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.     

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.     

Green luminescent ZnO:Cu<Superscript>2+</Superscript> nanoparticles for their applications in white-light generation from UV LEDs

Copper doped ZnO nanoparticles were synthesized by a chemical technique based on a hydrothermal method. The crystallite sizes, estimated by XRD and TEM/SEM for different doping percentage of Cu²⁺ (1–10%), were found to be in the range of ~10–15 nm. TEM/SEM images showed formation of uniform nanorods, the aspect ratio of which varied with doping percentage. Photoluminescence (PL) measurement showed strong green visible emission and PL intensity was found enhanced with increase in doping percentage. The increase in the PL intensity was mainly due to Cu incorporation in ZnO lattice. Currently, light-emitting diodes (LEDs) giving ultraviolet emission have been combined with broad-band visible green phosphors to make white-light LEDs. Thus, green luminescent ZnO:Cu²⁺ nanoparticles are seen as necessary and condemnatory constituent for white-light generation from UV LEDs, underlying the importance of the current work.     

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.     

Physical and Spectral Investigations of Cu<Superscript>2+</Superscript>-Doped Alkali Zinc Borate Glasses

Physical and spectral studies on 20ZnO + xLi₂O + (30-x)Na₂O + 50B₂O₃ (5 ≤ x ≥ 25) doped with 0.1 mol% of paramagnetic CuO impurity are carried out. Powder X-ray diffraction patterns of the glass samples confirm the amorphous nature. The physical parameters of all the glasses were also evaluated with respect to the composition. The electron paramagnetic resonance spectra of all these glasses exhibit resonance signals that are characteristic of Cu²⁺ ions. The optical absorption spectra also confirm the Cu²⁺ ion in tetragonally elongated octahedral site. Various crystal field, spin-Hamiltonian and bonding parameters are evaluated. It is observed that the mixed alkali effect is significant.     

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.     

Synthesis and characterization of Mn<Superscript>2+</Superscript>-doped ZnS nanoparticles

Mn²⁺-doped ZnS nanoparticles were prepared by chemical arrested precipitation method. The samples were heated at 300, 500, 700 and 900°C. The average particle size was determined from the X-ray line broadening. Samples were characterized by XRD, FTIR and UV. The composition was verified by EDAX spectrum. The hexagonal structure of the sample was identified. The size of the particles increased as the annealing temperature was increased. The crystallite size varied from 5 nm to 34 nm as the calcination temperature increased. At around 700°C, ZnS is converted into ZnO phase due to oxidation. The emission peak of the sample is observed at 300 nm resulting in blue emission. The solid state theory based on the delocalized electron and hole within the confined volume can explain the blue-shifted optical absorption spectra. UV-VIS spectro-photometric measurement shows an indirect allowed band gap of 3.65 eV.      

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     

Synthesis and characterization of ZnO:Co<Superscript>2+</Superscript> nanoparticles

This work investigates cobalt doped ZnO nanoparticles prepared by using wet chemical methods. The nanoparticles have a typical size of 3–8 nm. The electronic structure as well as the optical and magnetic properties of Co²⁺ have been characterized. X-ray diffraction spectra of the powder show wurtzite ZnO with no secondary Co phases. In the energy range below the bandgap, the optical absorption spectra show the internal d–d transitions related to Co²⁺ incorporated on the Zn lattice site in ZnO. Low temperature photoluminescence measurements confirm these results. Based on the analysis of the g-valuesfor bulk ZnO:Co., electron paramagnetic resonance measurements coincide with the simulation of Co-doped ZnO powder. Thus far, no evidence for ferromagnetism has been obtained. PACS 61.46.Df; 76.30.Fc; 78.67.Bf     

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.     

Nitrogen-doped carbon dots embedded in a SiO<Subscript>2</Subscript> monolith for solid-state fluorescent detection of Cu<Superscript>2+</Superscript> ions

We describe the simple fabrication of SiO₂ sol-gel monoliths embedding highly luminescent carbon nanodots (CDs) sensitive to metal ions. The pristine CDs we synthesize display an intense dual emission consisting in two fluorescence bands in the green and violet region, and we demonstrate that this photoluminescence is substantially unchanged when the dots are incorporated in the SiO₂ matrix. The emission of these CDs is quenched by interactions with Cu²⁺ ions, which can be used to detect these ions with a detection limit of 1 μM. The chromophores remain accessible to diffusing Cu²⁺ ions even after embedding CDs in the sol-gel monolith, where their detection capabilities are preserved. Such a result provides the proof-of-principle of a new sensing scheme, where CDs are exploited as active sensing centers of metal transition ions within a solid-state device. The different interaction mechanisms of CDs with copper, in liquid and solid phase, are analyzed in detail and discussed in terms of different accessibility of their chromophores when the dots are incorporated in the SiO₂ matrix.     

