CZ308875B6 - Hydrogen sensor based on plasmon-active fibres functionalized with a porous metal-organic layer for "remote" non-electrical detection - Google Patents

Abstract

The technical solution relates to an optical sensor element for detecting hydrogen. The basis of the sensor is a plasmon-active surface of an optical fibre with a deposited layer of a highly porous metallic-organic substance with a high affinity for hydrogen. Such a hydrogen sensor based on plasmon-active fibers consists of a multimode fibre on which a layer of plasmon-active metal is applied, which is modified with a diazonium salt of 4-amino-1,2-dithiolane-4-carboxylic acid and metallic organic 3-dimensional framework structures containing zinc and an organic ligand with unsaturated oxygen, sulfur or nitrogen centres. Gold, silver or copper 10 to 50 nm thick are used as the plasmon active metal.

Description

Hydrogen sensor based on plasmon-active fibers functionalized with a porous metallic organic layer for "remote" non-electrical detection

Field of technology

The invention relates to an optical element for remote detection of hydrogen without the use of electronic components and to an active detection area. A detection element based on plasmon-active optical fibers with a unique deposited layer of metallic-organic networks with high affinity for hydrogen is proposed. The element is prepared by means of a thin layer of plasmon-active metal, applied to the core of the optical fiber and subsequently functionalized with a porous metal-organic layer. The structure of this element guarantees plasmon absorption in air, high selectivity and affinity for hydrogen. The measurement results show changes in the refractive index of the porous layer due to hydrogen sorption and the spectral shift of plasmonic absorption. The proposed element demonstrates a high rate of response and regeneration, excellent selectivity to hydrogen, very low temperature dependence, functionality at room or reduced temperature. Hydrogen detection is not affected by ambient humidity. In addition, the designed hydrogen sensor shows very good reversibility, reproducibility and long-term stability. The intended application of the element is remote detection of the presence / leakage of hydrogen in technological environments where conventional electrical sensors cannot be used.

Prior art

The use of hydrogen as a clean and sustainable energy source has recently increased exponentially worldwide [1]. The key problem is that hydrogen is an odorless, extremely flammable and explosive gas (the lower explosive limit of hydrogen is 4% by volume in air). Therefore, the development of reliable sensor elements for detecting trace amounts of hydrogen is necessary to reduce the risk of explosion caused by hydrogen leakage during its production, storage, transport and use. Modern hydrogen sensors must meet the following requirements: they must have a very fast response, high sensitivity, selectivity to hydrogen and also low detection limits [2]. Various types of hydrogen sensors have been developed in recent decades, including semiconductor [3], thermoelectric [4], optical [5] or surface-acoustic [6]. It is optical sensors that offer a number of advantages over others, especially simplicity, low cost and efficiency of production and operation, high sensitivity, electrical insulation environment, the possibility of remote sensing and a small size of the device. The advantage is the possibility of easy integration with other devices [7]. Currently, several structures of hydrogen sensors based on optical fibers and their various configurations, such as Fabry-Perot interferometer [8] and Bragg gratings [9], These sensors they show a large detection range, but usually low sensitivity. An alternative approach is to use plasmon-based active fiber sensors, which leads to increased sensitivity to hydrogen [10] ·

Current plasmon-active fiber sensors use additional deposition of the layer on the plasmon active surface, which changes the refractive index in the presence of hydrogen, leading to an apparent shift of the plasmon absorption band [28]. Sensitive palladium or platinum-based metal layers are commonly used. , which usually provide a quick response, but are economically expensive to use [11]. An alternative solution is to use transition metal oxides such as TiCE, NiOx and WO3. In this case, their selectivity to hydrogen remains a major issue, especially in the presence of moisture, oxidizing gas and temperature fluctuations [12]. , high temperature interference, high influence of humidity [12], In our design, these mentioned problems are largely solved thanks to the use of advanced sensitive layer design based on porous metallic-organic layer.

References (1) Wang, Z .; Li, Z .; Jiang, I '.; Xu. X .; Wang, C. Ultrasensitive 1 lydrogen Sensor Based on PdO

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Loaded SnO2 Electrospun Nanofibers at Room Temperature. AC'SAppl. Mater. Interfaces 2013. 5 (2) Tsai. J.-H .; Niu, J.-S. Hydrogen Sensing Characteristics of AlGalnP / InGaAs Enhancement / Depletion-Mode Co-Integrated Doping-Channel Field-Effect Transistors. International Journal of Hydrogen Energy 2019. 44 (3). 2053-2058.

(3) Fahad, Η. M .; Gupta, N .; Han. R .; Desai, S. B .; Javey, A. Highly Sensitive Bulk Silicon Chemical Sensors with Sub-5 Nm Thin Charge Inversion Layers. ACS Nano 2018, 12 (3), 2048 2054.

(4) Kim, S .; Song, Y .; Lim, IL-R .; Kwon, Y.-T .; Hwang, T.-Y .; Song, E .; Lee, S .; Lee, Y.-L; Cho, H.-B .; Choa. Y.-H. Fabrication and Characterization of Thermochemical Hydrogen Sensor with Laminated Structure. International Journal of Hydrogen Energy 2017, 42 (1), 740-756.

