Spectral Investigations on Cu<Superscript>2+</Superscript>-Doped ZnO Nanopowders

Cu²⁺-doped ZnO nanopowders, synthesized at room temperature by mild and simple solution method, are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), optical, electron paramagnetic resonance (EPR) and Fourier-transform infrared (FT-IR) techniques. From XRD and SEM, the crystal structure is identified as hexagonal, and the average crystallite size is around 53 nm. Lattice cell parameters are evaluated. The optical and EPR spectral investigations suggest that the Cu²⁺ ion enters the host lattice in two tetragonally distorted octahedral sites. Crystal field, tetragonal field, spin Hamiltonian and bonding parameters are estimated.     

Studies on Interaction of Norfloxacin,Cu<Superscript>2+</Superscript>, and DNA by Spectral Methods

The interactions of norfloxacin (NFA), DNA, and Cu²⁺ are studied by fluorescence and UV-spectra method. According to the experimental results, it can be concluded that NFA can form a steady binary complex with Cu²⁺. There is a linear relationship between the Fluorescence intensity of the norfloxacin–Cu²⁺–DNA system and the concentration of DNA. And when the concentration of the NFA is 1.95×10⁻⁵ mol L⁻¹, they possess a good linearity in the concentration of DNA ranged from 4.7×10⁻⁶ to 2.8×10⁻⁵ mol L⁻¹.It is a good method due to the high sensitivity and selectivity.     

A Dual-Target Fluorescent Probe with Response-Time Dependent Selectivity for Cd<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A novel fluorescent probe (NT) was developed by merging 2-hydrazinylbenzothiazole with 2-hydroxy-1-naphthaldehyde for the detection of Cd²⁺ and Cu²⁺. The probe alone is almost nonfluorescent due to the isomerization of C=N in the excited state. The addition of Cd²⁺ can cause an immediate strong green fluorescence owing to the suppression of C=N isomerization by Cd²⁺-coordination. Furthermore, NT gives a delayed turn-on fluorescence response to Cu²⁺ although it is a vigorous fluorescence quencher, which was thanks to the inhibition of the electron transfer between excited fluorophore and paramagnetic Cu²⁺ by sulfur donor. Based on fluorescence spectra and ESI-MS analysis, the binding modes between NT and Cd²⁺/Cu²⁺ were proposed.     

Coumarin Based Fluorescent Probe for Colorimetric Detection of Fe<Superscript>3+</Superscript> and Fluorescence Turn On-Off Response of Zn<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A new coumarin based Schiff-base chemosensor-(E)-7-(((8-hydroxyquinolin-2-yl)methylene) amino)-4-methyl-2H-chromen-2-one (H ₁₁ L) was synthesized and evaluated as a colorimetric sensor for Fe³⁺ and fluorescence “turn on-off” response of Zn²⁺ and Cu²⁺ using absorption and fluorescence spectroscopy. Upon treatment with Fe³⁺ and Zn²⁺, the absorption intensity as well as the fluorescence emission intensity increases drastically compared to other common alkali, alkaline earth and transition metal ions, with a distinct color change which provide naked eye detection. Formation of 1:1 metal to ligand complex has been evaluated using Benesi-Hildebrand relation, Job’s plot analyses, ¹H NMR titration as well as ESI-Mass spectral analysis. The complex solution of H ₁₁ L with Zn²⁺ ion exhibited reversibility with EDTA and regenerate free ligand for further Zn²⁺ sensing. H ₁₁ L exhibits two INHIBIT logic gates with two different chemical inputs (i) Zn²⁺ (IN1) and Cu²⁺ (IN2) and (ii) Zn²⁺ (IN1) and EDTA (IN2) and the emission as output. Again, an IMPLICATION logic gate is obtained with Cu²⁺ and EDTA as chemical inputs and emission as output mode. Both free ligand as well as metal-complexes was optimized using density functional theory to interpret spectral properties. The corresponding energy difference between HOMO-LUMO energy gap for H ₁₁ L, H₁₁L-Zn²⁺ and H₁₁L-Cu²⁺ are 2.193, 1.834 and 0.172 eV, respectively.     

