JP2007119320A - Zinc oxide ultrafine particle which shows ultraviolet band-edge luminescence, and its manufacture method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacture method of a zinc oxide ultrafine particle which shows the ultraviolet band-edge luminescence. <P>SOLUTION: The light emitter is a metal oxide ultrafine particle light emitter which shows the ultraviolet band-edge luminescence and comprises a metal oxide ultrafine particle of which surface is silylated. The synthetic method of the metal oxide ultrafine particle light emitter is a method to synthesize a metal oxide ultrafine particle light emitter which emits ultraviolet rays and comprises hydrolyzing a metal raw material salt dissolved in an organic solvent by a base dissolved in the same organic solvent, synthesizing a metal oxide ultrafine particle and silylating the surface of the particle. Thereby, the oxide semiconductor ultrafine particle such as a zinc oxide ultrafine particle or the like which can be used as a third-order non-linear optical material which shows the ultraviolet band-edge luminescence can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oxide semiconductor ultrafine particle illuminant exhibiting ultraviolet band edge emission and a synthesis technique thereof, and more specifically, in an oxide semiconductor ultrafine particle, fluorescence from a trap level is completely quenched and ultraviolet light is emitted. The present invention relates to an oxide semiconductor ultrafine particle light emitter such as a zinc oxide ultrafine particle capable of emitting only band edge emission, and a synthesis technique thereof. The present invention has a nonlinear susceptibility and response speed required as a third-order nonlinear optical material, and also has a problem of toxicity and environmental pollution like conventional chalcogenide compounds, and deterioration with time like organic nonlinear materials. New technology for oxide semiconductor ultrafine particle light emitters that have no problems, can be safely manufactured in place of these materials, have excellent durability, and have excellent properties as a third-order nonlinear material・ Provide new products.

  Conventionally, various attempts have been made to develop oxide semiconductor ultrafine particles having a quantum size effect that can be mainly used for optical applications. For example, zinc oxide is an oxide semiconductor. By making zinc oxide into ultrafine particles, the electron levels become discrete and the bandwidth is widened. Thereby, the ultrafine particles have an exciton confinement effect due to the relationship between the ultrafine particles and the Bohr radius, and as a result, exhibit third-order optical nonlinearity.

  When the exciton is irradiated with strong light having the same phase and wavelength, such as laser light, higher-order polarization occurs, a) a nonlinear refractive index effect in which the refractive index changes depending on the wavelength, and b) the absorbance changes depending on the light intensity. Non-linear absorption effects, c) phase conjugate wave generation, d) stimulated Raman scattering, and the like appear. By using an optical element using a nonlinear optical effect, it is estimated that, for example, an optical computer using photons can be developed.

  The ultrafine particles are expected to be applied to ultraviolet diodes in addition to optical computers. A pn junction LED made of GaN having a direct transition type and a wide bandwidth (3.4 eV, ultraviolet region) emits light in a wavelength region from blue to ultraviolet. Zinc oxide is also a wurtzite direct-transition oxide semiconductor with a bandwidth of 3.2 eV and an ultraviolet region. Accordingly, zinc oxide is also expected to be applied to ultraviolet LEDs and the like.

  Further, the ultrafine particles can be developed for use as a lamp that emits light of a certain wavelength in the ultraviolet region. Currently, there is only a mercury lamp as a simple method for obtaining ultraviolet rays. The OPO laser emits light in the ultraviolet region, but such an expensive device cannot be used for general applications. Mercury lamps emit light only at some fixed wavelengths and cannot obtain arbitrary wavelengths. For example, a high-pressure mercury lamp uses ultraviolet light having a wavelength of 254 nm. Zinc oxide ultrafine particles can be made to emit light at arbitrarily different wavelengths by changing the size of the fine particles.

  On the other hand, a phosphor that emits fluorescence when excited by ultraviolet rays has recently been demanded in the field of biochemistry. In practice, fluorescent substances emitting fluorescence of different wavelengths as labels are attached to cells as antibodies, and ultrafine particles of CdS, CdSe, and ZnS have already been commercialized. However, since these materials are toxic, the surface must be treated so that they do not come into direct contact with cells. In order to solve this problem, the periphery of the fine particles is coated with silica, but there is a problem that the number of synthesis steps is increased by one. Since ZnS is less toxic than CdS and CdSe, those obtained by coating CdS and CdSe with ZnS have been synthesized recently, but they are not harmful even if they are low toxic.

