CN112723325B - Phosphorus-doped graphite-phase carbon nitride nanosheet as well as preparation method and application thereof - Google Patents
Phosphorus-doped graphite-phase carbon nitride nanosheet as well as preparation method and application thereof Download PDFInfo
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/0605—Binary compounds of nitrogen with carbon
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- 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"
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
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- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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- C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
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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"
- G01N2021/6432—Quenching
Abstract
The invention relates to the technical field of fluorescence detection, and provides a phosphorus-doped graphite-phase carbon nitride nanosheet as well as a preparation method and application thereof. The preparation method comprises the steps of preparing graphite-phase carbon nitride solid powder by adopting a thermal decomposition method, performing ultrasonic dispersion on the graphite-phase carbon nitride solid powder in water, and obtaining the phosphorus-doped graphite-phase carbon nitride nano-sheet through centrifugal separation and filtration. According to the invention, the phosphorus-doped graphite phase carbon nitride in the bulk phase is prepared into the nano-sheet with large specific surface area and holes by utilizing the element doping and ultrasonic stripping methods, and the obtained phosphorus-doped graphite phase carbon nitride nano-sheet has good fluorescence performance and stability, has selective response to iron ions, and is suitable for analysis and detection of trace iron ions. The results of the examples show that the detection limit of the phosphorus-doped graphite phase carbon nitride applied to the detection of iron ions can reach 1.63 mu mol/L.
Description
Technical Field
The invention relates to the technical field of fluorescence detection, in particular to a phosphorus-doped graphite phase carbon nitride nano-sheet, and a preparation method and application thereof.
Background
Hitherto, there are many methods for detecting metal ions, such as fluorescence, spectrophotometry, electrochemical methods, chromatography, and the like. Wherein the fluorescence method is characterized in that the concentration of the analyte can be calculated indirectly by measuring the decrease in fluorescence intensity after the introduction of the analyte. Compared with other methods, the fluorescence method can be used in a reversible way even without damaging the sample, the operation is simple, the trace detection can be realized, and the instrument and the equipment are simple.
Graphite phase carbon nitride (g-C) 3 N 4 ) As an organic nonmetallic semiconductor material capable of being responded by visible light, compared with the traditional semiconductor, the organic nonmetallic semiconductor material has a unique material structure and an electronic structure, and has the advantages in performance such as good wear resistance, high thermal stability, high chemical stability, good fluorescence performance and the like due to the covalent bond combined with C-N heterocycle. As the research is continued, g-C is found 3 N 4 Has good application prospect in the aspects of sensing, medicine, catalysis, luminescence regulation and control and the like.
Iron ions (Fe) 3+ ) Is one of the important nutritional elements in human health and in water environments, but excessive intake and accumulation of iron can lead to side effects and irreversible damage. At present, g-C is not utilized 3 N 4 Relevant reports of fluorescence detection of iron ions.
Disclosure of Invention
In view of this, the present invention provides a phosphorus-doped graphite phase carbon nitride (P-g-C 3 N 4 ) A nano-sheet and a preparation method and application thereof. The phosphorus doped graphite phase carbon nitride nano-sheet provided by the invention has good fluorescence performance and stability, has selective response to iron ions, and is suitable for analysis and detection of trace iron ions.
In order to achieve the above object, the present invention provides the following technical solutions:
a preparation method of a phosphorus-doped graphite phase carbon nitride nano-sheet comprises the following steps:
(1) Mixing a nitrogen-containing organic matter and ammonium phosphate salt, and then performing thermal decomposition to obtain phosphorus-doped graphite-phase carbon nitride solid powder;
(2) Mixing the phosphorus-doped graphite-phase carbon nitride solid powder with water, and then performing ultrasonic dispersion to obtain phosphorus-doped graphite-phase carbon nitride suspension;
(3) And (3) centrifugally separating the phosphorus-doped graphite-phase carbon nitride suspension, and filtering the obtained supernatant to obtain a colloidal solution of the phosphorus-doped graphite-phase carbon nitride nanosheets.
Preferably, the nitrogen-containing organic matter comprises melamine and/or urea; the ammonium phosphate salt comprises one or more of ammonium phosphate, monoammonium phosphate and diammonium phosphate; the molar ratio of the nitrogen-containing organic matter to the ammonium phosphate salt is 0.024:0.0004-0.0075.
