JP2013033029A - Method of quantifying gold nanoparticles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively quantifying gold nanoparticles in a measurement liquid where gold nanoparticles surface-modified with protection ligands are dispersed in alcohol.SOLUTION: A measurement liquid is heated to obtain gold nanoparticles as a residue. The obtained residue is added with chemical liquids produced by mixing nitric acid and hydrochloric acid or chloride to obtain a dissolved liquid where the residue is dissolved. The obtained dissolved liquid is analyzed by ICP-MS to detect the amount of gold nanoparticles in the measurement liquid.

Description

  The present invention relates to a method for quantifying gold nanoparticles in a measurement liquid in which gold nanoparticles surface-modified with a protective ligand are dispersed in alcohol.

  Fine particles in liquids such as pure water and alcohol used in the manufacturing process of semiconductor devices and the like are strictly controlled because they directly cause a decrease in yield. As device design dimensions decrease, the problem particle size also decreases. According to ITRS (International Technology Roadmap for Semiconductors), the DRAM half-pitch size in 2010 is 45 nm, and further miniaturization is expected in the future. Actually, from the ITRS 2008, a management item “Critical particle size” has been added for fine particles in pure water, even though analytical problems have not been overcome. In ITRS 2010, a guideline for managing fine particles having a size of 20 nm in 2011 and 10 nm in 2017 at a level of 4 particles / mL is shown. Similarly, regarding the fine particles in IPA (isopropyl alcohol), in 2011, it is required to manage fine particles having a size of 20 nm at a level of 1.0E + 04 (10,000) / mL.

  Filters such as microfiltration membranes (hereinafter referred to as MF membranes) and ultrafiltration membranes (hereinafter referred to as UF membranes) are used for highly maintaining and managing the number of fine particles in the liquid. In general, in the MF membrane, solid spherical particles such as PSL (Polystyrene Latex) are used as standard particles, and the removal rate is about 99%, which is called rated filtration accuracy (μm). On the other hand, in the UF membrane, filtration is performed using an indicator substance such as protein, and the molecular weight equivalent to 90% of the blocking rate is set as the fractional molecular weight. Therefore, it is not possible to directly compare the separation performance indexes of the two. However, recently, the rating in the MF film for the semiconductor industry has reached a particle size of 30 nm or less, and is effectively overlapping with the rating of the UF film. In addition, since the lower limit of the particle size of PSL particles as standard particles is about 20 nm, a new particle removal performance evaluation method for fine particle removal filters having a particle size of 30 nm or less is required.

  Therefore, in recent years, a new method using metal fine particles as described in Non-Patent Document 1 has been proposed as a particle removal performance evaluation method for a fine particle removal filter having a particle size of 30 nm or less. In this method, the particle removal performance of the filter is obtained by using gold nanoparticles as challenge particles and using DLS (dynamic light scattering method) or ICP-MS (inductively coupled plasma mass spectrometer) as a measuring device. Above all, the hydrophilic / hydrophobic and cationic / anionic properties of the gold nanoparticles are controlled by changing the protective ligand, and the adsorption characteristics of the filter (filtration membrane) are also evaluated.

  Here, there is also a proposal for wafer-like gold (metal) analysis as a high-sensitivity analysis method for gold. In Patent Document 1, in the analysis of gold, platinum, silver, and copper contaminating the silicon substrate surface, hydrofluoric acid vapor is sprayed on the substrate surface, and then aqua regia is dropped to decompose impurities on the substrate, and the decomposition and recovery thereof are performed. A method is disclosed in which the liquid is collected and analyzed by atomic absorption spectrometry.

  Further, in Patent Document 2, against the metal contamination such as platinum on the surface of the silicon wafer, the wafer surface is brought into contact with a rare water prepared by diluting aqua regia with pure water for a predetermined time, Is recovered, evaporated to dryness, redissolved in nitric acid or the like, and a method for quantifying the metal by ICP-MS or atomic absorption spectrometry (AAS) is disclosed.

