Oxygen Sensor Research Articles

UV-enhanced O2 sensing using β-Ga2O3 nanowires at room temperature

Oxygen sensors based on β-Ga2O3 nanowires were prepared by a chemical vapor deposition method and investigated in detail. β-Ga2O3 nanowires grew on sapphire substrate at 1100 °C with Au as a catalyst. The polycrystalline structure was confirmed according to the X-ray diffraction (XRD) patterns. Scanning electron microscope (SEM) images revealed the average diameter of the nanowires was 150 nm. The ratio of Ga to O was 0.765 according to energy dispersive spectroscopy (EDS) results. Photoluminescence emissions at 445 and 484 nm originated from oxygen vacancies and gallium-oxygen vacancy pairs. Both EDS results and photoluminescence revealed intrinsic oxygen vacancies in β-Ga2O3 nanowires. We coated the β-Ga2O3 nanowires on an interdigitated electrode to fabricated an oxygen sensor. Under ultraviolet light irradiation, at room temperature, the sensor’s response rise time and recovery time were 1034 s and 1283 s to 600 ppm oxygen, those were 1290 s and 1709 s to 1200 ppm oxygen. The mechanism of oxygen sensing was discussed.

Design and Preparation of Lifetime-Based Dual Fluorescent/Phosphorescent Sensor of pH and Oxygen and its Exploration in Model Physiological Solutions and Cells.

In the present report, a novel dual pH-O2 sensor based on covalent conjugate of rhodamine 6G and cyclometalated iridium complex with poly(vinylpyrrolidone-block-vinyltetrazole) copolymer is reported. In model physiological solutions the sensor chromophores display independent phosphorescent and fluorescent lifetime responses onto variations in oxygen concentration and pH, respectively. Colocalization studies on Chinese hamster ovary cells demonstrate the preferential localization in endosomes and lysosomes. The fluorescent lifetime imaging microscopy-phosphorescent lifetime imaging microscopy (FLIM-PLIM) experiments show that the phosphorescent O2 sensor provides unambiguous information onto hypoxia versus normoxia cell status as well as semi-quantitative data on the oxygen concentration in cells in between these two states. However, the results of FLIM measurements indicate that dynamic lifetime interval of the sensor (≈0.5ns between pH values 5.0 and 8.0) is insufficient even for qualitative estimation of pH in living cells because half-width of lifetime distribution in the studied samples is higher than the sensor dynamic interval. Nevertheless, the variations in rhodamine emission intensity are much higher and allow rough discrimination of acidic and neutral cell conditions. Thus, the results of this study indicate that the suggested approach to the design of dual pH-O2 sensors makes possible to prepare the biocompatible and water-soluble conjugate with fast cellular uptake.

Research Progress of Optical Dissolved Oxygen Sensors: A Review

Research Progress of Optical Dissolved Oxygen Sensors: A Review

Real-Time Monitoring of Oxygen-Consumption Rate in Mouse Liver Slices Incubated in Organ-on-a-Chip Devices.

We developed an organ-on-a-chip (OOC) based on precision-cut liver slices to assess liver function in real-time, both in health and disease, in a controlled and noninvasive manner. We achieved this by integrating fiber-optic-based oxygen sensors before and after the microchamber in which a liver slice was incubated under flow, to measure oxygen concentrations in the medium in real time. We first demonstrated that the basal oxygen consumption rate (OCR) of liver slices is a reliable indicator of liver slice viability. By monitoring basal OCR (2.9-5.7 pmol O2/min/μg protein) in incubation medium, we found that it correlated well to cellular adenosine triphosphate (ATP) content (3.0-7.9 pmol/μg protein) (r = 0.82, p < 0.0001). Second, we induced a diseased state in liver slices by targeting the mitochondria, as they play a critical role in liver function and disease. We exposed the liver slices to succinate in abundance (40 mM) for short periods (1 h) to rapidly boost mitochondrial OCR. Two successive treatments of succinate increased the OCR of liver slices by 1.5 pmol/min/μg each time. However, between treatments, the liver slice OCR did not return to its basal OCR, instead decreasing drastically by 60-70%, suggesting succinate toxicity. We confirmed this with ATP analysis (1.0 pmol/μg protein) and hematoxylin and eosin staining, which showed tissue necrosis and apoptosis. Our system could be an advantageous model for future studies assessing liver (patho)physiology in response to potentially toxic drugs or lifestyle-related liver diseases.

