Optical Hydrogen Gas Sensor Research Articles

Results of the gasochromic response on hydrogen of WO3 thin films deposited by electron beam evaporation

Among chromogenic materials, tungsten trioxide (WO3) is of great interest. It is a colourlesssemiconductor characterised by a lack of toxicity and high chemical stability. WO3 exhibits gasochromicproperties, meaning that the material undergoes reversible changes in optical properties when it isexposed to gas. These properties make tungsten oxide a suitable material for sensing applications. Thispaper presents the results of an analysis of the surface, structural and optical properties of tungstenoxide thin films fabricated by electron beam evaporation and annealed at 400C to 800C. Opticalproperties, including gasochromic properties, were determined from light transmission spectra inan atmosphere containing hydrogen at the concentrations ranging from 50 ppm to 500 ppm. Theoptical properties of WO3 films without and with a palladium catalyst layer are applied. Annealing thesamples at temperatures above 400C resulted in crystallisation of the layers, and further post-processmodification at 800C led to sublimation, the formation of islands of crystalline grains of large size anda significant deterioration in optical properties. A change in the light transmission coefficient occurredfor all samples with the catalyst layer applied after the introduction of a hydrogen-argon mixture.Based on the results, it can be concluded that the layers annealed at 400C had the best gasochromic properties due to the greatest changes in light transmission under hydrogen. The study confirmsthat it is possible to improve the gasochromic response of tungsten trioxide thin films produced byelectron beam evaporation using thermal modification, which, to the best of current knowledge, hasnot previously been achieved.Keywords: electronics, WO3, electron beam evaporation, gasochromic properties, optical properties,annealing, optical hydrogen gas sensor

Sensing mechanism of an optimized room temperature optical hydrogen gas sensor made of zinc oxide thin films

Using the radiofrequency (RF) magnetron sputtering method, zinc oxide (ZnO) thin films were optimized for the optical hydrogen gas sensor at 27 °C. To generate optically controlled thin films, the following parameters have been optimized: argon/oxygen (Ar/O2), RF power, gas concentration and deposition time. As a result, ZnO thin films optimized at 4 % of O2, 150 W RF and 180 min gas concentration. This work focused on the effect of deposition parameters that included deposition time, RF power, argon/oxygen (Ar/O2) gas percentage, and annealing condition on thin-film thickness, surface roughness, crystal phase, phonon modes, and optical bandgap. From the physical characterization, we found that the formed product is crystalline in nature (powdered XRD) and Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy (ATR-FTIR) analysis provided the surface functionality and bonding, while the UV–vis spectroscopy for the optical properties. AFM images show that the surface roughness is varying from 18.9 to 89.83 nm. The gas sensing mechanism of the RF-sputtered ZnO thin film was based on the surface reaction between adsorbed oxygen and the H2 gas where more oxygen was chemisorbed in the form of O2−, O−, and O2- by ZnO thin film. The calculated molar absorptivity, ε increased with the increase of RMS surface roughness whereby relatively high surface roughness is better to optically absorb H2 gas.

Bilayer plasmonic nano-lattices for tunable hydrogen sensing platform

Gas sensors are critical for facilitating the safety and integrity of systems used in the hydrogen energy and storage systems. It is challenging for any sensing technology to meet all the performance requirements for emerging applications, such as dynamic measuring range, response time, and sensitivity. Here, we propose an optical hydrogen gas sensor platform based on Pd bilayer plasmonic nano-lattices (BPNL), which is comprised of two parallel, subwavelength-separated hexagonal arrays of Pd nano-patchy particles and nano-holes. Optical transmission studies of the BPNL structure and its isolated sub-structures of nano-patches (NPs) and nano-hole arrays (NHs) upon hydrogen sorption show distinct optical isotherms with different spectral changes and response times in the visible-to-near-infrared region. Experiments and finite-difference time-domain (FDTD) calculations show that the strong electromagnetic coupling between localized and propagating plasmonic modes of the NPs and NHs, respectively, leads to the unique optical properties of the BPNL and their subsequent change upon hydrogen sorption. Notably, the BPNL structure possesses an extended optical response range and enhanced sensitivity for hydrogen detection. Additionally, the optical response time of the BPNL structure is an order of magnitude faster than that of the isolated array sensors in the low hydrogen pressure range. Finally, we demonstrate that the sensing characteristics of such a BPNL platform can be further improved by tuning its structural parameters.

