Calix[4]arene derivative functionalized lanthanide (Eu, Tb) SBA-15 mesoporous hybrids with covalent bonds: assembly, characterization and photoluminescence

Three kinds of novel macrocylic calix[4]arene derivatives functionalized SBA-15 type of mesoporous hybrids (Calix-S15, Calix-NO(2)-S15 and Calix-NH(2)-S15) are synthesized by co-condensation of tetraethoxysilane (TEOS) and modified organic ligand (Calix-Si, Calix-NO(2)-Si and Calix-NH(2)-Si) in the presence of Pluronic P123 surfactant as a template. The structural preservation of these three parent materials is confirmed by FTIR spectra, (29)Si MAS NMR spectra, XRD pattern, and N(2) adsorption-desorption measurements. The ternary mesoporous luminescent hybrids containing Ln(3+) (Eu(3+), Tb(3+)) complexes covalently attached to the functionalized ordered mesoporous SBA-15, which are designated as Ln(Calix-S15)phen, Ln(Calix-NO(2)-S15)phen and Ln(Calix-NH(2)-S15)phen, are obtained by introducing lanthanide ions and 1,10-phenanroline into the corresponding parent material via covalent bond assembling methods. XRD pattern, TEM and N(2) adsorption-desorption measurements are employed to characterize the mesostrcture of the resulting lanthanide mesoporous hybrids. The photoluminescent behavior (luminescence, lifetime, quantum efficiency, and energy transfer) for these chemically bonded mesoporous hybrids is studied in detail. Also, their quantum efficiencies are determined, which indicates that the different mesoporous hybrid material systems derived from different functionalized calix[4]arene derivative bridges present different luminescence behavior.     

Covalent linking of near-infrared luminescent ternary lanthanide (Er(3+), Nd(3+), Yb(3+)) complexes on functionalized mesoporous MCM-41 and SBA-15

The near-infrared (NIR) luminescent lanthanide ions, such as Er(III), Nd(III), and Yb(III), have been paid much attention for the potential use in the optical communications or laser systems. For the first time, the NIR-luminescent Ln(dbm)(3)phen complexes have been covalently bonded to the ordered mesoporous materials MCM-41 and SBA-15 via a functionalized phen group phen-Si (phen-Si = 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline; dbm = dibenzoylmethanate; Ln = Er, Nd, Yb). The synthesis parameters X = 12 and Y = 6 h (X denotes Ln(dbm)(3)(H(2)O)(2)/phen-MCM-41 molar ratio or Ln(dbm)(3)(H(2)O)(2)/phen-SBA-15 molar ratio and Y is the reaction time for the ligand exchange reaction; phen-MCM-41 and phen-SBA-15 are phen-functionalized MCM-41 and SBA-15 mesoporous materials, respectively) were selected through a systematic and comparative study. The derivative materials, denoted as Ln(dbm)(3)phen-MCM-41 and Ln(dbm)(3)phen-SBA-15 (Ln = Er, Nd, Yb), were characterized by powder X-ray diffraction, nitrogen adsorption/desorption, Fourier transform infrared (FT-IR), elemental analysis, and fluorescence spectra. Upon excitation of the ligands absorption bands, all these materials show the characteristic NIR luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions. The excellent NIR-luminescent properties enable these mesoporous materials to have potential uses in optical amplifiers (operating at 1.3 or 1.5 mum), laser systems, or medical diagnostics. In addition, the Ln(dbm)(3)phen-SBA-15 materials show an overall increase in relative luminescent intensity and lifetime compared to the Ln(dbm)(3)phen-MCM-41 materials, which was explained by the comparison of the lanthanide ion content and the pore structures of the two kinds of mesoporous materials in detail.     

