CN110132917B

CN110132917B - Cobalt-nitrogen double-doped carbon dot and preparation method and application thereof

Info

Publication number: CN110132917B
Application number: CN201910396646.9A
Authority: CN
Inventors: 路雯婧; 刘洋; 郭建花; 董川; 双少敏
Original assignee: Shanxi University
Current assignee: Shanxi University
Priority date: 2019-05-14
Filing date: 2019-05-14
Publication date: 2021-07-27
Anticipated expiration: 2039-05-14
Also published as: CN110132917A

Abstract

The invention discloses a cobalt-nitrogen double-doped carbon dot and a preparation method thereof, and application of the carbon dot in detection of tetracycline antibiotics. The carbon dots are prepared by taking iminodiacetic acid and cobalt chloride as raw materials and adopting a one-step hydrothermal method. The preparation method of the carbon dots is simple and convenient, and the carbon dots have good optical performance, good water solubility and good dispersibility due to the doping of the metallic cobalt element and the nitrogen element. Based on the internal filtration effect, the carbon dots can be used as fluorescent probes to quickly and sensitively detect tetracycline antibiotics. The tetracycline antibiotics can effectively quench the fluorescence of the carbon dots, and the content of the tetracycline antibiotics in the sample can be detected according to the change of the fluorescence. The method for detecting the tetracycline antibiotics provided by the invention is green, simple and convenient, can realize high selectivity and high-sensitivity direct detection on the content of the tetracycline antibiotics in a sample without additionally modifying a marker on a carbon spot, and has more advantages in practical application.

Description

Cobalt-nitrogen double-doped carbon dot and preparation method and application thereof

Technical Field

The invention relates to a fluorescent carbon dot, in particular to a cobalt-nitrogen double-doped carbon dot and a preparation method thereof, and the carbon dot is used for analyzing and detecting tetracycline antibiotics.

Background

Tetracyclines antibiotics (TCs) are a class of broad-spectrum antibacterial drugs found in the middle of the 20 th century. It has strong antibacterial ability to gram-positive and gram-negative bacteria such as rickettsia, mycoplasma, spirochete, chlamydia, etc., and can be used for treating various diseases of human and animals. In addition, TCs also have the advantages of high efficiency, low cost, good oral absorption, etc. Therefore, it has been widely used as an additive for animal feed. However, TCs are difficult to degrade and are likely to remain in foods such as meat and milk, and long-term use of such foods can cause bacterial resistance and bacterial colony disorder, thereby affecting human health and bringing serious consequences. It has been found that frequent intake of TCs can cause damage to the liver and kidneys of a human. Pregnant women are more susceptible to hepatotoxicity of TCs. In addition, extensive data suggests that prolonged repeated use of TC is detrimental to teeth because it affects tooth growth and formation, turning tooth color yellow. At present, the common methods for detecting TCs comprise a high performance liquid chromatography-mass spectrometry method, a surface enhanced Raman scattering method, an antibacterial screening test, an enzyme-linked immunosorbent assay and the like. However, these methods often require tedious sample pre-treatment procedures, complex and expensive instruments and professional skills, and have great obstacles in conventional food safety detection. Therefore, it is important to establish a simple, fast, selective and accurate method for detecting TCs.

To overcome these disadvantages, fluorescence sensing has attracted attention as an alternative method due to its advantages of high sensitivity, fast response time, and simple operation. Carbon Dots (CDs) are a novel fluorescent nano material and have the excellent performances of adjustable photoluminescence, good water solubility, low toxicity, low cost, light stability, chemical stability and the like. The fluorescent sensor has been well applied to the fields of biochemical sensing, biological imaging, environmental analysis and the like as a fluorescent sensor. However, carbon dots with specific targeting functions can be controllably prepared by a simple preparation process, and application to detection of specific analytes remains challenging.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a fluorescent carbon dot with excellent properties and a preparation method thereof, wherein the preparation method of the carbon dot is simple, convenient and quick; the prepared carbon dots have special luminous performance, can be applied to one-step detection of tetracycline antibiotics, and show good selectivity and sensitivity.

