KR101480763B1 - Multifunctional material with reversible phase transfer via layer-by-layer assembly and method for preparing the same - Google Patents

Abstract

The present invention relates to a reversible phase-shiftable multifunctional material produced by layered self-assembly and a method for producing the same, and more particularly, to a multi-functional material capable of reversibly phase- Or a polymer layer; Or a metal or metal oxide layer. According to the present invention, not only the organic solvent and the aqueous solution have a high dispersing power but also the density of the coated particles is remarkably high and stable in the external environment.

Description

TECHNICAL FIELD The present invention relates to a multifunctional material capable of reversibly phase-shifting and a method for preparing the same,

The present invention relates to a multifunctional material capable of reversibly phase-shifting, which is produced by using layered self-assembly showing various functionalities, as well as having a high dispersing power in various solvents up to an organic solvent and an aqueous solution and having a remarkably high density of coated particles, .

Layer-by-layer assembly technology is a technique for modifying a material surface through complementary interactions between particles, providing the means to control the properties and thickness of the material surface with the most general process. These techniques can be used for surface modification of non-volatile memory devices, light emitting diodes, supercapacitors and electrochemical sensor components depending on the type of particles used and the amount of adsorbed on the coatings, The application is broad in terms of being able to freely change and apply the chemical properties including the hydrophilicity, hydrophobicity and chemotaxis of the applied material according to G. Decher, Science 1997 , 277 , 1232-1237; F. Caruso, RA Caruso, H. Mohwald, Science 1998 , 282, 1111-1114; Y. Ko, Y. Kim, H. Baek, J. Cho, ACS Nano 2011 , 5 , 9918-9926; J.-S. Lee, J. Cho, C. Lee, I. Kim, J. Park, Y. Kim, H. Shin, J. Lee, F. Caruso, Nat . Mater . 2007 , 2 , 790-795; WK Bae, J. Kwak, J. Lim, D. Lee, MK Nam, K. Char, C. Lee, S. Lee, Nano Lett . 2010 , 10 , 2368-2373; SW Lee, J. Kim, S. Chen , PT Hammond, YS-Horn, ACS Nano, 2010, 4, 3889-3896; A. Yu, Z. Liang, J. Cho, F. Caruso, Nano Lett . 2003 , 3 , 1203-1207).

In most cases, conventional layered self-assembly techniques have been made through electrostatic attraction between constituent materials that are continuously deposited in an aqueous medium. However, the bonding and coating between materials using electrostatic attraction did not provide satisfactory strength in application to various fields. In order to overcome this problem, click chemical, disulfide bond, silanization, urea chemical, ester urethane (AM Pudsiadlo, AK Kaushik, EM Arruda, AM Waas, BS Shim, J. Xu, < RTI ID = 0.0 > H. Nandivada, BG Pumplin, J. Lahann, A. Ramamoorthy, NA Kotov, Science , 2007 , 318 , 80-83; J. Cho, J. Hong, K. Char, F. Caruso, J. Am . Chem . Soc 2006, 128, 9935-9942;. D. Wang, AL Rogach, F. Caruso, Chem Mater 2003, 15, 2724-2729;.. D. Wang, AL Rogach, F. Caruso, Nano Lett . 2002 , 2 , 857; e) M. Braun, C. Burda, MA El-Sayed, J. Phys . Chem. A. 2001 , 105 , 5548-5551; G. Schmid, N. Klein, L. Korste , Polyhedron, 1988, 7, 605-608; J. Simard, C. Briggs, AK Boal, VM Rotello, Chem . Commun . , 2000 , 1943-1944; DI Gittins, F. Caruso, Angew , Chem . Int . Ed . 2001 , 40 , 3001-3004).

However, in the case of the layered self-assembly technique using electrostatic attraction or hydrogen bonding, intergranular clearance occurs in the coating process due to the electrostatic repulsive force generated between adjacent coating particles having the same electric charge, And the degree of surface modification was not satisfactory. In addition, since such coating techniques presuppose hydrophilic or polar solvents, their application is very difficult in electronic devices or petrochemical industries that require low levels of leakage current.

Accordingly, there is a demand for a layered self-assembly technique that can be dispersed in various solvents ranging from an organic solvent to an aqueous solution, and is coated with a dense structure to have versatility.

It is an object of the present invention to provide a multifunctional material capable of reversibly phase-shifting by using layered self-assembly which not only has a high dispersion power in various solvents up to an organic solvent and an aqueous solution but also exhibits various functions.

It is another object of the present invention to provide a method for producing the above-mentioned multifunctional material capable of reversible phase transfer.

In order to accomplish the above object, the present invention provides a multi-functional material capable of reversibly phase-shifting, which is produced by using layered self-assembly of the present invention,

A dendrimer or polymer layer wherein the outermost layer comprises an amine group; or

Or a metal or metal oxide layer synthesized in an organic solvent.

A dendrimer or polymer layer comprising an amine group between the surface of the material in the form of a plate or particle and the outermost layer; And

The metal or metal oxide layers may be alternately laminated at least once each.

Further, a dendrimer or polymer layer containing an amine group on the substrate or in the form of particles in the form of a particle; And

The metal or metal oxide layer is alternately laminated at least once each,

A dendritic polymer or a polymer layer including an amine group may be laminated on the upper surface of the stacked metal or metal oxide layer.

The particles may be colloidal particles or carbon nanotubes.

The substrate may be a colloidal particle on which an amine group may be coated.

The dendrimer or polymer layer may comprise a dendrimer or polymer selected from the group consisting of poly (amidoamine), poly (ethyleneimine), and mixtures thereof.

The metal or metal oxide layer may comprise a metal or metal oxide selected from the group consisting of silver, gold, platinum, iron, iron oxide, manganese oxide, barium, barium oxide, titanium, titanium oxide and mixtures thereof.

The dendrimer or polymer layer and the metal or metal oxide layer may be covalently bonded to each other.

When the outermost layer of the multifunctional material is a dendrimer or a polymer layer containing an amine group, the multifunctional material may further include an electrostatic multilayer on the dendrimer or polymer layer.

Wherein the electrostatic multilayer comprises a multilayer in which positive charge polymer layers comprising a negatively charged CAT enzyme layer and an amine group are alternately stacked at least once each; Or a multilayer in which a negative charge polymer layer and a positively charged noble metal layer are alternately laminated at least one time each.

