Patent Application
20220379289
This application claims a priority to Chinese Patent Application No. 202010564353.X filed on Jun. 19, 2020, the disclosures of which are incorporated in their entirety by reference herein.
The present disclosure relates to the technical field of quantum dots, and in particular, the present disclosure relates to a quantum-dot ligand, a quantum-dot catalyst including the quantum-dot ligand, and a quantum-dot device including the quantum-dot catalyst.
Quantum dot materials have become an emerging research hotspot in the field of photocatalysis technology due to the advantages of small size, large specific surface area, strong light responsiveness, unique electronic state and optical absorption properties, etc. However, the current quantum dot photocatalysis has shortcomings such as easy recombination of photogenerated carriers (i.e., holes and electrons) and low loading rate of quantum dots on the electrode surface. The extraction and transport of holes in photogenerated carriers is relatively slow, which easily leads to the recombination of photogenerated holes and photogenerated electrons before they reach the electrode surface. This results in low catalytic activity of quantum dots, thereby seriously restricting the application of quantum dot materials in the field of photocatalysis technology.
In a first aspect, an embodiment of the present disclosure provide a quantum-dot ligand, including: a first ligand having a first group and a second group, in which a coordination bond is formed between the first group and a surface of quantum dot, and a hydrogen bond is formed between the second group and a hydroxyl group; and a second ligand having an inorganic ion, in which a coordination bond is formed between the inorganic ion and the surface of the quantum dot.
Optionally, the first ligand has a general formula of R1—R2—R3, in which R1 has a first group, R3 has a second group, and R2 has at least one selected from a carbazole-based structure, a triphenylamine-based structure, or a fluorene-based structure.
Optionally, R1 has a chemical formula of (CH2)nR4, 4≤n≤8, n is an integer, R4 is the first group; and R3 has a chemical formula of (CH2)nR5, 4≤n≤8, n is an integer, and R5 is the second group.
Optionally, R1 is a linear chain, one end of R1 is connected to R2, and the first group is located at the other end of R1.
Optionally, R3 is a linear chain, one end of R3 is connected to R2, and the second group is located at the other end of R3.
Optionally, R2 is
Optionally, the first group is at least one selected from thiol group, amino group or carboxyl group.
Optionally, the second group is at least one selected from amino group, hydroxyl group, carboxyl group, aldehyde group, carbonyl group or ether bond.
Optionally, the inorganic ion is at least one selected from O2−, S2−, Se2−, SCN− or halide ion.
Optionally, the first ligand is:
in which R4 is independently —SH, —NH2 or —COOH, and R5 is independently —OH, —NH2, —COOH, —CHO, —CO— or —O—.
In a second aspect, an embodiment of the present disclosure further provide a quantum-dot catalyst, including quantum dots and the quantum-dot ligand described in any one of the above embodiments, in which a coordination bond is formed between the first group in the first ligand and a surface of the quantum dot, and a coordination bond is formed between the inorganic ion and the surface of the quantum dot.
In a third aspect, an embodiment of the present disclosure further provides a quantum-dot device, including the quantum-dot catalyst described in any one of the above embodiments.
Optionally, the quantum-dot device further includes a positive electrode and a negative electrode, and the quantum-dot catalyst is located between the positive electrode and the negative electrode and is arranged as a layer.
Optionally, surfaces of the positive electrode and the negative electrode have hydroxyl groups, and hydrogen bonds are formed between the second group in the quantum-dot catalyst and the hydroxyl groups on the surfaces of the positive electrode and the negative electrode, respectively.
Optionally, the quantum-dot catalyst is arranged as a single layer of quantum dots or a multilayer of quantum dots.
The technical solutions according to the embodiments of the present disclosure have the following advantageous technical effects.
When the quantum-dot ligand according to the embodiment of the present disclosure is combined with the quantum dots, a coordination bond is formed between the first group and the surface of the quantum dot, hydrogen bond is formed between the second group and a hydroxyl group, and a coordination bond is formed between the inorganic ion and the surfaces of the quantum dots. By forming hydrogen bonds between the second group and the hydroxyl groups on the surface of the electrode, the second group can generate a strong interaction force with the hydroxyl groups to load the quantum dots on the surface of the electrode, thereby improving the loading rate of the quantum dots on the surfaces of the electrodes. The introduction of inorganic ions on the surfaces of the quantum dots is beneficial to reduce the potential barrier for holes to be extracted and separated from the quantum dots, thereby facilitating the separation and extraction of holes and electrons in photogenerated carriers, and is beneficial to hole transport. The quantum-dot catalysts of the embodiments of the present disclosure can enhance the catalytic activity of the quantum dots and improve the catalytic performance.
In order to make the objectives, the technical solutions, and the advantages of the examples of the present disclosure, the technical solutions in the embodiments of the present disclosure will be described clearly and completely hereinafter in conjunction with the drawings. Obviously, the following embodiments relate to a part of, rather than all of, the embodiments of the present disclosure. Based on following embodiments, a person skilled in the art may obtain the other embodiments, which also fall within the scope of the present disclosure.
Photocatalytic hydrogen production technology can convert solar energy into hydrogen energy, which is an effective way to fundamentally solve the energy crisis and environmental problems, so it has been widely concerned. However, the low photocatalytic efficiency limits the application prospects of photocatalytic hydrogen production technology. How to obtain high-performance and low-cost semiconductor photocatalytic materials has become a key issue in the development of photocatalytic technology. Quantum dot materials have become an emerging research hotspot in the field of photocatalysis technology due to the advantages of small size, large specific surface area, strong light responsiveness, unique electronic state and optical absorption properties, etc. In addition, cadmium selenide (CdSe) semiconductor photocatalytic materials possess suitable band gaps, unique crystal structure features, and exhibit excellent photocatalytic performance under visible light. However, the current quantum dots such as CdSe have disadvantages such as easy recombination of photogenerated carriers and low loading rate on the electrode surface. This results in the low catalytic activity of quantum dots, thereby severely restricting their application in the field of catalysis. How to improve the catalytic performance of quantum dots based on semiconductor materials such as cadmium selenide is an urgent problem to be solved.
In view of this, the present disclosure provides a quantum-dot ligand, a quantum-dot catalyst and a quantum-dot device, to solve the problems, such as low loading rate of quantum dots on the electrode surface, easy recombination of photogenerated charges, and slow extraction and transport of holes in photogenerated carriers, thereby improving the catalytic activity of quantum-dot catalysts.
In one aspect, the present disclosure provides a quantum-dot ligand, including a first ligand and a second ligand, in which the first ligand has a first group and a second group, a coordination bond can be formed between the first group and a surfaces of a quantum dot, and hydrogen bond can be formed between the second group and a hydroxyl group; in which the second ligand has inorganic ions, and a coordination bond can be formed between the inorganic ions and the surface of the quantum dot.
Specifically, hydrogen bonds can be formed between the second group and the hydroxyl groups on the surfaces of the electrodes, strong interaction force can be generated between the second group and the hydroxyl groups; and a coordination bond can be formed between inorganic ions in the second ligand and the surfaces of quantum dots such as CdSe. When the quantum-dot ligand according to the embodiment of the present disclosure is combined with the quantum dots such as CdSe, a coordination bond is formed between the first group and the surface of the quantum dot, hydrogen bond is formed between the second group and a hydroxyl group, and a coordination bond is formed between the inorganic ion and the surface of the quantum dot. By forming hydrogen bond between the second group and the hydroxyl groups on the surfaces of the electrode, the second group can generate a strong interaction force with the hydroxyl group to firmly load the quantum dots on the surfaces of the electrodes, thereby improving the loading rate of the quantum dots on the surfaces of the electrodes. The introduction of inorganic ions on the surfaces of the quantum dots is beneficial to reduce the potential barrier for holes to be extracted and separated from the quantum dots. The introduction of inorganic ions on the surfaces of quantum dots can be more beneficial to the separation and extraction of holes and electrons in photogenerated carriers, and is beneficial to hole transport, thereby avoiding secondary recombination of holes and electrons. The quantum dots containing the quantum-dot ligands of the present disclosure can be used as catalysts, to enhance the catalytic activity of the quantum dots and improve the catalytic performance.
