Abstract
A hydrogen detector colloidal solution based on the plasmonic properties of gold nanoparticles (GNPs) is presented. GNPs were prepared by pulsed laser ablation (PLA) of gold target in DI water. PdCl2 solution with different concentration was added to the obtained GNPs colloidal solutions. X-ray diffraction (XRD) confirmed the formation of metallic gold and presence of PdCl2 phases. Transmission electron microscope (TEM) images along with X-ray photoelectron spectroscopy (XPS) revealed formation of the core-shell-like structures of Pd2+/Au NPs. After hydrogenation, TEM revealed that the core-shell morphology changes into free NPs and XPS revealed formation of the metallic Pd phase. Voltammetry analysis showed a well absorption and desorption capability of hydrogen in this gold-PdCl2 plasmonic system. After adding PdCl2 aqueous solution, a red-shift from 522 to 526 nm was observed which was attributed to Pd2+ ion attraction by the negative surface charge of bare GNPs and formation a core-shell like morphology. The optical absorption peaks of PdCl2 (the range 207–236 nm) as well as the LSPR peak of GNPs were traced during diluted hydrogen (0.3–10%) injection in colloidal samples with different Au:Pd molar ratio. It was found that the PdCl2 peaks drop due to Pd2+→Pd0 conversion and more importantly, the gold peak undergoes blue shift due to change in chemical properties of GNPs surrounding. A good correlation between PdCl2 absorption intensity and gold LSPR peak position was found when hydrogen concentration was varied. In this correlation, a desirable detection capability for low concentrations of hydrogen (<4% range, the limit of hydrogen explosion) with a possible large number of points was observed. Finally, a model for the hydrogen sensing mechanism based on the LSPR effect was presented.
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