  In that respect, ZnO is also used in cosmetics and baby powder, and is considered to be harmless to the living body. This is a great advantage over chalcogenide compounds. Moreover, zinc is a nutrient that is indispensable for the human body as a trace essential element, and about 3 g of zinc is present in a human body having a weight of 70 kg.

  Currently, the application of ultrafine zinc oxide particles to optical computers is also expected. The current electronic computer is a von Neumann type computer that controls 0 and 1 by electrons. The number of clocks of the central operator of the desktop computer is currently the highest from 2 GHz to 3 GHz. These high-performance semiconductor elements are manufactured with a circuit line width of 90 nm. Development of next-generation devices has been promoted with the goal of a circuit line width of 65 nm. Furthermore, the development of an element having a circuit line width of 45 nm is being promoted as the next generation, which is expected to be put into practical use around 2010 (Non-patent Document 1).

  According to “Moore's Law”, the integration density of semiconductors is doubled in 18-24 months. However, according to a paper recently published by an American engineer, a manufacturing process with a circuit line width of 16 nm will be realized by 2018, even if conservatively estimated, this is a fundamental limitation (non-patent) Reference 2). Although it is different from the line width miniaturization technology of integrated circuits, NEC has announced the development of the world's smallest transistor, and it will be put to practical use in the vicinity of 2018 (Non-patent Document 3). After that, an optical computer that is even faster than an electronic computer will be required.

  An optical computer that performs all processing with light has not been realized yet, but in addition to optical fibers, technologies such as optical waveguides and current modulation of light-emitting diodes have been developed as optoelectronic devices that complement electrons with light. ing. In addition, basic research to realize optical computers such as photonic crystals has been conducted.

  In order to use nonlinear optical materials for optical computers, for example, optical memories and optical switches using optical bistable elements have been studied. Ultimately, the final goal is to process the signal entirely with light by an optical operator, but the current situation has not yet reached that point.

It was in 1983 that a nonlinear optical effect was discovered in semiconductor fine particles. Jain et al. First discovered a large non-linear effect in a glass filter doped with CdS _x Se _1-x that has been used for a long time as a sharp cut filter (Non-patent Document 4). In the initial research, a commercially available filter glass was used, but because the volume density of the fine particles was low, the non-linear susceptibility of the fine particles themselves was high, but the susceptibility of the whole glass was low. Since then, studies have been carried out to disperse microcrystals in glass at a high concentration.

  As the medium in which the fine particles are dispersed, a polymer can be used as the medium as long as it is transparent at the absorption edge wavelength of the fine particles. There is an example using an AS copolymer as a medium. In this case, the AS polymer and cadmium salt are dissolved in dimethylformamide and dried under reduced pressure to produce a film, and stored in hydrogen sulfide to produce CdS fine particles.

  Conventionally, the material that has been used to generate fine particles has been mainly researched on chalcogenide compounds because the nonlinear optical effect was first discovered in CdS-dispersed glass. (CdS, CdSe, CdTe, ZnS), but these compounds are toxic. Chalcogenide-based compounds have been actively studied in the 1990s following the study by Jain et al. Based on these studies, chalcogenide-based compounds have the nonlinear susceptibility and response speed required for third-order nonlinear materials.

  However, chalcogenide compounds are dangerous because toxic gases or chemicals are used during synthesis as described above. In the case of industrial production, unlike the synthesis of laboratory-scale samples, capital investment such as decomposition or adsorption to an adsorbent is necessary so that dangerous gases are not discharged untreated. Further, when the product is no longer needed, it is necessary to prevent the environmental pollution of the waste in some form even when it is disposed of because it is a cause of environmental pollution if it is disposed unprocessed. When a chalcogenide compound is used, capital investment for safety is inevitably required, and the cost is increased. Therefore, there are many problems in putting it to practical use.

  Various studies have also been conducted on organic nonlinear optical materials. Polydiacetylene is the main research object, but organic nonlinear optical materials are gradually deteriorated when irradiated with laser light with strong energy, and there is a problem that deterioration with time is larger than that of inorganic materials. . In addition, the nonlinear susceptibility also has a problem that it is about two orders of magnitude slower than the chalcogenide semiconductor ultrafine particles.

