Method for measuring thermodynamic data between quantum dot surface and ligand by using solvent volatilization

Abstract

The invention relates to the field of materials and physicochemistry, in particular to a method for measuring thermodynamic data between a quantum dot surface and a ligand by using solvent volatilization, which comprises the following steps: preparing a ligand modified quantum dot organic solvent solution with a certain concentration, and standing until the fluorescence intensity is stable; measuring the volatilization rate of the organic solvent at the target temperature; in the same environment, volatilizing the prepared quantum dot organic solvent solution, and detecting the fluorescence intensity of the quantum dots in real time to obtain a real-time fluorescence intensity-time curve that the fluorescence intensity changes along with time; the obtained fluorescence intensity-time curve is converted through the relation of fluorescence intensity-solvent volatilization-quantum yield to obtain the data relation between the ligand density and the quantum dot quantum yield at the t moment, and then thermodynamic data can be obtained through a corrected KSV equation according to the data relation. The method is simple, accurate and practical in operability.

Description

Technical Field

[0001] The invention relates to the fields of materials and physical chemistry, and in particular to a method for measuring thermodynamic data between a quantum dot surface and a ligand by utilizing solvent volatilization. Background Art

[0002] Fluorescence titration is a widely accepted method for quantitatively determining thermodynamic data of material interactions. It has the advantages of being sensitive, trace, accurate, and convenient, and has been widely used in the measurement of small molecules in the past. With the rise of nanoparticle materials, this method has begun to be applied to measure the interactions between nanoparticles and other substances. But it is worth noting that nanoparticles are a huge platform with a huge surface area. This means that, unlike the interactions between small molecules, the interactions between nanoparticles and other substances may not be assumed to be consistent with the past.

[0003] The mechanism of fluorescence quenching of ligands on the surface of quantum dots has been studied for a long time. Studies have shown that the fluorescence quenching mechanism on the surface of quantum dots is static quenching, which means that quantum dots will bind to ligands in the ground state, causing changes in fluorescence intensity. The binding mode between the fluorescent material M (quantum dots) and the ligand Q can be written as:

[0004]

[0005] The binding constant can be written as:

[0006]

[0007] Where n is the binding (dissociation) ratio of the ligand to the material in the quenching mechanism during the static quenching process.

[0008] For the same fluorescence cell, in a dilute quantum dot solution, the expression of fluorescence intensity according to the Lambert-Beer law can be written as:

[0009] F=2.303QY M I0εbc

[0010] Where b is the thickness of the light-absorbing layer and c is the concentration of the fluorescent substance.

[0011] This means that the fluorescence intensity is proportional to the amount of material concentration without physical property changes. On the other hand, the binding constant K is not a constant term here. In fact, the adsorption behavior of the ligand on the surface of the quantum dots shows a positive promotion and a strong correlation with the surface coverage, which means that the traditional fluorescence titration cannot obtain usable data because the traditional fluorescence titration method is based on an assumption that the thermodynamic data is constant. In our past work, we found that the thermodynamic data of the quantum dot surface has a clear relationship with the coverage of the ligand on the surface, that is, there is a strong correlation between the thermodynamic data K and the surface ligand Q. We have seen a lot of literature on quantum dot thermodynamic measurements, and there are many controversies about ligand-surface thermodynamics. This controversy usually involves 5 to 6 orders of magnitude, which may cause serious deviations or errors in the data we obtain. Due to this huge controversy, the measurement of quantum dot surface ligand thermodynamics has decreased in recent years. In recent years, with the rapid development of quantum dots, especially the popularity of quantum dot display materials and perovskite quantum dots, people have begun to pay attention to the importance of basic research on quantum dot surfaces. Summary of the invention

[0012] The purpose of the present invention is to provide a method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization, and dynamically detecting the ligand and quantum dot surface thermodynamic data as the ligand density changes by using a fluorescence titration method, which is simple, accurate and practically operable.

[0013] The solution adopted by the present invention to achieve the purpose is: a method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization, comprising the following steps:

[0014] (1) preparing a certain concentration of ligand-modified quantum dot organic solvent solution and allowing it to stand until the fluorescence intensity is stable;

[0015] (2) determining the volatilization rate of the organic solvent at a target temperature;

[0016] (3) In the same environment, the prepared quantum dot organic solvent solution is volatilized, and the fluorescence intensity of the quantum dots is detected in real time to obtain a fluorescence intensity-time curve showing the real-time fluorescence intensity changing with time;

[0017] (4) The obtained fluorescence intensity-time curve is converted through the relationship between fluorescence intensity-solvent evaporation-quantum yield to obtain the data relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the data relationship can be used to obtain the K SV Thermodynamic data were obtained from the equation.

[0018] Preferably, in step (1), the concentration of quantum dots is 1×10 -8 ~1×10 -6 M.

