CN112175611B

CN112175611B - Application of free radical initiator in adjusting and controlling maximum emission wavelength of carbon point fluorescence

Info

Publication number: CN112175611B
Application number: CN202011002283.5A
Authority: CN
Inventors: 李季; 王玉玉; 王学川; 张苑
Original assignee: Shaanxi University of Science and Technology
Current assignee: Shaanxi University of Science and Technology
Priority date: 2020-09-22
Filing date: 2020-09-22
Publication date: 2023-03-31
Anticipated expiration: 2040-09-22
Also published as: CN112175611A

Abstract

The invention researches the application of different free radical initiators in the regulation of the maximum emission wavelength of the carbon point fluorescence. Different from the traditional method that the fluorescence color of the carbon dots is regulated and controlled by using the polarity of different solvents, the carbon dot solution with different fluorescence colors can be obtained under the appropriate initiation condition by selecting different free radical initiators and controlling the dosage of the initiators. The method regulates and controls the fluorescence color of the known red fluorescent carbon dots on the basis of preparing the known red fluorescent carbon dots, and realizes the process that the carbon dots turn green from red to orange to yellow. The method has the characteristics of simple operation steps, rapidness, high efficiency, mild reaction conditions, stable carbon dot optical properties and the like.

Description

Application of free radical initiator in adjusting and controlling maximum emission wavelength of carbon point fluorescence

Technical Field

The invention belongs to the technical field of carbon dot luminescence, and particularly relates to application of a free radical initiator in regulation and control of the maximum emission wavelength of carbon dot fluorescence.

Background

Since the fluorescent carbon quantum dots are discovered in 2004, the fluorescent carbon quantum dots can be used as good electron acceptors and unique optical characteristics due to good water solubility, biocompatibility and low biological toxicity, and have great application prospects in the fields of ion detection, biological imaging, catalysis, photoelectric conversion and the like. There are many explanations on the mechanism of the optical characteristics of the carbon quantum dots, and many researches demonstrate the rule method of the optical characteristics of the carbon quantum dots by observing the particle size and the surface state of the carbon quantum dots, doping heteroatoms and other methods. The reaction solvent and the precursor are important factors for determining the optical properties of the carbon quantum dot, and the emission wavelength of the carbon quantum dot can be regulated and controlled by changing the solvent and the precursor. On the basis of the prepared red fluorescent carbon quantum dot solution, different types of free radical initiators are added, and different types of free radicals are induced by heating or ultraviolet radiation to regulate and control the maximum emission wavelength of fluorescence.

Disclosure of Invention

The invention aims to regulate and control the fluorescence color of one carbon dot by an initiator and realize the regulation and control of multiple fluorescence colors by controlling the type, initiation mode and addition amount of the initiator.

To achieve the purpose of the invention, on the basis of the prepared red carbon dot solution (which can be abbreviated as p-CDs hereinafter), the technical scheme of the invention comprises the following steps: 1. regulating and controlling the fluorescence color of the red carbon dots by adding Azobisisobutyronitrile (AIBN); 2. the fluorescence color of the red carbon dot is regulated by adding 2.2, 2-azobis (2-methylpropylammonium) dihydrochloride (V-50); 3. the fluorescence color of the red carbon dots is regulated and controlled by adding other water-soluble initiators.

The invention discloses an application of a free radical initiator in regulating and controlling the maximum emission wavelength of carbon dot fluorescence, which regulates and controls the fluorescence of a known red fluorescent carbon dot solution by adding different initiators on the basis of preparing the known red fluorescent carbon dot solution, and comprises the following steps:

1) Fluorescence color control of Azodiisobutyronitrile (AIBN) on red carbon dots

Adding 50-60 mu L of red carbon dot solution with the concentration of 4 mg/mL into 6 mL of ethanol solution, then adding 0-90 mg of Azobisisobutyronitrile (AIBN) initiator into the red carbon dot solution, and reacting in an oven at 60-70 ℃ for 12-24h to obtain carbon dot solutions with different fluorescence colors.

2) Fluorescence color control of 2, 2-azobis (2-methylpropylamidine) dihydrochloride (V-50) on red carbon dots

Adding 50-60 mu L of red carbon dot solution with the concentration of 4 mg/mL into 5mL of aqueous solution, then adding 0-50 mg of V-50 initiator into the solution, and reacting for 12 h in an oven at 60-70 ℃ or irradiating for 3-12 h under a 395 nm ultraviolet lamp to obtain carbon dot solutions with different fluorescence colors.

3) Fluorescence color control of other initiators on red carbon dots

60 mu L of red carbon dot solution with the concentration of 4 mg/mL is added into 6 mL of aqueous solution, then 0-10 mg of other kinds of initiators are added into the red carbon dot solution, and the mixture is reacted in an oven at the temperature of 60-70 ℃ for 0-12 h to obtain carbon dot solutions with different fluorescence colors.

The mass fraction of the red carbon dot solution in the step (a) is 4 mg/mL.

