A ratiometric luminescence probe for highly reactive oxygen species based on lanthanide complexes

Reactive oxygen species (ROS) are important mediators in a variety of pathological events, but the oxidative stress owing to excessive generation of ROS is implicated in many human diseases. In this work, we designed and synthesized a novel dual-functional chelating ligand, [4'-(p-aminophenoxy)methylene-2,2':6',2'-terpyridine-6,6'-diyl]bis(methylenenitrilo)tetrakis(acetic acid) (AMTTA), that can strongly coordinate with both Eu(3+) and Tb(3+) in aqueous solutions for the recognition and time-gated luminescence detection of highly ROS (hROS), hydroxyl radical ((?)OH), and hypochlorite (ClO(-)). The complexes AMTTA-Ln(3+) (Ln = Eu and Tb) are almost nonluminescent because of the photoinduced electron transfer from the electron-rich aminophenyl group to the terpyridine-Ln(3+) moiety but can rapidly react with hROS to afford highly luminescent complexes (4'-hydroxymethyl-2,2':6',2'-terpyridine-6,6'-diyl)bis(methylenenitrilo)tetrakis(acetate)-Ln(3+) (HTTA-Ln(3+)). Interestingly, when the AMTTA-Eu(3+)/Tb(3+) mixture (AMTTA/Eu(3+)/Tb(3+) = 2/1/1) was reacted with hROS, the intensity ratio of its Tb(3+) emission at 540 nm to its Eu(3+) emission at 610 nm, I(540)/I(610), showed a ratiometric response toward hROS, and the dose-dependent increase of the ratio displayed a double-exponential correlation to the concentration of hROS. This unique luminescence response allowed the AMTTA-Eu(3+)/Tb(3+) mixture to be used as a ratiometric probe for the time-gated luminescence detection of hROS.     

Novel red-emitting Ba2Tb(BO3)2Cl:Eu phosphor with efficient energy transfer for potential application in white light-emitting diodes

A novel red-emitting Ba(2)Tb(BO(3))(2)Cl:Eu phosphor possessing a broad excitation band in the near-ultraviolet (n-UV) region was synthesized by the solid-state reaction. Versatile Ba(2)Tb(BO(3))(2)Cl compound has a rigid open framework, which can offer two types of sites for various valence's cations to occupy, and the coexistence of Eu(2+)/Eu(3+) and the red-emitting luminescence from Eu(3+) with the aid of efficient energy transfer of Eu(2+)-Eu(3+)(Tb(3+)) and Tb(3+)-Eu(3+) have been investigated. Ba(2)Tb(BO(3))(2)Cl emits green emission with the main peak around 543 nm, which originates from (5)D(4) → (7)F(5) transition of Tb(3+). Ba(2)Tb(BO(3))(2)Cl:Eu shows bright red emission from Eu(3+) with peaks around 594, 612, and 624 nm under n-UV excitation (350-420 nm). The existence of Eu(2+) can be testified by the broad-band excitation spectrum, UV-vis reflectance spectrum, X-ray photoelectron spectrum, and Eu L(3)-edge X-ray absorption spectrum. Decay time and time-resolved luminescence measurements indicated that the interesting luminescence behavior should be ascribed to efficient energy transfer of Eu(2+)-Eu(3+)(Tb(3+)) and Tb(3+)-Eu(3+) in Ba(2)Tb(BO(3))(2)Cl:Eu phosphors.     

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.     

Highly luminescent Eu(3+) and Tb(3+) macrocyclic complexes bearing an appended phenanthroline chromophore

A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized. The 1:1 complexes with Eu(3+), Gd(3+), Tb(3+), and Yb(3+) have been prepared and studied in aqueous solution. For Gd.1, a relaxivity value of 2.4 mM(-1) s(-1) has been measured at 20 MHz and 25 degrees C, which indicates that there are no water molecules in the first coordination sphere of the metal ion. The analysis of high resolution (1)H NMR spectra of Yb.1 supports this view and suggests the direct involvement of the phen moiety in the coordination of the metal ion. For Eu.1 and Tb.1, the absorption and luminescence spectra, the overall luminescence efficiencies, and the metal-centered (MC) lifetimes were obtained; coordination features were also determined by comparing luminescence properties in water and deuterated water. For Eu.1 and Tb.1, the overall emission sensitization (se) process in air-equilibrated water was found to be notably effective with phi(se) = 0.21 and 0.11, respectively. A detailed study of the steps originating from light absorption at the phen unit and leading to MC sensitized emission was performed.     

