Micro-nano optical fiber probe for biochemical component detection based on infrared spectrum and detection equipment

Abstract

The invention provides a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy and detection equipment, and a preparation method of the micro-nano optical fiber probe comprises the following steps: S1, selecting one section of a multimode quartz optical fiber as a sensing area, and then removing a cladding layer and a coating layer of the sensing area to expose a bare fiber; s2, dripping a mixed acid solution prepared from hydrofluoric acid and citric acid to the bare fiber to corrode the bare fiber, and then cleaning and blow-drying; immersing the treated multimode quartz optical fiber into a silane coupling agent solution, reacting for 0.5-1 hour, and then drying; s3, immersing the multimode quartz optical fiber treated in the step S2 into a solution containing silver nanoparticles, and reacting for 10-20 minutes to obtain an optical fiber modified by the silver nanoparticles; and S4, sputtering a gold layer on the surface of the silver-modified optical fiber by adopting a vacuum magnetron sputtering technology to obtain the micro-nano optical fiber probe with the silver-gold film layer. After the surface of the silver nanostructure is covered with the gold film, oxygen, water, corrosive molecules and the like are effectively prevented from making direct contact with silver. In addition, both the gold and the silver can support a surface plasmon resonance (SPR) effect, and particularly, the prepared detection equipment can ensure the sensitivity of the SPR.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber SPR sensors, and particularly to a micro-nano optical fiber probe and a detection device for detecting biochemical components based on infrared spectroscopy. Background Art

[0002] Optical fiber surface plasmon resonance (SPR) sensors are a new type of optical fiber sensor developed on the basis of optical fiber technology and sensor technology. They have the inherent advantages of optical fiber sensors, as well as the advantages of high detection sensitivity and label-free of SPR sensors. Currently, they have been applied to physical parameter measurement, chemical substance detection, and biological quantity detection, etc. The emergence of optical fiber SPR sensors has made up for the deficiencies of traditional electrochemical sensors in substance detection and shown broad application prospects in the fields of chemistry, biology, environment, medicine, and food safety, etc.

[0003] Existing optical fiber SPR sensors often deposit a silver film on the surface of the optical fiber. However, the chemical stability of the silver film is poor and it is easy to oxidize in the air, especially in a humid or corrosive gas-containing environment. The oxidized silver film will change its optical and electrical properties, resulting in a weakening of the surface plasmon resonance effect, thereby reducing the sensitivity and accuracy of the sensor. Therefore, it is necessary to develop an optical fiber SPR sensor optical fiber probe that is not easily oxidized and has high sensitivity. Summary of the Invention

[0004] In view of this, the present invention provides a micro-nano optical fiber probe and a detection device for detecting biochemical components based on infrared spectroscopy.

[0005] The technical solution of the present invention is realized as follows: In the first aspect, the present invention provides a preparation method for a micro-nano optical fiber probe for detecting biochemical components based on infrared spectroscopy, including the following steps:

[0006] S1, select a section in the middle of a multi-mode quartz optical fiber as the sensing area, and then remove the cladding and coating layers of the sensing area to expose the bare fiber.

[0007] S2, drop a mixed acid solution prepared from hydrofluoric acid and citric acid onto the bare fiber to corrode the bare fiber, and then wash and dry it; then immerse the processed multi-mode quartz optical fiber in a silane coupling agent solution and react for 0.5 - 1 h, and then dry it.

[0008] Pure HF corrosion is often accompanied by the generation of bubbles, resulting in a large number of micropores or rough areas on the surface of the optical fiber, which is not conducive to the uniform deposition of subsequent metal nanoparticles and the improvement of optical performance. Corroding the bare fiber with a mixed acid solution prepared from hydrofluoric acid and citric acid can reduce the corrosion rate, improve the corrosion uniformity, increase the corrosion selectivity and surface smoothness, and facilitate the uniform deposition of subsequent metal nanoparticles.

[0009] By relying solely on the chemical reduction method, the morphology and distribution of silver nanoparticles obtained on the surface of bare optical fibers highly depend on the reaction conditions and are difficult to precisely control. Insufficient particle size distribution, density, and uniformity will affect subsequent sensing performance. In the present invention, the etched bare optical fiber is immersed in a silane coupling agent solution, and amino / thiol chemical modification is performed on its surface to enhance the adsorption of silver ions and the selectivity and density consistency of the directional growth of nanoparticles, thereby enhancing the sensitivity of the sensor.

[0010] Introduce amino (APTES) or thiol (MPTMS) functionalization on the fiber surface. The specific operation process is as follows:

[0011] S3. Immerse the multimode quartz optical fiber processed in step S2 into a solution containing silver nanoparticles and react for 10 - 20 min to obtain an optical fiber modified with silver nanoparticles.

[0012] S4. Use the vacuum magnetron sputtering technique to sputter a gold layer on the surface of the fiber modified with silver to obtain a micro - nano optical fiber probe with a silver - gold film layer.

[0013] The gold layer is extremely difficult to be oxidized. The silver film under the gold layer is not easily exposed to oxygen and corrosive media, greatly slowing down or even preventing the oxidation and sulfidation processes of silver; the continuous and dense gold film can also effectively block the penetration of active molecules in the environment to the silver layer. After covering the gold film on the surface of the silver nanostructure, the gold layer acts as a physical barrier, effectively isolating oxygen, water, corrosive molecules, etc. from direct contact with silver. In addition, both gold and silver can support the surface plasmon resonance (SPR) effect, which can ensure the sensitivity of SPR.

