Self-assembly preparation method of sub-10-nanometer spacing electrode pair

Abstract

The invention relates to a self-assembly preparation method of a sub-10-nanometer spacing electrode pair, which comprises the following steps: by taking DNA two-dimensional rectangular origami as a DNA template, respectively extending two groups of single-stranded DNA, namely extension chains, on the surface of the DNA template, respectively taking the two groups of extension chains as two connecting sites, respectively modifying gold nanorods by adopting two pairing chains to obtain gold nanorods modified by the two pairing chains, the two pairing chains are sulfydryl modified single-stranded DNA matched with the connecting sites respectively, and accurate directional arrangement of the gold nanorods on a DNA template is achieved by means of the complementary base pairing principle of DNA. Compared with the prior art, the method has the advantages that the distance between the electrode pairs is stabilized at the sub-10 nanometer scale, complicated photoetching equipment is not needed, the process flow is simple, the cost is relatively low, and a technical basis for batch preparation is provided for the development of the sub-10 nanometer electrode pairs of nanometer electronic devices.

Description

Technical Field

[0001] This invention relates to the field of nanoparticle-gap electrode pair fabrication technology, and in particular to a self-assembly fabrication method for sub-10 nanometer-gap electrode pairs. Background Technology

[0002] Sub-10 nm pitch electrode pairs serve as fundamental building blocks at the nanoscale, holding crucial application value in advanced devices and integrated circuits. These structures provide core functional interfaces for molecular electronic devices, quantum transport devices, and on-chip optoelectronic integrated systems, forming a vital foundation for achieving device miniaturization and performance breakthroughs.

[0003] Among existing nanofabrication technologies, electron beam lithography is the most commonly used and direct method for fabricating micro and nanostructures in integrated circuit processes. This technology uses a high-energy electron beam to directly write patterns on a resist layer, followed by standard process steps such as development, metallization, and lift-off to form electrode structures. However, when device feature sizes enter the sub-10 nanometer range, this technology faces severe challenges. First, electron scattering at the resist-substrate interface induces a significant proximity effect, leading to a decrease in the fidelity of the exposed pattern and causing dimensional deviations or even complete closure of the designed nanoscale gaps in the actual process. Second, in the subsequent metallization process, the nanoscale electrode structures are prone to deformation or adhesion due to thermal stress concentration and surface energy effects. These physical limitations severely restrict the reliability and yield of electron beam lithography in the fabrication of sub-10 nanometer node devices.

[0004] To overcome this technological bottleneck, DNA nanotechnology based on the principle of self-assembly has shown unique advantages. DNA origami technology can achieve spatial positioning with molecular-level precision through precise base pairing, with a theoretical resolution of up to 2 nanometers, providing a brand-new technical path for the controllable assembly of nanodevices.

[0005] Chinese patent CN 106770049 B discloses a method for constructing Dolmen structures based on DNA origami templates and gold nanorods. The method includes: preparing gold nanorods of a specific size; designing a rectangular DNA origami template and setting a trapping strand on the template; mixing DNA-modified gold nanorods with the DNA origami template in a certain proportion; and hybridizing the nanorods through gradient annealing to assemble them into a Dolmen structure on the origami template according to the design. This structure can be used to study the Fano resonance effect. The patent also discloses the basic procedures and parameters for the synthesis of gold nanorods, DNA modification, preparation and annealing of the DNA origami template, and the hybridization and assembly of the two.

[0006] Chinese patent CN 102382815 B discloses a method for site-specific self-assembly of binary plasmonic nanoparticles, which involves synthesizing gold nanorods and gold nanoparticles respectively; modifying the end faces of gold nanoparticles and gold nanorods with different DNA sequences (DNA1, DNA2); and designing a composite linker DNA (formed by hybridization of DNA3 and DNA4), one part of which is complementary to DNA1 on the gold nanoparticles and the other part is complementary to DNA2 on the gold nanorods; through DNA hybridization, the gold nanoparticles are specifically linked to the end faces of the gold nanorods to form discrete binary assemblies.

[0007] Patent CN108467010B discloses a metal pattern based on DNA nanostructures, its preparation method, and its application. The method includes: preparing a sulfur-modified DNA nanostructure and performing in-situ growth of metals at the sulfur modification sites. Utilizing the nanoscale addressability and structural diversity of DNA nanostructures, sulfur modification is performed on the DNA nanostructures to introduce sulfur-containing groups. Based on the strong affinity between metals and sulfur-containing groups, precise directional in-situ growth of various metals on DNA nanostructures is achieved, forming zero-dimensional, one-dimensional, two-dimensional, and three-dimensional high-resolution metal patterns.

