Ricerc@Sapienza

Sensors using surface plasmon resonance (SPR) are established as themethod of choice in label-free optical biosensing.
Their sensitivity for small refractive index changes at the surface originates from the enhanced evanescent
field at the surface of a thin metal layer. However, the small number of well-suited metals (Ag, Au) with
fixed optical constants limits a further refinement of the SPR performance in terms of dispersion and resonance
width. An alternative can be found in Bloch SurfaceWaves (BSW) sustained at specially designed dielectricmultilayer
stacks with low absorption losses. Due to the low losses an enormous narrowing of the resonance is obtained,
promising the reduction of the detection limit for such a label-free sensor. In order to deposit these
multilayers on plastic sensor chips, plasma ion assisted vacuum evaporation (PIAD) was applied as deposition
method. SiO2, TiO2, and Ta2O5 single layer properties were balanced in terms of absorption losses, stability in
aqueous environment and film stress. Dielectricmultilayer stacks could be designed in away, that resonance performance
is optimal and the total stack thickness as low as possible. Optimized Bloch stacks were successfully
coated on a large number of polymer chips. The application could be demonstrated by the detection of cancer biomarkers
using an analytical instrument that was developed with the BSWchips as core element.