[0014] Based on the above technical solutions, preferably, in step S4, before sputtering the gold layer, deposit a diffusion barrier layer Si3N4 on the surface of the fiber modified with silver by atomic layer deposition, and then sputter the gold layer on the surface of the diffusion barrier layer Si3N4.

[0015] There are defects such as weak bonding force and microscopic voids at the interface between silver and gold. In a complex environment (such as high humidity, corrosive atmosphere), the interface is prone to separation or penetration, resulting in the exposure of the silver layer and subsequent oxidation. After the interface fails, the long - term stability and repeatability of the sensor decrease, and even the surface plasmon resonance (SPR) activity is lost.

[0016] Si3N4 is a very dense and chemically inert material, which can extremely effectively block the ion migration and diffusion of metals such as silver and gold. It can also prevent Ag in the silver layer +Migrate outward and be oxidized, greatly improving the chemical stability and service life of the overall structure. Si3N4 has good interfacial compatibility with gold and silver, which can enhance the adhesion between film layers. The refractive index of Si3N4 is relatively high (about 2.0). As an intermediate layer or coating layer, it can regulate the distribution and resonance conditions of surface plasmon resonance (SPR) waves. Therefore, depositing the Si3N4 layer is mainly to improve the chemical stability, corrosion resistance and anti-diffusion ability of the structure, while also improving the film adhesion and adjusting the optical response of SPR.

[0017] Based on the above technical solutions, preferably, when depositing the diffusion barrier layer Si3N4, bis(diethylamino)silane and N2 plasma are used as precursors, the deposition temperature is 100 - 300 °C, and the deposition thickness is 2 - 5 nm.

[0018] Based on the above technical solutions, preferably, the parameters for the deposition process of the gold layer are: sputtering power 50 - 200 W, target-substrate distance 50 - 450 mm, sputtering pressure 1.0 - 2.0 Pa, thickness 20 - 40 nm, vacuum degree 1×10 -4 ~3×10 -4 Pa, the sputtering atmosphere is argon, and the gas flow rate is 50 - 200 sccm.

[0019] Based on the above technical solutions, preferably, in step S2, in the mixed acid solution, the volume concentration of hydrofluoric acid is 2% - 10%, and the mass concentration of citric acid is 1% - 5%.

[0020] Based on the above technical solutions, preferably, in step S2, the diameter of the bare fiber after corrosion is 10% - 30% of that before corrosion.

[0021] Based on the above technical solutions, preferably, in step S2, the silane coupling agent is 3-aminopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane, the volume concentration is 1% - 5%, and the solvent is ethanol.

[0022] Based on the above technical solutions, preferably, in step S3, the method for preparing the solution containing silver nanoparticles is: mix the silver nitrate solution and ammonia water evenly, add NaOH dropwise until the pH reaches 10, and then add the glucose solution. After stirring evenly, a solution containing silver nanoparticles is obtained.

[0023] Based on the above technical solutions, preferably, the mass concentration of the silver nitrate solution is 1%, the volume concentration of the ammonia water is 2%, the mass concentration of the glucose solution is 10%, and the volume ratio of the silver nitrate solution, ammonia water and glucose solution is 10:1 - 3:1 - 3.

[0024] In a second aspect, the present invention also provides a micro-nano optical fiber probe for detecting biochemical components based on infrared spectroscopy, which is prepared by the above method.

[0025] In a third aspect, the present invention also provides a device for detecting biochemical components based on infrared spectroscopy, including the above-mentioned micro-nano optical fiber probe.

[0026] The micro-nano optical fiber probe and detection device for detecting biochemical components based on infrared spectroscopy of the present invention have the following beneficial effects compared with the prior art:

[0027] (1) After covering the surface of the silver nanostructure with a gold film, the present invention effectively isolates silver from direct contact with oxygen, water, corrosive molecules, etc. In addition, both gold and silver can support the surface plasmon resonance (SPR) effect, which can ensure the sensitivity of SPR.

[0028] (2) The present invention deposits a Si3N4 layer between the silver-gold film layers. On the one hand, it can prevent the outward migration and oxidation of Ag+ in the silver layer, greatly improving the chemical stability and service life of the overall structure. On the other hand, Si3N4 has good interfacial compatibility with gold and silver, which can enhance the adhesion between the film layers. In addition, Si3N4 can also regulate the distribution and resonance conditions of the surface plasmon resonance (SPR) wave. Therefore, depositing the Si3N4 layer is mainly to improve the chemical stability, corrosion resistance and anti-diffusion ability of the structure, while also improving the film adhesion and adjusting the optical response of SPR. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic diagram of the physical object of the micro-nano optical fiber probe based on silver nanoparticles of the present invention;

[0031] Figure 2 It is a schematic diagram of the structure of the fiber optic sensor;

[0032] Figure 3 It is an effect diagram of the influence of different corrosion depths on the sensitivity of the sensor;

[0033] Figure 4 It is the moisture resistance performance of the micro-nano optical fiber probe based on silver nanoparticles of the present invention;

[0034] Figure 5 It is the sensitivity of the micro-nano optical fiber probe based on silver nanoparticles of the present invention;

[0035] Figure 6 Schematic diagram of the total reflection principle;

[0036] Figure 7 Schematic diagram of the evanescent wave;

[0037] Figure 8 Schematic diagram of the surface plasmon resonance effect. Specific implementation manners

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] The micro-nano fiber sensor of the present invention adopts a near-infrared multimode fiber sensing probe made of silica material, which is composed of a micro-nano fiber and a cladding layer located on the micro-nano fiber. The micro-nano fiber is composed of an etching region in the middle and a normal region connected to the outer end of the etching region.

