CN109932476B - Method for measuring coverage rate of ligand on surface of quantum dot - Google Patents
Method for measuring coverage rate of ligand on surface of quantum dot Download PDFInfo
- Publication number
- CN109932476B CN109932476B CN201711350124.2A CN201711350124A CN109932476B CN 109932476 B CN109932476 B CN 109932476B CN 201711350124 A CN201711350124 A CN 201711350124A CN 109932476 B CN109932476 B CN 109932476B
- Authority
- CN
- China
- Prior art keywords
- quantum dot
- ligand
- sample
- sample particles
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/549—Organic PV cells
Landscapes
- Luminescent Compositions (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
The invention provides a method for measuring the coverage rate of a ligand on the surface of a quantum dot. Determination of ligand coverage rate K of organic ligand containing sulfydryl or nitrogen on surface of quantum dot by potentiometric titration methodiAnd the method can be used for quality assessment of the quantum dots. If KiLess than 2 x 10‑10mol/cm2If the quantum dot quality is not good enough, K should be addediAfter the value is increased, the application such as solution or ink preparation is carried out. The method for determining the coverage rate of the ligand on the surface of the quantum dot has the advantages of accurate result and simple operation, and further can ensure the stability of the content of the ligand on the surface of the quantum dot, ensure the solubility of the quantum dots in different batches, avoid the coffee ring effect caused by different drying rates when the quantum dot solution is prepared into a film, and improve the pixel resolution, the starting voltage and the uniformity of the photoelectric efficiency of the quantum dot display panel.
Description
Technical Field
The invention relates to the technical field of quantum dots, in particular to a method for measuring the coverage rate of a ligand on the surface of a quantum dot.
Background
Quantum dots, refers to semiconductor nanocrystals whose geometric dimensions are smaller than the exciton bohr radius. The quantum dots have excellent optical properties such as wide absorption band, narrow fluorescence emission band, high quantum efficiency, good light stability and the like, and have great potential application in the fields of biomedicine, environmental energy, illumination display and the like. In recent years, the display technology based on quantum dot light emission receives high attention from the display industry, and compared with liquid crystal display and organic light emitting display, quantum dot light emission has the advantages of wider color gamut, higher color purity, simpler structure and higher stability, and is considered as a new generation display technology.
The preparation technology of the quantum dot display device comprises spin coating, ink jet printing and the like. The specific process of the two methods is to spray the quantum dot solution on the substrate material, and form a quantum dot film at a specific position after drying. The viscosity, surface tension and charge transport capacity of the quantum dot solution determine the wetting capacity, drying rate, coffee ring effect and photoelectric property of the film of the quantum dot liquid drop in the device preparation process, so that the quality of the quantum dot solution plays an important role in device preparation. In the preparation process of the quantum dot solution, the surface ligand of the quantum dot has an important influence on the quantum dot solution, and the surface ligand not only influences the photoelectric property of the quantum dot, but also influences the solubility and stability of the quantum dot solution. Common quantum dot surface ligands are carboxylic acids, amines, alkyl phosphides, alkyl phosphine oxides, alkyl phosphoric acids, thiols, and the like. The influence of the surface ligand on the optical performance of the quantum dot per se is shown as follows: the average particle diameter of the quantum dots is smaller than the bohr radius of excitons, excitons are exposed on the surface to a certain extent, and the surface is easily influenced to reduce the optical performance of the excitons; when the surface atomic number of the quantum dot is increased, the surface dangling bonds are also increased rapidly, the surface of the quantum dot has many defects due to insufficient atom coordination, the probability of non-radiative recombination is increased due to the existence of the defects such as electrons or holes, and the recombination efficiency of normal radiative recombination is greatly reduced. When a proper surface ligand is added, the surface dangling bonds of the quantum dots can be effectively reduced, excitons are not exposed on the surface any more, and the optical performance of the quantum dots is improved. The influence of the surface ligand on the solubility and stability of the quantum dot is shown as follows: the increase of dangling bonds on the surface of the quantum dot leads the surface free energy to be very large, the surface becomes abnormally active, the system is unstable, the quantum dot tends to aggregate to reduce the surface area, and the solubility of the quantum dot solution is reduced. After the surface ligand is introduced, one end of the ligand is connected to the surface atoms of the quantum dots, and the other end of the ligand is dissolved in the solution, so that the surface energy of the quantum dots can be reduced, the solubility of the quantum dots can be improved, and the generation of precipitation in the quantum dot solution can be effectively inhibited.
Therefore, the solubility of the quantum dots has a great influence on the preparation and performance of the device. Besides the solubility of the quantum dots and the types of the quantum dots, another important influence factor is the coverage rate of the ligands on the surfaces of the quantum dots. If the coverage rate of the surface of the quantum dot is low, the solubility of the quantum dot is poor, the uniformity of the quantum dot solution is poor, and the drying rate of the quantum dot solution and the coffee ring effect affect the quality of the luminescent layer film, which directly causes the problems of uneven quality of the printed panel, low pixel resolution, uneven lighting voltage, uneven photoelectric efficiency, and the like.
