Nanoparticle manufacturing apparatus and nanoparticle manufacturing method

Abstract

To provide a nanoparticle production device capable of performing a highly accurate temperature control and a method for producing nanoparticles.SOLUTION: There is provided a nanoparticle production device for producing nanoparticles by supplying a material solution to a reaction tube (1), wherein the reaction tube has a preheating part (13) and a reaction part (14) which are continuous, and a heating part electrically heated in contact with the preheating part and / or the reaction part is provided. The reaction tube is divided into a plurality of continuous heating sections and the heating part is preferably provided in at least one of each heating sections of the preheating part and the reaction part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus for producing nanoparticles and a method for producing nanoparticles. [Background technology]

[0002] Nanoparticles can be produced by a microreactor device. Nanoparticles can be produced by passing a material solution through a heated reaction tube (reaction tube, metal capillary) that constitutes the microreactor device. For example, Patent Document 1 discloses an invention relating to a microreactor device in which a preheating section formed of a metal capillary and a reaction section are integrally or separately configured. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5137051 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional microreactor devices were unable to perform high-precision temperature control, leading to variations in the quality of nanoparticles. In other words, because the preheating section is located at the inlet side where the material solution is supplied, the heating temperature does not become high enough, leading to insufficient nucleation. In addition, in the reaction section located after the preheating section, it was necessary to control the temperature so that the temperature could be maintained at a predetermined value throughout the entire area.

[0005] Therefore, the present invention has been made in consideration of the above points, and an object of the present invention is to provide a nanoparticle production apparatus and a nanoparticle production method capable of performing highly accurate temperature control. [Means for solving the problem]

[0006] The nanoparticle production apparatus of the present invention is a nanoparticle production apparatus for producing quantum dots by supplying a material solution to a reaction tube, the reaction tube being a continuous As a heating section The preheating section has a reaction tube shorter than that of the reaction section, and the preheating section and the reaction tube are 、 A heating section that is electrically heated is provided on the outer periphery of the reaction section. The amount of current flowing through each heating section of the heating unit is individually controlled, so that the temperature can be individually controlled for each heating section. It is characterized by:

[0007] In the present invention, it is preferable that the reaction section is divided into a plurality of continuous heating zones, and the heating section is provided in the preheating section and at least one of the heating zones of the reaction section.

[0008] In the present invention, it is preferable that a pulsed current is controlled to flow through the heating section.

[0009] In the present invention, it is preferable that the voltage applied to the heating portion is an alternating voltage.

[0010] In the present invention, it is preferable that each of the heating sections is equipped with a shunt switch circuit having an electrical resistance lower than the electrical resistance of the heating section, and that the current flowing through the heating section is increased or decreased by opening and closing the shunt switch circuit, thereby controlling the temperature of the preheating section and / or the reaction section.

[0011] In the present invention, for example, the heating part is a conductive tube that wraps around the reaction tube, or the heating part is an electric heating wire that is wound around the reaction tube.

[0012] In the present invention, it is preferable that the cross-sectional area of ​​the flow passage of the preheating section is smaller than the cross-sectional area of ​​the flow passage of the reaction section.

[0013] The present invention relates to a material solution, anti A method for producing nanoparticles for producing quantum dots by supplying a reaction tube to a continuous reaction tube. As a heating sectionThe preheating section has a reaction tube shorter than that of the reaction section, and the preheating section and the reaction tube are 、 The reaction section Each heating section The heating portion located on the outer periphery is heated by electrical current. At this time, the amount of current flowing through each heating section is individually controlled, and the temperature is individually controlled for each heating section. The method is characterized in that the material solution is supplied to the reaction tube in a state where the material solution is ... [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a part of an apparatus for producing nanoparticles according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a part of the nanoparticle production apparatus according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram showing a cross-sectional structure of a reaction tube used in the nanoparticle production apparatus according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a part of a nanoparticle production apparatus according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic diagram showing a cross-sectional structure of a reaction tube used in a nanoparticle production apparatus according to a second embodiment of the present invention. [Figure 6] FIG. 6 is an example of a circuit configuration for explaining a temperature control method applied to the nanoparticle producing apparatus according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram in which a current limiting means is added to the circuit of FIG. [Figure 8] FIG. 8 is a flow chart showing the operation of temperature control in the nanoparticle producing apparatus having the circuit of FIG. [Figure 9] FIG. 9 is a schematic diagram showing the pipe diameters of the preheating section and the reaction section. [Figure 10] FIG. 10 is a schematic diagram showing a method of controlling the temperature of the reaction tube of the embodiment used in the experiment. [Figure 11] FIG. 11 is a schematic diagram showing a temperature control method for the reaction tube of the comparative example used in the experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of the present invention (hereinafter, abbreviated as "embodiment") will be described in detail below. Note that the present invention is not limited to the following embodiment, and can be practiced in various modifications within the scope of the gist of the present invention.

[0016] <Nanoparticle manufacturing equipment> 1 is a schematic diagram showing a part of a nanoparticle synthesizing apparatus according to the present embodiment, which is a flow-type continuous nanoparticle synthesizing apparatus.

