Multi-mode full-printing preparation method of graphene-based biological field effect transistor

Abstract

The invention discloses a multi-mode all-printing preparation method of a graphene-based biological field effect transistor. The method comprises the following steps: preparing a graphene oxide channel layer on a substrate by using an electrofluid jet printing method; reducing by using a chemical vapor phase reduction method to obtain a reduced graphene oxide channel layer; preparing a conductive silver electrode of the field effect transistor based on an extrusion direct writing process; and grafting a biomolecular probe on the surface of the graphene channel layer by using a dispensing method. A high-performance reduced graphene oxide functional layer channel is prepared on the basis of an electrofluid jet printing technology and a chemical reduction process, and then a metal electrode is obtained on the basis of an extrusion direct writing technology. Materials with different rheological and electrical characteristics are integrated on a'one-point '3D printing platform, preparation of the graphene-based biological field effect transistor is completed by adjusting the structural form of the nozzle and integrating multiple processing modes, and the prepared biosensor has high sensitivity and short response time.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano manufacturing technology of two-dimensional biosensors, and in particular to a multi-modal full-printing preparation method of a graphene-based biofield effect transistor. Background Art

[0002] The development of one-dimensional field-effect transistors (FETs) is limited by the synthesis, modulation, scaling and integration of one-dimensional nanomaterials. In comparison, two-dimensional semiconductor nanomaterials benefit from their extreme surface-to-volume ratio and are more compatible with established microfabrication processes. Among two-dimensional materials, graphene has great development prospects due to its extremely high mobility. As a semi-metallic two-dimensional material, its conductance is moderately modulated by local electrostatic fields, allowing the material to be manipulated in a field-effect transistor configuration. Due to this moderate on-off modulation performance, graphene-based field-effect transistors are generally considered uncompetitive in pure electronic devices compared to state-of-the-art three-dimensional semiconductors (such as silicon) or even their one-dimensional counterparts, carbon nanotubes, but have significant advantages in the field of chemical and biochemical sensing.

[0003] Graphene-based field effect transistor (GFET) sensors include four key components (such as Figure 1 The GFET design includes at least three electrodes in order to operate as a field-effect transistor. The first two electrodes, called source (S) and drain (D), are in direct contact with the graphene and allow the flow of current in the graphene by applying a potential difference between them. The source and drain are made of a conductive material, usually the same metal: most studies use electron beam evaporation or thermal evaporation to evaporate highly conductive metals such as silver or gold on an adhesion layer such as titanium or nickel. Silver conductive ink can be used to prepare the electrodes, especially on large areas of graphene. The third electrode, called gate (G), is placed close to the graphene but not in direct contact. A potential difference is applied between the gate and drain (or source) to modulate the density and polarity of charge carriers in the graphene. A variety of configurations are used for the shape and location of the gate: The choice of configuration depends on the experimental protocol chosen for analyte delivery and detection. In biosensing experiments, GFETs are often operated directly in an electrolyte solution. In this configuration, the gate voltage is applied using a reference electrode immersed in the medium or a coplanar electrode patterned on the substrate. The coplanar gate electrode is patterned on the substrate in a similar way to the source and drain electrodes, using the deposition of metals such as platinum, silver, or gold. In both cases, the gate is coupled to the graphene through a double layer formed by the redistribution of ions in the electrolyte medium. These gate configurations are often referred to as "top gate" or "liquid gate".

[0004] At present, chemical vapor deposition and other complex manufacturing processes are widely used in the field of single-layer or few-layer graphene manufacturing. These manufacturing processes have high requirements on equipment. The various materials, tools and equipment involved in the preparation process also need to be controlled and managed with high precision to ensure that the products meet the expected performance indicators. In addition, manual semi-automatic operation is required in this process, which restricts its prospects for large-scale manufacturing. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a multimodal full-printing preparation method of a graphene-based bio-field effect transistor (Bio-FET).

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] In one aspect, the present invention provides a multimodal full-printing preparation method of a graphene-based bio-field effect transistor (Bio-FET), comprising the following steps:

[0008] 1) preparing a graphene oxide channel layer on a substrate by electrofluidic printing;

[0009] 2) using a chemical vapor reduction method to reduce the graphene oxide channel layer in step 1) to obtain a reduced graphene oxide channel layer;

[0010] 3) Preparation of conductive silver electrodes for field effect transistors based on extrusion direct writing process;

[0011] 4) Grafting biomolecular probes onto the surface of the graphene channel layer using a drop coating method.

