JP2009132771A - Core-shell-type semiconductor nanoparticle and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core-shell-type semiconductor nanoparticle that exhibits a suppressed blinking phenomenon and enhanced luminous intensity by improving a core-shell-type semiconductor nanoparticle from the viewpoint of an impurity concentration in a shell, core/shell lattice mismatch and the like, and to provide a manufacturing method of the nanoparticle. <P>SOLUTION: The core-shell-type semiconductor nanoparticle is a core-shell-type semiconductor nanoparticle having a core portion and a shell layer, where the impurity concentration in the shell layer is at most 5.0 atom percent and the core/shell lattice mismatching ratio is at most 15%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a core / shell type semiconductor nanoparticle and a method for producing the same. Specifically, in the nanoparticle phosphor having a core / shell structure, the external extraction efficiency of light emission from the core is optimized by optimally controlling the impurity concentration and shell thickness in the shell, and the lattice mismatch between the core and shell. TECHNICAL FIELD The present invention relates to a core / shell type semiconductor nanoparticle having an improved surface roughness and a method for producing the same.

  Among ultrafine particles such as semiconductors and metals, nano-sized particles having a particle diameter smaller than the wavelength of electrons (about 10 nm) have an effect of size finiteness on the movement of electrons as a quantum size effect. It is known that it exhibits unique physical properties different from those of bulk bodies.

  In general, a material that exhibits a quantum confinement effect in a nanometer-sized semiconductor material, for example, a semiconductor nanoparticle, is also referred to as a “quantum dot”. Such a quantum dot is a small lump within about 10 and several nanometers in which several hundred to several thousand semiconductor atoms are gathered, but when absorbing energy from an excitation source and reaching an energy excited state, the energy of the quantum dot Releases energy corresponding to the band gap. Therefore, by adjusting the size or material composition of the quantum dots, the energy band gap can be adjusted, and energy in various levels of wavelength bands can be used.

  In addition, semiconductor nanoparticles have the same composition and the feature that the emission wavelength can be controlled by changing the particle size. Compared to organic fluorescent dyes of the prior art, it is superior in terms of stability and brightness of light emission, and has attracted attention.

  In addition, it is also known that when the particle size is minimized to the size where the quantum effect appears, the quantum efficiency is improved by the quantum confinement effect that brings about strong excitons, and light emission that can be confirmed visually can be obtained. ing.

  A semiconductor nanoparticle having a core / shell structure, that is, a core / shell type semiconductor nanoparticle having a core part and a shell layer has a quantum well structure, so that movement of electrons can be suppressed by the shell layer, and luminous efficiency is improved. It is known.

  However, the shell layer that covers the surface of the core part cannot smoothly emit light emitted from the core particle part to the outside due to the difference in physical properties from the core particle part or the state of covering, and falls below the original ability to improve luminous efficiency. There is a concern that this is happening. Therefore, in order to further improve the luminous efficiency, the compatibility of the core / shell is good, and an improvement in the configuration of the shell is desired (for example, see Patent Documents 1 to 3).

  Patent Document 1 discloses semiconductor nanoparticles (also referred to as “quantum dots”) having a core / shell structure that has a core made of Si or Ge and is substantially free of defects. Further, it is disclosed that the quantum efficiency is adjusted by the shell thickness, the shell coverage ratio, and the like.

  Patent Document 2 discloses a semiconductor nanoparticle having a core / shell structure, in which a part of the shell is missing or a part of the core is amorphous.

  Patent Document 3 discloses a technique for improving quantum efficiency by surface-treating a semiconductor nanocrystal formed by a chemical wet synthesis method with a reducing agent.

However, Patent Documents 1 to 3 do not mention the impurity concentration in the shell and the lattice mismatch. Therefore, it is considered that there is room for improving the quantum efficiency and the emission intensity by making no improvement focusing on these factors.
JP 2006-513458 A JP 2007-197382 A JP 2005-101601 A

  The present invention has been made in view of the above-described problems and situations, and the problem to be solved is to improve the core / shell type semiconductor nanoparticles from the viewpoint of the impurity concentration in the shell, the lattice mismatch between the core and the shell, and the like. Thus, it is to provide a core / shell type semiconductor nanoparticle which suppresses the blinking phenomenon and has improved emission intensity and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have caused the lattice mismatch by controlling the impurity concentration in the shell, the lattice mismatch between the core and the shell to a specific condition range, etc. The present inventors have found that the blinking phenomenon considered to be improved and the emission intensity of the core / shell type semiconductor nanoparticles can be improved, leading to the present invention.

  That is, the subject concerning this invention is solved by the following means.

