Optical Gas Research Articles

Characterisation and mitigation of gas leaks at laparoscopy: an international prospective, multi-center cohort clinical trial.

Gas leaks polluting the operating room are common in laparoscopy. Studies defining methods for sensitive leak characterisation and mechanical mitigation in real world settings are, however, lacking. Mobile optical gas imagers (both a miniaturised Schlieren system and sensitive tripod-mounted near-infrared carbon dioxide camera (GF343, FLIR)) prospectively defined trocar-related gas leaks occurring either spontaneously or with instrumentation during planned laparoscopic surgery at three hospitals. A boutique Matlab-based analyser usingsequential frame subtraction categorisedleaks (class 0-no observable leak; class 1-marginally detectable leak; class 2-short-lived plume; class 3-energetic, turbulent jet). Concurrently, the usefulness of a novel vacuum-ring device (LeakTrap™, Palliare, Ireland) designed as a universal adjunct for existing standard laparoscopic ports at both abdominal wall and port valve level was determined similarly in a phase I/11 clinical trial along with the device's useability through procedural observation and surgeon questionnaire. With ethical and regulatory approval, 40 typical patients (mean age 58.6years, 20 males) undergoing planned laparoscopic cholecystectomy (n = 36) and hernia repair (n = 4) were studied comprising both control (n = 20) and intervention (n = 20) cohorts. Dual optical gas imaging was successfully performed across all procedures with minimal impact on procedural flow. In total, 1643 trocar instrumentations were examined, 819 in the control group (mean 41 trocar instrumentations/procedure) and 824 in the intervention group (mean 41.2 trocar instrumentations/procedure). Gas leaks were detected during 948(62.6%) visualised trocar instrumentations (in 129-7.8%-the imaging was obscured). 14.8% (110/742) and 60% (445/742) of leaks in control patients were class 0 and 3, respectively, versus 59.1% (456/770) and 8.7% (67/772) in the interventional group (class 3 v non-class 3, p < 0.0001, χ2). The Leaktrap proved surgically acceptable without significant workflow disruption. Laparoscopic gas leaks can be sensitively detected and consistently, effectively mitigated using straightforward available-now technology with most impact on the commonest, highest energy instrument exchange leaks.

Inverse design of refractory mid-wave infrared narrowband thermal emitters for optical gas sensing

Inverse design of refractory mid-wave infrared narrowband thermal emitters for optical gas sensing

Highly sensitive gas pressure sensor utilizing the harmonic vernier effect in parallel FPIs with femtosecond laser processing

This work proposes and prepares a high-sensitive fiber optic gas pressure sensor based on the first harmonic vernier effect (FHVE). It has two parallel Fabry-Perot interferometers (FPI), each made of a single-mode fiber and a small segment of capillary tube fused as a sensing cavity and a reference cavity, and the end face of the sensing cavity is cut into a thin slice with a femtosecond laser pulse to make it sensitive to gas pressure. When the sensing cavity's (FPI1) and reference cavity's (FPI2) free spectral ranges are close to each other, a traditional vernier effect occurs, and the gas pressure sensitivity approaches 58.49 nm/MPa, which is approximately 14.64 times that of the single sensing cavity (FPI1). When the free spectral range of the sensing cavity (FPI1) is roughly twice that of the reference cavity (FPI3), the first harmonic vernier effect is observed. This leads to a significant increase in gas pressure sensitivity, up to 141.80 nm/MPa, which is about 35.45 times higher than what a single sensing cavity (FPI1) would achieve. Furthermore, testing results reveal that the sensor is temperature insensitive, with a low cross-sensitivity of 3.1 × 10−5 MPa/°C for gas pressure to temperature. This device is made of pure quartz glass, has high mechanical strength, a sealed construction, is easy to fabricate, has a high sensitivity of gas pressure, and may be used to monitor pressure in extreme conditions such as offshore oil or underwater operations.

