KR20120055818A - Synthesis of graphitic carbon nitride having 3d cubic nano structure and selective detection method of copper ion using the same - Google Patents

Abstract

PURPOSE: The synthesis of carbon nitride in the form of a three-dimensional cubical shaped nano-structure and a method for selectively detecting copper ions using the same are provided to easily detect copper ions in an aqueous solution and under physiological conditions by implementing selective optical detection with respect to the copper ions based on fluorescent measurement. CONSTITUTION: Carbon nitride is synthesized by using three-dimensional cubical shaped mesoporous silica. The carbon nitride is obtained by the following: a cyanamide aqueous solution is introduced into a three dimensional cubical shaped mesoporous silica template; a centrifugal separation process and a drying process are implemented; the dried material is plasticized; the plasticized material is treated with ammonium hydrogen fluoride and is dried; and the silica template is eliminated.

Description

SYNTHESSIS OF GRAPHITIC CARBON NITRIDE HAVING 3D CUBIC NANO STRUCTURE AND SELECTIVE DETECTION METHOD OF COPPER ION USING THE SAME}

The present invention relates to the synthesis of carbon nitride having a nanostructure in the form of a three-dimensional cube and a selective method for detecting copper ions using the same, and more particularly to select the copper ion through the nanostructure of carbon nitride having inherent luminescence It relates to a method for detecting.

Carbon nitride is a binary compound in which carbon and nitrogen alternately form covalent bonds, and it is reported that carbon nitride in the form of molecules, graphite and crystalline forms exists.

Graphitic carbon nitride is the most stable allotrope of carbon materials. It has absorption wavelength around 400nm and has an optical bandgap of 2.1 eV and has semiconductor characteristics. There are reports of studies that can be used as photocatalysts in reactions that produce.

In addition, the optical properties of the carbon nitride can be applied to the optical sensing because it can be adjusted using various factors such as the degree of condensation of the precursor, induction of nanostructures.

Recently, due to the acceleration of environmental pollution, interest in the detection of metal ions in wastewater or various environments is increasing.

In particular, the concentration of metal ions has been analyzed using electrochemical methods or equipment such as AAS or ICP-MS, but interest in optical sensing is increasing due to the accuracy, speed and portability of the sensing.

Registered No. 10-0690199 call 'fluorescein derivative having a copper ion selective, their preparation and in vivo detection method using the copper ion ", the fluorescein derivative having the selectivity of the copper ion (Cu ^{+ 2),} thereof, Disclosed is a manufacturing method and a method for detecting copper ions in vivo using the same.

In Korean Patent No. 10-0959822, 'Magnetic Optical Sensor with Selective Luminescence to Metal Cations' includes a functional group that selectively binds to a metal cation and a light emitting receptor compound including a BODIPY (Borondipyrromethene Difluoride) -based luminophore. Disclosed is an adsorbent and an optical sensor using the same, characterized in that is produced by bonding to the surface.

As described above, studies on the method of using optical quantum dots or using a compound of various receptors and chromophores have been actively conducted.

However, in the case of quantum dots, since the material itself consists of heavy metals, there is a problem that can cause serious environmental pollution or toxicity.

In addition, when the compound of the receptor and the chromophore is used, a complicated conjugation process is required, and the soluble in the aqueous solution of the chromophore is low, so that it is difficult to apply to the physiological environment.

An object of the present invention is to provide a carbon nitride having a nanostructure in the form of a three-dimensional cube.

Another object of the present invention is to provide a method capable of selectively detecting copper ions without using a complex bonding process between a receptor and a chromophore using carbon nanostructures having the nanostructures.

Emission property of carbon nitride having a unique nano-structure of the three-dimensional cube of the present invention for achieving the above object is characterized by showing a selective reduction for copper ion (Cu ^{+ 2).}

 The carbon nitride is synthesized using mesoporous silica in the form of a three-dimensional cube.

The selective detection method of the copper ion of this invention consists of reacting the carbon nitride which has the said nanostructure and copper ion aqueous solution, and confirming the grade of reduction of carbon nitride intrinsic luminescence.

According to the present invention, carbon nitride having a nanostructure in the form of a three-dimensional cube has excellent selectivity with respect to copper ions and shows a marked decrease in fluorescence when forming a complex with copper ions. Can be used as a sensor.

In addition, selective optical sensing of copper ions is possible only by fluorescence measurement without complex organic receptor conjugation in aqueous solution, so that it can be easily detected in aqueous solution and physiological conditions.

