CN107955611B - Quantum dot composite microsphere containing higher fatty acid and preparation method thereof - Google Patents
Quantum dot composite microsphere containing higher fatty acid and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a quantum dot composite microsphere containing higher fatty acid and a preparation method thereof. The quantum dot composite microsphere comprises quantum dots and a silicon dioxide nano microsphere, wherein the quantum dots are self-assembled on the surface of the silicon dioxide nano microsphere, the silicon dioxide nano microsphere comprises a shell layer and a core, and the shell layer is made of SiO2And the inner core is higher fatty acid. The quantum dot composite microsphere disclosed by the invention not only can keep the excellent properties of high luminous efficiency, photochemical stability and the like of common quantum dots, but also has a specific temperature sensitive value of luminous intensity, and can be used for correlating specific temperature. The quantum dot also has good reusability, and the quantum dot cannot fall off.
Description
The application is a divisional application with the title of 'a quantum dot composite microsphere containing higher fatty acid and its preparation method' of application No. 2015109809637, application date 2015, 12 months and 22 days.
Technical Field
The invention relates to a quantum dot, in particular to a quantum dot composite microsphere containing higher fatty acid and a preparation method thereof.
Background
When the size of the material is reduced to nano level, the material will generate a plurality of novel and unique functional characteristics superior to the traditional material due to the nano effect, and has wide application value in the fields of microelectronics, bioengineering, chemical engineering, medicine and the like.
In recent years, due to the excellent optical characteristics of the nano luminescent material using transition metal as active ion, such as wide and continuous absorption wavelength, tunable fluorescence emission peak, long fluorescence lifetime, etc., the nano luminescent material shows wide application prospects in the fields of luminescent devices, fluorescence imaging, solar cells, fluorescence detection, biomarkers, etc. However, when the quantum dots are used in a light-emitting device or fluorescence detection, the red shift of the absorption peak wavelength and the wavelength of the photoluminescence spectrum of the quantum dots is generally less than 10nm in the range of 25-100 ℃. Although the light emission intensity has a certain linear relationship with temperature, the light emission intensity is very small with temperature change, and the small temperature change does not cause the light emission intensity to be greatly increased or reduced below the thermal quenching temperature. Therefore, the prior art cannot prepare quantum dots with very high temperature sensitivity.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the quantum dot composite microsphere containing the higher fatty acid and having very high temperature sensitivity.
The invention provides a quantum dot composite microsphere containing higher fatty acid, which is characterized by comprising quantum dots and silicon dioxide nano microspheres, wherein the quantum dots are self-assembled on the surface of the silicon dioxide nano microspheres, the silicon dioxide nano microspheres comprise a shell layer and a core, and the shell layer is made of SiO2And the inner core is higher fatty acid.
The quantum dots are quantum dots modified by mercaptocarboxylic acid; the surface of the silicon dioxide nano microsphere is modified by triamino silane and polyaluminium chloride, wherein the chemical formula of the triamino silane is H2N-CH2-CH2-NH-CH2-CH2-NH-(CH2)3-Si-(OCH3)3。
In the quantum dot composite microsphere, the SiO2The weight ratio of the fatty acid to the higher fatty acid is (0.2-1.2) to 1. And 1-20 layers of the quantum dots are self-assembled on the surface of the silicon dioxide nano microsphere.
The average grain diameter of the quantum dot composite microsphere is 55 nm-600 nm, preferably 65 nm-500 nm. The average grain diameter of the silicon dioxide nano-microspheres is 50 nm-600 nm, preferably 60 nm-500 nm.
The quantum dots are one or more of CdTe, CdSe, InP, InAs, CdSe/CdS, CdSe/ZnS, CdSe/ZnSe, CdTe/ZnS, CdHgTe/ZnS and HgTe/HgCdS quantum dots.
The higher fatty acid is C9～C18Preferably one or more of capric acid, lauric acid, myristic acid, palmitic acid, pearlescent ester acid, stearic acid, oleic acid and linoleic acid.
The invention also provides a preparation method of the quantum dot composite microsphere containing the higher fatty acid, which comprises the following steps:
(1) adding higher fatty acid and a surfactant into an ethanol water solution, heating to melt the higher fatty acid and uniformly stirring to prepare an emulsion containing the higher fatty acid, adding tetraethoxysilane into the emulsion, adding an aqueous alkali to adjust the pH value to 9-12, performing hydrolysis reaction, stirring, aging, filtering, washing and drying to obtain the silicon dioxide nano-microspheres coated with the higher fatty acid by silicon dioxide;
(2) and soaking the silicon dioxide nano microspheres in an aqueous solution of the quantum dots, filtering, washing and drying to obtain the quantum dot composite microspheres.
In the step (1), the weight ratio of the higher fatty acid to the surfactant to the ethanol aqueous solution is 10: 0.1-3.0: 20-100, and the weight ratio of ethanol to water in the ethanol aqueous solution is 1-5: 1; the weight ratio of the higher fatty acid to the tetraethoxysilane is 10: 5-40.
The surfactant is one or more of polyethylene glycol, sucrose ester, polysorbate, octadecyl benzene sulfonic acid, sodium dodecyl sulfate, sodium tetradecyl sulfate and sodium hexadecyl sulfate, and is preferably sodium dodecyl sulfate and/or sodium tetradecyl sulfate.
In the step (2), the aqueous solution of the quantum dots is the aqueous solution of the quantum dots modified by the mercapto carboxylic acid. The soaking time is 5min to 240 min.
Before the silicon dioxide nano microspheres are added into the water solution of the quantum dots, modifying the silicon dioxide nano microspheres by using a polyaluminium chloride solution and a triamino silane solution, and specifically comprising the following steps of: and (2) putting the silicon dioxide nano microspheres into a solution of polyaluminium chloride, filtering and drying, then adding the silicon dioxide nano microspheres into a triamino silane solution, stirring, filtering and drying. Wherein the concentration of the polyaluminium chloride solution is 0.20-0.01 wt%, and the triamino silane solution is an ethanol solution containing 0.5-2.0 wt% of triamino silane. The amount of the polyaluminum chloride solution and the triamino silane solution is not limited to the above range, and the silica-based nanospheres can be immersed in the polyaluminum chloride solution and the triamino silane solution. The mass ratio of the silicon dioxide nano microspheres to the triamino silane solution can be 1: 5-20. The mass ratio of the silicon dioxide nano-microspheres to the polyaluminium chloride solution can be 1: 5-20.
The water solution of the quantum dot is water-soluble quantum dot modified by mercaptocarboxylic acid, and the preparation method comprises the following steps: mixing tellurium powder, sodium borohydride and water, and reacting under an inert atmosphere environment and a constant temperature condition to obtain a quantum dot precursor solution; dissolving cadmium chloride in water, sequentially adding mercaptocarboxylic acid and sodium hydroxide solution to obtain a mixed solution, transferring the whole mixed solution to the lining of an autoclave, introducing nitrogen to remove oxygen, then adding the quantum dot precursor solution into the mixed solution, and carrying out hydrothermal reaction in the autoclave to obtain the hydrosoluble quantum dot modified by mercaptocarboxylic acid. The molar ratio of the tellurium powder, the sodium borohydride, the cadmium chloride and the mercapto carboxylic acid is 1: 20-60: 15-45: 6-15. The mercaptocarboxylic acids are preferably mercaptoacetic acid, 2-mercaptopropionic acid and 3-mercaptopropionic acid.
Compared with the prior art, the invention has the following advantages:
(1) the quantum dot composite microsphere disclosed by the invention not only can keep the excellent properties of high luminous efficiency, photochemical stability and the like of common quantum dots, but also has a specific temperature sensitive value of luminous intensity, and can be used for correlating specific temperature. The concrete expression is as follows: when the environmental temperature rises to the phase transition temperature of the higher fatty acid, the higher fatty acid in the quantum dot composite microsphere undergoes phase transition and changes from an opaque solid state to a transparent liquid state, so that the light transmittance of the silicon dioxide nano microsphere is greatly increased, and the intensity (luminous intensity) of the light political emission spectrum of the silicon dioxide nano microsphere is greatly increased; when the environmental temperature is lower than the phase transition temperature of the higher fatty acid, the transparent liquid state is changed into the opaque solid state, so that the light transmittance of the silica nano-microsphere is greatly reduced, and the intensity of the light spectrum (luminous intensity) of the light spectrum is greatly reduced. Therefore, quantum dot recombination has very strong temperature sensitivity near the phase transition temperature point.
When the quantum dot composite microsphere is applied to fluorescence detection, the tiny temperature change near the temperature sensitive value can be monitored by monitoring the place where the fluorescence in the whole system abnormally changes on line in real time. When the quantum dot light emitting diode is used for a quantum dot device, the light intensity of the quantum dot can be greatly changed by adjusting the temperature value.
The quantum dot composite microsphere is suitable for sample monitoring close to the phase transition temperature point of the higher fatty acid, and because different higher fatty acids have different phase transition temperature values, the temperature sensitive value of the higher fatty acid in the quantum dot composite microsphere can be changed by selecting the higher fatty acid with different phase transition temperatures, so that real-time monitoring of different samples can be realized.
(2) In the preparation process of the quantum dot composite microspheres, when tetraethoxysilane is hydrolyzed in an alkaline environment in a surfactant-containing higher fatty acid emulsion, silicon dioxide grows on the surfaces of emulsion droplets, and the obtained silicon dioxide nano microspheres have SiO with regular shapes, higher surface smoothness and more surface silicon hydroxyl groups2Shell layer of then SiO2The shell layer is treated by polyaluminium chloride and triamino silane solution, so that the surface charge of silicon dioxide is modified, and the polyamino group of triamino silane is combined with mercapto carboxylic acid to form three-dimensional multi-site press grafting, so that under the double actions of surface charge and multi-site grafting, the quantum dot is very firmly assembled on the surface of the dioxide nano microsphere, the falling-off of mercapto ligands on the surface of the quantum dot can be effectively prevented, the quantum dot has very good time stability, and the acid, alkali and oxidation resistance stabilities in certain acid, alkali and oxidation environments, and meanwhile, the good biocompatibility of the quantum dot is kept, so that the stability of the quantum dot in specific application is greatly improved.
(3) The quantum dot composite microsphere can be used in the aspects of quantum dots in luminescent devices, fluorescence imaging, solar cells, fluorescence detection, biomarkers and the like.
Detailed Description
The following examples further illustrate the preparation of the quantum dot composite microspheres containing higher fatty acids, but should not be construed as limiting the invention to the following examples, wherein wt% is the mass fraction.
Mercaptocarboxylic acid modified quantum dot solutionThe liquid is prepared by a preparation method conventionally used in the field. The invention relates to a metal salt containing quantum dot cation (the cation can be Zn for example)2+、Cd2+Or Hg2+) Complexing with mercapto carboxylic acid to form cation precursor, and then complexing with anion precursor (anion may be S, for example)2-、Se2-Or Te2-) And heating and refluxing to ensure that the quantum dots nucleate and grow, thereby preparing the mercapto carboxylic acid modified quantum dot solution. The heating reflux temperature is 60-90 ℃, and the time is 3-12 h. For example, the preparation method of the mercapto carboxylic acid modified cadmium telluride and cadmium selenide quantum dot solution can refer to CN102786037A, and the preparation method of the mercapto carboxylic acid modified zinc sulfide quantum dot solution can refer to CN 103242829A. The quantum dots can also be prepared by self-assembly of mercapto carboxylic acid modified cadmium sulfide, zinc selenide or zinc telluride solution. The following examples of the invention describe the preparation of mercaptocarboxylic acid-modified cadmium telluride.
Example 1
(1) 100g of myristic acid with the phase transition temperature of 52-54 ℃ and 20g of sodium dodecyl sulfate are added into 700g of ethanol water solution, wherein the mass ratio of absolute ethanol to water is 4: 1. Heating in water bath at 60 deg.C, and mechanically stirring for 30min after myristic acid melts to obtain uniformly dispersed emulsion; and (3) dropwise adding 80g of ethyl orthosilicate into the emulsion, adding a NaOH solution to adjust the pH value to 10, continuously stirring at constant temperature for 3 hours, aging at room temperature, filtering, washing and drying to obtain the silicon dioxide nano microspheres. The following characteristics can be obtained by characterization of scanning electron micrographs: the particle size of the silicon dioxide nano microspheres is 80 nm-110 nm, the particle size distribution is uniform, and the shape of the silicon dioxide nano microspheres is regular and the surface is smooth.
(2) Weighing 2mg of tellurium powder and 24mg of sodium borohydride, transferring the tellurium powder and the sodium borohydride into a small bottle with a bottle stopper, introducing nitrogen for 5min, and covering the bottle stopper. The syringe extracts 2mL of high purity water, injects it into a vial, and then discharges the gas generated by the reaction in the vial. The whole small bottle device is put into a water bath kettle, the reaction temperature is 32 ℃, and the small bottle device is taken out after 2 hours to prepare purple fresh precursor liquid.
