Resonant Coupling Effect by Metal Nanoparticles Modification: An Effective Strategy for High Sensitization of MOS-Based Chemiresistive Gas Sensors

Metal nanoparticle surface modification is a simple and efficient method to realize highly sensitive detection for chemiresistive gas sensors. Although a few theoretical explanations for the complicated matching relationship in the sensing system constructed from the modified metal, semiconductor material, and target gas have been proposed, there are no corresponding specific evaluation parameters based on the metal sensitization mechanism, which are crucial for the guidance of high-performance sensing materials design. Herein, taking MnO2-based chemiresistive gas sensors as examples, the improvement effect of the metal nanoparticles modification on the gas-sensing properties of MnO2-based chemiresistive sensors toward HCHO and NH3 is investigated. Combined with the first-principle calculations based on density functional theory (DFT), a novel resonant coupling model based on the impurity energy levels, originating from charge transfer between target gas and metal, is first proposed to reveal the sensitization mechanism that the coupling strength between metal and target gas determines the carrier concentration of MOS. Coupling strength is closely positive correlated with the response, which provides an effective parameter to semiquantitatively describe the sensitization effect of metal nanoparticles on target gas. Our work establishes a model that clarifies the matching correlation in the sensing system and excavates new road to further comprehend the metal sensitization mechanism, which will provide an effective theoretical guide for the design of high-performance gas-sensing materials.