A graphene oxide humidity sensor based on laser modulation technology

Abstract

The application discloses a graphene oxide humidity sensor based on a laser modulation technique, which comprises a dielectric layer, an interdigital electrode and a sensitive layer arranged on a substrate surface in sequence, and the dielectric layer and the sensitive layer are both thin films prepared by vacuum filtration of laser irradiated graphene oxide, and the graphene oxide humidity sensor has a high specific surface area, high sensitivity, low production difficulty and high quality.

Description

Technical Field

[0001] This invention relates to the field of sensor fabrication technology, and specifically to a graphene oxide humidity sensor based on laser modulation technology. Background Technology

[0002] With the increasing demand for environmental monitoring, intelligent manufacturing, and healthcare, the development of high-performance humidity sensors has been a hot research topic in materials science and microelectronics. Among them, humidity sensors based on graphene oxide have attracted widespread attention due to their excellent performance.

[0003] Graphene oxide is a two-dimensional carbon material rich in oxygen-containing functional groups, possessing a large specific surface area and highly tunable chemical properties. When graphene oxide is exposed to environments with varying humidity, its electrical and optical properties change significantly, providing a good foundation for humidity detection. Early research mainly focused on the development of simple resistive or capacitive graphene oxide humidity sensors, achieving some success.

[0004] With in-depth research into the sensing mechanism, researchers have developed more innovative humidity sensing solutions. For example, by utilizing the absorption characteristics of graphene oxide, an optically modulated humidity sensor can be constructed, enabling rapid and highly sensitive humidity detection.

[0005] Existing GO-based humidity sensors typically employ Hummers fabrication for GO preparation, resulting in a specific surface area of ​​200-500 m². 2 / g. Regarding deposition, methods such as drop coating, spin coating, and spray coating are employed. To further improve sensor sensitivity, increasing the specific surface area of ​​GO is crucial. Many existing works have focused on increasing the specific surface area of ​​GO. In the paper "Hydrothermal Dehydration for High-Yield Production of High-Quality Graphene" (Nat. Commun. 2013), a study was conducted using hydrothermal treatment to oxidize and exfoliate graphite, preparing a graphite with a specific surface area reaching 935 m². 2 / g of GO. In "High-Surface-Area Graphene-Based Supercapacitor Electrodes Prepared by Electrochemical Exposition" (Nat. Commun. 2014), GO was combined with SiO2 nanoparticles to prepare porous GO materials.

[0006] Traditional methods for increasing the specific surface area of ​​GO often involve adding many chemical reagents, resulting in problems such as difficulty in cleaning the material, difficulties in waste liquid treatment, and environmental pollution. Introducing other nanomaterials can also easily introduce impurities.

[0007] In GO deposition, methods such as drop coating, spin coating, and spray coating are often used. For example, in the paper "Ultrah i gh humi d ty sen yi v iv v si v ...

[0008] For GO deposition, traditional methods such as drop coating, spin coating, and spray coating have problems such as uncontrollable deposition morphology and thickness, and sensor performance being greatly affected by the deposition environment and temperature. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a graphene oxide humidity sensor based on laser modulation technology, which has a high specific surface area, high sensitivity, low production difficulty and high quality.

[0010] To address the aforementioned technical problems, this invention provides a graphene oxide humidity sensor based on laser modulation technology, comprising a dielectric layer, interdigitated electrodes, and a sensitive layer sequentially disposed on a substrate surface. Both the dielectric layer and the sensitive layer are thin films prepared by vacuum filtration of laser-irradiated graphene oxide.

[0011] Furthermore, graphene oxide is obtained through laser irradiation as follows:

[0012] Graphene oxide was ultrasonically dispersed in deionized water to form a graphene oxide dispersion.

[0013] The graphene oxide dispersion was placed in an ice-water environment and subjected to laser irradiation.

[0014] After laser irradiation, the sample was washed once with water and once with ethanol, and then dried to constant weight to obtain large-diameter graphene oxide (LGO).

