Graphene oxide sheet long afterglow material and preparation method and application thereof

Abstract

This invention discloses a long afterglow material of graphene oxide sheets, its preparation method, and its applications. The preparation method of the long afterglow material of graphene oxide sheets includes: using a graphene oxide electrode sheet as the working electrode, immersing the working electrode, counter electrode, and reference electrode in an electrolyte, applying direct current through an electrochemical workstation to make the voltage difference between the working electrode and the reference electrode 1.8~2.0V to form an electrochemical reaction circuit, and carrying out the electrochemical reaction until the current in the circuit containing the working electrode and counter electrode is ≤1mA, at which point the electrochemical reaction is stopped. The electrolyte is a saturated boric acid aqueous solution. This invention, through electrochemical intercalation and oxygen evolution reaction, allows the graphene oxide sheet to be exfoliated from the graphene oxide electrode sheet while simultaneously being in-situ composited with boric acid crystals, directly obtaining the long afterglow material of graphene oxide sheets in one step, thus avoiding the dangers and multi-step complexity of traditional methods.

Description

Technical Field

[0001] The present invention belongs to the technical field of long afterglow materials, and in particular relates to a long afterglow material of graphene oxide sheets and a preparation method and application thereof. Background Art

[0002] Long afterglow material is the abbreviation of long afterglow luminescent material, which is a photoluminescent material. Photoluminescence includes fluorescence, phosphorescence and delayed fluorescence, the latter two of which are also called afterglow. Afterglow refers to the residual luminescence, specifically, it refers to the slow release of energy in the form of light after the excitation light source stops irradiating, which manifests as continuous long-life luminescence.

[0003] Research has found that carbon dots have photoluminescent properties. The application of carbon dots in long afterglow materials is a research field that attracts great attention and provides great application potential in the fields of advanced anti-counterfeiting and encryption. Carbon dots are a type of zero-dimensional carbon-based nanomaterials with a size less than 10nm, mainly including graphene quantum dots, carbon quantum dots, carbon nanodots, carbonized polymer dots, etc. Studies have found that zero-dimensional graphene carbon dots in graphene quantum dots exhibit long afterglow properties and can be used to prepare long afterglow materials, but there are currently few reports on the use of two-dimensional graphene oxide sheets as a carbon material to prepare long afterglow materials. The two-dimensional graphene oxide sheets are essentially different from carbon dot materials such as graphene quantum dots. Structurally, the size of their sheets is much larger than 10nm, and hydroxyl and epoxy groups are randomly distributed on the surface of the sheets, while carboxyl and carbonyl groups are present at the edges of the sheets.

[0004] The conventional preparation methods of carbon-based long afterglow materials have the following disadvantages: 1) The preparation process mainly uses hydrothermal, solvent thermal and other methods, which are very dangerous; 2) The preparation of carbon materials and the final long afterglow material can only be carried out step by step and cannot be carried out in an integrated manner, resulting in low preparation efficiency. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a long afterglow material of graphene oxide sheets.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned graphene oxide sheet long afterglow material.

[0007] Another object of the present invention is to provide a use of the above-mentioned graphene oxide sheet long afterglow material to emit long afterglow under ultraviolet light excitation.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A graphene oxide sheet long afterglow material comprises: a boric acid crystal and a graphene oxide sheet doped in the boric acid crystal, wherein the graphene oxide sheet and the boric acid crystal are in-situ composited.

[0010] In the above technical solution, the content of graphene oxide sheets in the graphene oxide long afterglow material is 4 to 6wt%.

[0011] In the above technical solution, the width of the graphene oxide sheet in the graphene oxide long afterglow material is 45~150 nm.

[0012] A method for preparing a long afterglow material of a graphene oxide sheet comprises: using a graphite oxide electrode sheet as a working electrode, immersing the working electrode, a counter electrode and a reference electrode in an electrolyte, applying direct current through an electrochemical workstation so that the voltage difference between the working electrode and the reference electrode is 1.8-2.0V to form an electrochemical reaction circuit, performing an electrochemical reaction until the current in the loop where the working electrode and the counter electrode are located is ≤1mA and the electrochemical reaction is stopped, filtering the electrolyte after the electrochemical reaction and drying to obtain the long afterglow material of the graphene oxide sheet, wherein the electrolyte is a boric acid aqueous solution, and the boric acid aqueous solution is a saturated boric acid aqueous solution.

[0013] In the above technical solution, a platinum electrode is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode.