JP-A-5-218164 JP 2001-77158 A

Clean Technology 2009.2 P45-48 J.Phys.Chem.B 2004,108,2134-2139 `` Two-Step Functionalization of Neutral and Positively Charged Thiols onto Citrate-Stabilized Au Nanoparticles '' Chem. Mater., Vol. 16, No. 13, 2004 "A Simple Large-Scale Synthesis of Nearly Monodisperse Gold and Silver Nanoparticles with Adjustable Sizes and with Exchangeable Surfactants"

  In the said nonpatent literature 1, in the determination method of the gold nanoparticle using ICP-MS, hydrophilicity / hydrophobicity of gold nanoparticle and cationic / anionic property are controlled by changing a protective ligand, The adsorption characteristics of the filter (filtration membrane) are evaluated. However, no consideration is given to whether the use of such a protective ligand has an effect on the quantification of gold nanoparticles using ICP-MS.

  The object of the present invention is to accurately quantify gold nanoparticles whose surface is modified by a protective ligand dispersed in an alcohol such as IPA.

  The present invention relates to a method for quantifying gold nanoparticles in a measurement liquid in which gold nanoparticles surface-modified with a protective ligand are dispersed in alcohol, and the measurement liquid is heated to leave the gold nanoparticles as a residue. And a step of adding a chemical solution prepared by mixing nitric acid and hydrochloric acid or chloride to the obtained residue to obtain a solution obtained by dissolving the residue. Analyzing the dissolved solution by ICP-MS, and detecting the amount of gold nanoparticles in the measurement solution.

  In the step of obtaining the dissolution solution, it is preferable that the concentration of the chemical solution is changed depending on the type of the protective ligand.

  Further, in the step of obtaining the solution, it is preferable to irradiate ultrasonic waves after adding the chemical solution to the residue.

  The chemical solution is a mixture of nitric acid and hydrochloric acid, and preferably contains 1.5 to 7.5% by weight of nitric acid and 2.3 to 11.3% by weight of hydrochloric acid.

  Moreover, the said chemical | medical solution is a mixture of nitric acid and hydrochloric acid, Comprising: It is suitable that nitric acid 4.5-7.5 weight% and hydrochloric acid 6.8-11.3 weight% are included.

  The protective ligand is preferably thioctic acid or 10-carboxy-1-decanethiol.

  The alcohol is preferably IPA.

  Moreover, it is preferable that the measurement liquid is a filter filtrate used when evaluating the particle removal performance of the filter.

  According to the present invention, gold nanoparticles surface-modified with a protective ligand dispersed in alcohol can be accurately quantified.

It is a figure which shows the outline | summary of the processing system in which fixed_quantity | quantitative_assay of a gold nanoparticle is performed. It is a figure explaining the pre-processing means of fixed_quantity | quantitative_assay. It is a figure which shows the collection | recovery rate by the surface state of a gold nanoparticle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an outline of a processing system for evaluating the filter 18. First, a sample liquid in which gold nanoparticles are dispersed is prepared by adding and mixing gold nanoparticles into alcohol in the storage tank 10. In particular, it is preferable to use particles having a particle diameter of 30 nm or less as the gold nanoparticles, and gold nanoparticles having a particle diameter of 30 nm, 20 nm, 10 nm, or the like can be used.

  Further, the storage tank 10 is provided with an ultrasonic irradiation device 12, and the gold nanoparticles are reliably dispersed in the alcohol by the irradiation of the ultrasonic waves. As the ultrasonic irradiation device 12, a device for mixing various liquids or the like can be appropriately employed.

  The sample liquid in the storage tank 10 is supplied to the filter 18 via the valve 16 by the pump 14. Note that the pressure of the sample liquid supplied to the filter 18 is measured by the pressure gauge 20, and pressure loss in the filter 18 is checked.

  The filter 18 uses a filtration membrane such as an MF membrane or a UF membrane to be evaluated. For example, the polymer solution membrane separates the stock solution side from the filtrate side, and fine particles in the stock solution are separated by the filtration membrane. Filtered off.

  Then, the sample is sampled from the supply path to the filter 18 through the valve 22 and supplied to the preprocessing means S1. Further, the filtrate obtained by the filter 18 is sampled and supplied to the pretreatment means S2. Then, the sample solution and filtrate pretreated by the pretreatment means S1 and S2 are appropriately supplied to the ICP-MS 26, where the gold nanoparticle concentration is quantitatively analyzed.