  1. A core / shell type semiconductor nanoparticle having a core part and a shell layer, wherein the impurity concentration in the shell layer is 5.0 atomic% or less, and the lattice mismatch ratio between the core and shell is 15% or less. A core / shell type semiconductor nanoparticle characterized by being.

  2. 2. The core / shell type semiconductor nanoparticles according to 1 above, wherein the shell layer has a shell thickness of 0.1 to 5 nm.

  3. 3. The core / shell type semiconductor nanoparticles according to 1 or 2 above, wherein the core / shell type semiconductor nanoparticles have an average particle size of 0.1 to 10 nm.

4). 4. The core / shell type semiconductor nanoparticles according to any one of 1 to 3, wherein the core portion contains Si, and the shell layer contains SiO ₂ or ZnS.

  5). 5. The core / shell type semiconductor nanoparticle manufacturing method according to claim 1, wherein a high purity gas is used as a material for forming the shell layer. A method for producing nanoparticles.

  By the above means of the present invention, the core / shell type semiconductor nanoparticles are improved from the viewpoint of the impurity concentration in the shell, the lattice mismatch between the core and the shell, etc., the blinking phenomenon is suppressed, and the light emission intensity is improved. / Shell-type semiconductor nanoparticles and a method for producing the same can be provided.

  The core / shell type semiconductor nanoparticles of the present invention are core / shell type semiconductor nanoparticles having a core part and a shell layer, and the impurity concentration in the shell layer is 5.0 atomic% or less, and The lattice mismatch rate between shells is 15% or less. This feature is a technical feature common to the inventions according to claims 1 to 4.

As an embodiment of the present invention, the shell layer preferably has a shell thickness of 0.1 to 5 nm. Moreover, it is preferable that the average particle diameter of the said core / shell type semiconductor nanoparticle is 0.1-10 nm. Furthermore, it is preferable that the core part contains Si and the shell layer contains SiO ₂ or ZnS.

  The production method of the core / shell type semiconductor nanoparticles of the present invention is preferably a production method using a high-purity gas as a material for forming the shell layer.

  The present invention is characterized in that the blinking phenomenon after phosphor formation is suppressed by considering the lattice mismatch ratio between the core and shell, the impurity concentration in the shell, and the shell thickness. .

  In the present application, “blinking” means that the extinction time (extinction time) at which the emission intensity suddenly becomes almost zero (OFF) with respect to the irradiation time or irradiation amount when irradiating the excitation light lasts nearly several msec to 100 msec, The repetition of the phenomenon of obtaining the original emission intensity again.

The “time when the fluorescence intensity becomes almost zero” is the average time of the excitation light irradiation time, for example, when the OFF time of the emission intensity when the excitation light is irradiated for 5 minutes is 1 msec or more. . For example, if the decay time is repeated 3 times and is 10 msec, 50 msec, and 100 msec, 53 msec is the average decay time. On the other hand, if the irradiation dose is excitation light, the average decay time is, for example, 1000 mJ / cm ² in units expressed in mJ / cm ² .

  In the evaluation method of blinking, the emission intensity was traced with a resolution of 1 msec while applying excitation light, and the blinking frequency when irradiated for 5 minutes was measured. That is, the number of times when the light was emitted and when the light was extinguished was measured.

(Core / shell type semiconductor nanoparticles)
The core / shell type semiconductor nanoparticles of the present invention are semiconductor nanoparticles having a core portion (hereinafter also referred to as “core particles”) and a shell layer.

  Hereinafter, materials for forming the core portion and the shell layer will be described.

<Core part>
As the material for forming the core part of the core / shell type semiconductor nanoparticles of the present invention, various known fluorescent compounds and their raw materials can be used. For example, it can be formed using various semiconductor materials conventionally known as semiconductor nanoparticle materials. Specifically, for example, group IV, II-VI group, and group III-V semiconductor compounds of the periodic table of elements and raw material compounds containing elements constituting these compounds can be used.

  Among II-VI group semiconductors, in particular, MgS, MgSe, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, HgS, Mention may be made of HgSe and HgTe.

  Among group III-V semiconductors, GaAs, GaN, GaPGaSb, InGaAs, InP, InN, InSb, InAs, AlAs, AlP, AlSb, and AlS can be cited.

  Among group IV semiconductors, Ge and Si are particularly suitable.

  Of these various semiconductor materials, Si, Ge, InN, and InP are particularly preferable materials from the viewpoint of a composition that satisfies safety, and among these, the main components constituting the semiconductor nanoparticles of the present invention. As atoms, silicon (Si) and germanium (Ge) are most preferable. In the present application, the “main component atom constituting the semiconductor nanoparticle” means an atom having a maximum content ratio among atoms constituting the semiconductor nanoparticle.

