In this article we have studied the structure of Au-Pd core-shell nanoparticles, which is composed of a uniform Au inner core surrounded by Pd nanoparticles. This is done to a new ultrasensitive sensor with height performance characteristics, low-cost fabrication process for hydrogen detection. Hydrogen cannot be used like any other gas because of its explosive behavior at 4% concentration in the air and, to avoid any risk we need to control its concentration permanently. The Au– Pd core-shell nanoparticles (NPs) were synthesized according to a multi-reduction step method. The morphology, density, size, and structure of these nanoparticles can be controlled by the synthesis conditions. They were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The impact of Pd shell on the surface plasmon resonance (SPR) was investigated by finite difference time domain simulations (FDTD) and the absorption spectroscopy under different hydrogen concentrations ranging from 1% to 4%. We noticed a change in the optical behaviour and a shift of the SPR peak of our Au-Pd core-shell system towards the lowest wavelengths from the first hydrogenation dehydrogenation cycle.
We present in this work the study of metal insulator metal (MIM) structures on waveguides for hydrogen leak sensors. The configuration is based on a transducer layer deposited on the core of a multimode fiber optic. The reference transducer layer is a multilayer stack based on a silver, a silica and a palladium layer. The spectral modulation of the light transmitted by the fiber allows to detect hydrogen. The sensor is only sensitive to the transverse magnetic polarized light and the transverse electric polarized light can be used as a reference signal. The multilayer thickness defines the sensor performances in terms of sensitivity, SNR and time response. The silica thickness tunes the resonant wavelength, the silver (or gold) supports the plasmon and the palladium detects the hydrogen gas in the environment. This study synthesizes the sensor performances as a function of different parameters such as the sensitive materials, different thicknesses, numerical aperture, etc. and goes towards very promising nano-detectors based on the use of original nanoparticles.
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