[0008] Although some studies have been able to use DNA templates to arrange spherical nanoparticles, achieving stable sub-10 nanometer spacing and precise arrangement when manipulating directional gold nanorods to form electrode pairs remains a technical challenge that needs to be overcome. Summary of the Invention

[0009] The purpose of this invention is to achieve an extremely narrow gap nanoelectrode arrangement, providing a self-assembly method for sub-10 nm gap electrode pairs. This application utilizes a precise directional arrangement method for two gold nanorods to controllably synthesize pairs of extremely narrow gold nanorods within a hundred nanometer range. Combined with patterning technology, electrical pathways are constructed to form sub-10 nm gap electrode pairs, i.e., sub-10 nm gap electrode pairs.

[0010] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for the self-assembly of sub-10 nanometer spacing electrode pairs, comprising the following steps: Using a two-dimensional rectangular DNA template, two sets of single-stranded DNA strands, known as extended strands, are extended from its surface. These two extended strands serve as two linker sites. Two types of mating strands were used to modify gold nanorods, resulting in gold nanorods modified with two different mating strands. The two mating strands were respectively mated with thiol-modified single-stranded DNA molecules that matched the linker site. By utilizing the complementary base pairing principle of DNA, gold nanorods can be precisely oriented onto DNA templates.

[0011] The distribution of the two sets of extended strands determines the orientation and position of the two gold nanorods modified with different paired strands on the DNA template, thereby effectively controlling the relative spacing between the two gold nanorods on the DNA template.

[0012] In one embodiment of the present invention, a method for self-assembling a sub-10 nanometer spacing electrode pair is further provided, comprising the following steps: S1: Preparation of two sets of gold nanorods modified with paired chains: Among them, the pairing strand is a thiol-modified single-stranded DNA. After the pairing strand is activated, it is incubated with gold nanorods for modification. The DNA strand is fixed to the surface of the gold nanorods through the thiol group, resulting in two sets of gold nanorods modified with pairing strands. S2: Design and synthesis of DNA templates with characteristic extended strands: Design the required rectangular structure using DNA origami editing software, obtain the corresponding short-chain DNA sequence based on the scaffold DNA sequence, mix 10004 bases of scaffold DNA, short-chain DNA and extended-chain DNA in buffer, then perform an annealing process, remove excess short-chain DNA (ssDNA) using a centrifuge filter, and obtain a rectangular DNA template with characteristic linker sites after centrifugation. S3: Self-assembly of DNA template and two sets of gold nanorods: Gold nanorods bind to the extended strands on the template through the principle of complementary base pairing. By mixing the two sets of gold nanorods modified with paired strands with the DNA template in solution, adjusting the concentration of the two sets of gold nanorods modified with paired strands, and after annealing, a sub-10 nanometer spacing electrode pair is obtained.

[0013] In one embodiment of the invention, in step S1, tris(2-chloroethyl) phosphate is used to activate the thiol groups of the paired chains.

[0014] In one embodiment of the present invention, in step S1, after activating the paired strands, the DNA strands are incubated and modified with gold nanorods, and the DNA strands are immobilized on the surface of the gold nanorods by thiol groups. The specific method is as follows: After the paired chains are activated, they are mixed with an aqueous solution of gold nanorods. At this time, sodium dodecyl sulfate (SDS), TBE buffer, and hydrochloric acid (HCl) are added to the mixed solution to adjust the pH to 3, which promotes the adsorption process of the paired chains on the surface of gold nanorods. Subsequently, a salt aging process was carried out, in which sodium chloride (NaCl) solution was gradually added to the solution to increase the sodium ion content, further weaken the charge repulsion between DNA and the surface of gold nanorods, and increase the adsorption of paired strands. Subsequently, sodium hydroxide (NaOH) was added to adjust the pH of the solution to 8.0, and the solution was incubated overnight.

[0015] In one embodiment of the present invention, in step S1, the paired strand modified gold nanorods (DNA modified gold nanorods) are further purified by centrifugation precipitation.

