JP5410177B2 - Method for producing fluorescent cluster and fluorescent emission dispersion - Google Patents

Description

  The present invention relates to a method for producing a fluorescent cluster and a fluorescent emission dispersion.

  Conventionally, the fluorescence emission characteristic by the quantum size effect is known for the nanoparticle, for example, the semiconductor nanoparticle is applied as a fluorescence label etc.

  On the other hand, metals such as gold, silver, and copper do not have a discrete band gap, and quantum mechanical properties depend on the Fermi wavelength of conduction electrons, so only in a few to tens of small-diameter atomic clusters. Observed.

  Thus, it is necessary to reduce the particle size in order to make the metal nanoparticles exhibit fluorescence emission characteristics. However, there are currently limited methods for synthesizing metal nanoparticles having such a small particle size. is there.

  In addition, metal nanoparticles having fluorescent emission characteristics are expected to be applied to, for example, bioprobes, offset inks, invisible paints, phosphors for display panels, and the like. It is also desired to improve the sex.

  As a method for synthesizing metal nanoparticles having a particle size of several nm or less, Non-Patent Document 1 and corresponding Patent Document 1 describe synthesizing nanoparticles by sputtering gold or silver in an ionic liquid. However, none of the ionic liquids disclosed in Patent Document 1 function as a protective agent for metal nanoparticles due to their molecular structure, and the surface of the metal nanoparticles is not chemically modified (paragraph [0015]). Further, metal nanoparticles having an average particle size of less than 1.0 nm have not been obtained, and a dispersion having fluorescence emission characteristics has not been obtained.

Non-Patent Document 2 describes a method in which chloroauric acid is added to an ionic liquid and reduced with sodium borohydride to synthesize gold nanoparticles having an average particle diameter of 5 nm. However, the gold nanoparticles do not exhibit fluorescence emission characteristics. On the other hand, in Non-Patent Document 3, fluorescent clusters having an average particle size of 1.1 to 1.7 nm are obtained by reducing chloroauric acid with sodium borohydride in PTMP-pMAA / H ₂ O. In Non-Patent Document 4, fluorescent clusters (Au ₈ ) having an average particle diameter of 5 nm are obtained by reducing chloroauric acid with sodium borohydride in PEI / H ₂ O.

JP 2007-231306 A

Chem. Commun., 2008, 691-693 J. AM. CHEM. SOC. 2004, 126, 3026-3027 Chem. Commun., 2008, 3986 J. AM. CHEM. SOC. 2007, 129, 2412

  However, the methods of Non-Patent Documents 2 to 4 have a problem in that the use of sodium borohydride as a reducing agent is essential, so that purification and separation of salts and by-products are complicated.

  The present invention has been made in view of the circumstances as described above, and can obtain a fluorescent cluster without requiring a complicated purification and separation operation, and obtain a fluorescent cluster highly dispersible in an aqueous solvent. It is an object of the present invention to provide a method for producing a fluorescent cluster and a fluorescent emission dispersion liquid that can also be used.

  The present invention is characterized by the following in order to solve the above problems.

  1st: It includes the process of making the atom or molecule | numerator of a fluorescent cluster precursor contact the liquid of the organic salt or organic compound as a protective agent of the fluorescent cluster which has a functional group which can be coordinated to a fluorescent cluster A method for producing a fluorescent cluster.

  Second: The method for producing the first fluorescent cluster, further comprising the step of evaporating the solid state fluorescent cluster precursor to generate an atom or molecule of the fluorescent cluster precursor.

  Third: As a protective agent for the fluorescent cluster, the general formula XAY (A is a linear aliphatic hydrocarbon group, or a heteroatom, an aromatic hydrocarbon group, an aliphatic cyclic hydrocarbon group, and an aromatic complex. A linear divalent group containing any divalent group selected from a cyclic group in a linear structure, or any divalent group selected from a group having a substituent in these groups; X represents a salt structure of a monovalent organic cation and a counter anion, and Y represents a functional group capable of coordinating to a fluorescent cluster.) A method for producing the first or second fluorescent cluster.