Wherein the positive charge polymer layer in the electrostatic multilayer is selected from the group consisting of poly (allylamine hydrochloride) (PAH), polyethyleneimine (PEI), and polydiallyl dimethyl ammonium chloride (PDADMAC) And the negative charge polymer layer may be poly (acrylic acid) (PAA).

The positive charge precious metal may be selected from the group consisting of silver, gold, platinum and mixtures thereof.

According to another aspect of the present invention, there is provided a method for manufacturing a multi-functional material capable of reversibly phase-shifting using layered self-assembly according to the present invention, comprising:

Coating with a dendrimer or polymer comprising an amine group; or

Coating with a metal or metal oxide combined with a hydrophobic stabilizer can be performed at the end.

The hydrophobic stabilizer may be selected from the group consisting of oleic acid, oleylamine, palmitic acid, tetraoctylammonium bromide, and mixtures thereof.

When the dendrimer or the polymer is coated with a metal or a metal oxide, the hydrophobic stabilizer is substituted by an amine group of the dendrimer or polymer through an in-situ ligand exchange reaction with an amine group of the dendrimer or the polymer A covalent bond can be formed between the metal or metal oxide and the dendritic polymer or the polymer.

The hydrophobic stabilizer may have a functional group selected from the group consisting of a carboxyl group, a carboxylic acid salt, an ammonium group and an ammonium salt.

Coating with the dendrimer or polymer; And coating with a metal or a metal oxide can be repeatedly performed one to ten times.

If the coating with the dendrimer or polymer is performed last, it may further include coating the electrostatic multilayer after the dendrimer or polymer coating step.

Wherein the electrostatic multilayer comprises a multi-layer in which a negatively charged CAT enzyme coating and a positively charged polymer coating comprising an amine group are each coated alternately at least once; Or a multilayer in which the negative charge polymer coating and the positive charge precious metal coating are each coated alternately at least once.

Multifunctional materials that can be reversibly phase-shifted using the layered self-assembly of the present invention have a high dispersing power in various solvents from organic solvent to aqueous solution, and the density of the coated particles is remarkably high, so that various functionalities It has various functionalities and thus exhibits various functions when formed into a multi-layered structure), and is stable in an external environment. If the density of the coating particles is low, various coating materials do not have various functionalities even if they are deposited.

1 is a conceptual view illustrating a process of coating particles according to an embodiment of the present invention.
2 is an HR-TEM image of OAFe ₃ O 4 _NPs synthesized in toluene according to the present invention.
3 is an ATR-FTIR spectrum of (dendrimer / OAFe ₃ O 4 _NPs ) _n multilayers using an ISLE reaction according to one embodiment of the present invention.
4A is an ATR-FTIR spectrum of (dendrimer / OAAg _NPs ) _n multilayers prepared according to another embodiment of the present invention.
4B is an ATR-FTIR spectrum of (dendrimer / TOABrAu _NPs ) _n multilayers prepared according to another embodiment of the present invention.
Figure 5a is a graph of the double layer number (n) and the particle size to increase the _n multi-layer coated with SiO ₂ colloid (dendrimer / OAFe ₃ O _4NPs) prepared according to one embodiment of the invention.
Figure 5b is a HR-TEM image of a multi-layer ₉ coated with SiO ₂ colloid (dendrimer / OAFe ₃ O _4NPs) prepared according to one embodiment of the invention.
Figure 6 is QCM data of (dendrimer / OAFe ₃ O 4 _NPs ) _n multilayers prepared according to one embodiment of the present invention.
Figure 7a is a magnetic curve measured at 298 K of a (dendrimer / OAFe ₃ O 4 _NPs ) _n multilayer coated SiO ₂ colloid prepared according to one embodiment of the present invention.
Figure 7b is a magnetic curves measured in the (dendrimer / OAFe ₃ O _{4NPs) n} 5K a multi-layer-coated SiO ₂ colloids prepared according to one embodiment of the invention.
7C is a graph showing changes in ZFC and FC magnetization temperatures measured at 150 Oe.
8A is an HR-TEM image of an anionic Fe ₃ O 4 _NPs prepared in an aqueous solution according to another embodiment of the present invention.
8B is a graph showing changes in ZFC and FC magnetization temperatures of anion Fe ₃ O _4NPs measured at 150 Oe.
9A is an SEM image of a SiO ₂ colloid coated with (PAH / anion Fe ₃ O 4 _NPs ) ₁ multilayer prepared according to another embodiment of the present invention.
Figure 9b is an SEM image of yet made according to another embodiment (PAH / anion Fe ₃ O _{4NPs) 3} multi-layer with the coated SiO ₂ colloids of the present invention.
FIG. 10A is a graph showing changes in zeta-potential value caused by alternate deposition of anion enzyme (CAT) and cationic PAH in a multilayer SiO ₂ colloid coated with dendrimer (Dendrimer / OAFe ₃ O 4 _NPs ) _4.5 / dendrimer to be.
10B is a SEM image of a _4.5 (CAT / PAH) n multilayer coated colloid (n = 1, 2, 3, 4) prepared according to another embodiment of the present invention (dendrimer / OAFe ₃ O 4 _NPs ).
Figure 10c shows the colloidal phase migration from toluene to aqueous solution after (CAT / PAH) ₃ multilayer deposition on (dendrimer / OAFe ₃ O _{4 NPs} ) ₄ multilayer coated colloids (dendrimer / OAFe ₃ O 4 _NPs ) ₄ / dendrimer / (CAT / PAH) ₃ multilayer coated colloid.
Figure 10d shows the _circulation of a ₄ dendrimer / (CAT / PAH) ₃ multilayer coated colloid-modified ITO electrode (Dendrimer / OAFe ₃ O _{4 NPs} ) in pH 7.0 PBS containing 15 mM H ₂ O ₂ as a function of scan speed A graph of the cyclic voltammograms.
FIG. 11 is a graph _{showing the} relationship between the dendrimer (Dendrimer / OAFe ₃ O 4 _NPs ) _4.5 / dendrimer Potential values generated by alternate deposition of anion PAA and cationic DMAPAu _NPs in multilayer coated SiO ₂ colloid.
Figure 12a is a SiO ₂ colloid / (dendrimer / OAFe ₃ O _{4NPs) 4} (left) and SiO ₂ colloids / (dendrimer / OAFe ₃ O _{4NPs) 4} / dendrimer / (PAA / DMAP-Au _{NNPs) 5} (right) of the SEM Image.
12B is a surface plasmon resonance spectrum of SiO ₂ colloid / (dendrimer / OAFe ₃ O 4 _NPs ) _4.5 / (PAA / DMAP-Au _NPs ) _n in which the bilayer number (n) increases from 1 to 5. The dotted line is the surface plasmon resonance spectrum of DMAPAu _NPs in aqueous solution.
12C is a photographic image of a multilayer coated colloid coated with a magnetic response material (dendrimer / OAFe ₃ O 4 _NPs ) _4.5 / dendrimer / (PAA / DMAPAu _NPs ) _n .
Figure 12d is a (dendrimer _{/ OAFe 3 O 4NPs) 2,} ( dendrimer / OAFe ₃ O _{4NPs) 2} / dendrimer (dendrimer / OAFe ₃ O _{4NPs) 4} / dendrimer _{/ (PAA / DMAPAu NPs) 2} , ( dendrimer / OAFe ₃ O ( _4NPs ) ₄ / Dendrimer / (PAA / DMAPAu _NPs ) ₂ / (Dendrimer / OAFe ₃ O _4NPs ) ₂ is a photographic image of the multilayer coated colloid (left to right).
Figure 13 is a SEM image of a (dendrimer / TOAAu _NPs ) _n multilayer coated colloid prepared according to another embodiment of the present invention.