Azobisisobutyronitrile (AIBN) is used as oil-soluble initiator, and the 10 h half-life temperature is 65 ℃.

2, 2-azobis (2-methylpropylami) dihydrochloride (V-50) is a water-soluble photoinitiator with a 10 h half-life temperature of 56 ℃.

Other types of initiators include alpha-ketoglutaric acid, ammonium persulfate, and potassium persulfate, all of which are water-soluble initiators. In addition to the initiators listed in the examples, other free radical initiators will be included, such as: organic peroxide initiators such as cyclohexanone peroxide, dibenzoyl peroxide, and t-butyl hydroperoxide; azo initiators such as azobisisoheptonitrile.

Azo and alpha-ketoglutaric acid are used as regulating agents, and heating or ultraviolet radiation is used as an initiating mode.

The method specifically comprises the following steps:

1: fluorescence color control of Azodiisobutyronitrile (AIBN) on red carbon dots

Adding 50-60 mu L of red carbon dot solution with the concentration of 4 mg/mL into 6 mL of ethanol solution, then adding 0-90 mg of Azobisisobutyronitrile (AIBN) initiator, and reacting in an oven at 60-70 ℃ for 12-24h to obtain carbon dot solutions with different fluorescence colors.

2: fluorescence color control of 2, 2-azobis (2-methylpropylimidazole) dihydrochloride (V-50) on red carbon dots

3: fluorescence color control of other initiators on red carbon dots

The method for regulating the fluorescence color of the carbon dot by adopting the initiator has certain guiding significance for explaining the fluorescence conversion mechanism.

Drawings

FIG. 1 is a graph of UV and fluorescence spectra of carbon spots before and after AIBN treatment, in which: a) Ultraviolet absorption spectrogram of p-CDs in ethanol solution; b) Fluorescence emission spectrum of p-CDs at excitation wavelength of 420 nm; c) 10 mg of Azobisisobutyronitrile (AIBN) is added, and the carbon dot solution is an orange fluorescent ultraviolet absorption spectrogram; d) (ii) adding 10 mg of Azobisisobutyronitrile (AIBN), and a fluorescence emission spectrum at an excitation wavelength of 420 nm; e) 20 mg of Azobisisobutyronitrile (AIBN) is added, and the carbon dot solution is a yellow fluorescent ultraviolet absorption spectrogram; f) Adding 20 mg of Azobisisobutyronitrile (AIBN), and performing fluorescence emission spectrum at an excitation wavelength of 420 nm; g) 40 mg of Azobisisobutyronitrile (AIBN) is added, and the carbon dot solution is a green fluorescent ultraviolet absorption spectrogram; h) 40 mg of Azobisisobutyronitrile (AIBN) was added, and the fluorescence emission spectrum was measured at an excitation wavelength of 420 nm.

FIG. 2 is a graph of UV and fluorescence spectra of carbon spots before and after V-50 treatment, in which: a) Ultraviolet absorption spectrogram of p-CDs in deionized water solution; b) Fluorescence emission spectrum of p-CDs at an excitation wavelength of 420 nm; c) 30 mg of 2, 2-azobis (2-methylpropylimide) dihydrochloride (V-50) was added, and the carbon dot solution showed a yellow fluorescent UV absorption spectrum; d) Adding 30 mg of 2, 2-azobis (2-methylpropylamidine) dihydrochloride (V-50), and obtaining a fluorescence emission spectrum at an excitation wavelength of 420 nm; e) 50 mg of 2, 2-azobis (2-methylpropylamidine) dihydrochloride (V-50) was added, and the carbon dot solution showed a yellow fluorescent UV absorption spectrum; f) The fluorescence emission spectrum at an excitation wavelength of 420 nm was obtained by adding 50 mg of 2, 2-azobis (2-methylpropylamidine) dihydrochloride (V-50).

FIG. 3 is a graph of UV and fluorescence spectra of carbon spots before and after alpha-ketoglutaric acid treatment, in which: a) Ultraviolet absorption spectrogram of p-CDs in deionized water solution; b) Fluorescence emission spectrum of p-CDs at excitation wavelength of 420 nm; c) 2 mg of alpha-ketoglutaric acid is added, and the carbon dot solution is a green fluorescent ultraviolet absorption spectrogram; d) Adding 2 mg of alpha-ketoglutaric acid, and performing fluorescence emission spectrogram under the excitation wavelength of 420 nm; e) 10 mg of alpha-ketoglutaric acid is added, and the carbon dot solution is a green fluorescent ultraviolet absorption spectrum chart; f) Fluorescence emission spectrum at excitation wavelength of 420 nm with the addition of 10 mg of alpha-ketoglutaric acid.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to be limiting.

