Sub-10 nm catalyst and self-assembly preparation method and application thereof

Abstract

This invention relates to a catalyst, specifically a sub-10 nm catalyst and its self-assembly preparation method and application, comprising the following steps: pretreating DNA-modified Fe3O4 particles to remove free DNA strands; mixing scaffold DNA, short-chain DNA, and extended-chain DNA in a buffer solution and annealing to self-assemble into a DNA template; mixing the DNA-modified Fe3O4 particles and the DNA template in an incubation solution for co-incubation to obtain the catalyst. Compared with the prior art, this invention solves the problem of the difficulty in achieving precise quantity, accurate position, and consistent spacing of catalysts for CVD growth of CNTs with diameters less than 10 nm in the prior art. This method is based on the programmable characteristics of DNA origami, which allows for precise positioning of Fe3O4 nanoparticles, effectively controlling the spacing, arrangement, and concentration of the catalyst on the substrate, thereby achieving precise control of CVD growth of CNTs using this catalyst.

Description

Technical Field

[0001] This invention relates to a catalyst, specifically to a sub-10 nanometer catalyst and its self-assembly preparation method and application. Background Technology

[0002] CVD growth of CNTs relies on metal or metal oxide nanoparticles (such as Fe, Co, Ni, and their oxides) as catalysts, with iron oxides offering advantages such as low cost, stable processing, and easy availability. The diameter, chirality, density, and position of CNTs prepared by this method are directly controlled and limited by the size, composition, and spatial distribution of the catalyst particles. However, traditional methods (such as sputtering + annealing and colloidal deposition) struggle to achieve precise quantity, accurate positioning, and consistent spacing of catalysts with diameters less than 10 nm, severely restricting the reproducibility and integration of CNT devices.

[0003] DNA origami guides a long scaffold strand to fold into a pre-defined two-dimensional or three-dimensional nanostructure using hundreds of short DNA strands. It boasts advantages such as 2 nm positioning accuracy, high programmability, and good material compatibility. In recent years, this technology has been successfully used to arrange various functional units, including gold, silver, quantum dots, metal oxides, and proteins, providing a novel pathway for constructing non-photolithographic nanodevices. For example, CN108165544A discloses a large-scale DNA origami assembly method mediated by gold nanoparticles, but it only improves the self-assembly size of the DNA origami and still lacks the ability to position it on a substrate.

[0004] Furthermore, existing technology CN120102860A discloses a DNA origami structure based on functionalized magnetic nanoparticles, its preparation method, and its application, including the following steps: Step 1: Constructing a cavity-containing DNA origami structure using a self-assembly method; the short chains in the DNA origami structure include a first short chain, a second short chain, and a third short chain; Step 2: Connecting a thiol-functionalized first sequence to the first short chain, chelating ferrous ions on the first sequence to obtain a thiol-modified DNA origami structure; Step 3: Reducing the chelated ferrous ions on the thiol-modified DNA origami structure to obtain a magnetically functionalized DNA origami structure internally loaded with Fe2O3 particles; Step 4: Connecting an antibody to the second short chain in the DNA origami structure through base complementary pairing to obtain the desired DNA origami structure. This method constructs a magnetically functionalized DNA origami structure with Fe2O3 particles internally loaded through a self-assembly method. However, the main goal of this existing technology is to obtain highly efficient and controllable biomagnetic beads. Therefore, this scheme loads Fe2O3 particles into the internal cavity of the DNA origami structure. However, for the catalyst used in the CVD growth of CNTs, this structure is still difficult to achieve the precise control of the quantity, position and spacing as mentioned above. The active components are prone to agglomeration or uneven loading in the internal cavity.

