Spectroscopic properties and fluorescent recognition of dye sensitized layered lutetium-terbium hydroxides.

The layered rare earth hydroxides have attracted increasing interests due to their diverse chemical composition and tunable spectroscopic properties. In this paper, a novel Tb3+ activated layered lutetium hydroxide (LLuH:Tb) was fabricated, in which the inorganic NO3- ions were ion-exchanged with organic (ibuprofen or dodecylsulfonate) anions. After the ion-exchange reaction, the organic anions intercalated LLuH:Tb showed the distinct lamellar structure with the interlayer distance of about 2.56 nm, confirming the formation of inorganic/organic hybrid assembly. The dye ibuprofen-intercalated hybrid effectively promoted the characteristic 5D4 â†’ 7F5 green emission of Tb3+ in the host but failed to be exfoliated into nanosheet colloid. On the contrary, the dodecylsulfonate-intercalated hybrid was readily to be exfoliated into nanosheet colloid by dissolving in formamide solvent, but the green emission of Tb3+ was too weak to be observed. To take advantage of their respective merits and explore the practical uses, certain amounts of dye ibuprofen were directly added to the dodecylsulfonate-intercalated hybrid colloid. Excited with the ultraviolet light, the characteristic green fluorescence of Tb3+ was dramatically enhanced, indicating that the dye was a superior light-harvesting antenna to sensitize the activator Tb3+. The dye sensitized hybrid colloid was very stable at ambient temperature and exhibited excellent fluorescent recognition for Cu2+ ions over other metal ions in aqueous solution due to the large fluorescence quenching. The detection limit for Cu2+ ion reaches 7.63 × 10-7 mol/L, which is far lower than the limitation of Cu2+ in drinking water recommended by the World Health Organization (1.57 × 10-5 mol/L). The fluorescence enhanced/quenched sensor with excellent stability exhibits a high potential for the detection of Cu2+ in routine environmental water.

High drug-loading system of hollow carbon dots-doxorubicin: preparation, in vitro release and pH-targeted research.

Hollow carbon dots (HCDs), as drug carriers, and doxorubicin (DOX), as a model drug, were selected to prepare a HCDs-DOX-loading system. First, HCDs were prepared by a hydrothermal method and characterized by transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and nuclear magnetic resonance (13C NMR), UV-vis absorption, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopies (XPS). The HCDs were then used to load DOX. The drug-loading system of HCDs-DOX was characterized by zeta potential measurements, and UV-vis absorption and fluorescence spectroscopies. We then studied the drug loading, formation mechanism, cytotoxicity, in vitro release and pH-targeted properties. HCDs-DOX was found to have a high drug (DOX)-loading ratio (∼42.9%) and better sustained pH targeted-release and lower cytotoxicity than those of DOX. In the HCDs-DOX system, interactions between the HCDs and DOX were electrostatic resulting in the formation of -N[double bond, length as m-dash]C-via the coupling of -NH2 (on HCDs) and -C[double bond, length as m-dash]O (on DOX). In vitro release of HCDs-DOX conformed to the Weibull model and Fick diffusion, consistent with that of free DOX. We report, for the first time, that the: (i) functional groups on the HCD surfaces (not their hollow structure) play a key role in drug loading; (ii) the carrier (HCDs) did not change the in vitro release model or mechanism of DOX before and after loading by the HCDs.

Preparation, characterization and properties of four new trivalent lanthanide complexes constructed using 2-bromine-5-methoxybenzoic acid and 1,10-phenanthroline.

Four dinuclear trivalent lanthanide complexes of the general formula [Ln2(2-Br-5-MOBA)6(phen)2] (Ln = Nd(), Sm(), Ho(), Er(); 2-Br-5-MOBA = 2-bromine-5-methoxybenzoate, phen = 1,10-phenanthroline) were prepared and structurally characterized. The complexes to are isostructural with a coordination number of nine. The carboxylic acid ligands adopt bridging, bidentate chelating, and tridentate chelating bridging modes to coordinate with Ln(iii) ions. The structures of the complexes were confirmed on the basis of elemental analysis, molar conductance, thermogravimetric analysis (TGA), and IR and UV spectra. The heat capacities and thermal circulating processes of the prepared complexes were performed on a differential scanning calorimeter under a nitrogen atmosphere. Two remarkable solid-solid phase transitions existed both in the heat capacities and thermal circulating processes. The bacteriostatic activities of the complexes were evaluated against Candida albicans, Escherichia coli and Staphylococcus aureus. Besides, the luminescent property of complex was also investigated, and the magnetic properties of complexes and were also discussed in detail.