Nanocrystalline CaYAlO4:Tb3+/Eu3+ as promising phosphors for full-color field emission displays

Eu(3+) and/or Tb(3+)-doped CaYAlO(4) phosphor samples were synthesized by Pechini-type sol-gel method. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. For CaYAlO(4):Tb(3+), it is shown that the Tb(3+)-doping concentration has a significant effect on the (5)D(3)/(5)D(4) emission intensity of Tb(3+), which is attributed to the cross relaxation from (5)D(3) to (5)D(4). Under the 4f(8)→ 4f(7)5d excitation of Tb(3+) or low-voltage electron beams excitation, the CaYAlO(4):Tb(3+) phosphors show tunable luminescence from blue to cyan, and then to green with the change of Tb(3+)-doping concentration. The CaYAlO(4):Eu(3+) samples exhibit a reddish-orange emission of Eu(3+) corresponding to (5)D(0,1)→(7)F(0,1,2,3) transitions. Furthermore, a white emission can be realized in the single phase CaYAlO(4) host by reasonably adjusting the doping concentrations of Tb(3+) and Eu(3+) under low-voltage electron beams excitation. Compared with the commercial blue (Y(2)SiO(5):Ce(3+)) and green (ZnO:Zn) phosphors, CaYAlO(4):0.1%Tb(3+) and CaYAlO(4):5%Tb(3+) phosphors have higher CL intensity and stability under continuous electron bombardment. Due to the excellent CL properties and good CIE chromaticity coordinates, the as-prepared Tb(3+)/Eu(3+)-doped CaYAlO(4) nanocrystalline phosphors have potential application in FEDs devices.     

Luminescence of Tb3+ and Eu3+ doped amorphous zinc benzoates

The Tb(3+) and Eu(3+) doped amorphous zinc benzoate were prepared. Their infrared absorption, emission and excitation spectra were measured. The luminescence mechanisms of Tb(3+) and Eu(3+) in the amorphous substrate were discussed. The bonding modes of OCO group to Zn(2+) ion have two of symmetric and asymmetric bridging bidentate. The energy of the S(1) pi,pi* excited state of benzene ring can be transferred to Tb(3+) and Eu(3+) ion, and results in characteristic emission from the 5D(4)-->(7)F(j) of Tb(3+) and 5D(0)-->(7)F(j) of Eu(3+), respectively.     

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.     

Using Native Chemical Ligation for Site-Specific Synthesis of Hetero-bis-lanthanide Peptide Conjugates: Application to Ratiometric Visible or Near-Infrared Detection of Zn2+

The interest in ratiometric luminescent probes that detect and quantify a specific analyte is growing. Owing to their special luminescence properties, lanthanide(III) cations offer attractive opportunities for the design of dual-color ratiometric probes. Here, the design principle of hetero-bis-lanthanide peptide conjugates by using native chemical ligation is described for perfect control of the localization of each lanthanide cation within the molecule. Two zinc-responsive probes, r-LZF1^Tb|Cs124|Eu and r-LZF1^Eu|Cs124|Tb are described on the basis of a zinc finger peptide and two DOTA (DOTA=1,4,7,10-tetraaza-cyclododecane-1,4,7,10-tetraacetic acid) complexes of terbium and europium. Both display dual-color ratiometric emission in response to the presence of Zn²⁺. By using a screening approach, anthracene was identified for the sensitization of the luminescence of two near-infrared-emitting lanthanides, Yb³⁺ and Nd³⁺. Thus, two novel zinc-responsive hetero-bis-lanthanide probes, r-LZF3^Yb|Anthra|Nd and r-LZF3^Nd|Anthra|Yb were assembled, the former offering a neat ratiometric response to Zn²⁺ with emission in the near-infrared around 1000 nm, which is unprecedented.     

