A method for solvent-free preparation of nonlinear optical microcrystal array

Abstract

This invention provides a solvent-free method for preparing nonlinear optical micro-crystal arrays. A substrate is placed on top of a silicon pillar template. A raw material tank is positioned on one side of the upper part of the silicon pillar template, and a through-hole is positioned on one side of the substrate, with the raw material tank and through-hole corresponding in position. Powdered organic small molecules are added to the raw material tank through the through-hole. The temperature is increased; when the temperature exceeds the melting point of the organic small molecules, a sandwich structure is formed consisting of the substrate, the melt of the organic small molecules, and the upper surface of the silicon pillar. Driven by capillary force, the melt flows along the top of the silicon pillar until it covers the entire surface of the silicon pillar template. The temperature is then decreased; when the temperature falls below the solidification point of the organic small molecules, it is further cooled to room temperature, opening the sandwich structure and obtaining a nonlinear optical micro-crystal array on the substrate. The processing precision of the micro-crystal array in this invention is controlled by the size of the silicon pillar, achieving a precision of 1 μm. This provides a new approach for the array-based preparation of nonlinear organic microcrystals and their application in nonlinear optics and microelectronic circuits.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and specifically to a method for preparing nonlinear optical micro single-crystal arrays without solvents. Background Technology

[0002] The preparation of regularly arranged, single-crystal organic small molecule microstructures is one of the indispensable technologies for manufacturing electronic and optoelectronic components.

[0003] In recent years, various solution processing methods have been used to achieve the array-based preparation of small organic molecule materials, such as inkjet printing, microimprinting, capillary bridge induction, dip pen printing, and shear coating. These methods achieve the localized growth of small organic molecules by arraying microliquids, thereby precisely controlling the position and morphology of the small organic molecules.

[0004] However, the organic solvents used in these methods are harmful to the environment, the solubility of small molecules varies greatly in different solvents, and the single crystal properties of the arrays prepared due to the coffee ring effect caused by solvent evaporation cannot be guaranteed. These traditional methods for preparing small molecule single crystal arrays in liquid phase have great limitations. In particular, the liquid phase method cannot process insoluble materials.

[0005] Therefore, there is a need to provide a new, universal, simple, and efficient method for preparing organic micro single-crystal arrays. Summary of the Invention

[0006] This invention aims to solve the problem of preparing micron-sized organic small molecule structures by providing a solvent-free method for preparing nonlinear optical micro-single crystal arrays. By designing a silicon pillar template with a specially shaped micropillar array structure, the fluid after the small molecules melt can flow directionally along the top of the silicon pillar template due to capillary forces. After the temperature is reduced, the small molecule melt will return to a solid state from a fluid state and have good crystallinity. Thus, a regularly arranged, size-controllable micron-sized linear array of small molecules can be realized on the substrate and used for the generation of second harmonics in the field of nonlinear optics.

[0007] This invention provides a solvent-free method for fabricating nonlinear optical micro single-crystal arrays, comprising the following steps:

[0008] S1. Place the silicon pillar template on the experimental table, and place the substrate on top of the silicon pillar template. The silicon pillar template is prepared by photolithography and has a periodically repeating structure on its surface. A raw material tank is set on one side of the upper part of the silicon pillar template, and a through hole is set on one side of the substrate. The positions of the raw material tank and the through hole correspond.

[0009] S2. Add the powder of small organic molecules into the raw material tank through the through hole;

[0010] S3. Increase the temperature. When the temperature is higher than the melting point of the organic small molecules but lower than the decomposition temperature, the substrate, the melt of the organic small molecules and the upper surface of the silicon pillar form a sandwich structure. The melt flows along the top of the silicon pillar under the drive of capillary force until it covers the entire surface of the silicon pillar template.

[0011] S4. Lower the temperature. When the temperature is below the freezing point of the organic small molecules, lower it to room temperature to open the sandwich structure and obtain a nonlinear optical micro single crystal array on the substrate.

