Gold nanogratings on polymers for plasmonic biochemical sensors

A novel biochemical sensing approach based on a nanoplasmonic sensor chip, realized on polymers and combined with a specific receptor, has been presented. The plasmonic phenomena are excited and interrogated via two custom experimental configurations, exploiting polymer optical fibers (POFs) and designed holders. Both setups have been used to measure the disposable GNG on a PMMA chip, considering the PMMA chip as a waveguide, in the first configuration, or as a transparent substrate, in the second configuration.

The examined sensor configurations here presented have been realized and experimentally tested. To test the biosensing capabilities of the proposed method, as proof of concept, we have deposited on the sensor a receptor specific for an analyte.

The plasmonic GNG sensor has been fabricated how here schematically reported . The sample consists of a PMMA chip, on which is spun about two hundred nanometers thick positive PMMA e-beam resist layer. The nanograting pattern is obtained by an electron beam lithography (EBL) system. After the development process, a 40 nm thick gold film is deposited through a sputtering machine. The pattern covers an area of 1 mm² at the centre of the PMMA chip. The experimental results have shown a limit of detection four orders of magnitude lower than the one obtained by a biochemical sensor based on a continuous gold film on D-shaped POFs combined with the same receptor.