[0017] 1 mainly shows a heating reaction section constituting the nanoparticle synthesis apparatus. That is, the nanoparticle synthesis apparatus is equipped with a reaction tube 1 and a heating section 9, and further includes a downstream pipe 2 located downstream of the reaction tube 1, an upstream pipe 3 located upstream of the reaction tube 1, a back pressure valve 4 connected downstream of the reaction tube 1, and a check valve 5 connected upstream of the reaction tube 1.

[0018] (Reaction tube 1) The reaction tube 1 shown in Fig. 1 will be described. The reaction tube 1 is, for example, a glass tube or a stainless steel cylinder, but any material can be used as long as a continuous space is provided inside the reaction tube 1 through which the material solution can pass. For example, a reaction tube 1 made of titanium is preferable for maintaining a stable reaction because the tube wall is less deteriorated even under severe reaction conditions of high temperature and pressure.

[0019] As for the internal structure of the reaction tube 1, the size of the reaction tube 1 is not limited, but the reaction tube 1 has an outer diameter of several mm, an inner diameter of several hundreds μm, and a total length of approximately several thousands mm. Thus, the reaction tube 1 has a long and narrow space therein and is configured as a narrow tube with both ends open.

[0020] (Preheating section 13 and reaction section 14) As shown in Fig. 1, the reaction tube 1 has a preheating section 13 and a reaction section 14 as continuous heating sections. As such, there is no gap between the preheating section 13 and the reaction section 14, and the material solution passing through the reaction tube 1 can be transferred from the preheating section 13 to the heated reaction section 14 instantly.

[0021] Due to this configuration, a heating region that is continuously controlled at a predetermined temperature can be formed from the preheating section 13 to the reaction section 14, and the nucleation to nuclear growth reaction can be carried out stably and with high precision, thereby suppressing variation in the quality of the nanoparticles.

[0022] In addition, in FIG. 1, the tube diameters of the preheating section 13 and the reaction section 14 are the same, but as shown in FIG. 9, by making the tube diameter of the preheating section 13 smaller than that of the reaction section 14, the flow path cross-sectional area of ​​the preheating section 13 can be made smaller than that of the reaction section 14, and the time required to heat the preheating section 13 to a predetermined temperature can be more effectively shortened. Note that the shorter the temperature rise time in the preheating section 13 responsible for nucleation, the smaller the fluorescence half width (FWHM) of the generated quantum dots tends to be. Note that by having a flow path cross-sectional area of ​​the reaction section 14 larger than that of the preheating section 13, mass productivity can be improved.

[0023] (Heating part 9) As shown in Fig. 1, the heating part 9 is located on the outer periphery of the reaction tube 1. The heating part 9 is in contact with the reaction tube 1. By electrically heating the heating part 9, the preheating part 13 and the reaction part 14 in contact with the heating part 9 can be heated.

[0024] As shown in Fig. 1, the heating section 9 is provided with, from the upstream side, a first connection point 6, a second connection point 7, and a third connection point 8. Note that although the number of connection points may be four or more, Fig. 1 will be described assuming that there are three connection points.

[0025] As shown in FIG. 1, a first wiring 10 is connected to a first connection point 6, a second wiring 11 is connected to a second connection point 7, and a third wiring 12 is connected to a third connection point 8.

[0026] 1 corresponds to the heating section of the preheating section 13 responsible for nucleation of nanoparticles. Also, the second heating section 9b corresponds to the heating section of the reaction section 14 responsible for nucleation of nanoparticles.

[0027] Each of the wires 10, 11, and 12 is connected to a power source (not shown). This allows the heating section 9 to be electrically heated via the wires 10, 11, and 12, and the preheating section 13 and the reaction section 14 to be heated, respectively. The heating section 9 forms a continuous conductor from the first connection point 6 to the third connection point 8, and generates heat by electrical energy supplied by the current.

[0028] At this time, the voltage applied to the heating unit 9 may be either AC or DC. When AC is applied, the frequency is not limited. For example, when AC is applied, the frequency may be 60 to 200 Hz, which is close to the frequency of a commercial power source, or may be a high frequency exceeding 1 MHz.

[0029] As the frequency applied to the heating unit 9 increases, an increase in electrical resistance due to the skin effect appears in the conductor constituting the heating unit 9. For example, when the electrical resistance between the first connection point 6 and the third connection point 8 located at both ends of the heating unit 9 becomes too low, the electrical resistance can be increased due to the above-mentioned skin effect by applying a high-frequency AC current.

[0030] In addition, since a relatively large current (current exceeding 10 A, although not limited thereto) flows through the heating part 9 of this embodiment, it is necessary to make the contact resistance between the heating part 9 and each of the connection points 6, 7, and 8 as small as possible. If the contact resistance becomes large, heat will be generated due to the contact resistance, and the uniformity of the heat generation will be impaired. Therefore, in this embodiment, for example, copper terminals are fixed to the connection points 6, 7, and 8 by caulking, and further brazed to ensure electrical contact.

[0031] In Fig. 1, the second connection point 7 constitutes a common electrode for the first heating section 9a and the second heating section 9b of the heating section 9. With this, the preheating section 13 and the reaction section 14 of the reaction tube 1 can be constituted as a continuous heating section by electrically heating each of the heating sections 9a and 9b.