[0005] Therefore, for catalysts used in CVD growth of CNTs, there is a need to develop a preparation method that allows for precise control over the size, composition, and spatial distribution of catalyst particles. Summary of the Invention

[0006] The purpose of this invention is to address at least one of the aforementioned problems by providing a sub-10 nm catalyst, its self-assembly preparation method, and its application. This addresses the difficulty in achieving precise quantity, accurate positioning, and consistent spacing of catalysts for CVD CNT growth with diameters less than 10 nm in the existing technology. This solution leverages the programmable characteristics of DNA origami, precisely positioning Fe3O4 nanoparticles to effectively control the spacing, arrangement, and concentration of the catalyst on the substrate, thereby enabling precise control during the CVD CNT growth process.

[0007] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a method for the self-assembly preparation of a sub-10 nanometer catalyst, comprising the following steps: S1: Pre-treat DNA-modified Fe3O4 particles (DNA-IONPs) to remove free DNA strands; S2: The scaffold DNA, short-chain DNA, and extended-chain DNA are mixed in a buffer solution and annealed to self-assemble into a DNA template; wherein, the extended-chain DNA extends from the DNA template, and the DNA sequence of the extended-chain DNA is complementary to the DNA sequence of the DNA-modified Fe3O4 particles. S3: DNA-modified Fe3O4 particles and DNA template are mixed in an incubation solution and incubated together. Based on the principle of complementary base pairing, the DNA-modified Fe3O4 particles are fixed on the DNA template by the arrangement of extended strand DNA, thus obtaining a sub-10 nm catalyst.

[0008] Preferably, in step S1, the pretreatment is: purifying the DNA-modified Fe3O4 particles by ultrafiltration centrifugation.

[0009] Preferably, in step S1, the DNA-modified Fe3O4 particles contain: Fe3O4 particles have a diameter of less than 10 nanometers; The sequence of the DNA signature strand is: 5'(NH2)-TTCCTCTACCACCTACAT-3'.

[0010] Preferably, in step S2, the length of the scaffold DNA is 10004 bases, the length of the short-chain DNA is less than 70 bases, and the length of the extended-chain DNA is less than 90 bases. The buffer solution contains 1×TAE and 12.5 mM MgAC2, and the pH is adjusted to 9.0 using Tris. The scaffold DNA has a concentration of 10 nM in the buffer, the short-chain DNA has a concentration of 40 nM in the buffer, and the extended-chain DNA has a concentration of 40 nM in the buffer.

[0011] Preferably, in step S2, the annealing self-assembly is a stepped annealing procedure: First, the temperature is raised to 80℃; then it is gradually cooled to 60℃, and each temperature is maintained for >2 min; then it is gradually cooled to 25℃, and each temperature is maintained for >1 h; and the total time for annealing self-assembly is 40~200 h.

[0012] Preferably, in step S3, the amount of DNA-modified Fe3O4 particles mixed in excess with the amount of extended strand DNA on the DNA template; The incubation solution contains 1×TAE and 12.5 mM MgAC2, and the pH is adjusted to 9.0 using Tris.

[0013] Preferably, in step S3, the incubation reaction undergoes an annealing process: First, raise the temperature to 35℃ and hold for 1 hour; then gradually lower the temperature to 20℃ at a rate of 1℃ / h.

[0014] The second aspect of this invention discloses a sub-10 nanometer catalyst, which is obtained by any of the self-assembly preparation methods described above; The sub-10 nanometer catalyst comprises a DNA template and at least one DNA-modified Fe3O4 particle attached to the DNA template. The connection of DNA-modified Fe3O4 particles to a DNA template is achieved through complementary base pairing between the characteristic DNA strand on the surface of the DNA-modified Fe3O4 particles and the extended DNA strand on the DNA template.

[0015] Preferably, the extended strand of DNA is located at the center and / or side of the surface of the DNA template; In the DNA template, one column of bases is deleted every 64 base pairs along the long axis.

[0016] The third aspect of this invention discloses the application of a sub-10 nanometer catalyst as described above in the fabrication of CNT devices.