[0040] As Figure 2 shown, the biochemical component detection device based on infrared spectroscopy of the present invention includes a light source modulation system, a first planar gold mirror (planar gold mirror 1), a first off-axis parabolic mirror (off-axis parabolic mirror 1), an optical fiber connector, a second off-axis parabolic mirror (off-axis parabolic mirror 2), a second planar gold mirror (planar gold mirror 2), an MCT detector, and a signal processing and display integrated system.

[0041] The incident light generated by the light source after passing through the light source modulation system hits the first planar gold mirror, reaches the first off-axis parabolic mirror after reflection, and then after being focused by the first off-axis parabolic mirror, the light is coupled into the optical fiber connector and conducted to the optical fiber through the optical fiber connector. The optical fiber reflects multiple times inside the optical fiber sensing probe, interacts with the sample, and generates infrared light carrying sample information. Subsequently, the infrared light is transmitted to the second off-axis parabolic mirror through the optical fiber probe, reflected and reaches the second planar gold mirror, and the light after reflection enters the MCT detector. The MCT detector converts the infrared light signal into an electrical signal and transmits it to the signal processing and display integrated system to realize signal processing and display the result.

[0042] The optical fiber selects multimode quartz optical fiber (core diameter ≥ 200 μm), and the interface can be SMA905, SC, etc.

[0043] Among them, the light source and modulation control system: a near-infrared (tungsten halogen lamp) light source, which is a ceramic rod that operates at high temperatures and emits infrared radiation. In the mid-infrared region, it can typically provide a wavelength range of 2.5 - 25 μm; in the near-infrared region, it can typically provide a wavelength range of 0.8 - 2.5 μm.

[0044] Flat Gold Mirror: Mainly used for reflecting light, it has a high infrared reflectivity. Gold material has good reflection performance in the infrared band, so it can be used to reflect infrared light and transmit the light to different optical paths. The surface quality and flatness of the gold mirror are crucial for some high-precision measurements. The high reflection performance of the flat gold mirror is very important for maintaining the accuracy of the optical path.

[0045] Parabolic Mirror: It is an optical element that can focus parallel incident light to the focal point. In an infrared optical system, this mirror can be used to focus infrared light and make it concentrated at a point. Through ingenious design, the off-axis parabolic mirror can make the infrared radiation converge on the detector for observing distant infrared targets. The shape and curvature of the off-axis parabolic mirror can be used to correct some aberrations in the optical system and improve the imaging quality.

[0046] Optical fiber connector: The ferrule of this connector is made of ceramic or metal. Structurally, it is divided into two types: SMA905 (with aramid crimping ring) and HPSMA905 (without aramid crimping ring). Among them, the ferrule end face of the HPSMA905 optical fiber connector is further divided into with groove and without groove, and its tail can be selected with a 3.0 mm ferrule or a metal customized ferrule seat.

[0047] Mercury cadmium telluride (MCT) detector, also known as HgCdTe detector, is widely used in infrared (IR) sensing applications. The MCT detector can operate in a relatively wide spectral range, showing high sensitivity to infrared radiation. This high sensitivity is crucial for detecting weak signals and low-light conditions. The MCT detector has a fast response time, enabling real-time detection and rapid data acquisition. The noise level is relatively low, which helps to achieve a better signal-to-noise ratio and meet the requirements of high precision and accuracy of the equipment. The MCT detector can operate in a very wide temperature range, including low temperatures for some applications. This flexibility in temperature operation allows it to adapt to different environments and conditions. The MCT detector usually shows high quantum efficiency, ensuring that a high proportion of incident photons are effectively converted into electrical signals. This efficiency is beneficial for maximizing the detection of infrared radiation. The MCT detector is known for its long-term stability and reliability. The MCT detector is compact in size and light in weight, making it suitable for integration into portable devices, handheld instruments, and applications with limited space.

[0048] Signal Processing and Display Integration System: It includes an FPGA and a DSP (other hardware architectures such as GPU, ASIC, SoC, MCU, NPU, or cloud computing / edge computing platforms can be selected according to real-time performance, computing power requirements, and algorithm complexity). After the raw data obtained by ADC sampling is transmitted to the FPGA platform through a GTX (Gigabit Transceiver), the entire signal processing process, including preprocessing (such as denoising and normalization), dataset partitioning (divided into training set, validation set, and test set according to experimental requirements), feature extraction (extracting key features of spectral data), and quantitative or qualitative analysis (evaluating feature attributes through statistical or pattern recognition methods), is completed in sequence. And the spectral curve and quantitative and qualitative model performance indicators are displayed through an integrated display module.

[0049] To construct an infrared spectroscopy detection device based on a micro-nano fiber probe, the following steps are included:

[0050] Step 1: Generate infrared light through the optoelectronic module in the light source and modulation control, and guide it into the starting end of the optical path to ensure that the output wavelength of the light source is stable and the power is adjustable.

