KR101792663B1 - Composite of block copolymer and graphene quantum dots, producing method of the same and sensors comprising the same - Google Patents

Abstract

The present invention relates to a composite of a block copolymer and graphene quantum dots, a manufacturing method thereof and a sensor comprising the same and, more specifically, to a composite of a block copolymer and graphene quantum dots, capable of reversibly and stably responding to the temperature, pH and various metal ions at the same time and easily responding with excellent optical properties by synthesizing a stimuli-responsive block copolymer, a chain transfer agent and graphene quantum dots into a composite, to a manufacturing method thereof and to a sensor comprising the same.

Description

[0001] The present invention relates to a composite of a block copolymer and a graphene quantum dot, a method for producing the same, and a sensor including the copolymer and a graphene quantum dot,

The present invention relates to a complex of a block copolymer and a graphene quantum dot, a method for producing the same, and a sensor including the block copolymer. More particularly, the present invention relates to a composite of a block copolymer, a chain transfer agent and a graphene quantum dot A block copolymer and a graphene quantum dot, a method of manufacturing the same, and a sensor including the same.

Fluorescent materials, ranging from optical devices to chemical and biosensors, have received attention for application in numerous applications. In particular, a fluorescent multifunctional sensor that simultaneously responds to different stimuli is of interest because it can easily detect various stimuli in a complex environment. In general, the sensors operate in unison with different reactants (e.g., low molecular weight, polymeric or inorganic particles involved in stimulus-response) within a single platform.

However, the conventional sensor has a complicated production process, takes a lot of time and cost, and is problematic when the sensor material itself is toxic. In addition, a number of functional sensors based on low molecular weight and high molecular weight polymers have a limited ability to disperse in an aqueous solution medium and are limited in applications in the biotechnology field and the environment, and most fluorescence sensors have stimuli due to a change in photoluminescence (PL) There is a problem in that a costly light emitting (PL) detector is required in order to confirm the efficiency of the response.

Graphene Quantum Dots (GQDs), nano-sized graphene derivatives, have excellent optical properties due to quantum confinement and edge effects. The graphene quantum dot is a good candidate for a multi-sensing platform due to its tunable luminescent properties depending on particle size, pH or the presence of metal ions. In addition, the surface of the graphene quantum dot has an oxygen-containing group, which is excellent in solubility in water, and the functional group serves as a reactive site for surface modification. Despite the advantages of the graphene quantum dot as described above, there is still a need for further studies to improve various practical limitations for practical application of the graphene quantum dot.

Korean Patent No. 10-1339403

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a composite of a block copolymer and a graphene quantum dot capable of simultaneously detecting temperature, pH and various metal ions by synthesizing a graphene quantum dot and a block copolymer, And a sensor including the same.

The present invention relates to a method for producing a magnetic recording medium which comprises graphene quantum dots (GQDs), a chain transfer agent bound to the graphene quantum dots, a stimulus-sensitive polymer synthesized from the chain transfer agent, And a complex of graphene quantum dot and a block copolymer including a fluorescent polymer.

Further, the fluorescent polymer is P7AC.

The stimulus-responsive polymer may be selected from the group consisting of poly N-isopropylacrylamide (PNIPAAm), poly [2- (dimethylamino) ethyl methacrylate], poly [2- ), Poly (N, N-dimethylacrylamide), poly (N, N-diethylacrylamide), poly (N, N-diethylacrylamide), poly (vinylcaprolactame), polyethylene oxide, poly (vinylmethylether), polyhydroxyethylmethacrylate For example, polyhydroxyethylmethacrylate, poly (pentapeptide), poly (N- (3-aminopropyl) methacrylamide hydrochloride)), polyethylene (polyethylene) , Polymethylmethacrylate, and polypropylene. ≪ RTI ID = 0.0 > It characterized in that it comprises at least one emitter which is selected.

The chain transfer agent is also characterized in that it contains a dithiocarbonate or trithiocarbonate moiety.

The complex may be characterized by being responsive to at least one selected from the group consisting of temperature, pH, and metal ion.

The metal ions include at least one selected from the group consisting of Ag ²⁺ , Cd ⁺ , Au ³⁺ , Sn ²⁺ , Cu ²⁺ , Pb ²⁺ , Cr ³⁺ , Fe ³⁺ and Pd ²⁺ .

The present invention also relates to a method for preparing a polymer, which comprises the steps of (S1) preparing a mixture through a coupling reaction by dissolving a graphene quantum dot and a chain transfer agent, and adding a polymeric monomer and a free radical initiator to the mixture And a step (S3) of performing a polymerization reaction by adding a fluorescent radical monomer and a free radical initiator after the polymerization reaction in the step (S2) and the step (S2), and a process for producing a complex of a graphene quantum dot .

The present invention also provides a temperature sensitive sensor including the composite produced by the above production method.

In addition, a pH-sensitive sensor including the complex produced by the above production method is provided.

The present invention also provides a metal ion sensitive sensor including the composite produced by the above production method.

As described above, the complex of the block copolymer and the graphene quantum dot according to the present invention, the method for producing the same, and the sensor including the block copolymer have the effect of reversibly and stably sensing temperature, pH and various metal ions simultaneously.

In addition, the present invention has the effect of easily sensing temperature, pH, and various metal ions due to fluorescence color change that is visually recognized.

In addition, the sensor based on the graphene quantum dot of the present invention can be applied to various sensors depending on molecules to be grafted, and is also applicable to various fields such as optical, environmental, and bio.