[0032] As shown in FIG. 1, the preheating section 13 is shorter than the reaction section 14 in the reaction tube 1. Therefore, if the wall thickness and tube diameter of the reaction tube 1 are the same in the preheating section 13 and the reaction section 14, the preheating section 13, which has a shorter length, has a smaller electric resistance than the reaction section 14. For example, the length of the preheating section 13 from the first connection point 6 to the second connection point 7 is about 200 mm, whereas the length of the reaction section 14 from the second connection point 7 to the third connection point 8 is about 1000 mm. Thus, the length of the preheating section 13 is about 1 / 5 of the length of the reaction section 14. Therefore, if the wall thickness and tube diameter of the reaction tube 1 are the same, the electric resistance of the preheating section 13 is about 1 / 5 of the electric resistance of the reaction section 14.

[0033] In this embodiment, the heating sections 9a, 9b of the heating section 9 can be controlled separately. The temperature of the preheating section 13 and the reaction section 14 can be measured by a temperature detection means (not shown), or the temperature of each heating section 9a, 9b of the heating section 9 corresponding to the preheating section 13 and the reaction section 14 can be measured by a temperature detection means (not shown), and ON / OFF control can be performed using a PID based on each temperature so that the preheating section 13 and the reaction section 14 are kept at the set temperature. Note that the temperature detection means is not limited to this embodiment, and for example, a thermocouple, a thermistor, a radiation thermometer, etc. can be applied.

[0034] In this embodiment, even if the electrical resistance of the preheating section 13 becomes smaller than that of the reaction section 14, the preheating section 13 can be quickly raised to a predetermined temperature and can be stably maintained at the predetermined temperature by separately controlling the electrical current flow to each heating section 9a, 9b of the heating section 9.

[0035] Thus, in this embodiment, the heating section 9 is in contact with the preheating section 13 and the reaction section 14, and the heating section 9 is divided into successive heating sections 9a, 9b corresponding to the preheating section 13 and the reaction section 14. As a result, by controlling the current supply to each heating section 9a, 9b of the heating section 9, the preheating section 13 and the reaction section 14 can be controlled to maintain a predetermined temperature. Therefore, the nucleation in the preheating section 13 and the nucleus growth reaction in the reaction section 14 can be continuously controlled stably and with high precision, and the variation in quality of the nanoparticles can be suppressed.

[0036] A specific configuration of the heating part 9 in this embodiment will be described with reference to the drawings. In the first embodiment shown in Fig. 2 and Fig. 3, a conductive tube 41 surrounding the reaction tube 1 is provided as the heating part. The conductive tube 41 and the reaction tube 1 are in contact with each other. Here, the conductive tube 41 does not need to be in contact with the entire outer periphery of the reaction tube 1, and it is sufficient that the conductive tube 41 is in contact with at least a part of the outer periphery of the reaction tube 1.

[0037] As shown in FIG. 2, a plurality of connection points (electrodes) 42, 43, 51 are electrically connected to the conductive tube 41, and electric wires 44, 45, 52 are connected to the respective connection points 42, 43, 51. Each electric wire is connected to a power source (not shown). A first heating section 54a is located between the first connection point 42 and the second connection point 51 of the conductive tube 41, and corresponds to a preheating section of the reaction tube 1. A second heating section 54b is located between the second connection point 51 and the third connection point 43 of the conductive tube 41, and corresponds to a reaction section of the reaction tube 1. By electrically heating the first heating section 54a and the second heating section 54b of the conductive tube 41, the preheating section and the reaction section of the reaction tube 1 can be heated, respectively.

[0038] In the second embodiment shown in Fig. 4 and Fig. 5, an electric heating wire 46 wound around the reaction tube 1 constitutes a heating part. The electric heating wire 46 and the reaction tube 1 are in contact with each other. Here, the electric heating wire 46 does not need to be in contact with the entire outer periphery of the reaction tube 1, but may be in contact with at least a part of the outer periphery.

[0039] As shown in FIG. 4, a plurality of power supply leads 47, 48, 53 are drawn outward from the heating wire 46. Each of the power supply leads 47, 48, 53 is connected to a power source (not shown). The heating wire 46 between the power supply leads 48, 53 is a first heating section 55a, which corresponds to a preheating section of the reaction tube 1. The heating wire 46 between the power supply leads 47, 53 is a second heating section 55b, which corresponds to a reaction section of the reaction tube 1. By electrically heating the first heating section 55a and the second heating section 55b of the heating wire 46, the preheating section and the reaction section of the reaction tube 1 can be heated, respectively.

[0040] The heating wire 46 is, for example, a nichrome wire, but is not limited to a nichrome wire. Furthermore, the reaction tube 1 can be connected to the upstream pipe 3 and the downstream pipe 2 using a pipe joint 49.

[0041] (Backpressure valve 4) The back pressure valve 4 shown in Fig. 1 maintains the pressure in the reaction tube 1 at a constant value, stabilizes the flow of the sample solution, and suppresses boiling of the sample solution by maintaining the pressure at atmospheric pressure or higher, making it possible to synthesize at a temperature range that cannot be reached at normal pressure. For example, a back pressure regulator P-789 by GL Sciences can be used as the back pressure valve 4. The back pressure value can be appropriately selected depending on the reaction conditions.

[0042] (Check valve 5) The check valve 5 is attached to maintain the pressure in the reaction tube 1 together with the back pressure valve 4. By connecting the check valve 5, even if the pressure in the reaction tube 1 increases due to heating, backflow of the sample solution does not occur, and the pressure set by the back pressure valve 4 is appropriately maintained. For example, the check valve 5 can be an in-line check valve CV-3000 manufactured by GL Sciences.

