Acetone gas sensor based on few-mode optical fiber conical probe and preparation method thereof

Abstract

The invention discloses an acetone gas sensor based on a few-mode optical fiber conical probe and a preparation method thereof, and belongs to the crossing field of optical fiber sensing and acetone gas detection.The few-mode optical fiber conical probe comprises a substrate cladding, a conical fiber core is arranged at the center of the substrate cladding, and an optical fiber conical region cladding is arranged at the edge of the substrate cladding; the radius of the conical region cladding of the optical fiber is linearly reduced to the front end face of the circular conical region, and the surface of all the conical region cladding is modified with a three-level coating layer sensitive to acetone gas. Therefore, precise monitoring of a local area is realized, and the problem that the stability and repeatability of a sensing signal are reduced due to the fact that a modification mode of coating a functional material lacks an effective interface connecting layer and particles are easy to fall off is solved.

Description

Technical Field

[0001] This invention relates to the intersection of fiber optic sensing and acetone gas detection, and in particular to an acetone gas sensor based on a few-mode fiber tapered probe and its fabrication method. Background Technology

[0002] Acetone gas detection has significant applications in industrial safety monitoring and medical diagnosis, especially in scenarios such as diabetic breath analysis where high-sensitivity real-time monitoring methods are urgently needed. Traditional electrochemical sensors are susceptible to interference from ambient temperature and humidity, leading to measurement drift, while metal-oxide-semiconductor sensors suffer from inherent drawbacks such as high operating temperatures and high power consumption. Although fiber optic sensing technology can avoid electromagnetic interference, conventional transmissive grating structures are bulky and lack flexibility, making them unsuitable for portable detection. Existing fiber optic gas sensors mostly employ single-mode fiber structures, which have limited evanescent field strength and weak optical response to low concentrations of gas molecules; while direct coating with functional materials lacks an effective interface bonding layer, making them prone to particle shedding, resulting in decreased sensing signal stability and repeatability.

[0003] While some studies have attempted to improve sensitivity through modification with noble metal nanoparticles, the complex fabrication processes significantly increase costs, and the high-temperature treatments may damage the integrity of the fiber structure. Although multimode fibers can enhance light-matter interactions, the excessive number of modes leads to severe cross-sensitivity, making it difficult to achieve specific recognition of acetone molecules in mixed gas environments. Furthermore, the fabrication of tapered fiber probes has long relied on operator experience; insufficient precision in controlling the tapered region's morphology can easily lead to mechanical strength degradation and increased optical transmission loss, affecting the long-term reliability of the device. How to collaboratively address key issues such as sensitivity improvement, selectivity enhancement, interface stability optimization, and fabrication process controllability has become the core bottleneck in developing practical acetone fiber optic sensors. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide an acetone gas sensor based on a few-mode fiber tapered probe and its preparation method. It aims to address the issue of limited flexibility and applicability of existing sensors while maintaining high accuracy. High-sensitivity gas detection is achieved through structural modifications and surface enhancement layers on the tapered region, making it particularly suitable for non-invasive real-time monitoring of acetone in the breath of diabetic patients.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an acetone gas sensor based on a few-mode fiber tapered probe, comprising a few-mode fiber tapered probe, the few-mode fiber tapered probe comprising a substrate cladding, a tapered fiber core disposed at the center of the substrate cladding, a fiber tapered cladding disposed at the edge of the substrate cladding, the radius of the fiber tapered cladding linearly decreasing to the front end of the circular tapered region, and a three-level coating layer sensitive to acetone gas being modified on the surface of all tapered cladding.

[0006] A further improvement of the technical solution of the present invention is that the materials of the substrate cladding, the fiber cone cladding and the front end face of the circular cone are quartz glass, and the material of the circular fiber core is quartz glass doped with GeO2.

[0007] A further improvement of the technical solution of the present invention is that the three-level coating layer is composed of APTES-GO-ZIF-90 in sequence, that is, the materials from bottom to top are 3-aminopropyltriethoxysilane, graphene oxide and zeolite imidazole ester skeleton-90, respectively.

[0008] A further improvement of the technical solution of the present invention is that: the radius of the substrate cladding R1 = 62.5 μm, the bottom radius of the tapered fiber core is 10 μm, the radius of the front end face of the circular tapered region R3 ≥ 2.5 μm, and the length of the fiber tapered region cladding L ≥ 225 μm.

[0009] A method for fabricating an acetone gas sensor based on a few-mode fiber tapered probe, the specific steps of which are as follows:

[0010] Step 1: Select a step-index few-mode fiber with a core diameter of 20µm and suspend weights at both ends of the fiber.

[0011] Step 2: Place the optical fiber onto the fusion splicer, position the fusion cut and tapered parts in the discharge position of the fusion splicer, and set the discharge intensity and time of the fusion splicer.

[0012] Step 3: After the discharge begins, the step-type few-mode fiber breaks brittlely due to the gravity of the falling object, and a tapered probe with a front diameter of 6.5 μm is formed.

