Fiber Optic Oxygen Sensor Research Articles

Enhanced optical oxygen sensing property based on Pt(II) complex and metal-coated silica nanoparticles embedded in sol–gel matrix

This paper presents a metal enhanced optical oxygen sensor that comprises an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and silver metal-coated nanoparticles embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio IN2/IO2, where IN2 and IO2 represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results show that the oxygen sensor has a sensitivity of 167. The response time was 2.6s when switching from pure nitrogen to pure oxygen, and 36s when switching in the reverse direction. The experimental results show that compared to oxygen sensor based on Pt(II) complex immobilized in the sol–gel matrix, the proposed optical fiber oxygen sensor has higher sensitivity. In addition to the increased surface area per unit mass of the sensing surface, the metal-coated silica nanoparticles also increase the sensitivity because the metal-enhanced fluorescence. The proposed optical sensor has the advantages of low cost and high sensitivity for oxygen monitoring using a cheap LED as a light source.

Tapered polymer optical fiber oxygen sensor based on fluorescence-quenching of an embedded fluorophore

We have developed a new method of processing fiber optic oxygen gas sensors based on fluorescent quenching by directly and locally incorporating the fluorophore into the optical fiber that is going to serve as waveguide. This procedure circumvents the preparation steps of the sensing polymer matrix and the later coating of the optical fiber. The sensor combines a side illumination technique with the localized tapering of the fiber, where the fluorophore is placed, to increase the signal to noise ratio. We have fully characterized it and our sensor performance is comparable in sensitivity and response time to those based on polymer matrix fluorophore embedding. We also have studied the addition of a second fluorophore unresponsive to oxygen to serve as a reference for the stability of the excitation source.

Optical fiber oxygen sensor based on Pd(II) complex embedded in sol–gel matrix

A simple, low-cost technique for fabrication of high performance optical fiber oxygen sensor is described. An organically modified silicate (ORMOSIL) as a matrix for the fabrication of oxygen sensing film was produced. The technique is based on coating the end of an optical fiber with ormosil composite xerogel film sequestered with luminophore palladium (II) meso-tetrakis(pentafluorophenyl)porphyrin (PdTFPP) prepared by a sol–gel process. The composite xerogel studied is n-propyltrimethoxysilane (n-propyl-TriMOS)/tetraethylorthosilane (TEOS)/n-Octyltriethoxysilane (Octyl-triEOS). Result shows that, expect for PdTFPP-doped n-propyl-TriMOS/TEOS/Octyl-triEOS composite xerogel shows a high sensitivity and linear Stern–Volmer relationship which indicates the homogenous environment of the luminophore. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio IN2/IO2, where IN2 and IO2 represent the detected phosphorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental result reveals that the PdTFPP-doped n-propyl-TriMOS/TEOS/Octyl-triEOS oxygen sensor has sensitivity of IN2/I100O2=263.

A flowing liquid test system for assessing the linearity and time-response of rapid fibre optic oxygen partial pressure sensors

The development of a methodology for testing the time response, linearity and performance characteristics of ultra fast fibre optic oxygen sensors in the liquid phase is presented. Two standard medical paediatric oxygenators are arranged to provide two independent extracorporeal circuits. Flow from either circuit can be diverted over the sensor under test by means of a system of rapid cross-over solenoid valves exposing the sensor to an abrupt change in oxygen partial pressure, PO2. The system is also capable of testing the oxygen sensor responses to changes in temperature, carbon dioxide partial pressure (PCO2) and pH in situ. Results are presented for a miniature fibre optic oxygen sensor constructed in-house with a response time∼50ms and a commercial fibre optic sensor (Ocean Optics Foxy), when tested in flowing saline and stored blood.

Optical Fiber Oxygen Sensor Based on Ru (II) Complex and Porous Silica Nanoparticles Embedded in Sol-Gel Matrix

This paper presents a high-sensitivity oxygen sensor that comprises an optical fibre coated at one end with tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II) ([Ru (dpp)3]2+) and porous silica nanoparticles embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio IN2/IO2, where IN2 and IO2 represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results show that the oxygen sensor has a sensitivity of 26. The experimental results show that compared to oxygen sensor based on Ru (II) complex immobilized in the sol-gel matrix, the proposed optical fibre oxygen sensor has higher sensitivity. In addition to the increased surface area per unit mass of the sensing surface, the porous silica nanoparticles increase the sensitivity because a substantial number of aerial oxygen molecules penetrate the porous silica shell. The proposed optical sensor has the advantages of easy fabrication, low cost, fast response and high sensitivity for oxygen monitoring using a cheap LED as a light source.

