KR102333766B1 - Porous surfur doped graphitic carbon nitride nanosheet for selective detection of silver ion and photocatalytic degradation of organic material and method of manufacturing same - Google Patents

Abstract

Disclosed are a porous sulfur-doped graphitized carbon nanosheet and a method for manufacturing the same. The porous sulfur-doped graphitized carbon nanosheet of the present invention has an effect of selectively detecting ^{silver ions (Ag + ).} In addition, the porous sulfur-doped graphitized carbon nanosheet of the present invention has an effect of photocatalytic decomposition of organic materials under visible light.

Description

POROUS SURFUR DOPED GRAPHITIC CARBON NITRIDE NANOSHEET FOR SELECTIVE DETECTION OF SILVER ION AND PHOTOCATALYTIC DEGRADATION OF ORGANIC MATERIAL AND METHOD MATERIAL OF MANUFACTURING SAME}

The present invention relates to a porous sulfur-doped graphitized carbon nanosheet and a method for manufacturing the same, and more particularly, to a porous sulfur-doping capable of selectively detecting ^{silver ions (Ag + ) and photocatalytically decomposing an organic material.} It relates to graphitized carbon nanosheets.

Due to rapid industrialization, environmental pollution is receiving a lot of attention. The continuously released toxic pollutants such as heavy metals and dyes pose a serious risk to living organisms. Therefore, it is urgent to explore simple, reliable and efficient techniques that can detect heavy metal ions and remove dyes from aqueous solutions.

Silver is a widely used material because of its high thermal conductivity. Due to its widespread use in several industries such as agriculture, pharmaceuticals, mirrors and food, approximately 2,500 tonnes of silver is released into the environment each year. It has been found that silver ions (Ag ⁺ ) can bind through several metabolites and enzymes, and consequently interfere with their normal function. Today, silver is considered one of the most hazardous substances worldwide, with effects on aquatic life and public health. Therefore, ^{many analytical methods that can selectively recognize Ag +} have been studied, but most have problems such as high cost, long processing time, and low sensitivity.

Additionally, in addition to heavy metal ions, dyes are serious contaminants in the aquatic environment due to their persistent color, still toxicity at dilute concentrations, and carcinogenic potential, so under solar conditions, dyes must be broken down into _{less toxic molecules (CO 2} , minerals and H _{2 O).} there is a need to

An object of the present invention is to provide a porous sulfur-doped graphitized carbon nanosheet capable of selectively detecting ^{silver ions (Ag + ).}

Another object of the present invention is to provide a porous sulfur-doped graphitized carbon nitride nanosheet capable of photocatalytic decomposition of an organic material under visible light and a method for manufacturing the same.

According to an aspect of the present invention, a porous sulfur-doped graphitized carbon nanosheet comprising a pore (pin hole) and sulfur-doped graphitic carbon nitride (S-doped gC ₃ N _{4 ) is provided.} is provided

In addition, the sulfur-doped graphitized carbon may include a structure represented by Structural Formula 1 below.

[Structural Formula 1]

In addition, the pore size (pore diameter) may be 35 to 45 nm.

Also, the pore volume may be 0.5 to 0.65 cm ³ /g.

In addition, the porous sulfur-doped graphitized carbon nanosheet is silver ion (Ag ⁺ ) detection; and decomposition of organic matter under visible light; It may be for use in one or more selected from among.

In addition, the organic material is a dye, and the dye is one selected from the group consisting of methylene blue (MO), methyl orange (MO), rhodamine B (Rhodamine B) and malachite green (Malachite green). may include more than one.

According to another aspect of the present invention, (a) grinding a mixture comprising urea and thiourea; And (b) heat-treating the pulverized mixture to prepare a porous nanosheet including sulfur-doped graphitized carbon;

The grinding may also be performed using a mortar.

In addition, the heat treatment of step (b) may be performed at a temperature of 450 to 600 ℃.

In addition, the mixture may contain 200 to 400 parts by weight of thiourea based on 100 parts by weight of urea.

According to another aspect of the present invention, (1) preparing a porous sulfur-doped graphitized carbon nanosheet comprising sulfur-doped graphitized carbon; and (2) silver ions (Ag ⁺ ) and at least one of silver ion detection and photolysis of organic materials by administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing at least one of silver ions (Ag + ) and an organic material. A method for performing a dual function of a porous sulfur-doped graphitized carbon nanosheet comprising the step of performing is provided.

