A highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide and its preparation method

Abstract

The present invention belongs to the field of gas sensors and discloses a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide and a preparation method thereof. The sensor comprises, from bottom to top, an insulating substrate, interdigitated electrodes, and a gas-sensitive film based on n-type hydroxyl-reduced graphene oxide; the gas-sensitive film is prepared by converting oxygen-containing groups on the surface of graphene oxide into hydroxyl groups, or by converting oxygen-containing groups on the surface of graphene oxide into hydroxyl groups and then modifying them with calix[6]arene. The sensor uses n-type hydroxyl-reduced graphene oxide as a gas-sensitive film and utilizes a molecular olfactory sensing mechanism to provide material-gas targeting, thereby achieving room temperature, ultra-high selectivity, fast response rate, and wide detection range detection in DMMP detection; in particular, using HRGO@Calix[6]arene as a gas-sensitive film can simultaneously improve the stability of the sensor and the moisture resistance of the low-concentration detection resolution.

Description

Technical Field

[0001] The present invention belongs to the technical field related to nanomaterials and sensors, and more specifically, relates to a highly selective DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide and a preparation method thereof. Background Art

[0002] Sarin and other organophosphorus nerve agents pose a serious threat to human health and life in special social environments. Developing highly selective sensors for organophosphorus substances is of great significance. However, there are currently few reports on sensors for organophosphorus substances, and they generally lack selectivity.

[0003] In research on sensing nerve agents like sarin, dimethyl methylphosphonate (DMMP) is often used as a simulant because it is a similar organophosphorus compound and is less toxic. However, this also means that developing truly effective gas-sensing materials based on DMMP for detecting nerve agents like sarin requires understanding the common toxicity mechanisms of both the simulant and the nerve agent and designing them accordingly. Unfortunately, this is often overlooked in most studies, often resulting in poor selectivity.

[0004] Therefore, the development of new highly selective sensitive materials is particularly critical. Based on the fact that the biological olfactory system is naturally highly selective, it is of far-reaching significance to construct corresponding highly selective sensitive materials to achieve molecular olfactory sensing by mimicking the recognition mechanism of biological olfaction for specific markers. Summary of the Invention

[0005] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a highly selective DMMP room-temperature sensor based on n-type hydroxyl-reduced graphene oxide and a preparation method thereof. The purpose is to integrate n-type hydroxyl-reduced graphene oxide as a gas-sensitive material into a molecular olfactory sensor for detecting the sarin simulant DMMP at room temperature, thereby solving technical problems such as the low selectivity of DMMP detection in the prior art.

[0006] In order to achieve the above-mentioned purpose, in one aspect of the present invention, a highly selective DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide is provided, which comprises, from bottom to top: an insulating substrate, an interdigitated electrode, and a gas-sensitive film based on n-type hydroxyl reduced graphene oxide; wherein the gas-sensitive film based on n-type hydroxyl reduced graphene oxide is obtained by the following preparation method: by converting the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups, or by converting the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups and then performing cup[6]arene modification.

[0007] As a preferred embodiment of the present invention, the oxygen-containing groups on the surface of the graphene oxide are converted into hydroxyl groups, specifically by reducing the graphene oxide using an alkaline aqueous solution of sodium borohydride as a reducing agent.

[0008] As a preferred embodiment of the present invention, it is characterized in that the gas-sensitive film based on n-type hydroxyl-reduced graphene oxide is obtained by converting the oxygen-containing groups on the surface of the graphene oxide into hydroxyl groups and then modifying it with calix[6]arene, specifically, the graphene oxide is reduced using an alkaline aqueous solution of sodium borohydride as a reducing agent, and then the calix[6]arene is grafted onto the reduced graphene oxide by π-π stacking.

