A controllable assembly method for nanoparticles

Abstract

This disclosure discloses a method for controllable nanoparticle assembly. This method achieves controllable self-assembly of nanoparticles by constructing a "sandwich" structure consisting of a patterned silicon substrate, a mixed colloidal solution of nanoparticles and a surfactant, and a flat substrate. The large surface energy difference between the superhydrophobic structured silicon substrate and the superhydrophobic flat substrate allows the mixed colloidal solution to form micrometer-scale liquid bridges at the interface between the two substrates, inducing the directional assembly of the nanoparticles. The liquid bridges shrink, allowing the nanoparticles to form a large, regular nanostructure, resulting in a self-assembled structure of any shape on the upper substrate, similar to the silicon substrate.

Description

Technical Field

[0001] The present disclosure relates to the self-assembly of nanoparticles, belongs to the field of nanotechnology, and aims to provide a general method for controllable and orderly assembly of nanoparticles. Background Art

[0002] Since its inception, nanotechnology has had a revolutionary impact on human production and life. With the deepening of research and the continuous advancement of science and technology, nanotechnology has become crucial in modern science. As a new type of material, nanoparticles, due to their unique nanoscale characteristics, retain their inherent properties while exhibiting excellent properties in magnetism, conductivity, catalysis, and adsorption. They are widely used in optics, electronics, and biomedicine. Nanoparticle self-assembly is a crucial prerequisite for their application. Nanoparticle self-assembly involves arranging or stacking nanoparticles in a specific order through physical, chemical, or other methods to form ordered arrays with specific functions, achieving properties that differ from those of traditional materials. However, due to the wide variety of nanoparticles, synthesized nanoparticles suffer from poor monodispersity and uncontrollable particle size. Therefore, nanoparticle self-assembly technology has long been a hot topic of research. Existing nanoparticle self-assembly techniques include inkjet printing, template polymerization, imprinting, and interface induction methods. These techniques have broad application prospects and important research implications in lasers, solar cells, photocatalysis, and various optical devices.

[0003] However, existing methods for self-assembly of nanoparticles still have the following problems: the preparation process is complex and the cost is high; it is not conducive to large-scale, patterned assembly of nanoparticles; nanoparticles are difficult to transfer, and high requirements are placed on the monodispersity and regularity of nanoparticles. These difficulties need to be addressed. Summary of the Invention

[0004] The technical problem to be solved by the present disclosure is to design a "sandwich" structure based on wettability in response to the above-mentioned deficiencies in the prior art, and to provide a universal method for controllable assembly of existing nanoparticles.

[0005] To solve the above technical problems, the technical solution adopted by the present disclosure is as follows: The present disclosure provides a general method for controllable assembly of existing nanoparticles. The preparation method includes the following steps:

[0006] preparing a mixed colloidal emulsion formed by nanoparticles and surfactants with appropriate concentrations;

[0007] Super hydrophobic modified structured substrate, super hydrophilic modified upper substrate;

[0008] Constructing a "sandwich" structure of upper substrate-mixed colloidal emulsion-structured substrate, and forming a colloidal emulsion liquid bridge between the upper substrate and the mixed colloidal emulsion;

[0009] The colloidal emulsion liquid bridge evaporates and shrinks at a suitable temperature, and is deposited on the upper substrate to form a self-assembled three-dimensional structure of nanoparticles with controllable number of layers, thickness or structure;

[0010] The upper substrate on which the nanoparticles are deposited is peeled off from the gasket and the silicon substrate to obtain a controllable nanoparticle self-assembled three-dimensional structure.

[0011] Optionally, the surfactant includes sodium dodecylbenzenesulfonate (SDBS), sodium dodecylsulfonate (SDS), or Tween 20 or Tween 80; and / or, the concentration range of the surfactant is 0-1%wt.

[0012] Optionally, the nanoparticles include polystyrene (PS), polymethyl methacrylate (PMMA), fluorescent microspheres, silicon dioxide (SiO2), titanium dioxide (TiO2) or quantum dots (QD).

[0013] Optionally, the particle size distribution of the nanoparticles is from several nanometers to several hundred nanometers; and / or the dispersion of the nanoparticles is monodisperse or polydisperse; and / or the shape of the nanoparticles is regular or irregular.

[0014] Optionally, the characteristic size of the structured substrate is 1-10 microns, and the pattern of the structured substrate can be designed as a closed or non-closed pattern.

[0015] Optionally, the upper substrate includes ITO glass, polyacrylic acid (PAA) sheet, PMMA sheet or silicon sheet.

[0016] Optionally, the silicon wafer includes a SiO2@Si silicon wafer on which a SiO2 nanolayer is grown.

[0017] Optionally, it further includes a gasket arranged around the structured substrate; and / or the gasket is a PDMS gasket.

[0018] Optionally, the method further includes the steps of respectively arranging an upper cover sheet and a lower cover sheet above and below the "sandwich" structure.

[0019] Optionally, the method further includes applying pressure through the upper cover sheet and the lower cover sheet.

[0020] Compared with the prior art, the beneficial effect of the present disclosure is that the present disclosure provides a universal method for controllable assembly of existing nanoparticles. The present disclosure has no requirements for the regularity and monodispersity of the nanoparticles, and can form self-assembly under the regulation of appropriate surfactant concentration, which can solve the current situation that self-assembly technology relies on the regularity and monodispersity of nanoparticles. The three-dimensional structure of the nanoparticles formed by self-assembly can be designed and transferred. The number of layers and thickness of the three-dimensional structure of the nanoparticles can be controlled by the thickness of the gasket, the concentration of the nanoparticles and the surfactant, and solve the difficulty of the uncontrollable three-dimensional morphology of the self-assembled nanoparticles in the prior art. In addition, the self-assembly of the nanoparticles is carried out at room temperature, and there is no need to use a constant temperature and humidity chamber, which is low in cost and saves energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the exploded assembly architecture of the sandwich structure constructed for the embodiments of the present disclosure.

[0022] Figure 2 This is a scanning electron microscope image of the layer-controlled assembly method of the annular photonic crystal in Example 1 of the present disclosure.

[0023] Figure 3 These are optical micrographs, fluorescence micrographs, and scanning electron micrographs of the structure-controllable assembly method of polydisperse spherical fluorescent nanoparticles in Example 2 of the present disclosure.

[0024] Figure 4 These are optical micrographs, microfluorescence images, and scanning electron micrographs of the structure-controllable assembly method of polydisperse irregular quantum dots in Example 3 of the present disclosure. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0026] The present disclosure and the methods for implementing the present disclosure may be better understood by referring to the following detailed description of exemplary embodiments and the accompanying drawings. However, the present disclosure may be implemented in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. The same reference numerals may always refer to the same elements. In the accompanying drawings, the thickness of layers and regions may be exaggerated for clarity.

[0027] In order to make the objectives, technical solutions, and advantages of the present disclosure more clearly understood, the present disclosure is described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present disclosure and are not intended to limit the present disclosure. In addition, the technical features involved in the various embodiments of the present disclosure described below may be combined with each other as long as they do not conflict with each other.

[0028] Example 1

[0029] This embodiment is a method for assembling a ring photonic crystal with controllable number of layers, comprising the following steps:

[0030] (1) Take 6 parts of silica nanoparticles with a particle size of 200 nm (monodispersity <5%), ultrasonically disperse them in ultrapure water, and add a small amount of sodium dodecyl sulfate (SDS) to prepare mixed colloidal emulsions of nanoparticles and surfactants with SDS mass concentrations of 0, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt%, respectively, in which the mass percentage of nanoparticles is 10 wt%.

[0031] (2) The structured substrate uses a silicon substrate with a ring array, the inner and outer diameters of the rings are 6 microns and 10 microns respectively, and the center distance between the rings is 20 microns. The upper substrate is, for example, a flat silicon wafer. The ring-shaped silicon substrate is first washed with ethanol and acetone to remove the impurities such as the photoresist remaining on the surface during wet etching, and the flat silicon wafer is cleaned according to the normal process. The two substrates are subjected to different surface treatments to control their wettability. Among them, the flat silicon wafer is treated with oxygen plasma at a power of 200 watts and a treatment time of 5 minutes, and the contact angle of the flat substrate is close to 0°. After the structured substrate silicon substrate is treated with oxygen plasma with the same parameters, it is modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (fluorosilane) to form a superhydrophobic silicon substrate with a contact angle of 150.0±0.8°.

