(231e) Array of Nanostructured Electrode Tailored from Isolated to Continuum Monolayer for Chemical Sensing at Sub Parts per Trillion

Electrochemical sensors are the most ubiquitous chemical sensors. For example, glucometer, with worldwide market of over $2 billion is arguably the most successful biosensor in history. It is becoming evident that nanostructured sensing electrodes can enhance the performance of a device significantly due to their unique characteristic high mass transport rate compared to planar electrode. Fabrication of gold nanostructured arrays to enhance electrochemical reactions will be discussed. Metal scaffold on DNA or metal nanoparticles were used as nanostructures. The Electrochemical reactions are measured by differential reflectometry, a novel optical technique that probes fluctuations of the refractive index at the electrode/electrolyte interface. The electrochemical reactions were measured on a 6 µm diameter spot defined by the He/Ne laser beam. The refractive index at the electrode interface varies due to redox reactions. By modifying the surface from isolated nanoelectrode array to continuum nanostructured electrode, it was possible to control the nature of the diffusion layer. The catalytic action of the nanostructure and the nanoelectrode effect of diminishing diffusion were quantitatively explored as function of the modulation of the inter-nanostructure distance. Measurements of lead, arsenic and mercury in solution from parts-per-million to parts-per-trillion levels will be discussed.