The present invention relates to a multifunctional material capable of reversibly phase-shifting, which is produced by using layered self-assembly having various functionalities such as high dispersibility in various solvents from organic solvent to aqueous solution and high density of coated particles, .

Hereinafter, the present invention will be described in detail.

The reversibly phase-shiftable multifunctional material produced by the layered self-assembly of the present invention may be formed by stacking one or more layers on the surface of a substrate or a material in the form of particles,

A dendrimer or polymer layer wherein the outermost layer comprises an amine group; or

Metal or metal oxide layer.

Wherein the outermost layer comprises the dendrimer or polymer layer; Or a metal (or metal oxide) layer, the intermediate layer below the outermost layer may be any, but a dendrimer or polymer layer; Or a metal (or metal oxide) layer. Specifically, a dendrimer or polymer layer; Or the metal (or metal oxide) layer are alternately laminated at least once each.

The particles and the substrate are not particularly limited, but preferably, the particles may be one selected from the group consisting of colloidal particles and carbon nanotubes, and the substrate may be one selected from the group consisting of colloid particles, .

The dendritic polymer or the polymer layer containing the amine group may be freely selected and included if it is an amine group-containing compound. Preferably, a dendritic polymer or a polymer of poly (amidoamine) or poly (ethyleneimine) Preferably, dendritic particles of poly (amidoamine) or poly (ethyleneimine) may be included. This is because, when particles having an excessively large size are used, the gap between the particles may become wider and may not meet the purpose of the coating.

The metal or metal oxide layer may include at least one particle selected from the group consisting of silver, gold, platinum, iron, iron oxide, manganese, manganese oxide, barium, barium oxide, titanium and titanium oxide. However, the metal or metal oxide particles are merely examples, and those skilled in the art can select and include the metal or metal oxide particles to be freely coated according to the purpose. It is not limited. The metal or metal oxide layer may impart magnetism to the reversibly phase-shiftable multi-functional material according to the present invention.

Also, the multifunctional material capable of reversibly phase-shifting according to the present invention is characterized in that the amine group of the dendrimer or polymer layer and the particles of the metal or metal oxide layer are covalently bonded to each other.

Such covalent bonding may be achieved by first bonding the metal or metal oxide particles to a hydrophobic stabilizer selected from the group consisting of oleic acid, oleylamine, palmitic acid, tetraoctylammonium bromide, and mixtures thereof, ; And the hydrophobic stabilizer bound to the metal or metal oxide are reacted in an in-situ ligand exchange (hereinafter, referred to as ISLE) in a solvent, and a hydrophobic stabilizer bound to the metal or metal oxide is reacted with the dendritic polymer or the polymer Lt; / RTI > is substituted by an amine group. Thereby forming a metal or metal oxide layer in which the metal or metal oxide particles are packed in a dense manner.

More specifically, the hydrophobic stabilizer may include a functional group that is a carboxyl group, a carboxylate, an ammonium group, or an ammonium salt, and the functional group causes the hydrophobic stabilizer to form a weak bond with a metal or a metal oxide, A weak bond causes an intermediate stage ISLE reaction to take place by the dendrimer or the amine group of the polymer, so that the weak bond is replaced by a stronger bond between the amine group of the dendrimer or polymer and the metal or metal oxide. Therefore, the multifunctional materials capable of reversibly phase-shifting according to the present invention are strongly bonded, and the binding force is also a cause of high stability to the external environment in which the multifunctional materials capable of reversible phase transfer according to the present invention are visible.

According to the present invention, in the case where the outermost layer of the multifunctional material capable of reversible phase migration is a dendrimer or a polymer layer, the multifunctional material is manufactured using the electrostatic multilayer self-assembly further including the electrostatic multilayer on the dendrimer or polymer layer, Various functions can be given.

The electrostatic multilayer may be a multi-layered structure in which a positive charge polymer layer including a negative charge CAT enzyme layer and an amine group is alternately laminated at least once, or a multilayer structure in which a negative charge polymer layer and a positively charged noble metal layer are alternately stacked have. For example, the multilayer in which the negative charge CAT enzyme layer and the positive charge polymer layer including an amine group are alternately laminated at least one time may further impart electrostatic function and functionality as a catalyst, and each of the negative charge polymer layer and the positive charge precious metal layer The multilayer stacked alternately at least one time may further impart functionality as a catalyst.

The positively charged polymer layer comprising amine groups used in the electrostatic multilayer may be selected from the group consisting of poly (allylamine hydrochloride) (PAH), polyethyleneimine (PEI) and poly (diallyl dimethyl ammonium chloride) (PDADMAC) And the negative charge polymer layer may be poly (acrylic acid) (PAA), and the positive charge precious metal may be at least one selected from the group consisting of silver, gold and platinum.

When the outermost layer of the multifunctional material capable of reversible phase migration according to the present invention is a dendrimer or a polymer layer (hydrophilic layer), it is stably dispersed in an aqueous solution and the outermost layer is a metal or metal oxide layer (hydrophobic layer) In the case where the outermost layer is an electrostatic multi-layer (hydrophilic layer), it is stably dispersed in an aqueous solution. Therefore, depending on the constituents of the outermost layer, reversible phase shift in various solvents from an organic solvent to an aqueous solution It is possible.