[0051] Step 2: Project the infrared light onto the first plane gold mirror. By precisely adjusting the angle and position of the first plane gold mirror, the infrared light source can be projected onto the first off-axis parabolic mirror along the best reflection path.

[0052] Step 3: At the right focus of the first off-axis parabolic mirror, install a four-dimensional fiber optic adjustment bracket equipped with a fiber optic SMA905 interface, connect the near-infrared SPR fiber, and precisely adjust the spatial position to accurately focus the infrared light from the first off-axis parabolic mirror into the fiber.

[0053] Step 4: The fiber optic output end is also equipped with a second off-axis parabolic mirror to collimate and focus the outgoing light onto the second plane gold mirror.

[0054] Step 5: By adjusting the angles of the second off-axis parabolic mirror and the second plane gold mirror, the outgoing light is aligned with the light receiving port of the MCT (mercury cadmium telluride) detector to ensure that the detector captures optical signals with a high signal-to-noise ratio.

[0055] Step 6: The MCT detector converts the infrared light signal into an electrical signal.

[0056] Step 7: The electrical signal is transmitted to the signal processing and display integration system, and data preprocessing, feature extraction, and quantitative or classification algorithms are completed in sequence. Finally, the spectral curve, quantitative or classification results, and model performance indicators are displayed in real time through the integrated display module, realizing a full-process closed-loop from optical signal acquisition to visualization of analysis results.

[0057] The system structure of the infrared spectroscopy detection device based on the micro-nano fiber probe is as Figure 2 shown.

[0058] The working principle is as follows:

[0059] 1. Total reflection principle

[0060] A special phenomenon that occurs when light is reflected at the interface between two media. When light travels from a denser medium into a less dense medium and the angle of incidence is greater than a critical angle, the light will be completely reflected back and will no longer propagate into the less dense medium. The size of this critical angle depends on the refractive index difference between the two media. This phenomenon is called the total reflection principle. The critical angle can be obtained through Snell's law, and its schematic diagram is as Figure 6 shown.

[0061] Among them, n1 represents the medium with a higher refractive index, i.e., the optically denser medium; n2 represents the medium with a lower refractive index, i.e., the optically less dense medium; the incident ray is kI, and the corresponding angle of incidence is θ I ; the reflected ray is kR, and the corresponding angle of reflection is θR; the refracted ray is kT, and the corresponding angle of refraction is θ T ; the interface between the two media is the x-axis. According to Snell's law:

[0062] n1sinθ I = n2sinθ T (2.6)

[0063] To find the critical angle, it is necessary to change the angle of the incident ray so that the angle of refraction θ T is equal to 90°, and at this time the angle of incidence θ I is equal to the critical angle θ c :

[0064]

[0065] It can be seen from this that when light travels from a medium with a larger refractive index to a medium with a smaller refractive index, as long as the angle of incidence is greater than the critical angle, the incident light will propagate in the optically denser medium in the form of total reflection.

[0066] 2. Evanescent wave principle

[0067] The evanescent wave, also known as the evanescent wave, when light travels from an optically denser medium into an optically less dense medium and the angle of incidence increases to a certain angle so that the angle of refraction reaches the critical angle and the refracted light completely disappears, leaving only the reflected light, this phenomenon is called total reflection.

[0068] When studying total reflection from the perspective of wave optics, the light wave is not absolutely completely reflected back into the first medium at the interface, but penetrates about one wavelength deep into the second medium and flows along the interface for about half a wavelength distance before returning to the first medium and emerging in the direction of the reflected light. The wave along the surface of the second medium is called the evanescent wave or the evanescent wave, and its schematic diagram is as Figure 7 shown.

[0069] The evanescent wave decays rapidly in energy near the interface, but provides effective interaction with substances on the interface within a short distance, for sensing and analysis applications. By using the evanescent wave, it is possible to analyze and measure samples that come into contact with the fiber surface or the sensor interface. The penetration depth dp of the evanescent wave is related to the incident angle of light as shown in Equation (2.8):

[0070]

[0071] where λ0 is the wavelength of the detected light, n1 is the refractive index of the optically thinner medium, and θ is the angle between the incident light and the normal of the total reflection interface.

[0072] Another main parameter of the evanescent wave is the number of total reflections N. As the number of total reflections increases, the total amount of evanescent wave throughput also increases, which in turn leads to more sufficient contact between the sample to be measured and the evanescent wave, increasing the sensitivity. The formula for the number of total reflections is shown in Equation (2.9):

[0073]

[0074] where L and d are the length and thickness of the fiber region respectively, and θ is the angle between the incident light and the normal of the total reflection interface.

[0075] 3 Surface Plasmon Resonance

[0076] Plasma generally refers to a gas composed of a relatively high density of free positive and negative charges, where the number of positive and negative charged particles is almost equal. Considering the valence electrons on the metal surface as an electron gas moving under a uniform positive charge background, this is actually also a kind of plasma. When the metal is subjected to electromagnetic interference, the electron density distribution inside the metal becomes uneven. Due to the existence of the Coulomb force, some electrons will be attracted to the region with an excess of positive charges. The attracted electrons, due to gaining momentum, will stop at the equilibrium position of the gravitational and repulsive forces and move forward for a certain distance. After that, the repulsive force between the electrons will force the electrons that have gathered to leave this region again. As a result, a collective oscillation of the entire electron system will be formed, and the existence of the Coulomb force makes this collective oscillation repeat, and the resulting oscillation is called plasma oscillation, which is manifested in the form of a wave and is called a plasma wave.

[0077] The surface plasmon resonance effect, that is, the SPR effect, is a typical effect in wave optics. It means that when light undergoes total reflection on the interface with a metal film, an evanescent wave will be formed and enter the optically thinner medium, and there is also a certain plasma wave in the metal medium. When the two waves meet, resonance may occur. When the evanescent wave and the surface plasmon wave resonate, the detected reflected light intensity will be significantly reduced. The energy is transferred from the photon to the surface plasmon, and most of the energy of the incident light is absorbed by the surface plasmon wave, resulting in a sharp decrease in the energy of the reflected light. Its schematic diagram is asFigure 8 as shown

[0078] When total internal reflection occurs in the optical fiber, the evanescent wave resonates with the surface plasmon wave, and the detected reflected light intensity will be greatly reduced. Energy is transferred from photons to surface plasmons, and most of the energy of the incident light is absorbed by the surface plasmon wave, resulting in a sharp decrease in the energy of the reflected light.

[0079] The optical fiber probe includes a micro-nano optical fiber based on silver nanoparticles, and the structure is as Figure 2 shown. The cladding and a certain thickness of the core of a certain section in the middle of the optical fiber are stripped off, and then a sensing material (such as gold or silver) is coated on the exposed optical fiber. The incident light propagates in the core in a total reflection manner. When passing through this section of the core with the sensing material coated on the surface, under certain conditions, it can cause the collective oscillation of free electrons in the metal, thereby exciting surface plasmon polaritons. Its resonance wavelength is extremely sensitive to changes in the external medium, and the change of the external environment can be sensed as long as the optical signal is received at the other end of the core.

[0080] To make the incident light reach the sensing material to cause plasma resonance, it is necessary to remove a part of the cladding by methods such as stripping and etching. The preparation of micro-nano optical fibers has relatively high requirements for processing technology. Factors such as the smoothness of the optical fiber surface, the thickness and flatness of the gold film, and the diameter of the core may all affect the sensing performance.

[0081] The preparation method of the micro-nano optical fiber probe based on silver nanoparticles of the present invention is shown in the embodiments.

[0082] Embodiment 1

[0083] The preparation method of the micro-nano optical fiber sensor based on silver nanoparticles in this embodiment includes the following steps:

[0084] S1. Remove the protective layer of the middle 5 cm length of a 50 cm long multi-mode quartz optical fiber (core diameter 400 μm), and use a Miller pliers to strip the coating layer of 2 cm length under the protective layer; use a three-jaw Miller pliers to adjust the jaw size to correspond to the coating layer diameter of 700 μm and the cladding diameter of 440 μm respectively, and strip the protective layer and coating layer of 2 cm length of the optical fiber in sequence to obtain a bare optical fiber, and this bare optical fiber is used as the sensing area.

[0085] S2. Use a container made of polyethylene as the corrosion platform, place the bare optical fiber area at the upper center, and then use a rubber dropper to suck an appropriate amount of mixed acid solution prepared with hydrofluoric acid and citric acid (the volume concentration of hydrofluoric acid is 5%, and the mass concentration of citric acid is 3%) and drop it onto the bare optical fiber to corrode the bare optical fiber until the diameter of the corroded bare optical fiber is 20% of that before corrosion, and then wash and dry it.

[0086] Subsequently, the processed multimode quartz optical fiber was immersed in a 3-aminopropyltriethoxysilane ethanol solution with a volume concentration of 3%, reacted for 1 h, and then dried.

[0087] S3. Prepare a solution containing silver nanoparticles: Mix 10 mL of a silver nitrate solution with a mass concentration of 1% and 2 mL of an ammonia water solution with a volume concentration of 2%, and stir until the solution turns light yellow, indicating that particles formed by the reduction of silver ions are initially generated. Then, dropwise add NaOH until the pH reaches 10, and then add 2 mL of a glucose solution with a mass concentration of 10%. After stirring evenly, a solution containing silver nanoparticles is obtained.

[0088] The above solution was reacted in a water bath at 60 °C for 60 s. Then, the multimode quartz optical fiber processed in step S2 was immersed in the solution containing silver nanoparticles, reacted for 20 min, and soaked in deionized water for 2 min to terminate the reaction, obtaining an optical fiber modified with silver nanoparticles.

[0089] S4. Using the vacuum magnetron sputtering technique, a gold layer was sputtered on the surface of the optical fiber modified with silver to obtain a micro-nano optical fiber probe with a silver-gold film layer.

[0090] The parameters for the deposition process of the gold layer were a sputtering power of 100 W, a target-substrate distance of 150 mm, a sputtering pressure of 1.5 Pa, a thickness of 30 nm, a vacuum degree of 1×10 -4 Pa, a sample stage rotation speed of 15 r / min, a bias voltage of -50 V, a duty cycle of 70%, a sputtering atmosphere of argon, and a gas flow rate of 100 sccm.

[0091] Example 2

[0092] Compared with Example 1, in this example, before sputtering the gold layer in step S4, a diffusion barrier layer Si3N4 was deposited on the surface of the optical fiber modified with silver by atomic layer deposition, and then a gold layer was sputtered on the surface of the diffusion barrier layer Si3N4. The remaining steps were the same.

[0093] When depositing the diffusion barrier layer Si3N4, bis(diethylamino)silane (BDEAS) and N2 plasma were used as precursors, the deposition temperature was 100 - 300 °C, and the deposition thickness was 3 nm.

[0094] One cycle of Si3N4 growth was (BDEAS - Ar - N2 Plasma - Ar), and the corresponding time was (0.2 s - 15 s - 15 s - 15 s). The growth thickness of Si3N4 in one cycle was 0.02 nm, and 150 cycles of ALD growth were required for the 3 nm Si3N4 storage layer film.

[0095] Example 3

[0096] The preparation method of the micro-nano fiber optic sensor based on silver nanoparticles in this embodiment includes the following steps:

[0097] S1. The treatment of the bare fiber is the same as that in Embodiment 1.

[0098] S2. Compared with Embodiment 1, in the mixed acid solution prepared with hydrofluoric acid and citric acid, the volume concentration of hydrofluoric acid is 2%, and the mass concentration of citric acid is 1%, until the diameter of the bare fiber after corrosion is 10% of that before corrosion.

[0099] Subsequently, the treated multimode quartz fiber is immersed in an ethanol solution of 3-aminopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane with a volume concentration of 5% and reacted for 0.5 h, and then dried.

[0100] S3. Prepare a solution containing silver nanoparticles: Mix 10 mL of a silver nitrate solution with a mass concentration of 1% and 1 mL of ammonia water with a volume concentration of 2% and stir until the solution turns light yellow, indicating that particles formed by the reduction of silver ions are initially generated. Then, NaOH is added dropwise until the pH reaches 10, and then 1 mL of a glucose solution with a mass concentration of 10% is added. After stirring evenly, a solution containing silver nanoparticles is obtained.

[0101] The above solution is reacted in a water bath at 60 °C for 60 s, and then the multimode quartz fiber treated in step S2 is immersed in the solution containing silver nanoparticles and reacted for 10 min, and then soaked in deionized water for 2 min to terminate the reaction, obtaining a fiber modified with silver nanoparticles.

[0102] S4. Deposit a diffusion barrier layer of Si3N4 on the surface of the fiber modified with silver by atomic layer deposition, and then sputter a gold layer on the surface of the diffusion barrier layer Si3N4.

[0103] When depositing the diffusion barrier layer Si3N4, bis(diethylamino)silane and N2 plasma are used as precursors, the deposition temperature is 300 °C, and the deposition thickness is 5 nm. One cycle of Si3N4 growth is (BDEAS - Ar - N2Plasma - Ar), and the corresponding time is (0.2 s - 15 s - 15 s - 15 s). The growth thickness of Si3N4 in one cycle is 0.02 nm, and 250 cycles of ALD growth are required for the 5 nm Si3N4 storage layer film.

[0104] The parameters for the gold layer deposition process are: sputtering power 200 W, target-substrate distance 450 mm, sputtering pressure 1.0 - 2.0 Pa, thickness 40 nm, vacuum degree 3×10 -4 Pa, sample stage rotation speed 15 r / min, bias voltage -50 V, duty cycle 70%, sputtering atmosphere argon, gas flow rate 200 sccm.

[0105] Example 4

[0106] The preparation method of the micro-nano fiber sensor based on silver nanoparticles in this embodiment includes the following steps:

[0107] S1. The treatment of the bare fiber is the same as that in Embodiment 1.

[0108] S2. Compared with Embodiment 1, in the mixed acid solution prepared with hydrofluoric acid and citric acid, the volume concentration of hydrofluoric acid is 10%, and the mass concentration of citric acid is 5%. Until the diameter of the bare fiber after corrosion is 30% of that before corrosion, and then it is washed and dried.

[0109] Subsequently, the treated multimode quartz fiber is immersed in a 1% (volume concentration) ethanol solution of 3-aminopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane, and reacts for 1 h, and then is dried.

[0110] S3. Prepare a solution containing silver nanoparticles: Mix 10 mL of a 1% (mass concentration) silver nitrate solution and 3 mL of a 2% (volume concentration) ammonia water and stir until the solution turns light yellow, indicating that particles formed by the reduction of silver ions are initially generated. Then, NaOH is added dropwise until the pH reaches 10, and then 3 mL of a 10% (mass concentration) glucose solution is added. After stirring evenly, a solution containing silver nanoparticles is obtained.

[0111] The above solution reacts in a 60 °C water bath for 60 s, and then the multimode quartz fiber treated in step S2 is immersed in the solution containing silver nanoparticles and reacts for 20 min, and is soaked in deionized water for 2 min to terminate the reaction, obtaining a fiber modified with silver nanoparticles.

[0112] S4. Deposit a diffusion barrier layer Si3N4 on the surface of the fiber modified with silver by atomic layer deposition method, and then sputter a gold layer on the surface of the diffusion barrier layer Si3N4.

[0113] When depositing the diffusion barrier layer Si3N4, bis(diethylamino)silane and N2 plasma are used as precursors, the deposition temperature is 100 °C, and the deposition thickness is 2 nm. One cycle of Si3N4 growth is (BDEAS - Ar - N2Plasma - Ar), and the corresponding time is (0.2 s - 15 s - 15 s - 15 s). The growth thickness of Si3N4 in one cycle is 0.02 nm, and 100 cycles of ALD growth are required for the 2 nm Si3N4 storage layer film.

