CN109932476A - A kind of measuring method of quantum dot surface ligand coverage rate - Google Patents
A kind of measuring method of quantum dot surface ligand coverage rate Download PDFInfo
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Abstract
The present invention proposes a kind of measuring method of quantum dot surface ligand coverage rate.The coverage rate K of the ligand of organic ligand by potentiometric determination quantum dot surface containing sulfydryl or nitrogeni, can be used for the performance rating to quantum dot.If KiLess than 2*10‑10mol/cm2, then quantum dot quality defect need to be by KiValue carries out the application such as solution or ink configuration again after improving.Quantum dot surface ligand coverage rate is determined using this method, as a result accurate, it is easy to operate, further, it can guarantee the stability of quantum dot surface ligand content by means of the present invention, the dissolubility that can guarantee the quantum dot of different batches, when avoiding quantum dot solution preparation film forming because rate of drying it is different caused by coffee ring effect, the homogeneity that the pixel resolution of quantum dot display panel can be improved, open bright voltage, photoelectric efficiency.
Description
Technical field
The present invention relates to technology of quantum dots field more particularly to a kind of measuring methods of quantum dot surface ligand coverage rate.
Background technique
Quantum dot refers to that geometric dimension is less than the semiconductor nano of its Exciton Bohr Radius.Quantum dot is inhaled due to having
The excellent optical properties such as take-up is wide, fluorescent emission band is narrow, quantum efficiency is high, good light stability, in biomedical, environment energy
There is huge potential application in the fields such as source, illumination display.Display technology based on quantum dot light emitting is shown in recent years
The great attention of industry, compared with liquid crystal display and organic light emitting display, quantum dot light emitting colour gamut is wider, excitation purity is higher, knot
Structure is simpler, and stability is higher, it is considered to be display technology of new generation.
The technology of preparing of quantum dot displays part includes spin coating, inkjet printing etc..The detailed process of both methods be by
Quantum dot solution is injected on basis material, forms quantum dot film in specific position after drying.Viscosity, the table of quantum dot solution
Face tension and charge transport ability determine the wetting ability, rate of drying of quantum dot drop, coffee ring in device fabrication process
The photoelectric properties of effect and film, therefore, the quality of quantum dot solution play a crucial role device preparation.And it is measuring
In the process for preparation of son point solution, quantum dot surface ligand has an important influence quantum dot solution, and surface ligand not only influences
The photoelectric properties of quantum dot itself also will affect the dissolubility and stability of quantum dot solution.Common quantum dot surface ligand
For carboxylic acid, amine, alkyl phosphorus, alkylphosphine oxide, alkyl phosphoric acid, mercaptan etc..Influence of the surface ligand to quantum dot own optical performance
Show themselves in that the average grain diameter of quantum dot is less than Exciton Bohr Radius, exciton is exposed to surface to a certain extent, surface be easy by
Its optical property is reduced to influence；When quantum dot surface atom number increases, surface dangling bonds also can sharply increase, and atom is matched
The presence for the defects of position deficiency leads to quantum dot surface there are many defects, electronics or holes increases the general of non-radiative recombination
Rate, the combined efficiency for causing normal radiation compound substantially reduce.When surface ligand appropriate is added, quantum dot can be effectively reduced
Surface dangling bonds make exciton be no longer exposed to surface, improve the optical property of quantum dot.Surface ligand to quantum dot dissolubility and
The influence of stability shows themselves in that increasing for quantum dot surface dangling bonds can make its surface free energy very big, and surface becomes abnormal
Vivaciously, it is unstable to also result in system for this, and quantum dot can be intended to aggregation to reduce surface area, and it is molten that this will lead to quantum dot solution
Solution property reduces.After introducing surface ligand, one end of ligand is connected on quantum dot surface atom, and one end mixes with solution, can be subtracted
The surface energy of small quantum dot, improves the dissolubility of quantum dot, and effective inhibitory amount point solution generates precipitating.
Therefore, the dissolubility of quantum dot influences the preparation of device and performance very big.And the dissolubility of quantum dot in addition to
Other than quantum dot itself and ligand species, another important factor in order is the coverage rate of quantum dot surface ligand.If quantum dot
Surface coverage is low, then the dissolubility of quantum dot is poor, and the uniformity of quantum dot solution is poor, and the rate of drying of quantum dot solution
The quality of luminous layer film is affected with coffee ring effect, this is directly resulted in, and the panel quality that prints is uneven, pixel point
Resolution is low, opens bright voltage, the problems such as photoelectric efficiency is inhomogenous.
