Preparation method of multicolor room-temperature phosphorescent carbon dot and boron oxide composite material

Abstract

The invention relates to a preparation method of a multicolor room-temperature phosphorescent carbon dot-boron oxide composite material, which comprises the following steps: adding different conjugated molecules (2-aminoterephthalic acid, 2, 3-naphthalene dicarboxylic acid anhydride, 1, 8-naphthalene dicarboxylic acid anhydride and 1, 4, 5, 8-naphthalene tetracarboxylic anhydride) into an aqueous solution, stirring to obtain a transparent solution, adding boric acid, stirring to obtain a transparent solution, and drying to obtain the multicolor room-temperature phosphorescent carbon dot-boron oxide composite material. And carrying out in-situ pyrolysis in a drying oven to obtain the multicolor room-temperature phosphorescent carbon dot-boron oxide composite material. The method is characterized in that the multicolor room-temperature phosphorescent carbon dot and boron oxide composite material is obtained by a simple and feasible in-situ pyrolysis method. Besides, the sizes of the conjugated molecules of the precursor are regulated and controlled through a precursor engineering strategy, so that multicolor long-life room-temperature phosphorescence and long macroscopic time of the carbon dots are realized in a boron oxide matrix, the phosphorescence lives are 1.01 seconds, 1.56 seconds, 0.68 seconds and 72 milliseconds respectively, and the macroscopic time is as long as 16 seconds, 20 seconds, 14 seconds and 3 seconds respectively after an ultraviolet lamp is turned off. The medicines used for preparation are nontoxic, harmless and low in price, the preparation is simple, and the used time is short. The prepared multicolor room-temperature phosphorescent carbon dot and boron oxide composite material can be successfully applied to the fields of information encryption and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon dot material preparation, and in particular relates to a method for preparing a multicolor room temperature phosphorescent carbon dot@boron oxide composite material. Background Art

[0002] In recent years, room temperature phosphorescent (RTP) materials have attracted more and more attention due to their unique optical properties (long emission lifetime, large Stokes shift, effective elimination of self-absorption and background fluorescence, etc.), and have broad application prospects in information encryption, optical display and bioimaging. At present, traditional RTP materials mainly include inorganic compounds containing rare earth ions and organic compounds with molecular structures. However, the high cost, high toxicity, complex preparation process and poor stability of organic molecules of rare earth ions have severely restricted their further practical applications. Carbon dots (CDs), as an emerging carbon-based luminescent material, have attracted the attention of researchers due to their unique optical properties, good biocompatibility, low cost and easy preparation. In particular, researchers have begun to focus on the RTP properties of CDs-based materials in recent years. However, due to its unstable triplet excitons, molecular vibrational dissipation and environment-induced quenching, the excitation of RTP in CDs is seriously hindered.

[0003] At present, the RTP emission of CDs can be effectively achieved by adding heteroatoms (such as N, B, O, etc.) to promote n-π* transitions. This is because the inherent π-π* transitions of most CDs make their spin-orbit coupling (SOC) weak, resulting in the interslot crossing (ISC) process not easy to emit, and the introduction of appropriate n-π* transitions can solve this problem well. In addition, when CDs are incorporated into a rigid matrix, the matrix can protect and excite the triplet excitons of CDs through some confinement effects (such as hydrogen bonds, covalent bonds, spatial constraints, etc.) to produce effective RTP emission. Unfortunately, it is still a daunting challenge to achieve CDs-based composites with tunable RTP colors. At present, researchers have achieved multicolor RTP emission of CDs composites through indirect methods. This strategy is roughly to first synthesize CDs with multicolor fluorescence and then confine them to a rigid matrix for protection. However, the preparation of this method is too complicated and time-consuming. On the other hand, researchers have used citric acid to in situ form CDs in a rigid matrix and control the oxidation degree of CDs by setting the temperature and time of the reaction to achieve the regulation of the phosphorescence color of the composite from blue to red. However, achieving optimal control over the oxidation of CDs remains challenging. Therefore, a simple and efficient method is urgently needed to achieve multicolor RTP emission of CDs. Summary of the invention

[0004] In order to avoid the shortcomings of the prior art, the present invention provides a method for preparing a multicolor room temperature phosphorescent carbon dot@boron oxide composite material.

