Patent Application
20090159849
The present invention relates to a fluorescent and a method for producing the same. More specifically, the present invention relates to a fluorescent composed of a semiconductor nanoparticle for use in modification/dyeing for a biologically-relevant substance, illumination, display and the like, and to a method for producing the fluorescent.
Quantum size effects are produced when a semiconductor is reduced in size to the nanometer order, and consequently the band gap energy increases accompanying a reduction in the number of atoms. A semiconductor fluorescent nanoparticle made of a nanometer semiconductor generates fluorescence equivalent to the band gap energy of the semiconductor. In CdSe nanoparticles of [II-VI type semiconductors], the fluorescent color can be freely adjusted within the range of 500 to 700 nm by adjusting the particle diameter of the nanoparticles, and the nanoparticles have the high fluorescent property thereof (see Patent Document 1, for example).
The II-VI type semiconductors typified by a CdSe nanoparticle are inorganic semiconductors, and the possibility of application as fluorescent tags for biochemical analyses, fluorescence material for illumination and displays and the like has been suggested, due to being more stable than organic pigments. However, cadmium (Cd), mercury (Hg), lead (Pb) and other heavy metals contained in the II-VI type semiconductors involve a considerable environmental risk during production and use.
Recently, Restriction of Hazardous Substances (RoHS) has been issued in Europe for restricting the use of six hazardous substances which are harmful to the global environment and human health in electrical/electronic equipment, the substances being lead (Pb), cadmium (Cd), hexavalent chrome (Cr6+), mercury (Hg), polybromobiphenyl (PBB), and polybromodiphenylether (PBDE). As in the case of [such issuance of] the RoHS, the use of these heavy metals is restricted in many other cases.
Of such II-VI type semiconductors, ZnS, ZnSe or other compound semiconductor that does not contain these heavy metals has a large band gap and thus produces a fluorescence of short wavelength only, hence fluorescence wavelengths cannot be controlled in a wide range from visible light to near-infrared light. In addition, a nanoparticle that generates fluorescence of visible light at room temperature are developed for III-V type semiconductors and IV type semiconductors such as silicon and germanium. Because the III-V type semiconductors and IV type semiconductors such as silicon do not contain the abovementioned restricted heavy metals, [these semiconductors] are relatively less toxic and generate fluorescence of a visible-light region.
However, it is difficult to develop the III-V and IV type semiconductors in an industrial field requiring low cost [production], due to the high covalent bonding properties [of these semiconductors] and the troublesome processes required in the production thereof. Furthermore, a chalcopyrite compound is a semiconductor compound, and the use thereof as a solar cell light absorber or the like has been suggested. As with the II-VI type semiconductors, the chalcopyrite compound semiconductor is a direct transition semiconductor. The chalcopyrite compound semiconductor is expected to be used in the same manner as the nanoparticles of the II-VI type semiconductors as long as it is possible to obtain a quantum yield as high as that of the II-VI type semiconductors.
Therefore, the inventors of the present invention have conducted keen study in the aim of creating a new semiconductor fluorescent nanoparticle composed of a low toxic element. Through the study, [the inventors of the present invention] focused their attention especially on CuInS2 as a target material, which is a compound with a chalcopyrite structure, whose property is similar to that of CdSe, composited [this compound] with II-VI type compound such as ZnS, evaluated the fluorescent property, and contrived and proposed an invention that relates to a fluorescent having a fluorescent quantum yield of no more than 10% (Patent Document 2).
However, [as a method for synthesizing] a chalcopyrite nanoparticle itself that is not composited with the II-VI type semiconductors such as ZnS, there is only an example of a synthetic method using a monomolecular raw material, which cannot be synthesized by a simple synthetic method (Nonpatent Document 1). A chalcopyrite-type nanoparticle of CuInS2 having a fluorescent quantum yield of approximately 4% and an outer particle diameter of approximately 2 to 5 nm can be synthesized using the monomolecular raw material. However, because synthesis of the monomolecular raw material itself is complicated, a simpler synthetic method is industrially desired.
On the other hand, the chalcopyrite-type nanoparticle can be synthesized by a method of dissolving metallic salt, which is a raw material, into a solution containing a complex, but the fluorescent quantum yield of the nanoparticle obtained by this synthetic [method] is no more than 0.1%, which is difficult to be applied to practical use. Therefore, although it is possible to synthesize a CuInS2 nanoparticle, a material whose quantum yield exceeds 10% so as to be applied in a wide range of application has not yet been obtained. This is because it is extremely difficult to control defects of the chalcopyrite compound. Specifically, when an exciton excited by excitation light is captured by a defect of the material, a part of [the exciton] returns to the ground state without emitting light (called “radiationless transition”).
