CN113702333A

CN113702333A - Optical sensor with metal-organic frame-based MIM structure and preparation method thereof

Info

Publication number: CN113702333A
Application number: CN202110743917.0A
Authority: CN
Inventors: 刘建喜; 李智欢; 朱镇康; 刘维民
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2021-11-26

Abstract

The invention relates to an optical sensor with a metal-organic framework-based MIM structure and a preparation method thereof. In addition, by means of the interaction of antigens and antibodies among biological molecules, the high-efficiency adsorption of macromolecules on the surface of the MIM is realized, and a multi-scale high-sensitivity sensor is constructed.

Description

Optical sensor with metal-organic frame-based MIM structure and preparation method thereof

Technical Field

The invention belongs to the field of intelligent sensors, and particularly relates to an optical sensor with a metal-organic framework-based MIM structure and a preparation method thereof.

Background

The information technology relates to a communication technology, a computer technology, a remote sensing technology and other multi-field comprehensive technologies, is applied to various fields of national economy and national defense scientific research, such as intelligent home, agriculture, medical treatment, military, space exploration and the like, and is one of national economy basic and strategic industries. Among them, photonic technology is a core element of information technology because of its high-speed processing, transmission, and high-quality storage of information. However, the conventional optical device seriously affects the progress of miniaturization and high integration of the optical device because the sectional size of the optical waveguide is limited by the diffraction limit (λ/2n) and the bending dissipation of the optical waveguide.

Surface Plasmons (SPRs) are electromagnetic waves formed by oscillating and coupling incident light waves and free electrons on the Surface of metal (gold, silver, aluminum, copper, and the like), and can propagate on a metal-medium interface. Due to the surface wave characteristic of surface plasmons, plasmonic metal nanostructures can confine light within a sub-wavelength scale, thereby breaking the diffraction limit. Therefore, the surface plasmon can be used for manufacturing a nano-photonic chip with high integration level, and the light can be transmitted, controlled and integrated on the sub-wavelength dimension. As an important plasma waveguide, a Metal-dielectric-Metal (MIM) waveguide can localize a light wave in a sub-wavelength-scale intermediate dielectric layer (generally 50-100nm) and has a longer propagation length, and this unique property makes the MIM waveguide have a wide application prospect in many fields such as optical sensing, optical storage, and super-resolution imaging. The middle dielectric layer of the traditional MIM sensor is mostly a polymer layer, and the visual sensing of the analyte is realized by utilizing the response characteristic of the polymer thickness to external stimulation. However, the variation in the thickness of the polymer layer has non-uniformity, largely destroying the integrity of the high index metal layer, resulting in a reduction in the useful life of the sensor. Therefore, highly sensitive, long-lived MIM sensors are currently the focus of research.

Metal-Organic Frameworks (MOFs) are a class of nanoporous materials formed by self-assembly of Metal ions and Organic ligands through coordination bonds, and the MOFs not only have a pore structure similar to the zeolite molecular sieve rule, but also have higher specific surface area and porosity than those of the conventional porous materials, and have characteristics of designable composition structure, pore size and the like. The MOFs nano-porous material can analyze the components and the concentration of a detected object in a certain range, and the detected object is quickly and selectively adsorbed by utilizing the characteristic difference of pore channel structures, sizes, chemical environments and the like. It is noted that the MOFs may have their own properties, such as mass, crystal structure, electrical properties, optical properties, etc., after adsorbing the analyte. Therefore, the MOFs can be used as an MIM dielectric material to construct a novel MIM sensor by utilizing the specific physicochemical properties of the MOFs, so that high monitoring sensitivity can be realized.

Disclosure of Invention

The technical problem solved by the invention is as follows: in order to solve the problems of low sensing sensitivity and short service life of the existing MIM type optical sensor, the invention aims to provide the optical sensor with the metal-organic framework-based MIM structure and the preparation method thereof, the MOFs material is used as an intermediate dielectric layer, the preparation of the MOFs film on the surface of the substrate material is realized by different means by utilizing the rich pore channel structure of the MOFs material, the functional coupling of the MOFs film and the MIM structure is realized, the sensing sensitivity of the MIM optical waveguide sensor to a small molecule detection material is improved, and the large-scale red shift (50-100nm) of the spectrum can be observed within 2-5 s. By virtue of the interaction of antigen and antibody among biological molecules, the high-efficiency adsorption of macromolecules on the surface of the MIM can be realized, and the multi-scale high-sensitivity sensing is realized.

The technical scheme of the invention is as follows: a metal-organic frame-based MIM structure optical sensor comprises two plasmon metal layers and an intermediate dielectric layer, wherein the dielectric layer is MOFs.

The further technical scheme of the invention is as follows: the thickness ranges of the two plasmonic metals are 10-30nm of the thickness of the upper layer metal and 80-120nm of the thickness of the lower layer metal respectively.

The further technical scheme of the invention is as follows: a method of a metal-organic frame-based MIM optical sensor, comprising the steps of:

step 1: after selecting a substrate material, sequentially putting the substrate material into isopropanol, acetone and isopropanol to respectively carry out ultrasonic cleaning, and carrying out blow-drying and plasma treatment after cleaning;

step 2: putting the substrate material obtained in the step 1 into physical vapor deposition, and depositing the plasmon metal on the substrate material, wherein the target mass required by the upper layer metal is 4-10mg, and the target mass required by the lower layer metal is 40-50 mg; the deposition parameter current intensity is 60-80A, the deposition time is 1-5min, and the metal/substrate material is obtained;

and step 3: preparing a metal organic framework film, comprising the following substeps:

step 3.1: putting the metal/substrate material obtained in the step 2 into a self-assembly monomolecular solution of 16-mercapto hexadecanoic acid and 11-mercapto-1-undecanol for modification for 12-24 hours;

step 3.2: preparing an MOFs film with the thickness of 50-500nm on the surface of the modified base material of the iso-metal/base material by using a mother liquor method, a spin-coating method or a spraying method; finally obtaining a metal/MOFs/metal material for efficient sensing detection of small molecule detection;

and 4, step 4: and (3) placing the metal/MOFs/metal obtained in the step (3) in a solution containing biological components or organisms for quickly and efficiently adsorbing macromolecular detection substances, and realizing the detection of macromolecules by virtue of the changes of properties such as the refractive index and the light transmittance of the MIM thin film. And obtaining the metal-organic framework-based MIM structure optical sensor.

The further technical scheme of the invention is as follows: the concentration of the 16-mercapto hexadecanoic acid in the step 3.1 is 0.1-0.5mM, and the concentration of the 11-mercapto-1-undecanol is 0.1-0.5 mM.

The further technical scheme of the invention is as follows: the solution containing biological components or organisms in the step 4 is enzyme, protein, DNA, antibody, antigen or biological membrane.

Effects of the invention

The invention has the technical effects that: the method provided by the invention is simple to prepare and wide in universality, and compared with the traditional MIM sensor, the optical sensor obtained by the method has better sensing sensitivity and reusability. The effects of the invention mainly comprise the following two types: first, rapid sensing of small molecules. The MOFs material is used as an intermediate dielectric layer, and the strong interaction of the host and the object of the MOFs material is combined with the fine spectrum structure of the MIM structure, so that the high-efficiency adsorption and high-sensitivity detection of small molecules to be detected are improved; second, sensing of large molecules. The sensing of corresponding macromolecules is not easy to detect by MOFs materials due to the limitation of a pore channel structure, efficient adsorption of the macromolecules on the surface of an MIM is achieved by imitating the interaction of antigens and antibodies among biomolecules, and the detection of the macromolecules is achieved by utilizing the change of properties such as the refractive index and the light transmittance of the MIM film.

Drawings

FIG. 1 is a schematic diagram of a MOFs-based MIM optical sensor for sensing an object to be detected

FIG. 2 is a schematic diagram of the morphology of MOFs nanoparticles

FIG. 3 is a SEM image of the cross section of a MOFs-based MIM optical sensor sample

FIG. 4 is a graph showing sensing curves of MOFs-based MIM optical sensor for detecting object 1 and object 2

Detailed Description

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Referring to fig. 1-4, the following describes the technical solution of the present invention with reference to specific embodiments, but it should be understood that the scope of the present invention is not limited by the specific embodiments.