[0015] Furthermore, the concentration of the graphene oxide dispersion is 0.5-5 mg / mL.

[0016] Furthermore, during laser irradiation, the laser wavelength is 355-1064nm, the frequency is 5-100Hz, the energy is 100-500mJ, and the irradiation time is 2-5 hours.

[0017] Furthermore, the graphene oxide dispersion was placed in a beaker, and the beaker was placed in a container filled with ice water to obtain an ice water environment.

[0018] Furthermore, large-diameter graphene oxide (LGO) was prepared into an aqueous solution and then used to form a thin film by vacuum filtration.

[0019] Furthermore, the dielectric layer is imprinted on the substrate, the interdigital electrodes are deposited on the surface of the dielectric layer by inkjet printing, and the sensitive layer is imprinted on the interdigital electrodes.

[0020] Furthermore, the interdigitated electrodes are made of graphene.

[0021] Furthermore, the thickness of the dielectric layer and the sensitive layer is 300nm-800nm.

[0022] The beneficial effects of this invention are:

[0023] The dielectric and sensitive layers are modulated and fabricated using laser irradiation. These layers have more wrinkles and defects, resulting in a higher specific surface area. The entire process is completed solely in an aqueous solution, making it environmentally friendly and free of impurities. Vacuum filtration is then used in humidity sensor manufacturing, allowing the film to separate from filter paper while maintaining a certain porosity between layers, thus maximizing sensitivity. More importantly, the film obtained through vacuum filtration is smoother, and its thickness and morphology are more controllable, ensuring commercial mass production. Attached Figure Description

[0024] Figure 1 This is a flowchart of the laser irradiation process of the present invention;

[0025] Figure 2 This is a flowchart of the sensor manufacturing process of the present invention;

[0026] Figure 3 These are the FTIR images of LGO-1, LGO-2, LGO-4 of the present invention and ordinary GO;

[0027] Figure 4 This is the specific surface area testing structure of the present invention;

[0028] Figure 5 This is a SEM image of the LGO membrane used for filtration in this invention;

[0029] Figure 6 This is a SEM image of the ordinary GO membrane used for filtration in this invention;

[0030] Figure 7 These are the sensitivity performance test results of the M1 of this invention at multiple frequencies;

[0031] Figure 8These are the sensitivity performance test results of a common sensor at multiple frequencies;

[0032] Figure 9 These are the sensitivity performance test results of the M1 sensor of this invention and a conventional sensor at a frequency of 1Hz.

[0033] Figure 10 These are the sensitivity performance test results of the M1 sensor of this invention and a conventional sensor at a frequency of 10Hz.

[0034] Figure 11 These are the sensitivity performance test results of the M1 sensor of this invention and a conventional sensor at a frequency of 100Hz.

[0035] Figure 12 These are the sensitivity performance test results of M1 and M2 of the present invention at a frequency of 100Hz. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0037] An embodiment of the graphene oxide humidity sensor based on laser modulation technology of the present invention includes a dielectric layer, interdigitated electrodes, and a sensitive layer sequentially disposed on the surface of a substrate. Both the dielectric layer and the sensitive layer are thin films prepared by vacuum filtration of graphene oxide after laser irradiation. By maximizing the destructive effect of the laser on the laser wavelength and the dispersion liquid, a vacuum filtration raw material with a high specific surface area is obtained. The thin film is then prepared by vacuum filtration, which maximizes the sensitivity, thereby making the humidity sensor of excellent quality and high sensitivity.

[0038] In preparing the thin films for the dielectric and sensitive layers, graphene oxide was first treated with laser irradiation, followed by vacuum filtration to prepare the films. Before laser irradiation, the graphene oxide dispersion was placed in a beaker, which was then placed in a container filled with ice water to create an ice-water environment before laser irradiation. The following section compares the modulation of graphene oxide under different conditions:

[0039] LGO-1:

[0040] Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 1 mg / mL. The dispersion was irradiated for 3.5 h in an ice-water environment with a laser wavelength of 1064 nm, a laser irradiation frequency of 10 Hz, and an energy density of 350 mJ. The ice water was replaced every 30 minutes or less to ensure that GO would not be reduced due to excessive temperature. After irradiation, the dispersion was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-1.

[0041] LGO-2:

[0042] Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 1 mg / mL. The dispersion was irradiated with a laser at a wavelength of 1064 nm for 3.5 h without using an ice-water bath. The laser irradiation frequency was 10 Hz and the energy density was 350 mJ. The ice water was replaced every 30 minutes or less to ensure that GO would not be reduced due to excessive temperature. After irradiation, the dispersion was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-2.

[0043] LGO-3:

[0044] Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 1 mg / mL. The dispersion was irradiated for 2 hours under ice-water bath conditions with a laser wavelength of 1064 nm, a laser irradiation frequency of 10 Hz, and an energy density of 350 mJ. The ice water was replaced every 30 minutes or less to ensure that GO would not be reduced due to excessive temperature. After irradiation, the dispersion was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-3.

[0045] LGO-4:

[0046] Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 1 mg / mL. Without an ice-water bath, the solution was irradiated with a laser at a wavelength of 1064 nm for 5 hours. The laser irradiation frequency was 10 Hz and the energy density was 350 mJ. The ice water was replaced every 30 minutes or less to ensure that GO would not be reduced due to excessive temperature. After irradiation, the solution was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-4.

[0047] The laser-modulated LGO-1, LGO-2, and LGO-4 were compared with unmodulated graphene oxide (GO) using FTIR, as referenced. Figure 3 As shown, LGO-2 and LGO-4 at 3500 and 1750 cm -1 The significant decrease in the -OH and -COOH peaks proves that GO was reduced, and the ice-water bath condition was necessary.

[0048] By measuring and comparing the specific surface area of ​​LGO-1, LGO-3, and GO that has not been laser irradiated, reference was made. Figure 4 As shown, LGO-1 is the better choice, with a specific surface area as high as 1339 m². 2 / g, the specific surface area of ​​unirradiated GO is 484m². 2 / g, and the laser irradiation time of LGO-3 is shorter than that of LGO-1. The specific surface area of ​​LGO-3 is smaller than that of LGO-1. Therefore, when the concentration of graphene oxide is 1 mg / mL, the laser irradiation time is preferably 3.5 h. As the concentration of graphene oxide increases, the irradiation time can also be increased accordingly. (Is the description reasonable?) Yes

[0049] Thin films were prepared using LGO-1 as the raw material. Large-diameter graphene oxide was placed in deionized water to prepare an LGO-1 aqueous solution of 1 mg / mL. 0.55 mL of the LGO-1 aqueous solution was taken, and the LGO-1 was used to form a film by vacuum filtration. The filtration pressure was 0.1 MPa, and the filtration time was greater than 30 min to ensure that the air layer was removed. The thickness of the obtained film was 300 nm-800 nm. Two films were prepared in this way, which were used as the sensitive layer and the dielectric layer, respectively.

[0050] according to Figure 5 The SEM image shown shows that the films prepared using LGO-1 as a raw material have more wrinkled layers, a higher specific surface area, and can absorb more water molecules. (Refer to...) Figure 6 The image shown is a SEM image of ordinary GO sheets after vacuum filtration. The sheets are smoother, with more compact layers and a lower specific surface area. Therefore, vacuum filtration is a feasible method for preparing LGO membranes and using them in humidity sensor manufacturing. By adjusting the filtration pressure, the LGO membrane can be effectively separated from the filter paper while maintaining a certain porosity between layers, resulting in more wrinkled sheets and a higher specific surface area.

[0051] To prepare a humidity sensor, a thin film was used. A dielectric layer was imprinted onto a PET substrate, and interdigitated electrodes made of graphite were deposited on the surface of the dielectric layer using inkjet printing. Subsequently, a sensitive layer was imprinted onto the interdigitated electrodes to obtain the humidity sensor M1.