Realtime RONS monitoring of cold plasma-activated aqueous media based on time-resolved phosphorescence spectroscopy

Besides many efforts on the detection and quantification of reactive oxygen and nitrogen species (RONSs) in the aqueous media activated by the cold atmospheric plasma, to get a better insight into the dominant mechanism and reactive species in medical applications, a challenge still remains in monitoring the real-time evaluation of them. To this end, in the present work, relying on the photonic technology based on the time-resolved phosphorescence spectroscopy, real-time tracking of RONSs concentration in treated aqueous media is achieved by following the dissolved oxygen (DO) production/consumption. Using a photonic-based dissolved oxygen sensor, the dependence of real-time RONS concentration evaluation of plasma activated medium on plasma nozzle distance, non-thermal plasma jet exposure time, various culture media, and presence of cells is investigated. Analyzing the results, the activation parameters including the time of reaching maximum RONS concentration after treatment and defined activation parameter \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon\\:$$\\end{document} of the treated media for each case is measured and compared together. Moreover, employing the scavengers related to two involved ROSs, the dominant chemical reactions as well as ROS contributed in the DMEM medium is determined. As a promising result, the obtained correlation between the real-time DO level and viability and toxicity of the cancer cells, MCF-7 breast cancer cells, could enable us to exploit the present photonic setup as an alternative technique for the biological assessment.

In Vivo Lifetime Imaging of the Internal O2 Dynamics in Corals with near-Infrared-Emitting Sensor Nanoparticles.

Mapping of O2 with luminescent sensors within intact animals is challenging due to attenuation of excitation and emission light caused by tissue absorption and scattering as well as interfering background fluorescence. Here we show the application of luminescent O2 sensor nanoparticles (∼50-70 nm) composed of the O2 indicator platinum(II) tetra(4-fluoro)phenyltetrabenzoporphyrin (PtTPTBPF) immobilized in poly(methyl methacrylate-co-methacrylic acid) (PMMA-MA). We injected the sensor nanoparticles into the gastrovascular system of intact colony fractions of reef-building tropical corals that harbor photosynthetic microalgae in their tissues. The sensor nanoparticles are excited by red LED light (617 nm) and emit in the near-infrared (780 nm), which enhances the transmission of excitation and emission light through biological materials. This enabled us to map the internal O2 concentration via time-domain luminescence lifetime imaging through the outer tissue layers across several coral polyps in flowing seawater. After injection, nanoparticles dispersed within the coral tissue for several hours. While luminescence intensity imaging showed some local aggregation of sensor particles, lifetime imaging showed a more homogeneous O2 distribution across a larger area of the coral colony. Local stimulation of symbiont photosynthesis in corals induced oxygenation of illuminated tissue areas and formation of lateral O2 gradients toward surrounding respiring tissues, which were dissipated rapidly after the onset of darkness. Such measurements are key to improving our understanding of how corals regulate their internal chemical microenvironment and metabolic activity, and how they are affected by environmental stress such as ocean warming, acidification, and deoxygenation. Our experimental approach can also be adapted for in vivo O2 imaging in other natural systems such as biofilms, plant and animal tissues, as well as in organoids and other cell constructs, where imaging internal O2 conditions are relevant and challenging due to high optical density and background fluorescence.

