A new air exchange rate （AER） monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted i...A new air exchange rate （AER） monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs （0.1-10.0 hr-1）. AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO2 sensors coupled with data loggers. Indoor temperature, relative humidity （RH）, and CO2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved： duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr-l in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr-1 in fall, and 0.12 to 1.39 hr-1 in winter with a median AER of 1.15.展开更多
A type of CO2 sensor based on oxygen concentration cell was designed as following: Cell I: Pt | Au, O2, CO2| Na2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt or Cell lI: Pt|Au, O2, CO2|K2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt. (Na,K-β/β...A type of CO2 sensor based on oxygen concentration cell was designed as following: Cell I: Pt | Au, O2, CO2| Na2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt or Cell lI: Pt|Au, O2, CO2|K2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt. (Na,K-β/β'-AI2O3 is named by NKBA). The sensor signal is consistent with the Nernstian slope within the region of phase equilibrium for Na, K-β/β'-AI2O3 material. The relationship between CO2 sensor voltage response and phase equilibrium of solid electrolyte Na, K-β/β-AI2O3 is discussed in this paper.展开更多
The CO_2 sensing of PrFeO_3 and NdFeO_3 sensors were investigated. Experimental results show that the resistances for PrFeO_3 and NdFeO_3 in CO_2 gas are larger than those in air and the responses for PrFeO_3and NdFeO...The CO_2 sensing of PrFeO_3 and NdFeO_3 sensors were investigated. Experimental results show that the resistances for PrFeO_3 and NdFeO_3 in CO_2 gas are larger than those in air and the responses for PrFeO_3and NdFeO_3 sensors increase with an increase in room-temperature relative humidity. When exposed to1000 ppm CO_2, the response of PrFeO_3 thick film based on nano-powders annealed at 700℃can reach8.44 at 160℃for the background of wet air with 58%of room-temperature relative humidity (RH),which is much larger than the corresponding value (3.03) in wet air with 25%RH. The sensing response S of NdFeO_3 thick-film sensor based on nano-powders annealed at 600℃to 3000 ppm CO_2 at the operating temperature 200℃can reach 2.36 for the background of wet air with 72%RH, which is larger than the corresponding value (1.83) in the air with 25%RH. Compared with other CO_2 sensing materials, the PrFeO_3 sensor has larger response at lower operating temperature for CO_2 gas and may be used as a new CO_2 sensing material.展开更多
Tube-type CO_2 gas sensors based on NASICON (Na Super Ion Conductor) material were fabricated.The material was synthesized by conventional sol-gel method,and the resulted powders were characterized by XRD.The tube-typ...Tube-type CO_2 gas sensors based on NASICON (Na Super Ion Conductor) material were fabricated.The material was synthesized by conventional sol-gel method,and the resulted powders were characterized by XRD.The tube-type CO_2 sensor was prepared with the sensing electrode Li_2CO_3-BaCO_3 binary carbonates in molar ratio 1:1.5.The concentration of CO_2 range from 300μg/g to 3000μg/g,the sensitivity of the sensor was 62.3 mV/decade.The response and recovery time (90%)corresponding to the switching change between 300μg/g and 1000μg/g CO_2 were 20 s and 2 min,respectively.If the sensing electrode was modified with binary oxides,the steady time of the sensor could be greatly reduced from 30 min to 5 min and the stability and humid-resistance of the sensor were improved.展开更多
Response speed is one of the most important evaluation criteria for CO2 sensors. In this work, we report an ultrafast CO2 fluorescent sensor based on poly[oligo（ethylene glycol） methyl ether methacrylate]-b-poly[N,N...Response speed is one of the most important evaluation criteria for CO2 sensors. In this work, we report an ultrafast CO2 fluorescent sensor based on poly[oligo（ethylene glycol） methyl ether methacrylate]-b-poly[N,N-diethylaminoethyl methacrylate-r-4-（2- methylacryloyloxyethylamino）-7-nitro-2,1,3-benzoxadiazole] [POEGMA-b-P（DEAEMA-r-NBDMA）], in which DEAEMA units act as the CO2-responsive segment and 4-nitrobenzo-2-oxa-l,3-diazole （NBD） is the chromophore. The micelles composed of this copolymer could disassemble in 2 s upon CO2 bubbling, accompanying with enhanced fluorescence emission with bathochromic shift. Furthermore, the quantum yield of the NBD chromophore increases with both the CO2 aeration time and the NBD content. Thus we attribute the fluorescent enhancement to the inhibition of the photo-induced electron transfer between unprotonated tertiary amine groups and NBD fluorophores. The sensor is durable although it is based on ＂soft＂ materials. These micellar sensors could be facilely recycled by alternative CO2/Ar purging for at least 5 times, indicating good reversibility.展开更多
