Microwave manipulated graphene electrode cobalt-based complex molecular device and preparation method thereof

Abstract

The present application relates to the technical field of molecular device, and particularly relates to a microwave-operated graphene electrode cobalt-based complex molecular device and a preparation method thereof.The molecular device comprises a molecular junction composed of a graphene source electrode, a cobalt-based complex molecule and a graphene drain electrode.The graphene source electrode and the graphene drain electrode form a graphene electrode pair, and the cobalt-based complex molecule is connected between the graphene electrode pair by a covalent bond.The graphene source electrode and the graphene drain electrode are modified by edge carboxylation, and the carboxyl functional groups can form stable covalent bonds with the Co-based complex molecule, so that the Co-based complex molecule is anchored between the two electrodes to form a structurally stable molecular conductive path.The molecular device is constructed based on a nanoscale functional molecule, has a small volume and is conducive to realizing high-density integration.The preparation method has the advantages of simple operation, controllable conditions and high repeatability, and is conducive to large-scale production.

Description

Technical Field

[0001] This invention relates to the field of molecular device technology, and in particular to microwave-controlled graphene electrode cobalt-based complex molecular devices and their preparation methods. Background Technology

[0002] The development of quantum information technology has placed high demands on the precise manipulation of single-spin states. Microwave-driven electron spin resonance (ESR), with its non-contact, programmable, and low-heat-dissipation characteristics, has become the main method for realizing high-fidelity quantum logic in systems such as solid-state defect centers and superconducting qubits. In recent years, with the maturity of on-chip coplanar waveguides, three-dimensional superconducting resonators, and scanning probe microwave near-field technologies, microwave pulse sequences can achieve arbitrary shaping of amplitude, phase, and frequency on a sub-nanosecond scale, enabling single-spin-flip fidelity to exceed 99.9%, laying the engineering foundation for room-temperature scalable quantum devices. However, the above progress has mainly focused on inorganic crystal defects or artificial quantum dots. For chemically tunable single-molecule spin systems, there is currently a lack of universal microwave manipulation schemes compatible with solution, thin film, and crystal environments.

[0003] Traditional electron paramagnetic resonance (ESR) measurements depend on 10 12 ~10 13 For ensemble molecules of this magnitude, the spectral lines are severely broadened due to g-factor, zero-field splitting, hyperfine coupling, and heterogeneous distribution of molecular orientations. This results in intrinsic parameters being submerged within a linewidth of 0.1–1 mT, making it impossible to resolve the fine structure of individual complexes. Furthermore, ensemble averaging masks differences in intermolecular magnetization relaxation and chemical environment, making coherent manipulation and readout of specific spin states difficult. For transition metal complexes with high anisotropy and low symmetry, conventional ESR struggles to even determine the direction of their easy magnetization axis, let alone achieve directional flipping via microwave pulses, severely hindering the material selection and device fabrication of molecular spin qubits.

[0004] Single-molecule ESR, by coupling scanning probes, superconducting resonant cavities, or plasma nanoantennas with microwave technology, can focus microwave magnetic fields to the nanoscale, thereby selectively exciting individual molecules. Its advantages include: 1. Eliminating heterogeneous broadening, narrowing linewidth by two orders of magnitude, enabling the resolution of sub-megahertz zero-field splitting and hyperfine transitions; 2. Achieving single-molecule-limited spatial selectivity, with a flip fidelity >99%, and allowing for multi-molecule coupling measurements by combining with pulsed electron double resonance (PELDOR); 3. A 5-7 times improvement in coherence time T2 compared to the ensemble, providing a sufficiently long coherence window for room-temperature quantum logic; 4. Strong chemical designability, allowing for the modulation of the g-tensor, zero-field splitting D-value, and spin-lattice relaxation rate through ligand modification.

[0005] However, single-molecule ESR still faces significant challenges: First, the magnetic moment of a single molecule is only 1–10 μB, corresponding to a weak microwave permeability signal, requiring high-quality micro / nano resonators with femtotes-level sensitivity for magnetic field detection; second, 3d... 7 Ions exhibit large anisotropy and strong spin-orbit coupling, causing the transition frequency to change drastically with orientation. This requires microwave sources to rapidly hop frequencies and provide real-time feedback within a wide bandwidth of 0.1–40 GHz. Furthermore, vibration-rotation coupling at room temperature, conductive substrate noise, and paramagnetic impurities in oxygen molecules all shorten the coherence time, necessitating the development of chip-level architectures that are compatible with surface passivation, vacuum packaging, and low-temperature strong magnetic fields.