In addition, the silver ion detection is Ag ⁺ , Co ²⁺ , In ³⁺ , Ca ²⁺ , Cd ²⁺ , Fe ³⁺ , Cu ²⁺ , Fe ²⁺ , K ⁺ , La ³⁺ , Mn ²⁺ , Na ⁺ , Hg ²⁺ , Pb ²⁺ , and Zn ²⁺ silver ions (Ag ⁺ ) can be selectively detected.

Also, the step (2) may be a step of detecting silver ions in the aqueous solution by administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing ^{silver ions (Ag + ).}

In addition, the step (2) is (2-1) administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing ^{silver ions (Ag + );} and (2-2) performing the detection of silver ions in the aqueous solution by irradiating ultraviolet rays to the aqueous solution to which the porous sulfur-doped graphitized carbon nitride nanosheets are administered.

In addition, the step (2) may further include (2-3) performing silver ion detection of the aqueous solution by analyzing the fluorescence of the aqueous solution to which the porous sulfur-doped graphitized carbon nanosheets are administered. can

In addition, a limit of detection (LOD) of the silver ions may be 0.57 nM.

In addition, the step (2) may be a step of performing photolysis of the organic material by administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing an organic material.

In addition, the photolysis of step (2) may be performed using visible light.

Also, the step (2) may be a step of simultaneously performing silver ion detection and photolysis of the organic material by administering the porous nanosheet to an aqueous solution containing ^{silver ions (Ag + ) and an organic material.}

The porous sulfur-doped graphitized carbon nanosheet of the present invention has an effect of selectively detecting ^{silver ions (Ag + ).}

In addition, the porous sulfur-doped graphitized carbon nanosheet of the present invention has an effect of photocatalytic decomposition of organic materials under visible light.

1 is an XRD analysis result of _{gC 3} N ₄ prepared according to Example 1 and _{gC 3} N ₄ prepared according to Comparative Example 1 doped with sulfur atoms.
FIG. 2 is an FT-IR spectrum of _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. FIG.
FIG. 3 is a TEM image of _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. FIG.
4 is a nitrogen adsorption-desorption isotherm of sulfur atom-doped gC ₃ N _{4 prepared according to Example 1. FIG.}
5 is a pore size distribution of _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1.
6 is a high-resolution XPS core spectrum of (a) C1s, (b) N1s, (c) O1s, and (d) S2p of _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1.
7 is a UV-vis absorption, photoluminescence excitation and emission spectrum of a solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1, and the image inserted in FIG. 7 is visible in the solution. It is an image when irradiated with light (left) and UV light (365 nm, right).
FIG. 8 is a normalized fluorescence spectrum at various excitation wavelengths of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. FIG.
9 is a graph showing the photobleaching stability under 365 nm UV light for 300 minutes of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1.
10 is a graph showing the PL intensity according to the pH of the aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1.
11 is a fluorescence characteristic of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1 when no metal ions were added (blank) and when 15 different metal ions at a concentration of 20 μM were added. is an image showing
_{FIG. 12 shows the fluorescence intensity (F 0} ) of SCNPNS aqueous solution without metal ions added when no metal ions were added (blank) and when 15 different metal ions of 20 μM were added compared to SCNPNS with metal ions added. It is a graph showing the fluorescence intensity (F) F/F _{0 of the aqueous solution.}
13 is a result of Ag ⁺ _{detection experiment of pure gC 3} N ₄ prepared according to Comparative Example 1.
14 is a fluorescence spectrum of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1 for ^{silver ions (Ag +} ) at a concentration of 0 to 20 μM.
15 is a graph showing the dependence of the fluorescence intensity of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1 on ^{silver ions (Ag +} ) at a concentration of 0 to 20 μM, and the graph inserted in FIG. 15 is a graph showing the dependence of fluorescence intensity of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1 on ^{silver ions (Ag +} ) at a concentration of 0 to 1 μM.
16 is a schematic diagram illustrating a silver ion (Ag+) sensing mechanism of _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1.
17 is a graph showing _{C/C O} of MB and MO by photolysis and adsorption in the dark of SCNPNS prepared according to Example 1, and photocatalytic activity under visible light (photodegradation).
18 is a graph showing the absorbance of MO with time under visible light.
19 is a graph showing the absorbance (Absorbance) of MB according to time under visible light.
_{20 is a graph showing ln(C 0} /C) according to time of MO and MB.
21 is a schematic diagram showing a photocatalytic decomposition mechanism of MB dye of SCNPNS prepared according to Example 1 under visible light.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily carry out the present invention.