Listeria monocytogenes(LM)is a dangerous foodborne pathogen for humans.One emerging and validated method of indirectly assessing LM in food is detecting 3-hydroxy-2-butanone(3H2B)gas.In this study,the synthesis of 3-(...Listeria monocytogenes(LM)is a dangerous foodborne pathogen for humans.One emerging and validated method of indirectly assessing LM in food is detecting 3-hydroxy-2-butanone(3H2B)gas.In this study,the synthesis of 3-(2-aminoethylamino)propyltrimethoxysilane(AAPTMS)functionalized hierarchical hollow TiO_(2)nanospheres was achieved via precise controlling of solvothermal reaction temperature and post-grafting route.The sensors based on as-prepared materials exhibited excellent sensitivity(480 Hz@50 ppm),low detection limit(100 ppb),and outstanding selectivity.Moreover,the evaluation of LM with high sensitivity and specificity was achieved using the sensors.Such stable three-dimensional spheres,whose distinctive hierarchical and hollow nanostructure simultaneously improved both sensitivity and response/recovery speed dramatically,were spontaneously assembled by nanosheets.Meanwhile,the moderate loadings of AAPTMS significantly improved the selectivity of sensors.Then,the gas-sensing mechanism was explored by utilizing thermodynamic investigation,Gaussian 16 software,and in situ diffuse reflectance infrared transform spectroscopy,illustrating the weak chemisorption between the-NHgroup and 3H2B molecules.These portable sensors are promising for real-time assessment of LM at room temperature,which will make a magnificent contribution to food safety.展开更多
基金supported by the Scientific Research Projects for State Environmental Protection and Commonweal (No. 200709048)the National Natural Science Foundation of China (No. 20977054/B070704)+1 种基金the Innovation Fund of Nankai UniversityJoint Research Grant to Both Nankai University and Tianjin University sponsored by the Ministry of Education,China
文摘A new air exchange rate （AER） monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs （0.1-10.0 hr-1）. AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO2 sensors coupled with data loggers. Indoor temperature, relative humidity （RH）, and CO2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved： duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr-l in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr-1 in fall, and 0.12 to 1.39 hr-1 in winter with a median AER of 1.15.
文摘A type of CO2 sensor based on oxygen concentration cell was designed as following: Cell I: Pt | Au, O2, CO2| Na2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt or Cell lI: Pt|Au, O2, CO2|K2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt. (Na,K-β/β'-AI2O3 is named by NKBA). The sensor signal is consistent with the Nernstian slope within the region of phase equilibrium for Na, K-β/β'-AI2O3 material. The relationship between CO2 sensor voltage response and phase equilibrium of solid electrolyte Na, K-β/β-AI2O3 is discussed in this paper.
基金supported by National Natural Science Foundation of China(51272133,51472145,51772174 and 51472150)Shandong Natural Science Foundation(ZR2016EMM20)
文摘The CO_2 sensing of PrFeO_3 and NdFeO_3 sensors were investigated. Experimental results show that the resistances for PrFeO_3 and NdFeO_3 in CO_2 gas are larger than those in air and the responses for PrFeO_3and NdFeO_3 sensors increase with an increase in room-temperature relative humidity. When exposed to1000 ppm CO_2, the response of PrFeO_3 thick film based on nano-powders annealed at 700℃can reach8.44 at 160℃for the background of wet air with 58%of room-temperature relative humidity (RH),which is much larger than the corresponding value (3.03) in wet air with 25%RH. The sensing response S of NdFeO_3 thick-film sensor based on nano-powders annealed at 600℃to 3000 ppm CO_2 at the operating temperature 200℃can reach 2.36 for the background of wet air with 72%RH, which is larger than the corresponding value (1.83) in the air with 25%RH. Compared with other CO_2 sensing materials, the PrFeO_3 sensor has larger response at lower operating temperature for CO_2 gas and may be used as a new CO_2 sensing material.