[0009] As a preferred embodiment of the present invention, the graphene oxide is obtained by adjusting the temperature of the two-step oxidation reaction in the Hummer method to increase the content of oxygen-containing groups on the surface of the graphene oxide; wherein in the Hummer method, the temperature of the first step oxidation reaction is -1 to 5°C, and the temperature of the oil bath after adding deionized water in the second step oxidation reaction is 90 to 110°C.

[0010] In order to achieve the above-mentioned object, in another aspect of the present invention, a method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide as described in the first aspect of the present invention is provided, comprising: after printing interdigital electrodes on the surface of an insulating substrate, drop-coating an n-type hydroxyl-reduced graphene oxide solution or an n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene onto the interdigital electrodes and the surface of the insulating substrate, and after drying, obtaining a DMMP room temperature sensor.

[0011] As a preferred embodiment of the present invention, the method for preparing the n-type hydroxyl-reduced graphene oxide solution is specifically as follows:

[0012] An alkaline aqueous solution of sodium borohydride is used as a reducing agent and mixed with the graphene oxide solution to perform a reduction reaction to prepare the n-type hydroxyl-reduced graphene oxide solution.

[0013] As a preferred embodiment of the present invention, the method for preparing the n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene is specifically as follows:

[0014] An alkaline aqueous solution of sodium borohydride is used as a reducing agent and mixed with a graphene oxide solution to carry out a reduction reaction. Then, a calix[6]arene solution is added to react fully, and the mixture is filtered to obtain the n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene.

[0015] As a preferred embodiment of the present invention, in the reduction reaction, the sodium borohydride alkaline aqueous solution is first added dropwise to the graphene oxide solution at room temperature and mixed, and then the temperature is raised to 70-90° C. to activate the reduction reaction.

[0016] As a preferred embodiment of the present invention, the method for preparing graphene oxide is specifically as follows:

[0017] Graphite powder, sodium nitrate and potassium permanganate are dispersed in concentrated sulfuric acid and fully reacted at -1 to 5°C; the reaction conditions are changed to a 30 to 40°C oil bath, deionized water is added, the oil bath temperature is increased to 90 to 110°C, and fully reacted to obtain a golden precursor; the golden precursor is centrifuged and washed multiple times with deionized water until the pH of the solution is 6.5 to 7.5, and then dried to obtain the graphene oxide.

[0018] To achieve the above object, in another aspect of the present invention, a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide as described in the first aspect of the present invention is provided for detecting DMMP at room temperature.

[0019] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0020] 1. The sensor of the present invention uses n-type hydroxy-reduced graphene oxide as a gas-sensitive film, which includes a HRGO (n-type hydroxy-reduced graphene oxide) gas-sensitive film obtained by converting the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups, and a HRGO@Calix[6]arene (n-type hydroxy-reduced graphene oxide grafted with calix[6]arene) gas-sensitive film obtained by converting the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups and then modifying the calix[6]arene. The sensor utilizes a molecular olfactory sensing mechanism to provide material-gas targeting, thereby achieving room temperature, ultra-high selectivity, fast response rate, and wide detection range detection in DMMP detection. Specifically, since the phosphorus atoms in organic phosphorus substances including DMMP molecules have positive charge, they can be attracted by the electron-rich conjugated rings of n-type HRGO (electron transport) through cation-π interaction, and then anchored at the hydroxyl site through phosphorylation, thereby utilizing a molecular olfactory sensing mechanism to provide material-gas targeting.

[0021] 2. The HRGO@Calix[6]arene in the present invention, acting as both a conductive medium and a sensitive material, not only enables room-temperature detection with ultrahigh selectivity, fast response rate, and a wide detection range, but also improves the sensor's stability and moisture resistance for low-concentration detection resolution. Specifically, Calix[6]arene is grafted onto HRGO via van der Waals forces, altering the material's semiconductor properties, thereby improving the Schottky contact between the material and the gold electrode and enhancing the stability of the device. Furthermore, hydrophobic aromatic rings are introduced through Calix[6]arene, improving the sensor's moisture resistance for low-concentration detection resolution.

