Optical sensor for detecting cesium ions and / or measuring cesium ion concentration

Abstract

The invention relates to an optical sensor for detecting cesium ions in a fluid medium and / or measuring the concentration thereof, comprising a resonant structure (1), the surface of which is covered with a macrocyclic compound layer (2). The invention also relates to a method for covering the surface of a resonant structure (1) of an optical sensor with a macrocyclic compound layer (2), enabling the optical sensor to detect cesium ions in a fluid medium and / or to measure the concentration thereof.

Description

Technical Field

[0001] The present invention relates to an optical sensor for detecting cesium ions and / or measuring the concentration of cesium ions, and a method for enabling the optical sensor to perform the functions described. Background Art

[0002] Cesium ("Cs") plays an increasingly important role worldwide, especially in the fields of defense, aerospace, energy generation, electronic devices and medicine. Therefore, the demand for Cs in the international market has grown significantly. In contrast to the utility provided by Cs, Cs is an alkali metal with high reactivity, high fission yield and long half-life, so it is toxic and harmful to the environment and human health. Among the isotopes of Cs, 137 Cs poses the greatest threat to human health because it emits gamma rays and has a half-life of 30.17 years.

[0003] Researchers have been working to 137 Separation or removal of Cs contaminated media 137 Cs. Various materials and techniques have been introduced into methods for detecting or measuring Cs, such as flame atomic absorption spectrometry ("FAAS"), inductively coupled plasma mass spectrometry ("ICP-MS"), inductively coupled plasma optical emission spectrometry ("ICP-OES"), and ion chromatography ("IC"). Related methods of ICP-MS have been described by Cao et al. in a paper entitled "Simultaneous determination of radiocenesium ( 135 Cs, 137 Cs) and plutonium( 239 Pu, 240 Pu)isotopes in river suspended particles by ICP-MS / MS and SF-ICP-MS”.

[0004] However, the above methods also have many disadvantages, including the need for complex and expensive testing equipment, complex sample pretreatment, and / or the need for trained personnel to collect samples and analyze results, which further hinder the use of this method for field, in-situ measurements.

[0005] In patent application number CN113049573A, a ligand solution containing a macrocyclic compound is disclosed for detecting rubidium ions and cesium ions. Although it is known that macrocyclic compounds can bind metal cations in contaminated media, it is difficult to coat a specific macrocyclic compound on a test structure, especially on a substrate that can be used to detect Cs + There are difficulties in compact test structures to measure its concentration on site and in situ. Summary of the invention

[0006] The above-mentioned disadvantages and difficulties are overcome by the present invention as described in detail in the following paragraphs.

[0007] One aspect of the present invention provides an optical sensor for detecting cesium ions in a fluid medium and / or measuring its concentration, comprising a resonant structure, at least a portion of the surface of which is covered by a macrocyclic compound layer, characterized in that the macrocyclic compound is dibenzo-24-crown-8 bromide, and its material index varies depending on the amount of cesium ions bound to it.

[0008] Advantageously, dibenzo-24-crown-8 bromide is an ionophore capable of chemically binding to cesium ions in the medium, allowing the corresponding change in the material index to be detected and / or measured.

[0009] Advantageously, the resonant wavelength of the resonant structure shifts according to a change in the material index.

[0010] In one embodiment, the resonant structure comprises a test waveguide and a reference waveguide, the test waveguide being exposed to the medium and the reference waveguide being sealed to avoid any contact with the medium. Typically, the resonant structure is formed in silicon or silicon dioxide.

[0011] In one embodiment, the light source is configured to emit light of at least one wavelength, which is directed through the test waveguide and the reference waveguide, and a shift in the resonant wavelength is determined by comparing the spectra generated from the corresponding test waveguide and reference waveguide, the shift corresponding to the concentration of cesium ions in the medium. Advantageously, such comparison allows accurate measurement of shifts of <500 pm, resulting in sensitivity as low as 10 ppb of cesium ions.

[0012] In another embodiment, the optical sensor further comprises a spectral interrogator connected to the outputs of the test waveguide and the reference waveguide, capable of providing a reading of the wavelength or phase of the light.

[0013] Typically, the test waveguide and the reference waveguide have a width of 15 nm to 1000 nm and a length of 200 μm to 1 cm.

[0014] Typically, the light source comprises at least one laser source and is capable of emitting light in a wavelength range of 1500nm to 1600nm. Typically, the laser source is capable of scanning and emitting light in the above wavelength range in less than one second.

[0015] Typically, during testing, the exposable resonant structure is exposed to the medium for a period of time ranging from 30 seconds to 2 minutes.

