Spectrophotometric determination of copper(II) in pharmaceutical,biological and water samples by 4-(2′-benzothiazolylazo)-salicylic acid

A highly sensitive method is proposed to determine copper(II) ions by forming a stable complex through their interaction with 4-(2′-benzothiazolylazo)-salicylic acid (BTAS) at room temperature and pH of about 5.0. The complex gave a maximum absorption at λ = 485 nm with a molar absorptivity coefficient of 2.35·10⁴ l/(mol·cm). The linear range for the copper determination is 0.63–5.04 mg/l. The method can be applied to determine copper ions in different biological specimens like some drugs and water samples.     

Frequency modelling and solution of fluid–structure interaction in complex pipelines

Complex pipelines may have various structural supports and boundary conditions, as well as branches. To analyse the vibrational characteristics of piping systems, frequency modelling and solution methods considering complex constraints are developed here. A fourteen-equation model and Transfer Matrix Method (TMM) are employed to describe Fluid–Structure Interaction (FSI) in liquid-filled pipes. A general solution for the multi-branch pipe is proposed in this paper, offering a methodology to predict frequency responses of the complex piping system. Some branched pipe systems are built for the purpose of validation, indicating good agreement with calculated results.     

Nuclear spin–lattice relaxation and complex motion of macromolecules in solution

The NMR spectral densities of a complex motion consisting of a combination of anisotropic overall motion and internal motion have been derived. Two approximations of the equations derived for the cases of slow, J_slow (ω), and fast, J_fast (ω), internal motions are presented. These equations imply that reduction in spectral density of overall motion can be observed if the maxima of internal and overall motions spectral densities versus temperature are well separated, as for fast internal motion. Slow intramolecular motion influences the values of spectral densities of the overall motion if one of the two spins performs a motion, for example a proton in double minimum of the ¹⁵N-H?···?N hydrogen bond. The analysis presented reveals small differences between the temperature dependencies of spectral densities of the isotropic and anisotropic overall motions. The theory is illustrated by the ¹³C protonated carbon spin-lattice relaxation of α-cyclodextrin macromolecule, using the expected motional parameters: D _∥/D _⊥?≈?5 at room temperature and for a fast or slow internal motion.     

A europium(III) organic ternary complex applied in fabrication of?near UV-based white light-emitting diodes

A β-diketone, 2-acetylfluorene-4,4,4-trifluorobutane-1,3-dione (HAFTFBD), and its three europium(III) complexes, Eu(AFTFBD)₃⋅2H₂O, Eu(AFTFBD)₃(TPPO)₂ and Eu(AFTFBD)₃phen, were designed and synthesized, where TPPO was triphenylphosphine oxide and phen was 1,10-phenanthroline. The complexes were characterized by IR, UV-visible, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The results show that the Eu(III) complexes exhibit a high thermal stability,and wide and strong excitation bands when monitored at 613 nm. Excited by ∼395 nm near UV light, the complexes emitted strong and characteristic red light due to f–f transitions of the central Eu³⁺ ion, and no emission from the ligands was found. The photoluminescence mechanism of the europium(III) complexes was investigated and proposed as a ligand-sensitized luminescence process. Among the three europium(III) complexes, Eu(AFTFBD)₃phen exhibits the highest thermal stability and the most excellent photoluminescence properties. A bright red light-emitting diode was fabricated by coating the Eu(AFTFBD)₃phen complex onto an ∼395 nm-emitting InGaN chip, and the LED showed appropriate CIE chromaticity coordinates (x=0.66, y=0.33). A white LED with CIE chromaticity coordinates (x=0.32, y=0.32) was prepared with Eu(AFTFBD)₃phen as red phosphor, indicating that Eu(AFTFBD)₃phen can be applied as a red component for fabrication of near ultraviolet-based white light-emitting diodes.     