Kinetically controlled seed-mediated growth of narrow dispersed silver nanoparticles up to 120 nm: secondary nucleation, size focusing, and Ostwald ripening.

A facile synthesis method was developed based on the seed-mediated growth to get the narrow dispersed silver nanoparticles with controllable sizes ranging from 20 nm to larger than 120 nm. Environmentally friendly glucose acts as a reducing agent. Because of its weak reducing ability, the secondary nucleation is prevented in the seed-mediated growth, and the size of silver nanoparticles can be tuned continuously by the continuous addition of reactants. Controlling the supersaturation level is critical to suppress both the nucleation and Ostwald ripening, which can be realized by carefully controlling the addition rate of the reactants. We also set up a convenient method to determine the size and size-distribution of silver nanoparticles from the size-dependent absorption spectra of the colloids, and optimize the growth parameters using this method to get narrow dispersed silver nanoparticles.

Tris-(8-hydroxy-quinoline) aluminium/zirconium phosphate: a novel hybrid assembly with strong luminescence and prolonged lifetime.

A novel hybrid assembly of tris-(8-hydroxy-quinoline) aluminium intercalated into modified α-zirconium phosphate in aqueous media was fabricated successfully, resulting in the dramatically enhanced greenish-blue-light emission and prolonged excited-state lifetime.

Luminescence and energy transfer of organic chromophores bound to inorganic nano-lamellar frameworks.

Fluorescein, an organic chromophore with high fluorescence quantum yield, was bound to a cetyltrimethylammonium zirconium phosphate nano-lamellar framework and its luminescence properties and energy transfer from fluorescein to porphyrins were characterized. Upon the incorporation of fluorescein chromophore within the layered materials, not only was the interlayer distance of the framework adjusted from 39.6 to 24.7 angstroms, but also the luminescence properties of fluorescein were dramatically changed. The excitation maximum was red-shifted from 488 to 500 nm, and the emission peak was red-shifted from 510 to 525 nm. These results implied the formation of chromophore/framework hybrid assemblies. After fluorescein and tetra(p-methoxphenyl)porphine chromophores bound to the framework together, obvious energy transfer was observed, resulting in more effective fluorescence efficiency for the porphyrins. Without the framework, such energy transfer was absent in the same chromophore concentrations in aqueous solutions. Due to the unique microenvironments provided by the inorganic lamellar framework, the electronic interactions of the chromophores were tuned. Therefore, their emission properties were changed, and the energy transfer processes were promoted.

Effects of SO4(2-) or SiO3(2-) doping on the photoluminescence of NaEu(MoO4)2 nanophosphors for light-emitting diodes.

A series of red nanophosphors including NaEu(MoO4)2-x(SO4)x as well as NaEu(MoO4)2-x(SiO3)x (x = 0, 0.10, 0.20, 0.30, 0.40) were synthesized by hydrothermal and subsequent heat-treatment processes. The as-prepared pure and anion (SO4(2-) or SiO3(2-))-doped NaEu(MoO4)2 phosphors were indexed as a scheelite structure, which was revealed by X-ray diffraction data. The morphologies of SO4(2-)-doped NaEu(MoO4)2 powders were almost regularly spherical, and their grain sizes ranged from 300 to 400 nm. However, the grains of SiO3(2-)-doped phosphors appeared to be seriously inordinate and unconsolidated, as indicated by their scanning electron microscopy studies. All of the samples were excited with near-UV 395 nm light and showed the characteristic red emission of the Eu3+ 5D0 --> 7F2 transition. With the incorporation of SO4(2-) into the host, the red emission intensities of Eu3+ increased obviously and reached a maximum at x = 0.30. Nevertheless, the intensities of Eu3+ emission reduced dramatically after the SiO3(2-) doping. The optimized NaEu(MoO4)1.70(SO4)0.30 nanophosphor powders, with well-distributed fine grains and strong emission intensity, may be applied in the fabrication of phosphor-converted light-emitting diodes (LEDs).

