阅读说明：本技术 一种单晶铟微米片及其合成方法、应用 (Single crystal indium micron sheet and synthesis method and application thereof ) 是由 胡锦莲 高创 于 2021-08-09 设计创作，主要内容包括：本发明提供一种单晶铟微米片及其合成方法、应用,在有机溶剂中用化学方法合成。本发明所合成的铟微米片由厚度为35～80nm,长度为5～50μm,宽度为0.5～5μm或宽度为5～50μm的单晶铟构成。在惰性气氛下,将铟盐、柠檬酸盐和多元醇混合后,边搅拌边加热溶解,然后在70～150℃或室温下加入还原剂硼氢化盐进行还原反应,最后经快速冷却或直接在室温下,得到单晶铟微米片。本发明制备过程简单,一步湿化学合成结合后续快速冷却,或直接室温还原,实验要求较低,是一种操作方便且绿色环保的制备方法。(The invention provides a single crystal indium micron sheet, a synthesis method and application thereof, wherein the single crystal indium micron sheet is synthesized in an organic solvent by a chemical method. The indium micro-meter sheet synthesized by the invention is composed of single crystal indium with the thickness of 35-80 nm, the length of 5-50 mu m, the width of 0.5-5 mu m or the width of 5-50 mu m. Mixing indium salt, citrate and polyhydric alcohol in an inert atmosphere, heating and dissolving while stirring, then adding a reducing agent borohydride salt at 70-150 ℃ or room temperature for reduction reaction, and finally rapidly cooling or directly cooling at room temperature to obtain the single crystal indium micron sheet. The preparation method is simple in preparation process, low in experimental requirement due to the combination of one-step wet chemical synthesis and subsequent rapid cooling or direct room temperature reduction, and is convenient to operate and environment-friendly.)

1. A single crystal indium micron sheet, characterized in that: the single crystal indium micro-sheet is composed of single crystal indium having a thickness of 35 to 80nm, a length of 5 to 50 μm, a width of 0.5 to 5 μm or a width of 5 to 50 μm.

2. A method for synthesizing a single crystal indium micron sheet as defined in claim 1, wherein: the method comprises the following steps: mixing indium salt, citrate and polyhydric alcohol in an inert atmosphere, heating and dissolving while stirring, then carrying out reduction reaction on borohydride salt serving as a reducing agent at 70-150 ℃, and finally, rapidly cooling to obtain the single crystal indium micron sheet in an organic solvent.

3. The method for synthesizing a single-crystal indium micron sheet according to claim 2, wherein: the indium salt is indium chloride or indium nitrate or indium sulfate; the borohydride is sodium borohydride or potassium borohydride or lithium triethylborohydride; the citrate is disodium citrate, trisodium citrate or potassium citrate; the polyalcohol is diethylene glycol or tetraethylene glycol or ethylene glycol.

4. The method for synthesizing a single-crystal indium micron sheet according to claim 2, wherein: of the borohydride and indium salts, BH^4-And In³⁺The molar ratio of (1.5-2.5) to (1).

5. The method for synthesizing a single-crystal indium micron sheet according to claim 2, wherein: the mol ratio of the indium salt to the citrate is preferably (0.5-3): 1.

6. the method for synthesizing a single-crystal indium micron sheet according to claim 2, wherein: the reduction reaction time is 20 s-1 h.

7. The method for synthesizing a single-crystal indium micron sheet according to claim 2, wherein: the rapid cooling is that the cooling speed of the first ten minutes is not lower than 2 ℃/min.

8. The method for synthesizing a single-crystal indium micron sheet according to claim 7, wherein: the rapid cooling is cooling in water at 0-30 ℃.

9. A method for synthesizing a single crystal indium micron sheet as defined in claim 1, wherein: the method comprises the following steps: in an inert atmosphere, mixing indium salt, citrate and polyhydric alcohol, stirring and heating to dissolve, cooling to room temperature, adding borohydride solution at room temperature, and directly reducing at room temperature to obtain the single crystal indium micron sheet.

10. An application of the single crystal indium micro-meter sheet of claim 1 in the fields of micro-nano welding, vacuum sealing tabletting, electric conducting ink, micro-electrode, heat conducting ink, microfluid, flexible micro-nano photoelectric device and photocatalysis.

Technical Field

The invention belongs to the technical field of micro-nano material preparation and application, and particularly relates to a method for preparing single crystal indium micro-tablets.

Background

The indium is a low-melting-point metal, has good electric conduction and heat conduction performance, excellent photoelectric performance and excellent flexibility, and the micron sheet has important application prospect in the fields of micro-nano welding, electric conduction ink, micro-electrode, heat conduction ink, microfluid and flexible micro-nano photoelectric devices.