Summary of the invention
In view of above-mentioned deficiencies of the prior art, in order to ensure later-stage utilization quantum dot ink prepare QLED device quality of forming film
Stability, present invention firstly provides a kind of measuring methods of quantum dot surface ligand coverage rate.
A kind of measuring method of quantum dot surface ligand coverage rate characterized by comprising
Sample particle is provided, the individual particle in the sample particle includes quantum dot and is incorporated in having for the quantum dot surface
Machine ligand, the organic ligand are selected from organic ligand or nitrogenous organic ligand containing sulfydryl；
Measure the average grain diameter of particle in the sample particle；
The mass ratio of element sulphur or nitrogen and sample particle, the amount of being calculated in the sample particle described in potentiometric determination
Son point surface ligand coverage rate Ki；
Wherein, when the organic ligand of quantum dot surface is the organic ligand containing sulfydryl, element sulphur is free of in the quantum dot；When
When the organic ligand of quantum dot surface is nitrogenous organic ligand, not Nitrogen element in the quantum dot.
The present invention propose it is a kind of using potentiometric titration determine quantum dot surface ligand be the organic ligand containing sulfydryl or nitrogen
Ligand coverage rate method.The ligand of organic ligand by potentiometric determination quantum dot surface containing sulfydryl or nitrogen covers
Rate Ki, can be used for the performance rating to quantum dot.If KiLess than 2*10-10mol/cm2, then quantum dot quality defect need to be by KiValue
The application such as solution or ink configuration is carried out after raising again.Quantum dot surface ligand coverage rate is determined using method of the invention, is tied
Fruit is accurate, easy to operate, further, can guarantee the stability of quantum dot surface ligand content by means of the present invention, can protect
The dissolubility for demonstrate,proving the quantum dot of different batches, when avoiding quantum dot solution preparation film forming because rate of drying it is different caused by coffee ring
Effect, the homogeneity that the pixel resolution of quantum dot display panel can be improved, open bright voltage, photoelectric efficiency.
Specific embodiment
The present invention provides a kind of measuring method of quantum dot surface ligand coverage rate, to make the purpose of the present invention, technical side
Case and effect are clearer, clear, and the present invention is described in more detail below.It should be appreciated that specific reality described herein
It applies example to be only used to explain the present invention, be not intended to limit the present invention.
A kind of measuring method of quantum dot surface ligand coverage rate, wherein include:
S10 provides sample particle, and the individual particle in the sample particle includes quantum dot and is incorporated in the quantum dot surface
Organic ligand, the organic ligand be selected from organic ligand or nitrogenous organic ligand containing sulfydryl；
S20 measures the average grain diameter of particle in the sample particle；
The mass ratio of element sulphur or nitrogen and sample particle, calculates in sample particle described in S30 potentiometric determination
To quantum dot surface ligand coverage rate Ki；
Wherein, when the organic ligand of quantum dot surface is the organic ligand containing sulfydryl, element sulphur is free of in the quantum dot；When
When the organic ligand of quantum dot surface is nitrogenous organic ligand, not Nitrogen element in the quantum dot.
The present invention propose it is a kind of using potentiometric titration determine quantum dot surface ligand be the organic ligand containing sulfydryl or nitrogen
Ligand coverage rate method.The ligand of organic ligand by potentiometric determination quantum dot surface containing sulfydryl or nitrogen covers
Rate Ki, can be used for the performance rating to quantum dot.If KiLess than 2*10-10mol/cm2, then quantum dot quality defect need to be by KiValue
The application such as solution or ink configuration is carried out after raising again.Quantum dot surface ligand coverage rate is determined using method of the invention, is tied
Fruit is accurate, easy to operate, further, can guarantee the stability of quantum dot surface ligand content by means of the present invention, can protect
The dissolubility for demonstrate,proving the quantum dot of different batches, when avoiding quantum dot solution preparation film forming because rate of drying it is different caused by coffee ring
Effect, the homogeneity that the pixel resolution of quantum dot display panel can be improved, open bright voltage, photoelectric efficiency.