  In the present invention, the semiconductor nanoparticles need to be particles having a core / shell structure. In this case, the semiconductor nanoparticles are semiconductor nanoparticles having a core / shell structure composed of core particles composed of semiconductor particles and a shell layer covering the core particles, and the chemical composition of the core particles and the shell layer is It is preferable that they are different. Thereby, the band gap of the shell is preferably higher than that of the core.

  The shell is necessary for stabilizing the surface defects of the core particles and improving the luminance, and is important for forming a surface on which the surface modifier is easily adsorbed and bonded.

  Hereinafter, the core particles and the shell layer will be described.

  The average particle size of the core part (core particle) according to the present invention is preferably 0.5 to 10 nm. Furthermore, it is preferable that it is 0.1-5 nm, especially 0.1-3 nm.

  In the present invention, the average particle diameter of the semiconductor nanoparticles must originally be determined in three dimensions, but it is difficult because it is too fine, and in reality it must be evaluated with a two-dimensional image. Therefore, a transmission electron microscope (TEM) ) Is preferably obtained by averaging a large number of images taken by changing the shooting scene of the electron micrograph. Therefore, the number of particles photographed with a TEM is preferably 100 or more.

  It is also preferable to adjust the average particle diameter of the core so that the semiconductor nanoparticles according to the present invention emit fluorescence in the wavelength region of the infrared region, that is, emit infrared light.

<Dopant>
The semiconductor nanoparticle of the present invention preferably contains a hetero atom having a valence configuration equivalent to a main component atom constituting the semiconductor nano particle or an atom pair of the hetero atom as a dopant. In this case, it is preferable that the dopant is uniformly distributed on the surface of the semiconductor nanoparticles or in the vicinity thereof.

  The “valence electron” refers to an electron held in the outermost shell of an electron shell (K shell, L shell, M shell,...) That constitutes an atom. Therefore, when silicon (Si) is used as the main component atom constituting the semiconductor nanoparticle, four electrons are arranged in the outermost shell, and therefore an atom or an atom pair having an equivalent valence electron arrangement is Be. -Be (Be pair), Mg-Mg (Mg pair), Ge and the like.

  When the main component atoms constituting the semiconductor nanoparticles of the present invention are silicon (Si) or germanium (Ge), Be—Be is particularly preferable as the dopant.

  In the present invention, the dopant content is preferably on the surface of the semiconductor nanoparticles or in the vicinity thereof. Here, “in the vicinity of the surface” is within 30% of the radius from the surface of the semiconductor nanoparticles, particularly preferably within 15%.

  The distribution state of the dopant according to the present invention can be observed and measured by X-ray photoelectron spectroscopy (XPS / ESCA; XPS: X-ray Photoelectron Spectroscopy / ESCA: Electron Spectroscopy for Chemical Analysis). The X-ray photoelectron spectroscopic analysis method is a method for examining the state of a solid surface and the vicinity thereof (for example, the composition of elements) by measuring the kinetic energy of electrons that are emitted by monochromatic light (X-ray) irradiation.

<Shell layer>
Various semiconductor materials can be used as the semiconductor material used for the shell layer. Specific examples include, for example, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaS, GaN, GaP, GaAs, GaSb, InAs, InN, InP, InSb, AlAs, AlN, AlP. , AlSb, or a mixture thereof.

In the present invention, particularly preferred semiconductor materials are SiO ₂ and ZnS.

  Note that the shell layer according to the present invention may not completely cover the entire surface of the core particle as long as the core particle is not partially exposed to cause a harmful effect.

《Shell thickness》
The shell thickness of the shell layer is preferably 0.1 to 5 nm. Further, it is preferably 0.1 to 2 nm, particularly preferably 0.1 to 1 nm.

<Impurity of shell layer>
In the core / shell type semiconductor nanoparticles of the present invention, the impurity concentration in the shell layer is 5.0 atomic% or less. The impurity concentration is preferably 2.0 atomic% or less, particularly preferably 1.0 atomic% or less.

  The impurity concentration is adjusted by refining (purifying) the shell forming material.

  Specifically, it is preferable to use high-purity oxygen gas or HS gas having a purity of 5N or more as the shell forming material. Here, “purity 5N” means that the purity is 99.999% or more.

<Particle size of core / shell type semiconductor nanoparticles>
The average particle size of the semiconductor nanoparticles according to the present invention is preferably 0.1 to 10 nm. Furthermore, it is preferable that it is 0.1-5 nm, especially 0.1-3 nm.