Disclosure of Invention
In view of the defects of the prior art, in order to ensure the stability of the film forming quality of the QLED device prepared by using the quantum dot ink in the later period, the invention firstly provides a method for measuring the coverage rate of the ligand on the surface of the quantum dot.
A method for measuring the coverage rate of a ligand on the surface of a quantum dot is characterized by comprising the following steps:
providing sample particles, wherein each particle in the sample particles comprises a quantum dot and an organic ligand bound on the surface of the quantum dot, and the organic ligand is selected from a sulfydryl-containing organic ligand or a nitrogen-containing organic ligand;
determining the average particle size of the particles in the sample particles;
measuring the mass ratio of sulfur element or nitrogen element in the sample particles to the sample particles by a potentiometric titration method, and calculating to obtain the coverage rate K of the quantum dot surface ligandi；
When the organic ligand on the surface of the quantum dot is a sulfydryl-containing organic ligand, the quantum dot does not contain sulfur element; when the organic ligand on the surface of the quantum dot is a nitrogen-containing organic ligand, the quantum dot does not contain nitrogen elements.
The invention provides a method for determining the ligand coverage rate of a quantum dot surface ligand which is an organic ligand containing sulfydryl or nitrogen by using a potentiometric titration method. Measuring ligand coverage rate K of organic ligand containing sulfydryl or nitrogen on surface of quantum dot by potentiometric titrationiAnd the method can be used for quality assessment of the quantum dots. If KiLess than 2 x 10-10mol/cm2If the quantum dot quality is not good enough, K should be addediAfter the value is increased, the application such as solution or ink preparation is carried out. The method for determining the coverage rate of the ligand on the surface of the quantum dot has the advantages of accurate result and simple operation, and further can ensure the stability of the content of the ligand on the surface of the quantum dot, ensure the solubility of the quantum dots in different batches, avoid the coffee ring effect caused by different drying rates when the quantum dot solution is prepared into a film, and improve the pixel resolution, the lighting voltage and the uniformity of the photoelectric efficiency of the quantum dot display panel.
Detailed Description
The invention provides a method for measuring the coverage rate of a ligand on the surface of a quantum dot, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
A method for measuring the coverage rate of a ligand on the surface of a quantum dot comprises the following steps:
s10 providing sample particles, wherein individual particles in the sample particles comprise quantum dots and organic ligands bound to the surfaces of the quantum dots, wherein the organic ligands are selected from thiol-containing organic ligands or nitrogen-containing organic ligands;
s20 determining the average particle size of the particles in the sample particles;
s30, measuring the mass ratio of sulfur or nitrogen in the sample particles to the sample particles by using a potentiometric titration method, and calculating to obtain the coverage rate K of the quantum dot surface ligandi；
When the organic ligand on the surface of the quantum dot is a sulfydryl-containing organic ligand, the quantum dot does not contain sulfur element; when the organic ligand on the surface of the quantum dot is a nitrogen-containing organic ligand, the quantum dot does not contain nitrogen elements.
The invention provides a method for determining the ligand coverage rate of a quantum dot surface ligand which is an organic ligand containing sulfydryl or nitrogen by using a potentiometric titration method. Measuring ligand coverage rate K of organic ligand containing sulfydryl or nitrogen on surface of quantum dot by potentiometric titrationiAnd the method can be used for quality assessment of the quantum dots. If KiLess than 2 x 10-10mol/cm2If the quantum dot quality is not good enough, K should be addediAfter the value is increased, the application such as solution or ink preparation is carried out. The method for determining the coverage rate of the ligand on the surface of the quantum dot has the advantages of accurate result and simple operation, and further can ensure the stability of the content of the ligand on the surface of the quantum dot, ensure the solubility of the quantum dots in different batches, avoid the coffee ring effect caused by different drying rates when the quantum dot solution is prepared into a film, and improve the pixel resolution, the lighting voltage and the uniformity of the photoelectric efficiency of the quantum dot display panel.
The quantum dot surface ligand coverage rate test and calculation principle is as follows:
the sample particle is a collection of a plurality of single particles, each single particle comprises a quantum dot and a ligand bound on the surface of the quantum dotThe ligand in the invention is an organic ligand containing sulfydryl or nitrogen. Surface ligand coverage K in the present inventioniThe surface ligand coverage rate K can be calculated and obtained through the quantity of substances of characteristic elements in special groups combined with the quantum dotsi. Surface ligand coverage KiThis can be obtained by the following formula:
Ki=ml/(0.74MlmQSq/ρQVq) (formula 1)
Specifying mass m of a particular atom in a particular functional group in a surface ligand of a quantum dot in a sample particlelMolar mass MlTotal mass of sample particles is mQDensity is rhoQSurface area S of individual particles in sample particlesqVolume is VqThe sample particles were densely packed with a space utilization of 0.74, assuming spherical particles with an average particle size of d. When the organic ligand on the surface of the quantum dot is a sulfydryl-containing organic ligand, the characteristic element in the organic ligand is sulfur; when the organic ligand on the surface of the quantum dot is a nitrogen-containing organic ligand, the characteristic element in the organic ligand is a nitrogen element.