The quantum dot surface ligand coverage rate test Computing Principle are as follows:
The sample particle is the set of several individual particles, and the individual particle includes quantum dot and is incorporated in quantum dot surface
Ligand, the present invention in ligand be the organic ligand containing sulfydryl or nitrogen.Surface ligand coverage rate K in the present inventioniRefer to quantum
Point surface unit area in mating surface ligand substance amount, surface ligand by specific functional groups directly with quantum dot knot
It closes, by the amount of the substance of the characteristic element in the specific groups in conjunction with quantum dot, surface ligand coverage rate can be calculated
Ki.Surface ligand coverage rate KiIt can be obtained by following formula:
Ki=ml/(0.74MlmQSq/ρQVq) (formula 1)
It provides in sample particle, the quality of weird atom is m in specific functional groups in quantum dot surface ligandl, molecular matter
Amount is Ml, the gross mass of sample particle is mQ, density ρQ, individual particle surface area S in sample particleq, volume Vq, sample
Grain is in closs packing, space utilization rate 0.74, it is assumed that particle is spherical shape, mean particle size d.Wherein, work as quantum dot surface
Organic ligand when being organic ligand containing sulfydryl, the characteristic element in the organic ligand is element sulphur；Work as quantum dot surface
Organic ligand when being nitrogenous organic ligand, the characteristic element in the organic ligand is nitrogen.
Wherein, individual particle volume is, the surface area of individual particle, substitute into formula
After be calculated
Ki=mlρQd/4.44MlmQ(formula 2) need to remove the ligand number of teeth, for example, two when the organic ligand is multidentate ligand
When mercaptan, the ligand number of teeth is 2.
In above-mentioned formula 2, ρQIt can be according to searching related substances density or testing to obtain using Archimedes principle, d can basis
TEM test quantum dot size obtains.Therefore it needs to test to obtain m using suitable methodl/mQQuantum dot surface can be obtained
Ligand coverage rate.
In step S10 of the present invention, the quantum dot of selection can be selected from unitary quantum dot, binary quantum dot or ternary quantum
Point.
For example, the unitary quantum dot can be selected from Au, Ag, Cu, Pt or C quantum dot, but not limited to this；
The binary quantum dot can be selected from CdSe, ZnSe, PbSe, CdTe, ZnO, MgO, CeO2、NiO、TiO2, InP or CaF2Amount
It is sub-, but not limited to this；
The ternary quantum dots can be selected from CdZnSe, NaYF4、NaCdF4、ZnCdTe、CdZnSe/ZnSe、CdSe/CdZnSe/
CdZnSe/ZnSe or CdZnSe/CdZnSe/ZnSe quantum dot, but not limited to this.
The organic ligand containing sulfydryl for being incorporated in the quantum dot surface can be the same or different, described containing sulfydryl
Organic ligand is selected from one of a mercaptan, two mercaptan, mercaptoalcohol, mercapto-amine and mercaptan acid or a variety of.
Preferably, a mercaptan be selected from hexyl mercaptan, spicy thioalcohol, nonyl mercaptan, decyl mercaptan, undecyl mercaptan, lauryl mercaptan,
One of 13 mercaptan, tetradecanylthioalcohol, 16 mercaptan and stearylmercaptan are a variety of；
Preferably, two mercaptan are selected from 1,2- dithioglycol, 1,3- dimercaptopropane, Isosorbide-5-Nitrae-succinimide mercaptans, 1,5-, penta 2 sulphur
One of pungent two mercaptan of alcohol, 1,6- ethanthiol, 1,8- and two mercaptan of the 1,10- last of the ten Heavenly stems are a variety of；
Preferably, the mercaptoalcohol is selected from 2 mercapto ethanol, 3- sulfydryl -1- propyl alcohol, 4- sulfydryl-n-butyl alcohol, 5- sulfydryl -1-
One of amylalcohol, 6- sulfydryl -1- hexanol and 8- sulfydryl -1- octanol are a variety of；
Preferably, the mercaptan acid is selected from 2- thioacetic acid, 3- mercaptopropionic acid, 4- mercaptobutyric acid, dimercaptosuccinic acid, 6- sulfydryl
One of caproic acid, 4- mercaptobenzoic acid and cysteine are a variety of；
Preferably, the mercapto-amine is selected from 2-MEA, 3- mercaptopropylamine, 4- sulfydryl butylamine, 5- sulfydryl amylamine, 6- sulfydryl
One of hexylamine, 2- amino-3-mercaptopropionic acid, 2- aminothiophenol and mercaptoundecylamine are a variety of.