[0022] 3. The sensor in the present invention is developed based on graphene, and has excellent conductivity and high chemical activity at room temperature, meeting the requirements of room temperature sensing applications.

[0023] 4. The sensor of the present invention is a room temperature planar electrode type chemical resistance sensor, which is easy to prepare, does not require heating, is convenient to test, and is suitable for being carried on portable environmental detection equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the preparation process of a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to an example of the present invention;

[0025] Figure 2 X-ray diffraction patterns of GO, HRGO, SRGO and HRGO@Calix[6]arene materials corresponding to Examples 1-4 of the present invention, respectively;

[0026] Figure 3 Fourier transform infrared spectra of GO, HRGO, SRGO, Calix[6]arene and HRGO@Calix[6]arene materials corresponding to Examples 1-4 of the present invention respectively;

[0027] Figure 4 The full X-ray photoelectron spectra of GO in Example 1, HRGO in Example 2, and SRGO in Example 4 of the present invention;

[0028] Figure 5 The UV-visible absorption spectra of HRGO in Example 2, Calix[6]arene in Example 3, and HRGO@Calix[6]arene materials of the present invention are shown in FIG.

[0029] Figure 6 This is the current-voltage curve of the device obtained in Example 1 of the present invention;

[0030] Figure 7 This is the current-voltage curve of the device obtained in Example 2 of the present invention;

[0031] Figure 8 This is the current-voltage curve of the device obtained in Example 4 of the present invention;

[0032] Figure 9 This is the baseline drift of HRGO in Example 2 of the present invention;

[0033] Figure 10 This is the baseline drift of HRGO@Calix[6]arene in Example 3 of the present invention;

[0034] Figure 11This is the DMMP gas-sensitive response curve of the GO thin film sensor prepared in Example 1 of the present invention at room temperature;

[0035] Figure 12 This is the DMMP gas-sensitive response curve of the SRGO sensor prepared in Example 4 of the present invention at room temperature;

[0036] Figure 13 DMMP gas-sensitive response curves of the HRGO thin film sensor prepared in Example 2 of the present invention and the HRGO@Calix[6]arene thin film sensor prepared in Example 3 at room temperature;

[0037] Figure 14 DMMP gas-sensitive response curve of the HRGO thin film sensor prepared in Example 2 of the present invention at room temperature; Figure 14 a) is the gas-sensitive response curve within the period of 100 to 180 seconds, and b) is the gas-sensitive response curve within the period of 60 to 140 seconds;

[0038] Figure 15 DMMP gas-sensitive response curve of the HRGO@Calix[6]arene thin film sensor prepared in Example 3 of the present invention at room temperature; Figure 15 a) is the gas-sensitive response curve within the period of 100 to 180 seconds, and b) is the gas-sensitive response curve within the period of 60 to 140 seconds;

[0039] Figure 16 DMMP detection selectivity of the HRGO thin film sensor prepared in Example 2 of the present invention and the HRGO@Calix[6]arene thin film sensor prepared in Example 3 at room temperature;

[0040] Figure 17 DMMP gas-sensitive response curves of the RGO thin film sensors prepared in Examples 5 and 6 of the present invention at room temperature. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0042] Unless otherwise indicated, the raw materials and reagents used in the present invention are commercially available. All reagents are of commercial grade and used according to the standard received. The scientific and technical terms and abbreviations used in the present invention have the meanings commonly understood by those skilled in the art.

[0043] DMMP in the present invention is a sarin simulant, dimethyl methylphosphonate, which, as an organophosphorus compound, has a similar structure to sarin. GO in the present invention is shown as graphene oxide prepared by the modified Hummer method of the present invention, HRGO is shown as n-hydroxy-reduced graphene oxide, HRGO@Calix[6]arene is shown as n-hydroxy-reduced graphene oxide grafted with calix[6]arene, SRGO is shown as secondary reduced reduced graphene oxide, and RGO is shown as commercial reduced graphene oxide.