[0043] A liquid delivery pump, a flow meter, a sample solution tank, and the like (not shown) are connected to the upstream side of the check valve 5 via the upstream piping 3. In addition, a downstream side of the back pressure valve 4 is connected to devices (not shown) for testing and recovering the compound via the downstream piping 2.

[0044] In this embodiment, with the structure shown in FIG. 1, the sample solution is sequentially fed from the upstream piping 3 into the reaction tube 1, moves within the reaction tube 1 while reacting, and forms a unidirectional flow (see the arrow in FIG. 1) in which the sample solution flows into the downstream piping 2 after the reaction is completed.

[0045] <Operation when synthesizing nanoparticles using nanoparticle production equipment> Next, the operations performed when actually synthesizing nanoparticles using the nanoparticle production apparatus shown in FIG. 1 will be described in order.

[0046] After starting up the nanoparticle production apparatus of this embodiment, a liquid delivery pump (not shown) fills the reaction tube 1 with a material solution from a sample solution tank (not shown) via upstream piping 3 and check valve 5. After filling the reaction tube 1, the material solution is further supplied and sent through back pressure valve 4 and downstream piping 2 so as to fill the piping of the entire synthesis apparatus.

[0047] Next, power is supplied to each of the wirings 10, 11, and 12 by a power source (not shown). In this embodiment, as shown in Fig. 1, the second connection point 7 to which the second wiring 11 is connected is a common electrode for the first heating section 9a and the second heating section 9b of the heating unit 9, and the first connection point 6 to which the first wiring 10 is connected and the third connection point 8 to which the third wiring 12 is connected are disposed at positions opposite to each other with the second connection point 7 in between. As a result, in this embodiment, when AC is used for power supply, wiring can be performed so that the voltages of the first connection point 6 and the third connection point 8 alternate in phase.

[0048] As shown in FIG. 1, the first heating section 9a and the second heating section 9b of the heating unit 9 can be heated by electrical current separately, which makes it possible to separately control the temperatures of the preheating unit 13 and the reaction unit 14.

[0049] For example, when the potentials of the first connection point 6 and the third connection point 8 become higher than the potential of the second connection point 7 while the AC voltage is changing, the current flowing in from the first connection point 6 heats the first heating section 9a of the heating section 9, and as a result, heats the preheating section 13 of the reaction tube 1, and flows into the second connection point 7, which is a common electrode. On the other hand, the current flowing in from the third connection point 8 heats the second heating section 9b of the heating section 9, and as a result, heats the reaction section 14, and flows into the second connection point 7. At this time, the second connection point 7, which is a common electrode, has the lowest potential among the three connection points 6, 7, and 8, so the current flowing in from the first connection point 6 to the first heating section 9a of the heating section 9 does not flow beyond the second connection point 7 to the third connection point 8. The same applies to the current flowing in from the third connection point 8 to the second heating section 9b of the heating section 9. The same applies even if the voltages of the first connection point 6 and the third connection point 8 are different. Even in an alternating state in which the voltages of the first connection point 6 and the third connection point 8 are lower than those of the second connection point 7, the direction of the current flow is simply reversed as described above, and the current that has flowed in the first heating section 9a of the heating unit 9 does not flow to the second heating section 9b, and the current that has flowed in the second heating section 9b does not flow to the first heating section 9a. The above-described current flow can also be achieved in the same way when electricity is supplied using a DC power source, and control using DC is also possible.

[0050] In this manner, by using the second connection point 7 as a common electrode for the first heating section 9a and the second heating section 9b of the heating section 9, the continuous heating sections 9a and 9b can be controlled to be energized separately, and as a result, the temperatures of the preheating section 13 and the reaction section 14 of the reaction tube 1 can be controlled separately. This makes it possible to control the preheating section 13 and the reaction section 14 to be the same temperature or different temperatures.

[0051] In this manner, in this embodiment, the temperatures of the preheating section 13 and the reaction section 14 can be controlled separately, which makes it possible to obtain the following advantageous effects.

[0052] In the flow-type continuous nanoparticle synthesis apparatus of this embodiment, before and after the start of heating the reaction tube 1, the liquid delivery pump is driven to sequentially send the material solution into the reaction tube 1, and a flow-type continuous synthesis is performed. At this time, the material solution is heated in the preheating section 13 of the reaction tube 1 and a reaction starts, but since the material solution before heating continuously flows into the position close to the first connection point 6, the temperature tends to be lower than the downstream side of the first connection point 6. As a result, the temperature near the entrance of the preheating section 13 becomes lower.

[0053] In this embodiment, in order to prevent a temperature drop at the inflow portion of the material solution, a preheating section 13 is provided as a heating section for preheating in front of the reaction section 14, and temperature control is performed independently from the reaction section 14. The preheating section 13 is a preheating section for promoting nucleation prior to the synthesis of nanoparticles, and even if the preheating section 13 and the reaction section 14 are set to the same temperature, the heating section 9 allows individual temperature control, so that the energy input per unit length to heat the material solution can be made larger than that of the reaction section 14. As a result, the temperature drop near the first connection point 6 of the preheating section 13 can be suppressed as much as possible, and nucleation, which is important for manufacturing nanoparticles, can be performed accurately and stably.