EPR and Optical Study of Cu<Superscript>2+</Superscript> Ions Doped in Sodium Zinc Sulfate Tetrahydrate Single Crystals

Electron paramagnetic resonance (EPR) study of Cu²⁺-doped sodium zinc sulfate tetrahydrate is done at liquid nitrogen temperature. Two magnetically equivalent sites for Cu²⁺ are observed. The spin-Hamiltonian parameters determined by fitting the EPR spectra to the rhombic-symmetry crystalline field are g _x  = 2.2356, g _y  = 2.0267, g _z  = 2.3472, A _x  = 27 × 10⁻⁴ cm⁻¹, A _y  = 54 × 10⁻⁴ cm⁻¹and A _z  = 88 × 10⁻⁴ cm⁻¹. The ground state wave function is also determined. The g-anisotropy is evaluated and compared with the experimental value. With the help of optical study, the nature of bonding in the complex is discussed.     

Optical alignment of Cu<Superscript>2+</Superscript> axial centers in KTaO<Subscript>3</Subscript>: Spectral dependence of the effect

The Cu _Ta ²⁺ -V_O axial centers in crystalline KTaO₃ were found to undergo alignment under the action of polarized light. The sign of the effect is shown to change depending on the wavelength of the aligning light. A parallel study of the spectral response of photoconductivity of the same samples led to the conclusion that the alignment of the copper centers is driven not by reorientation but rather by an anisotropic recharging of the centers, which involves both the conduction and valence bands of the crystal. This interpretation was supported by a study of the kinetics of thermal destruction of the copper center alignment.     

Spectral Investigations on Ho3+ Doped Mixed Alkali Chloroborate Glasses

The optical absorption and emission spectra of two different Ho³⁺ doped mixed alkali chloroborate glasses have been studied in the ultraviolet-visible near-infrared regions. Various spectroscopic parameters like Racah (E¹, E², and E³), spin orbit (ξ_4f), and configuration interaction (α) parameters have been calculated. From the measured spectral intensities of the various absorption bands of Ho³⁺ ion, the Judd–Ofelt intensity parameters (Ω₂, Ω₄, and Ω₆) have been evaluated and covalency was studied as a function of x in the glass matrices. Using these parameters, radiative transition probabilities, radiative lifetimes, branching ratios, and integrated absorption cross-sections have been calculated and reported for certain excited states of Ho³⁺ ion. From the emission spectra, stimulated emission cross-sections are determined for the emission transitions, ⁵F₄, ⁵S₂?→?⁵I₈, and ⁵F₅?→?⁵I₈ in these two mixed alkali chloroborate glasses. An attempt has been made to throw some light on the environment of Ho³⁺ ions in these glass systems by studying the variation in various spectroscopic parameters.     

An EPR Study of Cu<Superscript>2+</Superscript> Doped Portlandite,Brucite and Hydrotalcite

The powder EPR spectra of portlandite (Ca(OH)₂), brucite (Mg(OH)₂) and hydrotalcite ([Mg₃Al(OH)₈]⁺[0.5CO ₃ ^- ·nH₂O]^-), doped with ⁶³CU²⁺, have been measured as a function of temperature. In all materials a static, temperature independent Jahn-Teller site and a dynamic, temperature dependent Jahn-Teller site was observed. In the rapidly reorienting situation the EPR spectrum of the dynamic site is still anisotropic. From the observed anisotropy it could be inferred that the hydroxyde ions surrounding the Cu²⁺ ion are situated at the vertices of an elongated octahedron which is compressed along its trigonal axis (c-axis). The angle between the axis of elongation of the Cu octahedra and the c-axis turned out to be 490 both for portlandite and brucite. The temperature range over which the averaged dynamic site could be observed varied considerably for the three materials.     

Intense Upconversion Luminescence of Yb<Superscript>3+</Superscript>-Er<Superscript>3+</Superscript> in Li<Subscript>2</Subscript>O Content Tungsten-tellurite Glasses

The Er³⁺ -Yb³⁺ codoped in Li₂O content tungsten -tellurite (TWL) transparent glasses are synthesized and measured the absorption, Raman and upconversion luminescence (UPL) spectra. At room temperature intense green emission peak at 560 nm ( ⁴S_3/2→⁴I_15/2) and red emission peak at 670 nm ( ⁴F_9/2→⁴I_15/2) of Er³⁺ observed even at minimum 86 mW pumping power of infrared 980 nm excitation. For structure of the TWL glass, Raman spectrum result revealed that an important role of WO₃ in the formation of glass network linkage with Li₂O. Under this influence estimated lifetime of the ⁴I_11/2 of Er³⁺ was 1.89 μs and due to lower phonon energy of the glass produce strong upconversion signal. The effect of Er₂O₃ concentration on emission intensity result indicated that green emission intensity initially increase in compare to red emission. Under the 980 nm pump power variation measured the relatively increases the red emission to the green emission intensity and analyze the possible upconversion mechanism and process.     