[0044] The present invention provides a highly selective DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide, such as Figure 1 As shown in the figure, the entire sensor consists of a three-layer planar structure, from bottom to top: an insulating substrate such as alumina ceramic, screen-printed gold interdigital electrodes, and HRGO or HRGO@Calix[6]arene sensitive film. The interdigital electrodes are obtained by screen-printing Au slurry onto an insulating substrate such as alumina ceramic, and the HRGO or HRGO@Calix[6]arene sensitive film is obtained by drop-coating and drying the corresponding material. The DMMP room temperature sensor can achieve real-time detection of hydrogen sulfide by applying a test potential on both sides of the interdigital electrodes.

[0045] The core transmission and sensing HRGO or HRGO@Calix[6]arene films are obtained by the following steps:

[0046] (1) GO was prepared using the improved Hummer method: 1.0-5.0 g of graphite powder, 0.25-1.25 g of sodium nitrate, and 3.0-15.0 g of potassium permanganate were dispersed in 23.0-115.0 mL of concentrated sulfuric acid (98%) and reacted uniformly at -1-5 °C; the reaction conditions were changed to a 30-40 °C oil bath, 50.0-250.0 mL of deionized water was added, and the oil bath temperature was increased to 90-110 °C to fully react and obtain a golden precursor; the precursor was washed with deionized water by centrifugation several times until the solution became neutral (6.5-7.5); and GO was obtained by drying.

[0047] (2) Preparation of HRGO material: Add 2-10 mL of NaBH4 alkaline aqueous solution (NaOH concentration: 0.005-0.02 mol / L, NaBH4 concentration: 3-9 g / L) to 6-30 mL of 0.5-1.0 g / L GO aqueous solution and disperse evenly; increase the solution temperature to 70-90 ° C, react for 2-3 hours to obtain a black solution; centrifuge the precursor source with ethanol and deionized water several times until the solution becomes neutral (6.5-7.5); dry to obtain HRGO.

[0048] Preparation of HRGO@Calix[6]arene material: 0.5-3 mg Calix[6]arene was added to 1-6 mL of 1-3 g / L HRGO solution and ultrasonically dispersed for 30-60 min to obtain a precursor; excess Calix[6]arene was filtered out using a 50-100 kDa ultrafiltration tube to obtain a HRGO@Calix[6]arene dispersion.

[0049] like Figure 1 As shown, the present invention designs a method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide. The details are as follows:

[0050] Preparation of HRGO thin film sensor: 1.0-3.0 mg of HRGO was dispersed in 0.5-1.0 mL of deionized water and ultrasonically dispersed for 10-20 minutes to obtain a black HRGO solution. The ceramic substrate with printed gold interdigital electrodes was placed on a heating table at 70-100°C. 5-10 μl of HRGO solution was pipetted and evenly added to the ceramic substrate. The HRGO thin film sensor was obtained after the solution evaporated.

[0051] Preparation of HRGO@Calix[6]arene thin film sensor: Place the ceramic substrate with printed gold interdigital electrodes on a heating platform at 70-100°C, use a pipette to absorb 5-10 μL of the prepared HRGO@Calix[6]arene dispersion, and evenly add it to the ceramic substrate. Wait for the solution to evaporate to obtain the HRGO@Calix[6]arene thin film sensor.

[0052] The above method will be further described in detail below with reference to the accompanying drawings and specific examples. It should be understood that the following examples are only used to illustrate the present invention, and the scope of protection of the present invention is not limited thereto.

