Why does sensitivity decrease?

The sensitivity of a gas sensor is one of its core performance indicators, which reflects the sensor's ability to respond to changes in target gas concentration. The decrease in sensitivity may be caused by various factors.

From the perspective of the sensor's own structure, aging of sensitive materials is a common cause. Taking metal oxide semiconductor gas sensors as an example, their sensitive materials will undergo physical and chemical changes due to repeated reactions with gases and environmental factors such as temperature and humidity during long-term use, resulting in a reduction in the active sites on the material surface and a decrease in the adsorption and reaction ability of the target gas, leading to a decrease in sensitivity.

In addition, the electrode material of the sensor may also change due to oxidation, corrosion, and other reasons, affecting the electronic transmission efficiency and thereby reducing sensitivity. For example, in humid environments, electrodes may undergo electrochemical corrosion, resulting in changes in surface roughness, increased resistance, and weakened signal output.

The external usage environment can also have a significant impact on sensitivity. When high concentrations of interfering gases are present, a covering layer may form on the surface of the sensor, hindering the contact between the target gas and sensitive materials and reducing sensitivity. For example, when using semiconductor gas sensors to detect combustible gases in environments containing a large amount of organic vapors, organic vapors may adsorb onto the surface of sensitive materials, affecting their response to combustible gases.

How to improve the selectivity of sensors?

Selectivity refers to the ability of a sensor to respond only to the target gas in an environment where multiple gases coexist. Improving selectivity is a key issue in the development and application of gas sensors.

Optimizing sensitive materials is an important way to improve selectivity. By selecting sensitive materials with specific chemical structures and physical properties, their specific adsorption and reaction towards target gases can be enhanced. For example, sensitive materials prepared using molecular imprinting technology can form holes inside the material that match the shape, size, and functional groups of the target gas molecules, thereby achieving high selectivity recognition of the target gas.

In terms of sensor structure design, multi-layer membrane structures or the addition of filter layers can be used. Multilayer membrane structures can achieve different functions between different layers, such as one layer for pre enrichment of target gases and another layer for specific detection. The filtering layer can block interfering gases and only allow the target gas to pass through. For example, in a gas sensor for detecting carbon dioxide, adding a layer of alkali lime filter can effectively remove acidic interfering gases and improve the selectivity of the sensor for carbon dioxide.

In addition, using intelligent algorithms to process sensor output signals can also improve selectivity. By training sensor response data from a large number of different gas combinations, a signal processing model can be established to accurately extract target gas information from complex signals, thereby improving the selectivity of sensors in practical applications.