[0054] The nanoparticles that react and are synthesized while passing through the reaction tube 1 flow through the downstream pipe 2 to an inspection device (not shown) or a tank for recovering the product, and this series of flows is made to proceed continuously by operating a pump (not shown) at a constant speed to keep the amount of liquid sent constant. After the material solution that had been retained in the reaction tube 1 at the beginning of the operation has flowed away, the nanoparticle production device of this embodiment can continuously produce a product containing nanoparticles with stable and uniform properties.

[0055] The circuit configuration for heating the reaction tube 1 by energization is not limited to the above-described one. For example, one of the connection points of the first heating section 9a and the second heating section 9b adjacent to each other in the heating part 9 may not be a common electrode, and heating control may be performed in a time-division manner by switching between a plurality of heating sections with a switch.

[0056] Furthermore, even if a current flows through the reaction tube 1 when the heating unit 9 is energized to heat the reaction tube 1, the material solution in this embodiment is composed of a substance with extremely low electrical conductivity, so that the influence of the current flowing through the reaction tube 1 surrounding the material solution or the voltage applied between each of the connection points 6, 7, and 8 can be ignored.

[0057] 1, the number of connection points is 3 and the number of heating sections is 2, but the numbers of connection points and heating sections are not limited. The distance between connection points, the ratio of the lengths of the heating sections, the length, thickness, and cross-sectional shape of the reaction tube 1 can also be changed in various ways depending on the type of nanoparticles to be synthesized.

[0058] Another example of nanoparticles manufactured by the flow method is quantum dots (QDs). Quantum dots are nanoparticles composed of hundreds to thousands of atoms and have a particle size of about several nm to tens of nm. Quantum dots are also called fluorescent nanoparticles, semiconductor nanoparticles, or nanocrystals.

[0059] By using the nanoparticle production apparatus of this embodiment, quantum dots with small variations in particle size and fluorescence half-width and high quantum efficiency can be stably produced.

[0060] <Temperature control using the nanoparticle production device of this embodiment> The temperature control of this embodiment will be described in more detail with reference to FIG. 6. The circuit diagram of FIG. 6 is an example of temperature control, and is not limited thereto. In the embodiment shown in FIG. 6, a conductive tube is disposed as the heating section 9 surrounding the reaction tube 1, as in FIG. 2 and FIG. 3. The reaction tube 1 and the heating section 9 are in contact with each other. The heating section 9 is divided into three heating sections. That is, the heating section 9 is provided with four connection points B, C, D, and E, and includes a first heating section 15 between the first connection point B and the second connection point C, a second heating section 16 between the second connection point C and the third connection point D, and a third heating section 17 between the third connection point D and the fourth connection point E.

[0061] As shown in FIG. 6, the wirings 21-24 are connected to the connection points B-E, and a power source 25 for providing energy for electrically heating the heating unit 9 is connected between the first wiring 21 connected to the first connection point B and the fourth wiring 24 connected to the fourth connection point E. Also, as shown in FIG. 6, the first wiring 21 and the second wiring 22 connected to the second connection point C (between points AX) are connected via a switch 26, constituting a first temperature control circuit 31. Also, the second wiring 22 and the third wiring 23 connected to the third connection point D (between points XY) are connected via a switch 27, constituting a second temperature control circuit 32. Also, the third wiring 23 and the fourth wiring 24 connected to the fourth connection point E (between points YD) are connected via a switch 28, constituting a third temperature control circuit 33. Also, reference numerals 34-36 shown in FIG. 6 indicate temperature detection means.

[0062] The reaction tube 1 shown in FIG. 6 is, for example, a glass tube connected from point P to point Q. A material solution is supplied into the reaction tube 1 by a pump (not shown) connected to the point P side, and the material solution flows in the direction from point P to point Q.

[0063] For example, the power supply 2 is an AC power supply, and although not limited thereto, supplies a voltage with an effective value of about 2 V and a current of up to about 100 A. The power supply 2 can be produced by connecting a voltage conversion transformer to a commercial power supply.

[0064] 6 are semiconductor switches. Each of the switches 26, 27, and 28 may be a relay or other relay device.

[0065] The temperature detection means 34 to 36 in this embodiment are, for example, thermocouples of type K. The temperature detection means is not limited to thermocouples, and a platinum temperature detector, an infrared sensor, a thermistor, etc. can also be used.

[0066] The switches 26-28 and the temperature detection means 34-36 are connected to a temperature control means (not shown), which controls the ON / OFF of the switches 26-28 based on the temperature count values ​​obtained from the temperature detection means 34-36 in a manner to be described later, so that a preset temperature is maintained.

[0067] The arrow direction in Fig. 6 indicates the direction of current flow. As described above, if power supply 25 is an AC power supply, the direction of current flowing through the circuit alternates, but to facilitate the explanation of the operation, the arrow direction is shown at a certain moment.

[0068] Next, an example will be described in which the heating section 9, which is electrically heated by one power source 25, is divided into a plurality of heating sections 15 to 17, and the temperature of each of the heating sections 15 to 17 is controlled independently.