1 is a schematic diagram of carbon nitride (c-mpg-C ₃ N ₄ ) having a nanostructure in the form of a three-dimensional cube.
2 is a graph showing the results of the Small Angle X-ray Scattering (SAXS) pattern by scattering of mesoporous silica KIT-6 and c-mpg-C ₃ N ₄ .
(Inset: Graph showing enlarged SAXS pattern in 1-3 ° range.)
3 is a photograph showing an image of c-mpg-C ₃ N _{4 with} a transmission electron microscope.
4 is a graphical representation of selective luminescent response to various metal ions.
Assay: carbon nitride with nanostructures in the form of three-dimensional cubes (c-mpg-C ₃ N _{4 )}
Grey: Carbon nitride without nanostructures (bulk gC ₃ N ₄ )
White: The change in luminescence of c-mpg-C ₃ N ₄ for copper ions when several metal and copper ions are present at the same time.
5 is a graph showing the reduced form of the luminescence change spectrum of c-mpg-C ₃ N _{4 with} the concentration of copper ions.
(Inset: Photograph showing the results of fluorescence microscopy images of c-mpg-C ₃ N ₄ according to the copper ion concentration; 1) 0M, 2) 100μM, 3) 1mM)
Figure 6 is a graph showing the relative luminescence reducing power of c-mpg-C ₃ N ₄ for each copper ion concentration when copper ions are present in the aqueous solution.
I ₀ : Luminescence of c-mpg-C ₃ N _{4 in} the absence of copper ions
I: reduced luminescence of c-mpg-C ₃ N _{4 with} each copper ion concentration
Figure 7 is a graph showing the relative luminescence decrease by copper ions of c-mpg-C ₃ N ₄ with the effect of temperature and light.
I ₀ : Luminescence of c-mpg-C ₃ N _{4 in} the absence of copper ions
I: reduced luminescence of c-mpg-C ₃ N _{4 with} each copper ion concentration

The present invention relates to the synthesis of carbon nitride having a nanostructure in the form of a three-dimensional cube and a selective detection method of copper ions using the same.

When detecting metal ions using 3D cubic mesoporous graphitic carbon nitride (c-mpg-C ₃ N ₄ ) synthesized in the present invention, many intrinsic properties of carbon nitride surface exist Of -NH ₂ / -NH-/-N = provides a coordinating bond site for the metal ions, causing adsorption of a large amount of metal ions.

Accordingly, in the case of c-mpg-C ₃ N ₄ , unlike the carbon nitride (bulk gC ₃ N ₄ ) having no nanostructure, the intrinsic luminescence of the c-mpg-C ₃ N ₄ is selectively reduced.

Therefore, the complicated bonding process of the conventional optical sensor for detecting copper ions can be omitted, and the simple and efficient fluorescence sensor can be implemented using carbon nitride in terms of biocompatibility characteristics and applicable in aqueous solution.

Here, fluorescence refers to a photochemical phenomenon in which photons having a specific light wave (excitation wavelength) collide with an indicator molecule and electrons are excited to a high energy level as a result of the collision.

Specifically, the present invention introduces a nanostructure in the form of a three-dimensional cube having mesoporous to carbon nitride having inherent luminescence through the nano-templating method, and the material is present in an aqueous solution. By selectively detecting copper ions among the ions, the intrinsic luminescence is reduced to detect nM concentration.

In the conventional method of optical sensing of copper, the detection limit using quantum dots is 7.1 μM and the detection limit is 380 nM in case of optical sensing of copper using inorganic nanoparticles with receptors.

On the other hand, in the present invention by using the c-mpg-C ₃ N ₄ to detect the copper ions only by fluorescence measurement without complex organic receptors in the aqueous solution, the detection limit of the copper ion method was 12 nM, and other systems Compared to the simple method, it can be detected in aqueous solution, and biocompatibility can be widely applied in fields such as biology and environmental engineering.

In addition, even in the presence of other ions and binary systems, the decrease in fluorescence for copper ions was not different from that of only copper ions.

Therefore, in the present invention, the selective optical sensing of copper ions is possible even using only carbon nitride having a nanostructure, without undergoing a complicated conjugation process between a receptor and a chromophore as in the conventional system, and in aqueous solution and physiological conditions. It was confirmed that it can be easily detected.

In addition, the present invention can also provide a fluorescent sensor that selectively detects copper ions (Cu ²⁺ ) using carbon nitride having the nanostructure.

The fluorescence sensor can be operated in an aqueous solution without using an organic solvent, and practical application for metal ion detection is possible.

The fluorescence sensor is configured in a conventional form in the art, preferably by attaching the fluorescence sensor on the suspension in the form of a fluorescence sensor or various solid forms such as paper, glass, plastic, metal, etc., which is portable and Ease of measurement can be further improved.

