SPR sensor based on defect disk coupled nanorod structure

Abstract

The present invention discloses an SPR sensor based on a defect disk coupled nanorod structure, comprising a silicon dioxide substrate and at least one metal nanounit arranged on the silicon dioxide substrate; each metal nanounit is composed of a metal nanodefect disk and a metal nanorod; there is a gap between the metal nanodefect disk and the metal nanorod; the metal nanodefect disk is a circle with a rectangular notch on the edge; the metal nanorod is a rectangle; the rectangular notch on the metal nanodefect disk faces the direction of the metal nanorod, and the center line of the wide side of the rectangular notch is perpendicular to the center line of the wide side of the metal nanorod. The present invention generates a dipole through the metal nanodefect disk and the metal nanorod, and the two dipoles are coupled to each other to generate a surface plasma resonance peak. By changing the geometric parameters of the metal nanounit, the resonance intensity and the resonance wavelength position of the surface plasma resonance can be regulated, and high sensitivity can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, and in particular to an SPR sensor based on a defect disk-coupled nanorod structure. Background Art

[0002] Surface plasmon resonance (SPR) is a physical optical phenomenon caused by the interaction between incident light waves and free electrons on the surface of metal conductors. Surface plasmon resonance has two outstanding advantages: one is that the substances on the metal surface are particularly sensitive, and trace molecular adsorption can lead to changes in the surface plasmon resonance frequency; the other is that it produces a significant local field enhancement on the metal surface. SPR sensors are sensors realized using the principle of surface plasmon resonance, and they have important applications in chemical analysis, biological monitoring and other fields. At present, SPR sensors include intensity modulation SPR sensors, angle modulation SPR sensors and phase modulation SPR sensors. Among them, the intensity modulation SPR sensor has the disadvantage that the accuracy of its results is easily affected by changes in the intensity of the light source, the angle modulation SPR sensor has a small dynamic range of detection, and the phase modulation SPR sensor has the disadvantages of complex system and troublesome data processing. Summary of the invention

[0003] The present invention aims to solve the problems of easy oxidation, poor stability and low sensitivity of the existing SPR sensor structure, and provides an SPR sensor based on a defect disk coupled nanorod structure.

[0004] To solve the above problems, the present invention is achieved through the following technical solutions:

[0005] The SPR sensor based on defect disk coupled nanorod structure includes a silicon dioxide substrate and at least one metal nano unit arranged on the silicon dioxide substrate; each metal nano unit is composed of a metal nano defect disk and a metal nano rod; there is a gap between the metal nano defect disk and the metal nano rod; the metal nano defect disk is a circle with a rectangular notch on the edge; the metal nano rod is a rectangle; the rectangular notch on the metal nano defect disk faces the direction of the metal nano rod, and the wide side center line of the rectangular notch is perpendicular to the midline of the wide side center line of the metal nano rod.

[0006] In the above solution, the wide side center line of the rectangular notch of the metal nano-defect disk or the extension line of the wide side center line passes through the center of the metal nano-defect disk.

[0007] In the above solution, the length of the rectangular notch of the metal nano-defect disk is equal to the radius of the metal nano-defect disk.

[0008] In the above scheme, the thickness h of the metal nano-defect disk and the metal nano-rod are equal.

[0009] In the above scheme, the material of the metal nano-defect disk and the metal nano-rod is gold.

[0010] In the above scheme, the resonance wavelength of the metal nanounit is regulated by changing the metal nano defect disk and the metal nanorod, the width of the rectangular gap, the width d of the metal nanorod and / or the length l of the metal nanorod.

[0011] In the above solution, when the number of the metal nano-units is more than 2, these metal nano-units are periodically arranged on the silicon dioxide substrate.

[0012] Compared with the prior art, the present invention generates dipoles through metal nano-defect disks and metal nanorods, and the two dipoles couple with each other to generate a surface plasmon resonance peak. By changing the geometric parameters of the metal nanounit, the resonance intensity and the resonance wavelength position of the surface plasmon resonance can be regulated, and high sensitivity can be obtained. Experimental results show that the maximum refractive index sensitivity (S) of the present invention for the medium with a refractive index of 1.00 to 1.08 in the 1000nm to 1600nm band is 470±10nm / RIU. The present invention adopts a wavelength-modulated SPR sensor, which has the advantages of high sensitivity, good stability, large dynamic range, and adaptability to a variety of coupling modes. In addition, the gold nanometal structure of the present invention has the characteristics of being more stable, not easy to oxidize, and having more excellent optical properties. The present invention has potential application prospects in biosensors such as environmental refractive index and micro-nano photonic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of the SPR sensor based on defect disk-coupled nanorod structure.

[0014] Figure 2 The graphs are transmission spectrum curves of setting the metal nano-defect disk alone, setting the metal nano-rod alone, and setting the metal nano-defect disk and the metal nano-rod simultaneously.

[0015] Figure 3 Transmission spectrum curves obtained by changing the distance g between the metal nanodefect disk and the metal nanorod (10nm, 15nm, 20nm, 25nm, 30nm).

