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 conductive reaction tube (1), wherein the reaction tube has a preheating part (13) and a reaction part (14) as a continuous heating section, each of the preheating part and the reaction part is heated by directly energizing the reaction tube. The reaction tube is divided into a plurality of continuous heating sections and each heating section of the preheating part and the reaction part is preferably heated by directly energizing the reaction tube.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 conductive reaction tube, the reaction tube having a preheating section and a reaction section as continuous heating sections, and the preheating section and the reaction section Each heating section is The preheating section is heated by directly passing electricity through the reaction tube, and the length of the reaction tube in the preheating section is shorter than that of the reaction section. The amount of current flowing through each heating section is individually controlled, making it possible to individually control the temperature for each heating section. It is characterized by:

[0007] In the present invention, it is preferred that the reaction tube is divided into a plurality of continuous heating zones, and each heating zone of the preheating zone and the reaction zone is heated by directly passing an electric current through the reaction tube. In the present invention, it is preferable that electrodes are provided at both ends of the heating section, and a common electrode is provided at the boundary between adjacent heating sections.

[0008] In the present invention, it is preferable that a pulsed current is controlled to flow in the heating section. In the present invention, for example, the voltage applied to the heating section is an alternating voltage.

[0009] In the present invention, it is preferable that a shunt switch circuit having an electrical resistance lower than the electrical resistance of the heating section is attached to each of the heating sections, and 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 heating section.

[0010] In the present invention, for example, a lining is provided on the liquid-contacting surface of the reaction tube. In the present invention, it is preferable that a flow path cross-sectional area of ​​the preheating section is smaller than a flow path cross-sectional area of ​​the reaction section.

[0011] The present invention is a method for producing nanoparticles for producing quantum dots by supplying a material solution to a conductive reaction tube, the reaction tube having a preheating section and a reaction section as continuous heating sections, the preheating section being shorter than the reaction section, Each heating section Each of them was heated by directly passing electricity through the reaction tube. At this time, the amount of current flowing through each heating section is individually controlled to individually control the temperature for each heating section.The method is characterized in that the material solution is supplied to the reaction tube in this state. [Brief description of the drawings]

[0012] [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 cross-sectional structure of a reaction tube used in a nanoparticle production apparatus. [Diagram 3] FIG. 3 is an example of a circuit configuration for explaining a temperature control method applied to the nanoparticle production apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram in which a current limiting means is added to the circuit of FIG. [Diagram 5] FIG. 5 is a flow chart showing the operation of temperature control in the nanoparticle producing apparatus having the circuit of FIG. [Figure 6] FIG. 6 is a schematic diagram showing the pipe diameters of the preheating section and the reaction section. [Figure 7] FIG. 7 is a schematic diagram showing a method for controlling the temperature of the reaction tube of the embodiment used in the experiment. [Figure 8] FIG. 8 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

[0013] 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.

[0014] <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.

[0015] Fig. 1 mainly shows the heating reaction section that constitutes the nanoparticle synthesis apparatus. That is, the nanoparticle synthesis apparatus is equipped with a reaction tube 1, 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.

[0016] (Reaction tube 1) The reaction tube 1 shown in Fig. 1 will be described. The reaction tube 1 is, for example, a cylinder made of stainless steel, but is not limited to stainless steel, and any material can be used as long as it is made of at least a continuous conductor from the first connection point (electrode) 6 to the third connection point (electrode) 8 shown in Fig. 1 and has a continuous space 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 harsh reaction conditions of high temperature and high pressure.

[0017] As for the internal structure of the reaction tube 1, as shown in FIG. 2, the inner wall surface 1a of the reaction tube 1 may be lined. Reference numeral 9 in FIG. 2 denotes a lining layer. The lining layer 9 is a coating film formed on the inner wall surface 1a of the reaction tube 1 for the purpose of preventing chemical corrosion and physical wear, and broadly includes coatings. The lining layer 9 generally refers to glass lining, Teflon (registered trademark) lining, etc., but in this embodiment, it also includes a thin film having physical properties different from the base material of the reaction tube 1 formed at least on the inner surface of the reaction tube in contact with the material solution by oxidizing or nitriding the surface of the metal itself, which is the reaction tube 1.

[0018] In addition, the size of the reaction tube 1 is not limited, but the outer diameter of the reaction tube 1 is several mm, the inner diameter is several hundreds of μm, and the total length (the length from the first connection point 6 to the third connection point 8 shown in FIG. 1) is about several thousands of mm. In this way, the reaction tube 1 has a long and narrow space inside and constitutes a metal thin tube with both ends open.

[0019] As shown in Fig. 1, the reaction tube 1 is provided with a first connection point 6, a second connection point 7, and a third connection point 8 from the upstream side. Although the number of connection points may be four or more, the number of connection points will be described as three in Fig. 1.

