Single boron cluster molecular switch for electrochemically regulating and controlling hindered Lewis acid-base pair effect

Abstract

The invention discloses a single boron cluster molecular switch for electrochemically regulating and controlling the effect of a hindered Lewis acid-base pair, and belongs to the technical field of molecular electronics. The single-boron cluster molecular switch capable of electrochemically regulating and controlling the action of the hindered Lewis acid-base pair, provided by the invention, is a single-molecular junction formed by a metal substrate, Lewis base and a metal needle tip; by changing the electrode potential of the electrolyte solution containing the Lewis acid, the interaction of the hindered Lewis acid-base pair is regulated and controlled, and the monomolecular switch is realized. Lewis base in the single-molecular junction and Lewis acid in an electrolyte solution can form a hindered Lewis acid-base pair under electrochemical regulation, so that conductivity of the single-boron cluster molecular junction is converted into a high-conductivity state from a low-conductivity state, namely a molecular switch function is realized. According to the invention, a single-molecule switch based on boron cluster molecules is designed by utilizing the principle of electrochemically regulating and controlling the effect of a hindered Lewis pair, and a new method is provided for the design of a high-performance nano electronic device.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular electronics, and in particular relates to a single boron cluster molecular switch for electrochemically regulating the action of a blocked Lewis acid-base pair. Background Art

[0002] As the miniaturization of silicon-based electronic devices approaches physical limits, their performance cannot meet the growing information processing needs of mankind, and there is an urgent need to seek new principle devices and new materials to replace traditional silicon-based devices. As a basic element of logic and storage circuits, single-molecule switches can store digital information by changing the molecular conductance and signals within the logic circuit. Molecular switches need to achieve switching functions through reversible transitions between at least two stable states, which requires the design of various complex molecules with bistable and multistable states, and the change of molecular conformation or spin / redox state through external stimuli such as electric fields, light, pH values ​​and mechanical forces. In this case, how to efficiently regulate the molecular electron transfer efficiency in the same molecular skeleton has become a key issue in the application of molecular switches in logic circuits.

[0003] Clusters are between single molecules and bulk materials, showing intermediate properties, unique quantum effects, rich electrical properties, and peculiar optical, magnetic, and catalytic properties, which are of great significance for the design of ultra-large-scale integrated circuits. In recent years, some progress has been made in the research of clusters in potential electronic applications, such as single-cluster switches, single-cluster transistors, and field effects. However, there are few reports on the reversible switching of conductivity and the realization of molecular switch functions by controlling the interaction between cluster electron donors and acceptors through weak interactions. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a single boron cluster molecular switch for electrochemically regulating the action of hindered Lewis acid-base pairs.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a single boron cluster molecular switch for electrochemically regulating the action of a blocked Lewis acid-base pair, wherein the single boron cluster molecular switch is a single molecule junction formed by a metal substrate-Lewis base-metal needle tip;

[0007] By changing the electrode potential of the electrolyte solution containing Lewis acid, the interaction of the hindered Lewis acid-base pair is regulated to achieve a single-molecule switch.

[0008] The present invention changes the electrode potential so that the Lewis base in the single molecule junction and the Lewis acid in the electrolyte solution form a hindered Lewis acid-base pair, thereby achieving reversible regulation of the single molecule conductivity and further realizing the single molecule switch function.

[0009] Preferably, the Lewis base is a boron cluster anion B 10 H 8 2- .

[0010] Further preferably, the structure of the Lewis base is:

[0011]

[0012] Preferably, the Lewis acid is an organic ammonium cation [NR 4 ] + , R=-CH 3 or -C 2 H 5 .

[0013] The organic ammonium cations in the present invention can interact with the boron cluster anions to form hindered Lewis acid-base pairs, significantly change the electronic structure of the boron cluster anions, enhance molecular electron transport, realize the continuous closing and opening functions of the single boron cluster molecular switch, and also serve as a supporting electrolyte.

[0014] Preferably, the electrode potential is -0.2 V and 0.3 V relative to a Pt reference electrode.