Preferably, the thermal decomposition temperature is 500-650 ℃, the time is 3.5-6 h, and the heating rate from the temperature of the thermal decomposition to the temperature of the thermal decomposition is 3-6 ℃/min.
Preferably, the mass ratio of the phosphorus doped graphite phase carbon nitride solid powder to water is 1:300-500.
Preferably, the ultrasonic dispersion time is 10-13 h, and the power is 50-70 Hz.
Preferably, the centrifugal separation comprises a first centrifugal separation and a second centrifugal separation which are sequentially carried out, wherein the rotating speed of the first centrifugal separation is 7000-9000 r/min, and the time is 6-9 min; the rotation speed of the second centrifugal separation is 10000-12000 r/min, and the time is 15-20 min.
Preferably, the filter membrane is an aqueous phase microporous filter membrane.
The invention provides the phosphorus-doped graphite phase carbon nitride nano-sheet prepared by the preparation method, and the size of the phosphorus-doped graphite phase carbon nitride nano-sheet is 50-100 nm.
The invention provides application of the phosphorus-doped graphite-phase carbon nitride nano-sheet in fluorescence sensing detection of iron ions.
The invention provides a preparation method of a phosphorus-doped graphite-phase carbon nitride nano-sheet. The invention prepares the blocky phosphorus-doped graphite-phase carbon nitride into the nano-sheets with large specific surface area and holes by utilizing the element doping and ultrasonic stripping methods, the obtained phosphorus-doped graphite-phase carbon nitride nano-sheets are uniformly and stably dispersed in a colloid solution, are not easy to agglomerate, have good fluorescence performance, show obvious Tyndall phenomenon and blue fluorescence characteristics, have selective response to iron ions, and are suitable for analysis and detection of trace iron ions in complex samples such as biology, food, environment and the like. The results of the examples show that the detection limit of the phosphorus-doped graphite phase carbon nitride nano-sheet can reach 1.63 mu mol/L when the phosphorus-doped graphite phase carbon nitride nano-sheet is applied to the detection of iron ions.
Drawings
FIG. 1 shows the preparation of P-g-C in the examples of the present invention 3 N 4 Schematic process of nanosheets;
FIG. 2 is a diagram of P-g-C in example 1 3 N 4 Solid powder and P-g-C 3 N 4 Microtopography of nanoplatelets, wherein (a) is P-g-C 3 N 4 SEM image of solid powder, (b) is P-g-C 3 N 4 The upper right inset of (b) the TEM image of the nanoplate is P-g-C 3 N 4 A fluorescence effect diagram of the nanosheet colloid solution under laser irradiation;
FIG. 3 is a diagram of P-g-C in example 1 3 N 4 Solid powder and P-g-C 3 N 4 XRD pattern of nanoplatelets;
FIG. 4 is a diagram of P-g-C in example 1 3 N 4 Solid powder and P-g-C 3 N 4 FT-IR map of nanoplatelets;
FIG. 5 is a diagram of P-g-C in example 1 3 N 4 Solid powder and P-g-C 3 N 4 Ultraviolet spectrum of the nanosheets;
FIG. 6 is a diagram of P-g-C in example 1 3 N 4 Solid powder and P-g-C 3 N 4 Fluorescence spectrum of the nanosheets, upper right inset is P-g-C 3 N 4 A fluorescence effect diagram of the nanosheet colloid solution under ultraviolet irradiation;
FIG. 7 is a diagram of P-g-C in example 2 3 N 4 The test result graph of the selectivity of the nano-sheet to the iron ions, wherein (a) is P-g-C 3 N 4 Adding Fe into the nano-sheet colloid solution 3+ ,Cu 2+ ,Al 3+ ,Zn 2+ ,Sr 2+ ,Mg 2+ ,Cr 2+ ,Bb 2+ The fluorescence intensity change pattern after that, (b) is to contain Cu 2+ ,Al 3+ ,Zn 2+ ,Sr 2+ ,Mg 2+ ,Cr 2+ ,Bb 2+ P-g-C of (C) 3 N 4 Adding Fe into the nano-sheet colloid solution 3+ A subsequent fluorescence intensity change map;
FIG. 8 is a diagram of P-g-C in example 3 3 N 4 Adding Fe into nano-sheet colloid solution 3+ Front and rear fluorescence lifetime curves;
FIG. 9 is P-g-C 3 N 4 Adding Fe with different concentrations into the nano colloid solution 3+ The following fluorescence intensity test results, the upper right inset is a linear fit curve.