[0017] The working principle of this invention is as follows: By modifying the surface (such as carboxyl, amino, click chemistry, etc.), Fe3O4 nanoparticles (Iron Oxide Nanoparticles, IONPs) can be covalently coupled to specific DNA sequences (DNA characteristic strands), thereby enabling the specific binding of Fe3O4 nanoparticles to preset sites (extended strand DNA) on DNA origami (DNA template).

[0018] Further utilization of APTES, Mg 2+ Methods such as adsorption and electrophoretic deposition can facilitate the efficient transfer of DNA origami structures and IONPs composite structures from the solution phase onto semiconductor-compatible substrates such as silicon, quartz, and sapphire. This allows the structures to be compatible with the patterning process of the substrate while maintaining structural integrity during the transfer process, thus meeting the requirements of subsequent CVD processes.

[0019] Compared with the prior art, the present invention has the following beneficial effects: In patterned arrays with micrometer-level spacing, conventional patterning techniques struggle to place a controllable number of sub-10 nm catalyst particles. To achieve controllable arrangement of catalyst nanoparticles smaller than 10 nm, this invention aims to provide a precise directional arrangement method for linking catalyst nanoparticles to modification sites on a DNA template constructed from DNA origami. This method enables the controllable synthesis of a single layer of DNA rectangular origami within a hundred nanometer range, and the binding of DNA-modified Fe3O4 nanoparticles using linker strands. Combined with patterning techniques and utilizing the DNA template as a bridge, the number of nanoparticles can be controlled within a micrometer-level spacing.

[0020] This invention utilizes the programmability and molecular-level precision of DNA origami technology. By changing the sequence position of the designed extended DNA strand, the number and position of template modification particles can be arbitrarily controlled, improving the iterative efficiency of the template arrangement method. The positioning accuracy of DNA origami is 2 nm, achieving sub-10 nm positioning that is difficult to achieve with electron beam lithography and EUV, thus exhibiting higher positioning precision.

[0021] Traditional catalyst placement methods often involve linear arrangement or aggregated arrays of particles in batches, making it difficult to arrange individual particles within a micrometer-wide space. DNA origami technology, however, can autonomously control the number of particles on a single template, enabling precise particle placement and control over the position of individual particles within a hundred-nanometer space. DNA origami possesses the ability to control sub-10nm structures while being compatible with coarse photolithography patterning techniques, facilitating the arrangement of micrometer-wide DNA origami arrays and providing a connecting bridge for constructing precise, clean, and orderly catalyst interfaces. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the self-assembly process of the 10-nanometer catalyst in this invention.

[0023] Figure 2 A flowchart illustrating the process of removing dissociated free DNA and UV-vis characterization images before and after removal.

[0024] Figure 3 The images show the SEM and AFM characterization of DNA-IONPs in Example 1.

[0025] Figure 4 This is a schematic diagram of the DNA rectangular template connecting one particle and its connection sites in Example 1.

[0026] Figure 5 This is an AFM characterization diagram of the DNA rectangular template with one particle connected in Example 1.

[0027] Figure 6 This is an AFM characterization diagram of the DNA rectangular template and the DNA-IONPs self-assembly structure in Example 1.

[0028] Figure 7 This is a schematic diagram of the rectangular DNA template connecting the four particles and their connection sites in Example 2.

[0029] Figure 8 The image shows the AFM characterization of the 4-particle self-assembled structure in Example 2.

[0030] Figure 9 This is an AFM characterization diagram of the free chain occupying the template connection sites in Comparative Example 1. Detailed Implementation

[0031] 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.

[0032] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available. Any other matters not covered herein can be addressed using existing technology.

[0033] This invention discloses a self-assembly preparation method for a positionable sub-10 nanometer catalyst. A two-dimensional rectangular DNA template is constructed using DNA origami nanotechnology. According to the positional requirements of the particle arrangement, single-stranded DNA (extended strand) is extended on the surface of the DNA rectangular template as a linker. Fe3O4 nanoparticles with specific DNA base sequences modified on their surface are co-incubated with the two-dimensional rectangular template. Based on the principle of complementary base pairing, the arrangement of DNA-modified Fe3O4 particles at the linker is fixed. By utilizing the relatively fixed spatial structure relationship between the catalyst particles and the rectangular DNA origami, the precise arrangement of sub-10 nanometer particles is achieved on a large-scale patterned substrate.

