LU502866B1

LU502866B1 - Iodine-doped Carbon Quantum Dots and Preparation Method and Application Thereof

Info

Publication number: LU502866B1
Application number: LU502866A
Authority: LU
Inventors: Yanmei Wen
Original assignee: Univ Guangdong Ocean
Priority date: 2022-01-26
Filing date: 2022-04-02
Publication date: 2023-08-04
Also published as: CN114369458B; WO2023142267A1; CN114369458A

Abstract

The invention provides an iodine-doped carbon quantum dots and preparation method and application thereof, and relates to the technical field of metal ion detection. According to the invention, iodine-doped carbon quantum dots are prepared by a one-step solvent method with p-iodobenzoic acid, m-iodobenzoic acid or o-iodobenzoic acid as raw materials. The preparation method is simple without complicated surface functionalization modification, the prepared and synthesized iodine-doped carbon quantum dots may be used as a fluorescent probe to rapidly, simply, conveniently, qualitatively and quantitatively detect Fe3+ at low cost, and thereby has important practical application value in the field of metal ion detection.

Description

DESCRIPTION LU502866

Todine-doped Carbon Quantum Dots and Preparation Method and Application

Thereof

TECHNICAL FIELD

The invention relates to the technical field of metal ion detection, and in particular to an iodine-doped carbon quantum dots and preparation method and application thereof.

BACKGROUND

Fe** is a trace element to maintain human health, plays an important role in many chemical and physiological processes, such as oxygen transport, electron conduction and enzyme catalysis.

However, excessive intake of iron ions may generate reactive oxygen species, disturb the stability of intracellular environment and lead to hemochromatosis, etc, while iron deficiency may lead to anemia, even cirrhosis and other diseases. With the rapid development of industry, excessive emission of Fe*” has increasingly become the main cause of water pollution, seriously threaten human life and health and ecological environment. Therefore, it is of great practical significance to study and develop a sensitive, rapid, simple, economical and reliable detection method for Fe*”.

At present, the methods for detecting Fe** ions include inductively coupled plasma mass spectrometry, atomic absorption spectrometry, chemical method and electrochemical method.

However, these known detection methods have some shortcomings, such as demanding conditions, high cost and cumbersome steps. Recently, with the development of fluorescent probes, fluorescent methods for detecting iron ions have attracted people's attention because of their high sensitivity and good selectivity. At present, there are many kinds of materials used to detect iron ions, such as gold nanoclusters, semiconductor quantum dots, graphite carbon polymers, etc. Although these fluorescent probe detection methods for Fe** are relatively mature, these fluorescent materials also have some shortcomings, such as the high price of metals, the toxicity of semiconductor quantum dots and the complexity of graphite carbon nitrogen polymers, which are not suitable for application, such as preparation of fluorescent materials for qualitative analysis of Fe**.

Carbon quantum dots (CQDs) are luminescent carbon nanoparticles, which are composed of spheroidal particles with a particle size of less than 10 nm. As a new type of "zero-dimensional"

nano-materials, carbon quantum dots has many excellent properties compared with traditionalU502866 organic fluorescent dye molecules, fluorescent proteins and semiconductor quantum dots, such as controllable photoluminescence, low toxicity, chemical inertness and good biocompatibility.

Therefore, they have been successfully used in various fields, such as biological imaging, sensors, photocatalysis and detection. At present, the common preparation methods of CQDs include arc discharge method, laser ablation method, ultrasonic method, chemical oxidation method, electrochemical method, microwave method, hydrothermal method and solvent method, among which one-step hydrothermal method and one-step solvent method are the simple and cheap methods to prepare carbon quantum dots with low toxicity.

In order to improve the fluorescence intensity and various properties of carbon quantum dots, it is necessary to carry out surface passivation modification or doping with heteroatoms.