  The core / shell type semiconductor nanoparticles according to the present invention can be adjusted to emit fluorescence in the range of 350 to 1100 nm, and the particles are applied to a biomolecule fluorescent labeling agent (biological substance fluorescent labeling agent). In some cases, light emission in the near-infrared region is also preferably used in order to eliminate the influence of light emission of living cells and improve the SN ratio.

《Core / shell lattice mismatch rate》
The “core / shell lattice mismatch ratio” of the core / shell type semiconductor nanoparticles of the present invention is 15% or less. The lattice mismatch rate is preferably 5.0 or less, and more preferably 2.0 or less, from the viewpoint of epitaxial crystal growth.

  In the present application, the “core / shell lattice mismatch ratio” is an absolute value of the percentage that can be calculated from the core lattice constant and the shell lattice constant, and from “1-shell lattice constant / core lattice constant”. Value value.

(Method for producing semiconductor nanoparticles)
As a manufacturing method of the semiconductor nanoparticles constituting the core part (core particle) of the core / shell type semiconductor nanoparticles of the present invention, a conventionally known manufacturing method by a liquid phase method or a gas phase method can be used. For the production of the core particles according to the present invention, the liquid phase method is particularly preferred.

<Liquid phase method>
Examples of the liquid phase method include a precipitation method, a coprecipitation method, a sol-gel method, a uniform precipitation method, and a reduction method. In addition, the reverse micelle method, the supercritical hydrothermal synthesis method, and the like are also excellent methods for producing nanoparticles (for example, JP 2002-322468, JP 2005-239775, JP 10-310770 A). No., JP 2000-104058 A, etc.).

In addition, when manufacturing semiconductor nanoparticles by a liquid phase method, it is preferable that it is a manufacturing method which has the process of reduce | restoring the precursor of the said semiconductor by a reductive reaction. Moreover, the aspect which has the process of performing reaction of the said semiconductor precursor in presence of surfactant is preferable. The semiconductor precursor according to the present invention is a compound containing an element used as the semiconductor material. For example, when the semiconductor is silicon (Si), the semiconductor precursor includes SiCl ₄ . Other semiconductor precursors include InCl ₃ , P (SiMe ₃ ) ₃ , ZnMe ₂ , CdMe ₂ , GeCl ₄ , tributylphosphine selenium and the like.

  The reaction temperature of the reaction precursor is not particularly limited as long as it is not lower than the boiling point of the semiconductor precursor and not higher than the boiling point of the solvent, but is preferably in the range of 70 to 110 ° C.

《Reducing agent》
As the reducing agent for reducing the semiconductor precursor, various conventionally known reducing agents can be selected and used according to the reaction conditions. In the present invention, from the viewpoint of the strength of reducing power, lithium aluminum hydride (LiAlH ₄ ), sodium borohydride (NaBH ₄ ), sodium bis (2-methoxyethoxy) aluminum hydride, trihydride (sec- butyl) lithium borohydride _{(LiBH (sec-C 4 H} 9) 3) and hydrogenated tri (sec-butyl) potassium boron reducing agent such as lithium triethylborohydride being preferred. In particular, lithium aluminum hydride (LiAlH ₄ ) is preferable because of its reducing power.

"solvent"
Various known solvents can be used as the solvent for dispersing the semiconductor precursor. Alcohols such as ethyl alcohol, sec-butyl alcohol, and t-butyl alcohol, and hydrocarbon solvents such as toluene, decane, and hexane are used. It is preferable to use it. In the present invention, a hydrophobic solvent such as toluene is particularly preferable as the dispersion solvent.

<Surfactant>
As the surfactant, various conventionally known surfactants can be used, and anionic, nonionic, cationic, and amphoteric surfactants are included. Of these, tetrabutylammonium chloride, bromide or hexafluorophosphate, tetraoctylammonium bromide (TOAB), or tributylhexadecylphosphonium bromide, which are quaternary ammonium salt systems, are preferred. Tetraoctyl ammonium bromide is particularly preferable.

  The reaction by the liquid phase method greatly varies depending on the state of the compound containing the solvent in the liquid. When producing nano-sized particles with excellent monodispersity, special care must be taken. For example, in the reverse micelle reaction method, the size and state of the reverse micelle serving as a reaction field vary depending on the concentration and type of the surfactant, so that the conditions under which nanoparticles are formed are limited. Therefore, a suitable surfactant needs to be combined with a solvent.

