KR101400006B1 - Highly Emissive Stable Noble Metal Nanocluster-Doped Double-Layered Silica Nanoparticles and Synthetic Methods Thereof - Google Patents

Abstract

Stable high - luminous noble metal nanoclusters were successfully synthesized by stabilization with a biocompatible buffer using thermal synthesis method. Two noble metal nanoclusters with different maximum emission wavelengths were prepared by controlling the amount of buffer solution. The synthesized noble metal nanoclusters were successfully introduced into the porous silica matrix and silica nanoparticles doped with fluorescent noble metal nanoclusters were prepared.
Sequential doping of fluorescent noble metal nanoclusters with TEOS and APTS results in a large matrix of fluorescent noble metal nanoclusters that emit high light and produce a silica matrix in which fluorescent noble metal nanoclusters are effectively protected even after repeated washing with polar solvents.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to stabilized high-luminous noble metal nanoclusters doped with double-layered silica nanoparticles,

The present invention relates to silica nanoparticles doped with high-luminous noble metal nanoclusters prepared by preparing stabilized high-luminous noble metal nanoclusters by stabilizing them with PIPES using a thermal synthesis method and doping them with a porous silica matrix.

Nanoporous materials (K. Ariga et al., Bull. Chem. Soc. Jpn. 85, 132 (2012), S. Cherevko et al., Nanoscale. 4, 568 (2012), Y. Turker et al., Chem . Eur. J. 18, 3695 ( 2012)) and the nanoparticles (D. Xu et al., J. Nanosci. Nanotechnol. 12, 3006 (2012),. MA Khaleque et al., J. Nanosci. Nanotechnol 12, Metals often increase their potential function in nanostructures as defined by, for example, 4384 (2012), EC Dreaden et al., Chem. Soc. Rev. 41, 2740 (2012) For example, gold and silver nanoclusters of tens of atoms exhibit significantly strong luminescence, mainly due to the molecular type transfer characteristics (J. Zheng et al., Annu. Rev. Phys. Chem. 58, 409 2007) and references therein, JP Wilcoxon et al., J. Chem. Phys., 108, 9137 (1998)). Fluorescent nanoclusters can be detected by sensing (C.-C. Huang et al., Chem. Int. Ed. 46, 6824 (2007), J. Sharma et al., Chem. Commun. 47, 2294 (See, for example, C.-J. Lin et al., J. Med. Biol. Eng. 29, 276 (2009), J. Yu et al., Chem. Int. Various synthetic methods for the production of fluorescent nanoclusters have been reported, and many of them have used specific templates, such as polymers (J. Zheng et al., J. Phys . Chem. Soc. 125 , 7780 (2003), Y. Bao et al., J. Phys. Chem. C 111, 12194 (2007), ST Selvan et al., J. Phys. Chem. B 103, 7441 (1999 )) and dendrimers (J. Zheng RM and Dickson, J. Am. Chem. Soc. 124, 13982 (2002), synthesized the mold, such as a) it is to control the growth of fluorescent noble metal nanoclusters Structure and chemical function of fluorescent noble metal nanoclusters Of biological template to precisely control purposes {e.g., DNA (S. Choi et al., Chem. Soc. Rev. 41, 1867 (2012) and references therein, G. Liu et al., Gold. Bull. 45, 69 (2012 J. Xu et al., Nano Rev. 3, 14767 (2012), J. Yu et al., Angew. Chem. Int. Ed. 46, 2028 (2007), J. Xie et al., J. Am . Efforts to improve the emission intensity, quantum yield and tunability of noble metal nanoclusters have been widespread over the years to facilitate application of this superior material in a variety of applications.

Recently, Martinez et al. Reported the synthesis and photophysical properties of gold nanoclusters using small organic molecules (Y. Bao et al., J. Phys. Chem., C 114, 15879 (2010)). In this study, biocompatible buffers such as HEPES, MES and PIPES, which also act as reducing agents for gold ions and are complexed with gold atoms, were used in the production of fluorescent gold nanoclusters. The synthesized nanoclusters are similar in size to most biomolecules, and the direct conjugation of nanoclusters of interest, including small, biocompatible synthetic compounds, is crucial to the use of fluorescent nanoclusters in imaging and sensing applications, have.