Detailed Description
The invention provides a preparation method of a phosphorus-doped graphite phase carbon nitride nano-sheet, which comprises the following steps:
(1) Mixing a nitrogen-containing organic matter and ammonium phosphate salt, and then performing thermal decomposition to obtain phosphorus-doped graphite-phase carbon nitride solid powder;
(2) Mixing the phosphorus-doped graphite-phase carbon nitride solid powder with water, and then performing ultrasonic dispersion to obtain phosphorus-doped graphite-phase carbon nitride suspension;
(3) And (3) centrifugally separating the phosphorus-doped graphite-phase carbon nitride suspension, and filtering the obtained supernatant to obtain the phosphorus-doped graphite-phase carbon nitride nanosheets.
The invention mixes the nitrogen-containing organic matter and ammonium phosphate salt and then carries out thermal decomposition to obtain the phosphorus doped graphite phase carbon nitride (P-g-C) 3 N 4 ) Solid powder. In the present invention, the nitrogen-containing organic matter preferably includes melamine and/or urea, more preferably melamine; the ammonium phosphate salt preferably comprises one or more of ammonium phosphate, monoammonium phosphate and diammonium phosphate, more preferably diammonium phosphate; the invention uses ammonium phosphate as phosphorus source, which can avoid the introduction of impurity; the molar ratio of the nitrogen-containing organic matter to the ammonium phosphate salt is preferably 0.024:0.0004 to 0.0075, more preferably 0.024:0.001 to 0.005.
In the present invention, the method for mixing the nitrogen-containing organic matter and the ammonium phosphate salt is preferably as follows: mixing the nitrogen-containing organic matter and ammonium phosphate salt, grinding, and stirring and mixing the mixed solid powder and water to obtain a mixed material liquid; and drying the mixed liquid, and grinding again to obtain the mixture of the nitrogen-containing organic matters and the ammonium phosphate salt. In the invention, the dosage ratio of the mixed solid powder to the water is preferably 3.2g to 50mL, the stirring and mixing time is preferably 1h, the drying temperature is preferably 60 ℃ and the time is preferably 12h; the grinding conditions are not particularly required, and the uniformly mixed solid powder can be obtained by adopting the conditions well known to the person skilled in the art.
In the present invention, the thermal decomposition temperature is preferably 500 to 650 ℃, more preferably 550 to 600 ℃, the thermal decomposition time is preferably 3.5 to 6 hours, more preferably 4 hours, and the rate of temperature rise to the thermal decomposition temperature is preferably 3 to 6 ℃/min; the thermal decomposition is preferably carried out in a pit furnace. In the thermal decomposition process, melamine is pyrolyzed to generate graphite-phase carbon nitride, and at the same time, phosphate ammonium salt is pyrolyzed to generate phosphorus atoms doped in the graphite-phase carbon nitride, so as to obtain phosphorus doped graphite-phase carbon nitride. The invention dopes phosphorus into graphite phase carbon nitride, which can lead the fluorescence peak of the graphite phase carbon nitride to have red shift and wide peak width, but does not change the wavelength range of light absorption of pure graphite phase carbon nitride.
After thermal decomposition is completed, the polymerization product obtained by the method is preferably naturally cooled to room temperature and then ground to obtain phosphorus-doped graphite-phase carbon nitride solid powder; the phosphorus-doped graphite-phase carbon nitride solid powder obtained by the invention is a bulk phase.
After the phosphorus-doped graphite-phase carbon nitride solid powder is obtained, the phosphorus-doped graphite-phase carbon nitride solid powder is mixed with water and then subjected to ultrasonic dispersion, so that the phosphorus-doped graphite-phase carbon nitride suspension is obtained. In the invention, the mass ratio of the phosphorus doped graphite phase carbon nitride solid powder to water is preferably 1:300-500, more preferably 1:350-450; the ultrasonic dispersion time is preferably 10 to 13 hours, more preferably 11 to 12 hours, and the power is preferably 50 to 70Hz, more preferably 55 to 65Hz. The invention peels off the bulk phase phosphorus-doped graphite phase carbon nitride solid powder through ultrasonic dispersion, and the obtained phosphorus-doped graphite phase carbon nitride suspension is a mixture of bulk phase phosphorus-doped graphite phase carbon nitride and nano lamellar phosphorus-doped graphite phase carbon nitride.
