JP5977104B2 - Brightness adjustment method for wavelength conversion nanoparticles - Google Patents

Description

The present invention relates to absorbent luminance adjusting how the wavelength conversion nanoparticles can improve the luminance (light emission luminance) of the wavelength conversion nanoparticles for generating light of a different wavelength from the light.

  Wavelength-converting nanoparticles that generate light with a wavelength different from the absorbed light are placed on the surface of the LED to change the emission color of the LED, or provided on the surface of the solar cell to convert the wavelength of incident light This improves the efficiency of the solar cell and is applied to various applications.

  Conventionally, as such wavelength conversion nanoparticles, those containing CdS have been proposed. However, since Cd has an adverse effect on the environment if the disposal process is mistaken, wavelength conversion nanoparticles are manufactured using ZnSe or the like. It has been proposed.

  However, since this type of production method produces wavelength conversion nanoparticles in an organic solvent, there is a possibility of conflicting with the PRTR method if the organic solvent is discarded. Therefore, it has been proposed to produce wavelength conversion nanoparticles in an aqueous solvent (see Non-Patent Document 1).

Narayan Pradhan, David M. Battaglia, Yongcheng Liu, and Xiaogang Peng, Nano Lett., Vol. 7, No. 2, 2007, 312-317

  However, in the method described in Non-Patent Document 1, wavelength-converted nanoparticles are produced at a temperature of 100 ° C. or less, and the obtained wavelength-converted nanoparticles have a very good emission luminance (emission intensity). It wasn't.

  Therefore, the present inventors have conducted research to make it possible to produce wavelength conversion nanoparticles having good emission luminance in an aqueous solvent, and have developed wavelength conversion nanoparticles having high emission luminance.

  However, according to recent research, it has been found that wavelength-converted nanoparticles in a solution have luminance fluctuations due to various influences such as the external environment after preparation. A technology that can be enhanced is desired.

The present invention has been made to solve the above problems, and its object is brightness adjustment how the wavelength conversion nanoparticles can increase the emission luminance of the wavelength conversion nanoparticles prepared solution further the It is to provide.

In the method of adjusting the brightness of the wavelength conversion nanoparticle of the present invention, the wavelength conversion nanoparticle doped with a metal ion serving as a light emission center for generating light of a specific wavelength in an inorganic nanoparticle is adjusted in a solution adjusted to a predetermined pH. After the production, a pH lowering treatment is performed to lower the pH of the solution in which the wavelength conversion nanoparticles are dispersed to a predetermined pH at the time of production.
Furthermore, as a manufacturing process for producing wavelength conversion nanoparticles, an ion source that provides a metal ion that becomes a luminescent center, an ion source that provides atoms that constitute the inorganic nanoparticle, and a hydrophilic substance that coordinates to the inorganic nanoparticle. A ligand is mixed in an aqueous solvent and the pH of the resulting solution is adjusted, and the solution after pH adjustment is heated to 150 ° C. to 250 ° C. under high pressure, Heating step of generating wavelength conversion nanoparticles.
In the mixing step, a solution containing N-acetyl-L-cysteine and Mn ions in the ion source at a molar ratio of 1: 1, N-acetyl-L-cysteine and Zn atoms in the source are included. Mix with a solution containing a molar ratio of 1: 4.8.

By performing this pH reduction treatment, the emission luminance of the wavelength conversion nanoparticles can be improved from the emission luminance at the time of manufacture, as is apparent from the experimental examples described later.
As described above, the reason why the emission luminance is improved by lowering the pH is that the wavelength conversion nanoparticles dispersed in the solution have a low emission luminance due to concentration quenching, as will be described in detail later. It is presumed that by performing a pH lowering treatment on this solution, metal ions are precipitated in the solution from the wavelength conversion nanoparticles, thereby reducing the influence of concentration quenching.

  Therefore, if the wavelength-converted nanoparticles whose luminance is adjusted in this way and whose emission luminance is increased are applied to, for example, a solar cell, the efficiency of the solar cell can be improved by converting ultraviolet rays into visible light. Has an effect.

