A Flexible Organic Field-Effect Transistor Breath Ammonia Sensor Utilizing Modified Graphene Oxide Nanosheets and Preparation Method Thereof

Abstract

The present invention discloses a flexible organic field-effect transistor breathing ammonia sensor using modified graphene oxide nanosheets and a preparation method thereof, belonging to the technical field of gas sensors. A flexible organic field-effect transistor breathing ammonia sensor using modified graphene oxide nanosheets includes, from bottom to top in sequence, a flexible substrate, a gate electrode, a flexible dielectric layer, an organic semiconductor layer, and source / drain electrodes. The raw materials of the organic semiconductor layer include poly[(bithiophene)-alternating-(2,5-bis(2-octyldodecyl)-3,6-bis(thienyl)-pyrrolopyrrolidone)], an elastomer, and modified graphene oxide. The nanomaterial OA-GO containing multiple functional groups has an adsorption effect on the target gas. By preparing a porous film containing OA-GO in the present invention, the surface area in contact with the gas can be increased, more binding sites can be exposed, and finally, highly sensitive and highly selective detection of the target gas NH3 can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and particularly relates to a flexible organic field-effect transistor breath ammonia sensor using modified graphene oxide nanosheets and a preparation method thereof. Background Art

[0002] Biomarker detection is expected to play a key role in the upcoming era of cloud medical treatment (CMT) due to its potential for early disease diagnosis and personalized health monitoring. Human exhaled gas contains thousands of different gases, some of which are closely related to the metabolism of different organs and have different levels between patients and healthy people, making it an ideal in vitro biomarker. Kidney disease is quietly becoming a hidden global epidemic with a high mortality rate among nephropathy patients. The concentration of NH 3 in exhaled breath is related to the concentration of urea in the blood and can be used to monitor the adequacy of dialysis for nephropathy patients. Traditional breath monitoring methods may require patients to wear uncomfortable devices or undergo complex examinations. Therefore, flexible gas sensors have broad application prospects in the health field. Flexible gas sensors based on organic field-effect transistors (OFETs) have advantages such as low operating temperature, signal amplification, low cost, and low power consumption. They can be directly attached to the skin or integrated into smart wristbands and clothes, can well adapt to the movement and posture changes of the human body, provide a more natural wearing experience, facilitate long-term monitoring, capture the real-time changes of breath gases, achieve continuous health tracking, and provide valuable information for understanding the respiratory health status of patients. In summary, since the existing detection of kidney diseases often requires cumbersome and complex operation procedures, specialized instrument equipment, and skilled operators, there is an urgent need to develop low-cost detection devices with higher sensitivity, simpler operation, and wider application range to achieve the detection and evaluation of early kidney diseases. Summary of the Invention

[0003] The purpose of the present invention is to provide a flexible organic field-effect transistor breath ammonia sensor using modified graphene oxide nanosheets and a preparation method thereof to solve the problems existing in the above-mentioned prior art.

[0004] One of the technical solutions provided by the present invention:

[0005] A flexible organic field-effect transistor breath ammonia sensor using modified graphene oxide nanosheets includes, from bottom to top, a flexible substrate, a gate electrode, a flexible dielectric layer, an organic semiconductor layer, and source / drain electrodes. The raw materials of the organic semiconductor layer include poly[(bithiophene)-alternating-(2,5-bis(2-octyldodecyl)-3,6-bis(thienyl)-pyrrolopyrrolidone)] (DPP-DTT), an elastomer (SEBS (H1221)), and modified graphene oxide; the modified graphene oxide is graphene oxide modified with long-chain oleylamine (OA-GO).

[0006] Preferably, the organic semiconductor layer is prepared from an organic semiconductor thin film; the preparation method of the organic semiconductor thin film includes the following steps: shearing a mixed solution containing OA-GO, DPP-DTT, and SEBS (H1221), then spin-coating it on an octadecyltrichlorosilane-modified silicon wafer, and annealing to obtain the organic semiconductor thin film.

