CO2 Sensor Research Articles

Gigantic enhancement in response of heterostructured CeO2/CdS nanospheres based self-powered CO2 gas sensor: A comparative study

In this study, a self-powered carbon dioxide (CO2) gas sensor with good sensitivity and selectivity has been developed from CeO2/CdS based triboelectric nanogenerator (TENG). Also, a comparative analysis of individual CeO2, CdS, and CeO2/CdS nanomaterials based on the resistive type and self-powered CO2 gas sensing has been performed. The CeO2/CdS was synthesized by hydrothermal method and characterized by XRD, FTIR, UV–visible spectroscopy, FESEM, TEM, and XPS. The XPS analysis of CeO2/CdS heterostructure confirmed that type II heterojunction was formed in CeO2 and CdS. The surface morphology of CeO2/CdS was found in regular nanospheres in the range of 30–60 nm. The resistive type CO2 gas sensor showed 3.96 sensor response at 1000 ppm of CO2, whereas, in the self-powered CO2 gas sensor, it was found 30 for the same concentration. The minimum response and recovery times were found 1835 and 835 ms respectively for 250 ppm. The self-powered CeO2/CdS TENG-based CO2 sensor is highly sensitive, selective, and quick responsive.

Real-time monitoring of CO2 gas using inverse opal photonic gel containing Poly(2-(dimethylamino)ethylmethacrylate

With the rapid progression of global climate changes and air pollution in recent years, there has been growing interest in the sensing and monitoring of CO2 gas. In the present study, an inverse opal photonic gel (IOPG) colorimetric sensor is demonstrated that is capable of real-time monitoring of CO2 gas in an open system without the necessity of a power supply. The IOPGs are fabricated via the opal-templated photo-polymerization of monomer mixtures of hydroxyethyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) or 2-(dimethylamino)propyl methacrylamide (DMAPMAm), followed by template removal. When the IOPG sensor is immersed in water with a steady flow of mixed CO2/N2 gas at various ratios, the CO2 molecules dissolve in the water and are converted to carbonate anions, which subsequently bind to the amino groups of pDMAEMA to build up osmotic pressure, thus leading to swelling of the IOPG. A comparison of the sensing and recovery capabilities of the two types of IOPG indicates that the pDMAEMA-containing IOPG exhibits a limit of detection below 1.2%, and 2.6 times faster CO2 desorption kinetics compared to the pDMAPMAm-containing IOPG. The swelling behavior of the CO2-responsive IOPG is rigorously investigated at various pH values, and temperatures by analyzing the reflectance spectra of the IOPG in the visible wavelength range. The usefulness of the pDMAEMA-IOPG as a real-time CO2 sensor was confirmed by applying it to various carbonated drinks.

Increased CO2 levels in the operating room correlate with the number of healthcare workers present: an imperative for intentional crowd control

The air in an operating room becomes more contaminated as the occupancy of the room increases. Individuals residing in a room can potentially emit infectious agents. In order to inhibit and better understand the epidemiology of surgical site infections, it is important to develop procedures to track room occupancy level and respiration. Exhaled CO2 provides a respiratory byproduct that can be tracked with IR light and is associated with human occupancy. Exhaled CO2 can also be used as an indirect measure of the potential release and level of infectious airborne agents. We show that non-dispersive infrared CO2 sensors can be used to detect CO2 in operating room air flow conditions of 20 air changes per hour and a positive pressure of 0.03 in. H2O. The CO2 concentration increased consecutively for occupation levels of one to four individuals, from approximately 65 ppm above the background level when one individual occupied the operating room for twenty minutes to approximately 300 ppm above the background when four individuals were present for twenty minutes. The amount of CO2 detected increases as the number of occupants increase, the activity level increases, the residency time increases and when the ventilation level is reduced.

