and P. A. Apanasevich for useful discussions.     

Structural characterisation of [Cu2(bptd) (H2O) Cl4] and [Ni2(bptd)2(H2O)4] Cl4·3H2O; evidence of null intramolecular exchanges by EPR and magnetic measurements

Using the 2,5-bis(2-pyridyl)-1,3,4-thiadiazole (bptd), we recently prepared [Cu₂(bptd) (H₂O) Cl₄] and [Ni₂(bptd)₂ (H₂O)₄] Cl₄, 3H₂O in which the magnetic centres are connected through one diazine+one chloro and two diazine ligand bridges, respectively. These two compounds are the first examples that show null intramolecular magnetic interactions despite M-M distances close to 3.7 Å within perfectly planar edifices:Down to , [Cu₂(bptd)Cl₄(H₂O)] is paramagnetic while, below T_t, half of the Cu²⁺ions interact, leading to residual paramagnetism of one Cu²⁺/f.u. Magnetic susceptibility measurements, EPR and pulsed EPR study indicate the original intermolecular nature of AF exchanges.[Ni₂(bptd)₂(H₂O)₄]Cl₄·3H₂O susceptibility obeys a Curie-law involving pure paramagnetism. Moreover, its EPR spectrum can be interpreted on the basis of virtual S=1 monomers. Below 70 K, Zero Field Splitting (D∼275 G) due to dipolar interactions without magnetic exchanges could be responsible for the LT spectra splitting. For both compounds, the thia role is suggested as partially responsible for the null-in-plane magnetic exchanges.     

Studies of the spin-Hamiltonian parameters, d–d transitions and defect structures for two tetragonal Cu centers in Ba2ZnF6:Cu crystal

Two theoretical methods, the perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM), are applied to calculate the spin-Hamiltonian parameters (g-factors g, g and hyperfine structure constants A, A, obtained from electron paramagnetic resonance (EPR) spectra) and d–d transitions (obtained from optical spectra) for two tetragonal Cu²⁺ centers in Ba₂ZnF₆:Cu²⁺ crystals. The Cu²⁺(I) ion replaces the Zn²⁺ ion at tetragonally compressed octahedral coordination and has the ground state ²A₁(|d_z²), whereas the Cu²⁺(II) ion is at an interstitial site with a square-planar F⁻coordination and has the ground state ²B₂(|d_x²-y²). The calculated spin-Hamiltonian parameters and d–d transitions from the PTM and CDM coincide and are in reasonable agreement with the experimental values. This suggests that both methods are effective for the theoretical studies of EPR and optical spectral data for 3d⁹ ions in tetragonal symmetry with different ground states. The defect structures of the two Cu²⁺ centers in Ba₂ZnF₆:Cu²⁺ are also estimated.     

Electrochemical behavior and DNA-binding properties of binuclear copper(II) complex containing mixed ligands of N-hydroxyethylaminoethyl oxamido and 2,2′-bipyridine

The electrochemical property of dinuclear copper(II) complex containing mixed ligands of N-hydroxyethylaminoethyl oxamido and 2,2′-bipyridine [Cu₂(bpy)₂(HAO) ₂ ²⁺ ] was studied with cyclic voltammetry. Cu₂(bpy)₂(HAO) ₂ ²⁺ had irreversible oxidation peaks in 0.1 mol/L NaCl solution at the stearic acid-modified carbon paste electrode. Cyclic voltammetry and absorption spectra measurements were used to study the interaction between Cu₂(bpy)₂(HAO) ₂ ²⁺ and herring fish sperm DNA. All the experimental results showed that Cu₂(bpy)₂(HAO) ₂ ²⁺ interacted with DNA mainly through electrostatic affinity to make tiny difference between Cu₂(bpy)₂(HAO) ₂ ²⁺ –ssDNA and Cu₂(bpy)₂(HAO) ₂ ²⁺ –dsDNA. The binding ratio and the binding constant of DNA–Cu₂(bpy)₂(HAO) ₂ ²⁺ were calculated as 1:1 and 6.41?×?10⁴, respectively. The redox peak current of Cu₂(bpy)₂(HAO) ₂ ²⁺ decreased markedly after its interaction with DNA. This was used to detect the concentration of DNA quantitatively.     

