JP5835925B2 - Method for producing wavelength conversion nanoparticles - Google Patents

Description

  The present invention relates to a method for producing wavelength-converting nanoparticles that generate light having a wavelength different from that of absorbed light, and nanoparticles produced by the production method.

  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. (For example, refer nonpatent literature 1).

  However, in the manufacturing method described in Non-Patent Document 1, since wavelength conversion nanoparticles are manufactured in an organic solvent, there is a possibility of conflicting with the PRTR method if the organic solvent is discarded. Therefore, it has also been proposed to produce wavelength conversion nanoparticles in an aqueous solvent (see, for example, Non-Patent Documents 2 and 3).

Narayan Pradhan and Xiaogang Peng, J.AM.CHEM.SOC.VOL.129, NO.11,2007,3339-3347 Narayan Pradhan, David M. Battaglia, Yongcheng Liu, and Xiaogang Peng, Nano Lett., Vol. 7, No. 2, 2007, 312-317 Abdelhay Aboulaich, Malgorzata Geszke, Lavinia Balan, Jaafar Ghanbaja, Ghouti Medjahdi, and Raphael Schneider, Inorg.Chem., VOL.49,2010,10940-10948

  However, in the methods described in Non-Patent Documents 2 and 3, wavelength conversion nanoparticles are produced at a temperature of 100 ° C. or less, and the obtained wavelength conversion nanoparticles have a very good emission intensity. There wasn't. Then, this invention was made | formed for the purpose of enabling manufacture of the wavelength conversion nanoparticle which has favorable light emission intensity in an aqueous medium.

The present invention, which has been made to achieve the above object, is a method for producing wavelength-converting nanoparticles, which comprises doping inorganic ions with metal ions serving as emission centers for generating light of a desired wavelength to produce wavelength-converting nanoparticles. An ion source that provides Mn ions as metal ions serving as the luminescent center, an ion source that provides atoms constituting the inorganic nanoparticles, and a hydrophilic ligand that coordinates to the inorganic nanoparticles; Are mixed in an aqueous solvent and the pH of the resulting solution is adjusted, and the solution after the pH adjustment is heated to 150 ° C. to 250 ° C. under high pressure to generate wavelength conversion nanoparticles. viewed including the step, which contained Zn as atoms constituting the inorganic nanoparticles, wherein the mixing step, the Mn ions in the ion source and the N- acetyl -L- cysteine 1: comprising 1 molar ratio Solution and N The acetyl -L- cysteine and Zn atoms in the ion source 1: a solution containing a molar ratio of 4.8, a method for manufacturing a wavelength conversion nanoparticles characterized by mixing, and the gist.

  The applicant of the present application has found that, even when the wavelength conversion nanoparticles are produced in an aqueous solvent, the wavelength conversion nanoparticles having good emission intensity can be obtained by heating to 150 ° C. to 250 ° C. did. This is thought to be because clean crystals can be formed by producing nanoparticles at a high temperature. However, when heated to a temperature higher than 250 ° C., the dope effect tends to be reduced due to the self-cleaning effect. That is, in the wavelength conversion nanoparticle, the energy of the light absorbed by the inorganic nanoparticle is doped into the inorganic nanoparticle, and the metal ion that becomes the emission center is converted into light having another desired wavelength. However, when a crystal is produced at a temperature higher than 250 ° C., there is a tendency that the metal ion serving as the emission center is excluded from the crystal of the inorganic nanoparticles. On the other hand, when the wavelength conversion nanoparticles are formed at a temperature of less than 150 ° C., the effect of heating cannot be sufficiently obtained, and the difference in emission intensity from the wavelength conversion nanoparticles generated in an aqueous solvent by a conventional method is excessive. Does not come out.

  Such generation of wavelength conversion nanoparticles under high temperature is performed under an appropriate high pressure according to the temperature. In addition, in the production, first, in the mixing step, the ion source that provides the metal ion serving as the emission center, the ion source that provides the atoms constituting the inorganic nanoparticle, and the inorganic nanoparticle are coordinated. A hydrophilic ligand is mixed in an aqueous solvent, and the pH of the resulting solution is adjusted. Subsequently, in the heating step, the pH-adjusted solution is heated to 150 ° C. to 250 ° C. under the high pressure.