  Thus, there is a demand for a material that can be produced safely and has excellent durability, in place of a compound that is dangerous to synthesize and an organic substance that is significantly deteriorated. The present inventors have previously developed a method of easily producing oxide semiconductor ultrafine particles by a hydrolysis method (Patent Document 3). When zinc oxide is used as a third-order nonlinear optical material, the output response to incident light must be extremely fast. The fluorescence appearing at 390 nm corresponds to the band gap energy of zinc oxide and exhibits a picosecond response speed. Further, as described later, it is necessary to emit band edge emission in the ultraviolet region.

First, the ultrafine particles of several nm synthesized by the present inventors are very fine. Therefore, compared to the bulk case, the ratio of atoms constituting the surface is much higher than that of atoms constituting the inside of the crystal. Here, if there is a 1 m ³ square cube, the surface area is 6 m ² . When this cube is divided into 10 nm cubes, one side is divided into 1 × 10 ^8, and 1 × 10 ²⁴ cubes with a total of 10 nm can be formed. The surface area of a cube having a side of 1 × 10 ⁻⁸ is 6 × 10 ⁻¹⁶ m. Multiplying the surface area by the number of cubes gives 6 × 10 ⁸ m ² .

  Thus, it can be seen that even the same material has an extremely large surface area when it is of nanometer size. In addition, the actual ultrafine particles are not clean cubes, have irregularities on the surface, and uneven surfaces. In ultrafine particles having a non-uniform surface, there are a large amount of unsaturated bonds surrounding surface defects. Here, a trap level where electrons and impurities are easily bonded can be formed. The fluorescence from 500 nm to 600 nm has a longer wavelength than the band edge emission, and is considered to be emission from the trap level. The emission from the trap level shows nanosecond response speed, which is several orders of magnitude slower than the band edge emission.

  As a result of investigations by the present inventors, zinc oxide ultrafine particles that completely quench the fluorescence from the trap level and emit only ultraviolet band edge emission have not yet been obtained. This problem used to be a problem even with chalcogenide-based ultrafine particles, but was solved by adsorbing a surfactant such as thiol on the trap (Non-Patent Document 5). In zinc oxide, there is an example in which a surfactant (tetraoctyl ammonium bromide, cyclohexane butyrate) is used for such applications (Non-Patent Documents 6 and 7). The surfactant is one in which a long-chain alkyl group is bonded to a hydrophilic end group. Since the oxide surface is hydrophilic, it is considered that ammonium nitrogen is coordinated and adsorbed to the trap.

  However, tetraoctyl ammonium bromide has too long an alkyl group. Therefore, when one surfactant molecule is adsorbed to a trap, the surfactant cannot be adsorbed between the adjacent traps of another surfactant molecule, and many traps are not adsorbed. It remains as it is. Looking at the emission spectrum, trap level emission is observed (Non-Patent Document 6). In addition, bromine contains an element that becomes a problem when put to practical use. There are problems with using such compounds. In addition, surfactants are effective for chalcogenide compounds, but zinc oxide, which is an oxide, seems to have little effect.

Patent No. 2021987 Patent No. 2125053 Japanese Patent Application No. 2004-072396 Nihon Keizai Shimbun June 18, 2004 morning edition Asahi Shimbun December 8, 2003 morning edition V.V.Zhirnov, R.K.Cavin, J.A.Hutchby, G.I.Bourunoff, Proceedings of the IEEE, vol.91, No.11, 1934 (2003) R.K.Jain, R.C.Lind, Journal of the Optical Society of America, vol. 73, 647 (1983) N. Herron, Y. Wang, H. Eckert, Journal of the American Chemical Society, vol. 112, 1322 (1990) S.Mahamuni, K.Bogohain, B.S.Bendre, V.J.Leppert, S.H.Risbud, Journal of Applied Physics, vol.85, No.5, 2861 (1999) G. Rodriguez-Gattorno, Patricia Santiago-Jacinto, L. Rendon-Varquez, J. Nemeth, I. Decany, D. Diaz, Journal of Chemical Physics B, vol. 107, 12597 (2003) V.K.LaMer and R.Dinegar, Journal of the American Chemical Society, vol.72, 4847 (1950) "Particle size measurement technology" edited by the Japan Society for Powder Technology, Nikkan Kogyo Shimbun (1994), pp.1-27 “Handbook of Infrared and Raman Spectra of Inorganic Compounds and Organic Salts” Volume 4 Infrared Spectra of Inorganic Compounds (3300-45cm-1), Richard A. Nyquist and Ronald O. Kagel., Academic Press, New York 1997, pp. 95