Therefore, a problem in reduction of quantum yield occurs in a compound having many defects. From this standpoint, in order to prevent the radiationless transition caused by defects, it is necessary to improve a process for synthesizing the compounds to synthesize a compound having as less defects as possible. Moreover, it is a known fact that coating II-VI type semiconductors, such as CdSe, with a semiconductor (ZnS, for example) having a larger band gap than the core semiconductor [of the II-VI type semiconductors] effectively prevents the exciton excited by the excitation light from reaching a particle surface having many defects and from performing radiationless transition due to the defects of the surface, so that the quantum yield thereof can be improved (Nonpatent Document 2).
[Patent Document 1] Published Japanese Translation No. 2003-524147 of the PCT International Publication
[Patent Document 2] PCT/JP2005/013185
[Nonpatent Document 1] B. O. Dabbousi, J. Rodriguez-Viejo, F. V. Mikulec, J. R. Heine, H. Mattoussi, R. Ober, K. F. Jensen, and M. G. Bawendi, J. Phys. Chem. B 1997, Vol. 101, p 9463-9475
[Nonpatent Document 2] S. L. Castro, S. G. Bailey, R. P. Raffaelle, K. K. Banger, and A. F. Hepp, J. Phys. Chem. B 2004, Vol. 108, p 12429-12435
The present invention has been contrived in view of the background described above, and achieves the following objects.
An object of the present invention is to provide a chalcopyrite semiconductor nanoparticle fluorescent having high quantum yield and low toxicity, and a method for producing [the fluorescent].
Another object of the present invention is to provide a compound having an outer particle diameter of 1 to 10 nm and a chalcopyrite structure, a nanoparticle fluorescent in the form of a solid solution having high quantum yield and an outer particle diameter of 1 to 20 nm, which is prepared by solid-solving II-VI type compound semiconductors or I-III-VI type compound semiconductors in the abovementioned compound, and a method for producing [this fluorescent].
Yet another object of the present invention is to provide a fluorescent having high quantum yield, which is composed of a composite particle obtained by coating the surface of a nanoparticle composed of a compound having a chalcopyrite structure with a semiconductor having a band gap wider than a band gap of this compound, and to provide a method for producing [this fluorescent].
A yet further object of the present invention is to provide a fluorescent having high quantum yield, which is composed of a composite particle obtained by coating the surface of a solid solution-type composite nanoparticle composed of a compound having a chalcopyrite structure and II-VI type or I-III-VI type compound semiconductors with a semiconductor having a band gap wider than band gaps of these compounds, and to provide a method for producing [this fluorescent].
In order to achieve the above objects, the present invention employs the following means.
The inventors of the present invention have improved a synthetic process for completing a metal, which is a raw material, with a complexing agent and thereafter heating or ripening [the metal] at room temperature, and have ended up inventing a compound nanoparticle having a fluorescent quantum yield of at least 3% but not more than 20% and a chalcopyrite-type structure. This compound nanoparticle has a fluorescent quantum yield of at least 10%, which has never been obtained before. The fluorescent quantum yield is the percentage of fluorescence emitted by a fluorescent excited by excitation light, in relation to the excitation light.
Throughout the present specification, “fluorescent quantum yield” is sometimes simply described as “quantum yield.” A method for measuring the fluorescent quantum yield in the present invention is as follows. First, the absorbency and fluorescence intensity of rhodamine B known to have a quantum yield of 73% and of a product of the present invention are measured, the results of the measurement are compared with each other, and the quantum yield of the product of the present invention is estimated.
“Ripening” above means heating [the metal] within the raw material at a temperature lower than the temperature for heating a reaction solution, for a predetermined amount of time, in order to react the metal with chalcogenite (hereinafter, “heating at low temperature” [or “low-temperature heating”] and “ripening” will be used to mean the same thing). “Heating temperature” here means the temperature at which the reaction solution reacts and eventually the nanoparticle is synthesized. Through this ripening [process], a cluster for nanoparticle formation is formed from the reaction solution, and thereby a nanoparticle is formed easily in a subsequent heating [process].
Low-temperature heating is performed at a temperature lower than the temperature used in the subsequent heating [process] For example, when the heating temperature is 100° C. to 300° C., the temperature for low-temperature heating is between 0° C. and 100° C. The length of ripening time or period takes several seconds to several hours, or a total of several tens of days. For example, leaving [the raw material solution] for 24 hours at a room temperature of 25° C. is in the range of this ripening [time period]. Also, leaving [the raw material solution] for 30 days at a room temperature of 25° C., for example, also is within the range of this ripening [time period].
