KR101762887B1 - Complex containing fluorescence nanoparticles and method for measuring dispersion state of suspension using the same - Google Patents

Abstract

The present invention relates to a composite comprising fluorescent nanoparticles and a method for measuring the dispersion state of a suspension using the fluorescent nanoparticle, and more particularly, to a method for preparing a composite comprising fluorescent nanoparticles such as quantum dots, And measuring the quantum efficiency value of the suspension to confirm the dispersion state of the suspension, and a method for measuring the dispersion state of the suspension using the fluorescent nanoparticle.
According to various embodiments of the present invention, the dispersion state of the suspension can be measured by introducing a composite containing fluorescent nanoparticles such as quantum dots into a suspension and measuring a quantum efficiency value that changes through the aggregation reaction.
In addition, the size of the composite can be adjusted according to the kind of the suspension to be measured, and the present invention is not limited to a specific type of suspension, and can be widely applied to various fields.

Description

The present invention relates to a complex containing fluorescent nanoparticles and a method for measuring the dispersion state of a suspension using the fluorescent nanoparticles.

The present invention relates to a composite comprising fluorescent nanoparticles and a method for measuring the dispersion state of a suspension using the fluorescent nanoparticle, and more particularly, to a method for preparing a composite comprising fluorescent nanoparticles such as quantum dots, And measuring the quantum efficiency value of the suspension to confirm the dispersion state of the suspension, and a method for measuring the dispersion state of the suspension using the fluorescent nanoparticle.

Quantum dots can be used in a variety of fields due to their unique optical properties. In particular, the quantum dot has characteristics that it is easy to control the emitted wavelength by controlling its size due to the quantum confinement effect. On the basis of these properties, the quantum dots are widely used in sensors, light emitting diodes, laser memory devices, photodetectors and solar cells, but they have a problem that their optical properties are significantly lowered when they are applied to suspensions and films due to their nano-sized nature.

Suspension or liquid phase particle dispersions in which fine particles are dispersed in a continuous phase solvent are classified into Newtonian fluids having a constant viscosity regardless of the change in shear rate and non-Newtonian fluids having a viscosity varying when the shear rate is changed .

In a non-Newtonian fluid, a suspension in which solid particles are dispersed in a liquid dispersion medium has a shear stress or a shear rate that increases due to the rheological properties of the fluid, which causes a reversible state change from a liquid phase to a solid phase, Fluid. Various inorganic oxides and polymeric colloid particles are used as the dispersion showing the shear thickening phenomenon, and studies of shear thickening fluid mainly using silica particles are being studied.

In order to confirm the dispersion state of the suspension having such characteristics, the viscosity of the suspension was measured and based on the measured viscosity, the characteristics of the suspension or the dispersion of the suspension were analyzed. Such a conventional analysis method has a problem that the calculation method is complicated and it is difficult to accurately analyze it.

Therefore, in the present invention, the dispersion state of the suspension can be measured by a simple method of measuring the quantum efficiency value of the suspension using fluorescent nanoparticles such as quantum dots.

Shear Thickening Behavior of Fumed Silica Suspension in Polyethylene Glycol - Department of Chemical Engineering, Hanyang University, Gyeonggi 426-791, Korea * KITECH Textile Ecology Laboratory, Gyeonggi 426-171, Korea

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the conventional problems, and it is an object of the present invention to provide a fluorescent nanoparticle composite comprising fluorescent nanoparticles such as quantum dots, a method of adding the complex to a suspension, And a method for measuring the dispersion state of a suspension using the fluorescent nanoparticle.

According to one representative aspect of the present invention, there is provided a composite comprising fluorescent nanoparticles for measuring a dispersion state of a suspension,

And the fluorescent nanoparticles are quantum dots. The present invention also relates to a composite for measuring the dispersion state of a suspension.

According to another exemplary aspect of the present invention, there is provided a method of preparing a composite comprising fluorescent nanoparticles for measuring a dispersion state of a suspension, the method comprising:

(A) fabricating a quantum dot,

(B) coating the core particles with the quantum dots, and

(C) coating the core particle coated with the quantum dots with the second shell particle. The present invention also relates to a method for producing a composite for dispersion state measurement of a suspension.