[0114] The parameters in the gold layer deposition process are: sputtering power 50 W, target-substrate distance 50 mm, sputtering pressure 2.0 Pa, thickness 20 nm, vacuum degree 2×10 -4 Pa, the sample stage rotation speed is 15 r / min, the bias voltage is -50 V, the duty cycle is 70%, the sputtering atmosphere is argon, and the gas flow rate is 50 sccm.

[0115] Embodiment 5

[0116] The preparation method of the micro-nano optical fiber sensor based on silver nanoparticles in this embodiment includes the following steps:

[0117] S1. The treatment of the bare fiber is the same as that in Embodiment 1.

[0118] S2. Compared with Embodiment 1, in the mixed acid solution prepared with hydrofluoric acid and citric acid, the volume concentration of hydrofluoric acid is 8%, and the mass concentration of citric acid is 2%. Until the diameter of the bare fiber after corrosion is 15% of that before corrosion, and then it is washed and dried.

[0119] Subsequently, the treated multimode quartz optical fiber is immersed in a 3-aminopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane ethanol solution with a volume concentration of 4% and reacted for 1 h, and then dried.

[0120] S3. Prepare a solution containing silver nanoparticles: Mix 10 mL of a silver nitrate solution with a mass concentration of 1% and 3 mL of an ammonia water solution with a volume concentration of 2% and stir until the solution turns light yellow, indicating that particles formed by the reduction of silver ions are initially generated. Then, NaOH is added dropwise until the pH reaches 10, and then 2 mL of a glucose solution with a mass concentration of 10% is added. After stirring evenly, a solution containing silver nanoparticles is obtained.

[0121] The above solution is reacted in a water bath at 60 °C for 60 s, and then the multimode quartz optical fiber treated in step S2 is immersed in the solution containing silver nanoparticles and reacted for 15 min, and then soaked in deionized water for 2 min to terminate the reaction, obtaining a silver nanoparticle-modified optical fiber.

[0122] S4. Deposit a diffusion barrier layer Si3N4 on the surface of the fiber modified with silver by atomic layer deposition method, and then sputter a gold layer on the surface of the diffusion barrier layer Si3N4.

[0123] When depositing the diffusion barrier layer Si3N4, bis(diethylamino)silane and N2 plasma are used as precursors, the deposition temperature is 250 °C, and the deposition thickness is 4 nm. One cycle of Si3N4 growth is (BDEAS-Ar-N2Plasma-Ar), and the corresponding time is (0.2 s - 15 s - 15 s - 15 s). The growth thickness of Si3N4 in one cycle is 0.02 nm, and 200 cycles of ALD growth are required for the 4 nm Si3N4 storage layer film.

[0124] The parameters for the gold layer deposition process are: sputtering power 150 W, target-substrate distance 400 mm, sputtering pressure 2.0 Pa, thickness 25 nm, vacuum degree 3×10 -4 Pa, sample stage rotation speed 15 r / min, bias voltage -50 V, duty cycle 70%, sputtering atmosphere argon, gas flow rate 100 sccm.

[0125] Comparative Example 1

[0126] Compared with Example 1, the gold layer was not sputtered in Comparative Example 1, and the rest was the same as in Example 1.

[0127] Comparative Example 2

[0128] Compared with Example 1, in Comparative Example 2, when corroding, it was not immersed in 3-aminopropyltriethoxysilane solution, and the silver nanoparticles were directly modified, and the rest was the same as in Example 1.

[0129] Comparative Example 3

[0130] Compared with Example 1, in Comparative Example 3, the diameter of the bare optical fiber after corrosion was 40% of that before corrosion, and the rest was the same as in Example 1.

[0131] Comparative Example 4

[0132] Compared with Example 1, in Comparative Example 4, the sputtering thickness of the gold layer was 50 nm, and the rest was the same as in Example 2.

[0133] Comparative Example 5

[0134] Compared with Example 2, in Comparative Example 5, the deposition thickness of the diffusion barrier layer Si3N4 was 8 nm, and the rest was the same as in Example 2.

[0135] I. Moisture Resistance Test

[0136] Five optical fiber SPR sensing probes prepared from Example 1 and Comparative Example 1 were selected respectively. The sensing probes were placed in the following environments for 48 h:

[0137] Moisture test method: Use a sealed humidity chamber, add distilled water at the bottom of the chamber or perform a water spraying operation to simulate a saturated humidity environment with a relative humidity (RH) greater than 95% and a temperature of 25 °C.

[0138] During the test, the optical fiber SPR sensing probes were placed in the above environments continuously for 48 h. The SPR resonance wavelength and reflection intensity of the probes were recorded before and after the experiment.

[0139] (1) Saturated humidity environment: Use a sealed humidity chamber, add distilled water at the bottom or spray water to simulate an environment with RH > 95% and 25 °C.

[0140] (2) Inject a gas box with 10 ppm H2S or SO2 into a sealed gas box to simulate a corrosive gas environment.

[0141] Before and after the experiment, the SPR resonance wavelength and reflection intensity of the probe were recorded with the same SPR test system. The SPR wavelength drift (Δλ, unit: nm) and the sensitivity attenuation ratio of the probe were statistically analyzed before and after the experiment.

