Abstract
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.
Highlights
Hydrogen is the most abundant element in nature
The main purpose of this work is to develop sensors for hydrogen detection at room temperature and at atmospheric pressure, which are sensitive to the detection at low hydrogen concentrations and at the same time very reactive to limit the risks of inflammation and explosion, since the energy required for the explosion is very low (0.017 mJ)
The absorbance spectrum of the Au and Au–Pd core–shell nanoparticles under vacuum (10−2 mbar) and room temperature is measured in the wavelength range from 400 nm to 800 nm [Fig. 4(a)]
Summary
The overwhelming majority of this element is chemically linked in H2O liquid form as well as in gaseous hydrocarbons. It is colorless, odorless, and tasteless and undetectable by human senses and extremely flammable.. Hydrogen detection often results from the effects generated by the interaction of hydrogen with a sensing material used. These effects can be catalytic-based, thermal conductivity-based, electrical and electrochemical-based, mechanical-based, opticalbased, and acoustic-based.. The response speed of the sensors is determined by adsorption and desorption and by the diffusion of the hydrogen atoms in the Pd films and by the phase transition reaction [α → β] of the Pd hydride formation at the high hydrogen level.. The response speed of the sensors is determined by adsorption and desorption and by the diffusion of the hydrogen atoms in the Pd films and by the phase transition reaction [α → β] of the Pd hydride formation at the high hydrogen level. The absorption of hydrogen by palladium is exothermic and at steady state follows the following reversible equation: x
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