According to another exemplary aspect of the present invention, there is provided a method of measuring a dispersion state of a suspension using a composite for measuring the dispersion state of the suspension, the method comprising:

(I) an aggregation reaction of a mixture of a suspension and a complex takes place, and

(Ii) measuring and analyzing the quantum efficiency of the aggregated mixture through step (i).

According to various embodiments of the present invention, the dispersion state of the suspension can be measured by introducing a composite containing fluorescent nanoparticles such as quantum dots into a suspension and measuring a quantum efficiency value that changes through the aggregation reaction.

In addition, the size of the composite can be adjusted according to the kind of the suspension to be measured, and the present invention is not limited to a specific type of suspension, and can be widely applied to various fields.

FIG. 1 is a schematic diagram showing a reaction occurring when nanoparticles of a core-shell structure, which is a complex according to an embodiment of the present invention, are introduced into a suspension and a light source is irradiated.
FIG. 2 is an image showing the result of SQS (silica @ quantum dot @ silica) nanoparticles analyzed by transmission electron microscopy (TEM).
FIG. 3A is a graph showing the results of measurement of the absorption and emission spectra of quantum dots, and FIG. 3B is a graph showing the results of measurement of absorption spectra of silica particles present in a solvent having a controlled refractive index. FIG.
FIG. 4 is a graph showing a quantum efficiency change according to the concentration of SQS nanoparticles and silica particles in the examples, wherein (a) shows the results according to the concentration of SQS nanoparticles, and (b) shows the results according to the silica particle concentration.
5 is a graph showing the results of measurement of PL (Photoluminescence) decay according to the concentration of SQS nanoparticles in the examples.
6 is a graph showing the results of measurement of? Max of emission spectrum according to the concentration of SQS nanoparticles in the examples.
FIG. 7 is a graph showing the results of measurement of the change in quantum efficiency according to the concentration of SQS nanoparticles in the examples.
8 is a graph showing the results of measurement of the change in quantum efficiency with respect to the SQS nanoparticles in the examples according to the degree of aggregation.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

According to one aspect of the present invention, there is provided a composite comprising fluorescent nanoparticles for measuring a dispersion state of a suspension, wherein the fluorescent nanoparticles are quantum dots.

According to one embodiment, the composite is preferably a core-shell structure comprising a core, a first shell surrounding the core and consisting of quantum dots, and a second shell surrounding the first shell.

The core can be used without restriction as long as it is the same size as the material dispersed in the suspension. Preferably, it is the same as the material dispersed in the suspension, more preferably silica.

The first shell is formed of quantum dots and is formed to surround the core. When the quantum dots are exposed to a light source, the quantum dots emit light. At this time, quantum dots aggregate due to a quantum confinement phenomenon. The agglomerated quantum dot scatters light again, which promotes absorption and reabsorption of the particles constituting the core and the second shell, thereby reducing the quantum efficiency.

Therefore, the present invention utilizes the property that the quantum efficiency is recovered, and it is confirmed that the dispersion state of the suspension can be measured according to the degree of recovery of the quantum efficiency.

Specifically, the quantum dot is preferably at least one selected from the group consisting of Cds, CdSe, CdTe, ZnS, and PbS, but is not limited thereto.

The second shell serves to facilitate water dispersion in the suspension, and also protects the quantum dots so that the quantum dots of the first shell and the external materials are not in contact with each other, thereby improving light stability.

It is preferable that the second shell uses the same material as the solid particles dispersed in the suspension, in order to facilitate water dispersion in the suspension. More preferably the same as the material used in the core, and silica.

If the diameter is less than 50 nm, it is difficult to apply fluorescent nanoparticles such as a quantum dot. When the diameter is more than 150 nm, the complex may have a diameter of 50 to 150 nm. It is undesirable because it may sink under the influence of gravity in the suspension.

The type of suspension to be applied in the present invention is not particularly limited, and can be applied to various fields.

However, it has been confirmed that the core-shell nanoparticles, which are the complexes, are most effective when applied to a silica suspension in which silica particles are dispersed, unlike other types of suspensions, wherein the core- 2 shell was silica, and the first shell was remarkably effective in measuring the dispersion degree of the suspension, unlike the other combinations, when CdSe / ZnS quantum dots were used.

