Acetone Gas Sensor For Analysis Of Exhaled Breath Of Diabetes

Disease diagnosis by specific volatile organic compounds(VOCs)in exhaled breath has been of particular concern due to noninvasive,rapid,economic,and simple compared with standard blood analysis and endoscopy.Breath acetone has been identified as a specific biomarker for diabetes,some modern gas analyze techniques have been used to detect VOCs in exhaled breath,such as gas chromatography-mass spectrometry(GC-MS),ion mobility spectrometry(IMS),selected ion flow tube mass spectrometry(SIFT-MS),proton transfer reaction-mass spectrometry(PTR-MS).Nevertheless,these techniques are not suitable for application as a portable gas sensor for their high cost,large size and complexity of operation.On the other hand,chemo-resistive gas sensors based on semiconducting metal oxides are promising materials for portable VOCs detector due to their small size,good reliability,simplicity of operation and low cost.Till now,a number of efficient semiconducting metal oxide sensors based on ZnO,SnO2,CeO2,WO3,Fe2O3,In2O3,TiO2 for the detection of acetone have been reported.Acetone concentration in exhaled breath is very low at ppm level.A highly sensitive and selective acetone sensor was required for the detection of such low concentration acetone and the difference between healthy people and diabetics.Much effort has been made by researchers to improve the acetone sensitivity of materials,0.2ppm of low level acetone can be detected without consideration the influence of humidity.It is not enough only make efforts on improving acetone sensitivity,the complex breath condition including the high humidity characteristics of exhaled breath also should be considered for practical applications.Under the high humidity circumstance,chemo-resistive gas sensors can detect 20ppb of ultra-low level acetone.This studies laid a solid foundation for the production of diabetes detector using semiconductor chemo-resistive sensors.However,semiconductor chemo-resistive sensors can not detect a specific gas like GC-MS,SIFT-MS analyze techniques and the response of this sensors is combined effect of all gas in exhaled breath.The other interference gas in breath must be studied when judge state of diabetes by acetone in exhaled breath.Besides,clinic tests must be performed to research if the chemo-resistive gas sensors has the capacity for distinguishing diabetics from healthy people and judging state of illness in practical application.The main results of this paper are as follows:1.0-10mol.%Re2O3-SnO2(Re = Sm,Gd,Pr)doped nanoparticles showed a significant gas-sensing response to acetone,and 5mol.%Sm2O3-SnO2 thick film sensor exhibit best sensing properties to acetone at an operating temperature of 240?,and the response under humidity of 20%RH to 0.5ppm acetone is improved to 4.51 contrast with 1.024 of pure SnO2.Considering the humidity in exhaled,the response of 5mol.%Sm2O3-SnO2 sensor to acetone at humidity of 20%RH,35%RH and 80%RH at 240C was studied.The results suggest that with the increase of humidity,the gas sensitivity of the component gradually decreases.As a result of the high concentration of carbon dioxide in the exhaled gas,the CO2 sensing performance of 5mol.%Sm2O3-SnO2 sensor was studied.The results suggest that the effect of CO2 on the detection of acetone in the exhaled breath could not be neglected.In order to eliminate the interference of CO2 to detect acetone,a gas-sensing test was conducted on the mixture of CO2 and acetone in this paper.The actual acetone content in exhaled breath of four diabetic patients and four healthy people was detected by GC-MS technique.The experimental results were compared with the results of 5mol.%Sm2O3-SnO2 gas sensor.2.Re2O3-SnO2(Re = Gd,Pr)thick film with different Re2O3 doping ratios were prepared by sol-gel and coprecipitation method.The results show that the 5mol.%Re2O3-SnO2 thick film annealed at 600? shows the best gas sensitivity to acetone at the operating temperature of 240?.The gas sensitivity of 5mol.%Gd2O3-SnO2 sensor to acetone is higher than 5mol.%Pr2O3-SnO2 sensor,and the recovery time of it is shorter,which is beneficial to the reuse of the device.However,5mol.%Pr2O3-SnO2 sensor showed better gas-sensing properties to CO2,and low concentration CO2 gas properties of this sensor was tested.Because of the good sensing properties to CO2,5mol.%Pr2O3-SnO2 sensor can not measure acetone in breath precisely.Therefore,5mol.%Gd2O3-SnO2 sensor is more suitable for the detection of acetone in breath,and 5mol.%Pr2O3-SnO2 sensor can be used for CO2 detection.3.HoFeO3 and Pd,carbon nanotubes doped HoFeO3 nanoparticles were prepared by sol-gel.Compared with the pure HoFeO3 gas sensor,the response of all the dopant sensor is improved,of which lwt.%CN-HoFeO3 material at the working temperature of 180? showed the best gas sensitivity to acetone.lwt.%CN-HoFeO3 sensor show different humidity sensitivity compared with pure HoFeO3 sensor,and the recovery response time of it is shorter than that of pure HoFeO3 gas sensor.It suggest that the lwt.%CN-HoFeO3 sensor can respond to gas more quickly and reproducibly.Besides,lwt.%CN-HoFeO3 sensor have a strong resolution to acetone,indicating that this sensor is more suitable for the detection of acetone in exhaled than pure HoFeO3 sensor.