Formaldehyde (HCHO) is a common indoor and outdoor pollutant that can cause adverse health effects and environmental problems. Therefore, the development of reliable and sensitive sensors for HCHO detection is of great importance. In this report, we compare three different types of sensors for HCHO measurement: electrochemical, optical, and photochemical.

Electrochemical sensors are based on the oxidation or reduction of HCHO on an electrode surface, which generates a measurable current or potential. Electrochemical sensors have the advantages of low cost, high sensitivity, fast response, and easy miniaturization. However, they also suffer from some drawbacks, such as interference from other gases, limited stability and selectivity, and need for frequent calibration.

Optical sensors are based on the absorption or emission of light by HCHO molecules or their derivatives. Optical sensors have the advantages of high selectivity, stability, and accuracy, as well as remote sensing capability. However, they also have some limitations, such as high cost, large size, complex operation, and low sensitivity.

Photochemical sensors are based on the enzymatic or chemical conversion of HCHO into a fluorescent or colorimetric product. Photochemical sensors have the advantages of high selectivity and sensitivity, as well as simple operation and low power consumption. However, they also face some challenges, such as low stability, short shelf life, and influence of temperature and humidity.

In conclusion, each type of sensor has its own merits and demerits for HCHO detection. The choice of the most suitable sensor depends on the specific application and requirements. For example, electrochemical sensors are more suitable for portable devices and online monitoring, while optical sensors are more suitable for laboratory analysis and remote sensing. Photochemical sensors are more suitable for low-cost and disposable devices.