[0069] First, the flow of current when all the switches 26 to 28 are off (the state in FIG. 6) will be described. When all the switches 26 to 28 are off, the current flowing from the power source 25 proceeds in the direction of the arrow and reaches point A. At this time, since the first switch 26 is off, the current does not flow to the first temperature control circuit 31, but flows entirely in the direction of the first connection point B. Next, the current flows through the first heating section 15, and the first heating section 15 is heated. The current that reaches the second connection point C does not flow to the second temperature control circuit 32 because the second switch 27 is off, but flows through the second heating section 16, and the second heating section 16 is heated. Similarly, since the third switch 28 is off, the current flows through the third heating section 17, and the third heating section 17 is heated. Then, the current reaches point F of the fourth wiring 24, but since the third switch 28 is off, the entire amount of current returns to the power source 25, and a closed circuit is formed.

[0070] In this way, when all the switches 26-28 are off, the entire current passes through the heating section 9, and the amount of current is the same in the first heating section 15, the second heating section 16, and the third heating section 17. Therefore, all the heating sections are heated in the same manner. As a result, the reaction tube 1 in contact with the heating section 9 is heated. At this time, the temperature control means (not shown) keeps each of the switches 26-28 off until the temperature of each of the heating sections 15-17 or the reaction tube 1 reaches a preset temperature.

[0071] When a certain time has passed and the temperature of the reaction tube 1 approaches a preset temperature, the temperature control means starts to appropriately control each switch 26-28 to maintain the preset temperature. At this time, since a material solution with a low temperature is always supplied to the reaction tube 1 at the inlet side of the first heating section 15 shown in FIG. 6, the temperature of the upstream part of the reaction tube 1 corresponding to the first heating section 15 tends to be lower than that of the downstream part of the reaction tube 1 corresponding to the second heating section 16 and the third heating section 17. Therefore, the downstream part of the reaction tube 1 tends to reach the preset temperature earlier than the upstream part of the reaction tube 1. Therefore, the specific procedure of the temperature control will be described using the second heating section 16 as an example.

[0072] When the temperature control means detects that the second heating section 16 or the part of the reaction tube 1 corresponding to the second heating section 16 has reached the set temperature based on the signal from the second temperature detection means 35, the temperature control means turns on the second switch 27. At this time, the first switch 26 and the third switch 28 are in the OFF state. In this state, the current flows from the power source 25 through the first wiring 21 and the first heating section 15, but since the second switch 27 is turned on, two types of current flow paths are formed between the second connection point C and the third connection point D. That is, a flow path through the second heating section 16 and a flow path through the second temperature control circuit 32. At this time, the electrical resistance of the flow path through the second temperature control circuit 32 is sufficiently lower than the electrical resistance of the second heating section 16. Therefore, most of the current flows through the second temperature control circuit 32, and the amount of current flowing through the second heating section 16 is reduced accordingly. Although not limited thereto, for example, the flow rate ratio of the current is 80% to the second temperature control circuit 32 and 20% to the second heating section 16. When the amount of current flowing through the second heating section 16 is reduced, the amount of heat generated is also reduced accordingly, and as a result, the temperature of the second heating section 16 can be reduced. A switch that creates a flow path for shunting the current flowing through the second heating section 16 is generally called a shunt switch, and a circuit (temperature control circuit) including the shunt switch is called a shunt circuit. In addition, the lower the resistance of the shunt circuit part in FIG. 6, the more current can be shunted to the shunt circuit side. Therefore, by making the electrical resistance of the shunt circuit lower than the electrical resistance of the heating section 9, the temperature control effect on the reaction tube 1 can be increased. However, even if the electrical resistance of the shunt circuit is equal to or higher than the electrical resistance of the heating section 9, it is possible to shunt a constant current according to the electrical resistance to the shunt circuit side, and in this case, the temperature control efficiency is low, but it is possible to perform temperature control.

[0073] Subsequently, the current that branches into two paths at the second connection point C joins again at the third connection point D. Therefore, the entire amount of current flows through the third heating section 17, and heating continues as usual.

[0074] In this manner, in an example in which only the second switch 27 of the switches 26 to 28 is turned on, normal heating is maintained in the first heating section 15 and the third heating section 17, and heating in the second heating section 16 is weakened compared to the first heating section 15 and the third heating section 17.

[0075] In the above description, only the second switch 27 is turned on, but when only the first switch 26 or only the third switch 28 is turned on, it is possible to weaken the heating only in the first heating section 15 or only in the third heating section 17. Even when more than one of the switches 26 to 28 are turned on, it is possible to weaken the heating in the heating section connected to the temperature control circuit that is turned on.

[0076] As described above, in the closed circuit in which the single power source 25 is connected to the heating part 9 surrounding the reaction tube 1, by providing a temperature control circuit for each of the multiple heating sections, the amount of current flowing in each heating section can be controlled, and heating control can be realized for each heating section.

[0077] <Current control means> 6, the amount of current increases or decreases depending on the operating state of the shunt switch, so attention must be paid to the capacity of the connected power source 25 to handle load fluctuations.

[0078] For example, when all the switches 26-28 are in an on state, most of the current flowing from the power source 25 flows from point A through a flow path including the first switch 26, point X, second switch 27, point Y, third switch 28, and point F, so that the current flowing through the heating unit 9 is small and the temperature of each of the heating sections 15-17 drops. At this time, the electrical resistance between points A and F as viewed from the power source 25 side drops significantly compared to when all the switches 26-28 are off, because there are two flow paths. Furthermore, because the electrical resistance of the flow path portion including the switches 26-28, i.e., the temperature control circuits 31-33, is designed to be lower, the drop in electrical resistance in an extreme case becomes almost equivalent to short-circuiting the output of the power source 25.