  Here, pre-processing means S1 and S2 will be described with reference to FIG. In this example, the sampled liquid to be measured is first heated and dried. That is, the liquid to be measured placed in the container is heated to about 100 ° C. to evaporate the alcohol and dry the gold nanoparticles as a residue. Next, a chemical solution is added to the residue, and the residue consisting of gold nanoparticles is dissolved in the chemical solution to obtain a measurement solution that is measured by ICP-MS26. And the obtained measurement solution is quantified by ICP-MS26. By providing the heating and drying step in this way, alcohol is removed and adverse effects on the analysis in the ICP-MS 26 are removed. Moreover, even if the density | concentration of a gold nanoparticle is low by this, when quantifying with ICP-MS26, it can raise concentration and can raise the precision of fixed_quantity | quantitative_assay.

  Here, the chemical solution added to the residue is for dissolving gold nanoparticles, and a mixed solution of nitric acid and hydrochloric acid (so-called aqua regia in which concentrated hydrochloric acid is mixed with concentrated nitric acid) is preferable. Alternatively, a mixed solution of nitric acid and chloride using chloride may be used.

That is, gold is dissolved by NOCl and Cl ₂ produced by the reaction of concentrated nitric acid (HNO ₃ ) and concentrated hydrochloric acid (HCl). Therefore, not only aqua regia but also a combination that generates NO ₃ and Cl is possible, and for example, concentrated HNO ₃ + NaCl / NH ₄ Cl, NaNO ₃ + concentrated HCl, or the like can be used.

  Thus, by adding a chemical | medical solution to a residue, the gold nanoparticle in a residue dissolves and it becomes a homogeneous liquid. Then, the measurement solution in which the gold nanoparticles are dissolved in this way is quantitatively analyzed by ICP-MS26. Thereby, the concentration of gold in the measurement solution can be detected, and the gold nanoparticle concentration in the solution can be quantified by conversion in consideration of the addition amount of the chemical solution.

  Here, in the treatment in the filter, the gold nanoparticles and the adsorption action of the filter affect the filtration performance. That is, if the gold nanoparticles mixed in the sample solution have an adsorption ability, the removal performance of the gold nanoparticles is enhanced. However, the gold nanoparticles in the sample liquid are standard particles and are not actually particles to be removed. Therefore, if the particle removal performance of the filter is evaluated, it is preferable to evaluate the filtration performance when there is no adsorption action.

  Therefore, in this embodiment, the surface state of the gold nanoparticle is adjusted with a protective ligand, and the filtration performance in a state where there is no adsorption action in the filter is evaluated.

  Note that a commercially available ICP-MS 26 can be used, and quantitative analysis can be performed without using a special technique. Using a standard sample having a plurality of concentrations, a calibration curve of the count value (CPS) and the gold nanoparticle concentration is prepared, and the count value obtained in the actual measurement is converted into the concentration.

  Here, as the ligand used when modifying the surface of gold, MEA (2-mercaptoethanoic acid), MPA (3-mercaptopropanoic acid), TA (thioctic acid), 11-MUDA (11-mercaptoundecanoic acid), Examples include Oleylamine (9-octadecenylamine) and 1-Dodecanethiol.

  When gold nanoparticles are subjected to surface modification using a protective ligand, the ease of dissolution of gold nanoparticle residues in a chemical solution such as a mixed solution of nitric acid and hydrochloric acid differs. For example, when hydrophobic surface modification is performed with a protective ligand in IPA, it is preferable to perform dissolution and recovery of gold nanoparticles with a mixed solution of high-concentration nitric acid and hydrochloric acid. Further, in order to promote dissolution, it is preferable to make the ultrasonic irradiation time relatively long.

