A method for realizing an in-situ controllable single-molecule rectifier based on intramolecular hydrogen bonding

Abstract

A method for achieving in-situ controllable single-molecule rectifiers based on intramolecular hydrogen bonds involves multiple fields such as molecular electronics, nanomaterials, and chemistry. We used scanning tunneling microscopy (STM) to measure the current-voltage characteristics of a class of β-diketone derivatives, revealing a significant rectification effect. This effect is attributed to the stable intramolecular hydrogen bonds present in the enol configuration of the β-diketone derivatives, and these intramolecular hydrogen bonds participate in charge transport. This discovery demonstrates that β-diketone derivative single-molecule junctions have the potential to achieve molecular rectifier performance within an extremely short molecular length of approximately 1 nanometer. Compared to previous molecular rectifiers with asymmetric and complex structures, the molecular rectifier functional groups in this method have simpler structures, are easier to synthesize and modify, have lower costs, and higher conductivity. Furthermore, by altering the external environment, the rectification performance of the molecules can be actively and in-situ controlled. In addition, the process of achieving the rectification function is energy-efficient and low-noise, which is beneficial for future integration into molecular devices.

Description

Technical Field

[0001] This invention is applied to the fabrication of nanoscale in-situ controllable rectifiers at the molecular scale, involving many fields such as molecular electronics, nanomaterials, and chemistry. Background Technology

[0002] With the rapid development of the information age, the size limit of silicon-based semiconductor electronic devices is gradually approaching, making the miniaturization and integration of electronic components such as rectifiers, switches, transistors, and memories increasingly urgent. In recent years, nanoscale oligomeric single molecules have been considered the best alternative to silicon-based semiconductors to break Moore's Law due to their broad range of candidate molecules with optical, electrical, ionic, magnetic, thermal, mechanical, and chemical reactivity, as well as their ease of modification. Developing single-molecule devices is seen as a potential solution to overcome this challenge. Therefore, molecular electronics is booming, with the development of next-generation molecular-level rectifier devices attracting significant attention. To date, various methods have been used to realize molecular rectifiers. For example, designing diblock molecules containing two conjugated modules with opposite electron requirements, similar to a semiconductor pn junction, can achieve molecular rectifier functionality. Other methods include transition metal gate-induced molecular rectifier designs and anchoring group-induced molecular rectifier designs. However, these molecular rectifiers require complex molecular structures, long lengths, low conductivity, and are difficult and costly to synthesize. Therefore, achieving rectification performance within short molecules is crucial. Furthermore, in current research on single-molecule rectifiers, it is extremely difficult to control the rectification characteristics in situ without damaging the circuit after introducing the molecule rectifier into the circuit.

[0003] Hydrogen bonding is a common intermolecular force, referring to the attractive force between a hydrogen atom in a strongly polar bond and an atom with high electronegativity, a lone pair of electrons, and a partial negative charge. Studies have shown that the presence of intramolecular hydrogen bonds could potentially enable molecular devices to possess rectifying properties; however, intramolecular hydrogen bonds are often unstable due to factors such as conformational instability. In β-diketone derivatives, intramolecular hydrogen bonds help stabilize their enol isomers. Conversely, precisely because their enol configuration is stable, the intramolecular hydrogen bonds in β-diketone derivatives are more stable than other hydrogen bonds.

[0004] Scanning Tunneling Microscope-Break Junction (STM-BJ) technology is often used to construct and study the electrical properties of single-molecule devices. This equipment is stable, simple to set up, easy to operate, and has high reproducibility.

[0005] Here, we used STM-BJ to measure the voltammetric characteristics of a class of β-diketone derivatives (with a molecular length of only about 1 nm and easy to synthesize), and found that they have a significant rectification effect, proving that the β-diketone derivative monolayer has the performance of a molecular rectifier. Furthermore, by altering the external environment through methods such as ultraviolet light irradiation, the rectification performance of the molecular rectifier can be controlled in situ. Summary of the Invention

[0006] This invention provides a method for realizing molecular rectifier functionality based on stable intramolecular hydrogen bonds. The rectification effect originates from the molecule itself and is independent of electrodes, solvents, instruments, and other environmental factors. Furthermore, it can be achieved in both monomolecular junctions and self-assembled molecular layers, demonstrating potential for integration. Additionally, the rectification performance of the molecular rectifier can be controlled in situ by altering the external environment through methods such as ultraviolet irradiation and changing polarity. The structure and conditions for forming the rectifier are simple and clear, the fabrication process is straightforward, and it is easy to integrate.

[0007] The experimental scheme adopted in this invention is as follows:

[0008] The structure used in this method consists of a gold-tipped top electrode, a molecular solution or self-assembled monolayer, a bottom electrode composed of a silicon substrate, a 10nm chromium plating layer, and a 200nm gold plating layer, forming a gold-molecule-gold monomolecular structure. STM-BJ technology was used to perform electrical tests on the monomolecular junction, scanning the current-voltage characteristic curve in the range of -1.5V to 1.5V.