[0052] See Figure 7 The humidity sensor M1 demonstrates excellent linearity and sensitivity in sensitivity tests at different frequencies. (See [link to relevant documentation]). Figure 8 The humidity sensor fabricated using ordinary GO not only has half the sensitivity of the humidity sensor M1, but also exhibits a significant decrease in sensitivity and consequently reduced linearity under high humidity conditions. (See also...) Figures 9 to 11 A comparison of the sensitivity of humidity sensor M1 and a humidity sensor made of ordinary GO at different frequencies shows that the LGO humidity sensor exhibits significantly higher sensitivity across a wide frequency range. Humidity sensor M1 achieves sensitivities of 3.5, 6.6, and 8.2 (1% RH) at 100Hz, 1kHz, and 10kHz, respectively. -1Especially in high humidity conditions, due to its abundant porosity, this sensor can adsorb and store a large number of water molecules. Therefore, compared with traditional non-laser irradiated humidity sensors, it still maintains extremely high sensitivity, effectively alleviating the nonlinear phenomenon that is usually difficult to solve under high humidity conditions. The graphene sensor prepared by conventional GO has sensitivities of 1.1, 3.6, and 4.6 (1% RH) at frequencies of 100Hz, 1kHz, and 10kHz, respectively. -1 ).

[0053] Thin films were prepared using LGO-1 as the raw material. Large-diameter graphene oxide was placed in deionized water to prepare an LGO-1 aqueous solution of 1 mg / mL. 2 mL of the LGO-1 aqueous solution was taken and the LGO-1 was used to form a film by vacuum filtration. The filtration pressure was 0.1 MPa and the filtration time was greater than 1 h to ensure that the air layer was removed. The thickness of the obtained film was 300 nm-800 nm. Two films were prepared in this way, which served as the sensitive layer and the dielectric layer, respectively. The dielectric layer was imprinted on a PET substrate. Interdigitated electrodes made of graphite were deposited on the surface of the dielectric layer by inkjet printing. Then the sensitive layer was imprinted on the interdigitated electrodes to obtain the humidity sensor M2.

[0054] For a test comparison of M1 and M2, see [link / reference]. Figure 12 Sensitivity performance tests at 100Hz indicate that the amount of LGO-1 aqueous solution should not be too large, meaning the amount of GO should not be excessive. This ensures the film thickness remains within a reasonable range and should not be too thick. Excessive GO content results in a less noticeable change in device capacitance after water molecule absorption, leading to decreased sensitivity. Furthermore, thicker films exhibit weaker adhesion to the substrate. Both humidity sensors M and M2 demonstrate superior performance compared to humidity sensors prepared using ordinary GO.

[0055] This application also takes the fabrication of sensors under irradiation with different laser parameters as an example:

[0056] LGO-5: Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 2 mg / mL. The dispersion was irradiated for 4 hours in an ice-water environment with a laser wavelength of 355 nm, a laser irradiation frequency of 80 Hz, and an energy density of 500 mJ. The ice water was replaced every 30 minutes or less to ensure that GO would not be reduced due to excessive temperature. After irradiation, the dispersion was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-5.

[0057] A thin film with high specific surface area was formed by vacuum filtration using LGO-5, and a humidity sensor M3 was fabricated using this film. Humidity sensor M3 exhibits good sensitivity, with sensitivities of 2.8, 5.2, and 7.2 (1% RH) at 100 Hz, 1 kHz, and 10 kHz, respectively. -1This technology has significant advantages over humidity sensors made from ordinary GO.

[0058] LGO-6: Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 2 mg / mL. The dispersion was irradiated for 3 hours in an ice-water environment with a laser wavelength of 980 nm, a laser irradiation frequency of 40 Hz, and an energy density of 400 mJ. The ice water was replaced every 30 minutes or less to ensure that GO was not reduced due to excessive temperature. After irradiation, the dispersion was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-6.