[0012] As a preferred embodiment, step 1) is specifically: preparing a graphene oxide channel layer on a substrate by electrofluidic printing of a graphene oxide precursor liquid; in the electrofluidic printing method, the printing height is 5 to 10 mm, the liquid flow rate is 60 to 90 μL / h, the filling line spacing is 0.1 to 0.5 mm, and the thickness of the obtained graphene oxide channel layer is 10 nm to 10 μm;

[0013] Preferably, in the electrofluid printing method, the substrate is connected to a negative high voltage of -2KV to -1KV, and the nozzle is connected to a positive high voltage of 2KV to 5KV;

[0014] Preferably, the substrate is a silicon wafer substrate or a silicon wafer substrate provided with a metal hollow mask plate;

[0015] Preferably, the graphene oxide precursor solution is a mixed solution of a graphene oxide suspension and an organic solvent; the organic solvent is selected from at least one of N-methylpyrrolidone (NMP), propylene carbonate (PC) and dimethyl sulfoxide (DMSO); in the technical solution of the present invention, the precursor solution prepared with the above organic solvents can avoid problems such as crystallization and clogging at the nozzle due to long-term exposure to air and under the influence of a strong electric field by regulating the physical properties of the solution, such as surface tension and boiling point, and can also alleviate the coffee ring and self-assembly unevenness that occur during the drying process of the graphene oxide precursor solution.

[0016] As a preferred embodiment, in step 2), the chemical vapor reduction method comprises the following steps: subjecting the graphene oxide channel layer to a constant temperature heating reaction with a reducing solution;

[0017] Preferably, the reducing solution is a mixed solution of hydroiodic acid and glacial acetic acid; preferably a mixed solution of hydroiodic acid and glacial acetic acid in a volume ratio of 0.7 to 1.3:1;

[0018] Preferably, the constant temperature heating temperature is 50-80°C, and the constant temperature heating time is 18-36h;

[0019] Preferably, the method further comprises a post-treatment operation of soaking in a methanol solution to remove residual iodine.

[0020] As a preferred embodiment, in step 3), a conductive silver electrode is obtained by extrusion printing of silver conductive ink using an extrusion direct writing process, and then the conductive silver electrode is sintered by heating at 100 to 200° C. for 30 min to 2 h; the conductive silver electrode includes a source electrode (S), a drain electrode (D) and a gate electrode (G); the line width resolution of the printing is 10 to 100 μm;

[0021] Preferably, the heating rate of the heating at 100-200° C. is 5-15° C. / min.

[0022] In the technical solution of the present invention, the layout of the graphene-based bio-field effect transistor is a coplanar gate electrode configuration, which can complete the entire preparation process through a multimodal printing process, greatly simplifying the process flow and reducing the difficulty of the preparation process compared to the traditional micro-nano processing preparation process. In the working state under this configuration, the gate is coupled with the graphene channel layer through the double electric layer formed by the redistribution of ions in the electrolyte medium, thereby completing the signal transduction process.

[0023] As a preferred embodiment, step 4) comprises the following steps: drop-coating the connecting molecule solution onto the exposed surface of the reduced graphene oxide channel layer for a primary reaction; after cleaning, drop-coating the biomolecule probe solution onto the exposed surface of the reduced graphene oxide channel layer for a secondary reaction to complete the probe grafting; and finally, passivation is performed;

[0024] In the technical solution of the present invention, the biomolecular probe is connected and fixed to the connecting molecule on the surface of the reduced graphene oxide channel layer by single-stranded DNA molecular sequence hybridization, cross-linking method or chemical bond affinity method to realize the signal transduction process of the biomolecular aptamer;

[0025] Preferably, the linker molecule solution is a dimethyl sulfoxide solution of 1-pyrenebutyric acid succinimide ester; the concentration of the dimethyl sulfoxide solution of 1-pyrenebutyric acid succinimide ester is 50 to 500 μM;

[0026] Preferably, the time of the primary reaction is 2 to 12 hours;

[0027] In some specific embodiments, the cleaning comprises cleaning with PBS solution and cleaning with ultrapure water;

[0028] Preferably, the concentration of the biomolecule probe solution is 500nM to 2μM;

[0029] Preferably, the secondary reaction time is 3 to 5 hours;

[0030] Preferably, the process further includes a cleaning process after the probe grafting is completed. In some specific embodiments, the cleaning process includes PBS solution cleaning and ultrapure water cleaning;

[0031] Preferably, the passivation is to drop a 100-200 mM ethanolamine solution onto the reduced graphene oxide channel layer and react for 1-2 hours for passivation; in the technical solution of the present invention, after the biomolecule probe is coupled to the graphene, some functional groups of the connecting molecule remain uncoupled, which may lead to poor coupling with non-target substances. The use of ethanolamine solution can passivate and block the unbound carboxylic acid reaction groups on the graphene surface;

[0032] Preferably, the passivation further includes a post-processing operation, and the post-processing includes cleaning and nitrogen drying.

