CN103630515B - A kind of nano-gold particle sensor and its manufacturing method - Google Patents

Abstract

The invention provides a nano gold particle sensor and a preparation method thereof. The end face of the multi-core fiber has a frustum structure, and the surface of the frustum is coated with a total reflection film. The end face of the fiber coated with a total reflection film is fixed with regularly arranged nano-gold particles, and the excitation light is injected into one core of the multi-core fiber. , the excitation light is reflected to the end face of the optical fiber at the frustum of the cone coating, and total internal reflection occurs at the end face of the optical fiber, the evanescent field generated excites the local surface plasmon resonance effect of the gold nanoparticles, and the reflected light passes through the interaction with the injected excitation light The fiber core is symmetrical and the fiber core is collected, and the change of the physical quantity of the external substance is sensed through the reflected light spectrum. The present invention combines multi-core optical fiber, near-field optical tweezers self-assembly technology with the local surface plasmon resonance effect of nano-gold particles, and the near-field optical tweezers composed of multi-core optical fibers can capture nano-gold particles, so that The distribution of capture regions is regularly arranged by optical self-assembly, with simple structure, smaller volume and high repeatability.

Description

A kind of nano-gold particle sensor and its manufacturing method

technical field

The invention relates to an optical fiber sensor, and also relates to a preparation method of the optical fiber sensor. Specifically, it is a nano-gold particle sensor and a manufacturing method thereof.

Background technique

Nano-gold particles refer to tiny particles of gold with a diameter of 1-100 nm, which are generally dispersed in hydrosol. As early as the Middle Ages, gold nanoparticles have been valued by people because of their unique optical properties. Gold nanoparticles can selectively absorb specific wavelengths of visible light and present colorful colors. Nanogold materials have specific surface effects, quantum size effects, and macroscopic quantum tunneling effects, and have superior properties that conventional materials do not have in terms of electrical, magnetic, optical, and chemical properties. Therefore, it has broad application prospects in catalysis, electronic materials, micro devices, reinforcement materials and sensor materials. Among them, the research on surface enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR) of nanoparticles is progressing rapidly.

Localized surface plasmon resonance (LSPR) is a physical optical phenomenon that occurs when incident light hits the surface of nanoparticles. When the frequency of incident light resonates with the collective oscillation frequency of metal free electrons, the resonance condition of LSPR is very sensitive to the dielectric environment around nanoparticles, and the macroscopic performance produces a strong absorption spectrum in a specific wavelength range. Since the LSPR phenomenon is generated by the light scattering of nanoparticles, LSPR does not require the complex optical system like the traditional SPR (surface plasmon resonance) technology, and can be realized by simple, portable and sensitive fiber optic spectrometers in biological sensing and analysis. Research in chemistry, clinical medicine, biological detection, etc.

It is difficult for gold nanoparticles to function alone, and a certain medium must be used as the carrier of the particles. The glass substrate is often used as the substrate, which is relatively large and difficult to meet the detection requirements of the micro environment. Optical fiber has good characteristics of light transmission, strong radiation resistance, and is less affected by external factors. Using optical fiber to transmit signals can adapt to harsh external environments. Therefore, using optical fiber as a substrate, nanoparticles are chemically assembled on the surface of the optical fiber and then collected and detected. The signal has strong practical application value.

At present, the combination of gold nanoparticles and optical fibers usually has the following methods: gold nanoparticles are decorated on the end face of the multimode fiber, gold nanoparticles are decorated on the side of the fiber, and gold nanoparticles are decorated in the air holes of the photonic crystal fiber.

