Co–Doping of Tin and Zinc into Indium Oxide Nanocrystals Using a Facile Hydrothermal Method

A simple and rapid synthetic route is developed to produce highly crystalline tin and zinc co-doped indium oxide (IZTO) nanocrystals. By using a flow-through reactor, an aqueous metal precursor stream was mixed with another stream of supercritical water containing a reducing agent to continuously produce the IZTO nanocrystals with a mean diameter of 28 nm. Typical reaction conditions were 450 °C, 30 MPa, and 7.0 s. The addition of hexanoic acid into the precursor mixture produced surface-modified IZTO nanocrystals with a smaller size of less than 20 nm. The obtained surface-modified IZTO nanocrystals changed their surface chemical property from hydrophilic to hydrophobic and thus dispersed well in organic solvents. In addition, this method is environmentally benign and compatible with industrial scale synthesis. Finally, as a promising transparent electrode material, the conductivity and transmittance of these IZTO nanocrystals were also measured.