According to another aspect of the present invention, there is provided a method of producing a composite comprising fluorescent nanoparticles for measuring a dispersion state of a suspension, the method comprising: (A) preparing a quantum dot; (B) And (C) coating the core particles coated with the quantum dots with the second shell particles. The core-shell nanoparticles for measuring the dispersion state of the suspension are provided.

The step (A) may be a step of producing a quantum dot, which is a first shell, and the quantum dot is preferably at least one selected from Cds, CdSe, CdTe, ZnS and PbS. In the present invention, Bae, W. K .; Kwak, J .; Lim, J .; Lee, D .; Nam, M. K .; Char, K .; Lee, C .; Lee, S., Multicolored Light-Emitting Diodes Based on All-Quantum-Dot Multilayer Films Using Layer-by-Layer Assembly Method. Nano Lett. 2010, 10, 2368-2373, but the present invention is not limited thereto.

In the present invention, quantum dots are used as the fluorescent nanoparticles, but any material that exhibits fluorescence characteristics when a light source is irradiated can be used.

ber 방법으로 합성하였으며, 상기 코어 입자가 용해된 용액을 양자점과 혼합하는 공정을 통해 양자점을 코팅시킬 수 있다.The step (B) is a step of coating a core particle with a quantum dot, for example,

ber method, and the quantum dots can be coated through a process of mixing the solution in which the core particles are dissolved with the quantum dots.

It is more preferable that the surface of the core particle is replaced with a hydrophobic hydrophilic functional group such as a hydroxyl group, a carboxyl group, or an amine group by using a capping agent in order to exclude the possibility of adsorption of unnecessary substances in addition to the quantum dots. As the surface stabilizer, it is preferable to use at least one selected from mercaptopropionic acid, mercaptoacetic acid, mercaptosuccinic acid, dithiotriethol, glutathione, histidine and thiol-containing silane.

In the step (C), the core particles coated with the quantum dots are coated with the second shell particles through the step (B), and the core particles coated with the quantum dots are charged into a solution containing the second shell particles For 1 to 20 hours.

According to still another aspect of the present invention, there is provided a method of measuring a dispersion state of a suspension using the composite for measuring the dispersion state of the suspension, comprising the steps of: (i) causing an aggregation reaction of a mixture of a suspension and a complex, And (ii) measuring and analyzing a quantum efficiency value of the mixture in which the coagulation reaction has been completed through the step (i). The present invention also provides a method for measuring the dispersion state of a suspension.

In the step (i), the complex is introduced into the suspension and an aggregation reaction occurs. In order to induce the aggregation reaction, a light source may be irradiated or an aggregation inducing substance may be added. Examples of the coagulation reaction inducing material include, but not limited to, NaCl.

Structural description of the complex is the same as the above-mentioned description, so it will be omitted.

The complex may be dispersed in a solvent if necessary. The solvent is preferably, but not limited to, distilled water.

At this time, it was confirmed that the dispersion state of the suspension can be measured with only a very small amount of the core-shell nanoparticles of about 0.1 wt%, within 10 wt% of the concentration of the complex solution.

The flocculation reaction time is preferably from 10 to 180 minutes, more preferably from 30 to 100 minutes, even more preferably from 50 to 70 minutes. If the reaction time is less than 10 minutes, the recovery time of the quantum efficiency is insufficient. If the reaction time is more than 180 minutes, the quantum efficiency is not recovered and is not necessary.

In this regard, FIG. 1 is a schematic diagram showing a reaction occurring in step (A) according to an embodiment of the present invention, and the following three-step reaction occurs rapidly.

ster Resonance Energy Transfer) 현상이 일어나게 된다.First, when light is irradiated at (450 nm), light is absorbed by the quantum dots, resulting in reabsorption due to the emission of quantum dots. (2) Light scattering between the complexes due to the refractive index difference between the surface of the composite and the solvent (3) FRET between the quantum dots inside the composite, or each complex, (F

ster Resonance Energy Transfer) phenomenon.

The FRET phenomenon can be represented by the following equation (1): electron acceptance divided by the distance R and electron acceptance.