Palladium thin films for plasmonic hydrogen gas sensing

In this study, I prepared BK7 glass slides coated by palladium (Pd) layer by PVD technique. These samples have been employed as plasmon active structures in classic Kretschmann-based SPR set-up. The application of H2 sensing structures based on palladium plasmonic active thin films have been tested and investigated. Hydrogen sensing properties of Pd films were investigated at room temperature The reflectances of p-polarized light from Pd thin films as a function of angle of incidence and wavelength were measured in synthetic air (or nitrogen) and in gas mixtures including hydrogen. Variations of the reflectance in the presence of hydrogen gas at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (0–2% vol/vol) without saturation behavior. The dynamic properties with various concentration of H2 at low temperature and dry gas mixtures was investigated and the effects of these factors on the hydrogen sensing properties were analyzed. Full Text: PDF ReferencesG. Korotcenkov, Handbook of Gas Sensor Materials: Properties, Advantages, and Shortcomings for Applications (Springer, New York 2013). CrossRef W. Jakubik, M. Urbanczyk, E. Maciak, "SAW hydrogen gas sensor based on WO3 and Pd nanostructures", Procedia Chemistry 1 (1), 200 (2009). CrossRef W. Jakubik, M. Urbanczyk, E. Maciak, T. Pustelny, "Bilayer Structures of NiOx and Pd in Surface Acoustic Wave and Electrical Gas Sensor Systems", Acta Physica Polonica A 116(3), 315 (2009). CrossRef E. Maciak, Z. Opilski, "Pd/V2O5 fiber optic hydrogen gas sensor", J. Phys. France IV 129, 137 (2005). CrossRef E. Maciak,. "Fiber optic sensor for H2 gas detection in the presence of methane based on Pd/WO3 low-coherence interferometric structure", Proc. SPIE 10455, UNSP 104550W (2017). CrossRef X. Bevenot, A. Truillet, C. Veillas, H. Gagnaire, M. Clement, "Hydrogen leak detection using an optical fibre sensor for aerospace applications", Sens. Actuators B 67, 57 (2000). CrossRef J. Homola, S.S. Yee, G. Gauglitz, "Surface plasmon resonance sensors: review", Sensors and Actuators B 54, 3 (1999). CrossRef H. Raether, Surface plasmons on smooth and rough surfaces and on gratings (Springer-Verlag, Berlin-Heidelberg 1988). CrossRef P. Tobiska, O. Hugon, A. Trouillet, H.Gagnarie, "An integrated optic hydrogen sensor based on SPR on palladium", Sensors and Actuators, B 74, 168 (2001). CrossRef Z. Opilski, E. Maciak, "Optical hydrogen sensor employing the phenomenon of the surface plasmons resonance in the palladium layer", Proc. SPIE 5576, 202 (2004). CrossRef T. Pustelny, E. Maciak, Z. Opilski, A. Piotrowska, E. Papis, K. Golaszewska, "Investigation of the ZnO sensing structure on NH3 action by means of the surface plasmon resonance method", European Physical Journal-Special Topics 154, 165 (2008). CrossRef E. Maciak, M. Procek, K. Kępska, A. Stolarczyk, "Study of optical and electrical properties of thin films of the conducting comb-like graft copolymer of polymethylsiloxane with poly(3-hexyltiophene) and poly(ethylene) glycol side chains for low temperature NO2 sensing", Thin Solid Films 618, 277 (2016). CrossRef