Multi-walled carbon nanotube-based ternary rare earth (Eu3+, Tb3+) hybrid materials with organically modified silica-oxygen bridge

A series of ternary rare earth (Eu(3+), Tb(3+)) complexes are covalently coated to the 3-aminopropyltriethoxysilane functionalized multi-walled carbon nanotube (MWCNT) by a simple in situ sol-gel method by the bifunctional silylated monomer TTA-Si and TAA-Si (TTA-Si and TAA-Si are 3-(triethoxysilyl)propylisocyanate (TEPIC) modified thenoyltrifluoroacetone (TTA) and trifluoroacetylacetone (TAA), respectively). The resulting materials are characterized by Fourier transform infrared spectra, scanning electronic microscope, transmission electron microscope, thermogravimetric analysis, ultraviolet visible diffused reflection measure, photoluminescence spectra, and X-ray diffraction. The photoluminesce measurements indicated that these hybrids exhibit characteristic red and green luminescence originating from the corresponding ternary rare earth ion (Eu(3+), Tb(3+)). The luminescence quenching effect of MWCNT networks have been successfully restrained by coating a relatively thicker silica-oxygen-based organic-inorganic complex. Furthermore, the fluorescence lifetimes and emission quantum efficiencies of Eu(3+) hybrid materials are also determined.     

Stable lanthanide luminescence agents highly emissive in aqueous solution: multidentate 2-hydroxyisophthalamide complexes of Sm(3+), Eu(3+), Tb(3+), Dy(3+)

Efficient lanthanide (Ln) luminescent probes require good ligand-to-metal energy transfer and high aqueous stability. A family of ligands based on 2-hydroxyisophthalamide chelating units is reported. These form highly stable, eight-coordinate Ln complexes. Several of these (Ln = Sm, Eu, Tb, Dy) emit in the visible region with good ligand-to-lanthanide energy transfer. The absolute quantum yields of the two Tb complexes studies (Phi = 0.59, 0.61) and high absorbance make these the brightest luminescent probes for time-resolved detection; the emission spectrum of one complex can be seen down to 10-15 M. The low overlap of the four different Ln complexes enables their simultaneous detection and discrimination.     

Luminescent lanthanide (Eu3+, Tb3+) hybrids with 4-vinylbenzeneboronic acid functionalized Si-O bridges and beta-diketones

4-Vinylphenylboronic acid ligand (VPBA) is functionalized with two crosslinking reagents (3-(triethoxysilyl)-propylisocyanate [TEPIC] and 3-(trimethoxysilyl) propyl methacrylate [TMPMA]) to achieve the two special molecular bridge VPBA-TEPIC and VPBA-TMPMA. Meanwhile, beta-diketone ligands (2-thenoyltrifluoroacetone [TTA], acetyl acetone [ACAC]) as the second ligands play the role of the main energy donor, which absorb abundant energy in ultraviolet-visible extent and then transfer the energy to the corresponding lanthanide ions (Eu(3+), Tb(3+)) to sensitize their emission of them. Eight binary and ternary Eu(3+), Tb(3+) hybrids with VPBA-TEPIC (VPBA-TMPMA) and TTA (ACAC) have been constructed, whose photoluminescence properties are studied in depth and suggest that the ternary hybrids show the favorable characteristic luminescent properties (longer lifetime and higher quantum efficiency).     

Photofunctional Eu3+/Tb3+ hybrids through sulfoxide linkages: coordination bonds construction, characterization and luminescence

New kinds of organic-inorganic hybrid materials consisting of rare earth (Eu(3+), Tb(3+)) complexes covalently bonded to a silica-based network have been obtained by a sol-gel approach. Three novel versatile molecular building blocks containing sulfoxide organic units have been synthesized by methylene modification reaction, which are used as the ligands of rare earth ions and also as siloxane network precursors. The obtained hybrids are characterized by chemical analysis and spectroscopic methods such as FTIR and UV; XRD and SEM. Photoluminescence measurements on the prepared hybrids were performed showing the intra-4f(n) emission in the visible (Eu(3+), Tb(3+)) region and in all the cases being sensitized by the sulfoxide ligands. The emission quantum efficiency and the Judd-Ofelt intensity parameters of Eu(3+) hybrid materials were also investigated in detail.     

