Design,synthesis and sensor activity of a highly photostable blue emitting 1,8-naphthalimide

This work reports on the design, synthesis and photophysical properties of a highly photostable blue emitting 1,8-naphthalimide, containing hindered amine radical scavenger moiety and a tertiary amine cation receptor. The novel compound was configured as “fluorophore-spacer-receptor” system based on photoinduced electron transfer. Photophysical characteristics of the examined compound were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compound to detect cations was evaluated by the changes in its fluorescence intensity in the presence of metal ions (Cu²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe³⁺ and Zn²⁺) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer resulting in enhancement of the 1,8-naphthalimide fluorescence intensity. Among the tested metal ions only Cu²⁺ was efficiently detected. Also, it is clearly shown that the 2,2,6,6-tetramethylpiperidine fragment, incorporated in the structure of the novel 1,8-naphthalimide, considerably improves the sensor's photostability, sensitivity and selectivity.     

Electrochemical luminescence of n-type ZnO semiconductor electrodes doped with rare earth metals under the anodic polarization

Electrochemical luminescence (ECL) at n-type ZnO semiconductor electrode was measured under anodic polarization. Scanning the potential imposed on the ZnO electrode, emission was suddenly observed around +20 V. Using the ZnO electrodes doped with rare earth metal ions as Sm³⁺, Eu³⁺, Dy³⁺, Ho³⁺ and Er³⁺, much brighter emission was obtained than the ECL of non-doped ZnO. These emission spectra are ascribed to the rare earth metal ions, respectively. This result would show that emission centers of doped ions were selectively excited by electrons that were injected from electrolyte to the electrode by avalanche breakdown under strong anodic bias on the ZnO.     

一种基于3,4-二取代-1,8-萘酰亚胺和双通道响应的Cu2+荧光分子探针

设计合成了一种新型3,4-二取代-1,8-萘酰亚胺衍生物H1,在多种金属离子的水溶液中,作为铜离子的一个选择性荧光探针．该探针在甲醇和水体积比为1:1的溶液中与Cu²⁺结合,其荧光强度增强且探针的H1的吸收光谱发生红移,同时探针溶液的颜色由黄色变成粉红色．此外,探针H1与Cu²⁺结合比为1:1.     

Molecular assembly and photophysical properties of Langmuir-Blodgett films with novel lanthanide complexes of long chain para-dodecanoyl and para-myristoyl oxybenzoate

Several ultrathin luminescent Langmuir-Blodgett (LB) films have been prepared by using the subphase containing the rare earth ions (Eu³⁺, Dy³⁺). The effect of the rare earth ions on the monolayer of p-dodecanoyloxybenzoate (12-OBA) and p-myristoyloxybenzoate (14-OBA) was investigated. IR spectra showed the rare earth ions were bound to the carboxylic acid head groups and the coordination took place between the polar head group and the rare earth ions. The layer structure of the LB films was demonstrated by low-angle X-ray diffraction. The AFM study revealed that the LB films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 241 nm. The LB films can give off strong fluorescence, and the signal can be detected from a single layer. The characteristic luminescence behaviors of LB films have been discussed compared with those of the complexes.     

A New Reactive 1,8-Naphthalimide Derivative for Highly Selective and Sensitive Detection of Hg<Superscript>2+</Superscript>

A 1,8-naphthalimide derivative with a reactive aliphatic hydroxyl was designed and synthesized as a fluorescent probe. Its structure was characterized by IR, ¹H NMR, ¹³C NMR, LC-MS and HPLC. The probe showed high selectivity and sensitivity to Hg²⁺ over other metal ions such as Pb²⁺, Na⁺, K⁺, Cd²⁺, Cr³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Fe²⁺, Co²⁺, Mn²⁺ and Mg²⁺ in MeCN/H₂O (15/85, v/v). The increase in fluorescence intensity was linearly proportional to the concentration of Hg²⁺ in the range of 18–40 μM with a detection limit of 1.38 × 10^?7 mol/L. The probe could work in a pH span of 4.3–9.0 and respond to Hg²⁺ quickly with strong anti-interference ability. Job’s plot suggested a 1:2 complex of the probe and Hg²⁺.     