Furthermore, a compound that is obtained by using this method had high quantum yield. Specifically, in a compound that is obtained by solid-solving other chalcopyrite type compound or II and VI group semiconductor compounds in the abovementioned chalcopyrite type compound (called “solid solution compound” hereinafter), the quantum yield was as high as 30%. This is a high quantum yield which has never been obtained before. Moreover, as with the conventional compounds, it has been found that the wavelength of this compound can be controlled by the composition and particle diameter [of this compound].
[Fluorescent]
The fluorescent of the present invention is composed of a first compound comprising a I, III and VI group compound with a chalcopyrite structure, such as CuInS2, CuGaS2 or AgInS2 (a compound comprising Cu or Ag as the I group element, In, Ga or Al as the III group element, and O, S, Se or Te as the VI group element), wherein the first compound is a particle having a quantum yield of at least 3% but not more than 20%, or preferably at least 10% but not more than 20%, and an outer particle diameter of 0.5 to 20.0 nm.
Moreover, the fluorescent of the present invention is preferably a nanoparticle of a solid solution compound which is obtained by solid-solving the abovementioned first compound and at least one compound of I, III and VI group compounds with chalcopyrite structures, which is a compound other than the first compound, and II and VI group compounds. The I-III-VI group compounds with a chalcopyrite structure, which is a compound other than the first compound, is preferably, for example, CuInS2, AgInS2, CuGaS2, AgGaS2, CuAlS2, AgAlS2, CuInSe2, AgInSe2, CuGaSe2, AgGaSe2, CuAlSe2, AgAlSe2, CuInTe2, AgInTe2, CuAlO2, AgAlO2, or the like.
The II-VI group compounds are preferably, for example, ZnO, ZnS, ZnSe, ZnTe, or the like. Furthermore, the fluorescent of the present invention is preferably a nanoparticle of the abovementioned solid solution compound in which the elements thereof are substituted with other elements of the same group, such as Cu, Ag, Al, Ga, In, O, S, Se, Te, Na, Li, and K. In addition, the fluorescent of the present invention is preferably composed of a composite particle which is obtained by coating on the abovementioned first compound or the abovementioned solid solution compound with one or more of the II and VI group compounds (e.g., ZnO, ZnS, ZnSe, ZnTe or the like) and the chalcopyrite-type compound, and is preferably a nanoparticle having a quantum yield of at least 66 but not more than 30%, or preferably at least 6% but not more than 25%.
Note that the outer particle diameter of the abovementioned first compound, the solid solution of the first compound, or the abovementioned composite particle or composite compound is 1.0 to 20.0 nm. Note that II and VI group semiconductors, such as CdS, CdSe, CdTe, HgS, HgSe, HgTe, PbS, PbSe, and PbTe, can be used as the II and VI group semiconductors to be solid-solved. In this case, such [II and VI group semiconductors] are used within legal restraints. In addition, as a compound for forming a solid solution composite particle by solid-solving the abovementioned first compound, III and V group semiconductors, such as InP, InN, InAs, GaP, GaN, GaAs, AlN, AlP, and AlAs, can be used. Also, it is preferable that a desired band gap be formed by the solid solution or its solid composition.
In this case, in such a composite compound, its band gap and fluorescent wavelength can be controlled by controlling the type of element to be solid-solved in the first compound and the solid-solving amount [of the element]. Furthermore, the first compound of the present invention and the composite compound obtained by solid-solving other element in the first compound are each obtained as a composite particle by forming a composite structure, which is obtained by coating the surface of the particle [of each of these compounds] with a second compound semiconductor having a band gap wider than those of these compounds, whereby a nanoparticle having a high quantum yield of 10% or above can be obtained.
The composite particle is a compound in which the first compound is composited with, within one particle, [the II and VI group semiconductors such as] ZnO, ZnS, ZnSe, and ZnTe, or, according to use application, one or a plurality of the II and VI group semiconductors such as CdS, CdSe, CdTe, HgS, HgSe, HgTe, PbS, PbSe, and PbTe, the III and V group semiconductors such as InP, InN, InAs, GaP, GaN, GaAs, AlN, AlP, and AlAs, or other chalcopyrite compound composed of I, III and VI group elements other than the first compound (these [compounds] are generically called “second compounds”), and it is preferable that [the composite particle] be a core-shell composite particle which is constructed by coating the first compound with the second compound.
