Syntheses, structures, and magnetic characterization of dicyanometalate(II) building blocks: [NEt4][(Tp*)MII(CN)2] [MII = Cr, Co, Ni; Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate

The syntheses and structures of three dicyanometalate(II) complexes, [NEt(4)][(Tp*)M(II)(CN)(2)].nMeCN.(1/2)Et(2)O (M(II) = Cr, 1, n = (1/2); Co, 2, n = 1; Ni, 3, n = 1) are described; magnetic studies indicate that 3 is diamagnetic while 1 and 2 are paramagnetic high- and low-spin S = 2 and (1/2) complexes, respectively.     

Conversion of ZnO nanorod arrays into ZnO/ZnS nanocable and ZnS nanotube arrays via an in situ chemistry strategy

Vertically aligned ZnO nanorods with uniform diameter and length have been synthesized on a zinc foil substrate with ammonium persulfate as oxidant via a facile, larger scale production and inexpensively synthesized method without any templates or additives. SEM and XRD studies indicate that ZnO nanorods are well-oriented along the c-axis. The PL spectrum indicates that our as-synthesized ZnO nanorods with a stronger and wider green emission are promising candidates as electron nanoconductors in nano-optoelectronic devices. Furthermore, by an effective thioglycolic acid-assisted solution route, well-aligned ZnO/ZnS nanocable and ZnS nanotube arrays have been successfully synthesized. ZnS nanotubes show a perfect hexagonal and obvious tubular shape. Our present strategy shows mild growth conditions and good reproducibility.     

Morphosynthesis of hierarchical hydrozincite with tunable surface architectures and hollow zinc oxide

Hydrozincite (Zn5(CO3)2(OH)6) microspheres with a tunable surface architecture have been successfully synthesized via a homogeneous precipitation method under solvothermal conditions. For a smooth hydrozincite microsphere, various building blocks such as nanocubes, nanorods, and nanosheets are arranged to cover a spherical surface by concisely controlling reaction time and the volume of ethylene glycol. Hexagonal Zn5(CO3)2(OH)6 with nanostep structures are also prepared without any additives. The hollow ZnO microspheres with a porous surface have been successfully fabricated via a solution-based method by the room-temperature treatment of filled Zn5(CO3)2(OH)6 microspheres composed of nanocubes. A possible growth mechanism of these hollow ZnO microspheres is proposed. The similar filled ZnO microspheres can also be obtained by a direct pyrolysis of Zn5(CO3)2(OH)6 microspheres composed of nanocubes at 450 degrees C.     

Coexistence of long-range ferromagnetic ordering and glassy behavior in one-dimensional bimetallic cyano-bridged polymers

Two new one-dimensional (1-D) 3d-5d cyano-bridged bimetallic assemblies, ([Co(3)(II)(DMF)(12)][W(V)(CN)(8)](2)])(infinity) (1) and ([Mn(3)(II)(bipy)(2)(DMF)(8)][W(V)(CN)(8)](2))(infinity) (2), have been synthesized and characterized, where bipy stands for 2,2'-bipyridine and DMF represents N,N-dimethylformamide. The X-ray analyses show that the two complexes belong to the P(-)1 space group with Z = 1 and C(52)H(84)N(28)O(12)Co(3)W(2), a = 11.690(3) A, b = 12.703(3) A, c = 13.712(3) A, alpha = 86.889(4) degrees, beta = 73.256(4) degrees, and gamma = 77.033(4) degrees for 1 and C(60)H(72)N(28)O(8)Mn(3)W(2), a = 10.672(2) A, b = 13.024(3) A, c = 16.000(3) A, alpha = 78.32(3) degrees, beta = 75.69(3) degrees, and gamma = 66.63(3) degrees for 2. The structures of the two complexes are similar and consist of 12-atom rhombic M(2)W(2)(CN)(4) (M = Co (1), Mn (2)) units, which act as a basic component to be repeatedly connected through W-C-N-M-N-C-W linkages to form a one-dimensional infinite 3,2-chain; these chains are well separated by the DMF molecules or 2,2'-bipyridines coordinated to the metal ions Co(2+) for 1 and Mn(2+) for 2. Magnetic studies, including linear and nonlinear ac susceptibility measurements, demonstrate that the long-range magnetic ordering and spin glass behavior coexist in the two 1-D compounds.     