(5) Wu, B .; Zhao, C \; Xu, B .; If. Y. Optical Fiber Hydrogen Sensor with Single Sagnac Interferometer Loop Basedon Vernier Effect. Sensors and Actuators B: Chemical 2018, 255, 30113016.

(6) Perez-Cortes, L .; Hernandez-Rodriguez, C .; Mazingue, T .; Lomello-Tafm, M. Functionality of (7) Li. OF.; Yan. WITH.; Wu. OF.; Li, H .; Wang, J .; Shen, W .; Wang. OF.; Fu, Y. Hydrogen Cias Sensor Based on Mesoporous ImCL with Fast Response / Recovery and Ppb Level Detection Limit. International Journal qfHydrogen Energy 2018, 43 (50), 22746-22755.

(8) Samsudin, M. R .; Shcc, Y. G .; Adikan, F. R. M .; Razak, B. B. A .; Dahari, M. Liber Bragg Gratings Hydrogen Sensor for Monitoring the Degradation of Transformer Oil. IEEE Sensors Journal 2016,16 (9), 2993-2999.

The essence of the invention

The essence of the invention lies in the design and optimization of the innovative structure of a hydrogen sensor with a plasmon-active layer, a functionalized metal-organic porous layer. The plasmon response is achieved by depositing a thin layer of noble metal on the core of the optical fiber. The shift of plasmon resonance makes it possible to monitor changes in the near environment of the optical fiber (ie changes in the refractive index). In the next step, selective sensitivity to hydrogen was achieved through surface-stimulated growth of the metal-organic layer with high affinity for hydrogen. The type of metal-organic layer was chosen for the following reasons: high specific surface area, high capacity for hydrogen adsorption (large pore volume), high selectivity for hydrogen, relatively cheap metals / compounds for preparation. The thickness of the metal-organic layer was optimized to achieve demonstrable plasmon resonance in air.

Due to the fact that the selected layers have a highly active surface, which is advantageous for hydrogen trapping, in the presence of hydrogen there are significant changes in their refractive index. These changes lead to a significant shift in plasmonic absorption and thus allow the detection of hydrogen by measuring the transmission spectra of the optical fiber. In addition, the results of the characterization of this newly prepared element show that in the presence of hydrogen, the plasmonic absorption increases by an order of magnitude, which allows detection by a single wavelength. Since the optical changes are dependent on the hydrogen concentration, it is also possible to accurately determine its concentration. The observed changes in hydrogen concentration have a linear dependence, which solves one of the significant and key problems - the nonlinear response in the proposed optical hydrogen sensors. The minimum detectable concentration was found to be 1.5% by volume of hydrogen in the air. At a hydrogen concentration greater than 20% by volume, the sensor response was saturated. The observed value of the plasmon peak shift reached 77 nm, which significantly exceeds the "scientific or commercial" use of an analogous structure. In addition, testing results of some "available" sensor elements showed their low sensitivity to the presence of moisture, oxidizing gases and temperature dependence.

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Explanation of drawings

Giant. 1

Scheme of preparation of sensor structure based on plasmon resonance and sensitive metal-organic layer.

Giant. 2

Sensor functionality tests: spectral transmittance as a function of hydrogen concentration.

Giant. 3

Reproducibility of sensor use, demonstration of monitoring the speed of its response and regeneration.

Giant. 4

Determination and comparison of "low" sensitivity of the sensor to the presence of additional gas.

Giant. 5

Tests of the effect of humidity on the response of the hydrogen sensor.

Giant. 6

Tests of the effect of temperature on the response of the hydrogen sensor.

Examples of embodiments of the invention

Example 1

A 1.5 cm long sheath was removed from a commercially available multimode fiber (diameter 800/400 μm - sheath / core). A 50 nm thick layer of gold was deposited on the optical fiber core by sputtering. The diazonium salt of 4-amino-1,2-dithiolane-4-carboxylic acid (ADT-COOH) was grafted onto the gold surface, followed by a 35 nm thick metallic organic structure IRMOF-20. The fiber ends were connected to a broad spectrum light source and spectrum analyzer via SMA (SubMiniature version A) connectors. The structure was used as a hydrogen sensor with a sensitive area of 1.5 cm for remote detection.

Example 2

A 1.2 cm long sheath was removed from a commercially available multimode fiber (diameter 800/400 μm - sheath / core). A 40 nm thick layer of silver was deposited on the fiber core by sputtering. The diazonium salt of ADT-COOH was grafted onto the silver surface, followed by a metallic organic structure of zinc plus PCN-12 25 nm thick. The fiber ends were connected to a broad spectrum light source and a spectrum analyzer via SMA connectors. The structure was used as a hydrogen sensor with a sensitive area of 1.2 cm for remote detection.

