Image processing of non-thermal glow discharge plasma during gas ionization process as a novel hydrogen detection system at parts per billion levels

摘要

A new hydrogen (H_2) detection system is introduced based on the image processing of non-thermal glow-discharge plasma of the ionization of H_2 at parts per billion (ppb) levels based on gas ionization process under vacuum condition (～8 torr). The system setup consists of a charge coupled device camera as detector. For this purpose, the blue component of the photographic image related to ionization-generated plasma is analyzed during applying a 853-V direct current potential to a two-electrode system including Al disk as cathode (diameter: 2.4 ± 0.1 mm) and multi-walled carbon nanotubes-modified disk (diameter: 6.5 ± 0.1 mm) as cathode with 700 ± 10 μm inter-electrode distance. Figures of merits of the fabricated sensor reveal two linear dynamic ranges between 5-36 and 36-180 ppb. Relative standard deviation of at most five replicate analyses during introduction of 90 ppb of H_2 standard solution (in air as solvent) is found as 2.29%. Also, the detection limit was evaluated to ～2.25 ppb. Except acetylene, no significant interfering effect is observed when introducing at least 1000 folds excess (mass/mass) of different foreign species. Reliability of the sensor is also evaluated via determination of H_2 in different industrial gas samples.