[0012] In a preferred embodiment of the solvent-free method for fabricating nonlinear optical micro single-crystal arrays described in this invention, in step S1, platforms are set at both ends of the silicon pillar template, with the platforms located on both sides of the top of the silicon pillar, and a raw material tank is set in the middle of the platform, with a diameter of 1 to 3 mm.

[0013] In a preferred embodiment of the solvent-free method for fabricating nonlinear optical micro single-crystal arrays described in this invention, the silicon pillar in step S1 is any of the following shapes: straight, curved, circular, triangular, square, and Y-shaped.

[0014] The top of the silicon pillar is hydrophilic, while the sides are hydrophobic.

[0015] In the solvent-free method for fabricating nonlinear optical micro single-crystal arrays according to the present invention, as a preferred embodiment, in step S1, the width of the silicon pillars is 2-100 μm, and the spacing between adjacent silicon pillars is 5-100 μm.

[0016] The method for preparing a nonlinear optical micro single-crystal array without solvent according to the present invention, as a preferred embodiment, in step S1, the substrate is any one of the following: silicon wafer, silicon dioxide wafer, glass sheet, quartz sheet, indium tin oxide conductive glass, polyethylene terephthalate, and polyimide.

[0017] In the solvent-free method for preparing nonlinear optical micro single-crystal arrays described in this invention, as a preferred embodiment, in step S2, the decomposition temperature of the organic small molecules is greater than their melting point temperature.

[0018] In the solvent-free method for preparing nonlinear optical micro single-crystal arrays according to the present invention, as a preferred embodiment, in step S2, the organic small molecule is any one of the following: DAT2 small molecule, MLS small molecule, DLS small molecule and OH1 small molecule.

[0019] In the solvent-free method for preparing nonlinear optical micro single-crystal arrays described in this invention, as a preferred embodiment, the amount of organic small molecules added in step S2 is 1-100 mg.

[0020] In a preferred embodiment of the solvent-free method for preparing nonlinear optical micro single-crystal arrays described in this invention, in step S3, the heating temperature is 100–500°C to allow the organic small molecules to reach their melting point and become fluids.

[0021] In a preferred embodiment of the solvent-free method for preparing nonlinear optical micro single-crystal arrays described in this invention, in step S4, the temperature is first slowly lowered to the solidification point of the organic small molecules, and then rapidly lowered to room temperature after the organic small molecules have become crystals.

[0022] A solvent-free method for fabricating nonlinear optical micro single-crystal arrays includes the following steps:

[0023] Small molecule powder is added into the pores of a silicon pillar template through perforated quartz sheets. The temperature is increased; when the temperature exceeds the melting point of the small molecules, they transform from a solid to a liquid. The quartz sheet, silicon pillars, and molten small molecules form a sandwich structure. Due to capillary forces, the melt flows along the top of the silicon pillars until it covers the entire template. The temperature is then slowly lowered; when it falls below the freezing point of the small molecules, they begin to crystallize. Ultimately, a regularly arranged array of small molecule micrometer-sized wires is obtained on the substrate. Figure 1 As shown.

[0024] Traditional methods for preparing single-crystal arrays of small organic molecules generally involve liquid-phase processing. Small molecules are dissolved in an organic solvent to form a solution of a certain concentration, and then liquid arrays are prepared using methods such as inkjet printing, blade coating, or dip pen printing. As the solvent evaporates, the solution concentration reaches saturation, and the small molecules begin nucleation and growth, eventually forming an array. However, these methods have significant drawbacks: crystal quality cannot be guaranteed, most organic solvents are harmful to health and cause environmental pollution, and some small molecules have very low solubility, making liquid-phase methods unable to process small molecules that are insoluble in organic solvents. The preparation method provided in this invention uses a melt method. The temperature is raised above the melting point of the small molecules, causing them to transform from a solid to a liquid. The quartz sheet, silicon pillars, and the molten small molecules form a sandwich structure. The melt flows along the top of the silicon pillars until it covers the entire silicon pillar template. Slow cooling allows the small molecules to crystallize, ultimately resulting in a regularly arranged micron-sized array of small molecules on the substrate. The processing time is also significantly shorter than the liquid-phase method, and it enables the preparation of large-area small-molecule single-crystal arrays, such as... Figure 5 As shown.

