A device for detecting ammonium concentration in water and fertilizer solution based on reflective optical fiber sensor

Abstract

The application discloses a device for detecting ammonium concentration in water and fertilizer solution based on a reflective optical fiber sensor, which comprises a host computer, a halogen lamp light source, a spectrometer, a Y-shaped optical fiber and a sensor, wherein the sensor comprises a multimode optical fiber and a single-mode optical fiber, the multimode optical fiber and the single-mode optical fiber are connected in cascade, one end of the multimode optical fiber is connected with the Y-shaped optical fiber, the other end of the multimode optical fiber is coaxially fused with the single-mode optical fiber, the outer surface and the end surface of the single-mode optical fiber are plated with a gold film, and the outer surface of the gold film is plated with an ammonium sensitive film. The device is simple in preparation and low in cost, and can quickly and accurately measure the ammonium concentration in the water and fertilizer solution.

Description

Technical Field

[0001] This invention relates to the technical field of facility agriculture testing, and in particular to a device for detecting ammonium concentration in water and fertilizer solutions based on a reflective fiber optic sensor. Background Technology

[0002] Ammonium ions are one of the essential nitrogen sources for plant growth. Appropriate concentrations promote plant growth and development, while excessively high or low concentrations can negatively impact crop growth and even lead to yield reduction. Fertilizer solutions are a crucial source of ammonium for plants. Therefore, accurate detection of ammonium concentration in fertilizer solutions is of great significance. Precise and rapid detection of ammonium concentration in fertilizer solutions can help precisely control fertilizer application rates, preventing soil acidification and nutrient imbalances caused by over-application, while also avoiding fertilizer waste and reducing production costs. Currently, the main technologies for detecting ammonium concentration in fertilizer solutions include chemical analysis methods and electrochemical sensor methods. Among chemical analysis methods, the ion-selective electrode method is simple to operate but susceptible to interference; the indophenol blue colorimetric method is sensitive but cumbersome; and the Nessler's reagent colorimetric method, while simple, carries the risk of toxicity. Among electrochemical sensor methods, electrochemical dissolution technology is simple to operate and sensitive but the electrodes are prone to contamination; electrochemiluminescence sensors have high sensitivity but high equipment costs. In addition, there are gas-sensitive sensor detection methods that require pretreatment, and liquid chromatography, suitable for laboratory analysis but with expensive equipment and complex operation, each with its own advantages and disadvantages.

[0003] Fiber optic sensors can be used to measure the concentration of chemical components. Their principle involves combining a fiber optic sensor with a sensitive membrane. When the analyte reacts with the sensitive membrane, the refractive index at that membrane changes. Fiber optic sensors are extremely sensitive to changes in refractive index, thereby enabling the detection of chemical component concentration. Among various fiber optic sensors, the SPR (Spark Refractive Index) sensor is used for refractive index measurement. The resonant wavelength of this type of sensor shifts with changes in refractive index, thus achieving refractive index measurement. SPR sensors have attracted attention due to their high sensitivity in refractive index measurement.

[0004] Therefore, based on the SPR type sensor, the proposed ammonium concentration detection device based on a reflective fiber optic sensor is of great significance for the accurate measurement of ammonium concentration in water-fertilizer solutions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an ammonium concentration detection device based on a reflective fiber optic sensor, thereby solving the current problem of measuring the ammonium concentration in water and fertilizer solutions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A device for detecting ammonium concentration in a water-fertilizer solution based on a reflective fiber optic sensor includes: a host computer, a halogen lamp light source, a spectrometer, a Y-type optical fiber, and a sensor. The sensor includes a multimode optical fiber and a single-mode optical fiber, which are cascaded together. One end of the multimode optical fiber is connected to the Y-type optical fiber, and the other end is coaxially fused to the single-mode optical fiber. The outer surface and end face of the single-mode optical fiber are coated with a gold film, and the outer surface of the gold film is coated with an ammonium-sensitive film.

[0008] Furthermore, the aforementioned ammonium-sensitive membrane is a carbon nanotube / platinum nanoparticle composite membrane.

[0009] Furthermore, the single-mode fiber has a length of 15 mm and the gold film has a thickness of 50 nm.

[0010] Further, the preparation process of the ammonium-sensitive membrane is as follows: First, 20 mg of multi-walled carbon nanotubes and 2% polyethyleneimine are dispersed in 40 mL of methanol solution. After thorough stirring, the mixture is ultrasonically treated and allowed to stand for separation. Then, the lower precipitate is taken and dissolved in 30 mL to 50 mL of methanol, followed by ultrasonic treatment and stirring until homogeneous. Then, 0.1 mol / L chloroplatinic acid solution and 0.1 mol / L sodium borohydride solution are added, and stirring is continued to ensure thorough mixing. Finally, 4 mL of chitosan solution is added, and ultrasonic and stirring treatment is performed to obtain a carbon nanotube / platinum nanoparticle composite membrane solution. The carbon nanotube / platinum nanoparticle composite membrane solution is deposited on the surface of a single-mode optical fiber using the dip-coating method to form the ammonium-sensitive membrane. The dip-coating time is set to 30 min and two dip-coating operations are performed. After dip-coating, the membrane is annealed at 90 °C. Attached Figure Description

[0011] The present invention includes the following figures:

[0012] Figure 1 This is a schematic diagram of an ammonium concentration detection device in a water-fertilizer solution based on a reflective fiber optic sensor provided by the present invention.