[0016] Figure 4 Transmission spectrum curves obtained by changing the rectangular gap width w (30nm, 40nm, 50nm, 60nm) of the metal nano-defect disk.

[0017] Figure 5Transmission spectrum curves obtained by changing the width d of the metal nanorods (15nm, 20nm, 25nm, 30nm, 35nm).

[0018] Figure 6 The transmission spectrum curves obtained by changing the length l of the metal nanorods (220nm, 230nm, 240nm, 250nm, 260nm).

[0019] Figure 7 To change the surrounding refractive index n (1.00, 1.02, 1.04, 1.06, 1.08), the transmission characteristic curve of the sensor is obtained.

[0020] Figure 8 It is a curve of refractive index n (1.00, 1.02, 1.04, 1.06, 1.08) and resonance wavelength.

[0021] Markings in the figure: 1, silicon dioxide substrate; 2-1, metal nano-defect disk; 2-2, metal nanorods. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific examples.

[0023] See also Figure 1 , an SPR sensor based on a defect disk coupled nanorod structure, comprising a silicon dioxide substrate 1, and at least one metal nanounit arranged on the silicon dioxide substrate 1. When there are multiple metal nanounits on the silicon dioxide substrate 1, these metal nanounits are periodically arranged on the silicon dioxide substrate 1. Each metal nanounit is composed of a metal nano defect disk 2-1 and a metal nanorod 2-2. There is a gap between the metal nano defect disk 2-1 and the metal nanorod 2-2. The metal nano defect disk 2-1 is a circle with a rectangular notch on the edge. The metal nanorod 2-2 is a rectangle. The rectangular notch on the metal nano defect disk 2-1 faces the direction of the metal nanorod 2-2, and the center line of the wide side of the rectangular notch is perpendicular to the midline of the center line of the wide side of the metal nanorod 2-2. When polarized light is incident on the surface of the metal nanounit, the metal nano defect disk 2-1 and the metal nanorod 2-2 are dipoles, and the two dipoles couple with each other to produce SPR resonance. The plane wave is incident vertically downward on the metal surface along the positive direction of the SPR sensor Z axis and polarized along the Y direction. The X and Y directions are set as periodic boundary conditions, and the Z direction is set as an absorbing boundary condition (PML) to ensure continuous distribution of the medium on the boundary.

[0024] One end of the rectangular notch on the metal nano defect disk 2-1 is located in the middle of the metal nano defect disk 2-1, and the other end extends to the edge of the metal nano defect disk 2-1. The center line of the wide side of the rectangular notch may coincide with the diameter of the metal nano defect disk 2-1, or may not coincide with the diameter of the metal nano defect disk 2-1. In a preferred embodiment of the invention, the center line of the wide side of the rectangular notch may coincide with the diameter of the metal nano defect disk 2-1, that is, the center line of the wide side of the rectangular notch or the extension of the center line of the wide side passes through the center of the metal nano defect disk 2-1. When the length of the rectangular notch is equal to or greater than the radius of the metal nano defect disk 2-1, the center line of the wide side of the rectangular notch passes through the center of the metal nano defect disk 2-1; when the length of the rectangular notch is less than the radius of the metal nano defect disk 2-1, the extension of the center line of the wide side of the rectangular notch passes through the center of the metal nano defect disk 2-1. In a preferred embodiment of the invention, the length of the rectangular notch is equal to the radius of the metal nano defect disk 2-1.

[0025] In the present invention, gold is selected as the material of the metal film, namely the metal nano-defect disk 2-1 and the metal nano-rod 2-2. The thickness h of the metal nano-defect disk 2-1 and the metal nano-rod 2-2 is consistent with 30nm. The length r of the rectangular notch of the metal nano-defect disk 2-1 is consistent with the radius of the metal nano-defect disk 2-1, which is 130nm, and the width w of the rectangular notch is 30nm to 60nm. The width d of the metal nano-rod 2-2 is 15nm to 35nm, and the length l of the metal nano-rod 2-2 is 220nm to 260nm. The distance g between the metal nano-defect disk 2-1 and the metal nano-rod 2-2 is 10nm to 30nm. The refractive index of the surrounding environment varies in the range of 1.00 to 1.08. In a preferred embodiment of the present invention, the width w of the rectangular notch is 50nm. The width d of the metal nano-rod 2-2 is 25nm, and the length l of the metal nano-rod 2-2 is 240nm. The distance g between the metal nano-defect disk 2 - 1 and the metal nano-rod 2 - 2 is 20 nm.

[0026] Figure 2 The transmission spectrum curves of the metal nano-defect disk 2-1, the metal nano-rod 2-2, and the metal nano-defect disk 2-1 and the metal nano-rod 2-2 are arranged on the silicon dioxide substrate 1 in the wavelength range of 1000nm to 1600nm. It can be seen from the figure that resonance will only occur when the metal nano-defect disk 2-1 and the metal nano-rod 2-2 are coupled on the silicon dioxide substrate 1 at the same time.