Indium metal is not only flexible, but also has strong adhesion with most substrates, and is commonly used as a vacuum sealing material of high-end devices. Therefore, the micron sheet can be used as a vacuum sealing tabletting of the micro-nano device. However, to date, there has been no literature report of large area single crystal indium micron sheets synthesized in solvents.

Indium metal can be oxidized to form indium oxide, which is a transparent semiconductor material. It is reacted with SnO₂Mixing to form Indium Tin Oxide (ITO). Therefore, the indium microchip can have potential application in the fields of flexible photoelectric devices, optical sensing, conductive glass, photocatalysis and the like after oxidation or other combination reactions.

Through retrieval, Chinese patent application No. 201210348342.3, 2013, 1 month and 2 days, discloses a solvothermal method for synthesizing nano flower spherical In₂Se₃The method of (DETA) hybrid material comprises the steps of taking indium salt and selenium powder as reactants, taking Diethylenetriamine (DETA) and Ethylene Glycol (EG) as solvents, carrying out solvothermal reaction in a reaction kettle with a polytetrafluoroethylene lining, washing, separating and drying in vacuum to obtain the product. However, this patent can only form semiconductor compounds, and cannot form single crystal metallic indium micro-slabs of larger size.

For another example, chinese patent application No. 201711085500.X, 2018, 3/27/s discloses a method for preparing single crystal indium nanowires, and a product and an application thereof, in which a zinc sheet and an indium source are used as precursors, a sulfur source is used as an adjuvant, and the single crystal indium nanowires wrapped by a layer of sulfide can be prepared by controlling the temperature and time of solvothermal treatment. However, the synthesis method is complex, the required reaction conditions are high, the product is wrapped by sulfide, the width of the nanowire is only 0.2 μm, a wider single crystal indium micron sheet cannot be synthesized, and the width cannot reach several microns.

To date, researchers have synthesized spherical indium nanoparticlesParticles, triangular and polygonal nanoparticles, and nanowires. However, no report has been found on the synthesis of large-area single-crystal indium micro-chips with large width in an organic solvent. In general, it is easier to synthesize larger areas of single-crystal nanoplatelets of oxides and other covalent compounds in chemical solvents because of some covalent species (ZnO and PbS)₂Etc.) are relatively easy to crystallize to form a large-area single crystal, but it is not easy to obtain a large-area single-crystal metal micro-flake in a solvent. Therefore, how to obtain a wide single crystal indium micron sheet with a large area is a problem which needs to be solved at present.

Disclosure of Invention

1. Problems to be solved

Aiming at various problems in the prior art, the invention provides the single crystal indium micron sheet, which can obtain a large-area single crystal indium micron sheet with micron-sized width in an organic solvent, and has good flexibility and strong adhesion with a substrate; meanwhile, the synthesis method is simple, green and environment-friendly, can be used for producing the single crystal indium micron sheet in a large scale, and has wide application prospect.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a single crystal indium micron sheet, characterized in that: the single crystal indium micro-sheet is composed of single crystal indium having a thickness of 35 to 80nm, a length of 5 to 50 μm, a width of 0.5 to 5 μm or a width of 5 to 50 μm.

A synthesis method of the single crystal indium micron sheet comprises the following steps: mixing indium salt, citrate and polyhydric alcohol in an inert atmosphere, heating and dissolving while stirring, then carrying out reduction reaction on borohydride salt serving as a reducing agent at 70-150 ℃, and finally, rapidly cooling to obtain the single crystal indium micron sheet in an organic solvent.

Further, the indium salt is indium chloride or indium nitrate or indium sulfate; the borohydride is sodium borohydride or potassium borohydride or lithium triethylborohydride; the citrate is disodium citrate, trisodium citrate or potassium citrate; the polyalcohol is diethylene glycol or tetraethylene glycol or ethylene glycol.

Further, theOf salts of boron hydrides and of indium, BH^4-And In³⁺The molar ratio of (1.5-2.5) to (1).

Further, the mol ratio of the indium salt to the citrate is preferably (0.5-3): 1.

further, the reduction reaction time is 20 s-1 h.

Further, the cooling speed of the rapid cooling in the first ten minutes is not lower than 2 ℃/min.

Further, the rapid cooling is cooling in water at 0-30 ℃.

A synthesis method of the single crystal indium micron sheet comprises the following steps: in an inert atmosphere, mixing indium salt, citrate and polyhydric alcohol, stirring and heating to dissolve, cooling to room temperature, adding borohydride solution at room temperature, and directly reducing at room temperature to obtain the single crystal indium micron sheet.