Smart Plants: Low-Cost Solution for Monitoring Indoor Environments

Humans tend to spend most of their life indoors, making the quality of indoor environments essential for human health and wellbeing. While several solutions for monitoring the indoor environment have been proposed, ranging from infrastructure-based monitoring solutions to cameras, these tend to require separate installation, making the sensors difficult to maintain and upgrade. In this article, we introduce the idea of using smart plants as an easy-to-deploy and affordable solution for monitoring the indoor environment. Plants are typically deployed close to humans and they increasingly are placed in containers that integrate sensors, such as soil moisture, temperature, humidity, and CO2 sensors. We demonstrate how these sensors can be used as an alternative technology for monitoring—and enriching—indoor spaces without needing to install proprietary sensors or other technology. Specifically, we show how smart plants can be used to estimate overall CO2 accumulation, occupancy information, and whether people use protective face masks or not. We also establish a research roadmap for the use of smart plants to monitor indoor environments.

Carbon dioxide sensor device based on biphenylene nanotube: A density functional theory study

Recent fabrication of biphenylene (BP) nanosheet, has motivated us to study its one-dimensional derivative, i.e., BP nanotube (BPNT) as a CO2 gas sensor using density functional theory calculations. The adsorption energy (Eads), ΔH, and ΔG of interaction between BPNT and CO2 are about −19.50, −13.60, and -18.49kJ.mol−1, respectively. The electrical properties of BPNT are not sensitive toward the CO2 molecule. Therefore, we used doping technique to explore the efficacy of Al- and Si-BPNT as CO2 sensors. Similar to pristine BPNT, the energy level of HOMO and LUMO of Si-BPNT is not affected by CO2 adsorption. In contrast, adsorption of CO2 by Al-BPNT leads to a −21.44 % reduction of Eg, indicating that Al-BPNT could be considered as a potential sensor for CO2 gas.

A Dual-Band Carbon Dioxide Sensor Based on Metal–TiO2–Metal Metasurface Covered by Functional Material

Highly sensitive and integrated optical multi-band CO2 sensors are significant at the shortwave infrared (SWIR) region and still lack research. A compact CO2 sensor composed of a Au-disk/TiO2-cylinder/Au-film metasurface coated by polyhexamethylene biguanide (PHMB) film, functioning at multi-band resonances as well as having high sensitivity to gas concentrations, is presented. It can be employed as a dual-band narrowband absorber, producing two strongly resonant modes at the SWIR region under a reflection-type framework of linearly polarized incidence. Moreover, the metasurface sensor possesses high refractive index sensitivity of 109.25 pm/ppm at around 1040 nm and 42.57 pm/ppm at around 1330 nm in the range of 200–600 ppm, which is suitable for detecting atmospheric CO2. Furthermore, the numerical results show that the sensitivity increases with a thicker PHMB film and optimizes at a thickness above 600 nm. The physical mechanism reveals that the higher order mode exhibits more extended near-field energy than the lower order mode, resulting in more sensitivity towards the surroundings. The design and results of our investigation show high-quality CO2 sensing performance which functions at dual spectrum bands in the SWIR region and is promising for integrated photonic applications.

Gas Sensors Based on Exfoliated g-C3N4 for CO2 Detection

We report on the investigation of graphitic carbon nitride (g-C3N4) for carbon dioxide (CO2) sensor applications. g-C3N4 is prepared by the thermal polycondensation of thiourea and sprayed onto a substrate with interdigitated electrodes. The resulting sensor device exhibited a high sensitivity to CO2 molecules of ~200 ppm, a high responsivity of ~730 ms at 40 °C and a full recovery time of 36 s. Furthermore, a set of various characterization measurements demonstrated the excellent stability of both the g-C3N4 nanosheets and the fabricated gas sensor device. Meanwhile, density functional theory (DFT) calculations for the bulk and monolayer models, based on tri-s-triazine, revealed the optoelectronic properties of g-C3N4 and the interaction energy with CO2, which is evaluated at −0.59 eV. This value indicates the very good affinity of g-C3N4 nanosheets to CO2 molecules. Our findings shed light on the potential for g-C3N4 to be used for the development of high-performing gas sensor devices.

