LU504175B1 - Application of graphitic carbon nitride in testing concentration of hexavalent chromium and l-cysteine - Google Patents
Application of graphitic carbon nitride in testing concentration of hexavalent chromium and l-cysteine Download PDFInfo
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- LU504175B1 LU504175B1 LU504175A LU504175A LU504175B1 LU 504175 B1 LU504175 B1 LU 504175B1 LU 504175 A LU504175 A LU 504175A LU 504175 A LU504175 A LU 504175A LU 504175 B1 LU504175 B1 LU 504175B1
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- XUJNEKJLAYXESH-REOHCLBHSA-N L-Cysteine Chemical compound SC[C@H](N)C(O)=O XUJNEKJLAYXESH-REOHCLBHSA-N 0.000 title claims abstract description 58
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical compound N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 title claims abstract description 54
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 238000012360 testing method Methods 0.000 title claims abstract description 39
- 238000001514 detection method Methods 0.000 claims abstract description 35
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 31
- 239000002096 quantum dot Substances 0.000 claims abstract description 25
- 235000013878 L-cysteine Nutrition 0.000 claims abstract description 10
- 239000004201 L-cysteine Substances 0.000 claims abstract description 10
- 239000000243 solution Substances 0.000 claims description 64
- 238000002156 mixing Methods 0.000 claims description 19
- 239000007853 buffer solution Substances 0.000 claims description 15
- 229910001430 chromium ion Inorganic materials 0.000 claims description 14
- 239000011259 mixed solution Substances 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 6
- 239000012085 test solution Substances 0.000 claims description 2
- 230000000171 quenching effect Effects 0.000 abstract description 9
- 238000010791 quenching Methods 0.000 abstract description 4
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 24
- 239000007864 aqueous solution Substances 0.000 description 8
- 239000012086 standard solution Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 230000035945 sensitivity Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000007850 fluorescent dye Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 239000012496 blank sample Substances 0.000 description 2
- 238000011088 calibration curve Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910001385 heavy metal Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 239000002135 nanosheet Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910017610 Cu(NO3) Inorganic materials 0.000 description 1
- 229910016874 Fe(NO3) Inorganic materials 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000012490 blank solution Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- -1 mercapto amino-acid Chemical class 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000035790 physiological processes and functions Effects 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
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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"
-
- C—CHEMISTRY; METALLURGY
- 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
- C09K11/67—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing refractory metals
- C09K11/68—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing refractory metals containing chromium, molybdenum or tungsten
-
- 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"
- G01N2021/6432—Quenching
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Immunology (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Optics & Photonics (AREA)
- Pathology (AREA)
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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
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- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
The present invention relates to an application of graphitic carbon nitride in testing concentration of hexavalent chromium or L-Cysteine. In the present invention, by taking a graphitic carbon nitride quantum dot solution as a detection reagent, the concentration of hexavalent chromium in a hexavalent chromium solution to be tested can be obtained accurately by means of the fluorescence quenching effect of hexavalent chromium on graphitic carbon nitride quantum dots. Fluorescence quenching on the graphitic carbon nitride quantum dots is realized by means of hexavalent chromium, so that the concentration of L-Cysteine can be obtained accurately.
Description
BL-5679
APPLICATION OF GRAPHITIC CARBON NITRIDE IN TESTING LUS04175
CONCENTRATION OF HEXAVALENT CHROMIUM AND L-CYSTEINE
[01] The present invention relates to the technical field of testing, and particularly relates to an application of graphitic carbon nitride quantum dots as fluorescent probes in testing concentration of hexavalent chromium ions or L-Cysteine.
[02] At present, in order to satisfy the needs of rapid economic development, heavy metal chromium ions have been applied to all walks of life, for example, metallurgical electroplating and production of plastics and color dyes. However, the ensuing problem is how to treat residues of heavy metal chromium ions in water bodies. Therefore, exploring and designing a method that features high selectivity and high sensitivity and is capable of rapidly monitoring concentration of hexavalent chromium in water bodies is of great significance.
