KR20220015528A - Shape-specific carbon quantum dots for multiple color emission and Method of preparing the same - Google Patents

Abstract

The present invention relates to a shape-specific carbon quantum dot capable of emitting multicolor fluorescence capable of controlling the shape, size, and fluorescence color of the carbon quantum dot through a reaction time and a solvent, and a method for manufacturing the same. The method for manufacturing a shape-specific carbon quantum dot of the present invention uses phloroglucinol, water and a catalyst, and can control the size and fluorescence color of the carbon quantum dot through time control at a temperature of 150 to 250 deg. C. The method for manufacturing a shape-specific carbon quantum dot of the present invention forms a triangular and quadrangular ring compound by dehydrating phloroglucin, and can manufacture blue, green, and yellow carbon quantum dots by controlling the time of a dehydration reaction.

Description

Shape-specific carbon quantum dots capable of emitting multi-color fluorescence and method for preparing the same

The present invention relates to a shape-specific carbon quantum dot capable of emitting multicolor fluorescence and a method for manufacturing the same, and more particularly, to a multicolor fluorescence emission capable of controlling the shape, size, and fluorescence color of the carbon quantum dot through a reaction time and a solvent. It relates to a shape-specific carbon quantum dot and a method for manufacturing the same.

Carbon quantum dots are carbon particles with a size of several nm. In 2004, a team led by Professor Walter scrivens at the University of South Carolina in the process of refining soot, a lot of research is being conducted with the goal of developing an efficient synthesis method. Carbon quantum dots are an amorphous carbon-type nanostructure, and are a completely new type of material that is distinguished from nanodiamonds, which are diamond-shaped nanostructures, and graphene, nanotubes, and fullerenes, which are graphite-type nanostructures. In the 21st century, many studies have been made on the shape and properties of various carbon nanostructures, particularly graphene, nanotubes, and fullerenes, while studies on the various properties of carbon quantum dots are lacking. Carbon quantum dots are attracting attention as candidates to complement the shortcomings of existing quantum dots because they not only use cheap and safe materials, but also have biocompatibility and stability.

Recently, various types of carbon quantum dots have been manufactured for the purpose of bio-imaging, photocatalysts, and detection of biomaterials or specific compounds. Carbon quantum dots have low toxicity and biocompatibility.

However, although carbon quantum dots have applicability in many fields, a chemical synthesis method that can be mass-produced is not well known. There is a difficult problem in controlling it.

Korean Registration No. 10-1403534 discloses a method for preparing carbon quantum dots by heating an organic compound, an organic solvent, and an accelerator in a high-pressure reactor at a high temperature of 220° C. The registered patent prepares carbon quantum dots in an organic solvent or high-temperature and high-pressure conditions, and controls the size of carbon quantum dots as a concentration of organic matter. However, there is a problem in that the organic solvent or high pressure method makes the process complicated and it is difficult to efficiently control the size of the carbon quantum dots by using the concentration of the organic material. In addition, in the Korean patent registration, there is no mention of a method capable of controlling the size of the carbon quantum dots as well as the shape and the fluorescence color.

The present invention is to provide a method for producing carbon quantum dots in a simple and environmentally friendly method.

An object of the present invention is to provide a method capable of controlling the shape and fluorescence color as well as the size of carbon quantum dots.

One aspect of the present invention is

mixing phloroglucinol, water and a catalyst;

A method for producing multicolor carbon quantum dots comprising heating a mixed solution to 150 to 250° C., wherein the method controls the size and fluorescence color of carbon quantum dots generated by controlling the time of the heating step. It relates to the manufacturing method.

In another aspect, the present invention relates to carbon quantum dots prepared by mixing phloroglucinol, water and a catalyst, wherein the carbon quantum dots are shape-specific carbon quantum dots that are triangular and quadrangular crystals.

The shape-specific carbon quantum dot manufacturing method of the present invention uses phloroglucinol, water and a catalyst, and can control the size and fluorescence color of the carbon quantum dots through time control at a temperature of 150 to 250 ° C.

