Morphology Modulation Of Metal Oxide Semiconductor Nanomaterials And Their Application In VOCs Gas Sensing

The advancement of nanotechnology has significantly contributed to the creation of reliable and diverse gas sensors.Among these sensors,those based on metal oxide semiconductor nanomaterials are particularly important in both scientific and industrial communities.They are widely used in various fields such as environmental monitoring,industrial safety,and medical diagnostics.The performance of gas sensors is evaluated based on response rate,sensitivity,and selectivity.However,the current devices demonstrate low performance,which limits their further development.To address this issue,we aim to enhance the sensing performance by optimizing the sensing materials.Our research focuses on metal oxide semiconductors and aims to overcome the challenges of insufficient gas-sensitive response and high operating temperature.We achieve this by employing size,composition,and morphology engineering,morphology regulation,surface electron regulation,and construction of heterojunctions.Through this,we aim to develop highly efficient gas sensors and understand the methods and laws of regulating their gas-sensitive performance.Our research also aims to explore the gas sensing mechanism and its potential practical applications.1.Based on size and morphology engineering,In₂O₃ precursors were prepared by formaldehyde assisted metal ligand cross-linking strategy and calcined at 450℃for 2h in air to prepare mesoporous In₂O₃ nanomaterials with uniform size,consistent morphology,small grain size,high oxygen vacancy content and large specific surface area.Due to the smaller grain size,a small change in the trapped electron density on the surface of the material causes a huge change in electrical conductivity,which improves its gas-sensitive performance;and the large number of oxygen vacancies provides potential sites for gas adsorption;the abundant pore space is conducive to gas diffusion and can promote mass transfer.It was characterized by a gas-sensitive sensing test system.The mesoporous In₂O₃-based TEA gas sensor shows high sensitivity（R=114,100 ppm）,good stability and selectivity,fast response/recovery capability（51/33 s）,and detection limits up to the ppb level.2.A WO₃/Fe₂O₃ heterojunction nanocomposite with peculiar morphology was designed.The WO₃ nanocomposites modified by Fe₂O₃ were prepared by a simple solvothermal method.The morphology and properties of WO₃/Fe₂O₃ can be changed by controlling the content of iron ions in the nanocomposites.The addition of Fe₂O₃changes the structure of WO₃ to form a unique candy-like morphology,which increases the surface adsorption area and the number of active sites and promotes gas adsorption and desorption.It was shown by XPS analysis that the introduction of Fe₂O₃ led to the change of W binding energy,resulting in the change of surface electron cloud density.In addition,the large amount of surface adsorbed oxygen contributes to the catalytic activity of the gas sensor.The n-n type heterojunctions are constructed to facilitate the electron transfer and adjust the thickness of the stacking and depletion layers,and the bending of the conduction and valence bands raises the height of the potential barrier,further increasing the resistive response in air.All cases enhance the response of the material to the gas.The sensor shows high sensitivity（R=17,30 ppm）,good stability and selectivity,fast response/recovery（15/162 s）,and low detection limits.3.Hollow Cu₂O@CuS nanocubes heterostructures were prepared by a multi-step templating strategy.The ultra-high BET specific surface area allows the hollow Cu₂O@CuS nanocubes to have more active sites,which promotes the adsorption and desorption of gases on the surface of Cu₂O@CuS materials.In addition,the unique hollow and pore structure promotes mass transfer,which provides a proper path for gas diffusion.The surface of Cu₂O@CuS contains abundant oxygen vacancies,which improves the sensing performance.In addition,the abundance of oxygen vacancies improves the adsorption ability to gas molecules with electron-donating groups,which gives the sensor a better selectivity.The p-p type heterojunctions are constructed to facilitate carrier separation and adjust the thickness of the stacking and depletion layers.The sensor shows high sensitivity（R=59.944,100 ppm）,good stability and selectivity,fast response/recovery（54/29 s）,and a detection limit of 108 ppb.This work provides a new idea for the rational design of gas sensing materials and the tuning of surface electronic structures.