Abstract 167: Nasal Sensor Capnographic Differences In Major Traumatic Brain Injury Patients Receiving Non-rebreather Mask Versus Nasal Cannula Oxygen Delivery

Background: The advent of highly sensitive End-Tidal CO2 (ETCO2) sensors allows effective monitoring of intubated patients in EMS. Previous work has explored the use of ETCO2 monitoring in non-intubated patients with sensors placed in the nares. However, little is known about the effect of passive O2 delivery [nasal cannula (NC) or high-flow, non-rebreather mask (NRB)] on ETCO2 measurement. Objective: To compare ETCO2 measurements in non-intubated Traumatic Brain Injury (TBI) patients receiving O2 via NC vs. NRB in the field. Methods: A subset of cases from the EPIC EMS TBI Study (NIH-1R01NS071049) were evaluated (4/13-4/18). Non-intubated cases from 5 EMS agencies providing monitor data, including continuous ETCO2. Start and end segments were excluded to remove artifact from initiation (“ramp-up”) or termination of monitoring. Statistics: Wilcoxon rank-sum test, two-sample t-test, and Chi-squared test were used as appropriate. Linear regression compared continuous variables in adjusted analyses (α = 0.05). Results: Included were 151 cases [median age: 52 (range: 9-91; 66% male)]. Of those, 62 (41%) received NCO2 and 89 (59%) via NRB. Patient-level mean ETCO2 was slightly lower in the NC group (mean = 26.9 mmHg; SD 6.7) compared to NRB (mean 30.2; SD 8.1; p=0.007). Differences in the mean were: Unadjusted: 3.3 (95% CI 0.9-5.7); Adjusted 2.7 (0.2-5.2). There were no significant differences in means of the patient-level lowest or highest recorded values. Conclusion: While there was a statistically lower ETCO2 in the NC versus NRB-oxygenated patients, it was around 3 mmHg and, thus, not clinically significant. This is surprising since: 1) the O2 flow rates and 2) the open-air (NC) versus mask (NRB) delivery methods are so dramatically different. Future study is needed to identify the clinical implications of using noninvasive ETCO2 measurement as a tool for monitoring ventilatory status and changes in non-intubated TBI (and other) patients in emergency settings.

Early processes in heme-based CO-sensing proteins

Carbon monoxide has been recognized relatively recently as signaling molecule, and only very few dedicated natural CO sensor proteins have been identified so far. These include in particular heme-based transcription factors: the bacterial sensor proteins CooA and RcoM. In these 6-coordinated systems, exchange between an internal protein residue and CO as a heme ligand in the sensor domain affects the properties of the DNA-binding domain. Using light to dissociate heme-ligand bonds can in principle initiate this switching process. We review the efforts to use this method to investigate early processes in ligand switching and signaling, with an emphasis on the CO-"trappingˮ properties of the heme cavity. These features are unusual for most heme proteins, but common for heme-based CO sensors.

English

The chemical analysis of CaCO3 contents of soils provide information about not only efficiency of soil for supplying plant with nutrients but also identification of factors affecting this efficiency in the soil. The aim of the current experiment was to develop new methods based on sensors and compare with conventional Scheibler method. The CO2 liberated by the action of HCl on CaCO3 content of the soil in a reaction bottle and an accumulation chamber was determined by pressure sensor and CO2 sensor, respectively. The CaCO3 contents of soils were estimated using the regression equation of standard curves. The CaCO3 contents of soils obtained using Scheibler calcimetric, pressure and CO2 sensor methods ranged from 0.20 to 54.74%, 0.25 to 54.10% and 0.55 to 53.05%, respectively. On the basis of linearity of calibration curve and high correlation with Scheibler calcimetric method it can be said that developed pressure and CO2 sensor methods appears to be very useful for quantification of CaCO3 contents of soils. The pressure sensor has provided the opportunity in developing a simple and handy device with an affordable cost to measure CaCO3 contents of soils as accurately as Scheibler calcimeter when compared with CO2 sensor method. Even if there is a good relationship between Scheibler calcimetric method and CO2 sensor method the cost of CO2 sensor method may limit the use in determination of CaCO3 contents of soils. However, CO2 sensor method can be used to monitor CO2 evolved in biochemical process such as respiration and fermentation

Characterization of Disposable Facemasks for COVID-19 Through Colorimetric Analysis

Many aspects of the world population’s daily life have been recently changed by the events following the SARS-COV-2 pandemic outbreak. Among all the consequences, wearing face masks has become a common routine to protect from virus transmission risks. This work presents a simple colorimetric system able to detect the carbon dioxide (CO2) saturation inside a disposable face mask, which is useful to determine the level of wear and degradation and to visually provide indications on its disposal time. The experiments were carried out by wearing a FFP2 face mask externally treated with a phenolphthalein solution and including in its breathing zone a CO2 sensor. Changes in face mask color were recorded by a camera and analyzed with ImageJ. A strong correspondence was found between the high values of CO2 detected by the sensor and the analyzed data. The results are promising and suggest further efforts in developing easy-to-use colorimetric methods as a visual indicator of the life cycle of a disposable face mask.

