Disclosure of Invention
The invention aims to provide a fluorescent probe material and a preparation method and application thereof, wherein the excitation wavelength is 1550nm in a near infrared two-region mode, the emission wavelength is in a near infrared one-region mode, the central wavelength is 980nm, background fluorescence is not generated in the detection process, and the high accuracy is achieved.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a fluorescent probe material, which comprises a core-shell nanocrystal and an oleic acid ligand coated on the surface of the core-shell nanocrystal, wherein the oleic acid ligand is electrostatically adsorbed on the surface of the core-shell nanocrystal; the composition of the core-shell nanocrystal is Na0.6K0.4BiaErbYb0.1F4@NaBicYbdF4Said Na0.6K0.4BiaErbYb0.1F4As a nucleus, the NaBicYbdF4Is a shell; wherein a is 0.5 to 0.7, b is 0.3 to 0.5, c is 0.7 to 0.9, and d is 0.1 to 0.3.
Preferably, the mass of the oleic acid ligand is 15-25% of the total mass of the core-shell nanocrystal and the oleic acid ligand.
The invention provides a preparation method of the fluorescent probe material in the technical scheme, which comprises the following steps:
mixing a first sodium salt, a potassium salt, a first bismuth salt, an erbium salt, a first ytterbium salt, a first fluorine source, first oleic acid, first oleylamine and a first solvent, and performing first growth to obtain a core nanocrystal;
mixing a second sodium salt, a second bismuth salt, a second ytterbium salt, a second fluorine source, second oleic acid, second oleylamine and a second solvent with the core nanocrystal to perform second growth to obtain a fluorescent probe material;
the molar ratio of the first sodium salt, the potassium salt, the first bismuth salt, the erbium salt, the first ytterbium salt and the first fluorine source is 0.6:0.4 (0.5-0.7) to 0.3-0.5) to 0.1: 4;
the molar ratio of the second sodium salt to the second bismuth salt to the second ytterbium salt to the second fluorine source is 1 (0.7-0.9) to 0.1-0.3) to 4;
the molar ratio of the first sodium salt to the second sodium salt is 0.6: 1.
Preferably, the first sodium salt and the second sodium salt independently comprise sodium nitrate or sodium chloride; the potassium salt comprises potassium carbonate; the first bismuth salt and the second bismuth salt independently comprise bismuth nitrate, bismuth chloride or bismuth oxychloride; the erbium salt comprises erbium nitrate or erbium chloride; the first ytterbium salt and the second ytterbium salt independently comprise ytterbium nitrate or ytterbium chloride.
Preferably, the first fluorine source and the second fluorine source are ammonium fluoride; the dosage ratio of the first fluorine source, the first oleic acid and the first oleylamine is (4-6) mmol, (5-10) mL, (1-2) mL.
Preferably, the dosage ratio of the second fluorine source, the second oleic acid and the second oleylamine is (4-6) mmol, (5-10) mL, (1-2) mL.
Preferably, the temperature of the first growth is 25-35 ℃ and the time is 30-60 min.
Preferably, the temperature of the second growth is 25-35 ℃ and the time is 60-90 min.
The invention provides an application of the fluorescent probe material in the technical scheme or the fluorescent probe material prepared by the preparation method in the technical scheme in quantitative detection of lead content in gasoline.
The invention provides a method for detecting lead content in gasoline, which comprises the following steps:
mixing gasoline containing different lead ion concentrations with a fluorescent probe material, detecting under the condition of 1550nm exciting light excitation, calculating integral intensity according to the obtained up-conversion spectrum, fitting a relation curve of the fluorescent integral intensity and the lead ion concentration, and obtaining the lead ion content in a gasoline sample according to the relation curve; the fluorescent probe material is the fluorescent probe material in the technical scheme or the fluorescent probe material prepared by the preparation method in the technical scheme.
