BIOREACTIVE SELF-ASSEMBLED MONOLAYERS ON HYDROGEN-PASSIVATED SI(111) AS A NEW CLASS OF ATOMICALLY FLAT SUBSTRATES FOR BIOLOGICAL SCANNING PROBE MICROSCOPY

This is the first report of bioreactive self-assembled monolayers, cov alently bound to atomically flat silicon surfaces and capable of bindi ng biomolecules for investigation by scanning probe microscopy and oth er surface-related assays and sensing devices. These monolayers are st able under a wide range of conditions and allow tailor-made functional ization for many purposes. We describe the substrate preparation and p resent an STM and SFM characterization, partly performed with multi-wa lled carbon nanotubes as tapping-mode super-tips. Furthermore, we pres ent two strategies of introducing in situ reactive headgroup functiona lities, One method entails a free radical chlorosulfonation process wi th subsequent sulfonamide formation. A second method employs singlet c arbene-mediated hydrogen-carbon insertion of a heterobifunctional, ami no-reactive trifluoromethyldiazirinyl crosslinker, We believe that thi s new substrate is advantageous to others, because it (i) is atomicall y flat over large areas and can be prepared in a few hours with standa rd equipment, (ii) is stable under most conditions, (iii) can be modif ied to adjust a certain degree of reactivity and hydrophobicity, which allows physical adsorption or covalent crosslinking of the biological specimen, (iv) builds the bridge between semiconductor microfabricati on and organic/biological molecular systems, and (v) is accessible to nanopatterning and applications requiring conductive substrates. (C) 1 997 Academic Press.