CN103630515A - Sensor for nano gold particles and preparation method thereof - Google Patents

Abstract

The invention provides a sensor for nano gold particles and a preparation method thereof. The end surface of a multi-core optical fiber is of a conical-platform structure; a total-reflection film is plated on the surface of the conical platform; the nano gold particles which are distributed regularly are fixed on the end surface of the optical fiber plated with the total-reflection film; exciting light is injected into one fiber core of the multi-core optical fiber, is reflected to the end surface of the optical fiber at the film-plated position of the conical platform and generates total internal reflection on the end surface of the optical fiber, and a generated evanescent field excites a localized surface plasmon resonance effect of the nano gold particles; the reflected light is collected by the fiber core symmetrical to the fiber core injected with the exciting light, and the change of the physical quantity of external substances is sensed by the spectrum of the reflecting light. The sensor and the preparation method have the advantages that the multi-core optical fiber, a self-assembly technology of a near-field optical tweezer and the localized surface plasmon resonance effect of the nano gold particles are combined, and the near-field optical tweezer of the multi-core optical fiber can be utilized for capturing the nano gold particles, so that the optical self-assembly and regular distribution is carried out on the nano gold particles according to the distribution rule of the capturing areas; the structure is simple, the volume is smaller and the repeatability is high.

Description

A kind of nano Au particle sensor and preparation method thereof

Technical field

What the present invention relates to is a kind of Fibre Optical Sensor, the present invention also relates to a kind of preparation method of Fibre Optical Sensor.A kind of nano Au particle sensor and preparation method thereof specifically.

Background technology

Nano Au particle refers to that diameter is at the golden molecule of 1～100nm, and General Decentralized is in the hydrosol.As far back as Middle Ages nano Au particle just because its unique optical property is subject to people's attention, nano Au particle can be selected to absorb to specific wavelength visible ray and presents colourful color.Nm of gold material has special surface effect, quantum size effect and macro quanta tunnel effect, has the superior function that conventional material does not possess aspect electricity, magnetics, optics and chemical property.Therefore, aspect catalysis, electronic material, micro element, reinforcing material and sensor material, having broad application prospects.The surface-enhanced Raman character of nano particle (Surface enhanced Raman scattering wherein, SERS), the progress of local surface plasma resonance (Localized surface plasmon resonance, LSPR) aspect is rapid.

Local surface plasma resonance (LSPR) is a kind of physical optics phenomenon producing when incident light incides nanoparticle surface.When incident light frequency and metal free electron collective oscillation frequency generation resonance, the resonant condition of LSPR is very responsive to nano particle dielectric environment around, and macro manifestations produces strong absorption spectrum in specific wavelength coverage.Because LSPR phenomenon is that light scattering by nano particle produces, therefore LSPR does not need traditional SPR(surface plasma body resonant vibration) the such complicated light path system of technology, can realize the research at aspects such as bio-sensing, analytical chemistry, clinical medicine, biological detection by simple, portable, sensitive fiber spectrometer.

Nano Au particle is difficult to play a role separately, must be by certain medium the carrier as particle.Using many is to adopt glass substrate as substrate, and volume ratio is larger, is difficult to realize the detection demand of microenvironment.Optical fiber has the characteristic of good transmission light, and capability of resistance to radiation is strong, affected by extraneous factor little, adopt optical fiber transmission signal can adapt to severe external environment, thereby after using optical fiber to adopt chemical method to be assembled into optical fiber surface nano particle as substrate, acquisition testing signal have very strong actual application value.

At present, nano Au particle is combined with optical fiber and is conventionally had following several mode: nano Au particle is modified at multimode optical fiber end face, nano Au particle is modified at optical fiber side and nano Au particle is modified in the airport of photonic crystal fiber.