Wherein the volume of the single particle is
Surface area of individual particles
Is calculated after being substituted into a formula
Ki=mlρQd/4.44MlmQ(formula 2), when the organic ligand is a polydentate ligand, the ligand denticity is removed, and when it is, for example, dithiol, the ligand denticity is 2.
In the above formula 2, [ rho ]QThe method can be obtained by searching the density of related substances or testing by using an Archimedes principle, and the d can be obtained by testing the size of the quantum dot according to a TEM. Thus, it is possible to provideNeeds to be tested by adopting a proper method to obtain ml/mQThus obtaining the ligand coverage rate of the quantum dot surface.
In step S10, the selected quantum dots may be selected from unary quantum dots, binary quantum dots, or ternary quantum dots.
For example, the unary quantum dots may be selected from Au, Ag, Cu, Pt, or C quantum dots, but are not limited thereto;
the binary quantum dots can be selected from CdSe, ZnSe, PbSe, CdTe, ZnO, MgO, CeO2、NiO、TiO2InP or CaF2Quantum dots, but not limited thereto;
the ternary quantum dots can be selected from CdZnSe and NaYF4、NaCdF4ZnCdTe, CdZnSe/ZnSe, CdSe/CdZnSe/CdZnSe/ZnSe or CdZnSe/CdZnSe/ZnSe quantum dots, but is not limited thereto.
The organic ligand containing sulfydryl bound on the surface of the quantum dot can be the same or different, and the organic ligand containing sulfydryl is selected from one or more of mono-thiol, dithiol, sulfydryl alcohol, sulfydryl amine and sulfydryl acid.
Preferably, the monothiol is selected from one or more of hexanethiol, octanethiol, nonanethiol, decanethiol, undecanethiol, dodecanethiol, tridecanethiol, tetradecanethiol, hexadecanethiol and octadecanethiol;
preferably, the dithiol is selected from one or more of 1, 2-ethanedithiol, 1, 3-propanedithiol, 1, 4-butanedithiol, 1, 5-pentanethiol, 1, 6-hexanedithiol, 1, 8-octanethiol and 1, 10-decanedithiol;
preferably, the mercaptoalcohol is selected from one or more of 2-mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol, 5-mercapto-1-pentanol, 6-mercapto-1-hexanol and 8-mercapto-1-octanol;
preferably, the mercapto acid is selected from one or more of 2-mercaptoacetic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, mercaptosuccinic acid, 6-mercaptohexanoic acid, 4-mercaptobenzoic acid and cysteine;
preferably, the mercaptoamine is selected from one or more of 2-mercaptoethylamine, 3-mercaptopropylamine, 4-mercaptobutylamine, 5-mercaptopentylamine, 6-mercaptohexylamine, 2-amino-3-mercaptopropionic acid, 2-aminothiophenol, and mercaptoundecanamine.
The nitrogen-containing organic ligands bound to the surfaces of the quantum dots may be the same or different, and the nitrogen-containing organic ligands are selected from one or more of primary amines, secondary amines, and tertiary amines.
Preferably, the primary amine is selected from one or more of benzylamine, n-butylamine, n-propylamine, cyclohexylamine, phenethylamine, n-hexylamine, isopropylamine, aniline, p-toluidine, p-chloroaniline, p-bromoaniline, p-methoxyaniline, 1, 4-butanediamine and 1, 5-pentanediamine;
preferably, the secondary amine is selected from one or more of dimethylamine, diphenylamine, diisooctylamine, ditridecylamine and N-methylaniline;
preferably, the tertiary amine is selected from one or more of dimethyl octylamine, dimethyl decylamine, dimethyl dodecylamine, dimethyl tetradecylamine, dimethyl hexadecylamine, dimethyl octadecylamine, dimethyl oleylamine, bis octylmethylamine, bis decylmethylamine and trioctylamine.
In one embodiment, in step S20 of the present invention, the transmission electron microscope analyzer may be used to determine the average particle size of the particles in the sample particles.
Specifically, the test conditions for determining the average particle size of particles in the sample particles by using a transmission electron microscope analyzer are as follows: the accelerating voltage is 200-300kV, the emission current is 7-20 muA, the working distance is 10-20mm, and the dead time is 20-40%.