[03] L-Cysteine (L-cys) is a mercapto amino-acid that plays an important role in physiological processes of living beings. Medical researches show that L-cys is related to many diseases, so it is of certain significance to monitoring the concentration of
L-cys.
[04] To solve the above problems, the present invention provides an application of graphitic carbon nitride quantum dots as fluorescent probes in testing concentration of hexavalent chromium ions or L-Cysteine (L-cys).
[05] The present invention further provides a method for testing concentration of hexavalent chromium ions by graphitic carbon nitride quantum dots, including the following steps:
[06] mixing a graphitic carbon nitride quantum dot solution with a Tri-HCI buffer solution to obtain a detection reagent, where the mixing time is >5min;
[07] performing a fluorescence intensity test on the detection reagent to obtain an initial fluorescence intensity Fo;
[08] mixing a hexavalent chromium solution to be tested with the detection reagent, performing a fluorescence intensity test on the obtained mixed solution to obtain a quenched fluorescence intensity F, and obtaining the concentration of hexavalent chromium in the hexavalent chromium solution to be tested according to a predetermined linear curve and a ratio Fo/F of the quenched fluorescence intensity F to the initial fluorescence intensity, where the predetermined linear curve is a linear relationship between Fo/Fstandard to the concentration of the hexavalent chromium ions; and the Fstandad is the quenched fluorescence intensity tested by detection reagents containing hexavalent chromium ions with different concentrations.
[09] The present invention further provides a method for testing concentration of
L-cys by graphitic carbon nitride quantum dots, including the following steps:
[10] performing a first mixing of a graphitic carbon niride quantum dot solution, a 1
BL-5679
Tri-HCI buffer solution and a hexavalent chromium solution, and performing a LU5041 75 fluorescence intensity test on the obtained test SOitiont0O obtain a quenched fluorescence intensity F1; and
[11] performing a second mixing of an L-cys solution to be tested and the detection reagent, performing a fluorescence intensity test on the obtained mixed solution to obtain a recovered fluorescence intensity F2, and obtaining the concentration of L-cys in the L-cys solution to be tested according to a predetermined linear curve and a ratio
F,/F1 of the recovered fluorescence intensity to the quenched fluorescence intensity; where the predetermined linear curve is a linear relationship between Fstandard/F1 to the concentration of L-cys;
[12] the Fstandara 1s the quenched fluorescence intensity tested by detection reagents containing L-cys with different concentrations; and
[13] the first mixing time is >5 min, and the second mixing time is >6 min.
[14] FIG. 1 is a fluorescence-concentration linear relationship diagram obtained by potassium dichromate standard solutions with different concentrations.
[15] FIG. 2 is a time-varying diagram of fluorescence intensities after a potassium dichromate solution is added into a graphitic carbon nitride quantum dot solution.
[16] FIG. 3 is a fluorescence absorption spectrum chart of the potassium dichromate solution.
[17] FIG. 4 is a fluorescence quenching effect diagram of different metal ions on the graphitic carbon nitride quantum dots.
[18] FIG. 5 is a fluorescence-concentration linear relationship diagram obtained by
L-Cysteine standard solutions with different concentrations.
[19] FIG. 6 is a time-varying diagram of fluorescence intensities after an L-Cysteine (L-cys) solution is added into a graphitic carbon nitride quantum dot solution.
[20] FIG. 7 is a time-varying diagram of fluorescence intensities of the graphitic carbon nitride quantum dots after the L-cys solutions with different concentrations are added.
[21] The present invention provides an application of graphitic carbon nitride quantum dots as fluorescent probes in testing concentration of hexavalent chromium ions or L-Cysteine (L-cys).