Room-temperature fluorescence of a charge-transfer complex of reserpine in aqueous and aqueous–ethanol media

The room-temperature fluorescence of a charge-transfer (CT) complex different from those of the component donor/acceptor in polar organic solvent is not very common. The phenomenon is even rarer in aqueous medium. The present work demonstrates that a CT complex formed between reserpine (Res) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in aqueous and aqueous–ethanol media exhibits fluorescence at room temperature that is entirely different from those of the components, Res and DDQ. With decreasing polarity of the medium on the addition of ethanol, the fluorescence intensity and also the fluorimetrically determined formation constant of the complex increase, but the fluorescence emission wavelength does not change significantly. The quantum yield of fluorescence of the CT complex systematically decreases with increasing ethanol content of the medium. That the observed fluorescence is due to the CT complex is established by the constancy of the assumed proportionality constant (β) between the fluorescence intensity and the complex concentration measured using different equilibrium concentrations of the complex and also by demonstrating the mirror image relationship between its excitation and emission spectra in aqueous medium. To our knowledge, this is the first report on the room-temperature fluorescence of a CT complex in aqueous solution.     

Temperature effect on fluorescence and UV–vis absorption spectroscopic properties of Dy(III) in molten LiCl–KCl eutectic salt

The spectroscopic properties of Dy(III) in molten LiCl–KCl eutectic salt at high temperature were investigated by time-resolved laser fluorescence spectroscopy (TRLFS) and UV–vis absorption spectroscopy. For the first time, a visible fluorescence of Dy(III) in high-temperature LiCl–KCl eutectic salt was measured due to the electronic transitions from ⁴I_13/2 and ⁴F_9/2 to ⁶H_J/2 (J=7,…,15). The effect of temperature on hypersensitivity for the electronic transitions from the ⁴I_13/2 excited state (～25700 cm^?1) of Dy(III) was confirmed by altering temperature in chloride eutectic salt in accord with optical absorption measurements. The molar absorptivity of ⁴I_13/2←⁶H_15/2 was enhanced with increasing temperature. The fluorescence intensity of Dy(III) followed a simple mono-exponential decay curve, suggesting the formation of a single chemical species in high-temperature LiCl–KCl molten salt.     

An efficient 2-linked carbazolyl β-diketonate europium(III) complex as red phosphor applied in LED

An efficient 2-linked carbazolyl β-diketonate europium(III) complex Eu(ETFMCTFBD)₃phen was designed and synthesized, where ETFMCTFBD was 1-(9-ethyl-7-(trifluoromethyl)-9H-carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione and phen was 1,10-phenanthroline. Eu(ETFMCTFBD)₃phen exhibits high thermal stability and excellent photoluminescence properties. The CIE chromaticity coordinates (x=0.668, y=0.331) are close to the National Television Standard Committee (NTSC) standard values for red. The lowest triplet energy was measured and suggests the photoluminescence process as a ligand-sensitized luminescence process (antenna effect). A bright red light-emitting diode was fabricated by coating the complex phosphor onto a ∼395 nm-emitting InGaN chip. All the results indicate that Eu(ETFMCTFBD)₃phen is a good candidate as a red component in the fabrication of white LEDs with a high color-rendering index.     

Structural feature of calf thymus deoxyribonucleic acid–ruthenium(III) interaction in aqueous solution by difference Fourier transformed infrared spectroscopy

Here is the report on the interaction of ruthenium(III) species with DNA in aqueous solution at pH 7.42 by Fourier transformed infrared difference spectroscopy. Under the physiological pH and molar ratio [Ruthenium]/[DNA]?=?1/80–1/20 direct binding to guanine-N7, adenine-N7, and surprising binding to exocyclic thymine-O2 was found. At low metal concentration no significant shift of the absorption bands was observed, only nonspecific electrostatic binding of ruthenium(III) with negatively charged phosphate groups occurred. The increase of ruthenium(III) concentration caused DNA double helix destabilization and direct binding of the metal cation to guanine-N7 and thymine-O2. At higher ruthenium(III) concentrations denaturation of the DNA helix is evident with no apparent binding of ruthenium(III) to adenine and cytosine. Helix opening allows migration of ruthenium(III) ions from phosphate to available nucleobases (guanine and thymine). No alteration of the sugar phosphate geometry was observed thus confirming that DNA remains in B conformation.     

