TW201731591A - Method for synthesizing quantum dot material with micro-fluid in which elements of groups IIB and VIA are mixed to form a quantum dot material having a predetermined particle size - Google Patents

Abstract

A method for synthesizing a quantum dot material with micro-fluid comprises the following steps: providing a precursor solution, a pressurizer, a guide tube, and a micro-reactor, wherein the precursor solution comprises a first precursor solution and a second precursor solution, the first precursor solution comprises an element of group IIB dissolving in an alcohol solvent, the second precursor solution comprises an element of group VIA dissolving in an alcohol solvent, the guide tube is connected to the micro-reactor and the pressurizer, the pressurizer comprises a first pressurizer and a second pressurizer, the pressurizer is pressurizable to a predetermined pressure, the micro-reactor is heatable to a predetermined temperature; then, filling the first precursor solution into the first pressurizer and filling the second precursor solution into the second pressurizer, allowing the pressure of the precursor solution to be pressurized to the predetermined pressure, using the guide tube to introduce the pressurized precursor solution into the micro-reactor with a predetermined flow rate to allow the precursor solution in the micro-reactor to be heated to the predetermined temperature such that the element of group IIB and the element of group VIA mix together to form a quantum dot material and the quantum dot material has a predetermined particle size.

Description

Method for synthesizing quantum dot materials by microfluidics

The invention relates to a method for preparing quantum dot materials, which realizes continuous quantum dot material synthesis by using a microfluidic system and a low-cost solvent.

Compared with traditional organic dye molecules and inorganic phosphors, quantum dot materials have strong fluorescence brightness, good light stability, and can emit a variety of different wavelengths of light with a single wavelength of laser. Characteristic, the emitted light has a narrow and symmetrical waveform and can be repeatedly excited, so the fluorescence aging can last. These characteristics attract the attention of scientists, and the application of nanometer quantum dots is becoming more and more diverse, which has the potential to replace traditional dyes and phosphors. Quantum dots absorb energy waves with higher energy and produce energy step jumps. When electrons fall from a high-energy state to a low-energy state, they emit light with a longer wavelength (reddish light). Quantum dots of different particle sizes emit different wavelengths of fluorescence. The smaller the quantum dot diameter, the smaller the wavelength of light after excitation (bluish), the larger the diameter, the longer the wavelength of light after excitation (reddish), With this feature we can control the quantum dot size and emit light of different wavelengths.

At present, quantum dots are widely used in blue lasers, light sensing components, single electron transistors, memory storage, catalysts, quantum computing, and the like. In the biomedical engineering, various fluorescent labels can be made, which are applied to the "gene barcode" or "protein barcode" for biological detection.

Many different methods have been applied to the manufacture of quantum dots, which are different from the traditional colloidal chemistry. To overcome the limitations of conventional batch production, some people have begun to take advantage of the advantages of microreactors in continuous flow systems, such as mass transfer. The heat transfer efficiency is high, the back mixing probability is small, and the reaction temperature and residence time can be better controlled as a preparation method of the quantum dot material. For example, Moghaddam et al. used cadmium acetate (Cd) and selenium (Se) powders to mix oleylamine (OLA), octadecene (ODE), and trioctylphosphine (TOP) to prepare precursors. The solution used in the process is a stainless steel tube microreactor with a diameter of 1 mm. The feed is passed through a high pressure liquid chromatography (HPLC pump) to continuously synthesize cadmium selenide CdSe quantum dots; Naughton et al. The cadmium and selenium powder are mixed with oleic acid, ODE and TOP to prepare the precursor solution. The pipeline used in the process is a stainless steel tube with an inner diameter of 2.2 mm. The feed is driven through the syringe pump to continuously synthesize CdSe quantum dots. And Chakrabarty et al. used cadmium nitrate and selenium powder mixed with TOP, OLA and sodium deoxycholate to prepare the precursor solution, and the microfluidic reaction device (stainless steel tube inner diameter 0.4 mm) to high pressure The syringe pump is fed and the CdSe quantum dots are continuously synthesized by the reaction of a supercritical fluid of hexane.

