A high-sensitivity light-emitting diode (LED)-based photoacoustic NO₂ sensor is demonstrated. Sensitive photoacoustic gas sensors based on incoherent light sources are typically limited by background noise and drifts due to a strong signal generated by light absorbed at the photoacoustic cell walls. Here, we reach a sub-ppb detection limit and excellent stability using cantilever-enhanced photoacoustic detection and perform a two-channel relative measurement. A white-light LED is used as a light source, and the spectrum is divided into two wavelength channels with a dichroic filter. The photoacoustic signals generated by the two wavelength channels are measured simultaneously and used to solve the NO₂ concentration. The background signal is highly correlated between the two channels, and its variations are suppressed in the relative measurement. A noise level below 1 ppb is reached with an averaging time of 70 s. This is, to the best of our knowledge, the first time a sub-ppb detection limit is demonstrated with an LED-based photoacoustic NO₂ sensor. As LEDs are available at a wide selection of emission wavelengths, the results show great potential for development of cost-effective and sensitive detectors for a variety of other trace gasses as well.

中文翻译：

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基于 LED 的光声二氧化氮传感器，检测限低于 ppb

展示了一种基于高灵敏度发光二极管 (LED) 的光声 NO ₂传感器。基于非相干光源的敏感光声气体传感器通常受到背景噪声和漂移的限制，这是由于光声单元壁吸收的光产生的强信号。在这里，我们使用悬臂增强光声检测达到了亚 ppb 检测限和出色的稳定性，并进行了双通道相对测量。使用白光LED作为光源，通过二向色滤光片将光谱分为两个波长通道。两个波长通道产生的光声信号同时测量，用于解决NO ₂专注。两个通道之间的背景信号高度相关，其变化在相对测量中得到抑制。以 70 秒的平均时间达到低于 1 ppb 的噪音水平。据我们所知，这是第一次使用基于 LED 的光声 NO ₂传感器证明亚 ppb 检测限。由于 LED 具有多种发射波长可供选择，因此结果表明，开发适用于各种其他痕量气体的经济高效且灵敏的检测器具有巨大潜力。