[0016] In yet another embodiment, the optical sensor further comprises a pair of multi-mode interferometers, wherein one of the pair of multi-mode interferometers is connected to the input end of the resonant structure to diverge light, and the other of the pair of multi-mode interferometers is connected to the output end of the resonant structure to converge light.

[0017] In yet another embodiment, the optical sensor further comprises: a silicon wafer interposer and a spot size converter connected to the input end of the multi-mode interferometer; and a waveguide, an input of which is connected to the light source and an output of which is connected to the silicon wafer interposer.

[0018] In another embodiment, the spectral interrogator includes: a pair of multi-mode interferometer-based reflectors and two pairs of micro-ring resonators.

[0019] Typically, when the macrocyclic compound is exposed to a medium containing a combination of different metal ions, the resonant wavelength of the resonant structure shifts over time.

[0020] Typically, the shift in resonant wavelength is a superposition of the resonant wavelength versus time curves for each metal ion in the composition, wherein the superposition can be used to train an artificial neural network to determine the presence and / or concentration of cesium ions in the medium.

[0021] Advantageously, the macrocyclic compound has unique kinetics in absorbing cesium ions, so that when the macrocyclic compound is exposed to a medium containing a certain concentration of cesium ions, it causes the resonant structure to provide a distinct resonant wavelength versus time curve, wherein the distinct curve can be used to identify cesium ions in the medium and / or measure the cesium ion concentration.

[0022] Another aspect of the present invention provides a method for covering the surface of a resonant structure of an optical sensor with a macrocyclic compound layer, so that the sensor can detect cesium ions and / or measure its concentration in a fluid medium, comprising the following steps: plasma treating the surface with oxygen; treating the surface with a 2% (v / v) 3-aminopropyltriethoxysilane (APTES) solution diluted with pure ethanol at room temperature for a first predetermined time period; characterized in that the surface is treated with 50 ml of a 100 mM dibenzo-24-crown-8 bromide (BDB24C8) solution diluted with a solvent; and leaving the surface to stand to allow the solvent in the BDB24C8 solution to evaporate, so that a macrocyclic compound layer is formed on the surface.

[0023] Typically, the macrocyclic compound is dibenzo-24-crown-8 bromide.

[0024] Dibenzo-24-crown-8 bromide is an ion carrier capable of chemically binding to cesium ions in a medium, so that the material index of dibenzo-24-crown-8 bromide varies depending on the amount of cesium ions bound thereto.

[0025] In one embodiment, the method further comprises the steps of drying the surface at 80°C for a first predetermined period of time; and treating the surface with a 0.1% (v / v) glutaraldehyde (GA) solution diluted with deionized water at room temperature for a second predetermined period of time.

[0026] Typically, the first predetermined time period is 1 hour, and the second predetermined time period is 20 minutes.

[0027] Typically, the solvent is methanol.

[0028] Typically, the optical sensor comprises a Mach-Zehnder interferometer.

[0029] Yet another aspect of the present invention provides an optical sensor manufactured by the above method.

[0030] Advantageously, the resonant wavelength of the resonant structure shifts according to a change in the material index.

[0031] Typically, when the macrocyclic compound is exposed to a medium containing a composition of different metal ions, the resonant wavelength of the resonant structure shifts over time, and the shift in the resonant wavelength is a superposition of the resonant wavelength versus time curves of each metal ion in the composition, wherein the superposition can be used to train an artificial neural network to determine the presence and / or concentration of cesium ions in the medium.

[0032] Advantageously, the macrocyclic compound has unique kinetics in absorbing cesium ions, so that when the macrocyclic compound is exposed to a medium containing a certain concentration of cesium ions, it causes the resonant structure to provide a distinct resonant wavelength versus time curve, wherein the distinct curve can be used to identify cesium ions in the medium and / or measure the cesium ion concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will now be described in more detail by way of example and with reference to the accompanying drawings, in which:

[0034] Figure 1 It shows the mechanism according to the present invention, that cesium cations are captured by the macrocyclic compound layer coated on the surface of the resonant structure;

[0035] Figure 2 showing that when the macrocyclic compound is exposed to a medium containing different metal ion compositions, the resonant wavelength of the resonant structure shifts over time;

[0036] Figure 3 It is shown that a higher wavelength of light is required to cause the resonant structure to resonate than when the resonant structure is not coated with the macrocyclic compound layer;

[0037] Figure 4is a plan view of a dielectric planar lightwave circuit (PLC) having waveguide segments of different widths;

[0038] Figure 5 is a top view of the sensor chip, the input of the sensor chip is connected to the laser source, and the output of the sensor chip is connected to the spectral interrogator;