Luminescence of yttrium niobium-tantalate doubly activated by europium and/or terbium under X-ray and electron beam excitation

This paper reports the luminescence emission spectra of Y(Ta,Nb)O₄ activated by rare earth ions such as Eu³⁺ and Tb³⁺. The influence of these rare earth ions on the luminescence of yttrium niobium-tantalate phosphors was investigated. The luminescent properties were studied under X-ray and electron beam excitations. Under these excitations, the emission centers of the rare earth activators (Eu³⁺,Tb³⁺) were found to contribute efficiently to the overall luminescence. Changing the mol concentration of the incorporated activators resulted in a broad variation of visible photoluminescence. Color cathodoluminescence images showed clearly the dependence of chromaticity on the different activators. With their various luminescence chromaticities, these rare earth activated phosphors are promising materials for solid-state lighting applications as well as for X-ray intensifying screens in medical diagnosis, providing a broad variation of visible photoluminescence from blue to red.     

Design and Synthesis of Highly Photostable Yellow–Green Emitting 1,8-Naphthalimides as Fluorescent Sensors for Metal Cations and Protons

Two highly photostable yellow–green emitting 1,8-naphthalimides 5 and 6, containing both N-linked hindered amine moiety and a secondary or tertiary cation receptor, were synthesized for the first time. Novel compounds were configured as “fluorophore–spacer–receptor” systems based on photoinduced electron transfer. Photophysical characteristics of the dyes were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compounds to detect cations was evaluated by the changes in their fluorescence intensity in the presence of metal ions (Cu²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Co²⁺) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer leading to an enhancement in the dye fluorescence intensity. Compound 5, containing secondary amine receptor, displayed a good sensor activity towards metal ions and protons. However the sensor activity of dye 6, containing a tertiary amine receptor and a shorter hydrocarbon spacer, was substantially higher. The results obtained indicate the potential of the novel compounds as highly photostable and efficient “off–on” pH switchers and fluorescent detectors for metal ions with pronounced selectivity towards Cu²⁺ ions.     

Sensitized fluorescence of Ce3+/Mn2+ system in phosphate glass

The preparation of sodium phosphate glasses singly and doubly doped with rare earth ion Ce³⁺ and transition metal ion Mn²⁺ by a melt quench method is described. The spectroscopic characterizations of the samples are conducted by absorption, excitation, and emission spectra. The orange red emission of divalent manganese sensitized by trivalent cerium ions in a phosphate glassy matrix has been investigated. Energy transfer (ET) from optically excited Ce³⁺ to Mn²⁺ in sodium phosphate glass, by nonradiative process is confirmed by fluorescence studies with various activator concentrations. The mechanism of ET is mainly electric dipole–dipole in nature.     

Electronic tongue — An array of non-specific chemical sensors — For analysis of radioactive solutions

A variety of novel sensing materials on the basis of phosphine oxides for solvent polymeric sensors have been developed and studied. It was found that phosphine oxide sensors exhibit good sensitivity to rare earth metal cations, such as La³⁺, Pr³⁺, Nd³⁺, Eu³⁺ and also to Y³⁺. Polymeric sensors can be comprised into electronic tongue sensor arrays that may allow detection of several rare-earth metal ions simultaneously in mixed solutions. Such sensor arrays are highly promising for environmental and industrial sensing, e.g., for analysis of spent nuclear fuel.     

