Understanding the chemical reception and electronic transduction mechanism in gas sensing with sulfide colloidal quantum dots

今天，需要低成本和高效率的传感器来检测低浓度（ppb水平）的有毒气体。目前，基于半导体氧化物（SMOX）的传统化学电阻传感器因其优异的传感器响应、鲁棒性和低成本而得到广泛应用。然而，基于SMOX的传感器需要在200°C到600°C之间的高工作温度，从而导致高功耗和安全问题。因此，全世界都在努力生产快速、灵敏、低温操作的气体传感器。金属硫化物是新兴的有前途的材料。在室温下，基于PbS的传感器对NO2和NH3表现出高响应，而已知ZnS对H2S表现出高响应。为了获得更好的结果，一项新的发展是将硫化物胶体量子点（CQDs）用于气体传感。CQDs具有非常大的表面体积比，能够与目标气体分子积极相互作用。此外，尺寸控制的硫化物CQDs的合成允许改变电子和光学性质。这个项目的目标是了解硫化物CQDs的化学接收。其他金属硫化物（如Bi2S3、SnS和ZnS）的结果将与PbS的结果进行比较。表面反应机制和可能的不稳定性来源将使用operando漫反射红外傅立叶变换（DRIFT）光谱识别。Operando功函数测量将提供对与表面化学相关的电荷转移过程的深入了解。结果将为传感模型提供输入。该模型将作为理解金属硫化物气敏的基础。

Today, there is a need for low-cost and highly efficient sensors to detect low concentrations (ppb level) of toxic gases. Currently, traditional chemiresistive sensors based on semiconducting oxides (SMOX) are widely used due to their excellent sensor responses, robustness and low cost. SMOX based sensors, however, require high operation temperatures between 200 °C and 600 °C resulting in both high power consumption and safety issues. As a result, there is a worldwide effort to produce rapid, sensitive, low temperature-operating gas sensors. Metal sulfides are emerging as promising materials. At room temperature, sensors based on PbS show high responses to NO2 and NH3, while ZnS is known to show a high response to H2S. For even better results, a new development is the use of sulfide colloidal quantum dots (CQDs) for gas sensing. CQDs have an extremely large surface-to-volume ratio capable of active interaction with target gas molecules. In addition, the size controlled synthesis of sulfide CQDs allows electronic and optical properties to be changed. The goal of this project is to understand the chemical reception of sulfide CQDs. The results of other metal sulfides, e.g. Bi2S3, SnS, and ZnS will be compared to those for PbS. The surface reaction mechanisms and possible sources of instability will be identified using operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Operando work function measurements will provide insight into the charge transfer processes associated with the surface chemistry. The results will provide the input for a sensing model. This model will serve as a basis for understanding gas sensing with metal sulfides.