CN111024662A

CN111024662A - Method for enhancing recognition capability of carbon dots on mercury ions

Info

Publication number: CN111024662A
Application number: CN201911277687.2A
Authority: CN
Inventors: 庞代文; 杨梦丽; 刘翠; 张志凌
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2019-12-11
Filing date: 2019-12-11
Publication date: 2020-04-17
Anticipated expiration: 2039-12-11
Also published as: CN111024662B

Abstract

The invention discloses a method for controllably enhancing the recognition capability of carbon points on mercury ions, which weakens the recognition capability of the carbon points on other ions by reasonably regulating and controlling functional groups on the surfaces of the carbon points, and simultaneously connects a DNA sequence capable of specifically recognizing the mercury ions on the surfaces of the carbon points to realize the purpose of selectively recognizing the mercury ions by the carbon points. The method has the advantages of mild reaction conditions, simple and convenient operation, strong applicability and the like, and can be widely applied to the fields of chemistry, biology, material science and the like.

Description

Method for enhancing recognition capability of carbon dots on mercury ions

Technical Field

The invention belongs to the technical field of chemistry and materials, and particularly relates to a method for enhancing the recognition capability of carbon dots on mercury ions.

Background

In recent years, carbon dots, as a novel luminescent carbon nanomaterial, have attracted much attention due to their characteristics of excellent optical properties, low toxicity, good water solubility, and the like, and are increasingly applied to sensing in the fields of imaging, catalysis, photoelectronics, and the like.

In the field of sensing applications, carbon spots capable of selectively detecting copper ions were reported in early studies in 2012 (Analyst 2012,137, 2637-: for example, Zhu et al propose that N- (2-aminoethyl) -N, N, N' -tris (pyridine-2-ylmethyl) ethane-1,2-diamine molecules are immobilized on the surface of carbon dots, so that selective detection of copper ions can be realized (Angew. chem. int. Ed.2012,51, 7185-7189); huang et al utilize carbon dots prepared by thermal hydrolysis of arginine and citric acid, and fluorescence can be selectively quenched by mercury ions (anal. Chim. acta.2018,1035, 203-210). However, the above reports generally focus on finding suitable synthesis precursors, reaction conditions and post-treatment methods when preparing carbon dots with selective recognition capability for metal ions, and such methods have certain blindness and low efficiency, and cannot realize purposeful regulation and control so as to achieve selective recognition for specific metal ions.

Disclosure of Invention

The invention mainly aims to provide a method for enhancing the mercury ion recognition capability of a carbon dot to realize selective recognition of the carbon dot to mercury ions aiming at the defects in the prior art.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for enhancing the recognition capability of carbon points to mercury ions comprises the following steps:

1) synthesizing carbon points, and obtaining carbon points I smaller than 3K through ultrafiltration;

2) dispersing the carbon dots I obtained in the step 1) in an organic solvent, then adding thionyl chloride, heating and drying by distillation to obtain acyl chlorinated carbon dots II;

3) dispersing the obtained acyl chlorinated carbon dots II in ultra-dry acetonitrile, then adding the mixture into an organic solution with amino cycloalkyne for stirring reaction, heating the mixture again to dryness, then adding a product obtained by the evaporation to dryness into dioxane for ultrasonic dispersion, then adding 1, 3-propane sultone and a catalyst, carrying out water bath stirring reaction, and then carrying out dialysis desalting to obtain carbon dots III (pC-dots);

4) adding the pC-dots obtained in the step 3) into a DNA sequence which is rich in T basic group and one end of which is modified with azide group, shaking, and connecting a section of DNA sequence which can specifically recognize mercury ions on the surface of the pC-dots by utilizing click reaction of ring tension to obtain the carbon dot pC-dots-DNA capable of improving the recognition capability of the mercury ions.

In the above scheme, the method for synthesizing carbon dots in step 1) is a method for oxidizing carbon fibers by using mixed acid reflux, and specifically comprises the following steps: adding carbon fiber powder into a mixed solution of concentrated nitric acid and concentrated sulfuric acid, heating to boil, carrying out heat preservation reaction, cooling to room temperature, and adjusting the pH value to 4-5.

In the scheme, the organic solvent in the step 2) is anhydrous acetonitrile.

In the scheme, the dosage ratio of the carbon dots I to the thionyl chloride in the step 2) (2-3) is 1mg: mL.

In the scheme, the heating and drying temperature is 60-70 ℃.

In the scheme, the mass ratio of the carbon point I to the cycloalkyne with the amino group is (2-3): 1.

In the above scheme, the amino-bearing cycloalkyne can be selected from azadibenzocyclooctyne amine or azadibenzocyclooctyne-PEG 4 amine, and the like.

In the scheme, the catalyst in the step 3) is triethylamine.

In the scheme, the mass ratio of the carbon point I to the 1, 3-propane sultone is (2-3) to 250; the dosage ratio of the carbon dots I to the catalyst is (2-3) 0.4mg: mL.

In the scheme, the stirring reaction time in the step 3) is 10-12 h; the water bath reaction temperature is 35-40 ℃, and the time is 20-24 h.

In the scheme, the mass ratio of the pC-dots to the DNA rich in the T basic group with one end modified with the azide group is (1-2): 1.

In the above scheme, the azide-modified T base-rich DNA is 5 '-N3-TTTTTTTTCCCTTTTTTTT-3'.

In the scheme, the shaking time is 3-4 h.

The principle of the invention is as follows:

1) the surface of the carbon dot contains rich oxygen-containing functional groups, wherein hydroxyl and carboxyl have strong chelating capacity with metal ions, so that the recognition selectivity of the carbon dot to the metal ions is low; in order to enhance the selective recognition capability of carbon points to mercury ions, carboxyl on the surfaces of the carbon points is acylated and chlorinated by thionyl chloride, then the carbon points are reacted with DBCO-NH2, 1, 3-propane sultone is further reacted with residual unreacted carboxyl and hydroxyl on the surfaces of the carbon points to form ester and ether, then a DNA sequence which is rich in T basic groups and can specifically recognize the mercury ions is connected to the surfaces of the carbon points, the interference of external metal ions is reduced due to the weak binding capability of sulfonic functional groups to the metal ions, and meanwhile, due to the specific recognition capability of the DNA sequence rich in T basic groups to the mercury ions, the selective recognition capability of the carbon points to the mercury ions is enhanced by the regulation and control of the surface functional groups under the condition that the particle size of the carbon points is not changed by reasonably regulating and controlling the surface structure of the carbon points.

2) According to the invention, a DNA sequence capable of specifically recognizing mercury ions is connected to the surface of pC-dots by adopting a click reaction of ring tension, but after cycloacetylene reacts with carbon points, the water solubility of the carbon points is poor, and the subsequent coupling with the DNA is not facilitated.

Compared with the prior art, the invention has the beneficial effects that:

1) according to the invention, through reasonably regulating and controlling functional groups on the surface of the carbon dots, the recognition capability of the carbon dots to other ions is weakened, and the specificity recognition capability of the DNA sequence rich in T basic groups to mercury ions is weakened, so that the selective recognition of the carbon dots to the mercury ions is realized under the condition of not changing the particle size of the carbon dots, the problems of poor selectivity, low efficiency and the like of the existing carbon dots to specific metals are effectively solved, and a brand new thought can be provided for the efficient selection of the specific metal ions.

2) The invention has mild reaction conditions, simple and convenient operation and strong applicability, can further realize the selective recognition of other metal ions (such as silver ions, copper ions, lead ions and the like) by selecting a proper DNA sequence, and has important research and popularization values.

Drawings

FIG. 1 shows (A) electron microscopic characterization, (B) X-ray photoelectron spectroscopy, (C) Raman spectroscopy, and (D) fluorescence spectroscopy of carbon dot I obtained in example 1.

FIG. 2 shows carbon dots I vs. metal ions Hg obtained in example 1²⁺,Pb²⁺,Mn²⁺,Ni²⁺,Bi³⁺Or Ag⁺The results are characterized selectively.

FIG. 3 is a schematic diagram of the process of modifying the surface functional group of the carbon dot I according to the present invention.

FIG. 4 shows the (A) IR spectra, (B) nuclear magnetic spectra, and (C) X-ray photoelectron spectra of pC-dots obtained in example 1.

FIG. 5 shows the pC-dots obtained in example 1 for metal ion (Hg)²⁺,Pb²⁺,Mn²⁺,Ni²⁺,Bi³⁺Or Ag^+；1mM⁾The results are characterized selectively.

FIG. 6 shows the confirmation of the pC-dots-DNA obtained in example 1 by agarose gel electrophoresis and the isolation of pC-dots-DNA.

FIG. 7 shows the pC-dots-DNA obtained in example 1 for metal ion (Hg)²⁺,Pb²⁺,Mn²⁺,Ni²⁺,Bi³⁺Or Ag^+；1mM⁾The results are characterized selectively.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the following examples, T-base-rich DNA of azide group was used as 5 '-N3-TTTTTTTTCCCTTTTTTTT-3' supplied by Biotechnology engineering (Wuhan) GmbH.

Example 1

1) adding 0.4g of carbon fiber powder into 30mL of mixed solution of concentrated nitric acid (66 wt%) and concentrated sulfuric acid (98 wt%) in a volume ratio of 3:1, heating and keeping boiling for 2h, cooling to room temperature, neutralizing with a proper amount of sodium bicarbonate until the pH value is 4-5, filtering with a 0.22 mu m filter membrane, dialyzing the filtrate for seven days with a dialysis bag with the molecular weight cutoff of 3,500Dalton, changing water 3-4 times every day, collecting the dialyzed solution, ultrafiltering with ultrafiltration tubes with the molecular weight cutoff of 100K, 50K, 30K, 10K and 3K respectively, and freeze-drying the part with the molecular weight of less than 3K into powder to obtain a carbon point I with the molecular weight of less than 3K;

2) adding 3mg of the carbon dot I obtained in the step 1) into 5mL of anhydrous acetonitrile, adding 1mL of thionyl chloride, heating at 70 ℃ for 30 minutes, completely dissolving carbon dot powder to obtain a yellowish-brown solution, and evaporating the solvent and the thionyl chloride to obtain an acyl chlorinated carbon dot II;

3) dispersing the obtained acyl-chlorinated carbon dot II in ultra-dry acetonitrile, and slowly adding into a solvent containing 1mg DBCO-NH₂Stirring and reacting (aza-dibenzocyclooctynylamine) in anhydrous acetonitrile at room temperature for 12 h; then evaporating the solvent by using a rotary evaporator, adding 10mL of dioxane, performing ultrasonic dispersion, adding 0.25g of 1, 3-propane sultone and 400 mu L of triethylamine (catalyst), and performing water bath stirring reaction for 24 hours at the temperature of 40 ℃; evaporating to remove the solvent of the obtained reaction system, adding water for dispersion, transferring the obtained dispersion liquid into a dialysis bag with the molecular cut-off of 3,500Dalton, dialyzing for 3-4 days, dialyzing with 0.1M NaCl solution on the first day, and using ultrapure water on the next three days to obtain a carbon point III which is recorded as pC-dots;

4) adding 15 mu g of DNA sequence which is modified with azide group at one end and is rich in T basic group into 30 mu g of pC-dots obtained in the step 3), and shaking for reaction for 4h to obtain pC-dots-DNA, thereby realizing the purpose of enhancing the recognition capability of carbon dots to mercury ions.

FIG. 1 shows (A) electron microscopy characterization, (B) X-ray photoelectron spectroscopy, (C) Raman spectroscopy, and (D) fluorescence spectroscopy of carbon dot I obtained in step 1) of the present example; the results show that: the carbon dots obtained by the mixed acid oxidation method have the particle size of 2.1nm, contain abundant oxygen-containing functional groups (such as carboxyl, hydroxyl, carbonyl and the like) on the surface, and have the characteristic that the emission wavelength does not change along with the change of the excitation wavelength. FIG. 2 shows the carbon point I vs. metal ions (Hg) obtained in this example²⁺,Pb²⁺,Mn²⁺,Ni²⁺,Bi³⁺Or Ag⁺⁾As a result of the selective characterization, it can be seen that Hg is 1mM²⁺、Pb²⁺、Mn²⁺、Ni²⁺、Bi³⁺Or Ag⁺When present, the fluorescence of the resulting carbon dot I was completely quenched (fig. 2).

Fig. 3 is a schematic diagram of a modification process of the surface functional group of the carbon dot I in steps 2) to 4) of this embodiment, which specifically includes: firstly, chloridizing carboxyl on the surface of a carbon point by thionyl chloride, then reacting with DBCO-NH2, and because of the problem of reaction efficiency, residual unreacted carboxyl on the surface of the carbon point, the invention further utilizes 1, 3-propane sultone as a protective agent to react with residual carboxyl and hydroxyl on the surface of the carbon point to form ester and ether, and then utilizes click reaction of cycloaddition to connect a DNA sequence which is modified with azide groups at one end and can specifically recognize mercury ions on the surface of the carbon point.

FIG. 4 shows the (A) IR spectrum, (B) nuclear magnetism, and (C) X-ray photoelectron spectrum characterization of pC-dots obtained in step 3) of this example, which indicates that our modification was successful; FIG. 5 shows the pC-dots pair of metal ions (Hg) obtained in this example²⁺,Pb² ⁺,Mn²⁺,Ni²⁺,Bi³⁺Or Ag^+；1mM⁾It can be seen that the fluorescence of the resulting pC-dots is hardly affected by the metal ions.

The pC-dots-DNA obtained in step 4) of this example was verified by electrophoresis on a 1% agarose gel; as can be seen from the gel electrophoresis, the electrophoretic migration-migration rate of the pC-dots-DNA grafted with DNA was significantly slowed (see FIG. 6).

FIG. 7 shows the fluorescent response of different metal ions to pC-dots-DNA, and it can be seen that only mercury ions can significantly quench the fluorescent signal; in addition, the selectivity coefficients of C-dots and pC-dots-DNA before and after modification (Table 1) are compared, and the selectivity coefficients of other metal ions to mercury ions after modification are reduced by several orders of magnitude, so that the effect of the modification means on enhancing the recognition capability of carbon points to mercury ions is further proved.

TABLE 1

The above embodiments are merely examples for clearly illustrating the present invention and do not limit the present invention. Other variants and modifications of the invention, which are obvious to those skilled in the art and can be made on the basis of the above description, are not necessary or exhaustive for all embodiments, and are therefore within the scope of the invention.

Claims

1. A method for enhancing the recognition capability of carbon points to mercury ions is characterized by comprising the following steps:

1) synthesizing carbon points, and performing ultrafiltration to obtain carbon points I smaller than 3K;

3) dispersing the obtained acyl chlorinated carbon dots II in an organic solvent, adding the organic solvent with amino cycloalkyne to perform a stirring reaction, heating and evaporating to dryness again, adding the evaporated product into dioxane to perform ultrasonic dispersion, adding 1, 3-propane sultone and a catalyst, performing a water bath stirring reaction, and performing dialysis desalting to obtain carbon dots III which are recorded as pC-dots;

4) adding the DNA sequence which is rich in T basic group and one end of which is modified with azide group into the carbon point III obtained in the step 3), and shaking to obtain the carbon point pC-dots-DNA capable of improving the recognition capability of mercury ions.

2. The method according to claim 1, wherein the organic solvent in step 2) is anhydrous acetonitrile.

3. The method according to claim 1, wherein the dosage ratio of the carbon point I to the thionyl chloride is (2-3) 1mg: mL; the mass ratio of the carbon point I to the cycloalkyne with the amino group is (2-3) to 1.

4. The method of claim 1, wherein the catalyst in step 3) is triethylamine.

5. The method according to claim 1, wherein the mass ratio of the carbon point I to the 1, 3-propane sultone is (2-3): 250; the dosage ratio of the carbon dots I to the catalyst is (2-3) 0.4mg: mL.

6. The method according to claim 1, wherein the stirring reaction time in the step 3) is 10-12 h; the water bath reaction temperature is 35-40 ℃, and the time is 20-24 h.

7. The method according to claim 1, wherein the mass ratio of pC-dots to T base-rich DNA having an azide group modified at one end thereof is (1-2): 1.

8. The method of claim 1, wherein the azide-modified T-base-rich DNA is 5 '-N3-TTTTTTTTCCCTTTTTTTT-3'.

9. The method according to claim 1, wherein the shaking time is 3-4 hours.