A Series of Lanthanide-Based Metal-Organic Frameworks Derived from Furan-2,5-dicarboxylate and Glutarate: Structure-Corroborated Density Functional Theory Study, Magnetocaloric Effect, Slow Relaxation of Magnetization, and Luminescent Properties.

Herein, through a dual-ligand strategy, we report eight isorecticular lanthanide(III) furan-2,5-dicarboxylic acid metal-organic frameworks (Ln-MOFs) with the general formula {[Ln(2,5-FDA)0.5(Glu)(H2O)2]· xH2O} n [Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), and Yb (8); 2,5-FDA2- = furan-2,5-dicarboxylate and Glu2- = glutarate; x = 0.5 for 1, 2, and 4 and x = 0 for 3 and 5-8], synthesized under solvothermal conditions by using an N, N'-dimethylformamide/H2O mixed solvent system. Crystallographic data reveal that all eight Ln-MOFs 1-8 crystallize in the orthorhombic Pnma space group. All of the MOFs are isostructural as well as isomorphous with distorted monocapped square-antiprismatic geometry around the Ln1 metal center. In Ln-MOFs 1-8, the 2,5-FDA2- and Glu2- ligands exhibit µ2-κ4,η1:η1:η1:η1 and µ3-κ5,η2:η1:η1:η1 coordination modes, respectively. Topologically, assembled Ln-MOFs 1-8 consist of the 2D cem topological type. The designed Ln-MOFs 1-8 are further explored for structure-corroborated density functional theory study. Meanwhile, room temperature photoluminescence properties of Ln-MOFs 2 and 4 and magnetic properties of Ln-MOFs 3 and 5 have been explored in detail. A highly intense, ligand-sensitized, Ln3+ f-f photoluminescence emission is exhibited by Ln-MOFs 2 [Eu3+ (red emission)] and 4 [Tb3+ (green emission)]. Magnetic studies suggest weak antiferro- and ferromagnetic interactions between adjacent GdIII ions in Ln-MOF 3, thereby displaying a large magnetocaloric effect. The magnetic data measured at T = 2 K and Δ H = 30 kOe depict that the -Δ Sm value per unit mass reaches 32.1 J kg-1 K-1, which is larger than most of the GdIII-based complexes reported. The alternating-current susceptibility measurements on Ln-MOF 5 revealed that out-of-phase signals are frequency- and temperature-dependent under both 0 and 2 kOe direct-current fields, thereby suggesting a typical slow magnetic relaxation behavior with two relaxation processes. This is further supported by the Cole-Cole plots at 2.4-6 K.

Solvothermal Synthesis of ZnO-Nitrogen Doped Graphene Composite and its Application as Catalyst for Photodegradation of Organic Dye Methylene Blue.

A facile one step solvothermal method is designed for the synthesis of visible light-sensitive ZnO-nitrogen doped graphene (ZNG) nano photocatalysts using ethylene glycol as a solvent as well as an agent to prevent aggregation of graphene layers. The deposition of ZnO nanoparticles onto the NG layers was confirmed by high resolution transmission electron microscope (HR-TEM), scanning electron microscope (SEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). UV-Vis spectroscopy (UV-Vis) was used to study the enhanced photocatalytic activity, which shows the red-shift of the band-edge as compared to ZnO nano particles. The enhancement in photocatalytic activity is possibly due to the synergistic effect of improved adsorptivity of dyes, enhanced visible light absorption and effective charge separation.

Nitrogen Doped Graphene Nickel Ferrite Magnetic Photocatalyst for the Visible Light Degradation of Methylene Blue.

A facile approach has been devised for the preparation of magnetic NiFe2O4 photocatalyst (NiFe2O4-NG) supported on nitrogen doped graphene (NG). The NiFe2O4-NG composite was synthesized by one step hydrothermal method. The nanocomposite catalyst was characterized by Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectroscopy (UV-Vis) and Vibrating sample magnetometry (VSM). It is found that the combination of NiFe2O4 nanoparticles with nitrogen-doped graphene sheets converts NiFe2O4 into a good catalyst for methylene blue (MB) dye degradation by irradiation of visible light. The catalytic activity under visible light irradiation is assigned to extensive movement of photogenerated electron from NiFe2O4 to the conduction band of the reduced NG, effectively blocking direct recombination of electrons and holes. The NiFe2O4 nanoparticles alone have efficient magnetic property, so can be used for magnetic separation in the solution without additional magnetic support.

Hydrothermal synthesis and crystal structure of novel bis(6-carboxypyridine-2-carboxylato-κ3O2,N,O6)nickel(II) trihydrate, Ni(Hpydc)2·3H2O.

The synthesis and crystal structure of the compound bis(6-carboxypyridine-2-carboxylato-κ(3)O(2),N,O(6))nickel(II) trihydrate, Ni(Hpydc)(2)·3H(2)O, with a supramolecular network is reported (H(2)pydc is pyridine-2,6-dicarboxylic acid). The compound has been prepared by hydrothermal methods. The crystal structure has been solved by direct methods using single-crystal X-ray diffraction data collected at 293 K and refined by full-matrix least-squares procedures to a final R value of 0.0323 for 2779 observed reflections. The compound has distorted octahedral geometry around the metal centre. The complex contains two identical singly ionized ligand molecules. The nickel(II) is bonded to four O atoms and two N atoms from the tridentate ligand molecules, which are nearly perpendicular to each other. Hydrogen-bonded interactions create a three-dimensional supramolecular porous network. The supramolecular structure accounts for the porous structure of the compound as is evident from the Brunauer, Emmett & Teller (BET) surface area of 80 m(2) g(-1). Thermal degradation of the compound shows that lattice water molecules give stability to the crystal structure.

Dual-Ligand Strategy Employing Rigid 2,5-Thiophenedicarboxylate and 1,10-Phenanthroline as Coligands for Solvothermal Synthesis of Eight Lanthanide(III) Coordination Polymers: Structural Diversity, DFT Study, and Exploration of the Luminescent Tb(III) Coordination Polymer as an Efficient Chemical Sensor for Nitroaromatic Compounds.

Lanthanide coordination polymers (Ln-CPs) are potential chemosensors when fabricated to depict a detectable change in optical properties on interaction with target analytes. This work investigates the interaction of nitroaromatic compounds with Ln-CPs leading to induced changes in fluorescence emission intensity, a crucial strategy to develop a selective and sensitive system for the sensing of nitroaromatics. Approaching toward this objective, solvothermal reactions of 2,5-thiophenedicarboxylic (2,5-TDC) acid, 1,10-phenanthroline (1,10-Phen), and Ln(NO3)3·xH2O are carried out to assemble eight Ln(III) coordination polymers [Ln2(2,5-TDC)3(1,10-Phen)2(H2O)2] [Ln = Pr (1), Nd (2)], {[Tb(2,5-TDC)1.5(1,10-Phen)(H2O)]·DMF} (3), and [Ln(2,5-TDC)1.5(1,10-Phen)]·xH2O (Ln = Tb (4), Dy (5), Ho (6), Er (7), and Yb (8)); x = 0 for CP 4, 5, 6, and 8 and x = 1 for CP 7 with two different space groups and dimensions. The as-synthesized polymers 1-8 are characterized by powder X-ray crystallography, infrared spectroscopy, and thermogravimetric analysis. The structure-corroborated density functional theory (DFT) studies are done on the selected CPs to investigate the interactions between different structural motifs of the assembled CPs. The luminescence properties of CP 4 are explored in detail and are found to be highly sensitive for the detection of p-nitrotoluene as indicated by the most intensive fluorescence quenching with the lowest limit of detection (0.88 ppm) and high quenching constant (4.3 × 104 M-1). Other nitro compounds (viz., o-nitrobenzaldehyde, m-nitroaniline, picric acid, m-dinitrobenzene, p-nitrophenol, and p-nitroaniline) are also screened for potential sensing by CP 4.

PEI functionalized NaCeF4:Tb3+/Eu3+ for photoluminescence sensing of heavy metal ions and explosive aromatic nitro compounds.

This work reports an eco-friendly hydrothermal approach for the synthesis of hexagonal NaCeF4:Tb3+/Eu3+ nanophosphors. The phase, morphology and optical properties were characterized by Powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and photoluminescence (PL) spectroscopy respectively. Herein, the as-synthesized nanophosphor was functionalized with amine rich polyethylenimine (PEI) resulting in development of a luminescent nanoprobe bearing dual sensing functions for hazardous nitroaromatics and heavy metal ions. The strong photoluminescence emission of Eu3+ ions was selectively quenched upon addition of toxic analytes at concentrations from 10 to 100 ppm due to complex formation between the analytes and PEI functionalized nanostructure. The synthesized nanomaterial shows sharp emission peaks at 493, 594, 624, 657 and 700 nm. Significantly, the peak at 594 nm shows a noticeable quenching effect on addition of toxic analytes to the aqueous solution of the nanocrystals. The nanophosphors are sensitive and efficient for the PA and Fe3+ ion detection with an LOD of 1.32 ppm and 1.39 ppm. The Stern-Volmer (SV) quenching constant (K SV) is found to be 2.25 × 105 M-1 for PA and 3.8 × 104 M-1 for Fe3+ ions. The high K SV value and low LOD suggest high selectivity and sensitivity of the nanosensor towards PA and Fe3+ ions over other analytes. Additionally, a reduced graphene oxide and nanophosphor based nanocomposite was also synthesized to investigate the role of energy transfer involving delocalized energy levels of reduced graphene oxide in regulating the luminescence properties of the nanophosphor. It was observed that PEI plays central role in inhibiting the quenching effect of reduced graphene oxide on the nanophosphor.

Studies on Morphology and Photoluminescent Properties of Tb3+ Doped YbPO4 Nanostructures Synthesized by Different Synthetic Methods.

