阅读说明：本技术 氧化石墨烯光纤光栅的纳米金壳lspr光极生物传感器 (Nano-gold shell LSPR (localized surface plasmon resonance) optode biosensor of graphene oxide fiber bragg grating ) 是由 罗彬彬 于 2019-10-22 设计创作，主要内容包括：本发明涉及光极生物分子传感器,具体涉及一种氧化石墨烯光纤光栅的纳米金壳LSPR光极生物传感器包括光纤纤芯,光纤包层,光纤涂覆层,光纤纤芯的末端有大角度倾斜光纤光栅,大角度倾斜光纤光栅的包层表面的涂覆层完全被去除,大角度倾斜光纤光栅末端的端面鍍有银反射膜,大角度倾斜光纤光栅的包层表面有硅烷层,硅烷层表面固定有纳米金壳粒子层,固定有纳米金壳粒子层的表面吸附有氧化石墨烯层,氧化石墨烯层的表面固定有生物分子敏感层。采用本发明方案的光极生物传感器结构,可增加光波消逝场所激发的LSPR与生物分子的作用距离,且便于集成和应用,具有很高的鲁棒性,可应用于生物、医学、环境监测、食品安全、生命科学等领域。(The invention relates to a photoelectrode biomolecule sensor, in particular to a nanogold shell LSPR photoelectrode biosensor of a graphene oxide fiber grating, which comprises a fiber core, a fiber cladding and a fiber coating layer, wherein the tail end of the fiber core is provided with a large-angle inclined fiber grating, the coating layer on the surface of the cladding of the large-angle inclined fiber grating is completely removed, the end surface at the tail end of the large-angle inclined fiber grating is provided with a silver reflecting film, the surface of the cladding of the large-angle inclined fiber grating is provided with a silane layer, the surface of the silane layer is fixedly provided with a nanogold shell particle layer, the surface of the layer fixedly provided with the nanogold shell particle layer is adsorbed with a graphene oxide layer, and the surface of the graphene oxide layer. The structure of the optode biosensor adopting the scheme of the invention can increase the action distance between LSPR excited by a light wave evanescent field and biomolecules, is convenient for integration and application, has very high robustness, and can be applied to the fields of biology, medicine, environmental monitoring, food safety, life science and the like.)

1. Oxidized graphene fiber grating's gold shell LSPR photoelectrode biosensor of nanometer, its characterized in that: including the fiber core, the fiber cladding, the end-to-end connection of fiber core has wide-angle slope fiber grating, the fiber cladding has fiber core section and grating section, the internal surface cladding of fiber core section is in the surface of fiber core, the surface cladding of fiber core section has the optical fiber coating, the surface cladding of the wide-angle slope fiber grating of grating section cladding, the surface cladding of the grating section of fiber cladding has the silane layer, 5 surfaces on silane layer have the cladding to have the gold shell particle layer of nanometer, the terminal of wide-angle slope fiber grating has the silver-colored reflectance coating with the terminal of fiber cladding, the surface cladding on gold shell particle layer of nanometer has graphene oxide layer, graphene oxide layer's fixed surface has the sensitive layer of biomolecule.

2. The LSPR optode biosensor of graphene oxide fiber grating as claimed in claim 1, wherein: the inclination angle of the inclined stripes of the large-angle inclined fiber grating is 60-85 degrees.

3. The LSPR optode biosensor of graphene oxide fiber grating as claimed in claim 1, wherein: the grating period is between 25 and 40 mu m.

4. The LSPR optode biosensor of graphene oxide fiber grating as claimed in claim 1, wherein: the outer diameter of the nano gold shell particle layer is 150 nm-200 nm.

5. The LSPR optode biosensor of graphene oxide fiber grating as claimed in claim 1, wherein: the length of the large-angle inclined fiber grating is between 20mm and 30 mm.

6. The LSPR optode biosensor of graphene oxide fiber grating as claimed in claim 1, wherein: the core mode to cladding mode light energy coupling is >20 dB.

7. The LSPR optode biosensor of graphene oxide fiber grating as claimed in claim 2, wherein: the reflectivity of the silver reflecting film is greater than 90%, and the number of layers of graphene oxide is 5-15.