  The ligand may be N-acetyl-L-cysteine. As the ligand, in addition to N-acetyl-L-cysteine, mercaptoacetic acid, mercaptopropionic acid, mercaptosuccinic acid and the like can be used.

Further, the present invention is a metal ion to be the luminescence center Ri Mn ions der, including Zn as 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 the light in the ultraviolet region into light in the visible region. it can. Therefore, in that case, it can be favorably applied to uses such as improving the efficiency of solar cells.

Solution and, before Symbol mixing step, comprising a solution containing the said ion source and N- acetyl -L- cysteine to provide a Mn ion, and the ion source and the N- acetyl -L- cysteine to provide a Zn atom theft and mixed. Therefore, the wavelength conversion nanoparticles Mn ions doped inorganic nanoparticles comprising Zn, it can be favorably manufactured.

The present invention also relates to a method for producing wavelength-converting nanoparticles, wherein a metal ion serving as an emission center that generates light of a desired wavelength is doped into inorganic nanoparticles to produce wavelength-converted nanoparticles, An ion source that provides a metal ion, an ion source that provides an atom constituting the inorganic nanoparticle, and a hydrophilic ligand that coordinates to the inorganic nanoparticle are mixed in an aqueous solvent. A mixing step for adjusting the pH of the obtained solution, and a heating step for generating the wavelength conversion nanoparticles by heating the pH-adjusted solution to 150 to 250 ° C. under high pressure, the inorganic nanoparticles In the mixing step, each ion source that provides each atom other than Se constituting the inorganic nanoparticles and the ligand are contained in an aqueous solvent. P of the resulting solution A first mixing step for adjusting, each ion source for providing each atom other than S constituting the inorganic nanoparticles, and the ligand are mixed in an aqueous solvent, and the obtained solution A second mixing step for adjusting pH, a third mixing step for mixing the solution after pH adjustment obtained in the first mixing step, and the solution after pH adjustment obtained in the second mixing step. If made, the ion source to provide metal ions of the luminescent center is mixed into the solution in the first mixing step or the second mixing step may be characterized Rukoto.

  When S and Se are included as atoms constituting the inorganic nanoparticles, inorganic nanoparticles composed of mixed crystals are generated, and the emission intensity is improved extremely well by appropriately adjusting the ratio of S and Se. Can do. However, the appropriate pH differs greatly between S and Se when the ion source is added to the reaction system.

  Therefore, as described above, in the first mixing step, each ion source that provides each atom (including S) other than Se constituting the inorganic nanoparticles and the ligand are mixed in an aqueous solvent. The pH of the resulting solution is adjusted, and in the second mixing step, each ion source that provides each atom (including Se) other than S constituting the inorganic nanoparticles and the ligand are provided. What is necessary is just to adjust the pH of the solution obtained by mixing in an aqueous solvent, and to mix the solution after those pH adjustments at a 3rd mixing process. In addition, the ion source which provides the metal ion used as the said light emission center is mixed with the said solution by the said 1st mixing process or the said 2nd mixing process. By doing so, it is possible to satisfactorily produce wavelength conversion nanoparticles made of mixed crystals as described above.

  Further, the solution after completion of the mixing step may be adjusted to a pH of 9 to 11, and in that case, the wavelength conversion having a very good light emission intensity by heating the solution to 150 ° C. to 250 ° C. under high pressure. Nanoparticles can be produced.

  Moreover, the wavelength conversion nanoparticle of this invention was manufactured with the manufacturing method of the wavelength conversion nanoparticle in any one of the said. For this reason, the wavelength conversion nanoparticle of this invention has very favorable light emission intensity.

It is explanatory drawing showing the manufacturing method of the wavelength conversion nanoparticle of a 1st, 2nd Example. It is a graph showing the emission and absorption spectrum of the wavelength conversion nanoparticle of 1st Example manufactured by the method. It is a graph showing the change of the said spectrum by neglecting the 1st Example. It is a graph showing the difference of the said spectrum by pH of the 1st example. It is a graph showing the change of the brightness | luminance by the various parameters of the 1st Example. It is a graph showing the change of the emission spectrum by the hybrid ratio of the wavelength conversion nanoparticle of 2nd Example manufactured by the said method.