Fault Injection with Multiple Fault Patterns for Experimental Evaluation of Demand-Controlled Ventilation and Heating Systems.

Heating, ventilation, and air-conditioning (HVAC) systems are large-scale distributed systems that can be subject to multiple faults affecting the electronics, sensors, and actuators, potentially causing high energy consumption, occupant discomfort, degraded indoor air quality and risk to critical infrastructure. Fault injection (FI) is an effective experimental method for the validation and dependability evaluation of such HVAC systems. Today's FI frameworks for HVAC systems are still based on a single fault hypothesis and do not provide insights into dependability in the case of multiple faults. Therefore, this paper presents modeling patterns of numerous faults in HVAC systems based on data from field failure rates and maintenance records. The extended FI framework supports the injection of multiple faults with exact control of the timing, locality, and values in fault-injection vectors. A multi-dimensional fault model is defined, including the probability of the occurrence of different sensor and actuator faults. Comprehensive experimental results provide insights into the system's behavior for concrete example scenarios using patterns of multiple faults. The experimental results serve as a quantitative evaluation of key performance indicators (KPI) such as energy efficiency, air quality, and thermal comfort. For example, combining a CO2 sensor fault with a heater actuator fault increased energy consumption by more than 70%.

Smart Wireless CO2 Sensor Node for IoT Based Strategic Monitoring Tool of The Risk of The Indoor SARS-CoV-2 Airborne Transmission

A close correlation between CO2 concentration and aerosol enables the wide utilization of CO2 concentration as a good representation of Severe Acute Respiratory Syndrome-Coronavirus-2 infection airborne transmission. On the other side, many indoor air-quality monitoring devices have been developed for indoor monitoring applications. However, most of them are multiparameter air-quality sensor systems and tend to consume relatively high power, are relatively large devices, and are fairly expensive; therefore, they not meet the requirement for indoor monitoring applications. This paper presents a smart wireless sensor node that can measure and monitor CO2 concentration levels. The node was designed to meet the requirements of indoor air-quality monitoring applications by considering several factors, such as compact size, low cost, and low power, as well as providing real-time, continuous, reliable, and remote measurement. Furthermore, the commercial off-the-shelf and low-power consumption components are chosen to fit with the low-cost development and reduce energy consumption. Moreover, a low-power algorithm and cloud-based data logger also were applied to minimize the total power consumption. This power strategy was applied as a preliminary development toward an autonomous sensor node. The node has a compact size and consumes low energy for one cycle of CO2 measurement, accompanied by high accuracy with very low measurement error. The experiment result revealed the node could measure and monitor in real-time continuous, reliable, and remote CO2 concentration levels in indoor and outdoor environments. A user interface visualizes CO2 concentration graphically and numerically using the Adafruit platform for easy accessibility over the Internet of Things. The developed node is very promising and suitable for indoor CO2 monitoring applications with the acquired data that could be utilized as an indicator to minimize the risk of indoor Severe Acute Respiratory Syndrome-Coronavirus-2 airborne transmission.

Local detection of gaseous carbon dioxide using optical fibers and fiber tapers of single-cell dimensions

The CO2 amount in the air and its monitoring is widely recognized as an important issue at this time. We are facing excessive CO2 production and global warming affecting not only the environment but also life at the lowest level. A variety of strategies have been designed to reduce atmospheric CO2, but one promising method is based on the application of biologically engineered microorganisms to actively consume a high volume of CO2. The paper presents the design, development, and characterization of two types of sensors for the local detection of gaseous carbon dioxide on microscopic scale. The first one was designed as a fiber optic CO2 measuring cell and the second was based on a CO2 sensitive fiber taper tip. The sensors were based on the absorption of guided visible light in a sensitive polymer layer. The sensors were characterized in the range of 0%−10.6% of carbon dioxide concentration with full linearity. A sensitivity of 0.25 ± 0.05 dB/% and a limit of detection of 7.1·10−3% have been determined for the sensing element. We have experimentally verified the operational reversibility of the CO2 sensing element over time. The time response of the sensor with the finally used sensitive layer of thickness of 600 nm was one second. Both sensors were designed for future application in biological research. Especially the second type of the sensor based on 3 µm silica glass taper tip (diameter corresponding to single-cell proportions) is suitable for laboratory testing of microorganisms and cells that actively consume gaseous carbon dioxide.