The step of determining the average particle size of particles in the sample particles using a transmission electron microscope analyzer comprises: and (3) dissolving the sample particles in a nonpolar solvent to prepare a quantum dot solution with the concentration of 1-5 mg/mL, dripping 5-10 drops of a small amount of quantum dot solution on a copper mesh after the solution is completely dissolved, and placing the copper mesh in a transmission electron microscope analyzer for test analysis d. Specifically, a sample is amplified and analyzed by the magnification factor of 70000-150000 times, a TEM picture is obtained by focusing a region with concentrated and uniformly dispersed quantum dots, then the TEM picture is analyzed by software, the length of a ruler is set, then 30-80 quantum dots are calibrated, and finally the average particle size d of sample particles is obtained by calculation.
In one embodiment, in step S30 of the present invention, the mass ratio m of elemental sulfur or elemental nitrogen in the sample particles to the sample particles is determined by the potentiometric titration methodl/mQ. The potentiometric titration test principle is that a metal inert electrode is used as an indicating electrode, and a working battery is formed by the reference electrode and a tested sample particle solution. With the addition of the titrant, the titrant chemically reacts with the measured ions, the concentration of the measured ions changes during the titration process, the potential between the indicating electrode and the reference electrode changes, and finally the titration endpoint is determined by the sudden change of the indicating electrode potential. In the titration process, mercaptan sulfur and silver ions on the organic ligand form mercaptan sulfur silver sediment, and according to the using amount of the titrant, the content ratio of the S element in the quantum dots is obtained; ClO in perchloric acid4 -And Cl in pH glass electrode-Forming electrode reaction, and obtaining the content ratio of the N element in the quantum dots according to the usage amount of the titrant;
wherein the electrode potential equation is:
。
r is the gas constant 8.31441J/(K mol), T is the temperature (unit: K), n is the number of electron transfers during the electrode reaction, F is the Faraday constant 96.487kJ/(V mol), EθIs 273.15K, the electrode potential in the standard state of 100kPa, [ oxidized form ]]/[ reduced form]Representing the ratio of the product of the concentrations of the species participating in the electrode reaction to the product of the concentrations of the reaction products.
Specifically, in one embodiment, the step S30 includes:
s301, dissolving the sample particles to obtain a sample particle solution;
s302, inserting an indicating electrode and a reference electrode into the sample particle solution, dropping a titrant into the sample particle solution for potentiometric titration, drawing an E-V titration curve, obtaining the use amount of a titration end point titrant according to the titration curve, and converting the use amount into sample particlesCalculating the mass ratio of the sulfur element or the nitrogen element to the sample particles to obtain the coverage rate K of the quantum dot surface ligandiWherein E is the potential and V is the volume consumed by the titrant.
Specifically, in step S301, 10 to 30mg of the sample particles are weighed and placed in a 250 mL conical flask or a titration cup matched with a potentiometric titrator with a corresponding range, 30 to 50mL of isopropanol is added as a solvent, and the sample particles are shaken to be completely dissolved in the solvent, so as to obtain the sample particle solution.
Specifically, in step S302, when the organic ligand on the surface of the quantum dot is a thiol-containing organic ligand, the titrant is a silver nitrate alcohol standard titration solution, the indicator electrode is a silver-silver sulfide electrode, and the reference electrode is a glass reference electrode. The preparation process of the silver nitrate alcohol standard titration solution comprises the following steps: dissolving 1.7-8.5 g of silver nitrate in 10 mL of deionized water in a 1000mL volumetric flask, and diluting with isopropanol to a scale mark to obtain 0.01-0.05mol/L silver nitrate alcohol standard titration solution. The preparation process of the silver-silver sulfide electrode is as follows:
(1) preparing an alkaline titration solvent, namely absorbing 1.6-3.2 g of anhydrous sodium acetate to dissolve in 25 mL of oxygen-free water, and then injecting into 975 mL of isopropanol to obtain 0.02-0.04mol/L of the alkaline titration solvent;
(2) firstly polishing a silver electrode silver terminal by using abrasive paper, then immersing the polished silver electrode silver terminal in 100 mL of alkaline titration solvent containing 5-8 mL of 1 wt% sodium sulfide solution, then slowly dripping 70-100 mL of silver nitrate alcohol standard titration solution from a burette under the stirring condition, and rotating an electrode to ensure that a silver sulfide plating layer is uniformly plated on the electrode silver terminal, wherein the titration time is controlled within 1-2 min.
Specifically, in step S302, when the organic ligand on the surface of the quantum dot is a nitrogen-containing organic ligand, the titrant is a perchloric acid standard titration solution, the indicator electrode is a pH glass electrode, and the reference electrode is a glass reference electrode. Wherein the perchloric acid standard titration solution is prepared by the following process: adding 8.5-17 mL of perchloric acid (70%) into a 1000mL volumetric flask, adding 100 mL of isopropanol to dissolve, and then adding dioxane to dilute to a scale mark to obtain 0.1-0.2mol/L perchloric acid standard titration solution.