Off-on Fluorescent Sensor from On-off Sensor: Exploiting Silver Nanoparticles Influence on the Organic Fluorophore Fluorescence

Turn-off fluorescence of organic fluorophore, 2-{[4-(2H-Naphtho[1,2-d][1,2,3]triazol-2-yl)-phenyl]carboxylic acid (NTPC), with metal ions (Fe³⁺, Cu²⁺, Pb²⁺) was converted into turn-on fluorescent sensor for biologically important Zn²⁺, Cu²⁺ and Fe³⁺ metal ions in aqueous solution at ppb level by exploiting strong fluorescence quenching phenomena of metal nanoparticles when organic fluorophores assembled in the vicinity of metallic surface. Amino acid attached phenolic ligands (L) were used as reducing as well as functional capping agents in the synthesis of silver nanoparticles (AgNPs). The hydrogen bonding functionality of L facilitated the assembling of NTPC in the vicinity of metallic surfaces that leads to complete quenching of NTPC fluorescence. The strong and selective coordination of L with metal ions (Zn²⁺, Cu²⁺ and Fe³⁺) separates the NTPC from the AgNPs surface that turn-on the NTPC fluorescence. HR-TEM and absorption studies confirm the metal coordination with L and separation of NTPC from the AgNPs surface. Mn²⁺ showed selective red shifting of NTPC fluorescence after 12 h with all sample. Effects of different amino acid attached phenolic ligands were explored in the metal ion sensitivity and selectivity. This approach demonstrates the multifunctional utility of metal NPs in the development of turn-on fluorescence sensor for paramagnetic heavy metal ions in aqueous solution.

Fluorescence Sensors for Selective Detection of Hg2+ Ion Using a Water-Soluble Poly(vinyl alcohol) Bearing Rhodamine B Moieties

The novel water-soluble poly(vinyl alcohol) with pendant rhodamine B moiety as colorimetric and fluorescene chemosensor for Hg²⁺ ions was prepared by grafting poly(vinyl alcohol) using rhodamine B hydrazide and hexamethylenediisocyanate as fluorescent dye and coupling agent, respectively. Because of their good water-solubility, the polymers binding rhodamine B can be used as chemosensors in aqueous media. With the addition of Hg²⁺ ions into the aqueous solution, visual color changes and fluorescence enhancements were detected. In addition, we also noticed that other metal ions such as Ag⁺, Cd²⁺, Co²⁺, Cu²⁺, K⁺, Mg²⁺, Ba²⁺, Fe²⁺, Ni²⁺, Pb²⁺, Cr³⁺, Fe³⁺ and Zn²⁺ cannot induce obvious changes to the fluorescence spectra of the polymer chemosensors. The combination of water solubility and positive fluorescence response as well as color change are hence particularly promising for the practical utility of the sensors.     

丹参酮Ⅱ-A与稀土离子形成配合物配位过程的研究

用NMR与光谱分析方法对丹参酮Ⅱ-A与Eu³⁺、Tb³⁺的配位机理进行了研究,确定了配合物的组成及配合物的结构.     

Effect of Pendant Group Length Upon Metal Ion Complexation in Acetonitrile by Di-Ionized Calix[4]Arenes Bearing Two Dansyl Fluorophores

A series of three di-ionizable calix[4]arenes with two pendant dansyl (1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims was synthesized. Structures of the three ligands were identical except for the length of the spacers which connected the two dansyl groups to the calix[4]arene scaffold. Following conversion of the ligands into their di-ionized di(tetramethylammonium) salts, absorption and emission spectrophotometry were utilized to probe the influence of metal cation (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ag⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Pb²⁺, Zn²⁺ and Fe³⁺) complexation in acetonitrile. Upon complexation with these metal cations, emission spectra underwent marked red shifts and quenching of the dansyl group fluorescence for the di-ionized ligand with the shortest spacer. A similar effect was noted for the di-ionized ligand with an intermediate spacer for all of the metal ions, except Ba²⁺. For the di-ionized ligand with the longest spacer, the metal cations showed different effects on the emission spectrum. Li⁺, Mg²⁺, Ca²⁺ and Ba²⁺ caused enhancement of emission intensity with a red shift. Other metal cations produce quenching with red shifts in the emission spectra. Transition metal cations interacted strongly with all three di-ionized ligands. In particular, Fe³⁺ and Hg²⁺ caused greater than 99% quenching of the dansyl fluorescence in the di-ionized ligands.     

