CN108083256A - The preparation method of high fluorescence property fluorescent carbon quantum dot and its in Cr（VI）Application in detection - Google Patents

Abstract

The invention discloses a method for preparing fluorescent carbon quantum dots with high fluorescence performance, comprising the following specific steps: A. dissolving (0.1-10 g) citric acid and (0.1-10 g) glycine in 1-20 mL water; B. dissolving The high-pressure reaction kettle is placed in an oven, heated for several hours under high temperature conditions, and then naturally cooled to room temperature to obtain a dark brown suspension containing fluorescent carbon quantum dots; C. After the obtained dark brown suspension is centrifuged to remove large particles, it passes through the large pores Resin adsorption, size exclusion gel or dialysis means, using water as the eluent to purify the crude product, purify fluorescent carbon quantum dots; D, the purified product is concentrated by a rotary evaporator at 45 ° C, and freeze-dried to obtain Purified fluorescent carbon quantum dots are white powder. The invention has low cost, simple and controllable preparation process, and the obtained carbon dots have high quantum yield, long fluorescence lifetime, high detection sensitivity and stability; simple and convenient operation, high sensitivity and good selectivity, and intuitive detection results , Quantitative detection.

Description

Preparation method of fluorescent carbon quantum dots with high fluorescence performance and its application in Cr(VI) detection application

technical field

The invention relates to the technical field of preparation and application of a fluorescence sensor with high fluorescence performance, in particular to a preparation method of a fluorescent carbon quantum dot with high fluorescence performance and its application in Cr(VI) detection.

Background technique

In the prior art, chromium is a widely used industrial material. Over the past few decades, industry and other anthropogenic processes have continuously released heavy metal ions into the environment. Cr(VI) is a toxic The World Health Organization has proposed a guideline limit of 0.05 mg/L for Cr in drinking water to detect Cr(VI) in order to monitor and reduce the risk of excessive Cr(VI) intake, especially in beverages and The risk in food is very important. In recent years, many analytical techniques have been successfully developed for the determination of Cr(VI) in different sample matrices, such as spectrophotometry, spectrofluorometry, flame atomic absorption spectrometry, inductively coupled plasma Bulk mass spectrometry, diffuse reflectance-Fourier transform infrared spectroscopy, etc., however, most of these methods are inconvenient due to the need for expensive equipment and complex pretreatments, limiting their use in rapid detection, and therefore, are highly desirable for development. A simple, sensitive, selective and low-cost method for Cr(VI) detection; fluorescent carbon quantum dots are a new type of carbon nanomaterials, due to their unique physical and chemical properties, such as low cost, simple synthesis route, Better biocompatibility, lower toxicity, high light and chemical stability, tunable excitation and emission spectra, these excellent properties make CD as a very potential nanosensor and has been successfully used in pH, Fluorescent detection of metal ions and biomacromolecular substances, however, still has several shortcomings that limit the further application of fluorescent carbon quantum dots. Ligand charge transfer) requires an intermolecular interaction between the chemical sensor and the target molecule, thus making the method complex and time-consuming, thus limiting practical applications. On the other hand, the quantum yield is a key indicator of fluorescent materials and is An important fundamental property that determines whether luminescent materials can be used in practical applications. The low quantum yield leads to low sensitivity in the detection system, which is one of the obstacles that prevent fluorescent carbon quantum dots from being used as fluorescent sensors. In order to overcome these shortcomings, high Quantum Yield of Fluorescent Carbon Quantum Dots and the Design of Fluorescence Measurement Systems Based on Alternative Mechanisms In the inner filter effect, since changes in absorbance are transformed exponentially into changes in fluorescence intensity, the sensitivity of this method is enhanced and can be compared with other mechanisms, based on The fluorescence measurement system of fluorescent carbon quantum dots with internal filter effect has been successfully developed. At the same time, doping is an effective method to improve the quantum yield. For example, B, N, S and P can improve the emission properties of carbon quantum dots. Among them, N doping Therefore, it is of great significance to develop fluorescent carbon quantum dots with high fluorescence performance for the detection of Cr(VI).

Contents of the invention

The purpose of the present invention is to provide a method for preparing fluorescent carbon quantum dots with high fluorescence performance.