[0019] Preferably, in step (1), the concentration of the ligand is: the concentration of the quantum dots is 1×10 3 ~5×10 4 M.

[0020] Preferably, in step (1), the organic solvent used is chloroform or n-hexane.

[0021] Preferably, in step (1), the ligand is at least one of oleic acid, butylamine, and a ligand containing mercaptopropionic acid.

[0022] Preferably, in step (1), the quantum dots are at least one of CdSe quantum dots, ZnS quantum dots and PbS quantum dots.

[0023] Preferably, in the step (2), the volatilization rate is determined by using the weight difference at certain time intervals and the density of the solvent.

[0024] Preferably, in step (2), the target temperature is higher than the freezing point of the organic solvent and lower than the boiling point of the organic solvent, and at least three values ​​are selected within this range as the target temperature values.

[0025] Preferably, in step (3), the volatilization amount of the organic solvent should be less than 50% of the original volume.

[0026] Preferably, in step (4), K before correction SV The equation is: F0 / F T =K SV [Q], where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate;

[0027] Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is:

[0028]

[0029] In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

[0030] The present invention has the following advantages and beneficial effects:

[0031] The method of the present invention can obtain quantum dot-ligand thermodynamic data with practical significance; at the same time, the method of dynamically detecting the thermodynamic data of quantum dots-ligands under different ligand densities by using the fluorescence titration method can simplify the operation of the experimenter to a certain extent, and the consistency in the data can greatly reduce the errors caused by operational errors, and it is simple, accurate and practically operable; it has universality and has strong practical significance and reference value in how to accurately obtain meaningful quantum dot thermodynamic data. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The change in fluorescence intensity (23° C.) obtained in Example 1 of the present invention as the volatilization process changes;

[0033] Figure 2 This is the experimental data processing curve obtained in Example 1 of the present invention. According to the slope, f can be obtained. a and k a (23℃);

[0034] Figure 3 The processed data obtained in Example 1 of the present invention is a Variation of k a The obtained curve (23°C);

[0035] Figure 4 This is a fluorescence pool diagram (23° C.) from the beginning to the end of the experiment in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0037] Before the experiment, the ligand-modified quantum dots were purified several times, and the quantum yield of the product obtained after each purification was detected. When the quantum yield after two purifications showed obvious differences, the purification was stopped and the product was set aside.

[0038] Example 1

[0039] Chloroform was used as solvent to prepare 80 mL of quantum dots with a concentration of 1×10 -7M, oleic acid concentration is 3.5mM quantum dot solution, (the quantum dot fluorescence emission peak used here is 600nm) placed in a 250mL separatory funnel; place the container in a constant temperature water bath to keep the appropriate temperature, and let it stand for at least 1 day. (such as 25℃, 31℃, 37℃ here); detect the volatilization rate of oleic acid solution in a fluorescence detection device at the corresponding temperature. The specific method is to select a marked fluorescence pool, use a pipette to inhale about 3mL of chloroform, first use an analytical balance to measure the overall mass, and then let it stand at the corresponding temperature, and record the time, and take it out after a period of time for measurement again. In the same environment, still select the marked fluorescence pool, put the configured quantum dot solution into the fluorescence detection device for volatilization after the initial measurement, and use the fluorescence detection device to detect the fluorescence intensity of the quantum dots in real time to obtain a real-time curve of fluorescence intensity changing with time. According to the detection method, the fluorescence intensity-time curve can be converted into the relationship between the fluorescence intensity-solvent evaporation-quantum yield to obtain the approximate relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the K value can be approximated by the data relationship. SV Thermodynamic data were obtained.

[0040] K before correction SV The equation is: F0 / F T =K SV [Q],

[0041] Where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate;

[0042] Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is:

[0043]

[0044] In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

[0045] like Figure 1As shown, the fluorescence intensity change (23°C) obtained in Example 1 of the present invention as the volatilization process changes, it can be seen from the figure: as the solvent evaporates, the concentration of quantum dots will gradually increase because they are colloids and cannot evaporate. The process of solvent volatilization is an extremely slow process, and we can approximate it as a reasonable thermodynamic approximation process to approach the ideal state. It can be seen that the upper line is the change in fluorescence intensity under the ideal state. If after volatilization, the ligands and quantum dots in the solvent do not interact, then the fluorescence intensity will change in the direction of the line. However, the actual fluorescence intensity change is the fitted curve below, which is far away from the ideal upper line. This means that there is an interaction between the ligands and quantum dots, and the magnitude of the interaction can be estimated by the thermodynamic approximation system.