[0013] Step 4: Apply hydrofluoric acid solution to the cone tip and etch for 30 minutes until the cone area is etched to ≥225 μm. Then, clean the remaining hydrofluoric acid solution on the cone tip with alcohol to obtain a few-mode fiber cone probe.

[0014] Step 5: Surface modification of the tip of the few-mode fiber tapered probe, including a three-stage coating layer.

[0015] A further improvement to the technical solution of the present invention is as follows: Step 5 is specifically as follows:

[0016] Step 5.1: Immerse the few-mode fiber tapered probe in freshly prepared piranha solution for 40 min to achieve surface hydroxylation, and rinse with deionized water for 10 min to remove residual piranha solution and unmodified hydroxyl groups on the surface.

[0017] Step 5.2: Dissolve 2mAPTES in a mixed solution of glycerol and ammonia to prepare a 5% APTES solution, and immerse the hydroxylated fiber probe in the solution; after immersion, wash the probe with anhydrous ethanol to remove unreacted APTES solution.

[0018] Step 5.3: After soaking the probe in APTES solution, soak it again in graphene dispersion diluted with deionized water to a concentration of 0.2 mg / mL. After adsorption for 30 min, wash off the unadsorbed graphene oxide with deionized water.

[0019] Step 5.4: Immerse the probe soaked in the graphene dispersion again in a 2 mg / mL ZIF-90 dispersion to complete the ZIF-90 modification; during the modification process, rinse with deionized water every 10 minutes to ensure uniform coverage;

[0020] Step 5.5: Place the modified fiber optic probe into a drying oven for drying.

[0021] A further improvement to the technical solution of the present invention is that the object to be dropped in step 1 is a 200g weight.

[0022] A further improvement to the technical solution of the present invention is that: in step 2, the discharge intensity of the welding machine is set to 180mA and the time is 20ms.

[0023] The technological advancements achieved by this invention, due to the adoption of the above-mentioned technical solutions, are as follows: By incorporating a few-mode fiber probe structure, it offers greater portability and stability. The probe-type fiber optic sensor can be directly placed or implanted into the measured medium, thereby enabling precise monitoring of localized areas. The few-mode fiber supports a limited number of orthogonal modes, exhibits weaker intermodal interference effects, and offers relatively simple mode control, effectively mitigating the mode cross-sensitivity problem.

[0024] By pioneering the "APTES-GO-ZIF-90 three-level architecture," a more stable bonding effect of the modified particles is achieved. By sequentially modifying the surface of the few-mode fiber with an APTES layer, a GO layer, and a ZIF-90 layer, the problem of particle detachment, which is prone to occur in the modification method of coating functional materials due to the lack of an effective interface bonding layer, is solved, thus avoiding a decrease in the stability and repeatability of the sensing signal. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the acetone gas sensor structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the three-level coating structure of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to embodiments:

[0029] like Figure 1 The diagram shows a schematic of an acetone gas sensor based on a few-mode fiber tapered probe. The sensor includes a few-mode fiber tapered probe, a substrate cladding 1, a tapered fiber core 4 at the center of the substrate cladding 1, and a fiber tapered cladding 2 at the edge of the substrate cladding 1. The radius of the fiber tapered cladding 2 linearly decreases to the circular tapered front face 3. A three-level coating 5 sensitive to acetone gas is applied to the surface of the tapered cladding 2. The substrate cladding 1, the fiber tapered cladding 2, and the circular tapered front face 3 are made of quartz glass, and the tapered fiber core 4 is made of GeO2-doped quartz glass. Figure 2 As shown, the three-level coating layer 5 is composed of APTES-GO-ZIF-90 in sequence, that is, the materials from bottom to top are 3-aminopropyltriethoxysilane, graphene oxide and zeolite imidazole ester framework-90, respectively. The structural parameters are as follows: the radius of the substrate cladding 1 is R1 = 62.5 μm, the bottom radius of the tapered fiber core 4 is 10 μm, the radius of the front end face 3 of the circular tapered region is R3 ≥ 2.5 μm, and the length of the fiber tapered region cladding 2 is L ≥ 225 μm.

[0030] The preparation method for the above-mentioned acetone gas sensor is as follows:

[0031] Step 1: Select a step-index few-mode fiber with a core diameter of 20µm and suspend 200g weights at both ends of the fiber.

[0032] Step 2: Place the optical fiber onto the fusion splicer, position the fusion cut and tapered parts in the discharge position of the fusion splicer, and set the discharge intensity and time of the fusion splicer; set the discharge intensity of the fusion splicer to 180mA and the time to 20ms.

[0033] Step 3: After the discharge begins, the step-type few-mode fiber breaks brittlely due to the gravity of the falling object, and a tapered probe with a front diameter of 6.5 μm is formed.

[0034] Step 4: Apply hydrofluoric acid solution to the cone tip and etch for 30 minutes until the cone area is etched to ≥225 μm. Then, clean the remaining hydrofluoric acid solution on the cone tip with alcohol to obtain a few-mode fiber cone probe.

[0035] Step 5: Surface modification of the tip of the few-mode fiber tapered probe, and modification of the three-level coating layer (5).