  Under such circumstances, in view of the above prior art, the present inventors completely extinguish the fluorescence from the trap level in the oxide semiconductor ultrafine particles and emit only ultraviolet band edge light emission. In an effort to synthesize ultrafine particle light emitters, in order to solve these problems, an attempt was made to obtain band edge emission by silylating the surface of oxide semiconductor ultrafine particles. Silylation of the surface of oxide ultrafine particles has never been attempted. As a result, it has been found that ultrafine oxide semiconductor particles emitting only ultraviolet band edge emission can be obtained, and further research has been made to complete the present invention. An object of the present invention is to provide an oxide semiconductor ultrafine particle light emitter that completely quenches fluorescence from a trap level and emits only ultraviolet band edge light emission, and an application product thereof. Another object of the present invention is to provide a technique for synthesizing the oxide semiconductor ultrafine particle light emitter.

The present invention for solving the above-described problems comprises the following technical means.
(1) A metal oxide ultrafine particle illuminant exhibiting ultraviolet band edge emission, and comprising a metal oxide ultrafine particle having a silylated surface.
(2) The light emitter according to (1), wherein the metal oxide ultrafine particles are zinc oxide, tin oxide, or transition element oxide ultrafine particles.
(3) The light emitter according to (1), wherein the metal oxide is zinc oxide and emits ultraviolet light having an arbitrary wavelength between 200 nm and 390 nm.
(4) A method for synthesizing a metal oxide ultrafine particle light emitter that emits ultraviolet light, wherein (a) a metal raw material salt dissolved in an organic solvent is hydrolyzed with a base dissolved in the same organic solvent, and metal oxidation is performed. (B) silylating the surface of the particles.
(5) The method according to (4) above, wherein zinc raw material salt dissolved in an organic solvent is hydrolyzed with a base dissolved in the same organic solvent to synthesize zinc oxide ultrafine particles.
(6) The method according to (4) above, wherein the hydrolysis is carried out in the temperature range of -80 to 80 ° C.
(7) The method according to (4) above, wherein the hydrolysis is performed using a base-catalyzed alkali metal hydroxide.
(8) The method according to (5) above, wherein the amount of the base is 1 to 2 mol times based on zinc.
(9) The method according to (4) above, wherein the organic solvent is hydrophilic.
(10) The method according to (4), wherein the base catalyst solution is instantaneously mixed by flowing down and hydrolyzed.
(11) The method according to (5), wherein a luminescent material that emits ultraviolet light having an arbitrary wavelength between 200 nm and 390 nm is synthesized.
(12) An optical member comprising the light emitter according to any one of (1) to (3) as a constituent element.

  Next, the present invention will be described in more detail. The present invention is a metal oxide ultrafine particle illuminant exhibiting ultraviolet band edge emission, and is characterized by comprising a metal oxide ultrafine particle having a silylated surface, and, as described above, The salt is dissolved in reflux in a solvent, and the metal salt is hydrolyzed using a base dissolved in the solvent as a catalyst to synthesize oxide semiconductor ultrafine particles such as zinc oxide ultrafine particles. Hereinafter, the present invention will be described in detail by taking the case of zinc oxide ultrafine particles as an example.

  First, a zinc salt is dissolved in a hydrophilic organic solvent such as alcohol, dimethylformamide, ether or acetone. Examples of the zinc salt include zinc acetate and zinc oxalate. As for the organic solvent, dust in the liquid is previously removed with a Millipore filter. The concentration of the zinc salt solution at this time is preferably 0.1 to 0.2M. The solution is refluxed for 2-4 hours. The base catalyst dissolves 1-2 mole times the zinc salt in the same solvent. However, the materials, methods, and means described above are not limited to these, and any equivalent or similar materials can be similarly employed.