The application of the single crystal indium micro-sheet in the fields of micro-nano welding, vacuum sealing tabletting, conductive ink, micro-electrode, thermal conductive ink, microfluid and flexible micro-nano photoelectric devices and photocatalysis.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a single crystal indium micron sheet, which has simple preparation process, lower experimental requirements due to combination of one-step wet chemical synthesis and subsequent quick cooling or direct room temperature reduction, and is a green and environment-friendly preparation method with convenient operation; the method for preparing the single crystal indium nanosheet through rapid cooling successfully synthesizes the large-width and large-area single crystal metal indium nanosheet in the polyhydric alcohol for the first time, and has the advantages of high yield, good flexibility, strong adhesion with a substrate, low synthesis temperature, simplicity in operation, high controllability and suitability for industrial large-scale production. Meanwhile, the method selects indium salt as a raw material, citrate as a surfactant, borohydride as a reducing agent and polyol as a solvent, has simple synthesis process and lower experimental requirements, and is a green and environment-friendly synthesis method.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image at different magnifications of a single crystal indium micron sheet of the present invention;

FIG. 2 is an X-ray diffraction (XRD) pattern of a single-crystal indium micro-slab of the present invention;

FIG. 3 is a high resolution TEM image of a single crystal indium nanoplate synthesized according to the present invention;

FIG. 4 is a TEM electron diffraction image of a synthesized single-crystal indium nanoplate of the present invention;

FIG. 5 is a Scanning Electron Microscope (SEM) image of a single-crystal indium micro-slab obtained in example 10 of the present invention.

Detailed Description

The invention is further described with reference to specific examples.

A method for synthesizing single crystal indium micron sheet comprises the following steps: the indium micron sheet is synthesized by a wet chemical method by taking polyhydric alcohol as a solvent, citrate as a surfactant and borohydride as a reducing agent. The specific experimental procedure is as follows. First, a suitable amount of polyol was poured into a three-necked flask and nitrogen was passed through. And then, pouring the citrate and the indium salt into a three-neck flask, heating to 70-150 ℃, and then preserving the heat for a period of time. Then, a proper amount of borohydride is weighed and prepared into a solution by using a proper amount of deionized water. And quickly pouring the solution of the borohydride salt into a three-neck flask, reacting for a period of time, and quickly cooling. And finally, centrifuging the cooled sample, washing with alcohol and centrifuging for a plurality of times, and dispersing the centrifuged sample in ethanol for preservation.

First, the inventors have found that the amount of reducing agent has a great influence on the structure of the product, and have conducted a set of comparative experiments by varying the amount of NaBH₄In an amount such that BH^4-：In³⁺The ratio of (A) to (B) is 10:1, 3:1, 2:1 and 4:3 respectively. When BH^4-：In³⁺At 10:1, adding NaBH₄After the solution is reacted, the color of the solution is changed from colorless to brownish yellow, the color of the solution is brownish black after the reaction is finished, no bright oil product is found, and the micron sheet cannot be generated; when BH^4-：In³⁺At a ratio of 3:1, the solution is changed from colorless transparency to light yellow gray, no bright oil product is found, and micron sheets cannot be produced; when BH^4-：In³⁺At a ratio of 2:1, it was found that a glossy product was formed, andto form indium micron sheets with the average length of 20 microns and the average width of 2.5 microns; when BH^4-：In³⁺At 4:3, adding NaBH₄After the solution is dissolved, the color of the solution is gradually changed from colorless transparency to gray, then the color is lightened again, and finally the solution is changed into colorless transparency. Therefore, the effect of the relative content of the reducing agent is very large for the synthesis of indium micro-tablets. When BH^4-：In³⁺The ratio is higher than 2:1, the color of the solution begins to darken with an increase in the ratio, and it can be judged that the particles at this time become smaller and it is difficult for the particles to form micron-sized pieces. When BH^4-：In³⁺When the ratio is less than 2:1, the obtained solution becomes shallow slowly as the ratio decreases, and even finally becomes a colorless transparent liquid. Thus, BH^4-：In³⁺The ratio of 2:1 is the optimal ratio for synthesizing the indium micron sheet. The inventors further made BH^4-：In³⁺When the ratio of (A) to (B) is 3:2 and (B) is 5:2, single crystal indium micro-slabs with the thickness of 35-80 nm, the length of 5-50 μm, and the width of 0.5-5 μm or 5-50 μm can be obtained.

The following examples are all in BH^4-:In³⁺This optimum ratio is 2: 1.

