Hydrothermal Synthesis and Properties of Controlled α‐Fe 2 O 3 Nanostructures in HEPES Solution

A facile, template‐free, and environmentally friendly hydrothermal strategy was explored for the controllable synthesis of α‐Fe 2 O 3 nanostructures in HEPES solution (HEPES=2‐[4‐(2‐hydroxyethyl)‐1‐piperazinyl]ethanesulfonic acid). The effects of experimental parameters including HEPES/FeCl 3 molar ratio, pH value, reaction temperature, and reaction time on the formation of α‐Fe 2 O 3 nanostructures have been investigated systematically. Based on the observations of the products, the function of HEPES in the reaction is discussed. The different α‐Fe 2 O 3 nanostructures possess different optical, magnetic properties, and photocatalytic activities, depending on the shape and size of the sample. In addition , a novel and facile approach was developed for the synthesis of Au/α‐Fe 2 O 3 and Ag/α‐Fe 2 O 3 nanocomposites in HEPES buffer solution; this verified the dual function of HEPES both as reductant and stabilizer. This work provides a new strategy for the controllable synthesis of transition metal oxide nanostructures and metal‐supported nanocomposites, and gives a strong evidence of the relationship between the property and morphology/size of nanomaterials.