Organophosphonate Functionalization of Al2O3-Coated Nanopores

We present a novel approach for the functionalization of aluminum oxide (Al 2 O 3 ) coated solid-state nanopores. Silicon nitride nanopores fabricated by e-beam lithography and reactive ion etching were coated with Al 2 O 3 using atomic layer deposition. Formation of self-assembled monolayers (SAMs) of organophosphonic acids (organophosphonates) at the pore walls was studied for three different precursor molecules, namely 1,10-decyldiphosphonic acid, 4-aminobutylphosphonic acid and 12-mercapto-dodecylphosphonic acid. We show by ionic conductance measurements that the nanopores were successfully functionalized with SAMs, leading to the anticipated reduction in pore diameter, hence pore conductance. Functionalized nanopores allow for specifically tailoring the interaction of pore-translocating biomolecules, e.g., for sensing applications.