In some embodiments of the present disclosure, the general formula of the first ligand may be R1—R2—R3, in which R1 has a first group, R3 has a second group, and R2 has at least one selected from a carbazole-based structure, a triphenylamine-based structure, or a fluorene-based structure.
For example, R2 can be a carbazole-based structure, and an exemplary structural formula of R2 can be:
For example, R2 can be a triphenylamine-based structure, and an exemplary structural formula of R2 can be:
For example, R2 can be a fluorene-based structure, and an exemplary structural formula of R2 can be:
The introduction of a carbazole-based structure, a triphenylamine-based structure or a fluorene-based structure into the ligands of the quantum dots is more beneficial to hole transport, that is, the ligands can quickly transfer the separated and extracted holes to the electrode for reduction reaction. Therefore, such ligands can enhance the catalytic activity of quantum dots and improve the catalytic performance.
In some embodiments of the present disclosure, the chemical formula of R1 has a chemical formula of (CH2)nR4, 4≤n≤8, n is an integer, R4 is the first group; and/or R3 has a chemical formula of (CH2)nR5, 4≤n≤8, n is an integer, and R5 is the second group. The carbon chains in R1 and R3 cannot be too long (no more than 8 carbon atoms), which is beneficial to the separation and extraction of holes and electrons in photogenerated carriers, and is beneficial to hole transport. Furthermore, the ligand can enhance the catalytic activity of the quantum dots and improve the catalytic performance.
In some embodiments of the present disclosure, R1 is a linear chain, one end of R1 is connected to R2, and the first group is located at the other end of R1. The ligand facilitates the formation of a coordination bond between the first group and the surfaces of the quantum dots. In some embodiments of the present disclosure, R3 is a linear chain, one end of R3 is connected to R2, and the second group is located at the other end of R3. The ligand facilitates the formation of hydrogen bond between the second group and hydroxyl groups on the surfaces of the electrodes, so that a strong interaction force is generated between the second group and the hydroxyl groups. This improves the loading rate of quantum dots on the surface of the electrodes.
In some embodiments of the present disclosure, R1 in the first ligand may contain 4 to 8 carbon atoms and have a group such as —SH, —NH2 or —COOH at an end away from R2; and R3 may contain 4 to 8 carbon atoms and have a group such as —OH, —NH2, —COOH, —CHO, —CO— or —O— at an end away from R2.
Optionally, the first group may include at least one of thiol group, amino group or carboxyl group. For example, the first group can be —SH, —NH2 or —COOH. The ligand facilitates the formation of a coordination bond between the first group and the surface of the quantum dots.
Optionally, the second group may include at least one selected from amino group, hydroxyl group, carboxyl group, aldehyde group, carbonyl group or ether bond. For example, the second group can be —NH2, —OH, —COOH, —CHO, —CO— or —O—, and the like. This facilitates the formation of hydrogen bond between the second group and a hydroxyl group, so that a strong interaction force is generated between the second group and the hydroxyl group. For example, as shown in
In some embodiments of the present disclosure, the inorganic ions may include at least one of O2−, S2−, Se2−, SCN−, or halide ions. For example, the halide ion can be F−, Cl−, Br− OR I−. The introduction of the above inorganic ions can be more beneficial to the separation and extraction of holes and electrons in photogenerated carriers, and is also beneficial to hole transport.
