Au–Pd core–shell nanoparticle film for optical detection of hydrogen gas

Hydrogen use, as a clean and almost infinite energy source, has an economic impact in many industries. The problem is that this gas cannot be used like any gas because of its explosiveness at 4% in the air, hence the need to know its concentration any time for security reasons. The permanent detection of hydrogen leaks is essential to monitor and to control the hydrogen concentration to prevent any possible risk. In our current research, we have developed hydrogen ultrasensitive sensors by depositing a thin film of Au–Pd core–shell nanoparticles (NPs) on a transparent glass substrate in order to detect hydrogen in its gaseous form. The colloidal Au–Pd core–shell NPs were synthesized according to a multi-reduction step method. The structural characterizations, the nature, and the density of Au–Pd core–shell NPs have been characterized by scanning electron microscopy and transmission electron microscopy. The morphology, size, and structure of Au–Pd core–shell NPs can be controlled under synthesis conditions. The size of the core–shell studied in this work is 13 nm for gold NP diameter and 0 nm–2.3 nm for palladium thicknesses. The physical properties of NPs, such as the optical absorbance response under hydrogen, strongly depend on the nature of the shell and the ratio between the core and the shell. At different hydrogen concentrations ranging from 1% to 4%, the optical response changes in the position of the surface plasmon resonance peak on the absorbance spectrum after the first loading/unloading hydrogen cycle.