[0142] The results are as follows: After aging of Example 1 (silver-gold layer), there are almost no obvious changes in the SPR wavelength and signal intensity, the film layer is stable, and there is no obvious failure on the surface, indicating that the gold layer effectively blocks oxidation and corrosion. After aging of Comparative Example 1 (without gold layer), the silver film on the surface is easily oxidized, loses luster or changes color, the SPR signal drifts greatly or disappears, the sensitivity decreases significantly, and some samples fail.

[0143] II. Sensitivity Test

[0144] 1. Influence of Corrosion Depth on Sensitivity

[0145] Based on the examples, other corrosion depths of 10%, 15%, 25% and 30% were set, and the absorption spectra of pure water were detected. The results are as Figure 3 shown. As the corrosion depth increases, the absorption spectrum signal of the pure water in the fiber optic sensing area gradually increases, indicating that increasing the corrosion depth can effectively improve the SPR sensing sensitivity. However, considering the actual application situation and comparing the fiber optic performance of different corrosion times, the fiber in the sensing area is too thin and easy to break. Therefore, during the actual processing and corrosion process, the corrosion depth is selected from 10% to 30%. After exceeding 30%, the fiber is easy to break.

[0146] 2. Comparison of Sensitivities between Examples and Comparative Examples

[0147] Take the prepared micro-nano SPR fiber optic probes of various types, immerse the fiber optic probes in NaCl solutions with different refractive indexes, and ensure that the probes are stably immersed and the sensing area is fully in contact with the solution during each solution test. For each NaCl solution, turn on the Fourier transform infrared spectrometer to collect spectral data and record the corresponding SPR resonance wavelength. Each solution with each refractive index is tested 3 times, and the average value is taken to reduce errors.

[0148] The results are as follows: Due to sufficient surface functionalization, corrosion optimization, and the cooperation of the gold layer in the examples, the SPR coupling is effectively enhanced, the signal response and the surface field strength are improved, and the highest sensitivity is shown.

[0149] In the comparative example group, due to the lack of a gold layer, the non-use of corrosion inhibitors, non-functionalization, or too large / small film thickness, etc., the sensitivity decreases significantly, and the signal response is discontinuous or weak under some conditions.

[0150] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a micro-nano optical fiber probe for detecting biochemical components based on infrared spectroscopy, characterized in that: It includes the following steps: S1, select a section in the middle of the multimode quartz optical fiber as the sensing area, then remove the cladding and coating layer of the sensing area to expose the bare fiber; S2, drop the mixed acid solution prepared from hydrofluoric acid and citric acid onto the bare fiber to etch the bare fiber, then wash and dry it; subsequently, immerse the treated multimode quartz optical fiber into the silane coupling agent solution, react for 0.5 - 1 h, and then dry it; S3, immerse the multimode quartz optical fiber treated in step S2 into the solution containing silver nanoparticles, react for 10 - 20 min to obtain the optical fiber modified with silver nanoparticles; S4, adopt the vacuum magnetron sputtering technology to sputter a gold layer on the surface of the optical fiber modified with silver to obtain the micro - nano optical fiber probe with a silver - gold film layer.

2. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 1, characterized in that: In step S4, before sputtering the gold layer, deposit the diffusion barrier layer Si3N4 on the surface of the optical fiber modified with silver by atomic layer deposition method, and then sputter the gold layer on the surface of the diffusion barrier layer Si3N4. When depositing the diffusion barrier layer Si3N4, bis(diethylamino)silane and N2 plasma are used as precursors, the deposition temperature is 100 - 300 °C, and the deposition thickness is 2 - 5 nm.

3. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 1, characterized in that: The parameters of the gold layer deposition process are as follows: sputtering power is 50 - 200 W, target-substrate distance is 50 - 450 mm, sputtering pressure is 1.0 - 2.0 Pa, thickness is 20 - 40 nm, vacuum degree is 1×10 -4 ~3×10 -4 Pa, the sputtering atmosphere is argon, and the gas flow rate is 50 - 200 sccm.

4. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 1, wherein: In step S2, in the mixed acid solution, the volume concentration of hydrofluoric acid is 2% - 10%, and the mass concentration of citric acid is 1% - 5%.

5. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 1, characterized in that: In step S2, the diameter of the bare fiber after corrosion is 10% - 30% of that before corrosion.

6. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 1, characterized in that: In step S2, the silane coupling agent is 3 - aminopropyltriethoxysilane or 3 - mercaptopropyltrimethoxysilane, the volume concentration is 1% - 5%, and the solvent is ethanol.

7. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 1, characterized in that: In step S3, the method for preparing the solution containing silver nanoparticles is: mix the silver nitrate solution and ammonia water evenly, add NaOH dropwise until the pH reaches 10, and then add the glucose solution, and stir evenly to obtain the solution containing silver nanoparticles.

8. The preparation method of a micro-nano optical fiber probe for biochemical component detection based on infrared spectroscopy according to claim 7, characterized in that: The mass concentration of the silver nitrate solution is 1%, the volume concentration of the ammonia water is 2%, the mass concentration of the glucose solution is 10%, and the volume ratio of the silver nitrate solution, ammonia water and glucose solution is 10:1 - 3:1 - 3.

9. A micro-nano optical fiber probe for detecting biochemical components based on infrared spectroscopy, characterized in that: Prepared by the preparation method described in any one of claims 1 - 8.

10. A biochemical component detection device based on infrared spectroscopy, characterized in that: It includes the micro - nano optical fiber probe described in claim 9.

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