Bifunctional Mixed-Lanthanide Cyano-Bridged Coordination Polymers Ln(0.5)Ln'(0.5)(H(2)O)(5)[W(CN)(8)] (Ln/Ln' = Eu(3+)/Tb(3+), Eu(3+)/Gd(3+), Tb(3+)/Sm(3+))

A new family of mixed-lanthanide cyano-bridged coordination polymers Ln(0.5)Ln'(0.5)(H(2)O)(5)[W(CN)(8)] (where Ln/Ln' = Eu(3+)/Tb(3+), Eu(3+)/Gd(3+), and Tb(3+)/Sm(3+)) containing two lanthanide and one transition metal ions were obtained and characterized by X-ray diffraction, photoluminescence spectroscopy, magnetic analyses, and theoretical computation. These compounds are isotypical and crystallize in the tetragonal system P4/nmm forming two-dimensional grid-like networks. They present a magnetic ordering at low temperature and display the red Eu(3+) ((5)D(0) → (7)F(0-4)) and green Tb(3+) ((5)D(4) → (7)F(6-2)) characteristic photoluminescence. The Tb(0.5)Eu(0.5)(H(2)O)(5)[W(CN)(8)] compound presents therefore green and red emission and shows Tb(3+)-to-Eu(3+) energy transfer.     

Photoactive rare earth (Eu3+, Tb3+) hybrids with organically modified silica covalently bonded polymeric chain

1,3-Bis(2-formylphenoxy)-2-propanol (BFPP) is grafted to 3-(triethoxysilyl)-propyl isocyanate (TESPIC) to prepare the organic precursor BFPP-Si. Then, the organic precursor BFPP-Si is coordinated with rare earth ion to obtain the luminescent center RE-BFPP-Si. Allylamine monomer (AM) is modified by TESPIC to form the precursor AM-Si which is then polymerized with the benzoyl peroxide as the initiator to form the polymer precursor PAM-Si. The other polymer precursor polyethylene glycol (PEG)-Si is achieved through the grafting reaction between PEG and TESPIC. Subsequently, the hybrid materials RE-BFPP-Si-PAM or RE-BFPP-Si-PEG are assembled in which RE-BFPP-Si and PAM-Si or PEG-Si connected with Si-O bonds through sol-gel process and characterized with scanning electronic microscopy, X-ray diffraction, and TG-DSC curves. Their photophysical properties are especially studied in details, indicating that the introduction of organic polymer chain is favorable for the luminescence lifetime and quantum efficiency.     

Photoluminescent Eu3+/Tb3+ hybrids from the copolymerization of organically modified silane

A novel series of organic/inorganic/polymeric hybrid materials have been constructed from covalently bonding rare earth complexes into the inorganic matrix and polymer backbone. Among functional linkage, 3-chloropropyltrimethoxysilane is used to modify the hydroxyl group of p-hydroxycinnamic acid via substitution reaction to form the precursor, and the precursor is subsequently used to covalently bonding to acrylic acid, methyl acrylate, and vinyltriethoxysilane, respectively, through copolymerization reaction to form the organic/inorganic/polymeric network. In addition, we introduce the monomer 1,10-phenanthroline as the second reagent ligand for constructing the ternary luminescent hybrid material systems (abbreviated as HC-PMA-RE, HC?=?p-hydroxycinnamic acid and 3-chloropropyltrimethoxysilane). The physical characterization and especially the photoluminescence property of ternary system are studied in detail, which present the regular microstructure and characteristic photoluminescence.     