[0046] like Figure 2 As shown, the processed data obtained in Example 1 of the present invention is a Variation of k a The obtained curve (23°C) can be seen from the figure: after a large number of data points are fitted to the curve and the ideal fluorescence intensity curve, the fitting curve of the modified Ksv equation is obtained. The slope and intercept of each point can finally get the corresponding f a and k a Here we pursue the realistic rationality of the data, and the slope is estimated by (y(t+1)-y(t)) / (x(t+1)-x(t)).

[0047] like Figure 3 As shown, the processed data obtained in Example 1 of the present invention is a Variation of k a The obtained curve (23℃); it can be seen that as f a The larger the k a It will also increase, which means that there is an obvious ligand effect as the ligand binds to the surface of the quantum dots. At the same time, in our process, this means that the increase in ligand concentration increases the binding constant between quantum dots and ligands, which is consistent with the conclusion of related work.

[0048] like Figure 4 As shown, this is a fluorescence pool diagram (23°C) of Example 1 of the present invention from the beginning to the end of the experiment. It can be seen from the figure that after three hours of volatilization, the solvent volume has been significantly reduced, and under the irradiation of ultraviolet light of the same intensity, the fluorescence intensity has changed significantly.

[0049] Example 2

[0050] Chloroform was used as solvent to prepare 2.5×10 -7M, 80mL of quantum dot solution of 3.5mM oleic acid (fluorescence emission peak position is 600nm), placed in a 250mL separatory funnel; place the container in a constant temperature water bath to maintain a suitable temperature, and let it stand for at least 1 day. (such as 23℃, 30℃, 37℃, 44℃ here); detect the volatilization rate of oleic acid solution in a fluorescence detection device at different temperatures. The specific method is to select a marked fluorescence pool, use a pipette to inhale about 3mL of chloroform, first use an analytical balance to measure the overall mass, then let it stand at the corresponding temperature, and record the time, and take it out after a period of time for measurement again. In the same environment, still select the marked fluorescence pool, put the configured quantum dot solution into the fluorescence detection device for volatilization after the initial measurement, and use the fluorescence detection device to detect the fluorescence intensity of the quantum dots in real time to obtain a real-time curve of fluorescence intensity changing with time. According to the detection method, the fluorescence intensity-time curve can be converted through the relationship between fluorescence intensity-solvent evaporation-quantum yield to obtain an approximate relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the K can be approximated through the data relationship. SV Thermodynamic data were obtained.

[0051] K before correction SV The equation is: F0 / F T =K SV [Q],

[0052] Where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate;

[0053] Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is:

[0054]

[0055] In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

[0056] Example 3

[0057] Chloroform was used as solvent to prepare 2.5×10 -7M, 80mL of 600nm emission CdSe quantum dot solution containing mercaptopropionic acid ligand in 5mM butylamine environment is placed in a 250mL separatory funnel; the container is placed in a constant temperature water bath to maintain a suitable temperature and stand for at least 1 day. (For example, 25°C, 31°C, and 37°C here); the volatilization rate of oleic acid solution is detected in a fluorescence detection device at different temperatures. The specific method is to select a marked fluorescence pool, use a pipette to inhale about 3mL of chloroform, first use an analytical balance to measure the overall mass, then stand at the corresponding temperature, and record the time, and take it out after a period of time for measurement again. In the same environment, still select a marked fluorescence pool, put the configured quantum dot solution into the fluorescence detection device for volatilization after the initial measurement, and use the fluorescence detection device to detect the fluorescence intensity of the quantum dots in real time to obtain a real-time curve of fluorescence intensity changing with time. According to the detection method, the fluorescence intensity-time curve can be converted through the relationship between fluorescence intensity-solvent evaporation-quantum yield to obtain an approximate relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the K can be approximated through the data relationship. SV Thermodynamic data were obtained.

[0058] K before correction SV The equation is: F0 / F T =K SV [Q],

[0059] Where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate;

[0060] Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is:

[0061]

[0062] In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

[0063] Example 4

[0064] Chloroform was used as solvent to prepare 2.5×10 -7M, 80mL of CdSe / ZnS quantum dot (fluorescence emission peak is 620nm) solution in 3.5mM oleic acid environment is placed in a 250mL separatory funnel; the container is placed in a constant temperature water bath to maintain a suitable temperature and stand for at least 1 day. (For example, 25°C, 31°C, 37°C here); the volatilization rate of the oleic acid solution is detected in a fluorescence detection device at different temperatures. The specific method is to select a marked fluorescence pool, use a pipette to inhale about 3ml of chloroform, first use an analytical balance to measure the overall mass, then stand at the corresponding temperature, and record the time, and take it out and measure again after a period of time. In the same environment, still select the marked fluorescence pool, put the configured quantum dot solution into the fluorescence detection device for volatilization after the initial measurement, and use the fluorescence detection device to detect the fluorescence intensity of the quantum dots in real time to obtain a real-time curve of the fluorescence intensity changing with time. According to the detection method, the fluorescence intensity-time curve can be converted through the relationship between fluorescence intensity-solvent evaporation-quantum yield to obtain an approximate relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the K can be approximated through the data relationship. SV Thermodynamic data were obtained.