Hereinafter, the Examples and Experimental Examples will only specifically explain the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by the Examples and Experimental Examples.

Example 1 Synthesis of Carbon Nitride (c-mpg-C ₃ N ₄ ) Having Nanostructures in Three-Dimensional Cube Form Using Nano Template Method

1) Synthesis of three-dimensional cubic mesoporous silica (mesoporous silica KIT-6)

6 g of P123 (BASF Corp.) was dissolved in a solution of 217.64 g of distilled water and 11.16 g of 37% HCl.

The solution was dissolved to the complete solution state, and 6 g of 1-butanol was added at once, and mixed at 35 ° C. for 1 hour to form Mixture 1.

12.9 g of tetraethyl orthosilicate (TEOS) was added to the mixture 1, placed in a sealed polypropylene bottle, and mixed for 24 hours under stabilized conditions to produce mixture 2.

Then, the mixture 2 was heated at 130 ° C. for 24 hours, and the obtained white precipitate was filtered and dried at 80 ° C. for 24 hours and calcined for 4 hours in an air atmosphere of 550 ° C., followed by KIT- 6 was obtained.

2) c-mpg-C ₃ N ₄ synthesis using KIT-6

1 g of the silica (KIT-6) template of 1) was added to 1 g of a 7 mM cyanamide aqueous solution, mixed for 1 hour, and then centrifuged and dried.

The dried resultant was calcined for 4 hours in a nitrogen atmosphere.

The calcined light yellow powder was treated with 4M NH ₄ HF ₂ for 24 hours to remove the silica template, then filtered, washed with water and ethanol and dried at 50 ° C. Carbon nitride (c-mpg-C ₃ N ₄ ) having a nanostructure in the form of a three-dimensional cube such as was synthesized.

Experimental Example 1 Nanostructure Analysis of Carbon Nitride (c-mpg-C ₃ N ₄ ) Having a Nanostructure in the Three-Dimensional Cube Form

1. Experimental Method

Interfacial measurement by scattering (Small Angle X-ray Scattering: SAXS) was performed, the results are as shown in FIG.

In addition, as shown in Figure 3, through the transmission electron microscope (TEM, Transmission Electron Microscope, 200nm) was confirmed the carbon nitride (c-mpg-C ₃ N ₄ ) synthesized in Example 1.

The structural properties of c-mpg-C ₃ N ₄ and KIT-6 are shown in Table 1 below.

Surface area
Surface area
S _bet
[m ² g ^-1 ] Collection space
Pore volume
[cm ³ g ^-1 ] w _BJH
[nm] ^[a] a
[nm] ^[b] d
(nm) ^[c] Bulk gC ₃ N ₄ 8 0.1 - - - c-mpg-C ₃ N ₄ 208 0.4 3.6 22.7 7.5 KIT-6 606 1.2 9.8 24.3 3.5

[a] w _BJH is the calculated value from the adsorption point of nitrogen sorption isotherm by BJH method

[b] XRD unit cell constant, a being a value calculated from the formula a = 6 ^1/2 (d ₂₁₁ )

[c] wall thickness, d is the estimated value from the TEM image

2. Experimental results

As shown in FIG. 2, c-mpg-C ₃ N ₄ was synthesized using mesoporous silica KIT-6 as a template, thereby confirming that it exhibits symmetry in the SAXS pattern.

In addition, as shown in Table 1 and Figure 3, the carbon nitride (c-mpg-C ₃ N ₄ ) synthesized in Example 1 was found to have a three-dimensional cube-shaped nanostructure.

Experimental Example 2 Confirmation of Fluorescence Change of Metal Nitride of Carbon Nitride Having 3D Nanostructure

1. Experimental Method

Experimental group: carbon nitride having a three-dimensional nanostructure of Example 1

Control: Carbon nitride without conventional nanostructures

1 mg each of the experimental group and the control group were prepared and dispersed in 1 ml of an aqueous solution in which metal ions of 1 mM concentration were present at 20 ° C. and mixed for 30 minutes. Then, the metal solution was removed by centrifugation, and then 1 ml of buffer solution was added thereto. Carbon nitride was dispersed again.

Fluorescence was measured by sampling 0.2 ml of dispersed carbon nitride.

2. Experimental results

As a result of the experiment, as shown in Figure 4, in the case of carbon nanostructures (Bulk g-, C ₃ N ₄ ; gray) without a control group Zn ^{2 +} , Hg ^{2 +} , Pb ^{2 +} , Co ^{2 +} , Mg ^{2 +, Cu 2 +, Fe} 3 +, Mn 2 +, Cd 2+, exhibited a 10% decrease in fluorescence without special selectivity for the metal ion of Ni ^{+ 2.}

On the other hand, carbon nitride (c-mpg-C ₃ N ₄ ; assay) having a three-dimensional nanostructure of the present invention, the experimental group, showed a fluorescence reduction of 96% for the same concentration of copper ions.

