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DDC: 530 × Publisher: Weinheim : Wiley-VCH × search.filters.applied.f.series: Advanced Optical Materials 9 (2021), Nr. 22 ×

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    Spectrometer‐free Optical Hydrogen Sensing Based on Fano‐like Spatial Distribution of Transmission in a Metal−Insulator−Metal Plasmonic Doppler Grating
    (Weinheim : Wiley-VCH, 2021) Chen, Yi‐Ju; Lin, Fan‐Cheng; Singh, Ankit Kumar; Ouyang, Lei; Huang, Jer‐Shing
    Optical nanosensors are promising for hydrogen sensing because they are small, free from spark generation, and feasible for remote optical readout. Conventional optical nanosensors require broadband excitation and spectrometers, rendering the devices bulky and complex. An alternative is spatial intensity-based optical sensing, which only requires an imaging system and a smartly designed platform to report the spatial distribution of analytical optical signals. Here, a spatial intensity-based hydrogen sensing platform is presented based on Fano-like spatial distribution of the transmission in a Pd-Al2O3-Au metal-insulator-metal plasmonic Doppler grating (MIM-PDG). The MIM-PDG manifests the Fano resonance as an asymmetric spatial transmission intensity profile. The absorption of hydrogen changes the spatial Fano-like transmission profiles, which can be analyzed with a “spatial” Fano resonance model and the extracted Fano resonance parameters can be used to establish analytical calibration lines. While gratings sensitive to hydrogen absorption are suitable for hydrogen sensing, hydrogen insensitive gratings are also found, which provide an unperturbed reference signal and may find applications in nanophotonic devices that require a stable optical response under fluctuating hydrogen atmosphere. The MIM-PDG platform is a spectrometer-free and intensity-based optical sensor that requires only an imaging system, making it promising for cellphone-based optical sensing applications. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH.
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    Tailoring Plasmonics of Au@Ag Nanoparticles by Silica Encapsulation
    (Weinheim : Wiley-VCH, 2021) Schultz, Johannes; Kirner, Felizitas; Potapov, Pavel; Büchner, Bernd; Lubk, Axel; Sturm, Elena V.
    Hybrid metallic nanoparticles (NPs) encapsulated in oxide shells are currently intensely studied for plasmonic applications in sensing, medicine, catalysis, and photovoltaics. Here, a method for the synthesis of Au@Ag@SiO2 cubes with a uniform silica shell of variable and adjustable thickness in the nanometer range is introduced and their excellent, highly reproducible, and tunable optical response is demonstrated. Varying the silica shell thickness, the excitation energies of the single NP plasmon modes can be tuned in a broad spectral range between 2.55 and 3.25 eV. Most importantly, a strong coherent coupling of the surface plasmons is revealed at the silver–silica interface with Mie resonances at the silica–vacuum interface leading to a significant field enhancement at the encapsulated NP surface in the range of 100% at shell thicknesses t ≃ 20 nm. Consequently, the synthesis method and the field enhancement open pathways to a widespread use of silver NPs in plasmonic applications including photonic crystals and may be transferred to other non-precious metals. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH