CN110724533B - S, Se-CQDs and method for detecting Cr (VI) pollutants by using same - Google Patents
S, Se-CQDs and method for detecting Cr (VI) pollutants by using same Download PDFInfo
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/88—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing selenium, tellurium or unspecified chalcogen elements
- C09K11/881—Chalcogenides
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N21/643—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" non-biological material
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N2021/6432—Quenching
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Abstract
The invention provides S, Se-CQDs and a method for efficiently detecting Cr (VI) pollutants by the S, Se-CQDs, belonging to the cross field of new nano-materials and environmental analysis, dissolving citric acid, mercaptoethylamine and sodium selenite in pure water, performing hydrothermal reaction, naturally cooling to room temperature, taking out the solution, centrifuging, separating supernatant, dialyzing the supernatant, freeze-drying to prepare doped carbon quantum dots S, Se-CQDs with high fluorescence intensity, the method has simple process and low cost for preparing S, Se-CQDs, and the prepared S, Se-CQD can efficiently detect Cr (VI) when proper vitamin C (Vc) is added, the fluorescence of the system Cr (VI) + S, Se-CQD can be recovered by 80%, and the method for detecting Cr (VI) by S, Se-CQD is simple, low in cost, obvious in selection difference and strong in anti-interference capability.
Description
Technical Field
The invention belongs to the crossing field of new nano materials and environmental analysis, and particularly relates to S, Se-CQDs and a method for detecting Cr (VI) pollutants by using the same.
Background
Cr (vi), one of the common valence states of chromium, is the most toxic and more easily absorbed by the human body, and can invade the human body through the digestive tract, respiratory tract, skin and mucous membrane, compared to metallic, trivalent or quadrivalent chromium. So far, the classical method for measuring Cr (VI) in water has a national standard, namely a diphenylcarbodihydrazide spectrophotometry (GB/T746-1987), but the method has certain limitations, such as the use of a test reagent with high toxicity, such as hydrazine substances, and the like, thereby causing environmental pollution or influencing human health. Other testing methods also have the defects of high detection limit, complicated steps or poor selectivity, or the traditional method has no possibility of being applied to the medical field based on biocompatibility consideration.
Chinese patent CN107748151A discloses a method for detecting the concentration of cr (vi) ions in a solution by using nitrogen-doped carbon quantum dots, comprising the following steps: step one, preparing equal volume nitrogen-doped carbon with same concentrationQuantum dots and a plurality of standard solutions containing Cr (VI) ions with different concentrations, and respectively detecting fluorescence intensity values I; step two, preparing a contrast solution with the same volume and the same concentration as the standard solution in the step one, and detecting the fluorescence intensity value I of the contrast solution0(ii) a And step three, establishing a linear relation with the concentration of Cr (VI) ions. The invention has the advantages of simple and convenient detection process, high sensitivity and low detection limit, and can realize real-line in-situ detection. So far, there are few reports on the efficient fluorescence characteristic of nitrogen-doped carbon quantum dots to further realize the efficient selective detection of Cr (VI), and metal ions can enable the nitrogen-doped carbon quantum dots to generate fluorescence quenching and corresponding F/F0The values are generally low (about 0.5) and the manner in which fluorescence recovery of nitrogen-doped carbon quantum dots in the system is caused is not specified.
Chinese patent CN109674676A discloses a green and environment-friendly hair styling finishing agent, a preparation method and application thereof, wherein the hair styling finishing agent is prepared from the following raw materials in parts by weight: 3-6 parts of citric acid, 1-3 parts of chlorophyll a, 0.1-0.8 part of mercaptoethylamine and 0.01-0.1 part of sodium selenite. The preparation method comprises the following steps: respectively dissolving citric acid and chlorophyll a in pure water, mixing, adding mercaptoethylamine and sodium selenite, and dissolving to obtain a mixed solution; transferring the mixed solution into a polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, and putting the stainless steel reaction kettle into an oven for hydrothermal reaction at the temperature of 140-; and taking out the solution when the temperature of the oven is reduced to room temperature, centrifuging for 10-30min under the conditions of 4000-10000r/min, taking the supernatant, dialyzing for 2-4 days by using a 200Da dialysis bag, and freeze-drying to obtain the green and environment-friendly hair styling finishing agent. However, the S, Se-CQDs obtained in the invention mainly utilize Se element to participate in 'cutting' disulfide bonds in hair, so the S, Se-CQDs are used as hair styling finishing agents and are not used for detecting Cr (VI) pollutants.
Aiming at the problems of environmental pollution, influence on human health, high detection limit, complex steps or poor selectivity and the like existing in the Cr (VI) detection method, an S, Se-CQDs and a method for detecting Cr (VI) pollutants by using the S, Se-CQDs are sought, so that the detection method is simple, low in cost and high in selectivity on Cr (VI) detection.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides S, Se-CQDs and a method for detecting Cr (VI) pollutants by using the S, Se-CQDs, wherein the method is simple, low in cost and high in selectivity, and can be used for efficiently detecting Cr (VI).
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides S, Se-CQDs and a method for detecting Cr (VI) pollutants by using the same, which comprises the following steps:
(1) and preparation of S, Se-CQDs: dissolving citric acid, mercaptoethylamine and sodium selenite in pure water, naturally cooling to room temperature after hydrothermal reaction, taking out the solution, centrifuging, separating supernatant, dialyzing and freeze-drying the supernatant to obtain S, Se-CQDs, preparing the S, Se-CQDs into solution by using the pure water, and diluting the solution by using PBS buffer solution to obtain an aqueous solution of the S, Se-CQDs;
(2) establishing a standard curve: diluting a Cr (VI) standard solution to obtain Cr (VI) standby solutions with different concentrations, mixing pure water, an S, Se-CQDs aqueous solution and the Cr (VI) standby solutions with different concentrations, supplementing the pure water to a constant volume, respectively measuring the fluorescence spectra of each group after mixing reaction, and recording the fluorescence peak value F of each group; replacing the Cr (VI) standby solution with pure water with the same amount, keeping the rest steps unchanged, and respectively measuring the fluorescence peak value F of each group after mixing reaction0(ii) a The concentration of Cr (VI) in each group is plotted on the abscissa for each group (F)0-F)/F0Drawing a standard curve for a vertical coordinate;
(3) cr (VI) detection: mixing pure water, the S, Se-CQDs aqueous solution and the sample to be detected, adding the pure water to a constant volume, reacting after mixing, measuring the fluorescence spectrum, recording the fluorescence peak value, and substituting the fluorescence peak value into the standard curve in the step (2) to obtain the concentration of Cr (VI) in the sample to be detected.
Further, the raw materials of the S, Se-CQDs comprise: 3-8 parts of citric acid, 0.2-2 parts of mercaptoethylamine and 0.01-0.1 part of sodium selenite.
Preferably, the raw materials of the S, Se-CQDs comprise: 4-6 parts of citric acid, 0.5-1 part of mercaptoethylamine and 0.05-0.08 part of sodium selenite.
Further preferably, the raw materials of the S, Se-CQDs comprise: 5 parts by weight of citric acid, 0.8 part by weight of mercaptoethylamine and 0.06 part by weight of sodium selenite.
Further, the volume of the pure water in the step (1) is 40m L, and after the pure water is fully dissolved, a proper amount of pure water is added until the total volume of the solution is 50m L.
Further, the hydrothermal reaction in step (1) is carried out in a polytetrafluoroethylene lining.
Further, the temperature of the hydrothermal reaction in the step (1) is higher than 140 ℃, and the reaction time is not less than 150 min.
Preferably, the temperature of the hydrothermal reaction in the step (1) is 150 ℃ and the reaction time is 150 min.
Further, the concentration of the aqueous solution of S, Se-CQDs in the step (1) is 0.2-1mg/m L.
Further, in step (1), the PBS buffer had a pH of 6.5 and a concentration of 0.1M.
Further, the centrifugation in the step (1) is carried out for 20min at 8000 r/min.
Further, the dialysis in the step (1) is specifically dialysis for 2 days by using a 200Da dialysis bag, and water is changed every 8 h.
Further, the concentration of Cr (VI) in the sample to be detected in the step (3) is controlled within the range of 0.2-120 mu M.
Further, pure water is added in the step (2) and the step (3) to a constant volume, specifically to a constant volume of 4m L, the addition amount of the S, Se-CQDs aqueous solution is 40 mu L, and the addition amounts of the Cr (VI) standby solution in the step (2) and the sample to be detected in the step (3) are both 100 mu L.
Further, the concentration of the Cr (VI) stock solution in the step (2) is 0.1-125 μ M.
The beneficial effects obtained by the invention are as follows:
1. the sulfur-selenium doped carbon quantum dots (S, Se-CQDs) with high fluorescence characteristic are prepared in one step by a hydrothermal method, the process is simple, the cost is low, and Cr (VI) can be efficiently detected;
2. the S, Se-CQDs prepared by the invention have obvious selectivity difference and strong anti-interference capability, and can detect Cr (VI)The test has high selectivity, and when the interference ions exist, the F/F of the test system is tested0A value close to 1; meanwhile, the system is subjected to fluorescence quenching when meeting Cr (VI), and proper vitamin C is added into the system to realize the fluorescence recovery of S, Se-CQDs.
Drawings
In FIG. 1, (a) is a TEM image of S, Se-CQDs; (b) fluorescence spectra of S, Se-CQDs at different excitation wavelengths;
FIG. 2, (a) is an XPS map of S, Se-CQDs; (b) se3d spectrum as XPS; (c) s2p spectrum as XPS; (d) c1s spectrum as XPS;
FIG. 3 is a graph of the linear range of S, Se-CQD detection for Cr (VI);
FIG. 4 is a graph showing selectivity of detection of S, Se-CQDs on Cr (VI);
FIG. 5 is a graph showing the fluorescence quenching and recovery of S, Se-CQDs in the presence of Cr (VI).
Detailed Description
It should be noted that the raw materials and apparatuses in the present application are all common commercial products, and therefore the sources thereof are not particularly limited.
Example 1
Dissolving 5.0g of citric acid, 0.8g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water in sequence, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 150 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 2
Sequentially dissolving 6.0g of citric acid, 0.8g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 150 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 3
Sequentially dissolving 8.0g of citric acid, 0.8g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 150 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 4
Dissolving 5.0g of citric acid, 1.2g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water in sequence, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 150 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200 dialysis Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 5
Dissolving 5.0g of citric acid, 0.8g of mercaptoethylamine and 0.1g of sodium selenite in 40m L pure water in sequence, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 150 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 6
Dissolving 5.0g of citric acid, 0.6g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water in sequence, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 150 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200 dialysis Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 7
Dissolving 5.0g of citric acid, 0.8g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water in sequence, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 180 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Example 8
Dissolving 5.0g of citric acid, 0.8g of mercaptoethylamine and 0.06g of sodium selenite in 40m L pure water in sequence, supplementing a proper amount of pure water to the total volume of 50m L after full dissolution, transferring the solution to a 50m L polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, putting the stainless steel reaction kettle in an oven at 140 ℃, carrying out hydrothermal reaction for 150min, taking out the solution after the temperature of the oven is reduced to room temperature, centrifuging for 20min at 8000r/min, separating supernatant, dialyzing for 2 days by using a 200 dialysis Da bag, changing water every 8h, and finally freeze-drying to obtain a target product, namely sulfur-selenium doped carbon quantum dots (S, Se-CQDs).
Comparative example 1
The only difference from example 1 was that citric acid (2.8g), mercaptoethylamine (2.2g), and sodium selenite (0.008g) were dissolved in 40m L pure water in this order.
Comparative example 2
The only difference from example 1 was that citric acid (8.2g), mercaptoethylamine (0.1g), and sodium selenite (0.15g) were dissolved in 40m L pure water in this order.
Comparative example 3
The only difference from example 1 is that the hydrothermal reaction temperature was 130 ℃.
Comparative example 4
The only difference from example 1 is that the hydrothermal reaction time was 120 min.
Structure, fluorescence characteristics, size and morphology of S, Se-CQDs
TEM and XPS measurements of S, Se-CQDs as described in example 1 were carried out using a Tecnai F30 field emission transmission electron microscope system (FEI Co.) with a working voltage of 200kV for TEM and PHI-5000C ESCAX photoelectron spectroscopy (Perkin-Elmer Co.) for XPS with a power of 25W, an Mg K α as an emission source, an X-ray beam diameter of 10mm, an energy analyzer with an energy of 29.35eV, and an analysis chamber pressure of 5 × 10 and 10 for the duration of the test was maintained at 5 E.V.-8Pa or less.
As can be seen from FIG. 1 (a), S, Se-CQDs are shaped like spheres with a particle size of about 6nm, and FIG. 1 (b) shows that the fluorescence peak positions of S, Se-CQDs are substantially unchanged at different excitation wavelengths, indicating that the fluorescence emission of S, Se-CQDs is not excitation-dependent. As can be seen from FIG. 2 (a), S, Se-CQDs are mainly composed of C, O, S, Se, and in FIG. 2 (b), there are signal peaks at 67.5eV and 62.9eV, indicating that there are S-Se and C-Se; in (C) of FIG. 2, there are signal peaks at 163.4eV and 164.2eV, indicating the presence of C-S and S-Se; FIG. 2 (d) shows 5 peaks, C ═ O (288.4eV), C-S (286.0eV), C-Se (285.4eV), C-N (284.8eV), and C-C (284.2eV), further demonstrating that the present invention successfully synthesizes S, Se-CQDs.
Second, comparison of fluorescence peaks of S, Se-CQDs
The products obtained in examples 1 to 8 and comparative examples 1 to 4 were prepared to 0.2mg/m L with pure water, diluted 10-fold with 0.1M, pH ═ 6.5 PBS, measured for their fluorescence spectra at an excitation wavelength of 350nm, and recorded as F corresponding to the respective fluorescence peaks1-F8And F11-F14. F was found by detecting and comparing the fluorescence peaks of S, Se-CQDs in examples 1 to 8 and comparative examples 1 to 42，F3，F4，F7And F1Is not clear from the differenceObviously, the absolute difference is less than 5 percent; f5Is about F 170% of the total amount of the raw materials, a large amount of black is generated deeply in the reaction system; f6Is about F150% of (A), F8Is about F165% of the total. F11<5％F1，F12<10％F1It shows that under the condition of the mixture ratio of the components outside the protection range of the application, the fluorescence intensity of the obtained corresponding product is lower: f13<2％F1The temperature of the hydrothermal reaction is preferably not less than 140 ℃, F14Is about F 140% of the total amount of the components, which indicates that the synthesis reaction time is preferably not less than 150 min.
Third, linear relation of Cr (VI) concentration to fluorescence intensity
Using the aqueous solution of S, Se-CQDs prepared in example 1 as 1mg/M L, 40. mu. L of this aqueous solution was added to a test tube, and then, various amounts of Cr (VI) solution were added thereto, pure water was added to a volume of 4M L, and the Cr (VI) concentrations were made to be 0. mu.M, 0.1. mu.M, 5. mu.M, 25. mu.M, 45. mu.M, 65. mu.M, 85. mu.M, 105. mu.M, 125. mu.M, 400. mu.M, 600. mu.M, 800. mu.M and 1000. mu.M, respectively, and after reaction for 30min, the fluorescence intensity was measured at an excitation wavelength of 350nm, wherein the fluorescence intensity at a concentration of 0. mu.M was designated as F0Calculating the corresponding fluorescence change rate (F) for each concentration0-F)/F0The results are plotted in FIG. 3.