[0027] By adjusting the geometric parameters of the metal nanounit, that is, changing the metal nanodefect disk 2-1 and the metal nanorod 2-2, the width of the rectangular notch, the width d of the metal nanorod 2-2 and / or the length l of the metal nanorod 2-2 (when the width d of the metal nanorod 2-2 is changed, the resonance intensity and the resonance wavelength position change at the same time; when the length l of the metal nanorod 2-2 is changed, the resonance wavelength position changes), the localized surface plasmon resonance between the metal nanoparticles will change due to the electric field coupling effect, thereby causing the resonance wavelength of the spectrum of the metal nanounit, that is, the resonance intensity or the resonance wavelength position to change, and at the same time, it has a higher sensitivity to the refractive index of the surrounding environment.

[0028] Figure 3 To change the transmission spectrum curve obtained by changing the distance g between the metal nanodefect disk 2-1 and the metal nanorod 2-2, the coupling distance g is increased from 10nm to 30nm in steps of 5nm. It can be seen from the figure that the resonance wavelength red-shifts with the increase of the distance g. Figure 4 The transmission spectrum curve obtained by changing the defect opening width w of the metal nano-defect disk 2-1 is that the defect opening width w increases from 30nm to 60nm in a step of 10nm. It can be seen from the figure that with the increase of the defect opening width w, the resonance wavelength blue-shifts. Figure 5 The transmission spectrum curve obtained by changing the width d of the metal nanorod 2-2 is as follows: the width d increases from 15 nm to 35 nm in steps of 5 nm. It can be seen from the figure that as the width d increases, the resonance wavelength blue-shifts. Figure 6 The transmission spectrum curve obtained by changing the length l of the metal nanorod 2-2 is that the width l is changed from 220nm to 260nm in steps of 10nm. It can be seen from the figure that as the width l increases, the resonance wavelength red-shifts. The above results show that the resonance wavelength can be effectively adjusted by changing the geometric parameters of the metal nanounit.

[0029] Figure 7 In order to change the refractive index n of the surrounding environment to obtain the transmission characteristic curve of the sensor, the refractive index n of the surrounding environment is increased from 1.00 to 1.08 in steps of 0.02. It can be seen from the figure that with the increase of the refractive index n, the resonance peak shows an obvious red shift. Figure 8 The relationship curve between different refractive indices n and the resonance wavelength is shown in Figure 1. Based on this relationship curve, according to the sensitivity (S) formula: S = dλ / dn (nm / RIU), it is expressed as the shift of the resonance wavelength caused by the change of the refractive index of the medium, and the sensitivity of the resonance peak is 470±10nm / RIU. The above results show that an optimal sensitivity can be obtained by reasonably setting the geometric parameters of the metal nanounit.

[0030] It should be noted that although the embodiments of the present invention described above are illustrative, they are not intended to limit the present invention, and therefore the present invention is not limited to the above specific embodiments. Without departing from the principles of the present invention, any other embodiments obtained by those skilled in the art under the guidance of the present invention are deemed to be within the protection of the present invention.

Claims

1. Based on defect disk coupled nanorod structure SPR sensor, its characteristics are: The invention comprises a silicon dioxide substrate (1), and at least one metal nano unit arranged on the silicon dioxide substrate (1); each metal nano unit is composed of a metal nano defect disk (2-1) and a metal nano rod (2-2); there is a gap between the metal nano defect disk (2-1) and the metal nano rod (2-2); the metal nano defect disk (2-1) is a circle with a rectangular notch on the edge; the metal nano rod (2-2) is a rectangle; the rectangular notch on the metal nano defect disk (2-1) faces the direction of the metal nano rod (2-2), and the wide side center line of the rectangular notch is perpendicular to the midline of the wide side center line of the metal nano rod (2-2).

2. The SPR sensor based on defect disk coupled nanorod structure according to claim 1 is characterized in that: The wide side center line of the rectangular notch of the metal nano-defect disk (2-1) or the extension line of the wide side center line passes through the center of the metal nano-defect disk (2-1).

3. The SPR sensor based on defect disk coupled nanorod structure according to claim 2 is characterized in that: The length of the rectangular notch of the metal nano-defect disk (2-1) is equal to the radius of the metal nano-defect disk (2-1).

4. The SPR sensor based on defect disk coupled nanorod structure according to claim 2 is characterized in that: The thickness h of the metal nano-defect disk (2-1) and the metal nano-rod (2-2) are equal.

5. The SPR sensor based on defect disk coupled nanorod structure according to claim 1 is characterized in that: The material of the metal nano defect disk (2-1) and the metal nano rod (2-2) is gold.

6. The SPR sensor based on defect disk coupled nanorod structure according to claim 1 is characterized in that: The resonance wavelength of the metal nano unit is regulated by changing the metal nano defect disk (2-1) and the metal nano rod (2-2), the width of the rectangular notch, the width d of the metal nano rod (2-2) and / or the length l of the metal nano rod (2-2).

7. The SPR sensor based on defect disk coupled nanorod structure according to claim 1 is characterized in that: When the number of the metal nano-units is 2 or more, the metal nano-units are arranged periodically on the silicon dioxide substrate (1).

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