FIG. 3 is an explanatory diagram illustrating a method for producing wavelength conversion nanoparticles of Example 1. 2 is a graph showing an emission spectrum of wavelength conversion nanoparticles produced by the production method of Example 1. FIG. FIG. 3 is an explanatory diagram showing a method for adjusting the luminance of wavelength-converted nanoparticles in Example 1. 4 is a graph showing an emission spectrum of wavelength conversion nanoparticles adjusted by the luminance adjustment method of Example 1. FIG. It is explanatory drawing which shows the reason which a brightness | luminance improves by the brightness | luminance adjustment method of Example 2. FIG. In Experimental example 1, it is a graph which shows the time-dependent change of the light-emission brightness | luminance at the time of changing pH with a carbon dioxide gas. In Experimental example 2, it is a graph which shows the time-dependent change of the luminescent brightness at the time of changing pH with hydrochloric acid. In Experimental example 3, it is a graph which shows the time-dependent change of the luminescent brightness at the time of changing the magnification of dilution.

Below, the brightness | luminance adjustment method of the wavelength conversion nanoparticle of this invention and embodiment of the wavelength conversion nanoparticle by which light emission brightness | luminance was adjusted by this brightness | luminance adjustment method are demonstrated.
[Embodiment]
-In this invention, pH of a solution can be reduced to the range of 6-8, for example with the pH reduction process with respect to the solution of pH 9-9 at the time of manufacture, for example. Thereby, as will be apparent from the experimental examples described later, the emission luminance of the wavelength conversion nanoparticles during production can be greatly improved.

  As the pH lowering treatment, “a method of lowering pH by adding an acidic solution to a solution in which wavelength conversion nanoparticles are dispersed”, “dilution of a solution by adding a diluted solution to a solution in which wavelength conversion nanoparticles are dispersed” The method for lowering the pH "and" the method for supplying the solution in which the wavelength conversion nanoparticles are dispersed with the gas for lowering the pH by dissolving in the solution "can be used.

  In addition, hydrochloric acid is mentioned as an acidic solution used in order to lower pH, but sulfuric acid, nitric acid, etc. can be considered besides that. Of these, hydrochloric acid is preferred because it has no fear of forming a precipitate with a doped metal (for example, Mn).

  On the other hand, examples of the gas used for lowering the pH include carbon dioxide (carbon dioxide), but hydrogen sulfide, hydrochloric acid gas, and the like are also conceivable. Of these, carbon dioxide is preferable because it is easy to handle for safety.

  Furthermore, Mn ions can be employed as the metal ions that serve as the emission center, and Zn can be included as the atoms constituting the inorganic nanoparticles. Inorganic nanoparticles containing Zn absorb light in the ultraviolet region well, and when the inorganic nanoparticles are doped with Mn ions, they can be generated by converting light in the ultraviolet region into light in the visible region. . Therefore, in that case, it can be favorably applied to uses such as improving the efficiency of solar cells.

In addition, after the wavelength conversion nanoparticles are manufactured, an inert gas such as argon (Ar) gas or nitrogen (N ₂ ) gas is supplied in or around the solution, and then pH reduction treatment is performed. Good. Since the luminance fluctuation can be suppressed by supplying the inert gas, the luminance can be maintained until the pH lowering process is performed.

  Furthermore, when the above-described luminance variation of the wavelength conversion nanoparticles is completely stopped and the luminance is maintained, the solution in which the wavelength conversion nanoparticles are dispersed may be solidified. Examples of the solidification method include a sol-gel method using glass as a binder and a method of mixing and solidifying in polyvinyl hydroxide.

  In addition, as a manufacturing process for producing wavelength conversion nanoparticles, an ion source that provides a metal ion serving as a luminescent center, an ion source that provides atoms constituting the inorganic nanoparticles, and a hydrophilic coordinated to the inorganic nanoparticles A mixing step of adjusting the pH of the resulting solution, and heating the pH-adjusted solution at 150 to 250 ° C. under high pressure to bring the solution into the solution. And a heating step for generating wavelength conversion nanoparticles.

That is, when the wavelength conversion nanoparticles are produced in an aqueous solvent, if they are produced by heating to 150 ° C. to 250 ° C., wavelength conversion nanoparticles having good emission luminance can be obtained.
In addition, N-acetyl-L-cysteine can be adopted as the ligand, but in addition to N-acetyl-L-cysteine, mercaptoacetic acid, mercaptopropionic acid, mercaptosuccinic acid, and the like can be used.