[0025] The width of a single column is 2 to 100 μm, the spacing between adjacent columns is 5 to 100 μm, the top of the silicon column has a large platform for easy flow, and the middle part has a small hole with a diameter of 1 to 3 mm for storing solid powder and molten fluid.

[0026] Preferably, the organic small molecule requires a decomposition temperature (T). d ) greater than melting point temperature (T)m ), selected from, but not limited to, one of DAT2, OH1, DLS, and MLS.

[0027] Preferably, the mass of the organic small molecule is 1-100 mg.

[0028] Preferably, the substrate is selected from one of silicon wafers, silicon dioxide wafers, and quartz wafers.

[0029] Preferably, the heating temperature is 100-500℃ to ensure that the small molecules reach their melting point and become a fluid. (Heating temperature T is between T...) d >T>T m )

[0030] Preferably, the template has a micropillar array structure, wherein the width of a single pillar is 2-100 μm, the spacing between adjacent pillars is 5-100 μm, the top of the silicon pillar has a large platform, and the middle part has a small hole with a diameter of 1-3 mm, as illustrated below. Figure 3 As shown.

[0031] The present invention has the following advantages:

[0032] This invention involves adding small molecule powder through small holes in a quartz crystal into the gaps between pre-designed silicon pillar templates. The silicon pillar template and the quartz sheet form a sandwich structure. This sandwich structure is placed on a heating device, and the temperature is increased. When the temperature exceeds the melting point of the small molecules, the melt flows along the top of the silicon pillars until it covers the entire template. The temperature is then slowly lowered until it falls below the freezing point of the small molecules, resulting in a regularly arranged micron-sized array of small molecules on the substrate. Compared to traditional liquid-phase methods for preparing organic small molecule arrays, this method ensures crystal quality, avoids the harm to health and the environment caused by organic solvents, and enables the array-based preparation of small molecules that are insoluble in organic solvents. This preparation method provides a new approach for the array-based preparation of other organic small molecules and their application in nonlinear optics and microelectronic circuits. Attached Figure Description

[0033] Figure 1 Example 2: Optical microscope image of an organic micro-single crystal array, illustrating a method for solvent-free fabrication of nonlinear optical micro-single crystal arrays.

[0034] Figure 2 Scanning electron microscope image of a silicon pillar template structure for a solvent-free method of fabricating nonlinear optical micro single-crystal arrays;

[0035] Figure 3 A schematic diagram of a sandwich structure for a solvent-free method of fabricating nonlinear optical micro single-crystal arrays;

[0036] Figure 4This is a schematic diagram of the small molecule fluid movement process after melting during the fabrication of a solvent-free method for preparing nonlinear optical micro single-crystal arrays.

[0037] Figure 5 An optical microscope image of a large-area organic micro-crystal array prepared in Example 2 of a method for preparing nonlinear optical micro-crystal arrays without solvents.

[0038] Figure 6a The chemical structure diagram of the small molecule in Example 2 of a method for preparing nonlinear optical micro single-crystal arrays without solvents;

[0039] Figure 6b The chemical structure diagram of the small molecule in Example 3 of a method for preparing nonlinear optical micro single-crystal arrays without solvents;

[0040] Figure 6c The chemical structure diagram of the small molecule in Example 4 of a method for preparing nonlinear optical micro single-crystal arrays without solvents;

[0041] Figure 6d The chemical structure diagram of the small molecule in Example 5 of a method for preparing nonlinear optical micro single-crystal arrays without solvents;

[0042] Figure 7 Example 2 illustrates a method for preparing nonlinear optical micro single-crystal arrays without solvents, where a small molecule single-crystal array is prepared to generate frequency doubling diagrams at different wavelengths. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0044] Example 1

[0045] A solvent-free method for fabricating nonlinear optical micro single-crystal arrays includes the following steps:

[0046] S1, such as Figure 3 As shown, a silicon pillar template is placed on the experimental stage, and the substrate is placed on top of the silicon pillar template. The silicon pillar template is prepared by photolithography and has a periodically repeating structure on its surface. A raw material tank is set on one side of the upper part of the silicon pillar template, and a through hole is set on one side of the substrate. The positions of the raw material tank and the through hole correspond.