The invention firstly utilizes the known method to prepare the red fluorescent carbon dot solution, and the specific steps are as follows: weighing 0.6 g of p-phenylenediamine, putting the p-phenylenediamine into 60mL of ethanol, pouring a proper amount of the uniformly mixed solution into a polytetrafluoroethylene reaction kettle at about 2/3 of the position, screwing down the solution, putting the solution in an oven, heating the solution to 180 ℃, and reacting for 12 hours. After cooling to room temperature, separating and purifying the burnt carbon dots in a chromatographic column by using dichloromethane and absolute ethyl alcohol to obtain red carbon dot solution (p-CDs) for cold storage and standby.

Example 1

Into eleven 20 mL sample bottles were added 6 mL of absolute ethanol, 60. Mu.L of a red dot solution with a mass fraction of 4 mg/mL, and 0 mg,6 mg,10 mg,20 mg,30 mg,40 mg,50 mg,60 mg,70 mg,80 mg, and 90 mg of Azobisisobutyronitrile (AIBN), respectively. The oven is heated to 70 ℃ and the reaction lasts for 12 h. The reacted solution was irradiated under an ultraviolet lamp of 395 nm, and the fluorescence was found to show changes of red, orange-red and yellow-green.

Example 2

6 mL of absolute ethyl alcohol and 60. Mu.L of a red carbon dot solution with a mass fraction of 4 mg/mL were added to six 20 mL sample bottles, and 0 mg,5 mg,10 mg,20 mg,30 mg and 40 mg of Azobisisobutyronitrile (AIBN) were sequentially added. The oven is heated to 70 ℃ and the reaction lasts 24 h. The reacted solution was irradiated under an ultraviolet lamp of 395 nm, and the fluorescence was found to show changes of red, orange-red and yellow, and yellow-green and green. Their fluorescence spectra are shown in FIG. 1.

In FIG. 1, in the ultraviolet absorption spectrum from a) to g), the peak appearance of the wavelength band of 200 to 350 nm is significantly changed after increasing the addition amount of the free radicals. The fluorescence spectrum from b) to h) shows that the maximum absorption wavelength starts to gradually shift to a short wavelength, which indicates that the structure of the original carbon dot starts to shift with the increase of the addition amount of azobisisobutyronitrile.

Example 3

In eight 5mL sample bottles, 6 mL of deionized water and 60. Mu.L of a red carbon dot solution with a mass fraction of 4 mg/mL were added, followed by 0 mg,2 mg,6 mg,10 mg,20 mg,30 mg,40 mg and 50 mg of 2, 2-azobis (2-methylpropylami) dihydrochloride (V-50). The reaction is carried out for 12 h under the irradiation of an ultraviolet lamp at 395 nm. The carbon dot aqueous solution without V-50 is easy to agglomerate, the carbon dot solution with V-50 is well dispersed, and the maximum emission wavelength of fluorescence becomes yellow as the amount of the initiator is increased. The ultraviolet and fluorescence emission spectra are shown in FIG. 2.

In the ultraviolet absorption spectrum from a) to e) in FIG. 2, the peak appearance of the wavelength band of 200 to 350 nm changes after increasing the addition amount of the free radicals. The fluorescence spectrum is shown in b) to f) that the maximum absorption wavelength is directly shifted to short wavelength, and in the process of shifting to short wavelength, the water solubility of the carbon dot is improved.

Example 4

6 mL of deionized water and 60 mu L of red carbon dot solution with the mass fraction of 4 mg/mL are respectively added into six 10 mL sample bottles, and 0 mg,2 mg,4 mg,6 mg,8 mg and 10 mg of alpha-ketoglutaric acid are sequentially added. The temperature of the oven is heated to 60 ℃, and the reaction lasts for 0 to 12 hours. The fluorescence spectrum is shown in FIG. 3.

In the ultraviolet absorption spectra from a) to e) in FIG. 3, the peak of the 200-300 nm band is changed immediately after the addition of the free radicals. The fluorescence spectrum is directly shifted to short wavelength from b) to f) as indicated by the absorption maximum wavelength.

The experimental formulation and reaction conditions of the above examples can be properly adjusted according to the nature of the radical initiator, the amount of the radical initiator is not limited, and the experiment can be performed by adjusting the temperature or photo initiation. The free radical initiator may be other organic peroxide initiator or azo initiator. While the present invention has been described in connection with the preferred embodiments, it is not intended to be limited to the embodiments.

Claims

1. The application of the free radical initiator in regulating and controlling the maximum fluorescence emission wavelength of the carbon dots is characterized in that the displacement of the maximum fluorescence emission wavelength of the carbon dots to the short wavelength direction is increased along with the increase of the dosage of the free radical initiator, and the method comprises the following steps:

adding 50-60 mu L of red carbon dot solution with the concentration of 4 mg/mL into 6 mL of ethanol, then adding not more than 90 mg of azobisisobutyronitrile, and reacting in a drying oven at 60-70 ℃ for 12-24h to obtain modified carbon dots with the fluorescence maximum emission wavelength shifted to the short wavelength direction;

the carbon dots regulated are red carbon dots.