Experimental research on a reflective optical fiber bundle hydrogen gas sensor

PurposeLong life and high hydrogen sensitivity are the crucial performance parameters for an optical fiber hydrogen sensing membrane, and these are the fundamental areas of study for an optical fiber hydrogen sensor. Considering that a traditional optical fiber hydrogen sensor based on pure palladium cannot meet the expectations for long life and rapid sensitivity simultaneously, the experiment in this paper designed a kind of reflective optical fiber bundle hydrogen gas sensor based on a Pd0.75–Ag0.25 alloy to achieve a hydrogen sensing system. This paper aims to discuss the issues with this system.Design/methodology/approachA reflective optical fiber bundle hydrogen sensor was made up of an optical fiber bundle and a Pd0.75–Ag0.25 alloy hydrogen membrane. A combination of optical fiber light intensity measurements and the reference calculation method were used to extract the hydrogen concentration information from within the optical fiber, and the relationship between the hydrogen concentration changes and the reflective light intensity in the optical fiber was established.FindingsThe reflective optical fiber bundle hydrogen gas sensor based on a Pd–Ag alloy membrane was shown to provide an effective way to detect hydrogen concentrations. The experimental results showed that a 20-30-nm-thick Pd0.75–Ag0.25 alloy membrane could reach high hydrogen absorption and sensitivity. Key preparation parameters which included sputtering time and substrate temperature were used to prepare the hydrogen membrane during the DC sputtering process, and the reflectivity of the Pd–Ag alloy membrane was enough to meet the requirements of long life and high hydrogen sensitivity for the optical fiber hydrogen sensor.Originality/valueThis paper seeks to establish a foundation for optimizing and testing the performance of the Pd–Ag alloy hydrogen sensing membrane for an optical fiber bundle hydrogen sensor. To this end, the optimal thickness and key preparation parameters for the Pd–Ag alloy hydrogen sensing membrane were discussed. The results of this research have proved that the reflective optical fiber hydrogen sensor based on a Pd0.75–Ag0.25 alloy is an effective approach and precisely enough for hydrogen gas monitoring in practical engineering measurements.

Experimental research of optical fiber hydrogen gas sensing system based on palladium-silver alloy

A novel optical fiber hydrogen sensing system based on palladium (Pd) and sliver (Ag) is proposed. By direct current (DC) magnetron process, Pd/Ag alloy ultra-thin films were deposited on the substrate to eliminate the hydrogen embrittlement of sensor based on pure Pd. Several samples with different thin film thicknesses were fabricated at different substrate temperatures and tested in the optical fiber hydrogen sensor setup. We do a series of experiments for obtaining optimum sputtering parameters, such as optimum sputtering temperature and thickness of Pd/Ag alloy film. The humidity effect and reliability experiment for the optical fiber hydrogen gas sensor are reported in detail. The testing results demonstrate the Pd/Ag alloy is a promising material for optical fiber hydrogen gas sensor.

A lossy mode resonance-based fiber optic hydrogen gas sensor for room temperature using coatings of ITO thin film and nanoparticles

In this article, the idea of employing lossy mode resonances (LMR) concertedly for gas sensing along with the reversible interaction of metal oxides with gases has been investigated. Fabrication and characterization of a LMR-based fiber optic probe with successive coatings of indium-tin oxide (ITO) film and nanoparticles over the unclad core of the fiber have been carried out for the detection of hydrogen gas (H2). The results have been compared with the probes having individual coatings of ITO thin film and nanoparticles. For calibrating and comparing, the wavelength interrogative spectra have been recorded for varying concentrations of H2 gas exploiting the sensor probes. A red shift of the spectrum has been observed with the increase in the concentration of the gas. The results uphold the fact that the LMR-based sensor with both thin film and nanoparticles layer has better sensitivity to H2 gas than the probes with the layer of either nanoparticles or thin film. A collective study on the three probes for different gases has predicted a maximum level of sensitivity for the probe with layers of thin film and nanoparticles along with the high selectivity and repeatability of the results for H2 gas. In addition to high sensitivity and selectivity, the proposed sensor can be used for online monitoring and remote sensing of the gas because of the fabrication of the probe on the optical fiber.

Fiber optic hydrogen gas sensor utilizing surface plasmon resonance and native defects of zinc oxide by palladium

We present an experimental study on a surface plasmon resonance (SPR) based fiber optic hydrogen gas sensor employing a palladium doped zinc oxide nanocomposite (ZnO(1−x)Pdx, 0 ≤ x ≤ 0.85) layer over the silver coated unclad core of the fiber. Palladium doped zinc oxide nanocomposites (ZnO(1−x)Pdx) are prepared by a chemical route for different composition ratios and their structural, morphological and hydrogen sensing properties are investigated experimentally. The sensing principle involves the absorption of hydrogen gas by ZnO(1−x)Pdx, altering its dielectric function. The change in the dielectric constant is analyzed in terms of the red shift of the resonance wavelength in the visible region of the electromagnetic spectrum. To check the sensing capability of sensing probes fabricated with varying composition ratio (x) of nanocomposite, the SPR curves are recorded typically for 0% H2 and 4% H2 in N2 atmosphere for each fabricated probe. On changing the concentration of hydrogen gas from 0% to 4%, the red shift in the SPR spectrum confirms the change in dielectric constant of ZnO(1−x)Pdx on exposure to hydrogen gas. It is noted that the shift in the SPR spectrum increases monotonically up to a certain fraction of Pd in zinc oxide, beyond which it starts decreasing. SEM images and the photoluminescence (PL) spectra reveal that Pd dopant atoms substitutionally incorporated into the ZnO lattice profoundly affect its defect levels; this is responsible for the optimal composition of ZnO(1−x)Pdx to sense the hydrogen gas. The sensor is highly selective to hydrogen gas and possesses high sensitivity. Since optical fiber sensing technology is employed along with the SPR technique, the present sensor is capable of remote sensing and online monitoring of hydrogen gas.