[0007] Since graphene oxide is modified by long-chain oleylamine, adjacent OA-GO entangle and aggregate with each other through long-chain oleylamine groups during the shearing process of the mixed solution, resulting in the appearance of holes in the organic semiconductor thin film after adding OA-GO, forming a porous thin film, thereby increasing the surface area in contact with gas and improving gas response.

[0008] More preferably, the preparation method of the mixed solution is: mixing an organic solution of OA-GO and a polymer solution containing DPP-DTT and SEBS (H1221) to obtain the mixed solution.

[0009] More preferably, the weight ratio of DPP-DTT to SEBS (H1221) is 2:1, and the total concentration of DPP-DTT and SEBS (H1221) in the polymer solution is 7.5 mg / mL.

[0010] More preferably, the mass concentration of OA-GO in the organic solution is 5 mg / mL.

[0011] More preferably, OA-GO accounts for 1-6% of the weight of DPP-DTT; more preferably, the modified graphene oxide accounts for 4% of the weight of DPP-DTT.

[0012] Preferably, the preparation method of OA-GO includes the following steps: mixing an equal volume of an aqueous suspension of GO (graphene oxide) and an ethanol solution of OA (oleylamine), vigorously stirring at room temperature, and vacuum drying to obtain OA-GO.

[0013] More preferably, the concentration of GO in the aqueous suspension is 8 mg / mL, and the concentration of OA in the ethanol solution is 10 μL / mL.

[0014] The nanomaterial GO has many advantages such as a significant specific surface area, easy synthesis, low preparation cost, good biocompatibility, environmental friendliness, and multiple functional groups. However, since graphene oxide is not dispersed in the organic solvent chlorobenzene, oleylamine-modified graphene oxide (OA-GO) was designed and synthesized. Due to the introduction of a hydrophobic long-chain alkyl group, OA-GO is well-dispersed in the chlorobenzene solvent and can be uniformly mixed with the polymer solution.

[0015] The second technical solution provided by the present invention:

[0016] A preparation method of the flexible organic field effect transistor breathing ammonia sensor using the modified graphene oxide nanosheets as described above, comprising transferring the gate, flexible dielectric layer, organic semiconductor layer, and source / drain electrodes layer by layer on the flexible substrate to prepare the flexible organic field effect transistor breathing ammonia sensor.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects:

[0018] The nanomaterial OA-GO containing multiple functional groups has an adsorption effect on the target gas. By preparing a porous film containing OA-GO in the present invention, the surface area in contact with the gas can be increased, more binding sites can be exposed, and finally the high-sensitivity and high-selectivity detection of the target gas NH 3 can be achieved.

[0019] OA-GO has a large specific surface area and many oxygen-containing polar functional groups (including carboxyl, hydroxyl, ether groups, etc.) on its surface, indicating its potential as a gas receptor material. The large specific surface area can expose abundant binding sites for more gas adsorption, and the polar functional groups can form weak interactions such as hydrogen bonds and molecular dipoles with ammonia. In summary, the addition of OA-GO improves the gas sensing response without affecting the electrical performance and stability of the device itself. Compared with other detection methods, this gas sensor based on flexible organic field effect transistors is expected to become a high-performance sensing platform for detecting various gas molecules due to its small size, simple operation, high sensitivity, and strong reliability.

[0020] The present invention detects the concentration of NH 3 by monitoring the change in the source-drain current (Ids) electrical signal in the I-t curve of the flexible organic field effect transistor gas sensor before and after the introduction of NH 3 . By comparing the presence or absence of holes formed by the aggregation of OA-GO in the organic semiconductor film, it is confirmed that the introduction of the porous film containing OA-GO can efficiently adsorb gas and improve the sensitivity of the device, and the theoretical detection limit can reach the ppb level. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0022] Figure 1 It is the synthesis route diagram of OA-GO in Example 1;

[0023] Figure 2 Infrared spectrum characterization diagrams of GO(a) and OA-GO(b);

[0024] Figure 3 In (a), it is a schematic diagram of the solution shearing process in S5 of Example 2; (b) is the AFM height map of the OA-GO / DPP-DTT / SEBS hybrid film (4%); (c) is the AFM phase image of the OA-GO / DPP-DTT / SEBS hybrid film (4%);