The technical solution adopted by the present invention for achieving the above object is: a preparation method of fluorescent carbon quantum dots with high fluorescence performance, comprising the following specific steps:

A. Dissolve (0.1-10 g) citric acid and (0.1-10 g) glycine in 1-20 mL water;

B. Place the autoclave in an oven, heat it under high temperature for several hours, and then cool it down to room temperature naturally to obtain a dark brown suspension containing fluorescent carbon quantum dots;

C, the obtained dark brown suspension is centrifuged to remove large particles, then adsorbed by macroporous resin, size exclusion gel or dialysis, using water as the eluent to purify the crude product and purify the fluorescent carbon quantum dots;

D. The purified product was concentrated by a rotary evaporator at 45° C., and then freeze-dried to obtain purified fluorescent carbon quantum dots as white powder.

The temperature of the oven in the step B is 150°C-250°C.

In the step B, the solution is heated in an oven for 5-50 hours.

In the step C, the size exclusion gel is one or more of cross-linked dextran, agarose gel and polyacrylamide gel.

The resin used for resin adsorption in the step C is D101 non-polar macroporous resin.

Another object of the present invention is to provide an application of fluorescent carbon quantum dots with high fluorescence performance in Cr(VI) detection.

The technical solution adopted by the present invention to achieve the above purpose is: the application of a fluorescent carbon quantum dot with high fluorescence performance in the detection of Cr(VI), including the following steps:

A. Prepare fluorescent carbon quantum dots as an aqueous solution of fluorescent carbon quantum dot probes with a concentration of 0.01-1 mg/mL, and prepare a Cr(VI) solution with a known concentration;

B. Add the fluorescent carbon quantum dot probe aqueous solution prepared in the previous step to water and the Cr(VI) solution prepared in the previous step, respectively as a control group and an experimental group, and detect the fluorescence intensity and the experimental group in the experimental group. Compared with the control group, the standard curve between the Cr(VI) concentration and the fluorescence intensity was obtained by modeling according to the Cr(VI) solution concentration and the corresponding fluorescence quenching intensity;

C. Take the Cr(VI) solution to be tested, add the fluorescent carbon quantum dot probe aqueous solution prepared in step A to the Cr(VI) solution to be tested, as the Cr(VI) solution sample to be tested, use the same method as in step B Using the same detection method, obtain the fluorescence intensity of the Cr(VI) solution sample to be tested, and combine the Cr(VI) concentration and fluorescence intensity standard curve obtained in step B to obtain the Cr(VI) concentration of the Cr(VI) solution sample to be tested .

The concentration of Cr(VI) in the Cr(VI) solution in the step A is 0.1-1000 μM.

The Cr(VI) solution is preferably potassium dichromate solution.

The concentration of the fluorescent carbon quantum dot probe aqueous solution in the step A is preferably 0.05 mg/ml.

The specific conditions for detecting the fluorescence intensity in the step B are to use a fluorescence spectrophotometer with a detection wavelength range of 280-700 nm, the excitation wavelength is 280-500 nm, and the wavelength of the fluorescence emission peak is 350-690 nm.

The excitation wavelength is preferably 340 nm, and the emission wavelength is preferably 410 nm.

The invention discloses a method for preparing fluorescent carbon quantum dots with high fluorescence performance and its application in Cr(VI) detection. The method for preparing fluorescent carbon quantum dots is low in cost, and the preparation process is simple and controllable. Yield, long fluorescence lifetime, high detection sensitivity and stability; the Cr(IV) detection method provided is based on the fluorescence properties of fluorescent carbon quantum dots, and the fluorescence quenching effect of Cr(IV) on carbon nanometers can be used to obtain The standard curve of Cr(IV) concentration, and the detection sensitivity of Cr(IV) concentration is high, and its detection limit is 2.96 μM; the Cr(IV) concentration detection method provided has the advantages of simple and convenient detection process, high sensitivity and good selectivity, The detection results are intuitive and can be quantitatively detected.

Description of drawings

Fig. 1 is a transmission electron micrograph of fluorescent carbon quantum dots prepared in Example 1 of a method for preparing fluorescent carbon quantum dots with high fluorescence performance and its application in Cr(VI) detection according to the present invention.

Fig. 2 is a particle size distribution diagram of fluorescent carbon quantum dots prepared in Example 1 of a method for preparing fluorescent carbon quantum dots with high fluorescent performance and its application in Cr(VI) detection according to the present invention.

Fig. 3 is an ultraviolet fluorescence spectrum diagram of medium fluorescent carbon quantum dots prepared in Example 1 of a method for preparing fluorescent carbon quantum dots with high fluorescent performance and its application in Cr(VI) detection according to the present invention.