………… (1)

... ... ... ... (One)

rster 반지름(Å)이다. FRET 효율은 50 %이고 하기 식 (2)에 의해 나타낼 수 있다.In the above formula (1), R ₀ is F

rster radius (Å). The FRET efficiency is 50% and can be expressed by the following equation (2).

………… (2)

... ... ... ... (2)

In the formula (2), K ² is a dipole direction factor, n is a middle refractive index, and Φ _D is a quantum yield of the donor depending on the absence of an acceptor. J (λ) is the interval between the donor emission spectrum and the acceptor absorption spectrum, which can be expressed by the following equation (3).

………… (3)

... ... ... ... (3)

In the above equation (3), FD (?) Is the fluorescence emission intensity of the donor and? A is the extinction coefficient of the acceptor. That is, the FRET effect is greatly affected by the overlap between donor release and acceptor absorption.

This FRET phenomenon can reduce the fluorescence intensity of the fluorescent nanoparticle-containing complex, but it has been confirmed that the FRET phenomenon has a greater effect on restoring the quantum efficiency due to scattering of light between the quantum dots inside the complex and each complex.

Therefore, the dispersion state of the suspension can be measured by measuring the value of the quantum efficiency recovered as described above using the composite comprising the fluorescent nanoparticles according to the present invention.

The step (ii) is a step of measuring and analyzing the quantum efficiency value of the mixture in which the aggregation reaction has been completed through the step (i).

The analysis is performed by comparing the measured value of the quantum efficiency with the reference value. As shown in FIG. 8, the reference value used for the analysis is a value formed by performing the degree of coagulation differently under the same experimental conditions. For example, as shown in FIG. 8, And quantum efficiency values are measured and measured. At this time, the measured sample value is preferably at least two.

That is, in the step (ii), the quantum efficiency value of the suspension subjected to the aggregation reaction is measured through the step (i), and the dispersion state of the suspension can be confirmed by comparing the quantum efficiency value with the reference value.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the present invention as set forth in the following claims. It is natural that it belongs to the claims.

In addition, the experimental results presented below only show representative experimental results of the embodiments and the comparative examples, and the respective effects of various embodiments of the present invention which are not explicitly described below will be specifically described in the corresponding part.

(Materials and apparatus)

1. Materials

Oxidation cadmium (CdO, 99.99%), zinc acetate _{(Zn (OAc) 2, 99.9} %, powder), sulfur (S, 99.9%, powder), selenium (Se, 99.99%, powder), trioctyl phosphine (triocrylphosphine , TOP, 90%), oleic acid (oleic acid, OA, 90% ), 1- octadecene (1-octadecene, ODE, 90 %), tetraethyl ortho silicate (tetraethyl orthosilicate, TEOS), ammonium hydroxide (NH ₄ OH , 5M), 3-mercaptopropyltrimethoxysilane (MPTMS, 95%), dimethyl sulfoxide (DMSO, 99.5%), chloroform and ethanol were all purchased from Sigma-Aldrich , And the purchased reagent was used without further purification. DI water was prepared using Millipore water purification (18 MΩ · cm) system.

2. Organization

The size and morphology of the synthesized quantum dot, silica and silica @ quantum dot @ silica nanoparticles were measured by Quasi-Elastic Light Scattering (Malvern Nano-ZS) and Transmission Electron Microscopy (JEOL JEM-2100 and JEM-2010).

The UV absorption spectra of the quantum dots and silica particles were measured using a spectrophotometer (Shimadzu 1650 PC) and the emission spectra were measured using a photoluminescence (PL) spectrometer (Perkin-Elmer LS 55).

The quantum efficiency was measured using Otsuka Electronics, QE-1000, and an integrating sphere was used together with a 450 nm Xenon laser as excitation energy source.

(Preparation Example 1: synthesis of quantum dot)

Add 0.2 mmol of CdO, 4 mmol of Zn (OAc) ₂ , and 5 mL of OA to a 100 mL flask, mix, and heat at 150 ° C for 30 minutes. 15 mL of ODE was added thereto under a nitrogen atmosphere, and the mixture was stirred and heated at a temperature of 300 ° C. to prepare a transparent solution of Cd (OA) ₂ and Zn (OA) ₂ .