  Next, both the solutions are kept at a predetermined temperature of -80 ° C to 60 ° C. When both temperatures are stabilized at a predetermined temperature, the basic catalyst solution is allowed to flow down instantaneously, preferably within 1 second, while stirring the zinc salt solution. In this case, nucleation occurs gradually unless it is within 1 second, so that the distribution of the generated zinc oxide ultrafine particle size becomes large. After flowing down, stirring is continued for about 30 minutes, and then the temperature is returned to room temperature. In the present invention, it is important that the basic catalyst flows down to the zinc salt solution in 1 second or less, and preferably it flows down instantaneously. Thereby, nucleation occurs intensively within a short time, and zinc oxide ultrafine particles having a uniform particle diameter are generated.

  Here, in order to silylate the surface of the ultrafine particles, alcohols having OH groups are removed using a rotary evaporator. When the alcohol is evaporated, the ultrafine particles adhering to the inside of the flask are scraped off with a spatula.

  Next, as a pretreatment for conducting the silylation reaction, the same hydrophobic organic solvent (dehydration) as that used for the silylation is removed in a glove box under an inert atmosphere (nitrogen) in order to completely remove trace amounts of alcohols and moisture. : 99.99%) in a flask and evaporated on a rotary evaporator. This operation is repeated about 3 times.

  Next, the flask is again put in the glove box, and about 100 ml of a hydrophobic organic solvent (dehydrated) is put in an inert atmosphere (nitrogen: 99.99%). Next, a predetermined amount of silylating agent is added. The stir bar is also placed in the flask at this time. Cap the flask and remove it from the glove box. In advance, the temperature of the oil bath is set to a temperature about 5 ° C. higher than the boiling point of the hydrophobic organic solvent. Examples of the silylating agent include trimethylmethoxysilane, trimethylethoxysilane, and triethylmethoxysilane.

  Remove the flat stopper of the flask, and quickly attach a condenser tube to the mouth of the flask so that air does not enter as much as possible. A calcium pipe containing calcium chloride is attached to the top of the cooling pipe to minimize the ingress of moisture. The flask is immersed in an oil bath and refluxed for about 6 to 10 hours while stirring at the boiling point of the hydrophobic solvent. By this operation, the silylating agent is bonded to the surface of the zinc oxide ultrafine particles, and the trap site is crushed. The silylated surface can be confirmed, for example, by the disappearance of 500 to 600 nm trap level emission from the fluorescence spectrum.

Next, the operation of the present invention will be described. In the present invention, first, monodispersed ultrafine particles are produced by the following process. First, when the base catalyst solution is instantaneously dropped into the raw material solution, the raw material salt is hydrolyzed by the base catalyst. The reaction formula, for example, the reaction formula for hydrolysis of the raw material salt in the case of producing zinc oxide is as shown in formula (1). In the formula, M represents an alkali metal. Since Zn (OH) ₂ is unstable, it immediately undergoes phase transition to zinc oxide as shown in formula (2).

  The zinc oxide concentration in the solvent suddenly becomes critically supersaturated, and nucleation of zinc oxide begins. When the concentration drops and passes the nucleation phase, it enters the growth phase. Thereafter, the solute concentration decreases to the solubility concentration, and the growth period ends. Thus, the condition for producing monodisperse ultrafine particles is that the nucleation phase and the growth phase are separated (VKLaMer and R. Dinegar, Journal of the American Chemical Society, vol. 72, 4847 (1950 ).). When the catalyst solution is gradually added to the zinc salt solution, the two periods are not separated, and thus the distribution of the ultrafine particle diameter is undesirably widened. As a result, when the catalyst solution is gradually added, a clear peak of excitons is not observed as shown in FIG. This is the reason why the catalyst solution flows down instantaneously into the zinc salt solution.

  Although the case of zinc oxide has been described above, the present invention is not limited to zinc oxide, and besides zinc oxide, tin oxide or transition element oxide (Ti, Cu, Co, Fe, etc.) Etc., the same oxide ultrafine particles can be synthesized using these metal salts and catalysts, and these are also the object of the present invention. In the present invention, these oxide semiconductor ultrafine particles can be synthesized and provided in the same manner as the zinc oxide ultrafine particles.

The inventive zinc oxide ultrafine particle exhibiting ultraviolet band edge emission of the present invention has the following characteristics. That is, (1) emits ultraviolet rays having an arbitrary wavelength between 200 nm and 390 nm, (2) the surface is silylated, and fluorescence from the trap level is quenched, (3) ultrafine particle diameter The distribution is 3 to 4 nm, (4) the response speed is 10 ⁻¹² seconds or less, (5) the particles after silylation show strong band edge emission near 365 nm, (6) the particles after silylation are 1015, It has a characteristic of showing absorption by an infrared absorption spectrum in the vicinity of 1050 cm ⁻¹ . In addition, the same characteristic was shown also about oxide semiconductors other than the said zinc oxide.

