High-performance Hydrogen Gas Sensors Research Articles

Characterization of Hydrogen Gas Sensitivity of ZnO Thin Films

ZnO thin films were prepared on a glass substrate by radio frequency (RF) magnetron sputtering without intentional substrate heating and then surfaces of the ZnO films were irradiated with intense electrons in vacuum condition to investigate the effect of electron bombardment on crystallization, surface roughness, morphology and hydrogen gas sensitivity. In XRD pattern, as deposited ZnO films show a higher ZnO (002) peak intensity. However, the peak intensity for ZnO (002) is decreased with increase of electron bombarding energy. Atomic force microscope images show that surface morphology is also dependent on electron bombarding energy. The surface roughness increases due to intense electron bombardment as high as 2.7 nm. The observed optical transmittance means that the films irradiated with intense electron beams at 900 eV show lower transmittance than the others due to their rough surfaces. In addition, ZnO films irradiated by the electron beam at 900 eV show higher hydrogen gas sensitivity than the films that were electron beam irradiated at 450 eV. From XRD pattern and atomic force microscope observations, it is supposed that intense electron bombardment promotes a rough surface due to the intense bombardments and increased gas sensitivity of ZnO films for hydrogen gas. These results suggest that ZnO films irradiated with intense electron beams are promising for practical high performance hydrogen gas sensors.

Hydrogen gas sensor utilizing a high proton affinity of <italic>p</italic>-diketodipyridylpyrrolopyrrole

Organic pigments were once extensively investigated as photoconductors for the electrophotographic photoreceptor. Nowadays, they play an important role as colorants for color copies as well as materials for optical discs, electroluminescence, FET etc. Here, we report another novel application of organic pigments for H2 gas sensors. A high-performance hydrogen gas sensor has been developed that utilizes a proton affinity of 1,4-diketo-3,6-bis-(4'-pyridyl)-pyrrolo-[3,4-c]-pyrrole (DPPP) known as a red pigment. We found that the N atom of the pyridyl ring of the DPPP can easily be protonated by protons dissociated from H2 to induce a remarkable change in electrical conductivity by several orders of magnitude. The appealing feature of the device is the reversible operation at room temperature as characterized by a change in electrical resistivity by two orders of magnitude even under 0.05 % H2.

Hydrogen Gas Sensor Utilizing a High Proton Affinity of Pyrrolopyrrole Derivatives

A high-performance hydrogen gas sensor has been developed that utilizes a proton affinity of 1,4-diketo-3,6-bis- (-pyridyl)-pyrrolo-[3,4-c]-pyrrole (DPPP) known as a red pigment. We found that the N atom of the pyridyl ring of the DPPP can easily be protonated by protons dissociated from to induce a remarkable change in electrical conductivity by several orders of magnitude. The sensor operates in two steps: the first step is the dissociation of by means of a sputtered Pd-layer, followed by capturing protons by the N atom of the pyridyl ring (proton acceptor). The device structure is: . The appealing feature of the device is the reversible operation at room temperature as characterized by a change in electrical resistivity by two orders of magnitude even under 0.05% . The material is quite stable and the device is simple and compact.