Studies of oxide films on aluminum and nanoparticle detection using scanning electrochemical microscopy

This dissertation describes the investigation of electrochemical reactivity on native oxide films of aluminum electrodes and the study of nanoparticle detection using scanning electrochemical microscopy (SECM). Chapter 1 is a brief introduction of the properties of the Al oxide surface and the methodologies of nanoparticle detection. The mechanism of molecular iontophoretic transport in porous membrane is also described. SECM is a scanning probe technique that amperometrically detects the faradaic reactions over the surfaces using a metal tip. A description of SECM is presented in Chapter 2.; The SECM study of spatially localized electrochemical activity at native oxide films on aluminum electrodes (Al/Al2O3 electrodes) is presented in Chapter 3. Local electron-transfer reactions at microscopic detects are visualized and characterized using two different redox mediators. Chapter 4 describes cyclic voltammetric measurements of chemical dissolution rate, Rdis, of the native Al2O3 films on electrochemically polished single-crystal ((100), (110) and (111) orientations) and polycrystalline Al electrodes in neutral pH solutions containing Cl -. Rdis is dependent on the surface orientation in the order: polycrystalline Al > Al(111) ∼ Al(110) > Al(100).; In Chapter 5, quantitative investigations of molecular transport through conically shaped pores in a polycarbonate membrane are performed using SECM. The iontophoretic and diffusional fluxes across a conically shaped pore are strongly dependent on the direction and magnitude of applied current as well as nature of redox molecule. Stochastic electrophoretic capture of individual nanoscale particles at the pore opening is demonstrated in Chapter 6. Particle capture is sensed using SECM. The inverse of time to capture nanoparticles is proportional to the particle concentration. Selective detection based on charge and size of nanoparticles is also demonstrated.