It is an object of the present invention to provide stable silica nanoparticles doped with solid-state light precious metal nanoclusters.

In an effort to develop a more effective synthesis strategy for producing useful gold nanoclusters of solid-state light using small molecules, the present inventors produced various fluorescent gold nanoclusters stabilized by small organic molecules. In particular, the present inventors conducted experiments using various buffer solutions under various reaction conditions and stabilized them using PIPES in a thermal synthesis strategy, thereby obtaining gold nanocrystals which are very stable and highly luminescent.

In particular, two gold nanoclusters with different maximum emission wavelengths were successfully synthesized by varying the amount of PIPES. The synthesized gold nanoclusters were also introduced into the porous silica matrix to produce silica nanoparticles doped with fluorescent gold nanoclusters.

The present invention

a) preparing a stable noble metal nanocluster by adding a biocompatible buffer solution to an aqueous solution containing a noble metal salt and stirring while heating;

b) mixing the nonionic surfactant, the nonpolar organic solvent, the polar solvent and the excess noble metal nanocluster solution prepared in step a) to prepare a microemulsion;

c) hydrolyzing and condensing the silica precursor by adding a silica precursor and an alkali catalyst in the prepared microemulsion to prepare silica nanoparticles doped with noble metal nanoclusters; And

d) adding to the silica nanoparticles doped with the noble metal nanoclusters an excessive amount of the noble metal nanocluster solution prepared in a) and an alkali catalyst, adding APTS (3-Aminopropyltrienthoxysilane) and stirring to obtain double-layer silica nanoparticles containing noble metal nanoclusters Emitting noble metal nanocrystal-doped double-layered silica nanoparticles.

Biocompatibility buffers are also referred to as "Good's buffers", which are pKa values of pH 6-8, are water-soluble, chemically stable and used in biochemical and biological research.

The present invention also relates to a method for preparing a biocompatible buffer solution, wherein the biocompatible buffer is selected from the group consisting of HEPES (4- (2-hydroxyethyl) -piperazine-1-ethanesulfonic acid, MES (2- piperazine-1-propane sulfonic acid), MOPS (3- (N-Morpholino) propanesulfonic acid), PIPES (1,5-piperazinediethanesulfonic acid), CHES (2- (Cyclohexylamino) (N-morpholino) butanesulfonic acid), MOPSO (3-hydroxyethyl) -2-aminoethanesulfonic acid), BES (2-hydroxypropanesulfonic acid) dihydrate), TAPS (N-Tris [hydroxymethyl] methyl-3-aminopropanesulfonic acid), HP (1- (2- Hydroxyethyl) piperidine and TAPSO (3 - [[1,3-dihydroxy-2- (hydroxymethyl) propan-2-yl] amino] -2-hydroxypropane-1-sulfonic acid. A method for preparing double-layer silica nanoparticles doped with luminescent noble metal nanoclusters to provide.

Also, the present invention provides a method for producing double-layer silica nanoparticles doped with a high luminous noble metal nanocluster, wherein the alkali catalyst is an ammonia aqueous solution.

The present invention also relates to a method for producing a high-luminous noble metal nanocluster, wherein the nonionic surfactant is polyoxyethylene glycol dodecyl ether, glycerin fatty acid ester, sucrose fatty acid ester or sorbitan fatty acid ester. To provide a method for producing double-layer silica nanoparticles.

Also, the present invention provides a method for producing double-layer silica nanoparticles doped with a high luminous noble metal nanocluster, wherein the polar solvent is water or an aqueous acid solution.

The present invention also provides a method for producing double-layer silica nanoparticles doped with a high luminous noble metal nanocluster, wherein the silica precursor is tetraethyl orthosilicate, tetramethyl orthosilicate or tetrapropyl orthosilicate.

