Robust Room-Temperature Ferromagnetism with Giant Anisotropy in Nd-Doped ZnO Nanowire Arrays

As an important class of spintronic material, ferromagnetic oxide semiconductors are characterized with both charge and spin degrees of freedom, but they often show weak magnetism and small coercivity, which limit their applications. In this work, we synthesized Nd-doped ZnO nanowire arrays which exhibit stable room temperature ferromagnetism with a large saturation magnetic moment of 4.1 μ_B/Nd as well as a high coercivity of 780 Oe, indicating giant magnetic anisotropy. First-principles calculations reveal that the remarkable magnetic properties in Nd-doped ZnO nanowires can be ascribed to the intricate interplay between the spin moments and the Nd-derived orbital moments. Our complementary experimental and theoretical results suggest that these magnetic oxide nanowires obtained by the bottom-up synthesis are promising as nanoscale building blocks in spintronic devices

Improved Size-Tunable Synthesis of Monodisperse Gold Nanorods through the Use of Aromatic Additives

We report an improved synthesis of colloidal gold nanorods (NRs) by using aromatic additives that reduce the concentration of hexadecyltrimethylammonium bromide surfactant to ∼0.05 M as opposed to 0.1 M in well-established protocols. The method optimizes the synthesis for each of the 11 additives studied, allowing a rich array of monodisperse gold NRs with longitudinal surface plasmon resonance tunable from 627 to 1246 nm to be generated. The gold NRs form large-area ordered assemblies upon slow evaporation of NR solution, exhibiting liquid crystalline ordering and several distinct local packing motifs that are dependent upon the NR’s aspect ratio. Tailored synthesis of gold NRs with simultaneous improvements in monodispersity and dimensional tunability through rational introduction of additives will not only help to better understand the mechanism of seed-mediated growth of gold NRs but also advance the research on plasmonic metamaterials incorporating anisotropic metal nanostructures

Engineering Catalytic Contacts and Thermal Stability: Gold/Iron Oxide Binary Nanocrystal Superlattices for CO Oxidation

Well-defined surface, such as surface of a single crystal, is being used to provide precise interpretation of catalytic processes, while the nanoparticulate model catalyst more closely represents the real catalysts that are used in industrial processes. Nanocrystal superlattice, which combines the chemical and physical properties of different materials in a single crystalline structure, is an ideal model catalyst, that bridge between conventional models and real catalysts. We identify the active sites for carbon monoxide (CO) oxidation on Au-FeO_<i>x</i> catalysts by using Au-FeO_<i>x</i> binary superlattices correlating the activity to the number density of catalytic contacts between Au and FeO_<i>x</i>. Moreover, using nanocrystal superlattices, we propose a general strategy of keeping active metals spatially confined to enhance the stability of metal catalysts. With a great range of nanocrystal superlattice structures and compositions, we establish that nanocrystal superlattices are useful model materials through which to explore, understand, and improve catalytic processes bridging the gap between traditional single crystal and supported catalyst studies