Determination of the fluorescence lifetime of glyoxal(C_2H_2O_2)water solution by beconvolution

This paper reports that the actual fluorescence lifetime 7.64±0.06ns of a10％-glyoxal water solution is determined for the first time from the laser-induced fluores-cence decay curve detected by the system with a response time in the order of magnitude ofnanosecond and processed by deconvolution on combination with phase plane method and iter-ative convolution method.The experimental method presented in this paper is regarded as aneffective method for measuring the fluorescence lifetime in nanoseconds or even in sub-nanoseconds by means of a detecting system with an order of magnitude of nanosecond.     

Synthesis and Reactivity of Mg(II)–Fe(II)–Fe(III) Hydroxycarbonates

Green rust-like compounds (GRs) were discovered as natural minerals in various hydromorphic soils, where anoxic conditions allow their stability. They may control some redox processes in aquifers and participate to the transformation of various pollutants. Since Mg(II) cations are present in the fields where GRs were discovered, a partial substitution of Mg(II) to Fe(II) leading to intermediate compounds between GRs and usual Mg(II)–Fe(III) hydroxysalts is suspected. Mg(II)–Fe(II)–Fe(II) hydroxycarbonates can be obtained as intermediate oxidation products of (Mg, Fe)(OH)₂ in carbonate-containing aqueous media obeying to [Fe^II _4(1–x)Mg^II _4x Fe^III ₂(OH)₁₂]²⁺ [CO₃ ^2– nH₂O]^–2. TMS spectra at 12 K are similar to those of GRs, i.e., two quadrupole doublets, one due to Fe(II) with a large isomer shift =1.29 mms^–1 (with respect to -iron at room temperature) and quadrupole splitting E _Q=2.76 mms^–1, the other one due to Fe(III) with smaller hyperfine parameters =0.49 mms^–1 and E _Q=0.44 mms^–1. Fe(II) ions oxidise rapidly into Fe(III) with dissolved O₂. The reactivity is similar to that of Fe(II)–Fe(III) hydroxysalts GR, and thus the potential of Mg(II)–Fe(II)–Fe(III) compounds for reducing pollutants.     

Study of tryptophan assisted synthesis of gold nanoparticles by combining UV–Vis, fluorescence, and SERS spectroscopy

We developed a rapid and non-toxic method for the preparation of colloidal gold nanoparticles (GNPs) by using tryptophan (Trp) as reducing/stabilizing agent. We show that the temperature has a major influence on the kinetics of gold ion reduction and the crystal growth, higher temperatures favoring the synthesis of anisotropic nanoparticles (triangles and hexagons). The as-synthesized nanostructures were characterized by UV–Vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), fluorescence, and surface-enhanced Raman scattering (SERS) spectroscopy. The UV–Vis measurements confirmed that temperature is a critical factor in the synthesis process, having a major effect on the shape of the synthesized GNPs. Moreover, fluorescence spectroscopy was able to monitor the quenching of the Trp fluorescence during the in situ synthesis of GNPs. Using Trp as molecular analyte to evaluate the SERS efficiency of as-prepared GNPs at different temperatures, we demonstrated that the Raman enhancement of the synthesized gold nanoplates is higher than that of the gold spherical nanoparticles.     

