High-sensitivity light-addressable potentiometric sensors using silicon on sapphire functionalized with self-assembled organic monolayers

The use of self-assembled organic monolayers as the insulator in light-addressable potentiometric sensors (LAPS) is shown for the first time. Silicon on sapphire (SOS) substrates were modified with 1-octadecene or undecylenic acid. Experiments with a photoresist pattern as the model system showed the same good spatial resolution that was previously obtained with a conventional insulator on SOS, but also a significant improvement in the photocurrent contrast and therefore the sensitivity of LAPS. Surface potential imaging was validated by studying micropatterns of poly(allylamine hydrochloride) (PAH) and DNA on a PAH template using LAPS. The results showed that self-assembled organic monolayers provide an excellent, reproducible, ultrathin insulator for LAPS, which can be readily functionalized and used for high-sensitivity LAPS imaging and sensing.