A Quantitative Fourier Transform Infrared Study of the Grafting of Aminosilane Layers on Lithium Niobate Surface

Due to its impressive optical properties, lithium niobate (LiNbO₃) is considered to be one of the most important ferroelectric materials. Its uses in sensing platforms require functionalization at the surface to enable the capture and quantifying of molecules. The current paper aims to demonstrate the covalent bonding of aminosilane layers to the LiNbO₃ surface. Fourier transform infrared (FT-IR) analysis reveals the presence of an NbO-Si bond observable as a shoulder at the same wavenumber (975 cm^-1) on the surfaces of LiNBO₃ as well as on those of Nb₂O₅, using 3-(aminopropyl)trimethoxysilane (APTMS) or 3-(aminopropyl)methyldimethoxysilane (APDMS) precursors. This covalent bonding is confirmed by the insolubility of the silane coating in dimethyl sulfoxide (DMSO). A kinetic study of the aminosilane layer growth obtained by quantitative FT-IR analysis is also carried out.