In this case, it is preferable that the lattice mismatch ratio indicating the mismatch in lattice constants between the first compound or its solid solution, which is the core, and the second compound, which is the shell, be not more than 10%, or preferably not more than 5%. When the lattice mismatch ratio is comparatively large, it is possible to form a composition gradient type composite particle in which the second compound gradiently changes the composition ratio [between the first and second compounds] while increasing the composition ratio from the surface of the surface of the first compound, which is the core, toward the surface of the particle. In this case, the stress between the first compound and the coating layer is relaxed by the slow composition change, hence defects due to the stress can be prevented and higher quantum yield can be achieved.
Moreover, [the particle] may be coated with two or more layers of two or more second compounds in accordance with the lattice mismatch ratio, band gap, energy positions of a conduction band and of a valence band, or the like. This is effective because, when the lattice mismatch ratio between the coating layer of the outermost shell and the chalcopyrite compound is large, the stress generated at the interface can be reduced. Even in the case of a particle coated with one layer of the second compound or a particle coated with two or more layers, it is preferable that the lattice mismatch ratio between the adjacent compounds be not more than 10, preferably not more than 5%, and it is also preferable that the second compound be a compound having a band gap wider than that of the first compound.
It is preferable that the outer diameter of the composite particle be 2 to 20 nm. The first compound composing the composite compound is preferably composed of the elements of copper (Cu), indium (In) and sulfur (S), while the second compound is preferably composed of the elements of silver (Ag), indium (In) and sulfur (S). In this case, the composition ratio of copper (Cu) to silver (Ag) is preferably X:1−X, where X is 0.01 to 0.99.
Furthermore, the first compound composing the composite compound is preferably composed of the elements of copper (Cu), indium (In) and sulfur (S), while the second compound is preferably composed of the elements of copper (Cu), gallium (Ga) and sulfur (S). In this case, the composition ratio of indium (In) to gallium (Ga) is preferably X:1−X, where X is 0.01 to 0.99.
Moreover, the first compound composing the composite compound is preferably composed of the elements of copper (Cu), indium (In) and sulfur (S), while the second compound is preferably composed of zinc sulfide (ZnS). In this case, the composition ratio of copper (Cu) to zinc (Zn) is preferably X:1−X, where X is 0.01 to 0.99.
In addition, the first compound composing the composite compound is preferably composed of the elements of copper (Cu), indium (In) and sulfur (S), while the second compound is preferably composed of zinc selenide (ZnSe). In this case, the composition ratio of copper (Cu) to zinc (Zn) is X:1−X, where X is 0.01 to 0.99.
The band gap of the first compound is determined by the particle diameter thereof and the elements composing the chalcopyrite type compound [of the same], but it is preferable that the band gap be in the range of 1.0 to 3.5 eV.
Furthermore, the quantum yield obtained when the first compound is excited by excitation light and thereby emits a light wave preferably exceeds 10.0% at room temperature, and is preferably not more than 30.0%. It is preferable that fluorescence emitted by the first compound be a light wave having a wavelength of 500 to 950 nm. Moreover, it is preferable that fluorescence emitted by the solid solution of the first compound be a light wave having a wavelength within the range of 500 to 850 nm.
[Method for Producing Fluorescent]
The method for producing a fluorescent according to the present invention is a method for producing a fluorescent, which comprises [the steps of] mixing a first solution with a second solution, and heat-treating [the mixed solution] under predetermined heat conditions. Also, the present invention provides a fluorescent produced by this producing method. The first solution is a solution which is prepared by dissolving and mixing raw material salts of a plurality of types of elements composing a compound having a chalcopyrite structure in a solution added with a complexing agent coordinating the plurality of types of elements. The second solution is a solution prepared by dissolving a chalcogenite compound.
The chalcogenite compound preferably forms a preferred chalcopyrite compound precursor by being heated or ripened in the presence of a metal ion. [As the chalcogenite compound], a salt of dithiocarbamic acid such as dimethyldithiocarbamic acid, diethyldithiocarbamic acid and dihexyldithyiocarbamic acid, a salt of xanthic acid such as hexadecyl xanthate and dodecyl xanthate, a salt of trithiocarboxylic acid such as hexadecyl trithiocarboxylic acid and dodecyl trithiocarboxylic acid, zinc of dithiophosphoric acid such as hexadecyl dithiophosphoric acid and dodecyl dithiophosphoric acid, a metallic salt having [a mixture of] cadmium, magnesium, manganese, nickel, copper, lead or the like with sulfur or the like, thioacetamide, alkylthiol, thiourea and derivatives thereof, or a compound which generates chalcogen such as sulfur, selenium and tellurium by heating and thereby decomposing trioctylphosphine selenide, trioctyl phosphine telluride or the like can be used.
