Preparation method of reversible rapid photoresponse multicolor fluorescent CDs material, obtained product and application

Abstract

The invention belongs to the field of functional material preparation, and particularly relates to a preparation method of a reversible quick-response multicolor fluorescent CDs material as well as an obtained product and application of the reversible quick-response multicolor fluorescent CDs material. The method is realized through the following steps: firstly, preparing N-CDs from naphthalene-1, 4, 5, 8-tetracarboxylic acid, urea, diethylamine and deionized water; then dissolving the N-CDs in tetraethylenepentamine (TEPA) solutions with different concentrations, so as to obtain N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions with different concentrations; according to the invention, wide-range tunable light response fluorescence color change from dark red to light green is realized for the first time, and the technical blank is filled; the method realizes the application of repeatable dynamic information coding, and shows huge application potential in the field of advanced dynamic information encryption. The method has the advantages that the photoresponse reversible multicolor fluorescence emission of the CDs material is quickly realized, the response time is as fast as 0.5 s, and the method has obvious advantages. The quick-response multicolor fluorescent CDs material is prepared by adopting a simple and quick method, the preparation process is simple, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the field of functional material preparation, and specifically relates to a preparation method of a reversible fast-response multicolor fluorescent CDs material and the obtained product and application. Background Art

[0002] Photoresponsive dynamic luminescent materials have specific response behaviors to light, and usually undergo changes in sunlight and fluorescence under ultraviolet light irradiation, which are the two most studied phenomena under ultraviolet light irradiation: photochromism and photoinduced fluorescence color change. Photoresponsive dynamic luminescent materials have rich luminescence color change properties and rapid responsiveness to ultraviolet light stimulation. They show great application potential in the fields of sensors, advanced anti-counterfeiting, optoelectronic applications, etc., and have been widely studied in recent years. Although the photoresponsive luminescent materials reported so far show good luminescence properties, they are mainly concentrated in organic small molecule materials. Relatively speaking, their synthesis process is relatively complicated and the preparation time is relatively long. Therefore, it is inevitable to further explore optical materials with simple preparation process and excellent photoresponsive luminescence properties.

[0003] Carbon dots (CDs), as a new type of fluorescent carbon nanomaterial that combines simple preparation, adjustable optical properties and wide application, have attracted much attention in many frontier fields such as smart material development and information security by modifying them to a certain extent to produce unique photoresponsive characteristics. In recent years, photoresponsive CDs have become a hot topic in the field of photostimuli-responsive materials. Gao's research group prepared fluorescent materials with ultraviolet light stimulus response emission by encapsulating spiropyran compounds in CDs-functionalized silica. Under ultraviolet light stimulation, they showed dynamic fluorescence behaviors of photochromism and fluorescence color change, and were successfully applied to dynamic anti-counterfeiting. Chen's research group used naphthylimide structures to embed on CDs and then embed them in polyvinylpyrrolidone to achieve the combination of photochromism and photoluminescence properties. The appearance color transitioned from colorless to brown within 100s, and the luminescence color transitioned from blue to yellow within 60s. At present, photoresponsive luminescent carbon dots have made great progress, but the photoresponse time is relatively long, especially it is not easy to restore the initial state or requires additional stimulation (such as heating) to restore the original state, which limits its application to a certain extent. Moreover, most of the reported photoresponsive dynamic luminescence is limited to monochromatic emission from one color to another, and research on photoresponsive multicolor CDs with wide tunable range is relatively rare, which limits its security in the field of information protection. Therefore, exploring a fast photoresponsive multicolor fluorescent CDs material with simple and fast preparation and excellent reversibility still faces great challenges. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for preparing a reversible fast-response multicolor fluorescent CDs material.

[0005] The present invention also provides a reversible fast-response multicolor fluorescent CDs material prepared by the preparation method.

