Supramolecular control of photonic response and sensing of nitric oxide using iron(III) corrole monolayers and their stacks

In this work,weassemble amphiphilic iron(III) corroles at air-water interfaces into well-defined quasi-two-dimensional molecular monolayers and theirs stacks for sensing of nitric oxide (NO). For this purpose, we use the Langmuir-Blodgett (LB) technique, which allows varying the packing density of iron(III) corrolesanchored to the aqueous subphase via one molecular side. The stacks of tendown to threemolecular monolayers on the front and back sides of the substrates are sufficiently optically dense to detect NO binding to the layers photometrically. This sensing with few layersdemonstrates the potential for electronic detection, where very thin surface functionalizationsenable efficient electronic communication between the layer and the (semi)conductor. Despite increasing optical densities, the spectral responses to NO exposure become smaller with increasing packing density until the collapse point of the monolayers is reached. This demonstrates that the highest molecular efficiency for binding and detection of NOis achieved at the smallest packing densities. This finding is relevant to all molecular sensor films with axial binding of analytesto the sensor moleculesand demonstrates the advantage of sensor molecule assembly into monolayers on water-air interfacesusing the LB technique.