New Application of a Known Molecule: Rhodamine B 8-hydroxy-2-quinolinecarboxaldehyde Schiff Base as a Colorimetric and Fluorescent “Off-On” Probe for Copper (II)

Rhodamine B 8-hydroxy-2-quinolinecarboxaldehyde Schiff base (1) has been investigated as a colorimetric and fluorescent “off-on” probe for the recognition of Cu²⁺ in aqueous solution. Probe 1 was synthesized by condensation of rhodamine B hydrazide and 8-hydroxy-2-quinolinecarboxaldehyde, which exhibited good selectivity for Cu²⁺ among a range of biologically and environmentally important metal ions. The Cu²⁺ recognition event undergoes a Cu²⁺ promoted hydrolysis of probe 1 to release rhodamine B and the recognition process is barely interfered by other coexisting metal ions.

The hole concentration on oxygen sites in the highT c superconductor Y1−Ba2−Cu3−O7−x

From XPS core level spectroscopy the average copper charge on the Cu sites in the high temperature superconductor Y₁Ba₂Cu₃O_7–x is determined as function of the oxygen vacancy concentrationx. Analysis of these data leads to the suggestion that there are holes on the oxygen sites in the basal plane of the crystal structure. The probability for holes on these oxygen ions is rather constant for 0x0.3 with a value of 0.64 and decreases to zero forx=0.5. The dependence of the superconducting transition temperature on the hole concentration is discussed. An energy level diagram for Cu²⁺ and Cu³⁺ in YBa₂Cu₃O_7–x is constructed.     

A comparison of high-T c superconductors: Specific heat in magnetic fields at very low temperatures

We discuss specific-heat,C(T), results on YBa₂Cu₃O_7–(=0.13, 0.99) and Bi₂Sr₂CaCu₂O₈. For completion, we compare these with literature data on La_1.85Sr_0.15CuO₄ and La₂CuO₄ by emphasizing the data at lowest temperatures,T0.45K. The strong upturn inC(T)/T found atB=0 is predominantly associated with a splitting of nuclear states by quadrupolar interactions. The shift of this upturn towards higher temperatures, when magnetic fields up to 8 T are applied, indicates additional hyperfine splitting. For YBa₂Cu₃O_6.87 and Bi₂Sr₂CaCu₂O₈, subtraction of the nuclear specific heat from the raw data reveals a spin-glass derived contribution ^*(T,B), with ^* being strongly depressed upon both warming and applying externalB-fields. The probable source for ^* T are impurity phases (in YBa₂Cu₃O_7–) and/or frustrated Cu²⁺ moments created by lattice defects. Any intrinsic linear specific heat, ⁱ , due to, e.g., spinon excitations or normal electronic carriers, would have to imply ⁱ <1 mJ/K² mole_f.u. for each of these two compounds.Dedicated to Prof. Dr. G. von Minnigerode on the occasion of his 60th birthday     

Effect of phase transition and particle size on thermoluminescence characteristics of nanocrystalline K2Ca2(SO4)3:Cu+ phosphor

A new K₂Ca₂(SO₄)₃:Cu⁺ nanocrystalline TLD phosphor was prepared by chemical coprecipitation method using calcium chloride, potassium chloride and ammonium sulphate as reactants and copper chloride (Cu₂Cl₂, as impurity) in the presence of ethanol. The samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Differential thermal and thermogravimetric analysis (DT-TGA) techniques. XRD and DTA data show that there is a phase transformation from orthorhombic to cubic occurring at around 550 K. The effects of impurity concentration, annealing temperature and γ rays dose on TL characteristics of the material have been studied. Different glow curves have been theoretically deconvoluted using computerized glow curve deconvolution (CGCD method) into simple glow peaks to determine their trapping parameters. The results show that different phases existing in the material on annealing might have reorganized the electron-traps (energy levels) and hole-traps (luminescence centers) and are responsible for changing glow curve structures. This is very important to know as any change in the glow curve structure would cause errors in estimation of doses of high-energy radiations and also may lose its reusability. The photoluminescence (PL) studies show that there are no redox reactions (Cu⁺

Cu²⁺) taking place and Cu remains in its Cu⁺ form after annealing and even after irradiation.     

Bis(2-Hydroxy-3-Isopropyl-6-Methyl-Benzaldehyde)Ethylenediamine: A Novel Cation Sensor

Novel substituted phenol-based new symmetrical bis(2-hydroxy-3-isopropyl-6-methyl-benzaldehyde)ethylenediamine (1) has been designed and synthesized. The compound 1 fluorometrically recognized Cu²⁺ ion in CH₃OH/H₂O (90:10, v/v) by exhibiting an increase in emission upon complexation. In addition, Cu²⁺ gave rise to a change in colour of the solution of compound 1, which was clearly visible to the naked eye under UV irradiation. The association constant (K) of compound 1 with Cu²⁺ ion was computed with the Benesi-Hildebrand plot and Scatchard plot at 43,000 M^?1 and 43,011 M^?1 respectively.