[0065] K before correction SV The equation is: F0 / F T =K SV [Q],

[0066] Where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate;

[0067] Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is:

[0068]

[0069] In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

[0070] Example 5

[0071] Configuration 2.5×10 -7M, 80mL of PbS quantum dot solution (fluorescence emission peak is 1300nm) in a 3.5mM oleic acid environment is placed in a 250mL separatory funnel; the container is placed in a constant temperature water bath to maintain a suitable temperature and stand for at least 1 day. (For example, 25°C, 31°C, and 37°C here); the volatilization rate of the oleic acid solution is detected in a fluorescence detection device at different temperatures. The specific method is to select a marked fluorescence pool, use a pipette to inhale about 3mL of chloroform, first use an analytical balance to measure the overall mass, then stand at the corresponding temperature, and record the time, and take it out and measure again after a period of time. In the same environment, still select the marked fluorescence pool, put the configured quantum dot solution into the fluorescence detection device for volatilization after the initial measurement, and use the fluorescence detection device to detect the fluorescence intensity of the quantum dots in real time to obtain a real-time curve of the fluorescence intensity changing with time. According to the detection method, the fluorescence intensity-time curve can be converted through the relationship between fluorescence intensity-solvent evaporation-quantum yield to obtain an approximate relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the K can be approximated through the data relationship. SV Thermodynamic data were obtained.

[0072] K before correction SV The equation is: F0 / F T =K SV [Q],

[0073] Where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate;

[0074] Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is:

[0075]

[0076] In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

[0077] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A method for measuring thermodynamic data between quantum dot surface and ligand using solvent volatilization, characterized in that: The following steps are involved: (1) preparing a certain concentration of ligand-modified quantum dot organic solvent solution and allowing it to stand until the fluorescence intensity is stable; (2) determining the volatilization rate of the organic solvent at a target temperature; (3) In the same environment, the prepared quantum dot organic solvent solution is volatilized, and the fluorescence intensity of the quantum dots is detected in real time to obtain a fluorescence intensity-time curve showing the real-time fluorescence intensity changing with time; (4) The obtained fluorescence intensity-time curve is converted through the relationship between fluorescence intensity-solvent evaporation-quantum yield to obtain the data relationship between the ligand density and the quantum yield of the quantum dots at time t, and then the data relationship can be used to obtain the corrected K SV Thermodynamic data were obtained from the equation.

2. The method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization according to claim 1, characterized in that: In step (1), the concentration of the quantum dots is 1×10 -8 ~1×10 -6 M.

3. The method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization according to claim 1, characterized in that: In step (1), the concentration of the ligand is: quantum dot concentration 1×10 3 ~5×10 4 M.

4. The method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization according to claim 1, characterized in that: In step (1), the organic solvent is chloroform or n-hexane.

5. The method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization according to claim 1, characterized in that: In step (1), the ligand is at least one of oleic acid, butylamine, and a ligand containing mercaptopropionic acid.

6. The method for measuring thermodynamic data between quantum dot surface and ligand by using solvent volatilization according to claim 1, characterized in that: In step (1), the quantum dots are at least one of CdSe quantum dots, ZnS quantum dots, and PbS quantum dots.

7. The method for measuring the thermodynamic data between the quantum dot surface and the ligand by using solvent volatilization according to claim 1, characterized in that: In step (2), the volatilization rate is measured using the weight difference at certain time intervals and the density of the solvent.

8. The method for measuring thermodynamic data between quantum dot surface and ligand by using solvent volatilization according to claim 1, characterized in that: In step (2), the target temperature is higher than the freezing point of the organic solvent and lower than the boiling point of the organic solvent, and at least three values ​​are selected within this range as the target temperature values.

9. The method for measuring thermodynamic data between quantum dot surface and ligand by using solvent volatilization according to claim 1, characterized in that: In step (3), the volatilization amount of the organic solvent should be less than 50% of the original volume.

10. The method for measuring thermodynamic data between quantum dot surface and ligand by using solvent volatilization according to claim 1, characterized in that: In step (4), K before correction SV The equation is: F0 / F T =K SV [Q], Where F0 is the initial fluorescence intensity of the material, F T is the fluorescence intensity after time t, [Q] is the concentration of the corresponding substrate; Since the mechanisms of fluorescence generation and quenching are different, the fluorescence correction coefficient fa is introduced to correct the Ksv equation. The corrected Ksv equation is: In the formula, K a is the binding constant, F0 / (F0-F t )Yes [Q] -1 A linear fit is performed with a slope of (f a K a ) -1 , the intercept is f a -1 , binding constant K a is the quotient of the intercept and the slope.

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