Fig. 4 is an X-photoelectron spectrum diagram of fluorescent carbon quantum dots prepared in Example 1 of a method for preparing fluorescent carbon quantum dots with high fluorescence performance and its application in Cr(VI) detection according to the present invention.

Fig. 5 is an infrared spectrum diagram of fluorescent carbon quantum dots prepared in Example 1 of a method for preparing fluorescent carbon quantum dots with high fluorescent performance and its application in Cr(VI) detection according to the present invention.

Fig. 6 is a standard curve for the detection of Cr(IV) by fluorescent carbon quantum dots in Example 2 of a method for preparing fluorescent carbon quantum dots with high fluorescence performance and its application in Cr(VI) detection according to the present invention.

Detailed ways

As shown in Figures 1 to 6, the preparation method of fluorescent carbon quantum dots with high fluorescence performance specifically includes the following steps: A. Dissolving (0.1-10 g) citric acid and (0.1-10 g) glycine in 1-20 mL In water; B, the autoclave is heated in an oven for several hours under high temperature conditions and cooled naturally to room temperature to obtain a dark brown suspension containing fluorescent carbon quantum dots, wherein the temperature range of the oven is 150°C-250°C, and the oven The heating time is 5 h-50 h; C. After the obtained dark brown suspension is centrifuged to remove large particles, the crude product is purified by macroporous resin adsorption, size exclusion gel or dialysis, using water as the eluent. Fluorescent carbon quantum dots, size exclusion gels include: one or more of Sephadex cross-linked dextran, Sepharose agarose gel, Bio-Gel P polyacrylamide gel, and the resin used for resin adsorption is D101 nonpolar D. The purified product was concentrated by rotary evaporation at 45°C, and then freeze-dried to obtain purified fluorescent carbon quantum dots, which were white powders; fluorescent carbon quantum dots with high fluorescence performance were detected in Cr(VI) The application in the method comprises the following steps: A. preparing the fluorescent carbon quantum dots as a fluorescent carbon quantum dot probe aqueous solution with a concentration of 0.01-1 mg/mL; configuring a series of Cr(VI) solutions with known concentrations, Cr (VI) The concentration range of Cr(VI) in the solution is 0.1-1000 μM, the Cr(VI) solution is preferably potassium dichromate solution, and the concentration of the fluorescent carbon quantum dot aqueous solution is preferably 0.05 mg/ml; B, adding water and step Add the fluorescent carbon quantum dot aqueous solution prepared in step A to the Cr(VI) solution prepared in A, and serve as the control group and the experimental group respectively, and detect the fluorescence intensity in the experimental group. Compared with the control group, according to the Cr(VI) solution concentration and The corresponding fluorescence quenching intensity was modeled to obtain a standard curve between Cr(VI) concentration and fluorescence intensity. The specific conditions for fluorescence intensity detection were: a fluorescence spectrophotometer with a detection wavelength range of 280-700nm was used, and the excitation wavelength was 280 -500 nm, preferably, the excitation wavelength is 340 nm, and the wavelength of the fluorescence emission peak is 350-690 nm, preferably, the emission wavelength is 410 nm; C, take the Cr(VI) solution to be measured, add the Cr(VI) solution to the test ) solution by adding the fluorescent carbon quantum dot aqueous solution prepared in step A, as the Cr(VI) solution sample to be tested, using the same detection method as in step B, to obtain the fluorescence intensity of the Cr(VI) solution sample to be tested, combined with The standard curve of Cr(VI) concentration and fluorescence intensity obtained in step B is used to obtain the Cr(VI) concentration of the Cr(VI) solution sample to be tested.

Example 1. Preparation of carbon nanofluorescent probes: Dissolve citric acid (0.35 g) and glycine (0.35 g) in 7 mL of water, and then transfer the solution to a poly(tetrafluoroethylene)-lined autoclave at 190 After heating in an oven at ℃ for 48 hours and naturally cooling to room temperature, a dark brown suspension containing fluorescent carbon quantum dots was obtained. After centrifuging at 4000 rpm for 10 minutes to remove large particles, a D101 macroporous adsorption resin column was used, and water was used as a wash. The crude product is purified by dehydration, and the fluorescent carbon quantum dots are concentrated by a vacuum rotary evaporator, and then freeze-dried to obtain purified fluorescent carbon quantum dots, which are white powders, and the particles of fluorescent carbon nanoparticles can be detected by transmission electron microscope TEM (as shown in Figure 1) The dispersion is good and the average particle size is 2.5 nm. The results of fluorescence spectrum and ultraviolet spectrum (as shown in Figure 2) show that there is a peak at 330 nm with n-π ^* transition phenomenon, and fluorescent carbon quantum dots are found by XPS (as shown in Figure 3) It mainly contains carbon, nitrogen, and oxygen. Through infrared spectroscopy (as shown in Figure 4), it is found that the surface of fluorescent carbon quantum dots mainly contains OH, ^* O=CO, CO, and O=CO ^* groups, which proves that the surface of carbon dots contains hydroxyl groups. , carboxyl and other hydrophilic groups.