[22] The present invention further provides a method for testing concentration of hexavalent chromium ions by graphitic carbon nitride quantum dots, including the following steps:
[23] mixing a graphitic carbon nitride quantum dot solution with a Tri-HCI buffer solution to obtain a detection reagent, where the mixing time is >5min;
[24] performing a fluorescence intensity test on the detection reagent to obtain an initial fluorescence intensity Fo; and
[25] mixing a hexavalent chromium solution to be tested with the detection reagent, performing a fluorescence intensity test on the obtained mixed solution to obtain a 2
BL-5679 quenched fluorescence intensity F, and obtaining the concentration of hexavalent LU5041 75 chromium in the hexavalent chromium solution to be tested according to a predetermined linear curve and a ratio Fo/F of the quenched fluorescence intensity F to the initial fluorescence intensity.
[26] In the present invention, the graphitic carbon nitride quantum dot solution is mixed with the Tri-HCI buffer solution to obtain the detection reagent, and the fluorescence intensity test is performed on the obtained detection reagent to obtain the initial fluorescence intensity Fo.
[27] In the present invention, the concentration of the graphitic carbon nitride quantum dots in the graphitic carbon nitride quantum dot solution is preferably 50 - 60 ug/mL, more preferably 56 pg/mL. In the present invention, the concentration of
Tri-HCI in the Tri-HCI buffer solution is preferably 0.05 - 0.2 mol/L, more preferably 0.1 mol/L. In the present invention, the volume ratio of the graphitic carbon nitride quantum dot solution to the Tri-HCI buffer solution is 1 : (1 - 3), more preferably 1 : 2.
[28] In the present invention, the mixing time is >5 min.
[29] After the initial fluorescence intensity Fo is obtained, the hexavalent chromium solution to be tested is mixed with the detection reagent, the fluorescence intensity test is performed on the obtained mixed solution to obtain the quenched fluorescence intensity F, and the concentration of hexavalent chromium in the hexavalent chromium solution to be tested is obtained according to the predetermined linear curve and the ratio Fo/F of the quenched fluorescence intensity F to the initial fluorescence intensity.
[30] In the present invention, the predetermined linear curve is the linear relationship between Fo/Fstandard to the concentration of the hexavalent chromium ions; and in the present invention, the Fstandad 1S the quenched fluorescence intensity tested by detection reagents containing hexavalent chromium ions with different concentrations.
[31] Example 1
[32] Preparation of a graphitic carbon nitride quantum dot aqueous solution:
[33] 10 g of melamine was dissolved in 50 mL of deionized water, magnetically stirring the mixture for 30 min, and then transferring the mixture to an 80°C drying oven for continuous drying for 24 h. The obtained solid particles were transferred to a crucible after the mixture was cooled to room temperature, and heat preservation was performed in a 550°C fit furnace for 4 h at a heating rate of 5°C/min. After the crucible was cooled to room temperature again, a sample was transferred to mortar to prepare a fine powder, and the obtained sample was bulk phase graphitic carbon nitride (BGCN).
[34] 5 g of the BGCN was placed in a ceramic crucible, the ceramic crucible was placed in an air atmosphere at 500°C for thermal oxidation etching for 2 h at the heating rate of 2°C/min to obtain a graphitic carbon nitride nanosheet.
[35] 0.2 g of the graphitic carbon nitride nanosheet was placed in a mixed solution of mL of sulfuric acid and 30 mL of nitric acid, assisted with ultrasonic exfoliation (500
W, 60 kHz) for 16 h, and then the mixed solution was diluted to 500 mL to form a white transparent colloid, so as to obtain a graphitic carbon nitride nanotube.
[36] After a solution to be mixed was subjected to a 0.45-micron filter membrane and was washed by a large amount of deionized water to remove excessive acid, the obtained white solid particles were dispersed to 60 mL of deionized water again, the 3
BL-5679 mixture was transferred to two 50 mL reaction kettles for reaction at 200°C for 10 h, LU504175 after the mixture was cooled to room temperature, the mixture was subjected to a 0.22-micron filter membrane to obtain a white solution which was the graphitic carbon nitride quantum dot aqueous solution (the concentration was 0.56 mg/mL).
[37] The obtained graphitic carbon nitride quantum dot aqueous solution was diluted by 10 times to obtain a graphitic carbon nitride quantum dot aqueous solution with the concentration of 56 pg/mL.