[0014] In the above technical solution, the boric acid aqueous solution is a saturated boric acid aqueous solution at 25°C.

[0015] In the above technical scheme, the method for obtaining the graphite oxide electrode sheet is: graphite oxide powder and conductive polytetrafluoroethylene glue are mixed until uniform, rolled to obtain a composite film, and a piece of the composite film is pressed on each side of the nickel mesh to obtain a graphite oxide electrode sheet. In terms of mass fractions, the ratio of graphite oxide powder to conductive polytetrafluoroethylene glue is (90~95): (5~10).

[0016] In the method for obtaining a graphite oxide electrode sheet, the conductive polytetrafluoroethylene glue is a mixture of conductive carbon black and polytetrafluoroethylene (PTFE) glue, and the ratio of the conductive carbon black to the polytetrafluoroethylene (PTFE) glue is 5:95 by mass.

[0017] In the method for obtaining a graphite oxide electrode sheet, the mass fraction of oxygen element in the graphite oxide powder is 25-50%.

[0018] In the method for obtaining a graphite oxide electrode sheet, graphite oxide powder and conductive polytetrafluoroethylene glue are mixed until uniform, and rolled 10 to 15 times at a pressure of 0.5 to 1 MPa to obtain a composite film.

[0019] In the method for obtaining a graphite oxide electrode sheet, a sheet of the composite film is pressed on each side of a nickel mesh at a pressure of 5 to 10 MPa.

[0020] In the method for obtaining a graphite oxide electrode sheet, the thickness of the composite film is 100-200 μm.

[0021] The above-mentioned graphene oxide sheet long afterglow material is used to emit long afterglow under ultraviolet light excitation.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The long afterglow properties of graphene oxide quantum dots have been reported, but the long afterglow properties of graphene oxide sheets have rarely been reported. In addition, the long afterglow materials prepared from graphene quantum dots are basically prepared from small molecule carbon sources by solvothermal or hydrothermal methods, which cannot guarantee the high selectivity of the reaction, that is, its product is strictly a mixture of different types of carbon dots, mainly graphene oxide quantum dots. In addition, its process has high requirements for equipment, high preparation cost and poor safety. The present invention uses graphene oxide electrode sheets as raw materials for electrochemical stripping, and the carbon product is pure graphene oxide sheets, and has low requirements for equipment, low preparation cost and good safety.

[0024] (2) The present invention uses electrochemical intercalation and oxygen evolution reaction to peel off the graphene oxide sheet from the graphite oxide electrode sheet and simultaneously in situ recombine with the boric acid crystal, thereby directly obtaining the graphene oxide sheet long afterglow material (the microstructure of the graphene oxide sheet long afterglow material is a small amount of graphene oxide sheets doped in a large amount of boric acid crystals) in one step, thereby getting rid of the danger of the traditional method and the complexity of the multi-step preparation. The preparation method of the present invention is highly efficient and less dangerous. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 TEM of the entire graphene oxide sheet in the long afterglow material of graphene oxide sheet prepared in Example 1;

[0026] Figure 2 TEM of the edge of the graphene oxide sheet in the long afterglow material of the graphene oxide sheet prepared in Example 1;

[0027] Figure 3 This is a photo of the long afterglow material of graphene oxide sheets prepared in Example 1 when the ultraviolet light is turned on;

[0028] Figure 4 These are photos of the long afterglow material of graphene oxide sheets prepared in Example 1 at different times after the ultraviolet lamp is turned off;

[0029] Figure 5 The luminescence decay curve of the long afterglow material of graphene oxide sheet prepared in Example 1;

[0030] Figure 6 This is a photo of the conventional graphene oxide sheet material prepared in Comparative Example 1 when the ultraviolet light is turned on;

[0031] Figure 7 This is a photograph of the conventional graphene oxide sheet material prepared in Comparative Example 1 1 second after the ultraviolet light is turned off;

[0032] Figure 8 The luminescence attenuation curve of the conventional graphene oxide sheet material prepared in Comparative Example 1;

[0033] Fig. 9 This is the luminescence decay curve of the pure boric acid material prepared in Comparative Example 5. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0035] Experimental principle: After applying voltage to the graphite oxide electrode, [B(OH)4] - Under the action of positive voltage, it will flow to the graphite oxide electrode sheet and embed into the graphite oxide on the surface of the graphite oxide electrode sheet. In addition, there will be an oxygen evolution reaction on the graphite oxide electrode sheet during this process. Under the joint action of the two, a small amount of graphene oxide sheets will be peeled off from the electrode and enter the electrolyte; at the same time, the oxygen evolution reaction will consume the water in the electrolyte, thereby precipitating boric acid crystals in the boric acid aqueous solution; the peeled graphene oxide sheets will combine with the precipitated boric acid crystals (in-situ compounding) to form a precipitate, and finally a long afterglow material of graphene oxide sheets will be obtained. The long afterglow material of graphene oxide sheets exhibits long afterglow characteristics excited by ultraviolet light.