[0033] In another aspect, the present invention provides application of the above preparation method in preparing a biosensor.

[0034] The above technical solution has the following advantages or beneficial effects:

[0035] The present invention adopts a multimodal full-printing method to prepare graphene-based biofield effect transistors, and the method is not bound by traditional micro-nano processing and manufacturing equipment. Among them, the multimodal full-printing method can realize the selection of functional precursor liquid for material deposition and structure modulation within a wide range of viscosity and conductivity, overcoming the limitations of the printing method that relies on a single ink delivery method. The full-printing preparation process mainly faces two major problems. One problem is that the printed graphene oxide channel layer is uneven, which is caused by the directional mass transfer in the droplet driven by capillary force flow during the solvent evaporation process; the other problem is that printing at room temperature cannot create a repeatable and stable connection between the metal electrode and the graphene channel layer. In response to the first problem, the present invention realizes the uniform distribution of liquid deposition by modulating the physical properties of the precursor liquid such as the boiling point and viscosity. Compared with processes such as extrusion printing, the film deposited by the electrofluidic printing method shows better layer uniformity and controllable thickness. When a strong electric field is applied to the graphene oxide precursor liquid at the nozzle, the ink is atomized at the orifice. The diameter of the atomized droplets ranges from 3 to 5 microns, and after impacting the substrate, the liquid film state is maintained, reducing mass transfer in the lateral direction, so that the microdroplets are evenly distributed in the target area. At the same time, a larger lateral size can be maintained on a micron scale. Since the high aspect ratio nanosheets produced are prone to shrinkage during printing and solvent evaporation, the precursor liquid system prepared based on the high boiling point solvent propylene carbonate is crucial for achieving a well-arranged and flat film. In response to the second problem, the present invention improves the connection between the silver electrode layer and the graphene channel layer by modulating the process parameters such as the filling line spacing and sintering temperature of the silver conductive ink. The density and thickness of the electrode layer will directly affect the conductivity of the electrode and the adhesion between the electrode and the substrate.

[0036] There are many methods for reducing graphene oxide, including electrochemical reduction, thermal reduction, and chemical reduction. In comparison, the electrochemical reduction method is time-consuming, and the total amount of reduced graphene oxide obtained is low; although the thermal reduction method can reduce almost defect-free graphene, it is impossible to implement covalent modification; the chemical reduction method has low cost, is easy to mass produce, and is convenient for further functional modification of graphene, and has significant application advantages. The present invention adopts a chemical vapor reduction method, and in-situ reduction on the printed graphene oxide channel layer can effectively reduce impurities and reduce the impact of other process steps. The heating operation and the introduction of acetic acid during the reduction process can also improve the effect of reduction. After the reduction of graphene oxide is completed by hydroiodic acid, the oxygen-containing groups contained in its surface show almost complete reduction. The conjugated structure in the original graphene is effectively restored, and a small amount of oxygen-containing groups still exist, mainly C=O and COOH at the edge of graphene oxide. At the same time, in order to reduce the residual iodine element, a methanol aqueous solution is used for cleaning after the reduction process.

[0037] The present invention prepares the bottom functional layer channel of graphene oxide based on the electrofluidic printing technology, adopts the chemical reduction process to prepare the high-performance reduced graphene oxide functional layer channel, and then obtains the metal electrode based on the extrusion direct writing technology. Compared with the traditional Bio-FET preparation process that relies on the CVD transfer graphene process and thermal evaporation, electron beam evaporation, etc. to deposit metal electrodes, all components of the Bio-FET in the present invention can adopt the printing process, and achieve semiconductor performance, which greatly reduces the difficulty and requirements of the FET device manufacturing process. The functional layer channel is modified and fixed with a biomolecule probe, which can directly contact the biomolecule to be tested or through the single-stranded DNA molecule and its reverse transcribed DNA through base complementary pairing or through the chemical bond between the bioaptamer molecules, so that the biomolecule to be tested contacts the surface of the field effect transistor sensor, with higher sensitivity and shorter response time.