Fiber optic room temperature ethanol sensor based on ZnSnO3/TiO2 with UV radiation sensitization

A fiber optic ethanol gas sensor with ZnSnO3 hollow cube/nano-TiO2 composite coating based on ultraviolet (UV) radiation sensitization was proposed, which can realize high sensitivity, high selectivity, and fast ethanol gas sensing at room temperature. The probe adopted a simple single-mode fiber (SMF)-multi-mode fiber-SMF structure. The ZnSnO3/TiO2 gas-sensitive film was coated on the sensing area by dip-coating method. Experiment results show that the probe sensitized by UV radiation has a linear sensitivity of 3.85 pm/ppm for ethanol gas at 0–250 ppm, which is about 6.6 times more sensitive than the probe without UV radiation (0.582 pm/ppm). In addition, the probe with UV radiation has good time measurement stability, a fast response time (response time is about 20 s, recovery time is about 60 s), and excellent ethanol gas selectivity. This study proves that UV radiation is an effective method to increase the sensitivity of gas sensing. This is also the first application of ZnSnO3/TiO2 composite material in fiber optic sensors. Combined with the advantages of fiber optic sensing, it shows anti-electromagnetic interference, micro size, high sensitivity, high selectivity, fast response, and remote sensing.

Resonant Gas Sensing in the Terahertz Spectral Range Using Two-Wire Phase-Shifted Waveguide Bragg Gratings.

The development of low-cost sensing devices with high compactness, flexibility, and robustness is of significance for practical applications of optical gas sensing. In this work, we propose a waveguide-based resonant gas sensor operating in the terahertz frequency band. It features micro-encapsulated two-wire plasmonic waveguides and a phase-shifted waveguide Bragg grating (WBG). The modular semi-sealed structure ensures the controllable and efficient interaction between terahertz radiation and gaseous analytes of small quantities. WBG built by superimposing periodical features on one wire shows high reflection and a low transmission coefficient within the grating stopband. Phase-shifted grating is developed by inserting a Fabry-Perot cavity in the form of a straight waveguide section inside the uniform gratings. Its spectral response is optimized for sensing by tailoring the cavity length and the number of grating periods. Gas sensor operating around 140 GHz, featuring a sensitivity of 144 GHz/RIU to the variation in the gas refractive index, with resolution of 7 × 10-5 RIU, is developed. In proof-of-concept experiments, gas sensing was demonstrated by monitoring the real-time spectral response of the phase-shifted grating to glycerol vapor flowing through its sealed cavity. We believe that the phase-shifted grating-based terahertz resonant gas sensor can open new opportunities in the monitoring of gaseous analytes.

Optimizing Gas Sensing Performance of CuO Nanoparticles via Sol-Gel Synthesis Approach for Efficient Detection of Ammonia Gas

In this study, we present a plastic optical fiber for volatile organic compound (VOC) gas sensing, where a small portion of the cladding was replaced by CuO sensing material. The structural characterization of the CuO was assessed via powder diffraction X-ray analysis (XRD) and morphological analysis done by SEM imaging. For a variety of VOC gas concentrations, such as ammonia, ethanol, and methanol (0-500 parts per million), as well as for various lengths (1.5 cm and 3 cm) of sensing materials coated on the optical fiber, the spectrum properties of the CuO-coated fiber optic gas sensor were investigated. The 3cm coated CuO over the clad modified region of the plastic optical fiber showed highest intensity of fluctuation towards ammonia gas at wavelengths of 682, 753, and 926 nm, indicating that it is more sensitive to the gas and has a faster response and recovery rate at room temperature than the other two gases.