In step S302, the specific potentiometric titration test conditions are: setting potential preset values dE (set) = 15-18mV, potential balance allowable values dE = 4-5mV, potential value recording time dt = 0.5-1s, minimum potential value recording time dt (min) = 0.5-1s, maximum potential value recording time dt (max) =5-10 s, and threshold value =200 mV/mL. Wherein, the potential value recording time means that after each drop of titrant is dripped, the titrant reacts with the sample for 0.5 to 1s and then the potential value is recorded, so that the titrant and the sample fully react, and the value is read after the potential value is stabilized. The minimum potential value recording time is the time required for the electrode to be fully contacted with the sample after the installation device is inserted into the electrode, and the initial minimum potential to be stable. The maximum potential value recording time means that after titration is finished, the potential value reaches the maximum value and waits for 5-10s until the potential does not change any more. The specific potentiometric titration test process is as follows: inserting a reference electrode and an indicating electrode into a container filled with the sample particle solution, and carrying out potentiometric titration by using the prepared silver nitrate alcohol standard titration solution or perchloric acid standard titration solution; adding a proper amount of titrant, and recording millivolts and milliliters after the potential is constant; when the end point is approached, the potential is constant after 5-10 min; in order to avoid the oxidation of the measured object by air during the titration, the titration time is shortened, and the titration cannot be interrupted; and finally, drawing an E-V titration curve by taking the E potential as a vertical coordinate and the volume V consumed by the titrant as a horizontal coordinate, obtaining the volume consumed by the titrant according to the potential jump point of the titration curve, converting the volume consumed by the titrant into the mass ratio of the sulfur or nitrogen element in the sample particles to the sample particles, and calculating to obtain the coverage rate K of the quantum dot surface ligandi。
The research shows that the coverage rate K of the ligand on the surface of the quantum dotiIf less than 2 x 10-10mol/cm2The solubility of the quantum dots is poor, and the quality of a film prepared into the film subsequently is influenced. Require to be connected with KiAfter the value is increased, the application such as solution or ink preparation is carried out. Increase KiValues can be carried out using the ligand re-exchange method. The specific process is as follows: firstly, quantum dots are dissolved in a nonpolar solvent, and then the same surface ligand is added to carry out the reaction at the temperature of between 25 and 150 DEG CAnd (6) exchanging. The nonpolar solvent comprises chloroform, normal hexane, heptane, octane, toluene, chlorobenzene, dichlorobenzene, carbon tetrachloride, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, cyclodecane, cycloundecane, octadecene and the like. The amount of ligand added during said ligand re-exchange should not be less than (2 x 10)-10-K1）n1/K1(formula 3, K)0Representing the coverage rate of the ligand on the surface of the target quantum dot, K1Representing the coverage rate of the quantum dot ligand measured for the first time, and n1 is the amount of ligand added for the first time in the preparation process of the quantum dot). By using the process, KiThe value is increased to more than 2 x 10-10mol/cm2The quantum dots can be applied to other solution properties.
The present invention will be described in detail below with reference to examples.
Example 1
A method for measuring the coverage rate of a ligand on the surface of a quantum dot comprises the following steps:
(1) determining the average size d of the particles, and providing a plurality of sample particles, wherein the particles comprise CdTe quantum dots and 1, 2-ethanedithiol ligands bonded on the surfaces of the CdTe quantum dots. Dissolving the sample particles in a heptane solution to prepare a 5 mg/mL solution, after the solution is completely dissolved, dripping 5 drops of the sample particle solution on a copper net, and placing the copper net in a transmission electron microscope analyzer for test analysis. The acceleration voltage was set at 200 kV, the emission current was set at 10. mu.A, the working distance was set at 15 mm, and the dead time was 20%. And (3) carrying out amplification analysis on the sample particles, firstly setting the amplification factor to be 70000 times, carrying out focusing analysis on the concentrated and uniformly dispersed areas of the sample particles, and taking TEM pictures of the sample particles. And analyzing the TEM picture, firstly setting the length of a ruler, then calibrating 30-80 sample particles, and calculating to obtain the average size d of the sample particles to be 7.0 nm.
