An ultra-long-life room temperature phosphorescent carbon dot@alumina@silicon oxide composite material and preparation method thereof

Abstract

The present invention relates to an ultra-long life room temperature phosphorescent carbon dot @ alumina @ silicon oxide composite material and a preparation method thereof. The preparation method comprises the following steps: adding glucose, urea and aluminum nitrate to an aqueous solution, stirring to obtain a transparent solution, adding mesoporous silica and stirring, freeze drying, and calcining through a muffle furnace to obtain an ultra-long life room temperature phosphorescent carbon dot @ alumina @ silicon oxide composite material. The ultra-long life room temperature phosphorescent carbon dot @ alumina @ silicon oxide composite material is directly obtained by a simple in-situ calcination method. In addition, ultra-long life phosphorescence and long visible time to the naked eye are successfully achieved by using low-cost alumina and mesoporous silica in carbon dot-based room temperature phosphorescent materials, and the phosphorescence lifetime is as high as 3.03 seconds, and the yellow-green phosphorescence visible to the naked eye is as long as 30 seconds after the ultraviolet lamp is turned off. The drugs used in the preparation are non-toxic, harmless and inexpensive, the preparation is simple and the time used is short, and no complicated and cumbersome steps are required after the preparation, which is particularly suitable for batch and low-cost preparation, and suitable for industrial-scale production and commercial applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dot material preparation, and in particular relates to an ultra-long life room temperature phosphorescent carbon dot@aluminum oxide@silicon oxide composite material and a preparation method thereof. Background Art

[0002] Room temperature phosphorescence is a material that can continue to emit light after the excitation light source is turned off. It has unique photophysical properties, rich excited state characteristics and excellent structural design. It shows great application prospects in the fields of displays, chemical sensors, biological imaging and anti-counterfeiting. In the past decade, the room temperature phosphorescent materials that have received widespread attention mainly include pure organic compounds based on molecular design and inorganic complexes designed based on transition metals or rare earth ions. However, due to the scarcity of rare earth resources, complex manufacturing processes, instability in humid environments and toxicity that cannot be ignored, the practical application prospects of organic compounds and inorganic complexes are not suitable for permanent consideration. In addition, room temperature phosphorescent materials also have problems such as short phosphorescence lifetime and poor stability. Therefore, it is very important to explore new room temperature phosphorescent materials with both ultra-long lifetime and excellent stability through simple, green and cost-effective methods.

[0003] As a rising star in the carbon material family, carbon dots have been widely used in fluorescence sensing, photoelectrocatalysis, energy conversion and storage due to their excellent optical properties, low toxicity, raw material diversity and low price. At present, the research on carbon dots mainly focuses on their excellent fluorescence properties and the regulation of multi-color full-color luminescence. In recent years, researchers have turned the research center of carbon dots to the more attractive room temperature phosphorescence. However, due to the weak spin-orbit coupling of carbon dots and the violent vibration and rotation of chromophores, they produce inefficient intersystem crossing and rapid non-radiative decay, resulting in short phosphorescence lifetime and poor stability. In order to solve these problems, researchers have introduced carbon dots into various rigid matrices to construct carbon dot-based room temperature phosphorescent materials to achieve long-life phosphorescence. However, the preparation process and regulation method of carbon dot-based room temperature phosphorescent materials involve multiple precursors and steps, which increases the complexity of the reaction and the screening time. Therefore, it is of vital significance to obtain carbon dot-based room temperature phosphorescent with ultra-long lifetime and high stability by a simple in situ preparation method. Summary of the invention

[0004] In order to avoid the shortcomings of the prior art, the present invention provides an ultra-long life room temperature phosphorescent carbon dot@aluminum oxide@silicon oxide composite material and a preparation method thereof.

[0005] One of the purposes of the present invention is to provide a dual-matrix protection method.

[0006] The second object of the present invention is to provide a simple and easy one-step calcination method.

[0007] The third object of the present invention is to provide an ultra-long life room temperature phosphorescent carbon dot@aluminum oxide@silicon oxide composite material.

[0008] The ultra-long-life room-temperature phosphorescent carbon dots@alumina@silicon oxide composite material prepared by the present invention is prepared by a simple in-situ calcination method using glucose, urea, aluminum nitrate and mesoporous silica as raw materials, and the preparation process includes the following specific steps:

[0009] 1. First, add 0.1-0.6 g glucose, 0.1-0.6 g urea and 1-5 g aluminum nitrate to 50 ml aqueous solution and stir for 1-5 hours to obtain a transparent solution;

[0010] 2. Under stirring conditions, add 0.5-2 g of mesoporous silica to the transparent solution obtained in step 1, and stir for 1-5 hours to obtain a transparent solution;

[0011] 3. Freeze-dry the transparent solution obtained in step 2 for 12-36 hours to obtain a white solid;

[0012] 4. The white solid obtained in step 3 is placed in a crucible with a cover, and calcined in a muffle furnace at 500-800° C. for 2-4 hours to obtain a carbon dot@alumina@silicon oxide composite material.