The nitrogenous organic ligand for being incorporated in the quantum dot surface can be the same or different, described nitrogenous organic
Ligand is selected from one of primary amine, secondary amine and tertiary amine or a variety of.
Preferably, the primary amine be selected from benzylamine, n-butylamine, n-propylamine, cyclohexylamine, phenyl ethylamine, n-hexylamine, isopropylamine,
Aniline, para-totuidine, parachloroanilinum, para-bromoaniline, P-nethoxyaniline, Putriscine and 1, one of 5- pentanediamine or
It is a variety of；
Preferably, the secondary amine is selected from one of dimethylamine, diphenylamines, two octodrines, double tridecyl amines and methylphenylamine
Or it is a variety of；
Preferably, the tertiary amine is selected from dimethyl octylame, dimethyldodecyl amide, dimethyl lauryl amine, dimethyl tetradecy lamine, diformazan
One of base cetylamine, dimethyl octadecylamine, dimethyl oil base amine, double octyl methyl amine, double decyl methyl amines and trioctylamine
Or it is a variety of.
In a kind of wherein embodiment, in step S20 of the present invention, the sample can be measured using transmission electron microscope analysis instrument
The average grain diameter of particle in product particle.
Specifically, measuring the test condition of the average grain diameter of particle in the sample particle using transmission electron microscope analysis instrument
Are as follows: acceleration voltage 200-300kV, emission current are 7-20 μ A, and operating distance is 10-20 mm, dead time 20%-40%.
The step of measuring the average grain diameter of particle in the sample particle using transmission electron microscope analysis instrument includes: to take sample
Grain is dissolved in the quantum dot solution that preparation concentration is 1-5 mg/mL in nonpolar solvent and takes a small amount of quantum after solution is completely dissolved
Copper mesh is placed in progress test analysis d in transmission electron microscope analysis instrument on copper mesh by point solution drop 5-10 drop.Specifically, first to sample
Product amplify analysis, and amplification factor is 70000-150000 times, and taken amount sub- point is concentrated and finely dispersed region is focused
TEM picture is obtained, then TEM picture is analyzed with software, length of the scale is first set, then 30-80 quantum dot is taken to carry out
Calibration, is finally calculated the average grain diameter d of sample particle.
In a kind of wherein embodiment, in step S30 of the present invention, using in the potentiometric determination sample particle
The mass ratio m of element sulphur or nitrogen and sample particlel/mQ.The potentiometric titration test philosophy is using metal-inert electrode
A working battery is formed as indicator electrode and reference electrode and sample particle solution.With the addition of titrant, with
It is chemically reacted by measured ion, ion concentration is tested in titration process and is changed, indicator electrode and reference electrode are caused
Between potential change, titration end-point is finally determined with the jumping of indicator electrode current potential.In titration process, on organic ligand
Mercaptan sulfur and silver ion are formed as mercaptan sulfur silver precipitating, according to the usage amount of titrant, so that obtaining S element accounts for containing for quantum dot
Amount ratio；ClO in perchloric acid4 -With the Cl in pH glass electrode-Electrode reaction is formed, according to the usage amount of titrant, thus
The content ratio of quantum dot is accounted for N element；
Wherein electrode potential equation are as follows:。
R is gas constant 8.31441J/ (K*mol), and T is temperature (unit: K), and n is turn of electronics in electrode process
Number is moved, F is Faraday constant 96.487kJ/ (V*mol), EθIt is 273.15K, the electrode potential under 100kPa standard state, [oxygen
Change type]/[reduced form] indicate to participate in the product and the ratio between reaction product concentration product of electrode reaction material concentration.
Specifically, in a kind of wherein embodiment, the step S30 includes:
S301 dissolves the sample particle, obtains sample particle solution；
S302 is inserted into indicator electrode, reference electrode in the sample particle solution, and it is molten that titrant is dropped to the sample particle
Constant-current titration is carried out in liquid, and draws E-V titration curve, and the usage amount of titration end-point titrant is obtained according to titration curve, is changed
It is counted as the mass ratio of element sulphur or nitrogen and sample particle in sample particle, quantum dot surface ligand coverage rate is calculated
Ki, wherein E is potential, and V is volume consumed by titrant.