The complexing agent preferably coordinates to the plurality of types of elements composing the compound having a chalcopyrite structure. [As the complexing agent], amine compounds such as oleylamine, octylamine, dodecylamine, hexadecylamine, tributylamine and octadecyldimethylamine, carboxylic acid compounds such as stearic acid, oleic acid and lauric acid, and thiol compounds such as dodecanethiol and octanethiol can be used.
It is preferable that, after mixing of all or some of these raw material solutions, the mixed solution be ripened or heated for the purpose of pretreatment. A preferred form of complexation is performed by the reaction of the mixed solution during the pretreatment, whereby a compound nanoparticle having higher fluorescent quantum yield can be formed. After the pretreatment, the mixed solution is preferably heated under predetermined heat conditions.
Under the predetermined pretreatment conditions, it is preferable that the first solution and the second solution be mixed and subjected to heat treatment at a temperature of 0° C. to 100° C. Also, under the predetermined pretreatment conditions, it is preferable that the first solution and the second solution be mixed and subjected to ripening treatment for a duration of at least one second to not more than 30 days. Under the predetermined heat conditions, it is preferable that [the mixed solution] be subjected to heat treatment at temperature within the range of 100° C. to 300° C. after the pretreatment.
Under the predetermined heat conditions, it is preferable that [the mixed solution] be subjected to heat treatment for one second to 30 hours after the pretreatment. Under the predetermined heat conditions, it is preferable that the first solution and the second solution be mixed, heated, and reacted in a microreactor having a flow channel of 50 μm to 5 mm. Moreover, a sulfur compound is preferably a thioacetamide.
Furthermore, it is preferable that the first solution be a solution which is prepared by dissolving and mixing copper (I) or copper (II) salt with indium (III) salt at a concentration of 0.01 to 0.1 mol/L in a solution added with a complexing agent coordinating copper (I) and indium (III). It is preferable that [the first solution] be produced from raw materials of copper (Cu), indium (In) and sulfur (S) at a composition ratio (feed ratio) of A:B:2, with A being 0.5 to 10.0 and B being 0.5 to 10.0.
Moreover, it is preferable that the first solution be a solution which is prepared by dissolving and mixing silver (I) salt and indium (III) salt at a concentration of 0.01 to 0.1 mol/L in a solution added with a complexing agent coordinating silver (I) and indium (III). It is preferable that [the first solution] be produced from raw materials of silver (Ag), indium (In) and sulfur (S) at a composition ratio (feed ratio) of A:B:2, with A being 0.5 to 10.0 and B being 0.5 to 10.0.
In addition, it is preferable that the first solution is a solution which is prepared by dissolving and mixing copper (I) or copper (II) salt with gallium (III) salt at a concentration of 0.01 to 0.1 mol/L in a solution added with a complexing agent coordinating copper (I) and indium (III). It is preferable that [the first solution] be produced from raw materials of copper (Cu), gallium (Ga), and sulfur (S) at a composition ratio (feed ratio) of A:B:2, with A being 0.5 to 10.0 and B being 0.5 to 10.0.
The compound with a chalcopyrite structure, which is the first compound and composed of I, III and VI group elements, may be known [compound], but it is particularly preferable that at least one type of element be selected from each group of the I group elements of Cu and Ag, from the III group elements of In, Ga and Al, and from the VI group elements of S, Se and Te respectively.
The mixing ratio between the chalcopyrite compound and a compound to be composited can be changed freely to the extent that a solid solution or a composite structure is formed, but it is preferred to composite a compound that is composited at a molar ratio of 0.01 to 10 times, preferably 0.1 to 5 times relative to one element of the chalcopyrite compound which is the first compound.
According to the present invention, the following effects can be accomplished.
The fluorescent of the present invention does not contain any heavy metal elements, such as mercury (Hg), lead (Pb) and cadmium (Cd), which are subject to control as hazardous substances harmful to the environment and human body, and is a compound composed of the I, III and VI group elements having a chalcopyrite structure, or a composite particle or composite compound containing this compound. Because this composite particle or composite compound contain groups I, III and VI chalcopyrite compounds or groups II and VI elements, it does not contain Hg, Pb, Cd and other heavy metal elements that are subject to control.