(2) Determining the mercaptan ligand coverage rate of the surface of the quantum dot by using a potentiometric titration method, wherein the method comprises the following steps:
preparing 0.0L mol/L silver nitrate alcohol standard titration solution, dissolving 1.7 g of silver nitrate in 10 mL of deionized water in a 1000mL volumetric flask, and diluting with isopropanol to a scale mark;
preparing an alkaline titration solvent, namely absorbing 1.6 g of anhydrous sodium acetate to dissolve in 25 mL of oxygen-free water, and then injecting into 975 mL of isopropanol;
preparing a silver-silver sulfide electrode, and 1) polishing a silver terminal of the silver electrode by using abrasive paper. 2) The polished silver electrode silver terminal was immersed in 100 mL of an alkaline titration solvent containing 5 mL of a 1 wt% sodium sulfide solution. 3) Under the condition of stirring, 70 mL of 0.01 mol/L silver nitrate alcohol standard titration solution is slowly added into the burette, and the electrode is rotated, so that the silver sulfide coating is uniformly plated on the silver terminal of the silver electrode. Controlling the titration time to be 2 min;
and fourthly, measuring the sample, namely accurately weighing 10 mg of sample particles, putting the sample particles into a 250 mL conical flask or a titration cup matched with an instrument with a corresponding measuring range, adding 50mL of isopropanol, and shaking to disperse the sample particles in the solvent. Potential preset values dE (set) = 16 mV, minimum titrant addition dv (min) = 0.02 mL, maximum titrant addition dv (max) = 0.2 mL, potential equilibrium allowed value dE = 4 mV, potential value recording time dt = 0.6 s, minimum potential value recording time dt (min) = 0.6 s, maximum potential value recording time dt (max) =6 s, threshold value =200 mV/mL are set. Filling a glass reference electrode and the silver-silver sulfide electrode prepared in the step 3) into a container filled with sample particles, and titrating by using 0.01 mol/L silver nitrate alcohol standard titration solution prepared in the step 1); and the mass ratio of the S element in the sampled particles to the sample particles was 4.1% by conversion based on the volume consumed by the titrant.
(3) Calculating the coverage rate K of the ligand on the surface of the quantum dotiThe density of CdTe quantum dots is 6.2 g/cm3According to the above test results, the CdTe quantum dot size is 7.0 nm, the mass ratio of S element in the thiol ligand in the quantum dot to the sample particles is 4.1%, and K is calculatediIs 1.05 x 10-9mol/cm2。KiValue greater than 2 x 10-10mol/cm2The method can be directly applied without ligand re-exchange.
Example 2
A method for measuring the coverage rate of a quantum dot ligand comprises the following steps:
(1) the average size d of the particles was determined, providing several sample particles comprising ZnO quantum dots and n-propylamine bound to the surface of the ZnO quantum dots. Dissolving the sample particles in a heptane solution to prepare a 5 mg/mL solution, after the solution is completely dissolved, dripping 5 drops of the sample particle solution on a copper net, and placing the copper net in a transmission electron microscope analyzer for test analysis. The acceleration voltage was set at 300kV, the emission current at 15 μ A, the working distance at 18 mm, and the dead time at 25%. And (3) carrying out amplification analysis on the sample, firstly setting the amplification factor to be 110000 times, carrying out focusing analysis on the region of the sample with concentrated and uniformly dispersed particles, and taking a TEM picture of the sample. And analyzing the TEM picture, firstly setting the length of a ruler, then calibrating 30-80 sample particles, and calculating to obtain the size d of the sample particles to be 8.5 nm.
(2) Determining the coverage rate of the ligand on the surface of the quantum dot by using a potentiometric titration method, wherein the method comprises the following steps:
firstly, preparing 0.1 mol/L perchloric acid standard titration solution, taking 8.5 mL perchloric acid (70%) in a 1000mL volumetric flask, adding 100 mL isopropanol to dissolve, and then adding dioxane to dilute to a scale mark;
secondly, testing the sample, namely accurately weighing 30mg of sample particles, placing the sample particles into a 250 mL conical flask or a titration cup matched with an instrument with a corresponding measuring range, adding 40 mL of isopropanol, and shaking to disperse the sample particles in the solvent. Potential preset values dE (set) = 15 mV, minimum titrant addition dv (min) = 0.01 mL, maximum titrant addition dv (max) = 0.1 mL, potential equilibrium allowed value dE = 5mV, potential value recording time dt = 0.7 s, minimum potential value recording time dt (min) = 0.7 s, maximum potential value recording time dt (max) = 8 s, threshold value =200 mV/mL are set. Loading a glass reference electrode and a pH glass electrode into a container filled with sample particles, and titrating by using 0.1 mol/L perchloric acid standard titration solution calibrated in the step 1); and the mass ratio of the N element in the sampled particles to the sample particles is 3.9 percent according to the conversion of the volume consumed by the titrant.
(3) Calculating the coverage rate K of the ligand on the surface of the quantum dot1The density of ZnO quantum dots is 5.9 g/cm3According to the above test results, the size of the ZnO quantum dot is 8.5 nm,the mass ratio of the N element in the amine ligand in the quantum dots to the sample particles is 3.9%, and the calculated K is 4.18 x 10-8 mol/cm2。K1Value greater than 2 x 10-10mol/cm2The method can be directly applied without ligand re-exchange.
The method for determining the coverage of the thiol or amine ligand on the surface of the quantum dot by using the potentiometric titration method provided in the embodiments of the present invention is described in detail above, and a person skilled in the art may change the idea of the embodiments of the present invention in the specific implementation and application scope.