1 is a schematic diagram of a complex of a block copolymer and a graphene quantum dot according to the present invention.
Fig. 2 is an illustration showing a method of synthesizing a complex of a block copolymer and a graphene quantum dot according to the present invention.
3 is a TGA curve for GQDs, RAFT-GQDs, PNIPAAm-GQDs, and bcp-GQDs.
FIG. 4A is an ATR-FTIR spectrum for GQDs, RAFT-GQDs, PNIPAAm-GQDs and bcp-GQDs. FIG. 4B shows IR spectra of PNIPAAm-GQDs and bcp-GQDs at 1,500 to 1,770 cm ^-1 . FIG. 4 (c) is the S 2p XPS spectrum for GQDs, RAFT-GQDs, PNIPAAm-GQDs and bcp-GQDs.
Figure 5 is a PL spectra and fluorescence image of GQD (a), RAFT-GQD (b), PNIPAAm-GQD (c) and bcp-GQD (d) for water at 365 nm UV.
Figure 6 is an excitation-dependent PL spectrum of a complex (bcp-GQDs) of a block copolymer and a graphene quantum dot in water according to the present invention.
7 is TEM and AFM images of GQDs (a, d), RAFT-GQDs (b, e), and bcp-GQDs (c, f).
FIG. 8 (a) is a PL spectrum for the temperature change of the complex (bcp-GQDs) of the block copolymer and graphene quantum dot according to the present invention, and FIG. 8 (b) And the graphene quantum dot complex (bcp-GQDs).
9 (a) is a graph showing the reversibility of fluorescence attenuation of a complex (bcp-GQDs) of a block copolymer and a graphene quantum dot according to the present invention between 25 and 40 ° C. FIG. 9 (b) (Bcp-GQDs) of graphene quantum dots (GQDs) and block copolymers and graphene quantum dots according to the present invention.
10 is a graph showing the reversibility of fluorescence lifetime (410 nm emission peak) of a complex (bcp-GQDs) of a block copolymer and a graphene quantum dot according to the present invention at 25 to 40 ° C.
11 (a) is a graph showing a PL intensity ratio of a complex (bcp-GQDs) of a block copolymer of the present invention and a graphene quantum dot according to pH value, and Fig. 11 (b) (Bcp-GQDs) of the block copolymer and graphene quantum dot of the present invention.
12 is a PL spectrum of a complex (bcp-GQDs) of a block copolymer and a graphene quantum dot according to the present invention dissolved in water according to temperature and pH conditions.
13 (a) is for the Cu ^{2 +} and Fe ^{3 +} of 100 μM And the PL spectra of the complex (bcp-GQDs) of the block copolymer and the graphene quantum dots of the present invention, and FIG. 13 (b) is 100 μM for metal ions (Ag ^2+, Cd ^+, Au ^{+ 3,} Sn ^{+ 2,} Cu ^{2 +, Pb 2 +, Cr} 3 +, Fe 3 + , and a graph showing the ratio of PL intensity for the Pd ^{+ 2),} FIG. 13 (c) is for the concentration of Fe ^{3 +} And the PL spectra of the complex (bcp-GQDs) of the block copolymer and the graphene quantum dots of the present invention, and FIG. 13 (d) is for the concentration of Fe ^{3 +} (I _{505 nm} / I _{410 nm} ) of the PL intensity of the complex (bcp-GQDs) of the block copolymer and graphene quantum dot of the present invention.
14 is a fluorescence decay graph of graphene quantum dots in a complex (bcp-GQDs) of a block copolymer and a graphene quantum dot of the present invention depending on the presence or absence of a metal ion (Fe ^{3 +} ).
15 is a temperature, metal ions, pH, and ^{100 μM (Cd +, Cu 2} +, Cr 3 +, Fe 3 +) in accordance with I ₅₀₅ of the composite (bcp-GQDs) of the block copolymer and the graphene quantum dots of the present invention _nm / I _{410 nm} graph.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The term " step "or" step of ~ " used throughout the specification does not mean "step for. Throughout this specification, the terms "A and / or B" mean "A or B, or A and B ".

Throughout this specification, the term "combination thereof" included in the expression of the machine form means one or more combinations or combinations selected from the group consisting of the constituents described in the expression of the machine form, And the like.

DISCLOSURE OF THE INVENTION The present invention has been accomplished in order to achieve the above technical object and as a result, it has been found that a method for producing a complex of a block copolymer and a graphene quantum dot has been developed, and a block copolymer and a block copolymer Pin quantum dot is reversibly and stably susceptible to temperature, pH and various metal ions at the same time, and can be easily sensitized with excellent optical properties, thereby completing the present invention.

Hereinafter, the present invention will be described in detail.

1 is a schematic diagram of a complex of a block copolymer and a graphene quantum dot according to the present invention.

As shown in FIG. 1, the complex of the block copolymer and the graphene quantum dot of the present invention includes graphene quantum dots (GQDs), a chain transfer agent bound to the graphene quantum dots, And a fluorescent polymer synthesized from a polymer surface growth method (grafting from) of the stimulus sensitive type polymer, wherein the graphene quantum dot has green fluorescence And the fluorescent polymer comprises P7AC (poly (7- (acryloyloxy) butoxy) coumarin), which expresses blue fluorescence. More specifically, the fluorescent polymer includes poly-7- (4- Coumarin dyes, Fluorone dyes, Oxazine dyes, Phenanthridine dyes, Cyanine dyes, and the like, which contain anthraquinone, And roda Comprising at least one selected from the group consisting of dye (Rhodamine dyes), but not always limited thereto.

The stimuli-sensitive polymer may be selected from the group consisting of poly (N-isopropylacrylamide), poly [2- (dimethylamino) ethyl methacrylate], poly [ (N, N-dimethylacrylamide), poly (N, N-dimethylacrylamide), poly (N, N-dimethylacrylamide) (N, N-diethylacrylamide), poly (vinylcaprolactame), polyethylene oxide, poly (vinylmethylether), poly Poly (hydroxyethyl methacrylate), poly (pentapeptide), poly (N- (3-aminopropyl) methacrylamide hydrochloride) ), Polyethylene, polymethylmethacrylate, and polypropylene. , But is not limited thereto.

The block copolymer (bcp) of the present invention is a combination of a stimulus-sensitive polymer and a fluorescent polymer. More specifically, a block copolymer (bcp) isopropylacrylamide polymer (P7AC-b-PNIPAAm polymer).

In addition, the chain transfer agent is for binding a block copolymer to a graphene quantum dot, and includes a dithiocarbonate or trithiocarbonate moiety, A trithiocarbonate chain transfer agent may be used. In particular, the chain transfer agent may be a reversible addition-fragmentation chain transfer agent such as tricyclodecanone, (RAFT) reagent (trithiocarbonate RAFT agent).