The present invention also provides a method for producing double-layer silica nanoparticles doped with a high-luminous noble metal nanocluster, wherein the noble metal is gold, silver or platinum.

In addition, the present invention provides double-layered silica nanoparticles doped with high luminous noble metal nanoclusters, which are produced by the above method.

The double-layered silica nanoparticles doped with the high-luminous noble metal nanoclusters according to the present invention can stably emit strong fluorescence even after repeated washing, and can be applied to various fields such as biosensing.

(I) of FIG. 1 (a) is a photograph of a gold aggregate initially formed in the reaction mixture, (II) is a photograph of a solution shone in a UV lamp, (III) This is a picture taken in the light of a lamp. (b) is the emission spectrum of HAuCl ₄ and PIPES aqueous reaction mixture stirred at 20 ° C. (i), 45 ° C. (ii), 60 ° C. (iii) and 90 ° C. (iv) for 2 to 3 days Nm).
2 (a) shows the excitation spectrum (dotted line, emission wavelength = 439 nm) and emission spectrum (solid line, excitation wavelength = 361 nm) of PIPES-Au NCs -Au NCs (NC-2) (dashed line, emission wavelength = 523 nm) and emission spectrum (solid line, excitation wavelength = 404 nm). Each right top is a photograph of PIPES-Au NCs underwater fluorescence observed by UV irradiation. (c) is a UV-visible light spectrum of PIPES-Au NCs (NC-1, solid line) and PIPES-Au NCs (NC-2, dotted line) in water.
3 (a) is the emission spectrum of PIPES-Au NCs (NC-1) in water (i) pH 2.5 (dotted line), (ii) pH 11.6 (dotted line) and (iii) pH 13 . The upper right is an enlargement of the spectrum of 420 to 500 nm. (b) shows the change of the emission spectrum while changing the solution from pH 2.5 to pH 13. The pH of the solution returned to pH = 13 (ii) and pH = 2.5 (iii) at pH = 2.5 (i).
FIG. 4 (a) is a TEM photograph of PIPES-Au NCs-doped silica nanoparticles, and FIG. 4 (b) shows PIPES-Au NCs (NC- (Emission wavelength = 437 nm, left side) and emission spectrum (excitation wavelength = 361 nm, right side). PIPES-Au NCs-doped silica nanoparticles were washed three times with ethanol.
5A shows the emission spectrum (excitation wavelength = 361 nm) of double-layer silica nanoparticles (solid line) doped with PIPES-Au NCs-doped silica nanoparticles (dotted line) and PIPES-Au NCs- to be. (b) shows the change in the radial intensity after repeatedly washing the PIPES-Au NCs-doped double-layer silica nanoparticles with ethanol.

Hereinafter, the configuration of the present invention will be described in more detail with reference to specific embodiments. However, it is apparent to those skilled in the art that the scope of the present invention is not limited to the scope of the following embodiments. Particularly, in the following examples, gold is used as a noble metal and PIPES is selected as a biocompatible buffer. However, the technical idea of the present invention is not limited to this range, and various applications are possible based on the description of the following embodiments. Do.

reagent

HAuCl ₄ .3H ₂ O (99.9%, Sigma-Aldrich), PIPES (1,4-piperazinediethanesulfonic acid, C ₈ H ₁₈ N ₂ O ₆ S ₂ , Sigma-Aldrich), polyoxyethylene glycol dodecyl ether _{((C 2 H 4 O)} 23 C1 2 H 25 OH, Brij35, Acros Organics), TEOS (tetraethylorthosilicate, 99%, Sigma-Aldrich), APTS {3- (aminopropyl) triethoxysilane, 98%, Sigma- _{Aldrich}, NH 4 OH (ammonium} hydroxide (NH4OH, 28-30 wt% ammonia, Sigma-Aldrich), cyclohexane _{(C 6 H 12, 99%} , Sigma-Aldrich), 1- hexanol (C ₆ H ₅ OH , 98%, Sigma-Aldrich), HCl, HNO ₃ , acetone and ethanol were used as obtained. All stock solutions were prepared before each reaction.