Then, 0.4 mmol of Se and 3 mmol of S were dissolved in TOP 2 mL, and the prepared solution was injected into the vessel of the flask containing the Cd (OA) ₂ and Zn (OA) ₂ solution for 10 minutes at 300 ° C To give CdSe / ZnS quantum dots. The step of redispersing the obtained CdSe / ZnS quantum dots in acetone and chloroform in excess was carried out three times and finally dispersed in chloroform to complete the synthesis.

(Preparation Example 2: Preparation of silica particles having a thiol group on its surface)

ber method 방법으로 실리카 입자를 제조하였으며, 구체적으로 다음의 조건으로 합성하였다.St

The silica particles were prepared by the ber method and were synthesized specifically under the following conditions.

2.68 mL of TEOS, 8.4 mL of distilled water and 1.44 mL of NH ₄ OH were dissolved in 47.78 mL of ethanol and stirred at room temperature for 6 hours to prepare silica particles. 15 μL of MPTMS was added to the silica particles, and the mixture was stirred at room temperature for 18 hours to obtain silica particles having thiol groups on their surfaces. The silica particles having the thiol groups thus obtained were redispersed in ethanol several times and prepared by centrifugation.

(Example: Preparation of silica @ quantum dot @ silica nanoparticles (SQS)

To a 70 mL vial was added 3 mL of the CdSe / ZnS quantum dot suspension of Preparation Example 1, and most of the chloroform was evaporated in a vacuum oven. Then, 2 mL of the silica particles of Production Example 2 dissolved in ethanol (50 mg / mL) was added, and the mixture was sonicated for 1 minute and then mixed with 20 mL of chloroform for 5 minutes. To this, 20 mL of chloroform, 1 mL of MPTMS, and 1 mL of NH ₄ OH were added and reacted for 1 hour to prepare quantum dot-coated silica (silica @ quantum dot).

The silica @ quantum dots were added to a mixed solution of 40 mL of ethanol, 1 mL of TEOS and 1 mL of NH ₄ OH, reacted for 12 hours, redispersed several times in ethanol and centrifuged to obtain silica @ quantum dot @ silica nano Particles were prepared.

(Test Example 1: TEM analysis of SQS nanoparticles)

SQS nanoparticles of the examples were analyzed by transmission electron microscopy (TEM) and the results are shown in FIG.

FIG. 2 (b) is an enlarged photograph of the surface of the SQS nanoparticles. Referring to FIG. 2, the average diameter according to each structure of the SQS nanoparticles can be observed. That is, the silica core is 110 ± 10 nm, the quantum dot shell is 5 ± 1 nm, and the silica @ quantum dot @ silica nanoparticle is 115 ± 10 nm.

The surface of the silica core is surrounded by approximately 250 quantum dots, and the quantum dot shell is surrounded by a thin silica layer.

(Test Example 2: Absorption and emission spectrum analysis of QD and Silica particles)

In order to separate the absorption spectrum from the light scattering in the UV-vis spectrum obtained from the silica suspension, a refractive index controlled solvent was prepared and the absorption spectrum was measured by adding 10 wt% silica particles to the solvent. 3.

Fig. 3 (a) shows the results of measurement of the absorption and emission spectra of the quantum dots, and (b) shows the results of measurement of the absorption spectrum of the silica particles present in the solvent with controlled refractive index.

Referring to FIG. 3 (a), a broad absorption spectrum band appears at 500 nm, a narrow emission peak at 495 nm, and a full-width-at-half-maximum (FWHM) of about 37.5 nm have.

In other words, the overlap between the absorption and emission spectra of the quantum dots shows that the quantum dots can absorb the emitted light.

On the other hand, referring to FIG. 3 (b), the refractive index of the silica particles varies depending on the wavelength, and the UV peak intensity is not high even at a high concentration of 10 wt% Able to know.

(The refractive index-matched solvent (RIM-S) was prepared by mixing distilled water and DMSO in a volume ratio of 12:88.)