After the phosphorus-doped graphite phase carbon nitride suspension is obtained, the invention carries out centrifugal separation on the phosphorus-doped graphite phase carbon nitride suspension, and filters the obtained supernatant fluid to obtain the phosphorus-doped graphite phase carbon nitride nano-sheet (P-g-C) 3 N 4 Nanoplatelets). In the present invention, the centrifugal separation preferably includes a first centrifugal separation and a second centrifugal separation which are sequentially performed, and the rotational speed of the first centrifugal separation is preferably 7000 to 9000r/min, more preferably 8000r/min, and the time is preferably 7 to 9min, more preferably 8min; the rotation speed of the second centrifugal separation is preferably 10000-12000 r/min, more preferably 10000-11000 r/min, and the time is preferably 15-20 min, more preferably 15-18 min. In the present invention, specifically, the supernatant obtained after the first centrifugation is subjected to the second centrifugation. The invention separates and removes undissolved sediment and large-size phosphorus doped graphite phase carbon nitride through a first centrifugal separation and a second centrifugal separation.
In the present invention, the filtration membrane is preferably an aqueous phase microporous membrane. The obtained filtrate is the colloidal solution of the phosphorus-doped graphite-phase carbon nitride nano-sheet, the finally obtained phosphorus-doped graphite-phase carbon nitride nano-sheet exists in the form of colloidal solution, and the phosphorus-doped graphite-phase carbon nitride nano-sheet is highly uniformly dispersed in the colloidal solution and has good stability. In the invention, the concentration of the obtained phosphorus doped graphite phase carbon nitride nanosheet colloid solution is preferably 0.06mg/mL.
The invention also provides the phosphorus-doped graphite phase carbon nitride nano-sheet prepared by the preparation method, and the size of the phosphorus-doped graphite phase carbon nitride nano-sheet is 50-100 nm, preferably 60-80 nm. The phosphorus doped graphite phase carbon nitride nano-sheet provided by the invention exists in a colloid solution form, the nano-sheet is highly and uniformly dispersed in the colloid solution, agglomeration is not easy to occur, the fluorescence performance is good, and the phosphorus doped graphite phase carbon nitride nano-sheet has selective response to iron ions.
The invention also provides application of the phosphorus-doped graphite-phase carbon nitride nano-sheet in fluorescence sensing detection of iron ions. In the present invention, the iron ions are particularly preferably iron ions in organisms, foods or environments, particularly such as complex water bodies. The specific detection method of the fluorescence detection is not particularly required, and the method well known by the person skilled in the art can be adopted; in the specific embodiment of the invention, the to-be-detected liquid is preferably added into the phosphorus doped graphite phase carbon nitride nanosheet colloid solution prepared by the scheme, the fluorescence intensity change before and after the addition is tested, and the iron ion content in the to-be-detected liquid is obtained through calculation according to the fluorescence quenching efficiency and a standard curve; the standard curve is a relation curve between fluorescence quenching efficiency and iron ion concentration, the method for obtaining the standard curve is not particularly required, and the method is well known to a person skilled in the art.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention.
FIG. 1 shows the preparation of P-g-C in the examples of the present invention 3 N 4 Schematic of the process of nanoplatelets, wherein first the bulk phase P-g-C is prepared by thermal decomposition of monoammonium phosphate and melamine 3 N 4 (i.e., P-g-C) 3 N 4 Solid powder) and then obtaining a suspension (including bulk phase P-g-C in the suspension) by ultrasonic dispersion 3 N 4 And P-g-C 3 N 4 Nanoplatelets) followed by a first centrifugation and a second centrifugation to obtain P-g-C 3 N 4 A nano-sheet.