Keita Mitsui (Applied Physics Letters, 85(18): 4231–4233, 2004) and others adsorbed a layer of gold nanoparticles on the end surface of the optical fiber, and used a reflective optical fiber LSPR sensing structure to measure the molecular affinity in real time. Reach the level of conventional total reflection type SPR device. Stokes and Tuan Vo-Dinh (Sensors and ActuatorsB-Chemical, 69(1-2):28-36, 2000) attached alumina nanoparticles and silver nanoparticles to one end of the optical fiber, and detected CFV (cresyl fast violet) in real time in the experiment. ) molecules and BCB (brilliant cresyl blue) molecules, the detection level of CFV molecules can reach 50ppb (1ppb=1×10 ^-6 mg/ml). Subsequently, Viets (Jumal of Ranman Spectroscopy, 31(7):625-631, 2000) successively proposed optical fiber probes with inclined end faces and tapered end faces. LinTSaojen (Journal of Supercritical Fluids, 41(2):317-325, 2007) et al. used a reflective optical fiber LSPR sensor to test the concentration of Ni 2+ in the liquid under a high pressure environment, and then tested the Ni ²⁺ concentration implanted on the end face of the optical fiber. Metal particles undergo monoclonal modification. This kind of end face modification method usually requires the use of multimode fiber, and because of the direct irradiation method, the excitation efficiency is generally not high.

To modify the gold nanoparticles on the side of the optical fiber needs to grind and corrode the optical fiber to the core or perform tapering treatment, and then modify a layer of metal nanoparticles to act as the sensitive unit of the sensor to interact with the outside world. In 2000, Ni Weihai (Journal of Physical Chemistry C, 112(22):8105-8109, 2008) and others assembled metal nanorods on the side of the corroded optical fiber, used the evanescent field to excite LSPR, and obtained the scattering spectrum for the environmental refraction The rate sensitivity reaches 200nm/RIU. Tang (Sens.Actuators B,119(1):105-109,2006) et al. coated nano-gold colloids on the surface of long-period fiber gratings in 2006 to detect changes in the refractive index of surrounding materials. This sensor can detect the concentration of glucose, and when deoxyribonucleoprotein (DNP) is immobilized on nano gold, the detection accuracy can reach 0.14mg/L. In 2011, Rani Dutta (Applied Optics, E138-E144, 2011) et al. studied the U-shaped optical fiber nanoparticle sensor based on the corrosion method. Due to the increase of the density of nanoparticles on the surface of the optical fiber, a red shift of its maximum absorption area was observed. The problem with this type of sensor is that when the optical fiber is processed by polishing, chemical corrosion, etc., the optical fiber becomes very fragile and is easy to break.

The air hole structure of photonic crystal fiber, which is a good carrier of gas and liquid in sensing, has been used to design the substrate of gold nanoparticle sensor. Light is transmitted in hollow photonic crystal fiber, and the light is confined in the core. Analysis The material is filled in the air holes, which greatly improves the interaction area between the light and the SERS substrate. The modification of gold nanoparticles in the air holes of photonic crystal fibers also has the problems of complex methods and difficulty in ensuring consistency.

In general, nano-gold particle sensors can be realized by the above methods, but they all have the disadvantages of low excitation efficiency, low repeatability and complicated methods. When using multimode optical fiber to modify the end surface of gold nanoparticles, the excitation efficiency is generally not high because the light source is directly irradiated; After treatment, it becomes very fragile, so that the repeatability of the nano-gold particle sensor made by this method is not high; the method of nano-gold particle modification in the air hole of the photonic crystal fiber also has the problem of complicated method and difficult to ensure consistency.

Contents of the invention

The purpose of the present invention is to provide a nano-gold particle sensor with simple structure, smaller volume and high repeatability. The object of the present invention is also to provide a method for making a nano-gold particle sensor.

The nano-gold particle sensor of the present invention includes a multi-core optical fiber, the end face of the multi-core optical fiber is in a truncated cone structure, a total reflection film is coated on the surface of the cone truncated film, and regularly arranged nanometer Gold particles are injected into one core of the multi-core optical fiber with excitation light, and the excitation light is reflected to the end face of the fiber at the frustum coating and undergoes total internal reflection at the end face of the fiber. The evanescent field generated locally excites the gold nanoparticles. In the field of surface plasmon resonance effect, the reflected light is collected through the fiber core symmetrical to the injected excitation light, and the change of the physical quantity of the external substance is sensed through the reflected light spectrum.