(Test Example 3: Change in quantum efficiency depending on the concentration of SQS nanoparticles and silica suspension)

SQS nanoparticles of the examples were added to distilled water (DI water) and RI-matched solvent, respectively, and prepared at concentrations of 0.1, 0.5, 1, 3.0, 6.0 and 12.0 wt% After injecting into a silica suspension, 0.1 M NaCl was added thereto to induce an aggregation reaction, and the change in measured quantum efficiency is shown in FIG.

Referring to FIG. 4 (a), the quantum efficiency decreases as the concentration of SQS particles increases under all conditions using distilled and refined solvents.

This phenomenon occurs because the scattering of light occurs at the surface of the SQS nanoparticles while the emission and reabsorption by the quantum dots increase as the concentration of the SQS nanoparticles increases.

However, the FRET phenomenon occurring between the quantum dots in the SQS nanoparticles does not have a significant effect at this time. This is because the average distance between SQS nanoparticles in the SQS suspension is longer than that of the CdSe / ZnS quantum dots, so that the FRET phenomenon occurring between the SQS nanoparticles is very small .

Thus, the quantum efficiency of the SQS suspension can be reduced due to the release and reabsorption by the quantum dots, as increased scattering of light from the surface of the SQS nanoparticles present in the SQS suspension increases the number of times the SQS nanoparticles are struck to be.

That is, it increases the reabsorption by the quantum dots and eventually reduces the quantum efficiency of the SQS suspension. Therefore, as the concentration of the SQS nanoparticles present in the suspension increases, the quantum efficiency decreases.

On the other hand, when the SQS nanoparticles are applied to a solvent whose refractive index is controlled, scattering of light generated from the surface of the SQS nanoparticles is substantially eliminated. That is, as shown in FIG. 4 (a), the quantum efficiency of the SQS nanoparticles dispersed in the solvent having a controlled refractive index is higher than that of distilled water.

FIG. 4 (b) is a graph showing a change in quantum efficiency in each solvent as the concentration of silica particles increases. It can be seen that as the concentration of silica particles increases, the quantum efficiency decreases.

(Test Example 4: PL decay analysis according to SQS nanoparticle concentration)

The SQS nanoparticles of the Examples were put into a solvent whose refractive index was controlled and were prepared for each concentration of 0.1, 0.5, 1, 3.0, 6.0 and 12.0 wt%, and PL (Photoluminescence) decay was measured under a light source of 500 nm. The results are shown in Fig. 5 and Table 1 below.

Particle concentration (%) τ (ns) ^a QY (%) Rate (ns ^-1 ) Lifetime (ns) K _radiative K _nonradiative τ _radiative τ _nonradiative 0.1 14.04 48 0.034 0.037 29.25 27.00 0.5 14.49 41 0.028 0.041 35.34 24.56 1.0 14.49 36 0.025 0.044 40.25 22.64 3.0 16.29 27 0.017 0.045 60.33 22.32 6.0 21.29 20 0.009 0.038 106.45 26.61 12.0 26.08 14 0.005 0.033 186.29 30.33

Referring to FIG. 5, photoluminescence represents a single-exponential decay regardless of the concentration of the particles. As the concentration of SQS nanoparticles increases, the curve slope of decay changes by a few nanoseconds. Since the PL decay time increases with increasing SQS particle concentration, FRET does not occur between each SQS nanoparticle. This suggests that the reabsorption of the photons emitted from the sample is a factor reducing the quantum efficiency at higher particle concentrations.

6 is a graph showing the SQS nanoparticles of the Example in a DI water and an RI-matched solvent, respectively. The SQS nanoparticles were prepared at concentrations of 0.1, 0.5, 1, 3.0, 6.0 and 12.0 wt% And then measuring the? Max of the emission spectrum according to the concentration of the SQS nanoparticles.

Referring to FIG. 6, the SQS nanoparticles are shifted to a longer wavelength as the SQS nanoparticles increase. Long wavelength shifts in the high emission spectra of QDs are generally caused by FRET and reabsorption from large quantum dots at small QDs. This is because the FRET is not greatly affected by the SQS concentration under the experimental conditions and this migration is due to the release and reabsorption by the QDs. This is because the quantum dots preferentially absorb the emission at a wavelength lower than the high wavelength, as shown in Fig. 2 described above.