[0006] Therefore, there is an urgent need to provide a new type of microwave-controlled molecular device. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the related art. Therefore, the first objective of the present invention is to provide a microwave-controlled graphene electrode cobalt-based complex molecular device; the second objective of the present invention is to provide a method for preparing a microwave-controlled graphene electrode cobalt-based complex molecular device.

[0008] To achieve the first objective, the technical solution adopted by this invention is as follows:

[0009] A microwave-controlled graphene electrode cobalt-based complex molecular device includes a graphene electrode pair and a Co-based complex molecule, wherein the Co-based complex molecule is assembled between the graphene electrode pair through a chemical reaction.

[0010] The structural formula of the Co-based complex molecule is shown below:

[0011] ;

[0012] R1 is selected from -OH or -NH2, and R2 is selected from halogens.

[0013] The graphene electrode pair employs edge carboxylation modification, allowing the carboxyl functional groups to form stable covalent bonds with Co-based complex molecules. This anchors the Co-based complex molecules between the two electrodes, creating a structurally stable molecular conductive pathway, i.e., a molecular junction. The Co-based complex molecules form a coordination structure centered on the Co ion, and their electronic structure (such as the d-orbital electronic configuration of Co and the molecular frontier orbital energy levels) is sensitive to microwave electromagnetic fields. Under the influence of a microwave field, the electronic states of the Co-based complex molecules (such as spin states and electronic transition behavior) change, thereby modulating the electronic transport characteristics of the molecular junction. By adjusting parameters such as the microwave frequency and power, precise control of the device's electrical performance can be achieved.

[0014] Preferably, R1 is selected from -NH2 and R2 is selected from Cl.

[0015] Preferably, under low-temperature conditions, microwaves can drive quantum state transitions of the spins of the Co-based complex molecules;

[0016] The low temperature range is -272.15℃ to -0.15℃.

[0017] Preferably, the microwave frequency range is 9 GHz to 11 GHz.

[0018] Preferably, the graphene electrode pair includes a graphene source electrode and a graphene drain electrode.

[0019] The gap between the graphene source electrode and the graphene drain electrode is 0.5 nm to 2 nm.

[0020] Preferably, a single Co-based complex molecule is connected between the graphene source electrode and the graphene drain electrode.

[0021] Preferably, the graphene electrode pair is made of a single-layer graphene film.

[0022] Preferably, the substrate is also included, wherein the graphene electrode pair is disposed on the surface of the substrate, and the substrate is selected from a silicon wafer covered with a SiO2 layer.

[0023] To achieve the second objective, the technical solution adopted by this invention is as follows:

[0024] A method for preparing microwave-controlled graphene electrode cobalt-based complex molecular devices, used to prepare any of the above-described microwave-controlled graphene electrode cobalt-based complex molecular devices, comprising the following steps:

[0025] S100: Using single-layer graphene film as raw material, edge-carboxylated graphene electrode pairs are prepared by photolithography and oxygen plasma technology.

[0026] S200. Using a condensation reaction, Co-based complex molecules are assembled between the graphene electrode pairs to obtain a microwave-controlled graphene electrode cobalt-based complex molecular device.

[0027] Preferably, the condensation reaction is an amide condensation reaction, and the carboxyl activator for the amide condensation reaction is selected from 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0028] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0029] This invention provides a microwave-controlled graphene electrode cobalt-based complex molecular device, comprising a graphene electrode pair and Co-based complex molecules. The Co-based complex molecules are assembled between the graphene electrode pairs via a chemical reaction. The graphene electrode pairs are modified with edge carboxylation, allowing the carboxyl functional groups to form stable covalent bonds with the Co-based complex molecules, anchoring the Co-based complex molecules between the two electrodes and forming a structurally stable molecular conductive pathway (molecular junction). This molecular device is constructed based on nanoscale functional molecules, resulting in a small device size that facilitates high-density integration, aligning with the miniaturization trend of micro- and nanoelectronic devices.