As can be seen from FIG. 3, when Cr (VI) is detected by using S, Se-CQDs, the fluorescence of S, Se-CQDs gradually decreases with the increase of the Cr (VI) concentration, and has a good linear relationship in the range of 0.1-125 μ M, R2The concentration of chromium ions in the national industrial wastewater discharge standard is 5 μ M, which is included in the linear range, 0.994, so S, Se-CQDs are feasible for detecting Cr (vi).
High-efficiency selective analysis of Cr (VI)
Experiment 1 Using an aqueous solution of S, Se-CQDs prepared in example 1 as 1mg/M L, pure water 3.86M L and an aqueous solution of S, Se-CQDs (1mg/M L) prepared in example 1 as 40. mu. L were added to a test tube, and then 100. mu. L of pure water or 100. mu. L containing a certain metal ion (M.mu. L and M.mu. L were added to the test tuben+) 0.01 mol/L), where "M" isn+Is "K+，Pb2+，Ca2 +，Fe3+，Na+，Ba2+，Mg2+，Mn2+，Ag2+，Hg2+，SO4 2-，NO3 2-，Cl-And the like, reacting for 30min after mixing, measuring the fluorescence spectrum at the excitation wavelength of 350nm, recording the fluorescence peak value of a sample added with 100 mu L solution containing certain metal ions as F, and recording the fluorescence peak value corresponding to a sample supplemented with 100 mu L pure water as F0Calculating F/F03.85M L pure water, 40 mu L aqueous solution of S, Se-CQDs (1mg/M L) prepared in example 1 and 10 mu L aqueous solution of Cr (VI) (0.01 mol/L) are added into a test tube, and then 100 mu L pure water or 100 mu L pure water containing certain metal ions (M is added into the test tuben+) The solution (0.01 mol/L) was mixed and reacted for 30min, the fluorescence spectrum was measured at an excitation wavelength of 350nm, the peak fluorescence value of the sample added with 100. mu. L of a solution containing a certain metal ion was recorded as F, and the peak fluorescence value of the sample supplemented with 100. mu. L of pure water was recorded as F0Calculating F/F0Values were plotted and FIG. 4 was obtained.
As can be seen from FIG. 4, the addition of Cr (VI) to S, Se-CQDs can quench the fluorescence of S, Se-CQDs significantly, and the quenching effect of Cr (VI) on the fluorescence of S, Se-CQDs is not changed significantly after the addition of interfering ions, which shows that S, Se-CQDs have high selectivity on Cr (VI) when used for detecting complex samples.
Experiment 2. mu. L the S, Se-CQDs solution of 1mg/m L prepared in example 1 was taken, and the volume was adjusted to 4m L with pure water, and then 100. mu. L Cr solution of 0.2. mu.g/m L was added6+After reacting for 30min, measuring the fluorescence intensity under the excitation wavelength of 350nm, and recording the fluorescence intensity of the sample without adding metal ions as F0Calculating the fluorescence change rate F/F corresponding to each ion0Fig. 5 is obtained.