<Gas phase method>
As a manufacturing method of the vapor phase method, (1) the opposing raw material semiconductor is evaporated by the first high temperature plasma generated between the electrodes, and in the second high temperature plasma generated by electrodeless discharge in a reduced pressure atmosphere. (2) a method for separating and removing nanoparticles from an anode made of a raw material semiconductor by electrochemical etching (for example, see JP-A-2003-515458), (3) A laser ablation method (for example, see JP-A No. 2004-356163), (4) a high-speed sputtering method (for example, see JP-A No. 2004-296781), or the like is used. A method of synthesizing a powder containing particles by reacting a raw material gas in a gas phase in a low pressure state is also preferably used.

<Post-processing after semiconductor nanoparticle formation>
In the method for producing semiconductor nanoparticles of the present invention, an embodiment including a step of performing post-treatment of any of plasma, heat, radiation, and ultrasonic treatment after formation of the semiconductor nanoparticles, particularly after formation of the shell is also preferable.

  In the case of plasma treatment, an appropriate one such as low temperature / high temperature plasma, microwave plasma, atmospheric pressure plasma is selected in consideration of the particle composition, crystallinity, and surface properties, but microwave plasma is preferable.

  For the heat treatment, any one of air, vacuum, and inert gas region is selected and heated, but the applied temperature region differs depending on the configuration of the phosphor particles. If the temperature is too high, the core and the shell may be distorted or peeled off. The effect is poor at low temperatures, and a temperature of 100 ° C. or higher and 300 ° C. or lower is preferably used.

  For the radiation treatment, X-rays, γ-rays, and neutron beams that require high energy are used, or vacuum ultraviolet rays (VUV), ultraviolet rays, short pulse lasers, etc., which are low in energy, are used. The processing time varies depending on the type of radiation. Since X-rays and the like have a high transmission power, a relatively short time is often required for any composition, and ultraviolet rays require a relatively long time of irradiation.

  Regarding the effects of these post-treatments, the fundamentals have not been elucidated, but the bonding efficiency at the interface between the core and shell of core / shell type particles has been strengthened and the passivation has been promoted, resulting in an increase in luminous efficiency. Estimated. It is estimated that the influence appears in the infrared light emitter and is reflected in the characteristics.

  In the present invention, the band gap of the shell layer is preferably higher than that of the core portion. The shell is necessary for stabilizing the surface defects of the core particles and improving the brightness, and in the case of using a fluorescent labeling agent, it is important for forming a surface on which the surface modifier is easily adsorbed and bound.

[Application example]
The core / shell type semiconductor nanoparticles of the present invention can be applied or used in various fields. In the following, a case where the present invention is applied to a fluorescent labeling substance (fluorescent labeling agent), particularly a biomolecule fluorescent labeling agent (biological substance fluorescent labeling agent) will be described.

(Fluorescent labeling substance)
The core / shell type semiconductor nanoparticles of the present invention (hereinafter abbreviated as “semiconductor nanoparticles” where appropriate) are used for fluorescently labeling a target substance by disposing an appropriate surface modifying compound on the surface thereof. It can be applied to fluorescent labeling substances (fluorescent labeling agents). In particular, a biomolecule fluorescent labeling agent (biosubstance fluorescent labeling agent) is provided on the surface of the particle to place a surface-modifying compound having affinity for or attached to the living body on the surface of the particle and fluorescently label a target substance such as a protein or peptide. It is suitable for use as an agent.

  When a biomolecule fluorescent labeling agent (biological substance fluorescent labeling agent) is used, the emission characteristics of the semiconductor nanoparticles can be adjusted by the particle size or the like so as to have infrared emission characteristics in the near infrared to infrared excitation. It is preferable from the viewpoints of non-invasiveness to biomolecules, permeability of living tissue, and the like.

  In the present invention, the surface modifying compound is preferably a compound having at least one functional group and at least one group capable of binding to semiconductor nanoparticles. The latter is a group that can be adsorbed to hydrophobic semiconductor nanoparticles, and the other is a functional group that has affinity for biological substances and binds to biomolecules. The surface modification compounds of each other may use various linkers that connect each other.

  As a group couple | bonded with a semiconductor nanoparticle, what is necessary is just a functional group couple | bonded with the semiconductor material for forming the said semiconductor nanoparticle. In the present invention, a mercapto group (thiol group) is particularly preferable as the functional group.

  Examples of the functional group that binds to the biological substance with affinity include a carboxyl group, an amino group, a phosphonic acid group, and a sulfonic acid group.

  Here, “biological substance” refers to cells, DNA, RNA, oligonucleotides, proteins, antibodies, antigens, endoplasmic reticulums, nuclei, Golgi bodies, and the like.