[0047] Platforms are set at both ends of the silicon pillar template, with the platforms located on both sides of the top of the silicon pillar. The raw material tank is set in the middle of the platform, and the diameter of the raw material tank is 1-3mm.

[0048] like Figure 2As shown, the silicon pillars can be any of the following shapes: straight, curved, circular, triangular, square, and Y-shaped; the top of the silicon pillar is hydrophilic and the sides are hydrophobic; the width of the silicon pillar is 2 to 100 μm, and the spacing between adjacent silicon pillars is 5 to 100 μm.

[0049] The substrate can be any of the following: silicon wafer, silicon dioxide wafer, glass sheet, quartz sheet, indium tin oxide conductive glass, polyethylene terephthalate, and polyimide;

[0050] S2. Add the powder of small organic molecules into the raw material tank through the through hole;

[0051] The decomposition temperature of small organic molecules is greater than their melting point temperature;

[0052] The organic small molecule is any one of the following: DAT2 small molecule, MLS small molecule, DLS small molecule and OH1 small molecule; the amount of organic small molecule added is 1 to 100 mg;

[0053] S3, such as Figure 4 As shown, when the temperature is increased, when the temperature is higher than the melting point of the organic small molecules but lower than the decomposition temperature, the substrate, the melt of the organic small molecules and the upper surface of the silicon pillar form a sandwich structure. The melt flows along the top of the silicon pillar under the drive of capillary force until it covers the entire surface of the silicon pillar template.

[0054] The heating temperature is 100–500℃ to bring the small organic molecules to their melting point and make them fluid;

[0055] S4. First, slowly cool down to the freezing point of the organic small molecules. After the organic small molecules become crystals, quickly cool down to room temperature to open the sandwich structure and obtain a nonlinear optical micro single crystal array on the substrate.

[0056] Example 2

[0057] A solvent-free method for fabricating nonlinear optical micro single-crystal arrays includes the following steps:

[0058] 1) Sonicate the quartz substrate with acetone, ethanol and isopropanol solutions for ten minutes each, clean it and then blow it dry with nitrogen.

[0059] 2) such as Figure 3 As shown, a quartz sheet is placed on top of a silicon pillar template, with the holes on the quartz sheet aligned with the small holes in the silicon pillar template below, to facilitate the addition of small molecule powders. The silicon pillar template is 4 μm wide, and the spacing between adjacent pillars is 20 μm.

[0060] 3) Add 30mg of DAT2 small molecule powder (molecular formula as follows) Figure 6a (As shown) Use the small key to insert into the small hole.

[0061] 4) such as Figure 4As shown, heat the entire system in step 3) above to 260 °C, but note that it is below 293 °C. The melting point of DAT2 is 235 °C and the decomposition temperature is 293 °C.

[0062] 5) Keep the system in step 4) above at 260 °C for 5 - 20 min to allow the fluid to flow fully until it covers the entire surface of the silicon column.

[0063] 6) Slowly cool down to 200 °C. After the fluid completely turns into crystals, quickly cool it down to room temperature. Disassemble the sandwich system, and a single crystal array is successfully prepared on the quartz substrate. The silicon column template can be reused.

[0064] 7) Use a femtosecond laser with a tunable wavelength as the light source. Second harmonic peaks corresponding to wavelengths from 740 nm to 900 nm can be observed, as Figure 7 shown, indicating that the prepared micron - wire single crystal array has good quality and can be used for second - harmonic generation.