The following effects are exhibited by the present invention.
(1) An oxide semiconductor ultrafine particle light emitter exhibiting ultraviolet band edge emission can be provided.
(2) In the oxide semiconductor ultrafine particles, fluorescence from the trap level can be completely quenched.
(3) It is possible to provide an oxide semiconductor ultrafine particle light emitter that can be used as an organic nonlinear optical material and a problem of toxicity and environmental pollution like the chalcogenide compound of the conventional material.
(4) An optical member made of zinc oxide ultrafine particles such as a third-order nonlinear optical material can be provided.
(5) The phosphor can be used as a labeling phosphor that emits fluorescence when excited by ultraviolet rays.
(6) Since the zinc oxide ultrafine particles are quantum dots, they can be used as solid elements of quantum computers.

  Next, the present invention will be specifically described based on examples. However, the examples show preferred examples of the present invention, and the present invention is not limited to the examples. .

(1) Synthesis of ultrafine particles 1.37 g of zinc acetate dihydrate was dissolved in 65 ml of ethanol and refluxed at 80 ° C. for 3 hours. On the other hand, 0.4 g of NaOH was dissolved and mixed in 40 ml of ethanol while being heated to about 60 ° C. Both were immersed in a constant temperature bath maintained at 20 ° C. When the temperature of both liquids reached 20 ° C., the NaOH solution was instantaneously poured down while stirring the zinc acetate solution. Thereafter, stirring was continued for 30 minutes to obtain a transparent colloid.

(2) Silylation The colloidal ethanol was removed with a rotary evaporator. The solid content adhering to the inner wall of the flask was scraped off with a spatula, placed in a glove box, and dehydrated tetrahydrofuran was placed in a 50 ml flask under a nitrogen (99.99%) atmosphere. The flask was removed from the glove box and attached to a rotary evaporator to evaporate the tetrahydrofuran. This operation was repeated three times to remove ethanol residues.

  Again, the flask was placed in a glove box, and 100 ml of tetrahydrofuran, 2 ml of trimethylethoxysilane as a silylating agent, and a rotor were placed in the flask under a nitrogen (99.99%) atmosphere. The flask was immersed in an oil bath and refluxed with stirring at the boiling point of tetrahydrofuran (66 ° C.) for 8 hours.

(3) Results FIG. 2 shows a high-resolution transmission electron microscope image of the colloid before silylation. The formation of ultrafine particles is observed. FIG. 3 shows the particle size distribution according to the Feret diameter (“Particle Size Measurement Technology” edited by the Powder Engineering Society, Nikkan Kogyo Shimbun (1994), pp. 1-27.). When curve fitting with a Gaussian function, the ultrafine particle diameter was found to be about 3.5 nm. Next, the colloid was put into a 1 mm quartz cell, and a visible ultraviolet absorption spectrum between 200 nm and 400 nm was measured. The result is shown in FIG. Absorption rises from around 350 nm, and the exciton peak is around 320 nm.

  FIG. 5 shows the fluorescence spectrum of zinc oxide ultrafine particles whose surface is not silylated. Strong light is observed from 350 nm toward the upper right, but this is because the incident light is Rayleigh scattered by dust in the solution, and the zinc oxide ultrafine particles are not emitting light. Fluorescence with a weak intensity is observed in the vicinity of a fluorescence wavelength of 345 nm with any wavelength of excitation light of 330 nm or less. Emits light in a straight line.

  FIG. 6 shows the fluorescence spectrum after silylation. In this case, strong fluorescence is observed near 365 nm. This is the band edge emission of ultrafine zinc oxide particles. By silylation, the strength increased about 10 times. As described above, the strong light emission that crosses the upper part of the graph diagonally is Rayleigh scattered light and not the fluorescence of zinc oxide.

  The band edge emission before silylation is 345 nm, whereas the band edge emission after silylation is shifted to 365 nm and longer wavelength side. In the case of a hydrophilic solvent, it is considered that zinc oxide ultrafine particles are likely to grow by Ostwald. Since the silylation reaction is carried out in a hydrophobic solvent such as tetrahydrofuran, the Ostwald growth is not as significant as in the case of a hydrophilic solvent, but it does not occur at all. Therefore, it is considered that grain growth of zinc oxide ultrafine particles is occurring.