In some embodiments of the present disclosure, as shown in
In some embodiments of the present disclosure, the structural formula of the first ligand may be:
in which R4 can be —SH, —NH2 or —COOH, and R5 can be —OH, —NH2, —COOH, —CHO, —CO— or —O—.
For example, the structural formula of the first ligand A can be:
A coordination bond can be formed between —SH in the first ligand A and the surface of the quantum dot, and hydrogen bonds can be formed between —CO— and the hydroxyl groups on the surface of the electrodes, so as to load the quantum dots on the surfaces of the electrodes.
In the process of preparing the quantum-dot ligand of the present disclosure, CdS/CdSe quantum dots could be selected as the quantum dots, and the original ligand is oleic acid. CdS/CdSe quantum dots were prepared by traditional hydrothermal method. After the preparation, ligand exchange was performed in a stratified solution of hexane and DMF (dimethylformamide). Specifically, 500 mg of the first ligand A was added to 100 mg of quantum dot, and after stirring for half an hour at room temperature, the quantum dots would be transferred to the DMF phase due to ligand exchange. The DMF phase was separated from the hexane phase, and methanol was added for precipitation. After centrifugation, the quantum dots were dissolved in DMF. The quantum dots were washed twice, thereby obtaining quantum dots whose ligand was the first ligand A. After dissolving the quantum dots whose ligand was the first ligand A in DMF, 200 mg of sodium sulfide was added, and after stirring at room temperature for half an hour, methanol was added for precipitation. After centrifugation, the quantum dots were dissolved in DMF. The quantum dots were washed twice, thereby obtaining quantum dots whose ligand is a mixture of the first ligand A and S2−. In addition, the ligands in the embodiments of the present disclosure may also be bound to the quantum dots by other existing methods, which will not be repeated herein.
In a second aspect, the present disclosure further provides a quantum-dot catalyst, including: a quantum dot and the quantum-dot ligand according to any one of the above embodiments. The quantum dots may be CdSe quantum dots. A coordination bond was formed between the first group in the first ligand and a surface of the quantum dot, and a coordination bond was formed between the inorganic ion and the surface of the quantum dot.
In the quantum-dot catalyst of the present disclosure, hydrogen bonds were formed between the second group in the first ligand and the hydroxyl groups on the surfaces of the electrodes, and a strong interaction force was generated between the second group and the hydroxyl groups to load the quantum dots on the surfaces of the electrodes, thereby improving the loading rate of quantum dots on the surface of the electrodes. The introduction of inorganic ions on the surfaces of the quantum dots could reduce the potential barrier for holes to be extracted and separated from the quantum dots, which was more beneficial to the separation and extraction of holes and electrons in photogenerated carriers, and was beneficial to hole transport. This avoided the secondary recombination of holes and electrons and improved the catalytic activity of the quantum dots.
In a third aspect, the present disclosure further provides a quantum-dot device, including: the quantum-dot catalyst described in any one of the above embodiments.
In the quantum-dot device of the present disclosure, the quantum-dot catalyst could improve the loading rate of the quantum dots, and could enhance the catalytic activity of the quantum dots, and improve the catalytic performance.
In the embodiment of the present disclosure, as shown in
For example, water could be electrolyzed by the quantum-dot device of the present disclosure. As shown in
Unless otherwise defined, technical terms or scientific terms used herein have the normal meaning commonly understood by one skilled in the art in the field of the present disclosure. The words “first”, “second”, and the like used herein does not denote any order, quantity, or importance, but rather merely serves to distinguish different components. The word “connected” or “connecting” and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “On”, “under”, “left”, “right” and the like are only used to represent relative positional relationships, and when the absolute position of the described object is changed, the relative positional relationship may also be changed, accordingly.
The above description is the optional embodiment of the present disclosure. It should be noted that one skilled in the art would make several improvements and substitutions without departing from the principles of the present disclosure. These improvements and modifications should also be regarded as the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202010564353.X | Jun 2020 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/100536 | 6/17/2021 | WO |