8. A method for manufacturing the nanogold-shell LSPR optode biosensor of the graphene oxide fiber grating according to claim 1, comprising the following steps:

1) the manufacturing of the large-angle inclined fiber grating, the large-angle inclined fiber grating is written in the single-mode fiber subjected to hydrogen loading treatment by adopting a frequency doubling Ar + laser with the wavelength of 244nm and a scanning amplitude mask plate technology, the grating inclination angle of the large-angle inclined fiber grating is 60-85 degrees, the grating period is 25-40 mu m, and after the large-angle inclined fiber grating is manufactured, the large-angle inclined fiber grating is placed in a natural convection oven at 80 ℃ for annealing treatment to obtain the stable spectral characteristic of the grating;

2) preparing a reflecting film, namely cutting the end face of one end of the large-angle inclined fiber grating by using a fiber cutter, ensuring that the end face is vertical to an axial plane, then soaking the cut end face of the large-angle inclined fiber grating into the prepared Torontis reagent for 25-35 minutes, taking out the cut end face of the large-angle inclined fiber grating, air-drying the cut end face of the large-angle inclined fiber grating in the air, and covering a layer of silver film with high reflectivity on the end face of one end of the large-angle inclined fiber grating;

3) hydroxylating the surface of the optical fiber, namely soaking the large-angle inclined optical fiber grating into 8mg/mL NaOH solution with the temperature of 40 ℃ for 3.5 hours, then soaking at normal temperature for 30 minutes, finally repeatedly washing the surface of the large-angle inclined optical fiber grating with deionized water, removing redundant impurities, and drying at 50 ℃ for 10 minutes;

4) silanization, namely soaking the large-angle inclined fiber grating in an MPTMS solution with 1% volume concentration prepared by glacial acetic acid in a 80-degree convection oven for 8-12 min to generate a mercapto group on the surface of the grating;

5) fixing nano gold shell particles, immersing the large-angle inclined fiber grating into the centrifuged nano gold shell solution for about 12 hours, and covalently bonding the nano gold shell particles with MPTMS molecules on the surface of the grating through gold-sulfur bonds;

6) amination of the nano-gold shell particle layer, soaking the large-angle inclined fiber grating fixed with the nano-gold shell particle layer in ethanolamine solution with the concentration of 10M for 1h at room temperature, and then cleaning with deionized water;

7) fixing a graphene oxide layer, immersing the large-angle inclined fiber grating subjected to the sixth step into the centrifuged graphene oxide dispersion liquid, and dehydrating and condensing amino groups on the surface of the nano-gold shell particle layer and carboxyl groups of the graphene oxide, so as to combine the amino groups and the carboxyl groups in a peptide bond form;

8) fixing a biomolecule sensitive layer, immersing the large-angle inclined fiber grating fixed with the graphene oxide layer into biomolecule sensitive liquid with specific identification on a target object to be detected, and enabling biomolecules to be combined with functional groups on the graphene oxide in a chemical bond mode.

Technical Field

The invention relates to an optode biomolecule sensor, in particular to a nanogold shell LSPR optode biosensor of a graphene oxide fiber grating.

Background

Graphene has the excellent characteristics of large specific surface area, high electron mobility, high conductivity, biomolecule affinity and the like, and an oxide of graphene oxide contains rich oxygen-containing functional groups such as carboxyl, hydroxyl and the like, so that covalent or non-covalent connection with biomolecules is facilitated. Therefore, the biochemical sensing technology formed by combining two-dimensional materials such as graphene, graphene oxide and the like with the traditional electrochemical, piezoelectric and optical (such as surface plasmon resonance sensors and various types of optical fiber sensors) sensors is widely researched.

In the field of biochemical detection, a Surface Plasmon Resonance (SPR) sensor is an optical sensor that is very sensitive to Refractive Index (RI) of an external medium. Various nano gold particles (such as gold nanospheres, star-shaped gold nanoparticles, gold nanorods, gold nanocages, gold nanoshells and the like) are used for replacing gold films to form Local SPR effect (LSPR for short), and due to the Local field enhancement effect of the LSPR, the sensitivity in the aspect of biochemical detection can be further enhanced. At present, most of the commercially available LSPR sensors are based on a Kretschmann prism coupling structure for angle detection, as shown in fig. 1, but such LSPR sensors have large volume, long scanning time and high price. Because the optical fiber has the advantages of corrosion resistance, electromagnetic interference resistance, small volume, remote sensing and the like, various optical fiber materials and devices can be used as an excitation platform to realize the miniaturization of the LSPR sensor, such as: LSPR sensors based on multimode silica (or polymer material) fibers, heterocore structured fibers or photonic crystal fibers, etc., all of which are of the type of pure fiber type LSPR sensors, but most of them have a major problem: the resonance bandwidth of the LSPR peak is typically between a few tens of nanometers to a hundred nanometers, and thus the quality factor (i.e., Q value) of the sensor is low.

Therefore, to overcome the problem of low quality factor (i.e., Q value) of the pure fiber LSPR sensor, in recent years, fiber grating-based LSPR sensors have been proposed, which mainly include three types: sensors based on Long Period Fiber Gratings (LPFG), optical Fiber Bragg Gratings (FBG) with the cladding removed, small angle (<11 °) Tilted Fiber Bragg Gratings (TFBG). The LPFG is a transmission type grating, has too high cross sensitivity of temperature and strain, and is not strong in practicability; the mechanical property of removed cladding FBG is reduced, small-angle TFBG has a plurality of dense cladding modes with narrow line width in near infrared band (1200 nm-1700 nm), so that LSPR effect can be easily excited by fixing nano gold particles on the surface of TFBG without complex design, but RI sensitivity of small-angle TFBG-LSPR sensor is far lower than that of traditional multimode fiber SPR sensor, and the narrow-line-width cladding modes in loss spectrum are too dense and numerous as shown in figure 2, so that accurate positioning of LSPR peak is inconvenient in practical application.

Currently, with the development of the above subjects including graphene materials, fiber grating sensing technology, LSPR sensing technology, etc., the integration of the respective advantages of graphene (graphene oxide), fiber grating sensing technology, and LSPR sensing technology is one of the important technical trends for manufacturing fiber grating LSPR biomolecular sensors with high performance, strong practicability, and strong stability.

However, a common problem in combining the above existing fiber LSPR techniques is: 1) most of the devices adopt a mode of detecting transmission spectrum, and a light source and a spectrum analyzer are respectively arranged at two ends of a sensor, so that the device is inconvenient to integrate and use; 2) the binding capacity of the nano-gold particles to the biomolecules is relatively weak (-1 pg/mm2), resulting in a small detection range of the biochemical sensor. Other personality issues are: 1) the LSPR spectrum excited by the pure fiber type LSPR sensor is in a certain wavelength range of 500 nm-900 nm, the bandwidth is generally larger than 50nm, and the pure fiber type LSPR sensor is a schematic diagram of the increase of the concentration of the molecules of the substance to be detected as shown in FIG. 3, so that the Q value of the sensor is very low, most of the sensors need to corrode or grind the fiber cladding to excite the LSPR, and the mechanical strength and the robustness of the sensor are reduced; 2) the cladding modes of the small-angle TFBG-LSPR sensor in the resonance spectrum envelope of a communication waveband (1500 nm-1600 nm) are too dense and numerous, and the accurate positioning of the LSPR peak is inconvenient in practical application.

Disclosure of Invention

The invention provides a nanogold shell LSPR optical-pole biosensor of a graphene oxide fiber grating, aiming at solving the problem of low quality factor of a pure fiber LSPR sensor.

The basic scheme provided by the invention is as follows: oxidized graphene fiber bragg grating's gold nanoparticle shell LSPR optode biosensor, the end-to-end connection of optic fibre core has wide-angle slope fiber bragg grating, the fiber cladding has fine core section and grating section, the internal surface cladding of fine core section is in the surface of optic fibre core, the surface cladding of fine core section has the optical fiber coating, grating section cladding wide-angle slope fiber bragg grating's surface, the surface cladding of the grating section of fiber cladding has the silane layer, 5 surfaces on silane layer have the cladding and have gold nanoparticle shell particle layer, the terminal of wide-angle slope fiber bragg grating and the terminal of fiber cladding have the silver-colored reflectance coating, furthermore, the surface cladding on gold nanoparticle shell particle layer has oxidized graphene layer, furthermore, oxidized graphene layer's fixed surface has the sensitive layer of biomolecule.

