Preparation,characterization and luminescence of transparent thin film of ionogels

The sol–gel fabrication of luminescent and transparent thin film of ionogels containing trivalent lanthanide complexes have been obtained from the silylated ionic liquid in the presence of lanthanide salts (Ln³⁺, Ln=Tb and Eu) and organic ligands. The resulting thin films were investigated by FT-IR spectroscopy, scanning electron microscopy and luminescence spectroscopy. FT-IR spectra reveal the hydrolysis and condensation of the silylated ionic liquid as well as the formation of luminescent lanthanide complexes in the thin films. Scanning electronic microscope images show the homogeneous characteristic of the thin films.     

Synthesis and photophysical characterization of highly luminescent silica films doped with substituted 2-hydroxyphthalamide (IAM) terbium complexes

Innovative Tb(3+) antenna complexes employing two different substituted 2-hydroxyphthalamide ligands (HxOH-IAM and bis-HxOH-IAM) acting simultaneously as coordinating sites and light collector units have been synthesized and successively anchored in silica layers by the sol-gel technique. The complexes show remarkable photoluminescence (PL) quantum yields in methanol solution, as high as 0.30 and 0.40 for (HxOH-IAM)(4)?Tb(3+) and (bis-HxOH-IAM)(2)?Tb(3+), respectively. The grafting of the Tb(3+) complexes in silica single layers accomplished by exploiting the terminal hydroxyl groups of the IAM chains results in highly transparent and homogeneous films displaying bright green emission and PL efficiencies of up to 0.40. The silica layers containing the (bis-HxOH-IAM)(2)?Tb(3+) show remarkable photostability even under prolonged and continuous irradiation (up to 3.5 h). The nature of the IAM ligands allows the photoexcitation of the complexes at wavelengths even longer than 350 nm, which is a spectral window suitable to develop luminescent lanthanide probes dedicated to bioanalyses and bioimaging applications.     

Sensitized emission from lanthanide-doped nanoparticles embedded in a semiconductor sol-gel thin film.

In(2)O(3) sol-gel thin films made with LaF(3):Ln(3+) (Ln=Er, Nd, and Eu) nanoparticles were prepared and showed sensitized emission of the lanthanide ions after In(2)O(3) matrix excitation. The excitation spectra showed an In(2)O(3) absorption band in addition to the excitation peaks of the lanthanide ions, clearly demonstrating that there is energy transfer from the In(2)O(3) matrix to Ln(3+) (Er(3+), Nd(3+), and Eu(3+)). Similarly, HfO(2) and ZrO(2) sol-gel thin films made with LaF(3):Ln(3+) nanoparticles also showed energy transfer from the semiconductor matrix to the lanthanide ions.     

Preparation and photochromism of Keggin-type molybdphosphoric acid/silica mesoporous composite thin films

Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized by evaporation induced self-assembly process in the presence of cetyltrimethyl ammonium bromide templates under acid conditions. The Keggin-type molybdphosphoric acid (PMo) is incorporated into the mesoporous silica thin films with amino-groups by wetness impregnation, and the PMo/silica mesoporous composite thin films are obtained. The results of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectra indicate the PMo molecules maintain Keggin structure and are homogeneously distributed inside mesopores. The composite thin films possess excellent reversible photochromic properties, and change from colorless to blue under ultraviolet irradiation. The photochromic mechanism of the composite thin films is studied by ultraviolet-visible (UV-vis), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) spectra. It is shown that intervalence charge transfer (IVCT) and ligand-to-metal charge transfer (LMCT) are the main reasons of photochromism. PMo anions interact strongly with amino-groups of the mesoporous suface via hydrogen bond and electrostatic force. After ultraviolet irradiation, the charge transfer occurs by reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo(VI, V), and the bleaching process of composite thin films is closely related to the presence of oxygen.     