Example 2, establishment of a standard curve between Cr(IV) concentration and fluorescence intensity: take the fluorescent carbon quantum dots in Example 1 and prepare a carbon nanoparticle solution with a concentration of 0.05 g/ml, and prepare 1 ml of each The carbon nanoparticle solution was used as the blank control group; another 15 centrifuge tubes were added with 1 ml of the prepared carbon nanoparticle solution, and then 5 ml of Cr(IV) were added to the 15 centrifuge tubes with concentrations of 5, 10, 20, respectively. 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 150, 200, 500, 1000 μM aqueous solution, after mixing thoroughly, the obtained carbon nanoparticles and the standard solution of Cr(IV) were allowed to stand for 1 min Finally, the fluorescence intensity F1 in the standard solution was detected by a fluorescence photometer whose detection wavelength range covers 280-700 nm. The detection conditions were that the excitation wavelength was 340 nm, the emission wavelength was 410 nm, and the fluorescence intensity of the blank control group was F0 (excitation wavelength was 340 nm, emission wavelength 410 nm ), draw the standard curve between fluorescence quenching intensity ((F ₀ - F ₁ )/F ₀ ) and Cr(IV) concentration as shown in Figure 5, the linear regression equation is (F ₀ -F ₁ )/F ₀ = 0.00274x +0.01637, R ² = 0.98, and the detection limit of Cr(IV) calculated according to the 3σ standard (signal-to-noise ratio) was 2.96 μmol/L.

Example 3, detection of actual samples: Take the fluorescent carbon quantum dots in Example 1, take tap water as a sample, and filter through a 0.22 μm membrane before analysis, the concentration of carbon dots is 0.05 mg/mL, take 1 ml of pure water Add 1 ml of prepared carbon nanoparticle solution as a blank control group, and measure the fluorescence intensity as F ₀ , take 1 ml of tap water and mix it with 1 ml of carbon nanoparticles at a concentration of 0.05 mg/ml to detect the fluorescence intensity F1, according to linear regression The equation is (F ₀ -F ₁ )/F ₀ = 0.00274x+0.01637, and the calculation result is not detected.

Example 4, the detection of actual samples: take the fluorescent carbon quantum dots in Example 1, prepare a 50 μM Cr(IV) ion solution as the sample, and filter it through a 0.22 μm membrane before analysis, and the concentration of carbon dots is 0.05 mg /mL, take 1 ml of pure water plus 1 ml of prepared carbon nanoparticle solution as a blank control group, the measured fluorescence intensity is F ₀ , take 1 ml of tap water and mix it with 0.05 mg/ml carbon nanoparticle The fluorescence intensity F ₁ was detected, according to the linear regression equation (F ₀ -F ₁ )/F ₀ = 0.00274x + 0.01637, the calculated result was 60.4 μM, and the recovery rate was 120.8%.

Example 5, detection of actual samples: take the fluorescent carbon quantum dots in Example 1, configure 100 μM Cr(IV) ion solution as the sample, and filter through a 0.22 μm membrane before analysis, and the concentration of carbon dots is 0.05 mg /mL, take 1 ml of pure water plus 1 ml of prepared carbon nanoparticle solution as a blank control group, the measured fluorescence intensity is F ₀ , take 1 ml of tap water and mix it with 0.05 mg/ml carbon nanoparticles To detect the fluorescence intensity F ₁ , according to the linear regression equation (F ₀ -F ₁ )/F ₀ = 0.00274x + 0.01637, the calculation result was 60.4 μM, and the recovery rate was 120.8%.

Example 6, the detection of actual samples: take the fluorescent carbon quantum dots in Example 1, prepare a 150 μM Cr(IV) ion solution as the sample, and filter it through a 0.22 μm membrane before analysis, and the concentration of carbon dots is 0.05 mg /mL, take 1 ml of pure water plus 1 ml of prepared carbon nanoparticle solution as a blank control group, the measured fluorescence intensity is F ₀ , take 1 ml of tap water and mix it with 0.05mg/ml carbon nanoparticles To detect the fluorescence intensity F ₁ , according to the linear regression equation (F ₀ -F ₁ )/F ₀ = 0.00274x + 0.01637, the calculation result was 153.5 μM, and the recovery rate was 102.3%.