Before use, all glass containers were washed with aqua regia and thoroughly rinsed with ultrapure water.

Example 1 Synthesis of PIPES-Stabilized Gold Nanoclusters (PIPES-Au NCs)

PIPES-Au NCs were prepared by mixing HAuCl ₄ aqueous solution (2.5 mL, 2.5 × 10 ^-5 mol) and PIPES aqueous solution (5 mL) at 20 ° C., Lt; 0 > C) for 2 to 3 days. A non-fluorescent precipitate was formed within the first 10 minutes and fluorescence PIPES-Au NCs was generated in the reaction mixture after stirring. Samples named NC-1 and NC-2 in the nanoclusters were prepared as follows. Two equivalents of PIPES (5 × 10 ^-5 mol) were mixed with HAuCl ₄ (2.5 × 10 ^-5 mol) in water and stirred at 90 ° C. for two days to produce NC-1. NC-2 was prepared by mixing 20 equivalents of PIPES (5 × 10 ^-4 mol) with HAuCl ₄ (2.5 × 10 ^-5 mol) in water and stirring at 90 ° C. for two days. After the reaction was completed, fluorescent PIPES-Au NCs was formed in the supernatant, and the nonpolar precipitate was still present in the reaction mixture. The latter was removed by filtration.

Example 2 Synthesis of PIPES-Au NCs-Doped Silica Nanoparticles and PIPES-Au NCs-Doped Double-Layered Silica Nanoparticles

To prepare PIPES-Au NCs doped silica (PIPES-Au NCs @ SiO ₂ ) nanoparticles, Brij 35 (2.00 g) was added to cyclohexane (7.7 mL) and 1-hexanol (1.6 mL) The mixture was ultrasonicated and mixed for about 30 minutes until it became a solution. PIPES-Au NCs aqueous solution (0.75 mL) was added and the reaction mixture was sonicated for 10 minutes. TEOS (0.05 mL, 0.224 mmol) was then added and stirred, and the reaction mixture was further stirred at room temperature for 30 min. NH ₄ OH (0.1 mL) was slowly added with stirring for TEOS hydrolysis and condensation, and the reaction mixture was stirred at room temperature for 12 hours. After the reaction was completed, the reverse microemulsion was destabilized by adding acetone (20 mL) and centrifuged at 2,000 rpm for 10 minutes.

APTS (0.05 ml, 0.21 mmol) was added to the reaction medium to prepare PIPES-Au NCs-doped bi-layer silica (PIPES-Au NCs @ DL-SiO ₂ ) nanoparticles (preliminarily synthesized gold nanocluster- Nanoparticles, reverse microemulsion containing PIPES-Au NCs and NH ₄ OH), the reaction mixture was stirred at room temperature for 12 hours. After completion of the reaction, the reverse microemulsion was destabilized by adding acetone (20 mL) and centrifuged at 2,000 rpm for 10 minutes. The synthesized silica nanoparticles were washed 1 to 7 times with ethanol (1 ml per wash) and centrifuged at 13,500 rpm for 3 minutes.

Example 3: Characterization

The obtained nanoparticles were photographed with a Hitachi S-4800 SEM microscope and a JEOL JEM-2010 Luminography (Fuji FDL-5000) Ultramicrotome (CRX) TEM microscope. Samples for TEM analysis were prepared by centrifuging the nanoparticle mixture twice at 3,000 rpm for 3 minutes at 8,000 rpm. The particles were then resuspended in 100 μl of ultrapure water and 10 μl of solution was fixed on a Cu lattice coated with Formvar. The UV-visible mine spectra were recorded with a UV Spectrophotometer (UV-1800 Shimadzu). The excitation and emission spectra were recorded with a fluorescence spectrometer (LS-55B Perkin Elmer).