[0053] Example 1: Graphene oxide (GO) thin film sensor, specifically prepared as follows:

[0054] (1) Preparation of GO: Add 1.0 g of graphite powder and 23.0 mL of H2SO4 (98%) to a conical flask and stir magnetically for 30 min; slowly add 0.25 g of sodium nitrate to the conical flask and stir magnetically for 30 min; control the temperature below 5°C, slowly add 3.0 g of potassium permanganate to the conical flask, and stir magnetically for 2 h to allow the reaction to complete; transfer the conical flask to a 37°C oil bath and stir magnetically for 30 min; add 50 mL of deionized water to the conical flask and increase the temperature of the oil bath to 98°C at the same time, stir magnetically for 20 min to obtain a golden precursor; wash the precursor with deionized water by centrifugation several times until the solution becomes neutral; dry the precursor in a drying oven at 65°C for 8 h to obtain GO.

[0055] (2) Preparation of GO thin film sensor: 3.0 mg of GO prepared in step (7) was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 min to obtain a yellow-brown GO solution; the alumina ceramic substrate with the gold electrode printed was placed on an 80°C heating table, 5 μL of GO solution was aspirated with a pipette, and evenly added to the alumina ceramic substrate, and the GO thin film sensor was obtained after the solution evaporated.

[0056] Example 2: A thin film sensor based on n-type hydroxylated reduced graphene oxide (HRGO) was prepared as follows:

[0057] (1) Preparation of HRGO: 10.0 mg of GO prepared according to step (1) of Example 1 above was dispersed in 15.0 mL of deionized water and ultrasonically dispersed for 10 min to obtain a GO aqueous solution; 100.0 mg of NaBH4 was added to 20.0 mL of 0.01 mol NaOH aqueous solution and ultrasonically dispersed for 1 min to obtain a NaBH4 alkaline aqueous solution; 5.0 mL of NaBH4 alkaline aqueous solution was dropwise added to the GO aqueous solution at room temperature and magnetically stirred for 10 min; the solution temperature was increased to 80°C and magnetically stirred for 2 h to obtain a black solution after sufficient reaction; the precursor source was centrifuged with ethanol and deionized water several times until the solution became neutral; the precursor was dried in a drying oven at 65°C for 8 h to obtain HRGO.

[0058] (2) Preparation of HRGO thin film sensor: 3.0 mg of HRGO was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 min to obtain a black HRGO solution; the ceramic substrate with the gold electrode printed was placed on an 80°C heating table, 5 μL of HRGO solution was aspirated with a pipette, and evenly added to the ceramic substrate. After the solution evaporated, the HRGO thin film sensor was obtained.

[0059] Example 3: A thin film sensor based on HRGO modified with Calix[6]arene (HRGO@Calix[6]arene) was prepared as follows:

[0060] (1) Preparation of HRGO@Calix[6]arene dispersion: 3.0 mg of HRGO prepared according to step (1) of Example 2 above was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 min to obtain a black HRGO solution; 0.5 mg of Calix[6]arene was added to the HRGO solution and ultrasonically dispersed for 40 min to obtain a precursor; excess Calix[6]arene was filtered out using a 50 kDa ultrafiltration tube to obtain a HRGO@Calix[6]arene dispersion.

[0061] (2) Preparation of HRGO@Calix[6]arene thin film sensor: Place the ceramic substrate with printed gold electrodes on a heating table at 80°C, use a pipette to draw 5 μl of HRGO@Calix[6]arene dispersion, and evenly drop it onto the ceramic substrate. Wait for the solution to evaporate to obtain the HRGO@Calix[6]arene thin film sensor.

[0062] Example 4: Secondary reduced reduced graphene oxide (SRGO) sensor, specifically as follows:

[0063] (1) Preparation of HRGO solution (single reduction): 30.0 mg of HRGO prepared according to step (1) of Example 2 above was dispersed in 30 mL of deionized water and ultrasonically dispersed for 40 min to obtain a black HRGO solution;

[0064] (2) Primary reduction: 1.0 mL, 32.1 mmol of hydrazine hydrate was added to the HRGO solution and magnetically stirred for 10 min; the solution temperature was raised to 80 °C and magnetically stirred for 12 h. After sufficient reaction, a black precursor was precipitated; the precursor was washed with deionized water several times and dried in a drying oven at 65 °C for 8 h to obtain SRGO powder.