However, the following description is not intended to limit the present invention to specific embodiments, and when it is determined that a detailed description of a related known technology may obscure the gist of the present invention in describing the present invention, the detailed description thereof will be omitted. .

The terminology used herein is only used to describe specific embodiments, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, element, or combination thereof described in the specification exists, but is one or more other features or It should be understood that the existence or addition of numbers, steps, acts, elements, or combinations thereof, is not precluded in advance.

First, a porous sulfur-doped graphitized carbon nitride nanosheet of the present invention will be described.

The present invention has a pore (pin hole), sulfur doped graphitic carbon nitride (Sulfur doped graphitic carbon nitride, S-doped gC ₃ N ₄ ) It provides a porous sulfur-doped graphitized carbon nanosheet containing.

The sulfur-doped graphitized carbon may include a structure represented by Structural Formula 1 below.

[Structural Formula 1]

The pore size (pore diameter) may be 35 to 45 nm.

The pore volume may be 0.5 to 0.65 cm ³ /g.

The porous sulfur-doped graphitized carbon nanosheet is silver ion (Ag ⁺ ) detection; and decomposition of organic matter under visible light; It may be for use in one or more selected from among.

The organic material may include at least one selected from the group consisting of phenolic compounds, pharmaceuticals (Acetaminophen, Ibuprofen, 5-fluorouracil, etc.) and dyes.

Here, as the organic material including the phenol unit structure as the phenol compound, phenol, o-cresol, m-cresol, or p-cresol may be exemplified, but the present invention is not limited thereto.

Examples of the pharmaceutical include, but are not limited to, acetaminophen, ibuprofen, or 5-fluorouracil.

Examples of the dye include methylene blue (MO), methyl orange (MO), rhodamine B (Rhodamine B), or malachite green, but is not limited thereto.

Hereinafter, a method for manufacturing a porous sulfur-doped graphitized carbon nitride nanosheet of the present invention will be described.

First, a mixture comprising urea and thiourea is ground (step a).

The mixture may contain 200 to 400 parts by weight of thiourea based on 100 parts by weight of urea. If the thiourea weight part is less than 200, the sulfur doping content is small, which is not preferable, and if it exceeds 400, it is not preferable because the porosity decreases.

Finally, the pulverized mixture is heat-treated to prepare a porous nanosheet including sulfur-doped graphitized carbon (step b).

The grinding may be performed using a mortar.

The heat treatment may be performed at a temperature of 450 to 600 °C. If the heat treatment temperature is less than 450° C., sulfur-doped graphitized carbon is not formed, which is not preferable, and when it exceeds 600° C., the yield of sulfur-doped graphitized carbon is low, and sulfur-doped graphitized carbon is decomposed, which is not preferable.

Hereinafter, a method for performing dual functions of the porous sulfur-doped graphitized carbon nitride nanosheet of the present invention will be described.

First, a porous sulfur-doped graphitized carbon nanosheet containing sulfur-atom-doped graphitized carbon is prepared (step 1).

Finally, silver ions (Ag ⁺ ) and at least one of silver ion detection and photolysis of the organic material by administering the porous sulfur-doped graphitized carbon nanosheet to an aqueous solution containing at least one of the organic materials (step 2).

The silver ion detection is Ag ⁺ , Co ²⁺ , In ³⁺ , Ca ²⁺ , Cd ²⁺ , Fe ³⁺ , Cu ²⁺ , Fe ²⁺ , K ⁺ , La ³⁺ , Mn ²⁺ , Na ⁺ , Silver ions (Ag ⁺ ) can be selectively detected among Hg ²⁺ , Pb ²⁺ , and Zn ^{2+ .}

The step (2) may be a step of detecting silver ions in the aqueous solution by administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing ^{silver ions (Ag + ).}

The step (2) includes (2-1) administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing ^{silver ions (Ag + );} and (2-2) performing detection of silver ions in the aqueous solution by irradiating ultraviolet rays to the aqueous solution to which the porous sulfur-doped graphitized carbon nitride nanosheets are administered.

The step (2) may further include (2-3) performing silver ion detection of the aqueous solution by analyzing fluorescence of the aqueous solution to which the porous sulfur-doped graphitized carbon nanosheets are administered; have.

The limit of detection (LOD) of the silver ions may be 0.57 nM.