  Here, when inorganic nanoparticles are doped with Mn ions, in the mixing step, a solution containing N-acetyl-L-cysteine and Mn ions in the ion source in a molar ratio of 1: 1; A solution containing acetyl-L-cysteine and Zn atoms in the ion source in a molar ratio of 1: 4.8 may be mixed.

  -Moreover, when including S and Se as an atom which comprises an inorganic nanoparticle, a mixing process, each ion source which provides each atom other than Se which comprises an inorganic nanoparticle, respectively, a ligand, A first mixing step of adjusting the pH of the resulting solution, each ion source that provides each atom other than S constituting the inorganic nanoparticles, and a ligand. A second mixing step of adjusting the pH of the solution obtained by mixing in a solvent, a solution after pH adjustment obtained in the first mixing step, and a solution after pH adjustment obtained in the second mixing step; And an ion source that provides metal ions serving as the emission center may be mixed into the solution in the first mixing step or the second mixing step.

  By doing so, it is possible to satisfactorily produce wavelength conversion nanoparticles made of mixed crystals as described above.

Below, the brightness | luminance adjustment method of the wavelength conversion nanoparticle of this invention and the specific Example of the wavelength conversion nanoparticle by which light emission brightness | luminance was adjusted with this brightness | luminance adjustment method are demonstrated.
a) First, the manufacturing method of the wavelength conversion nanoparticle of Example 1 is demonstrated.

  As shown in FIG. 1 (A), in this example, first, a Zn ion source (for example, zinc perchlorate) and N-acetyl-L-cysteine (hereinafter referred to as NAC) are 1: 4.8. An aqueous solution containing a molar ratio was mixed with an aqueous solution containing a Mn ion source (eg, manganese perchlorate) and NAC at a molar ratio of 1: 1. The former aqueous solution and the latter aqueous solution were mixed at a ratio of 10: 1 so that the Mn concentration with respect to the entire aqueous solution after mixing was 2 mol%.

Next, as shown in FIG. 1 (B), the pH was adjusted to 8.5 by adding NaOH to the aqueous solution.
Next, as shown in FIG. 1C, 1.2 mmol of Se ion source (for example, NaHSe) was added. In this case, the molar ratio of Zn: Se is (1: 0.6). Further, in this aqueous solution, that is, a ZnMnSe precursor (Precursor), it is presumed that the SH group of NAC is coordinated to a metal atom, and the carboxyl group of NAC promotes dissolution in an aqueous solvent.

  Next, as shown in FIG. 1 (D), the pH is adjusted to 10.5 by further adding NaOH to the aqueous solution, and then heated to 200 ° C. under high pressure (for example, 6 atmospheres) to convert the wavelength. Nanoparticles (ZnSe: Mn) were produced. The heating time was 10 minutes.

  Then, the wavelength conversion nanoparticles produced in this manner were irradiated with UV light having a wavelength of 325 nm using a fluorescence spectrometer (F2500, manufactured by Hitachi High-Technology Corporation), and the emission spectrum of the wavelength conversion nanoparticles was examined. .

  The results are shown in FIG. 2. In the wavelength conversion nanoparticles (ZnSe: Mn) of Example 1 in which Mn ions are doped into ZnSe-based inorganic nanoparticles, in the visible region of 540 nm to 640 nm (particularly 582 nm), A peak of emission luminance (hereinafter sometimes referred to as emission intensity when showing the size of the emission spectrum) appeared. In the figure, the peak intensity is 16000.

  Thus, in the wavelength conversion nanoparticle of the present Example, extremely strong emission luminance (emission intensity) was obtained compared to the wavelength conversion nanoparticle produced in the conventional aqueous solvent. This is thought to be because clean crystals can be formed by producing nanoparticles at a high temperature.

