Yi-Ju Chen | Leibniz Institute of Photonic Technology | Jena, Germany
Nanoparticle-based plasmonic sensors require broadband illumination and a spectrometer to analyze the spectral shift of the relatively broad localized surface plasmon resonance, rendering the detection of tiny spectral shift difficult. Here, we extend our previous design of plasmonic Doppler gratings (PDGs) [1,2] to develop metal-insulator-metal PDG (MIM-PDG) for hydrogen sensing (Fig.1(a)) and dielectric-loaded PDG (DL-PDG) for monitoring the carbon deposition (called “coking”) on the metallic surface of heterogeneous catalyst (Fig.1(b)). The PDG structure mimics the wave fronts of a moving point source to provide azimuthal angle-dependent chirped periodicity. Therefore, change in local environment is reported by the change in the azimuthal intensity profile. This allows for spectrometer–free plasmonic optical sensing. The MIM-PDG (Pd-Al2O3-Au) shows Fano-like transmission intensity profile, which is significantly broadened upon absorption of hydrogen gas from 0% to 4% (right panel, Fig.1(a)). The design of DL-PDGs (PMMA-C-Au) allows simple and cost-efficient realization of PDG coking sensors. The azimuthal reflection intensity profile changes with the thickness of carbon coking layer from 0 to 25 nm (right panel, Fig.1(b)).This provides an effective yet simple solution for on-site spectrometer-free optical monitoring of the coking effect on the heterogeneous catalyst.
 See, K. M. et al, Nanoscale 9 (2017), 10811-10819
 Lin, F. C. et al, Analytical Chemistry 91 (2019), 9382-9387