16 is a schematic diagram showing a silver ion (Ag ⁺ _{) sensing mechanism of gC 3} N ₄ (SCNPNS) doped with sulfur atoms of the present invention. Explained by the concept of Hard and Soft Acids and Bases (HSAB), Ag+ is a Soft Acid, and Nitrogen and Sulfur of SCNPNS are Soft Bases. According to HSAB, Soft Acids have strong interactions with Soft Bases. Therefore, Ag ⁺ ions can have strong affinity with SCNPNS. In addition, Ag ⁺ has a lower redox potential than the conduction band (CB) of SCNPNS, and consequently, photoinduced electron transfer (PET) ^{from CB of SCNPNS to Ag + results in fluorescence quenching.}

The step (2) may be a step of performing photolysis of the organic material by administering the porous sulfur-doped graphitized carbon nanosheet to an aqueous solution containing an organic material.

The photolysis in step (2) may be performed using visible light.

21 is a schematic diagram showing a photocatalytic decomposition mechanism of MB dye of SCNPNS prepared according to Example 1 under visible light. 21, a large amount of MB is adsorbed on the surface of SCNPNS due to the electrostatic interaction between the cationic MB dye and the negatively charged catalyst (SCNPNS) during the adsorption-desorption equilibrium process. . Sulfur doping is effective in narrowing the band gap by the interaction of the S 3p state with the N 2p, which improves the absorption of visible light and creates more electron-hole pairs. When visible light is exposed to SCNPNS, electrons in the valence band (VB) (+ 1.57 eV vs. NHE) migrate to the conduction band (CB) (-1.13 eV vs. NHE), resulting in photogenerated electrons and Holes are created Due to the pinhole porous nanosheet, more electrons and holes can be transferred to the surface of the SCNPNS. The photogenerated electrons can react with dissolved oxygen to produce peroxide radical anions. The peroxide radical anion reacts with water to form hydroxyl radicals. Finally, the generated active radicals (peroxide anion and hydroxyl radical) have an oxidation potential strong enough to decompose the dye molecule. Due to the redox potential (2.7V vs. NHE) of OH/OH-, the photogenerated hole of VB (1.57eV) cannot directly oxidize water to generate OH radicals, but the oxidation potential of MB (1.25V vs. NHE) ) is relatively small, so holes (h ⁺ ) can directly oxidize (decompose) MB.

The step (2) may be a step of simultaneously performing silver ion detection and photolysis of the organic material by administering the porous nanosheet to an aqueous solution containing ^{silver ions (Ag + ) and an organic material.}

[Example]

Hereinafter, the present invention will be described in more detail by way of examples. However, this is for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example 1: Graphitized carbon doped with sulfur atoms (S doped g-C ₃ N ₄ , SCNPNS)

The powder prepared by grinding 3 g of urea and 10 g of thiourea in an agate mortar for 15 minutes was transferred to an alumina crucible, and covered with a lid and alumina foil. The alumina crucible was raised in an air atmosphere at ^{a rate of 5° C. min −1} and heated to 520° C. for 2 hours. Thereafter, the crucible was cooled to room temperature (RT), and the obtained product was collected and pulverized _{to prepare graphitized carbon doped with sulfur atoms (S doped gC 3} N ₄ , SCNPNS) in powder form.

50 mg of SCNPNS in powder form was dispersed in 50 mL of water by ultrasonication for 2 hours, followed by centrifugation at 6000 rpm for 10 minutes to prepare a SCNPNS solution. This solution was used as a solution for ^{Ag + ion detection.}

Comparative Example 1: Graphitized carbon (pure g-C) ₃ N ₄ ) manufacturing

The powder prepared by grinding 10 g of urea in an agate mortar for 15 minutes was transferred to an alumina crucible, and covered with a lid and alumina foil. The alumina crucible was raised in an air atmosphere at ^{a rate of 5° C. min −1} and heated to 520° C. for 2 hours. Thereafter, the crucible was cooled to room temperature (RT), and the obtained product was collected and pulverized to prepare _{graphitized carbon nitride (pure gC 3} N _{4 ) in powder form.}

50 mg of graphitized carbon in powder form (pure gC ₃ N ₄ ) was dispersed in 50 mL of water by ultrasonication for 2 hours, and then centrifuged at 6000 rpm for 10 minutes to graphitize carbon (pure gC ₃ N ₄ ) solution was prepared.

[Test Example]

Test Example 1: Analysis of structural characteristics of SCNPNS

Test Example 1-1: XRD (X-ray Diffraction) analysis

XRD analysis was performed using (Rigaku, Cu-Kα radiation, D/max-2200pc, Rigaku, Tokyo, Japan, λ=1.5418 Å), where the accelerating operating voltage and applied current were 40 kV and 30 mA, respectively.