Example 3

A 0.7 cm long sheath was removed from a commercially available multimode fiber (diameter 150/5 μm - sheath / core). A 10 nm thick layer of copper was deposited on the fiber core. The diazonium salt of ADT-COOH was grafted onto the copper surface, followed by the metallic organic structure of zinc plus

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UiO-65 with a thickness of 30 nm. The ends of the fiber were connected to an LED (emission wavelength 630 nm) and a pn light intensity detector. The structure was used as a hydrogen sensor with a sensitive area of 0.7 cm for remote detection.

Example 4

The sensor element was placed in an environment containing a gradually increasing concentration of hydrogen. The results of the transmission optical measurements are shown in Figure 2 in real time at room temperature (24 ° C). It is clear that in the presence of hydrogen, the plasmon absorption band shifts and at the same time its intensity increases. The response values are strongly dependent on the hydrogen concentration, with increasing hydrogen concentration there is a greater shift. Even at 2% by volume hydrogen concentration, the plasmon band is shifted by 9 nm. At a 4% v / v hydrogen concentration (corresponding to the "lower" explosive range), the shift is 22 nm, which provides an excellent detection capability for this critical concentration. As can be seen, the design of the sensor provides an excellent opportunity to measure a hydrogen concentration in the range of 0 to 20% by volume. After reaching a 20% by volume hydrogen concentration, saturation was observed. In the case of a higher hydrogen concentration, the presence of hydrogen can be detected qualitatively.

Example 5

The sensor element was placed in an environment containing a gradually increasing concentration of carbon dioxide. The results of the transmission optical measurements are shown in Figure 3 in real time at room temperature (24 ° C). The sensor did not respond to a gradually increasing concentration of carbon dioxide. It can be said that the sensor shows a high sensitivity only for the presence of hydrogen and thus it is possible to detect the presence of hydrogen against the background of another technically relevant gas.

Example 6

The sensor element was placed in an environment containing successively a concentration of 8% by volume and 0% by volume of hydrogen. The results of the transmission optical measurements are shown in Figure 4 in real time at 30 room temperature (24 ° C). The observed characteristic responses of the element were reproducibly repeatable in the seven cycles tested, which means that the sensor shows good reproducibility for hydrogen detection with a maximum deviation below 3%. The stability of the hydrogen gas sensor was also tested by measuring the response of the device over 2 months (in 1 day increments) and the results are also shown in the right part of Fig. 4. The sensor showed a constant response independent of external environment 35 and storage conditions.

Example 7

The sensor element was placed in an environment containing alternately zero, and conversely gradually decreasing hydrogen concentration. The results of the transmission optical measurements are shown in Figure 4 in real time at room temperature (24 ° C). It is clear that the sensor showed demonstrable responses to all measured hydrogen concentrations and exposure of the sensor to a higher concentration (associated with subsequent sensor recovery) does not affect the measurement of a lower concentration. Thus, it can be stated that the proposed sensor design has excellent reproducibility and stability.

Example 8

The sensor element was placed in an environment containing a constant concentration of hydrogen (4% by volume and 20% by volume). The results of the transmission optical measurements are shown in Figure 4 in real time at different temperatures. As can be seen, the sensor shows a stable response in the temperature range 0 to 50 ° C. Temperature fluctuations “hardly affect the sensor response at higher hydrogen concentrations and lead to a slight shift (2%) of the sensor response at lower concentrations. Unlike a conventional sensor system, the sensitivity of the designed sensor design is independent of temperature changes, and in addition allows direct measurement of hydrogen concentration at room temperature as well as at low temperature.

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Example 9

The sensor element was placed in an environment containing a constant concentration of hydrogen (4% by volume resp.

% vol.). The results of the transmission optical measurements are shown in Fig. 5 in real time at 5 room temperature and elevated temperature with gradually increasing humidity as a variable. As can be seen, the response of the sensor remains independent of humidity and ambient temperature. In particular, both the position and the shape of the plasma absorption band remained the same. This proves that this proposed sensor design significantly outperforms currently available sensors in terms of their insensitivity to moisture.

Industrial applicability

The invention is useful for the production of optical hydrogen sensors for a wide range of fields, including its use, for example, in hydrogen production technology, safe hydrogen storage and the use of hydrogen in various technological processes. The invention allows remote detection of hydrogen with parameters exceeding currently currently available sensors.

Claims (3)

PATENT CLAIMS A hydrogen sensor based on plasmon-active fibers, characterized in that it consists of 5 multimode fibers with a diameter of 800/400 μm or 150/5 μm sheath / core, on which a layer of plasmon active metal which is modified with a diazonium salt is applied. 4-amino-1,2-dithiolane-4-carboxylic acids and metallic organic 3-dimensional framework structures containing zinc and an organic ligand with unsaturated oxygen, sulfur or nitrogen centers. Hydrogen sensor according to Claim 1, characterized in that gold, silver or copper with a layer thickness of 10 to 50 nm is used as the plasmon active metal. Hydrogen sensor according to Claims 1 and 2, characterized in that a metallic-organic frame structure with a high affinity for hydrogen and a thickness of 5 to 500 nm is used as the selective layer.