[0025] Figure 4 In (a), it is the atomic force microscope (AFM) characterization diagram of the roughness of the DPP-DTT / SEBS blend film in Example 2; (b) is the atomic force microscope (AFM) characterization diagram of the roughness of the OA-GO / DPP-DTT / SEBS (4%) blend film; (c) is the pore size distribution of different films and the relative height of the holes with respect to the film horizontal plane, where the red line is the OA-GO / DPP-DTT / SEBS (4%) blend film and the black line is the DPP-DTT / SEBS blend film;

[0026] Figure 5 Flow chart for constructing a flexible organic field effect transistor breathing ammonia sensor (OFET) using modified graphene oxide nanosheets in Example 2;

[0027] Figure 6 Characterization diagrams of the transfer and output curves of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) prepared in Example 2, where (a) is the transfer curve; (b) is the output curve;

[0028] Figure 7 Mobility comparison diagram of OA-GO / DPP-DTT-SEBS hybrid films with different OA-GO dosages (0%, 1%, 2%, 4%, 6% and 10%) in Example 2;

[0029] Figure 8 In (a), it is the ultraviolet spectrum characterization diagram of OA-GO and the blend films before and after adding OA-GO in Example 2; (b) is the infrared spectrum characterization diagram of the blend films before and after adding OA-GO in Example 2;

[0030] Figure 9 X-ray photoelectron spectroscopy (XPS) of the blend films before and after adding OA-GO in Example 2, where the blend film after addition is OA-GO / DPP-DTT / SEBS (4%); where (a), (b) and (c) are the X-ray photoelectron spectra of O 1s 、N 1s and C 1s respectively;

[0031] Figure 10 Variation of the mobility of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) along the parallel charge transport direction (a, c) and perpendicular to the charge transport direction (b, d) under the strain condition of 0 to 100%;

[0032] Figure 11 Responsivity comparison of the flexible OFET gas sensor to different concentrations of NH 3 (1 ppm and 2 ppm) before and after the addition of OA-GO;

[0033] Figure 12 In (a), the response and recovery of the real-time ISD electrical signal of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) to 1 to 5 ppm NH 3 ; (b) the real-time response diagram of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) to 1 to 5 ppm NH 3 ;

[0034] Figure 13 In (a), the selectivity of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) to different gases; Figure 13 In (b), the good linear fitting curve of the responsivity of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) exposed to different concentrations of NH 3 ; Detailed implementation manners

[0035] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0038] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this application are merely exemplary.

[0039] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0040] The room temperature of this invention refers to 25 ± 2 °C.

[0041] An embodiment of this invention constructs a blend-based polymer DPP-DTT, elastomer SEBS, and gas receptor material OA-GO as the active layer for a flexible gas sensor based on OFET. Since SEBS has a high fracture strain (550% strain), SEBS is selected as the elastomer. The addition of SEBS improves the stretchability of the semiconductor layer, and a stretchable flexible gas sensor is prepared. This device can comfortably adhere to the human skin and well adapt to various deformations such as bending, twisting, and stretching, and has the characteristic of high strain stability. The gas receptor material OA-GO has a large specific surface area and has many polar functional groups (including carboxyl, hydroxyl, ether groups, etc.). The large specific surface area can expose abundant binding sites for more gas adsorption, and weak interactions such as hydrogen bonds and molecular dipoles can be formed between the polar functional groups and ammonia. By preparing a porous film containing OA-GO, the surface area in contact with the gas can be increased, more binding sites can be exposed, and finally the highly sensitive and highly selective detection of the target gas NH 3 can be achieved. The addition of OA-GO improves the response of gas sensing and does not affect the electrical performance and stability of the device itself, realizing the rapid, ultrasensitive, and real-time monitoring of NH 3 .