[38] Testing of hexavalent chromium:
[39] 2 mL of a Tri-HCI buffer solution was dropwise added into 1 mL of the graphitic carbon nitride quantum dot aqueous solution with the concentration of 56 ug/mL to obtain a detection reagent, and the fluorescence intensity Fo (the excitation wavelength was 320 nm) of the detection reagent was tested; Fo was 1006361.
[40] A 0.02 mol/L potassium dichromate standard solution was respectively diluted to 100 mmol/L, 200 mmol/L, 250 mmol/L, 300 mmol/L, 400 mmol/L, 500 mmol/L and 600 mmol/L, and after 0.5 mL of the potassium dichromate standard solutions were mixed with the above detection reagent for 5 min, the fluorescence intensity Fstandard Was tested. Then, a linear relationship was established by taking Fo/F as a vertical coordinate and the concentration of hexavalent chromium in the potassium dichromate standard solution as the horizontal ordinate. As shown in FIG. 1, it can be known from FIG. 1 that a linear curve is Fo/Fstandara=0.92989+0.00232X, and a correlation coefficient
R?=0.9951. Within the range of 100-600 mmol/L, a good linear relationship is represented along with the concentration of hexavalent chromium and Fo/F.
[41] A hexavalent chromium solution to be tested was mixed with the detection reagent, the fluorescence intensity of the obtained mixed solution tested was 256470, and the fluorescence intensity was substituted into the linear curve to obtain the concentration of hexavalent chromium in the hexavalent chromium solution to be tested: 600 mmol/L.
[42] Tests:
[43] (1) Test for optimum fluorescence quenching time:
[44] Test method:
[45] 1 mL of the graphitic carbon nitride quantum dot aqueous solution was placed in a cuvette, 2mLof the Tri-HCI buffer solution was dropwise added, then 0.5 mL of the potassium dichromate solution with the concentration of 1 mmol/L was added, the fluorescence intensity was tested every 1 min, and the test result was shown in FIG. 2, where an illustration is a time-varying diagram of fluorescence intensity.
[46] It can be known from FIG. 2 that within the initial 1 min, the intensities of emission peaks of the graphitic carbon nitride quantum dot solution decrease dramatically and then tend to be stable. At 5 min, fluorescence has been completely quenched.
[47] The fluorescence absorption spectrum of the potassium dichromate solution is shown in FIG. 3, and it can be known from FIG. 3 that there are two absorption peaks at 257 nm and 353 nm. The absorption peak 353 nm is just close to the emission wavelength 360 nm of the graphitic carbon nitride quantum dot, so it is reasonably inferred that quenching of fluorescence of the graphitic carbon nitride quantum dots by 4
BL-5679 hexavalent chromium 1s induced by the inner filter effect. LU5041 75
[48] (2) Sensitivity test
[49] 2 mL of the Tri-HCI buffer solution was dropwise added into 1 mL of the graphitic carbon nitride quantum dot solution with the concentration of 56 pg/mL to test the fluorescence intensity as the fluorescence intensity of a blank solution.
[50] 2 mL of the Tri-HCI buffer solution was dropwise added into 1 mL of the graphitic carbon nitride quantum dot solution with the concentration of 56 pg/mL. 1 mL of an AI(NO3)3 solution with the concentration of 1 mol/L, 1 mL of a Ca(NOs3). solution with the concentration of 1 mol/L, 1 mL of a Ba(NOs), solution with the concentration of 1 mol/L, 1 mL of a Cd(NOs), solution with the concentration of 1 mol/L, 1 mL of a
Co(NOs), solution with the concentration of 1 mol/L, 1 mL of a Mg” solution with the concentration of 1 mol/L, 1 mL of a Sr(NOs), solution with the concentration of 1 mol/L, 1 mL of a Zn(NO3) solution with the concentration of 1 mol/L, 1 mL of a
Cu(NO3)» solution with the concentration of 1 mol/L, 1 mL of a Fe(NO3); solution with the concentration of 1 mol/L. and 1 mL of the potassium dichromate solution with the concentration of 1 mol/L were respectively added into the obtained mixed solution, fluorescent responses were then respectively tested, and results are shown in FIG. 4. It can be known from FIG. 4 that Cu**, Fe** and hexavalent chromium (Cr(VI)) have significant fluorescence quenching effect on the graphitic carbon nitride quantum dots, the fluorescence quenching effect of (Cr(VI)) is most obvious, and other metal ions hardly have the fluorescence quenching effect. The result shows that the sensitivity of the graphitic carbon nitride quantum dots on (Cr(VI)) is superior to that of other metal ions, so the graphitic carbon nitride quantum dots can be used as a promising fluorescent probe for testing of (Cr(VI)). When the solution to be tested contains Cu””,
Fe’ and (Cr(VI)) at the same time, the solution to be tested can be mixed with a sodium hydroxide solution with a certain concentration, and after Cu”* an d Fe”* are fully precipitated, (Cr(VI)) is then tested.