The method of preparing quantum dots by microreactor is mainly divided into organic-phase synthesis and aqueous-phase synthesis. In the organic phase synthesis system, long alkyl compounds such as tri-n-octylphosphine (TOP), trioctylphosphine oxide (TOPO), octadecene (ODE) and paraffin (paraffin), etc. It is often used as a heat transfer solvent and stabilizing reagents. However, the quantum dots synthesized in the organic phase solvent are not only water-insoluble, but also need to be transferred to the aqueous phase for subsequent applications. In addition, because of the hazardous nature of the reactants used, the entire synthetic procedure typically needs to be carried out at temperatures between 200 ° C and 400 ° C and in a nitrogen or glove box environment. Compared with the organic phase synthesis system, if an aqueous phase synthesis system can be used, the use of cheap and less toxic water can be used as a heat transfer solvent, which is simple, economical and environmentally friendly. However, although the aqueous phase synthesis system has the advantages of using the above-mentioned water as a solvent, in the aqueous phase synthesis system, the preparation process of the precursor solution is complicated, and it is possible to use toxic hydrogen selenide (H ₂ Se) or boron. Compounds such as sodium hydride (NaBH ₄ ) reducing agent can be prepared under a nitrogen atmosphere, and the synthesized quantum dot characteristics are poor and difficult to control, so there are still many problems that need to be improved and overcome.

In summary, in order to synthesize quantum dot materials with controllable quality and to develop a quantum dot material process that produces competitive continuous microfluidic reactions, it is necessary to select the solvent phase of the synthesis system, and the reactants and reactants. The selection and combination of the solvent and the preparation method of the precursor solution are discussed in depth to find a suitable combination and preparation method to achieve the above objectives.

In order to develop a quantum dot material having a competitive production cost and being a continuous microfluidic reaction, the present invention provides a method for synthesizing a quantum dot material by using a microfluid, which comprises the steps of: providing a precursor solution, a pressurization , a guiding tube and a micro-reactor, the precursor solution comprises a group II B element dissolved in an alcohol solvent and a group VI A element dissolved in an alcohol solvent, the guiding tube respectively Connecting the microreactor to the pressurizer, and the pressurizer is pressurized to a predetermined pressure, the microreactor can be heated to a predetermined temperature; injecting the precursor solution into the pressurizer, and causing the precursor solution Pressurizing the pressure to the predetermined pressure; using the guiding tube to press the pressurized precursor solution into the microreactor at a predetermined flow rate; heating the precursor solution in the microreactor to the predetermined temperature; The Group II B element and the Group VI A element in the precursor solution are mixed to form a quantum dot material having a predetermined particle size.

According to a preferred embodiment of the present invention, the ratio of the Group II B element to the Group VI A element has a mole ratio of 1:0.333 to 3.

According to a preferred embodiment of the present invention, the Group II B element is cadmium (Cd), and the Group VI A element is sulfur (S) or (Se).

According to a preferred embodiment of the present invention, the precursor solution comprises a first precursor solution and a second precursor solution, the first precursor solution being the Group II B element dissolved in an alcohol solvent, and the second precursor solution Is a group VI A element dissolved in an alcohol solvent, and the pressurizer comprises a first pressurizer and a second pressurizer, and the first precursor solution is respectively injected into the first pressurizer And the second precursor solution is injected into the second pressurizer.

According to a preferred embodiment of the present invention, the pressurizer is a high performance liquid chromatography pump (HPLC pump).

According to a preferred embodiment of the invention, the predetermined flow rate is from 0.5 to 10 mL per minute.

According to a preferred embodiment of the invention, the predetermined temperature is between 150 and 350 °C.

According to a preferred embodiment of the invention, the predetermined pressure is from 1 to 400 atm.

According to a preferred embodiment of the present invention, the mixing of the Group VI A element and the Group II B element in the precursor solution further comprises: mixing in a microfluidic state.

According to a preferred embodiment of the invention, the predetermined particle size is from 2 to 20 nm.

According to the method for synthesizing quantum dot materials by microfluids according to the present invention, a microfluidic reaction can be carried out under low temperature and high pressure conditions using a low-cost and non-toxic alcohol solvent to complete the preparation of quantum dot materials for continuous microfluidic reaction.