[0042] The raw materials used in the examples of the present invention are all commercially available chemically pure reagents, among which graphene oxide was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.; oleylamine was purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd.; polymer DPP-DTT was purchased from Shenzhen Ruixun Optoelectronic Material Technology Co., Ltd., and elastomer SEBS was purchased from Asahi Kasei Technology Co., Ltd. of Japan; anhydrous ethanol was purchased from Tianjin Xiensiopude Technology Co., Ltd.; isopropanol was purchased from Tianjin Jiangtian Chemical Technology Co., Ltd.; octadecyltrichlorosilane (OTS) was purchased from Beijing Bailingwei Technology Co., Ltd.; carbon nanotube aqueous dispersion was purchased from Chengdu Organic Chemistry Co., Ltd. of the Chinese Academy of Sciences; 300nm SiO 2 The N-doped silicon wafer of the layer was purchased from China Electronics Technology Group Corporation, and the carbon nanotubes were purchased from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences.

[0043] In the embodiments of the present invention, the electrochemical performance is measured by a Keithley 4200SCS semiconductor parameter analyzer. 3 A homemade gas analysis system was used, including a flow monitoring system, a homemade test chamber, and a Keithley 2636B semiconductor parameter analyzer. Ultraviolet-visible spectrometer (UV-3600 Plus), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) were used to characterize the blending of the semiconductor layer.

[0044] Example 1 Preparation method of OA-GO

[0045] S1. 40 mg of GO was dispersed in 5 mL of deionized water and ultrasonicated for 0.5 h to obtain a brown graphene oxide / water suspension; 50 μL of oleylamine was dissolved in 5 mL of ethanol to obtain a transparent solution, and the graphene oxide / water suspension was mixed with the oleylamine / ethanol solution and vigorously stirred at room temperature for 24 h;

[0046] S2. The above liquid was placed in a vacuum oven at 80°C and vacuum dried for 12 h to obtain a black powder, namely OA-GO.

[0047] Figure 1 is the synthesis route of OA-GO in Example 1;

[0048] Figure 2 Infrared spectra of GO (a) and OA-GO (b) are shown in Figure 1. Figure 2 In (b), we can see that after the condensation reaction between GO and OA, various oxygen-containing functional groups still exist, 1356 cm -1 The peak at 1100 cm -1The peak at [specific location] is due to the C-O stretching vibration in the ether group. When the nitrogen atom is connected to the carbonyl carbon, the lone pair electrons of nitrogen will stabilize the resonance form. Therefore, compared with GO, the peak of C=O in OA-GO is redshifted from 1743 cm -1 to 1700 cm -1 . In addition, new bands appear at 3400 cm -1 and 1461 cm -1 , indicating the formation of amide groups during the condensation with OA. The alkyl C-H stretching vibration peaks at 2921 cm -1 and 2825 cm -1 are caused by the long alkyl chain of OA.

[0049] Example 2 Preparation method of a flexible organic field effect transistor breathing ammonia sensor using modified graphene oxide nanosheets

[0050] S1. Substrate cleaning: First, ultrasonically clean the heavily n 2 -doped silicon wafer with a thermally grown SiO + layer in ultrapure water for 10 min to remove the dust on the substrate surface that is easy to clean. Then, ultrasonically clean it with acetone for 10 min to remove the dust on the substrate surface that is difficult to clean. Finally, ultrasonically clean it with isopropanol for 10 min to complete the final cleaning;

[0051] S2. Interface modification: First, treat the cleaned substrate with plasma in an oxygen environment for 10 min at a power of 80 W. Then, place the silicon wafer in the OTS modification solution (obtained by mixing n-heptane and OTS in a volume ratio of 1000:1), and let it stand at room temperature for 3 h for modification. Then, take out the silicon wafer and ultrasonically treat it in beakers containing n-hexane solution, chloroform solution, and isopropanol solution for 10 min in sequence;

[0052] S3. Formation of the organic semiconductor thin film: Dissolve DPP-DTT and SEBS (H1221) in a weight ratio of 2:1 into a chlorobenzene solvent to prepare a 7.5 mg / mL polymer solution (denoted as the DPP-DTT / SEBS mixed solution). Disperse the OA-GO prepared in Example 1 into chlorobenzene to prepare an OA-GO organic solution with a concentration of 5 mg / mL;