[0059] A thin film with good specific surface area was formed by vacuum filtration using LGO-6, and a humidity sensor M4 was fabricated based on it. Humidity sensor M4 exhibits good sensitivity, with sensitivities of 2.6, 4.7, and 6.7 (1% RH) at 100 Hz, 1 kHz, and 10 kHz, respectively. -1 This technology has significant advantages over humidity sensors made from ordinary GO.

[0060] LGO-7: Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion with a concentration of 0.5 mg / mL. The dispersion was irradiated for 2.5 h in an ice-water environment with a laser wavelength of 1064 nm, a laser irradiation frequency of 20 Hz, and an energy density of 150 mJ. The ice water was replaced every 30 minutes or less to ensure that GO was not reduced due to excessive temperature. After irradiation, the dispersion was washed once with water and once with ethanol, and then dried at 60 °C to constant weight to obtain LGO-7.

[0061] A thin film was formed using LGO-7 via vacuum filtration, exhibiting excellent specific surface area and higher flatness. A humidity sensor M5 was then fabricated using this film. The humidity sensor M5 demonstrates good sensitivity, with sensitivities of 2.3, 4.5, and 6.3 (1% RH) at 100 Hz, 1 kHz, and 10 kHz, respectively. -1 This technology has significant advantages over humidity sensors made from ordinary GO.

[0062] To improve specific surface area, this application proposes a laser-modulated specific surface area improvement process. This process utilizes laser irradiation of GO in an aqueous solution, and physical cooling weakens the GO reduction effect while creating more wrinkles and defects, thereby increasing the specific surface area. The entire process is completed solely in an aqueous solution, making it environmentally friendly and free of impurities.

[0063] Regarding deposition, this study marks the first time that vacuum filtration has been used to fabricate membranes for humidity sensors. By adjusting the filtration pressure, GO can be separated from the filter paper while maintaining a certain porosity between layers, thereby maximizing sensitivity. More importantly, the membrane obtained through vacuum filtration is smoother, and its thickness and morphology are more controllable, ensuring its commercial mass production.

[0064] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A graphene oxide humidity sensor based on laser modulation technique, characterized in that, The gas sensor comprises a dielectric layer, an interdigital electrode and a sensitive layer arranged on a substrate surface in sequence, wherein the dielectric layer and the sensitive layer are both prepared by vacuum filtration of graphene oxide after laser irradiation. The graphene oxide is irradiated by laser as follows: The graphene oxide is ultrasonically dispersed in deionized water to form a graphene oxide dispersion liquid; The graphene oxide dispersion liquid is placed in an ice water environment and irradiated by laser; After the laser irradiation, the graphene oxide is washed with water and ethanol in sequence once, and dried to constant weight to obtain large graphene oxide LGO; During the laser irradiation, the wavelength of the laser is 355-1064 nm, the frequency is 5-100 Hz, the energy is 100-500 mJ, and the irradiation time is 2-5 hours. The dielectric layer is imprinted on the substrate, the interdigital electrode is deposited on the surface of the dielectric layer by inkjet printing, and the sensitive layer is imprinted on the interdigital electrode. The graphene oxide dispersion liquid is placed in a beaker, and the beaker is placed in a container containing ice water to obtain an ice water environment.

2. The graphene oxide humidity sensor based on laser modulation technique as claimed in claim 1, wherein, The concentration of the graphene oxide dispersion liquid is 0.5-5 mg / mL.

3. The graphene oxide humidity sensor based on laser modulation technique as claimed in claim 1, wherein, The large graphene oxide LGO is configured into an aqueous solution, and a thin film is prepared by vacuum filtration.

4. The graphene oxide humidity sensor based on laser modulation technique as claimed in claim 1, wherein, The material of the interdigital electrode is graphene.

5. The graphene oxide humidity sensor based on laser modulation technique as claimed in claim 1, wherein, The thickness of the dielectric layer and the sensitive layer is 300-800 nm.

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