Rapidly Modulated Wide-Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring

Non-dispersive infrared (NDIR) gas monitoring has advantages of environment stability, convenient operation and maintenance, wide detection range, and multi-gas-detection capability. However, the conventional IR sources for NDIR gas monitoring, such as miniature lamps, microelectromechanical system (MEMS) light sources, and light-emitting diodes (LEDs), can only work at narrow modulation frequency and spectral range, or require complicated design and fabrication, because of the constraint of materials and work principle. These issues cause low data acquisition rate, poor anti-interference ability and limited gas compatibility to NDIR. Here, the super-aligned carbon nanotube (SACNT) film is developed as an IR source in NDIR gas monitoring system. It has a wide spectral range (0.2-334 mu m), a facile fabrication method, and can work up to a high frequency approximate to 150 kHz. A mechanical-chopper-free and wide-concentration-range monitoring equipment for CO2 and CH4 greenhouse gases is demonstrated with SACNT film IR source. The concentration ranges for CO2 and CH4 investigated in this paper are 0.0195-20.10% (v/v) and 0.10-17.11% (v/v), respectively. It can be easily applied to monitor other kinds of gases as well.