The invention provides a preparation method of cobalt-nitrogen double-doped carbon dots, which comprises the following steps:

1) putting iminodiacetic acid and cobalt chloride into a glass beaker, adding deionized water, fully stirring, performing ultrasonic dissolution for 10-30 minutes, transferring a reaction mixture into a hydrothermal reaction kettle, putting the hydrothermal reaction kettle into an oven, and reacting for 3-8 hours at 180 ℃ to obtain pink clear solution, wherein the mass ratio of the iminodiacetic acid to the cobalt chloride is as follows: 0.10-0.45: 0.15-0.60;

2) taking out the hydrothermal reaction kettle, naturally cooling, and filtering the reaction product by using a 0.22 mu m filter membrane to obtain a pure carbon dot aqueous solution;

3) and freeze-drying the carbon dot aqueous solution to obtain a blue carbon dot solid.

The blue fluorescent carbon dots prepared by the method have stable properties and good water solubility and dispersibility, the appearance of the blue fluorescent carbon dots is monodisperse quasi-spherical particles through TEM representation, and Co and N elements can be successfully doped into the carbon dot structure through XPS representation. The carbon dot preparation method is simple, convenient and quick, can obtain the target carbon dot by only one-step reaction, and does not need a complicated purification process. In addition, the carbon dots can be used for analyzing and detecting the tetracycline antibiotics with high selectivity and high sensitivity through an internal filtering effect due to special luminescence property, the tetracycline antibiotics are only added into the carbon dot solution, and the fluorescence intensity of the carbon dots is obviously quenched due to the fact that the antibiotics and the carbon dots compete to absorb excitation energy.

The application of the fluorescent carbon dots in label-free detection of tetracycline antibiotics provided by the invention comprises the following steps:

1) preparing a carbon dot solution with the concentration of 0.3 mg/mL;

2) respectively preparing standard stock solutions of tetracycline antibiotics with concentration gradients of 0.3, 0.6, 0.9 … … 5.7.7 and 6.0 mM;

3) adding tetracycline antibiotics with different concentrations into the carbon dot solution, measuring the fluorescence intensity of the carbon dot solution before and after reaction, and establishing a standard curve for detecting the tetracycline antibiotics according to the concentration of the tetracycline antibiotics and the change value of the relative fluorescence intensity of the carbon dot solution before and after reaction;

4) and quantitative detection: measuring the fluorescence intensity of the sample to be detected before and after the reaction with the carbon dots, calculating the change value of the relative fluorescence intensity before and after the reaction, and obtaining the content of the tetracycline antibiotics in the sample to be detected by referring to the standard curve obtained in the step 3).

The tetracycline antibiotics are tetracycline, oxytetracycline hydrochloride, chlortetracycline, doxycycline, methacycline, dimethylamino tetracycline, minocycline or doxycycline.

The invention has the following beneficial technical effects:

(1) the preparation method of the carbon dots provided by the invention does not need complicated pretreatment and purification steps, and the process is energy-saving and time-saving.

(2) The invention provides carbon dots with good water solubility; and maintain excellent optical stability under long-term illumination, high ionic strength and different pH ranges.

(3) The cobalt-nitrogen double-doped carbon dots have special excitation wavelength, can be mostly overlapped with the ultraviolet absorption wavelength of tetracycline antibiotics, and promote the fluorescence quenching of the carbon dots based on the internal filtering effect. Therefore, the carbon dots can be used as a fluorescent sensor to directly detect the tetracycline antibiotics.

(4) Compared with the traditional detection method, the method for detecting the tetracycline antibiotics by the carbon dots can achieve good detection effect without expensive analytical instruments and complex treatment processes, has excellent selectivity and sensitivity, and has superiority in actual operation.

Drawings

FIG. 1 is a TEM spectrum of a carbon dot prepared in example 1;

FIG. 2 is an XPS spectrum of carbon dots prepared in example 1;

FIG. 3 is a graph showing the overlap of the fluorescence spectrum of a carbon dot and the absorption spectrum of oxytetracycline;

FIG. 4 is a graph in which a fluorescence spectrum of a carbon spot and an absorption spectrum of tetracycline overlap;

FIG. 5 is a fluorescence emission spectrum of oxytetracycline detected at carbon spots prepared in example 1;

FIG. 6 is a schematic diagram of the selectivity of the carbon dot detection of tetracycline antibiotics prepared in example 1.

Detailed Description

The present invention is described in detail below with reference to examples, which show detailed embodiments and specific procedures, but the scope of the present invention is not limited to the following examples.

Example 1

The preparation method of the carbon dots comprises the following steps:

1) respectively putting 0.3g of iminodiacetic acid and 0.1190g of cobalt chloride into a glass beaker, adding into 10mL of deionized water, fully stirring, ultrasonically dissolving for 15 minutes, transferring the reaction mixture into a hydrothermal reaction kettle, putting into an oven, and reacting for 6 hours at 180 ℃ to obtain a pink clear solution;

Example 2

TEM and XPS characterization of the fluorescent carbon dots prepared in example 1 (see FIGS. 1-2) revealed that the carbon dots were monodisperse quasi-spherical particles containing mainly C, N, O, Co four elements.