[0030] Under constant bias, the spin state of cobalt ions in cobalt-based complexes can be altered by modulation with microwave signals. Experimental results show that cobalt-based complex molecules in the low-spin state undergo spin level transitions under microwave irradiation, exhibiting significant quantum state manipulation characteristics. This microwave-based non-contact manipulation eliminates the need for additional contact electrodes, avoiding signal interference at contact interfaces and making it more suitable for remote and precise control of micro / nano-scale devices.

[0031] Cobalt-based complex molecules are covalently linked to graphene electrode pairs, resulting in stronger bonds compared to physical adsorption. This effectively improves the operational stability and cycle life of molecular devices, as well as their chemical stability, ensuring long-term stable and reliable operation under complex conditions.

[0032] The preparation method provided by this invention has the advantages of simple operation, controllable conditions, and high repeatability, which is conducive to the large-scale preparation and industrialization of the device.

[0033] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the microwave-controlled graphene electrode cobalt-based complex molecular device provided in Embodiment 2 of the present invention.

[0035] Figure 2 This is a time-current (It) curve of a microwave-controlled graphene electrode cobalt-based complex molecular device provided in Embodiment 2 of the present invention.

[0036] Figure 3 This is the Rabi oscillation curve of the microwave-controlled graphene electrode cobalt-based complex molecular device provided in Embodiment 2 of the present invention.

[0037] Figure label:

[0038] 1. Graphene source electrode; 2. Co-based complex molecule; 3. Graphene drain electrode. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention, but cannot be used to limit the scope of this invention.

[0040] In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available, unless otherwise specified, and are carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0041] Example 1

[0042] Synthesize Co-based complex molecules with the following structural formulas:

[0043]

[0044] The process is as follows:

[0045] I. Synthesis of Compound I .

[0046] A magnetic stir bar was added to a dry 50 mL round-bottom flask. Benzo[a]naphtho[1,2-k]tetrabenzene (1 g), I₂ (3.2 g), and anhydrous dichloromethane (20 mL) were added sequentially, and stirred until dissolved. The flask was cooled to 0 °C in an ice-water bath. Concentrated HNO₃ (2 mL) was slowly added dropwise, controlling the dropping rate to keep the system temperature below 5 °C. After the addition was complete, the ice-water bath was removed, and the reaction system was heated to room temperature. The reaction was stirred for 12–16 h. A saturated sodium sulfite solution (10 mL) was added, and the mixture was stirred until the color of iodine in the system completely disappeared (to remove excess I₂). The organic phase was separated and collected. This organic phase was washed with saturated brine (10 mL), dried over anhydrous magnesium sulfate, and filtered. The filtrate was distilled under reduced pressure and purified by silica gel column chromatography (eluent: petroleum ether) to obtain compound I. Its characterization data are shown below:

[0047] 1 H NMR (500MHz, CDCl3): δ=9.01 (d, J =2.7, 2H), 8.81 (d, J =2.0, 2H), 8.15-8.10 (m, 2H), 8.01 (dd, J =9.1, 2.4, 2H), 7.96 (d, J =8.0, 2H), 7.91 (d, J =9.1, 2H), 7.85 (d, J =7.7, 2H), 7.77 (dd, J =7.7, 2.1, 2H).

[0048] 13 C NMR (125MHz, CDCl3): δ=136.64, 135.71, 133.29, 132.15, 132.12, 130.63, 129.84, 129.39, 127.87, 127.15, 126.50, 126.17, 125.57, 124.27, 95.09;

[0049] TOF-ESI (+) (m / z) C 30 H 16 I2: 629.93.

[0050] II. Synthesis of Compound II .