[0034] Furthermore, the self-assembly preparation method of this locatable sub-10 nm catalyst specifically includes the following steps: (1) Obtaining DNA-modified Fe3O4 particles (DNA-IONPs). There are several mature chemical methods for obtaining DNA-modified Fe3O4 particles, which can be purchased directly from manufacturers; or, IONPs can be encapsulated in carboxyl-containing polyethylene glycol (PEG-COOH), followed by co-incubation with amino-modified DNA strands, using amide bonds to fix the DNA characteristic strands onto the surface of IONPs; or DBCO-DNA can be linked to N3-IONPs through a click chemical reaction of azide groups (-N3) and dibenzocyclooctyl ester (DBCO-ester) (see existing published literature: Programmable Assembly of Iron Oxide Nanoparticles Using DNA Origami (https: / / dx.doi.org / 10.1021 / acs.nanolett.0c00484), or A general approach to DNA-programmable atom equivalents (https: / / dx.doi.org / 10.1038 / nmat3647)). It is important to note that all DNA-modified Fe3O4 particles, regardless of their origin, must be purified before use to remove excess free DNA strands and prevent them from occupying the linker sites on the rectangular template. Generally, ultrafiltration centrifugation can be used to purify DNA-modified IONPs: Add the sample to a centrifuge filter and centrifuge at 2400×g for 15 min. Then remove the solvent containing free DNA from the bottom of the ultrafiltration tube, add fresh TAE buffer (free of DNA) to the top layer, and repeat the centrifugation process five times. The purified DNA-IONPs should be used as soon as possible.

[0035] (2) Design and preparation of DNA templates with linker sites. The required rectangular structure was designed using DNA origami editing software, and the corresponding short-chain DNA sequence was obtained based on the scaffold DNA sequence. Scaffold DNA of 10004 bases (nt) in length, short-chain DNA less than 70 nt in length, and extended-chain DNA less than 90 nt in length were mixed in a buffer containing TAE, MgAC2, and Tris. An annealing procedure was then performed: first, the temperature was raised to 80℃; then, annealing was performed: first, the temperature was stepped down to 60℃, then gradually stepped down to 25℃, with the entire annealing time ranging from 40 to 200 h; during the step-down to 60℃, each temperature was maintained for >2 min; during the step-down to 25℃, each temperature was maintained for >1 h. Excess ssDNA was removed using a centrifugal filter with a pore size ranging from 10 kDa to 300 kDa, using a relative centrifugal force of 2400 × g, centrifuged for 2–5 min, and centrifuged at least 4 times. After centrifugation, wash with a buffer containing MgAC2, TAE, and Tris. Use a pipette to add 200–500 μL of buffer to the remaining solution, and aspirate an equal volume of the mixture back to complete one wash cycle. This further disperses the DNA template. Repeat the wash cycle at least 10 times after each centrifugation. The final mixture should contain both the remaining solution and the wash buffer. This yields a rectangular DNA template with linker sites. Based on the designed linker sites, each site is a region on the template containing several extended strands of DNA. These extended strands extend onto their surface, providing free DNA bases for pairing and binding DNA-IONPs.

[0036] (3) Self-assembly of DNA rectangular template and DNA-IONPs: DNA-IONPs bind to the extended strand on the template through the base complementary pairing principle. DNA-IONPs are mixed with the DNA rectangular template, and TAE buffer, MgAC2, and Tris are added to maintain template stability. An annealing procedure is required during incubation: first, the temperature is raised to 35℃, then gradually decreased to 20℃ at a rate of 1℃ / h, for a total annealing time of 16 h. After annealing, the assembled structure of DNA-IONPs and the DNA rectangular template is obtained.