(Test Example 5: Analysis of change in quantum efficiency with agglomeration reaction time)

The SQS nanoparticles of the example were added to DI water and RI-matched solvent, respectively, and added to a 12 wt% silica suspension at a concentration of 0.1 wt%. 0.1 wt% of 0.1 wt% M NaCl was added to induce flocculation reaction. Then, the change in quantum efficiency over time was measured starting from the point of time when the NaCl was added (0 hr), and the result is shown in FIG.

Referring to FIG. 7, SQS nanoparticles in the distilled water increase scattering of light due to agglutination reaction and increase the free path of light because of decreasing the cross-sectional area and the diffusion coefficient of aggregate. As a result, aggregation reduces reabsorption, thereby increasing quantum efficiency.

On the other hand, SQS nanoparticles in a controlled refractive index solvent exhibit less scattering of light due to agglutination reaction, resulting in less change in quantum efficiency.

(Test Example 6: Analysis of change in quantum efficiency according to degree of aggregation)

0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.35, respectively, for each concentration. The SQS nanoparticles of the Examples were added to distilled water to a concentration of 0.1 wt% , 0.4, 0.45, 0.5, and 0.6 M of NaCl were added to induce flocculation reaction, and the change in quantum efficiency was measured. The results are shown in FIG.

Referring to FIG. 8, it can be seen that the quantum efficiency increases as the molar (M) concentration of NaCl increases. This is because as the degree of cohesion increases, the absorption and reabsorption of light are reduced, which leads to a rapid recovery of quantum efficiency.

(Test Example 7: Measurement of dispersion state of suspension through analysis of quantum efficiency)

SQS nanoparticles of the Examples were added to distilled water to prepare 0.1 wt% of the solution, mixed with 12 wt% of silica suspension, and then added with NaCl according to the concentrations shown in Table 2 below to induce aggregation reaction. The results are shown in Table 2 below.

The concentration of NaCl (M) Measured quantum efficiency value 0.15 4.81 0.4 6.23 0.6 6.82 0.25 5.47

Referring to Table 2, it can be seen that the measured quantum efficiency is 4.81 in the case of 0.15 M NaCl, which is consistent with the results of FIG. 8 measured in Test Example 6, It can be confirmed that the values are all the same.

That is, these results show that the dispersed state of the suspension can be confirmed by injecting the SQS nanoparticles according to the present invention into the suspension and changing the measured quantum efficiency value when the aggregation reaction is induced.

Accordingly, according to various embodiments of the present invention, the dispersion state of the suspension can be measured by introducing a composite containing fluorescent nanoparticles such as quantum dots into a suspension and measuring the quantum efficiency value that changes through the coagulation reaction.

In addition, the size of the composite can be adjusted according to the kind of the suspension to be measured, and the present invention is not limited to a specific type of suspension, and can be widely applied to various fields.

Claims (20)

delete delete delete delete delete delete delete delete delete delete delete delete (I) an aggregation reaction of a mixture of a suspension and a complex takes place, and
(Ii) measuring and analyzing the quantum efficiency value of the mixture in which the aggregation reaction has been completed through the step (i)
Wherein said complex comprises fluorescent nanoparticles,
Wherein the fluorescent nanoparticle is a quantum dot.
14. The method of claim 13,
Wherein the aggregation reaction time in the step (i) is performed for 10 to 180 minutes. 14. The method of claim 13,
The composite may comprise:
core,
A first shell surrounding the core and formed of quantum dots, and
And a second shell surrounding the first shell. ≪ Desc / Clms Page number 20 >
14. The method of claim 13,
Wherein the quantum dot is at least one selected from Cds, CdSe, CdTe and PbS.
16. The method of claim 15,
Wherein the core and the second shell are identical to each other,
Wherein the core and the second shell are silica. ≪ RTI ID = 0.0 > 11. < / RTI >
16. The method of claim 15,
Wherein the core is silica,
The first shell is a CdSe / ZnS quantum dot,
Lt; RTI ID = 0.0 > 1, < / RTI > wherein said second shell is silica.
14. The method of claim 13,
Wherein said complex has a size of 50 to 150 nm in diameter.
14. The method of claim 13,
Wherein the suspension is a silica suspension.

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