The invention provides a fluorescent probe material, which comprises a core-shell nanocrystal and an oleic acid ligand coated on the surface of the core-shell nanocrystal, wherein the oleic acid ligand is electrostatically adsorbed on the surface of the core-shell nanocrystal; the composition of the core-shell nanocrystal is Na0.6K0.4BiaErbYb0.1F4@NaBicYbdF4Said Na0.6K0.4BiaErbYb0.1F4As a nucleus, the NaBicYbdF4Is a shell; wherein a is 0.5 to 0.7, b is 0.3 to 0.5, c is 0.7 to 0.9, and d is 0.1 to 0.3. The fluorescent probe material provided by the invention can emit 980nm up-conversion light under the excitation condition of a 1550nm laser, the excitation wavelength of the fluorescent probe material is 1550nm, the emission wavelength (980nm) is in a near-infrared region I, the center wavelength of the fluorescent probe material is 980nm, the excitation light and the emission light are both in a near-infrared region, background fluorescence is not generated in the detection process, and the accuracy is high. In Na0.6K0.4BiF4In the host lattice, Er3+And Yb3+All occupy Bi3+Lattice site, the energy of incident photon is Er in the nuclear nanocrystalline3+Ion absorption, corresponding to4I15→4I13Further filling by a two-photon absorption process4I11Energy level at which the energy of the radiated photons is transferred to Yb after the electrons return to the ground state3+Further fill Yb3+Is/are as follows2F5/2Energy level, resulting in up-converted luminescence with a central wavelength at 980 nm. In addition, by doping a small amount of Yb in the shell layer3+Can increase Yb3+For Er3+Ion(s)4I11The probability of electron capture on the energy level, and thus the up-conversion luminous efficiency is improved.
The oleic acid ligand contained on the surface of the fluorescent probe material provided by the invention can enable the core-shell nanocrystal to have good dispersibility in gasoline, and is beneficial to enlarging the interaction area of lead ions in the gasoline and the surface of the core-shell nanocrystal, and Er can be captured due to the excited state energy level of the lead ions after the lead ions in the gasoline are contacted with the surface of the core-shell nanocrystal3+Ion(s)4I11Electrons at the energy level, thereby reducing Yb3+The probability of electron capture of ions on the energy level is reduced, and the process reduces Er3+To Yb3+Energy transfer efficiency of (1), resulting in Yb3+The up-conversion luminescence intensity of ions at 980nm is gradually weakened along with the increase of the concentration of lead ions, and the fluorescent probe material designed by the invention has very high up-conversion luminescence intensity, so that the change amplitude of the fluorescence intensity along with the increase of the concentration of the lead ions is very obvious, a relation curve of the up-conversion luminescence intensity and the concentration of the lead ions can be well established, and the fluorescent probe material is further applied to quantitative detection of the lead content in gasoline.
Detailed Description
The invention provides a fluorescent probe material, which comprises a core-shell nanocrystal and an oleic acid ligand coated on the surface of the core-shell nanocrystal, wherein the oleic acid ligand is electrostatically adsorbed on the surface of the core-shell nanocrystal; the composition of the core-shell nanocrystal is Na0.6K0.4BiaErbYb0.1F4@NaBicYbdF4Said Na0.6K0.4BiaErbYb0.1F4As a nucleus, the NaBicYbdF4Is a shell; wherein a is 0.5 to 0.7, b is 0.3 to 0.5, c is 0.7 to 0.9, and d is 0.1 to 0.3.
The fluorescent probe material provided by the invention comprises core-shell nanocrystals, wherein the core-shell nanocrystals consist of Na0.6K0.4BiaErbYb0.1F4@NaBicYbdF4Said Na0.6K0.4BiaErbYb0.1F4As a nucleus, the NaBicYbdF4Is a shell; wherein a is 0.5-0.7, b is 0.3-0.5, c is 0.7-0.9, and d is 0.1-0.3; more preferably, a is 0.5, b is 0.4, c is 0.8, and d is 0.2.
The fluorescent probe material provided by the invention comprises an oleic acid ligand coated on the surface of the core-shell nanocrystal, and the oleic acid ligand is electrostatically adsorbed on the surface of the core-shell nanocrystal. In the invention, the mass of the oleic acid ligand is 15-25% of the total mass of the core-shell nanocrystal and the oleic acid ligand, and more preferably 20%.
The invention provides a preparation method of the fluorescent probe material in the technical scheme, which comprises the following steps:
mixing a first sodium salt, a potassium salt, a first bismuth salt, an erbium salt, a first ytterbium salt, a first fluorine source, first oleic acid, first oleylamine and a first solvent, and performing first growth to obtain a core nanocrystal;
mixing a second sodium salt, a second bismuth salt, a second ytterbium salt, a second fluorine source, second oleic acid, second oleylamine and a second solvent with the core nanocrystal to perform second growth to obtain a fluorescent probe material;
the molar ratio of the first sodium salt, the potassium salt, the first bismuth salt, the erbium salt, the first ytterbium salt and the first fluorine source is 0.6:0.4 (0.5-0.7) to 0.3-0.5) to 0.1: 4;
the molar ratio of the second sodium salt to the second bismuth salt to the second ytterbium salt to the second fluorine source is 1 (0.7-0.9) to 0.1-0.3) to 4;
the molar ratio of the first sodium salt to the second sodium salt is 0.6: 1.
In the present invention, unless otherwise specified, all the starting materials required for the preparation are commercially available products well known to those skilled in the art.
The method comprises the steps of mixing a first sodium salt, a potassium salt, a first bismuth salt, an erbium salt, a first ytterbium salt, a first fluorine source, first oleic acid, first oleylamine and a first solvent, and performing first growth to obtain the core nanocrystal. In the present invention, the first sodium salt preferably includes sodium nitrate or sodium chloride; the potassium salt preferably comprises potassium carbonate; the first bismuth salt preferably comprises bismuth nitrate, bismuth chloride or bismuth oxychloride; the erbium salt preferably comprises erbium nitrate or erbium chloride; the first ytterbium salt preferably comprises ytterbium nitrate or ytterbium chloride. In the present invention, the molar ratio of the first sodium salt, the potassium salt, the first bismuth salt, the erbium salt, the first ytterbium salt and the first fluorine source is 0.6:0.4 (0.5 to 0.7): 0.3 to 0.5):0.1:4, preferably 0.6:0.4 (0.55 to 0.65): 0.35 to 0.45):0.1:4, more preferably 0.6:0.4:0.6:0.4:0.1: 4.
In the present invention, the first fluorine source is preferably ammonium fluoride; the dosage ratio of the first fluorine source, the first oleic acid and the first oleylamine is (4-6) mmol, (5-10) mL, (1-2) mL, more preferably (4.5-5.5) mmol, (6-8) mL, (1.5-1.8) mL, and further preferably 5mmol, 7mL and 1.6 mL. The first oleylamine is utilized to reduce the energy barrier of the growth of the nanocrystal, and the nucleation and growth of the nanocrystal are further promoted. According to the invention, the first oleic acid is utilized to improve the dispersibility of the core nanocrystal, so that the uniform growth of the shell layer in the second growth process is promoted, and the core-shell nanocrystal with good dispersibility is obtained.
In the present invention, the first solvent is preferably ethylene glycol; the volume ratio of the first solvent to the first oleic acid is preferably 5 (5-10), and more preferably 5 (6-8).
In the invention, the first sodium salt, the potassium salt, the first bismuth salt, the erbium salt, the first ytterbium salt, the first fluorine source, the first oleic acid, the first oleylamine and the first solvent are preferably mixed by dissolving the first sodium salt, the potassium salt, the first bismuth salt, the erbium salt and the first ytterbium salt in the first solvent, stirring for 10-15 min, and then adding the first fluorine source, the first oleic acid and the first oleylamine to the obtained mixture. The stirring speed is not particularly limited in the invention, and the materials can be uniformly mixed according to the process well known in the field.
In the invention, the temperature of the first growth is preferably 25-35 ℃, the time is preferably 30-60 min, and more preferably 40-50 min; the first growth is preferably carried out under stirring conditions, and the rotation speed of the stirring is not particularly limited in the present invention, and the reaction can be smoothly carried out according to a process well known in the art.
In the first growth process, the first sodium salt, the potassium salt, the first bismuth salt, the erbium salt, the first ytterbium salt and the first fluorine source are subjected to low-temperature nucleation and high-temperature growth to obtain the core nanocrystal, and the first oleic acid is electrostatically adsorbed on the surface of the core nanocrystal.
After the first growth is completed, the present invention preferably performs centrifugal washing on the obtained product to obtain the core nanocrystal. In the invention, the washing reagent used for centrifugal washing is preferably a mixed solution of ethanol and cyclohexane, and the volume ratio of the ethanol to the cyclohexane is preferably 3: 1; the number of times of centrifugal washing is preferably 3-5 times. The first oleylamine on the surface of the core nanocrystal is removed by washing.
After obtaining the core nanocrystals, the present invention preferably disperses the core nanocrystals in cyclohexane for use.
After the core nanocrystal is obtained, a second sodium salt, a second bismuth salt, a second ytterbium salt, a second fluorine source, second oleic acid, second oleylamine and a second solvent are mixed with the core nanocrystal to perform second growth, so that the fluorescent probe material is obtained. In the present invention, the second sodium salt preferably includes sodium nitrate or sodium chloride; the second bismuth salt preferably comprises bismuth nitrate, bismuth chloride or bismuth oxychloride; the second ytterbium salt preferably comprises ytterbium nitrate or ytterbium chloride. In the invention, the molar ratio of the second sodium salt, the second bismuth salt, the second ytterbium salt and the second fluorine source is 1 (0.7-0.9): 0.1-0.3): 4, preferably 1 (0.75-0.85): 0.15-0.25): 4, and more preferably 1:0.8:0.2: 4. In the present invention, the molar ratio of the first sodium salt to the second sodium salt is 0.6: 1.
In the present invention, the second fluorine source is preferably ammonium fluoride; the dosage ratio of the second fluorine source, the second oleic acid and the second oleylamine is preferably (4-6) mmol, (5-10) mL, (1-2) mL, and more preferably (4.5-5.5) mmol, (5-10) mL, (1-2) mL. According to the invention, the second oleylamine is utilized to reduce the energy barrier of the growth of the nanocrystal, so that the nucleation and growth of the nanocrystal are promoted; the invention utilizes the second oleic acid to improve the dispersibility of the core-shell nanocrystal in gasoline, and is convenient for realizing the detection of lead ions in gasoline.
In the present invention, the second solvent is preferably ethylene glycol; the volume ratio of the second solvent to the second oleic acid is preferably 5 (5-10), and more preferably 5 (6-8).
In the present invention, the core nanocrystal is preferably used in the form of a dispersion, and the solvent used for the dispersion of the core nanocrystal is preferably cyclohexane; the concentration of the dispersion liquid of the core nanocrystal is not particularly limited, and the core nanocrystal can be sufficiently dispersed. The amount of the dispersion liquid of the core nanocrystal is not particularly limited, and the molar ratio of the first sodium salt to the second sodium salt can be met.
In the invention, the process of mixing the second sodium salt, the second bismuth salt, the second ytterbium salt, the second fluorine source, the second oleic acid, the second oleylamine and the second solvent with the core nanocrystal is preferably to dissolve the second sodium salt, the second bismuth salt and the second ytterbium salt in the second solvent, stir for 10-20 min, then add the second oleic acid and the second oleylamine to the obtained mixture, stir for 30-60 min at room temperature (25-35 ℃), then add the core nanocrystal dispersion, continue to stir for 50-70 min, and then add the second fluorine source. The stirring speed is not limited in particular, and the materials can be uniformly mixed according to the process known in the art.
In the invention, the temperature of the second growth is preferably 25-35 ℃, the time is preferably 60-90 min, and more preferably 70-80 min; the second growth is preferably carried out under stirring conditions. The stirring speed is not particularly limited in the invention, and the materials can be uniformly mixed according to the process well known in the field. In the second growth process, a second sodium salt, a second bismuth salt, a second ytterbium salt and a second fluorine source form nuclei on the surface of the core nanocrystal and grow to form a core-shell nanocrystal, and meanwhile, second oleic acid is electrostatically adsorbed on the surface of the core-shell nanocrystal.
After the second growth is completed, the obtained product is preferably subjected to centrifugal washing to form core-shell nanocrystals, so that the fluorescent probe material is obtained. In the invention, the washing reagent used for centrifugal washing is preferably a mixed solution of ethanol and cyclohexane, and the volume ratio of the ethanol to the cyclohexane is preferably 3: 1; the number of times of centrifugal washing is preferably 3-5 times. The second oleylamine on the surface of the core-shell nanocrystal is removed by washing.
The invention provides application of the fluorescent probe material in the technical scheme or the fluorescent probe material prepared by the preparation method in the technical scheme in quantitative detection of lead content in gasoline. The method of the present invention is not particularly limited, and the method may be applied according to a method known in the art.
The invention provides a method for detecting lead content in gasoline, which comprises the following steps:
mixing gasoline containing different lead ion concentrations with a fluorescent probe material, detecting under the condition of 1550nm exciting light excitation, calculating integral intensity according to the obtained up-conversion spectrum, fitting a relation curve of the fluorescent integral intensity and the lead ion concentration, and obtaining the lead ion content in a gasoline sample according to the relation curve; the fluorescent probe material is the fluorescent probe material in the technical scheme or the fluorescent probe material prepared by the preparation method in the technical scheme.
In the invention, the dosage ratio of the gasoline to the fluorescent probe material is preferably 10mL (0.2-0.4) mg, and more preferably 10mL to 0.3 mg. The specific concentration of the lead ions with different concentrations is not specially limited, and the lead ions can be adjusted according to actual requirements.
The process of calculating the integrated intensity and fitting the fluorescence integrated intensity-lead ion concentration relation curve is not particularly limited in the present invention, and the process can be performed according to the process well known in the art.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Containing oleic acid ligand Na0.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4The preparation method of the core-shell nanocrystal comprises the following steps:
(1) adding 0.6mmol of sodium nitrate, 0.2mmol of potassium carbonate, 0.5mmol of bismuth nitrate, 0.4mmol of erbium nitrate and 0.1mmol of ytterbium nitrate into 5mL of ethylene glycol, stirring for 10min, then adding 4mmol of ammonium fluoride, 10mL of oleic acid and 2mL of oleylamine, stirring for 40min at room temperature (30 ℃), centrifugally washing the obtained product for 3 times by using a mixed solution of ethanol and cyclohexane (volume ratio of 3:1), and obtaining Na0.6K0.4Bi0.5Er0.4Yb0.1F4Dispersing the nuclear nanocrystals in 5mL of cyclohexane for later use;
(2) adding 1mmol of sodium nitrate, 0.8mmol of bismuth nitrate and 0.2mmol of ytterbium nitrate into 5mL of ethylene glycol, stirring for 10min, then adding 10mL of oleic acid and 2mL of oleylamine, stirring for 40min at room temperature (30 ℃), then adding the nuclear nanocrystal dispersion obtained in the step (1), continuing stirring for 50min, then adding 4mmol of ammonium fluoride, continuing stirring for 70min at room temperature (30 ℃), centrifugally washing the obtained product for 3 times by using an ethanol and cyclohexane mixed solution (volume ratio is 3:1) to obtain Na containing an oleic acid ligand0.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4Core-shell nanocrystals (the mass of the oleic acid ligand is 20% of the total mass of the core-shell nanocrystals and the oleic acid ligand).
Example 2
The only difference from example 1 is: and (3) adding 0.1mmol of ytterbium nitrate in the step (2), namely, the doping concentration of ytterbium ions in the shell layer accounts for 10 mol%.
Example 3
The only difference from example 1 is: and (3) adding 0.3mmol of ytterbium nitrate in the step (2), namely, the doping concentration of ytterbium ions in the shell layer accounts for 30 mol%.
Comparative example 1
The only difference from example 1 is: and (3) adding 0mmol of ytterbium nitrate in the step (2), namely, the doping concentration of ytterbium ions in the shell layer accounts for 0 mol%.
Comparative example 2
The only difference from example 1 is: and (3) adding 0.4mmol of ytterbium nitrate in the step (2), namely, the doping concentration of ytterbium ions in the shell layer accounts for 40 mol%.
Comparative example 3
The only difference from example 1 is: the step of adding oleic acid is removed in the steps (1) and (2), and the oil-free acid ligand Na is obtained0.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4Core-shell nanocrystals.
Characterization and testing
1) For Na prepared in example 10.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4Performing powder X-ray diffraction test on the core-shell nanocrystals, wherein the results are shown in FIG. 1; as can be seen from FIG. 1, the diffraction peaks match well with standard PDF cards 27-1427 (lower vertical line in FIG. 1), indicating Na prepared in example 10.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4The core-shell nanocrystals are pure hexagonal phase.
2) The core-shell nanocrystals prepared in example 1 were subjected to transmission electron microscopy, and the results are shown in fig. 2; as can be seen from FIG. 2, Na prepared in example 10.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4The shape of the core-shell nanocrystal is uniform and the dispersibility is good.
3) Na prepared in example 1 was subjected to the excitation with a 1550nm laser (fluorescence spectrometer, laser power 800mW, and slit size of both incident and emergent light of 2mm)0.6K0.4Bi0.5Er0.4Yb0.1F4Core nanocrystal and Na0.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Y0.2F4The core-shell nanocrystals are respectively subjected to luminescence property test, and the results are shown in fig. 3 and 4; as can be seen from FIG. 3, the core-shell nanocrystals showed strong near-infrared-one-region up-conversion luminescence with a center wavelength of 980 nm. As can be seen from comparison of FIGS. 3 and 4, the product of example 1 was compared with Na0.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Y0.2F4Core-shell nanocrystals, Na0.6K0.4Bi0.5Er0.4Yb0.1F4The luminescence intensity of the core nanocrystal is obviously weaker, because the cladding of the shell layer enables the radiationless relaxation probability of the activated ions on the surface of the core-shell nanocrystal to be reduced, the luminescence intensity of the core-shell nanocrystal is stronger than that of the core nanocrystal, and the result shows that the product prepared in example 1 is the core-shell structure nanocrystal.
4) The core-shell nanocrystals prepared in examples 1 to 3 and comparative examples 1 to 2 were subjected to a luminescence property test under different ytterbium ion doping concentrations (excitation power is 0.5W, and slit widths of incident light and emergent light are both 2mm), and the results are shown in fig. 5; as can be seen from fig. 5, as the doping concentration of the ytterbium ion in the shell layer increases from 0 to 20 mol%, the upconversion luminescence intensity gradually increases, mainly because the energy transfer efficiency from the ytterbium ion to the erbium ion increases with the increase of the doping concentration of the ytterbium ion, whereas as the doping concentration of the ytterbium ion in the shell layer continues to increase to 40 mol%, the upconversion luminescence intensity gradually decreases instead, mainly because the higher doping concentration of the ytterbium ion increases the probability of radiationless relaxation between the active ions, resulting in the decrease of the upconversion luminescence intensity.