The amount of the blue light emitted from the block copolymer (P7AC-b-PNIPAAm) and the amount of green light emitted from the graphene quantum dot are controlled by the complex of the block copolymer and the graphene quantum dot of the present invention, Color change can be detected. That is, the fluorescence resonance energy transfer (FRET) between the block copolymer expressing the blue fluorescence and the graphene quantum dot expressing the blue fluorescence depends on the separation distance between the block copolymer and the blue fluorescence, By using the characteristics of the block copolymer to be reacted, it is possible to detect the color change according to the temperature change, and thus it can be applied to the change of pH and the response of various metal ions.

Wherein the metal ion comprises at least one selected from the group consisting of Ag ^{2 +} , Cd ⁺ , Au ^{3 +} , Sn ^{2 +} , Cu ^{2 +} , Pb ^{2 +} , Cr ^{3 +} , Fe ^{3 +} and Pd ^{2 +} But is not limited thereto.

A method for producing a complex of a block copolymer and a graphene quantum dot according to the present invention will be described with reference to the accompanying drawings.

Fig. 2 is an illustration showing a method of synthesizing a complex of a block copolymer and a graphene quantum dot according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The method for producing a complex of a block copolymer and a graphene quantum dot of the present invention includes, but is not limited to, the following steps.

The present invention relates to a method for preparing a polymer, comprising the steps of: (S1) preparing a mixture through a coupling reaction by dissolving a graphene quantum dot and a chain transfer agent; and adding a polymeric monomer and a free radical initiator to the mixture (S2) and a step (S3) of adding a fluorescent polymer monomer and a free radical initiator after the polymerization reaction in the step (S2) to perform a polymerization reaction (S3), and a method for producing a complex of a graphene quantum dot.

The manufacturing method of the present invention will be described separately for each step.

A step (S1) of dissolving the graphene quantum dot and a chain transfer agent to prepare a mixture through a coupling reaction is performed.

The step (S1) is a step of binding a chain transfer agent to the graphene quantum dot, wherein the chain transfer agent comprises a dithiocarbonate or trithiocarbonate functional group A chain transfer agent such as a trithiocarbonate chain transfer agent may be used. In particular, the chain transfer agent may be a reversible addition-trisiocarbonate- fragmentation chain transfer (RAFT) reagent (trithiocarbonate RAFT agent).

Coupling reaction is performed by adding graphene quantum dots, trithiocarbonate RAFT reagent, N, N'-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) to an organic solvent tetrahydrofuran (THF) It is dissolved at 20 ~ 30 ℃ for 12 ~ 24 hours. The coupling reaction means an esterification reaction using DCC (N, N'-dicyclohexylcarbodiimide) and DMAP (4-dimethylaminopyridine). The dissolved mixture is centrifuged at 5,000 to 15,000 rpm for 10 to 30 minutes in a centrifuge to obtain a precipitate, which is washed several times with diethyl ether. The washed product is vacuum dried and redispersed in dimethylformamide (DMF). The redispersed product is filtered with a 0.2-0.6 mu m polyvinylidene fluoride (PVDF) syringe filter to obtain a solution of RAFT-GQDs.

(S2) of adding a polymer monomer and a free radical initiator to the mixture to perform a polymerization reaction.

The mixture of the step (S2) means a mixed solution containing the RAFT-GQDs finally obtained in the step (S1). In step (S2), PNIPAAm is synthesized by RAFT-GQDs. RAFT-GQDs, NIPAAm (N-isopropylacrylamide) monomer and free radical initiator are added to DMF and dissolved. Place the dissolved mixture in a glass ampoule. The living radical polymerization reaction is performed at 50 to 70 ° C for 10 to 16 hours, and when the polymerization reaction is completed, precipitated PNIPAAm-GQDs are obtained. The PNIPAAm-GQDs are washed 2 to 5 times with cold diethyl ether and vacuum dried.

After the polymerization reaction in the step (S2), a fluorescent polymer monomer and a free radical initiator are added to perform a polymerization reaction (S3).

(Bcp-GQDs) of the block copolymer of the present invention and the graphene quantum dots, wherein the step (S3) is a step of mixing the DMAP with the PNIPAAm-GQDs obtained after the polymerization in the step (S2) (7- (4- (acryloyloxy) butoxy) coumarin) monomer and a free radical initiator are added to dissolve and the mixture dissolved in a vacuum for living radical polymerization reaction is put into a glass ampoule. The living radical polymerization reaction is carried out at 50 to 70 ° C for 10 to 16 hours, and when the polymerization reaction is completed, precipitated bcp-GQDs are obtained. The bcp-GQDs are washed 2 to 5 times with cold diethyl ether and vacuum dried.

The free radical initiator of step (S2) and step (S3) refers to a thermal initiator, and the thermal initiator may have a 10-hour half-life temperature of 70 占 폚 or lower, preferably 60 占 폚 or lower, more preferably 50 占 폚 or lower. On the other hand, in the present invention, the lower limit of the 10-hour half-life temperature of the thermal initiator is not particularly limited. However, if the 10-hour half-life temperature is too low, a photopolymerizable resin which does not initiate radical reaction may exist and cause a non-uniform curing reaction. Therefore, the half-life temperature can be appropriately controlled within a range of 30 占 폚 or more. By setting the half-life temperature of the thermal initiator to 70 占 폚 or less, the heat of reaction is kept low and the consumption of the thermal initiator is started at a relatively low temperature, so that the initiation is terminated relatively fast so that a photopolymerizable resin of the polymer can be formed in a short time do.

Further, the thermal initiator is characterized by being capable of absorbing ultraviolet rays. A thermal initiator capable of absorbing ultraviolet radiation can form radicals by ultraviolet absorption differently from general thermal initiators that form radicals by heat. The thermal initiator capable of absorbing ultraviolet rays can be used for photopolymerization under a mild condition as compared with a general thermal initiator since ultraviolet light can be absorbed in a wavelength range of 300 to 400 nm which is mainly used in a light polymerization condition under a mild condition as compared with a general thermal initiator. Therefore, even if the 10-hour half-life temperature of the general thermal initiator is maintained at 70 캜 or lower, the polymerization can be performed variously in the case of using a photopolymerization initiator capable of absorbing ultraviolet light maintaining the half-life temperature, It is advantageous in that polymerization under mild conditions is possible.

