High-selectivity DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide and preparation method of high-selectivity DMMP room temperature sensor

Abstract

The invention belongs to the field of gas sensors, and discloses a high-selectivity DMMP room temperature sensor based on n-type hydroxyl reduced graphene oxide and a preparation method of the high-selectivity DMMP room temperature sensor. The sensor comprises an insulating substrate, an interdigital electrode and a gas-sensitive film based on n-type hydroxyl reduced graphene oxide from bottom to top, the gas-sensitive film is prepared by converting an oxygen-containing group on the surface of graphene oxide into a hydroxyl group, or by converting the oxygen-containing group on the surface of graphene oxide into the hydroxyl group and then performing calix [6] arene modification. According to the sensor, n-type hydroxyl reduced graphene oxide is used as a gas-sensitive film, and a molecular olfaction sensing mechanism is utilized to enable the gas-sensitive film to have material-gas targeting property, so that room-temperature, ultrahigh-selectivity, fast-response-rate and wide-detection-range detection is realized in the aspect of DMMP detection; particularly, HRGO (at) Calix [6] arene is used as a gas-sensitive film, so that the stability of the sensor and the moisture resistance of low-concentration detection resolution can be improved at the same time.

Description

Technical Field

[0001] The 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 people's life and health in special social environments. It is of great significance to develop highly selective sensors for organophosphorus substances. However, there are few reports on sensors for organophosphorus substances, and they generally lack selectivity.

[0003] In the research on the sensing of nerve agents such as sarin, DMMP (dimethyl methylphosphonate) is often used as a simulant because they are both organophosphorus compounds and have weaker toxicity. But this also means that the exploration and development of gas-sensitive materials based on DMMP that can effectively detect nerve agents such as sarin requires exploring the common poisoning mechanism of the simulant and the nerve agent and carrying out corresponding designs. Unfortunately, this has been ignored in most studies, which often leads to poor selectivity.

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

[0005] In view of the above 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 of which is to integrate an 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 the technical problems of 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 the graphene oxide into hydroxyl groups and then modifying them with calix[6]arene.

[0007] As a preferred embodiment of the present invention, the oxygen-containing groups on the surface of 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, dripping 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] The sodium borohydride alkaline aqueous solution is used as a reducing agent and mixed with the graphene oxide solution to carry out a reduction reaction to obtain the n-type hydroxyl-reduced graphene oxide solution.

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

[0014] The sodium borohydride alkaline aqueous solution is used as a reducing agent and mixed with the graphene oxide solution to carry out a reduction reaction, and then the calix[6]arene solution is added to fully react, and 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 mixture is heated 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 centrifugally washed with deionized water for multiple times until the pH of the solution is 6.5 to 7.5, and dried to obtain the graphene oxide.

[0018] In order 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 solution conceived by the present invention has the following technical advantages compared with the prior art:

[0020] 1. The sensor of the present invention uses n-type hydroxyl-reduced graphene oxide as a gas-sensitive film, which includes a HRGO (n-type hydroxyl-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 hydroxyl-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, and uses a molecular olfactory sensing mechanism to make it have 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 the 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 using a molecular olfactory sensing mechanism to make it have material-gas targeting.

[0021] 2. HRGO@Calix[6]arene in the present invention, as both a conductive medium and a sensitive material, can not only achieve room temperature, ultra-high selectivity, fast response rate, and wide detection range detection, but also improve the stability of the sensor and the moisture resistance of low-concentration detection resolution. Specifically, Calix[6]arene is grafted onto HRGO through van der Waals forces, which changes the semiconductor properties of the material, thereby improving the Schottky contact between the material and the gold electrode and improving the stability of the device; at the same time, hydrophobic aromatic rings are introduced through Calix[6]arene, which improves the moisture resistance of the sensor's 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 in 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 This is a schematic diagram of the process flow of preparing 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 respectively corresponding to Examples 1-4 of the present invention;

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

[0028] Figure 5 The ultraviolet-visible absorption spectra of HRGO in Example 2, Calix[6]arene in Example 3, and HRGO@Calix[6]arene materials of the present invention;

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

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

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

[0032] Fig. 9 The baseline drift of HRGO in Example 2 of the present invention;

[0033] Fig.10 The baseline drift of HRGO@Calix[6]arene in Example 3 of the present invention;

[0034] Fig.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] Fig.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] Fig.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] Fig.14 DMMP gas-sensitive response curve of the HRGO thin film sensor prepared in Example 2 of the present invention at room temperature; Fig.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] Fig.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; Fig.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] Fig.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] Fig.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 purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 can be combined with each other as long as they do not conflict with each other.

[0042] Unless otherwise indicated, the raw materials or reagents used in the present invention are commercially available. All reagents are commercial grade and used according to the received standards. 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 organic phosphorus compound has a similar structure to sarin. GO in the present invention is a graphene oxide prepared by the following improved Hammer method of the present invention, HRGO is an n-type hydroxyl-reduced graphene oxide, HRGO@Calix[6]arene is an n-type hydroxyl-reduced graphene oxide grafted with calix[6]arene, SRGO is a secondary reduced reduced graphene oxide, and RGO is a commercial reduced graphene oxide.

