Nguyen T. Mai

Chemical Synthesis of Blue-emitting Metallic Zinc Nano-hexagons

We report a new ligand directed chemical synthesis of hexagonal shaped zinc nanoplates. The produced nano-hexagons (NHexs) display a thickness of about 20–40 nm and diameter ranging from about 200–350 nm, exhibiting a high aspect ratio. While zinc is traditionally highly susceptible to oxidation, these high surface area NHexs possess a remarkable resistance to atmospheric oxidation, owing to their unique surface crystalline faces and the fact that these particles are protected by organic surface ligands. The zinc NHexs size, morphology and chemical properties were characterized using transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy, among other techniques. Photoluminescence spectroscopy analysis revealed blue photoluminescence emission, making these NHexs potentially ideal for optics, optoelectronics or security printing.

Study on formation mechanism and ligand-directed architectural control of nanoparticles composed of Bi, Sb and Te: towards one-pot synthesis of ternary (Bi,Sb)2Te3 nanobuilding blocks

This paper reports a study on the formation mechanism of nanoparticles (NPs) composed of bismuth, antimony and tellurium for thermoelectric materials using a modified polyol synthetic route. Our one-pot synthesis technique has proven highly versatile in creating a wide range of different anisotropic NPs such as nanowires (NWs), nanodiscs (NDs), nanoribbons and nanospines (NDs studded on NWs) simply by modifying the capping species or elemental precursor feeding ratio used in the synthesis. However, an independent control of morphology and composition is still hugely challenging and the facile synthesis of (Bi,Sb)2Te3 solid solution NPs is not a trivial task, reflecting the complex nature of this multicomponent system. To achieve this goal, it is imperative to understand the formation mechanism based on a systematic investigation of mono- and binary elemental NP systems. Our study clearly shows the different actions of oleylamine (OAM) and decanethiol (DT) capping ligands in our synthesis reaction. In the case of DT capping system, Te NDs are first formed, and then, Bi and Sb are separately incorporated into the Te ND structure viacatalytic decomposition of Bi-DT and Sb-DT complexes on the Te ND surfaces. Therefore, the resulting NPs are phase segregated into Te, Bi2Te3 and Sb2Te3. On the other hand, in the case of the OAM capping system, Te NWs and Bi-Sb solid solution NPs are formed separately, and then, parts of Te NWs are transformed into (Bi,Sb)2Te3 phase via oriented attachment of Bi-Sb NPs and Te NWs. These findings are crucially important towards the one-pot synthesis of uniform (Bi,Sb)2Te3 nanobuilding blocks with controllable characteristics for highly efficient thermoelectric materials.