In addition, the selection of copper for the absence of a difference in the degree of fluorescence reduction (marked in white) for the copper ions of c-mpg-C ₃ N ₄ when the same concentrations of other metal ions are present simultaneously. Fluorescence reduction was confirmed.

FIG. 5 shows the fluorescence spectrum of c-mpg-C ₃ N ₄ (Excitation: 375 nm). As the concentration of copper ions (0 M, 100 μM, 1 mM) increases, the intensity of the fluorescence spectrum decreases, and c-mpg -C ₃ N ₄ was confirmed to gradually lose fluorescence as the concentration of copper ions increases.

Figure 6 shows the detection sensitivity at a low concentration of nM level using c-mpg-C ₃ N ₄ , the expression representing the fluorescence reduction (Stern-Volmer) is as follows.

I ₀ : Fluorescence intensity of carbon nitride in the absence of metal ions

I: Fluorescence intensity of carbon nitride in the presence of metal ions

K _sv : Stern-Volmer constant, the sensitivity of decrease of fluorescence according to metal ion concentration

Q: concentration of copper ions

In the case of the carbon nitride having the three-dimensional nanostructure of the present invention, the K _sv value is 7.352 × 10 ⁶ M ⁻¹ and the detection limit of this detection system is 12 nM (S / N = 3). It was found that the detection limit is better than that of the fluorescent sensor.

Experimental Example 3 Comparison of Fluorescence Reduction by Temperature and Light

The degree of luminescence reduction of c-mpg-C ₃ N ₄ on copper ions was investigated according to the effects of temperature and light.

As a result, it is shown in Figure 7 and Table 2 below.

Table 2 shows the calculated K _sv .

Reaction status
Reaction condition K _sv [× 10 ⁶ M ^-One ] 20 ℃ (visible light) 0.0458 ± 0.0008 37 ℃ (dark, dark) 0.0096 ± 0.0005 29 ℃ (dark) 0.0061 ± 0.0003 20 ℃ (dark) 0.0037 ± 0.0005

As shown in Table 2 and Figure 7, the value of K _sv increases with increasing temperature in a light-free environment, fluorescence reduction for the copper ions of c-mpg-C ₃ N ₄ is a semiconductor property with c-mpg-C ₃ N copper ion while excited is the ground state of _e-4 the c-mpg-C ₃ N diffuses ₄ through coordination bonding sites of the can be called dynamic quenching (dynamic quenching) according to a mechanism for binding have.

In addition, since the detection ability is increased at 37 ℃ than at room temperature (10 ~ 15 ℃) it can be expected that the efficiency is easily increased in the physiological environment and easy to apply.

Claims (8)

Copper ions (Cu ^{+ 2),} characterized in that it has a selectivity,
Carbon nitride having a nanostructure in the form of a three-dimensional cube.
The method of claim 1,
The carbon nitride is synthesized using mesoporous silica in the form of a three-dimensional cube,
Carbon nitride having a nanostructure in the form of a three-dimensional cube.
Adding a cyanamide aqueous solution to the mesoporous silica template in the form of a three-dimensional cube, followed by centrifugation and drying;
Firing the dry matter; and
After treating the calcined acidic ammonium fluoride (NH ₄ HF ₂ ) and dried to remove the silica template; comprising;
Method for preparing carbon nitride having a nanostructure in the form of three-dimensional cube
The method of claim 3,
The mesoporous silica template is dissolved in Pluronic (Pluronic) with a mixture of distilled water and hydrogen chloride (HCl), and then 1-butanol and tetraethyl orthosilicate (TEOS). After mixing to form a drying and firing step, characterized in that
Method for preparing carbon nitride having a nanostructure in the form of three-dimensional cube
A method for selectively detecting copper ions present in an aqueous solution environment or a living body using carbon nitride having a nanostructure of claim 1.
The method of claim 5,
The detection of the copper ions is carried out by reacting the carbon nitride having the nanostructure and the copper ion aqueous solution to determine the degree of reduction of carbon nitride intrinsic luminescence,
Selective detection method of copper ions.
The method of claim 6,
The detection of the copper ion is characterized in that carried out in a temperature range of 30 ~ 38 ℃ ℃ pH 7.0 ~ 7.2,
Selective detection method of copper ions.
A fluorescent sensor for selectively detecting copper ions using carbon nitride having a nanostructure of claim 1.

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