[0032] (3) Constructing a "sandwich" structure formed by the upper substrate 2-mixed colloidal emulsion 3-structured substrate 4, forming a colloidal emulsion liquid bridge between the upper substrate 2 and the mixed colloidal emulsion 3; specifically, using a pipette, aspirate 10 μl of the mixed colloidal emulsion of the six nanoparticles and SDS configured in step (1) respectively, and drop it into the annular structured substrate 4; wherein the structured substrate 4 can also be embedded in the PDMS gasket 5, specifically, the PDMS gasket 5 is, for example, an annular gasket arranged around the structured substrate.

[0033] The structured silicon substrate has a thickness of, for example, 500 microns and is cut into 1 cm x 1 cm squares. The upper substrate can be of any thickness and can be cut into rectangular blocks of, for example, 0.9 cm x 1.4 cm. A polymethyl dimethacrylate (PDMS) spacer is placed between the structured silicon substrate and the upper substrate. It can be cut into 1.2 cm x 1.2 cm squares, for example, with a hollowed-out 1.1 cm x 1.1 cm square in the center. The spacer can be, for example, 550 to 700 microns thick, thus forming a "sandwich" structure.

[0034] Furthermore, the method further includes the steps of arranging an upper cover sheet 1 and a lower cover sheet 6 above and below the "sandwich" structure, clamping the upper cover sheet 1, the "sandwich" structure and the lower cover sheet 6 with a clamp to form an assembly system of the sandwich structure, such as Figure 1 The upper cover sheet 1 and the lower cover sheet 6 are, for example, silicon sheets or glass sheets.

[0035] (4) The sandwich structure assembly system is placed at room temperature (e.g., approximately 20°C) for 48 hours. As the water in the emulsion evaporates, the emulsion shrinks in a certain direction, forming liquid bridges whose positions are strictly controlled by the silicon substrate. These liquid bridges provide isolated, confined spaces for the self-assembly of nanoparticles. After the self-assembly of the nanoparticles is completed, a three-dimensional nanoparticle structure with the same pattern as the silicon substrate can be obtained.

[0036] (5) Remove the sandwich structure fixture in step (4), peel off the upper cover sheet from the silicon substrate and the PDMS gasket, and obtain a ring-shaped assembly structure of silicon dioxide photonic crystals with different stacking layers, such as Figure 2 shown.

[0037] in, Figure 2 Figure 2 shows the effect of adding different concentrations of the surfactant SDS on the number of assembled nanoparticle rings. (a-a1) When no SDS was added, the number of assembled nanoparticle rings was 6; (b-b1) When the concentration of added SDS was 0.2 wt%, the number of assembled nanoparticle rings was 5; (c-c1) When the concentration of added SDS was 0.4 wt%, the number of assembled nanoparticle rings was 4; (d-d1) When the concentration of added SDS was 0.6 wt%, the number of assembled nanoparticle rings was approximately 3; (e-e1) When the concentration of added SDS was 0.8 wt%, the number of assembled nanoparticle rings was 2; (f-f1) When the concentration of added SDS was 1 wt%, the number of assembled nanoparticle rings was 1.

[0038] In this embodiment, the hydrophilic and hydrophobic properties between the nanoparticles are adjusted by adjusting the concentration of the surfactant in the mixed colloidal emulsion formed by the nanoparticles and the surfactant. The higher the concentration, the larger the super-hydrophobic area formed, the greater the repulsion between the nanoparticles, and the larger the distance between them.

[0039] For the three-dimensional structure formed by regular, monodisperse nanoparticles, the number of layers can be controlled, while for the three-dimensional structure formed by irregular, polydisperse nanoparticles, the thickness can be controlled.

[0040] Example 2

[0041] This embodiment provides a method for structure-controlled assembly of polydisperse spherical fluorescent nanoparticles, comprising the following steps:

[0042] (1) Polydisperse spherical fluorescent nanoparticles with an average particle size of 180 nm were ultrasonically dispersed in ultrapure water. Then, a small amount of sodium dodecyl sulfate (SDS) was added to prepare a nanoparticle mass concentration of 10 wt% and an SDS mass concentration of 0.8 wt%. After ultrasonication, a mixed colloidal emulsion dispersion of fluorescent nanoparticles and surfactants was formed.