[0079] Under such circumstances, power supply 25 is required to have the ability to pass a large current, but in the circuit configuration of FIG. 6, in some cases an extremely large current may flow through power supply 25, which may destroy power supply 25.

[0080] Therefore, in FIG. 7, a current limiting means 40 for controlling the overall current in response to the on / off states of the switches 26 to 28 is disposed in the circuit configuration of FIG.

[0081] The current limiting means 40 shown in Fig. 7 includes, for example, a microcomputer and a semiconductor switch. Note that neither the microcomputer nor the semiconductor switch are shown. The operating state of each of the switches 26 to 28 can be monitored in cooperation with a temperature control means (not shown). The semiconductor switch constituting the current limiting means 40 operates at a speed sufficiently faster than the frequency of the alternating current supplied by the power source 25, and finely divides the current flowing through the circuit by so-called PWM control, and controls the effective power value by changing the on / off time.

[0082] The operation of the microcomputer constituting the current limiting means 40 will be described with reference to the flow chart of FIG.

[0083] For example, all of the switches 26 to 28 are currently in an OFF state, and the entire amount of current flows through the heating unit 9. The amount of current at this time is assumed to be current amount 1.

[0084] The current limiting means 40 cooperates with the temperature control means to detect the number of the switches 26 to 28 that are turned on in step ST1 of FIG.

[0085] In step ST2, if none of the switches 26-28 are on, PWM1 is set (step ST3). That is, all of the switches 26-28 are off, and the current flowing through the heating unit 9 is 1. At this time, the on / off ratio of the PWM control, i.e., the duty ratio, is set to 100% (PWM1).

[0086] When it is found in step ST2 that there is a switch that is turned on, the number of switches that are turned on is detected in step ST4. For example, when any one of the switches 26 to 28 is turned on, the electrical resistance of 1 / 3 of the current flow path decreases, and the amount of current increases if no current limiting is performed. When any one of the switches 26 to 28 is turned on, the amount of current flowing to the power supply 25 is set to current amount 2. Hereinafter, when two switches are turned on simultaneously, the amount of current flowing to the power supply 25 is set to current amount 3, and when all three switches are turned on, the amount of current flowing to the power supply 25 is set to current amount 4. At this time, the relationship between the amounts of current is as follows: current amount 4>current amount 3>current amount 2>current amount 1 according to Ohm's law, assuming that the electrical resistance of the heating unit 9 is uniform from the first connection point B to the fourth connection point E, and that the connection points are attached to the heating unit 9 at equal intervals, and further that the resistance of the shunt circuit portion is also the same.

[0087] In this way, in order to prevent an excessive load from being applied to the power supply 25 regardless of the on / off state of the switches, the current limiting means 40 shown in FIG. 7 changes the on / off ratio of the PWM control, i.e., the duty ratio, according to the on / off state of the switches 26 to 28. For example, by halving the duty ratio, the effective current value flowing through the circuit can also be halved. In this way, by changing the duty ratio, a pulsed current flows in the heating section. In this embodiment, the pulsed voltage (current) may be applied intermittently (intermittent current application). Intermittent current application allows for more precise current control.

[0088] It is possible to measure in advance how the electrical resistance between points A and F changes depending on the number of switches that are turned on by passing a small amount of current, and thereby determine the duty ratio so that the effective current flowing through the circuit is constant. As described above, if the duty ratio is 100% (PWM1) when the current amount is 1 in step ST3, for example, when one switch is on and the current amount is 2, the duty ratio is 80% (PWM2) (step ST5), when two switches are on and the current amount is 3, the duty ratio is 60% (PWM3) (step ST6), and when three switches are on and the current amount is 4, the duty ratio is 40% (PWM4) (step ST7).

[0089] These duty ratios are stored in a microcomputer, and a pre-programmed program is used to sequentially switch PMW control according to the number of switches that are on, making it possible to maintain a constant effective current in all switch states.

[0090] Although the timing of the change in the on / off state of the switch is unpredictable, the microcomputer is fast enough to instantaneously follow the change in the switch state.

[0091] In FIG. 6 and FIG. 7, the first heating section 15 of the heating section 9 corresponds to the preheating section of the reaction tube 1, and the second heating section 16 and the third heating section 17 of the heating section 9 correspond to the reaction section of the reaction tube 1. In this way, the reaction section can be divided into a plurality of continuous heating sections. Therefore, when the preheating section is added, the reaction tube 1 is divided into three continuous heating sections. The number of heating sections may be three or more. When the number of heating sections is three or more, in order to individually control the temperature of each of the three or more heating sections of the heating section 9 with one power source 25, it is preferable to provide a shunt switch circuit having an electric resistance lower than the electric resistance of each heating section, and increase or decrease the current flowing through each heating section by opening and closing each shunt switch circuit, thereby controlling the temperature of each heating section.