As can be seen from FIG. 5, 0.2. mu.g/m L of Cr was added6+When the fluorescence of S, Se-CQDs is quenched by about 50%, a proper amount of V is added in S, Se-CQDscThen adding Cr6+The degree of fluorescence quenching of S, Se-CQDs is higher than that without addition of VcIs small; firstly, Cr is added into S, Se-CQDs6+Then adding VcFluorescent substanceLight intensity substantially equal to VcAre close to each other. VcCan affect S, Se-CQDs to Cr before and after quenching6+(ii) detection of (D), Explanation ofcCan be mixed with Cr6+A redox reaction occurs. Adding V firstcPart of Cr6+Reduction to Cr3+The fluorescence of S, Se-CQDs cannot be quenched; after quenching, add Re VcFluorescence intensity and initial addition of VcIndicates V in the systemcAnd the oxidized S and Se-CQDs also have redox reaction, thereby recovering the fluorescence. Therefore, it is presumed that S, Se-CQDs detect Cr6+Is due to S, Se-CQDs and Cr6+Redox reaction occurs in the process, which leads to the surface electron transfer of S, Se-CQDs and causes fluorescence quenching.
Finally, it should be noted that the above-mentioned contents are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, and that the simple modifications or equivalent substitutions of the technical solutions of the present invention by those of ordinary skill in the art can be made without departing from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. A method for detecting Cr (VI) pollutants by S, Se-CQDs is characterized by comprising the following steps:
(1) and preparation of S, Se-CQDs: dissolving citric acid, mercaptoethylamine and sodium selenite in pure water, naturally cooling to room temperature after hydrothermal reaction, taking out the solution, centrifuging, separating supernatant, dialyzing and freeze-drying the supernatant to obtain S, Se-CQDs, preparing the S, Se-CQDs into solution by using the pure water, and diluting the solution by using PBS buffer solution to obtain an aqueous solution of the S, Se-CQDs;
(2) establishing a standard curve: diluting a Cr (VI) standard solution to obtain Cr (VI) standby solutions with different concentrations, mixing pure water, an S, Se-CQDs aqueous solution and the Cr (VI) standby solutions with different concentrations, supplementing the pure water to a constant volume, respectively measuring the fluorescence spectra of each group after mixing reaction, and recording the fluorescence peak value F of each group; replacing the Cr (VI) standby solution with pure water with the same amount, keeping the rest steps unchanged, and respectively measuring the fluorescence peak value F of each group after mixing reaction0(ii) a The concentration of Cr (VI) in each group is plotted on the abscissa for each group (F)0-F)/F0Drawing a standard curve as a vertical coordinateA wire;
(3) cr (VI) detection: mixing pure water, the S, Se-CQDs aqueous solution and the sample to be detected, adding the pure water to a constant volume, reacting after mixing, measuring the fluorescence spectrum, recording the fluorescence peak value, and substituting the fluorescence peak value into the standard curve in the step (2) to obtain the concentration of Cr (VI) in the sample to be detected.
2. The method of claim 1, wherein: the S, Se-CQDs comprise the following raw materials: 3-8 parts of citric acid, 0.2-2 parts of mercaptoethylamine and 0.01-0.1 part of sodium selenite.
3. The method of claim 2, wherein: the S, Se-CQDs comprise the following raw materials: 4-6 parts of citric acid, 0.5-1 part of mercaptoethylamine and 0.05-0.08 part of sodium selenite.
4. The method of claim 1, wherein: the hydrothermal reaction in the step (1) is carried out in a polytetrafluoroethylene lining.
5. The method of claim 1, wherein: the temperature of the hydrothermal reaction in the step (1) is higher than 140 ℃, and the reaction time is not less than 150 min.
6. The method according to claim 1, wherein the concentration of the aqueous solution of S, Se-CQDs in step (1) is 0.2 to 1mg/m L.
7. The method of claim 1, wherein: in step (1), the PBS buffer had a pH of 6.5 and a concentration of 0.1M.
8. The method of claim 1, wherein: and (3) controlling the concentration of Cr (VI) in the sample to be detected in the range of 0.2-120 mu M.
9. The method of claim 1, wherein: the concentration of the Cr (VI) standby liquid in the step (2) is 0.1-125 mu M.
10. The method according to claim 1, wherein the Cr (VI) stock solution in step (2) and the sample to be tested in step (3) are added in an amount of 100 μ L.
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