Specifically, the thermal initiator is an azo compound, and the azo compound is 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile) Azobis (4-methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 2,2'-azobis [2 (2-imidazolin-2-yl) propane] dihydrochloride and 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate. Can be used. A thermal initiator having a 10-hour half-life temperature of 70 ° C or lower can be formed using at least one selected from the azo-based compounds, and the above effect can be exhibited by limiting the half-life.

The complex of the block copolymer and the graphene quantum dot obtained after the completion of the step (S3) can be applied as a temperature sensitive sensor, a pH sensitive sensor or a metal ion sensitive sensor.

Hereinafter, embodiments of the present invention will be described in detail.

The following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

<Material>

Vulcan CX-72 carbon black was purchased from Cabot Corporation. Potassium carbonate anhydrate (K ₂ CO ₃ , 99.5%), magnesium sulfate (MgSO ₄ , 99%), sodium hydroxide (NaOH powder, 98%) and hydrochloric acid (HCl, 10 M) Azobisisobutyronitrile (AIBN, 98%) was purchased from Junsei and purified by recrystallization from ethanol. 7-Hydroxy coumarin and other reagents were purchased from Sigma-Aldrich and N-isopropylacrylamide (NIPAAm, 99%) was purified by recrystallization with hexane. Distilled water (DI) was used in all experiments.

< Example  1 > 7- (4- ( Acryloyloxy ) butoxy ) coumarin  ( 7AC ) Synthesis of

Methods for the synthesis of 7AC monomers are known in the prior art (Yang, H. et al ., Nanoscale 2013, 5, 5720-5024, Feng, P. et al ., Polymer 2007, 48, 5859-5866).

Potassium carbonate anhydride (3.48 g, 24.8 mmol) was added to a mixture of 7-hydroxy coumarin (2 g, 12.4 mmol) and 1,4-dibromobutane (4.42 mL, 37.2 mmol) in acetone (120 mL) And then refluxed for 24 hours. The precipitate formed after refluxing was filtered and the solvent was removed. The filtered product was diluted with diethyl ether, and the separated organic layer was washed with distilled water and concentrated under reduced pressure with drying over magnesium sulfate. The reduced pressure concentrate was purified by column chromatography using silica gel, a mixture of hexane and ethyl acetate (eluent, eluent) to give 7- (4-bromobutoxy) -coumarin. Then, 7- (4-bromobutoxy) -coumarin (2.38 g, 9 mmol) and excess sodium acrylate (1.128 g, 12 mmol) were dissolved in ethanol (150 mL). Hydroquinone (0.02 g, 1.8 mmol) was added to the dissolved mixture and refluxed for 36 hours. The precipitate formed after refluxing was filtered and washed with ethanol. After the solvent was removed under reduced pressure, distilled water was added and extracted with diethyl ether. The extracted product was purified by column chromatography using silica gel and a mixture of hexane and ethyl acetate (eluent, eluent) to obtain a white 7AC (1.4 g, 61%) solid. ¹ H NMR data of 7AC is as follows.

^{1 H NMR (CDCl3): 7.62} (d, 1H), 7.34 (d, 1H), 6.80 (m, 2H), 6.41 (d, 1H), 6.24 (m, 1H), 6.11 (m, 1H), 5.81 (m, IH), 4.23 (s, 2H), 4.04 (s, 2H), 1.90 (s, 2H), 1.55 (s, 2H).

< Example  2> Trithiocarbonate  Synthesis of RAFT Chain Transfer Agent

(2 - ((butylsulfanyl) -carbonothioyl) sulfanyl)) - propanoic acid was synthesized by improving the prior art (Yang, H. et al ., Nanoscale 2013, 5, 5720-5024, Lim, J. et al . , J. Polym. Sci., Part A: Polym. Chem., 2011, 49, 3464-3474).

An aqueous sodium hydroxide solution (50%, 16.0 g) was added to a mixture of butanethiol (18.0 g, 200 mmol) and distilled water (30 mL) and acetone (10 mL) was further added to make a colorless solution. The solution was stirred at room temperature for 30 minutes. To the stirred solution was added carbon disulfide (14 mL, 17.6 g, 231 mmol) to obtain an orange solution. The solution was stirred for 30 minutes and then cooled in an ice bath. 2-Bromopropionic acid (31.4 g, 205 mmol) was then added dropwise to the cooled solution, and an aqueous sodium hydroxide solution (50%, 16.0 g) was further added. At this time, the container temperature was kept below 30 ° C to control the reaction. When the reaction (exothermic reaction) was completed, distilled water (30 mL) was added, and the mixture was stirred at room temperature for 24 hours. The stirred reaction mixture was diluted with water (50 mL). Then 10 M HCl _(aq) (60 mL) was added to the reaction mixture solution in an ice bath. At this time, a yellow oil was obtained, which was stored in an ice bath until the oil solidified. The solidified oil was separated by filtration, washing (using cold water) and drying. The separated product was recrystallized with hexane with gentle stirring to give light yellow solid crystals (34.8 g, 71.2%). The ¹ H NMR data of the light yellow solid crystal is as follows.

2H), 1.64 (m, 2H), 1.64 (d, 3H), 1.42 (d, 2H) 1.49 (m, 2 H), 0.94 (t, 3 H).

< Example  3> Grapina Of quantum dots (GQDs)  synthesis

GQDs were synthesized through chemical oxidation (Yang, H. et al ., ACS Macro Lett., 2014, 3, 985-990, Dong, YQ et al ., J. Mater. Chem. 2012, 22, 8764-8766) . Briefly, carbon black (1 g) was added to a mixture of nitric acid (100 mL) and distilled water (150 mL) and refluxed for 48 hours. The refluxed solution was cooled to room temperature and centrifuged at 6,000 rpm for 20 minutes. The supernatant obtained after the centrifugation was heated to obtain a reddish brown powder. The reddish brown powders (GQDs) were redispersed in tetrahydrofuran (THF) and filtered through an ultrafilter through a 0.22 μm microporous membrane, resulting in fluorescent GQDs.