1 is an XRD analysis result of _{gC 3} N ₄ prepared according to Example 1 and _{gC 3} N ₄ prepared according to Comparative Example 1 doped with sulfur atoms. Referring to FIG. 1 , gC ₃ N ₄ prepared according to Comparative Example 1 exhibited two characteristic peaks at about 13.08° and 27.8°. These two peaks coincide with those of _{gC 3} N _{4 .} The distinct peak at 27.8° is indexed in the (002) plane due to the stacking of the conjugated aromatic system. The peak at 13.08° _{is indexed in the (100) plane of gC 3} N ₄ , which is derived from repeated in-plane tri-s-triazine units. _{The main peak of gC 3} N ₄ (SCNPNS) doped with sulfur atoms prepared according to Example 1 shifted slightly to low angles, which may be due to the substitution of sulfur in the lattice atoms of carbon nitride. _{In addition, compared with gC 3} N ₄ prepared according to Comparative Example 1, the peak intensity of SCNPNS was slightly decreased after sulfur doping, suggesting exfoliation of _{bulk gC 3} N _{4 .}

Test Example 1-2: FT-IR (Fourier-transform infrared) analysis

FT-IR analysis was performed using (Bruker, Vertex 70 FT-IR spectrometer, 104-0033 Tokyo, Japan). FIG. 2 is an FT-IR spectrum of _{gC 3} N ₄ (SCNPNS) doped with sulfur atoms prepared according to Example 1. FIG. Referring to FIG. 2 , the FT-IR spectrum of SCNPNS shows ^{a wide band in the range of 3000 to 3500 cm -1} , which is due to the NH and OH vibratory stretching modes, and -NH, -NH ₂ and adsorbed H ₂ O The presence of a hydroxyl group can be confirmed. The distinct peaks in the range of 1200 to 1700 cm ^-1 (including 1250, 1324, 1411, 1454, 1571 and 1624 cm ^-1 ) correspond to the typical stretching vibrational modes of the CN heterocycle. The peak at 804 cm ^-1 belongs to the triazine unit mode, which is related to the condensed CN heterocycle. The oscillation band at 889 cm ⁻¹ is due to the cross-linked heptazine modification of NH. Sulfur doping ^{was revealed by a peak at 705 cm −1} , which is due to CS stretching oscillations.

Test Example 1-3: TEM (Transmission electron microscopy) analysis

(Tecnai, G2mF30 S-Twin AP Tech., Hillsboro, OR, USA, 200 kV) was used for TEM analysis. 3 is a TEM image of g-C3N4 (SCNPNS) doped with sulfur atoms prepared according to Example 1. Referring to FIG. 3 , _{it can be confirmed that pinholes exist in the nanosheet of gC 3} N ₄ doped with sulfur atoms, and in particular, the pinhole structure was clearly observed from the TEM image recorded at the 20 nm scale on the right side of FIG. 3 . . The formation of the pinhole structure is due to the release of gases during heating and condensation. The appearance of the pinhole structure indicates the porous nature of SCNPNS, and the porous structure provides more active sites, which is advantageous for sensing and photocatalytic applications.

Test Example 1-4: Nitrogen adsorption-desorption isotherm and pore size distribution analysis

N ₂ adsorption-desorption was measured using the Brunauer-Emmett-Teller (BET) method by a Micromeritics ASAP-2010 surface area analyzer (Corp., Norcross, GA, USA). 4 is a nitrogen adsorption-desorption isotherm of sulfur atom-doped g-C3N4 (SCNPNS) prepared according to Example 1. FIG. Referring to FIG. 4 , the isotherm curve of SCNPNS is classified as a type IV adsorption isotherm with an H3 hysteresis loop at high pressure, indicating a network of porous structures. Based on the desorption curve, the BET surface area of SCNPNS is calculated as ^{60.2 m 2} g ^{−1 .}

The Barret-Joyner-Halenda (BJH) pore size distribution of g-C3N4 (SCNPNS) doped with sulfur atoms prepared according to Example 1 is shown in FIG. 5 . Referring to FIG. 5 , the average pore size is about 39 nm and the pore volume is 0.59 cm ³ /g, suggesting the mesoporous properties of the synthesized SCNPNS. The mesoporous structure can provide a higher surface area and more active sites, which is very useful for environmental applications such as adsorption, photocatalysis and gas sensing.

