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Response Characteristics of Hydrogen Sensors Based on PMMA-Membrane-Coated Palladium Nanoparticle Films
journal contribution
posted on 2017-07-25, 00:00 authored by Minrui Chen, Peng Mao, Yuyuan Qin, Jue Wang, Bo Xie, Xiuzhang Wang, Deyan Han, Guo-hong Wang, Fengqi Song, Min Han, Jun-Ming Liu, Guanghou WangCoating a polymeric
membrane for gas separation is a feasible approach to fabricate gas
sensors with selectivity. In this study, poly(methyl methacrylate)-(PMMA-)membrane-coated
palladium (Pd) nanoparticle (NP) films were fabricated for high-performance
hydrogen (H2) gas sensing by carrying out gas-phase cluster
deposition and PMMA spin coating. No changes were induced by the PMMA
spin coating in the electrical transport and H2-sensing
mechanisms of the Pd NP films. Measurements of H2 sensing
demonstrated that the devices were capable of detecting H2 gas within the concentration range 0–10% at room temperature
and showed high selectivity to H2 due to the filtration
effect of the PMMA membrane layer. Despite the presence of the PMMA
matrix, the lower detection limit of the sensor is less than 50 ppm.
A series of PMMA membrane layers with different thicknesses were spin
coated onto the surface of Pd NP films for the selective filtration
of H2. It was found that the device sensing kinetics were
strongly affected by the thickness of the PMMA layer, with the devices
with thicker PMMA membrane layers showing a slower response to H2 gas. Three mechanisms slowing down the sensing kinetics of
the devices were demonstrated to be present: diffusion of H2 gas in the PMMA matrix, nucleation and growth of the β phase
in the α phase matrix of Pd hydride, and stress relaxation at
the interface between Pd NPs and the PMMA matrix. The retardation
effect caused by these three mechanisms on the sensing kinetics relied
on the phase region of Pd hydride during the sensing reaction. Two
simple strategies, minimizing the thickness of the PMMA membrane layer
and reducing the size of the Pd NPs, were proposed to compensate for
retardation of the sensing response.