Preparation of luminescent and mesoporous Eu3+/Tb3+ doped calcium silicate microspheres as drug carriers via a template route

Luminescent and mesoporous Eu(3+)/Tb(3+) doped calcium silicate microspheres (LMCS) were synthesized by using mesoporous silica spheres as the templates. The LMCS and drug-loaded samples were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N(2) adsorption/desorption, and photoluminescence (PL) spectra. The results reveal that the LMCS have uniform spherical morphology with a diameter around 400 nm and the mesopore size of 6 nm. The prepared samples exhibit little cytotoxicity at concentrations below 5 mg mL(-1) via MTT assay. In addition, drug storage/release properties of the LMCS were demonstrated for ibuprofen (IBU). The obtained LMCS can be used to encapsulate drugs and release them. Under excitation by UV light, the IBU-loaded samples still show the characteristic (5)D(0)-(7)F(1-3) emission lines of Eu(3+) and the characteristic (5)D(4)-(7)F(3-6) emission lines of Tb(3+). The PL intensity of Eu(3+) in the drug carrier system increases with the cumulative released amount of IBU, making the drug release able to be tracked or monitored by the change of luminescence of Eu(3+). The LMCS reported here with mesoporous structure, good biocompatibility and luminescent property can be a promising drug delivery carrier.     

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+.     

Luminescence and microstructures of Eu(3+)-doped Ca9LiGd(2/3)(PO4)7

A red-emitting phosphor, Eu(3+)-doped Ca(9)LiGd(2/3)(PO(4))(7), was synthesized by the conventional high-temperature solid-state reaction. X-ray powder diffraction (XRD) analyses confirmed the pure crystalline phase of Whitlockite-type structure. The excitation spectra of Eu(3+) doped Ca(9)LiGd(2/3)(PO(4))(7) were measured in the VUV and UV region indicating an efficient energy transfer process from the host and Gd(3+) to Eu(3+) ions. Upon excitation with VUV and UV radiation, the phosphor showed strong red emission around 611 nm corresponding to the forced electric dipole (5)D(0)→(7)F(2) transition of Eu(3+) ions. The VUV- and UV-excited luminescence spectra of Ca(9)LiGd(2/3)(PO(4))(7):Eu(3+) together with the dependence of the integrated emission intensities on the doping levels were investigated. The Eu(3+) ions were investigated by a tunable laser as an excitation source. The excitation spectra of (7)F(0)→(5)D(0) transitions suggest that there are two families of inequivalent sites for Eu(3+) in this host. The concentration quenching and crystallographic site-occupancy of Eu(3+) ions in Ca(9)LiGd(2/3)(PO(4))(7) host were discussed on the basis of the site selective excitation and emission spectra, the luminescence decay and its crystal structure.     

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.     

Highly Luminescent and Thermally Stable Lanthanide Coordination Polymers Designed from 4-(Dipyridin-2-yl)aminobenzoate: Efficient Energy Transfer from Tb(3+) to Eu(3+) in a Mixed Lanthanide Coordination Compound

Herein, a new aromatic carboxylate ligand, namely, 4-(dipyridin-2-yl)aminobenzoic acid (HL), has been designed and employed for the construction of a series of lanthanide complexes (Eu(3+) = 1, Tb(3+) = 2, and Gd(3+) = 3). Complexes of 1 and 2 were structurally authenticated by single-crystal X-ray diffraction and were found to exist as infinite 1D coordination polymers with the general formulas {[Eu(L)(3)(H(2)O)(2)]}(n) (1) and {[Tb(L)(3)(H(2)O)].(H(2)O)}(n) (2). Both compounds crystallize in monoclinic space group C2/c. The photophysical properties demonstrated that the developed 4-(dipyridin-2-yl)aminobenzoate ligand is well suited for the sensitization of Tb(3+) emission (Φ(overall) = 64%) thanks to the favorable position of the triplet state ((3)ππ*) of the ligand [the energy difference between the triplet state of the ligand and the excited state of Tb(3+) (ΔE) = (3)ππ* - (5)D(4) = 3197 cm(-1)], as investigated in the Gd(3+) complex. On the other hand, the corresponding Eu(3+) complex shows weak luminescence efficiency (Φ(overall) = 7%) due to poor matching of the triplet state of the ligand with that of the emissive excited states of the metal ion (ΔE = (3)ππ* - (5)D(0) = 6447 cm(-1)). Furthermore, in the present work, a mixed lanthanide system featuring Eu(3+) and Tb(3+) ions with the general formula {[Eu(0.5)Tb(0.5)(L)(3)(H(2)O)(2)]}(n) (4) was also synthesized, and the luminescent properties were evaluated and compared with those of the analogous single-lanthanide-ion systems (1 and 2). The lifetime measurements for 4 strongly support the premise that efficient energy transfer occurs between Tb(3+) and Eu(3+) in a mixed lanthanide system (η = 86%).     

