Well Defined Surface Chemistry on Supported Gold Microplates

Gold microplates are atomically flat, anisotropic particles that can be up to 100 microns wide and 40 nanometers in height.  By depositing them on the surface of ITO (Indium Tin Oxide) or glass, they can function as substrates for novel sensors or scanning probe microscopy studies. High-molecular weight polymer surfactants that preferentially bind to crystal facets are often needed in controlling the shapes of these plates during chemical synthesis. These polymers can be difficult to remove, and this poorly controlled surface chemistry limits the application. In order to address this problem, we have developed an alternative growth procedure that does not use polymer surfactants.  Instead, iodide, which may be more easily removed, was used to control the shapes. We have demonstrated the growth of large microplates supported on a number of different substrates (ITO, glass, silicon nitride), and have additionally shown that the iodide can be removed by dipping the surface in strong oxidizers or through electrochemical desorption. The surfaces were then able to support high quality self-assembled monolayers (SAMs), which can be used to control the surface chemical properties of the plates (charge, hydrophilicty, etc).  We are currently applying the microplate substrate in DNA biosensors.  We are also exploring the possibility of integrating the microplates with digital microfluidic systems, which will significantly improve the sensitivity, speed and throughput of DNA biosensors.