[0053] S4. Use a pipette to take 5 different volumes of the above OA-GO organic solution and add them to 5 portions of the polymer solution respectively for mixing. In the 5 portions of the OA-GO / DPP-DTT / SEBS mixed solution obtained, OA-GO accounts for 1%, 2%, 4%, 6%, and 10% of the weight of DPP-DTT respectively. Place the above 5 portions of the OA-GO / DPP-DTT / SEBS mixed solution and the DPP-DTT / SEBS mixed solution (0%) on a hot plate at 80 °C for heating and stirring for 2 h;

[0054] S5. Respectively use a solution shearing device to scrape the above OA-GO / DPP-DTT / SEBS mixed solution and DPP-DTT / SEBS mixed solution (0%) onto the above OTS-modified silicon wafer at a shearing speed of 0.37 mm / s and a substrate temperature of 60 °C, and then anneal at 150 °C on a hot stage for 30 min to reduce the generation of defects in the morphology and molecular structure of the polymer film, obtaining an organic semiconductor film;

[0055] S6. Preparation of flexible substrate: Dissolve SEBS (H1062) in toluene to prepare a toluene solution with a concentration of 200 mg / mL, then heat and stir on a hot stage at 70 °C for 15 h, pour the toluene solution into a petri dish, and let it stand overnight to obtain a flexible, stretchable transparent thick film, which is the flexible substrate;

[0056] S7. Preparation of flexible dielectric layer: Dissolve SEBS (H1052) in toluene to prepare a toluene solution with a concentration of 60 mg / mL, then heat and stir on a hot stage at 70 °C for 10 h, and finally spin-coat the dissolved SEBS toluene solution on the OTS-modified silicon wafer at 1000 rpm for 50 s, and then anneal on a hot stage at 90 °C for 15 min to obtain a flexible, stretchable transparent dielectric layer, which is the flexible dielectric layer;

[0057] S8. Preparation of electrodes: For the gate and source / drain electrodes, use a commercial spray gun to spray the carbon nanotube aqueous dispersion onto the unmodified silicon wafer. Specifically, for the preparation of the gate: Fix the silicon wafer (1×2 cm) on the table, and use a commercial spray gun to evenly spray 5 mL of the carbon nanotube aqueous dispersion (concentration 0.2 wt%) onto the silicon wafer; For the preparation of the source / drain: Fix the iron precision mask on the silicon wafer (1×1 cm) with a magnet, and use a commercial spray gun to evenly spray 5 mL of the carbon nanotube aqueous dispersion (concentration 0.2 wt%) onto the silicon wafer. The used mask has a channel width of 400 μm and a channel length of 100 μm;

[0058] S9. Transfer the gate, flexible dielectric layer, organic semiconductor layer, and source / drain layer layer by layer onto the prepared flexible substrate to prepare a flexible organic field-effect transistor ammonia sensor (flexible OFET gas sensor) using modified graphene oxide nanosheets.

[0059] Figure 3 In (a) is a schematic diagram of the solution shearing process in S5; (b) is an AFM height map (10 nm) of the OA-GO / DPP-DTT / SEBS mixed film (4%); (c) is an AFM phase image of the OA-GO / DPP-DTT / SEBS mixed film (4%); showing a nanofiber network structure, and the nanofibers are an ideal morphology for charge transport and mechanical deformation.

[0060] Figure 4 Figure (a) is the atomic force microscope (AFM) characterization diagram of the roughness of the DPP-DTT / SEBS blend film in Example 2, and figure (b) is the atomic force microscope (AFM) characterization diagram of the roughness of the OA-GO / DPP-DTT / SEBS (4%) blend film; figure (c) is the pore size distribution of different films and the relative height of the pores with respect to the film horizontal plane. The red line is the OA-GO / DPP-DTT / SEBS (4%) blend film, and the black line is the DPP-DTT / SEBS blend film. Taking the film as the horizontal plane, since the film has pores, there will be positive and negative values. The positive value represents the part of the pore that is higher than the film horizontal plane, and the negative value represents the part of the pore that is lower than the film horizontal plane. It can be seen that after adding 4% of OA-GO, the pores formed by shearing increase the surface roughness of the film from 0.69 nm to 2.12 nm. The formation of pores and the increase in roughness are beneficial to gas adsorption.