Generally, the doping of nitrogen, phosphorus and oxygen is more reported, the doping of fluorine and chlorine is rarely reported, and the doping of iodine is not reported. At present, heteroatoms are doped mostly with nitrogen, phosphorus, sulfur, silicon, boron and other elements. For example, Yang et al. prepared N-CQDs by electrochemical oxidation method;

Kang et al. synthesized S/N-CQDs with malic acid and L- cysteine as raw materials; Yang et al. introduced P into CQDs and found that it has bright fluorescence and good biocompatibility, and can be used in biological imaging, Gao et al. used glycerol and silane molecules (N-[3-(trimethoxysilyl) propyl] ethylenediamine, DAMO) to prepare Si-CQDs by one-pot solvothermal method; and Zhao et al. used m-carboxyphenylboronic acid (CPAB) to mix B into

CQDs, and detected Co** with high sensitivity. There were few cases of halogen doping. Ning et al. studied that N/CI-CQDs was prepared in the liquid eutectic mixture of choline chloride/glycerin as solvent; Zhang et al. prepared iodine-doped carbon quantum dots with

Iodixanol and glycine and used it in biological imaging; Ding et al. synthesized F/N-CQDs with 3- fluoroaniline, and showed potential as a temperature fluorescent sensor and a solid-state light emitting device suitable for various temperatures.

In these studies, doped carbon quantum dots are prepared by complicated surface functionalization modification, and the preparation process is too cumbersome to practically use.

At present, there are few reports about fluorescent probes without modifiers.

SUMMARY LU502866

The present invention provides an iodine-doped carbon quantum dots and preparation method and application thereof, in order to solve the above-mentioned problems in the prior art, so as to prepare iodine-doped carbon quantum dots which may be used for metal ion detection by a simple preparation method without surface functionalization modification.

To achieve the above objective, the present invention provides the following scheme:

In an embodiment, the present invention uses p-iodobenzoic acid, m-iodobenzoic acid or o-iodobenzoic acid as raw materials to prepare the iodine-doped carbon quantum dots by one-step solvent method.

In an embodiment, the preparation method comprises the following steps:

Mixing p-iodobenzoic acid, m-iodobenzoic acid or o-iodobenzoic acid with an organic solvent, reacting at 200 °C, cooling the system to room temperature after the reaction, centrifuging to take the supernatant, removing the organic solvent, filtering, dialyzing and freeze drying to obtain the iodine-doped carbon quantum dots.

In an embodiment, the organic solvent is ethanol, and the reaction duration is 6 h.

In an embodiment, the invention provides iodine-doped carbon quantum dots prepared by the preparation method.

In an embodiment, the invention provides an application of the iodine-doped carbon quantum dots in the field of metal ion detection.

In an embodiment, the invention provides the application of the iodine-doped carbon quantum dots as a fluorescent probe in the field of Fe** detection.

Effect of Invention

The invention uses p-iodobenzoic acid, m-iodobenzoic acid or o-iodobenzoic acid are as raw materials, directly prepares and synthesizes iodine-doped carbon quantum dots (I-CQDs) by a one-step solvent method, uses the I-CQDs as a fluorescent probe, and thereby quickly simply qualitatively and quantitatively detect Fe** at low cost.

According to the invention, the preparation method is simple without complicated surface functionalization modification and has important practical application value.

BRIEF DESCRIPTION OF THE FIGURES LU502866

In order to more clearly explain the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in the field, other drawings can be obtained according to these drawings without paying creative efforts.

FIG. 1 is a surface morphology diagram of I-CQDs prepared in Embodiment 1; (A): transmission electron microscope diagram of I-CQDs, (B): lattice spacing diagram of I-CQDs and (C): particle size distribution diagram of I-CQDs;

FIG. 2 is a fluorescence characteristic diagram of I-CQDs prepared in Embodiment 1; (A): ultraviolet absorption curve, maximum fluorescence excitation spectrum (EX) and maximum fluorescence emission spectrum (EM) of I-CQDs; (B): fluorescence emission spectra of I-CQDs at different excitation wavelengths;

FIG. 3 is the infrared (IR) and XPS spectra of I-CQDs prepared in Embodiment 1 and the narrow spectrum of each element; (A): infrared spectra of I-CQDs, (B): XPS spectra of I-CQDs, (C): C 1s spectra of I-CQDs, (D): O 1s spectra of I-CQDs and (E): I 3d spectrogram of I-CQDs;

FIG. 4 shows the sensitivity and selectivity of I-CQDs for detecting different metal ions; (A): influence of different metal ions on the fluorescence intensity of I-CQDs, (B): selectivity of

I-CQDs to Fe**, (C): influence of Fe” concentration on the fluorescence intensity of I-CQDs, and (D): exponential relationship between Fe*” concentration and [(Fo-F)/F].

DESCRIPTION OF THE INVENTION

Now, various exemplary embodiments of the present invention will be described in detail.

This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present invention.