result

In the present invention, gold nanoclusters are prepared by mixing HAuCl ₄ (2.5 × 10 ^-5 mol) aqueous solution with PIPES (5 ml, 1,4-piperazinediethanesulfonic acid) aqueous solution at 20 ° C., With stirring for two days. During the first 10 minutes during the reaction of PIPES and HAuCl ₄ in water, a nonpolar brown precipitate was formed (Fig. 1 (a) (I)). At this time, the supernatant was colorless and had no fluorescence (Fig. 1 (a) (II)). This precipitate, which was initially produced, appears to be composed of aggregates of reduced solid gold, although it is not fully characterized. Here, PIPES appears to function as an effective reducing agent to reduce HAuCl ₄ to gold solids in aqueous solution. When the reaction mixture was further stirred, the supernatant gradually changed to fluorescence (Fig. 1 (a) (III)). The maximum luminescence intensity of this solution was observed after 3 days at 20 ° C. When the reaction temperature was varied, the reaction time required to obtain the maximum emission varied. In particular, the strongest luminescence was observed in the reaction mixture stirred at 90 ° C for two days. Figure 1 (b) shows the emission spectrum (excited at 361 nm) in the reaction mixture reacted at various temperatures. The luminescence of the solution stirred at 90 캜 was about ten times stronger than that of the solution stirred at 20 캜. Since PIPES and HAuCl ₄ do not fluoresce in water, the newly generated phosphor will definitely be present in the supernatant. Synthesis Example of Conventional Fluorescent Gold Nanoclusters Stabilized by Small Molecules {Y. Bao et al., J. Phys. Chem. C 114, 15879 (2010)}, it is deduced that the phosphor produced in the thermal reaction of the present invention is PIPES-stabilized gold nanoclusters (PIPES-Au NCs).

Interestingly, gold nanoclusters with different emission profiles were synthesized by varying the amount of PIPES used in the reaction. Using 2 equivalents of PIPES (5 x 10 < ^-5 > mol), a blue nanocluster (called "NC-1" in the present invention) , Excitation at 361 nm}. On the other hand, when 20 equivalents of PIPES (5 x 10 ^-4 mol) were used, a gold nanocluster (referred to as "NC-2" in the present invention) b) Excitation at 404 nm. The quantitative yield of the two nanoclusters was evaluated in comparison with well known comparative substances (fluorescein and quinine sulfate) (JR Lakowicz, Principles of Fluorescence Spectroscopy , 3rd Ed .; Springer (2006) , And NC-2 was 3%. These values correspond to the gold nanoclusters stabilized with MES- and HEPES- {Y. Bao et al., J. Phys. Chem. C 114, 15879 (2010)}. 2 (c) shows the absorption spectra of aqueous solutions of NC-1 and NC-2. Although broad, NC-1 (solid line) exhibits an extinction band near about 360 nm, which is very close to the fluorescence maximum excitation value (Fig. 2 (a)). NC-2 showed absorber bands near the wavelengths of 330 and 410 nm. According to the literature, this absorption spectral profile is not due to the gold nanoclusters themselves, but rather to the metal-centered and / or ligand-to-metal charge transfer transitions It seems to be attributed to A. Vogler and H. Kunkely, Coord. Chem. Rev. 219-221, 489 (2001), T. Huang and RW Murray, J. Phys. Chem. B 105, 12498 (2001). Although accurate characterization of the PIPES-Au NCs structure is ongoing, noble metal nanoclusters composed of dozens of atoms are strongly dependent on size-dependent emission (J. Zheng et al., Annu. Rev. Phys. Based on the well-known fact that molecular-like transitions exhibit interesting photophysical properties, including the PIPES-Au NCs ( NC-1 and NC-2 ) . Both fluorescent PIPES-Au NCs were stable thermodynamically and photophysically, and were irradiated with Hg lamp (200 W) for two days. After heating for more than one week at 90 ℃, Was not observed.