[0051] In a dry 50 mL three-necked flask, a magnetic stir bar, 20 mg of Pd(PPh3)2Cl2, and 20 mg of CuI were added. After purging the air in the flask three times with nitrogen, anhydrous tetrahydrofuran (THF) (10 mL), compound I (1 g), and triethylamine (1.5 mL) were added sequentially. The mixture was stirred until homogeneous. Acetylene gas was introduced: the acetylene gas delivery tube was inserted below the surface of the reaction solution, and acetylene gas was slowly introduced. The reaction was stirred at room temperature for 6–8 h. After the reaction was completed, the triethylamine hydroiodide precipitate was removed by filtration. The filtrate was distilled under reduced pressure to remove THF and excess triethylamine. The residue was dissolved in dichloromethane (10 mL), washed sequentially with saturated brine (10 mL), dried over anhydrous magnesium sulfate for 30 min, filtered, and the filtrate was distilled under reduced pressure to obtain compound II. Its characterization data are shown below:

[0052] 1 H NMR (500MHz, CDCl3): δ=8.88 (d, J =2.5, 2H), 8.48 (d, J =2.4, 2H), 8.12 (dd, J =8.1, 0.8, 2H), 8.08-7.88 (m, 8H), 7.62 (dd, J =6.7, 2.2, 2H), 3.17 (s, 2H);

[0053] 13 C NMR (125MHz, CDCl3): δ=133.89, 132.15, 131.59, 131.32, 131.31, 130.95, 130.35 , 130.08, 127.87, 127.41, 126.53, 126.51, 126.17, 124.27, 120.02, 78.89, 78.04;

[0054] TOF-ESI (+) (m / z) C 34 H 18 : 426.93.

[0055] III. Synthetic Compound III .

[0056] In a dry 50 mL three-necked flask, a magnetic stir bar, 20 mg of Pd(PPh3)2Cl2, and 20 mg of CuI were added. The air in the flask was purged with nitrogen three times. Anhydrous THF (10 mL), compound II (1 g), p-aminoiodobenzene (2.3 g), and triethylamine (1.5 mL) were added sequentially. The mixture was stirred until homogeneous. The reaction system was heated to 40 °C and maintained at this temperature with stirring for 8–10 h. After the reaction was completed, the mixture was cooled to 15–25 °C. The triethylamine hydroiodide precipitate was removed by filtration. The filtrate was distilled under reduced pressure to remove THF and excess triethylamine. The residue was dissolved in dichloromethane (10 mL), washed twice with saturated brine (10 mL), dried over anhydrous magnesium sulfate for 1 h, filtered, and the filtrate was concentrated under reduced pressure to a viscous state. Anhydrous ethanol (5 mL) was added to the viscous substance and heated to dissolve it. The mixture was then cooled to 0 °C to crystallize. The crystals obtained by filtration were white, which is compound III. Its characterization data are shown below:

[0057] 1 H NMR (500MHz, CDCl3): δ=8.88 (d, J =2.5, 2H), 8.61 (d, J =1.9, 1H), 8.48 (d, J =2.4, 1H), 8.12 (dd, J =8.1, 0.8, 2H), 8.08-7.94 (m, 6H), 7.94-7.88 (m, 2H), 7.65-7.59 (m, 2H), 7.36-7.31 (m, 2H), 6.68-6.62 (m, 2H), 3.59 (s, 2H), 3.17 (s, 1H);

[0058] 13 C NMR (125MHz, CDCl3): δ=150.65, 133.89, 133.14, 132.15, 131.59, 131.32, 131.31, 131.08, 131.05, 130.96, 130.95, 130.35, 130.0 8, 128.90, 127.87, 127.41, 126.53, 126.51, 126.39, 126.17, 124.27, 120.49, 120.02, 114.99, 111.30, 90.57, 89.29, 78.89, 78.04;

[0059] TOF-ESI (+) (m / z) C 40 H 23 N: 517.18.

[0060] IV. Synthesis of Compound IV .

[0061] In a dry 100 mL round-bottom flask, add a magnetic stir bar, 1,4,8,11-tetraazacyclotetradecane (1 g), ethyl bromide hydrobromide (4 g), and anhydrous K₂CO₃ (6.1 g). Purge the air in the flask twice with nitrogen. Add anhydrous acetonitrile (20 mL), stir to disperse the solid evenly, set up a reflux apparatus, and heat to 80 °C (acetonitrile reflux temperature). Stir the reaction at this temperature for 12–16 h. After the reaction is complete, cool to room temperature, filter to remove the generated KBr and excess K₂CO₃ precipitate, wash the residue twice with acetonitrile (5 mL), and combine the filtrates. Distill the filtrate under reduced pressure to remove acetonitrile. Dissolve the residue in dichloromethane (15 mL), wash twice with saturated brine (10 mL), dry with anhydrous magnesium sulfate for 1 hour, and filter. The filtrate was concentrated under reduced pressure to a viscous state, and then purified by silica gel column chromatography (eluting solution: dichloromethane / methanol = 10:1 → 5:1 gradient elution). Filtration yielded a white solid, which was compound IV. Its characterization data are shown below:

[0062] 1 H NMR (500MHz, CDCl3): δ=3.84 (p, J =4.8, 1H), 3.54 (t, J =6.3, 2H), 3.02 (p, J =4.9, 1H), 2.86 (p, J =5.0, 1H), 2.80-2.72 (m, 10H), 2.72 (d, J =5.2, 1H), 2.70 (d, J =5.2, 1H), 2.65 (t, J =5.4, 2H), 2.55-2.48 (m, 4H), 1.76-1.65 (m, 4H);

[0063] 13 C NMR (125MHz, CDCl3): δ=62.51, 54.78, 52.27, 49.18, 47.60, 47.29, 47.07, 28.84, 26.96;

[0064] TOF-ESI (+) (m / z) C 11 H 27 N5: 229.226.

[0065] V. Synthesis of Compound V .

[0066] In a dry 100 mL three-necked flask, add a magnetic stir bar, compound IV (1 g), p-iodobenzene (4.4 g), CuI (0.21 g), o-phenanthroline (0.4 g), and anhydrous Cs2CO3 (7.1 g) in sequence. The air in the flask was replaced three times with nitrogen. Anhydrous N,N-dimethylformamide (DMF) (25 mL) was added, and the mixture was stirred to disperse the solid evenly. The temperature was raised to 120°C, and the reaction was carried out with stirring at this temperature for 24–30 h. The mixture was then cooled to 15–25°C, and the reaction solution was slowly poured into 50 mL of ice water. After stirring for 10 min, a solid precipitated. The precipitate was collected by filtration and dissolved in dichloromethane (15 mL). The precipitate was then washed twice with saturated brine (10 mL), dried over anhydrous magnesium sulfate for 2 h, and filtered to remove the desiccant. The filtrate was concentrated under reduced pressure to a viscous state and purified by silica gel column chromatography (eluting agent: dichloromethane / methanol = 15:1 → 10:1 gradient elution). The target fraction was collected as a pale yellow solid, which is compound V. Its characterization data are shown below:

[0067] 1 H NMR (500MHz, CDCl3): δ=7.54-7.48 (m, 2H), 6.79-6.73 (m, 2H), 3.54 (t, J=6.3, 2H), 3.25 (q, J=5.6, 4H), 3.12 (ddd, J=9.7, 5.2, 4.4, 1H), 2.90-2.79 (m, 5H), 2.82-2.76 (m, 3H), 2.79-2.72 (m, 2H), 2.65 (t, J=5.4, 2H), 2.55-2.48 (m, 4H), 1.84 (p, J=5.9, 2H), 1.74-1.65 (m, 1H);

[0068] 13 C NMR (125MHz, CDCl3): δ=149.48, 138.83, 115.95, 86.28, 62.51, 54.78, 52.28, 51.75, 49.11, 47.81, 47.69, 47.54, 47.02, 26.97, 26.92;

[0069] TOF-ESI (+) (m / z) C 17 H 30 IN5: 431.153.

[0070] VI. Synthesis of Compound VI .

[0071] In a dry 50 mL round-bottom flask, compound V (1 g) and anhydrous ethanol (20 mL) were added and stirred until completely dissolved. Then, CoCl₂·6H₂O (1.3 g) was added, and stirring continued for 30 min. The solution gradually turned into a pink turbid liquid. The reaction system was heated to 60 °C and maintained at this temperature with stirring for 4–6 h. The solution color deepened to a purplish-red (characteristic color of 1,4,8,11-tetraazacyclotetradecanecobalt(II) chloride). The reaction solution was cooled to 15–25 °C and concentrated to 1 / 3 of its original volume by vacuum distillation, yielding a purplish-red viscous liquid. Anhydrous diethyl ether (10 mL) was slowly added and stirred for 10 min, precipitating a purplish-red solid. The precipitate was collected by filtration. The precipitate was washed three times with anhydrous diethyl ether (5 mL each time) to remove unreacted material and dried under vacuum to obtain compound VI. Its characterization data are shown below:

[0072] 1 H NMR (500MHz, CDCl3): δ=7.46-7.36 (m, 4H), 3.49 (t, J =6.1, 2H), 3.38-3.32 (m, 2H), 3.02-2.83 (m, 12H), 2.80-2.73 (m, 2H), 2.5 1-2.46 (m, 2H), 2.39-2.32 (m, 2H), 1.84-1.75 (m, 2H), 1.71-1.62 (m, 2H);

[0073] 13 C NMR (125MHz, CDCl3): δ=142.18, 138.91, 131.13, 93.04, 49.17, 49.12, 48.88, 46.86, 46.25, 34.99, 33.76, 33.20, 30.56, 24.48, 23.88;

[0074] TOF-ESI (+) (m / z) C 17 H 30 ClCoIN5: 525.053.

[0075] VII. Synthesis of Co-based complex molecules of the target compound:

[0076] .

[0077] In a dry 50 mL three-necked flask, a magnetic stir bar, 20 mg of Pd(PPh3)2Cl2, and 20 mg of CuI were added. After purging the air in the flask three times with nitrogen, anhydrous THF (10 mL), compound III (1 g), compound VI (1 g), and triethylamine (1.5 mL) were added sequentially. The mixture was stirred until homogeneous. The reaction system was heated to 40 °C and maintained at this temperature with stirring for 8–10 h. After the reaction was completed, the mixture was cooled to 15–25 °C. The triethylamine hydroiodide precipitate was removed by filtration. The filtrate was distilled under reduced pressure to remove THF and excess triethylamine. The residue was dissolved in dichloromethane (10 mL) and then washed twice with saturated brine (10 mL). The residue was dried over anhydrous magnesium sulfate for 1 h, filtered, and the filtrate was concentrated under reduced pressure to a viscous state. Anhydrous ethanol (5 mL) was added and heated to dissolve the residue. The mixture was cooled to 0 °C to crystallize. The crystals obtained by filtration were white, which were the Co-based complex molecules. The characterization data are shown below:

[0078] 1 H NMR (500MHz, CDCl3): δ=8.88 (d, J=2.6, 2H), 8.61 (d, J=2.1, 2H), 8.12 (dd, J=8.1, 0.8, 2H), 8. 05-7.94 (m, 6H), 7.94-7.88 (m, 2H), 7.66-7.59 (m, 4H), 7.36-7.30 (m, 2H), 7.23-7.18 (m, 2H), 6.68-6.62 (m, 2H), 3.59 (s, 2H), 3.49 (t, J=6.1, 2H), 3.38-3.32 (m, 2H), 3.02-2.83 (m, 10H), 2 .80-2.73 (m, 2H), 2.51-2.46 (m, 2H), 2.39-2.32 (m, 2H), 1.84-1.75 (m, 2H), 1.71-1.62 (m, 2H);

[0079] 13 C NMR (125MHz, CDCl3): δ=150.65, 145.16, 133.89, 133.14, 132.64, 132.15, 131. 32, 131.08, 131.05, 130.96, 130.35, 129.39, 128.90, 127.87, 127.41, 126.51, 126.39, 126.17, 124.27, 120.49, 119.36, 114.99, 111.30, 90.57, 89.29, 89.25, 49.17, 49.12, 48.88, 46.86, 46.25, 34.98, 33.76, 33.20, 30.56, 24.48, 23.88;

[0080] TOF-ESI (+) (m / z) C 57 H 52 ClCoN6: 914.3274.

[0081] Example 2

[0082] The process for preparing microwave-controlled cobalt-based graphene electrode complex molecules is as follows:

[0083] I. Graphene-Silicon Wafer Composite Substrate.

[0084] The copper foil was ultrasonically cleaned sequentially with acetone and isopropanol for 10 min each, then immersed in 5% dilute hydrochloric acid for 5 min to remove the oxide layer. It was then rinsed with deionized water and dried with nitrogen. The dried copper foil was placed in a chemical vapor deposition (CVD) reaction chamber, heated to 1000℃, and annealed for 60 min with H2 (200 sccm) and Ar (200 sccm) gases. Then, methane (CH4, 20 sccm) was introduced as the carbon source, and the reaction was maintained at 1000℃ and 20 min with a hydrogen flow rate of 200 sccm. After the reaction, the foil was cooled to room temperature at a rate of 50℃ / min under an H2 / Ar atmosphere to obtain a single-layer graphene film.