磷灰石结构荧光粉Ba10(PO4)6F2:Ce3+,Tb3+的合成、发光和能量传递

采用高温固相法合成了系列Ce~(3+)和Ce~(3+)/Tb~(3+)激活的具有磷灰石结构荧光粉Ba_(10)(PO_4)_6F_2。用X射线衍射(XRD)、扫描电镜(SEM)、激发和发射(PLE和PL)光谱对样品进行了表征分析。研究结果表明:所合成的荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)具有氟磷灰石结构,样品微观呈现不规则形貌。荧光粉Ba10-x(PO4)6F2∶x Ce~(3+)的相对发射强度随着x增加而增强,当x=0.09时,荧光强度达到最大。荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的激发光谱为240～330 nm的宽带,发射光谱呈现出Ce~(3+)的5d→4f跃迁紫外光(335和358 nm)发射和Tb~(3+)的4f→4f跃迁绿光(542 nm)发射。光谱特性表明,发光过程中存在Ce~(3+)→Tb~(3+)能量传递,能量传递效率可以达到60%。计算Ce~(3+)和Tb~(3+)的临界距离为0.79 nm,能量传递机理是偶极-偶极交互作用。此外,详细论述了Ce~(3+)和Tb~(3+)之间的能量传递和发光的过程。通过调节Tb~(3+)的掺杂浓度,对荧光粉发光色坐标与Tb~(3+)的掺杂浓度之间的关系也进行了研究,随着Tb~(3+)的掺杂量从0增加0.52,荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的发射光谱色坐标可以从(0.149 4,0.045 1)蓝色区变化到(0.280 1,0.585 3)绿色区。     

Preparation of hybrid mesoporous silica luminescent nanoparticles with lanthanide(III) complexes and their exhibition of white emission

We chose dipicolinic acid as a tridentate chelating unit featuring ONO donors to react with lanthanide(III) ions to yield tight and protective N(3)O(6) environments around the lanthanide(III) ions. We immobilized the lanthanide(III)-dipicolinic acid complexes on colloidal mesoporous silica with diameter smaller than 100 nm by a covalent bond grafting technique and obtained nearly monodisperse luminescent Eu-dpa-Si and Tb-dpa-Si functionalized hybrid mesoporous silica nanomaterials. These hybrid nanomaterials were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, nitrogen adsorption-desorption, and photoluminescence spectroscopic techniques. The hybrid mesoporous silica nanoparticles exhibit intense emission lines upon UV-light irradiation, owing to the effective intramolecular energy transfer from the chromophore to the central lanthanide Eu(3+) and Tb(3+) ions. Furthermore, the functionalized nanomaterials can be turned to white light materials after annealing at high temperature.     

Luminescence properties of rhodamine 6G intercalated in surfactant/clay hybrid thin solid films

To develop the solid-state laser oscillator based on laser dye compounds, the incorporation of rhodamine 6G (R6G, a laser dye) in cetyltrimethylammonium (CTA+) cationic surfactant/montmorillonite clay hybrid (HpC) thin solid films was investigated. The R6G/HpC samples were prepared by immersing the HpC films into a R6G aqueous solution with various concentration. X-ray diffraction patterns of the films of HpC, measured before and after the intercalation of R6G, proved the coexistence of both the dye and surfactant in clay interlayer spaces. All prepared thin films exhibited luminescence. It indicates that CTA+ molecules play a role as a partial suppressor of the aggregation of R6G molecules which prevents fluorescence. Moreover, the luminescence property of the present thin films was observed to be dependent on the co-intercalated degree of R6G molecules, indicating that the R6G intercalating in HpC interlayer space molecules exist as two or more luminescence species in the clay interlayer space.     

Photoinduced electron transfer and geminate recombination for photoexcited acceptors in a pure donor solvent

Photoinduced electron transfer and geminate recombination are studied for the systems rhodamine 3B (R3B(+)) and rhodamine 6G (R6G(+)), which are cations, in neat neutral N,N-dimethylaniline (DMA). Following photoexcitation of R3B(+) or R6G(+) (abbreviated as R(+)), an electron is transferred from DMA to give the neutral radical R and the cation DMA(+). Because the DMA hole acceptor is the neat solvent, the forward transfer rate is very large, approximately 5x10(12) s(-1). The forward transfer is followed by geminate recombination, which displays a long-lived component suggesting several percent of the radicals escape geminate recombination. Spectrally resolved pump-probe experiments are used in which the probe is a "white" light continuum, and the full time-dependent spectrum is recorded with a spectrometer/charge-coupled device. Observations of stimulated emission (excited state decay-forward electron transfer), the R neutral radical spectrum, and the DMA(+) radical cation spectrum as well as the ground-state bleach recovery (geminate recombination) make it possible to unambiguously follow the electron transfer kinetics. Theoretical modeling shows that the long-lived component can be explained without invoking hole hopping or spin-forbidden transitions.     

