LED-Based Photoacoustic NO2Sensor with a Sub-ppb Detection Limit

Juho Karhu*, Tuomas Hieta, Farshid Manoocheri, Markku Vainio, Erkki Ikonen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

14 Citations (Scopus)
84 Downloads (Pure)


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.

Original languageEnglish
Pages (from-to)3303-3307
Number of pages5
JournalACS Sensors
Issue number9
Publication statusPublished - 24 Sept 2021
MoE publication typeA1 Journal article-refereed


  • high sensitivity
  • light-emitting diode
  • NO
  • photoacoustic spectroscopy
  • trace gas sensor


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