[0044] The highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide provided by the present invention is as follows: Figure 1 As shown in the figure, the entire sensor consists of a three-layer planar structure, which are: an insulating substrate such as alumina ceramic, screen-printed gold interdigital electrodes, and HRGO or HRGO@Calix[6]arene sensitive films. 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 films are obtained by drop-coating and drying the corresponding materials. The DMMP room temperature sensor can realize 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 by the improved Hammer 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 evenly 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 allow the reaction to be fully completed to obtain a golden precursor; the precursor was centrifuged and washed with deionized water 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 and react for 2-3 h to obtain a black solution; centrifuge the precursor 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: Add 0.5-3 mg Calix[6]arene to 1-6 mL, 1-3 g / L HRGO solution, and ultrasonically disperse for 30-60 min to obtain a precursor; filter out excess Calix[6]arene with 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 HRGO was dispersed in 0.5-1.0 mL deionized water, and ultrasonic dispersion was performed for 10-20 min to obtain a black HRGO solution; the ceramic substrate with the gold interdigital electrodes printed was placed on a 70-100°C heating table, 5-10 μl HRGO solution was absorbed with a pipette, and evenly added to the ceramic substrate, and 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 table 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 is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to explain 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, increase the temperature of the oil bath to 98°C, and 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 65°C drying oven 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 on it was placed on a heating table at 80°C, 5 μL of GO solution was aspirated with a pipette and evenly added to the alumina ceramic substrate. 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) is specifically 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 the 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 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 HRGO was dispersed in 1.0 mL deionized water and ultrasonically dispersed for 10 min to obtain a black HRGO solution. The ceramic substrate with the gold electrode printed on it was placed on a heating table at 80 °C, 5 μL HRGO solution was taken with a pipette and evenly added to the ceramic substrate. The HRGO thin film sensor was obtained after the solution evaporated.

[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 with 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 absorb 5 μl of HRGO@Calix[6]arene dispersion, and evenly drip it onto the ceramic substrate. Wait for the solution to evaporate to obtain the HRGO@Calix[6]arene thin film sensor.

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

[0063] (1) Preparation of HRGO solution (primary 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 gold electrode printed on it. The ceramic substrate was placed in a hot press at 90 °C and pressed for 1 min to obtain a 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 specifically prepared as follows:

[0067] 3.0 mg of commercial RGO was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 min to obtain a black RGO solution. The ceramic substrate with the gold electrode printed was placed on a heating table at 80°C, 5 μL of RGO solution was aspirated with a pipette and evenly added to the ceramic substrate. The commercial RGO sensor was obtained after the solution evaporated.

[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 specifically prepared as follows:

[0069] 3.0 mg of commercial RGO was dispersed in 1.0 mL of deionized water and ultrasonically dispersed for 10 min to obtain a black RGO solution. The ceramic substrate with the gold electrode printed was placed on a heating table at 80°C, 5 μL of RGO solution was aspirated with a pipette and evenly added to the ceramic substrate. The commercial RGO sensor was obtained after the solution evaporated.

[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. Fig.14 The sensitivity is defined as the difference between the device's resistance in the measured gas and its resistance in air divided by its resistance in air.

[0071] like Figure 2 , showing the characteristic diffraction peak near 10°, indicating that Example 1 successfully synthesized GO, the (200) diffraction peak of HRGO shows that GO was reduced, and the new (100) diffraction peak of SRGO shows that its reduction degree is greater than that of 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 and the broad hydroxyl vibration band at 3387.2cm-1 originated from hydrogen bonding are found in the HRGO spectrum. 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 band originated from hydrogen bonding in the original GO becomes sharper, narrower, and shifts to a higher wavenumber, indicating that the covalent hydroxyl feature is more prominent. The above results show that the oxygen-containing functional groups in HRGO are mainly hydroxyl groups. In the SRGO spectrum, the hydroxyl group at 2850.7cm-1 is the main oxygen-containing functional group in HRGO. 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 at further confirmed that Calix[6]arene had 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 largely removed in SRGO.

[0074] Table 1 shows the Hall effect test results of HRGO in Example 2 and HRGO@Calix[6]arene in Example 3 of the present invention, which are 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 the 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 continue to drift toward a high resistance value, and as shown in FIG. Fig. 9 The results show that the stability of the sensor is affected. The current-voltage curves of HRGO@Calix[6]arene in Example 3 are almost identical at different scan rates, and overlap at scan rates of 20mv / point and 200mv / point, showing an almost symmetrical linear relationship. This indicates 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. Fig.10 As shown, the sensor stability is improved.

[0080] like Fig.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 large resistance value.

[0081] like Fig.12 , indicating 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 Fig.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 Fig.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 Fig.15 , indicating 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. Fig.14 , Fig.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 Fig.16 , indicating 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 Fig.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, improves the stability of the device, and improves the recovery performance of the device, and improves the humidity resistance of 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 impossible for conventional commercial RGO.

[0088] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalent technology, the present invention is also intended to include these changes and variations. The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and their protection scope is not limited thereto. Equivalent substitutions or changes made by those skilled in the art on the basis of the present invention are all within the protection scope 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, interdigitated electrodes, 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 modifying them with calix[6]arene.

2. The highly selective DMMP room temperature sensor based on n-type hydroxyl-reduced graphene oxide according to claim 1, characterized in that: The method converts the oxygen-containing groups on the surface of graphene oxide into hydroxyl groups, specifically, by reducing the 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 prepared 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 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 Hammer method to increase the content of oxygen-containing groups on the surface of the graphene oxide; wherein in the Hammer 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, the n-type hydroxyl-reduced graphene oxide solution or the n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene is drop-coated on 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, characterized in that: The method for preparing the n-type hydroxyl-reduced graphene oxide solution is specifically as follows: The sodium borohydride alkaline aqueous solution is used as a reducing agent and mixed with the graphene oxide solution to carry out a reduction reaction to obtain 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, characterized in that: The method for preparing the n-type hydroxyl-reduced graphene oxide solution grafted with calix[6]arene is specifically as follows: The sodium borohydride alkaline aqueous solution is used as a reducing agent and mixed with the graphene oxide solution to carry out a reduction reaction, and then the calix[6]arene solution is added to fully react, and 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 firstly 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: 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 centrifugally washed with deionized water for multiple times until the pH of the solution is 6.5 to 7.5, and 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.

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