Internet of Things Based Water Quality Control System

Fish incubation, which involves the hatching of fish eggs, represents the process of embryogenesis until the embryo emerges from its protective shell. This intricate developmental journey is influenced by a combination of internal and external factors. External factors can be influenced by water quality that is not suitable for hatching fish eggs. Water quality, which includes temperature, dissolved oxygen, light intensity, salinity, and pH, is an important and limiting factor for living creatures that live in water, including chemical, biological, and physical factors. Poor water quality can prevent fish eggs from hatching and even cause death. The primary objective here is the creation of an Internet of Things (IoT)-based system designed for controlling water quality during fish incubation. This system is intended to aid fish farmers in effectively control the environmental conditions within their incubation ponds. The method used in designing IoT device is research and development, and it uses the Arduino Mega microcontroller as the main device to run pH sensors, turbidity sensors, oxygen sensors, temperature sensors, and relay modules. Water Quality Control System The fish incubation was successful. The average time needed to change the water temperature from 28.5 to 29 degrees Celsius is 4 minutes and 7 seconds; change the dissolved oxygen level from 11 to 11.5 is 3 minutes and 33 seconds; change the pH value of the water from 6.9 to 7.1; and maintain turbidity below 5 with an average time of 5 minutes and 58 seconds. Controlling water quality can speed up the fish egg incubation process for 8 hours.

Insight into insulation degradation mechanism of Al2O3 involved with positive and negative defects

Al2O3 with the desired electrical insulating properties and thermal shock resistivity has been extensively applied in the field of solid oxide fuel cells and oxygen sensors. However, degradation of the insulating Al2O3 layer is an intractable issue in practical applications. In this study, different point defect structures of Al2O3 were realized with the substitutional doping effect of ZrO2 and MgO. The MgO dopant provides positively charged oxygen vacancies, whereas the ZrO2 dopant tends to trigger negatively charged vacancy formation at Al3+ sites. The oxygen vacancy concentration of Al2O3 exhibits the following trend: MgO-doped Al2O3 > Al2O3 > ZrO2-doped Al2O3. Furthermore, the densification morphology, insulating properties, and oxygen vacancy migration of Al2O3 have been confirmed to be largely affected by the extrinsic factors. This study indicates that oxygen vacancy migration depends on the applied electric field at high temperatures. As the voltage and temperature increase, oxygen vacancy migration shows obvious electric-field-dependent characteristics, and its aggregation macroscopically shows hole defects. The defect position of Al2O3 is nonstoichiometric Al2O3-x with poor crystallinity. Therefore, it is believed that the oxygen vacancy migration triggered by the second phase directly determines the insulation performance and causes the degradation of Al2O3 materials.

A portable multi-taxa phenotyping device to retrieve physiological performance traits

Organismal phenotyping to identify fitness traits is transforming our understanding of adaptive responses and ecological interactions of species within changing environments. Here we present a portable Multi-Taxa Phenotyping (MTP) system that can retrieve a suite of metabolic and photophysiological parameter across light, temperature, and/or chemical gradients, using real time bio-optical (oxygen and chlorophyll a fluorescence) measurements. The MTP system integrates three well-established technologies for the first time: an imaging Pulse Amplitude Modulated (PAM) chlorophyll a fluorometer, custom-designed well plates equipped with optical oxygen sensors, and a thermocycler. We demonstrate the ability of the MTP system to distinguish phenotypic performance characteristics of diverse aquatic taxa spanning corals, mangroves and algae based on metabolic parameters and Photosystem II dynamics, in a high-throughput capacity and accounting for interactions of different environmental gradients on performance. Extracted metrics from the MTP system can not only provide information on the performance of aquatic taxa exposed to differing environmental gradients, but also provide predicted phenotypic responses of key aquatic organisms to environmental change. Further work validating how rapid phenotyping tools such as the MTP system predict phenotypic responses to long term environmental changes in situ are urgently required to best inform how these tools can support management efforts.

Baicalein induces apoptosis by targeting ribosomes in Candida auris.