Synthesis, crystal structures, and luminescence of organic-lanthanide complexes with nicotinate and isonicotinate ligands

Six lanthanide coordination compounds with two isomeric carboxylic acids, nicotinic acid (HL(1)) and isonicotinic acid (HL(2)), [(L(1))3Ln(H2O)2]2 (Ln = Eu, 1; Gd, 2; Tb, 3) and [( L(2))2Ln(H2O)4][NO3] (Ln = Eu, 4; Gd, 5; Tb, 6), have been synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1-3 are dimeric whereas 4-6 are polymeric, all with 8-coordination of Ln(3+). The distinction between these lanthanide complexes is readily accomplished from the 10 K high resolution electronic emission spectra. Spectral interpretation is given for the Eu(3+) complexes 1, 4, whereas the spectra of 3 and 6 are more complex. The relationships between spectroscopic and crystallographic site symmetries are discussed. The calculated second rank crystal field strengths of Eu(3+) in 1 and 4 are intermediate in magnitude.     

Luminescent nanoparticles prepared by encapsulating lanthanide chelates to silica sphere

The luminescent nanoparticles were prepared by encapsulating the [LnL₄]^? (Ln = Eu, Tb; L = BTFA, HFAA, TTFA, TFAA) complexes anion into the silicon framework. We firstly synthesized a series of novel siloxy-bearing lanthanide complex precursor, and then encapsulated them into the silica sphere by a modified Stöber process. As a result, four europium and two terbium tetrakis β-diketonate complexes functionalized silica sphere nanoparticles were obtained and characterized in detail using Fourier transform infrared spectra, X-ray diffraction, scanning electronic microscope, thermogravimetric analysis, luminescence excitation and emission spectroscopy, luminescence lifetime measurements, and diffuse reflectance UV–Vis spectroscopy. The result shows that these luminescent nanoparticles maintain the distinctive luminescence character of lanthanide chelate including broad excitation spectra, line-like emission spectra, high quantum efficiency, and long luminescent lifetime, which makes them great potential application in the synthesis of luminescent nanoparticle.     

Cationic lanthanide monoporphyrinates with Sm, Eu, Gd and Tb, synthesis and spectroscopic properties in aqueous and non-aqueous media

The synthesis of a new series of cationic monoporphyrinates with “light” lanthanide ions is reported. The meso-tetrakis(4-pyridyl)porphyrin, (tpyp)H₂, was used as the tetrapyrrole ligand, and the metallation reaction with the lanthanide ions in acetyl-acetonato form, leading to Ln(tpyp)acac, where Ln = Sm, Eu, Gd and Tb, was carried out. The cationic monoporphyrinates, Ln(tmepyp)acac, were synthesized via the corresponding Ln(tpyp)acac. These complexes are freely soluble in aqueous and non-aqueous solutions, like MeOH, H₂O or N,N-dimethylformamide. Their spectroscopic properties in water and DMF solutions are reported. All the complexes were characterized on the basis of their UV-vis, IR and ESR data. No ESR spectra were obtained for cationic porphyrins in DMF for Sm, Eu and Tb, while the spectra of Gd(tmepyp)acac in DMF exhibits smaller ΔH_pp (103.1 G) among the spectra of Gd^III complexes. The unexpected broad signal of Eu(t-mepyp)acac, ΔH_pp = 126.9 G, in H₂O is discussed in terms of the formal oxidation state +2 for the central ion.     

Photoinduced charge-transfer between ferrocene derivatives and chloroform molecules confined in poly(methyl methacrylate) thin films

The changes in the electronic absorption spectra (UV-Vis) (after photoexcitations) of poly(methyl methacrylate) (PMMA) thin films doped with a ferrocene derivative and containing chloroform molecules as impurities, have been studied as a function of photoexcitation wavelength (210–750 nm), photoexcitation time (duration), amount of ferrocene derivative in the film and amount of chloroform molecules present in the film. Occurrence of photoinduced charge-transfer between some ferrocene derivatives and chloroform molecules confined in the PMMA thin films has been observed. The effects of the substitution group (attached to the ferrocene unit) on the photoinduced changes are discussed.     