A highly luminescent complexes of Eu(III) and Tb(III) with norfloxacin and gatifloxacin doped in sol–gel matrix: A comparable approach of using silica doped Tb(III) and Eu(III) as optical sensor

Highly luminescent complexes of Eu and Tb ions with norfloxacin (NFLX) and gatifloxacin (GFLX) were prepared in sol–gel matrix. The red and green emissions of Eu and Tb ions were obtained by the energy transfer from the triplet state of (NFLX) and (GFLX) to the excited emitting states (⁵D₀ and ⁵D₄) of Eu and Tb, respectively. The intensity of the electric field emission bands (⁵D₀→⁷F₂, 617 nm and ⁵D₄→⁷F₅, 545 nm) of Eu and Tb ions were proportional to the concentration of (NFLX at pH 6.0) and (GFLX at pH 3.5) in acetonitrile with excitation wavelengths (λ_ex) (340 and 395) and (370 and 350 nm) for Eu and Tb ions, respectively. The monitored luminescence intensity of the system showed a good linear relationship with the concentration of NFLX within a range of 5×10^?9–5.8×10^?6 and 5×10^?8–1.0×10^?6 mol L^?1 with a correlation coefficient of 0.990, and for GFLX within a range of 2.4×10^?9–3.2×10^?5 and 5×10^?8–8.0×10^?6 mol L^?1 with a correlation coefficient of 0.995. The detection limit (LOD) was determined as 3.0×10^?9 and 1.0×10^?8 mol L^?1 for NFLX and 1.6×10^?10 and 2.0×10^?8mol L^?1 for GFLX. The limit of quantification (LOQ) is 9×10^?9 and 3.0×10^?8 and 4.8×10^?10 and 6.0×10^?8 in case of Eu and Tb, respectively.     

New Pd(II)–mechlorethamine complex: Synthesis,NMR study of hydrolytic activity and in vitro evaluation of antiradical property of new complex and its alkylating precursor

The reaction of PdCl₂ with anticancer-alkylating agent mechlorethamine hydrochloride (CH₃NH(C₂H₄Cl)₂ = HN2 x HCl), in the molar ratio 1:2, affords the complex [CH₃NH(C₂H₄Cl)₂]₂[PdCl₄] ([H2N2]₂[PdCl₄]). Novel Pd(II) complex and the complex precursor mechlorethamine hydrochloride were tested for their antiradical property. Both present weak interaction with 2, 29-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS). Assays with soybean lipoxygenase and with superoxide anion radicals in vitro showed very high radical scavenging activity of the complex, whereas the complex precursor mechlorethamine hydrochloride presents lower inhibition. Hydrolytic activity of new complex with N-acetylhistidylglycine (AcHis–Gly) was also studied. It was established that regioselective cleavage of the amide bond of the investigated dipeptide had occurred after heating at 60 °C and at pH = 1.5 for 36 h.     

Spectroscopic and Theoretical Study of Cyanidin–Aluminum (III) Complexes

Complexation of aluminum (III) with cyanidin, a natural anthocyanidin molecule, has been investigated in methanol and buffered solutions of pH 3.0 and 4.0. Electronic absorption spectroscopy was performed to characterize the stoichiometry and stability of the complexes formed. In investigated solvents, aluminum bonded moderately to cyanidin requiring large mole ratios of the components (up to 200) for the access of complexation. Molar ratio plots showed the formation of only one complex with stoichiometry aluminum (III):cyanidin of 1∶1 in both investigated media. Semiempirical calculations, performed in the Austin Model 1 parameterization, enabled the determination of the structural features of free compounds as well as complex structural modifications caused by chelation of Al(III).     

IR spectra of halothane–acetone complex in liquefied noble gases (Kr and Xe)

The interaction of semiconductor quantum dots and silver nanoparticles (AgNPs) with bacteriorhodopsin (BR), a membrane protein contained in the purple membrane (PM) of Halobacterium salinarum, is studied. It is shown that both types of nanoparticles are adsorbed efficiently on the surface of the purple membranes, modulating the parameters of the bacteriorhodopsin photocycle. Electrostatic interactions are found to be the main cause of the effect of nanoparticles on the bacteriorhodopsin photocycle. These results explain our earlier data on the “fixation” of the bacteriorhodopsin photocycle for protein molecules trapped after incubation of the purple membranes with silver nanoparticles near the location of the “hot spots” of the effect of surface-enhanced Raman scattering (SERS). It is demonstrated that exposure of silver nanoparticles with bacteriorhodopsin in SERS-active regions lowers the amount of bacteriorhodopsin molecules involved in phototransformations.     