< Example  4 > P7AC -b- PNIPAAm  Block copolymer (bcp) - Grapina  The complex of quantum dots (GQDs) (bcp- GQDs ) Synthesis of

The synthesis of the complex (bcp-GQDs) of P7AC-b-PNIPAAm block copolymer (bcp) -graffine quantum dot (GQDs) according to the present invention is as follows.

The trithiocarbonate RAFT agent (0.5 g, 2.1 mmol) obtained in Example 2, GQDs (0.1 g) obtained in Example 3, DCC (10 mg, 0.05 mmol) and 4-dimethylaminopyridine , 1 mg, 0.01 mmol) were mixed in THF overnight (room temperature conditions). The mixture was then precipitated with diethyl ether and centrifuged several times at 10,000 rpm for 20 minutes. The product obtained after centrifugation was vacuum dried, re-dispersed with dimethylformamide (DMF), and filtered with a 0.45 μm PVDF syringe filter to obtain a RAFT-GQDs solution.

The RAFT-GQDs solution (100 mg), NIPAAm monomer (0.5 g, 4.4 mmol) and AIBN (6 μmol) were dissolved in DMF (5 mL) and dissolved in a glass ampoule Was added. The polymerization reaction was carried out at 65 ° C for 12 hours. The polymerized product was precipitated twice with cold diethyl ether and vacuum dried to give a solution of PNIPAAm-GQDs.

The above PNIPAAm-GQDs solution (0.1 g), the 7AC monomer obtained in Example 1 (65 mg, 0.23 mmol) and AIBN (0.5 mg, 4 mol) were dissolved in DMF (5 mL) and dissolved in a vacuum , The dissolved product was introduced into a glass ampoule. The polymerization reaction was carried out at 65 ° C for 12 hours. The polymerized product was precipitated twice with cold diethyl ether and vacuum dried to obtain a complex (bcp-GQDs) of the P7AC-b-PNIPAAm block copolymer (bcp) -graffine quantum dot (GQDs) Respectively.

<Results and Discussion>

As shown in FIG. 2, the synthesis of the complex (bcp-GQDs) of the P7AC-b-PNIPAAm block copolymer (bcp) -graffine quantum dot (GQDs) of the present invention is illustrated. P7AC-b-PNIPAAm block copolymer (bcp) expressing blue fluorescence is synthesized using Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. First, a trithiocarbonate RAFT chain transfer agent is prepared by dissolving N, N'-dicyclohexylcarbodiimide (DCC) between the hydroxyl group of the surface of graphene quantum dots and the carboxyl group of the threthiocarbonate RAFT chain- ) Coupling reaction was carried out by covalent bonding to the surface of the graphene quantum dot to obtain grafting quantum dots (RAFT-GQDs) to which the tricyanocarbonate RAFT was bonded.

The RAFT-graphene quantum dot was repeatedly subjected to precipitation, centrifugation and filtration to completely remove uncrosslinked RAFT reagents and other chemical moieties.

The PNIPAAm block is then polymerized from the RAFT-graphene quantum dot, and the P7AC block, which is then blue-fluorescent, is also polymerized to form the P7AC-b-PNIPAAm block copolymer (bcp) -grape quantum dot ) (Bcp-GQDs) are synthesized.

The molecular weight of the PNIPAAm block is one of the most important factors for determining the separation distance between the P7AC-b-PNIPAAm block copolymer (bcp) and the graphene quantum dots (GQDs), and the P7AC block has a molecular weight of the PNIPAAm block and a molecular weight Is influenced by the brightness of the blue fluorescence. The total molecular weight of P7AC-b-PNIPAAm in the complex (bcp-GQDs) was 6.4 kg / mol, the polydispersity index (PDI) was 1.16, the molecular weight and PDI of PNIPAAm block were 5.9 kg / mol and 1.13 . The area chain density (δ) of the P7AC-b-PNIPAAm polymer bound to the graphene quantum dot was calculated to be 0.035 chain / nm ² . The area chain density (δ) was calculated based on an image of a transmission electron microscope (TEM), a weight fraction of graphene quantum dots, and an average size of graphene quantum dots using thermogravimetric analysis (TGA, see FIG. 3).

As shown in FIG. 4, the conjugation bonding structure of the P7AC-b-PNIPAAm block copolymer on the surface of graphene quantum dots (GQDs) is determined by attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR -FTIR) and X-ray Photoelectron Spectroscopy (XPS) measurements.

As shown in FIG. 4 (a), the ATR-FTIR spectrum of RAFT-QODs shows stretching vibration of the thiocarbonyl group (C = S) corresponding to the RAFT reagent at 1,072 cm ^-1 .

As shown in FIG. 4 (b), the amide peaks of PNIPAAm-GQDs and bcp-GQDs from the PNIPAAm block can be clearly observed at 1,530, 1,640 and 3,290 cm ^-1 . Compared with PNIPAAm-GQDs, bcp-GQDs showed slightly increased stretching peak at C = O at 1,722 cm ^-1 and decreased intensity of amide peak. This is due to the bonding of the C = O functional group of the P7AC block.

4 (c), XPS of RAFT-GQDs, PNIPAAm-GQDs and bcp-GQDs showed a sulfur peak (S 2p peak) corresponding to the bound RAFT reagent, and the graphene quantum dots (GQDs) No signal was observed anywhere. The S 2p peaks of the PNIPAAm-GQDs and bcp-GQDs were markedly reduced because of the reduced influence of sulfur by the conjugated block copolymer.

As shown in FIG. 5, the complex (bcp-GQDs) of the block copolymer and graphene quantum dot of the present invention shows solubility and stability in water. GQDs, RAFT-GQDs, PNIPAAm-GQDs and bcp-GQDs were completely dispersed in water, which can be seen from fluorescence images of GQDs, RAFT-GQDs and PNIPAAm-GQDs.