Enhanced stable luminescence and photochemical properties of ruthenium complex/zirconium phosphate hybrid assemblies.

The luminescent metal complex Ru(bpy)3Cl2.6H2O was directly intercalated into Zr(HPO4)2.6H2O nano-lamellar framework and characterized with respect to its optical and photochemical properties. The incorporation of the complex within the inorganic framework expands the interlayer distance from 10.4 to 15.2 A, and forms complex/framework hybrid assemblies. Upon binding to the framework, the metal-to-ligand charge transfer absorption of the complex is red-shifted from 452 to 462 nm, and the maximum emission is blue-shifted from 610 to 604 nm. The luminescence intensity of the complex/framework suspensions increases more than 2-fold as compared to aqueous solutions. The sub-micrometer (0.2-0.3 microm) particles of the hybrid assemblies result in the luminescence intensity of the suspensions quite stable. In addition, the excited state of Ru(bpy)3(2+) was photochemical quenched by Fe(CN)6(3-), and the Stern-Volmer results reveal that most Ru(bpy)3(2+) cations have entered into the layer of the framework.

Optical properties of porphyrin chromophores assembled in nano-lamellar zirconium phosphate.

The supra-molecular assemblies and optical properties of the symmetrical neutral porphyrin chromophore, meso-tetra(4-pyridyl)porphine, bound to a modified alpha-zirconium phosphate framework have been studied. The interlayer distance of the cetyltrimethylammonium zirconium phosphate framework is 39.6 angstroms. After the addition of meso-tetra(4-pyridyl)porphine to the framework, the X-ray powder diffraction (XRPD) patterns show that the interlayer distance of the framework is 30.3 angstroms, demonstrating the formation of novel assemblies. In the framework, organic chromophores are assumed to align in a canted monolayer. The interaction of organic chromophores with the framework causes noticeable red shifts of the Soret absorption band from 416 to 427 nm. In contrast, the luminescence peak is blue shifted from 660 nm in aqueous media to 648 nm when meso-tetra(4-pyridyl)porphine is bound to the framework. Furthermore, the emission yield of the organic chromophore in the framework is dramatically enhanced compared to that of organic aqueous solutions. The spectroscopic change of meso-tetra(4-pyridyl)porphine is ascribed to the unique microenvironments of the nano-lamellar framework. The juxtaposition of the porphyrin chromophores in the framework tunes their electronic interactions. In comparison, the organic chromophores also attempted to bind with another modified alpha-zirconium phosphate, n-butylammonium zirconium phosphate. However, the chromophores could not enter into n-butylammonium zirconium phosphate due to its smaller interlayer distance (18.8 angstroms).

Spectroscopic properties and intense red-light emission of (Ca, Eu, M)WO4 (M=Mg, Zn, Li).

The red-emitting phosphors of (Ca, Eu, M)WO4 (M=Mg, Zn, Li) were prepared through solid-state reactions, and their spectroscopic properties were studied. After the addition of a small amount of Mg2+, Zn2+ or Li+ in (Ca, Eu)WO4, the red-light emission intensity of Eu3+ increases obviously. In the luminescence spectra of the phosphors, the predominant transition emission is 5D0-->7F2 (616nm), whereas the other emissions are very weak. The excitation spectra are composed of interweaved ligand-to-metal charge-transfer bands (CTB) of W6+-O(2-) and Eu3+-O(2-), and a few 4f excitation transitions of Eu3+. Among the 4f excitation transitions of Eu3+, there are three strong excitation lines corresponding to 7F0-->5L6, 7F0-->5D2 and 7F0-->5D1 transitions, whose relative excitation intensity ratio is seriously affected when Li+ doped in the host. The new phosphors may be applied as red-emitting phosphors for white light emitting diodes.

[Effects of KCl on fluorescence of [Ru(bpy)3]2+ solution containing silver nanoparticles].