[0092] (Another embodiment) In the above, both the preheating section 13 and the reaction section 14 of the reaction tube 1 are heated by using the heating section 9, but for example, only one of the preheating section 13 and the reaction section 14 may be heated by using the heating section 9. In this case, the method of heating the reaction tube part not heated by the heating section 9 is not limited. As an example, when the reaction tube 1 is made of a conductive material such as stainless steel, the reaction tube 1 can be heated by directly passing electricity through it. For example, the heating section 9 is arranged only in the reaction section 14 of the reaction tube 1, and the reaction section 14 is heated by the electrical heating of the heating section 9, and the preheating section 13 is heated by directly passing electricity through it.

[0093] The heating section 9 can be made of any material as long as it is a continuous conductor, but it is preferable to use nichrome, an alloy of nickel and chromium. This is because nichrome has a small change in electrical resistance due to its own temperature rise when it is heated by current flow, and can create a more uniform temperature distribution throughout the entire heating section. The heating section 9 may be configured other than the configuration in which the conductive tube 41 shown in Figures 2 and 3 is arranged on the outer periphery of the reaction tube 1, and the configuration in which the heating wire 46 shown in Figures 4 and 5 is wound around the reaction tube 1. For example, the heating section 9 may be configured by coating the surface of an insulator such as a glass tube with a conductor such as carbon or plating it with a metal. When a conductor is applied, the thickness of the coating does not necessarily have to be uniform. EXAMPLES

[0094] The effects of the present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0095] (Example) As shown in FIG. 10, a plurality of heating sections, i.e., a preheating section and a reaction section, were provided in the reaction tube 1. The preheating section (between the first and second connection points) directly heated the reaction tube 1 by electrical current, and the reaction section (between the second and third connection points) heated the reaction tube 1 by electrical current through a block heater 50 as a heating section.

[0096] (Comparative Example) 11, the reaction tube 1 was not divided into a plurality of heating zones but was heated as a single heating zone. That is, in Comparative Example 1, unlike Example 1, no preheating zone was provided. The material solutions used in the above examples and comparative examples were the same, and were passed through a reaction tube to produce ZnCdSeS particles.

[0097] As shown in the experimental results below, it was found that the full width at half maximum (FWHM) of the generated ZnCdSeS particles can be made smaller in the example than in the comparative example, and a high quantum efficiency (QY) can be obtained.

[0098] [Table 1] [Industrial Applicability]

[0099] INDUSTRIAL APPLICABILITY The present invention can be used in a nanoparticle production apparatus capable of producing nanoparticles such as quantum dots, and in a method for producing nanoparticles. [Explanation of symbols]

[0100] 1: Reaction tube 2: Downstream piping 3: Upstream piping 4: Back pressure valve 5: Check valve 6: First connection point 7: Second connection point 8: Third connection point 9, 9a, 9b: Heating section (heating section) 10: First wiring 11: Second wiring 12: Third wiring 13, 15: Preheating section 14, 16, 17: Reaction section 15: First heating section 16: Second heating section 17: Third heating section 21~24: Wiring 25: Power supply 26: First switch 27: Second switch 28: The third switch 31: First temperature control circuit 32: Second temperature control circuit 33: Third temperature control circuit 34 to 36: Temperature detection means 40: Current limiting means 41: Conductive tube 42, 43, 51: Connection points 44, 45, 52: Wiring 46: Heating wire 47, 48, 53: Power supply leads 49: Pipe joint 50: Block heater 54a, 54b, 55a, 55b: heating section (heating section) B~E: Connection points

Claims

1. A nanoparticle manufacturing apparatus for manufacturing quantum dots by supplying a material solution to a reaction tube, comprising: the reaction tube has a preheating section and a reaction section as continuous heating sections, the preheating section has a length of the reaction tube shorter than that of the reaction section, a heating section which is electrically heated is provided at an outer periphery of the preheating section and the reaction section, The amount of current flowing through each heating section of the heating unit is individually controlled, thereby making it possible to individually control the temperature of each heating section. A nanoparticle manufacturing apparatus.

2. 2. The nanoparticle production apparatus according to claim 1, wherein the heating section is controlled so that a pulsed current flows through the heating section.

3. 3. The nanoparticle production apparatus according to claim 1, wherein the voltage applied to the heating section is an alternating voltage.

4. A nanoparticle manufacturing apparatus as described in any one of claims 1 to 3, characterized in that each of the heating sections is equipped with a shunt switch circuit having an electrical resistance lower than the electrical resistance of the heating section, and the current flowing to the heating section is increased or decreased by opening and closing the shunt switch circuit, thereby controlling the temperature of the preheating section and / or the reaction section.

5. 5. The nanoparticle production apparatus according to claim 1, wherein the heating unit is a conductive tube surrounding the reaction tube.

6. 5. The nanoparticle production apparatus according to claim 1, wherein the heating unit is an electric heating wire wound around the reaction tube.

7. 7. The apparatus for producing nanoparticles according to claim 1, wherein a cross-sectional area of ​​a flow passage in the preheating section is smaller than a cross-sectional area of ​​a flow passage in the reaction section.

8. A method for producing nanoparticles for producing quantum dots by supplying a material solution to a reaction tube, the method comprising the steps of: the reaction tube has a preheating section and a reaction section as continuous heating sections, the preheating section has a length of the reaction tube shorter than that of the reaction section, A method for producing nanoparticles, characterized in that the preheating section and the heating sections located on the outer periphery of each heating section of the reaction section are electrically heated, and at this time, the amount of current flowing through each heating section is individually controlled to individually control the temperature of each heating section, and the material solution is supplied to the reaction tube.

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