Tuning molecular aggregation to achieve highly bright AIE dots for NIR-II fluorescence imaging and NIR-I photoacoustic imaging

Currently, bright aggregation-induced emission luminogens (AIEgens) with high photoluminescence quantum yields (PLQYs) in the NIR-II region are still limited, and thus an efficient strategy to enhance NIR-II fluorescence performance through tuning molecular aggregation is proposed here. The synthesized donor–acceptor tailored AIEgen (DTPA-TBZ) not only exhibits an excellent absorptivity in the NIR-I region, but also good fluorescence signals in the NIR-II region with an emission extending to 1200 nm. Benefiting from such improved intramolecular restriction and aggregation, a significant absolute PLQY value of 8.98% was obtained in solid DTPA-TBZ. Encouragingly, the resulting AIE dots also exhibit a high relative PLQY of up to 11.1% with IR 26 as the reference (PLQY = 0.5%). Finally, the AIE dots were applied in high performance NIR-II fluorescence imaging and NIR-I photoacoustic (PA) imaging: visualization of abdominal vessels, hind limb vasculature, and cerebral vessels with high signal to background ratios was performed via NIR-II imaging; Moreover, PA imaging has also been performed to clearly observe tumors in vivo. These results demonstrate that by finely tuning molecular aggregation in DTPA-TBZ, a good NIR-I absorptivity and a highly emissive fluorescence in the NIR-II region can be achieved simultaneously, finally resulting in a promising dual-modal imaging platform for real-world applications to achieve precise cancer diagnostics.

A highly efficient dual-modal imaging platform by using bright AIE dots was constructed to achieve precise cancer diagnostics.     

Novel self-assembled MgO nanosheet and its precursors

A novel self-assembled microstructure, nestlike Mg(5)(CO(3))(4)(OH)(2).4H(2)O spheres, is formed by a self-assembly of nanosheets in the hydrothermal process. MgO with the similar morphology can be obtained by calcination of nestlike Mg(5)(CO(3))(4)(OH)(2).4H(2)O. MgO precursors with a uniform, ellipsoid-shaped, and smooth surface or flowerlike architecture, built by individual thin sheets, can be well-obtained by carefully controlling pH values of the initial reaction solution. The nestlike MgO exhibits a unique geometrical shape; its surface is composed of uniform MgO nanosheets. The unique MgO microstructure with high surface areas may possess promising applications as the sorbent for chemisorption and destructive adsorption of various pollutants.     

Syntheses of 2,3‐dicyano‐5a,8a‐dihydro‐5a‐hydroxycyclopentano[1′,2′:4,5]pyrrolo[2,3‐b]pyrazines and 2,3‐dicyanocyclohexano[1′,2′:4,5]pyrrolo‐[2,3‐b]pyrazines

Previously synthesized 2‐(3′‐chloro‐5′,6′‐dicyanopyrazin‐2′‐yl)cyclopentan‐1‐one 1 , obtained from the reaction of 2,3‐dichloro‐5,6‐dicyanopyrazine with 1‐pyrrolidino‐1‐cyclopentene, was further reacted with primary alkylamines to give mixtures of diastereomer of 5‐alkyl‐2,3‐dicyano‐5a,8a‐dihy‐dro‐5a‐hydroxycyclopentano[1′,2′:4,5]pyrrolo[2,3‐b]pyrazines 3a‐h in high yield. The reaction of 2‐alkylamino‐3‐chloro‐5,6‐dicyanopyrazine with 1‐pyrrolidino‐1‐cyclohexene gave 5‐alkyl‐2,3‐dicyanocyclopentano[1′,2′:4,5]pyrrolo[2,3‐b]pyrazines 5a‐b together with 5‐alkylamino‐2,3‐dicyano‐6‐pyrrolidinopyrazines 6a‐b . The products prepared are all of interest as potential pesticides and new fluorescent chromophores.     

Experimental studies of high order soliton compression effect and gain characteristics in femtosecond laser pulses Er3+-doped fiber amplifier

Seed laser pulses with average power of 146 μW and pulse duration of 480 fs were amplified to 14.5 mW. The pulse duration was compressed to 260 fs using 6 m high concentration E³⁺ _r -doped fiber under forward pumping. The amplified signal pulse energy was 0.691 nJ (corresponding to a peak power of 2 657.7 W) and the repetition rate was 20.84 MHz. Spectrum breakup was observed simultaneously. The spectrum of pulses amplified by 3 m E³⁺ _r -doped fiber remains a single peak under different pump power. The amplified pulse duration was compressed abnormally with the increasing pump power using the backward pumping; that is, the amplified pulses were compressed with the increasing pump power under low pump power. When the pump power reached 38 mW, the shortest amplified pulse duration was 309 fs. With further increase in pump power, the amplified pulses began broadening, accompanied by a single peak spectrum under different pump power.     

Degenerate lower dimensional tori in reversible systems

In this paper we prove the persistence of lower dimensional invariant tori with prescribed frequencies and singular normal matrices in reversible systems. The normal variable is two-dimensional and the unperturbed nonlinear terms in the differential equation for this variable have a special structure.