The present invention also provides a method for producing a reversibly phase-shiftable multifunctional material produced using layered self-assembly.

The method for preparing a multifunctional material according to the present invention comprises coating a substrate or a surface of a material in the form of particles with a dendrimer or a polymer containing an amine group, Or with a metal or metal oxide in combination with a hydrophobic stabilizer. Coating with the dendrimer or polymer; And coating with a metal or a metal oxide can be repeatedly carried out one to ten times in this order.

FIG. 1 is a conceptual view illustrating a process of coating particles according to an embodiment of the present invention, and will be described in detail with reference to FIG.

First, the particles are coated with a dendrimer or polymer containing an amine group. Such a coating is obtained by immersing the particles in a dendrimer or polymer solution containing an amine group for 5 to 15 minutes, then washing the weakly adsorbed dendrimer or polymer by holding the precipitate with a centrifuge, removing the residual solution and again immersing the same solvent. Thereafter, it is carried out again by precipitating with a centrifuge and removing the residual solution. Examples of the solvent for the solution include an alcohol or an aqueous solution capable of dissolving a dendrimer or polymer containing an amine group. For example, alcohols include methanol, ethanol or isopropyl alcohol.

If the immersion time is less than 5 minutes, sufficient coating may not be obtained, and if it exceeds 15 minutes, there is no additional effect in laminating one layer.

Next, the particles coated with the dendritic polymer or the polymer containing the amine group are coated with a metal or a metal oxide combined with a hydrophobic stabilizer. This may be accomplished by immersing the particles in a metal or metal oxide solution in combination with a hydrophobic stabilizer over a period of 25 to 35 minutes, followed by washing and drying. The solvent of the solution may be any organic solvent capable of dissolving the metal or metal oxide in combination with the hydrophobic stabilizer, and may be, for example, toluene, THF, chloroform or hexane.

If the immersion time is less than 25 minutes, sufficient coating may not be formed, and if it exceeds 35 minutes, there is no additional effect in laminating one layer. During the immersion in the metal or metal oxide solution combined with the hydrophobic stabilizer, the ISLE reaction as described above occurs to separate the hydrophobic stabilizer and form a strong covalent bond between the amine group of the dendrimer or polymer and the metal or metal oxide particle .

By repeating the above two steps, it is possible to obtain a desired lamination thickness, and it is possible to obtain a superposed coating by repeating 1 to 10 times, though not limited to the number of times.

Next, the dendrimer or polymer coating comprising the amine groups alternately and the surface coated with the metal or metal oxide are coated again with a dendrimer or polymer comprising an amine group. This coating condition is the same as that for coating with a dendrimer or a polymer containing the amine group.

The structure so formed may be expressed as a 'dendrimer or polymer layer containing a particle / a dendrimer or a polymer layer / a metal or a metal oxide layer containing an amine group _1-10 / amine group'.

Next, an electrostatic multilayer is coated on the surface coated with the dendrimer or polymer containing the amine group. This coating is performed by immersing the particles in an electrostatic multilayer solution for 1 to 15 minutes, followed by washing and drying. The solvent of the solution may be an alcohol or an aqueous solution capable of dissolving the electrostatic multilayer. For example, alcohols include methanol, ethanol or isopropyl alcohol.

If the immersion time is less than 30 seconds, the multilayer may not be sufficiently coated. If the immersion time is more than 15, no additional effect is obtained in laminating one layer.

Wherein the electrostatic multilayer comprises a multi-layer in which a negatively charged CAT enzyme coating and a positively charged polymer coating comprising an amine group are each coated alternately at least once; Or a negative charge polymer coating and a positive charge precious metal coating, each of which may be alternately coated at least once. By repeating the coating step, it is possible to obtain a desired lamination thickness, and it is possible to obtain a superposed coating by repeating 1 to 10 times, although not limited to the number of times.

This structure is formed by "particles / (or amine dendrimer polymer layer / metal or metal oxide layer comprising a) _1-10 / amine dendrimer or polymer layer / (polymer layer comprising a layer CAT / amine) comprising a _{1- 10} "or" particles / (dendrimer or polymer layer / metal or metal oxide layer containing an amine group) _1-10 / amine dendrimer or polymer layer / (the polyacrylic acid layer / a noble metal particle layer) containing an expression _1-10 as " .

In the case of the same structure (e.g., (polymer / metal) n), when self-assembled as in the present invention, the coating of nanoparticles in a more multilayered structure This is possible.

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 or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Manufacturing example  1: hydrophobic Stabilizers and  Synthesis of combined metal or metal oxides

OA - Fe ₃ O _4NPs Synthesis of

OA-stabilized Fe ₃ O ₄ with a diameter of about 5 nm was synthesized in toluene. _{Fe (acac) 3 (2 mmol} , Aldrich社), 1,2- hexahydro-decanediol (1,2- hexadecanediol, 10 mmol, Aldrich社), OA ( oleic acid, 5 mmol, Aldrich社), oleyl amine (oleylamine , 6 mmol, Aldrich) and benzyl ether (20 mL, Aldrich) were mixed and agitated while flowing nitrogen. The mixture was heated to 200 < 0 > C for about 2 hours and heated to reflux (about 300 < 0 > C) in a nitrogen atmosphere for 1 hour. The black mixture obtained by removing the heat source was cooled to room temperature. Ethanol (40 mL) was added to the mixture at atmospheric conditions and the black material was separated by centrifugation. The resulting black product was dissolved in hexane or toluene in the presence of OA (0.05 mL) and oleylamine (0.05 mL). Centrifugation (6000 rpm, 10 min) was applied to remove any undispersed residues. A blackish brown toluene dispersion of 5.1 nm Fe ₃ O ₄ nanoparticles was prepared, the concentration of which was 0.5 wt%.

DMAP - Au _NPs Synthesis of

30 mM aqueous solution HAuCl ₄ (chloroauric acid, 30 mL) was added to a 25 mM solution of TOABr (tetraoctylammonium bromide) dissolved in toluene (80 mL). The migration of HAuCl ₄ on toluene in a few seconds was clearly observed. To the mixture was added 25 mL of 0.4 M NaBH ₄ aqueous solution. After 10 minutes, the separated aqueous phase was removed and the toluene phase containing Au _NPs was washed with 0.1 MH ₂ SO ₄ , 0.1 M NaOH and H ₂ O. For phase transfer from toluene to aqueous solution, 0.1 M DMAP (80 mL) in water was added to a toluene solution (80 mL) containing TOA-stabilized Au _NPs . After 24 hours, the toluene-dispersed Au _NPs were completely phase-shifted into the aqueous phase and the separated toluene phase was removed.