[51] (3) Limit of detection:
[52] The Limit of Detection (LOD) can be calculated by an equation I:
LOG = x
[53] = Equation I
[54] In the equation I, X is a numerical factor selected by a confidence level, with a numerical value of 3, à is a relative standard deviation (n=6) of a blank sample in a parallel measurement condition, which is 0.008527, and S is sensitivity of a calibration curve (the slope of a standard curve is 0.00232). The LOD of the detection reagent on hexavalent chromium calculated is 11.03 mmol/L.
[55] Example 2
[56] Preparation of a graphitic carbon nitride quantum dot aqueous solution is the same as that in the Example 1.
[57] Testing of concentration of L-cys:
[58] 0.75 mL of a graphitic carbon nitride quantum dot aqueous solution with the concentration of 56 pg/mL, 1.5 mL of a Tri-HCI buffer solution with the concentration of 0.1 mol/L and 0.375 mL of a potassium dichromate solution with the concentration of 500 umol/L were mixed to obtain a detection reagent, and the fluorescence intensity F1
BL-5679 of the test solution was tested, which was 174951. LU504175
[59] A200 mmol/L L-cys standard solution was respectively diluted to 5 mmol/L, 10 mmol/L, 15 mmol/L, 20 mmol/L, 30 mmol/L, 40 mmol/L, 50 mmol/L and 60 mmol/L, and after 0.375 mL of the L-Cysteine standard solutions were mixed with the above detection reagent for 6 min, the fluorescence intensity Fstandard Was tested. Then, a linear relationship was established by taking Fstandard/F1 as the vertical coordinate and the concentration of L-cys in the L-cys standard solution as the horizontal ordinate. À linear curve 18 Fstandard/F1=0.99766+0.01115X, and a linear relationship map is shown in FIG. 5.
[60] An L-cyssolution to be tested was mixed with the detection reagent, the fluorescence intensity of the obtained mixed solution tested was 720772, and the fluorescence intensity was substituted into the linear curve to obtain the concentration of L-cys in the L-cys solution to be tested: 60 mmol/L.
[61] Tests:
[62] (1) Test for fluorescence recovery time:
[63] To determine the complete reaction time, the optimum fluorescence quenching time is further tested, where the test method includes:
[64] 1 mL of the graphitic carbon nitride quantum dot solution was placed in a cuvette, 2 ml of the Tri-HCI buffer solution was dropwise added, then 0.5 mL of the potassium dichromate solution with the concentration of 1 mmol/L was added, in 5 min, fluorescence was quenched, and then 0.5 mL of the L-cys solution with the concentration of 100 mmol/L was added into the solution to test time-varying change of the fluorescence intensity, and the test result is shown in FIG. 6. It can be known from
FIG. 6 that in the beginning 6 min, the fluorescence intensity increases continuously as the reaction time is prolonged, but in 6 min, the fluorescence intensity tends to be stable.
Therefore, it is determined that the fluorescence recovery time of the L-cys solution is 6 min.