Rare earth hybrid materials of organically modified silica covalently bonded to a GaN matrix: multicomponent assembly and multi-color luminescence

Three kinds of rare earth hybrid materials with enhanced thermostability and photoluminescence properties have been prepared for the first time by using a functionalized GaN matrix as one of the building blocks. A number of silane coupling agents (isocyanate triethoxysilane (ICTES), 3-chloropropyl triethoxysilane (CPTES) and 3-aminopropyl triethoxysilane (APTES)) behave as the covalent linkages for modification by both hydroxylation of GaN and functionalized photoactive ligands (4-mercaptobenzoic acid (MBA), 4-hydroxybenzoic acid (HBA) and nitrobenzoyl chloride (NBC)), resulting in the precursors (MBA-ICTES-GaN, HBA-CPTES-GaN and NBC-APTES-GaN). Subsequently, multicomponent photofunctional rare earth hybrid materials with the three precursors and 1,10-phenanthroline (Phen) are assembled and characterized by their FTIR spectra, UV-vis diffuse reflectance spectra, XRD patterns, and photoluminescent behaviour (luminescence, lifetime, quantum efficiency, and energy transfer). These results reveal that the Eu(3+) hybrids with the MBA-ICTES-GaN unit have a better luminescence intensity ratio, higher quantum efficiency and longer lifetime than those with the HBA-CPTES-GaN and NBC-APTES-GaN units. Meanwhile the hybrid Phen-Tb-HBA-CPTES-GaN possesses a stronger characteristic emission of Tb(3+) ions than the other two hybrids (Phen-Tb-MBA-ICTES-GaN and Phen-Tb-NBC-APTES-GaN). Moreover, two-color-based hybrid materials are fabricated by combining different molar ratios of Eu(3+) and Tb(3+) in the same system (Phen-RE-MBA-ICTES-GaN) with emission at a wavelength of 331 nm (RE = Eu, Tb) and yellow luminescence can be achieved.     

Efficient Near-infrared Down-conversion Phosphor of Ce~(3+)/Yb~(3+) Co-doped La_3Ga_5SiO_(14) and Its Spectral Structural Modulation

A series of near-infrared(NIR) down-conversion phosphors of La_3 Ga_5 SiO_(14)(LGS):Ce~(3+)/Yb~(3+)were synthesized via high-temperature solid-state reaction. Under excitation at 345 nm, the phosphors show strong NIR emission around 978 nm, which matches well with the optimal spectral response of crystalline silicon(c-Si)solar cells. The emission spectra and decay curves were used to demonstrate the energy transfer from Ce~(3+) to Yb~(3+).The energy transfer mechanism was discussed in detail, indicating that the energy transfer from Ce~(3+) to Yb3+ is dominated by a single photon process, and the energy transfer efficiency is up to 51%. In addition, La3 Ga5-zAlzSiO_(14)(z = 0, 1, 2, 3):Ce3+/Yb~(3+) were also synthesized. The NIR emission intensity of La3 Ga2 Al3 SiO14:1%Ce~(3+)/5%Yb~(3+) is 4.6 times that of LGS:1%Ce~(3+)/5%Yb~(3+), and the thermal relaxation was used to explain this phenomenon. The results show that La_3 Ga_(5-z)AlzSiO_(14)(z = 0, 1, 2, 3):1%Ce~(3+)/5%Yb~(3+) phosphors have the potential to increase the conversion efficiency of c-Si solar cells.     