The multi fiber optode (MuFO): A novel system for simultaneous analysis of multiple fiber optic oxygen sensors

A novel system for simultaneous operation of multiple fiber optic oxygen sensors (optodes) is described and characterized. The system is based on an array of one hundred several meter long freely positionable polymer optical fibers with an oxygen sensitive luminophore immobilized at the sensing end of each fiber. The opposite ends of the fiber optodes are fixed in a 10×10 matrix and placed in front of a CCD camera and a LED-light source. Oxygen measurements are conducted by simultaneous excitation of all optodes with the LEDs followed by simultaneous lifetime imaging of the one hundred fiber optodes with the camera. Automated digital image analysis allows for calculation of the luminescence lifetime of each fiber optode individually, which can be converted into oxygen partial pressures. The multi fiber optode (MuFO) system had an overall accuracy of 1% when tested at fixed temperatures and 5% when calibrated over a temperature range from 2 to 32°C and an average 90% response time of 16s. The system had an average precision of 0.2% air saturation and an average detection limit of 0.1% air saturation.The MuFO system can be adapted for trace level oxygen measurements and for other analytes such as pH, CO2, temperature and heavy metal ions by using different luminophore coatings and imaging approaches.

A Cylindrical-Core Fiber-Optic Oxygen Sensor Based on Fluorescence Quenching of a Platinum Complex Immobilized in a Polymer Matrix

A miniature (200 μm in diameter) cylindrical-core fiber-optic oxygen sensor has been developed for measuring rapid change in oxygen partial pressure (pO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The fiber-optic sensing element is based on a cylindrical-core waveguide structure formed by coating a thin medical grade polymer sensing film that contains immobilized Pt(II) complexes on silica optical fiber. The performance such as sensitivity and time response of the fiber-optic oxygen sensors were evaluated using luminescence intensity measurement. To determine accurately the response time of the fiber optic oxygen sensors, a test chamber was used to provide rapid changes in the partial pressure of oxygen. The result showed that the time response (time-constant, τ) of this cylindrical-core fiber optic oxygen sensor is less than 50 ms. To our knowledge, this is the fastest such sensor of this size covering the full dynamic range of pO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> from 0 to 100 kPa.

Optical oxygen sensing properties of Ru(II) complex and porous silica nanoparticles embedded in solgel matrix

This paper presents a high-sensitivity oxygen sensor that comprises an optical fiber coated at one end with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) ([Ru(dpp)3]2+) and porous silica nanoparticles embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio IN2 /IO2 , where IN2 and IO2 represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results show that the oxygen sensor has a sensitivity of 26. The response time was 2 s when switching from pure nitrogen to pure oxygen, and 7.7 s when switching in the reverse direction. The experimental results show that compared to an oxygen sensor based on Ru(II) complex immobilized in the solgel matrix, the proposed optical fiber oxygen sensor has higher sensitivity. In addition to the increased surface area per unit mass of the sensing surface, the porous silica nanoparticles increase the sensitivity because a substantial number of aerial oxygen molecules penetrate the porous silica shell. The proposed optical sensor has the advantages of easy fabrication, low cost, fast response, and high sensitivity for oxygen monitoring using a cheap LED as a light source.

Abundance, oxygen consumption and carbon demand of brittle stars in Young Sound and the NE Greenland shelf

We used sea floor photography to estimate brittle star abundance in Young Sound, NE Greenland and the adjacent shelf. From photos covering a total area of 78 m 2 and spanning a depth range from 20 to 310 m we found maximum average densities of >400 ind. m -2 at 40 to 80 m depth. Ophiocten sericeum was the dominant species. However, gradual changes in species and size composition with depth were observed. Average biomass was ~600 mg C m -2 with highest values at sites dominated by the large Ophiopleura borealis (up to 2190 mg C m -2 ). We measured average individual oxygen consumption of 3 dominant species at ambient temperature (-1.0°C) and salinity in incubation chambers using a fiber-optic oxygen sensor enabling continuous measurements. We established a general relation between individual disc diameter (D, mm) and oxygen consumption (R, µmol O2 h -1 ind. -1 ): R = 6.0 × 10 -4 × D 2.60 (R 2 = 0.96, n = 33), which facilitated the estimation of com- munity respiration and carbon demand from sea floor images. Peaks in total carbon demand were found in the fjord at 30 m (14 mg C m -2 d -1 ) and 160 m depth (13 mg C m -2 d -1 ), resulting from high densities of medium sized (10 to 15 mm disc diameter) O. sericeum, and the presence of the very large (20 to 35 mm disc diameter) O. borealis, respectively. At the other stations values ranged from 0.5 to 8 mg C m -2 d -1 . Overall, our results demonstrate that brittle stars, despite very low individual energy requirements, contribute significantly to marine carbon cycling in Young Sound as well as in the shelf areas off NE Greenland.

