We report the shape evolution process of Cu(2)O nanocrystals upon slow oxidation of Cu under ambient conditions, yielding novel hexagonal and triangular platelike morphologies. The shape of the obtained nanocrystals evolves from hexagonal to triangular to octahedral; the growth patterns are governed by kinetically and thermodynamically controlled growth. Preferential adsorption of I(-) on {111} planes of Cu(2)O nanoparticles induced the selective crystal growth of metastable platelike structures with {111} faces as the basal planes. On aging, the growth process appeared to shift into the thermodynamic regime and the thermodynamically stable octahedral shape is obtained. The possible growth mechanisms were investigated by varying the synthetic conditions. The band gap of Cu(2)O nanooctahedrons was determined by the classical Tauc approach to be 2.24 eV, which is blue shifted with respect to the bulk Cu(2)O value (2.17 eV). Results suggest that the slow oxidation process and use of crystallographic selective surfactants are essential for the appearance of anisotropic metastable shapes. In general, surface energy control by surfactant molecules might provide a convenient channel for tailoring nanocrystal shapes of metal oxides.

A facile and effective method to produce sub-10 nm Ag nanoparticles in a water solution is reported. Stabilization of the nanoparticles was achieved by hydrophobic interactions with the apolar primary faces of α-CD. In addition, hydrogen-bonding interactions between the exposed secondary -OH groups facilitated the threading of neighboring CDs, leading to the self-assembly of the Ag nanoparticles into 1-D “pearl necklace” arrays. The preparation of such metal nanoparticles unravels possibilities for the assembly of nanoparticles in 2- and 3-D patterns.

We report a high-yield facile synthesis of uniform single-crystalline γ-CuI nanocrystals with tetrahedral morphology from the reaction between Cu n and KI under ambient conditions. In our method, I- perform the roles of reactant and surface stabilizing agent, thereby reducing the complexity of the reaction by eliminating the need for an external capping agent. Nanotetrahedrons grow from single-crystalline seeds whose growth has been promoted by iodide-induced oxidative etching of twinned seeds. These nanocrystals have T d symmetry in which three triangular faces meet at each corner, and thus may be classified as platonic solids. Removal of excess free I- in solution initiates the dissolution of CuI nanotetrahedrons and simultaneous oxidation to CuO nanocages. Transmission electron microscopy was used to trace the hollowing process, and the nanoscale Kirkendall effect and other possible mechanisms were discussed for the formation of void interiors.

Ag2Se nanotubes have been successfully synthesized by UV photodissociation of adsorbed CSe2 on the surface of Ag nanowires under ambient conditions. Transmission electron microscopy was used to trace the growth of hollow interiors, allowing a detail study of the Kirkendall effect in 1-dimensional nanosystems. Voids were observed to grow from both ends of the nanowires along the longitudinal axis and ultimately merged to form hollow nanotubes. This phenomenon is attributed to the crystallographic selective adsorption of poly(vinylpyrolidone) on Ag nanowire templates. In addition, we observed the formation of dendrites on aging of the reaction mixture and explained its growth based on a diffusion-limited aggregation model.

By tuning the supersaturation during crystal growth, β‐Ag2MoO4 concave and convex crystals have been prepared with high‐index facets and a variety of morphologies, including {100}‐faceted cubes, {310}‐faceted concave cubes, {110}‐faceted octopods, {311}‐faceted trapezohedrons (TPH) and {331}‐faceted trisoctahedrons (TOH). The resulting suite of uniform crystals with well‐defined shapes enabled photocatalytic studies on Ag2MoO4.