A Non-Dispersive Infrared CO₂ Sensor with a Paraboloid Chamber and a Nanoforest-Enhanced Thermopile Detector

In this work, a high-performance non-dispersive infrared (NDIR) gas sensor adopting a gas chamber with paraboloid reflective structures and a novel thermopile detector integrated with nanoforests (NFs) is proposed. The paraboloid structures enable an optical path of 58 mm and allow 9.72% of optical rays from the light source to reach the detector. Meanwhile, the NFs in the infrared detector help to increase optical absorption of the detector, resulting in a 66% increase in sensor response and a more than doubled sensitivity. Primary results show that the prepared NDIR gas sensor exhibits a responsive range to CO 2 concentrations spanning from 0 to 5000 ppm, with a detection limit of 67 ppm, high repeatability, and a short response time of 22 s. This sensor is expected to have applications in fields such as indoor air quality monitoring and greenhouse detection.