High-Sensitivity Ozone Sensing Using 280 nm Deep Ultraviolet Light-Emitting Diode for Detection of Natural Hazard Ozone ()
1. Introduction
The importance of ozone sensing has recently increased, because ozone is harmful gas which is generated from industrial use of ozone for sterilization and cleaning of biomaterials and semiconductor devises and also water sterilization. Furthermore, ozone is produced in the surface air by photochemical reactions involving unburned fuel vapors and nitrogen oxides produced at high temperatures by car engines. So, the depletion of ozone is very important. So, continuous, high-sensitivity easy detection of ozone is indispensable.
Ozone sensing is currently conducted by monitoring the conductance change in thin-film-like semiconductors containing ZnO [1,2], In2O3 [3,4]. Previous studies have tried to measure ozone using a galvanic technique [5]. These devices have the advantages of being compact and very cheap, but their lifetime is less than one year and their accuracy is very low at ±50%. Ozone sensing using a Hg lamp was used for the purpose of solar-blind sensing in the aerospace industry [6,7]. Researchers have also applied UV light to the chemiluminometric measurement of atmospheric ozone [8]. There have been attempts to use optical fibers for sensing [9]. However, there are few reports on the determination of ozone concentration in the air using Hg lamp systems, because of the difficulties in accurate system construction with a high sensitivity suitable for ozone monitoring and with a long life that would provide an accuracy of approximately ±0.5%. An attempt was made to use a long-pass absorption chamber to achieve high sensitivity [10]. However, the cost of this system was very high and it was unstable. The life of the Hg lamp was only about one year and the size of the system was much larger than conventional sensors. Moreover, the Hg used in the lamp is a harmful metal, which has potentially detrimental environmental affects.
We recently developed a new type of ozone sensing system using a low-power deep ultra violet light emitting diode (hereafter DUV-LED) operated at the wavelength of 280 nm as a light source, instead of an Hg lamp. This system has the advantages of being very compact, having a long lifetime, and being free from any harmful materials.
In this report, we present our experimental results and demonstrate the utility of this system.
2. Experiments and Discussion
Figure 1 shows the typical spectra of a Hg lamp and DUV-LED operated at the wavelength of 280 nm. The