KeitaMitsui (Applied Physics Letters, 85 (18): 4231 – 4233,2004) etc. people is adsorbed last layer gold nano grain on fiber end face, adopt reflective optical fiber LSPR sensing arrangement, affinity to molecule is measured in real time, and sensitivity reaches the level of conventional total reflection type SPR device.Stokes and Tuan Vo-Dinh (Sensors and Actuators B-Chemical, 69 (1-2): 28-36,2000) aluminum oxide nanoparticle and silver nano-grain are attached to optical fiber one end, in experiment real-time detection CFV (cresyl fast violet) molecule and BCB (brilliant cresyl blue) molecule, wherein the detection level of CFV molecule can reach 50ppb(1ppb=1 * 10 ^-6mg/ml).Viets (Joumal of Ranman Spectroscopy, 31 (7): 625-631,2000) has successively proposed the optical fiber probe of angled end-face and tapered end face subsequently.The people such as Lin TSaojen (Journal of Supercritical Fluids, 41 (2): 317-325,2007) adopt reflection type optical fiber LSPR sensor, under hyperbaric environment to liquid in Ni ²⁺concentration has carried out again the metallic particles being implanted on fiber end face being carried out to the modification of monoclonal body after test.The method that this class end face is modified, need to be used multimode optical fiber conventionally, and owing to adopting the mode of direct irradiation, general launching efficiency is not high.

Nano Au particle is modified to optical fiber side need to be by optical fiber lapping, corrode to fibre core or draw cone to process, and then modifies last layer metal nanoparticle, as sensing unit and the external world of sensor having an effect.2000, Ni Weihai(Journal of Physical Chemistry C, 112 (22): 8105-8109,2008) etc. people is assembled in metal nano-rod the optical fiber side being corroded, utilize evanscent field to encourage LSPR, obtain scattering spectrum the sensitivity of environment refractive index is reached to 200nm/RIU.Tang(Sens.Actuators B, 119 (1): 105-109,2006) etc. people was coated onto long period fiber grating surface in 2006 nm of gold colloid, was used for surveying the change of ambient substance refractive index.This sensor can detecting glucose concentration, when in nm of gold fixedly during deoxyribonucleoprotein (DNP), accuracy of detection can reach 0.14mg/L.2011, the people such as Rani Dutta (Applied Optics, E138-E144,2011) have studied the U-shaped optical fiber nanoparticle sensor of making based on etch, owing to increasing the density of nano particle at optical fiber surface, observed the red shift in its absorption maximum region.The problem of this class sensor is that it is very fragile that optical fiber becomes, and is easy to fracture when optical fiber is after the methods such as rubbing down, chemical corrosion are processed.

The airport structure of photonic crystal fiber, it in sensing, is the good carrier of gas and liquid, be used to design and produce nano Au particle sensor base, light transmits in Hollow-Core Photonic Crystal Fibers, light is limited in fibre core, analyte is filled in airport, has so greatly improved the zone of action of light and SERS substrate.Nano Au particle is modified at and in the airport of photonic crystal fiber, exists equally method complicated and be difficult to guarantee conforming problem.

Generally speaking, nano Au particle sensor can be realized by above several method, but all has that launching efficiency is low, repeatability is not high and the shortcoming such as method is complicated.When using multimode optical fiber to carry out end face decorated nanometer gold particle, due to the mode of the Lights section employing direct irradiation, general launching efficiency is not high; When nano Au particle is modified to the side of optical fiber, because optical fiber is after the method such as rubbing down, chemical corrosion is processed, become very fragile, make the repeatability of the nano Au particle sensor that this method makes not high; Nano Au particle is modified at and in the airport of photonic crystal fiber, exists equally method complicated and be difficult to guarantee conforming problem.

Summary of the invention

The object of the present invention is to provide a kind of simple in structure, volume is less, the high nano Au particle sensor of repeatability.The present invention also aims to provide a kind of method for making of nano Au particle sensor.

Nano Au particle sensor of the present invention comprises multi-core fiber, the end face of described multi-core fiber is frustum structure, on frustum surface, be coated with total reflection film, be coated with on the fiber end face of total reflection film and be fixed with the nano Au particle that rule is arranged, in a fibre core of multi-core fiber, inject exciting light, exciting light is reflected onto fiber end face place at frustum plated film place, and in fiber end face experiences total internal reflection, the local surface plasma resonance effect of the evanscent field excitation nano gold particle producing, reflected light is collected by the symmetrical moral fibre core of the fibre core with injecting exciting light, by the variation of reflected light spectrum perception external substance physical quantity.

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

1, the distributing position of a plurality of fibre cores of described multi-core fiber is symmetrical about the optical fiber alignment of shafts, and in same public covering.