Claims (11)

1. a kind of preparation method of high fluorescence property fluorescent carbon quantum dot, which is characterized in that including step in detail below：

A, will（0.1-10 g）Citric acid and（0.1-10 g）Glycine is dissolved in 1-20 mL water；

B, autoclave is placed in baking oven and is heated for a period of hours rear cooled to room temperature under the high temperature conditions, obtained containing glimmering The dark brown suspension of light carbon quantum dot；

C, the dark brown suspension of gained is after being centrifuged off bulky grain, by macroporous resin adsorption, volume exclusion gel or saturating The means of analysis using water as eluent crude product, purify fluorescent carbon quantum dot；

D, purified product by under the conditions of 45 DEG C Rotary Evaporators concentrate, then freeze, the fluorescence carbon amounts purified It is sub-, it is white powder.

2. a kind of preparation method of high fluorescence property fluorescent carbon quantum dot according to claim 1, it is characterised in that：It is described The temperature of baking oven is 150 DEG C -250 DEG C in step B.

3. a kind of preparation method of high fluorescence property fluorescent carbon quantum dot according to claim 1, it is characterised in that：It is described Heating time is 5-50h to solution in an oven in step B.

4. a kind of preparation method of high fluorescence property fluorescent carbon quantum dot according to claim 1, it is characterised in that：It is described Volume exclusion gel is one or more of cross-link dextran, Ago-Gel and polyacrylamide gel in step C.

5. a kind of preparation method of high fluorescence property fluorescent carbon quantum dot according to claim 1, it is characterised in that：It is described Resin used in resin adsorption is D101 non-polar macroporous resins in step C.

6. a kind of high fluorescence property fluorescent carbon quantum dot according to claim 1 is in Cr（VI）Application in detection, it is special Sign is, comprises the following steps：

A, fluorescent carbon quantum dot is formulated as the fluorescent carbon quantum dot probe aqueous solution that concentration is 0.01-1 mg/mL, and configured Know the Cr of concentration（VI）Solution；

B, Cr obtained into water and in previous step（VI）Fluorescent carbon quantum dot obtained in previous step is added in solution to visit Pin aqueous solution, respectively as control group and experimental group, the fluorescence intensity in test experience group is compared with control group, according to Cr（VI） Solution concentration and the modeling of corresponding fluorescent quenching intensity, obtain Cr（VI）Standard curve between concentration and fluorescence intensity；

C, Cr to be measured is taken（VI）Solution, to Cr to be measured（VI）Fluorescent carbon quantum dot probe water obtained in step A is added in solution Solution, as Cr to be measured（VI）Solution example using the detection method identical with step B, obtains Cr to be measured（VI）Solution sample The fluorescence intensity of product, with reference to the Cr obtained in step B（VI）Concentration and Standardization curve for fluorescence intensity obtain Cr to be measured（VI）Solution The Cr of sample（VI）Concentration.

7. high fluorescence property fluorescent carbon quantum dot according to claim 6 is in Cr（VI）Application in detection, feature exist In：Cr in the step A（VI）Cr in solution（VI）Concentration be 0.1-1000 μM.

8. high fluorescence property fluorescent carbon quantum dot according to claim 7 is in Cr（VI）Application in detection, feature exist In：The Cr（VI）The preferred potassium bichromate solution of solution.

9. high fluorescence property fluorescent carbon quantum dot according to claim 6 is in Cr（VI）Application in detection, feature exist In：The concentration of fluorescent carbon quantum dot probe aqueous solution is preferably 0.05 mg/ml in the step A.

10. high fluorescence property fluorescent carbon quantum dot according to claim 6 is in Cr（VI）Application in detection, feature exist In：The actual conditions that fluorescence intensity detects in the step B is the fluorescence point for covering 280-700 nm using Detection wavelength scope Light photometer, excitation wavelength are 280-500 nm；The wavelength of fluorescence emission peak is 350-690 nm.

11. high fluorescence property fluorescent carbon quantum dot according to claim 10 is in Cr（VI）Application in detection, feature It is：The excitation wavelength is preferably 340 nm, and launch wavelength is preferably 410 nm.