In the present paper, the authors studied the effects of KCl on the fluorescence of [Ru(bpy)3]2+ solution containing silver nanoparticles by UV-Vis absorption spectra and fluorescence spectra. The results indicated that the stronger action between KCl and silver nanoparticles led to the vanishing of chain-like net structure formed between [Ru(bpy)3]2+ and silver nanoparticles and the formation of large particles and aggregates in the solution. Meanwhile, a new band at longer wavelength region appeared and the peak at long wavelength was red-shifted and broadened with the increase of KCl. With the increase in KCl content, the fluorescence decreases first and then increases till a constant value. The authors discussed the mechanism of the effects KCl on the fluorescence of [Ru(bpy)3]2+ solution containing silver nanoparticles in terms of interaction and energy transfer.

[Synthesis and fluorescence properties of the Tb(Ln) complexes with trimesic acid (Ln = Y, Gd)].

In the present paper two series of mixed rare earth complexes Tb(1-x)LnxBTC x nH2O (Ln = Y, Gd, x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by hydrothermal method. The contents of rare earth were measured by using EDTA titration method; the element analyses of C and H were performed by using Vario EL III elemental analyzer, and the IR spectra were recorded by FTIR-8900 infrared spectroscopy with KBr pellet. Then the molecular formula of the complexes were determined to be Tb(1-x)LnxBTC x 0.5H2O (Ln = Y, Gd). The fluorescence spectrum of all the complexes were recorded by using a Hitachi F-4500 fluorescence spectrophotometer at room temperature. The results indicated that all the complexes emitted characteristic fluorescence of Tb3+, and the fluorescence intensities of the complexes were obviously enhanced with doping rare earth ion of Y3+ or Gd3+. It was showed that Tb3+ was sensitized by doping rare earth ions. This may be because there was intra molecular energy transfer in the complexes. Being doped with the rare earth ion the emission peak positions did not change. Among the four emission peaks, 5D4 --> 7F5 (544 nm) was the strongest one, and it was found when the proportion is Y3+ : Tb3+ = 0.5 : 0.5 or Gd3+ : Tb3+ = 0.3 : 0.7, the fluorescence intensity of Tb(1-x)YxBTC x 0.5H2O or Tb(1-x)GdxBTC x 0.5H2O was the greatest, meanwhile the sensitization degree was bigger with doping Gd3+ than doping Y3+ at 544 nm.

Optical properties of transparent copper nanorod and nanowire arrays embedded in anodic alumina oxide.

Transparent copper nanorod/nanowire arrays and anodic alumina oxide composite films have been prepared by alternating current electrodeposition, and their linear optical properties have been systematically characterized by absorption spectra. In the experimental spectra, there exist transverse and longitudinal resonance peaks, which are caused by the surface-plasmon resonance along the diameter and the length of the copper nanorods, respectively. The transverse resonance peak is affected by the diameter and aspect ratio of the nanorod. The longitudinal resonance peak appears at longer wavelength when a polarized light illuminates the film with an angle of incidence of about 70 degrees , where the angle is defined with respect to the surface normal. Moreover, the longitudinal resonance mode is sensitive to the polarization direction when compared with the transverse resonance mode.

[Luminescence spectra of Sm3+ doped Sr2CeO4 synthesized through co-precipitation process].

The precursor powders of Sn3+ doped Sr2CeO4 were obtained by the application of (NH4)2C2O4 as a precipitant. After calcinations, the precursor powders became a white emitting fluorescent material. The XRD and emission spectra manifest that the optimum temperature and Sm3+ concentration for synthesizing Sr2CeO4:Sm are 1 050 degrees C and 1 mol%, respectively. The better the phosphor powders crystallize, the higher their emission intensities are. The excitation spectrum implies that the transition emissions of Sm3+ at 608 and 654 nm originate from the Ce4+ -O(2-) charge transfer (MLCT) resulting from the interaction of Ce4+ and the neighboring O2-. Therefore, it can be concluded that the host Sr2 CeO4 acts as a sensitizer, which transfers the energy to Sm3+. The emission intensity of the phosphor synthesized through co-precipitation is much higher than that of phosphor prepared using conventional solid state reactions.