Furthermore, the quantum yield of a product is improved more than ever before by performing pretreatment such as ripening the reaction solution for a predetermined amount of time. Therefore, the present invention can provide a fluorescent which is a semiconductor nanoparticle having low toxicity and high quantum yield.
Moreover, a product exhibiting fluorescence [within the range] from visible light to near-infrared light can be achieved by adjusting the elemental composition of the fluorescent and the contents of the elements. In addition, a fluorescence wavelength [in the range] from visible light to near-infrared light can be controlled by changing the temperature and time of heating the reaction solution.
The present invention can improve high quantum yield and thereby improve the quantum yield up to a maximum of approximately 28% by coating the chalcopyrite compound and its solid solution with a compound semiconductor having a band gap wider than a band gap of a core semiconductor.
Embodiments of the present invention will now be described hereinafter in detail using examples. The embodiments of the present invention are not limited to the following examples, and thus [examples] that exhibit the same effects by transforming the solutions and compounds to be used also fall within the scope of the present invention.
Here, Example 1 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared under argon atmosphere using argon gas. Copper iodide (I) and indium iodide (III) were dissolved at a concentration of 0.017 mol/L in oleylamine which is a complexing agent, to obtain a solution A. Oleylamine is a basic organic solvent and a coordinating solvent, and was used as a complexing agent for a metal ion and a stabilizing agent by coordinating the surface of a generated particle to prevent particle aggregation (this is the same for the following examples).
Thioacetamide was dissolved at a concentration of 0.034 mol/L in trioctyl phosphine to obtain a solution C. A reaction solution with a mixture of 18 mL of the solution A and 18 mL of the solution C was basically ripened for 24 hours at a temperature of 25° C. under argon atmosphere. Thereafter, the reaction solution was heated and reacted for 3 seconds to 10 minutes at a temperature of 160° C. to 280° C. Note that heating for 3 seconds to 2 minutes was performed using a microreactor having an inner diameter of 200 μm. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured. The results of the measurement are shown in the form of a graph.
(Ripening Effects)
The graph of
In this graph, the two graphs showing large fluorescence intensities show fluorescence intensities of the fluorescents that were generated from the reaction solutions ripened before being heated. In this graph, the graph showing a small fluorescence intensity shows fluorescence intensity of the fluorescent generated from the reaction solution that was not ripened. It is understood from this graph that the fluorescence intensities of the fluorescents that were generated from the reaction solutions ripened before being heated have increased more significantly than the fluorescence intensity of the fluorescent generated from the reaction solution that was not ripened.
(Heating Time)
The graph of
(Quantum Yield, Exceeding 10%)
Table 1 shows quantum yields, each of which represents a ratio of photons emitted by fluorescence to the number of photons of excitation light absorbed by each of the fluorescents shown in the graphs in
The rhodamine B used for measuring the quantum yields has a quantum yield of 73% at an excitation of 365 nm. Fluorescent property was measured using Spectrophotofluorometer FP6600 of JASCO corporation (Address: Hachioji-shi, Tokyo) (this is the same for the other following examples). All of the quantum yields shown in Table 1 are values exceeding 10%.
A=−log(I/I0) (Eq. 1)
where I0 is the intensity of incident light, and I is the intensity of transmitted light.
(Heating Temperature)
The vertical axis of the graph of
(Excitation Wavelength)
(Average Particle Diameter)
The average particle diameters of the products of
(Composition of the Raw Material)
(Structure)
The products of Example 1 were subjected to X-ray diffraction (XRD) measurement, and the results of [the measurement] are shown in the chart of
For the product synthesized at a heating temperature of 200° C. for a heating time of 10 seconds, the composition ratio, average particle, and quantum yield of the product are shown in Table 4 by using various raw material composition ratios.
Here, Example 2 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared under argon atmosphere using argon gas. Copper iodide and indium iodide were dissolved at a concentration of 0.017 mol/L in a mixed solution of octadecene and oleylamine which is a complexing agent, to obtain a solution A. The mixing ratio is X (%)=100×oleylamine/(octadecene+oleylamine), where X=100%, 50% and 10%.
Thioacetamide was dissolved at a concentration of 0.034 mol/L in trioctyl phosphine to obtain a solution C. A reaction solution with a mixture of 18 mL of the solution A and 18 mL of the solution C was ripened for 24 hours at a temperature of 25° C., and then heated for 3 seconds to 10 minutes at temperatures of 160° C., 200° C., and 240° C. Note that heating for 3 seconds to 2 minutes was performed using a microreactor having an inner diameter of 200 μm. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured.