Structural Properties of Cr<Superscript>3+</Superscript>-Doped Cadmium Oxide Nanopowders

The Cr³⁺-doped cadmium oxide nanopowder is prepared at room temperature by a mild and simple solution method. The prepared powder is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical, electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) techniques. The XRD powder pattern reveals the lattice structure and cell parameters are evaluated. The SEM image shows the stone-like morphology of the nanopowder. The optical absorption spectrum indicates the distorted octahedral site symmetry of Cr³⁺ ions. The crystal field Dq and interelectronic repulsion parameters B and C are evaluated. The EPR spectrum gives a resonance signal at g = 1.973 for Cr³⁺ ions. The FT-IR spectrum reveals the characteristic vibrations of cadmium oxide.     

Mid-Infrared Emission Characteristic and Energy Transfer of Ho<Superscript>3+</Superscript>-Doped Tellurite Glass Sensitized by Tm<Superscript>3+</Superscript>

We report on 2.0-μm emission characteristic and energy transfer of Ho³⁺-doped tellurite glass sensitized by Tm³⁺ upon excitation of a conventional 808 nm laser diode. The Judd-Ofelt strength parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho³⁺ have been calculated from the absorption spectra by using the Judd-Ofelt theory. Significant enhancement of 2.0-μm emission of Ho³⁺ has been observed with increasing Tm³⁺ doping up to 0.7 mol%. The energy transfer coefficient of the forward Tm³⁺→Ho³⁺ is approximately 17 times larger than that of the backward Tm³⁺←Ho³⁺ energy transfer. Our result indicates that the maximum gain of 2.0-μm emission, assigned to the transition of ⁵I₇→⁵I₈ of Ho³⁺, might be achieved from the tellurite glass at the concentration of 0.5 mol% of Tm₂O₃ and 0.15 mol% of Ho₂O₃. The high gain coefficient and quantum efficiency (1.16) along with the large value of the product of the stimulated emission cross-section and the measured radiative lifetime (4.12×10⁻²⁷ m²s) of the Ho³⁺/Tm³⁺-codoped tellurite glasses might find potential applications in efficient 2.0-μm laser.     

Synthesis and Properties of a Novel FRET-Based Ratiometric Fluorescent Sensor for Cu<Superscript>2+</Superscript>

A novel FRET-based probe LS3 was designed and synthesized. As expected, it exhibited high selectivity and sensitivity for detecting Cu²⁺ over other commonly coexistent metal ions. The detection limit was measured to be 0.0423 μM for Cu²⁺, which can meet the selective requirements for practical application. In addition, the newly synthesized compound 3a/b have potential value of further synthesizing more analogous FRET-based probes.     

Paramagnetic resonance and off-center location of Cu<Superscript>2+</Superscript> ions in ferroelectric lead germanate

This paper reports on the results of investigations into the orientation behavior of the splitting of the electron paramagnetic resonance spectrum due to the location of paramagnetic ions in different domains of Cu²⁺-containing lead germanate. The off-diagonal components of the tensor g for Cu²⁺ quasi-monoclinic centers are determined. A model for off-central displacement of copper ions is proposed with due regard for the revealed symmetry of paramagnetic centers, their superhyperfine structure, and the orientation of the magnetic axes.     

Recognition of H<Subscript>2</Subscript>PO<Stack><Subscript>4</Subscript><Superscript>-</Superscript></Stack> and Cu<Superscript>2+</Superscript> in Water by Luminescent Terbium Silica Xerogel

Terbium silica hybrid material with imidazole ring that can be emissive in water has been designed and showed host-guest interactions with specific ions (cations and anions). In detail, we studied the sensing abilities of this material by addition of the anions H₂PO₄^-, HSO₄^-, F^-, Cl^-, Br^- and I^- to water suspension of the derived powders. Only dihydrogen phosphate resulted in the quenching of the lanthanide luminescence (detection limit 10^-5 M). The same way was found in Cu²⁺ ions which also gave rise to luminescence quenching (detection limit 10^-5 M). More interestingly, luminescent sol-gel films were successfully prepared by the same materials and exhibited emission responses to H₂PO₄^- and Cu²⁺. For the sake of improving its mechanical property, the robust and flexible inorganic/PMMA hybrid material with sensing capability was also developed for future use.     

