At present, the sensing material are usually based on metal oxide semiconductor films. They generally need to work at high temperature above 300 °C. The high energy consumption is easy to make the equipment aging during long time detection.
Besides, it is difficult to reach the thermodynamic equilibrium state of oxygen between metal oxides and the variable external environment, which will affect the flow and distribution of oxygen vacancy, resulting in weak long-term stability. Therefore, the design and development of new non-oxide based low temperature sensing materials with stable performance is expected to solve the above problems. Layered two-dimensional metal sulfides, for example, SnS2, has excellent semiconductor properties and large specific surface area, which have attracted extensive attention in the field of gas sensitivity.
The substitution of sulfur atom for oxygen atom will not be limited by non-equilibrium state of oxygen thermodynamics mentioned above, and is expected to obtain more stable and reliable gas-sensitive performance. Its electronic structure can be modulated in a wide range by the number of layers and composition, making it the most promising candidate materials for semiconductor resistive gas sensing devices. Moreover, two-dimensional black phosphorus (BP), which is composed of two layers of atoms with a natural band gap, is expected to surpass graphene. Since the revival of two-dimensional BP in 2014, it has been a popular kind of sensing material. The carrier migration speed of BP is high, and its direct band gap can be adjusted by the number of layers. If p-type BP and n-type sulfide nanosheet are combined, p-n micro-nano structure heterostructure can be constructed, and electron-hole carriers can be transported and separated rapidly, which is expected to realize low temperature and high performance sensitivity.
In view of this, Prof. Zhengfei Dai from Xi'an Jiaotong University and Prof. Haibo Zeng from Nanjing University of Science and Technology have cooperated to constructe heterstructure based on SnS2 and BP through one-step solvothermal method. This Sn2+/Lewis acidity suppression can promote the adsorption and detection of acidic NO2. Thus, the SnS2/BP heterostructure sensor can detect trace levels of NO2 as low as 100 ppb with high response, fast response/recovery, good stability, and selectivity at room temperature. The high absorption energy of NO2 (−0.74 eV), as indicated by the density functional theory calculations, suggests that NO2 was chemically adsorbed on the SnS2/BP surface. This work opens up interesting opportunities for the rational design of highly efficient NO2 gas sensors through Lewis acidity modification and interface engineering.
See the article:
Liang, Zhengfei Dai, Yaoda Liu, Xu Zhang, Haibo Zeng. Suppression of Sn2+ and Lewis acidity in SnS2/black phosphorus heterostructure for ppb-level room temperature NO2 gas sensor. Science Bulletin, 2021, https://doi.org/10.1016/j.scib.2021.07.007
Source: http://www.scichina.com/english/