[0015] When the electrode potential is -0.2V, the Lewis acid and Lewis base have not yet interacted, that is, the organic ammonium cation and the boron cluster anion have not yet complexed to form a metal substrate-boron cluster anion-metal needle tip single molecule junction, and the one-dimensional conductivity histogram shows a low conductivity state, corresponding to the "off" state of the single molecule switch; when the electrode potential is increased to 0.3V, the organic ammonium cation will interact with the boron cluster anion to form a hindered Lewis acid-base pair, and form a metal substrate-hindered Lewis acid-base pair-metal needle tip single molecule junction, which significantly changes the electronic structure of the boron cluster anion and enhances molecular electron transport. It appears as a high conductivity state in the one-dimensional conductivity histogram, corresponding to the "on" state of the single molecule switch. By cyclically switching between the two potentials, the continuous "off" and "on" functions of the single boron cluster molecular switch can be achieved.

[0016] Preferably, the electrolyte solution containing Lewis acid is a propylene carbonate solution containing 50 mmol / L organic ammonium cations.

[0017] Preferably, the metal substrate and the metal needle tip are both made of gold.

[0018] Preferably, the metal substrate is a gold sheet with a length×width=10×15 mm and a thickness of 0.5 mm.

[0019] Preferably, the metal needle tip is a gold wire with a diameter of Φ=0.25 mm and a length of 1.5 cm.

[0020] The present invention also provides a method for preparing the single boron cluster molecular switch for electrochemically regulated hindered Lewis acid-base pair action as described in the above technical scheme, comprising the following steps: using electrochemical scanning tunneling microscope splitting technology, in an electrolyte solution containing Lewis base and Lewis acid, changing the distance between the needle tip and the substrate through piezoelectric ceramics to obtain the single boron cluster molecular switch for electrochemically regulated hindered Lewis acid-base pair action.

[0021] Preferably, the preparation method of the electrochemically regulated single boron cluster molecular switch with blocked Lewis acid-base pair action is specifically as follows: placing an electrolytic cell equipped with a metal substrate into a scanning tunneling microscope, adding 200 μL of an electrolyte solution containing a Lewis base and a Lewis acid to the electrolytic cell, and setting the bias voltage to 100 mV; controlling the metal needle tip to continuously approach and contact the metal substrate through piezoelectric ceramics, and when the current is detected to reach 50 nA, controlling the metal needle tip to continue to extend 1.2 nm toward the metal substrate, and then controlling the metal needle tip to move away from the metal substrate at a constant speed of 20 nm / s to form a metal substrate-Lewis base-metal needle tip single molecule junction.

[0022] The specific process of the present invention is:

[0023] (1) The needle tip is controlled by the piezoelectric ceramics of the scanning tunneling microscope to move closer to the metal substrate. When the current reaches the preset value of 50nA, the needle tip is controlled to extend 1.2nm further toward the metal substrate to ensure that the needle tip and the substrate are in contact. The piezoelectric ceramics control the needle tip to move away from the substrate at a constant speed. During the process of moving away, the needle tip first forms atomic contact with the metal substrate. As the distance between the needle tip and the substrate continues to increase, a large number of molecules anchored with gold in the solution are connected to the two ends of the electrode. As the needle tip moves further away, the molecules connected to the two ends of the electrode are disconnected, and finally a connection between the needle tip, a single molecule, and a metal substrate is formed. In this process, by recording the change of current over time or distance, a large amount of molecular conductivity data is obtained by repeating the operation. Finally, the obtained data is statistically analyzed and processed to obtain a one-dimensional conductivity map, and then the single molecule conductivity is obtained; by changing the electrode potential, the conductivity change of the single boron cluster molecule is obtained, and the minimum and maximum conductivity of the single boron cluster molecule under the continuously changing electrode potential are obtained.