5) Lead ions (0. mu. mol/L, 0.1. mu. mol/L, 0.2. mu. mol/L, 0.3. mu. mol/L, 0.4. mu. mol/L, 0.5. mu. mol/L, 0.6. mu. mol/L, 0.7. mu. mol/L, 0.8. mu. mol/L, 0.9. mu. mol/L, 1.0. mu. mol/L) were added to the cyclohexane solution (0.1mg/mL) containing the core-shell nanocrystals prepared in example 1, respectively, and the luminescence intensities thereof (excitation power of 0.5W, both incident light and emergent light width of 2mm) were measured, respectively, and the results are shown in FIG. 6; as can be seen from FIG. 6, Yb increased with the lead ion concentration3+The up-conversion luminescence intensity of ions at 980nm is obviously reduced, and the reduction amplitude is equal to that of Pb2+The ion concentrations are closely related; lithium ions, sodium ions, calcium ions, barium ions, iron ions or magnesium ions were added to the cyclohexane solution (0.1mg/mL) containing the core-shell nanocrystals prepared in example 1, respectively, and the luminescence intensity thereof was measured, and the cyclohexane solution (0.1mg/mL) was used as a control, and the results are shown in fig. 7; as can be seen from FIG. 7, Yb3+The upconversion luminescence intensity of the ion at 980nm is substantially unchanged; illustrating the core-shell nanocrystals prepared in example 1 canSpecifically recognizing lead ions.
Application example
1) 0.3mg of the core-shell nanocrystals prepared in example 1 was added to 10mL of gasoline containing different lead ion concentrations (0. mu. mol/L, 0.1. mu. mol/L, 0.2. mu. mol/L, 0.3. mu. mol/L, 0.4. mu. mol/L, 0.5. mu. mol/L, 0.6. mu. mol/L, 0.7. mu. mol/L, 0.8. mu. mol/L, 0.9. mu. mol/L, 1.0. mu. mol/L), respectively, and the luminescence intensities (excitation power 0.5W, both incident light and emergent light slit widths 2mm) were measured, and the results are shown in FIG. 8; as can be seen from FIG. 8, Yb3+The up-conversion luminescence intensity of the ions at 980nm is obviously weakened along with the increase of the concentration of lead ions, which shows that the fluorescent probe material can be used for detecting the lead content in gasoline.
2) 0.3mg of the acid ligand free core-shell nanocrystals prepared in comparative example 3 was added to 10mL of cyclohexane containing different lead ion concentrations (0. mu. mol/L, 0.1. mu. mol/L, 0.2. mu. mol/L, 0.3. mu. mol/L, 0.4. mu. mol/L, 0.5. mu. mol/L, 0.6. mu. mol/L, 0.7. mu. mol/L, 0.8. mu. mol/L, 0.9. mu. mol/L, 1.0. mu. mol/L) and the emission intensity was measured under the excitation of a 1550nm laser, as shown in FIG. 9; as can be seen from FIG. 9, Yb3+The upconversion luminous intensity of ions at 980nm is basically equal to Pb2+The ion concentration is irrelevant, which shows that the oleic acid ligand coats the nanocrystal, so that the nanocrystal has excellent dispersibility in cyclohexane, the effect of lead ions on the surface of the nanocrystal can be promoted, and the detection effect of the lead ions is directly influenced.
The above results show that Na of the present invention0.6K0.4Bi0.5Er0.4Yb0.1F4@NaBi0.8Yb0.2F4The core-shell nanocrystal can effectively and quantitatively detect the content of lead ions in gasoline, and the detection mechanism is as follows: oleic acid ligand on the surface of the core-shell nanocrystal enables the nanocrystal to be well dispersed in gasoline, and the interaction between lead ions and the surface of the nanocrystal is facilitated, and Er can be reduced by the lead ions3+To Yb3+Energy transfer efficiency of (1), resulting in Yb3+The up-conversion luminescence intensity at 980nm is gradually reduced, so that the lead content is detected.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.