[0039] Figure 6 is a top view of a Mach-Zehnder interferometer system built on a silicon-on-insulator platform; and

[0040] Figure 7 is a graph of transmittance versus resonant wavelength, showing that as Cs + As the concentration increases, the resonant wavelength shifts. DETAILED DESCRIPTION

[0041] Certain macrocyclic compounds can act as Cs cations (“Cs + ”) and can therefore be used to separate or remove Cs from contaminated media. + Combined with Cs + The ability is attributed to the cavity of the macrocycle and the Cs + The ionic radii of Cs + Factors that influence recognition, as well as stability and selectivity of recognition, include cavity size, shape, substitution effects, conformational flexibility, type of donor atom, and solvent for the macrocycle. + The macrocyclic compound provides Cs + A close-fitting cavity and a set of Cs + The surrounding oxygen atoms can be used to selectively separate Cs from complex media such as water and nuclear waste solutions. + Promising results have been achieved.

[0042] See also Figure 1 One form of optical sensor may be a Mach-Zehnder interferometer, comprising a resonant structure 1, such as a waveguide, coated with a layer 2 of a macrocyclic compound, namely brominated dibenzo-24-crown-8 ("BDB24C8"). BDB24C8 is a macrocyclic compound that is capable of chemically binding to Cs in a fluid medium (e.g., a liquid or gas). + ion carrier, and formed by BDB24C8 and Cs + Composition of complex 3.

[0043] The method for coating a macrocyclic compound layer 2 on the surface of a resonant structure 1 includes the following steps. First, in order to hydroxylate the surface, the surface is plasma treated with oxygen. Then, at room temperature, the surface is treated with a 2% (v / v) 3-aminopropyltriethoxysilane ("APTES") solution diluted with pure ethanol for 1 hour. Subsequently, the surface is completely dried at 80°C for 1 hour, and then the surface is treated with a 0.1% (v / v) glutaraldehyde ("GA") solution diluted with deionized water for 20 minutes at room temperature. Subsequently, the surface is treated with 50 ml of a 100 mM brominated dibenzo-24-crown-8 ("BDB24C8") solution diluted with a solvent (i.e., methanol). Finally, the surface is left to stand to allow the solvent in the BDB24C8 to evaporate, so that a macrocyclic compound layer 2 (i.e., BDB24C8) is formed or fixed on the surface.

[0044] The coated resonant structure 1 is used as Cs + The ligand BDB24C8 is functionalized and can therefore detect monovalent cations of Cs. + When the medium is BDB24C8, the material index will be based on the Cs + changes with the amount.

[0045] When the concentration of BDB24C8 immobilized on the surface increases, the Cs + Wider range of detection. Therefore, the concentration of BDB24C8 can be adjusted according to the test requirements to optimize the detection range.

[0046] Since the BDB24C8 layer is heterogeneously integrated with the resonant structure 1, the change in the material index will change the resonant condition of the surface of the resonant structure. Figure 2 As shown, when the macrocyclic compound is exposed to a medium with a composition of different metal ions, the resonant wavelength of the resonant structure will shift over time, and the shift of the resonant wavelength is the superposition of the curves of the resonant wavelength of each metal ion in the composition and time. The superposition can be used to train an artificial neural network to determine the presence and / or concentration of cesium ions in a medium. The macrocyclic compound has unique kinetics in absorbing cesium ions, so when the macrocyclic compound is exposed to a medium with a certain concentration of cesium ions, it causes the resonant structure to provide a distinct resonant wavelength versus time curve. The distinct curve can be used to identify cesium ions and / or measure cesium ion concentration in a medium.

[0047] The higher the concentration of cesium ions, the faster the resonant structure achieves the maximum resonant wavelength corresponding to the concentration.

[0048] The material index is a set of material properties that affect the characteristics of a layer. These properties include relative permittivity, thermal resistivity (°C.cm / W), and loss tangent. For silicon photonic sensors, the material index is usually the refractive index.

[0049] Resonance can be defined as a large amplitude vibration in a mechanical, electrical, or optical system caused by a relatively small periodic stimulus of the same or nearly the same period as the natural vibration of the system.

[0050] For optical sensors, resonance occurs on their resonant structures, and the periodic stimulus is a light wave with a specific wavelength, which is called the resonant wavelength, i.e., the wavelength of the light wave that causes the resonant structure to resonate.