2, the frustum structure of described fiber end face is symmetrical circular cone structure or symmetrical polygonal wedge structure.

3, the reflectance coating that described frustum surface is coated with is a kind of in metal film, full dielectric reflectance coating or electrolytic etching of metal matter reflectance coating.

The method for making of nano Au particle sensor of the present invention is:

The end face of the multi-core fiber of fibre core position symmetry is processed into frustum shape, at frustum plated surface total reflection film, put into silane coupling A PTMS and methanol solution, at its surperficial fixed function group, described functional group is amino or coloured glaze base, put into nano Au particle colloidal sol, in multi-core fiber, pass into laser, laser is reflected onto fiber end face place at frustum plated film place, and in fiber end face experiences total internal reflection, produce relevant evanscent field, in evanscent field near field, catch under effect nano Au particle is fixed, take out optical fiber, and remove unnecessary nano Au particle colloidal sol by washed with de-ionized water, form nano Au particle sensor.

The method for making of nano Au particle sensor of the present invention can also comprise: in described nano Au particle colloidal sol, nano Au particle particle can be the nanogold particle of spherical, bar-shaped, triangle, starlike or other patterns.

The present invention is based on following principle: the multi-core fiber end surface grinding of fibre core position symmetry is become to circular cone structure, and on the conical surface, plate one deck high reflectance total reflection film.As shown in Figure 4, the laser transmitting in fiber cores is reflexed to fiber end face at a certain angle by frustum offside reflection film, in fiber end face generation total reflection, although the energy of incident light wave is all reflected back optically denser medium when experiences total internal reflection, but still exist energy in the meagre one deck in the interface of optically thinner medium, gesture ripple suddenly, produces thus the near field of nano Au particle is caught.

Fig. 5 and Fig. 6 have shown respectively four-core fiber end face optical field distribution analogous diagram and the relevant evanscent field standing wave of twin-core fiber twin-beam.The multi-core fiber fibre core using due to us has symmetry and makes incident beam also have symmetry characteristic, the evanscent field that light beam produces will form and interfere in intersection point center, capture region is divided into light and dark interference region, captive nano Au particle moves under the effect of ligh trap power, according to the orderly arrangement of distribution form of near field of light gradient force potential well, thereby complete optics self assembling process.After nano Au particle is cured, removes and catch laser, in a core of multi-core fiber, pass to sense light, sense light goes out surface plasmons (LSPR) at the nanoscale gold particle surface excitation in total reflection district.

As shown in Figure 7, when light beam is radiated on spherical metal nano particle, oscillating electric field makes conduction electron one oscillates.When electron cloud has displacement with respect to atomic nucleus, the Coulomb interactions between electronics and atomic nucleus makes conduction electron one oscillates by static restoring force of generation.When incident light frequency is identical with intrametallic plasma oscillation frequency, will produce resonance, this resonance is the absorption to light with regard to exhibit metallic nano particle in macroscopic view.The shape of the density of its resonant frequency and electronics, electron effective mass, CHARGE DISTRIBUTION and size etc. are closely related.

The resonant condition of LSPR is very responsive to nano particle media environment around, and the particle around material of absorption will cause the red shift of LSPR resonant wavelength.According to Metal Ball extinction spectra formula:

$E\left(\mathrm{\λ}\right)=\frac{24{\mathrm{\π}}^2\mathrm{Na}{\mathrm{\ϵ}}_{\mathrm{out}}^{3/2}}{\mathrm{\λ}\ln 10}\left[\frac{{\mathrm{\ϵ}}_i\left(\mathrm{\λ}\right)}{{({\mathrm{\ϵ}}_r\left(\mathrm{\λ}\right)+\mathrm{\χ}{\mathrm{\ϵ}}_{\mathrm{out}})}^2+{\mathrm{\ϵ}}_i{\left(\mathrm{\λ}\right)}^2}\right]---\left(1\right)$

Wherein, E(λ) be delustring amount, absorb and the summation of scattering; N is the local density of nano particle; A is the radius of metal nano spheroid; ε _outthe specific inductive capacity that is metal nano spheroid surrounding medium (is assumed to be arithmetic number, and uncorrelated with wavelength; For spheroid, ε _outfront coefficient χ value is 2); λ is incident wavelength; ε _iit is the imaginary part of metal nano spheroid specific inductive capacity; ε _rit is the real part of metal nano spheroid specific inductive capacity.

