Concentration-Specific Hydrogen Sensing Behaviour In Monosized Pd Nanoparticle-Based Thin Films

A unique concentration-specific H2 sensing behaviour with a ‘pulsed' response at larger H2 concentrations and ‘saturated' response at lower concentrations has been observed in monosized and monocrystalline Pd nanoparticle-based films. The threshold concentration required for transition from ‘saturated' to ‘pulsed' response is very sensitive to measurement temperature and lies in the 2 to 10 % concentration range, this would allow to fabricate a simple hydrogen gas alarm system triggered by a decrease in resistance.

In the present study, H2 sensing response of monosized, monocrystalline and spherical Pd nanoparticle-based thin films with a controllable size in 15-25 nm range with a narrow size distribution (σg <1.10) has been investigated. The sensitivity and response of the electronic and geometric effects during H2 sensing have been determined as a function of nanoparticle size, H2 concentration and measurement temperature. It has been shown that the sensing behavior is highly concentration- specific and threshold concentration defining the change over from ‘saturated' response to ‘pulsed' response is a strong function of the measurement temperature. The present study provides a ‘proof of concept' for developing a sensor capable of detecting H2 concentration levels along with fast response of EE and high sensitivity of GE. Its characteristic change in mechanisms can be tuned by choosing a suitable operating temperature so that the reaching the H2 explosion limit results in a sudden decrease in resistance.