Silica Nanowire Arrays for Diffraction‐Based Bioaffinity Sensing

Arrays of electrodeposited silica nanowires (SiO 2 NWs) have been fabricated over large areas (cm 2 ) on fluoropolymer thin films attached to glass substrates by a combination of photolithography and electrochemically triggered sol–gel nanoscale deposition. Optical and scanning electron microscopy (SEM) measurements revealed that the SiO 2 NW arrays had an average spacing of ten micrometers and an average width of 700 nm with a significant grain structure that was a result of the sol–gel deposition process. The optical diffraction properties at 633 nm of the SiO 2 NW arrays were characterized when placed in contact with solutions by using a prism‐coupled total internal reflection geometry; quantification of changes in these diffraction properties was applied in various sensing applications. Bulk refractive index sensing by using the SiO 2 NW grating was demonstrated with a sensitivity of 1.30×10 −5  RIU. Toposelectively chemically modified SiO 2 NW arrays were used for diffraction biosensing measurements of surface binding events, such as the electrostatic adsorption of gold nanoparticles and the bioaffinity adsorption of streptavidin onto a biotin monolayer. Finally, the application of the SiO 2 NW arrays for practical medical‐diagnostic applications was demonstrated by monitoring the diffraction of SiO 2 NW arrays functionalized with a single‐stranded (ss)DNA aptamer to detect human α‐thrombin from solutions at sub‐pathologic nanomolar concentrations.