The emission spectrum and the method for measuring the (peak) emission intensity described below are the same as described above unless otherwise specified.
Also, the emission intensity on the vertical axis of the graph does not necessarily correspond to a unit such as candela, but is a value obtained by relatively comparing the intensities compared in the graph (the same applies hereinafter). Therefore, even for the same sample, values such as intensity do not always match values in graphs and the like described later.

b) Next, a method for adjusting the luminance of the wavelength conversion nanoparticles produced as described above will be described.
This brightness adjustment method is a processing method for further improving the light emission brightness at the time of manufacture. In this embodiment, the light emission brightness is improved by using carbon dioxide gas (CO ₂ ).

  First, as shown in FIG. 3 (A), 5 ml of an aqueous solution containing the wavelength conversion nanoparticles produced by the production method described above, that is, an aqueous solution having a pH of 10.5 in which the wavelength conversion nanoparticles are dispersed, is taken and glass having a volume of 10 ml. Placed in container 1.

Since the volume of the glass container 1 is larger than the amount of the aqueous solution to be charged, there is a space 3 in which gas (here, air) exists above the aqueous solution in the glass container 1.
Next, the opening 5 of the glass container 1 is sealed with a rubber stopper 7, and a parafilm (not shown) is wound around the rubber stopper 7 so that the rubber stopper 7 is not removed. 3 was fixed.

In addition, a pH measuring device (pH meter) 9 is inserted into the rubber stopper 7 so that the pH of the aqueous solution in the glass container 1 can be measured.
At this point, the glass container 1 is filled with an inert gas such as argon (Ar) gas or nitrogen (N ₂ ) gas and sealed, thereby degrading (decreasing) the luminance of the wavelength conversion nanoparticles. Can be prevented. That is, the brightness at that time can be maintained.

Separately from this, as shown in FIG. 3B, the pipe 13 was connected to the carbon dioxide cylinder 11, and the first injection needle 15 was attached to the tip of the pipe 13.
Then, as shown in FIG. 3C, the second injection needle 17 was inserted into the rubber stopper 7 of the glass container 1 so that the gas in the glass container 3 was discharged out of the glass container 1.

  Next, as shown in FIG. 3 (D), the first injection needle 15 is inserted into the rubber stopper 7 of the glass container 1, and carbon dioxide gas is supplied from the carbon dioxide gas cylinder 13 into the glass container 1 through the first injection needle 15. did. Specifically, carbon dioxide was supplied at 1000 cc / min for 5 minutes. Thereby, the gas in the glass container 1 (here, the air in the space 3 above the aqueous solution) was replaced with carbon dioxide.

When the change in pH of the aqueous solution was measured in this state, the pH gradually decreased after the carbon dioxide gas was injected, and the pH of the solution became 7.0 5 minutes after the carbon dioxide gas was injected.
Therefore, the emission spectrum of the wavelength-converted nanoparticles was examined with respect to this aqueous solution having a pH of 7.0 using a fluorescence spectrometer in the same manner as described above.

  As a result, the emission intensity (specifically, the emission peak intensity at 582 nm) of the wavelength conversion nanoparticles in the solution whose pH was lowered to 7.0 was about 1.4 times (see FIG. 6). Compared with the wavelength-converted nanoparticles immediately after production in the aqueous solution No. 5 were greatly improved. FIG. 6 shows an example in which the pH is adjusted to 7.5. Similarly, the emission intensity is greatly improved.

c) Next, the function and effect of this embodiment will be described.
In this example, as described above, in the wavelength conversion nanoparticle production process, the pH is adjusted to pH 10.5, which is higher than the conventional one, and then treated at high pressure (for example, 6 atm) and high temperature (for example, 200 ° C.). As a result, the emission luminance can be increased as compared with the prior art.

  In particular, in this embodiment, after the wavelength conversion nanoparticles are produced, the pH of the aqueous solution is lowered (for example, to pH 7.0) by supplying carbon dioxide gas to the aqueous solution in which the wavelength conversion nanoparticles are dispersed. As is clear from the experimental examples, the emission luminance of the wavelength conversion nanoparticles immediately after production can be further increased.