The resulting Au _NPs dispersed on the aqueous solution was stabilized by DMAP ligand.

Manufacturing example  2: negative ion Fe ₃ O _4NPs Synthesis of

Under a 2 M HCl 1M FeCl ₃ 20 mL and FeSO ₄ 5mL was added to 0.7 M NH ₄ OH 250mL with mechanical stirring for 1 hour. The black solid powder is separated by the help of the magnet.

This product was emulsified in aqueous solution and then 10 mL of 1M tetramethylammonium hydroxide solution was added. The concentration of this product is 0.5% by weight.

Example  1. Colloidal particles / ( Dendrimer / OAFe ₃ O _4NPs ) _n / Dendrimer's  formation

100 μL of the concentrated dispersion of the anionic 585 nm-SiO ₂ colloid (6.4 wt%) was diluted to 0.5 mL with deionized water. After the colloidal solution was centrifuged (8000 rpm, 5 minutes), the supernatant was removed and 0.5 mL of a 1 mg · mL ^-1 ethanol solution of dendrimer was added to the colloid, followed by ultrasonication and adsorption for a sufficient time. Excess dendrimer was removed by centrifugation three times (8000 rpm, 5 min) / wash cycle. A multilayer structure was prepared on dendrimer-coated -SiO ₂ colloid by adding 0.5 mL of OA-Fe ₃ O ₄ (5 mg · mL ^-1 ) in toluene, and after 10 minutes of deposition, excess OA-Fe ₃ O 4 _NPs And removed by centrifugation three times as described above. Next, toluene (or ethanol) of the dendrimer ^{(1 mg · mL -1) OA} -Fe 3 O 4NPs to 0.5 mL under the same conditions And deposited on the coated colloid. The process was repeated until the desired number of layers were deposited on the colloidal silica.

Example  2. Colloidal particles / ( Dendrimer / OA - Fe ₃ O _4NPs ) _n / Dendrimer / ( CAT / PAH )

Example 1 (a dendrimer _{/ OA-Fe 3 O 4NPs)} n / dendritic polymer multilayer-coated on the SiO ₂ colloid electrostatic type multi-layer of CAT / PAH prepared is deposited from an aqueous solution. For this method, the concentration of CAT and PAH is 1 mg · mL ^-1 . The CAT was obtained from cattle liver.

Example  3. Colloidal particles / ( Dendrimer / OA - Fe ₃ O _4NPs ) _n / Dendrimer / ( PAA / DMAP - Au _NPs ) Formation of

Example 1 (a dendrimer _{/ OA-Fe 3 O 4NPs)} n / dendritic polymer multilayer-coated on the SiO ₂ colloid electrostatic type multi-layer of PAA / DMAP-Au _NPs prepared is deposited from an aqueous solution. For this method, the concentration of PAA is 1 mg · mL ^-1 .

Test Example .

How to measure

QCM devices (QCM200, SRS) are used to test the mass of the deposited material after each adsorption step. The resonance frequency of the QCM electrode is about 5 MHz. The adsorbed amount of dendrimer and OA-Fe ₃ O _4NPs , Δ m , is calculated from the change in QCM frequency, Δ F , using the Sauerbrey equation:

[Equation 1]

Here, F ₀ (~5 MHz) is the basic resonance frequency of the crystal, A is the electrode area, and ρ _q , (~2.65 g × cm ^-2 ) and m _q (~2.95 × 10 ¹¹ g × cm ^-2 × s ^-2 ) are the shear rate and density of quartz, respectively.

The above equation can be simplified as follows:

&Quot; (2) "

Δ F (Hz) = 56.6xΔ m A

Where, Δ m _A is a quartz crystal microbalance mass change per unit area of m g × cm ^2.

Vibrational spectroscopic characterization of Au-coated Si substrates was performed using ATR-FTIR spectroscopy (Spectrum 400, Perkin Elmer) in ATR mode.

(Dendrimer _{/ OA-Fe 3 O 4NPs)} n multi-layer of the coated magnetic colloid was measured using a SQUID magnetometer (MPMS5).

Test Example  One. ISLE  Chemical analysis of the reaction

Of OA-Fe it is produced in toluene in diameter from about 5.1 ± 0.5 nm (Fig. 2) ₃ O _4NPs was deposited on the coated poly (amido amine) dendrimers substrate. OA ligand a border loosely on the surface of the Fe ₃ O _4NPs is easily substituted by the dendrimer through ISLE reaction due to the high affinity between the amine group of Fe ₃ O _4NPs and dendrimers. However, the -COO ^- group acts as a chelate ligand bound to Fe via two O atoms or as a monodentate ligand linked to Fe via one O atom.

The ISLE reaction between the OA ligand and the dendrimer is confirmed using Attenuated Total Reflectance (ATR) Fourier Transformation Infrared Spectroscopy (FTIR) (FIG. 3). NH stretching vibration (3300 cm ^-1 ) and NH bending vibration (1550 and 1650 cm ^-1 ) of the amine group, C═O stretching vibration (1740 cm ^-1 ) of OA ligand including carboxylic acid group and long aliphatic chain, and CH stretching vibrations (2850 and 2927 cm ^-1 ) are observed by OA-Fe ₃ O _4NPs and dendrimers. Therefore, the two absorption peaks due to C = O stretching and NH bending are due to the substrate / (dendrimer / OAFe ₃ O _4NPs ) ₁ .

The absorption peak intensity of C = O stretching (1740 cm ^-1 ) and CH stretching (2850 and 2927 cm ^-1 ) _originating in the OA ligand, when depositing a dendrimer layer on the film coated with OA-Fe ₃ O 4 _NPs , ≪ / RTI > This phenomenon means that the OA ligand is replaced by the dendritic layer on the surface of the upper Fe ₃ O ₄ layer when the outer layer is exchanged from the OA-Fe ₃ O ₄ to the dendritic layer through sequential absorption processes. Next, an absorption band occurs in OA ligand (e. G., C = O stretching and CH stretching) when the outer layers are exchanged in the dendrimer with OA-Fe ₃ O ₄ is observed again.