基金The authors acknowledge Natural Science Foundation of China （No.60174033）；ministry of education and Innovation Foundation of Jilin University
文摘Tube-type CO_2 gas sensors based on NASICON (Na Super Ion Conductor) material were fabricated.The material was synthesized by conventional sol-gel method,and the resulted powders were characterized by XRD.The tube-type CO_2 sensor was prepared with the sensing electrode Li_2CO_3-BaCO_3 binary carbonates in molar ratio 1:1.5.The concentration of CO_2 range from 300μg/g to 3000μg/g,the sensitivity of the sensor was 62.3 mV/decade.The response and recovery time (90%)corresponding to the switching change between 300μg/g and 1000μg/g CO_2 were 20 s and 2 min,respectively.If the sensing electrode was modified with binary oxides,the steady time of the sensor could be greatly reduced from 30 min to 5 min and the stability and humid-resistance of the sensor were improved.
基金financially supported by the National Natural Science Foundation of China (Nos. 51573086 and 21374058)the Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (No. sklpme2014-4-26)
文摘Response speed is one of the most important evaluation criteria for CO2 sensors. In this work, we report an ultrafast CO2 fluorescent sensor based on poly[oligo（ethylene glycol） methyl ether methacrylate]-b-poly[N,N-diethylaminoethyl methacrylate-r-4-（2- methylacryloyloxyethylamino）-7-nitro-2,1,3-benzoxadiazole] [POEGMA-b-P（DEAEMA-r-NBDMA）], in which DEAEMA units act as the CO2-responsive segment and 4-nitrobenzo-2-oxa-l,3-diazole （NBD） is the chromophore. The micelles composed of this copolymer could disassemble in 2 s upon CO2 bubbling, accompanying with enhanced fluorescence emission with bathochromic shift. Furthermore, the quantum yield of the NBD chromophore increases with both the CO2 aeration time and the NBD content. Thus we attribute the fluorescent enhancement to the inhibition of the photo-induced electron transfer between unprotonated tertiary amine groups and NBD fluorophores. The sensor is durable although it is based on ＂soft＂ materials. These micellar sensors could be facilely recycled by alternative CO2/Ar purging for at least 5 times, indicating good reversibility.
基金supported by the National Natural Science Foundation of China(No.32272399)the Shanghai Natural Science Foundation(No.21ZR1427500).
文摘Listeria monocytogenes(LM)is a dangerous foodborne pathogen for humans.One emerging and validated method of indirectly assessing LM in food is detecting 3-hydroxy-2-butanone(3H2B)gas.In this study,the synthesis of 3-(2-aminoethylamino)propyltrimethoxysilane(AAPTMS)functionalized hierarchical hollow TiO_(2)nanospheres was achieved via precise controlling of solvothermal reaction temperature and post-grafting route.The sensors based on as-prepared materials exhibited excellent sensitivity(480 Hz@50 ppm),low detection limit(100 ppb),and outstanding selectivity.Moreover,the evaluation of LM with high sensitivity and specificity was achieved using the sensors.Such stable three-dimensional spheres,whose distinctive hierarchical and hollow nanostructure simultaneously improved both sensitivity and response/recovery speed dramatically,were spontaneously assembled by nanosheets.Meanwhile,the moderate loadings of AAPTMS significantly improved the selectivity of sensors.Then,the gas-sensing mechanism was explored by utilizing thermodynamic investigation,Gaussian 16 software,and in situ diffuse reflectance infrared transform spectroscopy,illustrating the weak chemisorption between the-NHgroup and 3H2B molecules.These portable sensors are promising for real-time assessment of LM at room temperature,which will make a magnificent contribution to food safety.