Highly sensitive and linear calibration optical fiber oxygen sensor based on Pt(II) complex embedded in sol–gel matrix

A simple, low-cost technique for fabrication of high performance optical fiber oxygen sensor is described. An organically modified silicate (ORMOSIL) as a matrix for the fabrication of oxygen sensing film was produced. The technique is based on coating the end of an optical fiber with ORMOSIL composite xerogel films film sequestered with luminophore platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) prepared by a sol–gel process. The composite xerogels studied are 3,3,3-trifluoropropyltrimethoxysliane (TFP-TriMOS) or n-propyltrimethoxysilane ( n-propyl-TriMOS)/tetraethylorthosilane (TEOS)/ n-octyltriethoxysilane (Octyl-triEOS). Results show that, expect for PtTFPP-doped TFP-TriMOS or n-propyl-TriMOS/TEOS/Octyl-triEOS composite xerogels show the high sensitivity and linear Stern–Volmer relationship which indicate the homogenous environment of the luminophore. The sensitivities of the two oxygen sensors are quantified in terms of the ratio I N2/ I O2, where I N2 and I O2 represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results reveal that the PtTFPP-doped TFP-TriMOS/TEOS/Octyl-triEOS and n-propyl-TriMOS/TEOS/Octyl-triEOS oxygen sensors have sensitivities of 101 and 155, respectively. The experimental results confirm that the current oxygen sensors exhibit the linear Stern–Volmer plots and high-sensitive based on the oxygen indicator embedded in TFP-TriMOS or n-propyl-TriMOS/TEOS/Octyl-triEOS composite xerogels.

Development of a durable fiber-optic oxygen sensor for harsh underground environments

This paper focuses on effects of protection with a silicone resin to develop a fiber-optic oxygen sensor with long-term stability and durability in harsh underground environments. Ruthenium (II) complexes were used as oxygen-sensing compounds. A uniform composite film composed of silicone resin and the Ru complex was prepared with spin coating technique. A comparison of dissolved-oxygen (DO) sensitivity between the composite film and a Ru complex film was made by exposing to hot water (80 °C). The result of the accelerated degradation test showed that sensitivity of the Ru complex film was stable; meanwhile that of the composite film increased with exposure time in a short period. In order to improve stability, the Ru complex film overcoated with silicone resin was prepared. Differences in sensitivity for saturated DO (8.5 ppm) between with and without the silicone resin overcoating on the Ru complex film were investigated by exposing to the hot water and simulated underground water. These results revealed that the sensitivities and response times of the overcoated films were stable and slow, respectively, compared to those of non-overcoated films. Then, optodes were evaluated for effects of the overcoating on sensing properties by exposing to 100 vol.% oxygen gas. The experiment showed that: (1) the response time was significantly influenced by the thickness of the overcoating; and (2) response speed of the overcoated optode was slow by a factor of about 35 compared to that of the non-overcoated. We concluded that the overcoating was effective in the application to mid- and long-term oxygen monitoring in the harsh environments.

Continuous Real-time Viability Assessment of Kidneys Based on Oxygen Consumption

Background Current ex vivo quality assessment of donor kidneys is limited to vascular resistance measurements and histological analysis. New techniques for the assessment of organ quality before transplantation may further improve clinical outcomes while expanding the depleted deceased-donor pool. We propose the measurement of whole organ oxygen consumption rate (WOOCR) as a method to assess the quality of kidneys in real time before transplantation. Methods Five porcine kidneys were procured using a donation after cardiac death (DCD) model. The renal artery and renal vein were cannulated and the kidney connected to a custom-made hypothermic machine perfusion (HMP) system equipped with an inline oxygenator and fiber-optic oxygen sensors. Kidneys were perfused at 8°C, and the perfusion parameters and partial oxygen pressures (pO 2) were measured to calculate WOOCR. Results Without an inline oxygenator, the pO 2 of the perfusion solution at the arterial inlet and venous outlet diminished to near 0 within minutes. However, once adequate oxygenation was provided, a significant pO 2 difference was observed and used to calculate the WOOCR. The WOOCR was consistently measured from presumably healthy kidneys, and results suggest that it can be used to differentiate between healthy and purposely damaged organs. Conclusions Custom-made HMP systems equipped with an oxygenator and inline oxygen sensors can be applied for WOOCR measurements. We suggest that WOOCR is a promising approach for the real-time quality assessment of kidneys and other organs during preservation before transplantation.

