Nanoporous Glass Surface for Backscattered Waveguide Fluorescence Application

Nanoporous material-based sensors promise easier integration into portable devices. Here, we use a nanoporous layer (～130 nm thick) fabricated on a cover glass as a planar waveguide and integrated sensing surface. A combination of custom-built planar waveguiding experiments and the Zemax ray tracing model confirmed that the nanoporous surface produced an increased in-plane waveguide signal output in backscattering mode. Also, by addition of a fluorophore (coumarin 6) on the surface, the nanoporous glass showed increased interactions between the dye and in-plane waveguided light, resulting in 4–6× higher emission. Utilizing the nanoporous glass as an integrated chemical and mechanical surface, we report a fluorescent planar waveguide-based oxygen sensor that is operational in backscattering mode. We showed an 11× improvement in the sensing signal upon using an appropriate filter and a ～2× overall improvement for the nanoporous glass over plain glass in oxygen sensing. The Stern–Volmer (SV) plot confirmed an increase in the overall interactions between the dye, waveguided light, and the analyte gas for the observed improvements. Thus, having a inbuilt nanoporous layer on glass demonstrated improved performance for a surface integrated application