[0036] The raw material information involved in the following examples is as follows:

[0037] Graphite oxide powder: Model XF003, produced by Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.;

[0038] Conductive polytetrafluoroethylene glue: Model D-2CE, produced by Daikin, Japan. Conductive polytetrafluoroethylene glue is a mixture of conductive carbon black and polytetrafluoroethylene (PTFE) glue. The ratio of conductive carbon black to polytetrafluoroethylene (PTFE) glue is 5:95 by mass.

[0039] Boric acid: Model B111604-500g, produced by Aladdin Reagent Company.

[0040] Embodiment 1~3

[0041] A graphene oxide sheet long afterglow material comprises: boric acid crystals and graphene oxide sheets doped in the boric acid crystals, wherein the graphene oxide sheets and the boric acid crystals are in-situ composited. The content of the graphene oxide sheets in the graphene oxide sheet long afterglow material is Xwt%.

[0042] The preparation method of the above-mentioned graphene oxide sheet long afterglow material comprises: using a graphite oxide electrode sheet as a working electrode, a platinum electrode as a counter electrode, and a saturated calomel electrode as a reference electrode (three-electrode system), immersing the working electrode, the counter electrode and the reference electrode in an electrolyte, connecting the working electrode, the counter electrode and the reference electrode to the working electrode socket, the auxiliary electrode socket and the reference electrode socket of an electrochemical workstation in sequence respectively, applying direct current through the electrochemical workstation so that the voltage difference between the working electrode and the reference electrode is AV, forming an electrochemical reaction circuit, performing an electrochemical reaction until the current in the loop where the working electrode and the counter electrode are located is B mA and the electrochemical reaction is stopped, filtering the electrolyte after the electrochemical reaction, and drying it at 110° C. for 30 min to obtain the graphene oxide sheet long afterglow material, wherein the electrolyte is a saturated boric acid aqueous solution at 25° C.

[0043] The method for obtaining a graphite oxide electrode sheet is as follows: graphite oxide powder and conductive polytetrafluoroethylene glue are mixed until uniformly mixed, and rolled D times at a pressure of C MPa to obtain a composite film with a thickness of F μm, and a composite film is pressed on each side of a nickel mesh at a pressure of 10 MPa to obtain a graphite oxide electrode sheet. In terms of mass fraction, the ratio of graphite oxide powder to conductive polytetrafluoroethylene glue is 90:10, and the mass fraction of oxygen element in the graphite oxide powder is E%.

[0044] The values ​​of X, A, B, C, D, E and F are shown in Table 1.

[0045] Table 1

[0046]

[0047] The width of the graphene oxide sheet in the long afterglow material of the graphene oxide sheet prepared in Example 1 is 50-150 nm, the width of the graphene oxide sheet in the long afterglow material of the graphene oxide sheet prepared in Example 2 is 45-140 nm, and the width of the graphene oxide sheet in the long afterglow material of the graphene oxide sheet prepared in Example 3 is 50-140 nm.

[0048] Comparative Example 1

[0049] A method for preparing a conventional graphene oxide sheet-based material is basically the same as the "method for preparing a long afterglow material of graphene oxide sheets" in Example 1, with the only difference being that the voltage difference between the working electrode and the reference electrode in Comparative Example 1 is 2.2V".

[0050] Comparative Example 2

[0051] A method for preparing a conventional graphene oxide sheet-based material is basically the same as the "method for preparing a long afterglow material of graphene oxide sheets" in Example 1, with the only difference being that the voltage difference between the working electrode and the reference electrode in Comparative Example 2 is 1.7V.

[0052] Comparative Example 3

[0053] A method for preparing a conventional graphene oxide sheet-based material is basically the same as the "method for preparing a long afterglow material of graphene oxide sheets" in Example 1, with the only difference being that the mass fraction of oxygen element in the graphite oxide powder in Comparative Example 3 is 20%.

