| Functional nanocrystals (NCs) are crucial for modern science and technology due to their numerous novel properties. These distinct novel behaviors are always depending on their intrinsic characteristics, such as catalytic properties of metals due to a change of surface nature/composition and optical properties of semiconductors due to a change of band-gap. This work focuses on this study by choosing two typical systems, metal/alloy and semiconductor nanocrystals. In the metal system, shape-controlled platinum (Pt) and Pt-based alloy nanocrystals are the best candidates for next generation of fuel cell catalysts. However, the limited knowledge about the controlled-synthesis of these nanocrystals severely hindered the investigation on their catalytic properties and potential applications. In this work, Pt and Pt-based alloy nanocrystals with tunable size, morphology, and composition have been prepared through wet-chemical method by carefully choosing reaction parameters. Their surface structure/composition related electro catalytic properties have also been discussed. In the semiconductor system, indium-based nanocrystals, including indium phosphide (InP) and indium oxide (In2O3), have been studied. The emission wavelength of InP NCs has been tuned in a range from green to red by varying the particle size. The luminescence property is further enhanced by coating zinc sulfur shell on the InP NC. Furthermore, the structure behavior of indium oxide nanoctahedra has been in situ studied using a synchrotron x-ray diffraction method. Enhanced structure stability coming from the {111} surface was observed. The recovered sample shows different stability under electron beam irradiation. The fundamental insights gained from this work could help further understanding the mystery of nanocrystal synthesis and their structure-dependent novel properties. |