  As a method for bonding to semiconductor nanoparticles, a mercapto group can be bonded to particles by adjusting the pH to be suitable for surface modification. An aldehyde group, an amino group, and a carboxyl group are introduced into the other end, respectively, and a peptide bond can be formed with a biological amino group or carboxyl group. Moreover, even if an amino group, an aldehyde group, or a carboxyl group is introduced into DNA, oligonucleotide or the like, it can be similarly bonded.

  As a specific method for producing a biomolecule fluorescent labeling agent (biological substance fluorescent labeling agent) using the semiconductor nanoparticles of the present invention, for example, a hydrophilized semiconductor nanoparticle is combined with a molecular labeling substance via an organic molecule. A method of bonding can be mentioned. In the biomolecular fluorescent labeling agent (biomaterial fluorescent labeling agent) produced by this method, the molecular labeling substance can specifically bind to and / or react with the target biological substance, thereby enabling fluorescent labeling of the biological substance. It becomes.

  Examples of the molecular labeling substance include nucleotide chains, antibodies, antigens and cyclodextrins.

  The organic molecule is not particularly limited as long as it is an organic molecule capable of binding a semiconductor nanoparticle and a molecular labeling substance. For example, among proteins, albumin, myoglobin, casein, etc., and avidin, which is a kind of protein, are combined with biotin. It is also preferably used. The form of the bond is not particularly limited, and examples thereof include a covalent bond, an ionic bond, a hydrogen bond, a coordinate bond, physical adsorption, and chemical adsorption. A bond having a strong bonding force such as a covalent bond is preferable from the viewpoint of bond stability.

  Specifically, when the semiconductor nanoparticles are hydrophilized with mercaptoundecanoic acid, avidin and biotin can be used as organic molecules. In this case, the carboxyl group of the nanoparticle subjected to the hydrophilic treatment is preferably covalently bonded to avidin, the avidin is further selectively bonded to biotin, and biotin is further bonded to the molecular labeling substance (biomolecule fluorescent labeling agent ( Biological substance fluorescent labeling agent).

<Hydrophilic treatment of semiconductor nanoparticles>
Since the surface of the semiconductor nanoparticles described above is generally hydrophobic, for example, when used as a biomolecule labeling reagent, water dispersibility is poor as it is, and there are problems such as aggregation of particles. The surface of the semiconductor nanoparticles is preferably subjected to a hydrophilic treatment.

As a method of hydrophilization treatment, for example, there is a method of chemically and / or physically binding a surface modifier to the particle surface after removing the lipophilic group on the surface with pyridine or the like. As the surface modifier, those having a carboxyl group / amino group as a hydrophilic group are preferably used, and specific examples include mercaptopropionic acid, mercaptoundecanoic acid, aminopropanethiol and the like. Specifically, for example, 10 ⁻⁵ g of Ge / GeO ₂ type nanoparticles are dispersed in 10 ml of pure water in which 0.2 g of mercaptoundecanoic acid is dissolved, and stirred at 40 ° C. for 10 minutes to treat the surface of the shell. By doing so, the surface of the semiconductor nanoparticles can be modified with a carboxyl group.

  Specific preparations for surface modification of semiconductor nanoparticles are described in, for example, Dabbousi et al. (1997) J. Mol. Phys. Chem. B101: 9463, Hines et al. (1996) J. MoI. Phys. Chem. 100: 468-471, Peng et al. (1997) J. MoI. Am. Chem. Soc. 119: 7019-7029, and Kuno et al. (1997) J. MoI. Phys. Chem. 106: 9869.

(Fluorescent labeling substance and biomolecule detection system using it)
The fluorescent labeling substance according to the present invention has the above characteristics, and supplies the fluorescent labeling substance to a target living cell or tissue, and detects the fluorescence emitted by radiation excitation of the semiconductor nanoparticles. The present invention can be preferably applied to a biomolecule detection system characterized by detecting a biomolecule in a target living cell or living tissue.

  By adding the fluorescent labeling substance according to the present invention to a living cell or biological tissue having a target (tracking) biomolecule, it binds or adsorbs to the target molecule, and excitation light (radiation) having a predetermined wavelength is attached to the conjugate or adsorbent. ) And detecting fluorescence of a predetermined wavelength generated from the semiconductor nanoparticles (fluorescent semiconductor fine particles) in accordance with the excitation light, the fluorescence dynamic imaging of the target (tracking) biomolecule can be performed. That is, the fluorescent labeling substance according to the present invention can be used in a bioimaging method (technical means for visualizing biomolecules constituting a biological substance and dynamic phenomena thereof).

  The radiation for excitation includes visible light such as halogen lamps and tungsten lamps, LEDs, near-infrared laser light, infrared laser light, X-rays and γ-rays.