[0036] Step 5.1: Immerse the few-mode fiber tapered probe in freshly prepared piranha solution for 40 min to achieve surface hydroxylation, and rinse with deionized water for 10 min to remove residual piranha solution and unmodified hydroxyl groups on the surface.

[0037] Step 5.2: Dissolve 2mAPTES in a mixed solution of glycerol and ammonia to prepare a 5% APTES solution, and immerse the hydroxylated fiber probe in the solution; after immersion, wash the probe with anhydrous ethanol to remove unreacted APTES solution.

[0038] Step 5.3: After soaking the probe in APTES solution, soak it again in graphene dispersion diluted with deionized water to a concentration of 0.2 mg / mL. After adsorption for 30 min, wash off the unadsorbed graphene oxide with deionized water.

[0039] Step 5.4: Immerse the probe soaked in the graphene dispersion again in a 2 mg / mL ZIF-90 dispersion to complete the ZIF-90 modification; during the modification process, rinse with deionized water every 10 minutes to ensure uniform coverage;

[0040] Step 5.5: Place the modified fiber optic probe into a drying oven for drying.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An acetone gas sensor based on a few-mode fiber tapered probe, comprising a few-mode fiber tapered probe, characterized in that: The few-mode fiber tapered probe includes a base cladding (1), a tapered fiber core (4) is provided at the center of the base cladding (1), and a fiber tapered cladding (2) is provided at the edge of the base cladding (1). The radius of the fiber tapered cladding (2) decreases linearly to the front end face (3) of the circular tapered region. A three-level coating layer (5) sensitive to acetone gas is applied to the surface of all tapered cladding (2).

2. The acetone gas sensor based on a few-mode fiber tapered probe according to claim 1, characterized in that: The substrate cladding (1), the fiber cone cladding (2) and the circular cone front end face (3) are made of quartz glass, and the cone core (4) is made of GeO2-doped quartz glass.

3. An acetone gas sensor based on a few-mode fiber tapered probe according to claim 1, characterized in that: The tertiary coating layer (5) is composed of APTES-GO-ZIF-90 in sequence, that is, the materials from bottom to top are 3-aminopropyltriethoxysilane, graphene oxide and zeolite imidazole ester skeleton-90.

4. An acetone gas sensor based on a few-mode fiber tapered probe according to claim 1, characterized in that: The radius of the substrate cladding (1) is R1 = 62.5 μm, the bottom radius of the tapered fiber core (4) is 10 μm, the radius of the front end face (3) of the circular tapered region is R3 ≥ 2.5 μm, and the length of the fiber tapered region cladding (2) is L ≥ 225 μm.

5. A method for fabricating an acetone gas sensor based on a few-mode fiber tapered probe, used to manufacture the sensor according to any one of claims 1-4, characterized in that: The specific steps are as follows: Step 1: Select a step-index few-mode fiber with a core diameter of 20µm and suspend weights at both ends of the fiber. Step 2: Place the optical fiber onto the fusion splicer, position the fusion cut and tapered parts in the discharge position of the fusion splicer, and set the discharge intensity and time of the fusion splicer. Step 3: After the discharge begins, the step-type few-mode fiber breaks brittlely due to the gravity of the falling object, and a tapered probe with a front diameter of 6.5 μm is formed. Step 4: Apply hydrofluoric acid solution to the cone tip and etch for 30 minutes until the cone area is ≥225 μm. Then, clean the remaining hydrofluoric acid solution on the cone tip with alcohol. A few-mode fiber tapered probe was obtained; Step 5: Surface modification of the tip of the few-mode fiber tapered probe, and modification of the three-level coating layer (5).

6. The method for fabricating an acetone gas sensor based on a few-mode fiber tapered probe according to claim 5, characterized in that: Step 5 is detailed below: Step 5.1: Immerse the few-mode fiber tapered probe in freshly prepared piranha solution for 40 min to achieve surface hydroxylation, and rinse with deionized water for 10 min to remove residual piranha solution and unmodified hydroxyl groups on the surface. Step 5.2: Dissolve 2mAPTES in a mixed solution of glycerol and ammonia to prepare a 5% APTES solution, and immerse the hydroxylated fiber probe in the solution; After soaking, the probe was washed with anhydrous ethanol to remove unreacted APTES solution; Step 5.3: After soaking the probe in APTES solution, soak it again in graphene dispersion diluted with deionized water to a concentration of 0.2 mg / mL. After adsorption for 30 min, wash off the unadsorbed graphene oxide with deionized water. Step 5.4: Immerse the probe soaked in the graphene dispersion again in a 2 mg / mL ZIF-90 dispersion to complete the ZIF-90 modification; during the modification process, rinse with deionized water every 10 minutes to ensure uniform coverage; Step 5.5: Place the modified fiber optic probe into a drying oven for drying.

7. The method for fabricating an acetone gas sensor based on a few-mode fiber tapered probe according to claim 5, characterized in that: The object to be dropped in step 1 is a 200g weight.

8. The method for fabricating an acetone gas sensor based on a few-mode fiber tapered probe according to claim 5, characterized in that: In step 2, the fusion splicer is set to discharge intensity of 180mA and time of 20ms.

Images