In order to make this article more obvious and easy to understand, specifically to define the terms used in this article, it is described as follows:

The term "quantum dots (QDs)" means a quasi-zero-dimensional nano-scale semiconductor material in which the dimensions of the three dimensions of quantum dots are all below 100 nanometers (nm), and The electronic arrangement is quite tight, and the quantum confinement effect can be used to excite different colors of fluorescence. For example, cadmium selenide (CdSe) emits blue fluorescence at a particle size of 2 nm, and emits green fluorescence at a particle size of 2.5 nm. When the particle size is close to 6 nm, the fluorescence it emits is close to red.

The term "micro-reactor," which means a micro-channel or micro-fluidic reactor, is manufactured using precision machining techniques with features ranging from 10 to 300 microns (or 1000 microns). ) between the microreactors. The "micro" of the microreactor means that the passage of the process fluid is on the micron level, rather than the small size of the microreactor or the small yield of the product. Millions of tens of millions of microchannels can be included in a microreactor, thus enabling higher yields.

As shown in the steps S1-S5 in FIG. 1 and FIG. 2, the quantum dot synthesis of the present invention requires a precursor solution (not shown), a pressurizer 21 and 21', a guide tube 22, and a microreaction. The precursor solution (not shown) comprises a first precursor solution (not shown) and a second precursor solution (not shown), and the first precursor solution (not shown) only comprises Dissolving in a group II B element of an alcohol solvent, the second precursor solution (not shown) comprises only a group VI A element dissolved in an alcohol solvent, wherein the group II B element and the group VI A element The mole ratio is 0.333 to 3, and the guiding tube 22 is connected to the microreactor 23 and the pressurizing devices 21 and 21', respectively, and the pressurizing devices 21 and 21' can be pressurized to a predetermined time. Under pressure, the microreactor 23 can be heated to a predetermined temperature. Next, the first precursor solution (not shown) is injected into the first pressurizer 21, and a second precursor solution (not shown) is injected into the second pressurizer 21' to make the precursor solution ( The pressure is pressurized to the predetermined pressure, and the pressurized precursor solution (not shown) is introduced into the microreactor 23 at a predetermined flow rate by the guiding tube 22, and the microreaction is further carried out. The precursor solution (not shown) in the device 23 is heated to the predetermined temperature, and finally the group II B element and the group VI A element in the precursor solution (not shown) are mixed to form a quantum dot material 24 . The quantum dot material 24 has a predetermined particle size. The method provided by the present invention is described in detail by the following examples, which comprise the following steps:

Preparation Example 1

In order to provide a Group II B element dissolved in an alcohol solvent, in the preparation example, the Group II B element is cadmium (Cd), and after mixing 0.67 g of cadmium acetate with 85 ml of ethanol, acetic acid is added as a solvent to A clear Cd precursor solution was prepared as the first precursor solution. This is a preferred preparation of the present invention, and is not limited thereto, wherein the ethanol may be another alcohol solvent such as methanol, ethanol, isopropanol or a combination thereof.

Preparation Example 2

In order to provide a group VI A element dissolved in an alcohol solvent, in the preparation example, the group VI A element is selenium (Se), and 0.48 g of selenium powder is heated at 70 ° C with 4 ml of TOP and 81 ml of ethanol. Dissolved to prepare a clarified Se precursor reactant solution as a second precursor solution. This is a preferred preparation of the present invention, and is not limited thereto, wherein the ethanol may be another alcohol solvent such as methanol, ethanol, isopropanol or a combination thereof.

Preparation Example 3

In order to provide a group VI A element dissolved in an alcohol solvent, in the preparation example, the group VI A element is sulfur (S), and 0.192 g of sulfur powder is heated at 70 ° C with 4 ml of TOP and 81 ml of ethanol. Dissolved to prepare a clarified S precursor reactant solution as a second precursor solution. This is a preferred preparation of the present invention, and is not limited thereto, wherein the ethanol may be another alcohol solvent such as methanol, ethanol, isopropanol or a combination thereof.

