A method for measuring the thermodynamic data between quantum dot surface and ligand using solvent evaporation

Abstract

The present 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. The method comprises the following steps: preparing a ligand-modified quantum dot organic solvent solution of a certain concentration and allowing the solution to stand until the fluorescence intensity stabilizes; determining the volatilization rate of the organic solvent at a target temperature; volatilizing the prepared quantum dot organic solvent solution in the same environment and detecting the fluorescence intensity of the quantum dots in real time to obtain a fluorescence intensity-time curve showing the real-time fluorescence intensity changing with time; converting the obtained fluorescence intensity-time curve into a data relationship between the ligand density and the quantum dot quantum yield at time t through the relationship between fluorescence intensity-solvent volatilization-quantum yield, and then using the data relationship to calculate the relationship between the ligand density and the quantum dot quantum yield through a modified K SV The method of the present invention is simple, accurate and has practical operability.

Description

Technical Field

[0001] The present 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. Its advantages include sensitivity, traceability, accuracy, and convenience, making it widely used in small molecule measurements. With the rise of nanoparticles, this method has begun to be applied to measuring interactions between nanoparticles and other substances. However, it is important to note that nanoparticles are large platforms with enormous surface areas. This means that, unlike interactions between small molecules, interactions between nanoparticles and other substances may not be assumed to be consistent.

[0003] The mechanism of fluorescence quenching by 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 the quantum dots bind to the ligands in the ground state, causing changes in fluorescence intensity. The binding mode between the fluorescent material M (quantum dot) 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 concentration of the material without undergoing a change in physical properties. On the other hand, the binding constant K is not a constant term. In fact, the adsorption behavior of ligands on the surface of quantum dots is actively promoted and strongly correlated with surface coverage. This means that traditional fluorescence titrations cannot produce useful data, as they assume constant thermodynamic data. In our previous work, we found that the thermodynamic data of quantum dot surfaces are clearly related to the ligand coverage 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, but there is a lot of controversy regarding ligand-surface thermodynamics. This controversy often spans five to six orders of magnitude, resulting in significant bias or error in the data obtained. Due to this significant controversy, measurements of ligand thermodynamics on quantum dot surfaces have decreased in recent years. However, 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 thermodynamic data of the ligand and the quantum dot surface as the ligand density changes by using the fluorescence titration method. It 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) Prepare a certain concentration of ligand-modified quantum dot organic solvent solution and let it stand until the fluorescence intensity stabilizes;

[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 into the data relationship between the ligand density and the quantum yield of the quantum dots at time t through the relationship between fluorescence intensity-solvent evaporation-quantum yield, 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 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 step (2), the volatilization rate is measured 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] Where K a is the binding constant, F0 / (F0-F t ) to [Q] -1 Perform a linear fit 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 practically meaningful quantum dot-ligand thermodynamic data; at the same time, the method of dynamically detecting the quantum dot-ligand thermodynamic data under different ligand densities by using a fluorescence titration method can simplify the experimenter's operation to a certain extent, and the consistency of the data can greatly reduce the errors caused by operational errors. It is simple, accurate and practically operable; it has universal applicability 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 fluorescence intensity change (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 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 cell 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 multiple times, and the quantum yield of the product obtained after each purification was measured. When the quantum yield after two purifications showed a significant difference, 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 at 600nm) is placed in a 250mL separatory funnel; the container is placed in a constant temperature water bath to maintain a suitable temperature and let it stand for at least 1 day. (For example, here it is 25℃, 31℃, 37℃); the volatilization rate of the oleic acid solution is detected in a fluorescence detection device at the corresponding temperature. The specific method is to select a marked fluorescence pool, use a pipette to aspirate 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. After a period of time, take it out and measure it again. In the same environment, still select the marked fluorescence pool, put the prepared 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 fluorescence intensity curve over 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 dot 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] Where K a is the binding constant, F0 / (F0-F t ) to [Q] -1 Perform a linear fit 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 deviates far from the ideal upper line. This means that there is an interaction between the ligand and the quantum dots, and the magnitude of the interaction can be estimated by the thermodynamic approximation system.

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

[0047] like Figure 3 As shown in FIG. 1 , the processed data obtained in Example 1 of the present invention is obtained along with f a Variation of k a The obtained curve (23℃); it can be seen that as f a The larger the k a This means that there is a significant ligand effect as the ligand binds to the quantum dot surface. In our process, this means that increasing the ligand concentration increases the binding constant between the quantum dot and the ligand, which is consistent with the conclusions of related work.

[0048] like Figure 4 As shown, this is a fluorescence cell 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 same intensity of ultraviolet light, the fluorescence intensity has changed significantly.

