Constructing ZnTe Spherical Quantum Well for Efficient Light Emission.

ZnTe colloidal semiconductor nanocrystals (NCs) have shown promise for light-emitting diodes (LEDs) and displays, because they are free from toxic heavy metals (Cd). However, so far, their low photoluminescence (PL) efficiency (∼30%) has hindered their applications. Herein, we devised a novel structure of ZnTe NCs with the configuration of ZnSe (core)/ZnTe (spherical quantum well, SQW)/ZnSe (shell). The inner layer ZnTe was grown at the surface of ZnSe core with avoiding using highly active and high-risk Zn sources. Due to the formation of coherently strained heterostructure which reduced the lattice mismatch, and the thermodynamic growth of ZnTe, the surface or interface defects were suppressed. A high PL efficiency of >60% was obtained for the green light-emitting ZnSe/ZnTe/ZnSe SQWs after ZnS outer layer passivation, which is the highest value for colloidal ZnTe-based NCs. This work paves the way for the development of novel semiconductor NCs for luminescent and display applications.

Intercalation and delamination of Ti2SnC with high lithium ion storage capacity.

Li-ion batteries attract great attention due to the rapidly increasing and urgent demand for high energy storage devices. MAX phase compounds, layered ternary transition metal carbides and/or nitrides show promise as candidate materials of electrodes for Li-ion batteries. However, the highest specific capacity reported up to now is relatively low (180 mA h g-1), preventing them from use in real applications. Exploring more MAX phase compounds with delaminated two-dimensional structure is an effective solution to increase the specific capacity. Herein, we report the reversible electrochemical intercalation of Li+ into Ti2SnC (MAX phase) nanosheets. Owing to the synergistic effects of intercalation and dimethyl sulfoxide (DMSO)-assisted exfoliation, Ti2SnC nanosheets are successfully obtained via sonication in DMSO. Moreover, when using as an anode of a Li-ion battery, Ti2SnC nanosheets exhibited an increasing specific capacity with cycling due to the exfoliation of Ti2SnC nanosheets via reversible Li-ion intercalation. After 1000 charge-discharge cycles, Ti2SnC nanosheets delivered a high specific capacity of 735 mA h g-1 at a current density of 50 mA g-1, which is far better than other MAX phases, such as Ti2SC, Ti3SiC2 and Nb2SnC. The current work demonstrates the Li-ion storage potential and indicates a novel strategy for further intercalation and delamination of MAX phases.