Example 1
(1) Weighing 3g of melamine and 0.2g of diammonium hydrogen phosphate solid powder, fully grinding, adding 50mL of deionized water, stirring for 1h to fully mix, placing the mixed solution in an oven, drying at 60 ℃ for 12h, fully grinding, placing in an alumina crucible, placing in a pit furnace, keeping the temperature at 550 ℃ for 4h at a programmed heating rate of 4 ℃/min, naturally cooling to room temperature, and fully grinding into yellow P-g-C 3 N 4 The solid powder is ready for use.
(2) Weighing 100mg of P-g-C 3 N 4 Adding the solid powder into a beaker containing 100mL of deionized water, and continuously performing ultrasonic treatment for 10h to obtain P-g-C 3 N 4 A suspension; P-g-C 3 N 4 Centrifuging at 8000rpm/min for 8min, and collecting supernatantCentrifuging the solution at 10000rpm/min for 15min to obtain stable and uniform P-g-C 3 N 4 Nanosheets (denoted as P-gcn) colloidal solution.
For P-g-C 3 N 4 Solid powder and P-g-C 3 N 4 The microscopic morphology of the nanoplatelets is observed, and the result is shown in FIG. 2, wherein (a) in FIG. 2 is P-g-C 3 N 4 SEM image of solid powder, (b) is P-g-C 3 N 4 The upper right inset of (b) the TEM image of the nanoplate is P-g-C 3 N 4 A fluorescence effect diagram of the nanosheet colloid solution under laser irradiation; as can be seen from FIG. 2, P-g-C 3 N 4 SEM of solid powder is shown as a block of piles, while P-g-C 3 N 4 The TEM of the nanoplatelets is nano-sized and planar in structure, and by irradiating the colloidal solution with laser light, a light path is clearly observed, which is the tyndall effect of the colloid. As can be seen from the above results, the P-g-C obtained by the present invention 3 N 4 The solution of the nano-sheet is colloid solution and has high stability.
FIG. 3 is P-g-C 3 N 4 Solid powder and P-g-C 3 N 4 XRD patterns of nanoplatelets, FIG. 4 is P-g-C 3 N 4 Solid powder and P-g-C 3 N 4 FT-IR diagram of nanoplatelets. As can be seen from FIG. 3, P-g-C 3 N 4 The characteristic peak intensity of the nanoplatelets at 27.69 ° is significantly reduced due to the reduced inter-plane spacing of the C-N bonds. Meanwhile, the peak of the nanosheet sample at the (002) plane was found to slightly shift from 27.52 ° to 27.69 ° relative to the powdery sample, and the corresponding inter-plane was reduced from 0.32390 to 0.32206nm; it can be seen from FIG. 4 that the FT-IR spectrum of the material before and after peeling was substantially unchanged.
FIG. 5 is P-g-C 3 N 4 Solid powder and P-g-C 3 N 4 The ultraviolet spectrum of the nanosheets is shown in FIG. 6 as P-g-C 3 N 4 Solid powder and P-g-C 3 N 4 Fluorescence spectra of nanoplatelets, inset at upper right of FIG. 6 is P-g-C 3 N 4 And (3) fluorescent effect graph of the nano-sheet colloid solution under ultraviolet irradiation. As can be seen from FIG. 5, P-g-C 3 N 4 Compared with nano-sheetsThe band gap increases from 2.51eV to 2.62eV before stripping. Excitation studies at 370nm found bulk phase P-g-C 3 N 4 (i.e., P-g-C) 3 N 4 Solid powder) with highest emission intensity at 449nm, P-g-C 3 N 4 The emission intensity of the nano-sheet at 430nm is highest, the fluorescence peak of the sample after stripping is blue-shifted by 19nm compared with the sample before stripping due to the quantum efficiency generated by stripping, and the P-g-C 3 N 4 Peak width of nanosheets compared to bulk phase P-g-C 3 N 4 Is narrowed; as can be seen from the inset in FIG. 6, P-g-C was irradiated with 365nm ultraviolet light 3 N 4 The nanoplatelet colloidal solution exhibits a single stable blue fluorescence.