Adding 100mg of cadmium chloride into 100mL of water, stirring by a glass rod until cadmium chloride particles are completely dissolved, adding thioglycolic acid (TGA), transferring the whole liquid into the inner lining of the high-pressure kettle, introducing nitrogen, and removing oxygen for 30min to obtain a mixed solution.
Sealing the peroxide-removed cadmium chloride solution, extracting 1mL of a freshly prepared precursor solution by using an injector, quickly transferring the precursor solution into the cadmium chloride solution (the molar ratio of tellurium powder, sodium borohydride, cadmium chloride to thioglycollic acid is 1: 41: 33: 9), adding a sodium hydroxide solution to adjust the pH to 10, covering the cover, assembling the autoclave, and carrying out hydrothermal reaction at 80 ℃ for 12 hours to obtain a thioglycollic acid modified quantum dot aqueous solution.
(3) Adding 10g of silicon dioxide nano microspheres into 100mL of polyaluminum chloride solution, wherein the concentration of the polyaluminum chloride solution is 0.05 wt%, stirring for 10min, filtering and drying, and then adding the silicon dioxide nano microspheres into 100mL of triamino silane solution, wherein the solvent of the solution is absolute ethyl alcohol, the concentration of the triamino silane solution is 0.5 wt%, and the chemical formula of the triamino silane is H2N-CH2-CH2-NH-CH2-CH2-NH-(CH2)3-Si-(OCH3)3Stirring for 30min at 20 ℃, and then filtering, washing and drying to obtain the modified silicon dioxide nano microspheres.
(4) And (3) soaking 10g of modified silicon dioxide nano-microspheres in the mercaptoacetic acid modified quantum dot aqueous solution, reacting for 15min at room temperature, filtering, washing with water, and drying to obtain the composite quantum dot microspheres.
(5) Adding 10g of composite quantum dot microspheres into 20mL of phosphate buffer mixed solution (the pH value is 6.8), detecting a mixed solution system at different temperatures by using a fluorescence spectrophotometer, and measuring the fluorescence spectrum of the system under the conditions that the excitation wavelength of quantum dots is 400nm and the spectral passbands of an incident slit and an emergent slit of the fluorescence spectrophotometer are both 5nm to obtain the relative fluorescence intensity.
TABLE 1
| 30℃ | 40℃ | 50℃ | 56℃ | 60℃ | 65℃ | |
| Relative fluorescence intensity (a.u.) | 205 | 203 | 214 | 825 | 836 | 835 |
Example 2
(1) 100g of palmitic acid with the phase transition temperature of 62-63 ℃ and 20g of sodium tetradecyl sulfate are added into 500g of ethanol aqueous solution, wherein the mass ratio of absolute ethanol to water is 4: 1. Heating in 70 ℃ water bath, and mechanically stirring for 30 minutes after the palmitic acid is molten to obtain uniformly dispersed emulsion; and (3) dropwise adding 160g of tetraethoxysilane into the emulsion, adding a NaOH solution to adjust the pH value to 10, continuously stirring at a constant temperature for 4 hours, aging at room temperature, filtering, washing and drying to obtain the silicon dioxide nano microspheres. The following characteristics can be obtained by characterization of scanning electron micrographs: the particle size of the silicon dioxide nano microspheres is 80 nm-120 nm, the particle size distribution is uniform, and the shape of the silicon dioxide nano microspheres is regular and the surface is smooth.
(2) Weighing 2mg selenium powder and 24mg sodium borohydride, transferring into a small bottle with a bottle stopper, introducing nitrogen for 5min, and covering the bottle stopper. The syringe extracts 2mL of high purity water, injects it into a vial, and then discharges the gas generated by the reaction in the vial. And (3) putting the whole small bottle device into a water bath kettle, reacting at the temperature of 32 ℃, and taking out after 2 hours to prepare the purple-bag fresh precursor liquid.
Adding 100mg of cadmium chloride into 100mL of water, stirring by a glass rod until cadmium chloride particles are completely dissolved, adding thioglycolic acid (TGA), transferring the whole liquid into the inner lining of the high-pressure kettle, introducing nitrogen, and removing oxygen for 30min to obtain a mixed solution.