At the beginning of PIPES-Au NCs synthesis, nanoparticle aggregates are formed and then these nanoparticle aggregates appear to react with PIPES to form PIPES-Au NCs. Gold cluster form of this type is not entirely new, especially it was gold cluster is reported to be generated by the nanoparticles etching, which was protected by the synthetic template, such as small organic molecules and polymers (J. Zheng et al., J. Am. Chem. Soc. 125 , 7780 (2003), Y. Bao et al., J. Phys. Chem. C 114, 15879 (2010), H. Duan and S. Nie, J. Am. 129, 2412 (2007)). We believe that the etching of pre-fabricated aggregates by PIPES is a key step in the production of gold nanoclusters. In addition, the etching step is expected to be performed more efficiently at higher temperatures, according to our experimental results. Other reaction conditions, such as pH, are also important for the preparation of gold nanoclusters. When HAuCl ₄ and PIPES were mixed for the first time, the pH of the solution was about 5. When NaOH was added to change the pH of the solution, it became basic (pH> 7) during the reaction and inhibited PIPES-Au NCs formation. Interestingly, the maximum emission of the pre-synthesized PIPES-Au NCs slightly changed as the solution pH varied. The NC-1 aqueous solution of Fig. 2 (a) was acidic (pH ~ 2.5). When NaOH was added to change the reaction pH to 11.6, the emission spectrum of NC-1 shifted to about 10 nm blue (Fig. 3 (a)) compared to the initial emission. When the reaction pH was increased to 13, the emission spectrum of NC-1 shifted towards the blue color (~ 10 nm at maximum emission). Proton additive-dependent luminescence of PIPES-Au NCs can provide structural information because the maximum emission of PIPES-Au NCs is due to the H + ion concentration derived mainly from the -SO ₃ H substituent of the gold and PIPES complexes Because it is dependent. The change in pH of the solution, which was repeated between 2.5 and 13, shifted or restored the maximum emission wavelength of the PIPES-Au NCs relative to the original wavelength. However, the luminescence intensity gradually decreases because the PIPES-Au NCs are decomposed under basic conditions (Fig. 3 (b)).

The stability of fluorescent gold nanoclusters is known to be easily affected by the external environment. In addition, since the size of the gold nanoclusters is small, it is very difficult to further functionalize specific molecules in the gold nanoclusters (C.-AJ Lin et al., ACS Nano 3, 395 (2009), MA Habeeb Mohammed and T. Pradeep, Small 7 204 (2011)). This can be a critical limitation on the applicability of gold nanoclusters. Although the PIPES stabilized gold nanoclusters of the present invention are very stable, functionalizing molecules in gold nanoclusters is still a challenging attempt. A useful strategy to solve this problem is to encapsulate the gold nanoclusters fabricated in a particular matrix. Particularly, porous silica (silicon dioxide) is a very attractive candidate because it is known that the surface of silica nanoparticles is easy to functionalize by other molecules (A. Guerrero-Martnez et al . , Adv. Mater. 22, 1182 2010), LM Liz-Marzn et al., In: Handbook of Surfaces and Interfaces of Materials, (Ed: HS Nalwa), Academic Press, San Diego, USA 2001). However, there are few examples of inclusion of fluorescent gold or silver nanoclusters in silica shells (MA Habeeb Muhammed and T. Pradeep, Small 7 204 (2011), Z. Zhang et al., Talanta 85, 2695 (2011)). In order to synthesize silica nanoparticles doped with monodisperse spherical fluorescent gold nanoclusters, reverse microemulsion method was used, which has been known as an effective method for synthesizing fluorescent silica nanoparticles through chemical dye doping (S. Santra et al. , Adv. Mater. 17, 2165 (2005), S. Santra et al., J. Biomed. Opt. 6, 160 (2001), RP Bagwe et al., Langmuir 20, 8336 (2004), J. Pak and H. Yoo, submitted.). The microemulsion was prepared by mixing Brij 35, co-surfactant (1-hexanol), organic solvent (cyclohexane), water, and PIPES-Au NCs (NC-1) aqueous solution. TEOS (0.224 mmol) was hydrolyzed in the microemulsion with NH ₄ OH and condensed in the presence of PIPES-Au NCs. FIG. 4 (a) shows TEM images of the thus synthesized PIPES-Au NCs-doped silica nanoparticles (PIPES-Au NCs @ SiO ₂ NPs). The synthesized silica nanoparticles were very spherical and narrow in size (average particle diameter = 58 ± 6 nm; more than 100 nanoparticles were measured). In addition, the synthesized silica nanoparticles were well dissolved in water and fluoresced. PIPES-Au NCs @ SiO2 NPs (solid line) in FIG. 4 (b) shows the excitation spectrum and the emission spectrum of PIPES-Au NCs m (NC-1) )). ≪ / RTI > The maximum emission peak of PIPES-Au NCs @ SiO2 NPs near 440 nm was obtained when excited at 361 nm in water. The silica nanoparticles synthesized in reverse microemulsion without gold nano cluster doping did not show luminescence under the same conditions as in Fig. 4 (b).