[0024] (2) After obtaining the corresponding conductance value, the control potential is scanned between the lowest conductance and the highest conductance to obtain the corresponding current value. When the single boron cluster molecule corresponds to the highest current or conductance value, the single boron cluster molecular switch is in the "on" state; when the single boron cluster molecule corresponds to the lowest current or conductance value, the single boron cluster molecular switch is in the "off" state; the potential change from -0.2V to 0.3V is the process of the single boron cluster molecular switch from off to on.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] The present invention provides a single boron cluster molecular switch based on electrochemically regulated hindered Lewis acid-base pair action. The single boron cluster molecular switch is a single molecule junction formed by a metal substrate-Lewis base-metal needle tip. The Lewis base in the single molecule junction can form a hindered Lewis acid-base pair with the Lewis acid in the electrolyte solution under electrochemical regulation, thereby realizing the conversion of the single boron cluster molecular junction conductivity from a low conductive state to a high conductive state, that is, realizing the function of the molecular switch.

[0027] The present invention utilizes the principle of electrochemical regulation of the action of hindered Lewis acid-base pairs to design a single-molecule switch based on boron cluster molecules, providing a new method for the design of high-performance nanoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0029] Figure 1 Schematic diagram of a single boron cluster molecular switch of a four-electrode system constructed in Example 1 of the present invention;

[0030] Figure 2 The schematic diagram of the single boron cluster molecular switch for electrochemically regulating the action of the hindered Lewis acid-base pair in the present invention;

[0031] Figure 3 This is a graph showing the change of current with potential during potential scanning of a single boron cluster molecular switch in Example 1 of the present invention;

[0032] Figure 4 1. A one-dimensional conductivity cycle diagram of a single boron cluster molecular switch at different potentials in Example 1 of the present invention;

[0033] Figure 5 This is a graph of the boron cluster molecular conductance and potential cycle number of the electrochemically regulated hindered Lewis acid-base single boron cluster molecular switch in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0037] Example 1

[0038] (1) Place a 10mL reagent bottle, a 100mL volumetric flask, an electrolytic cell, and an O-ring in a beaker, add a piranha solution with a volume ratio of concentrated sulfuric acid: hydrogen peroxide = 7:3, and soak for 1 hour. After soaking, pour the piranha solution into a waste liquid tank for centralized treatment, rinse repeatedly with a large amount of ultrapure water, and then boil it with ultrapure water for 3 times (the volumetric flask is not heated). After cleaning, place it in a 105℃ oven and dry it for later use.

[0039] (2) Weigh 27.634 mg C 8 H 8 B 10 N 4 H 8 and 1.1485g[N(C 2 H 5 ) 4 ]ClO 4 Place in a 100 mL volumetric flask, dilute with propylene carbonate and dissolve by ultrasonication to obtain C 8 H 8 B 10 N 4 H 8 The concentration was 1mM, [N(C 2 H 5 ) 4 ]ClO 4 Electrolyte solution with a concentration of 50 mM.

[0040] (3) First, wipe the tweezers and scissors clean with cotton dipped in anhydrous ethanol. Then, use the tweezers to clamp the gold wire with a purity of 99.999% and Φ = 0.25 mm. Use the scissors to cleanly cut 1.5 cm long gold wire to obtain a gold wire with a sharp tip and a smooth cross-section. Wrap the gold wire with paraffin wax, leaving only the tip of the needle exposed.

[0041] (4) A gold sheet with a length, width and thickness of 15 mm × 10 mm × 0.5 mm is used as a metal substrate, and is used together with an Au (111) single crystal electrode as a working electrode. The metal substrate is located in the middle of the electrolytic cell, and the Au (111) single crystal electrode is located in the middle of the metal substrate. A circle of platinum wire is wrapped around the inner wall of the electrolytic cell as a counter electrode, and an external platinum wire is used as a reference electrode. An O-ring is placed in the groove of the electrolytic cell to make the metal substrate fit better with the electrolytic cell and prevent the solution from leaking. The main material of the electrolytic cell is polychlorotrifluoroethylene.