[0065] In this embodiment, through the Figure 2 silicon column template shown, a threshold space for directional flow is provided for the molten organic small - molecule fluid. After cooling, the fluid will solidify into small - molecule solids (single crystals), and thus an orderly arranged organic micro - single crystal array is obtained, as Figure 1 and 5 shown. At the same time, the crystals of the micron - wires prepared in this invention have good quality and controllable size. Organic small - molecule single crystal arrays with corresponding sizes can be prepared by designing the sizes of the corresponding templates.

[0066] Example 3

[0067] A method for solvent - free preparation of non - linear optical micro - single crystal arrays, comprising the following steps:

[0068] 1) Ultrasonic clean the quartz substrate in acetone, ethanol, and isopropanol solutions for 10 minutes each. After cleaning, dry it with nitrogen.

[0069] 2) As Figure 3 shown, cover the quartz wafer on the silicon column template. Align the holes on the quartz wafer with the small holes of the silicon column template below to facilitate adding small - molecule powder. The width of the silicon column template is 4 μm, and the distance between adjacent columns is 20 μm.

[0070] 3) Add 20 - 30 mg of MLS small - molecule powder (the molecular formula is as Figure 6b shown) to the small holes using a small key.

[0071] 4) As Figure 4 shown, heat the entire system in step 3) above to 180 °C, but note that it is below 253 °C. The melting point of MLS is 166 °C and the decomposition temperature is 253 °C.

[0072] 5) Keep the system in 4) above at 180℃ for 5-20 minutes to allow the fluid to flow fully and cover the entire surface of the silicon pillar.

[0073] 6) Slowly cool down to 140°C. After the fluid has completely turned into crystals, quickly cool down to room temperature. Disassemble the sandwich system. The single crystal array was successfully fabricated on the quartz substrate. The silicon pillar template can be reused.

[0074] In this embodiment, by Figure 2 The silicon pillar template shown provides a confined space for the directional flow of the molten organic small molecule fluid. After cooling, the fluid will solidify into a small molecule solid (single crystal), thus obtaining a neatly arranged array of organic micro single crystals.

[0075] Example 4

[0076] A solvent-free method for fabricating nonlinear optical micro single-crystal arrays includes the following steps:

[0077] 1) Sonicate the quartz substrate with acetone, ethanol and isopropanol solutions for ten minutes each, clean it and then blow it dry with nitrogen.

[0078] 2) such as Figure 3 As shown, a quartz sheet is placed on top of a silicon pillar template, with the holes on the quartz sheet aligned with the small holes in the silicon pillar template below, to facilitate the addition of small molecule powders. The silicon pillar template is 4 μm wide, and the spacing between adjacent pillars is 20 μm.

[0079] 3) Add 10-30 mg of DLS small molecule powder (molecular formula as follows) Figure 6c (As shown) Use the small key to insert into the small hole.

[0080] 4) such as Figure 4 As shown, the entire system in 3) above is heated to 200°C, but note that it is below 253°C. The melting point of MLS is 185°C and the decomposition temperature is 253°C.

[0081] 5) Keep the system in 4) above at 200℃ for 5 to 20 minutes to allow the fluid to flow fully and cover the entire surface of the silicon pillar.

[0082] 6) Slowly cool down to 160°C. After the fluid has completely turned into crystals, quickly cool down to room temperature. Disassemble the sandwich system. The single crystal array was successfully fabricated on the quartz substrate. The silicon pillar template can be reused.

[0083] In this embodiment, by Figure 2 The silicon pillar template shown provides a confined space for the directional flow of the molten organic small molecule fluid. After cooling, the fluid will solidify into a small molecule solid (single crystal), thus obtaining a neatly arranged array of organic micro single crystals.

[0084] Example 5

[0085] A solvent-free method for fabricating nonlinear optical micro single-crystal arrays includes the following steps:

[0086] 1) Sonicate the quartz substrate with acetone, ethanol and isopropanol solutions for ten minutes each, clean it and then blow it dry with nitrogen.

