MCF最新热点文章-2019年10月
聚焦当前研究热点，关注 MCF公众号
以下最新发表的热点文章，是MCF基于评审报告所遴选出来的，以供大家阅读探讨，至2019年12月底可免费获取全文。
Copper surface doping to improve the structure and surface properties of manganese-rich cathode materials for sodium ion batteries
Tao Chen, Weifang Liu, Yi Zhuo, Hang Hu, Jing Guo, Yaochi Liu, Jun Yan and Kaiyu Liu
Mater. Chem. Front., 2019, 3, 2374-2379
https://doi.org/10.1039/C9QM00522F
A facile copper surface doping process is proposed to enhance the surface structural stability of manganese-rich layered oxide cathodes. Herein, the surface structure of P2-type Na0.67Mn0.6Ni0.2Co0.2O2 was stabilized via the formation of a copper-rich surface layer. This layer can reduce the dissolution of manganese in the electrolyte and inhibit side reactions at the electrode/electrolyte interface. Expanded surface lattice channels induced by copper doping contributed to the improvement of Na⁺ mobility. In addition, it can be deduced from scanning transmission electron microscopy (STEM) images that copper surface doping resulted in a surface transition from the P2 phase to P3 phase. Electrochemical impedance spectroscopy (EIS) measurements confirmed that both the irreversible reaction resistance and charge transfer resistance of the copper surface-doped Na0.67Mn0.6Ni0.2Co0.2O2 (Cu-MNC) were significantly reduced. More importantly, the Cu-MNC electrode delivered an initial specific capacity of 122.2 mA h g⁻¹ with retention of up to 83.3% after 150 cycles at 0.2C. After refreshing the sodium metal anode and electrolyte, it showed a high specific capacity of 102.4 mA h g⁻¹ with retention of 84.14% after 200 cycles. These results open up a new method to optimize manganese-rich oxide materials for SIBs.
Zeolite-confined carbon dots: tuning thermally activated delayed fluorescence emission via energy transfer
Hongyue Zhang, Jiancong Liu, Bolun Wang, Kaikai Liu, Guangrui Chen, Xiaowei Yu, Jiyang Li and Jihong Yu
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00549H
Confining carbon dots (CDs) in zeolites may boost the thermally activated delayed fluorescence (TADF) emission. However, so far only blue-emissive CD-based TADF materials are reported, and rationally tuning the TADF emission of these materials remains challenging. Herein, by in situ embedding different emissive CDs into a zeolite matrix, we have successfully prepared a series of CD@zeolite composites with tunable TADF emission from blue to green by utilizing energy transfer (ET) between confined CDs. The as-prepared CD@zeolite composites exhibit lifetimes varying from 271 ms to 860 ms and quantum yields ranging from 20% to 42%. The ET process occurs from the singlet excited state of the blue emissive CD donor to the singlet excited state of green emissive CD acceptors with different polymerization degrees, promoting tunable TADF with cyan, mint green and olive green emission. The design concept proposed in this work may open a way to judicious tuning of the emission of TADF materials, and thus may broaden the applications of CD-based TADF materials.
Design and performance study of high efficiency/low efficiency roll-off/high CRI hybrid WOLEDs based on aggregation-induced emission materials as fluorescent emitters
Zeng Xu, Jiabao Gu, Jian Huang, Chengwei Lin, Yuanzhao Li, Dezhi Yang, Xianfeng Qiao, Anjun Qin, Zujin Zhao, Ben Zhong Tang and Dongge Ma
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00539K
Generally, hybrid white organic light-emitting diodes (WOLEDs) are constructed with blue fluorophores and yellow or green/red phosphors, and the fluorophores and phosphors used have to be doped into proper hosts to avoid the exciton quenching caused by molecular aggregation, which brings difficulties in device structure design and fabrication. In this paper, we fabricated high efficiency/low efficiency roll-off/high CRI hybrid WOLEDs based on aggregation-induced emission (AIE) luminogens (AIEgens) with non-doping features as the fluorophore emitters. The resulting WOLEDs were constructed by two AIEgens that emit blue and green light, respectively, and a doped red phosphor, greatly simplifying the device structure. Encouragingly, the hybrid WOLEDs simultaneously achieved high efficiency (PEmax = 50.5 lm W⁻¹, EQEmax = 20.5%), low efficiency roll-off (PE1000nit = 32.9 lm W⁻¹, EQE1000nit = 18.9%), and high CRI (≥90). Our results indicate that AIEgens are promising material systems for manufacturing high-performance white OLEDs with a simple device structure.
A polymorphic fluorescent material with strong solid state emission and multi-stimuli-responsive properties
Ji-Yu Zhu, Chun-Xiang Li, Peng-Zhong Chen, Zhiwei Ma, Bo Zou, Li-Ya Niu, Ganglong Cui and Qing-Zheng Yang
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00518H
A bright difluoroboron β-diketonate derivative 1 showing four emission colors (green, yellow, orange and red) with high quantum yields (41–74%) in four polymorphs and one amorphous state is reported. Green-emissive crystals (1-G and 1-G′) exhibit dimeric aggregation structures due to the strong molecular π–π interaction but exhibit hypsochromic emission compared to yellow-emissive crystals (1-Y) with monomeric aggregation because of lacking such π–π interactions. These novel emission phenomena are rationalized by theoretical calculations. High fluorescence sensitivity of compound 1 to its molecular packing modes results in excellent responsive behavior to multiple external stimuli thereby showing reversible change of emission colors under mechanical grinding, heating, solvent fuming and hydrostatic pressure.