[0005] One of the purposes of the present invention is to provide a simple and easy in-situ pyrolysis method.

[0006] A second object of the present invention is to provide a precursor engineering design strategy.

[0007] The third object of the present invention is to provide a multicolor room temperature phosphorescent carbon dot@boron oxide composite material.

[0008] The multicolor room temperature phosphorescent carbon dot@boron oxide composite material prepared by the present invention is prepared by an in-situ pyrolysis method using different conjugated molecules (2-aminoterephthalic acid, 2, 3-naphthalene dicarboxylic anhydride, 1, 8-naphthalene dicarboxylic anhydride, 1, 4, 5, 8-naphthalene tetracarboxylic anhydride) and boric acid as raw materials. The preparation process includes the following specific steps: 1. First, add 0.1-0.4 g of different conjugated molecules (2-aminoterephthalic acid, 2, 3-naphthalene dicarboxylic anhydride, 1, 8-naphthalene dicarboxylic anhydride, 1, 4, 5, 8-naphthalene tetracarboxylic anhydride) to 50 mL of aqueous solution and stir for 1-3 hours to obtain a transparent solution; 2. Under stirring conditions, add 2-4 g of boric acid to the transparent solution obtained in step 1, and continue stirring for 1-3 hours to obtain a transparent solution; 3. The transparent solution obtained in step 2 is placed in an oven at 160-200° C. for pyrolysis for 6-10 hours to obtain a multicolor room temperature phosphorescent carbon dot@boron oxide composite material.

[0009] Beneficial effects of the present invention: 1. The present invention provides a method for preparing a multicolor room temperature phosphorescent carbon dot@boron oxide composite material, which is characterized in that different conjugated molecules and boric acid are used as raw materials and prepared by in-situ pyrolysis, and only common laboratory equipment is required, and no special equipment is required, and the process is simple and easy to operate; 2. This method provides a precursor engineering design strategy, which can prepare multi-color (blue, green, yellow and red) room temperature phosphorescent carbon dots@boron oxide composites by simply adjusting the precursor conjugated molecules; 3. The phosphorescence lifetimes of the multicolor room temperature phosphorescent carbon dots@boron oxide composites obtained by this method were 1.01 seconds, 1.56 seconds, 0.68 seconds and 72 milliseconds, respectively. After turning off the UV light, the phosphorescence visible to the naked eye lasted for 16 seconds, 20 seconds, 14 seconds and 3 seconds, respectively. 4. The drugs used in the present invention are non-toxic, harmless and inexpensive, and are simple to prepare and take a short time. No complicated steps are required after preparation, and they are particularly suitable for batch and low-cost preparation, and are suitable for industrial-scale production and commercial applications; 5. The multicolor (blue, green, yellow and red) room temperature phosphorescent carbon dots@boron oxide composite material provided by the present invention can be successfully applied to fields such as information encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments or the description of the prior art will be briefly introduced with drawings below, but the drawings in the following description are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 This is a transmission electron micrograph of the blue room temperature phosphorescent carbon dot@boron oxide composite material prepared in Example 1 of the present invention, and the inset is a high resolution transmission electron micrograph.

[0012] Figure 2 This is an X-ray diffraction pattern of the multicolor room temperature phosphorescent carbon dot@boron oxide composite material prepared in Examples 1-4 of the present invention.

[0013] Figure 3 This is a phosphorescence spectrum of the multicolor room temperature phosphorescent carbon dot@boron oxide composite material prepared in Examples 1-4 of the present invention.

