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This paper proposes a new cataluminescence gas sensor using nanoporous In2O3 as the sensing material for the detection of acetic acid vapor. The sensor shows excellent selectivity and promising sensitivity for industrial and environmental monitoring of acetic acid.
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Nanoporous In2O3-based Cataluminescence Sensor for Acetic Acid Vapor Xiaoan Cao Department of Environmental Science and Engineering Institute, Guangzhou University,P.R. China
Content Ⅰ. INTRODUCTION Ⅱ. EXPERIMENTAL SECTION Ⅲ. CONCLUSIONS
Ⅰ. INTRODUCTION Investigate significance • The effects of pollutants present in air have generated an extensive scientific and public concern due to possible negative impacts on human, plant and animal life. • Carboxylic acids are one of the most dominant classes of organic compounds found in the atmosphere.
Exposure to acetic acid (AA) occurs worldwide to workers in the food, solvent, medical and chemical industries. • Gas sensors are especially useful for the on-site and real-time detection of hazardous gas species. However, there are few papers reported to detect gaseous acetic acid with sensors. • Looking for the rapid detecting techniques of acetic acid vapor is of particular interest.
Investigate background • Cataluminescence (CTL)-based gas sensors have been developed since the 1990s. • CTL is a kind of chemiluminescence (CL) emitted during catalytic oxidation of gaseous species. • CTL was first observed by Bresse et al. during the catalytic oxidation of carbon monoxide on a thoria surface in 1976. Red catalyst O2 Ox
Since 2000, the expanding availability of nanoparticles has attracted scientists’ attention for applying it to CTL sensors. For example, nanosize ZrO2, TiO2_based CTL sensors for determination of gas samples, such as ethanol, aldehyde have been reported. • The sensors have shown high sensitivity to gases, as nanoparticles have higher surface areas, better adsorption characteristics than bulk material.
Investigate content • In the present paper, we propose a new CTL gas sensor by using nanoporous In2O3 catalyst for the detection of acetic acid. To the best of our knowledge, this is the first report of detecting acetic acid with CTL sensor and the first report of using In2O3 as sensing material for CTL sensor.
Ⅱ. EXPERIMENTAL SECTION 1. Apparatus and Materials Fig. 1. Schematic diagram of the CTL detection system.
2. Choice of Cataluminescence materials Table 1. Comparison of signal-to-noise ratio of six air pollutions on some materials
3. Optimization of experimental conditions Fig. 3. CTL response profiles of different concentrations of acetic acid. Fig. 4. Wavelength dependence of CTL intensity of acetic acid.
Fig. 5. Temperature dependence of CTL intensity of acetic acid. Fig. 6. Effect of flow rate of carrier air on CTL intensity of acetic acid.
4. The linear regression equations • The linear regression equations : I = 1.724c-15.14 (25-500 ppm,r=0.999), I = 2.213c-230.1 (500-2500 ppm, r=0.996). • I is the relative CTL intensity, c is the concentration and r is the regression coefficient. • The detection limit (3) was 8.0ppm. The relative standard deviation was 3.47 % (n=6) for 100 ppm acetic acid vapor.
According to the ASTM D3620-04 standard specification for glacial acetic acid, the standard permitted concentration of acetic acid vapor in air is less than 10 ppm (25 mg/m3). • The detection limit of the acetic acid vapor is below the standard permitted concentrations, the proposed sensor can be used for safety control and air quality monitoring of the content of acetic acid in the workplace.
n-Hexane Toluene chloroform Formic acid Ammonia Benzene Formaldehyde Acetaldehyde Ethanol Acetic acid 0 10 20 30 40 50 60 70 80 90 100 Relative CTL intensity (%) 5. Selectivity Fig. 7. CTL responses of different compound on the sensor.
6. Determination of Acetic Acid in the Artificial Air Samples Table 2. Acetic acid analysis in artificial samples
Ⅲ. CONCLUSIONS • The CTL sensor of acetic acid vapor by using nanoporous In2O3 as sensing material was proposed in this paper. • The sensor possesses excellent selectivity to acetic acid among the ten contamination gases. • Rapid response, high sensitivity promise this sensor a bright future for acetic acid determination in industrial and environmental monitoring.
Further research on sensing mechanisms of nanoporous In2O3 will be carried on to look for the possible way to improve sensitivity and find out more excellent sensing materials consequently.
Acknowledgment • Gratefully acknowledge the financial support by the National Natural Science Foundation of China (20677013). • Natural Science Foundation of Guangdong Province, China (5001879). • Science and Technology Project Foundation of Guangdong province (2006B12401012).