scholarly journals A Miniaturised, Fully Integrated NDIR CO2 Sensor On-Chip

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5347
Author(s):  
Xiaoning Jia ◽  
Joris Roels ◽  
Roel Baets ◽  
Gunther Roelkens
Keyword(s):  
Water Vapor ◽  
Limit Of Detection ◽  
Wafer Level ◽  
Water Vapor Absorption ◽  
Optical Source ◽  
Fully Integrated ◽  
Term Stability ◽  
Long Term Stability ◽  
Co2 Sensor

In this paper, we present a fully integrated Non-dispersive Infrared (NDIR) CO2 sensor implemented on a silicon chip. The sensor is based on an integrating cylinder with access waveguides. A mid-IR LED is used as the optical source, and two mid-IR photodiodes are used as detectors. The fully integrated sensor is formed by wafer bonding of two silicon substrates. The fabricated sensor was evaluated by performing a CO2 concentration measurement, showing a limit of detection of ∼750 ppm. The cross-sensitivity of the sensor to water vapor was studied both experimentally and numerically. No notable water interference was observed in the experimental characterizations. Numerical simulations showed that the transmission change induced by water vapor absorption is much smaller than the detection limit of the sensor. A qualitative analysis on the long term stability of the sensor revealed that the long term stability of the sensor is subject to the temperature fluctuations in the laboratory. The use of relatively cheap LED and photodiodes bare chips, together with the wafer-level fabrication process of the sensor provides the potential for a low cost, highly miniaturized NDIR CO2 sensor.

scholarly journals Highly Responsive and Ultrasensitive Non-Enzymatic Electrochemical Glucose Sensor Based on Au Foam

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1203 ◽  
Author(s):  
Nannan Shen ◽  
Haijun Xu ◽  
Weichen Zhao ◽  
Yongmei Zhao ◽  
Xin Zhang
Keyword(s):  
High Selectivity ◽  
Glucose Sensor ◽  
Limit Of Detection ◽  
Surface Enhanced Raman Spectroscopy ◽  
Au Nanoparticle ◽  
Quantitative Detection ◽  
Term Stability ◽  
Long Term Stability ◽  
Surface Enhanced Raman

Glucose concentration is an important physiological index, therefore methods for sensitive detection of glucose are important. In this study, Au foam was prepared by electrodeposition with a dynamic gas template on an Au nanoparticle/Si substrate. The Au foam showed ultrasensitivity, high selectivity, and long-term stability in the quantitative detection of glucose. The foam was used as an electrode, and the amperometric response indicated excellent catalytic activity in glucose oxidation, with a linear response across the concentration range 0.5 μM to 12 mM, and a limit of detection of 0.14 μM. High selectivity for interfering molecules at six times the normal level and long-term stability for 30 days were obtained. The results for electrochemical detection with Au foam of glucose in human serum were consistent with those obtained with a sensor based on surface-enhanced Raman spectroscopy and a commercial sensor. This proves that this method can be used with real samples. These results show that Au foam has great potential for use as a non-enzymatic glucose sensor.

scholarly journals Water vapor δ<sup>2</sup>H and δ<sup>18</sup>O measurements using off-axis integrated cavity output spectroscopy

2009 ◽  
Vol 2 (4) ◽  
pp. 2055-2085 ◽  
Author(s):  
P. Sturm ◽  
A. Knohl
Keyword(s):  
Water Vapor ◽  
Concentration Dependence ◽  
Temperature Sensitivity ◽  
Dew Point ◽  
Calibration System ◽  
Term Stability ◽  
Long Term Stability ◽  
Cavity Output ◽  
Isotope Measurements