[0037] (4) Sample characterization analysis. DNA template solution needs to be deposited on the surface of the hydrophilized silicon wafer. The silicon wafers cut to an appropriate size were 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, the wafers were rinsed and diluted with deionized water 4 times. Then, the wafers were rinsed with deionized water and then purged with clean nitrogen gas, and this process was repeated 4 times. 10 μL of sample solution was dropped onto the surface of the hydrophilized silicon wafer and kept in a humid chamber for 40 min. The wafers were then soaked and cleaned with a mixture of ethanol and water and purged with clean nitrogen gas, and this process was repeated at least 4 times. The deposited silicon wafers were placed in a clean petri dish and sealed with sealing film for characterization. For AFM characterization, the deposited silicon wafers were placed on the AFM sample stage and the surface morphology was imaged using the gas phase tapping mode. For SEM characterization, the deposited silicon wafers were fixed on the sample stage and the sample was injected through the SEM sample transfer chamber. The surface morphology was imaged using the InLens mode.

[0038] Example 1 This embodiment designs, prepares, and characterizes a self-assembled structure of a centrally arranged sub-10 nm catalyst.

[0039] This embodiment discloses a self-assembly preparation method for a localizable sub-10 nm catalyst. A rectangular template constructed using DNA origami serves as a construction platform, with pre-set connection sites on its surface to connect DNA-modified Fe3O4 nanoparticles (IONPs). The IONPs are smaller than 10 nm and are precisely fixed to the surface of the DNA rectangular template according to the connection sites. Specifically, this embodiment designs a method for arranging a single Fe3O4 nanoparticle at the center of a DNA rectangular template constructed from DNA origami, including the following steps: Figure 1 As shown.

[0040] Step 1: Prepare DNA-modified Fe3O4 nanoparticles (DNA-IONPs).

[0041] In this embodiment, magnetic nanoparticles (Fe3O4 nanoparticles) were purchased from Nanjing Yasiming Biotechnology Co., Ltd. IONPs were encapsulated in carboxyl-containing polyethylene glycol (PEG-COOH), followed by co-incubation with amino-modified DNA strands. The DNA signature strand was immobilized onto the surface of the IONPs using amide bonds. The sequence of the DNA signature strand is: 5'(NH2)-TTCCTCTACCACCTACAT-3'.

[0042] It should be noted that in some other embodiments, DNA-modified Fe3O4 nanoparticles can be purchased directly, or DBCO-DNA can be linked to N3-IONPs via a click chemistry reaction of an azide group (-N3) and dibenzocyclooctylene ester (DBCO-ester) according to existing publicly available technologies. Whether synthesized in the laboratory or customized by the manufacturer, the only requirement is to immobilize the specified DNA sequence onto the surface of sub-10 nm Fe3O4 particles.

[0043] To prevent free DNA from occupying the linker sites on the rectangular template, the dissociated free DNA needs to be removed, such as... Figure 2 As shown. Ultrafiltration centrifugation was performed using a 30 kDa (500 μL) ultrafiltration centrifuge tube. 200 μL of 5 μM DNA-IONPs sample was added to the centrifuge filter, along with 300 μL of 1×TAE buffer. The tube was centrifuged at 2400×g for 15 min. The solution containing free DNA at the bottom of the ultrafiltration tube was then removed, and 1×TAE buffer without DNA was added to the upper layer of the ultrafiltration tube. The centrifugation operation was repeated four times.

[0044] The absorption peak at 260 nm was characterized using UV-Vis. The height of this peak is positively correlated with the base content of DNA. Figure 2 As shown, the absorbance of the free DNA after four purifications decreased to 0.17, far less than the 5.62 of the sample solution, indicating that the lower filtrate contained virtually no free DNA. The purified particle solution was diluted to 200 nM with 1×TAE buffer. The purified DNA-IONPs should be used as soon as possible.

