Macroporous silicon templated from silicon nanocrystallite and functionalized Si-H reactive group for grafting organic monolayer

This paper reports the development of a new fabrication process for highly porous and highly functional macroporous silicon (m-PSi). This new fabrication process involves two steps of electrochemical etching and one step of sonication detachment, and it uses silicon nanocrystallites as a template to form a honeycomb-like macroporous structure. The Surface fabricated by this process has been characterized in comparison with the m-PSi surface fabricated by a one-step etching process. Scanning electron microscopy (SEM) images show that both m-PSi Surfaces have nearly similar pore diameters (1-2 mu m), but their porous microstructures are very different: the Surface fabricated by two-step etching exhibits a smooth and shallow pore structure, while the other Surface exhibits a rough and deep pore structure. Fourier transform infrared spectroscopy (FTIR) analyses reveal that the former is functionalized with a reactive Si-H group, while the latter is functionalized with a stable Si-O-Si group. To evaluate the Si-H reactive group, an allyl polyethylene glycol (PEG) is employed to modify the surface through hydrosilylation. SEM, FTIR, X-ray photoelectron spectroscopy, and water contact angle measurements are used to characterize the PEG-grafted m-PSi Surface. PEG-grafted m-PSi substrates may have wide applications in biosensors, chemosensors, and biochips. (C) 2009 Elsevier Inc. All rights reserved.