[0038] The present invention integrates materials with different rheological and electrical properties on a "one-point" 3D printing platform, and completes the preparation of graphene-based biofield effect transistors by adjusting the structure of the nozzle and integrating multiple processing methods, such as extrusion direct writing and electrospray deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the structure of a graphene-based field effect transistor in the prior art.

[0040] Figure 2 It is a schematic diagram of the structure of the graphene-based biofield effect transistor in Example 1. DETAILED DESCRIPTION

[0041] The following embodiments are only some embodiments of the present invention, rather than all embodiments. Therefore, the detailed description in the embodiments of the present invention provided below is not intended to limit the scope of the present invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0042] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0043] Example 1

[0044] (1) Using an electrohydrodynamic printing method to prepare a patterned graphene channel layer on a 500 micron thick four-inch silicon dioxide / silicon substrate using a graphene oxide precursor solution; in the electrohydrodynamic printing method, the flow rate is set to 90 μL / h, the printing height is set to 10 mm, the substrate is connected to a negative high voltage of -1 KV, and the needle tip is connected to a positive high voltage of 3 KV. The characteristic size of the channel layer, i.e., the length and width of the filling pattern, is 1 mm×1 mm, and the thickness is 10 nm; wherein the graphene oxide precursor solution is composed of a graphene oxide solution, propylene carbonate, and ethanol in a volume ratio of 1:1:1. The graphene oxide solution is purchased from Hangzhou Gaoxun Technology Co., Ltd., and the product model is GX-GO-2, which is a water-based solution of graphene oxide nanosheets with a concentration of 5 mg / mL. The lateral size of the graphene oxide nanosheets is 20 to 30 μm, the oxygen content is 30 to 40%, and the thickness is 1 nm;

[0045] (2) placing the patterned graphene channel layer obtained in step (1) into a chemical reactor, adding a mixed solution of acetic acid and hydroiodic acid in a volume ratio of 55:45, and reacting at 50° C. for 24 hours; taking it out and soaking it in a mixed solution of methanol and water in a volume ratio of 1:1 for 30 minutes to remove residual iodine, thereby obtaining a patterned ultrathin reduced oxide graphene channel layer with semiconductor properties;

[0046] (3) A conductive silver electrode was obtained by printing the silver conductive ink using an extrusion direct writing process, with a printing height of 2 μm and a flow rate of 20 μL / h; after printing, the conductive silver electrode was sintered in an oven at 150°C (heating rate of 5°C / min) for 30 min to obtain a patterned conductive silver electrode with a line width of 50 μm, thereby obtaining a graphene field effect transistor;

[0047] (4) applying a 50 μM dimethyl sulfoxide solution of 1-pyrenebutyric acid succinimidyl ester (PBASE) to the reduced graphene oxide channel layer of the graphene field effect transistor and soaking it for 2 hours, and then rinsing it with 1×PBS solution and ultrapure water; in this step, the pyrene group at one end of the 1-pyrenebutyric acid succinimidyl ester molecule is adsorbed to the surface of the field effect transistor through π-π stacking;

[0048] A 20 μL 1 μM SARS-CoV-2 single-stranded DNA molecular probe solution was drop-coated onto the exposed surface of the reduced graphene oxide channel layer and reacted at room temperature for 3 h to complete the probe grafting process. After grafting, the layer was rinsed with 1× PBS solution and ultrapure water and dried with nitrogen gas.

[0049] (5) Passivation: 20 μL of 100 mM ethanolamine solution was drop-coated on the reduced graphene oxide channel layer and reacted for 2 h. The layer was then washed with ultrapure water and dried with nitrogen gas to obtain a graphene-based biofield effect transistor.

[0050] The structure of the graphene-based biofield effect transistor prepared in this embodiment is shown in FIG. Figure 2 shown.

[0051] Example 2

[0052] The preparation process of the graphene-based biofield effect transistor in this embodiment is the same as that in Example 2, except that in step (2), the reaction temperature after adding a mixed solution of acetic acid and hydroiodic acid in a volume ratio of 55:45 is 60°C.

[0053] Example 3

[0054] The preparation process of the graphene-based biofield effect transistor in this embodiment is the same as that in Example 2, except that in step (2), the reaction temperature after adding a mixed solution of acetic acid and hydroiodic acid in a volume ratio of 55:45 is 60°C; the biomolecular probe solution in step (4) is 20 μL of 500 nM new coronavirus nucleic acid single-stranded DNA molecular probe solution.

