Formation, Structure, and Reactivity of Amino-Terminated Organic Films on Silicon Substrates

Effects of various preparation conditions on the structure and reactivity of amino-functionalized organic films on silicon substrates were investigated using Fourier transform infrared spectroscopy (FTIR), ellipsometry, contact angle measurement, and fluorescence microscopy. Amino-terminated organic films were prepared on silicon wafers by self-assembling 3-aminopropyltriethoxysilane (APTES) in two different types of solutions (anhydrous toluene and aqueous solution) for varied deposition times, cured at different conditions, and washed by sonication in water. In aqueous solution, structurally comparable APTES films with a thickness of ~10 Å were formed via electrostatic interactions. However, deposition from an anhydrous toluene solution produces APTES films with a wide range of thickness (10 – 144 Å) by either covalent or non-covalent interactions depending upon the deposition time, although thicker films are mechanically unstable in aqueous solutions and proper curing process is required to form physically stable films. Chemical modifications of amino groups on APTES films to three different linkers, N-hydroxysuccinimide (NHS) ester, hydrazide, and maleimide ester, are demonstrated.