Soliton refraction by an optical soliton gas

Soliton refraction by an optical soliton gas

A cooperative model to lower cost and increase the efficiency of methane leak inspections at oil and gas sites

Methane is a potent greenhouse gas that tends to leak from equipment at oil and gas (O&amp;G) sites. Conventional leak detection and repair methods for fugitive methane emissions are labor-intensive and costly because they involve time-consuming close-range, component-level inspections at each site. This has prompted duty holders to examine new methods and strategies that could be more cost-effective. We examined a cooperative model in which multiple duty holders of upstream O&amp;G sites in a region use shared services to inspect on-site equipment using optical gas imaging camera or Method 21. This approach was hypothesized to be more efficient and cost-effective than independent inspection programs by each duty holder in the region. To test this hypothesis, we developed a geospatial simulation model using empirical data from 11 O&amp;G-producing regions in Canada and the United States. We used the model to compare labor cost, transit time, mileage, vehicle emissions, and driving risk between independent and co-op leak inspection programs. The results indicate that co-op leak inspection programs can generate relative savings in labor costs (1.8%–34.2%), transit time (0.6%–38.6%), mileage (0.2%–43.1%), vehicle emissions (0.01–4.0 tCO2), and driving risk (1.9%–31.9%). The largest relative savings and efficiency gains resulting from co-op leak inspection programs were in regions with a high diversity of duty holders, which was confirmed with simulations of fictitious O&amp;G sites and road networks spanning diverse conditions. We also found reducing leak inspection time by 75% with streamlined methods can additionally reduce labor cost by 8.8%–41.1%, transit time by 5.6%–20.2%, and mileage by 2.60%–34.3% in co-op leak inspection programs. Overall, this study demonstrates that co-op leak inspection programs can be more efficient and cost-effective, particularly in regions with a large diversity of O&amp;G duty holders, and that methods to reduce leak inspection time can create additional savings.

Methane venting from uncontrolled production storage tanks at conventional oil wells—Temporal variability, root causes, and implications for measurement

Uncontrolled oil production storage tanks are important but poorly understood sources of methane (CH4) emissions in the upstream oil and gas sector. This study reports and analyzes directly measured, temporally varying CH4 emission rates, total gas vent rates, and vent gas CH4 fractions from storage tanks at eight active upstream oil production sites in Alberta, Canada. Using a built-for-purpose optical mass flux meter (VentX) supplemented by an ultrasonic flow meter and quantitative optical gas imaging camera where possible, mean vent rates (whole gas) among tanks in the study ranged from 37 to 598 m3/d; however, at some individual tanks, instantaneous flow rates could vary significantly from 0 to over 4,000 m3/d for minutes at a time, while unsteady CH4 volume fractions varied by up to 41% absolute. Root cause analysis revealed the limits of estimating vented emissions from oil production volumes using an assumed gas–oil ratio, especially in cases where produced gas from wells fully or partially bypasses separators. The analysis of the acquired data also demonstrated how 1-h duration vent measurements recommended in some regulations are insufficient to reliably estimate emissions from unsteady tanks. These two factors are the likely reason for significantly underreported vent rates in the present sample and are thought to be a key cause of the mismeasurement/underestimation of tank venting that has driven persistent gaps between bottom-up inventories and top-down measurements. Finally, detailed statistical analyses were completed to suggest minimum sampling durations and instrumentation requirements for direct measurements of tanks and minimum sample sizes for discrete (“snapshot”) surveys of both individual tanks and multitank surveys under different scenarios. Results show that caution is warranted when interpreting snapshot measurements of individual tanks, but aggregate emissions of multiple tanks should be accurately measurable with readily achievable sample sizes. These results are expected to be especially valuable to ongoing efforts seeking to develop robust protocols for gas certification and measurement, reporting, and verification (MRV) of CH4 emissions in the oil and gas sector.

Liquid-crystal-based fiber laser sensor for non-invasive gas detection.

This Letter reports a new optical fiber gas sensor for measuring breath acetone. The sensor is based on photonic bandgap (PBG) mode laser emission sensing technology using liquid crystal (LC), which is combined with silica fiber and chiral nematic liquid crystal (CNLC), thus providing an ultra-compact, fast-response and simple-to-produce sensing system with a fast response that can accurately and quantitatively determine the concentration of respiratory acetone within the normal oral temperature range (35-38°C). Since LCs are affected by temperature, we propose a method that eliminates the influence of the temperature to solve the problem of the temperature influence when measuring gas. The detection of acetone leads to splitting of the dual laser peaks, with a linear correlation of 0.99. The sensor has a limit of detection of 65 ppm for acetone vapor and thus is suitable for breath acetone detection in diabetic patients.