[0061] Figure 5 It is the flow chart for constructing a flexible organic field effect transistor ammonia sensor (OFET) using modified graphene oxide nanosheets in Example 2.

[0062] Performance measurement test

[0063] The electrical properties were characterized by a Keithley 4200SCS semiconductor parameter analyzer. Figure 6 Figures are the transfer and output curve characterization diagrams of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) prepared in Example 2. Figure (a) is the transfer curve, indicating that the number of carriers can be controlled by the externally applied gate voltage Vg, that is, it has gate-tunable hole charge transport characteristics; figure (b) is the output curve, showing a clear transition from the linear state to the saturation state, and the saturation current is almost flat.

[0064] Figure 7 Figure is the mobility comparison diagram of OA-GO / DPP-DTT-SEBS hybrid films with different OA-GO dosages (0%, 1%, 2%, 4%, 6% and 10%) in Example 2. When 2% of OA-GO is added, the device has the highest carrier mobility. When 6% of OA-GO is added, the carrier mobility decreases significantly. Considering the requirements of gas sensing and device performance, 4% of OA-GO is selected to be blended with DPP-DTT / SEBS as the active layer.

[0065] Figure 8Figure (a) shows the UV spectra of the blend films before and after adding OA-GO in OA-GO and Example 2. The blend film after addition is the OA-GO / DPP-DTT / SEBS(4%) blend film. The highest energy peak near 420 nm is attributed to the π-π* transition of DPP-DTT. The two peaks observed near 750 nm and 820 nm are attributed to the 0-1 and 0-0 oscillator transitions of DPP-DTT respectively. The low-energy 0-0 peak is attributed to polymer aggregation. After adding a small amount of OA-GO, the intensity of the 0-0 peak increases, indicating that the addition of OA-GO can promote the formation of ordered DPP-DTT aggregates.

[0066] Figure 8 Figure (b) shows the infrared spectra of the blend films before and after adding OA-GO in Example 2. The blend film after addition is OA-GO / DPP-DTT / SEBS(4%). For the OA-GO / DPP-DTT / SEBS hybrid material, the peak at 3072 cm -1 is the result of the N-H stretching vibration in the secondary amide group of OA-GO. The broad peak at 3500 - 3200 cm -1 is the O-H stretching vibration peak of the hydroxyl group, which is not visible in the pure polymer (DPP-DTT + SEBS).

[0067] Figure 9 Figure shows the X-ray photoelectron spectroscopy (XPS) of the blend films before and after adding OA-GO in Example 2. The blend film after addition is OA-GO / DPP-DTT / SEBS(4%); among them, (a), (b) and (c) are the X-ray photoelectron spectra of O 1s , N 1s and C 1s respectively. The X-ray photoelectron spectra of O 1s , N 1s and C 1s are compared. There are many oxygen-containing functional groups on the surface of OA-GO. After mixing OA-GO, the O peak increases significantly, and the N / C peak shows no significant change before and after mixing OA-GO.

[0068] Test on the tensile strain stability of the flexible OFET gas sensor:

[0069] Step 1: Fix the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) prepared in Example 2 on a self-made stretching stage;

[0070] Step 2: Stretch from the original state to 100%;

[0071] Step 3: Test the change in the electrical properties of the flexible organic field-effect transistor before and after stretching using a Keithley 4200SCS semiconductor parameter analyzer.

[0072] Figure 10 For the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS(4%) under 0-100% strain conditions, the changes in mobility when the sensor is along the parallel charge transport direction (a, c) and perpendicular to the charge transport direction (b, d); the transfer curves of the flexible OFET gas sensor along the parallel channel length direction and perpendicular to the channel length direction at 0%, 20%, 40%, 60%, 80% and 100% strain change little. When the device is stretched to 100% strain along the parallel channel length direction, the mobility of the flexible OFET gas sensor decreases from 1.01 to 0.81 cm 2 V -1 s -1 ( Figure 10 as shown in (c)); when the flexible OFET gas sensor is stretched to 100% strain perpendicular to the channel length direction, the mobility of the device decreases from 0.98 to 0.72 cm 2 V -1 s -1 ( Figure 10 as shown in (d)).

