JP6661871B2 - Method for producing noble metal nanoparticle multimer, method for recovering noble metal nanoparticle isomer, method for controlling absorption spectrum of noble metal nanoparticle isomer, and method for controlling optical characteristics of noble metal nanoparticle isomer - Google Patents

Description

  The present technology relates to a method for producing a precious metal nanoparticle multimer, a method for recovering a precious metal nanoparticle isomer, a method for controlling the absorption spectrum of the precious metal nanoparticle isomer, and a method for controlling the optical characteristics of the precious metal nanoparticle isomer. .

  There is an increasing need for nanoscale materials in various fields such as semiconductors, electronics and medicine. By integrating materials having a nanoscale size, new functions can be developed. For this reason, the integration technology and the integrated structure are notable technologies and materials (see Patent Document 1).

  Nanoscale materials, such as semiconductor nanoparticles and metal nanoparticles, have provided new functions due to their quantum effects. Here, “nano-scale material” refers to a material having a particle size in the range of 1 to 100 nm. Metal nanoparticles, which are nanoscale materials, can generate localized light (near-field light) of a size corresponding to their radius, and have optical characteristics such as a large electric field and absorption wavelength depending on their size and shape. I have. In addition, a structure in which the metal nanoparticles are coupled to each other with a spacing of several to 10 nm can generate a large electric field or very bright near-field light in the gap, and can control optical characteristics.

  Nanoscale materials are expected to be applied to optoelectronics such as optical devices, high-sensitivity sensors, catalysts, energy, and imaging. In order to apply to these, it is technically required to control the size, shape, and interval of the metal nanostructure. Making the shape of the metal nanoparticle into a nanorod greatly enhances the sensitivity, and it is possible to control the optical characteristics. However, nanorods vary in size and shape, and cannot maintain uniform sensitivity and optical characteristics. In addition, there is a concern about toxicity in use in a living body. The current state of the method of controlling the distance between metal nanoparticles is mainly performed on a substrate, and many chemical and physical methods have been proposed (see Patent Document 2). However, these proposed methods have limited uses because of the use of fixing techniques.

  In a dispersion solution, if the structure (multimer) can be controlled in size, shape, and interval to maintain uniform sensitivity and optical characteristics, it can be used in various solvents. This is expected to have a synergistic effect by forming a complex with other substances, and can be used in ecological water systems such as in vivo and in vitro. From this, development in many fields is expected in the future.

JP 2012-2510 A International Publication No. 2011/135924

  An object of the present invention is to provide a method for producing a precious metal particle multimer having uniform characteristics by controlling the distance between particles of precious metal nanoparticles of uniform size and shape in a liquid and binding them. .

In order to solve the problem, the present invention provides the following method for producing a noble metal nanoparticle polymer.
The method for producing a noble metal nanoparticle polymer of the present invention,
A step of dispersing in a solvent noble metal nanoparticles bonded to an alkyl chain having a reactive group on the surface,
Step of obtaining a noble metal nanoparticle polymer by replacing the solvent with a solvent having a high salt concentration,
including.

  It is possible to provide a method for producing a precious metal particle multimer having uniform characteristics.

It is a mimetic diagram for explaining the manufacturing method of the noble metal nanoparticle multimer which is an embodiment of the present invention, (a) is a schematic diagram showing a manufacturing process of a noble metal nanoparticle multimer, (b) is manufactured It is a schematic diagram which shows the noble metal nanoparticle dimer, and (c) is an enlarged view of the bonding part in (b). FIG. 2 is a schematic diagram illustrating a method for recovering the isomer of a multimeric dispersion of noble metal nanoparticles of the present invention by electrophoresis. 30nm of the present invention, 40 nm, the alkyl chain length in 50nm noble metal nanoparticles _{- (CH 2) 5 -,} - (CH 2) 7 -, - (CH 2) 10 -, - (CH 2) 15 - in organic molecules 3 is an agarose gel electrophoresis image of a bound multimeric dispersion. 30nm of the present invention, 40 nm, the alkyl chain length in 50nm noble metal nanoparticles _{- (CH 2) 5 -,} - (CH 2) 7 -, - (CH 2) 10 -, - (CH 2) 15 - in organic molecules It is an absorption spectrum of a bound dimer. Alkyl chain length of 40nm noble metal nanoparticles of the present invention _{- (CH 2) 5 -,} - (CH 2) 7 -, - (CH 2) 10 -, - (CH 2) 15 - dimer bound in organic molecules It is a photograph of distance observation between particles of a body by a cryo-TEM method. Alkyl chain length of 40nm noble metal nanoparticles of the present invention _{- (CH 2) 5 -,} - (CH 2) 7 - monomers bound in organic molecules, dimers, the absorption spectrum of the trimer. Alkyl chain length of 40nm noble metal nanoparticles of the present invention - _{(CH 2) 7} - 0.5xTBE buffer dimer bound organic molecule, the absorption spectrum dispersed acetone, ethanol solvent.