Sealing the peroxide-removed cadmium chloride solution, extracting 1mL of a freshly prepared precursor solution by using an injector, quickly transferring the precursor solution into the cadmium chloride solution (the molar ratio of selenium powder to sodium borohydride to cadmium chloride to thioglycollic acid is 1: 41: 33: 9), adding a sodium hydroxide solution to adjust the pH to 10, covering the cover, assembling the autoclave, and carrying out hydrothermal reaction at 80 ℃ for 12 hours to obtain a thioglycollic acid modified quantum dot aqueous solution.
(3) And (3) soaking 10g of silicon dioxide nano microspheres in the mercaptoacetic acid modified quantum dot aqueous solution, reacting for 15min at room temperature, filtering, washing with water, and drying to obtain the composite quantum dot microspheres.
(4)10g of the composite quantum dot microspheres are added into 20mL of phosphate buffer mixed solution (the pH value is 6.8), a mixed solution system at different temperatures is detected by a fluorescence spectrophotometer, and the excitation wavelength of the quantum dots is 540 nm. And (3) measuring the fluorescence spectrum of the system under the condition that the spectral passbands of the incident slit and the emergent slit of the fluorescence spectrophotometer are both 5nm to obtain the maximum relative fluorescence intensity.
TABLE 2
| 40℃ | 50℃ | 60℃ | 65℃ | 68℃ | 72℃ | |
| Relative fluorescence intensity (a.u.) | 98 | 95 | 207 | 622 | 640 | 638 |
Example 3
(1) 100g of lauric acid with the phase transition temperature of 43-45 ℃ and 30g of octadecyl benzene sulfonic acid are added into 900g of ethanol water solution, wherein the mass ratio of absolute ethanol to water is 3: 1. Heating in a water bath at 50 ℃, and mechanically stirring for 30 minutes after lauric acid is melted to obtain uniformly dispersed emulsion; and (3) dropwise adding 240g of tetraethoxysilane into the emulsion, adding a NaOH solution to adjust the pH value to 10, continuously stirring at a constant temperature for 4 hours, aging at room temperature, filtering, washing and drying to obtain the silicon dioxide nano microspheres. The particle size of the silicon dioxide nano microspheres is 80 nm-140 nm, and the distribution is uniform.
(2) Weighing 2mg selenium powder and 24mg sodium borohydride, transferring into a small bottle with a bottle stopper, introducing nitrogen for 5min, and covering the bottle stopper. The syringe extracts 2mL of high purity water, injects it into a vial, and then discharges the gas generated by the reaction in the vial. And (3) putting the whole small bottle device into a water bath kettle, reacting at the temperature of 32 ℃, and taking out after 2 hours to prepare the purple-bag fresh precursor liquid.
100mg of zinc nitrate is added into 100mL of water, a glass rod is stirred until zinc nitrate particles are completely dissolved, thioglycolic acid (TGA) is added, the whole liquid is moved into an autoclave liner, nitrogen is introduced to remove oxygen for 30min, and mixed liquid is obtained.
Sealing the zinc nitrate solution with the peroxide removed, extracting 1mL of the freshly prepared precursor solution by using an injector, quickly transferring the precursor solution into the zinc nitrate solution (the molar ratio of selenium powder to sodium borohydride to zinc nitrate to thioglycolic acid is 1: 41: 33: 9), adding a sodium hydroxide solution to adjust the pH to 10, covering the cover, assembling the autoclave, and carrying out hydrothermal reaction at 80 ℃ for 12 hours to obtain a thioglycolic acid modified quantum dot aqueous solution.
(3) Adding 10g of silicon dioxide nano microspheres into 100mL of polyaluminum chloride solution, stirring for 10min, filtering and drying, and then adding the silicon dioxide nano microspheres into 100mL of triamino silane solution, wherein the solvent of the solution is absolute ethyl alcohol, the concentration of the triamino silane solution is 1 wt%, and the chemical of the triamino silane is H2N-CH2-CH2-NH-CH2-CH2-NH-(CH2)3-Si-(OCH3)3) Stirring for 30min at 20 ℃, filtering, washing and drying to obtain the modified silicon dioxide nano-microspheres.
(4) And adding 10g of modified silicon dioxide nano microspheres into the mercaptoacetic acid modified quantum dot aqueous solution, stirring and dispersing, reacting for 15min at room temperature, filtering, washing with water, and drying to obtain the composite quantum dot microspheres.