Enhanced oxygen sensing properties of Pt(II) complex and dye entrapped core–shell silica nanoparticles embedded in sol–gel matrix

This paper presents a highly sensitive oxygen sensor that comprises an optical fiber coated at one end with platinum(II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core–shell silica nanoparticles embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio I 0/ I 100, where I 0 and I 100 represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results show that the oxygen sensor has a sensitivity ( I 0/ I 100) of 166. The response time was 1.3 s when switching from pure nitrogen to pure oxygen, and 18.6 s when switching in the reverse direction. The experimental results show that compared to oxygen sensors based on PtTFPP, PtOEP, or Ru(dpp) 3 2+ dyes, the proposed optical fiber oxygen sensor has the highest sensitivity. In addition to the increased surface area per unit mass of the sensing surface, the dye entrapped in the core of silica nanoparticles also increases the sensitivity because a substantial number of aerial oxygen molecules penetrate the porous silica shell. The dye entrapped core–shell nanoparticles is more prone to oxygen quenching.

Design of a test system for fast time response fibre optic oxygen sensors

A test system has been developed that can be used to calibrate and determine the time response, linearity and temperature sensitivity of a fibre optic oxygen sensor. The simple system obviates the need for precision gas standards and the requirement to generate a true square wave step response, which is seldom achievable. The sensor is mounted in a small chamber containing air or a known fraction of oxygen. By means of a computer-controlled switch, the absolute pressure within the chamber can be changed rapidly to a new steady state value. The partial pressure of oxygen changes in direct proportion to the absolute pressure, and so the accuracy and linearity and response time of the PO2 calibration are limited only by those of the absolute pressure sensor. The temperature sensitivity of a commercial sensor and a means of correction are also described.

Optical oxygen sensors based on Pt(II) porphyrin dye immobilized on S-layer protein matrices

This paper describes the development of planar and fiber optic oxygen sensors utilizing surface layer (S-layer) proteins as immobilization matrix for oxygen sensitive dyes. S-layer proteins have the intrinsic capability to reassemble into two-dimensional arrays in suspension and at interfaces. Due to their crystalline character the distribution of functional groups, such as carboxylic groups, is repeated with the periodicity of the lattice and thus allows the reproducible and geometrically distinct binding of functional molecules. For the development of oxygen sensors an oxygen sensitive Pt(II) porphyrin dye was covalently bound to the S-layer matrix. Measurement of the oxygen concentration was performed by phase modulation fluorimetry. Setups comprising low cost optoelectronic components like LEDs and silicon photodiodes were constructed. For both sensor setups (planar and fiber optic) variations in the oxygen concentrations resulted in distinct and reproducible changes in luminescence lifetime and intensity. The luminescence quenching efficiency of these sensors was found to be 1.5–1.9 (expressed as the ratio of signal under nitrogen and air) which compares well to other sensor systems using luminophores embedded in polymer matrices. These results demonstrated the application potential of S-layers as immobilization matrices in the development of (bio-)sensors.

A Quantitative Kinetic Study of Polysorbate Autoxidation: The Role of Unsaturated Fatty Acid Ester Substituents

To study the role of unsaturated fatty acid ester substituents in the autoxidation of polysorbate 80 using quantitative kinetics. Oxidation kinetics were monitored at 40 degrees C in aqueous solution by tracking head space oxygen consumption using a fiber optic oxygen sensor with phase shift fluorescence detection. Radical chain initiation was controlled using an azo-initiator and assessed by Hammond's inhibitor approach, allowing oxidizability constants (k(p)/(2k(t))(1/2)) to be isolated. Reaction orders were determined using modified van't Hoff plots and mixed polysorbate micelles. The oxidizability constant of polysorbate 80 ((1.07 +/- 0.19) x 10(-2) M(-1/2) s(-1/2)) was found to be 2.65 times greater than polysorbate 20 ((0.404 +/- 0.080) x 10(-2) M(-1/2) s(-1/2)). The additional reactivity of polysorbate 80 was isolated and was first-order in the unsaturated fatty acid ester substituents, indicating that the bulk of the autoxidative chain propagation is due to these groups. This data, and the observation of a half-order dependence on the azo-initiator, is consistent with the classical autoxidation rate law (-d[O(2)]/dt = k(p)[RH](R(i)/2k (t))(1/2)). Polysorbate 80 autoxidation follows the classical rate law and is largely dependent on the unsaturated fatty acid ester substituents. Clarification of the substituents' roles will aid formulators in the selection of appropriate polysorbates to minimize oxidative liabilities.