As shown in Fig. 4 (b), the emission intensity of PIPES-Au NCs @ SiO2 NPs was much lower than that of PIPES-Au NCs. This seems to be due to the fact that PIPES-Au NCs are highly hydrophilic and difficult to be doped into anionic charged silica matrix. Also, PIPES-Au NCs tend to leak from the pores of the silica nanoparticles, which significantly reduces the emission intensity of the silica nanoparticles.

Thus, the present inventors have established a novel and simple synthesis strategy for the production of organic light-doped solid-state monodispersed silica nanoparticles. This method is based on the sequential condensation of TEOS and APTS {3- (aminopropyl) triethoxysilane} in an inverse microemulsion to form a bilayer. Due to the high doping ratio of the organic dyes and the improved protection against the possibility of dye leaching by the silica matrix, the synthesized bilayer silica nanoparticles showed much stronger luminescence than the bilayer silica nanoparticles. In order to improve the doping rate of PIPES-Au NCs into the silica matrix and to increase the luminescence of the silica nanoparticles, we doped PIPES-Au NCs into the bilayer silica (PIPES-Au NCs @ DL-SiO ₂ NPs). For the synthesis of PIPES-Au NCs @ DL-SiO ₂ NPs, TEOS (0.224 mmol) and APTS (0.021 mmol) were sequentially hydrolyzed and NH ₄ OH was added in the reverse microemulsion to obtain PIPES-Au NCs ≪ / RTI > Figure 5 (a) compares the emission spectra of PIPES-Au NCs @ DL-SiO ₂ NPs (solid lines) and PIPES-Au NCs @ SiO ₂ NPs (dotted lines) in ethanol under similar conditions, NCs-doped bilayer silica nanoparticles show much higher luminescence ratios. This seems to be due to the higher probability that PIPES-Au NCs is doped into the silica matrix of PIPES-Au NCs @ DL-SiO ₂ NPs, ie, bilayer nanoparticles. Figure 5 (b) shows that the PIPES-Au NCs @ DL-SiO ₂ NPs show little change in luminescence after repeated washing with ethanol, suggesting that the PIPES-Au NCs are well protected in the silica matrix . The inner-outer structure of PIPES-Au NCs @ DL-SiO ₂ NPs appears to be effective in protecting PIPES-Au NCs.

Nano-sized fluorescent silica nanoparticles are one of the most widely studied topics for applications in biomedical and biosensing technologies (G. Yao et al., Anal. Bioanal. Chem . 385, 518 (2006), R. Tapec et al., J. Nanosci. Nanotechnol ., 2, 405 (2002), AV Blaaderen and A. Vrij, Langmuir 8, 2921, (1992)). Silica nanoparticles are known to be highly biocompatible, non-toxic and well-mixed with water due to their high porosity, and this property makes silica nanoparticles more useful (A. Guerrero-Martnez et al, Adv. Mater . 22, 1182 (2010), LM Liz-Marzn et al, in:. Handbook of Surfaces and Interfaces of Materials, (Ed: HS Nalwa), Academic Press, San Diego, USA 2001). In addition, PIPES-Au NCs @ DL-SiO2 NPs are expected to have amine groups on their surface and may be used to functionalize other molecules (RP Bagwe et al., Langmuir 22, 4357 (2006), R. Zhang et al. , Langmuir 25,10153 (2009)). It is expected that PIPES-Au NCs @ DL-SiO2 NPs prepared by the process of the present invention due to its ability to function as well as effective luminescence can be used in more applications after functionalization of specific groups on the surface of silica nanoparticles .

