Stable, nanometer‐thick oxygen‐containing plasma polymer films suited for enhanced biosensing

Abstract

Stable surface functionalization is required in many applications such as in biosensing. For this purpose, hydrocarbon‐based plasma polymer films (PPFs) were investigated by controlling cross‐linking and film structure at the nanoscale, while functional groups were incorporated using a CO2/C2H4 low pressure plasma. In particular, an oxygen‐rich termination layer of 1 nm (top layer) was gradually deposited onto a more cross‐linked PPF (base layer) with varying thickness (<20 nm) yielding highly stable yet functional a‐C:H:O films as compared to conventional oxygen‐rich PPFs. Such stabilized nano‐layers provided a homogeneous functionalization of Au‐coated (flat) biochips as used for immunosensing as well as of nanostructured Au‐coated surfaces explored for enhanced biosensing. The used periodic grating coated by the highly stable a‐C:H:O nano‐layer can be adjusted to the required environmental refractive index range yielding a distinct sensitivity enhancement for biosensing.