Specifically, in step S301, weighs sample particle described in 10-30mg and be placed in 250 mL conical flasks or corresponding range
In the mating titration cup of potentiometric titrimeter, 30-50mL isopropanol is added as solvent, rocking is completely dissolved the sample particle
In the solvent, the sample particle solution is obtained.
Specifically, in step S302, when the organic ligand of quantum dot surface is the organic ligand containing sulfydryl, the titration
Agent is silver nitrate alcohol standard titration solution, and the indicator electrode is silver-sulfide electrode, and the reference electrode is glass reference electricity
Pole.Wherein the process for preparation of the silver nitrate alcohol standard titration solution is as follows: with 10 mL deionized waters in 1000mL volumetric flask
It dissolves 1.7-8.5 g silver nitrate and it is molten to obtain 0.01-0.05mol/L silver nitrate alcohol standardized titration with isopropanol to graduation mark
Liquid.Wherein the preparation process of the silver-sulfide electrode is as follows:
(1) preparation of alkaline titration solvent is drawn 1.6-3.2 g anhydrous sodium acetate and is dissolved in 25 mL anaerobic waters, is then injected into
Into 975 mL isopropanols, 0.02-0.04mol/L alkalinity titration solvent is obtained；
(2) polish silver electrode silver terminal with sand paper first, then the silver electrode silver terminal after polishing be immersed in containing 5-8 mL,
In 100 mL alkalinity titration solvents of 1 wt% sodium sulfide solution, then under agitation, 70- is slowly instilled from buret
100 mL silver nitrate alcohol standard titration solutions, and rotating electrode, make to vulcanize silvering and are equably plated in electrode silver terminal, when titration
Between control in 1-2 min.
Specifically, in step S302, when the organic ligand of quantum dot surface is nitrogenous organic ligand, the titrant
For perchloric acid standard titration solution, the indicator electrode is pH glass electrode, and the reference electrode is glass reference electrode.Wherein
The process for preparation of the perchloric acid standard titration solution is as follows: increase chloric acid (70%) 8.5-17 mL in 1000mL volumetric flask,
Add 100 mL of isopropanol dissolve after, then plus dioxane be diluted to graduation mark, obtain 0.1-0.2mol/L perchloric acid standardized titration
Solution.
In step S302, specific constant-current titration test condition are as follows: setting current potential preset value dE (set)=15-18
MV, potential balance permissible value dE=4-5 mV, potential value record time dt=0.5-1 s, and minimum level value records time dt
(min)=0.5-1 s, maximum potential value record time dt (max)=5-10 s, threshold value=200 mV/mL.Wherein, current potential
After the value record time refers to that every drop titrant drop is entered, it is made to re-record potential value with example reaction 0.5-1s, it is therefore an objective to allow drop
Determine agent and sample sufficiently reacts, reading numerical values again after stablizing potential value.The minimum level value record time refers to that mounting device is inserted
After entering electrode, electrode comes into full contact with sample, and initial minimum level, which reaches, stablizes the required time.Maximum potential value records the time
After the completion of referring to titration, potential value reaches maximum, 5-10 s is waited, until current potential is no longer changed.Specific constant-current titration
Test process are as follows: reference electrode and indicator electrode are inserted into the container equipped with sample particle solution, with the nitric acid of above-mentioned preparation
Silver-colored alcohol standard titration solution or perchloric acid standard titration solution carry out constant-current titration；Appropriate titrant is added, after current potential is constant,
Record millivolt and ml；When close to terminal, it is constant to reach current potential by 5-10 min；To avoid measured object during titration empty
Gas oxidation, should shorten titration time, titration cannot be interrupted；Finally, using E potential as ordinate, volume V consumed by titrant is
Abscissa draws E-V titration curve, and obtains volume consumed by titrant according to titration curve potential break point, then convert
At the mass ratio of sulphur in sample particle or nitrogen and sample particle, quantum dot surface ligand coverage rate K is calculatedi。
It has been investigated that the quantum dot surface ligand coverage rate KiIf being less than 2*10-10mol/cm2, then quantum dot is molten
Solution property is not good enough, influences the subsequent film quality for being prepared into film.It need to be by KiValue carries out solution or ink configuration etc. again and answers after improving
With.Improve KiLigand can be used in value, and exchange process carries out again.Detailed process are as follows: quantum dot is first dissolved in nonpolar solvent, then plus
Enter surface ligand of the same race to swap at 25-150 DEG C.The nonpolar solvent include chloroform, n-hexane, heptane, octane,
Toluene, chlorobenzene, dichloro-benzenes, carbon tetrachloride, decane, hendecane, dodecane, tridecane, the tetradecane, pentadecane, hexadecane, 17
Alkane, octadecane, cyclodecane, ring hendecane, octadecylene etc..The amount for the ligand that the ligand is added in exchange process again must not
Less than (2*10-10-K1) n1/K1(formula 3, K0Represent target quantum dot surface ligand coverage rate, K1Represent the quantum dot measured for the first time
Ligand coverage rate, n1 are the amount of ligand being added for the first time in quantum dot preparation process).Using this process by KiValue is increased to greater than 2*
10-10mol/cm2Quantum dot can be carried out to other solution applications.