[0006] Another object of the present invention is to provide an application of the above-mentioned reversible fast-response multicolor fluorescent CDs material.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: The present invention provides a method for preparing a reversible fast-response multicolor fluorescent CDs material, comprising the following steps: (1) Synthesis of N-CDs Naphthalene-1,4,5,8-tetracarboxylic acid, urea, diethylamine and deionized water were ultrasonically mixed and then the mixture was subjected to microwave heating reaction. After the reaction was completed, the mixture was cooled to room temperature to obtain CDs powder, which was then washed and purified with deionized water to obtain N-CDs. (2) Preparation of N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions of different concentrations N-CDs were dissolved in tetraethylenepentamine (TEPA) solutions of different concentrations to obtain N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions of different concentrations.

[0008] Preferably, in step (1), the mass volume ratio of the naphthalene-1,4,5,8-tetracarboxylic acid, urea, diethylamine and deionized water is 0.3 g:3 g:1 mL:10 mL.

[0009] Preferably, in step (1), the microwave heating is carried out at a power of 275-285 W for 10 min.

[0010] Preferably, in step (2), in the tetraethylenepentamine (TEPA) solution, the volume ratio of tetraethylenepentamine to deionized water is 1:0-1500.

[0011] Preferably, in step (2), the mass volume ratio of the N-CDs to tetraethylenepentamine (TEPA) solution is 40 mg: 1-16 mL.

[0012] The present invention also provides a multicolor fluorescent CDs material prepared by the above preparation method.

[0013] The present invention further provides the application of the multi-color fluorescent CDs material in the field of repeatable dynamic information encryption.

[0014] The present invention rapidly prepares CDs (N-CDs) containing rich functional groups by a microwave method, and then introduces tetraethylenepentamine solution to modify the surface of N-CDs (N-CDs / TEPA), thereby realizing fast and reversible ultraviolet light response behavior. N-CDs / TEPA can realize the transformation of sunlight and fluorescent color within 0.5s at the fastest, and can directly restore the original state by shaking. Importantly, the method provided by the present invention realizes a wide range of tunable light-responsive fluorescence color changes from deep red to light green by simply adjusting the concentration of tetraethylenepentamine solution, which has not been reported in previous studies. A series of characterizations show that the introduction of tetraethylenepentamine solution of different concentrations may form different numbers of naphthaleneimide structures on the surface of N-CDs, and produce different numbers of free radical anions after ultraviolet light irradiation, thereby realizing light-responsive multicolor fluorescence behavior. According to the dependence of different concentrations of N-CDs / TEPA on ultraviolet light response time, the application of repeatable dynamic information encoding is realized, showing great application potential in the field of advanced dynamic information encryption. The advantage of this work is that it can quickly realize the photoresponsive reversible multicolor fluorescence emission of CDs materials, with the fastest response time reaching 0.5s, which has obvious advantages.

[0015] The beneficial effects of the present invention are: (1) The present invention uses a microwave solid phase reaction method to quickly prepare a composite material with rapid reversible ultraviolet light response, which can achieve the transition between sunlight and fluorescent colors within 0.5 seconds and can be directly restored to the original state by shaking; (2) This invention has realized for the first time a wide range of tunable light-responsive fluorescence color changes from deep red to light green, filling the gap in this technology; it has realized the application of repeatable dynamic information encoding, showing great application potential in the field of advanced dynamic information encryption. The advantage of this work is that it can quickly realize the light-responsive reversible multicolor fluorescence emission of CDs materials, with the fastest response time of 0.5s, which has obvious advantages.

[0016] (3) The present invention adopts a simple and quick method to prepare a fast-response multicolor fluorescent CDs material, and the preparation process is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 XRD pattern of N-CDs prepared in Example 1; Figure 2 is the Fourier transform infrared spectrum of N-CDs prepared in Example 1; Figure 3 . (a) Fluorescence spectra of N-CDs / TEPA solutions with different concentrations before UV irradiation; (b) Fluorescence spectra of N-CDs / TEPA solutions with different concentrations after UV irradiation; Figure 4. Reversible fluorescence spectra of N-CDs / TEPA solutions with different concentrations; Figure 5 . (a) UV-visible absorption spectra of N-CDs / TEPA solutions with different concentrations before UV irradiation; (b) UV-visible absorption spectra of N-CDs / TEPA solutions with different concentrations after UV irradiation; Figure 6 . Application of reproducible dynamic information encoding based on time-dependent fluorescence of photoresponse. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0019] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0020] Example 1 1. Synthesis of N-CDs 0.3 g of naphthalene-1,4,5,8-tetracarboxylic acid, 3 g of urea, 1 ml of diethylamine and 10 ml of deionized water were mixed in a beaker and ultrasonically mixed. The mixture was then placed in a household microwave oven, thawed and heated for 10 minutes until the reaction was complete, and then cooled to room temperature to obtain CDs powder, named N-CDs. Finally, it was washed and purified with deionized water.