Luminescent ruthenium(II) bipyridine-calix[4]arene complexes as receptors for lanthanide cations

The synthesis and photophysical properties of novel luminescent ruthenium(II) bipyridyl complexes containing one, two, or six lower rim acid-amide-modified calix[4]arene moieties covalently linked to the bipyridine groups are reported which are designed to coordinate and sense luminescent lanthanide ions. All the Ru-calixarene complexes synthesized in this work are able to coordinate Nd(3+), Eu(3+), and Tb(3+) ions with formation of adducts of variable stoichiometry. The absorbance changes allow the evaluation of association constants whose magnitudes depend on the nature of the complexes as well as on the nature of the lanthanide cation. Lanthanide cation complex formation affects the ruthenium luminescence which is strongly quenched by Nd(3+) ion, moderately quenched by the Eu(3+) ion, and poorly or moderately increased by the Tb(3+) ion. In the case of Nd(3+), the excitation spectra show that (i) the quenching of the Ru luminescence occurs via energy transfer and (ii) the electronic energy of the excited calixarene is not transferred to the Ru(bpy)(3) but to the neodymium cation. In the case of Tb(3+), the adduct's formation leads to an increase of the emission intensities and lifetimes. The reason for this behavior was ascribed to the electric field created around the Ru calix[4]arene complexes by the Tb(3+) ions by comparison with the Gd(3+) ion, which behaves identically and can affect ruthenium luminescence only by its charge. However, especially for compounds 1 and 3, it cannot be excluded that some contribution comes from the decrease of vibrational motions (and nonradiative processes) due to the rigidification of the structure upon Tb(3+) complexation. In the case of Eu(3+), compounds 1, 2, and 4 were quenched by the lanthanide addition but the quenching of the ruthenium luminescence is not accompanied by europium-sensitized emission which suggests that an electron-transfer mechanism is responsible for the quenching. On the contrary, compound 3 exhibits enhanced emission upon addition of Eu(3+) (as nitrate salt); it is suggested that the lack of quenching in the [3.2Eu(3+)] adduct is due to kinetic reasons because the electron-transfer quenching process is thermodynamically allowed.     

Upconversion luminescence and mechanisms of Tm(3+)/Yb(3+)-codoped oxyhalide tellurite glasses

To obtain efficient blue upconversion laser glasses, upconversion luminescence and mechanisms of Tm(3+)/Yb(3+)-codoped oxyhalide tellurite glasses were investigated under 980 nm excitation. The results showed that upconversion blue and red emission intensities of Tm(3+) first increase, reach its maximum at Tm(2)O(3)%=0.1 mol %, and then decrease with increasing Tm(2)O(3) content. The effect of Tm(2)O(3) content on upconversion intensity is discussed, and possible effect mechanisms are evaluated. The investigated results were conducing to increase upconversion luminescence efficiency of Tm(3+).     

Structure and photoluminescence tuning features of Mn(2+)- and Ln(3+)-activated Zn-based heterometal-organic frameworks (MOFs) with a single 5-methylisophthalic acid ligand