<Molecular / cell imaging method>
The semiconductor nanoparticle of the present invention can be used as a fluorescent labeling substance by binding a probe molecule (search molecule) that specifically reacts with a molecule present inside or on the surface of a target cell tissue. .

  In the present application, “target” refers to a biomolecule or the like targeted by a semiconductor nanoparticle, for example, a protein that is preferentially expressed in tissues and cells, a Golgi body in a cell, a nucleus And membrane proteins. Examples of suitable target substances include, but are not limited to, enzymes and proteins, cell surface receptors; nucleic acids; lipids and phospholipids.

  In the present invention, as a probe molecule, it is preferable to employ an appropriate probe molecule corresponding to a target (measurement) substance for the purpose of imaging the inside of a living body, measuring intracellular substance dynamics, and the like.

  The biomolecule fluorescent labeling agent (biological substance fluorescent labeling agent) using the semiconductor nanoparticles of the present invention can be applied to various conventionally known molecular / cell imaging methods. Examples thereof include molecular / cell imaging methods such as laser injection, microinjection, and electroporation. Among these methods, it is preferable to apply to a molecular / cell imaging method by a laser injection method.

  Here, the “laser injection method” refers to an optical method in which a cell is directly irradiated with laser light, a minute hole is formed in the cell, and a foreign substance such as a gene is introduced.

  The “microinjection method” refers to a method in which a foreign substance such as a gene is directly injected and introduced into a cell mechanically by air pressure using a fine needle (micropipette, microsyringe).

  The “electroporation method” (also referred to as “electroporation method”) is a physical method in which an electrical stimulus is applied to a cell to induce deformation of the cell to introduce a foreign substance such as a gene into the cell. Say the method. For example, when a high voltage of several thousand V / cm is applied to a cell suspension with a pulse of several tens of microseconds, DNA is incorporated into the extracellular fluid using the fact that the external fluid is taken in through a small hole that occurs in the cell membrane for a short time This is a method in which a sample to be injected is added and introduced into cells.

<Comparative example 1>: When the shell is SiO ₂ , the purity of the shell raw material is low, and the shell thickness is large Si is used as the core forming material, SiO ₂ is used as the shell forming material, and oxygen gas having a purity of 3N is used as the shell raw material. It was. The manufacturing method uses a spraying device to flow the oxygen gas as a carrier gas at a flow rate of 1.5 L / min as in the case of the reaction gas while keeping the raw material in a sprayed state, transport it to the heating unit, and fire at a heating temperature of 1200 ° C. Then, the particles were collected so as to be collected.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a lattice mismatch ratio between the core and shell of 0.8%.

  The crystallinity, impurity concentration, shell thickness, and emission intensity of the shell of the formed particles are measured by XRD, AES, TEM, and a fluorometer, respectively, and the emission intensity is traced with a resolution of 1 msec while applying excitation light. The blinking frequency when irradiated for 5 minutes was measured. As for the result, the half width of the shell material is 0.48 ° (from the result obtained by XRD measurement of the particle, the diffraction angle at the position of half of the background and the highest peak is represented), and the shell thickness is The impurity concentration was 1 nm or more and 4.21 atomic%. In order to compare the blinking frequency and emission intensity of the particles obtained in Comparative Example 1 with the emission intensity of particles obtained under other production conditions, the emission intensity is set as a reference emission intensity. This sample is referred to as Comparative Example Particle 1.

<Comparative example 2>: When the shell is ZnS, the purity of the shell raw material is low, and the shell thickness is thin Si is used as the core forming material, ZnS is used as the shell forming material, and Zn metal having a purity of 3N and HS gas are used as the shell raw material. Was used.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a core / shell lattice mismatch of 0.4%.

  The formed particles were measured and evaluated in the same manner as in Comparative Example 1. The half width of the shell material is 0.38 °, the shell thickness is less than 1 n, the impurity concentration is 3.05 atomic%, the blinking frequency, and the emission intensity are 60 and 1.25 times the emission intensity of Comparative Example 1, respectively. there were. This sample is referred to as Comparative Example Particle 2.

<Comparative Example 3>: shell with SiO _2, low purity of the shell material, when the shell is thin.

Si was used as the core forming material, SiO ₂ was used as the shell forming material, and oxygen gas having a purity of 3N was used as the shell raw material.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a lattice mismatch ratio between the core and shell of 0.8%.

  The formed particles were measured and evaluated in the same manner as in Comparative Example 1. The half width of the shell material is 0.44 °, the shell thickness is less than 1 nm, the impurity concentration is 3.21 atomic%, the blinking frequency and the emission intensity are 70 and 1.18 times the emission intensity of Comparative Example 1, respectively. Met. This sample is referred to as Comparative Example Particle 3.