Abstract. We present a detailed assessment of a commercially available water vapor isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ measurements of δ2H and δ18O in water vapor. This method, based on off-axis integrated cavity output spectroscopy, is an alternative to the conventional water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the analyzer in terms of precision, memory effects, concentration dependence, temperature sensitivity and long-term stability. A calibration system based on ink jet technology is used to characterize the performance and to calibrate the analyzer. Our results show that the precision at an averaging time of 15 s is 0.16‰ for δ2H and 0.08‰ for δ18O. The isotope ratios are strongly dependent on the water mixing ratio of the air. Taking into account this concentration dependence as well as the temperature sensitivity of the instrument we obtained a long-term stability of the water isotope measurements of 0.38‰ for δ2H and 0.25‰ for δ18O. The accuracy of the WVIA was further assessed by comparative measurements using IRMS and a dew point generator indicating a linear response in isotopic composition and H2O concentrations. The WVIA combined with a calibration system provides accurate high resolution water vapor isotope measurements and opens new possibilities for hydrological and ecological applications.

scholarly journals Water vapor δ<sup>2</sup>H and δ<sup>18</sup>O measurements using off-axis integrated cavity output spectroscopy

2010 ◽  
Vol 3 (1) ◽  
pp. 67-77 ◽  
Author(s):  
P. Sturm ◽  
A. Knohl
Keyword(s):  
Water Vapor ◽  
Concentration Dependence ◽  
Temperature Sensitivity ◽  
Dew Point ◽  
Calibration System ◽  
Term Stability ◽  
Long Term Stability ◽  
Cavity Output ◽  
Isotope Measurements

Abstract. We present a detailed assessment of a commercially available water vapor isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ measurements of δ2H and δ18O in water vapor. This method, based on off-axis integrated cavity output spectroscopy, is an alternative to the conventional water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the analyzer in terms of precision, memory effects, concentration dependence, temperature sensitivity and long-term stability. A calibration system based on a droplet generator is used to characterize the performance and to calibrate the analyzer. Our results show that the precision at an averaging time of 15 s is 0.16‰ for δ2H and 0.08‰ for δ18O. The isotope ratios are strongly dependent on the water mixing ratio of the air. Taking into account this concentration dependence as well as the temperature sensitivity of the instrument we obtained a long-term stability of the water isotope measurements of 0.38‰ for δ2H and 0.25‰ for δ18O. The accuracy of the WVIA was further assessed by comparative measurements using IRMS and a dew point generator indicating a linear response in isotopic composition and H2O concentrations. The WVIA combined with a calibration system provides accurate high resolution water vapor isotope measurements and opens new possibilities for hydrological and ecological applications.

scholarly journals Influence of Heat Disturbance on the Performance of YSZ based CO2 Sensor with Compound of Li2CO3-BaCO3-Nd2O3 as Auxiliary Sensing Electrode

2020 ◽  
Vol 23 (4) ◽  
pp. 244-251
Author(s):  
Guangwei Wang ◽  
Hongzhen Chen ◽  
Yuanhui Wu
Keyword(s):  
Heat Treatment ◽  
Water Vapor ◽  
Co2 Concentration ◽  
Similar Response ◽  
Operational Environment ◽  
Long Term Stability ◽  
Co2 Sensor ◽  
Sensing Material ◽  
Content System

Suddenly changes and fluctuations of temperature often occur in the operational environment of the CO2 electrochemical sensor. In this work, the YSZ based potentiometric CO2 sensor having Li2CO3-BaCO3-Nd2O3 compound as its auxiliary sensing material was prepared. And the effects of several types of heat disturbance on the performance of this kind of sensor ware studied. The results indicate that the sensors after heat disturbances respond similarly with the sensor as prepared, which presents rapid and correct response for the change of CO2 concentration within the experimental range of 271-576802 ppm. The sensors, with or without heat disturbance, respond well as different extents of abrupt alteration of CO2 concentration occurs, and the EMF outputs recover rapidly as the concentration of CO2 change back to the base value. At the constant concentration of CO2, the EMFs of the sensors with or without heat treatment decrease slowly as the time increases, the reason for this phenomenon might be the accumulation of inert substances on the electrode interfaces and ageing of electrodes. However, heat treatment can improve the long-term stability of the sensor to some extent. Furthermore, this type of sensor works stably with the existence of water vapor (10%), it has similar response curve in the dry and water vapor content system. After some further investigations and improvements, it might be potentially applied in the practical combustion atmosphere.

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