(5) Adding 10g of the composite quantum dot microspheres into 20mL of phosphate buffer mixed solution (the pH value is 6.8), and detecting the mixed solution system at different temperatures by using a fluorescence spectrophotometer, wherein the excitation wavelength of the quantum dots is 470 nm. And (3) measuring the fluorescence spectrum of the system under the condition that the spectral passbands of the incident slit and the emergent slit of the fluorescence spectrophotometer are both 5nm to obtain the maximum relative fluorescence intensity.
TABLE 3
| 25℃ | 35℃ | 41℃ | 46℃ | 50℃ | 55℃ | |
| Relative fluorescence intensity (a.u.) | 149 | 142 | 163 | 704 | 724 | 719 |
Comparative example 1
(1) 20g of sodium dodecyl sulfate is added into 700g of ethanol water solution, wherein the mass ratio of absolute ethanol to water is 4: 1. Heating in a water bath at 50 ℃, mechanically stirring for 30 minutes, then dropwise adding 80g of ethyl orthosilicate, adding a NaOH solution to adjust the pH value to 10, continuously stirring for 3 hours at constant temperature, aging at room temperature, filtering, washing and drying to obtain the silicon dioxide nano microspheres. The following characteristics can be obtained by characterization of scanning electron micrographs: the grain diameter of the silicon dioxide nanometer microsphere is 80 nm-110 nm.
(2) Weighing 2mg of tellurium powder and 24mg of sodium borohydride, transferring the tellurium powder and the sodium borohydride into a small bottle with a bottle stopper, introducing nitrogen for 5min, and covering the bottle stopper. The syringe extracts 2mL of high purity water, injects it into a vial, and then discharges the gas generated by the reaction in the vial. And (3) putting the whole small bottle device into a water bath kettle, reacting at the temperature of 32 ℃, and taking out after 2 hours to prepare the purple-bag fresh precursor liquid.
Adding 100mg of cadmium chloride into 100mL of water, stirring by a glass rod until cadmium chloride particles are completely dissolved, adding thioglycolic acid (TGA), transferring the whole liquid into the inner lining of the high-pressure kettle, introducing nitrogen, and removing oxygen for 30min to obtain a mixed solution.
Sealing the peroxide-removed cadmium chloride solution, extracting 1mL of a freshly prepared precursor solution by using an injector, quickly transferring the precursor solution into the cadmium chloride solution (the molar ratio of tellurium powder, sodium borohydride, cadmium chloride to thioglycollic acid is 1: 41: 33: 9), adding a sodium hydroxide solution to adjust the pH to 10, covering the cover, assembling the autoclave, and carrying out hydrothermal reaction at 80 ℃ for 12 hours to obtain a thioglycollic acid modified quantum dot aqueous solution.
(3) Adding 10g of silicon dioxide nano microspheres into a mercaptoacetic acid modified quantum dot aqueous solution, stirring and dispersing, reacting for 15min at room temperature, filtering, washing with water, and drying to obtain the composite quantum dot microspheres.
(4) Adding 10g of the composite quantum dot microspheres into 20mL of phosphate buffer mixed solution (the pH value is 6.8), detecting a mixed solution system at different temperatures by using a fluorescence spectrophotometer, and measuring the fluorescence spectrum of the system under the conditions that the excitation wavelength of the quantum dots is 400nm and the spectral passbands of the incident slit and the emergent slit of the fluorescence spectrophotometer are both 5nm to obtain the relative fluorescence intensity.
TABLE 4
| 30℃ | 40℃ | 50℃ | 56℃ | 60℃ | 65℃ | |
| Relative fluorescence intensity (a.u.) | 990 | 987 | 975 | 970 | 969 | 967 |
As can be seen from the data in tables 1-3: once the environmental temperature of the composite quantum dot microsphere of each embodiment is slightly higher than the phase transition temperature of the higher fatty acid, the higher fatty acid in the quantum dot composite microsphere has undergone phase transition and changes from an opaque solid state to a transparent liquid state, so that the light transmittance of the quantum dot composite microsphere is greatly increased, the intensity of the photo-chemical luminescence spectrum (luminescence intensity) of the quantum dot composite microsphere is greatly increased, and the quantum dot composite has very strong temperature sensitivity near the phase transition temperature dots. In contrast, the composite quantum dot microsphere of comparative example 1 has very small change of fluorescence intensity in the process of raising the environmental temperature, is not beneficial to monitoring by an instrument under the influence of fluorescence noise, and has poor temperature sensitivity.
Test example 1
Taking the composite quantum dot microspheres of examples 1-3 and comparative example 1, and then respectively forming films on conductive glass by adopting a spin coating film forming technology commonly used in the field, thereby preparing different fluorescent thin film sensing materials. The repeated use test of the fluorescent film sensing material contains 0.5 mug/L of copper ion solution. The results show that: after the fluorescent film sensing composite material of the embodiments 1-3 is used for 10 times, the fluorescence can be recovered to more than 95% of the original fluorescence, and the problem of quantum dot falling does not occur; the fluorescence of the fluorescent film sensing composite material of the comparative example 1 is reduced to 90% after being used for 5 times, reduced to below 80% after being used for 7 times, and has quantum dot falling off phenomenon, and the fluorescent film sensing composite material can not be used any more after being used for 10 times.
Claims (5)
1. The preparation method of the quantum dot composite microsphere containing the higher fatty acid is characterized in that the quantum dot composite microsphere containing the higher fatty acid comprises quantum dots and silica nano microspheres, the quantum dots are self-assembled on the surfaces of the silica nano microspheres, the silica nano microspheres comprise shell layers and cores, and the shell layers are SiO2The inner core is higher fatty acid, and the higher fatty acid is C9～C18Higher fatty acids of (a); in the quantum dot composite microsphere, the SiO2The weight ratio of the fatty acid to the higher fatty acid is (0.2-1.2): 1; the quantum dots are one of CdTe, CdSe, InP, InAs, CdSe/CdS, CdSe/ZnS, CdSe/ZnSe, CdTe/ZnS, CdHgTe/ZnS and HgTe/HgCdS quantum dots;
the preparation method of the quantum dot composite microsphere containing the higher fatty acid comprises the following steps:
(1) adding higher fatty acid and a surfactant into an ethanol water solution, heating to melt the higher fatty acid and uniformly stirring to prepare an emulsion containing the higher fatty acid, adding tetraethoxysilane into the emulsion, adding an aqueous alkali to adjust the pH value to 9-12, performing hydrolysis reaction, stirring, aging, filtering, washing and drying to obtain the silicon dioxide nano-microspheres coated with the higher fatty acid by silicon dioxide;
(2) soaking the silicon dioxide nano microspheres in a quantum dot water solution, filtering, washing and drying to obtain quantum dot composite microspheres;
the quantum dots are quantum dots modified by mercaptocarboxylic acid; the surface of the silicon dioxide nano microsphere is modified by triamino silane and polyaluminium chloride, wherein the chemical formula of the triamino silane is H2N-CH2-CH2-NH-CH2-CH2-NH-(CH2)3-Si-(OCH3)3；
Before the silicon dioxide nano microspheres are added into the water solution of the quantum dots, modifying the silicon dioxide nano microspheres by using a polyaluminium chloride solution and a triamino silane solution, and specifically comprising the following steps of: adding the silicon dioxide nano microspheres into a solution of polyaluminium chloride, filtering and drying, then adding into a triamino silane solution, stirring, filtering and drying; the concentration of the polyaluminium chloride solution is 0.20-0.01 wt%, and the triamino silane solution is an ethanol solution containing 0.5-2.0 wt% of triamino silane.
2. The preparation method of the quantum dot composite microsphere according to claim 1, characterized in that: the average grain diameter of the quantum dot composite microspheres is 55 nm-600 nm.
3. The preparation method of the quantum dot composite microsphere according to claim 1, characterized in that: the higher fatty acid is one of capric acid, lauric acid, myristic acid, palmitic acid, pearlescent ester acid, stearic acid, oleic acid and linoleic acid.
4. The method for preparing quantum dot composite microspheres containing higher fatty acids according to claim 1, wherein the method comprises the following steps: the weight ratio of the higher fatty acid to the surfactant to the ethanol aqueous solution is 10: (0.1-3.0): (20-100), wherein the weight ratio of ethanol to water in the ethanol water solution is (1-5) to 1; the weight ratio of the higher fatty acid to the tetraethoxysilane is 10: (5-40), wherein the surfactant is one or more of polyethylene glycol, sucrose ester, polysorbate, octadecyl benzene sulfonic acid, sodium dodecyl sulfate, sodium tetradecyl sulfate and sodium hexadecyl sulfate.
5. The method for preparing quantum dot composite microspheres containing higher fatty acids according to claim 1 or 4, wherein: the water solution of the quantum dots is the water solution of the quantum dots modified by the mercapto carboxylic acid.
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