[0054] Comparative Example 4

[0055] A method for preparing a conventional graphene oxide sheet-based material is basically the same as the "method for preparing a long afterglow material of graphene oxide sheets" in Example 1, with the only difference being that the mass fraction of oxygen element in the graphite oxide powder in Comparative Example 4 is 55%.

[0056] Comparative Example 5

[0057] A preparation method of a pure boric acid material comprises: immersing a working electrode, a counter electrode and a reference electrode in an electrolyte, wherein the working electrode and the counter electrode are platinum electrodes, and the reference electrode is a saturated calomel electrode; the working electrode, the counter electrode and the reference electrode are respectively connected to a working electrode socket, an auxiliary electrode socket and a reference electrode socket of an electrochemical workstation in sequence; applying direct current through the electrochemical workstation so that the voltage difference between the working electrode and the reference electrode is 1.9 V to form an electrochemical reaction circuit; performing an electrochemical reaction until the current in the loop where the working electrode and the counter electrode are located is 0.6 mA and the electrochemical reaction is stopped; filtering the electrolyte after the electrochemical reaction and drying it at 110° C. for 30 min to obtain the pure boric acid material, wherein the electrolyte is a saturated boric acid aqueous solution at 25° C.

[0058] In Comparative Example 5, an inert platinum electrode is used instead of the graphite oxide electrode sheet. Comparative Example 5 does not involve a peeling reaction of graphene oxide, but only involves a reaction of electrolyzing water to crystallize boric acid, and the product is pure boric acid crystals.

[0059] The graphene oxide sheet long afterglow material prepared in Example 1 was washed with deionized water to remove the boric acid crystals therein, and then subjected to TEM test. Figure 1 As shown. Figure 1 The structure of multiple graphene oxide sheets can be seen, and the sizes of the graphene oxide sheets are not uniform (such as graphene oxide sheets with widths of approximately 50 nm, 110 nm, and 150 nm, respectively), indicating that the graphene oxide sheets in the long afterglow material of the graphene oxide sheets prepared in Example 1 are two-dimensional, non-zero-dimensional graphene oxide quantum dots.

[0060] Figure 2 TEM of the edge of the graphene oxide sheet in the long afterglow material of the graphene oxide sheet prepared in Example 1. Figure 2 It can be observed that the edges of the graphene oxide sheets exist in the form of a single layer.

[0061] The long afterglow characteristics of the graphene oxide sheet long afterglow material prepared in Example 1, the conventional graphene oxide sheet material prepared in Comparative Example 1, and the pure boric acid material prepared in Comparative Example 5 were tested under the following conditions: the excitation wavelength was 365 nm, the excitation power was 10 mW, and the excitation time was 2 seconds. The test results are shown in Figure 2. Figure 3~Figure 9 shown. Figure 3 This is a photo of the long afterglow material of graphene oxide sheets prepared in Example 1 when the ultraviolet light is turned on; Figure 4 These are photos of the graphene oxide sheet long afterglow material prepared in Example 1 at 1s, 2s, 3s, 4s, 5s, 6s, 7s and 8s after the ultraviolet lamp is turned off; Figure 5 The luminescence decay curve of the long afterglow material of graphene oxide sheet prepared in Example 1; Figure 6 This is a photo of the conventional graphene oxide sheet material prepared in Comparative Example 1 when the ultraviolet light is turned on; Figure 7 This is a photograph of the conventional graphene oxide sheet material prepared in Comparative Example 1 1 second after the ultraviolet light is turned off; Figure 8 The luminescence attenuation curve of the conventional graphene oxide sheet material prepared in Comparative Example 1; Fig. 9 This is the luminescence decay curve of the pure boric acid material prepared in Comparative Example 5.

[0062] like Figure 4 As shown, after the ultraviolet lamp is turned off, the long afterglow material of the graphene oxide sheet prepared in Example 1 exhibits a long afterglow characteristic. Under the excitation of 365nm ultraviolet rays, it emits blue light with a peak of 485nm and an afterglow time of 7 s. Figure 5 The luminous attenuation curve is Figure 4 Confirmed, from Figure 5 It can be seen that after 7.4 s, the luminescence attenuation curve no longer changes and there is no afterglow.

[0063] The graphene oxide sheet long afterglow material obtained in Example 2 emits blue light with a peak of 485 nm and has an afterglow luminescence time of 7.2 s. The graphene oxide sheet long afterglow material obtained in Example 3 emits blue light with a peak of 485 nm and has an afterglow luminescence time of 7.5 s.

