Nano-hybrid ZnO platforms for biosensing applications

Organic/Inorganic (O/I) nanoplatforms of ZnO/polystyrene (PS)/SiO2, both chemically and topographically nanostructured, have been fabricated by using a hybrid bottom up approach of colloidal lithography, silicon-based self assembled monolayer deposition, metal-organic chemical vapour deposition (MOCVD) and/or wet chemistry synthesis. The resulting materials consist of ZnO (or SiO2) nanoring arrays grown on PS colloidal nanoparticles previously assembled onto silicon oxide (or zinc oxide) substrates. The synthetic approach - i.e., MOCVD vs. wet chemistry - as well as the fine tuning of the deposition parameters, allow controlling the growth of nanostructured ZnO films, with thickness ranging from few tens to hundreds of nanometers and topography changing from continuous nanorings to patterned nanorods arrays. As proof of working of the prepared nanoplatforms in biomolecule sensing applications, both optical properties changes and mass uptake have been tested respectively by in situ and ex situ protein adsorption experiments. Indeed, the interface between the nanostructured materials and selected model proteins (including albumin, lysozyme and ferritin) has been investigated by advanced characterization techniques, including laser scanning confocal microscopy and related fluorescence recovery after photobleaching application, atomic force microscopy and SNOM, angular dependent X-ray photoelectron spectroscopy, as well as by conventional UV-visible and (ATR) FTIR spectroscopies. The sensing capability of the nanostructured materials have been checked at different experimental conditions, depending both on the substrate (such as shape and aspect ratio of the nano-sized units, as well as chemical contrast, e.g., ZnO vs. PS vs. SiO2) as well as on the protein solution (such as bulk concentration, pH and ionic strength, protein composition).