[First embodiment]
Next, the embodiments of the present invention will be described with specific examples. FIG. 1 is an explanatory view showing a method for producing wavelength conversion nanoparticles of the first embodiment and the second embodiment described later. 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%.

  Subsequently, pH was adjusted to 8.5 by adding NaOH to the aqueous solution, and 1.2 mmol of a Se ion source (for example, NaHSe) was further added as shown in FIG. In this case, the molar ratio of Zn: Se is (1: 0.6). In this aqueous solution (Precursor of ZnMnSe), 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. By further adding NaOH to the aqueous solution, the pH is adjusted to 10.5 as shown in FIG. 1 (C), and then heated to 200 ° C. under high pressure (for example, 6 atm), thereby converting the wavelength conversion nanoparticles (ZnSe). : Mn). The heating time was 10 minutes.

  FIG. 2 compares the emission / absorption spectrum of the obtained wavelength conversion nanoparticle (ZnSe: Mn) with the emission / absorption spectrum of the inorganic nanoparticle (ZnSe) obtained by omitting the aforementioned Mn ion source. It is a graph to represent. The 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 to the intensity, brightness, and the like in the graph described later. Therefore, even for the same sample, values such as intensity do not always match values in graphs and the like described later.

  As shown in FIG. 2, in the wavelength conversion nanoparticles (ZnSe: Mn) of the first example in which Mn ions are doped into ZnSe-based inorganic nanoparticles, a peak of emission intensity appeared in the visible region of 540 nm to 640 nm. . On the other hand, in the inorganic nanoparticles (ZnSe) not doped with Mn ions, the emission intensity peak hardly appeared in the visible region. Further, the absorption spectra of both were completely coincident and had a peak in the ultraviolet region of less than 400 nm. For this reason, if the wavelength conversion nanoparticle of a present Example is applied to a solar cell etc., an ultraviolet-ray can be converted into visible light and the efficiency of a solar cell can be improved. Moreover, in the wavelength conversion nanoparticle of a present Example, the luminescence intensity extremely stronger than the wavelength conversion nanoparticle manufactured in the conventional aqueous solvent was obtained. This is thought to be because clean crystals can be formed by producing nanoparticles at a high temperature.

  Next, FIG. 3 is a graph showing a change in the spectrum when the wavelength conversion nanoparticles produced as described above are left in the solution. In FIG. 3, the emission spectrum immediately after manufacture is multiplied by 10. As shown in FIG. 3, it was found that the absorption spectra of the two coincided completely, but the emission intensity increased greatly upon standing.

  FIG. 4 shows the first example obtained by heating after adjusting to pH 10.5 in the step of FIG. 1C as described above, and heating after adjusting to pH 5 in the step of FIG. 1C. It is a graph showing the difference of the emission and absorption spectrum with the sample obtained by doing this. As shown in FIG. 4, both exhibit substantially the same spectrum, but it can be seen that heating after adjustment to pH 10.5 has emission intensity over a wider wavelength region.

  FIG. 5A is a graph showing a change in luminance when the heating time is changed in Example 1. FIG. As shown in FIG. 5 (A), it was found that the emission intensity (luminance) of the wavelength conversion nanoparticles was the strongest when the heating time was 20 minutes. Note that the heating time during which the emission intensity is the strongest may vary depending on the heating temperature.

  FIG. 5 (B) is a graph showing a change in luminance when Example 1 manufactured with the heating time fixed at 20 minutes was left in the solution. As shown in FIG. 5B, it was found that the emission intensity (luminance) of the wavelength conversion nanoparticles was the strongest when left for 20 days. Note that the standing time at which the emission intensity is strongest may change depending on the solvent or its additive.

  FIG. 5C is a graph showing a change in luminance when the dopant ratio (that is, mol% of Mn in the whole Zn + Mn as a cation) is changed in Example 1. As shown in FIG. 5C, it was found that the emission intensity (luminance) of the wavelength conversion nanoparticles was the strongest when the dopant ratio was 2%.