[0043] (2) Circular, strip, triangular and square silicon substrates with a characteristic size of 2 microns were used. The four silicon substrates were first washed with acetone and ethanol to remove the residual photoresist and other impurities remaining during the etching process. Four flat ITO glasses were cleaned according to the normal process. The two substrates were subjected to different surface treatments to control their wettability. Among them, the ITO glass was treated with oxygen plasma at a power of 200 watts and a treatment time of 5 minutes, and the contact angle of the ITO glass was close to 0°. After the four silicon substrates with different structures were treated with oxygen plasma with the same parameters, they were modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (fluorosilane) to obtain superhydrophobic silicon substrates with a contact angle of 150.0±0.8°.

[0044] (3) Use a pipette to draw 10 μl of the mixed colloidal emulsion dispersion of the nanoparticles and SDS prepared in step (1) and drop it onto the circular, strip, triangular and square silicon substrates embedded in the PDMS pad and placed in the lower cover. Then, cover them with ITO glass and the upper and lower cover plates, and clamp them with a clamp to form a "sandwich" structure assembly system.

[0045] (4) The sandwich structure assembly system was placed at room temperature (approximately 20°C) for 48 hours. As the water in the emulsion evaporates, the emulsion shrinks in a certain direction, forming liquid bridges whose positions are strictly controlled by the silicon substrate. These liquid bridges provide isolated and confined spaces for the self-assembly of nanoparticles. After the nanoparticles are self-assembled, a three-dimensional structure of fluorescent nanoparticles with the same pattern as the silicon substrate can be obtained.

[0046] (5) Remove the "sandwich" structure fixture in step (4), peel off the upper substrate from the silicon substrate and the PDMS gasket, and obtain the assembly structure of fluorescent nanoparticles with different structures. Figure 3 shown.

[0047] Example 3

[0048] This embodiment is a method for structure-controlled assembly of polydisperse irregular quantum dots, comprising the following steps:

[0049] (1) Polydisperse irregular quantum dots with an average particle size of 5 nanometers were ultrasonically dispersed in ultrapure water to form an emulsion. Next, a small amount of sodium dodecyl sulfate (SDS) was added to the emulsion to prepare a nanoparticle concentration of 10 wt% and an SDS concentration of 0.8 wt%. After ultrasonication, a mixed colloidal emulsion dispersion of fluorescent nanoparticles and surfactants was formed.

[0050] (2) Using circular, strip, triangular and square silicon substrates with a characteristic size of 2 microns, the four structural silicon substrates were first washed with acetone and ethanol to remove the residual photoresist and other impurities remaining during the structural etching process. Four flat ITO substrates were cleaned according to the normal process. The two substrates were subjected to different surface treatments to control their wettability. Among them, ITO was treated with oxygen plasma at a power of 200 watts and a treatment time of 5 minutes, resulting in an ITO contact angle close to 0°. After the four silicon substrates with different structures were treated with oxygen plasma with the same parameters, they were modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (fluorosilane) to obtain superhydrophobic silicon substrates with a contact angle of 150.0±0.8°.

[0051] (3) Use a pipette to take 10 μl of the mixed dispersion of quantum dots and SDS prepared in step (1) and drop it onto the circular, strip, triangular and square silicon substrates embedded in the PDMS gasket and placed on the lower cover. Then, cover them with ITO glass and the upper and lower cover plates, and clamp them with a clamp to form a "sandwich" structure assembly system.

[0052] (4) The sandwich structure assembly system is placed at room temperature (approximately 20°C) for 48 hours. As the water in the emulsion evaporates, the emulsion shrinks in a certain direction, forming liquid bridges whose positions are strictly controlled by the silicon substrate. These liquid bridges provide isolated and confined spaces for the self-assembly of nanoparticles. After the nanoparticles are self-assembled, a three-dimensional quantum dot structure with the same pattern as the silicon substrate can be obtained.

[0053] (5) Remove the sandwich structure fixture in step (4), peel off the upper substrate, silicon pillar substrate and PDMS gasket, and obtain the assembly structure of quantum dot nanoparticles with different structures, such as Figure 4 shown.