[0016] In one embodiment of the present invention, the centrifugal precipitation method uses a centrifugal force of 16000×g and centrifugation for 20 min. After the gold nanorods precipitate, the upper layer solution is removed, and the bottom precipitate is retained. Then, a washing buffer containing TBE and SDS is added, and the centrifugation operation is repeated three times.

[0017] The two groups of DNA-modified gold nanorods, purified by centrifugation, were dispersed in a buffer solution containing TBE and SDS and stored at 4°C for characterization and use.

[0018] In one embodiment of the present invention, the buffer solution in step S2 further contains TAE, MgAC2, and Tris.

[0019] In one embodiment of the present invention, the annealing procedure in step S2 is as follows: first, the temperature is raised to 80°C, followed by annealing, with the temperature first gradually decreasing to 60°C, and then gradually decreasing to 25°C, for a total annealing time of 40~200 h. When gradually decreasing to 60°C, each temperature is held for >2 min. When gradually decreasing to 25°C, each temperature is held for >1 h.

[0020] In one embodiment of the present invention, in step S2, the centrifugal filter has a pore size range of 10 kDa to 300 kDa, a relative centrifugal force of 2400×g is used, and the centrifugation is carried out for 2 to 5 minutes, and the centrifugation is carried out at least 4 times.

[0021] In one embodiment of the present invention, in step S2, after centrifugation, the DNA template is rinsed with a buffer containing TAE, MgAC2 and Tris. The bottom of the remaining solution after centrifugation is rinsed with the buffer each time to further disperse the DNA template. Each rinse is performed at least 10 times.

[0022] In one embodiment of the present invention, in step S2, the linker site is a region on the DNA template, in which there are several extended strands. Each extended strand has its own fixed position. The extended strand is fixed at the position and extends into a free DNA strand that can be used for pairing, in order to bind the gold nanorod modified by the pairing strand. One gold nanorod will pair with several extended strands of one linker site. In one embodiment of the present invention, in step S3, the gold nanorods bind to the extended chains on the template through the base complementary pairing principle. Two different sets of extended chains and pairing chains respectively position two different gold nanorods. The two different connection sites on the template cannot be occupied or mixed, so as to improve the positioning accuracy of the ultra-narrow spacing of the template.

[0023] In one embodiment of the present invention, in step S3, TAE buffer, MgAC2, and Tris are added after mixing to maintain the stability of the template.

[0024] In one embodiment of the present invention, in step S3, the annealing process involves first heating to 35°C, then gradually cooling to 20°C at a cooling rate of 1°C / h, and the entire annealing time is 16 h.

[0025] In a more specific embodiment of the present invention, a method for self-assembling a sub-10 nanometer spacing electrode pair is provided, comprising the following steps: (1) Preparation of two sets of gold nanorods modified with paired strands. The two sets of paired strands used were modified with thiol groups at their ends (5' or 3'). The paired strands needed to be activated first (using TCEP to activate thiol DNA) before being incubated with gold nanorods for modification. The DNA strands were immobilized on the surface of the gold nanorods through the thiol groups. The thiol groups of the paired strands were activated with tris(2-chloroethyl) phosphate (TCEP). After incubation in solution, the mixture was mixed with an aqueous solution of gold nanorods. Sodium dodecyl sulfate (SDS), TBE buffer, and hydrochloric acid (HCl) were added to the mixed solution to adjust the pH to 3, which promoted the adsorption process of the paired strands on the surface of the gold nanorods. Subsequently, a salt aging process was carried out, in which sodium chloride (NaCl) solution was gradually added to the solution to increase the sodium ion content, further weakening the charge repulsion between DNA and the surface of gold nanorods and increasing the adsorption of paired strands. Then, sodium hydroxide (NaOH) was added to adjust the pH of the solution to 8.0 and incubated overnight. The purified DNA-modified gold nanorods were centrifuged at 16000×g for 20 min using a centrifugation precipitation method. After precipitation, the supernatant was removed, and the bottom precipitate was retained. Wash buffer containing TBE and SDS was then added, and the centrifugation process was repeated three times. The two groups of purified DNA-modified gold nanorods were dispersed in buffer containing TBE and SDS and stored at 4°C for characterization and use.