The emergence of the "super fungus" Candida auris poses a significant threat to human health, given its multidrug resistance and high mortality rates. Therefore, developing a new antifungal strategy is necessary. Our previous research showed that Baicalein (BE), a key bioactive compound from the dried root of the perennial herb Scutellaria baicalensis Georgi, has strong fungistatic properties against C. auris. Nevertheless, the antifungal activity of BE against C. auris and its mechanism of action requires further investigation. In this study, we explored how BE affects this fungus using various techniques, including scanning electron microscopy (SEM), Annexin V-FITC apoptosis detection, CaspACE FITC-VAD-FMK In Situ Marker, reactive oxygen species (ROS) assay, singlet oxygen sensor green (SOSG) fluorescent probe, enhanced mitochondrial membrane potential (MMP) assay with JC-1, DAPI staining, TUNEL assay and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Our findings revealed that BE induced several apoptotic features, including phosphatidylserine (PS) externalization, metacaspase activation, nuclear condensation and DNA fragmentation. BE also increased intracellular ROS levels and altered mitochondrial functions. Additionally, transcriptomic analysis and RT-qPCR validation indicated that BE may induce apoptosis in C. auris by affecting ribosome-related pathways, suggesting that ribosomes could be new targets for antifungal agents, in addition to cell walls, membranes, and DNA. This study emphasizes the antifungal activity and mechanism of BE against C. auris, offering a promising treatment strategy for C. auris infection.

O2-Sensitive Inks for Measuring Total (Aerobic) Viable Count Using Micro-Respirometry

The popular method of micro-respirometry (μR) for measuring total viable (aerobic) count (TVC) utilises luminescence-based O2 sensors that are difficult to fabricate and therefore expensive. A simple method is described for making inexpensive, ink-based potential substitutes that utilise the same O2-sensitive dyes. The sensitivity of such inks is readily increased by using dyes with a long lifetime in the absence of O2, τo, and/or an ink resin/polymer with a high O2 permeability, Pm(O2). Response modelling of the μR-based TVC system and subsequent testing using a range of O2 sensors of different sensitivity show that there is little to be gained by making the O2 sensor either very sensitive or insensitive, and that the best O2 sensors are dyes such as Pt(II) tetraphenyltetrabenzoporphyrin (PtBP), with τo = ca. 40–50 μs. Further work shows that a simple-to-make PtBP ink can be used as a direct replacement for the expensive O2 sensor used in commercial instruments for measuring TVC based on μR. In addition, the PtBP can be replaced by an even less expensive O2-sensitive dye, Pt(II) meso-tetra(pentafluorophenyl)porphyrin (PtTFPP). The potential use of inexpensive O2-sensitive inks as an alternative to any expensive commercial counterpart based on the same O2-sensitive dye is discussed briefly.

In-situ Observation of the Environmental Resistance of Pure Iron Using Hydrogen and Oxygen Sensors in the Environment Simulating Hydrogen Combustion

In-situ Observation of the Environmental Resistance of Pure Iron Using Hydrogen and Oxygen Sensors in the Environment Simulating Hydrogen Combustion

Evaluation of Environmental Behavior of Pure Iron in an Ammonia Atmosphere by Using a Hydrogen and an Oxygen Sensor

Evaluation of Environmental Behavior of Pure Iron in an Ammonia Atmosphere by Using a Hydrogen and an Oxygen Sensor

Multimaterial Digital-Light Processing of Metal-Organic Framework (MOF) Composites: A Versatile Tool for the Rapid Microfabrication of MOF-Based Devices.