Influence of co-doping different rare earth ions on CaGa2S4: Eu, RE(RE=Ln) phosphors

Photoluminescent phosphors CaGa₂S₄: Eu²⁺, RE³⁺ (RE³⁺ including all rare earth ions except for Sc³⁺, Pm³⁺, Eu³⁺ and Lu³⁺) were prepared by sintering at high temperature in a reductive atmosphere, and their luminescent properties were studied intensively. The influences of co-doping rare earth ions on their luminescent properties were also investigated. No remarkable differences were found from excitation spectra of co-doped phosphors CaGa₂S₄: Eu²⁺, RE³⁺ in contrast with that of phosphor CaGa₂S₄: Eu²⁺, but there were a few differences in emission spectra of Ce³⁺, Pr³⁺ or Ho³⁺ co-doped phosphors. Phosphors CaGa₂S₄: Eu²⁺, RE³⁺ (RE=Ce, Pr, Gd, Tb, Ho and Y) had persistent afterglow, and very short afterglow was shown for Nd³⁺ or Er³⁺ co-doped phosphors, but no long afterglow appeared when auxiliary activator was La³⁺, Sm³⁺, Dy³⁺, Tm³⁺ or Yb³⁺. Among the phosphors with long-lasting phosphorescence, in our experiments, CaGa₂S₄: Eu²⁺, Ho³⁺ had the longest and the highest brightness long yellow afterglow. Thermo-luminescence of all co-doped phosphors was measured to find the answer of different influences from different rare earth auxiliary activators.     

A highly Selective Fluorescent Sensor for Monitoring Cu<Superscript>2+</Superscript> Ion: Synthesis,Characterization and Photophysical Properties

A new fluorescent sensor, 4-allylamine-N-(N-salicylidene)-1,8-naphthalimide (1), anchoring a naphthalimide moiety as fluorophore and a Schiff base group as receptor, was synthesized and characterized. The photophysical properties of sensor 1 were conducted in organic solvents of different polarities. Our study revealed that, depending on the solvent polarity, the fluorescence quantum yields varied from 0.59 to 0.89. The fluorescent activity of the sensor was monitored and the sensor was consequently applied for the detection of Cu²⁺ with high selectivity over various metal ions by fluorescence quenching in Tris-HCl (pH = 7.2) buffer/DMF (1:1, v/v) solution. From the binding stoichiometry, it was indicated that a 1:1 complex was formed between Cu²⁺ and the sensor 1. The fluorescence intensity was linear with Cu²⁺ in the concentration range 0.5–5 μM. Moreso, the detection limit was calculated to be 0.32 μM, which is sufficiently low for good sensitivity of Cu²⁺ ion. The binding mode was due to the intramolecular charge transfer (ICT) and the coordination of Cu²⁺ with C = N and hydroxyl oxygen groups of the sensor 1. The sensor proved effective for Cu²⁺ monitoring in real water samples with recovery rates of 95–112.6 % obtained.     

Optical Transmittance and Irradiation Resistance of Rare-Earth (Ce3☎, Tb3☎, Pr3☎) Doped Heavy Germanate Glasses

In this work we investigated the possibility of using scintillating rare earth Ce^3?, Tb^3?, and Pr^3? ions to optically activate germanate glass matrices. Glasses were characterised in terms of radiation resistance, UV-VIS transmittance and luminescence spectra. Their radiation induced response was found to be dependent on glass composition and these trivalent rare earth ions turned out to be efficient in suppressing formation of colour centres absorbing light in the visible range.     