[0054] This disclosure achieves controllable self-assembly of nanoparticles by constructing a "sandwich" structure. The large surface energy difference between a superhydrophobic structured silicon substrate and a superphilic flat substrate allows a mixed colloidal solution to form a micron-scale liquid bridge at the interface between the two substrates, which induces the directional assembly of nanoparticles. The liquid bridge shrinks, allowing the nanoparticles to form a large-area, regular nanostructure, and a self-assembled structure of any shape, identical to the silicon substrate, is formed on the upper substrate. The patterning of the nanoparticles is controlled by designing the structure of the silicon substrate; the number and thickness of the nanoparticle layers are controlled by adjusting the height of the spacer, the nanoparticle colloid, and the surfactant concentration, thereby precisely controlling the three-dimensional structure of the self-assembled nanoparticles and achieving designable, transferable, and large-area controllable self-assembly of nanoparticles on the substrate. This method addresses key issues existing in nanoparticle deposition processes, such as low efficiency, high cost, and difficulty in controlling the deposition morphology, greatly accommodating the application of nanoparticles in optical wave transmission, electrical components, field-effect transistors, electrodes, and various detectors.

[0055] The embodiments described above are merely descriptions of preferred embodiments of the present disclosure. The preferred embodiments do not exhaust all details, nor do they limit the present invention to the specific embodiments described. Any modifications and improvements to the technical solutions of the present disclosure made by persons of ordinary skill in the art without departing from the spirit of the present disclosure shall fall within the scope of protection defined by the claims of the present disclosure.

Claims

1. A method for controllable self-assembly of nanoparticles, characterized in that: The following steps are involved: preparing a mixed colloidal emulsion formed by nanoparticles and surfactants; Super hydrophobic modified structured substrate, super hydrophilic modified upper substrate; A "sandwich" structure of upper substrate-mixed colloidal emulsion-structured substrate is constructed, and a colloidal emulsion liquid bridge is formed between the upper substrate and the mixed colloidal emulsion; wherein, The structured substrate is embedded in the gasket, and the gasket is arranged around the structured substrate; the upper cover sheet and the lower cover sheet are arranged above and below the "sandwich" structure, and the upper cover sheet, the "sandwich" structure, and the lower cover sheet are clamped with a clamp to form a sandwich structure assembly system; The colloidal emulsion bridge evaporates and shrinks at room temperature and is deposited on the upper substrate to form a nanoparticle self-assembled three-dimensional structure with controllable number of layers, thickness or structure; the number of layers and thickness of the nanoparticle self-assembled three-dimensional structure are controlled by the thickness of the spacer and the concentrations of the nanoparticles and surfactant; The upper substrate on which the nanoparticles are deposited is peeled off from the gasket and the silicon substrate to obtain a controllable nanoparticle self-assembled three-dimensional structure.

2. The method for controllable self-assembly of nanoparticles according to claim 1, characterized in that: The surfactant includes sodium dodecylbenzenesulfonate (SDBS), sodium dodecylsulfonate (SDS), Tween 20 or Tween 80; and / or the concentration range of the surfactant is 0-1%wt.

3. The method for controllable self-assembly of nanoparticles according to claim 1, characterized in that: The nanoparticles include polystyrene (PS), polymethyl methacrylate (PMMA), fluorescent microspheres, silicon dioxide (SiO2), titanium dioxide (TiO2) or quantum dots (QD).

4. The method for controllable self-assembly of nanoparticles according to claim 3, characterized in that: The particle size distribution of the nanoparticles ranges from several nanometers to several hundred nanometers; and / or the dispersion of the nanoparticles is monodisperse or polydisperse; and / or the shape of the nanoparticles is regular or irregular.

5. The method for controllable self-assembly of nanoparticles according to claim 1, characterized in that: The characteristic size of the structured substrate is 1-10 micrometers, and the pattern of the structured substrate can be designed as a closed or non-closed pattern.

6. The method for controllable self-assembly of nanoparticles according to claim 1, characterized in that: The upper substrate includes ITO glass, polyacrylic acid (PAA) sheet, PMMA sheet or silicon sheet.

7. The method for controllable self-assembly of nanoparticles according to claim 6, characterized in that: The silicon wafer includes a SiO2@Si silicon wafer on which a SiO2 nanolayer is grown.

8. The method for controllable self-assembly of nanoparticles according to claim 1, characterized in that: The gasket is a PDMS gasket.

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