[0045] The purified DNA-IONPs were characterized using SEM and AFM, respectively. Figure 3 As shown, based on the height information of AFM, the size of DNA-IONPs is 4.2 nm, and the diameter is relatively uniform.

[0046] Step 2: Prepare a rectangular DNA template for the central modification site.

[0047] See Figure 4 A rectangular, monolayer DNA template structure was designed using the open-source Scadnano software (https: / / scadnano.org / ), with dimensions of 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 a theoretical size of 39.6 nm × 192 nm. Three sets of unpaired extension strands were designed at the center of the designed DNA template structure as linking sites for immobilizing DNA-IONPs. The sequence of the three extensions is: (DNA template) -5'-ATGTAGGTGGTAGAGG-3'.

[0048] vcsM13 ssDNA was used as the scaffold DNA strand, with a full length of 10,004 bases. By introducing the scaffold DNA strand sequence, pinned short DNA strand sequences were obtained. To reduce the overall distortion of the template along its long axis, one column of bases was deleted every 64 bytes.

[0049] Scaffold DNA, short-strand DNA, and extended-strand DNA were dispersed in a low-concentration TE buffer, then mixed and dispersed in TAE / Mg. 2+ Buffer solution containing 10 nM scaffold DNA, and 40 nM for each short and extended DNA strand. TAE / Mg 2+ The buffer solution contained 1×TAE and 12.5 mM MgAC2, and the pH was adjusted to 9.0 using Tris. The mixed solution was transferred to PCR-specific centrifuge tubes and annealed in PCR equipment, with a volume of 70 μL per PCR tube. This 10004 nt long monolayer DNA scaffold could be annealed using the same procedure, employing a two-stage cooling method: First, heating from room temperature to 85°C at a rate of 6°C / s and holding for 15 min; then, a first rapid cooling phase (85°C → 60°C): decreasing the temperature in integer increments of 1°C at a rate of 0.1°C / s, holding for 2 min at each temperature; followed by a second slow cooling phase (60°C → 20°C): decreasing the temperature in integer increments of 1°C at a rate of 0.1°C / s, holding 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 has completed self-assembly, and the assembly solution can be stored at 4°C for a long time without purification.

[0050] To reduce excess ssDNA in the DNA template solution during the assembly of DNA templates and nanoparticles, a 100 kDa ultrafiltration centrifuge tube was used to purify the DNA template solution. The DNA template in the centrifuge tube was washed and centrifuged at 2400 × g for 5 min using a washing solution of 1×TAE, 12.5 mM MgAC2, and pH 9.0. The solution containing free DNA was then removed from the bottom of the ultrafiltration tube, and a DNA-free buffer solution of 1×TAE, 12.5 mM MgAC2, and pH 9.0 was added to the upper layer of the ultrafiltration tube. This centrifugation process was repeated four times. The purified DNA template solution should be used as soon as possible.

[0051] The prepared DNA rectangular template was used to make AFM samples, and the characterization results are as follows: Figure 5 As shown, the single-layer rectangular template has a clear shape and stable structural edges. The template has a length of 171 nm and a width of 43 nm.

[0052] Step 3: Self-assembly of DNA rectangular template and DNA-IONPs.

[0053] DNA-IONPs were mixed with a rectangular DNA template in solution and incubated. The ratio of DNA-IONPs to rectangular DNA template in the incubation solution was 10:1, with DNA-IONPs in excess. The incubation solution contained 1×TAE, 12.5 mM MgAC2, and the pH was adjusted to 9.0 using Tris. An annealing program was required during incubation: the temperature was first raised to 35°C and held for 1 h, followed by a stepwise decrease to 20°C at a rate of 1°C / h, for a total annealing time of 16 h.