Methylene blue as a DNA probe for a comparative study of Cd, Pb and Cr ions binding to calf thymus DNA

Methylene blue (MB) was developed as a sensitive DNA probe for a comparative study of Cd²⁺, Pb²⁺ and Cr³⁺ ions binding with calf thymus DNA (ctDNA). The fluorescence intensity of the MB-ctDNA system increased dramatically when heavy metal ions (Cd²⁺, Pb²⁺ and Cr³⁺ ions) were added, which indicated that some of the bound MB molecules were released from the ctDNA base pairs. To compare the binding affinity of these three different heavy metal ions with ctDNA, the relationships between the fluorescence intensity of the MB-ctDNA-M (Metal ions) system and the concentration ratio of [M]/[DNA(p)] were investigated. The results showed that the order of the binding affinity of heavy metal ions with ctDNA had the following sequence: Cr³⁺> Cd²⁺>Pb²⁺. This order was further proved by the effects of heavy metal ions on the number of MB bound to ctDNA, the measurements of binding constants of these heavy metal ions to ctDNA, and the effects of heavy metal ions on the absorption of the MB-ctDNA system. In addition, the interaction mechanisms of Cd²⁺, Pb²⁺ and Cr³⁺ ions with ctDNA were also discussed in detail. These results indicated that their interaction mechanisms are related to the concentration ratios of heavy metal ions to DNA.     

Electron paramagnetic resonance and magnetic susceptibility of rare-earth hydrazone compounds

The magnetic properties of the rare earth molecular compounds with hydrazone ligands containing Nd³⁺, Gd³⁺, and Yb³⁺ have been investigated by electron paramagnetic resonance (EPR) and magnetization measurements. For the Gd-compound, partially resolved fine structure due to Gd³⁺ and exchange narrowing effects at low temperatures are observed in the EPR spectra, suggesting, consistent with the EPR and dc magnetic susceptibility, weak antiferromagnetic exchange interactions. Paramagnetic behavior sustained down to low temperatures is derived for Yb³⁺ ions, whereas substantial ferromagnetic exchange coupling is inferred for the lighter Nd³⁺ ions, indicating significant variations of the exchange integrals along the lanthanide series. Received 29 April 2002 Published online 31 July 2002     

Analysis of hyperfine structure of Rare‐Earth Ions in Single Crystals by Electron Paramagnetic Resonance Spectroscopy

Electron paramagnetic spectroscopy of rare‐earth ions in single crystals is an interesting tool to analyze the hyperfine structure of the ground state of the rare‐earth. This can be useful for coherent spectroscopy and quantum information applications where the hyperfine structure of the electronic levels is used. Moreover, in some cases, the electron paramagnetic resonance hyperfine structure of interacting rare‐earth ions allows us to retrieve the isotropic exchange interaction between the two interacting ions. We illustrate these points with the hyperfine structure of Yb³⁺ ions in vanadate crystals, the hyperfine structure of Er³⁺ ions in Y₂SiO₅, and the hyperfine structure of Yb³⁺ pairs in CsCdBr₃.     

Effects of metal ion on the water structure studied by the Raman O?H stretching spectrum

Raman spectra in the O H stretching region of aqueous salt solutions were measured and compared, and the effects of metal ions on water structure deduced. The effects of alkali ions, alkaline ions or the first‐row transition metals on water structure were found to be similar. Differences of metal ionic effects on water structure exist among Na⁺, Mg²⁺ and Al³⁺, and between Ca²⁺ and Mn²⁺ and Al³⁺ and Fe³⁺. The factors that influence the metal ionic effects on the water structure are the ionic charge, the outmost electronic structure and ionic size, the ionic charge being the most important. With a five‐component Gaussian deconvolution of the Raman spectra of the aqueous solutions of NaCl, MgCl₂, AlCl₃ and FeCl₃ with concentrations of 0 to ∼1mol/l, the ionic effects were found to be similar on the bands at 3233, 3393, 3511 and 3628 cm⁻¹, but different on the band at 3051 cm⁻¹. With increasing polarization of the metal ion, the band at 3051 cm⁻¹, due to strong hydrogen bonding, increases. Copyright © 2009 John Wiley & Sons, Ltd.