  Fourth: As a protective agent for the fluorescent cluster, the general formula A′-Y (A ′ is a linear aliphatic hydrocarbon group, or a hetero atom, an aromatic hydrocarbon group, an aliphatic cyclic hydrocarbon group, And any one monovalent group selected from a linear monovalent group containing a divalent group selected from aromatic heterocyclic groups in a linear structure, or a group having a substituent in these groups Wherein Y represents a functional group capable of coordinating to the fluorescent cluster.) The method for producing the first or second fluorescent cluster is characterized by using an organic compound represented by the following formula.

  5: The method for producing any one of the first to fourth fluorescent clusters, wherein the fluorescent cluster precursor is a metal or a semiconductor.

  Sixth: The method for producing the fifth fluorescent cluster, wherein the fluorescent cluster precursor is at least one metal selected from gold, silver, and copper.

  Seventh: A fluorescent emission dispersion liquid, wherein the fluorescent clusters obtained by any one of the first to sixth methods are dispersed in a solvent.

  According to the production method of the present invention, a fluorescent cluster can be obtained without requiring a complicated purification and separation operation. In addition, a fluorescent cluster having high dispersibility in a solvent can be obtained.

  That is, when atoms or molecules of the fluorescent cluster precursor are brought into contact with a liquid of an organic salt or an organic compound, the atoms and the like aggregate, and the particle size increases according to the reaction time and grows. However, by using an organic salt or organic compound liquid having a functional group capable of coordinating with the fluorescent cluster, the functional group chemically modifies to an atom or the like to act as a protective agent and suppress aggregation. For this reason, the particle growth of the cluster is suppressed, and for example, a cluster of less than 1 nm can be obtained, whereby the cluster exhibits fluorescence.

  Since the fluorescence emission dispersion liquid of the present invention uses the fluorescent cluster obtained by the above production method, it can emit strong fluorescence by photoexcitation and can have high dispersion stability.

1 is a fluorescence spectrum of the silver cluster dispersion liquid of Example 12. FIG.

  Hereinafter, the present invention will be described in detail.

  In the present invention, as the fluorescent cluster precursor, for example, a metal or a semiconductor can be used, and these can be used as a gas, a liquid, or a solid. A metal or a semiconductor may be used individually by 1 type, and may use 2 or more types together.

Examples of metals include gold (Au) , silver (Ag) , copper (Cu) , platinum (Pt) , palladium (Pd) , nickel (Ni) , indium (In) , aluminum (Al) , and iron (Fe). , Rhodium (Rh) , ruthenium (Ru) , osmium (Os) , cobalt (Co) , molybdenum (Mo) , zinc (Zn) , vanadium (V) , tungsten (W) , titanium (Ti) , manganese (Mn) And chromium (Cr) . Of these, gold, silver, and copper are preferable.

Examples of the semiconductor include ZnS, CdS, CdSe, In ₂ O ₃ , SiO ₂ , SnO ₂ , TaO ₅ , TiO ₂ , BaTiO ₃ , Si, Se, Te, InAgS ₂ , and InCuS ₂ .

  In the present invention, as a method of generating atoms or molecules of the fluorescent cluster precursor, for example, a method similar to a dry film forming method such as a physical vapor deposition method or a chemical vapor deposition method can be used. A physical vapor deposition method in which atoms or molecules are evaporated from the fluorescent cluster precursor is preferable, and examples thereof include a sputtering method, a vacuum vapor deposition method, and an ion plating method.

  As the evaporation principle, in the case of the sputtering method, for example, a DC sputtering method, a magnetron sputtering method, a high frequency sputtering method, an ion beam sputtering method, or the like can be used. In the case of the vacuum deposition method, for example, a resistance heating method, a far infrared heating method, an electron beam heating method, an arc heating method, a high frequency induction heating method, or the like can be used. In the case of the ion plating method, for example, a high frequency excitation method, an ion beam method, a cluster method, or the like can be used.

  When producing fluorescent clusters by sputtering, for example, as a vapor deposition apparatus, a vapor deposition chamber that can be evacuated, and a cathode that is installed on the upper surface of the vapor deposition chamber and on which a fluorescent cluster precursor of a target material can be mounted A thing provided with the anode installed in the position which counters a cathode can be used.

  A fluorescent cluster precursor is attached to the cathode, and an organic salt or organic compound as a protective agent for the fluorescent cluster is accommodated in a container on the anode, or placed on a plate on the anode capable of holding the liquid. The container or plate is preferably installed together with a heating / cooling device so that the organic salt or the organic compound can be heated and cooled.

  Then, a high voltage is applied to the cathode in a state where the inside of the vapor deposition chamber is in a vacuum or a gas atmosphere such as argon gas to generate a glow discharge in the vapor deposition chamber, and the gas ions generated by the glow discharge cause the fluorescence of the target material to By colliding with the cluster precursor, atoms or molecules constituting the fluorescent cluster precursor are evaporated. When the evaporated atoms or molecules come into contact with the organic salt or organic compound liquid on the lower anode, a fluorescent cluster is generated in or on the liquid.

  The gas pressure, vapor deposition current, reaction time, and reaction temperature may be set as appropriate according to the raw material and vapor deposition apparatus. For example, the reaction time can be set in the range of several tens of seconds to several hours.

  The organic salt or organic compound as the protective agent used in the present invention has a functional group capable of coordinating with the fluorescent cluster, and has a low vapor pressure and is liquid or solid at room temperature. At the time of contact with the atoms or molecules of the fluorescent cluster precursor, the organic salt or organic compound as the protective agent is heated as necessary and used as a liquid.

As the organic salt as the protective agent, for example, those represented by the general formula XAY can be used. Here, the A portion has a role of lowering the vapor pressure, a role of adjusting the solubility of the fluorescent cluster in the solvent, and a role of controlling the particle size of the fluorescent cluster. A is a linear aliphatic hydrocarbon group or a divalent group selected from a hetero atom, an aromatic hydrocarbon group, an aliphatic cyclic hydrocarbon group, and an aromatic heterocyclic group. Any divalent group selected from a linear divalent group included in the structure or a group having a substituent in these groups is shown. Examples of the linear aliphatic hydrocarbon group include an alkylene group, an alkenylene group, an alkynylene group, and the like. Such substituents can include, for example, C ₁ -C ₆ alkyl group, C ₁ -C ₆ alkenyl group, C ₁ -C ₆ alkynyl, C ₆ -C ₁₀ aryl group, and a halogen atom.

A is preferably — (CH ₂ ) _n — (n represents an integer of 0 to 20) or — (CH ₂ ) _m —B— (CH ₂ ) _n — (m is an integer of 0 to 20, n represents an integer of 0 to 20, and m + n is 1 to 40, preferably 2 to 30. B is an oxygen atom, a sulfur atom, a nitrogen atom, an aromatic hydrocarbon group, an aliphatic cyclic hydrocarbon group. Or an aromatic heterocyclic group. Here, examples of the aromatic hydrocarbon group include C _{6 to} C ₁₀ arylene groups such as a p-phenylene group, and examples of the aliphatic cyclic hydrocarbon group include C ₆ to C groups such as a p-cyclohexylene group. C ₁₀ cycloalkylene groups can be mentioned, and examples of the aromatic heterocyclic group include aromatic heterocyclic groups containing C _{6 to} C ₁₀ oxygen atoms, sulfur atoms, and / or nitrogen atoms such as p-pyridylene groups. Can be mentioned.

  X represents a salt structure of a monovalent organic cation and a counter anion. Examples of the salt structure include structures of imidazolium salts, pyridinium salts, pyrrolidinium salts, phosphonium salts, ammonium salts, guanidinium salts, isouronium salts, and isothiouronium salts.

The counter anion of X includes bromide ion (Br ⁻ ), chloride ion (Cl ⁻ ), iodo ion (I ⁻ ), bis (oxalate (2-)-O, O ′) borate ion (B (C ₂ O ₄ ) ₂ ^-), tetrafluoroborate ion (BF ₄ ^-), hexafluorophosphate ion (PF ₆ ^-), trifluoroacetate sulfonate ion (CF ₃ SO ₃ ^-), trifluoroacetate ion (CF ₃ CO ₂ ^-), methane Sulfonate ion (CH ₃ SO ₃ ⁻ ), octyl sulfonate ion (C ₈ H ₁₆ SO ₃ ⁻ ), p-toluenesulfonate ion (C ₆ H ₄ CH ₃ SO ₃ ⁻ ), bis (trifluoromethylsulfonyl) imide ion (( CF ₃ SO ₂ ) ₂ N ⁻ ), bis (perfluoroethylsulfonyl) imide ion ((C ₂ F ₅ SO ₂ ) ₂ N ⁻ ), 2,2,2-trifluoro-N- (trifluoromethanesulfonyl) acetamide ion (CF ₃ SO ₂ ) (CF ₃ CO) N ⁻ , N- (trifluoromethanesulfonyl) -pentafluoroethylsulfonamide (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ ) N ⁻ , nitrate ion (NO ₃ ⁻ ), thiocyanate Ion (SCN ⁻ ), dicyanamide ion (N (CN) ₂ ⁻ ), tricyanomethanide ion (C (CN) ₃ ⁻ ) and the like.

  Y is a functional group capable of coordinating to the fluorescent cluster, and having this functional group can function as a protective agent for the fluorescent cluster. Specific examples thereof include a thiol group, a carboxyl group, a hydroxyl group, a phosphonic acid group, a phosphoric acid group, a sulfino group, a sulfo group, an amino group, an isocyano group, and a nitrile group.

As the organic compound as the protective agent, for example, one represented by the general formula A′-Y can be used. Here, A ′ has a role of lowering the vapor pressure, a role of adjusting the solubility of the fluorescent cluster in the solvent, and a role of controlling the particle size of the fluorescent cluster. A ′ represents a straight-chain aliphatic hydrocarbon group or any divalent group selected from a hetero atom, an aromatic hydrocarbon group, an aliphatic cyclic hydrocarbon group, and an aromatic heterocyclic group. Any monovalent group selected from a linear monovalent group included in the chain structure or a group having a substituent in these groups is shown. Examples of the linear aliphatic hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group. Such substituents can include, for example, C ₁ -C ₆ alkyl group, C ₁ -C ₆ alkenyl group, C ₁ -C ₆ alkynyl, C ₆ -C ₁₀ aryl group, and a halogen atom.

A ′ is preferably CH ₃ (CH ₂ ) _n- (n represents an integer of 0 to 22) or CH ₃ (CH ₂ ) _m -B- (CH ₂ ) _n- (m is 0 to 22). , N represents an integer of 0 to 22, and m + n is 1 to 44, preferably 2 to 30. B is an oxygen atom, sulfur atom, nitrogen atom, aromatic hydrocarbon group, aliphatic cyclic A hydrocarbon group or an aromatic heterocyclic group). Here, examples of the aromatic hydrocarbon group include C _{6 to} C ₁₀ arylene groups such as a p-phenylene group, and examples of the aliphatic cyclic hydrocarbon group include C ₆ to C groups such as a p-cyclohexylene group. C ₁₀ cycloalkylene groups can be mentioned, and examples of the aromatic heterocyclic group include aromatic heterocyclic groups containing C _{6 to} C ₁₀ oxygen atoms, sulfur atoms, and / or nitrogen atoms such as p-pyridylene groups. Can be mentioned.

  Y is a functional group capable of coordinating to the fluorescent cluster, and having this functional group can function as a protective agent for the fluorescent cluster. Specific examples thereof include a thiol group, a carboxyl group, a hydroxyl group, a phosphonic acid group, a phosphoric acid group, a sulfino group, a sulfo group, an amino group, an isocyano group, and a nitrile group.

  Fluorescent cluster precursor atoms or molecules are brought into contact with the above organic salt or organic compound liquid as a protective agent, and then separated and purified by, for example, filtration, ultracentrifugation, reprecipitation with a solvent, etc. Clusters can be obtained as powder. According to the present invention, a fluorescent cluster having an average particle diameter of preferably less than 2.0 nm, more preferably less than 1.0 nm can be obtained.

  This fluorescent cluster can be dispersed in an aqueous solvent such as water or alcohol or a hydrophobic solvent by appropriately selecting the type of the protective agent. The dispersion is irradiated with excitation light, and fluorescence is observed in the long wavelength region. For example, in the case of a gold cluster, fluorescence of blue, red, etc. is observed by UV (365 nm) irradiation. In the case of silver clusters, fluorescence is observed in blue, near infrared, etc. by UV irradiation. In the case of a copper cluster, fluorescence such as red is observed by UV irradiation.

  The fluorescent cluster and dispersion thereof obtained by the present invention are suitable for use in, for example, bioprobes, offset inks, invisible paints, phosphors for display panels, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

  An organic salt or an organic compound shown in Table 1 was placed in a glass container, and this was placed in a heating / cooling device on an anode in a magnetron sputtering apparatus.

  On the other hand, a gold, silver, or copper target was mounted as a target material for the fluorescent cluster precursor at an upper position facing the container. Thereafter, the inside of the vapor deposition chamber was controlled to a degree of vacuum capable of sputtering, and sputtering was performed for 1 to 10 minutes in a state where the organic salt was heated to a melting point or higher by a heating / cooling device to be a liquid.

  Thereafter, the liquid in the container was collected, separated and purified according to a conventional method, and a fluorescent cluster was obtained as a powder. This was dispersed in water and methanol, and the dispersibility of the dispersion and the fluorescence upon UV (365 nm) irradiation were confirmed. Moreover, about silver, fluorescence was confirmed using the fluorescence spectrum. In Example 14, the fluorescence in the long wavelength region was visually observed by directly irradiating the particles with excitation light instead of the dispersion. Moreover, about Example 15, 16, the obtained fluorescent cluster was disperse | distributed to hexane and fluorescence was observed visually. The results are shown in Table 1, and the near-infrared fluorescence spectrum of the silver cluster dispersion of Example 12 is shown in FIG.

  From Table 1, the gold, silver, and copper fluorescent clusters were well dispersed in water or methanol by appropriately selecting the type of protective agent. The dispersion was visually observed in the long wavelength region when irradiated with excitation light. In the case of the silver cluster of Example 12, no fluorescence was observed visually, but fluorescence was observed in the near infrared (FIG. 1).

  In Example 14, although the dispersibility in water or methanol was not good, fluorescence was observed visually by directly irradiating the particles with excitation light.

  In Examples 15 and 16, the gold and silver fluorescent clusters were well dispersed in hexane. The dispersion was visually observed in the long wavelength region when irradiated with excitation light.

  Moreover, when the size of the fluorescent cluster of Examples 1-16 was observed with TEM, the average particle diameter was less than 2.0 nm, and many were less than 1.0 nm.

Claims (2)

Any metal selected from Au, Ag, Cu, Pt, Pd, Ni, In, Al, Fe, Rh, Ru, Os, Co, Mo, Zn, V, W, Ti, Mn, and Cr in the solid state , Or ZnS, CdS, CdSe, In ₂ O _Three , SiO ₂ , SnO ₂ , TiO ₂ , BaTiO _Three And evaporating any semiconductor selected from Si, Se, and Te, and the evaporated metal or semiconductor is represented by the general formula X-A-Y (A is-(CH ₂ ) _n -(N represents an integer of 0 to 20) or-(CH ₂ ) _m -B- (CH ₂ ) _n -(M represents an integer of 0 to 20, n represents an integer of 0 to 20, and m + n is 1 to 40. B represents an oxygen atom, a sulfur atom, a nitrogen atom, C ₆ ~ C _Ten Arylene group, C ₆ ~ C _Ten A cycloalkylene group, or C ₆ ~ C _Ten And an aromatic heterocyclic group containing an oxygen atom, a sulfur atom, and / or a nitrogen atom. ). X represents the structure of an imidazolium salt, pyridinium salt, pyrrolidinium salt, phosphonium salt, ammonium salt, guanidinium salt, isouronium salt, or isothiouronium salt, and Y represents a thiol group, carboxyl group, hydroxyl group, phosphonic acid group, A phosphoric acid group, a sulfino group, a sulfo group, an amino group, an isocyano group, or a nitrile group is shown. And a step of bringing the organic salt into contact with a liquid of an organic salt represented by the following formula: A fluorescent emission dispersion, wherein the fluorescent cluster obtained by the method according to claim 1 is dispersed in a solvent.