A resonance (ε in denominator _r+ 2 ε _out) while approaching zero, reached the resonant condition of LSPR.From this model, can find out, the LSPR spectral characteristic of the metal nano spherical particles in extraneous dielectric environment depends on several aspects: the DIELECTRIC CONSTANT ε of the radius a of nano particle, nano-particle material and nano particle environment of living in _i, ε _rand ε _out.When nano Au particle particle is desirable free electron metal, ε _rcan be by Drude model representation:

${\mathrm{\&epsiv;}}_r=1-\frac{{{\mathrm{\&epsiv;}}_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HDA0000439290550000011.png,HDA0000439290550000012.png"\; state="\{\{state\}\}">p</figure-callout>}}}^2}{{{\mathrm{\&epsiv;}}_{\mathrm{out}}}^2+{\mathrm{\&gamma;}}^2}---\left(2\right)$

Wherein, γ is the frequency of fadings of metal, ω _outit is incident light frequency.ω _pbe the resonant frequency of metal, can be expressed from the next:

ω _p=(N'e ²/mε) ^1/2 （3）

Wherein, N' is free electron density, and m is electron mass, and ε is the specific inductive capacity of material relative vacuum.

Due at visible ray and ultraviolet light wave band, γ << ω _p, and when resonance, (ε _r+ 2 ε _out) → 0, simultaneously according to the relation between wavelength and frequency (λ=2 π c/ ω), and the relation between refractive index and specific inductive capacity, formula (2) can be rewritten into

$\mathrm{\&lambda;}={\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HDA0000439290550000011.png,HDA0000439290550000012.png"\; state="\{\{state\}\}">p</figure-callout>}}\sqrt{2{\mathrm{\&epsiv;}}_{\mathrm{out}}+1}=\sqrt{2}{\mathrm{\&lambda;}}_p{n}_{\mathrm{out}}---\left(4\right)$

Wherein, λ _pthe resonant wavelength of metal, n _outit is metal nano spheroid refractive index around.

When different by the medium refraction index of the known nano-scale gold particle sub-surface of formula (4), resonant positions (resonance angle or resonant wavelength) is by difference.Reflected light returns from symmetrical fibre core through end face reflection, then is received by spectrometer, by observation, measures the sensing that ambient substance refractive index is carried out in the position of resonance peak or the variation of intensity.

The present invention has provided a kind of nano Au particle sensor and preparation method thereof.Multi-core fiber, near-field optical tweezers self-assembling technique are combined with nano Au particle local surface plasma resonance effect (LSPR), the near-field optical tweezers that utilizes multi-core fiber to form is caught nano Au particle, make nano Au particle carry out optics self assembly rule according to the capture region regularity of distribution and arrange, the fiber end face that utilizes end surface grinding technology to control different cone angle and height is realized reflective local surface plasma resonance type optical fiber sensor.Utilize multi-core fiber to be combined with nano Au particle, can dwindle greatly the volume of sensor, the evanscent field excited nano gold particle local surface plasma resonance effect (LSPR) of utilizing total reflection to produce, overcome the shortcoming of conventional reflective sensor, can effectively improve the sensitivity of sensor, meanwhile, simple based on multi-core fiber nano Au particle self assembly sensor job operation, there is repeatability, for nano Au particle sensing technology provides a kind of effective method and technology.

The present invention combines multi-core fiber, near-field optical tweezers self-assembling technique with nano Au particle local surface plasma resonance effect (LSPR), the near-field optical tweezers that utilizes multi-core fiber to form can be caught nano Au particle, making nano Au particle carry out optics self assembly rule according to the capture region regularity of distribution arranges, realized the new construction of nano Au particle sensor, have simple in structure, volume is less, repeated advantages of higher.

Accompanying drawing explanation

Fig. 1 is nano Au particle sensor one-piece construction schematic diagram.

Fig. 2 is nano Au particle working sensor principle schematic.

Fig. 3 is four-core fiber nano Au particle sensor construction schematic diagram.

Fig. 4 is that evanscent field of the present invention is caught nano Au particle schematic diagram.