  A transmission photomicrograph after silylation is shown in FIG. FIG. 8 shows the particle size distribution. The particle diameter is 4.3 nm, and grain growth occurs. When tetrahydrofuran is used, it is considered that the grain growth was relatively small because the reaction temperature was relatively low at 66 ° C.

FIG. 9 shows infrared absorption spectra of zinc oxide before and after silylation. Zinc oxide before silylation shows strong absorption in the vicinity of 400 cm ⁻¹ . After silylation, new absorption is generated around 1015,1050 cm ⁻¹ . This is the absorption by Zn—O—Si (“Handbook of Infrared and Raman Spectra of Inorganic Compounds and Organic Salts” Volume 4 Infrared Spectra of Inorganic Compounds (3300-45 cm ⁻¹ ), Richard A. Nyquist and Ronald O. Kagel. ., Academic Press, New York 1997, pp. 95.), showing that the surface of zinc oxide is silylated. Although the absorption by Zn-O-Si should also appear in the vicinity of 400 cm- ¹ , it overlaps with the absorption of zinc oxide, and this absorption is not clear. As described above, trapping by silylation is effective for oxide fine particles.

  As described above in detail, the present invention relates to zinc oxide ultrafine particles exhibiting ultraviolet band edge emission and a method for producing the same, and according to the present invention, the fluorescence from the trap level is completely quenched, and the ultraviolet band edge is obtained. An oxide semiconductor ultrafine particle light emitter that emits only light can be provided. The present invention can be completely manufactured in place of a conventional chalcogenide compound, a compound that is dangerous to synthesize, such as an organic nonlinear optical material, or a material that is significantly deteriorated, and is excellent. It is useful for providing new technologies and new products related to durable third-order nonlinear optical materials and their applied products.

The result of having observed the peak of the exciton when changing time to flow down a catalyst solution with the ultraviolet absorber is shown. The high-resolution transmission electron microscope image of the colloid before silylation is shown. The particle size distribution by Feret diameter is shown. The measurement result of the visible ultraviolet absorption spectrum between 200 nm and 400 nm is shown. The fluorescence spectrum of the zinc oxide ultrafine particles whose surface is not silylated is shown. The fluorescence spectrum after silylation is shown. A transmission micrograph after silylation is shown. The particle size distribution is shown. 2 shows infrared absorption spectra of zinc oxide before and after silylation.

Claims (12)

  A light-emitting body comprising a metal oxide ultrafine particle light emitter exhibiting ultraviolet band edge emission and comprising a metal oxide ultrafine particle having a silylated surface.   The light-emitting body according to claim 1, wherein the metal oxide ultrafine particles are zinc oxide, tin oxide, or transition element oxide ultrafine particles.   The light-emitting body according to claim 1, wherein the metal oxide is zinc oxide and emits ultraviolet light having an arbitrary wavelength between 200 nm and 390 nm.   A method for synthesizing a metal oxide ultrafine particle luminescent material that emits ultraviolet light, wherein (1) a metal raw material salt dissolved in an organic solvent is hydrolyzed with a base dissolved in the same organic solvent, and a metal oxide ultrafine particle is obtained. (2) A method for synthesizing a metal oxide ultrafine particle light emitter, wherein the surface of the particle is silylated.   The method according to claim 4, wherein the zinc raw material salt dissolved in an organic solvent is hydrolyzed with a base dissolved in the same organic solvent to synthesize zinc oxide ultrafine particles.   The process according to claim 4, wherein the hydrolysis is carried out in the temperature range from -80 to 80C.   The process according to claim 4, wherein the hydrolysis is carried out using a base-catalyzed alkali metal hydroxide.   6. The method according to claim 5, wherein the amount of the base is 1 to 2 mole times that of zinc.   The method of claim 4, wherein the organic solvent is hydrophilic.   The method according to claim 4, wherein the base catalyst solution is instantaneously mixed down and hydrolyzed.   The method according to claim 5, wherein a phosphor that emits ultraviolet light having an arbitrary wavelength between 200 nm and 390 nm is synthesized.   An optical member comprising the light emitter according to claim 1 as a constituent element.