Preparation of carbon quantum dots and their application in detecting melamine

Abstract

The invention discloses a preparation method of carbon quantum dots and its application in detecting melamine. A preparation method of carbon quantum dots comprises the following steps: placing butterfly pea flowers in a reaction kettle, adding water, taking out centrifugation after reaction, filtering with a filter membrane, and obtaining the carbon quantum dots. The carbon quantum dots prepared by the invention using butterfly pea flowers can produce a fluorescence quenching effect on melamine within 20 seconds, which can greatly shorten the detection time of melamine, and the raw materials for preparing butterfly pea flower carbon quantum dots are green, healthy, non-toxic and harmless, and the preparation method is simple and fast.

Description

Technical Field

[0001] The invention relates to the technical field of nanomaterials, and in particular to the preparation of carbon quantum dots and the application of the carbon quantum dots in detecting melamine. Background Art

[0002] At present, the main methods for detecting melamine include high performance liquid chromatography (HPLC), mass spectrometry (MS), capillary electrophoresis (CE), surface enhanced Raman spectroscopy (SERS), etc. Although these methods are relatively accurate, they require expensive instruments and cumbersome operations. Compared with the above methods, the carbon quantum dot detection method has the characteristics of low cost, simple operation, fast and effective, and is considered to be a very potential detection method. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a preparation method of carbon quantum dots and their application in detecting melamine.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] The first aspect of the present invention provides a method for preparing carbon quantum dots, comprising the following steps:

[0006] The butterfly pea flower is placed in a reaction kettle, water is added, and after the reaction, the flower is taken out for centrifugation and filtered with a filter membrane to obtain the carbon quantum dots.

[0007] Preferably, the butterfly pea flower adopts butterfly pea flower dry powder, and the mass ratio of the butterfly pea flower dry powder to water is 1: (40-80); further preferably, the mass ratio of the butterfly pea flower dry powder to water is 1: (50-70).

[0008] In the present invention, the butterfly pea flower dry powder can be dried by using fresh butterfly pea flower, the implementation of the present invention is not limited to the drying method of butterfly pea flower dry, and the specific moisture content of butterfly pea flower dry is not required, and commercially available butterfly pea flower dry can be used; the butterfly pea flower dry powder of the present invention can be ground by using a grinder, and the present invention does not require the particle size of the butterfly pea flower dry powder, and is suitable for reaction in a reactor.

[0009] Preferably, after adding the water, stirring is performed for 20-40 minutes, and then the reactor is covered to carry out the reaction; further preferably, after adding the water, stirring is performed for 25-35 minutes, and then the reactor is covered to carry out the reaction.

[0010] Preferably, the reaction temperature is 180-220°C; further preferably, the reaction temperature is 190-210°C; even further preferably, the reaction temperature is 195-205°C.

[0011] Preferably, the reaction time is 5-7 h; further preferably, the reaction time is 5.5-6.5 h; even further preferably, the reaction time is 6 h.

[0012] Preferably, the centrifugal rotation speed is 8000-12000 r / min; further preferably, the centrifugal rotation speed is 9000-11000 r / min.

[0013] Preferably, the centrifugation time is 1-3 min; the number of centrifugation is ≥ 2 times.

[0014] Preferably, the membrane filtration uses a 0.22 μm filter membrane.

[0015] In the preparation method of carbon quantum dots of the present invention, the supernatant obtained by membrane filtration is the mother liquor of carbon quantum dots; the solid-liquid ratio (R, mg / mL) of the mother liquor of carbon quantum dots is 15-18 mg / mL.

[0016] The second aspect of the present invention provides a carbon quantum dot prepared by the carbon quantum dot preparation method.

[0017] Preferably, the optimal excitation wavelength of the carbon quantum dots is 470 nm.

[0018] Preferably, the average particle size of the carbon quantum dots is 1-5 nm; further preferably, the average particle size of the carbon quantum dots is 2-4 nm.

[0019] The third aspect of the present invention provides the application of the carbon quantum dots in the detection of melamine.

[0020] Preferably, the melamine detection is suitable for 10 -5 ~7×10 -5 mol / L concentration range.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The carbon quantum dots prepared by using butterfly pea flowers can produce a fluorescence quenching effect on melamine within 20 seconds, and can greatly shorten the detection time of melamine. In addition, the raw materials for preparing the butterfly pea flower carbon quantum dots are green, healthy, non-toxic and harmless, and the preparation method is simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is the fluorescence emission spectrum of B-CDs carbon quantum dots;

[0024] Figure 2 TEM image showing the morphology of B-CDs carbon quantum dots;

[0025] Figure 3 This is the full XPS spectrum of B-CDs carbon quantum dots;

[0026] Figure 4 FTIR graph of B-CDs as carbon quantum dots;

[0027] Figure 5 This is the fluorescence quenching diagram of B-CDs carbon quantum dots to melamine;

[0028] Figure 6 This is the effect of common pharmaceutical small molecules on the fluorescence intensity of carbon quantum dots. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0031] Example 1

[0032] This embodiment provides a method for preparing butterfly pea flower fluorescent carbon quantum dots, which specifically includes the following steps:

[0033] Take 1.0g of butterfly pea flower dry and grind it into butterfly pea flower powder with a grinder. Place the butterfly pea flower powder in a 100mL reactor, add 60mL of deionized water, and stir it on a magnetic stirrer for 30 minutes. After stirring, take out the stirrer, cover the reactor, put it in a drying oven, and heat it at 200℃ for 6 hours. After the heating stops, take out the brown-yellow carbon quantum dot dispersion, pour it into two 100mL centrifuge tubes in equal parts, and centrifuge it twice at 10000r / min in a centrifuge, each time for 2min. After centrifugation, filter the supernatant with a filter membrane with a pore size of 0.22μm. The dispersion obtained by the above steps is the mother liquor of butterfly pea flower fluorescent carbon quantum dots, which needs to be kept away from light. The mother liquor of butterfly pea flower fluorescent carbon quantum dots is referred to as B-CDs below, and the solid-liquid ratio (R, mg / mL) of the mother liquor of the carbon quantum dots is 16.66mg / mL.

[0034] Take 3mL B-CDs in a fluorescence cuvette, increase the incident wavelength by 10nm from 400nm to 500nm as the excitation wavelength, and plot the obtained emission spectrum on the same image to obtain the fluorescence emission spectrum of B-CDs carbon quantum dots ( Figure 1 ).

[0035] Depend on Figure 1 It can be seen that the fluorescence intensity of B-CDs is the highest at an excitation wavelength of 470 nm. Therefore, the optimal excitation wavelength of B-CDs is 470 nm.

[0036] The B-CDs carbon quantum dots obtained in the experiment were imaged by transmission electron microscopy to obtain the morphology characterization TEM image of the B-CDs carbon quantum dots, as shown in Figure 2 As shown, the fluorescent carbon quantum dots are spherical or quasi-spherical, the particles are evenly dispersed, there is no agglomeration phenomenon, the particle size is very small, and the average particle size is about 3nm.

[0037] The elemental composition of the fluorescent carbon quantum dots was analyzed and characterized by X-ray photoelectron spectroscopy. The experimental results are shown in Figure 3 .from Figure 3 From the full spectrum scanning XPS diagram, it can be seen that the peak of the fluorescent carbon quantum dots at 531.4 eV is O 1s, with an atomic percentage of about 53.76%, the peak at 398.8 eV is N 1s, with an atomic percentage of about 14.87%, and the peak at 285.0 eV is C 1s, with an atomic percentage of about 37.37%. It can be seen that the fluorescent carbon quantum dots prepared by the hydrothermal method are mainly O, C and N elements.

[0038] The chemical bonds of the synthesized B-CDs were characterized by FTIR spectroscopy, e.g. Figure 4 As shown. In the figure, 3491.16 cm -1 The OH / NH stretching vibration absorption peak at 1639.49 cm -1 The characteristic absorption band at is that of aromatic CN heterocycle.

[0039] After adding different concentrations of melamine to B-CDs, the fluorescence intensity of CDs gradually decreased with the increase of melamine concentration, from 10 -9 mol / L to 10 -3 mol / L fluorescence was completely quenched. At the same time, the linear relationship between the quenching efficiency F / F0 and the melamine concentration was investigated. The results showed that 10 -5 ~7×10 -5 There is a good linear relationship within the concentration range of 1 mol / L, indicating that this method is sensitive and rapid for the detection of melamine in food.

[0040] Prepare 1.0 mol / L melamine, lactose, chloramphenicol, kanamycin, dopamine, tetracycline (TC), KCl, NaCl, MgCl2, CaCl2, and ZnCl2 solutions as interfering substances. First, add 3 mL of B-CDs to the fluorescence cuvette, and measure the emission spectrum and fluorescence intensity of the blank sample at an excitation wavelength of 470 nm. Then, take 3 μL of each of the above solutions and add them to the fluorescence cuvette containing 3 mL of B-CDs solution. Mix well for 3 minutes and then perform fluorescence detection. The fluorescence intensity of the B-CDs after adding the interfering substances is compared with the fluorescence intensity of the corresponding blank B-CDs, and the results are shown in the figure. Figure 6 As shown, according to Figure 6 Analysis shows that melamine has a good quenching effect on the fluorescence intensity of B-CDs, while the quenching effect of other interfering substances is not obvious and even enhances the fluorescence. Therefore, it can be judged that B-CDs has a good selectivity for melamine in milk.

[0041] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. Application of carbon quantum dots in melamine detection, It is characterized in that The method for preparing carbon quantum dots comprises the following steps: Placing butterfly pea flowers in a reaction kettle, adding water, taking them out after the reaction, centrifuging them, and filtering them with a filter membrane to obtain the carbon quantum dots; The butterfly pea flower adopts butterfly pea flower dry powder, and the mass ratio of the butterfly pea flower dry powder to water is 1: (40-80); The reaction temperature is 180-220°C; the reaction time is 5-7h; The optimal excitation wavelength of the carbon quantum dots is 470 nm.

2. The use according to claim 1, It is characterized in that After adding the water, stir for 20-40 minutes, and then cover the reactor to carry out the reaction.

3. The use according to claim 1, It is characterized in that The centrifugal speed is 8000-12000r / min.

4. The use according to claim 1, It is characterized in that The average particle size of the carbon quantum dots is 1-5 nm.

5. The use according to claim 1, It is characterized in that The melamine test is applicable to 10 -5 ~7×10 - 5 mol / L concentration range.

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