[0042] (5) Pipette 200 μL of the electrolyte solution in step (2) into the electrolytic cell in step (4), control the electrode potential to be -0.2 V relative to the Pt reference electrode, and keep the bias voltage of the gold needle tip and the gold substrate unchanged at 100 mV. Control the piezoelectric ceramic to make the gold needle tip approach the gold substrate and contact it. When the current reaches 50 nA, control the metal needle tip to continue to extend 1.2 nm toward the metal substrate, and then control the metal needle tip to move away from the metal substrate at a constant speed of 20 nm / s, forming a gold substrate-boron cluster anion-gold needle tip single molecule junction, completing the construction of a four-electrode system single boron cluster molecular switch.

[0043] Figure 1 Schematic diagram of a single boron cluster molecular switch of a four-electrode system constructed in Example 1 of the present invention. Figure 1 It can be seen that when the single-molecule switch is in the "off" state, the organic ammonium ions and the boron cluster anions do not complex; when the single-molecule switch is in the "on" state, the organic ammonium ions and the boron cluster anions interact with each other to form hindered Lewis acid-base pairs.

[0044] Figure 2 The schematic diagram of the single boron cluster molecular switch for electrochemically controlling the action of the hindered Lewis acid-base pair in the present invention. Figure 2 It can be seen that when the electrode potential is -0.2V, the organic ammonium ions in the electrolyte solution will not complex with the boron cluster anions, and the single-molecule switch is in the "off" state; when the electrode potential is 0.3V, the organic ammonium ions will interact with the boron cluster anions, and the single-molecule switch is in the "on" state.

[0045] In order to verify the feasibility of electrochemically regulating the single boron cluster molecular switch of the blocked Lewis acid-base in Example 1, the bias voltage of the scanning tunneling microscope was controlled to be constant at 100mV, and the gold needle tip was controlled by piezoelectric ceramics to approach the gold substrate and then move away. When the boron cluster single molecule signal was detected during the process of moving away, the gold needle tip was fixed and the electrode potential was controlled to change from -0.2V to 0.3V relative to the Pt reference, and the current change at this time was recorded. The results are shown in FIG. Figure 3 shown. Figure 3 This is a graph showing the change of current with potential during potential scanning of a single boron cluster molecular switch in Example 1. Figure 3 It can be observed that the current suddenly changes from 0.61nA at the beginning to 1.94nA, realizing the process of single boron cluster single molecule switch from off to on.

[0046] In order to test the reversibility and stability of the switch, the conductivity cycle test of the single boron cluster single molecule switch was carried out. The results are shown in Figure 4. First, the electrode potential was controlled at -0.2V. At this time, the organic ammonium ions in the electrolyte solution had not yet complexed with the boron cluster anions to form a gold substrate-boron cluster anion-gold needle tip single molecule junction, which was displayed as a lower conductivity value in the one-dimensional conductivity histogram, corresponding to the "off" state of the single molecule switch; then the potential was increased to 0.3V, at which time the organic ammonium ions interacted with the boron cluster anions to form a hindered Lewis acid-base pair, and formed a gold substrate-hindered Lewis acid-base pair-gold needle tip single molecule junction, which significantly changed the electronic structure of the boron cluster anions, enhanced molecular electron transport, and showed a higher conductivity value, corresponding to the "on" state of the single molecule switch. The potential was further reduced to -0.2V, and the high conductivity state disappeared and transformed into a low conductivity state. The two potentials were switched 20 times in a cycle, and the conductivity value changed accordingly with the potential, showing good reversibility and stability.

[0047] Figure 5 The graph of the boron cluster molecular conductance and potential cycle number of the electrochemically controlled hindered Lewis acid-base single boron cluster molecular switch in Example 1. Figure 5 It can be seen that when the electrode potential is -0.2V, it exhibits a lower conductivity value. When the potential is increased to 0.3V, it exhibits a higher conductivity value. The two potentials are switched 20 times, and the conductivity value changes accordingly with the potential.