For example, when the concentration of the mixed solution of nitric acid and hydrochloric acid is increased while keeping the ultrasonic irradiation time constant, this improves the recovery rate of gold nanoparticles in the residue. Further, when the concentration of the mixed solution of nitric acid and hydrochloric acid is kept constant and the ultrasonic irradiation time is changed, the recovery rate is improved. For example, when gold nanoparticles in IPA are surface-modified with thioctic acid or 10-carboxy-1-decanethiol, the nitric acid concentration (asHNO ₃ ) of the mixed solution of nitric acid and hydrochloric acid is 1. When 5 wt% and hydrochloric acid concentration (asHCl) are less than 2.3 wt%, the recovery rate is low, and even when the nitric acid concentration (asHNO ₃ ) is 7.5 wt% and the hydrochloric acid concentration (asHCl) is 11.3 wt% or more, recovery is possible. There is no change in rate. Therefore, it is preferable that the mixed solution of nitric acid and hydrochloric acid has a nitric acid concentration (asHNO ₃ ) of 1.5 to 7.5 wt% and a hydrochloric acid concentration (asHCl) of 2.3 to 11.3 wt%. In the case of gold nanoparticles in pure water, a sufficient recovery rate can be obtained even if the mixed solution of nitric acid and hydrochloric acid has a nitric acid concentration (asHNO ₃ ) of 0.75 wt% and a hydrochloric acid concentration (asHCl) of about 1.15 wt%. .

(1) Comparison of recovery rate according to surface state of gold nanoparticles Gold nanoparticles were quantified by the method shown in FIG.

  A gold nanoparticle stock solution (commercial product: manufactured by BBI, particle size: 30 nm) was once heated to dryness, and then the residue containing gold nanoparticles was dissolved in a mixed solution of nitric acid and hydrochloric acid. -Quantified by MS.

  Specifically, first, a gold nanoparticle solution in which various gold nanoparticles (30 nm) were added to ultrapure water so as to be 0.5 ng / L was prepared. At this time, the surface was modified with different protective ligands. Specifically, since the commercially available gold nanoparticle itself is already surface-modified with a hydrophilic protective ligand, it is surface-modified with two hydrophobic protective ligands, resulting in a total of three surfaces. Adjusted to the condition.

  In this example, as the protective ligand, (i) citric acid, (ii) thioctic acid, (iii) 10-carboxy-1-decanethiol (10-Carboxy-1- decanethiol or 11-Mercaptoundecanoic acid) was used.

  Here, as described above, the gold nanoparticle stock solution (commercial product: manufactured by BBI, particle size: 30 nm) has already been surface-modified with hydrophilic (i) citric acid. Therefore, as the gold nanoparticles surface-modified with the hydrophilic protective ligand in this example, the above-mentioned commercially available product was used as it was.

The surface modification of the gold nanoparticles with the hydrophobic protective ligands (ii) and (iii) was specifically performed by the following method.
(Ii) Surface modification method with thioctic acid [1] 5 ml of a gold colloid (30 nm, 0.1 wt%) manufactured by BBI is taken.
[2] 45 ml of thioctic acid adjusted so as to be 10 times the mole of gold is added.
[3] Adjust to pH 11 with 1N NaOH.
[4] Stir for 16 hours.
[5] The supernatant is removed by centrifugation (11800 rpm, 10 ° C., 10 minutes).
By the above method, about 1 wt% of a colloidal gold concentrate surface-modified with thioctic acid was obtained.
(Iii) Surface modification method using 10-Carboxy-1-decanethiol or 11-Mercaptoundecanoic acid [1] The gold colloid concentrate obtained by (ii) above is further subjected to the following operations: Implemented.
[2] 45 ml of 10-carboxy-1-decanethiol adjusted so as to be 25 moles per mole of gold is added.
[3] Adjust to pH 11 with 1N NaOH.
[4] Stir for 16 hours.
[5] The supernatant is removed by centrifugation (11800 rpm, 10 ° C., 10 minutes).
By the above method, about 1 wt% of a colloidal gold concentrate surface-modified with 10-carboxy-1-decanethiol was obtained.

  (I) is hydrophilic, and ultrapure water was used as a solution (liquid property). The ligands (ii) and (iii) are relatively hydrophobic, and IPA (isopropyl alcohol) was used as a solution.

  A sample solution containing gold nanoparticles whose surface was modified with a protective ligand was heated and dried to precipitate a residue containing gold nanoparticles. Then, a predetermined amount of a mixed solution of nitric acid and hydrochloric acid was added to the residue to dissolve it, and ultrapure water was added to the residue to dilute it, and a predetermined concentration was determined by ICP-MS.