As shown in FIGS. 5 and 6, the complex (bcp-GQDs) of the block copolymer of the present invention and the graphene quantum dot (bcp-GQDs) of the present invention exhibits a P7AC block expressing blue fluorescence and a graphene quantum dot expressing green fluorescence simultaneously It shows fluorescence. This demonstrates the possibility that the complex of the block copolymer of the present invention and graphene quantum dot (bcp-GQDs) can be applied as a fluorescence sensor capable of adjusting fluorescence properties.

As shown in FIG. 7, the chemical properties of the block copolymer (bcp-GQDs) of the block copolymer of the present invention and the graphene quantum dot (bcp-GQDs) are shown by high resolution Transmission Electron Microscopy (HRTEM) Atomic Force Microscope (AFM) was used to measure and compare the mean size and height of GQDs, RAFT-GQDs, and bcp-GQDs. The average size and height of the GQDs are 11.1 nm and 0.71 nm, the average size and height of the RAFT-GQDs are 11.8 nm and 0.73 nm, and the average size and height of the bcp-GQDs are 26.6 nm and 3.88 nm, respectively. The average size and height of bcp-GQDs were significantly increased compared to the average size and height of GQDs and RAFT-GQDs. This is caused by the presence of a chain of a block copolymer (bcp) bonded to the surface of graphene quantum dots (GQDs). Specifically, the block copolymer (bcp) P7AC-PNIPAAm Pin GQDs on the surface of the substrate.

FIG. 8A is a graph showing the emission (PL) characteristics of the complex dispersed in water (pH 7), in order to know the temperature response of the complex (bcp-GQDs) of the block copolymer and the graphene quantum dot according to the present invention Show. All samples for emission characterization were fabricated at a very low concentration (30 ppm) to prevent PL quenching of the P7AC block by other graphene quantum dot (GQDs) substrates in aqueous solution (water). The PL spectrum of the complex dispersed in the aqueous solution at room temperature exhibited near-white fluorescence. The PL spectrum had an emission peak of P7AC block at 410 nm and an emission peak of GQDs at 505 nm ) Peak. When the temperature of the aqueous solution rises to 40 캜, the intensity of the blue emission peak at 410 nm sharply decreases, while the emission peak at 505 nm is significantly increased.

As shown in FIG. 8 (b), in order to explain the reversibility of the quantification according to the change in PL intensity and the response of the block copolymer (bcp-GQDs) to the block copolymer and graphene quantum dots on the temperature side, The ratio of the intensities of the luminescence (PL) in _nm (I _{505 nm} / I _{410 nm} ) is plotted as a graph with repetitive cycles in aqueous solution at different temperatures. As the temperature increased from 25 ° C to 40 ° C, the I _{505 nm} / I _{410 nm} value increased significantly from 0.91 to 2.27. These changes were reproduced in repetitive heating-cooling cycles.

Also interesting is the ability of the block copolymer (bcp) of the present invention to interact with both the strong covalent bond between the block copolymer (bcp) and the graphene quantum dots (GQDs) and the good dispersing power of the graphene quantum dots (GQDs) Pin quantum dot (GQDs) complexes.

The hue response of the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention as a temperature sensitive type is determined by the change in the structure (shape) of the PNIPAAm chain in the lower critical solution temperature (LCST) Lt; / RTI &gt; At the lowest critical solution temperature (LCST) 32 ° C or lower, the PNIPAAm chain of the complex of the block copolymer (bcp) and graphene quantum dots (GQDs) expands while having hydrophilicity in water. That is, the distance between the P7AC block expressing blue fluorescence and the graphene quantum dot (GQDs) expressing green fluorescence is long enough to suppress fluorescence resonance energy transfer (FRET). At a minimum critical solution temperature (LCST) of 32 占 폚 or more, the PNIPAAm chain is folded, whereby the fluorescence resonance energy transfer (FRET) from the high energy of the P7AC block to the low energy of the graphene quantum dots As it is promoted, white fluorescence becomes green fluorescence.

As shown in Fig. 9 (a), the efficiency of the fluorescence resonance energy transfer (FRET) can be evaluated by measuring the lifetime of the phosphor. The decay of the fluorescence intensity of P7AC from the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention at 410 nm of the emission peak is obtained by measuring the fluorescence intensity of the time- (Time-Resolved Fluorescence, TRF). The result of the time-resolved fluorescence (TRF) indicates that the complex of the block copolymer (bcp) and the graphene quantum dots (GQDs) is temperature-sensitive and the complex of the block copolymer (bcp) and the graphene quantum dots Gt; (LCST) &lt; / RTI &gt; above the lowest critical solution temperature (LCST). The results of the time-resolved fluorescence (TRF) are shown in Table 1 below.

25 ℃ 40 ℃ τ ₁ 1.73 0.52 A ₁ (%) 96.34 83.87 τ ₂ 7.91 2.19 A ₂ (%) 3.66 16.13 τ _ave 1.96 0.79

As shown in Table 1, at 25 ° C below the lowest critical solution temperature (LCST) of the PNIPAAm block, the emission of the P7AC block is τ ₁ = 1.73 ns (population A ₁ = 96.34%) and τ ₂ = 7.91 ns (population A ₂ = 3.66%) with an average lifetime of 1.96 ns (τ _ave ). Conversely, at 40 ° C above the lowest critical solution temperature (LCST) of the PNIPAAm block, the emission decay time of the P7AC block is τ ₁ = 0.52 ns (population A ₁ = 83.87%) and τ ₂ = 2.19 ns 0.79 ns with a life expectancy of the attenuated components of (population A ₂ = 16.13%) and proceeds rapidly (τ _ave).

The short lifetime of the emission of the P7AC block results from the nonradiative decay rate increase due to the fluorescence resonance energy transfer (FRET) from the high energy of the P7AC block to the low energy of the graphene quantum dot (GQDs) Respectively. In addition, the trend of the time-resolved fluorescence (TRF) appears repeatedly, and it can be confirmed that it corresponds to the reversibility test of the light emission (PL) spectra as shown in FIG.