Example 3

Ultraviolet absorption spectra of oxytetracycline and tetracycline, respectively, and fluorescence excitation and emission spectra of the carbon dots prepared in example 1 were scanned. As shown in FIGS. 3-4, the fluorescence excitation peaks of the carbon spots largely overlap with the absorption spectra of oxytetracycline and tetracycline.

Example 4

2mL of the aqueous fluorescent carbon dot solution (0.3mg/mL) prepared in example 1 was placed in a fluorescence cuvette, 0.2mL of tetracycline antibiotic solutions with concentrations of 0.3, 0.6, 0.9 … … 5.7.7, and 6.0mM were added, respectively, mixed well, and emission spectrum (. lamda.) was scanned in a fluorescence photometer_ex＝338nm，λ_em429nm), the fluorescence intensity of the carbon dots is gradually reduced along with the gradual increase of the content of the oxytetracycline in the solution, and the detection range and the detection limit of the oxytetracycline by the carbon dots are calculated according to the relation between the concentration of the oxytetracycline and the change value of the relative fluorescence intensity. (see FIG. 5)

Example 5

2.0mL of the aqueous fluorescent carbon dot solution (0.3mg/mL) prepared in example 1 was placed in a fluorescence cuvette, 0.2L of a 6mM oxytetracycline, tetracycline, ampicillin, streptomycin sulfate, chloramphenicol, erythromycin, and norfloxacin solution was added, mixed well, and the emission spectrum (. lamda.) was scanned in a fluorescence photometer_ex＝338nm，λ_em429nm) and the fluorescence intensity of the carbon dot solution before and after the addition of different antibiotics is recorded, and the selectivity of the carbon dot to tetracycline antibiotics is observed by calculating the relative fluorescence intensity. Referring to FIG. 6, tetracycline antibiotics significantly quenched the fluorescence at the carbon spots compared to other antibiotics.

Claims

1. The application of the cobalt-nitrogen double-doped carbon dots in detection of tetracycline antibiotics is characterized in that the cobalt-nitrogen double-doped carbon dots are prepared by the following method:

1) putting iminodiacetic acid and cobalt chloride into a glass beaker, adding deionized water, fully stirring, performing ultrasonic dissolution for 10-30 minutes, transferring a reaction mixture into a hydrothermal reaction kettle, putting the hydrothermal reaction kettle into an oven, and reacting for 3-8 hours at 180 ℃ to obtain a pink clear solution, wherein the mass ratio of the iminodiacetic acid to the cobalt chloride is as follows: 0.10-0.45: 0.15-0.60;

2. The use of the cobalt-nitrogen double-doped carbon dot according to claim 1 for detecting a tetracycline antibiotic, wherein the tetracycline antibiotic is tetracycline, oxytetracycline hydrochloride, chlortetracycline, doxycycline, methacycline, dimethylaminocycline, minocycline, or doxycycline.

3. A method for detecting tetracycline antibiotics by using cobalt-nitrogen double-doped carbon spots is characterized by comprising the following steps:

1) preparing a cobalt-nitrogen double-doped carbon dot solution with the concentration of 0.3 mg/mL;

4) and quantitative detection: measuring the fluorescence intensity of the sample to be measured before and after the reaction with the carbon dots, calculating the change value of the relative fluorescence intensity before and after the reaction, and obtaining the content of the tetracycline antibiotics in the sample to be measured by referring to the standard curve obtained in the step 3);

the cobalt-nitrogen double-doped carbon dots are prepared by the following method:

A) putting iminodiacetic acid and cobalt chloride into a glass beaker, adding deionized water, fully stirring, performing ultrasonic dissolution for 10-30 minutes, transferring a reaction mixture into a hydrothermal reaction kettle, putting the hydrothermal reaction kettle into an oven, and reacting for 3-8 hours at 180 ℃ to obtain a pink clear solution, wherein the mass ratio of the iminodiacetic acid to the cobalt chloride is as follows: 0.10-0.45: 0.15-0.60;

B) taking out the hydrothermal reaction kettle, naturally cooling, and filtering the reaction product by using a 0.22 mu m filter membrane to obtain a pure carbon dot aqueous solution;

C) and freeze-drying the carbon dot aqueous solution to obtain a blue carbon dot solid.