In conclusion, the present inventors synthesized solid gold nano clusters (PIPES-Au NCs) through stabilization using PIPES in a thermal synthesis method. The synthesized PIPES-Au NCs was very stable under acidic conditions and the luminescence changed in a pH-dependent manner. Two gold nanoclusters with different maximum emission wavelengths were produced by varying the amount of PIPES used.

The synthesized gold nanoclusters were successfully encapsulated in a porous silica matrix to produce silica nanoparticles doped with fluorescent PIPES-Au NCs. Successive doping of PIPES-Au NCs with TEOS and APTS results in a large matrix of PIPES-Au NCs, a high emission, and a silica matrix in which the PIPES-Au NCs are effectively protected even after repeated washings with polar solvents.

Claims (8)

a) preparing a stable noble metal nanocluster by adding a biocompatible buffer solution to an aqueous solution containing a noble metal salt and stirring while heating;
b) mixing the nonionic surfactant, the nonpolar organic solvent, the polar solvent and the excess noble metal nanocluster solution prepared in step a) to prepare a microemulsion;
c) hydrolyzing and condensing the silica precursor by adding a silica precursor and an alkali catalyst in the prepared microemulsion to prepare silica nanoparticles doped with noble metal nanoclusters; And
d) adding a noble metal nanocluster solution prepared in step a) and an alkali catalyst to the nano-clusters doped with noble metal nanoclusters, adding 3-aminopropyltrienthoxysilane (APTS) and stirring to prepare double-layer silica nanoparticles containing noble metal nanoclusters Wherein the high-luminous noble metal nanoclusters are doped with a high-luminous noble metal nanocluster.
The method according to claim 1,
The biocompatible buffer may be one selected from the group consisting of HEPES (4- (2-hydroxyethyl) -piperazine-1-ethanesulfonic acid), MES (2- (N-Morpholino) sulfonic acid), MOPS (3- (N-Morpholino) propanesulfonic acid), PIPES (1,5-piperazinediethanesulfonic acid), CHES (2- (Cyclohexylamino) 2-aminoethanesulfonic acid), BES (N-Bis- (2-hydroxyethyl) -2-amino-ethanesulfonic acid), MOBS (4- (N-Morpholino) butanesulfonic acid), MOPSO (3-Morpholino- hydroxypropanesulphonic acid), POPSO (Piperazine-1,4-bis (2-hydroxypropanesulfonic acid) dihydrate), TAPS (N-Tris [hydroxymethyl] methyl-3-aminopropanesulfonic acid) Wherein the high luminous noble metal nanocluster is at least one selected from the group consisting of TAPSO (3 - [[1,3-dihydroxy-2- (hydroxymethyl) propan-2-yl] amino] -2-hydroxypropane- Lt; RTI ID = 0.0 > nanoparticles < / RTI >
The method according to claim 1,
Wherein the alkali catalyst is an aqueous solution of ammonia, wherein the high-luminous noble metal nanoclusters are doped with ammonia.
The method according to claim 1,
Wherein the nonionic surfactant is a polyoxyethylene glycol dodecyl ether, a glycerin fatty acid ester, a sucrose fatty acid ester, or a sorbitan fatty acid ester. Way.
The method according to claim 1,
Wherein the polar solvent is water or an aqueous solution of an acid.
The method according to claim 1,
Wherein the silica precursor is tetraethyl orthosilicate, tetramethyl orthosilicate or tetrapropyl orthosilicate. 2. The method of claim 1, wherein the silica precursor is tetraethyl orthosilicate, tetramethyl orthosilicate or tetrapropyl orthosilicate.
The method according to claim 1,
Wherein the noble metal is gold, silver or platinum. ≪ RTI ID = 0.0 > 11. < / RTI >
8. A high-luminous noble metal nanocluster-doped double-layered silica nanoparticle prepared by the method of any one of claims 1 to 7.

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