[0051] Adding a macrocyclic compound layer on the surface of the resonant structure changes the conditions for the resonant structure to resonate. Figure 3 As shown, the wavelength of the light wave needs to be longer than the wavelength of the light wave when the resonant structure is not coated with the macrocyclic compound layer to cause the resonant structure to resonate. + With the increase of concentration, the material index of the macrocyclic compound layer changes, and the resonant wavelength of the resonant structure increases accordingly.

[0052] Resonant structures are important components of optical sensors in which macrocyclic compounds are able to affect the wavelength of light passing through the structure. When light passes through the structure, the electric field propagates out of the structure walls in the form of an evanescent field. The evanescent field is easily affected by the surrounding environment and is therefore easily affected by the macrocyclic compound layer located on the outer surface of the structure. Since the material index of the macrocyclic compound is affected by Cs + The absorption of the structure changes, the evanescent field is affected by the change, and the resonant wavelength of the light passing through the structure increases accordingly.

[0053] refer to Figure 4 , the optical sensor can be a dielectric planar lightwave circuit ("PLC") having waveguide segments of different widths, usually arranged in pairs. Each end of the PLC has a fiber array assembly to which a fiber adapter is connected. The fiber adapter adapts the fiber to the PLC and vice versa. The circuit can be mass-produced by semiconductor wafer processing. At least one waveguide segment is coated with a macrocyclic compound layer. The coated waveguide segment acts as a resonant structure of the PLC.

[0054] See also Figure 5 , can be in one or more mm 2 Multiple PLCs are deployed on a large-scale sensor chip 4. For each PLC, one waveguide segment 5 is exposed, while the other waveguide segment 6 is sealed to avoid contact with the medium (or not coated with a macrocyclic compound). During the test, the exposed waveguide segment 5 provides a contact with the Cs in the medium. + The wavelength spectrum corresponding to the concentration of Cs is shown in Figure 2, while the sealed waveguide section 6 provides the same+ The input of the PLC is connected to a plurality of laser sources 7, and the output of the PLC is connected to the reference wavelength spectrum corresponding to the conditions of Cs + The detector is connected to the spectral interrogator 8.

[0055] refer to Figure 6 , the resonant structure can also be deployed in a Mach-Zehnder interferometer ("MZI") system, which is built on a silicon-on-insulator ("SOI") platform. The input of the MZI system is a III-V waveguide 9, which is connected to a silicon wafer interposer and a spot size converter ("SSC") 10. The interposer has a silicon dioxide SiO2 cladding with a width of 6μm and a thickness of 0.07μm. The output of the interposer and SSC is coupled to a 1x2 multimode interferometer ("MMI") 11, whose output diverges to an unbalanced MZI 12 and a waveguide sensing section 13, which is a resonant structure coated with a BDB24C8 layer on the surface. The waveguide sensing section 13 is a silicon dioxide SiO2 cladding with a width of 15nm to 1000nm, a thickness of 220nm, and a length of 200μm to 1cm. The other end of the unbalanced MZI 12 and the waveguide sensing section 13 converge to a 2x1 MMI 14, which couples them to an interrogator 15 that is fully integrated in the system. The MMIs 11 and 14 deployed at the two ends are vertical grating couplers, preferably transverse mode ("TM"). The interrogator 15 includes a pair of MMI-based reflectors 16, 17, and two pairs of microring resonators ("MRR") 18, 19, 20, 21. The MZI system provides readout parameters in units of phase or λ (i.e., wavelength) with a wavelength range of 1500nm to 1600nm and a resolution as low as 1pm.

[0056] When performing tests using an MZI system, the following sequence may be observed. First, a drop of distilled water is added to the surface of the MZI system as a blank sample. Second, the drop of distilled water is removed from the surface. Third, a known Cs + The solution of 100% concentration was added to the surface. After 30 seconds to 2 minutes, the solution was removed from the surface. Then, a drop of distilled water was added to the surface again. Last but not least, the laser was scanned from a wavelength of 1500nm to 1600nm and the output of the sensor was measured.

[0057] refer to Figure 7 , the output of the sensor can be displayed as a graph of transmittance versus resonant wavelength. + As the concentration increases, the resonant wavelength tends to shift to the right, that is, it becomes higher. This shift can be as high as 500pm or more, and the experimentally observed shift range is 340pm to 430pm, which can be used to identify Cs in the medium. + presence and measure its concentration.

[0058] The above method is relatively simple, but produces a highly sensitive and selective optical sensor capable of detecting Cs at concentrations ranging from 10 ppb to 200 ppm in aqueous or non-aqueous environments. + Compared to ICP-MS or ICP-OES methods, multiple BDB24C8-coated resonant structures (e.g., mirror resonators) are set up in a photonic platform (e.g., Mach-Zehnder interferometer) and occupy a smaller space. Despite the smaller footprint, the optical sensor is still able to accurately detect Cs + and measure its concentration.