Nano gold particle sensor of the present invention can also comprise:

1. The distribution positions of the multiple cores of the multi-core optical fiber are symmetrical to the center of the main axis of the optical fiber, and are in the same common cladding.

2. The truncated cone structure of the optical fiber end face is a symmetrical truncated cone structure or a symmetrical polygonal wedge structure.

3. The reflective film coated on the surface of the frustum is one of metal film, all-dielectric reflective film or metal electrolyte reflective film.

The preparation method of nano gold particle sensor of the present invention is:

Process the end face of the multi-core optical fiber with symmetrical core positions into a frustum shape, coat the surface of the frustum with a total reflection film, put it into the silane coupling agent APTMS and methanol solution, and fix functional groups on its surface. The group is amino or mercapto, put it into the nano-gold particle sol, pass the laser into the multi-core optical fiber, the laser is reflected to the end face of the optical fiber at the coating of the frustum of the cone, and total internal reflection occurs at the end face of the optical fiber, resulting in coherent evanescence In the evanescent field, the nano-gold particles are fixed under the action of the evanescent field near-field capture, the optical fiber is taken out, and the excess nano-gold particle sol is washed with deionized water to form a nano-gold particle sensor.

The manufacturing method of the nano-gold particle sensor of the present invention may also include: in the nano-gold particle sol, the nano-gold particle particles may be spherical, rod-shaped, triangular, star-shaped or other shapes of gold nanoparticles.

The invention is based on the following principle: grind the end faces of multi-core optical fibers with symmetrical core positions into a truncated conical structure, and coat a layer of high reflectivity total reflection film on the conical surfaces. As shown in Figure 4, the laser light transmitted in the fiber core is reflected to the end face of the fiber at a certain angle by the reflective film on the side of the truncated cone, and total reflection occurs at the end face of the fiber. medium, but there is still energy in the thin layer of the interface of the optically sparse medium, that is, the evanescent wave, which results in the near-field capture of gold nanoparticles.

Figure 5 and Figure 6 respectively show the simulation diagram of the light field distribution on the end face of the four-core fiber and the standing wave of the coherent evanescent field of the double-core fiber with two beams. Due to the symmetry of the multi-core fiber core we use, the incident beam also has symmetric characteristics, and the evanescent field generated by the beam will form interference at the center of the intersection point, dividing the capture area into light and dark interference areas, and the trapped gold nanoparticles The particles move under the action of the optical trap force, and are arranged in an orderly manner according to the distribution form of the near-field optical gradient force potential well, thereby completing the optical self-assembly process. After the gold nanoparticles are solidified, the capture laser is removed, and the sensing light is passed through one core of the multi-core optical fiber. The sensing light excites the localized surface plasmon effect (LSPR) on the surface of the nanoscale gold particles in the total reflection area.

As shown in Figure 7, when a beam of light shines on a spherical metal nanoparticle, the oscillating electric field causes the conduction electrons to oscillate together. When the electron cloud is displaced relative to the nucleus, the Coulomb interaction between the electron and the nucleus will generate an electrostatic restoring force to make the conduction electrons oscillate together. When the frequency of the incident light is the same as the plasmon oscillation frequency in the metal, resonance will occur, and this resonance represents the absorption of light by metal nanoparticles on a macroscopic scale. Its resonance frequency is closely related to the density of electrons, the effective mass of electrons, and the shape and size of charge distribution.

The resonance conditions of LSPR are very sensitive to the medium environment around the nanoparticles, and the adsorbed substances around the particles will cause the red shift of the resonance wavelength of LSPR. According to the metal sphere extinction spectrum formula:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; twenty\; four</span>}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; Na</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&chi;</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

where E(λ) is the extinction quantity, i.e. the sum of absorption and scattering; N is the local density of the nanoparticle; a is the radius of the metal nanosphere; _εout is the dielectric constant of the medium surrounding the metal nanosphere (assumed to be a positive real number , and is independent of wavelength; for spheres, the coefficient χ value before ε _out is 2); λ is the incident wavelength; ε _i is the imaginary part of the dielectric constant of metal nanospheres; ε _r is the real part of the dielectric constant of metal nanospheres department.