As for the mixed solution of nitric acid and hydrochloric acid, nitric acid (commercial product: Ultrapur, 61 wt% (asHNO ₃ ) manufactured by Kanto Chemical Co., Ltd.) and hydrochloric acid (commercial product: Ultrapur, 31 wt% (asHCl) manufactured by Kanto Chemical Co., Ltd.) are volumetric. The mixture at a ratio of 1: 3 was used as the stock solution.

Here, the addition amount of the mixed solution of nitric acid and hydrochloric acid and the irradiation time of ultrasonic waves were changed, and the contribution to the recovery rate was evaluated. The result is shown in FIG. Here, the recovery condition 1 is that the concentration of the mixed solution of nitric acid and hydrochloric acid is as follows: nitric acid concentration (asHNO ₃ ) 1.5 wt%, hydrochloric acid concentration (asHCl) 2.3 wt%, ultrasonic irradiation time 5 minutes, recovery condition 2 The concentration of the mixed solution of nitric acid and hydrochloric acid is as follows: nitric acid concentration (asHNO ₃ ) 3.0 wt%, hydrochloric acid concentration (asHCl) 4.5 wt%, ultrasonic irradiation time 10 minutes, recovery condition 3 is a mixed solution of nitric acid and hydrochloric acid The concentration of nitric acid is 4.5 wt% nitric acid (asHNO ₃ ), 6.8 wt% hydrochloric acid (asHCl), and the ultrasonic irradiation time is 10 minutes. In addition, the density | concentration of the mixed solution of nitric acid and hydrochloric acid was performed by adding 2, 4, 6 mL of the above-mentioned mixed solution stock solution of nitric acid and hydrochloric acid to ultrapure water and adjusting the amount of water after the addition to 20 mL.

Thus, in the example of the above (i) in which citric acid (hydrophilic protective ligand) is used as the ligand and ultrapure water is used as the liquid, high recovery is achieved in any of the recovery conditions 1 to 3. It can be seen that there is almost no influence of the protective ligand on dissolution by addition of a mixed solution of nitric acid and hydrochloric acid after heating to dryness. On the other hand, in the above examples (ii) and (iii) using thioctic acid, 10-carboxy-1-decanethiol (protective ligand having a hydrophobic functional group) as a ligand and IPA as a liquid, There are significant changes in recovery conditions. That is, the concentration of the mixed solution of nitric acid and hydrochloric acid needs to be high to some extent. Also, it is better that the ultrasonic irradiation time is longer. Specifically, as in the recovery condition 3, the concentration of the mixed solution of nitric acid and hydrochloric acid is as follows: nitric acid concentration (asHNO ₃ ) 4.5 wt%, hydrochloric acid concentration (asHCl) 6.8 wt% or more, and ultrasonic irradiation time 10 It can be seen that the recovery rate is very high when it is more than a minute.

(2) Particle removal performance evaluation of filters (IPA)
Using a test apparatus corresponding to the system shown in FIG. 1, a sample solution (raw water) in which gold nanoparticles were dispersed in IPA was filtered, and the particle removal performance of the filter was evaluated. That is, a predetermined amount of raw water was stored in the storage tank 10, nitrogen gas was pumped therein, and the entire amount was supplied to the filter 18 for filtration. And while sampling raw | natural water (S1) previously, the filtrate was sampled.

  Obtained by diluting gold nanoparticles (BBI) having a particle size of 20 nm with IPA (manufactured by Tokuyama Co., Ltd., Toxo IPA SE (trade name)) and modifying the surface of the gold nanoparticles with a protective ligand The raw water was passed through the filter 18.

  As the protective ligand, (iii) 10-carboxy-1-decanethiol described above was used.

  As the filter 18, an Optimizer DLE disposable filter (trade name) manufactured by Nihon Integris Co., Ltd., having a membrane type: MF membrane, a material: UPE (ultra high molecular weight polyethylene), and a particle removal diameter: 5 nm was used.