    Hereinafter, a method for producing a noble metal nanoparticle multimer dispersion, which is an embodiment of the present invention, will be described with reference to FIG. FIG. 1 is a schematic diagram for explaining a method for producing a noble metal nanoparticle multimer according to an embodiment of the present invention, and FIG. 1 (a) is a schematic diagram showing a process for producing a noble metal nanoparticle multimer. (B) is a schematic diagram showing a manufactured noble metal nanoparticle dimer, and (c) is an enlarged view of a bonding portion of the noble metal nanoparticle dimer in (b).

  The size of the noble metal nanoparticles 1 of the present invention is desirably in a particle size range of 10 to 100 nm, and it is preferable that the shape has no variation in particle size and sphere, and that the particles are dispersed without aggregation. It is preferable to select a noble metal nanoparticle having good coloration characteristics at the wavelength of light to be used, and among them, gold nanoparticle shows red coloration due to plasmon resonance in natural light, so that it is easy to see and preferably used. Can be.

  Hereinafter, the case where the noble metal nanoparticles 1 are the gold nanoparticles 1 will be described as an example.

  A dispersion of the gold nanoparticles 1 is precipitated by centrifugation 2 and dispersed in a solvent 3 containing a salt (inorganic salt, organic salt). Since the noble metal nanoparticles tend to be aggregated due to the rotation speed of centrifugation and the salt concentration as the particle size increases, it is preferable to use the optimum rotation speed and salt concentration for each particle size. The rotation speed used is 1000 rpm to 12000 rpm, and the salt concentration used is 10 mM to 80 mM.

  Organic molecules 4 are added to the gold nanoparticle dispersion. The organic molecule 4 has a connecting molecule 5 such as a thiol group or a disulfide group, and is connected to the gold nanoparticle surface. The functional group is not particularly limited as long as it can be connected, and the thiol group 5 can be easily bonded to the noble metal nanoparticle and can be firmly bonded.

The alkyl chains of the organic molecule 4 having the linking molecule 5 form a monomolecular layer by self-assembly due to the aggregation of the molecules due to intermolecular force interaction such as van der Waals force and hydrophobic interaction. Form. It is said that the monomolecular film formed on the substrate changes in thickness by 0.2 nm each time the number of methylene units (—CH ₂ —) in the alkyl chain increases or decreases by one.

The organic molecule 4 having a linking molecule preferably has an alkyl chain 6 having 3 to 20 carbons. The distance between particles can be controlled to about 0.5 to 4 nm by the number of methylene units (—CH ₂ —) in the alkyl chain.

The terminal functional group of the alkyl chain of the organic molecule 4 is desirably carboxylic acid 7. In FIG. 7, it is shown as a carboxyl group, but exists as COO ^{− in the} solvent 3 containing a salt. When the terminal has a negative charge, the gold nanoparticle 1 repels and can maintain the dispersion in the buffer solvent.

  The connection temperature 8 between the gold nanoparticles 1 and the organic molecules 4 is preferably set to 30 to 60 ° C.

  The connection time 9 between the gold nanoparticles 1 and the organic molecules 4 is preferably 30 minutes to 3 hours.

  After the above, the organic molecule 4 and the gold nanoparticle 1 are connected to form the complex 10. Washing 12 is performed with a solvent 3 containing a salt in order to remove the organic molecules 11 that have not been quickly bound.

  After washing 12, the gold nanoparticle composite 10 is dispersed in a solvent 13 containing a salt. It is preferable that the salt concentration is higher than that of the solvent 3 containing the salt at the time of connection, and the salt concentration used is 40 mM to 320 mM.

By increasing the salt concentration, the gold nanoparticles approach each other, and the alkyl chains 6 connected to each other are assembled and bonded by the intermolecular force interaction, so that a metal nanoparticle multimer can be formed. The distance between particles can be kept constant by the alkyl chain 6, and the distance between particles can be controlled by increasing or decreasing the number of methylene units (—CH ₂ —) in the alkyl chain.

  The above dispersion is annealed 14 at a temperature of 70 to 120 ° C. for 1 to 7 minutes. Annealing can increase the binding efficiency of the gold nanoparticle multimer.