[0013] Beneficial effects of the present invention:

[0014] 1. The ultra-long-lifetime room-temperature phosphorescent carbon dot@alumina@silicon oxide composite material prepared by the present invention overcomes the limitations of low phosphorescence lifetime and low visible time of existing carbon dot-based room-temperature phosphorescent materials, and obtains excellent ultra-long-lifetime phosphorescent emission;

[0015] 2. The present invention provides an ultra-long life room temperature phosphorescent carbon dot@alumina@silicon oxide composite material and a preparation method thereof, wherein the composite material is prepared by using glucose, urea, aluminum nitrate and mesoporous silica as raw materials through a simple in-situ calcination method, and only requires common laboratory equipment for preparation without special equipment. In addition, the process is simple and easy to operate;

[0016] 3. The ultra-long-lifetime room-temperature phosphorescent carbon dots@alumina@silicon oxide composite material prepared by the present invention has a phosphorescence lifetime of more than 3 seconds under an excitation wavelength of 365 nm, and yellow-green phosphorescence visible to the naked eye for up to 30 seconds after the ultraviolet light is turned off;

[0017] 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;

[0018] 5. The carbon dot@alumina@silicon oxide composite material prepared by the present invention can be successfully applied in the field of information encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 1 This is a transmission electron microscope image of the carbon dot@alumina@silicon oxide composite material prepared in Example 1 of the present invention.

[0021] Figure 2 This is the X-ray diffraction pattern of the carbon dot@alumina@silicon oxide composite material prepared in Example 1 of the present invention.

[0022] Figure 3 This is a phosphorescence spectrum of the carbon dot@alumina@silicon oxide composite material prepared in Example 1 of the present invention.

[0023] Figure 4 This is a phosphorescence lifetime diagram of the carbon dot@aluminum oxide@silicon oxide composite material prepared in Example 1 of the present invention.

[0024] Figure 5 These are state diagrams of the carbon dot@alumina@silicon oxide composite materials prepared in Examples 1-3 and Comparative Example 1 under sunlight, under 365 nm ultraviolet light, and after turning off the light.

[0025] Figure 6 This is a photo of the application of the carbon dot@alumina@silicon oxide composite material prepared in Example 1 of the present invention in information encryption. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Embodiment 1:

[0030] First, 0.3 g of glucose, 0.4 g of urea and 3 g of aluminum nitrate were added to 50 ml of aqueous solution and stirred for 3 hours to obtain a transparent solution; under stirring conditions, 1 g of mesoporous silica was added to the obtained transparent solution and stirred for 3 hours to obtain a transparent solution; the transparent solution was freeze-dried for 24 hours to obtain a precursor; the precursor was placed in a covered crucible and calcined at 700°C in a muffle furnace for 3 hours to obtain a carbon dot@alumina@silica composite material.

[0031] Embodiment 2:

[0032] First, 0.1 g of glucose, 0.6 g of urea and 5 g of aluminum nitrate were added to 50 ml of aqueous solution and stirred for 5 hours to obtain a transparent solution; under stirring conditions, 2 g of mesoporous silica was added to the obtained transparent solution and stirred for 5 hours to obtain a transparent solution; the transparent solution was freeze-dried for 36 hours to obtain a precursor; the precursor was placed in a covered crucible and calcined at 800°C in a muffle furnace for 4 hours to obtain a carbon dot@alumina@silica composite material.

[0033] Embodiment 3:

[0034] First, 0.6 g of glucose, 0.1 g of urea and 1 g of aluminum nitrate were added to 50 ml of aqueous solution and stirred for 1 hour to obtain a transparent solution; under stirring conditions, 0.5 g of mesoporous silica was added to the obtained transparent solution and stirred for 1 hour to obtain a transparent solution; the transparent solution was freeze-dried for 12 hours to obtain a precursor; the precursor was placed in a covered crucible and calcined at 500°C in a muffle furnace for 2 hours to obtain a carbon dot@alumina@silica composite material.