Rare-earth (Eu, Tb) hybrids through amide bridge: Chemically bonded self-assembly and photophysical properties

This work focuses on the construction of a series of chemically bonded rare-earth/inorganic/organic hybrid materials (TCH-Si-Ln, TCH-Si-Ln-Phen and TCH-Si-Ln-Bipy: Phen = 1,10-phenanthroline, Bipy = 2,2′-bipyridyl) using TCH-Si as an organic bridge molecule that can both coordinate to rare-earth ions (Eu³⁺ and Tb³⁺) and form an inorganic Si-O-Si network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation through a sol-gel process. All of these hybrid materials exhibit homogeneous microstructures and morphologies, suggesting the occurrence of self-assembly of the inorganic network and organic chain. Measurements of the photoluminescent properties of these materials show that the ternary europium systems present stronger luminescent intensities than the binary hybrids, indicating that the introduction of the second ligands can sensitize the luminescence emission of the europium hybrid systems. However, in the terbium systems, this phenomenon was not observed.     

Hybrid materials of MCM-41 functionalized by lanthanide (Tb, Eu) complexes of modified meta-methylbenzoic acid: Covalently bonded assembly and photoluminescence

Novel organic-inorganic mesoporous hybrid materials were synthesized by linking lanthanide (Tb³⁺, Eu³⁺) complexes to the mesoporous MCM-41 through the modified meta-methylbenzoic acid (MMBA-Si) using co-condensation method in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as template. The luminescence properties of these resulting materials (denoted as Ln-MMBA-MCM-41, Ln=Tb, Eu) were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the ordered mesoporous structure. Moreover, the mesoporous material covalently bonded Tb³⁺ complex (Tb-MMBA-MCM-41) exhibits the stronger characteristic emission of Tb³⁺ and longer lifetime than Eu-MMBA-MCM-41 due to the triplet state energy of organic legend MMBA-Si matches with the emissive energy level of Tb³⁺ very well.     

Lanthanide (Eu3+, Tb3+) centered hybrid materials using modified functional bridge chemical bonded with silica: molecular design, physical characterization, and photophysical properties

1,3-Bis(2-formylphenoxy)-2-propanol (BFPP) was first synthesized and then grafted to 3-(triethoxysilyl)propyl isocyanate (TESPIC) to achieve a molecular precursor BFPP-Si through the hydrogen-transfer nucleophilic addition reaction between the hydroxyl group of BFPP and the isocyanate group of TESPIC. Then, a chemically bonded lanthanide/inorganic/organic hybrid material (BFPP-Si-Ln) was constructed using BFPP-Si as a bridge molecule that can both coordinate to lanthanide ions (Eu3+ or Tb3+) and form an inorganic Si-O network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation processes. Furthermore, two types of ternary rare-earth/inorganic/organic hybrids (BFPP-Si-Dipy-Ln and BFPP-Si-Phen-Ln) were assembled by the introduction of the second ligands (4,4'-bipyridyl and 1,10-phenanthroline) into the above system. All of these hybrid materials exhibit homogeneous microstructures and morphologies, suggesting the occurrence of self-assembly of the inorganic network and organic chain. Measurements of the photoluminescent properties of these materials show that the ternary rare-earth/inorganic/organic hybrids present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary hybrids, indicating that the introduction of the second ligands can sensitize the luminescence emission of the lanthanide ions in the ternary hybrid systems.     

Rare earth (Eu, Tb) mesoporous hybrids with calix[4]arene derivative covalently linking MCM-41: Physical characterization and photoluminescence property

MCM-41 mesoporous silica has been functionalized with two kinds of macrocylic calixarene derivatives Calix[4] and Calix[4]Br (Calix[4]=P-tert-butylcalix[4]arene, Calix[4]Br=5.11,17.23-tetra-tert-butyl-25.27-bihydroxy-26.28-bibromopropoxycalix[4]arene) through condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as a template. Novel organic-inorganic mesoporous luminescent hybrid containing RE³⁺ (Eu³⁺, Tb³⁺) complexes covalently attached to the functionalized ordered mesoporous MCM-41, which are designated as RE-Calix[4]-MCM-41 and RE-Calix[4]Br-MCM-41, respectively, are obtained by sol-gel process. It is found that they all have high surface area, uniform in the mesostructure and good crystallinity. Measurement of the photoluminescence properties show the mesoporous material covalently bonded Tb³⁺ complexes (Tb-Calix[4]-MCM-41 and Tb-Calix[4]Br-MCM-41) exhibit the stronger characteristic emission of Tb³⁺ and longer lifetime than the corresponding Eu-containing materials Eu-Calix[4]-MCM-41 and Eu-Calix[4]Br-MCM-41 due to the triplet state energy of modified organic ligands Calix[4]-Si and Calix[4]Br-Si match with the emissive energy level of Tb³⁺ very well.     

