Various sizes and shapes of Mn 3 O 4 nanocrystals have been prepared in a one-pot synthesis in extremely dilute solution by soft template self-assembly. To better control size and shape, the effects of varying the growth time, reaction temperature, surfactant, and manganese source were examined. The average size of octahedral Mn 3 O 4 crystallites was found to be related to the reaction time, while higher reaction temperature (150 °C ) and the use of a cetyltrimethylammonium bromide/poly(vinylpyrrolidone) (CTAB/PVP) mixture allowed construction of a better-defined octahedral morphologies. When PVP or poly(ethylene oxide)-poly(propylene oxide) (P123) was used as template, large-scale agglomeration resulting in loss of the octahedral morphology occurred and crystallites with a quasi-spherical shape were obtained. The nano-octahedral crystallites were shown to be an efficient catalyst for the oxidation of methylene blue.

A facile, efficient, and unique self-assembly process for the preparation of the macroscopic, free-standing, Ag-reduced, graphene oxide (Ag-RGO) Janus films, which exhibit a unique asymmetry of their two surfaces with macroscopic dimensions, is presented. A novel strategy using an evaporation-induced, self-assembly (EISA) process is shown to be a powerful and flexible method for synthesizing well-defined Janus thin films.

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