In attempts to investigate whether the photoluminescence properties of the Zn-based heterometal-organic frameworks (MOFs) could be tuned by doping different Ln(3+) (Ln = Sm, Eu, Tb) and Mn(2+) ions, seven novel 3D homo- and hetero-MOFs with a rich variety of network topologies, namely, [Zn(mip)](n) (Zn-Zn), [Zn(2)Mn(OH)(2)(mip)(2)](n) (Zn-Mn), [Mn(2)Mn(OH)(2)(mip)(2)](n) (Mn-Mn), [ZnSm(OH)(mip)(2)](n) (Zn-Sm), [ZnEu(OH)(mip)(2)](n) (Zn-Eu1), [Zn(5)Eu(OH)(H(2)O)(3)(mip)(6)·(H(2)O)](n) (Zn-Eu2), and [Zn(5)Tb(OH)(H(2)O)(3)(mip)(6)](n) (Zn-Tb), (mip = 5-methylisophthalate dianion), have been synthesized hydrothermally based on a single 5-methylisophthalic acid ligand. All compounds are fully structurally characterized by elemental analysis, FT-IR spectroscopy, TG-DTA analysis, single-crystal X-ray diffraction, and X-ray powder diffraction (XRPD) techniques. The various connectivity modes of the mip linkers generate four types of different structures. Type I (Zn-Zn) is a 3D homo-MOF with helical channels composed of Zn(2)(COO)(4) SBUs (second building units). Type II (Zn-Mn and Mn-Mn) displays a nest-like 3D homo- or hetero-MOF featuring window-shaped helical channels composed of Zn(4)Mn(2)(OH)(4)(COO)(8) or Mn(4)Mn(2)(OH)(4)(COO)(8) SBUs. Type III (Zn-Sm and Zn-Eu1) presents a complicated corbeil-like 3D hetero-MOF with irregular helical channels composed of (SmZnO)(2)(COO)(8) or (EuZnO)(2)(COO)(8) heterometallic SBUs. Type IV (Zn-Eu2 and Zn-Tb) contains a heterometallic SBU Zn(5)Eu(OH)(COO)(12) or Zn(5)Tb(OH)(COO)(12), which results in a 3D hetero-MOF featuring irregular channels impregnated by parts of the free and coordinated water molecules. Photoluminescence properties indicate that all of the compounds exhibit photoluminescence in the solid state at room temperature. Compared with a broad emission band at ca. 475 nm (λ(ex) = 380 nm) for Zn-Zn, compound Zn-Mn exhibits a remarkably intense emission band centered at 737 nm (λ(ex) = 320 nm) due to the characteristic emission of Mn(2+). In addition, the fluorescence intensity of compound Zn-Mn is stronger than that of Mn-Mn as a result of Zn(2+) behaving as an activator for the Mn(2+) emission. Compound Zn-Sm displays a typical Sm(3+) emission spectrum, and the peak at 596 nm is the strongest one (λ(ex) = 310 nm). Both Zn-Eu1 and Zn-Eu2 give the characteristic emission transitions of the Eu(3+) ions (λ(ex) = 310 nm). Thanks to the ambient different crystal-field strengths, crystal field symmetries, and coordinated bonds of the Eu(3+) ions in compounds Zn-Eu1 and Zn-Eu2, the spectrum of the former compound is dominated by the (5)D(0) → (7)F(2) transition (612 nm), while the emission of the (5)D(0) → (7)F(4) transition (699 nm) for the latter one is the most intense. Compound Zn-Tb emits the characteristic Tb(3+) ion spectrum dominated by the (5)D(4) → (7)F(5) (544 nm) transition. Upon addition of the different activated ions, the luminescence lifetimes of the compounds are also changed from the nanosecond (Zn-Zn) to the microsecond (Zn-Mn, Mn-Mn, and Zn-Sm) and millisecond (Zn-Eu1, Zn-Eu2, and Zn-Tb) magnitude orders. The structure and photoluminescent property correlations suggest that the presence of Mn(2+) and Ln(3+) ions can activate the Zn-based hetero-MOFs to emit the tunable photoluminescence.     

Unique emission from polymer based lanthanide alloys

The incorporation of metal-ligand interactions into macromolecules imparts them with unique and potentially useful properties. We report novel macromolecules prepared via ATRP that contain activated esters for subsequent incorporation of terpyridine. The addition of lanthanide ions (Eu3+ and Tb3+) gave metal functionalized polymers that exhibited excellent emission of either pink (Eu3+) or green (Tb3+) light. A unique yellow luminescence was generated when these two different metal ions were incorporated into the same molecular backbone at a 1:1 ratio, producing an alloy. Upon heating above 50 degrees C, selective thermochromism, from yellow to orange/pink, was observed.     

Facile synthesis and multicolor luminescent properties of uniform Lu2O3:Ln (Ln=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanospheres

Multicolor Lu(2)O(3):Ln (Ln=Eu(3+), Tb(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu(2)O(3) phase with high purity. The SEM images show the obtained Lu(2)O(3):Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu(2)O(3):Ln (Ln=Eu(3+) and Tb(3+)) NCs exhibit bright red (Eu(3+), (5)D(0)→(7)F(2)), and green (Tb(3+), (5)D(4)→(7)F(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu(2)O(3):Ln (Ln=Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) NCs display the typical up-conversion (UC) emissions of green (Er(3+), (4)S(3/2),(2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow-green (Ho(3+), (5)F(4), (5)S(2)→(5)I(8)), respectively.