S. Sakurai, J. Cho
Binghamton University SUNY,
Keywords: ZnO, nanoplates, a-axis, 2-dimensional, photocatalytic, templated growth, hydrothermal
Summary:Two-dimensional (2-D) nanomaterials have recently received considerable attentions with their unique characteristics, which were not seen in their bulk and 1D counterparts. Zinc oxide (ZnO) is one of the most promising functional materials as it is chemically stable, non-toxic and available at low cost. To synthesize the 2-D ZnO platelets, ZnO has to grow in the a-axis while suppressing its growth in the c-axis. This growth pattern can be achieved with the aid of a seed layer of r-plane (1-102)-oriented aluminum oxide (Al2O3) as its lattice mismatch with a-plane (11-20) of ZnO is only 1.53%. This r-plane oriented alumina layer was prepared on Si (111) substrate, on which ZnO nanoplates were hydrothermally grown. Such nanoplates contained very high concentration of the surface defects and were off-stoichiometric, thereby making them very sensitive to external stimuli such as light and environment. These ZnO nanoplate surfaces (mainly, c-planes) showed the photoelectric properties that strongly depend on the presence of oxygen and temperature. This makes a great opportunity for these nanostructures to tailor surface functionalities by engineering the defect concentration and type of the exposed ZnO surfaces. For instance, it exhibited very effective photocatalytic surfaces for degradation of organic contaminants when being treated by high energy e-beam radiation. On the other hand, wet UV-oxidation made the nanoplate surfaces effectively passivated by reducing surface defects. As a result, the templated growth of the 2-D ZnO nanoplates enables to create a functional surface that can be very responsive to the external stimuli. This presentation will highlight current research progresses made for the control of the size, aspect ratio, and the packing density of the aligned nanoplates and their post treatments to tailor the photocatalytic properties of the nanoplate-stacked surfaces.