Patterning Metal-Organic Frameworks (MOFs) is essential for their use in sensing, electronics, photonics, and encryption technologies. However, current lithography methods are limited in their ability to pattern more than two MOFs, hindering the potential for creating advanced multifunctional surfaces. Additionally, balancing design flexibility, simplicity, and cost often results in compromises. This study addresses these challenges by combining Digital-Light Processing (DLP) with a capillary-assisted stop-flow system to enable multimaterial MOF patterning. It demonstrates the desktop fabrication of multiplexed arbitrary micropatterns across cm-scale areas while preserving the MOF's pore accessibility. The ink, consisting of a MOF crystal suspension in a low volatile solvent, a mixture of high molecular weight oligomers, and a photoinitiator, is confined by capillarity in the DLP projection area and quickly exchanged using syringe pumps. The versatility of this method is demonstrated by the direct printing of a ZIF-8-based luminescent oxygen sensor, a 5-component dynamic information concealment method, and a PCN-224-based colorimetric sensor for amines, covering disparate pore and analyte sizes. The multi-MOF capabilities, simplicity, and accessibility of this strategy pave the way for the facile exploration of MOF materials across a wide range of applications, with the potential to significantly accelerate the design-to-application cycle of MOF-based devices.

Catalysis of oxygen reduction reaction by iron porphyrin and its sensing application

Hemin, or iron porphyrin, serves as a non-noble metal catalyst for the oxygen reduction reaction (ORR). The stability of hemin is maintained in high salt concentrations, functioning as an ORR redox catalyst in the aqueous phase. Hemin facilitates the development of an oxygen sensor that transitions the ORR mechanism from a 2-electron to a more efficient 4-electron process. This sensor demonstrates excellent reproducibility (RSD<5%), with a wide linear range of 38.9–613 μM, a sensitivity of 0.136 ± 0.003 μA μM−1, and a limit of detection (3SB/m) of 11.8 μM.

Singlet oxygen detection in vivo is hindered by nonspecific SOSG staining

Singlet oxygen is considered an important cell damaging agent due to its propensity to react with organic compounds. This drives the interest in developing methods for determination of 1O2. Simplicity of application and high sensitivity makes fluorescent probes a popular choice for in vivo 1O2 detection. Despite its proclaimed cell-impermeability, the commercially available Singlet Oxygen Sensor Green (SOSG) is widely applied to support assertions of 1O2 involvement in cell and tissue damage. Our investigation, however, demonstrate that different microbial species and cancer cells become fluorescent when exposed to SOSG under conditions which exclude generation of 1O2. Cells, permeabilized with chlorhexidine or by heat exposure under anaerobic conditions, exhibited SOSG fluorescence. Permeabilized cells could be stained with SOSG even 24 h post-permeabilization. Since SOSG is cell impermeable, the main factor that led to fluorescent staining was plasma membrane damage. Spectral analyses of different batches of SOSG revealed that SOSG endoperoxide (SOSG-EP) did not increase even after prolonged storage under the recommended conditions. The commercial preparations of SOSG, however, were not SOSG-EP free, which can produce erroneous results when SOSG staining is used as a proof of singlet oxygen production in vivo.

Smart Wearable Device for Enhancing Safety and Efficiency of Coal Miners

The task of ensuring worker safety in underground coal mines has never been simple. It has always been challenging to ensure worker safety in underground coal mines. Coal miners are seriously injured or killed as a result of numerous fatal and non-fatal accidents all over the world. Accidents occur as a result of lack of monitoring of mining areas and failure to implement proper safety measures. In this review, the coal miner's smart wearable safety device is implemented. A smart wearable safety device that will monitor the miner's health and provides precautionary measures for the miner's safety has been developed with the advent of the Industrial Internet of Things (IIoT). Integrating smart wearable safety devices with various health sensors such as a pulse rate sensor, temperature sensor, blood oxygen sensor, gas sensor, and camera, and then connecting it to Node MCU, and the internet enhances the safety of coal miners. Sensors constantly transmit sensor data to the cloud, and if an unusual situation arises, it notifies the responsible person in the control room as well as the miners. Since deep underground mining is especially susceptible to toxic gases, low levels of oxygen, and hazardous gases, the MQ gas sensor family can detect them. The proposed system is primarily used to improve working conditions inside coal mines and to ensure workers' safety.