Influence of oxygen gas concentration on hydrogen sensing of Pt/WO3 thin film prepared by sol–gel process

High-performance hydrogen gas sensors are needed to ensure safe use of hydrogen gas as a clean energy resource. Pt catalyst-loaded tungsten oxide (Pt/WO3), which shows gasochromism, is an excellent candidate for optical hydrogen gas sensor applications. Pt/WO3 turns blue in a hydrogen gas atmosphere and its electrical conductivity also changes at the same time.This study investigated the influence of partial pressures of hydrogen and oxygen gases on the gasochromism of Pt/WO3. Using elementary gasochromic reactions as a basis, we estimated the concentration of hydrogen injected into a WO3 lattice from the equilibrium of elementary reaction velocities. The estimation suggested that the inverse of the hydrogen concentration in WO3 was inversely proportional to the partial pressure of hydrogen and was proportional to that of oxygen. Additionally, the estimation agreed well with the results of Pt/WO3 gasochromic properties. Therefore, we were able to confirm the dependence of gasochromism on the partial pressures of hydrogen and oxygen gases, and substantiate that Pt/WO3 is capable of detecting hydrogen gas concentrations in various atmosphere conditions where oxygen gas partial pressures change.

Eye-readable gasochromic and optical hydrogen gas sensor based on CuS–Pd

A CuS–Pd nanohybrid functions as a naked eye detectable H2 chemochromic and optical sensor by taking an advantage of a decrease in localized surface plasmon resonance due to a reduction in free carrier density.

A low temperature operated NO2 gas POF sensor based on conducting graft polymer

It has developed a simple POF sensor that is used to detection and measure concentration of nitrogen dioxide, at low temperatures (about 50°C). In this work, we present thermal profiling process of sensor head type POF, and application of sensing structure based on grafted polymer preparation by dip-coating technique. Were performed characterization prepared structures and tests with various concentration NO2 at low temperature and dry atmosphere. Full Text: PDF References E. Maciak, Z. Opilski, M. Urbanczyk, "Pd/V2O5 fiber optic hydrogen gas sensor", J. de Physique IV 129, 137 (2005). CrossRef T. Pustelny, M. Procek, E. Maciak, A. Stolarczyk, S. Drewniak, M. Urbanczyk, M. Setkiewicz, K. Gut, Z. Opilski, "Gas sensors based on nanostructures of semiconductors ZnO and TiO2", Bulletin of the Polish Academy of Sciences: Technical Sciences, 60(4), 853 (2012). CrossRef G. Mauthner, K. Landfester, A. Köck, H. Brückl, M. Kast, C. Stepper, E. J. W. List, "Inkjet printed surface cell light-emitting devices from a water-based polymer dispersion", Org. Electron. Physics, Mater. Appl. 9, 164 (2008). CrossRef A.Stolarczyk et al. Polish patent application nr P.407784 RR10.

Influence of Catalyst Loading Method on Titania-Based Optical Hydrogen Gas Sensing Properties

We reported that titania ceramic coating loaded with palladium catalyst worked as an optical hydrogen gas sensor at room temperature. The palladium metal of this sensor worked as a catalyst not only for room-temperature operation but also for high selectivity to hydrogen gas. Precise control of metal/ceramic interface between the titania and the palladium was very important in order to improve the sensor performance such as sensitivity, response time, recovery time. Influence of a difference in palladium-catalyst loading method (photodeposition and sputtering) on the optical hydrogen gas sensing properties for the titania-based sensor was investigated. It was found that the catalytic loading process significantly affected the optical hydrogen characteristics of the titania-based coating.