Example 2
Test P-g-C 3 N 4 The selectivity of the nano-sheet to iron ions is as follows: selecting different metal ions (Fe 3+ ,Cu 2 + ,Al 3+ ,Zn 2+ ,Sr 2+ ,Mg 2+ ,Cr 2+ ,Bb 2+ ) Added to the P-g-C prepared in example 1 respectively 3 N 4 In the nanosheet colloid solution (the concentration is 0.06 mg/mL), the addition amount of metal ions is 1mmol/L; the fluorescence intensity of the solution after each metal ion was measured, and fluorescence quenching efficiency (I/I 0 Wherein I is fluorescence intensity after adding metal ion, I 0 Fluorescence intensity when no metal ion is added);
to P-g-C prepared in example 1 3 N 4 Adding Cu into the nano-sheet colloid solution 2+ ,Al 3+ ,Zn 2+ ,Sr 2+ ,Mg 2+ ,Cr 2+ ,Bb 2+ The addition amounts are 1mmol/L, the fluorescence intensity is tested, and then Fe is added into the solution 3+ The addition amount was 0.04mmol/L. Test of added Fe 3+ Fluorescence intensity of the post-solution.
The results are shown in FIG. 7, FIG. 7 is P-g-C 3 N 4 The test result graph of the selectivity of the nano-sheet to the iron ions, wherein (a) is P-g-C 3 N 4 Adding Fe into the nano-sheet colloid solution 3+ ,Cu 2+ ,Al 3+ ,Zn 2+ ,Sr 2+ ,Mg 2+ ,Cr 2+ ,Bb 2+ The fluorescence intensity change pattern after that, (b) is to contain Cu 2+ ,Al 3+ ,Zn 2+ ,Sr 2+ ,Mg 2+ ,Cr 2+ ,Bb 2+ P-g-C of (C) 3 N 4 Adding Fe into the nano-sheet colloid solution 3+ A graph of the change in fluorescence intensity. As can be seen from FIG. 7 (a), fe 3+ The fluorescence intensity of the added solution is obviously reduced, and the fluorescence quenching rate is obviously higher than that of other metal ions, which indicates that the P-g-C of the invention 3 N 4 The nano-sheet can be used as a fluorescent probe for detecting Fe 3+ . As can be seen from FIG. 7 (b), fe is added when in solution 3+ When the concentration is 25 times smaller than that of other metal ions, the fluorescence intensity of the solution can still be further quenched, which indicates that the other metal ions are opposite to Fe 3+ Has little influence, and the P-g-C of the invention is explained 3 N 4 Nano-sheet pair Fe 3+ Has higher selectivity.
Example 3
P-g-C 3 N 4 Nano-sheet pair Fe 3+ Determination of the detection limit of (2)
(1) Quench type
By determination of P-g-C 3 N 4 Adding Fe into nano-sheet colloid solution 3+ The front and back lifetime curves determine the type of fluorescence quenching process, toward P-g-C 3 N 4 Adding Fe into nano-sheet colloid solution 3+ As shown in FIG. 8, the fluorescence lifetime curves before and after the addition of Fe can be seen from FIG. 8 3+ After that, P-g-C 3 N 4 The fluorescence lifetime of the nanoplatelet colloidal solution is unchanged. Indicating P-g-C 3 N 4 And Fe (Fe) 3+ The fluorescence quenching process in between results mainly from the static quenching process. The static quenching process follows the Stern-Volmer procedure, as shown in formula I:
in formula I: f (F) 0 And F represents the absence and presence of the detector Fe, respectively 3+ Time P-g-C 3 N 4 Fluorescence intensity of nanoplatelet colloidal solution; q represents the concentration of the detection object; k (K) SV Is the quenching effect coefficient.
Fluorescence quenching efficiency can be linearly fitted by equation. The invention uses Fe with different concentrations 3+ The solutions were added to the P-g-C solution separately 3 N 4 In the nano colloid solution (the concentration is 0.06 mg/mL), the relative fluorescence intensity and Fe are measured 3+ The concentrations of the solutions were 1. Mu. Mol/L, 2. Mu. Mol/L, 3. Mu. Mol/L, 4. Mu. Mol/L, 5. Mu. Mol/L, 6. Mu. Mol/L, 7. Mu. Mol/L and 8. Mu. Mol/L, respectively. Obtaining Fe according to the test result of fluorescence intensity 3+ The results of the fitting curves of concentration and fluorescence quenching efficiency are shown in FIG. 9. As can be seen from the linear fitting curve in FIG. 9, P-g-C 3 N 4 Fluorescence intensity of nanosheet colloid solution and Fe 3+ The linear relation between the ion concentration and 1-8 mu mol/L is F 0 F=0.01188 c+1.23148, fitting the map correlation coefficient R 2 0.966.