Below by embodiment, the present invention is described in detail.
Embodiment 1
A kind of measuring method of quantum dot surface ligand coverage rate, comprising:
(1) the average-size d for determining particle, provides several sample particles, and the particle includes CdTe quantum and is incorporated in
The 1,2- dithioglycol ligand on CdTe quantum surface.Sample particle is dissolved in n-heptane solution, the solution of 5 mg/mL is prepared,
After solution is completely dissolved, take 5 drop of a small amount of sample particle solution drop on copper mesh, by copper mesh be placed in transmission electron microscope analysis instrument into
Row test analysis.Setting acceleration voltage is 200 kV, and for emission current in 10 μ A, operating distance is set as 15 mm, dead time 20
%.Analysis is amplified to sample particle, it is 70000 times that amplification factor, which is first arranged, takes sample particle concentration and finely dispersed area
Domain is focused analysis, shoots its TEM picture.TEM picture is analyzed, length of the scale is first set, then takes 30-80 sample
Particle is demarcated, and the average-size d that sample particle is calculated is 7.0 nm.
(2) quantum dot surface mercaptan ligand coverage rate is determined using potentiometric titration, comprising:
1. the preparation of 0.0l mol/L silver nitrate alcohol standard titration solution, water-soluble with 10 mL deionizations in 1000mL volumetric flask
1.7 g silver nitrates are solved, with isopropanol to graduation mark；
2. the preparation of alkaline titration solvent is drawn 1.6 g anhydrous sodium acetates and is dissolved in 25 mL anaerobic waters, is then injected into 975
In mL isopropanol；
3. the preparation of silver-sulfide electrode, 1) polish silver electrode silver terminal with sand paper.2) the silver electrode silver terminal after polishing is soaked
5 mL are not being contained, in 100 mL alkalinity titration solvents of 1 wt% sodium sulfide solution.3) under agitation, from buret
It is slowly added into 70 mL, 0.01 mol/L silver nitrate alcohol standard titration solution, and rotating electrode, plates vulcanization silvering equably
In silver electrode silver terminal.Titration time is controlled in 2 min；
4. sample measures, the mating titration of instrument that 10 mg sample particles are placed in 250 mL conical flasks or corresponding range is accurately weighed
In cup, 50 mL isopropanols are added, shaking is dispersed in sample particle in solvent.It is arranged current potential preset value dE (set)=16
MV, minimum titrant additive amount dV (min)=0.02 mL, maximum titrant additive amount dV (max)=0.2 mL, current potential are flat
Weigh the mV of permissible value dE=4, and potential value records the s of time dt=0.6, and minimum level value records time dt (min)=0.6 s,
Maximum potential value records time dt (max)=6 s, threshold value=200 mV/mL.Glass is packed into the container equipped with sample particle
Glass reference electrode and above-mentioned steps 3) preparation silver-sulfide electrode, with above-mentioned steps 1) prepare 0.01 mol/L silver nitrate
Alcohol standard titration solution is titrated；And the volume according to consumed by titrant converts to obtain the S element in samples taken particle
Mass ratio with sample particle is 4.1%.
(3) quantum dot surface ligand coverage rate K is calculatedi, the density of CdTe quantum is 6.2 g/cm3, according to above-mentioned test
As a result, CdTe quantum, having a size of 7.0 nm, the mass ratio of S element and sample particle is 4.1% in mercaptan ligand in quantum dot,
Calculate KiFor 1.05*10-9mol/cm2。KiValue is greater than 2*10-10mol/cm2, can be exchanged again without ligand, directly application is
It can.