The 2<Superscript>1/3</Superscript> rule for magnetic susceptibility of gadolinium

The dependences of the magnetization M and the magnetic susceptibility χ = ∂M/∂H of pure gadolinium (the concentration of foreign impurities is lower than 0.1 wt %) on the temperature T and the magnetic field H have been measured using a Quantum Design MPMS-5XL SQUID magnetometer. In this material, inhomogeneities of the atomic structure should not lead to a nonuniform distribution of the magnetic characteristics (including the Curie temperature T _C) over the volume of the sample. The obtained dependences of M and χ have been used to investigate the possibility of suppressing magnetic inhomogeneities of other types by magnetic fields with a strength of up to 50 kOe. It has been assumed that these inhomogeneities are suppressed when the specific relationship, namely, the 2^1/3 rule is fulfilled. The rule relates the portions of the dependence χ(T, H) which at the temperature T = T _C and at the maximum in the curve χ(T) (T = T _m ) depend on H in accordance with the H ^2/3 law. It has been shown that the portions separated from the experimental curves χ(T _C, H) and χ(T _m , H) obey the 2^1/3 rule.     

Green,blue, red,near-infrared up-conversion luminescence of Yb<Superscript>3+</Superscript>/Er<Superscript>3+</Superscript>/Tm<Superscript>3+</Superscript> co-doped YVO<Subscript>4</Subscript> nanoparticles

YVO₄:Yb³⁺,Er³⁺; YVO₄:Yb³⁺,Tm³⁺; and YVO₄:Yb³⁺,Er³⁺,Tm³⁺ were all synthesized via sol-gel method with a subsequent thermal treatment. Specifically, YVO₄:Yb³⁺,Er³⁺,Tm³⁺ phosphors were prepared with different annealing temperatures to study the influence of temperature. The transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffractometer (XRD), and photoluminescent (PL) spectrofluorometer were used to investigate the morphology, crystal structure, and up-conversion luminescent properties of all samples. In summary, all samples were granular-like nanoparticles and well crystallized with the same tetragonal phase as YVO₄. Under the irradiation at 980 nm, YVO₄:Yb³⁺,Er³⁺ phosphors can generate green emission at 525 and 553 nm and red emission at 657 nm, while YVO₄:Yb³⁺,Tm³⁺ phosphors can generate blue emission at 476 nm, red emission at 648 nm, and near-infrared emission at 800 nm. Notably, YVO₄:Yb³⁺,Er³⁺,Tm³⁺ samples can exhibit green emission, blue emission, red emission, and near-infrared emission at the same time, which might endow the as-prepared samples with potential applications in many fields, such as luminous paint, infrared detection, and biological label.     

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.     

A Ratiometric and near-Infrared Fluorescent Probe for Imaging Cu<Superscript>2+</Superscript> in Living Cells and Animals

We have rationally constructed a novel ratiometric and near-infrared Cu²⁺ fluorescent probe based on a tricarbocyanine chromophore. The new probe NIR-Cu showed a ratiometric fluorescent response to Cu²⁺ with a large emission wavelength shift (up to 142 nm) in the far-red to near-infrared region. The probe also displayed a large variation in the fluorescence ratio (I₆₃₆/I₇₇₈) to Cu²⁺ species with high sensitivity and selectivity. Additionally, the developed probe NIR-Cu was suitable for fluorescence imaging of Cu²⁺ in living cells and mice.     

Preparation and biodistribution of <Superscript>59</Superscript>Fe-radiolabelled iron oxide nanoparticles

We report on the ⁵⁹Fe radiolabelling of iron oxide nanoparticle cores through post-synthetic isotope exchange (⁵⁹Fe-IONP_ex) and precursor labelling (⁵⁹Fe-IONP_pre). Scanning electron microscopy and dynamic light scattering measurements showed no impact of radiolabelling on nanoparticle size or morphology. While incorporation efficiencies of these methods are comparable—83 and 90% for precursor labelling and post-synthetic isotope exchange, respectively—⁵⁹Fe-IONP_pre exhibited much higher radiochemical stability in citrated human plasma. Quantitative ex vivo biodistribution study of ⁵⁹Fe-IONP_pre coated with triethylene glycol was performed in Wistar rats. Following the intravenous administration, high ⁵⁹Fe concentration was observed in the lung and the organs of the reticuloendothelial system such as the liver, the spleen and the femur.     

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.     

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.     

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.