Ternary luminescent lanthanide-centered hybrids with organically modified titania and polymer units

Nicotinic acid (NA) is grafted to titanium alkoxide to achieve functional precursor Ti-NA, which then is coordinated to lanthanide ions (Tb³⁺/Eu³⁺) to prepare the binary titania hybrid materials Ti-NA-Eu/Ti-NA-Tb via a sol–gel process in the presence of water. Furthermore, two types of ternary titania hybrid materials, Ti-NA-Ln-PMAA/Ti-NA-Ln-PVP, are assembled by the introduction of the organic polymers polymethacrylic acid (PMAA)/polyvinylpyrrolidone (PVP) into the above system. The FTIR spectra of these titania hybrid materials confirm their basic composition, and the X-ray diffraction patterns reveal that they are amorphous. Luminescence spectra and lifetimes of these titania hybrids are recorded, revealing that these hybrid materials with organic polymers exhibit longer luminescence lifetimes and higher quantum efficiencies.     

Synthesis,characterization, and photoluminescence of SrBPO5:R,Na+ (R = Eu3+, Tb3+) phosphor for solid state lighting

A series of phosphors SrBPO₅:R,Na⁺ (R = Eu³⁺, Tb³⁺) were prepared by high-temperature solid-state synthesis, and their phase purity, morphology, IR spectra, and UV-Vis photoluminescence properties were investigated. The f-f transitions of Eu³⁺ and Tb³⁺ ions in the host lattice were assigned and discussed. The excitation and emission spectra indicate that SrBPO₅:Eu³⁺,Na⁺ and SrBPO₅:Tb³⁺,Na⁺ can be effectively excited by ultraviolet (394 and 370 nm), and exhibit reddish orange emission and yellowish green emission, respectively. The influence of the doping concentration on the relative emission intensity of Eu³⁺/Tb³⁺ was investigated, and the critical distance R_c was estimated in term of the concentration quenching data. The present study suggests SrBPO₅:R,Na⁺ (R = Eu³⁺, Tb³⁺) phosphor can be a potential candidate as an UV-convertible phosphor for white light-emitting diodes (LEDs).     

Solvothermal synthesis and characterization of Ln (Eu3+, Tb3+) doped hydroxyapatite

Luminescent Ln (Eu3+, Tb3+) doped hydroxyapatite (Eu:HAp, Tb:HAp) phosphors were successfully fabricated via the cetyltrimethylammonium bromide (CTAB)/n-octane/n-butanol/water microemulsion-mediated solvothermal process. The structure, morphology, and optical properties were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra as well as the kinetic decays, respectively. The XRD results reveal that the obtained Eu:HAp and Tb:HAp show the characteristic peaks of hydroxyapatite in a hexagonal lattice structure. It is observed that the as-prepared luminescent samples exhibit rod-like morphology with well dispersed and non-aggregated size distribution. Upon excitation by UV radiation, the phosphors demonstrate the characteristic 5D 0-7F 1-4 emission lines of Eu3+ and the characteristic 5D4-7F 3-6 emission lines of Tb3+. Moreover, the photoluminescence intensities (PL) of Eu3+ and Tb3+ can be tuned by altering the solvothermal temperature and the doping concentration of Eu3+ and Tb3+.     