  The above dispersion is left at room temperature for 15 minutes or more after annealing.

  The dispersion is washed 12 with a salt-free solvent 15. By removing the salt, a dispersion 19 containing a gold nanoparticle polymer (monomer 16, dimer 17, trimer 18, etc.) dispersed in the dispersion is produced while keeping the binding site at a fixed distance. can do.

The gold nanoparticle multimer dispersion liquid 19 changes from red coloration by plasmon resonance of the single gold nanoparticles to reddish purple to purple color. This color change methylene units of the particle size and the alkyl chain - different difference numbers (-CH _2).

  Hereinafter, a method for separating and recovering an isomer dispersion of noble metal nanoparticles, which is an embodiment of the present invention, will be described with reference to FIG. FIG. 2 is a schematic diagram illustrating a method for recovering the isomer of the multimeric dispersion of the noble metal nanoparticles of the present invention by electrophoresis.

The gold nanoparticle polymer dispersion 19 is precipitated by centrifugation 2, and the precipitated gold nanoparticle polymer is purified and separated by gel electrophoresis 21. Since the mobility of the polymer 19 of gold nanoparticles varies depending on the number of particles, the polymer 19 can be separated into a band on the gel 22. The smaller the number of particles, the faster the movement, the order of the monomer 16, the dimer 17, the trimer 18, and the tetramer. In this separated state, the production efficiency of the gold nanoparticle polymer dispersion 19 can be confirmed. . The separated monomer band 16 is red, and the bands of multimers (dimer 17, trimer 18, tetramer, etc.) are purple-purple. This color change methylene units of the particle size and the alkyl chain - different difference numbers (-CH _2).

  The gold nanoparticle multimer dispersion 19 contains multimers having different particle numbers, such as a monomer 16, a dimer 17, a trimer 18, and a tetramer. As a production method of converting the dispersion 19 into a multimer dispersion liquid (equivalent dispersion liquid) 27 having the same number of particles, a method of preparing a gel 22 is provided at the downstream of the injection well 23 into which the precipitated gold nanoparticle multimer 19 is injected. A collection well 24 is created at the position. The gel 22 is placed in an electrophoresis tank containing a buffer, and the gold nanoparticle polymer 19 precipitated by centrifugation 2 is injected into the injection well 23, and a voltage 26 is applied from one side. Thereby, when the band portion of the target multimer separated on the gel reaches the collection well 24, the same amount dispersion liquid 27 of the gold nanoparticles can be obtained by sucking and collecting with the pipetteman 25 or the like. .

  The recovered isomer dispersion liquid 27 can be washed 12 with a solvent 15 containing no salt by centrifugation 2 and dispersed in a dispersion solvent 28. The dispersion solvent 27 can be changed as long as it does not change the structure of the multimer, such as water, buffer, alcohols, organic solvents, etc., does not cause plasmon resonance, or does not cause aggregation.

In the isomer dispersion liquid 27 of the present invention, since the distance between the particles is bound to each other at 0.5 to 4 nm, an absorption spectrum can be obtained on the longer wavelength side in addition to the absorption spectrum of the gold nanoparticles near 525 nm. The absorption spectrum on the longer wavelength side is controlled by the number of methylene units (—CH ₂ —) in the alkyl chain, which keeps the particle size and the distance between the gold nanoparticles. Due to the absorption wavelength on the longer wavelength side, the isomer dispersion liquid 27 has a purple-violet color.

  The isomer dispersion liquid 27 of the noble metal nanoparticles of the present invention can generate a large electric field or very bright near-field light at the joint 20.

A neutral type gold nanoparticle dispersion solution manufactured by Tanaka Kikinzoku Kogyo with particle diameters of 30 nm, 40 nm, and 50 nm was used. Gold nanoparticle concentration is 30 nm: a ^{3.7 × 10 11 /ml,40nm:1.6×10 11 /ml,50nm:8.0×10 10} / ml.

  Bis (p-sulfonatophenyl) phenylphosphine dihydrate dipotassium salt (BSPP) was added to this gold nanoparticle solution to a concentration of 1 mg / ml, incubated at 50 ° C. for 1 hour, and centrifuged to separate the gold nanoparticle. Let the particles settle. Centrifugation is performed at a rotation speed of 30 nm: 6500 rpm, 40 nm: 5000 rpm, and 50 nm: 3500 rpm for 15 minutes.

  Next, 30 nm: TBE50 (50 mM NaI, 0.5 × TBE, 0.5 mg / ml BSPP), 40 nm: TBE40 (40 mM NaCl, 0.5 × TBE, 0.5 mg / ml BSPP) were added to the precipitate of the gold nanoparticles. 50 nm: redispersed in a buffer solvent containing a salt of TBE30 (30 mM NaCl, 0.5 × TBE, 0.5 mg / ml BSPP).

Then, the gold nanoparticle dispersion, alkyl chain length of alkanethiol _{- (CH 2) 5 -:} 5- _{carboxy-1-pentane-thiol, - (CH 2) 7 -} : 7- carboxy-1-heptanoic _{thiol, - (CH 2) 10 -} : 10- _{carboxy-1-decanethiol, - (CH 2) 15 -} : 15- carboxy-1 added pentadecane thiol respectively, gold nanoparticles for 1 h at 50 ° C. Connect to the surface.

  Next, centrifugation is performed at the above-mentioned rotation speed for 15 minutes, and washing with a buffer solution containing the above-mentioned salt is performed to remove unbound alkanethiol.

  Next, 30 nm: TBE200 (200 mM NaCl, 0.5 × TBE, 0.5 mg / ml BSPP), 40 nm: TBE160 (160 mM NaCl, 0.5 × TBE, 0.5 mg / ml BSPP) were added to the precipitate of the gold nanoparticles. 50 nm: Redispersed in a buffer solvent containing a salt of TBE120 (120 mM NaCl, 0.5 × TBE, 0.5 mg / ml BSPP), and annealed at 92 ° C. for 5 minutes.

  Next, after leaving at room temperature, centrifugation is performed for 15 minutes at the above rotation speed, and washing is performed with 0.5 × TBE to remove salts. Thereby, a dispersion liquid in which a gold nanoparticle multimer was formed was obtained.

  The production efficiency of the gold nanoparticle polymer dispersion is confirmed by centrifuging the gold nanoparticle polymer dispersion, injecting the precipitate on an agarose gel, and performing electrophoresis. The electrophoresis conditions are 1.5% agarose gel, 0.5 × TBE running buffer, voltage of 175 V, loading buffer of Ficoll 400 for 15 minutes.

FIG. 3 shows the alkyl chain lengths of alkanethiols having particle diameters of 30 nm, 40 nm, and 50 nm,-(CH ₂ ) ₅ -,-(CH ₂ ) ₇ -,-(CH ₂ ) _10- , and-(CH ₂ ) _15- . It is a result image of agarose electrophoresis of a multimer dispersion liquid. Moving in the order of smaller number of particles, bands separated from each other such as a monomer, a dimer, a trimer, and a tetramer can be confirmed. The monomer band exhibits red, and the bands such as dimer, trimer, and tetramer exhibit reddish purple to deep purple. The color of this multimer depends on the alkyl chain length of the alkanethiol that links between the particles.

FIG. 4 shows the results of the alkyl chain lengths of alkanethiol having particle diameters of 30 nm, 40 nm, and 50 nm,-(CH ₂ ) ₅ -,-(CH ₂ ) ₇ -,-(CH ₂ ) _10- , and-(CH ₂ ) _15- . FIG. 4 shows the measurement results of the absorption spectrum of the dimer collected by centrifuging the gold nanoparticle dispersion and injecting the precipitate on the recovery agarose gel shown in FIG. 2 and performing electrophoresis. In addition to the absorption peak near 525 nm, an absorption peak appears on the longer wavelength side, and appears on the longer wavelength side as the alkyl chain length of the alkanethiol becomes shorter. The larger the particle size, the longer the wavelength. Maximum absorption wavelength appearing in the long wavelength side alkyl chain length _{- (CH 2) 5 -,} - (CH 2) 7 -, - (CH 2) 10 -, - (CH 2) 15 - in order particle size 30 nm: 589 nm, 574 nm, 560 nm, none. Particle diameter 40 nm: 628 nm, 609 nm, 594 nm, 574 nm. Particle size 50 nm: 655 nm, 630 nm, 599 nm, 591 nm.

Figure 5 is an alkyl chain length of the particle diameter 40nm alkanethiol _{- (CH 2) 5 -,} - (CH 2) 7 -, - (CH 2) 10 -, - (CH 2) 15 - cryo transmission electron It is a microscope (TEM) observation image. Since the method is a method of observing by freezing in a solvent state, the bonding distance of the gold nanoparticle dimer in the solvent is observed. It was found that the distance between the particles increased with the number of the ethylene units (-CH2-) in the alkyl chain. The average results of measuring the distance between the particles of the dimer from the image _{- (CH 2) 5 - ::} 0.97nm, - (CH 2) 7 -: 1.45nm, - (CH 2) 10 -: 2. _{21nm, - (CH 2) 15} -: was 3.91Nm.

FIG. 6 shows the measurement results of the absorption spectra of the monomer, dimer, and trimer of the alkyl chain length-(CH ₂ ) _5- and-(CH ₂ ) _7-of alkanethiol having a particle diameter of 40 nm. Monomers having an alkyl chain length of — (CH ₂ ) ₅ — show a single absorption peak at 528 nm, dimers show absorption peaks at 528 nm and 627 nm, and trimers show absorption peaks at 528 nm and 665 nm. . The monomer having an alkyl chain length of-(CH ₂ ) _7- has a single absorption peak at 527 nm, a dimer has absorption peaks at 527 nm and 609 nm, and a trimer has absorption peaks at 527 nm and 643 nm. . It was found that the trimer showed an absorption peak in the longer axis direction more than the dimer, and the shorter the alkyl chain length, the more the peak appeared in the longer axis direction.

FIG. 7 is a measurement result of an absorption spectrum obtained by dispersing a dimer dispersion of an alkanethiol having a particle diameter of 40 nm with an alkyl chain length of — (CH ₂ ) ₇ — in a 0.5 × TBE buffer, acetone, and ethanol solvent. Although a slight shift occurs in the absorption spectrum depending on the solvent, a long wavelength peak is observed. This proved that the solvent could be replaced.

  The noble metal nanoparticle multimer of the present invention can control the size, shape, and spacing in a dispersion solvent, and increase or decrease the particle diameter and the alkyl chain of the connecting molecule to increase or decrease the wavelength of the localized plasmon. Can be changed freely. Expected to be used in optoelectronics such as optical devices, high-sensitivity sensors, and catalysts, and because it is a solvent dispersion, it is expected to be used in medical fields such as interactive reactions with other substances, ecosystems, and biosensors. it can.

DESCRIPTION OF SYMBOLS 1 ... Gold nanoparticle, 2 ... Centrifugation, 3 ... Solvent containing salt, 4 ... Organic molecule, 5 ... Linked molecule, 6 ... Alkyl chain, 7 ... Terminal Functional group, 8: connection temperature, 9: connection time, 10: gold nanoparticle composite with organic molecules connected, 11: unconnected organic molecules, 12: washing, 13 ... Solvent containing salt at a higher concentration than solvent 3, 14 ... Annealing, 15 ... Salt-free solvent, 16 ... Monomer, 17 ... Dimer, 18 ... Trimer, 19: Gold nanoparticle multimer dispersion, 20: binding part, 21: electrophoresis, 22: gel, 23: injection well, 24: collection Well, 25: Pipetman, 26: Voltage, 27: Isomeric dispersion, 28: Dispersion solvent

Claims (8)

One of the alkyl chains has a reactive group that can be connected to the surface of the noble metal nanoparticle, the other terminal functional group is a step of dispersing the noble metal nanoparticle in which the organic molecule containing a carboxylic acid is bonded in a solvent,
A step of obtaining a noble metal nanoparticle polymer by replacing the solvent concentration with a solvent having a higher salt concentration than the dispersion step ,
A method for producing a noble metal nanoparticle multimer comprising:   The method for producing a noble metal nanoparticle multimer according to claim 1, comprising a step of separating the noble metal nanoparticle multimer by gel electrophoresis. The method for producing a noble metal nanoparticle multimer according to claim 1, wherein the method is a noble metal nanoparticle multimer composed of noble metal nanoparticles having a particle size of 10 to 100 nm .   4. The method of claim 1, wherein the reactive group is at least one selected from the group consisting of a thiol group and a disulfide group. 5.   The method for producing a noble metal nanoparticle polymer according to any one of claims 1 to 4, wherein the alkyl chain includes an alkyl chain having 3 to 20 carbon atoms. The method for producing a precious metal nanoparticle multimer according to any one of claims 1 to 3, wherein a distance between the noble metal nanoparticles constituting the precious metal nanoparticle multimer is 0.5 to 4 nm.   The method according to any one of claims 1 to 7, wherein the solvent in which the noble metal nanoparticles are dispersed is at least one selected from the group consisting of water, an organic solvent, and an alcohol. Method. A noble metal nanoparticle obtained by recovering a band portion of the noble metal nanoparticle multimer produced by the production method according to any one of claims 1 to 7 by the number of particles by gel electrophoresis. A method for producing an isomer of a noble metal nanoparticle, comprising a step of obtaining an isomer .