Wavelength and metal dependence in the photofragmentation of a gas-phase lanthanide beta-diketonate complex

The time-of-flight mass spectra of tris(2,2,6,6-tetramethyl-3,5-heptanedionato) lanthanide(III) [or Ln(thd)3 with Ln = Eu, Tb, Gd] produced by laser-induced multiphoton ionization in a supersonic expansion were studied as a function of laser excitation wavelength. Resonance-enhanced multiphoton ionization (REMPI), monitoring the Eu(I) ion signal from gas-phase Eu(thd)3, was observed in three distinct visible-excitation regions, corresponding to electronic absorption transitions on neutral Eu(0) atoms. The confirmation of the presence of Eu(0) atoms in the beam supports the proposed mechanism for the production of Ln atoms through sequential dissociation of neutral thd ligands from the metal following photoexcitation into ligand-to-metal charge-transfer (LMCT) states. Evidence is also presented that the LnO+ and LnOH+ fragments observed in the mass spectrum are produced via a separate, competing fragmentation pathway. The branching ratios between the two fragmentation pathways are compared for Ln(thd)3 (Ln = Eu, Tb, Gd). The ligand-dissociation pathway that produces Ln atoms appears to be more favorable in Ln(thd)3 complexes with low-lying LMCT states. Finally, the observation of the Tb2(thd)6+ dimer and its associated fragmentation pattern, as well as the presence of metal carbides, which are relevant to carbon contamination in chemical vapor deposition, is discussed.     

Lanthanide sensitization in II-VI semiconductor materials: a case study with terbium(III) and europium(III) in zinc sulfide nanoparticles

This work explores the sensitization of luminescent lanthanide Tb(3+) and Eu(3+) cations by the electronic structure of zinc sulfide (ZnS) semiconductor nanoparticles. Excitation spectra collected while monitoring the lanthanide emission bands reveal that the ZnS nanoparticles act as an antenna for the sensitization of Tb(3+) and Eu(3+). The mechanism of lanthanide ion luminescence sensitization is rationalized in terms of an energy and charge transfer between trap sites and is based on a semiempirical model, proposed by Dorenbos and co-workers (Dorenbos, P. J. Phys.: Condens. Matter 2003, 15, 8417-8434; J. Lumin. 2004, 108, 301-305; J. Lumin. 2005, 111, 89-104. Dorenbos, P.; van der Kolk, E. Appl. Phys. Lett. 2006, 89, 061122-1-061122-3; Opt. Mater. 2008, 30, 1052-1057. Dorenbos, P. J. Alloys Compd. 2009, 488, 568-573; references 1-6.) to describe the energy level scheme. This model implies that the mechanisms of luminescence sensitization of Tb(3+) and Eu(3+) in ZnS nanoparticles are different; namely, Tb(3+) acts as a hole trap, whereas Eu(3+) acts as an electron trap. Further testing of this model is made by extending the studies from ZnS nanoparticles to other II-VI semiconductor materials; namely, CdSe, CdS, and ZnSe.     

烟酸稀土分子杂化发光材料的制备与性能研究

利用烯-巯加成的方法,合成了一种带有三联吡啶基团的有机硅氧烷,该中间体用核磁共振、红外、质谱等手段进行了表征确认.以该中间体作为第二配体,加入稀土(Eu3+、Tb3+)烟酸配合物,在正硅酸乙酯的存在下用溶胶-凝胶法原位制备了稀土(Eu3+、Tb3+)烟酸配合物与二氧化硅基质以共价键相连的烟酸稀土分子杂化发光材料.通过红外光谱、紫外-可见光漫反射光谱、荧光光谱和寿命测试表征了制备的杂化发光材料.荧光光谱数据表明在杂化材料中,由于三联吡啶配体通过有效的分子内传能过程将其激发态的能量传递给稀土离子的发射能级,从而极大地提高了稀土离子的特征发射.掺铕离子的最强发射为617nm,是纯红光发射;而掺铽离子的最强发射为543nm,是典型的绿光发射.掺铕和铽的分子杂化材的荧光寿命分别为0.66ms,0.68ms,同时荧光衰减均为一级指数衰减,说明稀土离子在杂化材料中分散得很均匀.     