When the resonance term (ε _r +2ε _out ) in the denominator is close to zero, the resonance condition of LSPR is reached. From this model, it can be seen that the LSPR spectral characteristics of metal nanosphere particles in the external dielectric environment depend on several aspects: the radius a of the nanoparticle, the dielectric constant ε _i of the nanoparticle material and the environment in which the nanoparticle is located, ε _r and ε _out . When the gold nanoparticles are ideal metals with free electrons, ε _r can be expressed by the Drude model:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

where γ is the attenuation frequency of the metal and ω _out is the frequency of the incident light. ω _p is the resonant frequency of the metal, which can be expressed by the following formula:

ω _p =(N'e ² /mε) ^1/2 (3)

Among them, N' is the density of free electrons, m is the electron mass, and ε is the dielectric constant of the material relative to vacuum.

Since in the visible and ultraviolet light bands, γ<<ω _p , and at resonance, (ε _r +2ε _out )→0, at the same time according to the relationship between wavelength and frequency (λ=2πc/ω), and the relationship between refractive index and medium The relationship between electric constants can be rewritten as formula (2)

$\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

where _{λp is the resonance wavelength of the metal, and nout is} the refractive index around the metal nanosphere.

It can be seen from formula (4) that when the refractive index of the medium on the surface of gold nanoparticles is different, the position of the resonance peak (resonance angle or resonance wavelength) will be different. The reflected light is reflected by the end face and returned from the symmetrical core, and then received by the spectrometer, and the refractive index of the surrounding material is sensed by observing and measuring the position or intensity of the resonance peak.

The invention provides a nano gold particle sensor and a manufacturing method thereof. Combining the self-assembly technology of multi-core optical fiber and near-field optical tweezers with localized surface plasmon resonance (LSPR) of gold nanoparticles, the near-field optical tweezers composed of multi-core optical fibers are used to trap gold nanoparticles, so that the gold nanoparticles are The distribution law of the capture area is arranged regularly for optical self-assembly, and the end face grinding technology is used to control the end faces of optical fibers with different taper angles and heights to realize the reflective localized surface plasmon resonance optical fiber sensor. The combination of multi-core optical fiber and gold nanoparticles can greatly reduce the size of the sensor, and the evanescent field generated by total reflection is used to excite the localized surface plasmon resonance effect (LSPR) of gold nanoparticles, which overcomes the shortcomings of traditional reflective sensors. , can effectively improve the sensitivity of the sensor, and at the same time, the processing method of the nano-gold particle self-assembly sensor based on the multi-core optical fiber is simple and repeatable, which provides an effective method and technology for the nano-gold particle sensing technology.

The present invention combines the self-assembly technology of multi-core optical fiber and near-field optical tweezers with localized surface plasmon resonance effect (LSPR) of nano-gold particles, and the near-field optical tweezers composed of multi-core optical fibers can capture nano-gold particles, making The gold particles are regularly arranged by optical self-assembly according to the distribution law of the capture area, realizing a new structure of nano-gold particle sensor, which has the advantages of simple structure, smaller volume and high repeatability.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of the nano-gold particle sensor.

Fig. 2 is a schematic diagram of the working principle of the nano-gold particle sensor.

Fig. 3 is a schematic diagram of the structure of a four-core optical fiber nano-gold particle sensor.

Fig. 4 is a schematic diagram of trapping gold nanoparticles in the evanescent field of the present invention.

Fig. 5 is a simulation diagram of light field distribution on the end face of a four-core optical fiber.

Figure 6 shows the coherent evanescent field standing wave of the dual-core fiber dual-beam.

Fig. 7 is a schematic diagram of localized surface plasmon resonance of spherical metal nanoparticles.