As a result of the absorption bands for NH bending (1550 and 1650 cm ^-1 ) and NH stretching (3300 cm ^-1 ) due to the absorption of the dendritic layer containing amine groups, the ISLE reaction has been found to be effective for the dendrimer / OA-Fe ₃ O 4 _NPs It is assumed to be the driving force for self-assembly. Thus, the FTIR spectrum _demonstrates that the driving force between the dendrimer and OA-Fe ₃ O 4 _NPs is generated by the ISLE reaction between the OA and the NH ₂ group. In addition, OA-Ag _NPs And TOA-Au _NPs can be self-assembled (LbL) with a polymer containing an amine group using an ISLE reaction (Fig. 4).

Based on these results, 5.1 nm OA-Fe ₃ O _4NPs are deposited on a dendrimer-coated SiO ₂ colloid with a diameter of 585 ± 5 nm and the dendrimer is absorbed by the colloid coated with OA-Fe ₃ O _4NPs .

5A is a graph of particle size and SEM image (n = 1 and 9) of a multilayered SiO ₂ colloid coated with an increasing number of bilayer (n) and (dendrimer / OA-Fe ₃ O _4NPs ) _n (Dendrimer / OA-Fe _{3 4NPs} O) _n multilayered coated colloids in diameter without colloidal aggregation when double layer number (n) is to be increased from 0 to 9 is increased from about 585 ± 5 nm to 691 ± 6 nm.

Figure 5b (dendrimer _{/ OA-Fe 3 O 4NPs)} 9 multilayer as HR-TEM images of the coated SiO ₂ colloid nanocomposites multi-layer (e.g., (dendrimer _{/ OA-Fe 3 O 4NPs)} 9 multi-layer) uniform, and the The dense coating was confirmed using high-resolution transmission electron microscopy (HR-TEM). B of 5b is an enlarged image of A, indicating that it is coated densely on SiO ₂ colloid.

_Although the quantitative density of OA-Fe ₃ O _4NPs on a colloid substrate can not be determined precisely, a flat Au electrode and a quartz crystal microbalance (QCM) have a surface area of about 1.08 × 10 ^-8 cm ² which can be evaluated in the OA-Fe ₃ O _4NPs amount adsorbed on the colloidal 585nm.

The average amount of absorbed OA-Fe ₃ O 4 _NPs calculated using the QCM frequency variation is about 1307 ng · cm ^-2 . _{Given that} the density and volume of 5.1 nm OA-Fe ₃ O 4 _NPs are 5.17 g · cm ^-3 and 6.95 × 10 ^-20 cm ³ , the amount of one NPs is about 3.59 × ^{10 -10} ng. Thus, the number of OA-Fe ₃ O ₄ NPs in a single layer adsorbed on the surface area of 1.08 × 10 ^-8 cm ² and colloid is about 38,900 NPs / SiO ₂ colloid.

Figure 6 is a (dendrimer / OA-Fe ₃ O _4NPs) as QCM data of _n multi-layer, mass frequency change -ΔF a dendritic polymer according to the increase of Number of floors OA-Fe ₃ O _4NPs absorption through QCM Au deposited on a flat electrode Respectively. Dendrimers with OA-Fe ₃ O _4NPs alternating deposition results for each of 13 Hz, each layer -ΔF (~ 230 ng · cm ^-2 of Δm) and 74 Hz in the -ΔF (of ~ 1307 ng · cm ^-2 Δm) are .

Test Example  2. Magnetic properties of iron oxide-based colloids

(Dendrimer / OAFe ₃ O _{4 NPs} ) ₄ The magnetization of the multilayer coated colloids was investigated using a superconducting quantum interference device (SQUID) magnetometer.

The magnetic curves of the multilayer films measured at room temperature ( T = 298K) show no coercive, residual magnetic or magnetic hysteresis suggestive of typical superparamagnetic behavior and are reversible (Figure 7a). At the liquid helium temperature ( T = 5K), the magnetic curves revealed distinct hysteresis phenomena and loops in both the hindered superparamagnetic properties and the two broad directions commonly observed for the magnets of ferromagnets (Fig. 7b). The magnetization temperature of the multilayer coated colloid of dendrimer / OA-Fe ₃ O _{4NPs was measured} at 300 K to 5 K using an applied magnetic field of 150 Oe (FIG. 7C). In the interference temperature, the zero-field-cool (zero-field-cooled, ZFC ) and field-Cool (FC) deviation between the magnetization is about 30K with respect to about 5 nm OA-Fe ₃ O The nanocomposites multi-layer coating to _4NPs to be. The interference temperature of Fe ₃ O _4NPs cut at 5 nm diameter is about 30K. The disturbance temperature of the Fe ₃ O ₄ NPs aggregate migrates to a significantly higher temperature when the discrete aggregate is converted to a 3D NPs aggregate due to the relatively strong dipole interactions between the magnetic moments of the independent particles.

According to this previous result, hinder the dipole interactions between the dendrimer / OA-Fe ₃ O _4NPs multi-layer is to protect the unique magnetic properties of the cut off NPs because the inserted dendritic polymer layer separating the NPs, thus effectively magnetic NPs do.

For colloids coated with alternating layers of an aqueous solution and about 8.4 ± 2.6 nm anion Fe ₃ O 4 _NPs (Figure 8a) synthesized with cationic poly (allylamine hydrochloride) (PAH), the packing density of anion Fe ₃ O 4 _NPs is the same (Fig. 9) due to electrostatic repulsion between water-soluble NPs at charge. As a result, an important magnetization curve for these colloidal particles can not be obtained.

8B and 9, FIG. 8B is a graph showing the temperature correlation between zero-field-cool (ZFC) and field-cool (FC) magnetization of anionic Fe ₃ O 4 _NPs measured at 150 Oe , No obvious cut-off temperature is observed due to the distribution of anions of large size Fe ₃ O _4NPs .

Furthermore, Figure 9a (PAH / anion Fe ₃ O _4NPs) a _first multilayer is SEM image of the coated SiO ₂ colloids, Figure 9b (PAH / anion Fe ₃ O _{4NPs) 3} Multilayer the SEM image of the coated SiO ₂ colloid to be. The self-assembled colloidal (PAH / anion Fe ₃ O _{4NPs) n} multi-layer is made from a 1 mg mL ^-1 and PAH aqueous solution containing 0.2 M NaCl and 2 mg mL ^-1 and negative ions Fe ₃ O ₄ aqueous solution. As shown in FIG. 9B, it can be seen that even when stacked in a multilayer structure, the electrostatic repulsion between negative-charged nanoparticles can not deposit densely.

