Lang Liu

Porous CNT@Li4Ti5O12 coaxial nanocables as ultra high power and long life anode materials for lithium ion batteries

Porous CNT@Li4Ti5O12 core–sheath coaxial nanocables were designed using a sol–gel method combined with a following low temperature reflux process and a short post-annealing in the presence of bamboo-like polymer nanotubes acting as a template and a carbon source. As anodes for lithium ion batteries, coaxial nanocables exhibit a high reversible capacity of 322.5 mA h g−1 at 200 mA g−1 after 200 cycles. They also have excellent rate capability and superior long-term cycling stability at high current density, which could attain a high discharge capacity of 198.7 mA h g−1 at 2000 mA g−1 for up to 2000 cycles. Compared with the Li4Ti5O12 nanoparticles, the enhanced electrochemical performance of the CNT@Li4Ti5O12 nanocomposites benefits from the shortened Li+ diffusion distance, large contact surface area, high conductivity, and good structure stability of the coaxial nanocables, which simultaneously solves the major problems on the loss of electrical contact and the aggregation of particles for Li4Ti5O12 anodes. The material with a nanocable structure is a potential candidate for developing advanced electrochemical energy storage systems with high power and long life.

Coal based magnetic activated carbon as a high performance adsorbent for methylene blue

AbstractnCoal based magnetic activated carbons (MACs) were prepared by using the two-stage carbonization and activation of coal in the presence of Fe2O3 as the magnetic source. Compared with the single-stage carbonization and activation, the two-stage temperature method was found to be efficient for the preparation of MACs with the high specific surface area and good magnetic properties in a lower alkali/carbon ratio. The as-synthesized MACs at optimized conditions exhibited specific surface areas of up to 2075xa0m2/g and optimal saturation magnetization of as high as 15.02xa0emu/g. Moreover, as an adsorbent, the efficiency of removing methylene blue (MB) from aqueous solutions is excellent. Based on MB adsorption behaviors at various conditions, including initial dye concentration, contact time and temperature, MACs prepared at optimized conditions exhibited a maximum equilibrium MB adsorption capacity of 871xa0mg/g. The data of adsorption kinetics and isotherms could be well fitted by using the pseudo-second-order equation and the Freundlich model. Importantly, MACs can be separated and recovered easily by applying a magnetic field. Therefore, the coal-based magnetic activated carbons might be a promising candidate of high efficiency, low cost for removal of organic dyes.

Anatase/rutile titania anchored carbon nanotube porous nanocomposites as superior anodes for lithium ion batteries

Anatase/rutile titania anchored carbon nanotube (TiO2@CNT) porous nanocomposites are fabricated using TiCl3 and polymer nanotubes as the titanium and carbon sources, respectively, by a hydrothermal process with subsequent heat treatment. As anodes for lithium ion batteries, the electrochemical performance of the nanocomposites is highly dependent on the crystal phase and content of TiO2. Compared with anatase TiO2/C nanocomposites, the TiO2@CNT nanocomposites exhibit high reversible capacity, excellent rate capability and superior long-term cycling stability at high current densities. The enhanced electrochemical performance of the nanocomposites results from the shortened Li+ diffusion distance, large contact surface area and sufficient conductivity. In addition, the crystal interface effect of mixed-phase TiO2 could improve the dispersion rate of electrons, which is conducive to the rapid transport of Li+ and the electrons.

Photophysical properties of palladium/platinum tetrasulfonyl phthalocyanines and their application in triplet–triplet annihilation upconversion

Triplet photosensitizers showing strong absorption in the red/deep red spectral region, high intersystem crossing, a long-lived triplet state and a high triplet state energy level are crucial for triplet–triplet annihilation upconversion. Herein we selected two tetrasulfonyl-substituted phthalocyanine (Pc) Pt(II) and Pd(II) complexes (Pd-Pc and Pt-Pc) likely to meet the above criteria. The complexes showed prolonged triplet state lifetimes (15.9 μs and 3.03 μs) and high triplet state energy levels (1.5 eV) as compared to a Pc complex bearing electron donating groups (triplet lifetimes <3.0 μs; triplet energy levels ≈1.2 eV). Weak fluorescence was observed for Pd-Pc, whereas a fluorescence/phosphorescence dual emission feature was observed for Pt-Pc. Based on the phosphorescence emission, intermolecular triplet–triplet-energy-transfer (TTET) experiments and TD–DFT computations, the T1 state energy levels of Pd-Pc and Pt-Pc were determined as 1.25 eV and 1.5 eV, respectively. The two complexes were used for triplet–triplet-annihilation upconversion, with deep red excitation at 658 nm, upconversion with a quantum yield of 0.63% and an anti-Stokes shift of 3996 cm−1 was achieved.

Solid-state photochromic behavior of pyrazolone 4-phenylthiosemicarbazones

Solid-state photochromic materials have attracted much more attention due to their actual potential applications in photoactive devices. Here, three new compounds (1-phenyl-3-methyl-4-(3-fluoro/chloro/bromobenzal)-5-hydroxypyrazole 4-phenylthiosemicarbazones) were synthesized, which exhibited reversible solid state photochromic properties upon UV/Vis light irradiation. Their photochromic properties, first-order kinetics and fatigue resistance were investigated by time-dependent UV-Vis absorption spectroscopy. The results showed that their fatigue resistance and addressability were enhanced with the increase in the electron-withdrawing ability of the substituents on the phenyl group at the 4-position of the pyrazolone ring. Thus, 1-phenyl-3-methyl-4-(3-fluorobenzal)-5-hydroxypyrazole 4-phenylthiosemicarbazone exhibited good photochromic properties and high fatigue resistance. Based on single crystal X-ray diffraction and FT-IR analyses, the photochromic mechanism involved intra/intermolecular proton transfer.