Fig. 8 is a refractive index test system composed of nano-gold particle optical fiber sensor.

detailed description

Figure 1 shows the overall structure of the gold nanoparticle sensor. In the figure, 1 is a multi-core fiber whose distribution positions of multiple cores are symmetrical about the center of the fiber axis, 2 is a processed multi-core fiber end face in the shape of a frustum of a cone, 3 is a total reflection film, and 4 is a multi-core fiber coated with a reflective film. Optical fiber end face, 5 is nano gold particles.

Fig. 2 is a schematic diagram of the working principle of the nano-gold particle sensor. In the figure, 1 is a multi-core optical fiber in which the distribution positions of multiple cores are symmetrical with respect to the center of the fiber axis; Optical fiber end face, 5 is nano gold particles, 6 is a core of multi-core optical fiber, 7 is sensing light, 8 is reflected light to be measured, 9 is a symmetrical core symmetrical to 6.

Fig. 3 is a schematic diagram of the structure of a four-core optical fiber nano-gold particle sensor. In the figure, 1 is a multi-core fiber whose distribution positions of multiple cores are symmetrical about the center of the fiber axis, 2 is a processed multi-core fiber end face in the shape of a frustum of a cone, 3 is a total reflection film, and 4 is a multi-core fiber coated with a reflective film. Optical fiber end face, 5 is nano gold particles.

Fig. 8 is a refractive index test system composed of nano-gold particle optical fiber sensor. In the figure, 10 is a light source, 11 is a circulator, 12 is a single-core optical fiber, 13 is a coupler, 14 is a multi-core optical fiber, 15 is a fabricated nano-gold particle optical fiber sensing probe, 16 is a substance solution to be measured, and 17 is a spectrometer.

The present invention can be realized in the following ways:

Take a section of multi-core optical fiber 1 with a symmetrical core position, and cut and process the end face of the optical fiber into a plane perpendicular to the axis of the optical fiber by using an optical fiber cutting technology. Use the fiber end grinding technology to process the fiber end face into a frustum shape 2, use vacuum coating equipment to coat a layer of high reflectivity gold film 3 on the fiber conical structure, put the fiber into the silane coupling agent APTMS and methanol solution, in Its surface immobilizes functional groups (amino or mercapto groups), puts the optical fiber into the nano-gold particle sol, passes through the laser in the multi-core optical fiber, and the laser is reflected to the end face of the optical fiber at the frustum coating, and the end face of the optical fiber 4 Total internal reflection occurs and a coherent evanescent field is generated. Due to the near-field capture effect of the evanescent field, the gold nanoparticles 5 are uniformly arranged on the end face 4 of the optical fiber. After the gold nanoparticles are fixed, the optical fiber is taken out and cleaned with deionized water. The excess nano-gold particle sol forms a nano-gold particle sensor.

Fabrication of the four-core optical fiber nano-gold particle sensor, Figure 3 is a schematic diagram of the structure of the four-core optical fiber nano-gold particle sensor.

1. Optical fiber pretreatment: Take a section of four-core optical fiber, use optical fiber strippers to strip the coating layer at one end of the optical fiber for about 30mm, and clean the optical fiber cladding with alcohol.

2. Use a fiber cutter to cut the processed part of the fiber to form a flat end face.

3. Use the optical fiber polishing technology to grind the fiber end into a truncated cone with α=36°, and the grinding depth is 44.4 μm.

4. Use the vacuum coating technology to coat the end face of the frustum of the cone ground in step 3 with a gold film.

5. Soak the optical fiber treated in step 4 in 96% H ₂ SO ₄ and 30% H ₂ O ₂ at a volume ratio of 3:1 for 30 minutes to clean the surface.

6. Wash the optical fiber processed in step 5 three times with deionized water and twice with alcohol.

7. Immerse the cleaned optical fiber in the silane coupling agent APTMS and methanol solution with a volume ratio of 1:10 for 30 minutes.

8. Rinse the optical fiber treated in step 7 with deionized water 3 times.

9. Put the optical fiber processed in step 8 into the centrifuged gold nanoparticle sol, inject the excitation light into an optical fiber core, and then generate an evanescent field formed by total internal reflection at the end face of the optical fiber, because the evanescent field Near-field capture effect, the gold nanoparticles are regularly arranged on the end face of the optical fiber.