Photophysical properties of novel lanthanide (Tb3+, Dy3+, Eu3+) complexes with long chain para-carboxyphenol ester p-L-benzoate (L=dodecanoyloxy, myristoyloxy, palmitoyloxy and stearoyloxy)

In this paper, a series of 12 binary luminescent lanthanide coordination compounds with long chain p-carboxyphenol ester were assembled. Both elemental analysis and infrared spectroscopy allowed to determine the complexes formula: LnL3, where Ln=Tb, Dy, Eu; L=p-dodecanoyloxybenzoate (12-OBA), p-myristoyloxybenzoate (14-OBA), p-palmitoyloxybenzoate (16-OBA) and p-stearoyloxybenzoate (18-OBA), respectively. The photophysical properties of these complexes were studied in detail with various of spectroscopies such as ultraviolet-visible absorption spectra, low temperature phosphorescence spectra and fluorescent spectra. The ultraviolet-visible absorption spectra showed that some bands shift with the different chain length of p-carboxyphenol ester. From the low temperature phosphorescent emission, the triplet state energies for these four ligands were determined to be around 24,242 cm-1 (12-OBA), 24,612 cm-1 (14-OBA), 24,084 cm-1 (16-OBA) and 24,125 cm-1 (18-OBA), respectively, suggesting they are suitable for the sensitization of the above lanthanide ions, especially for Tb3+ and Dy3+. The fluorescence excitation and emission spectra for these lanthanide complexes of the four ligands take agreement with the above predict from energy match.     

Characterization of rhodamine 6G aggregates intercalated in solid thin films of laponite clay. 2 Fluorescence spectroscopy

The photoluminescence response of Rhodamine 6G (R6G) laser dye intercalated into solid thin films of Laponite (Lap) clay is studied as a function of dye loading. Fluorescence spectroscopy (steady-state and time-resolved techniques) was used to characterize the R6G species adsorbed into the solid films. For very diluted R6G loadings (40% CEC), with a reminiscent fluorescence band at around 600 nm.     

Vibrational spectroscopy of dimethylchlorooctadecylsilane covalently bonded to ultrathin silica films immobilized on Ag surfaces

FTIR and Raman spectroscopies have been used to characterize the structure and conformational order of dimethylchlorooctadecylsilane (DOS) covalently bonded to ultrathin silica films supported on Ag substrates. Ultrathin silica films of ca. 30 A thickness prepared from sol-gel methods are immobilized on Ag surfaces modified with a self-assembled monolayer of (3-mercaptopropyl)trimethoxysilane (3MPT). This layered structure provides a unique opportunity for acquiring complementary spectral data from both FTIR and Raman spectroscopies, which are useful in elucidating alkylsilane conformation pertaining to stationary phases for reversed-phase liquid chromatography (RPLC). Characterization of octadecyltrichlorosilane (OTS) layers on thin silica films of ca. 800 A thickness on 3MPT-modified Ag surfaces has been reported previously. Differences between the ultrathin silica films used in this study and the thin silica films used in this previous study are considered. The results from both FTIR and Raman spectroscopy presented here suggest that bonded DOS alkyl chains are in a disordered, liquid-like state with close to monolayer surface coverage.     

Single oscillator model and refractive index dispersion properties of ternary ZnO films by sol gel method

The optical constants of the NiMnZnO thin films prepared by spin-coating method were determined using transmittance and reflectance spectra. The optical band gap of the NiMnZnO thin films was found to be in the range of 3.20–3.35 eV. The refractive index dispersion of the NiMnZnO films obeys the single oscillator model. The dispersion energy and oscillator energy values of the NiMnZnO films were found to be in the range of 6.46–9.85 and 4.82–5.54 eV, respectively. The real and imaginary parts of the dielectric constants of the NiMnZnO films were determined. The reflectance spectra of the NiMnZnO films give a peak and the presence of this peak is due to the photoexcitation process, in which, the electrons are excited from valence band to the conduction band. The obtained results suggest that the optical constants and refractive dispersion energy parameters of the films are controlled by the molar ratios of NiMnZnO films.     

Photoconductivity in Mesostructured Thin Films

Mesostructured silica films are widely studied due to their different structures, properties and variety of possible applications. Sodium dodecyl sulfate (SDS)-templated sol-gel silica films possess highly ordered lamellar phase structure. It is expected that molecules and polymer chains line up with these layered structures when incorporated into the films. Mesostructured thin films were doped with Dispersed Red 1 (DR1) and carbazole ((C₆H₄)₂NH)). The films were poled by corona discharge at 120 C. Absorption spectra were recorded as function of the polarization time. Dependence of the absorption coefficient with polarization time was fitted with a Langevin-Debye equation. It shows a saturation level after 60 minutes of polarization. We compare the efficiency of mesostructured thin films with that of amorphous films. The photoconductivity technique was used to determine the charge transport mechanism of these films. From current density versus electrostatic applied field, the parameters for the photovoltaic effect and photoconductivity were determined. Results of the mesostructured thin films are also compared to those of KNbO₃ crystals.