Impact of the Cationic Moiety of Ionic Liquids on Chemoselective Artificial Olfaction.

Ionogels and derived materials are assemblies of polymers and ionic liquids characterized by high stability and ionic conductivity, making them interesting choices as gas sensors. In this work, we assessed the effect of the ionic liquid moiety to generate ionogels and hybrid gels as electrical and optical gas sensors. Six ionic liquids consisting of a constant anion (chloride) and distinct cationic head groups were used to generate ionogels and hybrid gels and further tested as gas sensors in customized electronic nose devices. In general, ionogel-based sensors yielded higher classification accuracies of standard volatile organic compounds when compared to hybrid material-based sensors. In addition, the high chemical diversity of ionic liquids is further translated to a high functional diversity in analyte molecular recognition and sensing.

Optical Dual Gas Sensor for Simultaneous Detection of Nitric Oxide and Oxygen

This work presents a new optical dual sensor based on PtTFPP-containing electrospun fibers and CsPbBr3 perovskite quantum dots (PQDs) for simultaneous detection of oxygen (O2) and nitric oxide (NO) gases, wherein PtTFPP-containing electrospun fibers for O2 sensing was based on electrospinning process fabricated by platinum(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) complex immobilized in cellulose acetate (CA) matrix. CsPbBr3 PQDs were used as NO-sensitive material and coated on the surface of PtTFPP-containing electrospun fibers. Both materials were excited by a UV LED with a central wavelength of 380 nm, and the fluorescence intensities of sensing materials were recorded and analyzed with a spectrometer. The experiment results show that the optical NO and O2 sensors have linear Stern–Volmer plots, and the sensitivities are around 2.7 and 10.7, respectively. The response and recovery times of the optical NO sensor are 71 and 109 s, respectively. For optical O2, response and recovery times are 60 and 65 s, respectively. The optical dual sensor with a new method based on fluorescent dye containing electrospun fibers and coated with CsPbBr3 PQDs has been successfully developed to detect NO and O2 gases simultaneously. The optical dual gas sensor provides great potential for practical applications with low cost and ease of fabrication.

Enhanced Acetone Sensing at Room Temperature using Tailored Co3O4 Nanostructures-Coated Optical Fibers: An Application towards Non-invasive Blood Glucose Sensor

Detection of acetone molecules is of paramount importance in the fields of healthcare, air quality monitoring and industrial uses. Herein, we proposed a room temperature Co3O4 nanoparticles coated optical fiber acetone gas sensor. Structural, morphological and uniformity coating of synthesized Co3O4 nanoparticles were investigated using X-ray diffraction and electron microscopy techniques. Interestingly, sensing studies uncovered the linear characteristic in output detector current with change in 0-2.5 ppm acetone concentration for all the sensors (named as F-S350, F-S500 and F-S1000 sensors coated with nanoparticles annealed at 350, 500 and 1000°C, respectively). The F-S350 sensor divulged a significant increase in output current, sensitivity around 15 times higher and reduced limit-of-detection (LoD) values with regard to F-S1000 device. Furthermore, the sensing parameters were augmented by exposed to lower acetone concentration. The experimental findings established the F-S350 sensor as a superior device, which is explained by the evanescent field distribution outside coating region of fiber through FDTD simulation. Typically, the concentration of acetone gas in diabetic patients is above 1.8 ppm than healthy people (range 0.3-0.9 ppm), and therefore the proposed room temperature F- S350 device having LoD value 0.15 ppm can be deemed as a biomarker for the detection of acetone molecules in diabetic patients.