Effect of pseudohalides in pentadentate-iron(III) complexes studied by DFT and Mössbauer spectroscopy

Mononuclear iron complexes in which the iron(III) ion is coordinated by a pentadentate Schiff base ligand L⁵ with two phenolate, two imino and one amino group can exhibit a spin crossover. In this contribution experimental results are presented for complexes with cyanate and thiocyanate as co-ligands. Furthermore, theoretical results of quantum chemical calculations of energies and entropies for the low-spin and high-spin state are shown and compared with Mössbauer results. We also demonstrate how the ligand field of the monodentate co-ligand influences the spin crossover energies and entropies in [Fe^IIIL⁵NCY] complexes.     

Photodynamics of Ga_(Zn)–V_(Zn) complex defect in Ga-doped ZnO

The wide-band-gap II–VI compound semiconductor ZnO is regarded as a promising single-photon emission(SPE)host material. In this work, we demonstrate that a(GaZn–VZn)-complex defect can readily be obtained and the density can be controlled in a certain range. In analogy to nitrogen vacancy centers, such a defect in ZnO is expected to be a new single photon source. The optical properties of the(GaZn–VZn)-complex defect are further studied by photoluminescence and time-resolved photoluminescence spectra measurements. The electron transitions between the defect levels emit light at ～ 650 nm with a lifetime of 10–20 nanoseconds, indicating a good coherent length for SPE. Finally, a two-level emitter structure is proposed to explain the carrier dynamics. We believe that the photodynamics study of the(GaZn–VZn)-complex defect in this work is important for ZnO-based quantum emitters.     

Identification of Structure and Position of Cu(II) Ion in Aquomethylmelonatozinc(II) Host by Powder XRD, EPR, FT-IR and UV–Vis Spectroscopy

Single-crystal electron paramagnetic resonance studies of Cu(II)-doped aquomethylmelonatozinc(II) are carried out at 300 K. Angular variation of copper hyperfine lines in the three orthogonal planes shows the presence of a single site in substitutional position, with spin Hamiltonian parameters: g ₁₁ = 2.076, g ₂₂ = 2.100, g ₃₃ = 2.379; A ₁₁ = 2.40 mT, A ₂₂ = 3.22 mT and A ₃₃ = 13.47 mT. The low value for the hyperfine structure parameter value for A ₃₃ has been explained by taking into account a considerable admixture between d_{x² - y²} d_{{x^{2} - y^{2} }} ground state and d_z² d_{{z^{2} }} excited state, with admixture coefficients being a = 0.291, b = 0.951, c = 0.054, d = 0.031 and e = −0.031, where coefficients a and b correspond to coefficients for d_z² d_{{z^{2} }} and d_{x² - y²} , d_{{x^{2} - y^{2} }} , respectively. Few other calculated parameters such as κ = 0.35, P = 303 × 10⁻⁴ cm⁻¹; α = 0.88 and α′ = 0.47 indicate considerable covalency. Powder X-ray diffraction, Fourier transform infrared and ultraviolet-visible data confirm the structure of host complex and presence of the dopant.     

Study on the Cofluorescence Effect of Europium (III)–Yttrium (III)–Balofloxacin–Sodium Dodecyl Sulfate System and Its Analytical Application

A new fluorescence enhancement phenomenon in the europium(III)–balofloxacin–sodium dodecyl sulfate system was observed when yttrium(III) was added. Based on this, a sensitive cofluorescence assay for the estimation of balofloxacin was established. Under the optimized conditions, the enhanced fluorescence signal was linear over the concentration of balofloxacin ranging from 3.0 × 10^?9 to 7.0 × 10^?6 mol L^?1 with a correlation coefficient of 0.9993. The detection limit (3 σ) was determined as 8.3 × 10^?10 mol L^?1. The presented method was successfully applied to determination of balofloxacin in pharmaceutical preparations, human serum, and urine. The possible fluorescence enhancement mechanism was also discussed.