[0055] The graphene-based biofield effect transistors prepared in Examples 1-3 of the present invention can be used for the detection of the new coronavirus, among which Example 3 has the highest sensitivity and the fastest response speed.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multimodal full-printing preparation method for graphene-based biological field effect transistors, characterized in that: The following steps are involved: 1) preparing a graphene oxide channel layer on a substrate by electrofluidic printing; 2) using a chemical vapor reduction method to reduce the graphene oxide channel layer in step 1) to obtain a reduced graphene oxide channel layer; 3) Preparation of conductive silver electrodes for field effect transistors based on extrusion direct writing process; 4) Grafting biomolecular probes onto the surface of the graphene channel layer using a drop coating method.

2. The multimodal full printing preparation method according to claim 1, characterized in that: Step 1) is specifically: preparing a graphene oxide channel layer on a substrate by electrofluidic printing of a graphene oxide precursor liquid; in the electrofluidic printing method, the printing height is 5 to 10 mm, the liquid flow rate is 60 to 90 μL / h, the filling line spacing is 0.1 to 0.5 mm, and the thickness of the obtained graphene oxide channel layer is 10 nm to 10 μm; Preferably, in the electrofluid printing method, the substrate is connected to a negative high voltage of -2KV to -1KV, and the nozzle is connected to a positive high voltage of 2KV to 5KV; Preferably, the substrate is a silicon wafer substrate or a silicon wafer substrate provided with a metal hollow mask.

3. The multimodal full printing preparation method according to claim 2, characterized in that: The graphene oxide precursor solution is a mixed solution of a graphene oxide suspension and an organic solvent; the organic solvent is selected from at least one of N-methylpyrrolidone (NMP), propylene carbonate (PC) and dimethyl sulfoxide (DMSO).

4. The multimodal full printing preparation method according to claim 1, characterized in that: In step 2), the chemical vapor reduction method comprises the following steps: subjecting the graphene oxide channel layer and the reducing solution to a constant temperature heating reaction; Preferably, the reducing solution is a mixed solution of hydroiodic acid and glacial acetic acid; preferably a mixed solution of hydroiodic acid and glacial acetic acid in a volume ratio of 0.7 to 1.3:1; Preferably, the constant temperature heating temperature is 50-80°C, and the constant temperature heating time is 18-36h; Preferably, the method further comprises a post-treatment operation of soaking in a methanol solution to remove residual iodine.

5. The multimodal full printing preparation method according to claim 1, characterized in that: In step 3), a conductive silver electrode is obtained by extrusion printing of silver conductive ink using an extrusion direct writing process, and then the conductive silver electrode is sintered by heating at 100 to 200° C. for 30 min to 2 h; the conductive silver electrode includes a source electrode (S), a drain electrode (D) and a gate electrode (G); the line width resolution of the printing is 10 to 100 μm; Preferably, the heating rate of the heating at 100-200° C. is 5-15° C. / min.

6. The multimodal full printing preparation method according to claim 1, characterized in that: The layout of the graphene-based biofield effect transistor is a coplanar gate electrode configuration.

7. The multimodal full printing preparation method according to claim 1, characterized in that: Step 4) includes the following steps: drop-coating the connecting molecule solution onto the exposed surface of the reduced graphene oxide channel layer for a primary reaction; after cleaning, drop-coating the biomolecule probe solution onto the exposed surface of the reduced graphene oxide channel layer for a secondary reaction to complete the probe grafting; and finally, passivation.

8. The multimodal full printing preparation method according to claim 7, characterized in that: The linker molecule solution is a dimethyl sulfoxide solution of 1-pyrenebutyric acid succinimide ester; the concentration of the dimethyl sulfoxide solution of 1-pyrenebutyric acid succinimide ester is 50-500 μM; Preferably, the time of the primary reaction is 2 to 12 hours; Preferably, the concentration of the biomolecule probe solution is 500nM to 2μM; Preferably, the secondary reaction time is 3 to 5 hours; Preferably, the process further includes a cleaning process after the probe grafting is completed; Preferably, the passivation is performed by drop-coating a 100-200 mM ethanolamine solution onto the reduced graphene oxide channel layer and reacting for 1-2 hours for passivation.

9. The multimodal full printing preparation method according to claim 7, characterized in that: The passivation step also includes post-processing operations, which include cleaning and nitrogen drying.

10. Use of the multimodal full-printing preparation method according to any one of claims 1 to 9 in the preparation of a biosensor.

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