  Therefore, if the wavelength-converting nanoparticles whose luminance is adjusted and the emission luminance is increased in this way are applied to a solar cell or the like, it is remarkable that the efficiency of the solar cell can be improved by converting ultraviolet rays into visible light. There is an effect.

d) Next, a modification of the present embodiment will be described.
For example, as the Zn ion source, zinc chloride, zinc acetate, zinc nitrate, etc. can be used in addition to the above-described zinc perchlorate. In addition to the above-described manganese perchlorate, manganese chloride, manganese acetate, manganese bromide, and the like can be used as the Mn ion source.

  Further, as the Se ion source, selenourea, hydrogen selenide gas, etc. can be used in addition to the above-mentioned NaHSe. Further, as the ligand, mercaptoacetic acid, mercaptopropionic acid, mercaptosuccinic acid and the like can be used in addition to the aforementioned NAC.

  Furthermore, S may be used instead of Se. Even in that case, it is desirable to adjust the pH to 10.5 after the step of FIG. In that case, sodium sulfide, thiourea, hydrogen sulfide gas, or the like can be used as the S ion source used in the step of FIG. 1B so that the molar ratio of Zn: S is 1: 0.6. It is desirable to do.

Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be omitted or simplified.
As described above, the pH value to be adjusted after the step of FIG. 1A differs between when Se is used as the anion constituting the inorganic nanoparticles and when S is used.

  Therefore, in Example 2, wavelength conversion nanoparticles in which inorganic nanoparticles as a so-called mixed crystal semiconductor were doped with Mn ions using both Se and S as anions were produced by the following method.

a) First, the manufacturing method of the wavelength conversion nanoparticle of Example 2 is demonstrated.
In this example, the precursor aqueous solution of ZnMnSe produced by the steps of FIGS. 1A and 1B described above, and in place of Se as described above in the steps of FIGS. 1A and 1B. A ZnS: Mn precursor aqueous solution prepared using S was prepared separately.

And after adjusting to pH10.5, both were mixed and the wavelength conversion nanoparticle was obtained by heating at 200 degreeC for 10 minutes. In this wavelength conversion nanoparticle, the ratio of Se and S can be freely adjusted and can be expressed by a general formula of ZnSe _x S _1-x : Mn (0 <X <1). Hereinafter, ZnSe _x S _1-x is referred to as ZnSeS.

  The emission spectrum immediately after the production of the wavelength conversion nanoparticles immediately after the production was measured. The result is shown in FIG. 4 (in FIG. 4, an example in which the mixing ratio (X) is different) is shown. By adding S to the wavelength conversion nanoparticles (ZnSe: Mn), the emission intensity in the vicinity of 400 nm is obtained. It was found that the peak decreased and the peak of the emission intensity near 600 nm became stronger.

That is, for example, when X = 0.6, the emission intensity of the wavelength conversion nanoparticles (specifically, the emission peak intensity at 587 nm) was 52,000.
b) Next, a method for adjusting the luminance of the wavelength conversion nanoparticles produced as described above will be described.

The brightness adjustment method in this embodiment is the same as that in the first embodiment.
Specifically, as shown in FIG. 3, 5 ml of a pH 10.5 aqueous solution in which wavelength conversion nanoparticles are dispersed is taken and placed in a glass container 1 having a volume of 10 ml, and then the glass container 1 is sealed with a rubber stopper 7. To do.

Thereafter, after the second injection needle 17 was inserted into the rubber stopper 7, the first injection needle 15 was inserted, and carbon dioxide gas was supplied from the carbon dioxide gas cylinder 13 into the glass container 1 through the first injection needle 15.
When the change in pH was measured in this state, the pH of the solution became 7.0 after 5 minutes from the injection of carbon dioxide gas.

Therefore, the emission spectrum of the wavelength-converted nanoparticles was examined with respect to this aqueous solution having a pH of 7.0 using a fluorescence spectrometer in the same manner as described above.
As a result, the emission intensity (specifically, the emission peak intensity at 587 nm) of the wavelength conversion nanoparticles in the solution whose pH was lowered to 7.0 was about 80000 (see FIG. 7), and the aqueous solution with pH 10.5. It was greatly improved compared to the wavelength-converted nanoparticles immediately after production.

