Chemical Reactions and Self-assembly in Nano-confined Environments: the Development of New Catalytic Microcontact Printing Techniques and Multicomponent Inorganic Janus Particles

Abstract

Modern patterning and fabrication techniques provide powerful opportunities for the preparation of micro- and nanostructured objects with applications in fields ranging from drug delivery and bioimaging to organic based electronic devices and real time biochemical sensors. In this thesis we report a systematic study focused on the development of new unconventional patterning and fabrication techniques with applications in the preparation of functional micro- and nanostructured devices.Catalytic microcontact printing is a powerful technique that offers a simple and effective methodology for patterning chemically-functionalized surfaces with sub-100 nm accuracy. By avoiding diffusive mechanisms of pattern replication it effectively obviates the most significant limitation of traditional microcontact printing - lateral molecular ink diffusion. Moreover, catalytic microcontact printing significantly expands the diversity of patternable surfaces by using prefunctionalized substrates and gives rapid facile access to chemically discriminated surfaces that can be further functionalized with organic and biological molecules. We have developed several catalytic microcontact printing techniques that transfer pattern from an elastomeric stamp bearing an immobilized catalyst to a preformed functionalized self-assembled monolayer. By avoiding diffusive pattern transfer we were able to replicate features with sub-50 nm edge resolution. We also demonstrated that catalytic printing can be expanded to technologically important substrates not accessible through conventional soft lithography, by patterning reactive organic monolayers grafted to chemically passivated silicon.The non-symmetric structure of Janus particles produces novel physical properties and unusual aggregation behavior that makes these materials attractive candidates for drug delivery and as nano-sensors and nano-probes, SERS and PEF imaging agents, small molecules carriers, and switchable devices. We have developed a new protocol for preparation of non-spherical inorganic Janus particles comprising metallic and semiconductor layers. The method allows for precise control over the composition, shape and size and permits fabrication of non-symmetrical particles, the opposite sides of which can be orthogonally functionalized using well-established organosilane and thiol chemistries.