[0026] (2) Design and synthesis of DNA templates with characteristic extended strands. The required rectangular structure was designed using DNA origami editing software, and the corresponding short-strand DNA sequence was obtained based on the scaffold DNA sequence. 10004 bases (nt) of scaffold DNA, short-strand DNA, and extended-strand DNA were mixed in a buffer containing TAE, MgAC2, and Tris. An annealing program was then performed, first heating to 80℃, followed by stepwise cooling to 60℃, then further stepwise cooling to 25℃, with a total annealing time of 40–200 h. During stepwise cooling to 60℃, each temperature was maintained for >2 min. During stepwise cooling to 25℃, each temperature was maintained for >1 h. Excess ssDNA was removed using a centrifugal filter. The centrifugal filter pore size ranged from 10 kDa to 300 kDa, and a relative centrifugal force of 2400 × g was used for 2–5 min, with at least 4 centrifugations. After centrifugation, the sample was rinsed with a buffer containing MgAC2, TAE, and Tris. Each time, rinse the bottom of the remaining solution with buffer after centrifugation to further disperse the DNA template, repeating the rinse at least 10 times. Obtain a rectangular DNA template with characteristic linker sites. Based on the designed linker sites, each site contains several extended strands, each with its own fixed position. These extended strands are fixed at their positions and extend into free DNA strands that can be used for pairing with the gold nanorods modified with the pairing strands. One gold nanorod will pair with several extended strands at one linker site.

[0027] (3) Self-assembly of DNA template and two sets of gold nanorods. The gold nanorods bind to the extended strands on the template via complementary base pairing. Two different extended strands and pairing strands respectively locate two different gold nanorods. The two different linkage sites on the template cannot be occupied or mixed, improving the ultra-narrow spacing positioning accuracy of the template. By mixing the modified two sets of gold nanorods with the DNA template in solution, adjusting the concentration of the two sets of gold nanorods, and adding TAE buffer, MgAC2, and Tris to maintain template stability, the temperature was first raised to 35℃, then stepped down to 20℃ at a rate of 1℃ / h, with a total annealing time of 16h. After annealing, the assembled structures of the two sets of gold nanorods and the DNA template were obtained.

[0028] This application also provides a method for characterizing the prepared sub-10 nanometer spacing electrode pair, including: (1) Characterization analysis of the sample using atomic force microscopy (AFM). For AFM characterization, a DNA template solution needs to be deposited on the surface of the hydrophilic silicon wafer. The silicon wafer cut to an appropriate size is placed in a piranha solution of concentrated sulfuric acid and hydrogen peroxide (30%wt) in a volume ratio of 7:3 for cleaning. After cleaning, it is diluted with deionized water 4 times. Then, the silicon wafer is cleaned with deionized water and then blown clean with clean nitrogen gas, and this is repeated 4 times. 10 μL of sample solution is dropped onto the surface of the hydrophilic silicon wafer and kept in a humid chamber for 40 min. The silicon wafer is cleaned by soaking in a mixed solution of ethanol and water and then blown clean with clean nitrogen gas, and this is repeated at least 4 times. The silicon wafer after deposition is placed in a clean petri dish and sealed with sealing film for AFM characterization. The deposited silicon wafer is placed on the AFM sample stage and the surface morphology is imaged by selecting the gas phase tapping mode. (2) Characterization analysis of the sample using transmission electron microscopy (TEM). For TEM imaging, the carbon support film copper mesh needs to be treated with glow discharge to obtain hydrophilic properties. 4 μL of sample solution was dropped onto the front surface of the copper mesh and deposited for 3 min. Excess solution was then blotted away with clean filter paper near the edge of the copper mesh. Next, negative staining was performed using 1% wt uranium acetate solution, typically 4 μL was dropped and deposited for 7 s. Excess solution was then blotted away with clean filter paper near the edge of the copper mesh. The copper mesh was then placed on a sample holder and inserted into a TEM vacuum chamber to acquire morphological images.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1. By utilizing the programmability and molecular-level precision of DNA origami technology, precise control of the spacing between gold nanorods was achieved by designing two sets of sequence-specific and spatially positioned linkers.

[0030] 2. It ensured that the electrode pair spacing was stable at the sub-10 nanometer scale, overcoming the process bottleneck faced by electron beam lithography and other technologies at the sub-10 nanometer scale, and realizing the reliable fabrication of sub-10 nanometer gap electrode pairs based on self-assembly technology.