In the shape-specific carbon quantum dot manufacturing method of the present invention, a triangular or rectangular compound is formed by dehydrating phloroglucin, and blue, green, and yellow carbon quantum dots can be prepared respectively by controlling the time of the dehydration polymerization reaction.

The shape-specific carbon quantum dot manufacturing method of the present invention can control the triangular and square shape, size, and fluorescence color of carbon quantum dots through reaction time and solvent.

1 shows the manufacturing process of carbon quantum dots of the present invention in which size and fluorescence are controlled with time.
2 is a TEM image, XRD pattern, Raman spectrum and current measurement curve of the carbon quantum dots prepared in the present invention.
3 shows the fluorescence characteristics of the carbon quantum dots prepared in the present invention.
4 shows fluorescence characteristics according to a solvent in which carbon quantum dots are dispersed.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the description or drawings of the following embodiments. That is, the terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In addition, terms such as "comprises" or "have" described in this specification are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or the It should be understood that the above does not preclude the possibility of the existence or addition of other features or numbers, steps, operations, components, parts, or combinations thereof.

The shape-specific carbon quantum dot manufacturing method of the present invention includes a mixing step and a heating step.

The mixing step is a step of mixing phloroglucinol and a catalyst in water.

The phloroglucinol is an organic compound having a structure of the following formula (1).

Phloroglucinol has symmetrical active protons and active hydroxyl groups. That is, phloroglucinol has a triple symmetric structure and there are three OH groups and three H groups. The OH group of one molecule reacts with the H group of the other molecule, and the H ₂ O falls through the dehydration condensation reaction and bonds. Due to this triple symmetric structure, one molecule is bound to three other molecules in three meta-positions, and as the reaction time is increased, more molecules are combined to form carbon quantum dots that emit different colors.

Phloroglucinol removes adjacent -OH and -H groups by dehydration condensation reaction at high temperature by heat and catalyst, so that the ring of phloroglucinol is made up of three molecules of carbon quantum dots (CQD). due to the reaction pathway. On the other hand, hydroxyquinol and pyrrogallol, which are isomers of phloroglucinol, cannot form shape-specific carbon quantum dots as in the present invention.

The phloroglucinol may be added in an amount of 90 to 110 mg compared to 1 ml of water.

The catalyst may be sulfuric acid or the like capable of accelerating the dehydration condensation reaction of phloroglucinol.

The heating step is a step of heating the mixed solution to 150 ~ 250 ℃. The heating step is a step in which the dehydration condensation reaction of phloroglucinol is continuously performed to generate nanoparticle crystals.

The heating step may be 150 ~ 250 ℃, preferably 180 ~ 220 ℃. The heating step may be performed without a separate pressurization.

In the heating step, the pressure may be atmospheric pressure.

In the heating step, the phloroglucinol molecules are dehydrated and polymerized to form a cyclic compound, and the phloroglucinol molecules are additionally dehydrated and condensed to the cyclic compound to form triangular and quadrangular crystalline carbons. It may include a crystallization step of growing into quantum dots.

Since the heating step occurs at a high temperature of 150 to 250 ° C, solvents such as nitric acid, hydrogen peroxide, and potassium permanganate evaporate directly at high temperature to obtain a carbonized mass as a final product, but since the boiling point of sulfuric acid is very high (~ 340 ℃) can act as a catalyst in a high-temperature reaction. Therefore, sulfuric acid is preferable as the catalyst.

Referring to FIG. 1 , the step of forming the compound in the ring form is a step in which a hexagonal ring (six membered ring cyclization, 環化) is formed by dehydration of the phloroglucinol molecules and the compound is formed.

The crystallization step is a step in which the phloroglucinol atoms are additionally grown into crystals by a dehydration reaction in the cyclic compound.

Referring to FIG. 1 , in the crystallization step, -OH in phloroglucinol is disposed at 1, 3, and 5 carbons, so that it can be uniformly grown into triangular and rectangular crystals.

In the present invention, the size and fluorescence color of the generated carbon quantum dots can be controlled by adjusting the time of the heating step.

More specifically, the present invention prepares blue carbon quantum dots by maintaining the time of the heating step for 20 to 35 minutes, maintaining the time of the heating step for 45 to 60 minutes to produce green carbon quantum dots, and the heating By maintaining the time of the step for 80 to 100 minutes, it is possible to prepare yellow carbon quantum dots.

In the present invention, by controlling the heating time, a blue carbon quantum dot having a size of 3 to 5 nm, a green carbon quantum dot having a size of 4 to 6 nm, and a yellow carbon quantum dot having a size of 5 to 8 nm can be prepared.

In this way, unlike the conventional method of decomposing organic matter at high temperature and high pressure, carbonizing, and crystallizing nanoparticles into nanoparticles, the present invention can produce carbon quantum dots by dehydration condensation reaction at high temperature.

In the present invention, carbon quantum dots can be obtained by centrifuging the mixed solution after the heating reaction step. For example, in the present invention, centrifugation may be performed at 5,000 to 20,000 rpm.

The shape-specific carbon quantum dots prepared by the above method may be triangular and quadrangular crystals.

The blue carbon quantum dots may have a size of 3 to 5 nm, the green carbon quantum dots may have a size of 4 to 6 nm, and the yellow carbon quantum dots may have a size of 5 to 8 nm.

The fluorescence color of the green carbon quantum dots and the yellow carbon quantum dots may be redshifted as the polarity of the dispersed solvent increases.

Hereinafter, the present invention will be described in detail with reference to the accompanying embodiments and drawings. However, the accompanying examples only illustrate specific embodiments of the present invention, and are not intended to limit the scope of the present invention.

Example 1

Production of carbon quantum dots

200 mg of phloroglucinol (phloroglucinol) was added to a 100-mL glass beaker, and then 2 mL of water and concentrated H2SO4 were added respectively. The pale yellowish solution was stored in a hot-air oven preheated to a constant temperature of 190 °C and the reaction time was maintained for 25, 50 and 90 min, respectively, for blue, green and yellow carbon quantum dots (B-CQDs, G-CQDs and Y- CQDs) were obtained. After each period of thermal reaction, the beaker was immediately removed and cooled to room temperature. After 5 mL of deionized water was added to each product, centrifugation was performed at high speed (13000 rpm) to collect CQDs, which were washed with water, and then dialyzed against DI water for 72 hours (a cellulose ester membrane with a molecular weight of 500 Da). use). The dialyzed product was dried, dispersed in ethanol, and filtered using a 0.22-micron filter (3 filtration cycles). Finally, the filtrate was dried to obtain CQDs powder, respectively.

Figures 2a-c are HR-TEM of B-CQDs, G-CQDs and Y-CQDs, Figure 2d is an XRD pattern, 2e is a Raman spectrum, 4f is an I-t curve. Referring to FIG. 2-c, the obtained carbon quantum dots have a size of 3 to 5 nm (B-CQDs), 4 to 6 nm (G-CQDs), and 5 to 8 nm (Y-CQDs), and the shapes are triangular and square. decision can be confirmed.

Referring to Figure 2d, it can be seen that the high crystallinity peaks around 16.8°, 21.6°, 22.9°, 25.2° and 27.3° of the precursor were converted into broad peaks through polymerization, dehydration, and carbonization processes.

Figure 3a is a UV-vis absorption spectrum of phloroglucinol and the prepared carbon quantum dots. Although phloroglucinol shows a peak at 266 nm, it can be seen that the peaks of B-CQDs, G-CQDs and Y-CQDs are redshifted to 280 nm, 289 nm, and 305 nm, respectively. Figure 3a shows that as the reaction time is longer, larger quantum dots are generated, and the redshift phenomenon is also larger.

Figure 3b shows the excitation and emission spectra of B-CQDs, G-CQDs and Y-CQDs dispersed in ethanol. Referring to FIG. 3B , all three carbon quantum dots have excitation wavelengths of 345 to 350 nm, but the maximum emission wavelengths are located at 438 nm, 512 nm, and 550 nm. Figure 3c shows the PL emission wavelength according to various excitation wavelengths. This shows that the carbon quantum dots dispersed in ethanol are excitation wavelength dependent. Figure 3d is a graph showing the quantum yield measured using quinine sulfate (quinine sulfate). The quantum yields of B-, G-, and Y-CQDs are 1.03, 23, and 6,95%, respectively.