Multi-functional resonant micro-sensor for simultaneous magnetic, CO2, and CH4 detection

We present a highly sensitive multi-parameter sensor for magnetic and gas detection. The device is based on an in-plane doubly clamped micro-beam micro-resonator, which is electrothermally heated. It acts as a Lorentz force magnetic sensor of high sensitivity, good linearity, good repeatability, and low hysteresis effect. It also functions as a gas-sensor based on the cooling/heating effect of the micro-beam as demonstrated for carbon dioxide (CO2) and methane (CH4) detection. The CO2/CH4 sensor shows high sensitivity and excellent linearity. In addition, we demonstrate simultaneous magnetic and gas detection by tracking the frequency shift of the first two symmetric and anti-symmetric modes at the same time. We show that the sensitivity of the magnetometer is gas-independent and only depends on the frequency shift of the second mode, which is unaffected by variations of the thermal axial load. For the first time, high sensitivity to magnetic fields, CO2, and CH4 is demonstrated using the same device. The demonstrated simultaneous and highly-sensitive multi-parameter sensing platform using a single resonator is promising for smart environmental and monitoring applications.

Enhanced ZIF-8-enabled colorimetric CO2 sensing through dye-precursor synthesis

The accumulation of carbon dioxide (CO2) within enclosed spaces, along with volatile organic compounds, under certain humidity, temperature, and ventilation conditions is associated with detrimental human health symptoms such as fatigue. Color-based chemical sensing is a promising approach to detect CO2 levels relevant to indoor air quality through producing fast, quantifiable output visible to the naked eye. In a prior work, a colorimetric gas sensor was fabricated through synthesizing the metal-organic framework, ZIF-8, as the adsorbent, followed by post-synthetic mixing with a dye, phenol red (PSP), and primary amine, ethylenediamine (ED). While this sensor (termed PSP-ED/ZIF-8) maintained its structural integrity in atmospheric conditions and exhibited an increasing fuchsia-to-yellow color change with increasing CO2 levels in dry environment, the colorimetric response greatly suffered in the presence of humid CO2. In this work, a significantly improved colorimetric CO2 sensor (referred to as ED/PSP:ZIF-8) is accomplished through directly incorporating phenol red in the ZIF-8 metal and linker precursor solutions and then blending with ethylenediamine. MATLAB-generated color distributions and in-situ ultraviolet-visible (UV-Vis) spectroscopic studies quantitatively demonstrate an enhanced colorimetric gas response of ED/PSP:ZIF-8 compared to that of PSP-ED/ZIF-8 across an important range of CO2 for indoor air quality monitoring (500 – 3500 ppm) and across a range of humidity. The new sensor also exhibits high selectivity to CO2 compared to select volatile organic compounds, such as acetone and ethanol, which contribute to human health symptoms experienced indoors. The enhanced performance is attributed to the proposed incorporation of phenol red within ZIF-8, while maintaining the chemical stability of the MOF.

DFT based comparative study of pristine gCN and gCN-ZnO composite as a sensor for CO and CO2 gases

• Graphitic carbon nitride and ZnO composite (gCN-ZnO) is reported for CO and CO 2 sensing. • CO and CO 2 shows strong interaction with gCN-ZnO composite as compare to pristine gCN. • Adsorption energy for gCN-ZNO is −11.03 eV and −16.61 eV for CO and CO 2 respectively. • The adsorption energy for gCN-ZnO composite are 8 times (CO) and 12 times more (CO 2 ) than pristine gCN. In the present study sensing behavior of pristine gCN and gCN-ZnO composite towards CO and CO 2 gases has been analyzed using DFT. Structural and electronic properties such as adsorption energy, band structure and density of states (DOS) have been investigated. The study reveals that the sensing performance of gCN is enhanced by incorporating ZnO and hence gCN-ZnO composite is a better material for CO and CO 2 gas sensing.