  Thus, wavelength conversion nanoparticles (ZnSeS: Mn) using both Se and S can provide better emission intensity than Example 1, and further improve the efficiency when applied to solar cells and the like. I found out that

c) Here, the principle by which the light emission luminance can be increased by the above-described pH lowering process will be described.
As shown in FIG. 5 (A), in the case of the production method of this example, an aqueous solution of a precursor containing Zn, Se, S, and Mn was adjusted to pH 10.5 and 200 ° C. at 6 atmospheres. When heated at, wavelength converted nanoparticles (ZnSeS: Mn) are produced.

  In this state, as shown in FIG. 5B, since a large amount of Mn is contained in ZnSeS, the emission luminance is reduced by so-called concentration quenching in which light emission is reduced by the influence of a large number of Mn. Concentration quenching is disclosed in, for example, “N. Pradhan, J. A. M. CHEM. SOC. 129, 11, 2007, 3339”.

  Thereafter, as shown in FIG. 5C, when the pH is lowered by exposing the aqueous solution to, for example, carbon dioxide gas, excess Mn is dissolved from the ZnSeS into the aqueous solution. The reason why Mn is dissolved in the aqueous solution is that Mn is considered to have a characteristic that it is more likely to be eluted when it is close to acidity (compared to high alkali) such as acid (dilute acid) or neutrality.

  As a result, the amount of Mn in ZnSeS is reduced, so that the influence of concentration quenching is reduced, and it is estimated that the light emission luminance is improved.

Next, the third embodiment will be described, but the description of the same contents as the second embodiment will be omitted.
In this example, the method for producing wavelength-converting nanoparticles is the same as in Example 2. However, in the subsequent luminance adjustment method, the difference is that hydrochloric acid (HCl) is used instead of carbon dioxide gas. Will be described.

First, wavelength conversion nanoparticles (ZnSeS: Mn) were produced by the same production method as in Example 2, and an aqueous solution in which the wavelength conversion nanoparticles were dispersed was put into a 5 ml container.
Then, 10 μl of 1N HCl was added and mixed while rotating the aqueous solution with a stirrer bar.

Next, the pH of the mixed aqueous solution was measured.
Then, the introduction of HCl and the measurement of pH were repeated, and when the target pH (for example, pH 7.0) was reached, the treatment was terminated.

  After this pH lowering treatment, when the emission intensity of the wavelength conversion nanoparticles in the aqueous solution of pH 7.0 (specifically, the emission peak intensity at 582 nm) was examined, it was about 1.4 times (see FIG. 6). Compared with the wavelength-converted nanoparticles immediately after production in an aqueous solution having a pH of 10.5, it was greatly improved.

  In this method, the pH can be finely adjusted by diluting the concentration of HCl. However, if it does so, since the input amount will increase and the initial wavelength conversion nanoparticle (ZnSeS: Mn) density | concentration will be diluted, in order to keep high concentration, it is more advantageous to use high concentration HCl.

  In the present example, the wavelength-converted nanoparticles whose brightness is adjusted by the pH lowering treatment with hydrochloric acid have a light emission brightness that is better than that of Example 1, so that the efficiency can be further improved if applied to solar cells and the like. Be made.

Next, the fourth embodiment will be described, but the description of the same contents as the second embodiment will be omitted.
In this example, the method for producing wavelength-converting nanoparticles is the same as that in Example 2, except that in the subsequent luminance adjustment method, dilution is performed using pure water (H ₂ O) instead of carbon dioxide. Therefore, different brightness adjustment methods will be described.

First, wavelength conversion nanoparticles (ZnSeS: Mn) were produced by the same production method as in Example 2, and an aqueous solution in which the wavelength conversion nanoparticles were dispersed was put into a 5 ml container.
Then, while rotating the aqueous solution with a stirrer bar, 10 μl of pure water was added, mixed and diluted.

Next, the pH of the diluted aqueous solution was measured.
Then, the introduction of the pure water and the measurement of the pH were repeated, and when the target pH (for example, pH 7.0) was reached, the treatment was terminated.

  After this pH lowering treatment, the emission intensity (specifically, the emission peak intensity at 582 nm) of the wavelength conversion nanoparticles in an aqueous solution of pH 7.0 was examined, and was about 3 times (100 times dilution in FIG. 8). As compared with the wavelength conversion nanoparticles immediately after the production in an aqueous solution having a pH of 10.5, it was greatly improved.