[0087] 2) such as Figure 3 As shown, a quartz sheet is placed on top of a silicon pillar template, with the holes on the quartz sheet aligned with the small holes in the silicon pillar template below, to facilitate the addition of small molecule powders. The silicon pillar template is 4 μm wide, and the spacing between adjacent pillars is 20 μm.

[0088] 3) Add 10-30 mg of OH1 small molecule powder (molecular formula as shown) Figure 6d (As shown) Use the small key to insert into the small hole.

[0089] 4) such as Figure 4 As shown, the entire system in 3) above is heated to 240°C, but note that it is below 325°C. The melting point of OH1 is 212°C and the decomposition temperature is 325°C.

[0090] 5) Keep the system in 4) above at 240℃ for 5 to 20 minutes to allow the fluid to flow fully and cover the entire surface of the silicon pillar.

[0091] 6) Slowly cool down to 180°C. After the fluid has completely turned into crystals, quickly cool down to room temperature, disassemble the sandwich system, and the single crystal array has been successfully fabricated on the quartz substrate. The silicon pillar template can be reused.

[0092] In this embodiment, by Figure 2 The silicon pillar template shown provides a confined space for the directional flow of the molten organic small molecule fluid. After cooling, the fluid will solidify into a small molecule solid (single crystal), thus obtaining a neatly arranged array of organic micro single crystals.

[0093] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for solvent-free fabrication of nonlinear optical micro single-crystal arrays, characterized in that: Includes the following steps: S1. Place the silicon pillar template on the experimental table, and place the substrate on top of the silicon pillar template. The silicon pillar template is prepared by photolithography and has periodically repeating silicon pillars on its surface. Platforms are set on both sides of the top of the silicon pillars, and raw material tanks are set on the platforms. A through hole is set on one side of the substrate, and the positions of the raw material tanks and the through holes correspond. The top of the silicon pillar is hydrophilic and the sides are hydrophobic. S2. The organic small molecule powder is added to the raw material tank through the through hole; the decomposition temperature of the organic small molecule is greater than the melting point temperature, and the organic small molecule is any one of the following: DAT2 small molecule, MLS small molecule, DLS small molecule and OH1 small molecule; S3. Increase the temperature. When the temperature is higher than the melting point of the organic small molecules but lower than the decomposition temperature, the organic small molecules reach the melting point and become a fluid. The silicon pillar provides a confined space for the directional flow of the molten organic small molecule fluid. The melt flows along the top of the silicon pillar under the drive of capillary force until it covers the entire surface of the silicon pillar template. The substrate, the melt of the organic small molecules and the upper surface of the silicon pillar form a sandwich structure. S4. Lower the temperature. When the temperature is lower than the freezing point of the organic small molecules, lower the temperature to room temperature and open the sandwich structure to obtain a nonlinear optical micro single crystal array on the substrate that corresponds to the shape and position of the top of the silicon pillar. The silicon pillar template can be reused.

2. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S1, the raw material tank is located in the middle of the platform, and the diameter of the raw material tank is 1~3 mm.

3. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S1, the silicon pillar can be any of the following shapes: straight, curved, circular, triangular, square, and Y-shaped.

4. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S1, the width of the silicon pillar is 2~100 μm, and the spacing between adjacent silicon pillars is 5~100 μm.

5. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S1, the substrate is any one of the following: silicon wafer, quartz wafer, indium tin oxide conductive glass, polyethylene terephthalate, and polyimide.

6. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S2, the amount of the organic small molecule added is 1~100mg.

7. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S3, the heating temperature is 100~500℃ to make the organic small molecules reach their melting point and become fluid.

8. The method for solvent-free fabrication of nonlinear optical micro single-crystal arrays according to claim 1, characterized in that: In step S4, the temperature is first slowly lowered to the freezing point of the organic small molecules, and then rapidly lowered to room temperature after the organic small molecules turn into crystals.

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