Fig. 5 is four-core fiber end face optical field distribution analogous diagram.

Fig. 6 is the relevant evanscent field standing wave of twin-core fiber twin-beam.

Fig. 7 is the local surface plasma resonance schematic diagram of spherical metal nano particle.

Fig. 8 is the refraction index test system that nano Au particle Fibre Optical Sensor forms.

Embodiment

Fig. 1 has provided nano Au particle sensor one-piece construction.In figure, 1 distributing position that is a plurality of fibre cores is about the multi-core fiber of optical fiber alignment of shafts symmetry, the 2 multi-core fiber end faces for the frustum shapes through processing, and 3 be total reflection film, and 4 is the multi-core fiber end face that plates reflectance coating, and 5 is nano Au particle.

Fig. 2 is nano Au particle working sensor principle schematic.In figure, 1 distributing position that is a plurality of fibre cores is about the multi-core fiber of optical fiber alignment of shafts symmetry, the 2 multi-core fiber end faces for the frustum shape through processing, 3 is total reflection film, 4 for plating the multi-core fiber end face of reflectance coating, 5 is nano Au particle, 6 fibre cores that are multi-core fiber, and 7 is sense light, 8 is reflected light to be measured, and 9 is the symmetrical fibre core with 6 symmetries.

Fig. 3 is four-core fiber nano Au particle sensor construction schematic diagram.In figure, 1 distributing position that is a plurality of fibre cores is about the multi-core fiber of optical fiber alignment of shafts symmetry, the 2 multi-core fiber end faces for the frustum shapes through processing, and 3 be total reflection film, and 4 is the multi-core fiber end face that plates reflectance coating, and 5 is nano Au particle.

Fig. 8 is the refraction index test system that nano Au particle Fibre Optical Sensor forms.In figure, 10 is light source, and 11 is circulator, and 12 is single-core fiber, and 13 is coupling mechanism, and 14 is multi-core fiber, and 15 is the nano Au particle optical fiber sensing probe of making, and 16 is test substance solution, and 17 is spectrometer.

The present invention can realize in the following way:

Get the multi-core fiber 1 of one section of fibre core position symmetry, utilize fiber cut technology that fiber end face is cut into the plane perpendicular to shaft axis of optic fibre.Utilize optical fiber end grinding technology that fiber end face is processed into frustum shape 2, utilize vacuum coating equipment at optical fiber circular cone structure plating one deck high reflectance gold film 3, optical fiber is put into silane coupling A PTMS and methanol solution, at its surperficial fixed function group (amino or coloured glaze base), optical fiber is put into nano Au particle colloidal sol, in multi-core fiber, pass into laser, laser is reflected onto fiber end face place at frustum plated film place, and in fiber end face 4 experiences total internal reflection, produce relevant evanscent field, because effect is caught in evanscent field near field, nano Au particle 5 is evenly arranged on fiber end face 4, after nano Au particle fixes, take out optical fiber, and take out unnecessary nano Au particle colloidal sol by washed with de-ionized water, form nano Au particle sensor.

The making of four-core fiber nano Au particle sensor, Fig. 3 is four-core fiber nano Au particle sensor construction schematic diagram.

1. the pre-service of optical fiber: get one section of four-core fiber, utilize the about 30mm of coat of optical fiber wire-stripping pliers peeling optical fibre one end, with alcohol, fibre cladding is cleaned up.

2. the part of with optical fiber cutter, optical fiber processing being crossed is cut, and forms smooth end face.

3. utilize optical fiber lapping technology optical fiber end to be ground to the frustum of a cone of α=36 °, grinding the degree of depth is 44.4 μ m.

4. the gold-plated film of frustum of a cone end face that utilizes vacuum coating technology that step 3 is ground.

5. the H that the concentration that the optical fiber after processing by step 4 is soaked in to volume ratio and is 3:1 is 96% ₂sO ₄with 30% H ₂o ₂middle immersion 30 minutes, clean surface.

6. by optical fiber washed with de-ionized water 3 times after processing by step 5, alcohol cleans twice.

7. the optical fiber that cleaned is immersed in the silane coupling A PTMS of volume tourney 1:10 and methanol solution 30 minutes.

8. by optical fiber deionized water rinsing 3 times after processing by step 7.

9. the optical fiber after processing by step 8 is put into the nano Au particle colloidal sol of centrifugal mistake, exciting light is injected in a fiber cores, at fiber end face, produce the evanscent field being formed by total internal reflection phenomenon, because effect is caught in evanscent field near field, nano Au particle is arranged on fiber end face by rule.

10. the optical fiber that fixes nano Au particle by step 9 is taken out, use washed with de-ionized water to take out unnecessary nano Au particle colloidal sol.

Utilize the refractive index of nano Au particle fiber sensor measuring different material.

Fig. 8 is for utilizing nano Au particle Fibre Optical Sensor to form refraction index test system schematic.The light that light source 10 sends is coupled in single-core fiber 12 through circulator 11, through coupling mechanism 13 and multi-core fiber 14, realize with the power of multi-core fiber and being coupled, the nano Au particle optical fiber sensing probe 15 of making inserts in test substance solution 16, and reflected light returns by spectrometer 17 and surveys reflectance spectrum by original route.Can adopt modulation of source wavelength technology, realize resonant mode length scanning and survey, the wavelength place that plasma resonance occurs will there will be reflectivity minimum, and the resonance wavelength of measuring different its reflections of material will produce translation.Because there is the optical fiber frustum of total reflection, there is certain angle of regulation range, also there is a scope in the incident light wave that produces resonance, therefore can adopt wide spectrum light source to cause local surface plasma sub-resonance, detect the relation of output spectrum and wavelength at the endpiece of optical fiber.

On the basis of theoretical research, the fiber optic detection system that utilization is built, the probe of making different cone angle is realized the measurement of different material, by detecting the experiments such as the identical refraction index solution test of refractive index, heterogeneity, the detection of soluble protein concentration of the aqueous solution such as glucose, glycerine, study the concrete application of optical fiber nano Au particle self assembly sensor in biological detection.

Claims (7)

1. a nano Au particle sensor comprises multi-core fiber, the end face of described multi-core fiber is frustum structure, it is characterized in that: on frustum surface, be coated with total reflection film, be coated with on the fiber end face of total reflection film and be fixed with the nano Au particle that rule is arranged, in a fibre core of multi-core fiber, inject exciting light, exciting light is reflected onto fiber end face place at frustum plated film place, and in fiber end face experiences total internal reflection, the local surface plasma resonance effect of the evanscent field excitation nano gold particle producing, reflected light is collected by the symmetrical moral fibre core of the fibre core with injecting exciting light, by the variation of reflected light spectrum perception external substance physical quantity.

2. nano Au particle sensor according to claim 1, is characterized in that: the distributing position of a plurality of fibre cores of described multi-core fiber is symmetrical about the optical fiber alignment of shafts, and in same public covering.

3. nano Au particle sensor according to claim 1 and 2, is characterized in that: the frustum structure of described fiber end face is symmetrical circular cone structure or symmetrical polygonal wedge structure.

4. nano Au particle sensor according to claim 1 and 2, is characterized in that: the reflectance coating that described frustum surface is coated with is a kind of in metal film, full dielectric reflectance coating or electrolytic etching of metal matter reflectance coating.

5. the method for making of a nano Au particle sensor claimed in claim 1, it is characterized in that: the end face of the multi-core fiber of fibre core position symmetry is processed into frustum shape, at frustum plated surface total reflection film, put into silane coupling A PTMS and methanol solution, at its surperficial fixed function group, put into nano Au particle colloidal sol, in multi-core fiber, pass into laser, laser is reflected onto fiber end face place at frustum plated film place, and in fiber end face experiences total internal reflection, produce relevant evanscent field, in evanscent field near field, catch under effect nano Au particle is fixed, take out optical fiber, and remove unnecessary nano Au particle colloidal sol by washed with de-ionized water, form nano Au particle sensor.

6. the method for making of nano Au particle sensor according to claim 5, is characterized in that: in described nano Au particle colloidal sol, nano Au particle particle can be the nanogold particle of spherical, bar-shaped, triangle, starlike or other patterns.

7. according to the method for making of the nano Au particle sensor described in claim 5 or 61, it is characterized in that: described functional group is amino or coloured glaze base.

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