Furthermore, the inclination angle of the inclined stripes of the large-angle inclined fiber grating is 60-85 degrees.

Furthermore, the grating period is between 25 and 40 μm.

Further, the outer diameter of the nano gold shell particle layer is 150 nm-200 nm.

Further, the length of the large-angle inclined fiber grating is between 20mm and 30 mm.

Further, the core mode to cladding mode light energy coupling is >20 dB.

Furthermore, the reflectivity of the silver reflecting film is greater than 90%, and the number of graphene oxide layers is 5-15.

Compared with the prior art, the scheme has the advantages that:

1) according to the invention, the nano gold shell particles are used as a carrier for exciting the LSPR, the size of the outer diameter of the shell is designed to be 150-200 nm, the resonance absorption spectrum of the LSPR effect can cover 500-1600 nm, and the silane layer on the surface of the optical fiber is mainly used for fixing the nano gold shell particles in an electrostatic mode or a covalent bond mode.

2) The invention uses a large-angle inclined fiber grating as a platform for exciting the surface nano gold shell particles LSPR. The inclination angle of the large-angle inclined fiber grating is between 60 and 85 degrees, the grating period is between 25 and 40 microns, and simultaneously, due to the optical fiber birefringence effect caused by large-angle inclined stripes of the large-angle inclined fiber grating, the spectrum of the large-angle inclined fiber grating has strong polarization correlation, a fiber core fundamental mode can be coupled to a TM/TE mode of a forward-propagating high-order cladding mode, a series of polarization-related resonance peaks with the interval of dozens of nm exist in a transmission spectrum of 1250nm to 1650nm, and the full spectrum of a certain large-angle inclined fiber grating is shown in figure 5; only the TM mode and the TE mode of each polarization-dependent resonance peak can be excited by adjusting the polarization direction of incident linearly polarized light, or the TM mode and the TE mode can be excited at the same time in equal intensity, and as shown in FIG. 6, the polarization-dependent characteristic spectrums of the TM mode and the TE mode of a certain large-angle inclined fiber grating in a communication waveband (namely, a C/L waveband) are shown. Therefore, any one TM mode or TE mode of a high-order cladding mode resonant peak of the large-angle inclined fiber grating in a transmission spectrum of 1250 nm-1650 nm can cause the resonant absorption of the LSPR by taking the nano-gold shell particles as a carrier on the surface of the large-angle inclined fiber grating. In addition, the spectral bandwidth of the TM mode or the TE mode of the large-angle inclined fiber grating is 2 nm-4 nm, so that the sensor has a very high Q value compared with a pure fiber type LSPR sensor.

3) The end face of the tail end of the large-angle inclined fiber grating is plated with the silver reflecting film with high reflectivity, the silver reflecting film has the function of reflecting a TM mode or a TE mode of a high-order cladding mode of the large-angle inclined fiber grating, and the reflected light energy is recoupled into a fiber core through the large-angle inclined fiber grating and is transmitted, so that the form of the nano gold shell LSPR optode of the large-angle inclined fiber grating is formed. In addition, the invention can increase the action length of the LSPR wave excited by the light wave evanescent field and external biomolecules, thereby increasing the sensitivity of the sensor.

4) The graphene oxide layer is attached to the nanogold shell particle layer, the biomolecule sensitive layer sensitive to the specificity of the object to be detected is attached to the graphene oxide layer, the graphene oxide layer has a large specific surface area, effective adsorption sites for sensitive layer biomolecules in a unit volume can be greatly increased, and therefore the detection range of the sensor to the concentration of the object to be detected can be greatly enlarged. When the target biological molecules are combined with the biological molecule sensitive layer, the LSPR absorption spectrum intensity is changed, the effective refractive index of a cladding mode is changed, the reflected resonance wavelength is changed, the LSPR absorption spectrum intensity and the resonance wavelength are in a direct proportion relation with the concentration of the target biological molecules in a certain detection range, and the concentration and other information of the target biological molecules can be calculated by detecting the LSPR absorption spectrum intensity and the resonance wavelength through a spectrum analyzer at a reflection end.