Embodiment 2
A kind of measuring method of quantum dot ligand coverage rate, comprising:
(1) the average-size d for determining particle, provides several sample particles, and the particle includes ZnO quantum dot and is incorporated in ZnO
The n-propylamine of quantum dot surface.Sample particle is dissolved in n-heptane solution, the solution of 5 mg/mL is prepared, it is complete to solution
After dissolution, takes a small amount of 5 drop of sample particle solution drop on copper mesh, copper mesh is placed in transmission electron microscope analysis instrument and carries out test point
Analysis.Setting acceleration voltage is 300 kV, and for emission current in 15 μ A, operating distance is set as 18 mm, 25 % of dead time.To sample
Analysis is amplified, it is 110000 times that amplification factor, which is first arranged, takes sample particle concentration and finely dispersed region is focused
Analysis, shoots its TEM picture.TEM picture is analyzed, length of the scale is first set, then 30-80 sample particle is taken to be marked
Fixed, the size d that sample particle is calculated is 8.5 nm.
(2) quantum dot surface ligand coverage rate is determined using potentiometric titration, comprising:
1. the preparation of 0.1 mol/L perchloric acid titrand takes (70%) 8.5 mL of perchloric acid in 1000mL volumetric flask, adds
100 mL of isopropanol dissolution after, then plus dioxane be diluted to graduation mark；
2. sample test accurately weighs the mating titration of instrument that 30 mg sample particles are placed in 250 mL conical flasks or corresponding range
In cup, 40 mL isopropanols are added, shaking is dispersed in sample particle in solvent.It is arranged current potential preset value dE (set)=15
MV, minimum titrant additive amount dV (min)=0.01 mL, maximum titrant additive amount dV (max)=0.1 mL, current potential
The mV of permissible value dE=5 is balanced, potential value records the s of time dt=0.7, and minimum level value records time dt (min)=0.7
S, maximum potential value record time dt (max)=8 s, threshold value=200 mV/mL.It is packed into the container equipped with sample particle
Glass reference electrode and pH glass electrode, with above-mentioned steps 1) calibration 0.1 mol/L perchloric acid standard titration solution dripped
It is fixed；And the volume according to consumed by titrant converts to obtain the quality of the N element element and sample particle in samples taken particle
Than being 3.9%.
(3) quantum dot surface ligand coverage rate K is calculated1, the density of ZnO quantum dot is 5.9 g/cm3, according to above-mentioned test
As a result, ZnO quantum dot, having a size of 8.5 nm, the mass ratio of N element element and sample particle is in amine ligand in quantum dot
3.9%, calculating K is 4.18*10-8 mol/cm2。K1Value is greater than 2*10-10mol/cm2, can exchange again without ligand, directly answer
With.
It is provided for the embodiments of the invention above and a kind of determines quantum dot surface mercaptan or amine using potentiometric titration
The method of ligand coverage rate is described in detail, for those of ordinary skill in the art, think of according to an embodiment of the present invention
Think, there will be changes in the specific implementation manner and application range, in conclusion the content of the present specification should not be construed as pair
Limitation of the invention, all any changes made according to design philosophy of the present invention are all within protection scope of the present invention.
Claims (13)
1. a kind of measuring method of quantum dot surface ligand coverage rate characterized by comprising
Sample particle is provided, the individual particle in the sample particle includes quantum dot and is incorporated in having for the quantum dot surface
Machine ligand, the organic ligand are selected from organic ligand or nitrogenous organic ligand containing sulfydryl；
Measure the average grain diameter of particle in the sample particle；
The mass ratio of element sulphur or nitrogen and sample particle, the amount of being calculated in the sample particle described in potentiometric determination
Son point surface ligand coverage rate Ki；
Wherein, when the organic ligand of quantum dot surface is the organic ligand containing sulfydryl, element sulphur is free of in the quantum dot；When
When the organic ligand of quantum dot surface is nitrogenous organic ligand, not Nitrogen element in the quantum dot.