[0065] (3) Preparation of SRGO sensor: 1.0 mg of SRGO powder was placed on a ceramic substrate with a printed gold electrode. The ceramic substrate was placed in a hot press at 90 °C and pressed for 1 min to obtain the SRGO sensor.

[0066] Example 5: A corresponding sensor was prepared based on commercial reduced graphene oxide No. 1 (commercial RGO No. 1). The reduced graphene oxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. and was prepared as follows:

[0067] 3.0 mg of commercial RGO was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 minutes to obtain a black RGO solution; the ceramic substrate with printed gold electrodes was placed on an 80°C heating table, 5 μL of RGO solution was pipetted with a pipette and evenly added to the ceramic substrate. After the solution evaporated, a commercial RGO sensor was obtained.

[0068] Example 6: A corresponding sensor was prepared based on commercial reduced graphene oxide No. 2 (commercial RGO No. 2). The reduced graphene oxide was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd. and was prepared as follows:

[0069] 3.0 mg of commercial RGO was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 minutes to obtain a black RGO solution; the ceramic substrate with printed gold electrodes was placed on an 80°C heating table, 5 μL of RGO solution was pipetted with a pipette and evenly added to the ceramic substrate. After the solution evaporated, a commercial RGO sensor was obtained.

[0070] The materials or thin film devices prepared in the above embodiments are subjected to corresponding structural characterization and performance characterization. When performing performance characterization on thin film devices, a static test system is used for testing: the device is placed in a 20L sealed chamber, a certain concentration of the test gas is introduced into the chamber, and the change in the current value is observed. Figure 14 The sensitivity is defined as the difference between the device's resistance in the measured gas and its resistance in air, divided by the device's resistance in air.

[0071] like Figure 2 , showing a characteristic diffraction peak near 10°, indicating that Example 1 successfully synthesized GO, the (200) diffraction peak of HRGO indicates that GO is reduced, and the new (100) diffraction peak of SRGO indicates that its reduction degree is aggravated compared with HRGO; the (200) diffraction peak in HRGO@Calix[6]arene shifts to the left, indicating that Calix[6]arene has been successfully grafted onto HRGO.

[0072] like Figure 3 , shown in the spectrum of GO, located at 1044.1 cm -1 and 1731.2cm -1 The characteristic peaks of CO and C=O are also clearly visible, including 1213.7 cm -1 The phenolic hydroxyl vibration peak, 1623.2 cm -1 The hydroxyl bending vibration peak of HRGO and the broad hydroxyl vibration band at 3387.2cm-1 originated from hydrogen bonding are found. This result indicates that GO itself introduces many oxygen-containing groups including hydroxyl groups. In the HRGO spectrum, the CO and C=O vibration peaks completely disappear, while the phenolic hydroxyl vibration peak and the hydroxyl bending vibration peak are retained. In addition, the stretching vibration bands originated from hydrogen bonding in the original GO become sharper and narrower, and shift to higher wavenumbers, indicating that the covalent hydroxyl features are more prominent. The above results show that the oxygen-containing functional groups in HRGO are mainly hydroxyl groups. In the SRGO spectrum, the oxygen-containing functional groups at 2850.7cm- 1 and 2920.9cm -1 The CH stretching vibration peak at 752.8 cm is used as a reference. The phenolic hydroxyl vibration peak in the original HRGO disappears, and the hydroxyl bending vibration peak and the stretching vibration band derived from hydrogen bonds are significantly weakened compared with HRGO. -1 、1467.2cm -1 and 3292.1cm -1 The peaks observed at 1559.2 cm correspond to the CH and hydroxyl vibrations of Calix[6]arene. -1 The characteristic C=C vibration peak further confirms that Calix[6]arene has been successfully grafted onto HRGO.