Test Example 1-5: XPS (X-ray photoelectron spectroscopy) analysis

XPS analysis was performed using an Al K-alpha radiation X-ray source and ESCALAB220i (VG Scientific, Thermo. Scientific, East East Grinstead, UK). 6 is a high-resolution XPS core spectrum of (a) C1s, (b) N1s, (c) O1s, and (d) S2p of _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. Referring to FIG. 6(a), the C1s core spectrum is divided into four peaks centered at 284.6, 285.8, 287.8 and 288.5 eV. The peak at 284.6 eV indicates sp ² graphite C=C bonds, while the peak at 285.8 eV indicates the CN group. ^{The main strong peak at 287.8 eV indicates sp 2} carbon-nitrogen bonds (NC=N) of aromatic ring systems such as s-triazine units and pyridine-like structures, while the peak at 288.5 eV is tertiary nitrogen N-( C) ₃ groups, ie the nitrogen is ^{bonded to 3 sp 2} carbon atoms in the CN network.

Referring to FIG. 6(b), the asymmetric N1s spectrum can be separated into two peaks with binding energies at 398.4 eV and 400.4 eV, which are sp ² -Hybridized nitrogen (C=NC) and amino with hydrogen atoms, respectively. It represents a functional group (CNH).

Referring to Fig. 6(c), the core spectrum of O1s has two symmetrical peaks around 532 eV and 534 eV, indicating the presence of N-C-O groups and water adsorbed on the surface, respectively.

Referring to Figure 6 (d), which shows the core of the spectrum S 2p _1/2 at 163.9eV, which represents a combination of sulfur CS substituted nitrogen in place of the grid SCNPNS.

Test Example 2: UV-Vis and Fluorescence Characterization of SCNPNS

7 is a UV-vis absorption, photoluminescence (PL) excitation and emission spectrum of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1, and the image inserted in FIG. 7 is the aqueous solution It is an image when irradiated with visible light (left) and UV light (365 nm, right). Ultraviolet-visible (UV-vis) absorption spectra were recorded using a Varian Cary 100 UV-vis spectrophotometer (Markham, ON, Canada). Fluorescence emission spectra were measured using a fluorescence emission spectrometer (Quantal Master, Photon Technology International, Lawrenceville, USA) equipped with a Xe lamp (Arc Lamp Housing, A-1010B™), monochromator and power supply (Brytexbox, NJ, USA). was recorded using Referring to FIG. 7 , the photoluminescence (PL) spectrum of SCNPNS showed a strong PL emission peak at 445 nm under 350 nm excitation. Also, referring to the image inserted in FIG. 7 , the SCNPNS aqueous solution was almost transparent under visible light, but produced strong blue fluorescence under 365 nm UV light irradiation.

FIG. 8 is a normalized fluorescence spectrum at various excitation wavelengths of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. FIG. Referring to FIG. 8 , as the excitation wavelength increased from 290 nm to 380 nm in 10 nm increments, the normalized PL intensity increased up to 350 nm for the excitation wavelength, but the PL intensity decreased when the excitation wavelength exceeded 350 nm, where the emission wavelength There was no movement of Therefore, it was confirmed that the maximum excitation and emission wavelengths of SCNPNS were 350 nm and 445 nm, respectively. This excitation-independent fluorescence phenomenon suggests that SCNPNS exhibits a single-emission fluorescence center with high crystallinity.

9 is a graph showing the photobleaching stability under 365 nm UV light for 300 minutes of an aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. Referring to FIG. 9 , it was confirmed that it was stable without photobleaching even under UV light illumination for 300 minutes using a high-pressure mercury vapor lamp.

To obtain optimal conditions for quantitative analysis application, the effect of pH on the fluorescence intensity of SCNPNS was investigated by varying the pH in the range of 2 to 13. 10 is a graph showing the PL intensity (fluorescence intensity) according to the pH of the aqueous solution containing _{gC 3} N ₄ doped with sulfur atoms prepared according to Example 1. Referring to FIG. 10 , it was confirmed that the fluorescence intensity of SCNPNS was pH dependent. While the fluorescence intensity gradually increased as the pH increased from 2 to 7, the fluorescence intensity was rapidly decreased in strong basicity, that is, pH 10 to 12 due to deprotonation of nitrogen in a basic environment. This affects the exciton distribution, resulting in low PL intensity. The highest PL intensity was observed at pH 7, consistent with physiological pH conditions. Therefore, a neutral pH of 7 was used in the fluorescence detection experiments of SCNPNS for the selective detection of various heavy metal ions.