[0073] The application of the flexible OFET gas sensor to gas detection includes the following steps:

[0074] Step 1: Use a self-made analysis system, including a flow monitoring system, a self-made test chamber and a Keithley 2636B semiconductor parameter analyzer. Adopt dynamic gas distribution, and precisely control the gas to be introduced into the chamber at a flow rate of 1000 mL / min through a multi-channel gas flowmeter. Place the flexible gas sensor in the chamber, connect the electrodes using gold wires and gallium-indium alloy, then seal the chamber. First, introduce dry air, and then test the I-t curve of the flexible OFET and obtain the numerical value I of the output signal current. 0 ;

[0075] Step 2: Adjust the gas distributor and continuously introduce NH 3 for 1 minute. It can be observed in the I-t curve that the source-drain current (I ds ) decreases significantly, and the numerical value I of the output signal current is obtained. g ;

[0076] Step 3: Calculate the sensing output signal and test the response to NH 3 in the concentration range of 1-5 ppm. The sensitivity S calculated according to the slope of the relationship between the responsivity and the concentration, where the calculation formula for the sensing output signal is:

[0077]

[0078] where (I 0 -I g ) is the change in the source-drain current I 3 before and after the introduction of NH ds , and I 0 is the reference measured in dry air.

[0079] The gas sensing characteristics were studied using the self-made analysis system above. Toxic gases (NO, SO 2 , H 2 S, NH 3 , CO, acetone, ethylene, methanol) were dynamically mixed with dry air (background gas) through a multi-channel gas flowmeter to precisely control the concentration of the gas to be measured, and introduced into the chamber at a flow rate of 1000 mL / min. The concentration of NH 3 was detected by monitoring the change in the source-drain current (Ids) in the I-t curve of the flexible organic field-effect transistor. The response was directly evaluated as follows: R = (I 0 -I g ) / I g ×100%, where (I 0 -I g ) is the change in the source-drain current I ds before and after the introduction of the target gas, and I 0 is the reference measured in dry air.

[0080] The flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) prepared in Example 2 was applied to the detection of the concentration of NH 3 , including the following steps:

[0081] Step 1: Place the flexible gas sensor in the chamber, connect the electrodes using gold wires and gallium-indium alloy, then seal the chamber, introduce dry air, and then test the I-t curve of the flexible OFET and obtain the value I 0 of the output signal current;

[0082] Step 2: Adjust the gas mixer and continuously introduce NH 3 for 1 min. A significant decrease in the source-drain current (Ids) can be observed in the I-t curve, and the value I g of the output signal current is obtained;

[0083] Step 3: Calculate R = (I 0 -I g ) / I g ×100% as the sensing output signal. Test the response to NH 3 in the concentration range of 1 - 5 ppm.The sensitivity S calculated according to the slope of the relationship between the response and the concentration of the response.

[0084] The flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) prepared in Example 2 and the flexible OFET gas sensor of DPP-DTT / SEBS were respectively placed in the above self-made test chamber. Dynamic gas distribution was used, and the gas was accurately controlled to be introduced into the chamber at a flow rate of 1000 mL / min through a multi-channel gas flow meter to test the sensor NH 3 Response.

[0085] Figure 11 For the flexible OFET gas sensor before and after the addition of OA-GO, the response comparison for different concentrations of NH 3 (1 ppm and 2 ppm). When the device is exposed to the target gas environment to be measured, gas molecules enter the semiconductor interior from the semiconductor surface and diffuse to the conductive channel. For a p-type OFET device, when a negative VG is applied, more hole carriers are enriched in the semiconductor layer near the gate position, and a conduction current will be generated after connecting the source and drain electrodes. The reducing gas NH 3 has a lone pair of electrons and a strong electron-donating effect. When it contacts the semiconductor layer molecules, weak intermolecular forces are generated, including various forms such as molecular dipole, hydrogen bond, and π-π conjugation, reducing the hole carrier density in the semiconductor layer. Under the same test conditions, Ids decreases, and the response signal to NH 3 can be determined by analyzing the relative change value of the current.