[0014] Figure 4 This is a phosphorescence lifetime diagram of the multicolor room temperature phosphorescent carbon dot@boron oxide composite material prepared in Examples 1-4 of the present invention.

[0015] Figure 5 These are photos of the multicolor room temperature phosphorescent carbon dot@boron oxide composite materials prepared in Examples 1-4 of the present invention under sunlight, under 365nm ultraviolet light, and after turning off the light.

[0016] Figure 6 These are photos of the application of the multicolor room temperature phosphorescent carbon dots@boron oxide composite materials prepared in Examples 1-4 of the present invention in information resolution and anti-counterfeiting. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution 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.

[0018] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0019] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0020] Embodiment 1: First, 0.4 g of 2-aminoterephthalic acid was added to 50 mL of aqueous solution and stirred for 2 hours to obtain a transparent solution. Under stirring conditions, 3 g of boric acid was added to the obtained transparent solution and stirred for another 2 hours to obtain a transparent solution. The transparent solution was pyrolyzed in an oven at 180°C for 8 hours to obtain a blue room temperature phosphorescent carbon dot@boric acid composite material.

[0021] Embodiment 2: First, 0.3 g of 2, 3-naphthalene dicarboxylic anhydride was added to 50 mL of aqueous solution and stirred for 2 hours to obtain a transparent solution. Under stirring conditions, 4 g of boric acid was added to the obtained transparent solution and stirred for 3 hours to obtain a transparent solution. The transparent solution was placed in an oven at 200°C for 10 hours to obtain a green room temperature phosphorescent carbon dot@boric acid composite material.

[0022] Embodiment 3: First, 0.2 g of 1, 8-naphthalene dicarboxylic anhydride was added to 50 mL of aqueous solution and stirred for 3 hours to obtain a transparent solution. Under stirring conditions, 2 g of boric acid was added to the obtained transparent solution and stirred for 2 hours to obtain a transparent solution. The transparent solution was placed in an oven at 160°C for 6 hours to obtain a yellow room temperature phosphorescent carbon dot@boron oxide composite material.

[0023] Embodiment 4: First, 0.1 g of 1, 4, 5, 8-naphthalenetetracarboxylic anhydride was added to 50 mL of aqueous solution and stirred for 1 hour to obtain a transparent solution. Under stirring conditions, 2 g of boric acid was added to the obtained transparent solution and stirred for another hour to obtain a transparent solution. The transparent solution was placed in an oven at 160°C for 6 hours to obtain a red room temperature phosphorescent carbon dot@boron oxide composite material.

[0024] Figure 1 This is a transmission electron micrograph of the blue room temperature phosphorescent carbon dot@alophane composite material prepared in Example 1. The inset is a high resolution transmission electron micrograph. Figure 1 It can be seen that the CDs formed in situ by 2-aminoterephthalic acid are uniformly distributed in the amorphous boron oxide matrix; the in situ synthesized CDs have obvious carbon cores with a lattice fringe spacing of 0.21 nm, corresponding to the (100) crystal plane of graphitic carbon.

[0025] Figure 2 The X-ray diffraction pattern of the multicolor room temperature phosphorescent carbon dots@boron oxide composite material prepared in Examples 1-4. Figure 2It can be seen that the broad peak centered at 23.1° shows a characteristic peak, which corresponds to the (002) plane of graphite carbon, a typical feature of graphitized carbon structure. In addition, typical characteristic peaks of boron oxide are shown at 14.7°, 27.7° and 40.1°, which also indicates that the intramolecular hydrogen bonds between boric acid molecules are destroyed at high temperatures, resulting in dehydration and condensation to form boron oxide, further proving the successful preparation of the composite material.

[0026] Figure 3 The phosphorescence spectra of the multicolor room temperature phosphorescent carbon dots@boron oxide composite materials prepared in Examples 1-4. Figure 3 It can be seen that under optimal excitation, the corresponding optimal phosphorescence wavelengths of the multicolor (blue, green, yellow and red) room temperature phosphorescent carbon dots@boron oxide composites are 485 nm, 540 nm, 585 and 665 nm, respectively.