In this example, the wavelength-converted nanoparticles whose brightness is adjusted by the pH reduction treatment by dilution have a better light emission brightness than that of Example 1, so that the efficiency can be further improved if applied to solar cells and the like. Be made.
[Experiment 1]
Next, Experimental Example 1 performed for confirming the effect of the present invention will be described.

In this experimental example, the relationship between pH and time-dependent change in emission luminance (emission intensity) was examined using the luminance adjustment method of Example 2.
Specifically, an aqueous solution in which wavelength conversion nanoparticles (Zn: Se: S: Mn = 1: 0.3: x: 0.05, x = 0.3) produced by the method of Example 2 are dispersed ( With respect to pH 10.5), nitrogen gas was first sealed, and nitrogen gas and argon gas were replaced after one day.

Next, 6 days after the production, carbon dioxide gas was sealed instead of argon gas, and the pH of the aqueous solution was lowered to pH 7.5.
Then, the change with time in the emission intensity (Mn emission peak intensity: 582 nm) in the above-described sample was examined. The result is shown in FIG.

As shown in FIG. 6, the emission intensity of the sample adjusted to pH 7.5 increased greatly immediately after the pH was lowered, and then gradually increased. In addition, white turbidity did not arise.
From this experiment, it was found that when nitrogen gas (or argon gas) was filled immediately after production, the emission intensity was maintained and hardly decreased.

Further, it was found that when the argon gas was replaced with carbon dioxide gas and the pH was lowered to pH 7.5, the emission intensity increased greatly.
[Experiment 2]
Next, Experimental Example 2 performed to confirm the effect of the present invention will be described.

In this experimental example, the relationship between the pH and the time-dependent change in emission luminance (emission intensity) was examined using the luminance adjustment method of Example 3.
Specifically, a sample in which pH 10.5 of the aqueous solution was lowered to pH 8, pH 7, and pH 6 by adding hydrochloric acid to the aqueous solution in which the wavelength conversion nanoparticles produced by the method of Example 3 were dispersed. Was made. Moreover, the sample which does not add hydrochloric acid as a comparative example was also produced.

And the change with time of the emission intensity (Mn emission peak intensity: 582 nm) in each sample was examined. The result is shown in FIG.
As shown in FIG. 7, the luminescence intensity of the samples of pH 8, pH 7, and pH 6 increased greatly immediately after the pH was lowered, then gradually increased, and reached the almost upper limit after about 30 days.

Among these samples, particularly, the pH 6 sample showed the largest increase in emission intensity at first, and thereafter, the emission intensity was higher than that of the pH 8 and pH 7 samples.
On the other hand, in the samples of Comparative Examples having pH of 10 and 5, the emission intensity rapidly increased from 6 to 10 days, but after 10 days, the emission intensity decreased and became cloudy.

  From this experiment, when the pH was lowered to pH 6-8 from the pH immediately after production, the emission intensity increased greatly, and the emission intensity decreased even after a long time (two months or more). It was suitable.

In this experimental example, the pH at the time of production was set to 10.5. However, according to the study by the present inventors, the same effect can be obtained even when the pH at the time of production is set to 9 to 11. I know.
[Experiment 3]
Next, another experimental example 3 will be described.

In this experimental example, the relationship between pH and luminance change with time was examined using the luminance adjustment method of Example 4.
Specifically, wavelength conversion nanoparticles (Zn: Se: S: Mn = 1: 0.3: 0.3: 0.05) were dispersed by the manufacturing method of Example 3 as a stock solution used in the experiment. An aqueous solution was prepared, and an aqueous solution having a pH of 7.0 was obtained by adding 1N HCl in the same manner as in Example 3.

And this aqueous solution was diluted 1 time, 2 times, 5 times, 10 times, 100 times, and 200 times using a pH 7.0 HCl solution.
Then, each diluted solution is diluted with ultrapure water and adjusted to be 200 times that of the stock solution (that is, adjusted so that the concentrations of the wavelength conversion nanoparticles are uniform). Emission peak intensity: 582 nm). The result is shown in FIG. In addition, FIG. 8 shows the time-dependent change of the emitted light intensity after adjusting by adding ultrapure water.