Effects of oxygen volume fraction, temperature and diffusion layer thickness on the sensing characteristics of limiting current oxygen sensor

Oxygen sensors are prepared by Pt paddle bonding method with dense diffusion barrier of short-circuited yttria-stabilized zirconia (YSZ) solid electrolyte. Different from the previous normal diffusion and Knudsen diffusion mechanisms, the limiting current equation of this type oxygen sensor is derived based on the diffusion of oxygen ions in the dense diffusion barrier. The effects of oxygen volume fraction, temperature and diffusion layer thickness on the limiting current density are investigated. The relationship between the physical quantities in the experiment is consistent with the derived equation.

Thermodynamics of gaseous strontium and calcium cerates studied by Knudsen effusion mass spectrometry and estimation of relative electron ionization cross-section for CeO2(g).

Ceria-based systems are of great interest because of their unique properties. Such systems may be used as anode materials for SOFCs or in oxygen sensors. Theexploitation of these materials often requires high temperatures. In such conditions, the partial or complete evaporation of materials is possible. Therefore, knowledge of the values of partial pressures and thermodynamic properties is essential to predict and/or prevent possible consequences and accidents. Knudsen effusion mass spectrometry was used to determine partial pressures of vapor species over the SrO-CeO2 and CaO-CeO2 systems. Measurements of partial pressures were performed with a MS-1301 mass spectrometer. Vaporization was carried out using molybdenum or tungsten effusion cells. A theoretical study of gaseous strontium and calcium cerates was performed by several quantum chemical methods: density functional theory (DFT) M06, DFT PBE0, and MP2. The minimum value of relative electron ionization cross-section for CeO2 was estimated. In the temperature range of 2218-2249 K above the SrO-CeO2 system and of 2128-2208 K above the CaO-CeO2 system, gaseous M, MO, MO, CeO2, O, O2 and MCeO3 (M = Sr, Ca) were found. Energetically favorable structures of gaseous SrCeO3 and CaCeO3 were found, and vibrational frequencies were evaluated in the "rigid rotor-harmonic oscillator" approximation. On the basis of the equilibrium constants of gaseous reaction MO + CeO2 = MCeO3, the standard formation enthalpy of gaseous SrCeO3 (-913 ± 26 kJ/mol) and of gaseous CaCeO3 (-917 ± 26 kJ/mol) at 298 K were determined. The estimated value of relative electron ionization cross-section for CeO2 is in agreement with the general rule applicable for dioxides. The stability of SrCeO3 and CaCeO3 gaseous species was confirmed by KEMS. Gas-phase reactions involving gaseous SrO (CaO) and CeO2 with gaseous SrCeO3(CaCeO3) were studied. Enthalpy of formation reaction of gaseous SrCeO3(CaCeO3) from gaseous SrO (CaO) were evaluated theoretically, and the obtained value is in agreement with the experimental one.

Thin Film Semiconductor Metal Oxide Oxygen Sensors: Limitations, Challenges, and Future Progress

Among oxygen sensors, types such as polymer-, ceramic-, or carbon-based ones may be distinguished. Particular interest in semiconductor metal oxide (SMO) sensors has recently been observed. This is due to their easy fabrication process, high control over the final product (dopants, posttreatment, etc.), and high concentration of oxygen vacancies, by which they show significant changes in electrical properties when exposed to analyte. In this review, different types of sensors are described and categorized. Importantly, their limitations, challenges and principles of sensing mechanism are also discussed, wherein attention is primarily paid to semiconductor metal oxide (SMO) oxygen sensors. This comprehensive review provides an in-depth analysis of the existing literature on planar SMO oxygen sensors, focusing on various materials, fabrication techniques, and sensing mechanisms. It also critically assesses the challenges and limitations in current research, offering insights into future directions for developing highly efficient and reliable sensors. Currently, most oxygen resistive sensors are a few micrometers thick and operate at high temperatures, which leads to high power consumption. To highlight importance of this topic, a market overview is also presented.