As shown in FIG. 9 (b), the dramatic color change as a temperature response can be explained by the DLS analysis and the change in the complex size of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention. Particles of temperature-independent graphene quantum dots (GQDs) have a hydrodynamic diameter of 12 nm through the measurement of High-Resolution-TEM. In contrast, the particle size of the complex of the block copolymer (bcp) and graphene quantum dot (GQDs) is temperature dependent because of the structural change of the chain of the block copolymer bound to the graphene quantum dot (GDQs) surface. The particle size of the complex of the block copolymer (bcp) and the graphene quantum dots (GQDs) is constant at 16 nm and the graphene quantum dots (GQDs) have a particle size of about 12 nm at the minimum critical solution temperature (LCST) Do. (FRET) from the high energy of the P7AC block to the low energy of the graphene quantum dots (GQDs) when the LCT is above the minimum critical solution temperature (LCST), the separation between the P7AC block and the graphene quantum dots (GQDs) The distance is short enough that strong green fluorescence is expressed in the complex of block copolymer (bcp) and graphene quantum dot (GQDs).

The hydrodynamic particle size of the complex of block copolymer (bcp) with graphene quantum dots (GQDs) increases to 45 nm when it is below the minimum critical solution temperature (LCST). Below this minimum critical solution temperature (LCST), the separation distance between the P7AC block and the graphene quantum dots (GQDs) widen significantly and suppresses fluorescence resonance energy transfer (FRET). The hydrodynamic particle size of the complex of block copolymer (bcp) and graphene quantum dot (GQDs) below the minimum critical solution temperature (LCST) can be overestimated during DLS analysis because the block copolymer is much swollen by the solvent Thus, the increase in the particle size of the complex of block copolymer (bcp) and graphene quantum dot (GQDs) is not equivalent to increasing the separation distance between the block copolymer (bcp) and the graphene quantum dot (GQDs). However, it should be noted that the tendency of the particle size of the block copolymer (bcp) and the graphene quantum dot (GQDs) depending on the temperature change is consistent with the PNIPAAm structure and the PL spectrum of FIG.

As a result of the above analysis, the dramatic temperature-dependent color response of the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention changes only from the high energy of the P7AC block And is induced by fluorescence resonance energy transfer (FRET) at a low energy of the graphene quantum dots (GQDs).

(Bcp) and graphene quantum dots (GQDs) according to the change of pH and metal ion to explain that the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention can be used as a multi- Were studied.

Figure 11 shows PL characteristics where the complex of block copolymer (bcp) and graphene quantum dot (GQDs) is pH dependent. In the aqueous solution in which the block copolymer (bcp) and the graphene quantum dots (GQDs) complex are dissolved, the hue changes to a color differentiating to the eye (pH 1 - blue, pH 7 - white, pH 11 - cyan) . For example, when the value of I _{505 nm} / I _{410 nm} is 0.20, the pH is 1, when I _{505 nm} / I _{410 nm} is 0.71, the pH is 3, and when I _{505 nm} / I _{410 nm} is 0.94, . This means that as the aqueous solution becomes acidic, the emission of graphene quantum dots decreases at 505 nm. Also, the lower I _{505 nm} / I _{410 nm} value is lowered near the basicity. For example, if the I _{505 nm} / I _{410 nm} value is 0.63, the pH is 9, and if I _{505 nm} / I _{410 nm} is 0.59, the pH value is 11.

11, the intensity of PL at 410 nm was almost constant regardless of the change in pH, and the emission intensity of graphene quantum dots (GQDs) was changed from the graphene quantum dots (GQDs) Is induced by the protonation or deprotonation of emissive sites (for example, oxygenzen groups and free zigzag sites) and is markedly reduced in strongly acidic and strongly basic conditions .

Therefore, the range of pH can be adjusted by comparing the amount of emission of green to the amount of blue light, and color response can be achieved. Although the conventional polymer-based pH-sensitive sensor is modified only at a specific pH value, the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention has a color There is an advantage of observing the pH value.

Also, as shown in FIG. 12, by using a complex of the block copolymer (bcp) of the present invention and graphene quantum dots (GQDs) as a sensor, it is possible to simultaneously measure temperature and pH change. The change in PL and color of the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) at different pH conditions (for example, pH 1-11) was observed in the range of temperature change.

The complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention can detect various metal ions. As shown in FIG. 13, the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) has a dose-dependent color difference and can sensitively detect various metal ions. Experiments on the metal ion response using the complex were carried out in an aqueous solution at pH 7 at 25 ° C, and the concentration of metal ions was fixed at 100 μM.

Figure 13 (a) shows the PL spectrum change of the block copolymer (bcp) and yes composite quantum dots of the pin (GQDs) for the induction of Cu ^{+ 2} and Fe ^{+ 3.} The aqueous solution in which the complex of the block copolymer (bcp) and the graphene quantum dots (GQDs) are dissolved changes from white to cyan when 100 μM Cu ^{2 +} is added, and when 100 μM Fe ^{2 +} is added, . This phenomenon results from the emission peak of graphene quantum dots (GQDs) at 505 nm in the presence of different metal ions.

As shown in FIG. 13 (b), it should be noted that the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention is composed of Ag ^{2 +} , Cd ⁺ , Au ^{3 +} , Sn ^{2 +, Cu 2 +, Pb 2} +, Cr 3 +, Fe 3 + , and but can be a response to a change in color of the metal ions comprising at least one selected from the group consisting of Pd ^{2 +,} but not always limited thereto. And, it can be applied as a metal ion sensitive sensor by using it. Since the degree of reduction of green fluorescence-emitting graphene quantum dots (GQDs) depends on the kind of metal ions, multicolor recognition of the complex of the block copolymer (bcp) and graphene quantum dot (GQDs) Depending on the type of the film.

In addition, the concentration of the metal ions determines the color response of the complex of the block copolymer (bcp) and graphene quantum dots (GQDs). For example, FIG. 13 (c), as shown in the block copolymer (bcp) of 505 nm and yes in the PL intensity of the composite quantum dots of the pin (GQDs) according to the concentration of Fe ^{3 +} The effect can be confirmed that the PL intensity gradually decreases as the concentration of Fe ^{3 +} increases.