Example 1

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 1.52X 10^-3Adding mol disodium citrate into a three-neck flask, heating to 100 deg.C in an oil bath while stirring, maintaining the temperature for 30min, adding a solution containing 4 × 10^-3The solution color changed rapidly from colorless to gray in 1.6mL of a solution of mol sodium borohydride in water. After 5min of reaction, the mixture is transferred to room temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m. Wherein, after cooling in water for 1.5 minutes, the generation of bright substances in the solution can be observed by naked eyes, and finally, after cooling for 1 hour, the solution is centrifugally washed by alcohol, then is put into ethanol for storage, and after being dispersed in the ethanol for precipitation for 12 hours, white and bright precipitates are found at the bottom. The product was characterized by SEM, XRD and TEM, respectively, as follows:

(1) SEM analysis of indium nanoplates

As shown in fig. 1. As can be seen from a (1100 times) and B (5000 times) in fig. 1, the synthesized product is dominated by approximately rectangular and long trapezoidal micro-slabs, with a few triangular micro-slabs and also a few nanoparticles, with a yield of the micro-slabs of 93%. The indium micro-meter plate is generally laid on a substrate, and in order to measure the thickness of the micro-meter plate, a certain section of the bent micro-meter plate is partially enlarged, as shown by C (30000 times) and D (130000 times) in FIG. 1, and the thickness is measured to be about 45nm, and at the same time, the indium micro-meter plate is very flexible when bent. In addition, the indium micron sheet solution is dripped on substrates such as glass, silicon wafers and the like, and the micron sheet can be perfectly and flatly paved on the surface of the substrate. The indium micron sheet has strong adhesiveness on a plurality of substrates, and can be tiled on the substrates, so that the indium micron sheet has potential application in the aspects of micro-nano vacuum sealing and micro-nano welding.

(2) XRD analysis of indium nanoplates

Phase analysis of the indium nanoplate by XRD showed that strong diffraction peaks appeared only at diffraction off-angles (2. theta.) of 32.94 ℃ and 69.09 ℃ as shown in FIG. 2, corresponding to (011) and (022) crystal planes (see standard data JCPDS: 05-0642 for indium), indicating that crystal orientation growth was good and the flat plane was the (011) crystal plane.

(3) TEM analysis of indium nanoplates

The microscopic morphology and crystal structure of the indium nanoplatelets were further analyzed by TEM as shown in fig. 3 and 4. Fig. 3 is a high-resolution TEM lattice image of the indium nanoplatelets, which shows that the indium nanoplatelets have a single crystal structure and the crystal planes thereof are arranged in order. FIG. 4 is a TEM electron diffraction pattern of the nanosheets, showing that the diffraction pattern is an aligned pattern of spots, and further showing that the indium nanosheets have a single crystal structure.

Example 2

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 1.52X 10^-3Adding mol disodium citrate into a three-neck flask, stirring, heating to 100 deg.C, maintaining the temperature for 30min, adding a solution containing 4 × 10^-3And (3) reacting the sodium borohydride with 1.6mL of a water solution of mol for 5min, and then moving the mixture to an ice-water mixture at 0 ℃ for rapid cooling. Finally obtaining the final product with a thickness of 35-80 nm and a length of 5-c50 μm and a width of 0.5 to 5 μm.

Example 3

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 1.52X 10^-3Adding potassium citrate mol into three-neck flask, stirring, heating to 100 deg.C, maintaining the temperature for 30min, adding into a flask containing 4 × 10^-3And (3) reacting 1.6mL of an aqueous solution of mol sodium borohydride for 15min, and then transferring the solution to room-temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m.

Example 4

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 1.52X 10^-3Adding mol disodium citrate into a three-neck flask, stirring, heating to 100 deg.C, maintaining the temperature for 30min, adding a solution containing 4 × 10^-3And (3) reacting the 1.6mL aqueous solution of mol sodium borohydride for 20min, and then transferring the solution to room-temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m.

Example 5

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 1.52X 10^-3Adding mol disodium citrate into a three-neck flask, stirring, heating to 80 deg.C, maintaining the temperature for 30min, adding a solution containing 4 × 10 sodium citrate^-3And (3) reacting 1.6mL of an aqueous solution of mol sodium borohydride for 5min, and then transferring the solution to room-temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m.

Example 6

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 1.52X 10^-3Adding mol disodium citrate into three-neck flask, stirring, heating to 120 deg.C, maintaining for 30min, adding 4 × 10 sodium citrate^-31.6mL of water solution of mol sodium borohydride is reacted for 5min, and then the mixture is moved to room temperature water to be rapidly cooled. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m.