Sorption-Induced Fiber Optic Plasmonic Gas Sensing via Small Grazing Angle of Incidence.

Sensing technologies based on plasmonic nanomaterials are of interest for various chemical, biological, environmental, and medical applications. In this work, w e report an incorporation strategy of colloidal plasmonic nanoparticles (pNPs) in microporous polymer for realizing distinct sorption-induced plasmonic sensing. This approach is demonstrated by introducing tin-doped indium oxide pNPs into a polymer with intrinsic microporosity (PIM-1). The composite film (pNPs-polymer) provides distinct and tunable optical features on the fiber optic (FO) platform that can be used as a signal transducer for gas sensing (e.g., CO2 ) under atmospheric conditions. The resulting pNPs-polymer composite demonstrates high sensitivity response on FO in the evanescent field configuration, provided by the dramatic response of modes above the total-internal-reflection angle. Furthermore, by varying the pNPs content in the polymer matrix, the optical behavior of the pNPs-polymer composite can be tuned to affect the operational wavelength by over several hundred nanometers and the sensitivity of the sensor in the near-infrared range. W e also show that the pNPs-polymer composite film exhibits remarkable stability, over a period of more than ten months, by mitigating the physical aging issue of the polymer. This article is protected by copyright. All rights reserved.

Optical CO2 gas sensor based on liquid crystals in a textile grid

Given the increasing concerns about global warming, it is undeniable that measuring and controlling carbon dioxide (CO2) levels, a colorless and odorless greenhouse gas, is of great value. In this respect, liquid crystals (LCs) as an anisotropic material hold promise for fabricating such gas sensors. Here, we report a sensitive optical gas sensor for real-time monitoring of CO2 gas, exploiting a textile grid impregnated with LC and diethanolamine (DEA) as a CO2-sensitive material. The sensing mechanism relies on the reorientation of LC molecules upon the interaction of gas analytes with DEA. By tracing optical texture changes and extracting the corresponding intensities, CO2 gas concentrations ranging from 300 to 10,000 ppm were detected. The sensor exhibits a response time of 12 seconds and a recovery time of 7 seconds at 800 ppm. The sensor is simple and cost-effective.

Influence of Sn4+ substitution on the ZnO crystal structure and their enhanced fibre optic gas sensing and photocatalytic degradation performance

An efficient ZnO specimen with Sn4+ substitution was synthesized through facile co-precipitation method, and the specimens were characterized well with sophisticated instruments. The Sn4+ substituent performed a key function in narrowing the band gap and inhibiting the rate of photogenerated electro-hole recombination. The obtained 5% Sn4+ doped ZnO spcimen exhibits excellent photocatalytic performance of organic dye degradation, which was obviously superior than other syntheiszed catalysts. Gas sensing properties of bare ZnO and Snsubstituted ZnO were studied using clad modified fiber optic gas sensor. The different concentrations from 0 to 500 ppm of ammonia, methanol and ethanol were used for gas sensing measurement and results showed that the 5% Sn4+ doped ZnO catalyst had the greatest gas-sensing activity on ethanol. The findings of this work revealed that Sn4+ substitution for Zn2+ may provide an alternate strategy to improving ZnO gas sensing and photocatalytic activity.

Graphene/Polyaniline Film Optical Fiber Ammonia Gas Sensor With Excellent Sensing Performance

The possibility to improve the detection index of the optical ammonia gas sensors on the basis of the graphene/polyaniline (graphene/PANI) coated Mach–Zehnder interferometric optical fiber structure with etched thinned core fiber(e-TCF) is investigated. Based on the analysis of the output wavelength, a significant increase in sensitivity and stability of the ammonia sensors is achieved by using TCF. Experimental results show that its sensitivity is -27.8 pm/ppm, the response time is 32 s, dip wavelength error is lower than ±0.02 nm, and the dip intensity error is lower than ±0.002 dB in the stability test. This research illustrates that the proposed sensor has numerous advantages, including small size, strong anti-electromagnetic interference, and excellent repeatability characteristics. Furthermore, it can be applied in biomedical detection applications as it can improve the detection resolution of ammonia concentration at room temperature.