[0054] After incubation, to reduce excess DNA-IONPs in the incubation solution, the solution was purified using 100 kDa ultrafiltration centrifuge tubes, taking advantage of the significant shape difference between the two. The tubes were centrifuged at 2400×g for 3 min, then the solution containing free DNA-IONPs at the bottom of the ultrafiltration tube was removed. A buffer solution of 1×TAE, 12.5 mM MgAC2, and pH 9.0 was added to the upper layer of the ultrafiltration tube. This centrifugation process was repeated 3 times, followed by the replacement with a new 100 kDa ultrafiltration centrifuge tube. A total of 3 100 kDa ultrafiltration centrifuge tubes were used, and a total of 9 centrifugations were performed.

[0055] The prepared IONP-rectangular template was characterized by AFM, and the characterization results are shown in the figure. Figure 6 Individual DNA-IONPs were assembled on a rectangular DNA template. The overall height of this self-assembled structure was 4.2 nm, with a template height of 1.1 nm and a difference height of 3.1 nm.

[0056] Example 2 This embodiment designs, prepares, and characterizes a self-assembled structure with four sub-10 nm catalysts arranged in a specific pattern.

[0057] The present invention discloses a self-assembly preparation method for a localizable sub-10 nanometer catalyst. By modifying the position and number of extended strands on a rectangular template constructed from DNA origami, four catalyst nanoparticles can be controllably loaded at a single rectangular template position.

[0058] The particle source for the method of arranging four Fe3O4 nanoparticles around the DNA origami in this invention is the same as in Example 1, only the position and number of the extended strands of the rectangular template are modified, such as... Figure 7 As shown.

[0059] Step 1: Prepare DNA-modified Fe3O4 nanoparticles (DNA-IONPs).

[0060] The requirements for catalyst nanoparticles are the same as in step 1 of Example 1.

[0061] Step 2: Prepare a rectangular DNA template with 4 modification sites.

[0062] Based on the rectangular template of Example 1, using the same scaffold strand DNA and twist correction, the extended strand DNA in the central region was deleted, and 4 extended strand DNA were extended on each of the two narrow sides of the rectangular template, with the sequence: (DNA template)-5'-ATGTAGGTGGTAGAGG-3', forming 4 linking sites on the rectangular template, each linking site containing 2 extended strand DNA.

[0063] The processes of DNA solution mixing, buffer concentration, annealing, filtration, and purification were all consistent with those in Example 1. The prepared DNA rectangular template had the same shape as the template in Example 1.

[0064] Step 3: Self-assembly of DNA rectangular template and DNA-IONPs.

[0065] The incubation reaction was carried out using the same particle concentration (excess particle concentration) and template concentration as in Example 1.

[0066] The self-assembled structures after incubation were characterized by AFM, such as... Figure 8 As shown, the results indicate that four DNA-IONPs were successfully loaded on both sides of the narrow side of the rectangular DNA template. The average height of this self-assembled structure is 5.5 nm, with an average template height of 1.5 nm and a height difference of 4 nm. The long axis spacing between particles is 160 nm, while the short axis spacing is affected by particle size and interparticle interactions, ranging from 14 to 22 nm. Due to the magnetic interactions between Fe3O4 nanoparticles and their tendency to aggregate, some templates only have one large aggregated particle, affecting their distribution uniformity.

[0067] Comparative Example 1 The iron oxide particles (Fe3O4 particles) in this comparative example were not purified from free DNA.

[0068] This comparative example is based on the scheme of Example 1, with the only difference being that the iron oxide particles are not purified by ultrafiltration and centrifugation, while the other steps remain unchanged.

[0069] When unpurified iron oxide particles are directly mixed and incubated with a DNA template, the free strands in the iron oxide particles occupy the binding sites on the rectangular template, preventing the particles from attaching to the template surface. (Reference) Figure 9As shown, in the dried sample characterized by AFM, after the free strand binds to the template, the AFM characterization height in the center of the template is 0.8 nm, which is consistent with the width of the double helix DNA in the dried sample. This indicates that the free strand and the extended strand undergo base pairing, which hinders the self-assembly process of the particles and the template.

