Jianhua Tian

Submicron-sized mesoporous anatase TiO2 beads with a high specific surface synthesized by controlling reaction conditions for high-performance Li-batteries

The effect of reaction temperature and aging time on TiO2 precursor beads synthesized using a sol–gel method was studied. The size of the precursor beads decreased and deformed spheres appeared with increasing temperature. Meanwhile, TiO2 precursor beads grew with the aging time up to a reaction time of 18 h. Using a solvothermal process for the precursor beads, submicron-sized mesoporous anatase TiO2 beads (SMATBs) with a specific surface of 153.2 m2 g−1, much higher than initially reported, were synthesized by controlling the reaction conditions and were successfully employed as negative electrode for Li-ion batteries. The specific capacities of the submicron-sized mesoporous TiO2 beads are much higher than those of their counterparts at high charge–discharge rates. In the first cycle, the TiO2 beads showed discharge capacities of 172.0 mA h g−1, 129.6 mA h g−1, 117.1 mA h g−1 and 56.7 mA h g−1 at charge–discharge rates of 1 C (1 C = 170 mA g−1), 5 C, 10 C and 30 C, respectively. 85.1% discharge capacities were retained after 200 cycles at 1 C charge–discharge rate. After 600 cycles, there is still 81.8% discharge capacity retained at 5 C charge–discharge rate. Moreover, the TiO2 beads also exhibitied 86.9 mA h g−1 and 34.0 mA h g−1 discharge capacities at 10 C and 30 C charge–discharge rates over 600 cycles, respectively. In addition, the Coulombic efficiency is nearly 100% at each cycle at various charge–discharge rates.

Novel photochromic and electrochromic diarylethenes bearing triphenylamine units

Six novel photochromic and electrochromic diarylethenes containing triphenylamine units were synthesized by the McMurry reaction. The properties of photochromism, electrochromism, fluorescence and electrochemistry were investigated in detail. The results showed that these compounds exhibited reversible photochromism, changing from colorless to yellow after irradiation with 302 nm UV light both in solution and in PMMA amorphous film. When arriving at the photostationary state, the fluorescent intensity was quenched to about 40%. In the cyclic voltammetry curves, there were a reversible redox couple and one or two irreversible oxidation peaks. The potential of the reversible oxidation peak is adopted as the excitation voltage of electrochromism. The electrochromic devices could be simulated with an equivalent circuit, R(CR)(CR), by electrochemical impedance spectroscopy, and the transformation between colorless and blue was realized, which required 8.6 to 12.1 s for color switching and 8.9 to 12.8 s for bleaching. The reflectance minima of these compounds are in the range from 709.7 to 781.7 nm after coloring. The results showed that diarylethenes containing triphenylamine units possessed both photochromic and electrochromic properties.