Wuliji Hasi

Two-/three-dimensional open lanthanide–organic frameworks containing rigid/flexible dicarboxylate ligands: synthesis, crystal structure and photoluminescent properties

Three series of two-dimensional and three-dimensional lanthanide coordination polymers {[Ln(ox)1.5(H2O)3]·mH2O}n [Ln = Ce (1), m = 2 and Pr (2), m = 3, H2ox = oxalic acid], {[Ln(ox)2(H3O)]·EtOH·3H2O}n [Ln = Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10) and Yb (11), EtOH = ethanol] and {[Ln2(IMDC)2(H2O)3]·mH2O}n [Ln = Sm (12), Eu (13), Gd (14), Tb (15) and Dy (16), where m = 2.25 except for 15 where m = 1.75, H3IMDC = imidazole-4,5-dicarboxylic acid] have been synthesized under hydrothermal conditions. All the coordination polymers have been characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Coordination polymers 1–11 exhibit two different structural types: the 2-D structure of coordination polymers 1–2 are a (6,3)-connected hcb network, coordination polymers 3–11 appear as a 3-D diamond structure with 66-network topology. Coordination polymers 12–16 are 3-D structures constructed from the bridged carboxyl group of IMDC3−, in which IMDC3− bridged the DNA-like double-helix line and the triple-helix line, intertwined and connected into a 1-D chain and then conformed into a 3-D structure along the ab plane. The different structures of the two dicarboxylate ligands (oxalic acid as a flexible ligand and imidazole-4,5-dicarboxylic acid as a rigid planar ligand) were described and discussed. Furthermore, the luminescent properties in the visible region and the fluorescence lifetimes of the coordination polymers exhibited the characteristic transitions of the corresponding lanthanide ions. It was noted that coordination polymers 5 and 7 have long solid-state fluorescence lifetimes of 824.84 and 733.87 μs, respectively. The NIR emission spectra of the Nd (3), Sm (4 and 12), Dy (8 and 16) and Yb (3) coordination polymers in the solid-state were measured. The singlet excited state (30 842 cm−1 for oxalic acid, 32 258 cm−1 for H3IMDC) and the lowest triplet state energy level (23 753 cm−1 for oxalic acid and 22 371 cm−1 for H3IMDC) of the H2ox and H3IMDC ligand were calculated on the basis of the UV-Vis absorbance edges of the ligand and the phosphorescence spectrum of the Gd(III) coordination polymers 6 and 14 at 77 K, respectively. The relationship between the lowest triplet state energy level of the two dicarboxylate ligands and lowest resonance energy levels of the Sm(III), Eu(III), Tb(III) and Dy(III) ions were described and discussed. The results showed that the energy transfer from the oxalic acid ligands is much more effective than H3IMDC.

Syntheses and structures of blue-luminescent mercury(II) complexes with 2,6-bis(imino)pyridyl ligands.

Seven five-coordinate 2,6-bis(imino)pyridyl mercury complexes, [2,6-(ArN horizontal lineCMe)(2)C(5)H(3)NHgCl(2).nCH(3)CN] (Ar = C(6)H(5), n = 1.5, 1; Ar = 2,6-(i)Pr(2)C(6)H(3), n = 0, 2; Ar = 2,6-Me(2)C(6)H(3), n = 1, 3; Ar = 2-MeC(6)H(4), n = 1, 4; Ar = 4-MeC(6)H(4), n = 1, 5; Ar = 2,4,6-Me(3)C(6)H(2), n = 1, 6; Ar = 2,6-Et(2)C(6)H(3), n = 0, 7), were synthesized by reactions of the corresponding bis(imino)pyridine ligands with HgCl(2) in CH(3)CN, and in good yield. The structures of complexes 1-6 were determined by single-crystal X-ray diffraction. In all complexes, the metal center is tridentately chelated by the ligand and further coordinated by two chlorine atoms, resulting in a distorted trigonal bipyramidal geometry. All complexes have blue luminescence at room temperature in solution and the solid state. At 293 K in a CH(2)Cl(2) solution, the fluorescent emission maxima for complexes 1-7 are at lambda = 395, 400, 407, 403, 427, 415, and 403 nm, respectively, which can be attributed to ligand-centered pi* --> pi transitions.

1-D helical chain, 2-D layered network and 3-D porous lanthanide–organic frameworks based on multiple coordination sites of benzimidazole-5,6-dicarboxylic acid: synthesis, crystal structure, photoluminescence and thermal stability

One-dimensional to three-dimensional lanthanide coordination polymers 1–8 based on benzimidazole-5,6-dicarboxylic acid (H3BIDC) have been synthesized under hydrothermal conditions at different pH values, generally formulated as {[Pr(HBIDC)(ox)0.5(H2O)]·H2O}n (1), [Yb(HBIDC)(ox)0.5(H2O)2]n (2), and [Ln(HBIDC)(ox)0.5(H2O)3]n [Ln = Ho (3), and Tb (4)] and {[Ln(H2BIDC)(HBIDC)(H2O)3]·3H2O}n [Ln = Tb (5), Sm (6), Dy (7), and Gd (8), H2ox = oxalic acid]. All coordination polymers have been characterized by elemental analysis, infrared spectra and single-crystal X-ray diffraction. The structural diversity, luminescence and thermal properties of all coordination polymers have been investigated. Coordination polymers 1–8 exhibit four different structural types: topological analysis has given the 3-D pcu network, with the point symbol of {412·63} in coordination polymer 1. Coordination polymer 2 exhibits a 4-connected 44 topology, and coordination polymers 3–4 appear as 2-D (6,3)-connected hcb network topology. The 1-D helical infinite chain of coordination polymers 5–8 around the crystallographic 21 axis spread along the b axis direction, with different 1-D helical infinite chains forming 3-D supramolecular framework via hydrogen bonds and π–π stacking interactions. The coordination polymers 4 and 5 could be triggered to have intense characteristic lanthanide-centered green luminescence under UV excitation in the solid state at room and liquid nitrogen temperature, or dispersed in CH2Cl2 at 77 K. In coordination polymers 4 and 5, the oxalic acid introduced into coordination polymer 4 as a second ligand further sensitized the trivalent terbium ion, and resulted in longer fluorescence lifetimes of coordination polymer 4 (1058.58 μs at 298 K, 679.42 μs at 77 K in the solid-state, 867.82 μs in CH2Cl2 at 77 K) than coordination polymer 5 (595.06 μs at 298 K, 583.19 μs at 77 K in the solid-state, 584.38 μs in CH2Cl2 at 77 K). In coordination polymers 6 and 7, we not only measured emission spectra in the visible region, but also detected the infrequent NIR emission spectra in the near infrared region of samarium and dysprosium ions. The singlet excited state (30 303 cm−1) and the lowest triplet state energy level (24 390 cm−1) of H3BIDC ligand were calculated based on the UV-vis absorbance edges of ligand and the phosphorescence spectrum of Gd(III) coordination polymer (8) at 77 K, showing that the effective extent of energy transfer from H3BIDC ligand to lanthanide ions follows the sequence of Tb3+, Dy3+ > Sm3+. Finally, thermal behaviors of all coordination polymers were studied by thermogravimetric analysis, which exhibited high thermal stability.

Investigation of stimulated Brillouin scattering media perfluoro-compound and perfluoropolyether with a low absorption coefficient and high power-load ability

The correlations between stimulated Brillouin scattering (SBS) characteristics of perfluoro-compound (PFC) and perfluoropolyether (PFPE) and their chemical structure are analyzed in detail and a series of new PFC and PFPE are reported. In the Nd:YAG laser system, the absorption coefficient, optical breakdown threshold (OBT), SBS threshold, and Brillouin frequency shift of new media such as FC-87, FC-43, HT-55, and DET are measured. Parameters such as gain coefficient, Brillouin linewidth, and phonon lifetime are calculated. The results demonstrate their good SBS properties: the absorption coefficients are below 10(-3)cm(-1) and OBTs are above 100 GW/cm(2). These media also exhibit a series of unique physicochemical properties, i.e., high heat-resistance, high oxidation stability, good chemical inertness, and insulation properties. The discovery of new media not only diversifies SBS medium, but also improves the performance of the SBS system, thereby laying a good foundation for the application of a SBS phase conjugation mirror in a high-power laser system.

Rapid and sensitive SERS method for determination of Rhodamine B in chili powder with paper-based substrates

Surface-enhanced Raman spectroscopy (SERS) was used for detecting Rhodamine B (RB) which is often added illegally to chili powder. Based on density functional theory, the Raman spectrum of RB was calculated and characteristic peaks of RB were assigned to the corresponding vibrational modes. RB was detected utilizing paper-based SERS substrates which were fabricated via a liquid–liquid interface-mediated self-assembly technique. Meanwhile, with simple sample pretreatment, the detection limit could reach 10−6 g g−1 for RB in chili powder (5 × 10−7 g mL−1 in extraction agent). Within the concentration range from 10−2 g g−1 to 10−6 g g−1, Raman intensity follows a certain function in relation to the concentration of RB. The recovery of this method ranges from 96.4% to 108.9%, which gives rapid and reliable quantitative detection of RB in chili powder. Therefore, the proposed SERS method is suitable for on-site detection and analysis of RB in chili powder.