Respiration rates in marine heterotrophic bacteria relate to the cytometric characteristics of bacterioplankton communities

Respiration in marine bacteria (fraction &lt;0.6 µm) was investigated in 5 distinct coastal ecosystems. Respiration rates were estimated from the decrease of dissolved oxygen (O2) concentrations measured with a fibre-optic oxygen sensor (optode) during short-term incubations (5 to 6 hours) in the dark. Sub-populations of heterotrophic bacteria were defined and enumerated by flow cytometric analysis. Respiration rates ranged from 0.04 to 0.14 µmol O2l−1h−1and were not correlated to total bacteria abundances. In contrast, they significantly increased with the relative proportion of HDNA cells (i.e. high deoxyribonucleic acid content) within the bacterioplankton community. These results stress the need to relate bacterial respiration rates to the absolute and relative abundance of the different cytometrically defined sub-populations found in bacterial assemblages, rather than to total cell counts. This result indicates that only a fraction of bacterial cells may contribute to bacterial respiration, which indicates a reconsideration of the relevance of some previous estimates of bulk bacterial respiration and the related biogeochemical fluxes may be required.

Long-term Stability of Oxygen Sensitive Membrane using Ruthenium Complex for Corrosion Monitoring of Radioactive-waste Repository

In order to monitor corrosion risk of radioactive-waste repository, a fiber-optic oxygen sensor for long-term use was proposed and its durability at high temperature was evaluated. The sensing mecha-nism is based on quenching of luminescence by oxygen. Many kinds of Ruthenium complexes which have different counter-anion and ligand were utilized as oxygen-sensitive dye. Several Ru-complexes were dispersed into silicone resin. Excitation is achieved with a blue LED (470 nm) and the emitted light at around 610 nm is collected by optical fiber. The sensing membranes showed high sensitivity and quick response to gaseous and dis-solved oxygen. Comparison of sensitivity and durability of the Ru-complexes were performed. Degradation behaviors of the sensors in air at 150 ºC were investigated. Also short-term degradation test in hot water (80 ºC) was conducted. Screening of the sensors is un-derway to find the most stable sensor in such environment by this test.

Ratiometric fiber-optic oxygen sensors based on sol–gel matrix doped with metalloporphyrin and 7-amino-4-trifluoromethyl coumarin

Abstract This paper develops highly sensitive ratiometric fiber-optic oxygen sensors incorporating a sol–gel matrix doped with platinum or palladium tetrakis pentafluorophenyl porphine (PtTFPP or PdTFPP) metalloporphyrins as the oxygen-sensitive material and 7-amino-4-trifluoromethyl coumarin (AFC) as the reference dye. Using an LED with a central wavelength of 400 nm as an excitation source, it is shown that the emission wavelengths of the oxygen-sensitive dye and the reference dye have no spectral overlap and therefore permit the oxygen concentration to be measured using a ratiometric-based method. The sensitivities of the PtTFPP-doped and PdTFPP-doped oxygen sensors are evaluated in terms of the ratio I N 2 / I O 2 , where I N 2 and I O 2 correspond to the detected luminescence intensities in pure nitrogen and pure oxygen, respectively. The experimental results reveal that the PtTFPP and PdTFPP sensors both yield linear Stern–Volmer plots and have sensitivities of around 33 and 74, respectively. In addition, the response time of the PtTFPP-doped sensor is found to be 2.8 s when switching from a fully deoxygenated environment (i.e. 100% nitrogen) to a fully oxygenated environment, and 5.8 s when switching in the reverse direction. The corresponding response times of the PdTFPP-doped sensor are 7.9 and 58.9 s, respectively. The ratiometric sensing approach presented in this study not only yields high sensitivity and reversibility, but also has the advantage of suppressing the effects of spurious fluctuations in the intensity of the excitation source and optical transmission properties of the optic fiber.

Optical Sensors for Corrosion Systems: I. Oxygen Sensing

Sensing the chemical environment in confined spaces that characterize localized corrosion requires special instrumentation beyond the capability of classical electrochemical instrumentation. We describe a fiber-optic oxygen sensor based on fluorescence quenching of a ruthenium phenanthroline complex that is small, fast, and rugged enough to be used in the field. The sensitivity of the dual-fiber probe is 0.9 Torr and 0.01 mg/L oxygen in the gas and aqueous phases, respectively. The sensor utilizes a polydimethylsiloxane matrix for the dye that will facilitate further miniaturization for corrosion studies.