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

• Published in: Journal of colloid and interface science 2009-08, Vol.336 (2), p.723-729
• Main Authors: Guo, Dong-Jie, Wang, Jing, Tan, Wei, Xiao, Shou-Jun, Dai, Zhen-Dong
• Format: Article
• Language: English
• Subjects: Biosensing Techniques - methods; Bonding; Chemistry; Colloidal state and disperse state; Contact angle; Electrochemistry; Etching; Exact sciences and technology; General and physical chemistry; Hydrosilylation; Nanocrystals; Nanoparticles - chemistry; Poly(ethylene glycol); Polyethylene Glycols; Porosity; Porous materials; Porous silicon; Scanning electron microscopy; Silicon; Silicon - chemistry; Silicon Compounds - chemistry; Surface grafting; Surface physical chemistry; Surface Properties
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2009.04.030

Two-step electrochemical etching and sonication detachment are involved in the fabrication process for high-porosity macroporous silicon whose surface can be effectively functionalized with organic monolayer assembly. 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 μm), 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.