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Orthogonal chemical functionalization of patterned Au/TiW substrate for selective immobilization of nanoparticles

The evolution of nanobiosensors stresses the need for multi-material nanopatterned surfaces to enhance sensing performances. Titanium tungsten (TiW) has been mastered and routinely implemented in nanoelectronic devices, in a reproducible way and at industrial production scales. Such a material may be envisioned for use in (bio)chemical nanoelectronic sensors, but the surface functionalization of such material has yet to be studied. In the present article, the orthogonal chemical functionalization of patterned Au on TiW substrates has been explored for the first time. Surface functionalizations were assessed by x-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy and time-of-flight secondary ion mass spectrometry imaging. Au/TiW patterned substrates were functionalized with mercapto-undecamine. Thanks to the orthogonality of thiol/Au versus phosphonic acid/TiW reactions, only the Au features were modified leading to the amine derivatized surface. This allowed for the localizing of carboxy-functionalized nanoparticles by electrostatic interaction on Au with a selectivity above 10 when compared to TiW.