Claims (12)
1. A method for measuring the coverage rate of a ligand on the surface of a quantum dot is characterized by comprising the following steps:
providing sample particles, wherein each particle in the sample particles comprises a quantum dot and an organic ligand bound on the surface of the quantum dot, and the organic ligand is selected from a sulfydryl-containing organic ligand or a nitrogen-containing organic ligand;
determining the average particle size of the particles in the sample particles;
measuring the mass ratio of sulfur element or nitrogen element in the sample particles to the sample particles by a potentiometric titration method, and calculating to obtain the coverage rate K of the quantum dot surface ligandiDefining the amount of substance binding to the surface ligand per unit area of the surface of the quantum dot as the coverage rate K of the ligand on the surface of the quantum dotiIn which K isi＝mlρQd/(4.44MlmQ)，mlIs the mass of elemental sulfur or elemental nitrogen, M, in the organic ligandlIs the molar molecular mass of elemental sulfur or elemental nitrogen in the organic ligand, mQIs the total mass of the sample particles, pQIs the density of the sample particles, d is the average particle size of the sample particles;
when the organic ligand on the surface of the quantum dot is a sulfydryl-containing organic ligand, the quantum dot does not contain sulfur element; when the organic ligand on the surface of the quantum dot is a nitrogen-containing organic ligand, the quantum dot does not contain nitrogen elements.
2. The method for measuring the ligand coverage on the surface of the quantum dot according to claim 1, wherein the step of measuring the mass ratio of the elemental sulfur or the elemental nitrogen in the sample particle to the sample particle by a potentiometric titration method comprises:
dissolving the sample particles to obtain a sample particle solution;
inserting an indicating electrode and a reference electrode into the sample particle solution, dropping a titrant into the sample particle solution for potentiometric titration, drawing an E-V titration curve, obtaining the use amount of a titration end-point titrant according to the titration curve, and converting the use amount into the mass ratio of sulfur or nitrogen elements in the sample particles to the sample particles, wherein E is the potential, and V is the volume consumed by the titrant.
3. The method for determining the ligand coverage on the surface of the quantum dot according to claim 2, wherein the potentiometric titration is performed under the following test conditions: setting a potential preset value of 15-18mV, a potential balance allowable value of 4-5mV, a potential value recording time of 0.5-1s, a minimum potential value recording time of 0.5-1s, a maximum potential value of 5-10s and a threshold value of 200 mV/mL.
4. The method for measuring the ligand coverage rate on the surface of the quantum dot according to claim 2, wherein when the organic ligand on the surface of the quantum dot is a sulfydryl-containing organic ligand, the titrant is a silver nitrate alcohol standard titration solution, and the indicator electrode is a silver-silver sulfide electrode.
5. The method for measuring the ligand coverage on the surface of the quantum dot according to claim 2, wherein when the organic ligand on the surface of the quantum dot is a nitrogen-containing organic ligand, the titrant is a perchloric acid standard titration solution, and the indicator electrode is a pH glass electrode.
6. The method for measuring the ligand coverage on the surface of the quantum dot according to claim 1, wherein the quantum dot is a univariate quantum dot, a binary quantum dot or a ternary quantum dot.
7. The method for measuring the ligand coverage on the surface of the quantum dot according to claim 6, wherein the univalent quantum dot is selected from Au, Ag, Cu, Pt or C quantum dots;
the binary quantum dots are selected from CdSe, ZnSe, PbSe, CdTe, ZnO, MgO and CeO2、NiO、TiO2InP or CaF2Quantum dots;
the ternary quantum dots are selected from CdZnSe and NaYF4、NaCdF4ZnCdTe, CdZnSe/ZnSe, CdSe/CdZnSe/CdZnSe/ZnSe or CdZnSe/CdZnSe/ZnSe quantum dots.
8. The method for measuring the ligand coverage rate on the surface of the quantum dot according to claim 1, wherein the organic ligand containing sulfydryl is selected from one or more of mono-thiol, dithiol, sulfydryl alcohol, sulfydryl amine and sulfydryl acid.
9. The method for measuring the ligand coverage on the surface of the quantum dot according to claim 1, wherein the nitrogen-containing organic ligand is selected from one or more of primary amine, secondary amine and tertiary amine.
10. The method for measuring the coverage rate of the ligand on the surface of the quantum dot according to claim 1, wherein a transmission electron microscope analyzer is used for measuring the average particle size of particles in the sample particles.
11. The method for determining the coverage rate of the ligand on the surface of the quantum dot according to claim 10, wherein the conditions for determining the average particle size of the particles in the sample particles by using a transmission electron microscope analyzer are as follows: the accelerating voltage is 200-300kV, the emission current is 7-20 muA, the working distance is 10-20mm, and the dead time is 20-40%.