[0031] 3. It does not require complex photolithography equipment, has a simple process flow, and low cost, providing a technical basis for the mass production of sub-10 nanometer electrode pairs for nanoelectronic devices. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process for preparing sub-10 nanometer spacing electrode pairs in this invention.

[0033] Figure 2 This is a schematic diagram of the SEM characterization of gold nanorods.

[0034] Figure 3 This is a schematic diagram of AFM characterization of DNA before and after modification with gold nanorods.

[0035] Figure 4 This is a schematic diagram of a rectangular DNA template and its linker sites.

[0036] Figure 5 A three-view schematic diagram of thermal fluctuations simulated using a finite element modeling framework for a DNA rectangular template.

[0037] Figure 6 This is a schematic diagram of AFM characterization of a rectangular DNA template.

[0038] Figure 7 This is a schematic diagram of TEM characterization of a rectangular DNA template.

[0039] Figure 8 This is a schematic diagram of AFM characterization after the DNA template and gold nanorods self-assemble.

[0040] Figure 9 This is a schematic diagram of TEM characterization of the DNA template and gold nanorods after self-assembly. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0042] This invention discloses a self-assembly preparation method for sub-10 nm pitch electrode pairs. A rectangular plane constructed using DNA origami is used as a template. Two connection sites with a pre-set spacing of less than 10 nm are pre-set on its surface. Extension strands are designed at the two connection sites to connect gold nanorods modified with paired strands. The gold nanorods are modified with two different DNA paired strands and pair with the extension strands of the template to fix the relative positions of a pair of gold nanorods on the DNA template, thereby preparing ultra-narrow pitch electrode pairs.

[0043] Example 1: The method for preparing sub-10 nanometer spacing electrode pairs in this invention includes the following steps, such as... Figure 1 As shown: Step 1: Prepare two sets of gold nanorods modified with paired chains.

[0044] The AuNRs before modification were characterized using SEM, such as... Figure 2 As shown, the gold nanorods have an average length of 73 nm and an average diameter of 10 nm. Two sets of paired strands with different base sequences were used, each modified with a thiol group at the 5' end. These strands required activation before being incubated with the gold nanorods for modification (Sequence 1 is: 5'-HS-TT). CCTCTACCACCTACAT-3'; Sequence 2 is: 5'-HS-TTCCATCTCTTCTTCACC-3'). The thiol groups of the paired strands were activated using TCEP, which was mixed with the two sets of paired strands at a molar ratio of 200 and incubated for 1 hour. The activated paired strand solution was then added to the gold nanorod solution, and SDS, TBE buffer, and HCl were added to the mixture to adjust the pH to 3, promoting the adsorption of the paired strands on the gold nanorod surface. Subsequently, 5 M NaCl solution was added to the solution in nine equal amounts every 20 minutes. The salt aging process weakens the charge repulsion between DNA and the gold nanorod surface, increasing the adsorption of paired strands. Then, sodium hydroxide (NaOH) was added to adjust the pH to 8.0, and the solution was incubated overnight. At this point, the final solution contained 0.02% SDS, 0.5×TBE, and 0.5 M NaCl, in addition to the gold nanorods and paired strands.

[0045] After incubation, the DNA-modified gold nanorods were purified by centrifugation to remove free paired strands. The nanorods were centrifuged at 16000×g for 20 min. After precipitation, the supernatant was removed, and the bottom precipitate was retained. Wash buffer containing 0.5×TBE and 0.02% SDS was added to disperse the precipitate, and the centrifugation process was repeated three times. The two groups of purified DNA-modified gold nanorods were dispersed in buffer containing 0.5×TBE and 0.02% SDS and stored at 4°C for characterization and use.

[0046] The AuNRs before and after modification were characterized using AFM, such as... Figure 3 As shown, the diameter of the unmodified AuNRs was 10 nm, which was relatively uniform; the average diameter of the modified AuNRs was 15 nm, and the DNA on the surface increased the diameter.

[0047] Step 2: Prepare a rectangular DNA template.

[0048] See Figure 4 A rectangular, single-layer DNA template structure was designed using the Scadnano open-source web software (https: / / scadnano.org / ). In this embodiment, the DNA ligation method was generated by the software. This embodiment provides an illustrative structural design; the specific structural dimensions are not specified. Figure 4 The dimensions are labeled as 18H×565B (H stands for Helix, representing the number of double helices, 1H=2.2 nm; B stands for Base pair, representing the number of base pairs, 1B=0.34 nm), and the theoretical dimensions are 39.6 nm×192 nm.