[0059] In addition, the above method uses non-toxic solvents. The optical sensor prepared by this method has a compact structure and can be used for on-site, in-situ detection and measurement of Cs + , so it has great commercial value, especially in the fields of nuclear energy and water quality monitoring industries.

[0060] It should be understood by those skilled in the art that the present invention may also include further additional modifications that do not affect its overall functionality.

Claims

1. An optical sensor for detecting cesium ions in a fluid medium and / or measuring its concentration, comprising: A resonant structure (1), wherein at least a portion of the surface of the resonant structure is covered by a macrocyclic compound layer, Characterized in that the macrocyclic compound is dibenzo-24-crown-8 bromide, and its material index varies according to the amount of cesium ions bound thereto.

2. An optical sensor according to claim 1, wherein dibenzo-24-crown-8 bromide is an ion carrier capable of chemically binding to cesium ions in the medium, so that the resonant wavelength of the resonant structure (1) shifts over time according to the corresponding change of the material index, and the shift can be detected and / or measured.

3. The optical sensor according to claim 2, wherein the resonant structure comprises a test waveguide (5) and a reference waveguide (6), the test waveguide (5) being able to be exposed to the medium, and the reference waveguide (6) being sealed to avoid contact with the medium.

4. The optical sensor of claim 3 , wherein the light source is configured to emit light of at least one wavelength, the light being guided through the test waveguide and the reference waveguide, the shift in the resonant wavelength being determined by comparing spectra generated from the corresponding test waveguide and reference waveguide, the shift corresponding to the concentration of cesium ions in the medium.

5. An optical sensor according to claim 4, further comprising a spectral interrogator (8) connected to the outputs of the test and reference waveguides (5, 6) and capable of providing a reading of the wavelength or phase of the light.

6. The optical sensor according to claim 5, wherein each of the test waveguide and the reference waveguide (5, 6) has a width of 15 nm to 1000 nm and a length of 200 μm to 1 cm.

7. The optical sensor according to claim 6, wherein the light source (7) comprises at least one laser source and is capable of emitting light in a wavelength range of 1500 nm to 1600 nm.

8. The optical sensor according to claim 5, wherein during the test the test waveguide (5) is exposed to the medium for a period of time ranging from 30 seconds to 2 minutes.

9. The optical sensor according to claim 8, further comprising a pair of multi-mode interferometers (11, 14), wherein one of the pair of multi-mode interferometers is connected to the input end of the resonant structure (1) to diverge light, and the other of the pair of multi-mode interferometers is connected to the output end of the resonant structure (1) to converge light.

10. The optical sensor according to claim 9, further comprising: A silicon wafer interposer and a spot size converter (10) connected to an input end of the multimode interferometer (11); A waveguide (9), wherein the input of the waveguide is connected to the light source, and the output of the waveguide is connected to the silicon wafer interposer.

11. The optical sensor of claim 10, wherein the spectral interrogator comprises: A pair of reflectors (16, 17) based on a multi-mode interferometer and two pairs of micro-ring resonators (18, 19, 20, 21).

12. A method for covering the surface of a resonant structure (1) of an optical sensor with a layer of a macrocyclic compound (2), so that the sensor can detect cesium ions in a fluid medium and / or measure its concentration, comprising the following steps: plasma treating the surface with oxygen; as well as treating the surface with a 2% (v / v) 3-aminopropyltriethoxysilane (APTES) solution diluted in pure ethanol at room temperature for a first predetermined period of time; Characterized in that the surface is treated with 50 ml of a 100 mM solution of dibenzo-24-crown-8 bromide (BDB24C8) diluted with a solvent; and The surface is left to stand to allow the solvent in the BDB24C8 solution to evaporate, so that the macrocyclic compound layer (2) is formed on the surface.

13. The method according to claim 12, wherein the macrocyclic compound is dibenzo-24-crown-8 bromide, and its material index varies depending on the amount of cesium ions bound thereto.

14. The method according to claim 13, further comprising the steps of: drying the surface at 80° C. for the first predetermined period of time; and The surface is treated with a 0.1% (v / v) glutaraldehyde (GA) solution diluted in deionized water at room temperature for a second predetermined period of time.

15. The method according to claim 14, wherein the first predetermined time period is 1 hour, and the second predetermined time period is 20 minutes.

16. The method according to claim 14, wherein the solvent is methanol.

17. The method of claim 14, wherein the optical sensor comprises a Mach-Zehnder interferometer.

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