[0009] The technical advantages of this invention are: This method utilizes intramolecular interaction forces to achieve molecular rectifier performance. The rectification effect originates from the supply and acceptance of intramolecular forces within the molecule, requiring no molecular structural asymmetry and independent of external control, achieving nanoampere-level rectification performance and a rectification ratio of 2.1 times within an extremely short molecular length of approximately 1 nanometer. The molecular rectifier functional groups have simple structures, are easy to synthesize and modify, have low cost, and high conductivity. Notably, the rectification performance of the molecular rectifier can be controlled in situ by altering the external environment through ultraviolet irradiation, changing polarity, etc. During operation, this type of rectifier offers diversity in the use of substrate and electrode materials, and the groups that generate intramolecular interaction forces are easily modified, resulting in minimal bias voltage across the electrodes and achieving low energy consumption. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a β-diketone derivative unimolecular junction.

[0011] Figure 2 The figure shows the voltammetric characteristics of the enol unimolecular junction of the β-diketone derivative.

[0012] Figure 3This is a schematic diagram of a unimolecular structure of a β-diketone derivative after the breaking of intramolecular hydrogen bonds, where the enol form is converted to the ketone form.

[0013] Figure 4 The figure shows the voltammetric characteristics of a keto unaryl junction of a β-diketone derivative.

[0014] Figure 5 A comparison of the voltammetric characteristics of keto and enol unimolecular junctions of β-diketone derivatives.

[0015] In the figure: 1 is the top electrode, 2 is the bottom electrode, 3 is the analyte molecule, 1,3-bis(pyridin-4-yl)propane-1,3-dione (enol form), and 4 is 1,3-bis(pyridin-4-yl)propane-1,3-dione (keto form). Detailed Implementation

[0016] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] Example: The top electrode (1) is a gold electrode made of a gold ball calcined in the outer flame of a butane flame by a gold wire with a diameter of 0.25 mm. The bottom electrode is a gold electrode made by sputtering a 10 nm chromium layer and a 200 nm gold layer on a 1×2 cm silicon substrate. The analyte molecule 1,3-bis(pyridin-4-yl)propane-1,3-dione has an enol configuration (3, containing intramolecular hydrogen bonds) in the nonpolar solvent 1,2,4-trichlorobenzene (TCB). A 0.1 mM solution of 1,3-bis(pyridin-4-yl)propane-1,3-dione in TCB was prepared for later use. 1.5 μL of the target solution was then dropped between the top electrode (1) and the bottom electrode (2) using a pipette to obtain the following result: Figure 1 The single-molecule junction is shown. The current-voltage characteristic curves were measured using an STM-BJ instrument, yielding... Figure 2 The current-voltage characteristic curve shown is for a rectification ratio of 2.1 (obtained by statistical fitting of no less than 1000 curves).

[0018] To break intramolecular hydrogen bonds and convert the molecular configuration to the keto form, thereby achieving in-situ control of molecular rectification properties, the monomolecular junction was irradiated with 365 nm ultraviolet light (UV flashlight, 20 cm away from the molecular junction). After 2 hours, the molecule was completely converted to the keto form, yielding the following result: Figure 3 The single-molecule junction is shown. At this point, the current-voltage characteristic curve is measured using an STM-BJ instrument, yielding... Figure 4 The current-voltage characteristic curve shown is without rectification performance (obtained by statistical fitting of no less than 1000 curves).

[0019] Figure 5 for Figure 2 and Figure 4The combined diagram clearly shows that after the analyte changes from the enol form to the keto form, the conductivity decreases and the rectification ratio is 1, thus achieving in-situ control of the rectification performance.

[0020] Although the invention has been described in conjunction with the experiments conducted to date, it is not limited to the disclosed embodiments, but is intended to cover equivalent methods within the spirit and scope of the appended claims.

Claims

1. A method for realizing in-situ controllable single-molecule rectifier function based on intramolecular hydrogen bond, characterized in that: The asymmetric structure and the additional electron transport channel brought by the stable intramolecular hydrogen bond realize the performance of the single-molecule rectifier in the electrode-molecule-electrode single-molecule junction, and the rectification performance of the molecule can be controlled in situ by changing the external environment; The electrode-molecule-electrode single-molecule junction is composed of a top electrode, a molecular solution or a self-assembled monolayer, and a bottom electrode; The molecule in the electrode-molecule-electrode single-molecule junction is 1,3-bis (pyridine-4-yl) propane-1,3-dione, and the to-be-tested molecule 1,3-bis (pyridine-4-yl) propane-1,3-dione is in enol form in a non-polar solvent 1,2,4-trichlorobenzene; The means for changing the external environment is to irradiate the electrode-molecule-electrode single-molecule junction with ultraviolet light of 365 nm, and after 2 hours, the 1,3-bis (pyridine-4-yl) propane-1,3-dione is completely converted into ketone.

2. The method of claim 1, wherein the method is characterized by: The electrode-molecule-electrode single-molecule junction is constructed by STM-BJ.

3. The method of claim 1, wherein the method is characterized by: The intramolecular hydrogen bond includes O—H…O.

4. The method of claim 1, wherein the method is characterized by: The rectification performance comes from the molecule itself, and the two electrode materials used include one of gold, silver, and copper.

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