[0073] like Figure 4 , showing that the C / O of GO in Example 1, HRGO in Example 2, and SRGO in Example 4 are 3.63, 2.45, and 8.71, respectively. Figure 3 This indicates that HRGO achieves the selective reduction of GO and converts most of the oxygen-containing groups into hydroxyl groups, while these hydroxyl groups are greatly removed in SRGO.

[0074] Table 1 shows the Hall effect test results of the HRGO in Example 2 and the HRGO@Calix[6]arene in Example 3 of the present invention, as follows:

[0075] Table 1: Hall effect test results of HRGO and HRGO@Calix[6]arene materials

[0076]

[0077] As shown in Table 1, the materials of Example 2 and Example 3 both exhibit negative Hall coefficients, showing characteristics of n-type semiconductors.

[0078] like Figure 5 , showing weak broad peaks at 247 nm and 834 nm, indicating that Calix[6]arene was grafted onto HRGO via π-π stacking.

[0079] like Figure 6 、 Figure 7 and Figure 8 , showing that the current-voltage curves of SRGO in Example 4 almost overlap at different scan rates and present a curved symmetrical linear relationship, indicating the fact that SRGO is in ohmic contact with the gold electrode; the current-voltage curves of HRGO in Example 2 overlap at scan rates of 20mv / point and 200mv / point, and present an asymmetric nonlinear relationship at different scan rates, indicating the fact that HRGO is in Schottky contact with the gold electrode, which causes the baseline resistance of the sensor to continuously drift toward a high resistance value, and as shown in FIG. Figure 9 The results show that the stability of the sensor is affected. In Example 3, the current-voltage curves of HRGO@Calix[6]arene at different scan rates almost overlap, and overlap at scan rates of 20mv / point and 200mv / point, showing an almost symmetrical linear relationship. This shows that the introduction of Calix[6]arene greatly improves the Schottky contact between HRGO and the gold electrode, and the direction of the baseline resistance drift is changed and the drift degree is greatly reduced. Figure 10 As shown, this improves sensor stability.

[0080] like Figure 11, showing that the sensor of Example 1 cannot effectively detect 50ppm and 100ppm of DMMP, which is not conducive to practical detection applications due to its disadvantage of large resistance value.

[0081] like Figure 12 , which shows that the sensor of Example 4 cannot maintain a stable response to 50 ppm of DMMP, which is not conducive to practical detection applications.

[0082] like Figure 13 , showing that the sensors of Example 2 and Example 3 can detect 5 to 100 ppm of DMMP, and the sensor of Example 3 has a stronger recovery ability.

[0083] like Figure 14 , showing that the sensor of Example 2 has a response rate of seconds, but the baseline resistance fluctuates greatly, and the low-concentration detection resolution is significantly affected by humidity.

[0084] like Figure 15 , showing that the sensor of Example 3 has a response rate of seconds, and the baseline resistance fluctuation is very small, and the low concentration detection resolution is not significantly affected by humidity. Figure 14 、 Figure 15 , indicating that the introduction of Calix[6]arene greatly improved the stability of HRGO and the humidity resistance of low-concentration detection resolution.

[0085] like Figure 16 , showing that the sensors of Example 2 and Example 3 have ultra-high selectivity. This indicates that the introduction of Calix[6]arene does not destroy the original selectivity of HRGO.

[0086] like Figure 17 , showing that the sensors of Example 5 and Example 6 are both unable to detect 50 ppm of DMMP.

[0087] According to the above results and analysis, n-type HRGO achieves selective reduction of GO, reduces the inherent high resistance of GO, introduces a large number of hydroxyl active sites, and achieves ultra-high selectivity and rapid detection of DMMP. Furthermore, Calix[6]arene is grafted onto HRGO through π-π stacking, which improves the Schottky contact between HRGO and the gold electrode while retaining the high selectivity of HRGO, thereby improving the stability of the device, the recovery performance of the device, and the humidity resistance of the low-concentration detection resolution. The HRGO and HRGO@Calix[6]arene sensors prepared by the present invention rely on a unique molecular recognition mechanism to achieve fingerprint-level rapid detection of DMMP at room temperature, which is unattainable by conventional commercial RGO.