10. Take out the optical fiber on which the gold nanoparticles have been fixed in step 9, and wash with deionized water to remove excess gold nanoparticle sol.

Measuring the refractive index of different substances using nano-gold particle fiber optic sensor.

Fig. 8 is a schematic diagram of a refractive index measurement system composed of a nano-gold particle optical fiber sensor. The light emitted by the light source 10 is coupled into the single-core optical fiber 12 through the circulator 11, the power coupling with the multi-core optical fiber is realized through the coupler 13 and the multi-core optical fiber 14, and the prepared nano-gold particle optical fiber sensing probe 15 is inserted into the substance to be tested In the solution 16, the reflected light returns to the original path and the reflection spectrum is detected by the spectrometer 17. Light source modulation wavelength technology can be used to realize resonant wavelength scanning detection. The reflectivity will be the lowest at the wavelength where plasma resonance occurs, and the resonant wavelength reflected by different substances will be shifted. Because the optical fiber cone with total reflection has a certain angle adjustment range, the incident light wave that generates resonance also has a range, so a wide-spectrum light source can be used to induce localized surface plasmon resonance, and the output spectrum and the wavelength relationship.

On the basis of theoretical research, use the built optical fiber detection system to make probes with different cone angles to achieve the measurement of different substances, by detecting the refractive index of aqueous solutions such as glucose and glycerin, testing solutions with the same refractive index with different components, and soluble protein concentration Detection and other experiments, to study the specific application of optical fiber nano-gold particle self-assembly sensor in biological detection.

Claims (7)

1. A nano-gold particle sensor comprises a multi-core optical fiber, the end face of the multi-core optical fiber is a truncated cone structure, and it is characterized in that: the surface of the truncated cone is coated with a total reflection film, and the end face of the optical fiber coated with a total reflection film is fixed Regularly arranged gold nanoparticles, inject excitation light into one core of the multi-core optical fiber, the excitation light is reflected to the end face of the fiber at the frustum of the cone coating, and total internal reflection occurs at the end face of the fiber, resulting in an evanescent field Excite the localized surface plasmon resonance effect of nano-gold particles, the reflected light is collected through a fiber core that is symmetrical to the fiber core that injects the excitation light, and the change of the physical quantity of the external substance is sensed through the reflected light spectrum. 2. The nano-gold particle sensor according to claim 1, characterized in that: the distribution positions of the multiple cores of the multi-core optical fiber are symmetrical with respect to the center of the main axis of the optical fiber, and are in the same common cladding. 3. The nano-gold particle sensor according to claim 1 or 2, characterized in that: the truncated-cone structure of the optical fiber end face is a symmetrical truncated-conical structure or a symmetrical polygonal wedge-shaped structure. 4. The nano-gold particle sensor according to claim 1 or 2, characterized in that: the reflective film coated on the surface of the cone is one of a metal film, an all-dielectric reflective film or a metal electrolyte reflective film. 5. a kind of preparation method of nano-gold particle sensor as claimed in claim 1 is characterized in that: the end face of the multi-core optical fiber with fiber core position symmetry is processed into frustum shape, is coated with total reflection film on the surface of frustum, puts In the silane coupling agent APTMS and methanol solution, fix functional groups on its surface, put it into the nano-gold particle sol, pass the laser into the multi-core optical fiber, and the laser is reflected to the end face of the optical fiber at the frustum coating, and then Total internal reflection occurs at the end face of the optical fiber to generate a coherent evanescent field. The gold nanoparticles are fixed under the near-field capture of the evanescent field, the optical fiber is taken out, and the excess nano-gold particle sol is cleaned with deionized water to form gold nanoparticles. particle sensor. 6. The manufacturing method of the nano-gold particle sensor according to claim 5, characterized in that: in the nano-gold particle sol, the nano-gold particle particles are spherical, rod-shaped, triangular or star-shaped gold nano-particles. 7. The method for making a gold nanoparticle sensor according to claim 5 or 6, wherein the functional group is an amino group or a mercapto group.