Embodiment 1

Providing the Cd forebody solution of Preparation Example 1 as the first precursor solution and the Se precursor solution of Preparation Example 2 as a second precursor solution, a high performance liquid chromatography pump (HPLC pump) as a pressurizer, A guiding tube and a microreactor are connected to the microreactor and the HPLC pump, respectively. In the ratio of Cd:Se Moir number to 1:2, the Cd forequarter solution and the Se precursor solution were respectively injected into the HPLC pump. The maximum pressure of the HPLC pump was 500 atm, but the maximum check valve can withstand. The pressure is 400 atm, so after the pressure of the forequarter solution is pressurized to the predetermined pressure (less than 400 atm), the pre-pressurization solution is used at a predetermined flow rate by the guide tube under the condition that the check valve can withstand 1.8 ml/min is continuously injected into the micro-reactor which has been heated to 250 ° C, and the precursor solution is heated to the predetermined temperature of 250 ° C, and then mixed, heated, reacted and cooled in a microfluid state to make the precursor solution The Group VI A element Se and the Group II B element Cd are mixed to form a cadmium selenide CdSe quantum dot material.

Embodiment 2

Providing the Cd precursor solution of Preparation Example 1 as the first precursor solution and the S precursor solution of Preparation Example 3 as a second precursor solution, a high performance liquid chromatography pump (HPLC pump) as a pressurizer, A guiding tube and a microreactor are connected to the microreactor and the HPLC pump, respectively. In the ratio of Cd:S Moir number to 1:2, S precursor solution and Cd precursor solution were respectively injected into the HPLC pump. The maximum pressure of the HPLC pump was 500 atm, but the maximum check valve can withstand. The pressure is 400 atm, so after the pressure of the forequarter solution is pressurized to the predetermined pressure (less than 400 atm), the pre-pressurization solution is used at a predetermined flow rate by the guide tube under the condition that the check valve can withstand 1.4 ml/min was continuously injected into the micro-reactor which had been heated to 270 ° C, and the precursor solution was heated to the predetermined temperature of 270 ° C, and then mixed, heated, reacted and cooled in a microfluid state to make the precursor solution The Group VI A element Se and the Group II B element Cd are mixed to form a cadmium sulfide CdS quantum dot material.

Analysis example one

The CdSe quantum dot material prepared in the first embodiment of the present invention is irradiated with a fluorescent lamp as shown in FIG. 3A and the result of irradiation with a UV lamp is as shown in FIG. 3B. It can be seen that the CdSe quantum dot material is irradiated by a UV lamp. Produces green fluorescence. The CdSe quantum dot material was dropped on the surface of the tantalum wafer, and the sample obtained after drying was subjected to X-ray diffraction (XRD) to determine the X-ray diffraction pattern. The results are shown in FIG. It was confirmed by comparison with the database of JCPDS that the synthesized powder was confirmed to be CdSe (PDF # 88-2346), and the product synthesized in Example 1 of the present invention was CdSe. Next, the observation of the particle shape and the particle diameter by a transmission electron microscope (TEM) shows that the CdSe quantum dot material has a predetermined particle diameter of 2-20 nm, and the results are as shown in FIGS. 5A, 5B and 5C. It is indicated that the CdSe quantum dot material has a particle size of 6 nm, 7.3 nm or 7.5 nm.

Analysis example two

The CdS quantum dot material prepared in the second embodiment of the present invention is irradiated with a fluorescent lamp as shown in FIG. 6A and the result of irradiation with a UV lamp is as shown in FIG. 6B. It can be seen that the CdS quantum dot material is irradiated by a UV lamp. Produces green fluorescence. The CdS quantum dot material was dropped on the surface of the tantalum wafer, and the sample obtained after drying was subjected to X-ray diffraction (XRD) to determine the X-ray diffraction pattern. The results are shown in FIG. After comparison with the JCPDS database, it was confirmed that the synthesized powder was confirmed to be CdS (PDF #75-0581), indicating that the product synthesized in Example 1 of the present invention was CdS. And the CdS quantum dot material has a predetermined particle diameter of 2-20 nm.

Based on the above preparation examples, examples and analysis examples, it is shown that the present invention can mainly utilize alcohol as a solvent, instead of previously using tri-n-octylphosphine (TOP), trioctylphosphine oxide (TOPO). , octadecene (ODE) and paraffin (paraffin) and other expensive and toxic solvents to reduce the cost and risk of synthetic quantum dot materials; and continuous non-stop production of quantum dot materials, low temperature and high pressure in microfluidics In the environment, the state of the supercritical fluid can be reached, and the quantum dot material can be prepared in a large amount, stably and rapidly.