Anion/cation induced optical switches based on luminescent lanthanide (Tb3+ and Eu3+) hydrogels

Two novel silica based lanthanide complexes (Tb(a)(2) and Eu(a)(2)) were encapsulated into poly(acrylic acid) host. Both Tb(III) and Eu(III) containing hydrogels have typical and easily distinguished narrow line emissions occurring in the green and red region respectively. Particularly, the excitation wavelength for Eu complex can be extended into nearly visible light range (λ(ex) = 395 nm). Interestingly, we discover that these target materials not only exhibit selective emission response towards HSO(4)(-) (detection limit 10(-5) M) compared with CH(3)COO(-), F(-), Cl(-), Br(-) and I(-) but also give unique quenching to Cu(2+) (detection limit 10(-5) M) (tested cations: Cu(2+), Pd(2+), Cd(2+), Co(2+) and Mn(2+)). More importantly, this kind of materials can be recycled more than 10 times.     

Brilliant Sm, Eu, Tb, and Dy chiral lanthanide complexes with strong circularly polarized luminescence

The synthesis, characterization, and luminescent behavior of trivalent Sm, Eu, Dy, and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, g(lum), recorded for the Eu(III) complex is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments.     

Mesoporous hybrids containing Eu complexes covalently bonded to SBA-15 functionalized: Assembly, characterization and photoluminescence

A novel series of luminescent mesoporous organic-inorganic hybrid materials has been prepared by linking Eu³⁺ complexes to the functionalized ordered mesoporous SBA-15 which was synthesis by a co-condensation process of 1,3-diphenyl-1,3-propanepione (DBM) modified by the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC), tetraethoxysilane (TEOS), Pluronic P123 surfactant as a template. It was demonstrated that the efficient intramolecular energy transfer in the mesoporous material Eu(DBMSi-SBA-15)₃phen mainly occurred between the modified DBM (named as DBM-Si) and the central Eu³⁺ ion. So the Eu(DBMSi-SBA-15)₃phen showed characteristic emission of Eu³⁺ ion under UV irradiation with higher luminescence quantum efficiency. Moreover, the mesoporous hybrid materials exhibited excellent thermal stability as the lanthanide complex was covalently bonded to the mesoporous matrix.     

Novel photofunctional multicomponent rare earth (Eu3+, Tb3+, Sm3+ and Dy3+) hybrids with double cross-linking siloxane covalently bonding SiO2/ZnS nanocomposite

Zinc sulfide (ZnS) quantum dot is modified with 3-mercaptopropyltrimethoxysilane (MPTMS) to obtain MPTMS functionalized SiO(2)/ZnS nanocomposite. Novel rare earth/inorganic/organic hybrid materials are prepared by using 3-(triethoxysilyl)-propyl isocyanate (TESPIC) as an organic bridge molecule that can both coordinate to rare earth ions (Eu(3+), Tb(3+), Sm(3+) and Dy(3+)) and form an inorganic Si-O-Si network with SiO(2) ZnS nanocomposite after cohydrolysis and copolycondensation through a sol-gel process. These multicomponent hybrids with double cross-linking siloxane (TESPIC-MPTMS) covalently bonding SiO(2)/ZnS and assistant ligands (Phen = 1,10-phenanthroline, Bipy = 2,2'-bipyridyl) are characterized and especially the photoluminescence properties of them are studied in detail. The luminescent spectra of the hybrids show the dominant excitation of TESPIC-MPTMS-SiO(2)/ZnS unit and the unique emission of rare earth ions, suggesting that TESPIC-MPTMS-SiO(2)/ZnS unit behaves as the main energy donor and effective energy transfer take place between it and rare earth ions. Besides, the luminescent performance of Bipy-RE-TESPIC-MPTM-SiO(2)/ZnS hybrids are superior to that of Phen-RE-TESPIC-MPTMS-SiO(2)/ZnS ones (RE=Eu, Tb, Sm, Dy), which reveals that Bipy or Phen only act as structural ligand within the hybrid systems.