Test Example 3: Ag of SCNPNS ⁺ Selective Fluorescence Detection

^{Different metal ions (Co 2+} , In ³⁺ , Ca ²⁺ , Cd ²⁺ , Fe ³⁺ , Cu ²⁺ , Fe ²⁺ , Ag ⁺ , K ⁺ , La ³⁺ at room temperature (RT), pH 7 , Mn ²⁺ , Na ⁺ , Hg ²⁺ , Pb ²⁺ and Zn ²⁺ ) were investigated for selectivity of SCNPNS. 100 μL of SCNPNS solution was added to 3 mL of 20 μM metal ion solution. The reaction mixture was incubated at room temperature for 5 min, fluorescence images were taken under excitation at λ=350 nm, and fluorescence spectra were recorded. A reference solution without addition of metal ions was prepared, which is indicated as blank in FIGS. 11 and 12 .

The fluorescence image results are shown in FIG. 11 . Referring to FIG. 11 , it ^{was confirmed that the SCNPNS solution to which Ag +} was added showed significant fluorescence quenching, while fluorescence quenching was not observed for other metal ions.

The fluorescence intensity (F ₀ ) of the SCNPNS solution to which metal ions were not added compared to the fluorescence intensity (F) of the SCNPNS solution to which metal ions were added, F/F _{0 ,} was calculated and shown in FIG. 12 . Referring to FIG. 12 , ^{it was confirmed that, among all metal ions, only Ag +} ions induced a substantial decrease in the fluorescence intensity of SCNPNS. These results indicate that SCNPNS has high selectivity for ^{Ag +} ions and can be used for detection of ^{Ag + .} The ^{high selectivity of SCNPNS for Ag +} was due to the synergistic effect of N and S in SCNPNS, where N had a strong chelating affinity with ^{Ag + .}

In addition, Ag ⁺ _{detection experiment was performed on pure gC 3} N ₄ prepared according to Comparative Example 1, and the results are shown in FIG. 13 . Referring to FIG. 13 , _{it was confirmed that the percent fluorescence extinction of gC 3} N ₄ prepared according to Comparative Example 1 with respect to a ^{similar concentration of Ag +} ions was less than that of SCNPNS of Example 1. This indicates that the substitution of S plays an important role in ^{Ag + ion detection.}

^{Ag +} detection experiment of SCNPNS for ^{Ag +} at different concentrations (0 to 20 μM) was performed in the same manner as above. 14 is a fluorescence spectrum of a SCNPNS solution for ^{Ag +} at a concentration of 0 to 20 μM. Referring to FIG. 14 , it was confirmed that the fluorescence intensity of SCNPNS gradually decreased as the concentration of ^{Ag + increased from 0 to 20 μM.}

15 is a graph showing the dependence of the fluorescence intensity of the SCNPNS solution on ^{Ag +} at a concentration of 0 to 20 μM. Referring to FIG. 15 , it was confirmed that the linear calibration plot did not fit over the 0 to 20 μM concentration range. However, referring to the graph inserted in FIG. 15 , (F ₀ -F)/F ₀ showed good linearity in the range of 0 to 1 μM (1000 nM). The linear regression equation was (F ₀ -F)/F ₀ = -0.02 + 0.259 x C, and R ² = 0.9979. Where F ₀ is the fluorescence intensity of SCNPNS solution of the absence of Ag ^+, F is the fluorescence intensity of SCNPNS solution of having the Ag ^+, C is the concentration of Ag ^+.

The limit of detection (LOD) was determined to be 57 nM at a signal-to-noise ratio of 3 using Equation (1) below.

In Equation (1), σ is the standard deviation (n = 6) of the blank SCNPNS solution, and s is the slope of the calibration plot.

Test Example 4: Decomposition of dyes using SCNPNS as a photocatalyst under visible light

The photocatalytic activity of SCNPNS on methylene blue (MB) as a cationic dye and methyl orange (MO) as an anionic dye was tested under visible light. To activate the photocatalytic reaction, a 100 W halogen lamp equipped with a UV cut filter (JB-420, Nantong Haisheng Optical Co., Lt, China) was used as a visible light source. The photoreactor was placed on a magnetic stirrer in the open to obtain sufficient oxygen for the photolysis reaction. The temperature of the photoreactor was kept constant by circulation of water in an outer jacket surrounding the photoreactor. A mixture was prepared by dispersing 50 mg of a photocatalyst in 100 mL of a 10-ppm dye solution. Before visible light irradiation, the mixture was continuously stirred in the dark for 30 minutes to establish an adsorption-desorption equilibrium, and then the light source was turned on. During the experiment, 3 mL of the sample solution was collected at predetermined time intervals and then centrifuged to remove the photocatalyst. Finally, the sample solution was analyzed to estimate the degree of photolysis through the absorption intensity of the test dye (MB or MO) at the maximum absorption wavelength by UV-vis spectrophotometer.