The above is only the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made by the scope of the present invention and the contents of the description of the invention, All remain within the scope of the invention patent.

S1-S5‧‧‧ steps
21‧‧‧First pressurizer
21'‧‧‧Second pressurizer
22‧‧‧ Guide tube
23‧‧‧Microreactor
24‧‧‧Quantum point materials

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing a method of synthesizing a quantum dot material by microfluidics in the present invention. 2 is a device configuration diagram illustrating the configuration relationship of each component in the present invention. Figure 3A is a photograph showing the results of the product of Example 1 irradiated with a fluorescent lamp. Figure 3B is a photograph showing the results of the fluorescence of the product of Example 1 after irradiation with a UV lamp. Figure 4 is a graph showing the results of X-ray diffraction (XRD) determination of the product of Example 1. Fig. 5A is a graph showing the results of observation of the particle shape and particle size of the product of Example 1 by a transmission electron microscope (TEM). Fig. 5B is a graph showing the results of particle shape and particle size observation by a transmission electron microscope (TEM) of the product of Example 1. Figure 5C is a graph showing the results of particle size and particle size observation by a transmission electron microscope (TEM) of the product of Example 1. Figure 6A is a photograph showing the results of the product of Example 2 under irradiation with a fluorescent lamp. Figure 6B is a photograph showing the results of the fluorescence of the product of Example 2 after irradiation with a UV lamp. Figure 7 is a graph showing the results of X-ray diffraction (XRD) determination of the product of Example 2.

S1-S5‧‧‧ steps

Claims (10)

A method for synthesizing quantum dot materials by microfluidy comprises the steps of: providing a precursor solution, a pressurizer, a guiding tube and a micro-reactor, wherein the precursor solution comprises a solution a group II B element of an alcohol solvent and a group VI A element dissolved in an alcohol solvent, the guiding tube is connected to the microreactor and the presser, respectively, and the pressurizer can be pressurized to a predetermined Pressure, the microreactor can be heated to a predetermined temperature; injecting the precursor solution into the pressurizer, and pressurizing the precursor solution pressure to the predetermined pressure; using the guiding tube to pressurize the precursor solution to a predetermined flow rate is injected into the microreactor; the precursor solution in the microreactor is heated to the predetermined temperature; and the Group II B element and the Group VI A element in the precursor solution are mixed to form a quantum dot material, The quantum dot material has a predetermined particle size. The method of synthesizing a quantum dot material by a microfluid as described in claim 1, wherein the Group II B element and the Group VI A element have a mole ratio of 1:0.333 to 3. The method of synthesizing a quantum dot material by a microfluid as described in claim 1, wherein the Group II B element is cadmium (Cd), and the Group VI A element is sulfur (S) or (Se). The method of synthesizing a quantum dot material by a microfluid as described in claim 1, wherein the precursor solution comprises a first precursor solution and a second precursor solution, wherein the first precursor solution is dissolved in an alcohol solvent. a Group B element, the second precursor solution is a Group VI A element dissolved in an alcohol solvent, and the pressurizer comprises a first pressurizer and a second pressurizer, and the first precursor solution is respectively Injection into the first pressurizer, and the second precursor solution is injected into the second pressurizer. The method of synthesizing a quantum dot material by a microfluid as described in claim 1, wherein the pressurizer is a high performance liquid chromatography pump (HPLC pump). A method of synthesizing a quantum dot material by microfluidics as recited in claim 1, wherein the predetermined flow rate is from 0.5 to 10 mL per minute. A method of synthesizing a quantum dot material by microfluidics as recited in claim 1, wherein the predetermined temperature is from 150 to 350 °C. A method of synthesizing a quantum dot material by microfluidics as recited in claim 1, wherein the predetermined pressure is from 1 to 400 atm. The method of synthesizing a quantum dot material by a microfluid as described in claim 1, wherein the group VI A element and the group II B element in the precursor solution are mixed and mixed in a microfluid state. A method of synthesizing a quantum dot material by microfluidics as recited in claim 1, wherein the predetermined particle size is 2-20 nm.