Development of an atmospheric fluorocarbon plasma jet generated by pulse modulated microwave discharge

Atmospheric fluorocarbon plasma plays an important role in the surface modification of insulating materials like polymers. The existing fluorocarbon plasma is usually generated by dielectric barrier discharge, which has a low concentration of reactive species and may cause insufficient surface fluorination. This work attempts to develop an atmospheric fluorocarbon plasma jet using a coaxial transmission line resonator by microwave discharge with locally enhanced electric field and high density. The gas temperature is reduced by pulse modulation technology. Three kinds of working gases, pure CF4, Ar/CF4 and He/CF4, are utilized to generate the atmospheric microwave fluorocarbon plasma jet. The discharge images, optical emission spectra, electron densities and gas temperatures are studied experimentally. The results show that the Ar/CF4 plasma jet has the best comprehensive performance, such as strong discharge intensity and controllable gas temperature. The electron density of the Ar/CF4 plasma jet has a magnitude of 1020 m−3, indicating a higher density than that of the frequently used dielectric barrier discharge. With the other conditions unchanged, the gas temperature at the end of the Ar/CF4 plasma jet can be reduced from 410.2 to 347.3 K by decreasing the duty cycle of the modulated pulse from 0.5 to 0.1. Thence, the microwave Ar/CF4 plasma jet is considered to be a promising fluorocarbon plasma source for surface fluorination of polymers.

Methane emissions from shale gas production sites in southern Sichuan, China: A field trial of methods

Shale gas is an important alternative natural gas source that can meet China's growing energy demand. However, methane emissions during shale gas production could largely determine whether it could be considered as a bridging clean energy source. In this study, we performed methane emission measurements using three methods (on-site optical gas imaging, on-site methane patrolling, and downwind measurement) at shale gas production sites in Sichuan province, China, covering 18 well sites with 81 wells. The results showed that flowback water tanks were the major methane sources, with valves, separators, chemical injection pumps, and pneumatic controllers as other sources. The methane concentrations inside the 18 sites ranged from 1.42 to 459 μmol mol−1, with over 59% of the sites having the highest concentration less than 50 μmol mol−1. The optical gas imaging method, with its low detection limit over 5000 μmol mol−1, could not capture the emission effectively. The three successful downwind measurements resulted in site level emission rates between 0.02 and 0.17 kg h−1. When divided by the number of wells at each site, the emission intensity was 4%–28% of the wellhead emission factor for natural gas production in China. More measurements are required to better quantify methane emissions from shale gas sites in China. For sites in mountainous regions or long-term low-wind regions, detection methods other than downwind measurements should be suitable for quantifying site-level emissions.

An Ultrasensitive Gas Pressure Sensor Based on Single-Core Side-Hole Fiber With Optical Vernier Effect

An ultrasensitive optical fiber gas pressure sensor with the Optical Vernier effect (OVE) is proposed based on fusion splicing a piece of the Single-core and Side hole (SCSHF) fiber between the No-core fiber (NCF) and the hollow core fiber (HCF). The fabrication process only refers to the operation of fusion splicing, which is suitable for mass production. The theoretical sensing principles of the proposed sensor are explicitly elucidated in this paper. The sensor can be used as a probe in a narrow place because it works based on the reflected mode. The experimental results demonstrated that the sensor could detect the gas pressure change with a sensitivity of ∼183 nm/MPa in the range of 0∼100 kPa. Repeated experiments are also conducted to verify the sensor's excellent sensing repeatability and long-term stability. In addition, the sensor possesses a low-temperature cross-sensitivity of ∼2.4 kPa/℃. Thus, the proposed sensor is expected to leverage its practical functionalities in sensing areas requiring high sensitivity, a simple fabrication process, and long-term stability.