4a and 4b are PL emission distribution curves of G-CQDs and Y-CQDs dispersed in various solvents, respectively. G-CQDs were redshifted from 435 (blue, ethyl acetate) to 512 nm (green, ethanol), and for Y-CQDs from 446 nm (blue, ethyl acetate) to 566 nm (yellow orange, DMSO).

Referring to Figure 4a, the PL maximum emission wavelengths of G-CQDs are 435 nm (ethyl acetate), 436 nm (THF), 435 nm (acetonenitrile), 470 nm (water), 500 nm (DMF), 501 nm (DMSO), and 512 nm (ethanol) )am.

Referring to Figure 4b, the PL maximum emission wavelength of Y-CQDs is 446nm (ethyl acetate), 449nm (THF), 459nm (acetonenitrile), 520nm (DMF) 535nm (water), 550nm (ethanol), 566nm (DMSO) am. Y-CQDs and G-CQDs show solvent-dependent color development at a wavelength of 350 nm. The maximum emission wavelengths of Y-CQDs and G-CQDs were 77-120 nm, respectively, and were redshifted.

4c and 4d are UV-visible absorption spectra of Y-CQDs and G-CQDs in different polar solvents. Referring to FIGS. 4c and 4d , it can be seen that the absorption spectra of Y-CQDs and G-CQDs are located near 305 nm, and the absorption spectra are almost similar regardless of the characteristics of the solvent.

In the above, preferred embodiments of the present invention have been described in detail, but these are only for the purpose of explanation and the protection scope of the present invention is not limited thereto.

Claims (11)

mixing phloroglucinol, water and a catalyst;
A method for producing multicolor carbon quantum dots comprising heating a mixed solution to 150 to 250° C., wherein the method controls the time of the heating step to control the size and fluorescence color of the generated carbon quantum dots. A method for manufacturing red carbon quantum dots. According to claim 1, wherein the heating step comprises the steps of dehydrating the phloroglucinol atoms to form a cyclic compound, and additionally dehydrating the phloroglucinol atoms to the cyclic compound by dehydrating the phloroglucinol atoms. and a crystallization step of growing into square crystals of carbon quantum dots. According to claim 1, wherein the multi-color carbon quantum dot manufacturing method is a shape-specific carbon quantum dot manufacturing method, characterized in that to generate blue carbon quantum dots by maintaining the time of the heating step for 20 to 35 minutes. According to claim 1, wherein the multi-color carbon quantum dot manufacturing method is a shape-specific carbon quantum dot manufacturing method, characterized in that by maintaining the time of the heating step for 45 to 60 minutes to generate a green carbon quantum dot. According to claim 1, wherein the multi-color carbon quantum dot manufacturing method is a shape-specific carbon quantum dot manufacturing method, characterized in that to generate a yellow carbon quantum dot by maintaining the time of the heating step for 80 to 100 minutes. The method of claim 1, wherein the catalyst is sulfuric acid. The method of claim 1, wherein the heating step is performed at atmospheric pressure. The method according to claim 1, wherein 90 to 110 mg of phloroglucinol is added relative to 1 ml of water. The carbon quantum dots prepared according to any one of claims 1 to 8, wherein the carbon quantum dots are shape-specific carbon quantum dots, characterized in that triangular and quadrangular crystals. The shape-specific carbon quantum dot according to claim 9, wherein the blue carbon quantum dot has a size of 3 to 5 nm, the green carbon quantum dot has a size of 4 to 6 nm, and the yellow carbon quantum dot has a size of 5 to 8 nm. The shape-specific carbon quantum dot according to claim 6, wherein the fluorescence color of the green carbon quantum dot and the yellow carbon quantum dot is redshifted as the polarity of the dispersed solvent increases.

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