[0086] Figure 12 In (a), it is the response and recovery of the real-time ISD electrical signal of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) to 1 to 5 ppm NH 3 ; (b) is the real-time response diagram of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) to 1 to 5 ppm NH 3 .

[0087] Figure 13 In (a), it is the selectivity of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) to different gases; it can be seen that the response value of the sensor to 2 ppm NH 3 is 128%, which is significantly higher than the response values of H 2 S, SO 2 , NO, CO, and organic volatile gases such as 50 ppm of methanol, acetone, and ethylene at 10 ppm. This means that the sensor has excellent NH 3 detection selectivity and anti-interference ability; Figure 13In (b), the good linear fitting curve of the response of the flexible OFET gas sensor of OA-GO / DPP-DTT / SEBS (4%) exposed to different concentrations of NH 3 proves that the sensor has a good linear fitting curve of the response when exposed to different concentrations (1 - 5 ppm) of NH 3 with a detection limit of 9.19 ppb and high sensitivity.

[0088] The above is only the preferred specific embodiment 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 those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets, characterized in that: The invention comprises, from bottom to top, a flexible substrate, a gate, a flexible dielectric layer, an organic semiconductor layer and a source / drain electrode, wherein the raw materials of the organic semiconductor layer comprise poly[(dithiophene)-alternating-(2,5-di(2-octyldodecyl)-3,6-di(thienyl)-pyrrolopyrroledione)], an elastomer and modified graphene oxide; the modified graphene oxide is graphene oxide modified with long-chain oleylamine; The method for preparing the organic semiconductor layer comprises the following steps: shearing a mixed solution containing modified graphene oxide, poly[(dithiophene)-alternating-(2,5-di(2-octyldodecyl)-3,6-di(thienyl)-pyrrolopyrroledione)] and an elastomer, then coating the solution on a silicon wafer modified with octadecyltrichlorosilane, and annealing to obtain an organic semiconductor film, namely the organic semiconductor layer; the shearing speed is 0.37 mm / s; The modified graphite oxide accounts for 4% by weight of the poly[(dithiophene)-alt-(2,5-di(2-octyldodecyl)-3,6-di(thienyl)-pyrrolopyrroledione)]].

2. The flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets according to claim 1, characterized in that: The preparation method of the mixed solution is: mixing the organic solution of the modified graphite oxide and a polymer solution containing poly[(dithiophene)-alternating-(2,5-di(2-octyldodecyl)-3,6-di(thienyl)-pyrrolopyrroledione)] and an elastomer to obtain the mixed solution.

3. The flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets according to claim 2, characterized in that: The weight ratio of the poly[(bis-thiophene)-alternating-(2,5-di(2-octyldodecyl)-3,6-di(thienyl)-pyrrolopyrroledione)] and the elastomer is 2:1, and the total concentration of the poly[(bis-thiophene)-alternating-(2,5-di(2-octyldodecyl)-3,6-di(thienyl)-pyrrolopyrroledione)] and the elastomer in the polymer solution is 7.5 mg / mL.

4. The flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets according to claim 2, characterized in that: The mass concentration of modified graphite oxide in the organic solution is 5 mg / mL.

5. The flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets according to claim 1, characterized in that: The preparation method of the modified graphene oxide comprises the following steps: mixing an aqueous suspension of graphene oxide and an ethanol solution of oleylamine in equal volumes, vigorously stirring at room temperature, and vacuum drying to prepare the modified graphene oxide.

6. The flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets according to claim 5, characterized in that: The concentration of graphene oxide in the water suspension is 8 mg / mL, and the concentration of oleylamine in the ethanol solution is 10 μL / mL.

7. A method for preparing a flexible organic field effect transistor respiratory ammonia sensor using modified graphene oxide nanosheets according to any one of claims 1 to 6, characterized in that: The gate, the flexible dielectric layer, the organic semiconductor layer and the source / drain are transferred layer by layer on the flexible substrate to prepare the flexible organic field effect transistor respiratory ammonia sensor.

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