[0064] like Figure 6 and Figure 7 As shown, after the UV lamp is turned off, the screen is directly dark. The conventional graphene oxide sheet material prepared in Comparative Example 1 does not show long afterglow characteristics. Figure 6 The color is brighter, mainly because the content of graphene oxide sheets in the conventional graphene oxide sheet-based material prepared in Comparative Example 1 is relatively small, and the intrinsic color is relatively light. Figure 8 The luminous attenuation curve is Figure 6 Confirmed, from Figure 8It can be seen that there is no afterglow after 0.8 s after the UV lamp is turned off, and there is no obvious long afterglow characteristic.

[0065] from Fig. 9 It can be seen that the afterglow intensity after 0 s is weak and the duration is extremely short (compared to Figure 5 The data of Comparative Example 5 and Examples 1 to 3 fully illustrate that although the boric acid crystal plays a key auxiliary role in the long afterglow luminescence of the graphene oxide sheet long afterglow material, the boric acid crystal itself does not have obvious afterglow luminescence characteristics, and the long afterglow characteristics of the obtained graphene oxide sheet long afterglow material are derived from the composite structure of the graphene oxide sheet and the boric acid crystal in situ composite.

[0066] The conventional graphene oxide sheet-based materials obtained in other comparative examples also did not show obvious long afterglow characteristics. This was mainly due to inappropriate reaction conditions, which made it impossible to effectively peel off the graphene oxide sheets from the graphite oxide electrode and effectively recombine with the boric acid crystals in situ, thereby failing to form a material structure with long afterglow characteristics.

[0067] According to the results of the above long afterglow characteristics test Figure 5 , Figure 8 and Fig. 9 It can be seen that the long afterglow material of graphene oxide sheets prepared in Example 1 not only has the longest afterglow time, but also has the strongest luminescence intensity.

[0068] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing a long afterglow material of graphene oxide sheets, characterized in that: include: A graphite oxide electrode sheet is used as a working electrode, and the working electrode, a counter electrode and a reference electrode are immersed in an electrolyte. A direct current is applied through an electrochemical workstation so that the voltage difference between the working electrode and the reference electrode is 1.8-2.0V to form an electrochemical reaction circuit. The electrochemical reaction is performed until the current in the loop where the working electrode and the counter electrode are located is ≤1mA, and the electrochemical reaction is stopped. The electrolyte after the electrochemical reaction is filtered and dried to obtain a graphene oxide sheet long afterglow material, wherein the electrolyte is a boric acid aqueous solution, and the boric acid aqueous solution is a saturated boric acid aqueous solution.

2. The preparation method according to claim 1, characterized in that: The platinum electrode was used as the counter electrode and the saturated calomel electrode was used as the reference electrode.

3. The preparation method according to claim 1, characterized in that: The boric acid aqueous solution is a saturated boric acid aqueous solution at 25°C.

4. The preparation method according to claim 1, characterized in that: The method for obtaining a graphite oxide electrode sheet is as follows: graphite oxide powder and conductive polytetrafluoroethylene glue are mixed until uniform, and a composite film is obtained by rolling, and a piece of the composite film is pressed on each side of a nickel mesh to obtain a graphite oxide electrode sheet. The ratio of graphite oxide powder to conductive polytetrafluoroethylene glue is (90-95): (5-10) by weight.

5. The preparation method according to claim 4, characterized in that: The conductive polytetrafluoroethylene adhesive is a mixture of conductive carbon black and polytetrafluoroethylene adhesive. Calculated by weight, the ratio of the conductive carbon black to the polytetrafluoroethylene adhesive is 5:

95.

6. The preparation method according to claim 4, characterized in that: The mass fraction of oxygen in graphite oxide powder is 25~50%.

7. The graphene oxide sheet long afterglow material obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The graphene oxide sheet long afterglow material comprises: boric acid crystals and graphene oxide sheets doped in the boric acid crystals, the graphene oxide sheets and the boric acid crystals are in-situ composited, and the content of the graphene oxide sheets in the graphene oxide sheet long afterglow material is at least 4wt%.

8. The graphene oxide sheet long afterglow material according to claim 7, characterized in that: The content of graphene oxide sheets in the long afterglow material is 4 ~6 wt%.

9. The graphene oxide sheet long afterglow material according to claim 7, characterized in that: The width of the graphene oxide sheet in the graphene oxide sheet long afterglow material is 45-150 nm.

10. Use of the long afterglow material of graphene oxide sheets as claimed in claim 7 to emit long afterglow under ultraviolet light excitation.

Images