Purpose - Graphene is a two-dimensional material. Its use has many advantages in gas sensing, but its long desorption process is problematic. The aim of this paper is to design a graphene-based gas sensor, study the response to NO2 gas concentrations and find ways to accelerate the desorption process.Design/methodology/approach - In one group, the sensor was placed in air to measure its initial resistance. Then, it was exposed to the NO2 gas at a certain concentration. Finally, the sensor was exposed to light immediately after NO2 gas exposure was ended. In another group, the sensor was heated using a heating plate at a stable temperature, before taking the measurements. Then the adsorption and desorption experiments were carried on.Findings - Illumination and heating at a suitable temperature can expedite desorption of NO2 molecules on graphene.Originality/value - In the paper, two main methods are introduced to accelerate the desorption process when the NO2 gas is absorbed on graphene. Through a series of experiments and analysis, the authors found that the recovery time could be reduced observably and the recovery performance of the graphene-based NO2 sensor could be improved effectively.

Properties of the gas sensing and the method of the desorption about graphene have been discussed. By analyzing the response and desorption time of the NO2 molecule on graphene,we discussed the gas sensing proper?ties of graphene. In the experiments,the graphene has fast and high response to NO2 gas,while the recovery prog?ress is quite slow,that is to say the desorption time is very long. The analysis states that by heating and illumina?tion, the desorption time could be decreased effectively,and the adsorption property would be improved.

A nitrogen dioxide (NO2 )detecting system based on laser internal modulation and differential detection was designed in order to real-time monitor NO2 concentration in the air.According to the characteristics of NO2 ab-sorption peak,the blue laser operating at 450nm was selected as the light source.The internal modulation technology was used,and the output light intensity and frequency were controlled through modulating the drive current by TTL (Transistor-Transistor Logic).The NO2 concentration was measured at room temperature and atmospheric pressure, and experimental data were processed with the least square method.The results show that the detection limit of the system is 6ppm and a fitting coefficient is 0.9996.

Graphene can sense even a molecule’ s change due to its unique two-dimensional structure with high specific surface area.Through the calculation and analysis, we have studied properties of graphene.And the band structure, charge distribution and DOS of the molecule–graphene adsorption systems are calculated to verify the effects of the adsorption of nitrogen dioxide ( NO2 ) molecule on the graphene’ s electronic properties. The results support our idea, these works would contribute to understand the properties of the graphene and pro-vide an idea of graphene based NO2 gas sensor.