[0049] Example 2

[0050] Chloroform was used as solvent to prepare 2.5×10 -780mL of a quantum dot solution containing 3.5mM oleic acid (fluorescence emission peak position at 600nm) was placed in a 250mL separatory funnel; the container was placed in a constant temperature water bath to maintain a suitable temperature and allowed to stand for at least 1 day. (For example, here it was 23°C, 30°C, 37°C, and 44°C); the volatilization rate of the oleic acid solution was detected in a fluorescence detection device at different temperatures. The specific method is to select a labeled fluorescence cell, use a pipette to aspirate about 3mL of chloroform, first measure the overall mass using an analytical balance, then let it stand at the corresponding temperature and record the time. After a period of time, take it out and measure it again. In the same environment, still select the labeled fluorescence cell, and after the initial measurement, place the prepared quantum dot solution in a fluorescence detection device for volatilization. The fluorescence intensity of the quantum dots is detected in real time using the fluorescence detection device to obtain a real-time fluorescence intensity curve 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 dot at time t, and then the K value can be approximated by 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] Where K a is the binding constant, F0 / (F0-F t ) to [Q] -1 Perform a linear fit 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 -780mL of a 600nm emitting CdSe quantum dot solution containing mercaptopropionic acid ligands in a 5mM butylamine environment was placed in a 250mL separatory funnel. The container was placed in a constant temperature water bath to maintain a suitable temperature (such as 25°C, 31°C, and 37°C in this case) and allowed to stand for at least 1 day. The volatilization rate of the oleic acid solution was measured in a fluorescence detection device at different temperatures. The specific method is to select a labeled fluorescence cell, use a pipette to aspirate approximately 3mL of chloroform, first measure the total mass using an analytical balance, then let it stand at the corresponding temperature, record the time, and remove it after a period of time and measure it again. In the same environment, the labeled fluorescence cell was still selected. After the initial measurement, the prepared quantum dot solution was placed in a fluorescence detection device for volatilization. The fluorescence intensity of the quantum dots was measured in real time using the fluorescence detection device to obtain a real-time fluorescence intensity change curve over 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 dot at time t, and then the K value can be approximated by 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] Where K a is the binding constant, F0 / (F0-F t ) to [Q] -1 Perform a linear fit 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 -780mL of a CdSe / ZnS quantum dot solution (fluorescence emission peak at 620nm) in a 3.5mM oleic acid environment was placed in a 250mL separatory funnel; the container was placed in a constant temperature water bath to maintain a suitable temperature and allowed to stand for at least 1 day. (For example, here it was 25°C, 31°C, and 37°C); the volatilization rate of the oleic acid solution was measured in a fluorescence detection device at different temperatures. The specific method is to select a labeled fluorescence cell, use a pipette to aspirate approximately 3ml of chloroform, first measure the overall mass using an analytical balance, then let it stand at the corresponding temperature and record the time. After a period of time, take it out and measure it again. In the same environment, still select the labeled fluorescence cell, and after the initial measurement, place the prepared quantum dot solution in a fluorescence detection device for volatilization. The fluorescence intensity of the quantum dots is detected in real time using the fluorescence detection device to obtain a real-time fluorescence intensity change curve over 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 dot at time t, and then the K value can be approximated by 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] Where K a is the binding constant, F0 / (F0-F t ) to [Q] -1 Perform a linear fit 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 -780mL of PbS quantum dot solution (fluorescence emission peak at 1300nm) in a 3.5mM oleic acid environment is placed in a 250mL separating funnel; the container is placed in a constant temperature water bath to maintain a suitable temperature and allowed to stand for at least 1 day. (For example, here it is 25°C, 31°C, and 37°C); 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 cell, use a pipette to aspirate 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. After a period of time, take it out and measure it again. In the same environment, still select the marked fluorescence cell, put the prepared 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 fluorescence intensity curve over 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 dot at time t, and then the K value can be approximated by 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] Where K a is the binding constant, F0 / (F0-F t ) to [Q] -1 Perform a linear fit 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 description 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 principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.

Claims

1. A method for measuring thermodynamic data between quantum dot surfaces and ligands using solvent evaporation, characterized by: The following steps are involved: (1) Prepare a certain concentration of ligand-modified quantum dot organic solvent solution and let it stand until the fluorescence intensity stabilizes; (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 fluorescence intensity-time curve was converted into the relationship between fluorescence intensity-solvent evaporation-quantum yield. t The data relationship between the ligand density and the quantum yield of the quantum dots at the moment can be used to obtain the corrected K SV Thermodynamic data were obtained from the equation; In step (4), K before correction SV The equation is: , 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: ； Where K a is the binding constant, F0 / (F0-F t )right[ Q ] -1 Perform a linear fit 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.

2. The method for measuring thermodynamic data between quantum dot surfaces and ligands using solvent volatilization according to claim 1, wherein: In step (1), the concentration of the quantum dots is 1×10 -8 -1×10 -6 M.

3. The method for measuring thermodynamic data between quantum dot surfaces and ligands using solvent volatilization according to claim 1, wherein: In step (1), the concentration of the ligand is: quantum dot concentration 1×10 3 -5×10 4 M.

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

8. The method of measuring thermodynamic data between quantum dot surface and ligand 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 of measuring thermodynamic data between quantum dot surface and ligand 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.

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