2. the measuring method of quantum dot surface ligand coverage rate according to claim 1, which is characterized in that described to be dripped with current potential
The method of determining measures the mass ratio of element sulphur or nitrogen and sample particle in the sample particle, and quantum dot surface ligand is calculated
Coverage rate KiThe step of include:
The sample particle is dissolved, sample particle solution is obtained；
It is inserted into indicator electrode, reference electrode in the sample particle solution, titrant is dropped in the sample particle solution
Constant-current titration is carried out, and draws E-V titration curve, the usage amount of titration end-point titrant is obtained according to titration curve, is converted into
Quantum dot surface ligand coverage rate K is calculated in the mass ratio of sulphur or nitrogen and sample particle in sample particlei, wherein E
For potential, V is volume consumed by titrant.
3. the measuring method of quantum dot surface ligand coverage rate according to claim 2, which is characterized in that the constant-current titration
Test condition are as follows: setting current potential preset value be 15-18 mV, potential balance permissible value be 4-5 mV, potential value record the time
For 0.5-1 s, minimum level value records the time as 0.5-1 s, and maximum potential value is recorded as 5-10 s, threshold value=200 mV/
mL。
4. the measuring method of quantum dot surface ligand coverage rate according to claim 2, which is characterized in that work as quantum dot surface
Organic ligand when being organic ligand containing sulfydryl, the titrant is silver nitrate alcohol standard titration solution, the indicator electrode
For silver-sulfide electrode.
5. the measuring method of quantum dot surface ligand coverage rate according to claim 2, which is characterized in that work as quantum dot surface
Organic ligand be nitrogenous organic ligand when, the titrant be perchloric acid standard titration solution, the indicator electrode be pH
Glass electrode.
6. the measuring method of any one of -5 quantum dot surface ligand coverage rates according to claim 1, which is characterized in that according to
Formula Ki=mlρQd/4.44MlmQThe quantum dot surface ligand coverage rate K is calculatedi, wherein m1For S in sample particle or N
Element quality, ρQFor sample particle density, d is the average grain diameter of particle in the sample particle, M1For S or N element mole point
Protonatomic mass, mQFor the gross mass of sample particle.
7. the measuring method of quantum dot surface ligand coverage rate according to claim 1, which is characterized in that the quantum dot is
Unitary quantum dot, binary quantum dot or ternary quantum dots.
8. the measuring method of quantum dot surface ligand coverage rate according to claim 7, which is characterized in that the unitary quantum
Point is selected from Au, Ag, Cu, Pt or C quantum dot；
The binary quantum dot is selected from CdSe, ZnSe, PbSe, CdTe, ZnO, MgO, CeO2、NiO、TiO2, InP or CaF2Quantum
Point；
The ternary quantum dots are selected from CdZnSe, NaYF4、NaCdF4、ZnCdTe、CdZnSe/ZnSe、CdSe/CdZnSe/
CdZnSe/ZnSe or CdZnSe/CdZnSe/ZnSe quantum dot.
9. the measuring method of quantum dot surface ligand coverage rate according to claim 1, which is characterized in that described containing sulfydryl
Organic ligand is selected from one of a mercaptan, two mercaptan, mercaptoalcohol, mercapto-amine and mercaptan acid or a variety of.
10. the measuring method of quantum dot surface ligand coverage rate according to claim 1, which is characterized in that described nitrogenous
Organic ligand is selected from one of primary amine, secondary amine and tertiary amine or a variety of.
11. the measuring method of quantum dot surface ligand coverage rate according to claim 1, which is characterized in that using transmission electricity
The average grain diameter of particle in sample particle described in mirror analysis-e/or determining.
12. the measuring method of quantum dot surface ligand coverage rate according to claim 11, which is characterized in that using transmission electricity
The test condition of the average grain diameter of particle in sample particle described in mirror analysis-e/or determining are as follows: acceleration voltage 200-300kV, transmitting
Electric current is 7-20 μ A, and operating distance is 10-20 mm, dead time 20%-40%.
13. the measuring method of the 1 or 12 quantum dot surface ligand coverage rates according to claim 1, which is characterized in that using saturating
The step of average grain diameter of particle includes: to amplify analysis to sample in sample particle described in radio mirror analysis-e/or determining, is put
Big multiple is 70000-150000 times, takes sample particle concentration and finely dispersed region is focused to obtain sample particle
TEM picture analyzes the TEM picture with software, takes 30-80 quantum dot to be demarcated, sample particle is calculated
Average grain diameter.
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