The invention adopts the technical scheme that an optical sensor with a metal-organic framework base MIM structure and a preparation method thereof, namely, an MOFs film is used as an MIM middle dielectric layer to endow the sensor with excellent sensing performance. As shown in fig. 1, the MOFs film is used as the middle dielectric layer of the MIM, and can efficiently adsorb the external small molecule to be detected, so that the refractive index of the material is changed, thereby affecting the reflection spectrum of the MIM. In addition, for the macromolecule to be detected, biomass molecules can be anchored on the surface of the upper layer gold film, the effect of antigen and antibody is simulated, and the macromolecule to be detected is adsorbed on the surface of the gold film, so that the transmittance or the refractive index of the device is changed, and the change of the spectrum is further influenced.

The method is specifically carried out according to the following steps:

step 1: designing an optimized metal-organic frame-based MIM structure, comprising the following substeps:

substep 1: calculating the optimal thickness of a plasmon metal layer (gold, silver, aluminum, copper and the like) under the condition that the MOFs film with the same thickness is used as an intermediate dielectric layer by using a time domain finite difference method and a Bragg diffraction formula;

substep 2: on the premise of substep 1, simulating the influence trend of the MOFs layer thickness on MIM optics to realize the regulation and control of light;

step 2: preparing a high-quality plasmon metal film (gold, silver, aluminum, copper and the like) on the surface of a substrate material, taking gold as an example, and comprising the following substeps:

substep 1: selecting specific substrate material (such as silicon wafer, quartz and glass) and carrying out surface treatment;

substep 2: putting the substrate material in the substep 1 into Physical Vapor Deposition (PVD), adjusting the quality of the target material, the PVD current intensity and the deposition time, and controlling the deposition thickness and quality of the gold film on the substrate material;

and step 3: the preparation of the metal organic framework film comprises the following substeps:

substep 1: putting the Au/substrate material obtained in the step 1 into a self-assembly monomolecular solution of 16-mercapto hexadecanoic acid (MHDA) and 11-mercapto-1-undecanol (MUD) for modification for 12-24 hours;

substep 2: preparing an MOFs film with the thickness of 50-500nm on the surface of the modified substrate material by using a mother liquor method, a spin-coating method, a spraying method and the like;

and 4, step 4: the preparation of the metal-organic frame-based MIM optical sensor comprises the following sub-steps:

substep 1: according to the simulation result obtained in the step 1, depositing a gold film with a certain thickness on the surface of the MOFs/Au substrate material to obtain the wavelength-controllable MIM optical sensor in the visible light band;

substep 2: the Au/MOFs/Au thin film obtained in substep 1 is placed in a solution of a biological component or a living body (enzyme, protein, DNA, antibody, antigen, biofilm, etc.), and an MIM type optical sensor can be obtained.

Substep 3: the liquid evaporation device is linked with a spectrometer to test the sensing performance of the MOFs-based MIM optical sensor;

the thickness of the plasmonic metal in the step 1 is 10-30nm and 80-120 nm.

In the method for processing the substrate material in the substep 1 in the step 2, the method comprises the following steps: the substrate material silicon wafer is sequentially ultrasonically cleaned in isopropanol, acetone and isopropanol for 10-30min, and is treated by oxygen plasma for 3-5min after being dried by nitrogen.

The target material mass in the step 2 is 4-10mg and 40-50 mg; the deposition parameter current intensity is 60-80A, and the deposition time is 1-5 min.

The concentration of MHDA, MUD in step 3, substep 1 is 0.1-0.5 mM.

The preparation method of the MOFs thin film in the step 3 and the substep 2 (taking HKUST-1 prepared by a spin coating method as an example) comprises the following steps: firstly, trimesic acid (BTC) is prepared into an aqueous suspension by ultrasound and is directly added into Cu (NO)₂In an aqueous solution of (1), wherein Cu²⁺、BTC、H₂The mass of O is 10-100mg, 20-200mg and 22.22-222.2 g respectively. After stirring at room temperature for 1h, the product was collected by centrifugation and washed with ethanol to remove unreacted BTC. Finally, dispersing and spin-coating in ethanol.

The thickness of the upper layer plasmon metal film in the step 4, the substep 1 is 10-30 nm.

In order to verify the applicability of the MOFs film for preparing the MIM optical sensor, a classical MOFs material HKUST-1 is taken as an example, a nanoparticle spin coating method is selected for preparing the MOFs-based MIM optical sensor on the surface of a glass substrate material, and the specific steps are as follows:

step 1: preparation of HKUST-1 nanoparticles:

firstly, 0.6mmol of trimesic acid (BTC) is dispersed in 6ml of water, prepared into an aqueous suspension by simple ultrasound,thereafter, 0.3mmol of Cu (NO) are rapidly added with vigorous stirring₂An aqueous solution of (a). Wherein Cu²⁺、BTC、H₂The mass of O is 10-100mg, 20-200mg and 22.22-222.2 g respectively. After the above mixed solution was stirred at room temperature for 1 hour, the product was collected by centrifugation at 9000rpm, and washed with ethanol to remove unreacted BTC. The resulting product was finally dispersed in ethanol (10-100mg/ml) for subsequent spin coating. The morphology is shown in FIG. 2, and the particle size of HKUST-1 is about 50 nm.

Step 2: treatment of the base material:

firstly, ultrasonically cleaning a glass substrate in isopropanol, acetone and isopropanol for 10-30min respectively in sequence, drying the glass substrate by using nitrogen, and then treating the glass substrate by using oxygen plasma for 3-5min to increase the number of surface hydroxyl functional groups and improve the hydrophilicity of the glass surface.

And step 3: deposition and treatment of 10-30nm gold film:

firstly, the treated glass substrate material is placed in a Physical Vapor Deposition (PVD) cavity, 4-10mg of gold target material is weighed, and deposition is carried out for 1-5min under the current intensity of 60-80A. Secondly, soaking the obtained gold film in MHDA of 0.1-0.5Mm for 12-24 hours to obtain the MHDA modified gold film.

And 4, step 4: preparing the MOFs film on the surface of a gold/glass substrate material:

the ethanol solution of HKUST-1 nanoparticles obtained in step 1 is prepared into a solution of 10-100mg/ml, and is spin-coated for 60s at 4000-6000rpm, and the process is repeated for 3 times. Wherein, the material obtained after spin coating is placed in an oven with the temperature of 100 ℃ for constant temperature 15min and cooled to the room temperature.

And 5: preparation of MOFs-based MIM optical sensor:

and (4) repeating the step (3) on the basis of the material in the step (4) to obtain an Au/MOFs/Au sample. And placing the obtained Au/MOFs/Au thin film in a solution (enzyme, protein, DNA, antibody, antigen, biological membrane and the like) containing biological components or organisms for 12-24 hours to obtain the wavelength-tunable MOFs-based MIM sensor. The cross-sectional view of MIM is shown in FIG. 3, which shows that the spin coating thickness of HKUST-1 nanoparticles is 250 nm.

Step 6: sensing performance detection of MOFs-based MIM optical sensor:

the sensing detection of different detection objects is realized by building a liquid evaporation device, designing and customizing a sensing chamber and finally converting a sensing signal into a visual optical signal through devices such as optical fibers and the like. And (3) putting 10 mu L of the solvent to be detected into a liquid evaporation device, and sending the detected object into the sensor cavity by using 100sccm nitrogen, so as to realize high-precision and high-sensitivity detection. The sensing performance is shown in fig. 4, in which the abscissa represents the wavelength, the ordinate represents the intensity of the reflection peak, the black curve is a curve before sensing, and the gray curve is a change curve after the detection objects 1 and 2 are adsorbed. The result shows that the MOFs-based MIM optical sensor has excellent sensing performance on molecules to be detected, can respond to a detected object within 2-5s, and has extremely high sensing sensitivity (the red shift ranges of the sensing wavelengths of the detected object 1 and the detected object 2 are respectively 100nm and 80 nm).

Claims

1. The metal-organic frame-based MIM structure optical sensor is characterized by comprising two plasmon metal layers and an intermediate dielectric layer, wherein the dielectric layer is MOFs.

2. The metal-organic frame-based MIM structure optical sensor according to claim 1, wherein the two plasmonic metals have a thickness in the range of 10-30nm for the upper layer metal and 80-120nm for the lower layer metal.

3. A method of making a metal-organic frame-based MIM optical sensor according to claim 1 comprising the steps of:

4. The method for fabricating a metal-organic frame-based MIM structure optical sensor according to claim 3, wherein the concentration of 16-mercaptohexadecanoic acid in step 3.1 is 0.1 to 0.5mM, and the concentration of 11-mercapto-1-undecanol is 0.1 to 0.5 mM.

5. The method for fabricating a metal-organic framework-based MIM structure optical sensor according to claim 3, wherein the solution containing biological components or organisms in step 4 is an enzyme, protein, DNA, antibody, antigen, or biofilm.