Boosting Room Temperature Sensing Characteristics Of ZnO Sensors Photoactivation By UV Light Modulation

As environmental pollution and air quality concerns intensify,gas sensors play a pivotal role in monitoring atmospheric conditions.However,most current gas sensors rely on energy-intensive thermal excitation methods,posing safety risks and limiting their applicability,particularly in portable devices.To address these issues,roomtemperature photonic excitation,offering advantages like cost-efficiency and reduced energy consumption,has emerged as a promising alternative.Nonetheless,roomtemperature UV-activated gas sensors face challenges,including low sensitivity,poor humidity resistance,and insensitivity to VOCs.These issues stem from variations in energy input,affecting gas molecule diffusion and material adsorption properties at ambient temperatures.To overcome these challenges and enhance the performance and versatility of room-temperature UV-activated gas sensors,further research and innovation are imperative in the realm of environmental monitoring.This study focuses on zinc oxide(ZnO),a typical semiconductor oxide,as the research subject.It investigates the gas-sensing characteristics of room-temperature UV-excited gas sensors.By varying parameters such as UV pulse frequency,material composites,and surface treatments,this research has successfully enhanced the gas sensor’s sensitivity,humidity resistance,and responsiveness to volatile organic compounds(VOCs).The primary findings of this study are summarized as follows:1.Mechanism Enhancement of ZnO Gas Sensor Response via Pulsed UV Light Modulation:In response to the problem of low sensitivity under continuous UV irradiation at room temperature,a strategy involving Pulsed UV Light Modulation(PULM)was proposed.This approach,based on ZnO material synthesized through a precipitation method,was extensively studied for sensor response characteristics at different pulse frequencies.The sensor was exposed to both continuous UV(CU)and PULM,and its response to gases such as NO2,H2S,and C3H9N was observed.Notably,PULM demonstrated significant success in improving gas sensitivity.It effectively decouples the surface electron exchange from enhanced resistance response,utilizing UV-on phases for surface cleaning and generation of Reactive Oxygen Species(ROS),while UV-off phases prevent target gas desorption and baseline resistance reduction.This improvement strategy effectively addresses the issue of target gas desorption under CU mode,resulting in a substantial enhancement in response to ppb-level trace gases,increasing from 1.9(CU,20 ppb NO2)to 131.1(PULM,20 ppb NO2),and lowering the NO2 detection limit from 2.6 ppb(CU)to 0.8 ppb(PULM).2.H2O2 Treatment Enhancing ZnO Sensor Sensitivity to O3 in High Humidity Conditions:To combat the problem of poor humidity resistance leading to humidity poisoning in sensors,a strategy involving reduction of surface oxygen vacancies and grain size reduction was employed in combination with PULM activation.This approach significantly improved the sensitivity of ZnO sensors to O3 in a high-humidity environment at room temperature.ZnO nanospheres with a diameter of approximately 15 nm were synthesized using a precipitation method and treated with H2O2.The sensors were then subjected to gas sensitivity studies under high-humidity conditions using both continuous UV and pulsed UV light modulation.This strategy successfully enhanced the response of sensor to O3 in high humidity,with the response increasing from 5.6(CU)to 300(PULM)for 300 ppb O3 at 30%RH.Conventional ZnO sensors are prone to water poisoning in environments exceeding 30%RH at room temperature,while this method enables ZnO sensors to detect trace-level O3 even at 90%RH,with a detection limit of 3 ppb.3.Investigating the Impact of Surface Treatment on Gas-Sensitive Properties of ZnO-Based Composite Materials:Addressing the Insensitivity of Sensors to VOCs.Various strategies,including the compositing of multiple materials,noble metal sensitization,and plasma treatment under different excitation conditions,were employed to improve the gas-sensing response.It was found that the most effective approach involved noble metal sensitization of ZnO materials,coupled with surface treatment through Ar/H2 plasma,significantly enhancing the gas-sensing performance of ZnO.The research also revealed that UV activation promoted internal redox reactions,thereby increasing the sensitivity for VOC detection.In conclusion,this research offers new ways to improve gas sensors.PULM technology enhances trace gas detection,lowers limits,and benefits environmental monitoring and air quality control.Improved ozone detection in high humidity has meteorological and environmental applications.Increased VOC sensitivity aids industrial safety and pollution monitoring.These sensors have versatile applications,improving the environment,quality of life,and industry.