[0085] The graphene was transferred onto a clean quartz sheet using transparent tape. Polymethyl methacrylate (PMMA) was then spin-coated onto the graphene surface at 4000 rpm for 40 seconds, followed by curing at 180°C for 2 minutes. Excess graphene on the back of the copper foil was etched using oxygen plasma to obtain a PMMA-monolayer graphene-copper foil structure. This structure was cut into 1cm × 1cm pieces and dissolved in a 1M FeCl3 solution to remove the copper foil on the back. The pieces were then immersed in a 0.1M HCl aqueous solution for 10 minutes to remove residual metal ions, and rinsed three times with deionized water to obtain a PMMA-supported monolayer graphene film.

[0086] The graphene foil was transferred onto a silicon wafer covered with a SiO2 layer (300 nm thick), and then sequentially immersed in a 1 wt% HCl aqueous solution for 5 min, rinsed with deionized water, immersed in a 0.01 M KOH aqueous solution for 2 min, rinsed again, and dried to remove adhesive, thus obtaining a graphene-silicon wafer composite substrate.

[0087] II. Constructing graphene source electrode and graphene drain electrode.

[0088] Photoresist was spin-coated onto the graphene surface of a graphene-silicon composite substrate (3000 rpm, 40 s spin-coating time), pre-baked at 180°C for 1 min, and then exposed to ultraviolet light (80 mJ / cm²) using a strip mask. 2 The graphene strips were patterned by developing a solution of methyl isobutyl ketone and isopropanol (volume ratio 1:3) and fixing it with isopropanol.

[0089] Subsequently, the unprotected areas of graphene were etched using oxygen plasma to obtain edge-carboxylated graphene point electrode structures. Then, nano-gap structures were formed between the graphene strips using an electrical ablation method. The continuity of each electrode pair was tested using a probe station and source meter to screen for nano-gap graphene electrode pairs with gap sizes of approximately 0.5–2 nm.

[0090] The conductivity of the graphene array electrodes was tested under a 50mV bias voltage, and samples with conductivity currents on the order of pA or fA were selected for subsequent steps. The nano-gap graphene electrode pair includes a graphene source electrode and a graphene drain electrode.

[0091] III. Preparation of molecular knots.

[0092] The selected interstitial graphene electrode pairs were placed in a two-necked flask, and 5 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) solution, 10 mL of pyridine, and 5 mL of a 0.5 mM Co-based complex molecule (prepared in Example 1) pyridine solution were added. The mixture was reacted under a nitrogen atmosphere for 48 h, allowing the –NH2 groups at both ends to react with the –COOH groups at the ends of the graphene electrodes to form amide covalent bonds, achieving single-molecule self-assembly. After the reaction, the electrodes were washed three times each with deionized water and acetone, and dried under nitrogen to obtain a microwave-controlled graphene electrode cobalt-based complex molecular device, such as… Figure 1 As shown, it includes a molecular junction composed of a graphene source electrode 1, a Co-based complex molecule 2, and a graphene drain electrode 3, with the Co-based complex molecule 2 connected between the graphene source electrode 1 and the graphene drain electrode 3.

[0093] The cobalt-based graphene electrode molecular device prepared above was subjected to low-temperature microwave manipulation tests using the Physical Property Measurement System (PPMS) from Quantum Design, USA. Test conditions:

[0094] The molecular device was fixed to the top of the PPMS sample holder, ensuring the c-axis was parallel to the vertical magnetic field of the cavity. A 0.3 mm diameter niobium-titanium (NbTi) superconducting coplanar waveguide (running along the quartz tube wall) was introduced, with the waveguide loop tightly attached to the sample surface (gap ≤ 50 µm). The other end was connected to a room temperature vector microwave source (0.1–20 GHz, +30 dBm) via a vacuum feedthrough. The system was evacuated to <10 °C. – 4 After torsion, the temperature was reduced to 2K at a rate of 5K / min and stabilized.