5) On the other hand, the graphene oxide has a certain enhancement effect on the LSPR effect of the nano-gold shell particles, and the sensitivity of the scheme is further increased.

6) As the temperature sensitivity of any high-order cladding mode of the large-angle inclined fiber grating in the transmission spectrum of 1250 nm-1650 nm is 3.0 pm/DEG C-7.0 pm/DEG C and is lower than the temperature coefficient of the traditional FBG sensor, the LSPR effect of exciting the nano-gold shell by taking the large-angle inclined fiber grating as a platform has very good temperature stability.

The invention has the advantages of the common optical fiber LSPR sensor, small and light sensor size and high refractive index sensitivity. The scheme has compact, unique and ingenious structure, the nano gold shell particle layer is fixed on the surface of the large-angle inclined fiber grating, the end face of one end of the large-angle inclined fiber grating is coated with the high-reflectivity silver film, and the reflective structure is convenient to integrate and use in practical application and has high robustness. The most key point of the sensor is that the outer diameter of the nano gold shell particle shell is designed to be 150-200 nm, the resonance absorption spectrum of the LSPR effect can be ensured to cover 500-1600 nm, and the TM mode or TE mode of any high-order cladding mode resonance peak of the large-angle inclined fiber grating in the transmission spectrum of 1250-1650 nm can cause the resonance absorption of the LSPR by taking the nano gold shell particle layer as a carrier.

Furthermore, the graphene oxide layer is fixed on the nano-gold shell particle layer, so that effective adsorption sites for sensitive layer biomolecules in unit volume are greatly increased, the defect that the dynamic range of the conventional optical fiber LSPR sensor for biomolecule detection is low is overcome, meanwhile, the sensor has a certain enhancement effect on the LSPR effect of the nano-gold shell particles, and the sensitivity of the sensor is further increased. In a word, the nanogold-shell LSPR optode biosensor of the graphene oxide fiber grating integrates the advantages of all the conventional fiber LSPR sensors, avoids the defects of various fiber LSPR sensors, and can be widely applied to ultra-trace detection of biochemical substance molecules in the fields of biology, medicine, environmental monitoring, food safety, life science and the like, such as DNA/RNA/miRNA, antibodies/antigens, bacteria, viruses and the like.

Drawings

FIG. 1 is a prism LSPR sensor structure;

FIG. 2 is a schematic diagram of the transmission spectrum of a small angle TFBG-LSPR sensor;

fig. 3 is a diagram illustrating the spectrum of a pure fiber type LSPR sensor as a function of refractive index.

Fig. 4 is a schematic diagram of the LSPR resonance absorption spectrum of the nano-gold shell particles obtained by the experiment.

FIG. 5 shows the transmission spectrum characteristics of a large-angle tilted fiber grating (a) at 1250-1650 nm;

FIG. 6 is a polarization dependent characteristic spectrum of full TM mode excitation and full TE mode excitation, and TM mode/TE mode excitation, etc. in the C/L band.

Fig. 7 is a schematic structural diagram of an embodiment of a nanogold shell LSPR optode biosensor of a graphene oxide fiber grating according to the present invention.

Fig. 8 is a schematic diagram of optical path transmission of an embodiment of the nanogold shell LSPR optode biosensor of the graphene oxide fiber grating of the present invention.

Fig. 9 is a schematic view of a sensing system of the nanogold shell LSPR optode biosensor of the graphene oxide fiber grating of the present invention.

Fig. 10 is a schematic diagram of a change of a spectrum signal of the nanogold shell LSPR optode biosensor of the graphene oxide fiber grating according to the present invention.

Detailed Description

The following is further detailed by the specific embodiments:

description of reference numerals: the optical fiber grating comprises an optical fiber core 1, an optical fiber cladding 2, an optical fiber coating layer 3, a large-angle inclined optical fiber grating 4, a silane layer 5, a nanogold shell particle layer 6, a graphene oxide layer 7, a biomolecule sensitive layer 8, a silver reflecting film 9, a bandwidth light source 10, an optical fiber polarizer 11, an optical fiber polarization controller 12, a 3dB coupler 13, a nanogold shell LSPR (laser induced polarization response) optotype biosensor 14 of a graphene oxide optical fiber grating, an optical spectrum analyzer 15 and a computer 16.