[0020] 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.

[0021] The reaction tube 1 from the first connection point 6 to the second connection point 7 shown in FIG. 1 is a preheating section 13 responsible for nucleation of nanoparticles, and the reaction tube 1 from the second connection point 7 to the third connection point 8 is a reaction section 14 responsible for nucleation growth of nanoparticles.

[0022] For example, each of the wires 10, 11, and 12 is connected to a power source (not shown). This allows the reaction tube 1 to be energized via the wires 10, 11, and 12, and energy for heating the preheating section 13 and the reaction section 14 can be supplied to the reaction tube 1. As described above, the reaction tube 1 forms a continuous conductor at least from the first connection point 6 to the third connection point 8, and therefore generates heat due to the electric energy supplied by energization. In other words, the reaction tube 1 is a reaction vessel and also serves as a heater that supplies thermal energy for the reaction of the material solution.

[0023] In this case, the voltage applied to the preheating section 13 and the reaction section 14 of the reaction tube 1 may be either AC or DC. When AC is applied, its frequency is not limited. For example, when AC is applied, the frequency may be 60 to 200 Hz, which is close to that of a commercial power source, or may be a high frequency exceeding 1 MHz.

[0024] As the frequency applied to the reaction tube 1 increases, an increase in electrical resistance due to the skin effect appears in the conductor constituting the reaction tube 1. For example, when a reaction tube 1 made of thick and wide stainless steel is used and the electrical resistance between the first connection point 6 and the third connection point 8 located at both ends of the reaction tube 1 becomes too low, the electrical resistance can be increased due to the above-mentioned skin effect by applying a high frequency AC current.

[0025] In addition, since a relatively large current (current exceeding 10 A, although not limited thereto) flows through the reaction tube 1 of this embodiment, it is necessary to make the contact resistance between the reaction tube 1 and each of the connection points 6, 7, and 8 as small as possible. If the contact resistance becomes large, heat is generated due to the contact resistance, which impairs the uniformity of heat generation. 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.

[0026] (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.

[0027] In Fig. 1, the second connection point 7 constitutes a common electrode for the preheating section 13 and the reaction section 14. Thereby, by energizing the reaction tube 1 between the first connection point 6 and the second connection point 7 and energizing the reaction tube 1 between the second connection point 7 and the third connection point 8, the preheating section 13 and the reaction section 14 can be configured as a continuous heating section.

[0028] As described above, in this embodiment, the preheating section 13 and the reaction section 14 are characterized in that they are heated by directly passing electricity through the reaction tube 1, respectively.

[0029] 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. The electrical resistance of the stainless steel tube used in this embodiment at room temperature per 1000 mm is, for example, 1.2Ω when actually measured, so that the electrical resistance of the preheating section 13 is about 0.24Ω and the electrical resistance of the reaction section 14 is about 1.2Ω.

[0030] In this embodiment, the power supply can be controlled separately for the preheating section 13 and the reaction section 14. The power supply can be controlled by measuring the temperatures of the preheating section 13 and the reaction section 14 using a temperature detection means (not shown), and on / off control using a PID can be performed based on each temperature so that the preheating section 13 and the reaction section 14 are maintained 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.

[0031] In this embodiment, even if the electrical resistance of the preheating section 13 becomes smaller than that of the reaction section 14, by separately controlling the electrical currents of the preheating section 13 and the reaction section 14, the preheating section 13 can be quickly heated to a predetermined temperature and can be stably maintained at the predetermined temperature.

[0032] In addition, in this embodiment, the preheating section 13 and the reaction section 14 are a continuous heating section, and there is no gap between the preheating section 13 and the reaction section 14. Therefore, a heating region that is continuously controlled to 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 performed stably and with high precision, thereby suppressing variation in the quality of the nanoparticles.

[0033] In the above, the tube diameters of the preheating section 13 and the reaction section 14 are the same, but by making the tube diameter of the preheating section 13 smaller than that of the reaction section 14 as shown in FIG. 6, 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. 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 can be. The reaction section 14 can have a flow path cross-sectional area larger than that of the preheating section 13, thereby improving mass productivity.

[0034] (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.

[0035] (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.

[0036] 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, the downstream side of the back pressure valve 4 is connected to devices (not shown) that inspect and recover the compound via the downstream piping 2.

[0037] In this embodiment, with the structure shown in FIG. 1, the sample solution is sequentially sent from the upstream piping 3 to 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 to the downstream piping 2 after the reaction is completed.

[0038] <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.

[0039] 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.

[0040] 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 used as a common electrode for the preheating section 13 and the reaction section 14, 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.

