Nanostructured carbon/silicon composite opto-electrochemical devices for sensing and energy harvesting applications

My research activity deals with fabrication, characterization and functionalization techniques of silicon-based nanostructures and systems, such as silicon nanowires and nanostructured porous silicon. In particular, I focused my final dissertation thesis on the synthesis and study of a new class of carbon/silicon nanocomposites, produced by a recently discovered carbonization chemistry of porous silicon. Such a new chemistry has been optimized in order to obtain samples amenable for applications into a liquid dynamic environment. The employed carbon nanocasting process provides both a stable and conductive hybrid nanomaterial, allowing the carbonized porous silicon film to act as working electrode in aqueous media. The electrode stability has been tried out in different liquids as well as under voltage applied. Moreover, the optical properties of the nanostructure enable its use as a sensor for electrically charged species in buffer solutions, such as biomolecular complexes. By application of an electrical potential difference between the working and a counter electrode, the sensor is able to simultaneously attract and detect both positively than negatively charged targets. In the case of electroadsorbed biomolecules, indications on the retention of their functional activity after releasing from the electrode surface are also provided. Furthermore, an electrical measurement system has been added to the optical one in order to monitor, in real-time with the optically transduced signal, the current flowing between the two electrodes during the sensing experiments. A few prototypes which synchronize the optical and electrical responses of the sensor have been fabricated and their performances tested by varying the electrical parameters. These new combined opto-electrochemical devices can potentially find applications both in future label-free sensing than in next-generation energy harvesting technologies.