(Fluorescence)
The graph of
Here, Example 3 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared using argon gas under argon atmosphere. Gallium iodide, copper iodide, and indium iodide were dissolved in oleylamine which is a complexing agent, to obtain a solution A. Note that copper iodide was dissolved at a concentration of 0.017 mol/L. Furthermore, gallium iodide and indium iodide were mixed at a mixing ratio of 1−X:X, where X=0, 0.2, 0.4, 0.6, 0.8 and 1.0, so that [the concentration of] the both becomes 0.017 mol/L.
Thioacetamide was dissolved at a concentration of 0.034 mol/L in trioctyl phosphine to obtain a solution C. A reaction solution with a mixture of 18 mL of the solution A and 18 mL of the solution C was ripened for 24 hours at a temperature of 25° C., and then heated for 3 seconds to 10 minutes at temperatures of 160° C., 200° C., and 240° C. Note that heating for 3 seconds to 2 minutes was performed using a microreactor having an inner diameter of 200 μm. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured.
(Fluorescence)
The graph of
(Absorbency)
(Effects of Addition of Gallium, Tuning)
As shown in this figure, the maximum values of absorption wavelengths and the fluorescence wavelengths can be controlled by the molar ratio between indium (In) and gallium (Ga) and the heating temperatures. Also, it is understood that [the maximum values of absorption wavelengths and the fluorescence wavelengths] can be controlled the range of 550 to 700 nm by the molar ratio between indium (In) and gallium (Ga) and the heating temperatures.
(Effects of Addition of Gallium, Quantum Yield)
Table 6 shows quantum yields, each of which represents a ratio of photons emitted by fluorescence to the number of photons of excitation light absorbed by each of the fluorescents shown in
Here, Example 4 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared under argon atmosphere using argon gas. Silver iodide, copper iodide, and indium iodide were dissolved in oleylamine which is a complexing agent, to obtain a solution A. Note that indium iodide was dissolved at a concentration of 0.017 mol/L. Silver iodide and copper iodide were mixed at a mixing ratio of 1−X:X, where X=0, 0.2, 0.5 and 1.0, so that [the concentration of] the both becomes 0.017 mol/L.
Thioacetamide was dissolved at a concentration of 0.034 mol/L in trioctyl phosphine to obtain a solution C. A reaction solution with a mixture of 18 mL of the solution A and 18 mL of the solution C was ripened for 24 hours at a ripening temperature of 25° C., and then heated for 3 seconds to 10 minutes at temperatures of 160° C., 200° C., and 240° C. Note that heating for 3 seconds to 2 minutes was performed using a microreactor having an inner diameter of 200 m. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured.
(Fluorescence)
The graph of
Note that the [obtained] products are solid solution-type compounds of CuInS2 and AgInS2. The lattice mismatch ratio between CuInS2 and AgInS2 is approximately 6.3% in the ratios of a axes and approximately 1.9% in the ratios of c axes. Table 7 shows quantum yields of the fluorescents shown in the graph of
Here, Example 5 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared under argon atmosphere using argon gas. Copper iodide and indium iodide were dissolved at a concentration of 0.017 mol/L in oleylamine which is a complexing agent, to obtain a solution A. A trioctyl phosphine solution in which zinc diethyldithiocarbamate is dissolved at a concentration of 0.017 mol/L was prepared as a solution B.
Thioacetamide was dissolved at a concentration of 0.034 mol/L in trioctyl phosphine to obtain a solution C. A solution with a mixture of 18 mL of the solution A and 18 mL of the solution C was mixed with the solution B so that the mixing ratio of copper (Cu) to zinc (Zn) becomes Cu:Zn=1:2, 1:1, 1.0:0.5, and 1.0:0.2, whereby [a reaction solution] was prepared. The reaction solution was ripened and thereafter heated for 3 seconds to 10 minutes at temperatures of 160° C., 200° C. and 240° C. Note that heating for 3 seconds to 2 minutes was performed using a microreactor having an inner diameter of 200 μm. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured.
(Fluorescence)
Table 8 shows the results of generating fluorescents by heating them for 5 minutes at a temperature of 200° C. based on a plurality of charge compositions. [Table 8] also shows the results of Patent Document 2 for comparison. It was possible to control the maximum values of fluorescence wavelengths within the range of 650 to 750 nm. Table 8 shows quantum yields. Note that [the obtained] products are solid solution-type compounds of CuInS2 and ZnS. The lattice mismatch ratio between CuInS2 and ZnS is approximately 2.2%.