[0027] Figure 4 This is a phosphorescence lifetime diagram of the multicolor room temperature phosphorescent carbon dots@boron oxide composite material prepared in Examples 1-4. Figure 4 It can be seen that the time-resolved decay spectrum is fitted using a three-exponential function according to the following formula: τ avg =∑α i τ i 2 / ∑α i τ i The corresponding phosphorescence lifetimes of the multicolor (blue, green, yellow and red) room temperature phosphorescent carbon dots@boron oxide composites were calculated to be 1.01 s, 1.56 s, 0.68 s and 72 ms, respectively.

[0028] Figure 5 The state diagrams of the multicolor room temperature phosphorescent carbon dots@boron oxide composite materials prepared in Examples 1-4 under sunlight, 365nm ultraviolet light irradiation, and after turning off the light. Figure 5 It can be seen that the prepared multicolor (blue, green, yellow and red) room temperature phosphorescent carbon dots@boron oxide composite materials have visible phosphorescence for 16 seconds, 20 seconds, 14 seconds and 3 seconds respectively after turning off the UV light.

[0029] Figure 6 This is a photo of the application of the carbon dot@alophane composite material prepared in Example 1 in information encryption and anti-counterfeiting. Figure 6 It can be seen that under 365 nm UV light, "heart", "U", "J" and "N" all show blue fluorescence. After turning off the UV light, the duration and color of the continuous luminescence are different. As time goes by, the last encrypted pattern "J" is recognized. The results show that the prepared multi-color room temperature phosphorescent carbon dots@boron oxide composite material is successfully used for time encryption anti-counterfeiting applications.

[0030] Obviously, those skilled in the art can make various changes and modifications to the method for preparing a multicolor room temperature phosphorescent carbon dot@boron oxide composite material described in 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 claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a multicolor room temperature phosphorescent carbon dot@boron oxide composite material, comprising the following steps: First, 0.1-0.4 g of different conjugated molecules (2-aminoterephthalic acid, 2, 3-naphthalene dicarboxylic anhydride, 1, 8-naphthalene dicarboxylic anhydride, 1, 4, 5, 8-naphthalene tetracarboxylic anhydride) were added to 50 mL of aqueous solution and stirred for 1-3 hours to obtain a transparent solution. Under stirring conditions, 2-4 g of boric acid was added to the obtained transparent solution and continued to stir for 1-3 hours to obtain a transparent solution. The obtained transparent solution was placed in an oven at 160-200°C for pyrolysis for 6-10 hours to obtain a multicolor room temperature phosphorescent carbon dot@boron oxide composite material.

2. The method for preparing the multicolor room temperature phosphorescent carbon dots@boron oxide composite material according to claim 1, characterized in that: The different conjugated molecules are 2-aminoterephthalic acid, 2, 3-naphthalene dicarboxylic anhydride, 1, 8-naphthalene dicarboxylic anhydride, and 1, 4, 5, 8-naphthalene tetracarboxylic anhydride.

3. The method for preparing the multicolor room temperature phosphorescent carbon dots@boron oxide composite material according to claim 1, characterized in that: The amount of 2-aminoterephthalic acid used was 0.4 g, the amount of 2, 3-naphthalene dicarboxylic anhydride used was 0.3 g, the amount of 1, 8-naphthalene dicarboxylic anhydride used was 0.2 g and the amount of 1, 4, 5, 8-naphthalene tetracarboxylic anhydride used was 0.1 g.

4. The use of the multicolor room temperature phosphorescent carbon dots@boron oxide composite material prepared by the preparation method according to claim 1, characterized in that: The multicolor room temperature phosphorescent carbon dot@boron oxide composite material is applied to information encryption.

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