Preparation of Cu<Superscript>2+</Superscript>/NTA-derivatized branch polyglycerol magnetic nanoparticles for protein adsorption

In this report, we described the preparation of Cu²⁺/nitrilotriacetic acids (NTA)-derivatized branch polyglycerol magnetic nanoparticles for protein adsorption with avoidance of nonspecific interactions at the same time. Magnetic nanoparticles (MNPs) were synthesized by the coprecipitation method. The transmission electron microscopy results showed that the average diameter of MNPs was 15.8 ± 4.6 nm. X-ray photoelectron spectroscopy and Fourier Transform infrared measurements indicated that branch polyglycerols were grafted on MNPs via the ring-opening polymerization of glycidol and that Cu²⁺ ions had been successfully immobilized on the surface of MNPs. The protein immobilization effect was characterized by UV–Vis spectrum. The results proved that Cu²⁺/NTA-derivatized branch polyglycerol magnetic nanoparticles effectively adsorbed bovine haemoglobin and rarely adsorbed lysozyme and γ-globin.     

Electron paramagnetic resonance of Ce<Superscript>3+</Superscript> and Nd<Superscript>3+</Superscript> impurity ions in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6.13</Subscript>

The electron paramagnetic resonance (EPR) spectra of Ce³⁺ and Nd³⁺ impurity ions in unoriented powders of the YBa₂Cu₃O_6.13 compound are observed and interpreted for the first time. It is demonstrated that, upon long-term storage of the samples at room temperature, the EPR signals of these ions are masked by the spectral line (with the g factor of approximately 2) associated with the intrinsic magnetic centers due to the significant increase in its intensity.     

On the Luminescence of Ce<Superscript>3+</Superscript>, Eu<Superscript>3+</Superscript>, and Tb<Superscript>3+</Superscript> in Novel Borate LiSr<Subscript>4</Subscript>(BO<Subscript>3</Subscript>)<Subscript>3</Subscript>

This paper reports on the photoluminescence (PL) and time-resolved properties of Ce³⁺, Eu³⁺, and Tb³⁺ in novel LiSr₄(BO₃)₃ powder phosphors. Ce³⁺ shows an emission band peaking at 420 nm under 350-nm UV excitation. Energy transfer from Ce³⁺ to Mn²⁺ takes place in the co-doped samples. Eu³⁺ shows red emission under near UV excitation. LiSr₄(BO₃)₃:Eu³⁺ phosphor could be a suitable candidate for phosphor-converted solid state lighting. The luminescence lifetime is 2.13 ms for Eu³⁺ in LiSr₄(BO₃)₃:0.001Eu³⁺. As Eu³⁺ concentration increasing, the decay curves deviate from exponential behavior. Tb³⁺ shows the strongest ⁵D₄→⁷ F₅ emission line at 540 nm. Decay curves of ⁵D₄→⁷ F₅ and ⁵D₃→⁷ F₅ emission with different Tb³⁺ concentrations were also measured. Cross-relaxation process is discussed based on the decay curves.     

Analytical Evaluation of Cu<Superscript>2+</Superscript> Selective Behavior of calix[4]arene Derivative

The present article describes the solvatochromic effect including solvent system selection, time study and a detailed complexation study along with exploration of extraction properties of 5,11,17,23-tetrakis[(diethylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4) that bears nitrogen atom as a donor group available for chelating metal ions. Complexation properties of 4 toward selected transition metal ions have been investigated by UV-visible and fluorescence spectroscopies. The% efficiency of 4 toward selected transition metal ions was found in order Cu²⁺> Ni²⁺> Hg²⁺> Zn²⁺> Co²⁺> Cd²⁺> Pb²⁺. It has been noticed that 4 is not only proved to be an efficient Cu²⁺ selective chromoionophore but also possesses an effective extraction property for transferring Cu²⁺ ions from an aqueous to dichloromethane layer. The FT-IR spectroscopic method has also been applied for further confirmation of the complexation phenomenon of 4 with Cu²⁺ ion and found adequate.     

Neutron transition densities for the 2<Superscript> + </Superscript>-8<Superscript> + </Superscript> multiplet of states in <Superscript>90</Superscript>Zr

Neutron transition densities for the 2 ⁺ -8 ⁺ levels in ⁹⁰Zr were extracted in the process of analyzing scattering at 400 MeV. They were compared with the calculated neutron transition densities and with the experimental proton transition densities. Radial distributions of the experimental neutron and proton transition densities for each state were found to be different.Received: 9 January 2004, Revised: 4 April 2004, Published online: 14 September 2004PACS: 25.40.Ep Inelastic proton scattering - 21.10.-k Properties of nuclei; nuclear energy levels