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instruments capable of performing high sensitivity, high precision, high specificity, high spatial resolution, and fast in situ measurements. TDLAS is an effective method to measure these gases' mixing ratios and multiple parameters with these advantages. The methane detection system based on TDLAS can simultaneously detect CH4, C2H2, and C2H4 rapidly and effectively in open environment, and the response time is less than 2 s. The MDLs of these three gases can meet the requirements for the detection of natural gas leakage to petrochemical industry. The accuracy of making an alarm is 100%, which can be used in natural gas station and valve room gas leakage detection. The detection limit of CO detection system based on TDLAS technology is 0.25 ppm with an integration time of 30 s, which basically realizes the high sensitivity detection of CO in the near infrared and satisfies the requirements for those situation that have a higher measurement requirement of CO such as alarming of coal spontaneous combustion and mine safety production. The experimental results of H2S show that the system based on TDLAS has a good linearity and stability with a quick response time of 24 s and a low detection limit of 240 ppb. This indicates that the system has the feasibility of realtime online monitoring in many applications. The measurement system of CO2 isotopologues has realized the high measurement precision of 0.2‰ for δ13C; the next step is to carry out calibration to get the correct isotope ratios and achieve long-term stability measurements. Good understanding of the important roles of HONO in the key chemical processes of hydroxyl radicals and the sources of HONO requires correct detection of the HONO mixing ratios. A QCL-based instrumental system was designed to measure the atmospheric HONO. The regression analysis indicates good correlation between HONO and NO2. But increasing HONO mixing ratios with decreasing NO2 also indicates other sources of HONO formation. Finding the missing sources and the formation mechanism of HONO in the atmosphere is still

Although parts of these gas analysis experiments are just results under laboratory conditions, we are improving the stability and SNR of these systems with the aim of putting them into practical application. To date we have developed all-fiber gas sensor to detect CH4, O2, C2H2, and C2H4, portable CH4 sensors, CO2 analyzer, CO analyzer, and so on. Some of them have been put into the application. The development of these gas sensors would be beneficial for the implementation of environmental protection policies and expand their application in energy, public safety, and medical science. The TDLAS technology also shows high potential for monitoring all kinds of hazardous gases in the atmosphere from surface layer to troposphere combined with a wide spectral application range from the near infrared to mid-infrared.

This work is partly supported by National Natural Science Foundation of China (Grant No. 41775128, 41405034, 11204319), the External Cooperation Program of the Chinese Academy of Sciences (Grant No. GJHZ1726), the Special Fund for Basic Research on Scientific Instruments of the Chinese Academy of Science (Grant No. YZ201315), and the Chinese Academy of Science President's International Fellowship Initiative (PIFI, 2015VMA007). Finally, the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Minis-

a great challenge for tropospheric HONO chemistry.

Acknowledgements

234 Green Electronics

try, is gratefully acknowledged.

Xiaojuan Cui1,2, Fengzhong Dong1,2,3\*, Zhirong Zhang1,2, Hua Xia1,2, Tao Pang1 , Pengshuai Sun<sup>1</sup> , Bian Wu<sup>1</sup> , Shuo Liu1,3, Luo Han1,3, Zhe Li1,3 and Runqing Yu1,3

\*Address all correspondence to: fzdong@aiofm.ac.cn

1 Anhui Provincial Key Laboratory of Photonic Devices and Materials, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei Anhui, China

2 Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China

3 University of Science and Technology of China, Hefei, China