It should be understood that the terms used in this invention are only for describing specific embodiments, and are not used to limit the invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range 1s also specifically disclosed. Any stated value or intermediate value within the stated range and any other stated value or every smaller range between intermediate values within the stated range is also included in the present invention. The uppet/502866 and lower limits of these smaller ranges can be independently included or excluded from the range.

Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by the ordinary technicians in the field of this invention.

Although the present invention only describes the preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials related to the documents. In case of conflict with any incorporated documents, the contents of this specification shall prevail.

Without departing from the scope or spirit of the present invention, it is obvious to those skilled in the art that many modifications and changes can be made to the specific embodiments of the present invention. Other embodiments obtained from the description of the present invention will be obvious to the skilled person. The specification and examples of this application are exemplary only.

The words "comprising", "including", "having" and "containing" used in this paper are all open terms, that is, they mean including but not limited to.

Embodiment 1

A preparation method of iodine-doped carbon quantum dots (I-CQDs);

Weighing 0.5 g of p-iodobenzoic acid, adding 40 mL of absolute ethyl alcohol, putting it in a magnetic stirrer to disperse evenly, pouring it into a 100 mL reaction kettle lined with polytetrafluoroethylene (PTFE), and keeping the temperature at 1000 r/min at 200°C for 6 h.

After the reaction, cooling to room temperature, centrifuging at 10000 r/min for 15 min, collecting supernatant, evaporating ethanol with rotary evaporator at 50°C, filtering the obtained solution with microporous membrane with aperture of 0.22 um, dialyzing with dialysis bag (molecular weight of 12000) for 3 hours, changing deionized water every 1 hour, and freeze drying to obtain light yellow solid.

The iodine-doped carbon quantum dots (I-CQDs) prepared in Embodiment 1 is characterized: (1) Surface morphology and particle size distribution

The surface morphology and size distribution of I-CQDs are analyzed by transmissiddJ502866 electron microscope (TEM). FIG. 1 is the surface morphology of I-CQDs. FIG. 1(A) is a transmission electron microscope image of [-CQDs, and it can be seen from FIG. 1(A) that the prepared I-CQDs is spherical particles with uniform size and distribution. I-CQDs is analysed by high-resolution transmission electron microscope, and the calculated lattice spacing of carbon dots is 0.32 nm, as shown in Figure 1(B). Image J software is used to make statistics on the particle size of randomly selected I-CQDs particles and then make a histogram, as shown in

Figure 1(C). After calculation, the average particle size is 6.42+1.50 nm.

FIG. 2 is the fluorescence characteristic diagram of I-CQDs.

The ultraviolet absorption spectrum, fluorescence emission spectrum and fluorescence excitation spectrum of [-CQDs are measured, and then the optical characteristics of I-CQDs are analysed.

The ultraviolet absorption curve, maximum fluorescence excitation light spectrum (EX) and maximum fluorescence emission spectrum (EM) of I-CQDs are shown in Figure 2(A). It can be seen from Figure 2(A) that I-CQDs has obvious strong absorption in the ultraviolet absorption spectrum around 220 nm, compared with the fluorescence excitation spectrum and fluorescence emission spectrum, it can be seen that I-CQDs has obvious Stokes phenomenon.

The fluorescence emission spectra of I-CQDs at different excitation wavelengths are shown in Figure 2(B). It can be seen that when the excitation wavelength (Aex) changes from 290 nm to 350 nm, the emission wavelength (hem) shifts from 350 nm to 430 nm. When the excitation wavelength is 330 nm, the maximum emission wavelength is 408 nm. With 0.1 mol/L H2SO4 quinine sulfate as reference, the fluorescence quantum yield of I-CQDs is 36.2%.

FIG. 3 shows the infrared spectrum and XPS spectrum of I-CQDs and the narrow spectrum of each element. Specifically, FIG. (A) is infrared spectra of I-CQDs, FIG. (B) is XPS spectra of

I-CQDs, FIG. (C) is C 1s spectra of I-CQDs, FIG. (D) is O 1s spectra of I-CQDs and FIG. (E) is

I 3d spectrogram of I-CQDs;

Embodiment 2

The preparation process is the same as that of Embodiment 1 with m-iodobenzoic acid as raw material.

Embodiment 3

The preparation process is the same as that of Embodiment 1 with o-iodobenzoic acid &$/502866 raw material.