[0095] Testing process:

[0096] First, the DC magnetization M(H) was measured using the built-in pickup coil of the PPMS; then, a microwave source was turned on, and the magnetic field was scanned at a fixed frequency ν, recording the resonant field H corresponding to the decrease in magnetization. res Then, fix the magnetic field H=H res Time-resolved measurements were performed using a π / 2–τ–π pulse mode (τ = 0.1–5µs). The magnetization reversal amplitude ΔM was obtained through phase-locked detection, and the Rabi frequency Ω was obtained by fitting the data. R And spin coherence time T2; after each set of data is measured, the PPMS is automatically heated to 10K and held for 30s to eliminate thermal drift;

[0097] The microwave control conditions were set as follows: transmission frequency of 10 GHz, output power of −10 dBm, single-shot sweep mode, frequency range of 9–11 GHz, step size of 100 MHz, and dwell time of 10 ms. The sweep was performed and signal changes were observed. The results are as follows. Figure 2 As shown, the results indicate that under constant bias conditions, the electronic spin state of Co ions in Co-based complexes can be altered by microwave signal modulation. When no microwave signal is applied, the source-drain current remains at a stable baseline value. When the microwave signal is turned on, the source-drain current exhibits obvious periodic oscillation characteristics over time within the microwave action time interval. After the microwave signal is turned off, the source-drain current rapidly recovers to the initial stable state.

[0098] The Rabi oscillations of the cobalt-based graphene electrode molecular device prepared above were tested using the Physical Property Measurement System (PPMS) from Quantum Design, Inc., as follows: Figure 3As shown in the figure, τ represents the duration of the applied microwave pulse, and P represents the spin-state readout signal intensity of the device after microwave excitation. The figure reveals that as the microwave pulse width increases, the detected output signal P undergoes periodic changes, exhibiting typical Rabi oscillation characteristics, meaning the signal amplitude fluctuates periodically in a cosine manner. This result demonstrates that microwave-controlled graphene electrode cobalt-based complex molecular devices can achieve stable and controllable coherent quantum state manipulation under microwave drive. This result verifies that Co-based complex molecules possess excellent quantum coherence characteristics and high-fidelity microwave response capabilities in a graphene electrode environment, laying a solid foundation for their application in quantum information processing, single-molecule spintronic devices, and other fields.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microwave-controlled graphene electrode cobalt-based complex molecular device, characterized in that, It includes graphene electrode pairs and Co-based complex molecules, wherein the Co-based complex molecules are assembled between the graphene electrode pairs through a chemical reaction; The structural formula of the Co-based complex molecule is shown below: ； R1 is selected from -OH or -NH2, and R2 is selected from halogens.

2. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 1, characterized in that, R1 is selected from -NH2, and R2 is selected from Cl.

3. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 1, characterized in that, Under low-temperature conditions, microwaves can drive quantum state transitions of the spin of the Co-based complex molecules; The low temperature range is -272.15℃ to -0.15℃.

4. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 3, characterized in that, The frequency range of microwaves is 9 GHz to 11 GHz.

5. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 1, characterized in that, The graphene electrode pair includes a graphene source electrode and a graphene drain electrode. The gap between the graphene source electrode and the graphene drain electrode is 0.5 nm to 2 nm.

6. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 5, characterized in that, A single Co-based complex molecule is connected between the graphene source electrode and the graphene drain electrode.

7. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 1, characterized in that, The graphene electrode pair is made of a single-layer graphene film.

8. The microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 1, characterized in that, It also includes a substrate, wherein the graphene electrode pair is disposed on the surface of the substrate, the substrate being selected from a silicon wafer covered with a SiO2 layer.

9. A method for preparing microwave-controlled graphene electrode cobalt-based complex molecular devices, characterized in that, The method for preparing the microwave-controlled graphene electrode cobalt-based complex molecular device as described in any one of claims 1 to 8 comprises the following steps: S100: Using single-layer graphene film as raw material, edge-carboxylated graphene electrode pairs are prepared by photolithography and oxygen plasma technology. S200. Using a condensation reaction, a Co-based complex is assembled between the graphene electrode pairs to obtain a microwave-controlled graphene electrode cobalt-based complex molecular device.

10. The method for preparing the microwave-controlled graphene electrode cobalt-based complex molecular device as described in claim 9, characterized in that, The condensation reaction is an amide condensation reaction, and the carboxyl activator for the amide condensation reaction is selected from 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

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