Test Example  3. Hydrophobic iron oxide The nanoparticle (NPs) layer and  Hydration enzyme colloid

On the basis of the above results, excellent dispersion and multifunctional colloids (for example, enzymes or metal colloids capable of being magnetically induced) are prepared in organic solvents and aqueous solutions. ISLE multilayer coated colloids, but prepared through OA-Fe ₃ O alternating deposition (alternating deposition) of _4NPs (toluene bottom) and the dendrimer (alcohol and) in an organic solvent, the outer dendritic layer [e.g., SiO ₂ / (dendrimer / OA -Fe ₃ O _4NPs ) _n / dendrimer] can be dispersed in an aqueous solution (eg, pH 3 to 10) without colloid agglomeration. This phenomenon is due to amine protonation of the dendrimer, which induces electrostatic repulsion between the colloids that are adjacent in the aqueous solution.

In addition, the electrostatic multilayer can be deposited on an ISLE multilayer coated colloid, which is dispersed in an aqueous solution.

To confirm this, the negative charge catalyzed enzyme (CAT) and positively charged PAH were added to the colloid coated with a dendrimer layer (for example SiO ₂ / (Dendrimer / OAFe ₃ O _{4 NPs} ) ₄ / dendrimer) 9 aqueous solution. 5.6 CATs with isoelectric points are known to have negative charge at pH> 5.6 and positive charge at pH <5.6.

First, electrophoresis experiments were performed to monitor CAT / PAH multilayer growth on ISLE multilayer coated colloids (Fig. 10A) because zeta potential was marked as an indicator of stable growth for electrostatic multilayer films. When the colloid, which is an outer dendrimer layer prepared in an organic solvent, is dispersed in an aqueous solution of pH 9.0, the initial zeta potential of the colloid is about +29.2 ± 0.7 mV. However, when CAT and PAH are alternately adsorbed to the colloid of the dendritic layer, the zeta potential of the anion CAT and the cation PAH stably and uniformly arrives at - 37.3 ± 1.1 mV to + 23.5 ± 1.4 mV, indicating electrostatic multilayer growth went. Uniform adsorption of (CAT / PAH) _{n = 1 to 4} multilayers on the ISLE multilayer coated colloid was confirmed by SEM (Fig. 10B).

Based on the stable growth of the CAT / PAH multilayer, the possibility of colloids coated with ISLE multilayer and electrostatic multilayer was investigated. As shown in FIG. 10C, the ISLE multilayer coated colloids, which are phase shifted into aqueous solution due to the continuous adsorption of the capacitive CAT / PAH multilayer, gather near the portable magnets disposed near the plastic tube. Colloidal responsive to the magnet is the CAT with a ham group (heme groups) including iron, so effective catalyst with respect to H ₂ O ₂ is expected to cause electrical catalysis (electrocatalytic) reaction with H ₂ O _2.

Figure 10d is from 0 to - 0.8 V of the potential relative to the range within the increase in the 50 mV × s ^-1 to 250 mV × s ^-1 scan speed in pH 7.0 phosphate buffered saline ISLE multi-layer coating of colloidal / (CAT / PAH) ₃ and the modified indium tin oxide (ITO) electrode. The catalytic current was greatly increased at increasing scans, which is characteristic of electrocatalytic reduction processes. The ITO electrode showed no current response within the potential range.

Ham iron (heme) CAT (e.g., CAT-Fe ^III) has been reported from the ham porphine ^{[(CAT-Fe IV = O} ) ^and] H ₂ O ₂ with a reactive oxidizing agent containing a cation radical. Next (CATFe ^IV = O) ^and i is the oxidation of the H ₂ O ₂ occurred receives an electron from H ₂ O ₂ as a radical compound [(CATFe ^IV = O) ^and - form. I radical compounds can accept secondary electrons by rebuilding iron ham CAT. Catalyst H ₂ O ₂ ^and of the current (CATFe ^IV = O) Is determined by the decrease. However, all CAT / PAH multilayer domains deposited on magnetic colloids are not electrochemically activated due to limited electron transfer distance between the CAT molecules and the electrode surface. Thus, it was concluded that the electrocatalytic reaction of the enzyme and the magnetic colloid was due to the multiple layers of CAT near the electrodes. These results show that the combination of hydrophobic and hydrophilic multilayer with different functions can provide a desired multifunctionality and design for the colloid.

Test Example  4. Magnetic Plasmon  Hydration colloid with resonance characteristics

Between the organic solvent and the aqueous solution, a noble metal NPs-coated colloid showing a magnetic reaction capable of reversible phase transfer.

Cationic Au _NPs (DMAPAu _NPs ) stabilized by a 4-dimethylaminopyridine (DMAP) ligand, which displays a surface plasmon absorption peak at 520 nm, has a dendrimer layer [ ie SiO ₂ / (dendrimer / OA- (Acrylic acid) (PAA) of pH 4 in a colloid coated with an aqueous solution of anionic poly (acrylic acid) (Fe ₃ O 4 _NPs ) _4.5 / dendrimer]. Similar to the (CAT / PAH) _n multilayer coated colloid shown in Figure 10a, this colloid exhibits a zeta potential that is regularly changed from -15.2 ± 1.1 mV to +32.9 ± 1.8 mV for PAA and DMAP-Au _NPs , Au _NPs are alternately deposited on the dendrimer coated colloid (Figure 11).

Electrostatic PAA / DMAP-Au _NPs multilayer (dendrimer / OAFe ₃ O 4 _NPs ) _4.5 / dendrimer The method deposited on the coated colloid produces a more rigid structure without inducing colloid aggregation (FIG. 12A). In addition, the number of PAA / DMAP-Au _NPs bilayers increased from 1 to 5, and the surface plasmon absorption peak became clear due to DMAP-Au _NPs , especially red at 590 nm (FIG. 12B). In addition, the resulting colloid is strongly influenced by the external magnetic field due to the OA-Fe ₃ O _{4 NPs} layer beneath the multiple layers of DMAP-Au _NPs (FIG. 12C).