Embodiment 4 Sensitivity and selectivity of I-CQDS to metal ion detection

In order to study the application prospect of I-CQDs in the field of metal ion detection, adding I-CQDs solution with a certain concentration to the solution containing Fe**, Na”, K*,

Ba”, Zn”, Ca”, Ni”, Cd”*, Cu”*, Fe”, CO?" and A1** respectively, so that the concentration of metal cations in the system 1s all 0.01 mol/L; measuring the fluorescence emission spectra of the quantum dot solutions containing different metal ions under the excitation light of 330 nm, and judging the selectivity and sensitivity of I-CQDs for quenching different metal ions according to different fluorescence intensities.

The sensitivity and selectivity of I-CQDs for detecting different metal ions are shown in

Figure 4.

FIG. 4(A) shows the effects of different metal ions on the fluorescence intensity of I-CQDs.

Compared with other metal ions, Fe** may obviously quench the fluorescence of carbon quantum dots, while other substances have no obvious effect on the fluorescence intensity of carbon quantum dots. Therefore, I-CQDs can be used to detect Fe“.

In order to further study the influence of I-CQDs on the detection of Fe” when Fe** coexists with other metal cations, mixed solutions of Fe’ and other metal cations are prepared respectively, and the fluorescence intensity is tested after mixing them with I-CQDs. The test results are shown in Figure 4(B). It can be seen that when I-CQDs coexists with other metal cations, I-CQDs also has obvious fluorescence quenching effect on Fe”, and the fluorescence intensity after quenching is hardly affected by coexisting ions, which indicates that I-CQDs has a strong ability to resist the interference of other metal ions in the detection of Fe”.

In order to study the relation between I-CQDs and the concentration of Fe** for quenching, the prepared Fe*” solution is added into I-CQDs, the concentration of Fe*” in the mixed system is 0-200 uM, and the fluorescence intensity of I-CQDs solution with different concentrations of

Fe** is measured at 330 nm excitation wavelength, as shown in Figure 4(C). As can be seen from

FIG. 4(C), with the increase of Fe*” concentration, the fluorescence intensity gradually decreases and the fluorescence quenching effect gradually increases.

FIG. 4(D) shows that the relative fluorescence intensity [(Fo-F)/F] of I-CQDs treated withJ502866

Fes+ has a good exponential correlation with the concentration of Fes. In the range of Fe** concentration of 5-200 uM, the fitting linear regression equation is as follows: [(Fo-F)/F]=0.442e"(0.008*x)-e"(-0.007x), R?=0.9963, wherein R°=0.9963 indicates that the fitting curve has extremely high exponential correlation in the range of 0-200 um. Experiments show that Fe** may be sensitively detected at low concentration, and the concentration of Fe?” is exponentially distributed with the relative fluorescence intensity. Therefore, it is suitable for the detection of samples with medium and low Fe** concentration.

In this invention, the concentration of iron ions is in the range of 0-50 uM, the fluorescence quenching efficiency accords with the linear equation: y=0.00636x-0.00782 (R’=0.9922), and the detection limit is 0.47 pm.

The above-mentioned embodiments only describe the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, all kinds of modifications and improvements made by ordinary technicians in the field to the technical scheme of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

CLAIMS LU502866

1. A preparation method of iodine-doped carbon quantum dots, characterized in that the iodine-doped carbon quantum dots are prepared through one-step solvent method with p-iodobenzoic acid, m-iodobenzoic acid or o-iodobenzoic acid as raw materials.

2. The preparation method of iodine-doped carbon quantum dots according to claim 1, characterized by comprising the following steps: mixing p-lodobenzoic acid, m-iodobenzoic acid or o-iodobenzoic acid with an organic solvent, reacting at 200 °C, cooling the system to room temperature after the reaction, centrifuging to take the supernatant, removing the organic solvent, filtering, dialyzing and freeze drying to obtain the iodine-doped carbon quantum dots.

3. The preparation method according to claim 2, characterized in that the organic solvent is ethanol.

4. The preparation method according to claim 2, characterized in that the reaction duration is 6 h.

5. An iodine-doped carbon quantum dot prepared by the preparation method according to claims 1-4.

6. An application of iodine-doped carbon quantum dots according to claim 5 in the field of metal ion detection.

7. The application of iodine-doped carbon quantum dots according to claim 5 as a fluorescent probe in Fe** detection.