  FIG. 5D is a graph showing a change in luminance when the pH value adjusted in the step of FIG. 1C in Example 1 is changed. As shown in FIG. 5D, it was found that when the pH was adjusted to 10.5, the emission intensity (luminance) of the wavelength conversion nanoparticles was the strongest.

  FIG. 5E is a graph showing a change in luminance when the heating temperature is changed in Example 1. As shown in FIG. 5E, it was found that when the heating temperature was 200 ° C., the emission intensity (luminance) of the wavelength conversion nanoparticles was the strongest.

  1A to 1C in FIG. 1 corresponds to the mixing step, and the subsequent heat treatment corresponds to the heating step. Further, the present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the gist of the present invention. 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.

[Second Embodiment]
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. Then, the wavelength conversion nanoparticle which doped the inorganic nanoparticle as what is called a mixed crystal semiconductor with Mn ion using both Se and S as an anion with the following method was manufactured as 2nd Example.

In the present embodiment, the ZnMnSe precursor solution prepared by the steps shown in FIGS. 1A and 1B and the Se solution in the steps shown in FIGS. 1A and 1B as described above. ZnS: Mn precursor solution prepared using S instead of 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 the general formula ZnSe _X S _1-X : Mn (0 <X <1).

  FIG. 6 is a graph showing a change in the emission spectrum depending on the hybridization ratio of the wavelength conversion nanoparticles of the second example. As shown in FIG. 6, it was found that by adding S to the wavelength conversion nanoparticles (ZnSe: Mn), the emission intensity peak near 400 nm decreased and the emission intensity peak near 600 nm increased. Therefore, it has been found that the wavelength conversion nanoparticles using both Se and S can provide even better emission intensity and can be further improved in efficiency when applied to solar cells and the like.

  In each of the above embodiments, Zn and Mn are used as the cation. However, 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.

Claims (7)

A method for producing wavelength-converting nanoparticles, comprising doping inorganic ions with metal ions that are emission centers that generate light of a desired wavelength to produce wavelength-converting nanoparticles,
An ion source that provides Mn ions as metal ions serving as the luminescent center, an ion source that provides atoms that constitute the inorganic nanoparticles, and a hydrophilic ligand that coordinates to the inorganic nanoparticles. Mixing in an aqueous solvent and adjusting the pH of the resulting solution;
A heating step in which the pH-adjusted solution is heated to 150 ° C. to 250 ° C. under high pressure to generate wavelength conversion nanoparticles;
Including
Containing Zn as an atom constituting the inorganic nanoparticles,
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 producing wavelength-converting nanoparticles, comprising mixing a solution containing a molar ratio of 1: 4.8. A method for producing wavelength-converting nanoparticles, comprising doping inorganic ions with metal ions that are emission centers that generate light of a desired wavelength to produce wavelength-converting 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;
A heating step in which the pH-adjusted solution is heated to 150 ° C. to 250 ° C. under high pressure to generate wavelength conversion nanoparticles;
Including
As atoms constituting the inorganic nanoparticles, S and Se are included,
The mixing step includes
A first mixing step of adjusting the pH of the resulting solution by mixing each ion source providing each atom other than Se constituting the inorganic nanoparticles and the ligand in an aqueous solvent; ,
A second mixing step of adjusting the pH of the resulting solution by mixing each ion source that provides each atom other than S constituting the inorganic nanoparticles and the ligand in an aqueous solvent; ,
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
The method for producing wavelength-converting nanoparticles, wherein the ion source that provides the metal ions serving as the emission center is mixed with the solution in the first mixing step or the second mixing step.   The method for producing wavelength-converting nanoparticles according to claim 2, wherein the metal ion serving as the emission center is Mn ion.   The method for producing wavelength-converting nanoparticles according to claim 3, wherein Zn is contained as an atom constituting the inorganic nanoparticles.   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; The method for producing wavelength-converting nanoparticles according to claim 4, wherein a solution containing a molar ratio of 1: 4.8 is mixed.   The said ligand is N-acetyl- L-cysteine, The manufacturing method of the wavelength conversion nanoparticle of any one of Claims 1-5 characterized by the above-mentioned.   The method for producing wavelength conversion nanoparticles according to any one of claims 1 to 6, wherein the solution after completion of the mixing step is adjusted to a pH of 9 to 11.