The morphology dependent optical properties of Tb3+ in YbPO4 host lattice have been investigated. 10 % Terbium doped ytterbium phosphate (YbPO4:Tb3+) nanostructures (NSs) were synthesized by five different synthetic methods i.e. sonochemical method, hydrothermal method, solvothermal method, sacrificial template method and coprecipitation method. Structural facets and optical properties of fabricated nanoparticles were studied in detail by powder X-ray diffraction (PXRD), Fourier transform infrared spectrum (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectra (EDS), and photoluminescence (PL) techniques. We have investigated the impact of synthetic procedures employed on the morphology and uniformity of synthesized NSs and consequently on the optical properties of the NSs. The intense green emission from the nanophosphor shows that phosphor can be used in IR-sensors, LEDs and as solar spectrum converters.

A series of 3D lanthanide coordination polymers decorated with a rigid 3,5-pyridinedicarboxylic acid linker: syntheses, structural diversity, DFT study, Hirshfeld surface analysis, luminescence and magnetic properties.

Single crystal X-ray diffraction studies reveal the formation of six new coordination polymers (CPs) with the general formulas [Dy(3,5-pdc)(3,5-pdcH)(H2O)2]n·nH2O (1), [Pr2(3,5-pdc)3(H2O)2]n·2n(H2O) (2), [Sm2(3,5-pdc)3(H2O)3]n·nH2O (3), {[Eu2(3,5-pdc)3(H2O)3(CH3CHO)]n·n[2(H2O)(DMF)]} (4), {[Gd2(3,5-pdc)3 (H2O)2]n·2nH2O} (5) and [Er(3,5-pdc)(adip)0.5(H2O)]n (6) (where 3,5-pdc2- = fully deprotonated; 3,5-pdcH- = partially deprotonated 3,5-pyridinedicarboxylic acid; adip2- = fully deprotonated adipic acid; and DMF = dimethylformamide) by solvothermal self-assembly of lanthanide ions with rigid 3,5-pyridinedicarboxylic acid as a linker and adipic acid as an auxiliary flexible spacer (only coordinated in CP 6). CPs 1 and 2 crystallize in the triclinic P1[combining macron] space group, whereas CPs 3, 4 and 6 crystallize in the monoclinic P21/n, P21/c and C2/c space groups, respectively. CP 5 exhibits the trigonal R3 space group. The 3,5-pdc ligand exhibits eight diverse coordination modes in CPs 1-6, whereas the adipic acid spacer in CP 6 shows only one coordination mode (µ4-κO:κO,O:κO:κO,O). The organic ligands interconnect with metal ions to generate 3D metal-organic frameworks with a variety of intriguing topologies. Theoretical studies, DFT calculations and Hirshfeld surface analysis support the structures adopted by the various CPs. CPs 3 (Sm) and 4 (Eu) emit strong ligand-sensitized characteristic f-f luminescence. Weak ferromagnetic interactions have been studied at low temperatures for CP 1 and CP 5.

Synthesis, Structural and Optical Characterization of Copper and Rare Earth doped CdS Nanoparticles.

Cadmium sulphide (CdS) nanoparticles doped with Cu(2+) and co-doped with rare earth metallic ions (RE3(+)) have been synthesized by co-precipitation method. The synthesized nanoparticles were been characterized by powder X-ray diffraction studies (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size by dynamic light scattering (DLS), UV-visible spectroscopy (UV), and photoluminescence (PL) studies. It is observed that CdS nanoparticles can be co-doped with copper and rare earth metallic ions without altering XRD pattern as indicated by X-ray diffraction results. SEM results show that synthesized particles show spherical aggregation and TEM results show that these particles assembled to give a flower-like morphology. Absorption spectra of all the samples show strong blue shift from bulk CdS. Interesting luminescence pattern with enhanced intensity has been observed for co-doped CdS nanoparticles at room temperature.

Synthesis, crystal structure, photoluminescence, and DFT studies of bis(1,10-phenanthroline)di(κ(2)OO' nitrato)cadmium(II) [Cd(phen)2(NO3)2].

A cadmium 1,10-phenanthroline complex, [Cd(phen)2(NO3)2] has been synthesized by and its crystal structure determined. The compound is monoclinic, C2/c, a=11.5008(2), b=15.3523(2), c=13.2767(2)Å, ß=103.610(2), Z=4. The compound is monomeric with a octacoordinate cadmium ion bonded to two bidentate 1,10-phenanthroline molecules and two bidentate nitrate units. The metal ion is bis-chelated by two N-heterocycles as well as by two nitrate ions in a distorted dodecahedral CdN4O4 coordination environment. The complex is thermally stable up to 110°C. Photophysical investigation reveals that complex is luminescent in the solid state. The molecular geometry, harmonic vibrational frequencies and bonding features of complex [Cd(phen)2(NO3)2] in the ground-state have been calculated by using the density functional B3LYP method with 3-21G (d, p) as higher basis set. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulate infrared spectrum of the title compound which show good agreement with observed spectrum.