[0048] Comparative Example 1

[0049] The difference from Example 1 is that the C in step (2) 8 H 8 B 10 N 4 H 8 Replace with C 16 H 12 N 2 The remaining steps are the same as in Example 1. The control electrode potential is changed from -0.2 V to 0.3 V relative to the Pt reference, and the conductivity value does not change with the potential, indicating that the single-molecule switch function cannot be achieved by changing the Lewis base (ie, without the boron cluster anion).

[0050] Comparative Example 2

[0051] The difference from Example 1 is that [N(C 2 H 5 ) 4 ]ClO 4 Replaced by KPF 6 The remaining steps are the same as in Example 1. The control electrode potential is changed from -0.2 V to 0.3 V relative to the Pt reference, and the conductivity value does not change with the potential, indicating that the single molecule switch function cannot be achieved by changing the Lewis acid.

[0052] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A single boron cluster molecular switch for electrochemically regulating the action of a hindered Lewis acid-base pair, characterized in that: The single boron cluster molecular switch is a single molecule junction formed by a metal substrate-Lewis base-metal needle tip; By changing the electrode potential of the electrolyte solution containing Lewis acid, the interaction of the hindered Lewis acid-base pair is regulated to achieve a single-molecule switch.

2. The electrochemically controlled single boron cluster molecular switch for hindered Lewis acid-base pair action according to claim 1, characterized in that: The Lewis base is a boron cluster anion B 10 H8 2- .

3. The electrochemically controlled single boron cluster molecular switch for hindered Lewis acid-base pair action according to claim 1, characterized in that: The Lewis acid is an organic ammonium cation [NR4] + , R=-CH3 or -C2H5.

4. The single boron cluster molecular switch for electrochemically controlling the hindered Lewis acid-base pair according to claim 1, characterized in that: The electrode potentials were -0.2 V and 0.3 V relative to a Pt reference electrode.

5. The electrochemically controlled single boron cluster molecular switch for hindered Lewis acid-base pair action according to claim 1, characterized in that: The electrolyte solution containing Lewis acid is a propylene carbonate solution containing 50 mmol / L organic ammonium cations.

6. The electrochemically controlled single boron cluster molecular switch for hindered Lewis acid-base pair action according to claim 1, characterized in that: The metal substrate and the metal needle tip are both made of gold.

7. The single boron cluster molecular switch for electrochemically controlling the hindered Lewis acid-base pair according to claim 6, characterized in that: The metal substrate is a gold sheet with a length×width=10×15 mm and a thickness of 0.5 mm.

8. The single boron cluster molecular switch for electrochemically controlling the hindered Lewis acid-base pair according to claim 6, characterized in that: The metal needle tip is a gold wire with a diameter of Φ=0.25 mm and a length of 1.5 cm.

9. The method for preparing the electrochemically controlled hindered Lewis acid-base pair single boron cluster molecular switch according to any one of claims 1 to 8, characterized in that: The following steps are involved: The electrochemical scanning tunneling microscope split junction technology is adopted to change the distance between the needle tip and the substrate through piezoelectric ceramics in an electrolyte solution containing Lewis base and Lewis acid, thereby obtaining the single boron cluster molecular switch for electrochemically regulating the blocked Lewis acid-base pair action.

10. The preparation method according to claim 9, characterized in that: The preparation method of the electrochemically regulated single boron cluster molecular switch that blocks the action of Lewis acid-base pairs is specifically as follows: placing an electrolytic cell equipped with a metal substrate in a scanning tunneling microscope, adding 200 μL of an electrolyte solution containing Lewis base and Lewis acid to the electrolytic cell, and setting the bias voltage to 100 mV; controlling the metal needle tip to continuously approach and contact the metal substrate through piezoelectric ceramics, and when the current is detected to reach 50 nA, controlling the metal needle tip to continue to extend 1.2 nm toward the metal substrate, and then controlling the metal needle tip to move away from the metal substrate at a constant speed of 20 nm / s to form a metal substrate-Lewis base-metal needle tip single molecule junction.

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