At this time, the water flow conditions of the MF membrane were water flow method: total filtration, water flow pressure: 0.1 MPa, filtration flow rate: 67 mL / min. The raw water before and after the filter (S1) and the filtrate (S2) were sampled. The sampled raw water is heated to dryness to precipitate a residue containing gold nanoparticles, and then a predetermined amount of a mixed solution of nitric acid and hydrochloric acid is added to the residue to dissolve it, and ultrapure water is added to this. It diluted and quantified by ICP-MS as predetermined concentration. On the other hand, the sampled filtrate was once heated to dryness, dissolved in a mixed solution stock solution of nitric acid and hydrochloric acid, adjusted to a predetermined concentration with ultrapure water, and quantified by ICP-MS. Note that the above-mentioned recovery condition 3 was adopted as the recovery condition. The concentration of the mixed solution of nitric acid and hydrochloric acid was nitric acid concentration (asHNO ₃ ) 4.5 wt%, hydrochloric acid concentration (asHCl) 6.8 wt%, and the ultrasonic irradiation time was 10 minutes.

  The results are shown in Table 1.

このように、このフィルターの微粒子捕捉率は、９９．９８％であることがわかった。従って、本実施例により、ＩＴＲＳにおける２０ｎｍ粒子の管理指標（１．０Ｅ＋０４個／ｍＬ）を満たすレベルでのフィルターの評価が可能であることがわかった。

Thus, the fine particle capture rate of this filter was found to be 99.98%. Therefore, according to the present example, it was found that the filter can be evaluated at a level satisfying the management index (1.0E + 04 particles / mL) of 20 nm particles in ITRS.

  In this way, when a sample solution in which the surface of the gold nanoparticle is modified with a relatively hydrophobic protective ligand and dispersed in alcohol is used, a mixture of nitric acid and hydrochloric acid is mixed after heating to dryness. Although it is possible to dissolve the gold nanoparticles with a solution, it was necessary to use a mixed solution of high-concentration nitric acid and hydrochloric acid, and it was found preferable to perform ultrasonic irradiation.

  Furthermore, the filter can be evaluated by quantifying the gold nanoparticles in the sample before and after the filter using the gold nanoparticle quantification method of the present embodiment.

  10 storage tanks, 12 ultrasonic irradiation devices, 14 pumps, 16 valves, 18 filters, 20 pressure gauges, 22, 24 valves, 26 ICP-MS.

Claims (8)

A method for quantifying gold nanoparticles in a measurement liquid in which gold nanoparticles surface-modified with a protective ligand are dispersed in alcohol,
Heating the measurement liquid to form gold nanoparticles as a residue;
A step of adding a chemical solution prepared by mixing nitric acid and hydrochloric acid or chloride to the obtained residue to obtain a solution in which the residue is dissolved; and
Analyzing the obtained solution by ICP-MS and detecting the amount of gold nanoparticles in the measurement solution;
A method for quantifying gold nanoparticles, comprising: The method for quantifying gold nanoparticles according to claim 1,
In the step of obtaining the dissolution solution, the concentration of the chemical solution is changed depending on the type of the protective ligand. The method for quantifying gold nanoparticles according to claim 2,
In the step of obtaining the solution, a gold nanoparticle quantification method comprising irradiating an ultrasonic wave after adding the chemical solution to the residue. The method for quantifying gold nanoparticles according to claim 3,
The said chemical | medical solution is a mixture of nitric acid and hydrochloric acid, Comprising: Nitric acid 1.5-7.5 weight% and hydrochloric acid weight%, The determination method of the gold nanoparticle characterized by the above-mentioned. The method for quantifying gold nanoparticles according to claim 3,
The said chemical | medical solution is a mixture of nitric acid and hydrochloric acid, Comprising: Nitric acid 4.5-7.5 weight% and hydrochloric acid 6.8-11.3 weight%, The determination method of the gold nanoparticle characterized by the above-mentioned. The method for quantifying gold nanoparticles according to claim 4 or 5,
The method for quantifying gold nanoparticles, wherein the protective ligand is thioctic acid or 10-carboxy-1-decanethiol. In the determination method of the gold nanoparticle according to any one of claims 1 to 6,
The method for quantifying gold nanoparticles, wherein the alcohol is IPA. In the determination method of the gold nanoparticles according to any one of claims 1 to 7,
The method for quantifying gold nanoparticles, wherein the measurement liquid is a filtrate of a filter.

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