One of the methods for detecting hydrogen is a sensor using palladium nanoparticles dispersed on a substrate.Utilizing the property of palladium that expands in volume when it absorbs hydrogen, it is detected that the dispersed palladium nanoparticles expand in volume when they come into contact with hydrogen gas and conduct when they come into contact with each other (electrical resistance decreases). In principle.In this sensor, the key to increasing sensitivity is to make the particle spacing as small as possible so that the nanoparticles come into contact with each other with a slight volume change.However, it has been difficult to control the spacing of nanoparticles.
The research group at the Graduate School of Osaka University has developed a unique particle spacing evaluation method using "sound" and applied it to the production of palladium nanoparticles, which has 12 times greater hydrogen detection capability (electrical resistance) than before. We succeeded in producing palladium nanoparticles showing the change).
The research group focused on nanoparticles formed on the substrate in the early stages of palladium deposition.In metal film formation, nanoparticles are first formed, which grow and come into contact with each other to form a continuous film.If the film formation is interrupted immediately before the formation of the continuous film, the distance between the nanoparticles can be extremely reduced.
Until now, it was difficult to evaluate the distance between particles during film formation, but we succeeded in using a unique method that utilizes the resonance (sound) of the piezoelectric material.When the piezoelectric body is vibrated on the back surface of the substrate, an electric field is generated around it, and the vibration energy of the piezoelectric body is consumed to generate an electric current in palladium.At the moment of contact with the palladium nanoparticles, the energy consumption is maximized, and as a result, the damping of the vibration of the piezoelectric body is maximized.In other words, when monitoring how the piezoelectric material reverberates, when the nanoparticles come into contact with each other, they suddenly stop reverberating.
Palladium nanoparticles with excellent hydrogen detection capability brought about by this method are expected to be applied to high-sensitivity hydrogen sensors that can detect even low-concentration hydrogen.
Paper information:[Applied Physics Letters] Precise control of hydrogen response of semicontinuous silicide film using piezoelectric resonance method