It can be seen from FIG. 8 that the emission intensity increases as the degree of dilution increases.
Needless to say, the present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the scope of the present invention.

  (1) For example, in each of the above embodiments, Zn and Mn are used as cations, but the type of cation can be variously changed, such as using Cd instead of Mn. Further, S or Se, Mn, and Zn may be mixed in any order.

(2) Moreover, the brightness | luminance adjustment method of this invention can be utilized also for brightness | luminance adjustment of the wavelength conversion nanoparticle etc. which were manufactured with the manufacturing method of the nonpatent literature 1 mentioned above, for example.
That is, the emission luminance can be improved by performing the above-described pH reduction treatment on the wavelength conversion nanoparticles produced in a solution having a predetermined pH value.

DESCRIPTION OF SYMBOLS 1 ... Glass container 3 ... Space 5 ... Opening 7 ... Rubber stopper 9 ... pH meter

Claims (7)

After producing wavelength-converting nanoparticles in which inorganic nanoparticles are doped with metal ions that are emission centers that generate light of a specific wavelength, in a solution adjusted to a predetermined pH,
Wherein the pH of the solution wavelength converting nanoparticles are dispersed, the pH reduction process to reduce below a predetermined pH during manufacturing a brightness adjusting method of line power sale wavelength conversion nanoparticles,
As a manufacturing process for manufacturing the wavelength conversion nanoparticles,
In an aqueous solvent, an ion source that provides a metal ion serving as the emission center, an ion source that provides an atom constituting the inorganic nanoparticle, and a hydrophilic ligand that coordinates to the inorganic nanoparticle. A mixing step of mixing and adjusting the pH of the resulting solution;
Heating the pH-adjusted solution to 150 ° C. to 250 ° C. under high pressure to produce wavelength conversion nanoparticles in the solution; and
Have
In the mixing step, a solution containing N-acetyl-L-cysteine and Mn ions in the ion source in a molar ratio of 1: 1; N-acetyl-L-cysteine and Zn atoms in the ion source; A method for adjusting the luminance of wavelength-converting nanoparticles, comprising mixing a solution containing a molar ratio of 1: 4.8.   The brightness adjustment of the wavelength conversion nanoparticles according to claim 1, wherein the pH of the solution is adjusted to 9 to 11 during the production, and then the pH is reduced to a range of 6 to 8 by the pH reduction treatment. Method.   The method for adjusting the brightness of wavelength-converted nanoparticles according to claim 1 or 2, wherein the pH is lowered by adding an acidic solution to a solution in which the wavelength-converted nanoparticles are dispersed.   The wavelength-converting nanoparticle according to any one of claims 1 to 3, wherein the pH is lowered by diluting the solution by adding a diluted solution to the solution in which the wavelength-converting nanoparticles are dispersed. Particle brightness adjustment method.   The pH is lowered by supplying a gas that lowers the pH of the solution by dissolving in the solution into the solution in which the wavelength conversion nanoparticles are dispersed. Brightness adjustment method of wavelength conversion nanoparticle.   The wavelength conversion according to any one of claims 1 to 5, wherein after the wavelength conversion nanoparticles are manufactured, an inert gas is supplied around the solution, and then the pH reduction treatment is performed. Nanoparticle brightness adjustment method. As atoms constituting the inorganic nanoparticles, S and Se are included,
The mixing step includes
The ion source that provides each atom other than Se constituting the inorganic nanoparticles and the N-acetyl-L-cysteine are mixed in an aqueous solvent, and the pH of the resulting solution is adjusted. One mixing step,
The ion source that provides each atom other than S constituting the inorganic nanoparticles and the N-acetyl-L-cysteine are mixed in an aqueous solvent, and the pH of the resulting solution is adjusted. Two mixing steps;
A third mixing step of mixing the solution after pH adjustment obtained in the first mixing step and the solution after pH adjustment obtained in the second mixing step;
Consists of
Ion source to provide a metal ion to be the light emitting center, according to any one of claims 1 to 6, characterized in that it is mixed with the solution in the first mixing step or the second mixing step Brightness adjustment method of wavelength conversion nanoparticle.