[0049] VCSM13 ssDNA (single-stranded DNA derived from VCSM13 helper phage, a known biological material) was used as the scaffold strand, with a full length of 10,004 bases. By introducing the scaffold strand, short, pinned sequences were obtained. The extended strand portions of the two linker sites corresponded to the paired strands, with sequence 1 corresponding to: 5'-ATGTAGGTGGTAGAGG-3'; and sequence 2 corresponding to: 5'-GGTGAAGAAGAGATGG-3'.

[0050] To reduce the overall distortion of the template along its long axis, one column of bases was deleted every 64 bytes. The modified structure was then imported into the CanDo open-source web platform software, CanDo (https: / / cando-dna-origami.org / ), to simulate the overall distortion correction effect on the DNA template. CanDo uses a mechanical model of DNA to predict the 3D shape and flexibility of programmed DNA, assuming the double helix structure is a uniform elastic rod with axial tensile, torsional, and bending stiffness. Following the CanDo manual, the exposed free strands at both ends were removed.

[0051] like Figure 5 As shown, the thermal wave three-view diagram (RMSF) reveals that the distortion characteristics are reduced, and the overall structure is a planar region. By comparing this framework simulation with experimental characterization, it can be confirmed that the designed DNA template structure effectively prevents overall distortion.

[0052] The scaffold chains and short chains were dispersed in a low concentration of TE buffer, and then mixed and dispersed in TE / Mg buffer. 2+ The buffer solution contains a final concentration of >100 nM for each ssDNA. The mixed solution contains 1×TAE, 12.5 mM MgAC2, and the pH is adjusted to 9.0 using Tris.

[0053] The mixed solution was transferred to PCR-specific centrifuge tubes and annealed in the PCR instrument. Each PCR tube contained 70 μL of solution. A two-stage cooling method was used for annealing. First, the temperature was raised from room temperature to 85°C at a rate of 6°C / s and held for 15 min. Then, a first rapid cooling phase (85°C → 60°C) was performed: the temperature was decreased in integer increments of 1°C at a rate of 0.1°C / s, held for 2 min at each temperature. This was followed by a second slow cooling phase (59°C → 20°C; the transition from the first rapid cooling phase to the second slow cooling phase is usually automatic; in this example, the temperature change rate from 60°C to 59°C was 0.1°C / s): the temperature was decreased in integer increments of 1°C at a rate of 0.1°C / s, held for 5 min at each temperature. After annealing, the temperature was rapidly reduced from 20°C to 4°C at a rate of 6°C / s. At this point, the DNA template had completed self-assembly and could be stored long-term at 4°C.

[0054] To reduce excess ssDNA in the DNA template solution, the assembly solution was purified using a 30 kDa filter-concentrated centrifuge tube. The DNA template in the centrifuge tube was washed and centrifuged using a washing solution of 1×TAE, 12.5 mM MgAC2, and pH 9.0, repeated four times. The purified DNA template solution should be used as soon as possible. The prepared rectangular DNA template was used to create AFM and TEM samples, and the characterization results are as follows: Figure 6 , Figure 7 As shown, from Figure 6 AFM characterization shows that the single-layer rectangular template has a clear shape and stable structural edges. From Figure 7 TEM characterization revealed that the rectangular template had a length of 176 nm and a width of 33 nm.

[0055] Step 3: Self-assembly of DNA template with two sets of gold nanorods.

[0056] The modified gold nanorods and DNA template were mixed and incubated in solution. The incubation solution contained 1×TAE, 12.5 mM MgAC2, and the pH was adjusted to 9.0. The temperature was first raised to 35℃, then stepped down to 20℃ at a rate of 1℃ / h, for a total annealing time of 16 h. The concentrations of the two gold nanorods were adjusted to ensure they were equal in amount in the solution, and the molar ratio of DNA template to the two gold nanorods was 1:3:3, thus obtaining a complete assembly of the two gold nanorods and DNA template, i.e., a sub-10 nm spacing electrode pair.

[0057] After incubation, the gold nanorods were assembled with the DNA template and then characterized by AFM and TEM. See [link to documentation]. Figure 8 , Figure 9 .from Figure 8AFM characterization showed that the two gold nanorods and one DNA template were bound together, consistent with the designed structure. The height information of the gold nanorods and the template was significantly different, with a height ratio of 10:1.