Example 7

80mL of tetraethylene glycol were first placed in a three-neck flask, purged with nitrogen and stirred, and then 2X 10^-3mol of indium nitrate and 1.2X 10^-3Adding mol trisodium citrate into three-neck flask, heating to 100 deg.C in oil bath while stirring, maintaining the temperature for 20min, adding trisodium citrate with 4 × 10 content^-3The solution color changed rapidly from colorless to gray in 1.6mL of an aqueous solution of mol potassium borohydride. After reacting for 4min, the reaction solution is transferred to room temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 40-80 nm, the length of 5.5-50 mu m and the width of 0.5-5 mu m.

Example 8

80mL of ethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 1X 10 was placed^-3mol of indium sulfate and 2X 10^-3Adding mol disodium citrate into a three-neck flask, heating to 100 deg.C in an oil bath while stirring, maintaining the temperature for 30min, adding a solution containing 4 × 10^-3The solution color changed rapidly from colorless to gray in mol of lithium borohydride in 1.6mL of water. After reacting for 3min, the reaction solution is transferred to room temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m.

Example 9

80mL of diethylene glycol were first placed in a three-necked flask, nitrogen was introduced and the flask was stirred, and then 2X 10 was placed^-3mol of indium chloride tetrahydrate and 4X 10^-3Adding mol disodium citrate into a three-neck flask, heating to 100 deg.C in an oil bath while stirring, maintaining the temperature for 30min, adding a solution containing 4 × 10^-3And (3) reacting the 1.6mL aqueous solution of mol lithium triethylborohydride for 20s, and then transferring the solution to room-temperature water for rapid cooling. Finally obtaining the indium micron sheet with the thickness of 35-80 nm, the length of 5-50 mu m and the width of 0.5-5 mu m.

In summary, the formation of the micron sheet in the above embodiments requires subsequent rapid cooling, the crystal growth is related to the temperature gradient, and the larger the temperature gradient, the more latent heat of crystallization is taken away, and therefore the faster the crystal growth speed is; the smaller the temperature gradient, the taken away junctionThe less latent heat of the crystal and thus the slower the growth rate of the crystal, or no growth. Example 1 addition of NaBH reducing agent at 100 deg.C₄After that, the color of the solution changed rapidly from colorless to gray. After cooling in water at 25 deg.C for 1.5 min, the production of bright substances in the solution was observed visually, the product was mainly indium micron sheet, and the yield was about 93%. If the solution is not cooled in room temperature water or ice water, but is cooled in room temperature air or in an oil bath pan, the color of the solution is not changed after cooling, the solution is still gray, and the product is indium nanoparticles after electron microscope analysis. Comparing the two conditions, after the synthesis at 70-150 ℃, the later-stage quick cooling in water is the key for forming the indium micron sheet. Therefore, the inventor can propose a two-step assumption about the growth of the indium micron sheet of the invention: in the first step, NaBH is carried out at 100 DEG C₄After reduction, indium nanoparticles are generated; and secondly, in the process of rapid cooling, because of a large temperature gradient, the single crystal particles are grown into the single crystal indium micron sheet by orientation connection.

To further investigate the conditions for the formation of indium nanoplatelets, the inventors also synthesized single crystal indium nanoplatelets by direct reduction at room temperature.

Example 10

First, 1.9mmol disodium citrate and 2.5mmol InCl were weighed₃·4H₂O and 100mL of diethylene glycol, disodium citrate and InCl were first stirred at 100 deg.C₃·4H₂O was dissolved sufficiently, followed by cooling to room temperature, and then 5mmol of NaBH was added₄The aqueous solution (2) was slowly dropped at room temperature to carry out the reduction reaction. The solution initially appeared brownish yellow and then slowly became brownish black, and after 10 minutes of reaction, indium micro-flakes were gradually produced, and the growth of the micro-flakes continued for up to 30 minutes, and after 1 hour of reaction, the solution was centrifuged. As shown in fig. 5, which is an optical microscopic image of the room temperature synthesized indium nanoplatelets, the product was polygonal indium nanoplatelets having a large area, and the average length and width were about 30 μm, and it can be seen that the growth rates of the nanoplatelets in both directions were almost similar at room temperature.

The indium micron sheet prepared by the method has important application prospects in the aspects of micro-nano welding, vacuum sealing tabletting, conductive ink, microelectrodes, thermal conductive ink, microfluid, flexible micro-nano photoelectric devices and photocatalysis.

The invention is described and illustrated in greater detail, but is not intended to be limited thereby. It should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.