Since 2021, Do Van Minh, a student of K63 at the Institute of Technical Physics, has come up with the idea of ​​designing and manufacturing a device to measure toxic gases in the environment. Under the guidance of the lecturer, Minh, together with Truong Hong Cuong, Nguyen Thi Mai Anh, and Nguyen Ngoc Minh, implemented the idea.

After 2 years of research, the student group's toxic gas measuring device has been upgraded through 3 versions, with 3 main parts including the shell, electronic control circuit, signal processing and measuring chamber.

Minh said that in industrial production environments, many types of toxic gases often appear, such as NOx, NH3, H2S and COx groups, in which NOx, H2S, NH3 groups directly affect human health. The standard concentration of these gases in the working environment is allowed to be below 50 ppm. The measuring device manufactured by the group can detect toxic gases at low levels (10 ppm gas concentration) and will give a warning.

The most important and difficult point is to research a sensor that can operate like a switch that allows the circuit to be turned on and off like in an electric circuit. In this application, the toxic gas acts as an external impact that makes the switch work by changing the resistance. The group chose V2O5 as the material for the gas sensor application. At room temperature, V2O5 can respond to a single gas, Ammonia (NH3), but for other toxic gases such as H2S, CO, CO2, NO2... there is almost no change, meaning that the sensor cannot respond to gases other than NH3, showing that the sensor has high selectivity within the gas concentration limit of 500 ppm that the group studied.

Minh said that practical testing showed that the device can detect the presence of toxic gases in the environment and give a warning. When the gas concentration exceeds the standard level of 50 ppm, the device will give a warning with a buzzer signal. In addition to the warning, the device is also integrated with a screen, displaying the concentration value of the gas to be measured and drawing a signal curve of the concentration change.

Currently, there are many types of products on the market that measure toxic gases in the environment, imported from China, Germany, Japan, priced from several million to hundreds of millions of VND. There are some products developed by Vietnam, but most of the gas measuring heads (sensor chips) must be imported from abroad.

Professor Nguyen Duc Hoa, Deputy Director of the International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, and instructor, assessed that this is a student research product, from material manufacturing, sensor chips, to measuring circuits and data display... The product is only at the testing stage, but "the advantage is that the group has manufactured a sensor chip, with outstanding features such as low power consumption, high response rate and the ability to detect toxic gases at low concentrations", said Mr. Hoa. He suggested that the product needs to improve in design and some operating features to be suitable and convenient for daily use.

The group's research recently won second prize in the 2022 National Student Scientific Research Competition.

Bich Thao