[0041] By directly wiring to the connection points 6, 7, and 8 of the preheating section 13 and the reaction section 14 shown in FIG. 1, it is possible to directly energize the preheating section 13 and the reaction section 14, and it is also possible to separately control the temperatures of the preheating section 13 and the reaction section 14, which have different electrical resistances from each other.

[0042] 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 from the first connection point 6 flows into the second connection point 7, which is a common electrode, while heating the preheating part 13 of the reaction tube 1. On the other hand, the current flowing from the third connection point 8 flows into the second connection point 7 while heating the reaction part 14. 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 from the first connection point 6 into the preheating part 13 does not flow beyond the second connection point 7 to the third connection point 8. The same applies to the current flowing from the third connection point 8 into the reaction part 14. 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 that of the second connection point 7, the direction of current flow described above is simply reversed, and the current that has flowed to the preheating section 13 does not flow to the reaction section 14, and the current that has flowed to the reaction section 14 does not flow to the preheating section 13. The above-mentioned 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.

[0043] In this way, by using the second connection point 7 as a common electrode for the preheating section 13 and the reaction section 14, it is possible to separately control the energization of the preheating section 13 and the reaction section 14 as continuous heating sections. This makes it possible to control the preheating section 13 and the reaction section 14 to have the same temperature or different temperatures.

[0044] 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.

[0045] 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 the temperature tends to be lower at a position close to the first connection point 6 than downstream of the first connection point 6 because the material solution before heating flows continuously into the position. In other words, if the distribution of electrical resistance in the length direction of the reaction tube 1 is uniform, the heat generated by passing an electric current is also uniform. As a result, the temperature is lower near the first connection point 6, which is the inlet of the material solution.

[0046] 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, individual temperature control is possible, 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.

[0047] 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.

[0048] 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 between the adjacent preheating section 13 and reaction section 14 may not be a common electrode, and heating control may be performed in a time-division manner by switching between multiple heating sections with a switch.

[0049] In addition, when electricity is applied to the reaction tube 1, the reaction tube 1 is filled with a material solution. Since the material solution in this embodiment is composed of a substance with extremely low electrical conductivity, 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] <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. 3. The circuit diagram of FIG. 3 is an example of temperature control, and is not limited thereto. In the embodiment shown in FIG. 3, the reaction tube 1 is divided into three heating sections. That is, the reaction tube 1 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.

[0054] As shown in FIG. 3, the wires 21-24 are connected to the connection points B-E, and a power source 25 for providing energy for heating the reaction tube 1 is connected between the first wire 21 connected to the first connection point B and the fourth wire 24 connected to the fourth connection point E. Also, as shown in FIG. 3, the first wire 21 and the second wire 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 wire 22 and the third wire 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 wire 23 and the fourth wire 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, the reference numerals 34-36 shown in FIG. 3 denote temperature detection means.

[0055] The reaction tube 1 shown in FIG. 3 is a metal tube electrically 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 flows in the direction from point P to point Q.

[0056] 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.

[0057] 3 are semiconductor switches. Each of the switches 26, 27, and 28 may be a relay or other relay device.

[0058] 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.

[0059] 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.

[0060] The arrow direction in Fig. 3 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.

[0061] Next, an example in which the reaction tube 1 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 will be described.

[0062] First, the flow of current when all the switches 26-28 are off (the state in FIG. 3) will be described. When all the switches 26-28 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 all flows in the direction of the first connection point B. Then, the current flows through the first heating section 15, and the first heating section 15 is heated. When the current reaches the second connection point C, since the second switch 27 is off, the current does not flow to the second temperature control circuit 32, but flows through the second heating section 16 of the reaction tube 1, 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 of the reaction tube 1, and the third heating section 17 is heated. The current then reaches point F of fourth wire 24, but because third switch 28 is off, the entire amount of current returns to power source 25, forming a closed circuit.

[0063] When all the switches 26 to 28 are off in this manner, the entire current passes only through the reaction tube 1, 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. At this time, a temperature control means (not shown) keeps each of the switches 26 to 28 off until the temperature of each of the heating sections 15 to 17 reaches a preset temperature.

[0064] 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 the switches 26-28 to maintain the preset temperature. At this time, since a material solution having a low temperature is always supplied to the inlet side of the first heating section 15 shown in FIG. 3, the temperature of the first heating section 15 tends to be lower than that of the second heating section 16 and the third heating section 17. Therefore, the second heating section 16 and the third heating section 17 tend to reach the preset temperature earlier than the first heating section 15. Therefore, a specific procedure of temperature control will be described using the second heating section 16 as an example.

[0065] When the temperature control means detects that the second heating section 16 has reached the set temperature based on the signal from the second temperature detection means 35, it 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 of the reaction tube 1, 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. 3, 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 reaction tube 1, 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 reaction tube 1, a certain current according to the electrical resistance can be shunted to the shunt circuit side, and in this case, the temperature control efficiency is low, but it is possible to perform temperature control.