In addition, the possibility of phase agreement in hydrated colloids with magnetic and metallic properties returned to the organic phase was investigated. The dendrimer layer is adsorbed on the colloid coated with the DMAP-Au _NPs layer in the outer solvent in the ethanol solvent. Next, OA-Fe ₃ O _4NPs was continuously deposited on said dendritic polymer is deposited colloidal using ISLE induced layer self-assembly in a toluene solvent. The resulting colloid showed high dispersion stability of the multifunctional colloid in toluene (Figure 12d).

In particular, various hydrophobic NPs including OA-stabilized transition metal oxides such as OA-Fe ₃ O ₄ NPs and OA- or TOA-stabilized metal NPs can be efficiently applied. TOA-metal NPs dispersed in toluene can be deposited on dendrimer-coated colloids due to the high binding energy between the primary amine groups and metal NPs similar to the ISLE reaction between the dendrimer and OA-Fe ₃ O ₄ NPs. (Dendrimer / TOAAu _NPs ) _{n For} multi-layered colloids, this colloid exhibits a highly protruding surface structure leading to a dense surface area of the TOA-Au _NPs layer when the number of bilayers (n) increases from 1 to 7 13).

Also, as noted above, colloids can be well dispersed in aqueous solutions when the dendrimer layer is coated on the outside. Demonstrates that easy integration of hydrophobic and hydrophilic multilayers can be used to significantly improve the function of colloids, which can perform reversible phase transfer of colloidal functionality integrated and broaden their potential application range.

In conclusion, we hydrophobic multi-layer [e.g., (dendrimer / OAFe ₃ O _{4NPs) n]} and the capacitive multi-layer [e.g., (CAT / PAH) _n or _{(PAH / DMAP-Au NPs)} n] is coated with a functional colloid Can be successfully prepared using an ISLE-induced electrostatic self-assembly method. Importantly, the function of the colloid can be easily made and integrated using the advantages of hydrophobic (e.g., ISLE-induced) and hydrophilic (e.g., electrostatic) layered self-assembly. This is capable of reversible phase transfer in a lighter environment than conventional methods reported by other research groups and proves effective in the preparation of functional colloids. These multifunctional colloids can be widely used in many applications, such as catalysts, sensors and optical guides, regardless of the type of solvent.

Claims (19)

(a) a substance in the form of a substrate or a particle, and
(b) a plurality of coating layers alternately stacked on the surface of the substrate or on the surface of the particle-like material, (b1) a polymer coating layer comprising an amine group, and (b2) a metallic coating layer combined with a hydrophobic stabilizer
A reversible phase-shiftable multi-functional material,
The metal-based coating layer is a metal coating layer or a metal oxide coating layer,
Wherein the reversible phase-shiftable multi-functional material is formed by layer-self-assembly of the polymer coating layer and the metal-based coating layer. The reversible phase-shiftable multi-functional material according to claim 1, wherein the outermost layer of the reversible phase-shiftable multi-functional material is a polymer coating layer comprising the amine group (b1). 3. The reversibly phase-shiftable multi-functional material according to claim 1 or 2, wherein the polymer is a dendrimer. The reversibly phase-shiftable multi-functional material according to claim 1, wherein the polymer layer comprises a polymer selected from the group consisting of polyamidoamine, polyethyleneimine, and mixtures thereof. The method of claim 1, wherein the metal or metal oxide layer is a metal or metal oxide selected from the group consisting of silver, gold, platinum, iron, iron oxide, manganese oxide, barium, barium oxide, titanium, titanium oxide, Functional material capable of reversibly phase-shifting. The reversible phase-shiftable multi-functional material according to claim 1, further comprising an electrostatic multilayer on the polymer coating layer when the outermost layer of the multi-functional material is a polymer coating layer. [7] The reversible phase-shiftable multi-functional material according to claim 6, wherein the electrostatic multi-layer is a multi-layer structure in which a negative charge CAT enzyme layer and a positive charge polymer layer are alternately laminated at least one time. [7] The reversible phase-shiftable multi-functional material according to claim 6, wherein the electrostatic multilayer is a multi-layer structure in which a negative charge polymer layer and a positively charged noble metal layer are alternately laminated at least one time. The method of claim 7, wherein the positively charged polymer layer is at least one selected from the group consisting of polyallylamine hydrochloride (PAH), polyethyleneimine (PEI), and polydiallyldimethylammonium chloride (PDADMAC) This is a versatile material. The reversible phase-shiftable multi-functional material according to claim 8, wherein the negative charge polymer layer is a polyacrylic acid (PAA). The reversible phase-shiftable multi-functional substance according to claim 8, wherein the noble metal is selected from the group consisting of silver, gold, platinum and mixtures thereof. (I) a polymer coating layer comprising an amine group and (ii) a metal-based coating layer in combination with a hydrophobic stabilizer, on the surface of the substrate or on the surface of the material in the form of particles in the form of a reversibly phase-shiftable multifunctional material As a method,
Wherein the polymer coating layer and the metal coating layer are formed in a layered self-assembly manner in the reversible phase-
Wherein the reversible phase-shiftable multifunctional material comprises at least one of (i) a polymer coating layer comprising an amine group and (ii) a metal-based coating layer combined with the hydrophobic stabilizer,
Wherein the outermost layer of the reversibly phase-shiftable multi-functional material is (i) a polymer coating layer comprising an amine group,
Wherein the metal-based coating layer is a metal coating layer or a metal oxide coating layer. 13. The method of claim 12, wherein the hydrophobic stabilizer is oleic acid, oleylamine, palmitic acid, tetraoctylammonium bromide, or a mixture thereof. 13. The method of claim 12, wherein the hydrophobic stabilizer has a functional group selected from a carboxyl group, a carboxylic acid salt, an ammonium group, or an ammonium salt. 13. The method of claim 12, wherein the coating layer comprises (i) a polymer comprising an amine group; And (ii) the coating is alternately repeated one to ten times with a metal-based coating layer combined with the hydrophobic stabilizer. 13. The method of claim 12, further comprising coating an electrostatic multilayer on the top surface of the outermost layer. 17. The method of claim 16, wherein the electrostatic multi-layer is a multi-layer, wherein the negative charge CAT enzyme coating and the positive charge polymer coating are coated alternately at least once each. 17. The method of claim 16, wherein the electrostatic multilayer is a multi-layer structure wherein the negative charge polymer coating and the positive charge noble metal coating are alternately coated at least one time. 19. The method of any one of claims 12 to 18, wherein the polymer is a dendrimer.

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