Characteristics of an Optical Fiber Hydrogen Gas Sensor Based on a Palladium and Yttrium Alloy Thin Film

To improve the hydrogen sensor characteristics, the choice of doping atoms in Pd is crucial. A novel palladium (Pd) and yttrium (Y) thin film is prepared and utilized to design a reflected optical fiber hydrogen gas sensor. The performance and mechanical properties of the hydrogen sensor are examined. Experimental results show that the response value of the sensor decreases evidently and rapidly with increasing hydrogen concentration, the first drift of zero point of sensors increases as hydrogen concentration increases, and frequent use can reduce the drift of the sensor and increase repeatability. The sensor with Pd-Y alloy film possesses smaller zero point drift and better resistance to hydrogen embrittlement than that with pure Pd film after several hydrogen loading/unloading cycles. Several thin film samples with different thicknesses are fabricated and tested. The sensitivity of the sensor is higher at low-concentration hydrogen and thick film.

Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film

Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H(2)]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd(0.91)Y(0.09) alloy ultrathin film have potential applications in hydrogen detection and measurement.

Low Temperature Preparation and Optical Hydrogen Response of Pd/Titania Composite Film

Photocatalytic titania coatings loaded with palladium catalyst were prepared onto soda-lime glass substrates by using a low temperature synthesis for application of optical hydrogen gas sensor. Titania coatings were formed on the glass substrate by a sol-gel spin-coating process followed by a hot water treatment at 55°C. Metallic palladium nanoparticles were deposited onto the titania coatings, which obtained with addition of poly(ethylene glycol) (PEG) and without PEG after the hot water treatment, by means of a photodeposition technique at room temperature using UV-light irradiation. The whole fabrication process was carried out under atmospheric pressure. The Pd-photodeposited titania coating obtained with addition of PEG after hot water treatment showed higher hydrogen sensing properties than that obtained without PEG.

A fiber-optic hydrogen gas sensor with low propagation loss

An optical fiber hydrogen gas sensor, whose clad region constitutes a gas sensing area, was developed. For gas leakage monitoring purposes, sensing devices with wider sensing region are highly desirable. The reported sensor has potential to detect the hydrogen leakage anywhere along the sensing fiber. The sensing principle was based on the absorption of the evanescent-wave interaction in the clad region composed of tungsten trioxide (WO 3) and platinum (Pt) layer. This two-layered thin film was fabricated by electron beam (EB) deposition method. The WO 3 layer was directly deposited on the quartz glass fiber core, and the Pt layer was deposited on top of the WO 3 layer afterward. Hydrogen atoms are easily intercalated into WO 3 causing the semitransparent WO 3 film to be transformed to blue tungsten bronze. This color change resulted in increase of optical fiber propagation loss. The Pt layer serves as catalyst to stimulate the reaction. Proper thickness of the sensing layer was crucial to the ideal operation. Thicker WO 3 layer results in higher sensitivity, with the sacrifice of the increase in propagation loss. The loss increase limits the practical sensing length. The optimal thickness of WO 3 layer was determined to be 50 nm, whereas that of Pt catalyst was 5 nm. The propagation loss of this sensor device was lower than that of the device fabricated by sol–gel (SG) method, which was previously developed. The fast response speed and good reproducibility were also observed. The EB deposition method was effective to control optical properties of the sensor device with ease and highly promising technology for realizing distributed sensor devices.

Development of a prototype optical hydrogen gas sensor using a getter-doped polymer transducer for monitoring cumulative exposure: Preliminary results

A novel prototype optical sensor for monitoring cumulative hydrogen gas exposure was fabricated and evaluated. Chemical-to-optical transduction was accomplished by detecting the intensity of 670 nm laser light transmitted through a hydrogen getter-doped polymer film mounted at the end of an optical fiber; the transmittance of the composite film increased with uptake of hydrogen by the embedded getter. The composite film consisted of the hydrogen getter 1,4-bis(phenylethynyl)benzene, also known as DEB, with carbon-supported palladium catalyst embedded in silicone elastomer. Because the change in transmittance was irreversible and occurred continuously as the getter captured hydrogen, the sensor behaved like a dosimeter, providing a unique indication of the cumulative gas exposure.

Effect of sputter etching of glass substrate for optical hydrogen gas sensor using Pd thin films

Effect of sputter etching of glass substrate for optical hydrogen gas sensor using Pd thin films

Effect of humidity on sensing characteristics of optical readable hydrogen gas sensor using Palladium film

Effect of humidity on sensing characteristics of optical readable hydrogen gas sensor using Palladium film