[0066] 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 to the third heating section 17, and heating continues as usual.

[0067] 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.

[0068] 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.

[0069] As described above, in the closed circuit in which the single power source 25 is connected to the reaction tube 1, by providing a temperature control circuit for each of the multiple heating zones, the amount of current flowing in each heating zone can be controlled, and heating control can be realized for each heating zone.

[0070] <Current control means> 3, 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.

[0071] 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 reaction tube 1 is small, and the temperature of each heating section 15-17 drops. At this time, the electrical resistance between points A and F as seen from the power source 25 side drops significantly compared to when all the switches 26-28 are in an off state, because there are two flow paths. Furthermore, 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, so that in an extreme case, the drop in electrical resistance is almost equivalent to short-circuiting the output of the power source 25.

[0072] Under such circumstances, power supply 25 is required to be capable of passing a large current, but in the circuit configuration of FIG. 3, in some cases an extremely large current may flow through power supply 25, which may destroy power supply 25.

[0073] Therefore, in FIG. 4, 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.

[0074] The current limiting means 40 shown in Fig. 4 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.

[0075] The operation of the microcomputer constituting the current limiting means 40 will be described with reference to the flow chart of FIG.

[0076] For example, all of the switches 26 to 28 are now in an OFF state, and the entire current flows through the reaction tube 1. The current amount at this time is defined as current amount 1.

[0077] 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.

[0078] 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 reaction tube 1 is 1. At this time, the on / off ratio of the PWM control, i.e., the duty ratio, is set to 100% (PWM1).

[0079] 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 26-28 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 26-28 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 reaction tube 1 is uniform from the first connection point B to the fourth connection point E, and that the connection points are attached to the reaction tube 1 at equal intervals, and further that the resistance of the shunt circuit part is also the same.

[0080] 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. 4 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.

[0081] 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).

[0082] 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.

[0083] 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.

[0084] In Fig. 3 and Fig. 4, the first heating section 15 is a preheating section (hereinafter referred to as the preheating section 15), and the second heating section 16 and the third heating section 17 are reaction sections (hereinafter referred to as the reaction sections 16 and 17). That is, in the embodiment shown in Fig. 3 and Fig. 4, the reaction sections 16 and 17 are divided into a plurality of continuous heating sections. In Fig. 3 and Fig. 4 as well, each heating section of the preheating section 15 and the reaction sections 16 and 17 is heated by directly passing electricity through the reaction tube.

[0085] 3 and 4, the reaction sections 16 and 17 are divided into two heating sections, but they may be divided into three or more. If the preheating section 15 is added, the number of heating sections will be three or more. When there are three or more heating sections, in order to control the temperature of each heating section individually 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 to increase or decrease the current flowing through each heating section by opening and closing each shunt switch circuit to control the temperature of each heating section. EXAMPLES

[0086] 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.

[0087] (Example) As shown in FIG. 7, a reaction tube was provided with multiple heating zones, including a preheating zone and a reaction zone, and each heating zone was heated by direct current.

[0088] (Comparative Example) As shown in Fig. 8, the reaction tube 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.

[0089] 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.

[0090] [Table 1] [Industrial Applicability]

[0091] 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]

[0092] 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: Lining layer 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: First 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 B~E: Connection points

Claims

1. A nanoparticle production apparatus for producing quantum dots by supplying a material solution to a conductive reaction tube, comprising: The reaction tube has a preheating section and a reaction section as continuous heating sections, Each heating section of the preheating section and the reaction section is heated by directly passing electricity through the reaction tube, The preheating section has a reaction tube shorter in length than the reaction section, A nanoparticle production device capable of individually controlling the amount of current flowing through each heating section, thereby enabling individual temperature control for each heating section.

2. Electrodes are provided at both ends of the heating section, 2. The nanoparticle production apparatus according to claim 1, further comprising a common electrode provided at a boundary between adjacent heating sections.

3. 3. The nanoparticle production apparatus according to claim 1, wherein a pulsed current is controlled to flow in the heating section.

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

5. A nanoparticle manufacturing apparatus as described in any one of claims 1 to 4, 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 through the heating section is increased or decreased by opening and closing the shunt switch circuit, thereby controlling the temperature of the heating section.

6. 6. The apparatus for producing nanoparticles according to claim 1, wherein a lining is provided on a liquid-contacting surface of 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 conductive reaction tube, comprising the steps of: The reaction tube has a preheating section and a reaction section as continuous heating sections, The preheating section has a reaction tube shorter in length than the reaction section, a material solution is supplied to the reaction tube while controlling the temperature of each heating section individually by individually controlling the amount of current flowing through each heating section.

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