Functionalization and bioimmobilization of silicon surfaces with Si-N bonded monolayer

A new method for selective surface functionalization of silicon with a silicon-nitrogen bonded (Si-N) monolayer and subsequent bioimmobilization is presented. The Si-N monolayer was studied using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), fluorescence spectroscopy, and capacitance-voltage (C-V) measurements using an electrolyte insulator semiconductor (EIS) sensor. A symmetric ethylene diamine (EDA, C2H4 (NH2)2) molecule was used as a precursor compound for monolayer formation in an inert environment in the liquid phase. XPS results show the attachment of EDA molecules proceeds via dissociative and dative bond formation whereas free amine groups on the surface were used for further immobilization of biomolecules. SEM shows selective functionalization and bioimmobilization on a patterned surface such as a silicon nanowire on silicon oxide substrate. Biosensing experiments with bioimmobilized surfaces were carried out in aqueous buffer and show high sensitivity for biosensing.