As is shown in _{13 (d), I 505 nm} / I value of _{410 nm} is the quantitative measure of the concentration of Fe ^{3 +} to decrease linearly, through which in the concentration of Fe ^{3 +} 0 ~ 50 μM range .

The above results can be explained by the formation of nonradiative metal-GQD complexes by interaction between graphene quantum dots (GQDs) and metal ions that are electrophilic, Can be explained by fluorescence quenching by charge exchange from excited GQDs to metal ions. For example, as shown in Figure 14, a block copolymer (bcp) and graphene fluorescence decay of the quantum dots (GQDs) graphene quantum dots (GQDs) in the complex of (fluorescence decay) when the Fe ^{3 +} of 100 μM is present It goes fast. Since the formation of the complex of the metal-graphene quantum dots is highly dependent on the concentration of metal ions and due to the close bonding between the metal ion and the graphene quantum dots (GQDs), the block copolymer (bcp) and the graphene quantum dots ) Can be sensitized to colors different from each other depending on the concentration of metal ions, and PL sensitivities are separately observed for various metal ions (see Fig. 13 (b)).

In addition, the metal ion sensing properties of the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention with temperature and pH change were studied. As shown in FIG. 15, it can be confirmed that the complex of the block copolymer (bcp) and the graphene quantum dot (GQDs) of the present invention is very stable and sensitive to temperature, pH and different metal species simultaneously.

Therefore, the complex of the block copolymer (bcp) and the graphene quantum dots (GQDs) of the present invention can respond to various external stimuli in a color capable of simultaneously identifying it, and thus can be applied to a variety of applications such as environmental sensing application, water quality analysis, It can be applied to the field.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (14)

Graphene Quantum Dots (GQDs);
A chain transfer agent coupled to the graphene quantum dot;
A stimulus-sensitive polymer synthesized from the chain transfer agent; And
And a fluorescent polymer synthesized from the stimulus-sensitive polymer,
The graphene quantum dot and the chain transfer agent are dissolved to effect a coupling reaction, and a stimulus-sensitive polymeric monomer and a free radical initiator are added to the mixture to perform a polymerization reaction. After the polymerization reaction, a fluorescent polymer monomer and a free radical initiator are added A complex of a block copolymer and a graphene quantum dot, characterized by being obtained by the polymerization reaction carried out.
The method according to claim 1,
Wherein the fluorescent polymer is poly-7- (4- (acryloyloxy) butoxy) coumarin (P7AC).
The method according to claim 1,
The fluorescent polymer may be at least one selected from the group consisting of Coumarin dyes, Fluorone dyes, Oxazine dyes, and phenanthrene dyes including poly-7- (acryloyloxy) butoxy) coumarin (P7AC) Wherein the block copolymer is any one selected from the group consisting of phenanthridine dyes, cyanine dyes, and rhodamine dyes.
The method according to claim 1,
The stimulus-responsive polymer may be selected from the group consisting of poly N-isopropylacrylamide (PNIPAAm), poly [2- (dimethylamino) ethyl methacrylate], poly [2- ), Poly (N, N-dimethylacrylamide), poly (N, N-diethylacrylamide), poly (N, N-diethylacrylamide), poly (vinylcaprolactame), polyethylene oxide, poly (vinylmethylether), polyhydroxyethylmethacrylate For example, polyhydroxyethylmethacrylate, poly (pentapeptide), poly (N- (3-aminopropyl) methacrylamide), polyethylene, Selected from the group consisting of polymethylmethacrylate and polypropylene. Wherein the block copolymer is one of a graft copolymer and a graphene quantum dot.
The method according to claim 1,
Wherein the chain transfer agent is a dithiocarbonate or trithiocarbonate functional group. The complex of the block copolymer and the graphene quantum dot is characterized in that the chain transfer agent is a dithiocarbonate or trithiocarbonate functional group.
(S1) dissolving the graphene quantum dot and the chain transfer agent to prepare a mixture through a coupling reaction;
Adding a polymeric monomer and a free radical initiator to the mixture to perform a polymerization reaction (S2); And
And a step (S3) of adding a fluorescent polymer monomer and a free radical initiator to the polymerization reaction (S3) after the polymerization reaction in the step (S2), to thereby prepare a complex of graphene quantum dot and the block copolymer.
The method according to claim 6,
The coupling reaction of step (S1) is an esterification reaction using DCC (N, N'-dicyclohexylcarbodiimide) and DMAP (4-dimethylaminopyridine), and the preparation of a complex of a block copolymer and a graphene quantum dot Way.
The method according to claim 6,
The polymerization reaction in the step S2 is a living radical polymerization reaction in which NIPAAm (N-isopropylacrylamide) monomer, which is a polymer monomer, and AIBN (azobisisobutyronitrile), which is a free radical initiator, are added and is carried out at 50 to 70 ° C for 10 to 16 hours Wherein the block copolymer is a graft copolymer.
9. The method of claim 8,
The polymerization reaction in the step S3 is a living radical polymerization reaction with 7AC (7- (4- (acryloyloxy) butoxy) coumarin) monomer as a fluorescent polymer monomer and AIBN (azobisisobutyronitrile) as a free radical initiator. In the presence of a catalyst for 10 to 16 hours.
10. The method according to claim 8 or 9,
The free radical initiator may be selected from the group consisting of 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis Azobis [2- (2-imidazolin-2-yl) propane (2-methylpyrrolidone), 2,2'- ] Dihydrochloride and 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate. The complex of the block copolymer and graphene quantum dot &Lt; / RTI &gt;
10. A temperature sensitive sensor comprising a composite produced by the method of any one of claims 6 to 9.
10. A pH-sensitive sensor comprising a composite produced by the method of any one of claims 6 to 9.
A metal ion sensitive sensor comprising a composite produced by the method of any one of claims 6 to 9.
14. The method of claim 13,
Wherein the metal ion includes at least one selected from the group consisting of Ag ^{2 +} , Cd ^{2 +} , Au ^{3 +} , Sn ^{2 +} , Cu ^{2 +} , Pb ^{2 +} , Cr ^{3 +} , Fe ^{3 +} and Pd ^{2 +} Wherein the sensor is a metal ion sensitive sensor.

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