(2) Detection limit
The fluorescence quenching efficiency can be fitted by the fitting equation in (1), and the detection shows that when Fe 3+ The quenching was substantially complete 9min after the addition, with the following 9min as standard. Further, the detection Limit (LOD) is calculated by formula II:
in formula II, K is a numerical factor selected for the confidence level, herein determined to be 3, δ is the relative standard deviation (n=7) of the blank sample under parallel measurement conditions, and S is the sensitivity of the calibration curve.
Calculation by formula II shows that for Fe 3+ The detection limit LOD was about 1.63. Mu. Mol/L at a signal-to-noise ratio of 3.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (7)
1. The application of the phosphorus-doped graphite-phase carbon nitride nano-sheet in detecting iron ions by fluorescence sensing is characterized in that the preparation method of the phosphorus-doped graphite-phase carbon nitride nano-sheet comprises the following steps:
(1) Mixing a nitrogen-containing organic matter and ammonium phosphate salt, and then performing thermal decomposition to obtain phosphorus-doped graphite-phase carbon nitride solid powder;
(2) Mixing the phosphorus-doped graphite-phase carbon nitride solid powder with water, and then performing ultrasonic dispersion to obtain phosphorus-doped graphite-phase carbon nitride suspension;
(3) Centrifugally separating the phosphorus-doped graphite-phase carbon nitride suspension, and filtering the obtained supernatant to obtain a colloidal solution of the phosphorus-doped graphite-phase carbon nitride nanosheets;
the size of the phosphorus doped graphite phase carbon nitride nano-sheet is 50-100 nm; the concentration of the phosphorus doped graphite phase carbon nitride nanosheet colloid solution is 0.06mg/mL; the detection method comprises the following steps: and adding the liquid to be measured into the phosphorus-doped graphite-phase carbon nitride nanosheet colloid solution, testing the change of fluorescence intensity before and after the addition, and calculating according to fluorescence quenching efficiency and a standard curve to obtain the iron ion content in the liquid to be measured.
2. Use according to claim 1, characterized in that the nitrogen-containing organic matter comprises melamine and/or urea; the ammonium phosphate salt comprises one or more of ammonium phosphate, monoammonium phosphate and diammonium phosphate; the molar ratio of the nitrogen-containing organic matter to the ammonium phosphate salt is 0.024:0.0004-0.0075.
3. The use according to claim 1, wherein the thermal decomposition temperature is 500-650 ℃, the time is 3.5-6 h, and the rate of rise of the temperature to the thermal decomposition temperature is 3-6 ℃/min.
4. The use according to claim 1, wherein the mass ratio of the phosphorus doped graphite phase carbon nitride solid powder to water is 1:300-500.
5. The use according to claim 1, wherein the time of the ultrasonic dispersion is 10-13 h and the power is 50-70 Hz.
6. The use according to claim 1, wherein the centrifugation comprises a first centrifugation and a second centrifugation performed in sequence, the first centrifugation being performed at a rotational speed of 7000 to 9000r/min for a time of 6 to 9min; the rotation speed of the second centrifugal separation is 10000-12000 r/min, and the time is 15-20 min.
7. The use according to claim 1, wherein the filtration membrane is an aqueous phase microporous membrane.
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| CN105670620A (en) * | 2016-03-14 | 2016-06-15 | 山东农业大学 | Preparation method of doped carbon nitride fluorescent quantum dots |
| CN109553077A (en) * | 2019-01-24 | 2019-04-02 | 济南大学 | A kind of preparation method of triangle phosphorus, sulfur doping azotized carbon nano piece |
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| CN105417507A (en) * | 2015-12-10 | 2016-03-23 | 济南大学 | Preparing method for carbon nitride nano particles and obtained product |
| CN105670620A (en) * | 2016-03-14 | 2016-06-15 | 山东农业大学 | Preparation method of doped carbon nitride fluorescent quantum dots |
| CN109553077A (en) * | 2019-01-24 | 2019-04-02 | 济南大学 | A kind of preparation method of triangle phosphorus, sulfur doping azotized carbon nano piece |
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