Carbonized polymer dots/TiO2 photonic crystal heterostructures with enhanced light harvesting and charge separation for efficient and stable photocatalysis
Yue Zhao, Qingsen Zeng, Tanglue Feng, Chunlei Xia, Chongming Liu, Fan Yang, Kai Zhang and Bai Yang
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00556K
TiO2 photonic crystals (PCs) are widely interesting in photocatalysis due to their slow photon effect for efficient light harvesting. However, their performance is limited by the narrow absorption range and fast charge recombination. In this work, an efficient strategy is developed to enhance the light harvesting and charge lifetime through fabricating TiO2 PC/carbonized polymer dot (CPD) heterostructures. The CPDs with a band gap of 2.08 eV are used to broaden the light absorption range. The energy level of CPDs matches well with TiO2 PCs, forming a type-II heterojunction. The staggered energy levels of CPD/TiO2 PC heterostructures are helpful for charge separation and thus suppressed charge recombination, which is demonstrated by the transient photovoltage (TPV) measurements. Therefore, the CPD/TiO2 PC heterostructures exhibit obviously better photocatalytic performance than individual TiO2 PCs. The combination of CPDs and inorganic semiconductors provides a variety of possibilities for the further development of high-efficiency photocatalysts.
Anion replacement in silver chlorobromide nanocubes: two distinct hollowing mechanisms
Sasitha C. Abeyweera, Shea Stewart and Yugang Sun
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00544G
Silver chlorobromide nanocubes have shown promise as a class of sacrificial template for the synthesis of silver-based hollow nanostructures through chemical transformation reactions. Strong chemical bonding between silver and sulfur enables the transformation of AgCl0.5Br0.5 nanocubes into hollow nanoshells of silver–sulfur compounds. During these transformations, factors such as the crystalline structure and nature of the shell material influence the reaction kinetics, and thus the structural and morphological evolution of the hollow structures. Herein, we systematically investigate the hollowing mechanism and associated reaction kinetics for the controlled conversion of AgCl0.5Br0.5 nanocubes into hollow nanostructures. The use of sulfide anions (S2−) and benzenethiolate anions (BT−) for the anion exchange reaction with halide ions has been compared to illustrate the hollowing mechanisms. The S2− ions are comparable in size to the halide ions, resulting in a nano-scale Kirkendall effect that is mainly responsible for the formation of hollow Ag2S nanoshells. In contrast, the Kirkendall effect is absent from forming hollow nanoshells of silver benzenethiolate (AgBT) because the much larger size of BT− ions relative to halide ions hinders their diffusion in the solid AgBT lattice. The molecular-type layered structure of AgBT also disfavors both the inward and outward diffusion of ions through the AgBT shells, thus leading to an overall reduction in the kinetics of the transformation reaction. The transformation reaction is driven only by the dissolution of AgCl0.5Br0.5 and reprecipitation of Ag+ and BT− ions. These results allow for understanding of the underlying factors in hollowing mechanisms to enable the controlled synthesis of well-defined hollow nanostructures with desired properties for a broad range of potential applications.
Tuning aggregation-induced emission nanoparticle properties under thin film formation
Javad Tavakoli, Scott Pye, A. H. M. Mosinul Reza, Ni Xie, Jian Qin, Colin L. Raston, Ben Zhong Tang and Youhong Tang
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00585D
The most frequently used approach to preparing aggregation-induced emission fluorogen (AIEgen) particles is precipitation. Therefore, the addition of an AIEgen solution into water results in the formation of AIEgen particles in a very short time. Within such a short period of time and in the absence of proper mixing under shear, AIE particles are likely to be distributed in a wide range of sizes, thereby affecting their ultimate brightness and applications. Despite numerous attempts, the size of AIEgen particles is still within the range of 200–300 nm. For the first time, we developed a facile robust and cost-effective method for the fabrication of aggregation-induced emission nanoparticles with tuneable particle sizes <100 nm, high quantum yield, and excellent photostability. The direct diffusion of nanoparticles within the cell or in a single-celled organism, as an advantage of size reduction, opens new opportunities for biological and material studies. Such a significant reduction in AIE nanoparticle size has the potential for developing more efficient techniques for characterizing advanced nanomaterials and understanding biological processes and detection strategies.
Push–pull type quinoidal perylene showing solvent polarity dependent diradical character and negative solvatochromism
Wangdong Zeng and Jishan Wu
Mater. Chem. Front., 2019, Advance Article
https://doi.org/10.1039/C9QM00566H
Synthesis and physical properties of a new push–pull type quinoidal perylene (DA-Per) are reported. Three resonance forms, a closed-shell quinoid, an open-shell diradicaloid and a closed-shell zwitterion, all contribute to the ground-state electronic structure. The molecule shows solvent polarity dependent diradical character and negative solvatochromism, which can be explained by the subtle balance among the three resonance forms in different solvent environments.