17 is a graph showing _{C/C O} of MB and MO by photolysis and adsorption in the dark of SCNPNS and photocatalytic activity under visible light. C is the concentration after photolysis, adsorption, and photodegradation, and C0 is the initial concentration. Referring to FIG. 17 , it was confirmed that the photolysis of MO and MB dyes was negligible, but the difference between the adsorption and photocatalytic degradation of MB and MO dyes was obvious. In the dark condition, the adsorption of MO on the SCNPNS surface was almost negligible, but 34% of MB was adsorbed to the SCNPNS. To understand the reason for the different adsorption performance of MB and MO dyes, the zeta potential of SCNPNS was measured using a zeta analyzer and was measured to be -7.23 mV. Referring to FIG. 17 , it can be seen that the photocatalytic degradation performance for MB is superior to that of MO, and after 180 minutes, only 14% of MO is decomposed whereas 90% of MB is decomposed.

18 and 19 are graphs showing absorbance of MO and MB with time under visible light, respectively. 18 and 19 , MB was almost decomposed within 180 minutes, but it was confirmed that there was little change in the absorbance of MO.

Quantitative measurements of photocatalytic performance for MB and MO dyes were investigated using the Langmuir-Hinshelwood kinetics model. 20 shows a plot of ln(C ₀ /C ) versus time (t) for the photocatalytic performance of SCNPNS. The linear relationship between ln(C ₀ /C) and time indicates that the photocatalytic degradation of MB and MO follows pseudo-first-order kinetics. Referring to FIG. 20, it can be seen that the kinetic rate constants of SCNPNS are 0.01153 min ^-1 and 6.5×10 ^-4 min ^-1 for the photocatalytic decomposition of MB and MO dyes, respectively, and the maximum photocatalytic performance is observed for MB dyes. and the rate constant was 18 times higher than that of MO. The good photocatalytic performance for MB was due to the negative charge and porous structure of SCNPNS, resulting in greater adsorption and better photocatalytic activity for the cationic MB dye compared to the anionic MO dye.

As mentioned above, although preferred embodiments of the present invention have been described, those of ordinary skill in the art can add, change, delete or It will be possible to variously modify and change the present invention by addition, etc., which will also be included within the scope of the present invention. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form. The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

Claims (19)

delete delete delete delete delete delete delete delete delete delete (1) preparing a porous sulfur-doped graphitized carbon nanosheet containing sulfur-doped graphitized carbon; and
(2) performing silver ion detection of the aqueous solution by administering the porous sulfur-doped graphitized carbon nanosheet to an aqueous solution containing silver ions (Ag ^{+ );}
A method for detecting silver ions of a porous sulfur-doped graphitized carbon nanosheet comprising a. 12. The method of claim 11,
The silver ion detection is Ag ⁺ , Co ²⁺ , In ³⁺ , Ca ²⁺ , Cd ²⁺ , Fe ³⁺ , Cu ²⁺ , Fe ²⁺ , K ⁺ , La ³⁺ , Mn ²⁺ , Na ⁺ , Hg ²⁺ , Pb ²⁺ , and silver ion detection method for selectively detecting silver ions (Ag ^{+ ) from among Zn 2+ .} delete 12. The method of claim 11,
The step (2) is
(2-1) administering the porous sulfur-doped graphitized carbon nanosheets to an aqueous solution containing silver ions (Ag ^{+ );} and
(2-2) performing silver ion detection of the aqueous solution by irradiating the aqueous solution to which the porous sulfur-doped graphitized carbon nanosheets are administered with ultraviolet rays; 15. The method of claim 14,
The step (2) is
(2-3) performing silver ion detection of the aqueous solution by analyzing fluorescence of the aqueous solution to which the porous sulfur-doped graphitized carbon nanosheets are administered; How to perform 12. The method of claim 11,
The silver ion detection performing method, characterized in that the limit of detection (LOD) of the silver ion is 0.57nM. delete delete 12. The method of claim 11,
The step (2) is
Silver ion detection performing method, characterized in that by administering the porous nanosheet to an aqueous solution containing silver ions (Ag ⁺ ) and an organic material, the silver ion detection of the aqueous solution and the photolysis of the organic material are simultaneously performed.

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