12. The method for determining the ligand coverage on the surface of the quantum dot according to claim 10 or 11, wherein the step of determining the average particle size of the particles in the sample particles by using a transmission electron microscope analyzer comprises the following steps: and (3) carrying out amplification analysis on the sample, wherein the amplification factor is 70000-150000 times, focusing the concentrated and uniformly dispersed area of the sample particles to obtain a TEM picture of the sample particles, analyzing the TEM picture by using software, calibrating 30-80 quantum dots, and calculating to obtain the average particle size of the sample particles.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711350124.2A CN109932476B (en) | 2017-12-15 | 2017-12-15 | Method for measuring coverage rate of ligand on surface of quantum dot |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711350124.2A CN109932476B (en) | 2017-12-15 | 2017-12-15 | Method for measuring coverage rate of ligand on surface of quantum dot |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109932476A CN109932476A (en) | 2019-06-25 |
| CN109932476B true CN109932476B (en) | 2022-05-24 |
Family
ID=66980024
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711350124.2A Active CN109932476B (en) | 2017-12-15 | 2017-12-15 | Method for measuring coverage rate of ligand on surface of quantum dot |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109932476B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111007197A (en) * | 2019-12-24 | 2020-04-14 | 中检科健(天津)检验检测有限责任公司 | Method for rapidly determining thioglycollic acid content |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102277157B (en) * | 2011-05-30 | 2014-06-11 | 中国科学院苏州纳米技术与纳米仿生研究所 | Near-infrared silver sulphide quantum dot as well as preparation method and application thereof |
| CN104807791B (en) * | 2015-04-20 | 2017-11-21 | 南京农业大学 | A kind of method detected based on quantum dot gold nano assembling superstructure to bisphenol-A |
-
2017
- 2017-12-15 CN CN201711350124.2A patent/CN109932476B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN109932476A (en) | 2019-06-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Liu et al. | Hydrothermal synthesis of monodisperse Ag2Se nanoparticles in the presence of PVP and KI and their application as oligonucleotide labels | |
| KR101562689B1 (en) | Methods for preparing nanocrystals using electron transfer agents | |
| CN109932405B (en) | Method for measuring content of ligand on surface of quantum dot and method for preparing quantum dot ink | |
| CN109932476B (en) | Method for measuring coverage rate of ligand on surface of quantum dot | |
| US8057781B2 (en) | Fabrication method for chalcopyrite powder | |
| CN109932267B (en) | Method for measuring coverage rate of ligand on surface of quantum dot | |
| CN109932326B (en) | Method for measuring coverage rate of ligand on surface of quantum dot | |
| Miao et al. | Photodegradation of mercaptopropionic acid-and thioglycollic acid-capped CdTe quantum dots in buffer solutions | |
| CN111378425A (en) | Composite material and preparation method thereof | |
| CN109932325B (en) | Method for measuring content of ligand on particle surface and method for preparing quantum dot ink | |
| Deng et al. | Chronopotentiometric synthesis of quantum dots with efficient surface-derived near-infrared electrochemiluminescence for ultrasensitive microchip-based ion-selective sensing | |
| EP3865556B1 (en) | Preparation method for quantum dots | |
| CN109932373B (en) | Method for measuring coverage rate of ligand on surface of quantum dot | |
| CN109932285B (en) | Method for measuring content of ligand on surface of quantum dot and method for preparing quantum dot ink | |
| JP2010032343A (en) | MANUFACTURING METHOD OF SnO2 GAS SENSOR, AND MANUFACTURING METHOD OF SnO2 CARRYING HAVING NOBLE METAL NANOPARTICLES | |
| CN109932378B (en) | Method for measuring coverage rate of ligand on surface of quantum dot | |
| Li et al. | Stable water-soluble quantum dots capped by poly (ethylene glycol) modified dithiocarbamate | |
| CN109946331B (en) | Method for measuring content of ligand on surface of quantum dot and method for preparing quantum dot ink | |
| CN109932357B (en) | Method for measuring coverage rate of ligand on surface of quantum dot | |
| Chomoucka et al. | Synthesis of Glutathione Coated Quantum Dots | |
| CN109932377A (en) | A kind of measuring method of quantum dot surface ligand coverage rate | |
| CN109932358B (en) | Method for measuring content of ligand on surface of quantum dot and method for preparing quantum dot ink | |
| Hynek et al. | Electrochemical characterization of various synthesized quantum dots and the effect of aging and storage way | |
| AU2021104485A4 (en) | A process for synthesis of chromium doped tellurium dioxide nanostructures for egfet ph sensor application | |
| CN109932274A (en) | The measuring method and quantum dot ink formulation method of quantum dot surface ligand content |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| CB02 | Change of applicant information |
Address after: 516006 TCL science and technology building, No. 17, Huifeng Third Road, Zhongkai high tech Zone, Huizhou City, Guangdong Province Applicant after: TCL Technology Group Co.,Ltd. Address before: 516006 Guangdong province Huizhou Zhongkai hi tech Development Zone No. nineteen District Applicant before: TCL Corp. |
|
| CB02 | Change of applicant information | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |