Synthesis of 3D ordered macroporous indium tin oxide using polymer colloidal crystal template

Three-dimensional (3D) ordered macroporous indium tin oxide (ITO) is prepared using a polymer colloidal crystal template that is formed by self-assembly of the monodisperse poly(methyl methacrylate) (PMMA) microspheres. The morphologies and BET surface area of the macroporous material is examined by scanning electron microscope, transmission electron microscopy and N-2 adsorption/desorption. Results indicate that the macroporous material has highly ordered arrays of the uniform pores replicated from the PMMA colloidal crystal template when the polymer colloidal crystal template is removed by calcinations at 500 degrees C. The pore diameter (about 450 nm) of macroporous ITO slightly shrank to the PMMA microspheres. The BET surface area and pore volume of the macroporous material are 389 m(2) . g(-1) and 0.36 cm(3).g(-1), respectively. Moreover, the macroporous ITO, containing 5 mol% Sn and after annealing under vacuum, shows the minimum resistivity of rho = 8.2x10(-3) Omega.cm. The conductive mechanism of macroporous ITO is discussed, and it is believed that the oxygen vacancies are the major factor for excellent electrical properties.