[0058] from Figure 9 TEM characterization revealed that the spacing between the two gold nanorods was 6.0–8.0 nm.

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for self-assembling a sub-10 nanometer spacing electrode pair, characterized in that, Includes the following steps: Using a two-dimensional rectangular DNA template, two sets of single-stranded DNA strands, known as extended strands, are extended from its surface. These two extended strands serve as two sets of linker sites. Two types of mating strands were used to modify gold nanorods, resulting in two sets of mating strand-modified gold nanorods. The two mating strands were respectively mated with thiol-modified single-stranded DNA molecules that matched the linker site. By utilizing the complementary base pairing principle of DNA, gold nanorods can be precisely oriented onto DNA templates. The distribution of the two sets of extended strands determines the orientation and position of the two sets of gold nanorods modified with different paired strands on the DNA template, thereby effectively controlling the relative spacing between the two gold nanorods on the DNA template.

2. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 1, characterized in that, Includes the following steps: S1: Preparation of two sets of gold nanorods modified with paired chains: Among them, the pairing strand is a thiol-modified single-stranded DNA. After the pairing strand is activated, it is incubated with gold nanorods for modification. The DNA strand is fixed to the surface of the gold nanorods through the thiol group, resulting in two sets of gold nanorods modified with pairing strands. S2: Design and synthesize DNA templates with characteristic extended strands: Design the required rectangular structure using DNA origami editing software, obtain the corresponding short-chain DNA sequence based on the scaffold DNA sequence, mix the scaffold DNA, short-chain DNA and extended strand DNA in a buffer, and then perform an annealing process. Remove excess short-chain DNA (ssDNA) using a centrifuge filter. After centrifugation, obtain a rectangular DNA template with characteristic linker sites. S3: Self-assembly of DNA template and two sets of gold nanorods: Gold nanorods bind to the extended strands on the template through the principle of complementary base pairing. By mixing the two sets of gold nanorods modified with paired strands with the DNA template in solution, adjusting the concentration of the two sets of gold nanorods modified with paired strands, and after annealing, a sub-10 nanometer spacing electrode pair is obtained.

3. The self-assembly preparation method for a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S1, tris(2-chloroethyl) phosphate is used to activate the thiol groups of the paired chains.

4. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S1, after activating the paired strands, they are incubated and modified with gold nanorods. The specific method for immobilizing the DNA strands onto the surface of the gold nanorods through thiol groups is as follows: After the paired chains are activated, they are mixed with an aqueous solution of gold nanorods. At this time, sodium dodecyl sulfate, TBE buffer, and hydrochloric acid are added to the mixed solution to adjust the pH to 3, which promotes the adsorption process of the paired chains on the surface of gold nanorods. Then, a salt aging process is carried out, in which sodium chloride solution is gradually added to the solution; Then, sodium hydroxide was added to adjust the pH of the solution to 8.0, and the solution was incubated overnight.

5. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S1, the paired-chain modified gold nanorods are also purified by centrifugal precipitation.

6. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, The annealing procedure in step S2 is as follows: first, heat to 80°C, then perform annealing treatment, first step-cool down to 60°C, then step-cool down to 25°C, the entire annealing time is 40~200 h, when step-cooling down to 60°C, each temperature is held for >2 min, when step-cooling down to 25°C, each temperature is held for >1 h.

7. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S2, the linker site is a region on the DNA template containing several extended strands. Each extended strand has its own fixed position. The extended strand is fixed at the position and extends into a free DNA strand that can be used for pairing, in order to bind the gold nanorod modified by the pairing strand. One gold nanorod will pair with several extended strands at one linker site.

8. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S3, the gold nanorods bind to the extended chains on the template through the principle of complementary base pairing. Two different sets of extended chains and paired chains respectively position two different gold nanorods. The two different connection sites on the template cannot be occupied or mixed, so as to improve the positioning accuracy of the ultra-narrow spacing of the template.

9. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S3, after mixing, additional TAE buffer, MgAC2, and Tris are added to maintain template stability.

10. The self-assembly preparation method of a sub-10 nanometer spacing electrode pair according to claim 2, characterized in that, In step S3, the annealing process involves first heating to 35°C, then gradually cooling to 20°C at a cooling rate of 1°C / h, with the entire annealing time being 16 h.

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