Research on the enhancement of power-load of two-cell SBS system by choosing different media or mixture medium

In order to enhance the power-load of two-cell stimulated Brillouin scattering (SBS) system, methods of using different media and mixed medium are proposed. In theory, the amplification function of two-cell system of different medium with close vicinity in the Brillouin frequency shift (BFS) is analyzed. Also the variation of BFS of the mixed medium with the mixing ratio is analyzed. In the two-cell SBS system pumped by Q-switched Nd:YAG laser, the SBS system performance characteristics are investigated with different media and mixed medium. The experimental results indicate that the Stokes can be sufficiently amplified by choosing different medium with close vicinity in the BFS; the power-load performance is enhanced as well as the maximum amplification efficiency the Stokes by choosing mixed medium.

The Current Trends in SBS and phase conjugation

The current trends in stimulated Brillouin scattering and optical phase conjugation are overviewed. This report is formed by the selected papers presented in the “Fifth International Workshop on stimulated Brillouin scattering and phase conjugation 2010” in Japan. The nonlinear properties of phase conjugation based on stimulated Brillouin scattering and photo-refraction can compensate phase distortions in the high power laser systems, and they will also open up potentially novel laser technologies, e.g., phase stabilization, beam combination, pulse compression, ultrafast pulse shaping, and arbitrary waveform generation.

Syntheses, structures, and luminescent properties of Zn(II) and Cd(II) complexes: 3-D supramolecules based on 2,6-bis(imino)pyridine ligands constructed by hydrogen bonding interactions

Six 5-coordinate 2,6-bis(imino)pyridine metal complexes, [2,6-(ArN=CMe)2C5H3NMCl2 · nCH3CN] (Ar = 4-MeC6H4, M = Zn, n = 0.5, Zn1, M = Cd, n = 1, Cd1; Ar = 2,6-Et2C6H3, M = Zn, n = 0.5, Zn2, M = Cd, n = 0.5, Cd2; Ar = 2,4,6-Me3C6H2, M = Zn, n = 1, Zn3, M = Cd, n = 1, Cd3), were synthesized in acetonitrile by the reactions of the corresponding bis(imino)pyridines with ZnCl2 or CdCl2 · 2.5H2O, respectively. The structures of Zn1–Zn3 and Cd1–Cd3 were determined by the single-crystal X-ray diffraction. In all complexes, the ligand is tridentate with further coordination by two chlorides, resulting in a distorted trigonal bipyramid. All complexes self-assemble through hydrogen bonding interactions to form a 3-D supramolecular structure. At 298 K in dichloromethane, all complexes have blue luminescent emissions at 405–465 nm, which can be attributed to ligand-centered π* → π transitions. The zinc and cadmium centers play a key role in enhancing fluorescent emission of the ligands.

High amplification and low noise achieved by a double-stage non-collinear Brillouin amplifier

We report a double-stage non-collinear Brillouin amplifier structure with high amplification and low noise, achieving an energy amplification of 6 x 10(11) and a signal-to-noise ratio of 10(3) for an input signal of 5.5 x 10(-14)J in the regime above the pumps stimulated Brillouin scattering threshold. The signal of the first-stage amplifier is efficiently amplified and separated from the noise output. The saturation amplification with noise suppressing is implemented in the second stage. The design principles of system parameters such as the intersection angle between the pump and signal beams, the pump energy, and the beam diameter are given.

Rapid fabrication of self-assembled interfacial film decorated filter paper as an excellent surface-enhanced Raman scattering substrate

An excellent paper-based SERS substrate was easily fabricated by utilizing interfacial films formed in the mixture of Ag colloid and CH2Cl2. This interfacial film coating method significantly improves the fabrication efficiency of SERS substrates. The substrate has a high coverage of silver nanoparticles (Ag NPs) and can be tailored to arbitrary shapes. The SERS substrate exhibits high sensitivity (EF ∼ 4 × 107) and gives uniform SERS signals with a relative standard deviation (RSD) of 8.08% (spot-to-spot) and 8.65% (batch-to-batch) using 4-mercaptobenzoic acid (4-MBA) as a Raman probe. In addition, this SERS substrate with excellent stability can be stored for more than 30 days. The limit of detection was found to be 10−8 M for 4-MBA. In general, this SERS substrate is qualified for rapid and simple trace detection of various analytes.