Preparation And Application Of Novel Gas Sensors For Detecting Several Lung Cancer Related VOCs

Lung cancer is currently the most common malignancy with the highest morbidity and mortality in the world.It has no special symptoms at an early stage,so it is usually diagnosed in the middle and late stages,which misses the best time for treatment.Regular medical examination helps early detection and treatment of lung cancer.However,the current clinical lung cancer detection technology cannot meet the needs of large-scale lung cancer diagnosis.Exhaled breath analysis has been considered as an alternative method for safe and convenient diagnosis of diseases because these gases originate directly from the lungs and have excellent specificity for lung diseases,which is suitable for the screening of clinical lung cancer.This research aims to develop a novel gas sensor element with high response to volatile organic compounds（VOCs）of lung cancer markers from the perspective of preparation of new materials and design of new methods.This research is likely to render a new inexpensive strategy for quickly diagnosing lung cancer in large scale,which is very meaningful for the early discovery and prevention of the disease.The main content is divided into the following three parts:（1）Nanoporous gold leaf as signal amplification agent for detection of VOCs with quartz crystal microbalanceIn this work,a novel sensing framework by coupling nanoporous gold leaf（NPGL）and sensitive materials on quartz crystal microbalance（QCM）sensor was developed for detection of volatile organic compounds（VOCs）.The bi-layer structure was established by two-step modification process,where NPGL served as loading platform to anchor more sensitive materials and provide larger surface area.Sensitive materials for different target analytes were optimized,as well as selection of the most suitable NPGL.Morphology of the bi-layer was characterized and sensing performances including detection range,response time,reversibility,stability,etc.,were investigated.Thermodynamics and kinetics of gas adsorption process were studied by employing several classical models.It was found that adsorption of the tested VOCs was more accurately represented by Freundlich isotherm and adsorption kinetics of these VOCs fitted well with pseudo second-order kinetics.The results of on-line monitoring brought about admirable sensing properties,fully indicating that the QCM sensor modified with composite layer of sensitive material/NPGL has promising application prospect for real-time detection.（2）Facile synthesis of hollow MnFe₂O₄ nanoboxes based on galvanic replacement reaction for fast and sensitive VOCs sensorHollow MnFe₂O₄ nanoparticles were successfully synthesized based on simple galvanic replacement reaction with Mn₃O₄ as a precursor.The chemical composition and nanostructure of the as-prepared samples were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy.MnFe₂O₄ was applied to decorate interdigital electrodes and the obtained sensors were used to detect fourteen kinds of volatile organic compounds at different operation temperature from 160°C to 280℃.Results show that the sensor has good sensitivity,repeatability and long-term stability for ethanol gas determination at 210℃.The detection linear range for ethanol is 2⁴00 ppm,and the response and the recovery time was 7.5 s and 8.0 s,respectively.Besides,the fabricated sensor also displayed decent performance in measuring n-decane in the concentration range of2⁴00 ppm at 260℃.Finally,gas-sensing mechanism of the prepared sensor was clearly studied.（3）Hollow Ce@ZnO microsphere gas sensor based on UV excitation strategy for the detection of VOCs at low temperatureCe-doped hollow ZnO microspheres were prepared by hard template method and used as sensitive materials to construct semiconductor VOCs sensors.The materials were characterized by scanning electron microscopy,transmission electron microscopy,and X-ray diffraction.The sensitivity of the sensors was studied using a self-made gas sensor working test system.The results show that the sensor has good sensitivity,reproducibility and long-term stability for acetone gas detection under 365 nm UV excitation.The linear range for acetone detection at 80℃was 0.1¹00 ppm with 11.2 response intensity,and the response and recovery times were 32 s and 60 s,respectively.This sensor provides a new method for the specific identification of acetone gas,which is expected to develop a lung cancer diagnostic sensor array system at low working temperature.