The graph of
Here, Example 6 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared using argon gas under argon atmosphere. Copper iodide and indium iodide were dissolved at a concentration of 0.017 mol/L in oleylamine which is a complexing agent, to obtain a solution A. Zinc iodide was dissolved at a concentration of 0.034 mol/L in the complexing agent of oleylamine to obtain a solution B. Thioacetamide was dissolved at a concentration of 0.034 mol/L in trioctyl phosphine to obtain a solution C.
A solution with a mixture of 18 mL of the solution A and 18 mL of the solution C was mixed with a solution having a mixture of 18 mL of the solution B and 18 mL of the solution C so that the mixing ratio of copper (Cu) to zinc (Zn) becomes Cu:Zn=1:1, 1:2 and 1:3, whereby [a reaction solution] was prepared. The reaction solution was ripened and thereafter heated for 3 seconds to 10 minutes at heating temperatures of 160° C., 200° C. and 240° C. Note that heating for 3 seconds to 2 minutes was performed using a microreactor having an inner diameter of 200 μm. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured.
(Fluorescence)
Table 9 shows the results of generating fluorescents by heating them for 5 minutes at a temperature of 200° C. based on a plurality of charge compositions. [Table 8] also shows the results of Patent Document 2 as comparative examples. It was possible to control the maximum values of fluorescence wavelengths within the range of 650 to 750 nm. Table 9 also shows quantum yields of the products. Note that [the obtained] products are solid solution-type compounds of CuInS2 and ZnS. The lattice mismatch ratio between CuInS2 and ZnS is approximately 2.2%.
The graph of
Example 7 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared under argon atmosphere using argon gas. A solution D was prepared by mixing a 20 mL solution in which zinc acetate was dissolved at a concentration of 0.04 mol/L in octadecene in which oleic acid was dissolved at a concentration of 2%, with a 10 mL trioctyl phosphine solution in which selenium was dissolved at a concentration of 0.4 mol/L.
In Example 1 described above, the products obtained by the method described in Example 1 were added to the 30 mL solution D at a concentration of 0.008 mol/L, and heated at a temperature of 100° C. to 300° C., whereby a coating type composite particle was synthesized. Note that the lattice mismatch ratio between CuInS2 and ZnSe is approximately 2.6%. Table 10 shows the composite ratio (Zn/Cu) and particle diameters of the products.
(Fluorescence)
The graph of
(Quantum Yield)
Table 10 shows quantum yields, each of which represents a ratio of photons emitted by fluorescence to the number of photons of excitation light absorbed by each of the fluorescents shown in the graphs in
(Mixing Ratio between Cu and Zn in Reaction Solution)
Each of graphs in
Here, Example 8 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared using argon gas under argon atmosphere. A trioctyl phosphine solution in which zinc diethyldithiocarbamate was dissolved at a concentration of 0.04 mol/L was prepared as a solution E. In Example 1 described above, the products obtained by the method described in Example 1 were added to the 30 mL solution E at a concentration of 0.008 mol/L, and heated, whereby a coating type composite particle was synthesized. Note that the lattice mismatch ratio between CuInS2 and ZnS is approximately 2.2%. Table 11 shows the composite ratio (Zn/Cu) and particle diameters of the products.
(Fluorescence)
The graph of
(Quantum Yield)
Table 11 shows quantum yields, each of which represents a ratio of photons emitted by fluorescence to the number of photons of excitation light absorbed by each of the fluorescents shown in the graphs in
(Mixing Ratio Between Cu and Zn in Reaction Solution)
Each of graphs in
Here, Example 9 for producing the fluorescent of the present invention will now be described. Reaction solutions were all prepared under argon atmosphere using argon gas. Copper iodide (I) and indium iodide (III) were dissolved at a concentration of 0.017 mol/L in oleylamine which is a complexing agent, to obtain a solution A. Selenium was dissolved at a concentration of 0.034 mol/L in Trioctylphosphine to obtain a solution D.
A reaction solution with a mixture of 18 mL of the solution A and 18 mL of the solution D was basically ripened for 24 hours at a temperature of 25° C. under argon atmosphere. Thereafter, the reaction solution was heated and reacted for 10 minutes at a temperature of 200° C. to 280° C. Thus obtained products were diluted with toluene, and absorbency/fluorescence spectrum [of each product] was measured.
(Heating Effects)
The graph of
Table 12 shows the quantum yields, outer particle diameters and average diameter of the fluorescents showing the graphs in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-339526 | Nov 2005 | JP | national |
| 2006-304592 | Nov 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/322989 | 11/17/2006 | WO | 00 | 5/23/2008 |