[0088] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, to the extent such modifications and variations fall within the scope of the present invention and its equivalents, the present invention is intended to encompass such modifications and variations. The above-described embodiments are merely preferred embodiments for the purpose of fully illustrating the present invention and are not intended to limit the scope of protection. Any equivalent substitutions or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention.

Claims

1. A highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide, characterized in that: From bottom to top, this includes: An insulating substrate, an interdigitated electrode, and a gas-sensitive film based on n-type hydroxyl-reduced graphene oxide; wherein the gas-sensitive film based on n-type hydroxyl-reduced graphene oxide is obtained by the following preparation method: by converting the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups, or by converting the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups and then performing calix[6]arene modification.

2. The highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to claim 1, characterized in that: The conversion of oxygen-containing groups on the surface of graphene oxide into hydroxyl groups is specifically carried out by reducing graphene oxide using an alkaline aqueous solution of sodium borohydride as a reducing agent.

3. The highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to claim 1, characterized in that: The gas-sensitive film based on n-type hydroxyl-reduced graphene oxide is obtained by converting the oxygen-containing groups on the surface of the graphene oxide into hydroxyl groups and then modifying it with calix[6]arene. Specifically, the graphene oxide is reduced using an alkaline aqueous solution of sodium borohydride as a reducing agent, and then the calix[6]arene is grafted onto the reduced graphene oxide by π-π stacking.

4. The highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to any one of claims 1 to 3, characterized in that: The graphene oxide is obtained by adjusting the temperature of the two-step oxidation reaction in the Hummer method to increase the content of oxygen-containing groups on the surface of the graphene oxide; wherein in the Hummer method, the temperature of the first step oxidation reaction is -1 to 5°C, and the temperature of the oil bath after adding deionized water in the second step oxidation reaction is 90 to 110°C.

5. A method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide, characterized in that: include: After printing the interdigital electrodes on the surface of the insulating substrate, an n-type hydroxyl-reduced graphene oxide solution or an n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene is drop-coated onto the interdigital electrodes and the surface of the insulating substrate, and after drying, a DMMP room temperature sensor is obtained.

6. The method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide according to claim 5, wherein: The preparation method of the n-type hydroxyl-reduced graphene oxide solution is specifically as follows: An alkaline aqueous solution of sodium borohydride is used as a reducing agent and mixed with the graphene oxide solution to perform a reduction reaction to prepare the n-type hydroxyl-reduced graphene oxide solution.

7. The method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide according to claim 5, wherein: The method for preparing the n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene is specifically as follows: An alkaline aqueous solution of sodium borohydride is used as a reducing agent and mixed with a graphene oxide solution to carry out a reduction reaction. Then, a calix[6]arene solution is added to react fully, and the mixture is filtered to obtain the n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene.

8. The method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to any one of claims 6 to 7, characterized in that: In the reduction reaction, the sodium borohydride alkaline aqueous solution is first added dropwise to the graphene oxide solution at room temperature and mixed, and then the temperature is raised to 70-90° C. to activate the reduction reaction.

9. The method for preparing a highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to any one of claims 6 to 7, characterized in that: The preparation method of the graphene oxide is specifically as follows: Graphite powder, sodium nitrate and potassium permanganate are dispersed in concentrated sulfuric acid and fully reacted at -1 to 5°C; the reaction conditions are changed to a 30 to 40°C oil bath, deionized water is added, the oil bath temperature is increased to 90 to 110°C, and fully reacted to obtain a golden precursor; the golden precursor is centrifuged and washed multiple times with deionized water until the pH of the solution is 6.5 to 7.5, and then dried to obtain the graphene oxide.

10. A highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide is used to detect DMMP at room temperature.

Images