[0013] Figure 2 This is a schematic diagram of the sensor structure of the present invention;

[0014] Figure 3 This is a schematic diagram of the spectral curve of the sensor of the present invention measuring the ammonium concentration;

[0015] Figure 4 This is a schematic diagram of the linear interval fitting curve for measuring ammonium concentration using the sensor of the present invention.

[0016] Figure labeling: 1. Host computer; 2. Spectrometer; 3. Halogen lamp source; 4. Y-type optical fiber; 5. Sensor; 51. Cladding; 52. Gold film; 53. Carbon nanotube / platinum nanoparticle composite film. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description of the specific structure, principle, and working process of the present invention is provided in conjunction with specific embodiments and with reference to the accompanying drawings.

[0018] like Figure 1 The image shows a device for detecting ammonium concentration in a water-fertilizer solution based on a reflective fiber optic sensor, as proposed in this invention. Its working process is as follows: Light emitted from a halogen lamp source is transmitted through a Y-shaped fiber to a multimode fiber, then enters a single-mode fiber. It is reflected back at the end face of the single-mode fiber and transmitted again through the Y-shaped fiber to a spectrometer for detecting spectral shift. The multimode and single-mode fibers are fused together using a fusion splicer. The single-mode fiber is 15 mm long and coated with a 50 nm gold film. The outer surface of the gold film is coated with a carbon nanotube / platinum nanoparticle composite film.

[0019] When light emitted from a halogen lamp is transmitted from a multimode fiber to a single-mode fiber, some of the light couples into the cladding because the core diameter of the multimode fiber is much larger than that of the single-mode fiber. At this time, some of the light transmitted in the cladding leaks into the gold film outside the cladding, causing surface plasmon resonance. This results in energy loss in the output spectrum, causing a resonance valley at a specific wavelength. When the external ammonium concentration changes, the resonant wavelength of this resonance valley shifts, thus enabling the measurement of the ammonium concentration.

[0020] In this invention, when the ammonium concentration changes, the concentration of ammonia gas generated by the ammonium reduction reaction attached to the carbon nanotubes changes, causing a change in the refractive index, which in turn affects the resonant wavelength λ of the resonance valley corresponding to the ammonium concentration. n Movement occurs, such as Figure 3 As shown.

[0021] Where, Δλ n Δ represents the shift in resonant wavelength at the resonant valley corresponding to the ammonium concentration. n and represent the changes in nitrate concentration, respectively. a This is the shift sensitivity coefficient of the resonant wavelength corresponding to the resonant valley when the ammonium concentration changes. In this invention, when the structural parameters of the sensor probe are fixed, a It is a fixed value.

[0022] Those skilled in the art will understand that various changes, modifications, and substitutions can be made to the embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A device for detecting ammonium concentration in a water-fertilizer solution based on a reflective fiber optic sensor, comprising: The host computer, halogen lamp light source, spectrometer, Y-type optical fiber and sensor are characterized in that the sensor includes multimode optical fiber and single-mode optical fiber, which are cascaded together. One end of the multimode optical fiber is connected to the Y-type optical fiber, and the other end is coaxially fused to the single-mode optical fiber. The outer surface and end face of the single-mode optical fiber are coated with a gold film, and the outer surface of the gold film is coated with an ammonium ion sensitive film.

2. The ammonium concentration detection device in a water-fertilizer solution based on a reflective fiber optic sensor according to claim 1, characterized in that... The ammonium-sensitive membrane is a carbon nanotube / platinum nanoparticle composite membrane.

3. The ammonium concentration detection device in a water-fertilizer solution based on a reflective fiber optic sensor according to claim 1, characterized in that... The single-mode fiber is 15 mm in length.

4. The ammonium concentration detection device in a water-fertilizer solution based on a reflective fiber optic sensor according to claim 1, characterized in that... The thickness of the gold film is 50 nm.

5. The ammonium concentration detection device in a water-fertilizer solution based on a reflective fiber optic sensor according to claim 2, characterized in that... The preparation process of the ammonium-sensitive membrane is as follows: First, 20 mg of multi-walled carbon nanotubes and 2% polyethyleneimine are dispersed in 40 mL of methanol solution. After thorough stirring, the mixture is ultrasonically treated and allowed to stand for separation. Then, the lower precipitate is taken and dissolved in 30 mL to 50 mL of methanol, followed by ultrasonic treatment and stirring until homogeneous. Then, 0.1 mol / L chloroplatinic acid solution and 0.1 mol / L sodium borohydride solution are added and stirred to ensure thorough mixing. Finally, 4 mL of chitosan solution is added and ultrasonic and stirring treatment is performed to obtain a carbon nanotube / platinum nanoparticle composite membrane solution. The carbon nanotube / platinum nanoparticle composite membrane solution is deposited on the surface of a single-mode optical fiber using the dip-coating method to form the ammonium-sensitive membrane. The dip-coating time is set to 30 min and two dip-coating operations are performed. After dip-coating, the membrane is annealed at 90 °C.

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