An evaluation of the risk of airborne transmission of COVID-19 on an inter-city train carriage.

Experiments were conducted in an UK inter-city train carriage with the aim of evaluating the risk of infection to the SARS-CoV-2 virus via airborne transmission. The experiments included in-service CO2 measurements and the measurement of salt aerosol concentrations released within the carriage. Computational fluid dynamics simulations of the carriage airflow were also used to visualise the airflow patterns, and the efficacy of the HVAC filter material was tested in a laboratory. Assuming an infectious person is present, the risk of infection for a 1-h train journey was estimated to be 6 times lower than for a full day in a well-ventilated office, or 10-12 times lower than a full day in a poorly ventilated office. While the absolute risk for a typical journey is likely low, in the case where a particularly infectious individual is on-board, there is the potential for a number of secondary infections to occur during a 1-h journey. Every effort should therefore be made to minimize the risk of airborne infection within these carriages. Recommendations are also given for the use of CO2 sensors for the evaluation of the risk of airborne transmission on train carriages.

Flexible sensor patch for continuous carbon dioxide monitoring.

Monitoring and measurement of carbon dioxide (CO2) is critical for many fields. The gold standard CO2 sensor, the Severinghaus electrode, has remained unchanged for decades. In recent years, many other CO2 sensor formats, such as detection based upon pH-sensitive dyes, have been demonstrated, opening the door for relatively simple optical detection schemes. However, a majority of these optochemical sensors require complex sensor preparation steps and are difficult to control and repeatably execute. Here, we report a facile CO2 sensor generation method that suffers from none of the typical fabrication issues. The method described here utilizes polydimethylsiloxane (PDMS) as the flexible sensor matrix and 1-hydroxypyrene-3,6,8-trisulfonate (HPTS), a pH-sensitive dye, as the sensing material. HPTS, a base (NaOH), and glycerol are loaded as dense droplets into a thin PDMS layer which is subsequently cured around the droplet. The fabrication process does not require prior knowledge in chemistry or device fabrication and can be completed as quickly as PDMS cures (∼2 h). We demonstrate the application of this thin-patch sensor for in-line CO2 quantification in cell culture media. To this end, we optimized the sensing composition and quantified CO2 in the range of 0–20 kPa. A standard curve was generated with high fidelity (R 2 = 0.998) along with an analytical resolution of 0.5 kPa (3.7 mm Hg). Additionally, the sensor is fully autoclavable for applications requiring sterility and has a long working lifetime. This flexible, simple-to-manufacture sensor has a myriad of potential applications and represents a new, straightforward means for optical carbon dioxide measurement.

Photo-responsive highly sensitive CO2 gas sensor based on SnO2@CdO heterostructures with DFT calculations

In this work, the photo-responsive behaviour of SnO2 decorated CdO heterostructures-based CO2 sensor was investigated in irradiation of light. The SnO2@CdO heterostructures were synthesized by a hydrothermal process. The crystal structure, surface morphology, composition, and optical properties of as-synthesized materials were examined by XRD, Raman, FESEM, EDS, HRTEM, XPS, and UV-Vis analyses. From the FESEM and TEM analysis, the SnO2 nanospheres decorated on CdO nanocubes can be observed. The SnO2 decorated CdO heterostructure detects the CO2 gas at room temperature. In dark condition, the CO2 sensing of SnO2@CdO heterostructure was poorly observed, although in illumination of visible light the sensing performance were enhanced. The sensor response of SnO2@CdO heterostructure in dark and illumination were found to 4.65 and 10.67 respectively at 1400 ppm of CO2. Whereas for 200 ppm the sensor response was found to 4.20 with 4 and 6 s response and recovery times. Since in illumination of light, the photo-generated carriers are suggested to be responsible for the enhancement of the sensing characteristics of SnO2@CdO heterostructured film. In this work, SnO2 decorated CdO heterostructured-based light-induced CO2 gas sensor has been reported for the first time. Also, the DFT has performed on the optimized SnO2@CdO nanocomposite without and with CO2 interaction. Some electronic parameters like band gap, electron affinity, and ionization potential were calculated for optimized composite and suggested for better understanding of the sensing phenomenon.