[0070] 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 the self-assembly preparation of a sub-10 nm catalyst, characterized in that, Includes the following steps: S1: Pre-treated DNA-modified Fe3O4 particles to remove free DNA strands; S2: The scaffold DNA, short-chain DNA, and extended-chain DNA are mixed in a buffer solution and annealed to self-assemble into a DNA template; wherein, the extended-chain DNA extends from the DNA template, and the DNA sequence of the extended-chain DNA is complementary to the DNA sequence of the DNA-modified Fe3O4 particles. S3: DNA-modified Fe3O4 particles and DNA template are mixed in an incubation solution and incubated together. Based on the principle of complementary base pairing, the DNA-modified Fe3O4 particles are fixed on the DNA template by the arrangement of extended strand DNA, thus obtaining a sub-10 nm catalyst.

2. The method for self-assembly preparation of a sub-10 nanometer catalyst according to claim 1, characterized in that, In step S1, the pretreatment is as follows: the DNA-modified Fe3O4 particles are purified by ultrafiltration centrifugation.

3. The method for self-assembly preparation of a sub-10 nanometer catalyst according to claim 1, characterized in that, In step S1, the DNA-modified Fe3O4 particles contain: Fe3O4 particles have a diameter of less than 10 nanometers; The sequence of the DNA signature strand is: 5'(NH2)-TTCCTCTACCACCTACAT-3'.

4. The method for self-assembly preparation of a sub-10 nm catalyst according to claim 1, characterized in that, In step S2, the length of the scaffold DNA is 10004 bases, the length of the short-chain DNA is less than 70 bases, and the length of the extended-chain DNA is less than 90 bases. The buffer solution contains 1×TAE and 12.5 mM MgAC2, and the pH is adjusted to 9.0 using Tris. The scaffold DNA has a concentration of 10 nM in the buffer, the short-chain DNA has a concentration of 40 nM in the buffer, and the extended-chain DNA has a concentration of 40 nM in the buffer.

5. The method for self-assembly preparation of a sub-10 nm catalyst according to claim 1, characterized in that, In step S2, the annealing self-assembly is performed as a stepped annealing procedure: First, the temperature is raised to 80℃; then it is gradually cooled to 60℃, and each temperature is maintained for >2 min; then it is gradually cooled to 25℃, and each temperature is maintained for >1 h; and the total time for annealing self-assembly is 40~200 h.

6. The method for self-assembly preparation of a sub-10 nm catalyst according to claim 1, characterized in that, In step S3, the amount of DNA-modified Fe3O4 particles mixed in excess with the amount of extended strand DNA on the DNA template. The incubation solution contains 1×TAE and 12.5 mM MgAC2, and the pH is adjusted to 9.0 using Tris.

7. The method for self-assembly preparation of a sub-10 nanometer catalyst according to claim 1, characterized in that, In step S3, the incubation reaction undergoes an annealing process: First, raise the temperature to 35℃ and hold for 1 hour; then gradually lower the temperature to 20℃ at a rate of 1℃ / h.

8. A sub-10 nanometer catalyst, characterized in that, It is obtained by the self-assembly preparation method as described in any one of claims 1 to 7; The sub-10 nanometer catalyst comprises a DNA template and at least one DNA-modified Fe3O4 particle attached to the DNA template. The connection of DNA-modified Fe3O4 particles to a DNA template is achieved through complementary base pairing between the characteristic DNA strand on the surface of the DNA-modified Fe3O4 particles and the extended DNA strand on the DNA template.

9. A sub-10 nanometer catalyst according to claim 8, characterized in that, The extended strand of DNA is located at the center and / or side of the surface of the DNA template; In the DNA template, one column of bases is deleted every 64 base pairs along the long axis.

10. The application of a sub-10 nanometer catalyst as described in claim 8 or 9 in the fabrication of CNT devices.

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