[65] Fluorescence recovery test for the L-cys solutions with different concentrations:
[66] 0.75 mL of a graphitic carbon nitride quantum dot solution with the concentration of 56 pg/mL, 1.5 mL of a Tri-HCI buffer solution with the concentration of 0.1 mol/L and 0.375 mL of a potassium dichromate solution with the concentration of 250 pmol/L were mixed to obtain a detection reagent;
[67] then the L-cys solutions with different concentrations were added into the detection reagent for mixing for 6 min, the fluorescence intensity was tested, and the result is shown in FIG. 7: in the range of 5-60 mmol/L, with increase of the concentration of L-cys, the fluorescence intensities of the graphitic carbon nitride quantum dots increase continuously and are in a linear relationship, and next to 60 mmol/L, with increase of the concentration of L-cys, the fluorescence intensity no longer changes. It can be inferred that the L-cys solution with low concentration (<60 mmol/L) is capable of being powerfully bonded with the graphitic carbon nitride quantum dots. Continuous increase of the concentration may not affect the structure of the whole system greatly, and the electronic interactions thereof have been stable in the low concentration L-cys solution. Surfaces of the graphitic carbon nitride quantum dots are positively charged. Compared with hexavalent chromium, L-cys has a stronger 6
BL-5679 electrostatic adsorption action with the graphitic carbon nitride quantum dots to replace LU5041 75 and occupy adsorption potentials of hexavalent chromium so as to weaken the inner filter effect induced by hexavalent chromium, so fluorescence of the graphitic carbon nitride quantum dots is recovered.
[68] Limit of detection:
[69] The Limit of Detection (LOD) can be calculated by an equation I:
[70] x Equation I
[71] In the equation I, X is a numerical factor selected by a confidence level, with a numerical value of 3, J is a relative standard deviation (n=6) of a blank sample in a parallel measurement condition, which is 0.015275, and S is sensitivity of a calibration curve (the slope of a standard curve is 0.01115). The LOD of the detection reagent on
L-cys is 4.11 mM. 7
Claims (3)
1. An application of graphitic carbon nitride in testing concentration of hexavalent chromium orL-Cysteine (L-cys).
2. A method for testing concentration of hexavalent chromium ions by graphitic carbon nitride, comprising the following steps: mixing the graphitic carbon nitride quantum dot solution with a Tri-HCI buffer solution to obtain a detection reagent, wherein the mixing time is >5min; performing a fluorescence intensity test on the detection reagent to obtain an initial fluorescence intensity Fo; and mixing a hexavalent chromium solution to be tested with the detection reagent, performing a fluorescence intensity test on the obtained mixed solution to obtain a quenched fluorescence intensity F, and obtaining the concentration of hexavalent chromium in the hexavalent chromium solution to be tested according to a predetermined linear curve and a ratio Fo/F of the quenched fluorescence intensity F to the initial fluorescence intensity; wherein the predetermined linear curve is a linear relationship between a Fo/Fstandard to the concentration of the hexavalent chromium ions; and the Fstandard is the quenched fluorescence intensity tested by detection reagents containing hexavalent chromium ions with different concentrations.
3. A method for testing concentration of L-Cysteine (L-cys) by graphitic carbon nitride, comprising the following steps: performing a first mixing of a graphitic carbon nitride quantum dot solution, a Tri-HCI buffer solution and a hexavalent chromium solution, and performing a fluorescence intensity test on the obtained test solution to obtain a quenched fluorescence intensity F1; and performing a second mixing of an L-cys solution to be tested and the detection reagent, performing a fluorescence intensity test on the obtained mixed solution to obtain a recovered fluorescence intensity F2, and obtaining the concentration of L-cys in the L-cys solution to be tested according to a predetermined linear curve and a ratio F,/F1 of the recovered fluorescence intensity to the quenched fluorescence intensity; wherein the predetermined linear curve is a linear relationship between a Fstandard/F1 to the concentration of L-cys; the Fstandard is the quenched fluorescence intensity tested by detection reagents containing L-cys with different concentrations; and the first mixing time is >5 min, and the second mixing time is >6 min. 8
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