<Example 1>: When the shell is SiO ₂ , the purity of the shell raw material is 5N, and the shell thickness is thin Si is used as the core forming material, SiO ₂ is used as the shell forming material, and oxygen gas having a purity of 5N is used as the shell raw material. Using.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a lattice mismatch ratio between the core and shell of 0.8%.

  The formed particles were measured and evaluated in the same manner as in Comparative Example 1. The half width of the shell material is 0.34 °, the shell thickness is less than 1 nm, the impurity concentration is 2.15 atomic%, the blinking frequency and the emission intensity are 25 and 1.33 times the emission intensity of Comparative Example 1, respectively. Met. This sample is referred to as Example Particle 1.

<Example 2>: When the shell is SiO ₂ and the purity of the shell raw material is 6N and the shell thickness is thin Si is used as the core forming material, SiO ₂ is used as the shell forming material, and oxygen gas having a purity of 6N is used as the shell raw material. Using.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a lattice mismatch ratio between the core and shell of 0.8%.

  The formed particles were measured and evaluated in the same manner as in Comparative Example 1. The half width of the shell material is 0.26 °, the shell thickness is less than 1 nm, the impurity concentration is 1.53 atomic%, the blinking frequency and the emission intensity are 10 and 1.45 times the emission intensity of Comparative Example 1, respectively. Met. This sample is referred to as Example Particle 2.

<Example 3>: When the shell is ZnS, the purity of the shell raw material is 6N, and the shell thickness is thin Si is used as the core forming material, ZnS is used as the shell forming material, and the 6N purity Zn metal and HS gas are used as the shell raw material. Was used.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a core / shell lattice mismatch of 0.4%.

  The formed particles were measured and evaluated in the same manner as in Comparative Example 1. The half width of the shell material is 0.21 °, the shell thickness is less than 1 nm, the impurity concentration is 1.21 atomic%, the blinking frequency and the emission intensity are 5 and 1.53 times the emission intensity of Comparative Example 1, respectively. Met. This sample is referred to as Example Particle 3.

<Example 4>: shell with SiO _2, purity of the shell material is 6N, Si as if the core-forming material shell is thick, the SiO ₂ used as the shell-forming material, the purity 6N oxygen gas to the shell material Using.

  The core / shell type semiconductor nanoparticles produced (formed) as described above had a lattice mismatch ratio between the core and shell of 0.8%.

  The formed particles were measured and evaluated in the same manner as in Comparative Example 1. The half width of the shell material is 0.30 °, the shell thickness is 1 nm or more, the impurity concentration is 2.07 atomic%, the blinking frequency and the emission intensity are 30 and 1.35 times that of Comparative Example 1, respectively. Met. This sample is referred to as Example Particle 4.

  The above measurement and evaluation are summarized in Table 2.

  The following can be said from the results shown in Table 2.

  (L) From the results of Example 2, Example 4, Comparative Example 1, and Comparative Example 3, the crystallinity in the shell differs depending on the thickness of the shell, and light emitted from the core is scattered depending on the thickness. It is thought that there is a decrease that is reflected and partly not released to the outside.

  (2) From the results of Example 1, Example 2, and Comparative Example 3, it was considered that the impurity concentration in the shell was changed by the raw material used for the shell material, and that this caused defects in the shell. It is considered that the crystallinity has changed and the emission intensity is affected.

  From the above examples and comparative examples, the luminous efficiency can be improved by taking into account the three factors of the lattice mismatch ratio between the core and the shell, the impurity concentration in the shell, and the shell thickness. It was also possible to suppress the phenomenon.

Claims (5)

A core / shell type semiconductor nanoparticle having a core part and a shell layer, wherein the impurity concentration in the shell layer is 5.0 atomic% or less, and the lattice mismatch ratio between the core and shell is 15% or less. A core / shell type semiconductor nanoparticle characterized by being. The core / shell type semiconductor nanoparticles according to claim 1, wherein the shell layer has a shell thickness of 0.1 to 5 nm. The core / shell type semiconductor nanoparticles according to claim 1 or 2, wherein the core / shell type semiconductor nanoparticles have an average particle size of 0.1 to 10 nm. The core / shell type semiconductor nanoparticles according to any one of claims 1 to 3, wherein the core part contains Si, and the shell layer contains SiO ₂ or ZnS. The core / shell type semiconductor nanoparticle manufacturing method according to any one of claims 1 to 4, wherein a high purity gas is used as a material for forming the shell layer. A method for producing semiconductor nanoparticles.