[0035] Comparative Example 1:

[0036] First, 1 g of glucose was added to 50 ml of aqueous solution and stirred for 2 hours to obtain a transparent solution; the transparent solution was transferred to a 100 ml reactor and subjected to hydrothermal reaction at 150°C for 2 hours, and then cooled to room temperature to obtain a brown suspension; the brown suspension solution was centrifuged at 8000 rpm for 10 minutes in a high-speed centrifuge, and the lower sediment in the centrifuge tube was removed to obtain a brown supernatant; the brown supernatant was dialyzed with a 1000 Da dialysis bag for 48 hours to obtain a carbon dot solution; 5 ml of the obtained carbon dot solution, 0.4 g of urea and 3 g of aluminum nitrate were added to 50 ml of aqueous solution and stirred for 3 hours to obtain a yellow transparent solution; under stirring conditions, 1 g of mesoporous silica was added to the obtained yellow transparent solution and stirred for 3 hours to obtain a yellow transparent solution; the yellow transparent solution was freeze-dried for 24 hours to obtain a precursor; the precursor was placed in a covered crucible and calcined at 700°C in a muffle furnace for 3 hours to obtain a carbon dot@alumina@silica composite material.

[0037] Figure 1 This is a transmission electron micrograph of the carbon dot@alumina@silicon oxide composite material prepared in Example 1. The inset is a high-resolution transmission electron micrograph. Figure 1 It can be seen that the composite material is a uniform silica nanosphere encapsulating a layer of amorphous alumina. The carbon dots synthesized in situ by glucose are encapsulated in silica and alumina.

[0038] Figure 2 The X-ray diffraction pattern of the carbon dot@alumina@silicon oxide composite material prepared in Example 1 is shown in FIG. Figure 2 It can be seen that the broad peak at 23° indicates that the prepared composite material exhibits an amorphous structure.

[0039] Figure 3 This is the phosphorescence spectrum of the carbon dot@alumina@silicon oxide composite material prepared in Example 1. Figure 3 It can be seen that after excitation at 365 nm, phosphorescence is detected after a delay, with the emission band centered around 535 nm.

[0040] Figure 4 This is the phosphorescence lifetime diagram of the carbon dot@alumina@silicon oxide composite material prepared in Example 1. Figure 4 It can be seen that the time-resolved decay spectrum was fitted with a three-exponential function, and the phosphorescence lifetime was calculated to be 3.03 seconds at room temperature, indicating that the prepared carbon dot@alumina@silicon oxide composite material has an ultra-long lifetime.

[0041] Figure 5 The state diagrams of the carbon dot@alumina@silicon oxide composite materials prepared in Examples 1-3 and Comparative Example 1 under sunlight, under 365 nm ultraviolet light, and after turning off the light, respectively. Figure 5 It can be seen that Example 1 exhibits the longest visible time to the naked eye, which is as long as 30 seconds. The visible time to the naked eye of the carbon dot@alumina@silicon oxide composite materials prepared in other Examples 2-3 and Comparative Example 1 is relatively short.

[0042] Figure 6 This is a photo of the carbon dot @alumina @silicon oxide composite material prepared in Example 1 for information encryption application. Figure 6 It can be seen that under 365 nm UV light, the digital combination is recognized as "8888". After turning off the UV light, the encrypted information "3396" can be obtained. After stopping the excitation for 10 seconds, the final encrypted information "7755" is displayed. The results show that the prepared carbon dot @aluminum oxide @silicon oxide phosphor powder is successfully used for time encryption applications.

[0043] Obviously, those skilled in the art can make various changes and modifications to the ultra-long-lifetime room temperature phosphorescent carbon dot@aluminum oxide@silicon oxide composite material and its preparation method 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 an ultra-long life room temperature phosphorescent carbon dot@alumina@silicon oxide composite material, comprising the following steps: First, 0.1-0.6g of glucose, 0.1-0.6g of urea and 1-5g of aluminum nitrate are added to 50ml of aqueous solution, and stirred for 1-5 hours to obtain a transparent solution; under stirring conditions, 0.5-2g of mesoporous silica is added to the transparent solution, and stirred for 1-5 hours to obtain a transparent solution; the transparent solution is freeze-dried for 12-36 hours to obtain a white solid; the white solid is placed in a covered crucible, and calcined at 500-800°C in a muffle furnace for 2-4 hours to obtain a carbon dot@alumina@silica composite material.

2. The method for preparing the ultra-long life room temperature phosphorescent carbon dot@alumina@silicon oxide composite material according to claim 1, characterized in that: The amount of glucose used was 0.3 g and the amount of urea used was 0.4 g.

3. The method for preparing the ultra-long life room temperature phosphorescent carbon dot@alumina@silicon oxide composite material according to claim 1, characterized in that: The amount of aluminum nitrate used is 3 g, and the amount of mesoporous silica used is 1 g.

4. The method for preparing the ultra-long life room temperature phosphorescent carbon dot@alumina@silicon oxide composite material according to claim 1, characterized in that: The calcination temperature was 700°C and the reaction time was 3 hours.

5. Application of the ultra-long life room temperature phosphorescent carbon dots@alumina@silicon oxide composite material obtained by the preparation method according to claim 1, characterized in that: The ultra-long life room temperature phosphorescent carbon dot@aluminum oxide@silicon oxide composite material is applied to information encryption.

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