[0021] 2. Preparation of N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions of different concentrations The same amount of N-CDs was dissolved in tetraethylenepentamine (TEPA) solutions of different concentrations to obtain eight N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions of different concentrations: 0: 1, 1: 1, 10: 1, 100: 1, 300: 1, 500: 1, 1000: 1 and 1500: 1. Specifically, 40 mg of N-CDs powder was placed in 8 centrifuge tubes. Then, N-CDs / TEPA solutions with different concentrations were prepared by adding the following amounts of TEPA and deionized water: 1 mL TEPA (0:1), 1 mL deionized water and 1 mLTEPA (1:1), 1 mL deionized water and 100 μL TEPA (10:1), 1 mL deionized water and 10 μL TEPA (100:1), 3 mL deionized water and 10 μL TEPA (300:1), 5 mL deionized water and 10 μL TEPA (500:1), 10 mL deionized water and 10 μL TEPA (1000:1), and 15 mL deionized water and 10 μL TEPA (1500:1).

[0022] Figure 1 The XRD patterns of N-CDs are shown. Three obvious sharp peaks are shown at 2θ=19.88°, 2θ=22.48° and 2θ=26.41°, all corresponding to the (002) crystal plane of graphitic carbon. In addition, there are two sharp peaks at 2θ=28.09° and 2θ=29.79°, which may be due to the cyanuric acid structure formed inside CDs during microwave heating. The XRD pattern shows that N-CDs have sharp diffraction peaks, indicating that N-CDs have good crystallinity.

[0023] Figure 2 The Fourier transform infrared spectra of N-CDs are shown to characterize the functional group structure of N-CDs. -1 and 3410 cm -1 There are two main absorption peaks at , which are attributed to the stretching vibration of C=C / C=O and NH / OH, respectively. Infrared spectroscopy analysis shows that the surface of N-CDs may contain abundant amino and carboxyl functional groups.

[0024] Effect Example The performance of the N-CDs prepared in Example 1 and N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions of different concentrations was characterized, specifically: Figure 3 The fluorescence spectra of N-CDs / TEPA solutions with different concentrations before and after ultraviolet irradiation are shown. N-CDs / TEPA with different concentrations all show the phenomenon of light-induced fluorescence color change. The different concentrations lead to different light response fluorescence colors after ultraviolet irradiation. As the concentration of TEPA decreases, the light response fluorescence color gradually shifts to blue, realizing light-induced multicolor fluorescence emission. Among them, the solution with a concentration of 0:1 has a fluorescence emission wavelength of 663 nm before ultraviolet irradiation, and the emission wavelength shows two main emission wavelengths at 660 nm and 858 nm after ultraviolet irradiation. The fluorescence color turns red and bright, which can be achieved quickly within 0.5s. The solutions with concentrations of 1:1 and 10:1 have green fluorescence colors before irradiation, with wavelengths of 552 nm and 541 nm, respectively. After irradiation, they turn into bright red and orange fluorescence, with wavelengths of 721 nm and 596 nm, respectively. The solutions with concentrations of 100:1, 300:1 and 500:1 all showed green fluorescence before irradiation, and turned to yellowish fluorescence after irradiation, with emission wavelengths of 564 nm / 613 nm, 562 nm and 557 nm, respectively. The solutions with concentrations of 1000:1 and 1500:1 all showed blue fluorescence before irradiation, with wavelengths of 452 nm and 474 nm, respectively, and turned to green fluorescence after irradiation, with wavelengths of 531 nm and 521 nm, respectively.

[0025] In addition, the light-responsive fluorescence of N-CDs / TEPA at different concentrations showed excellent reversibility, and could be restored to its original state by vibration shaking, and could be repeatedly cycled between continuous UV irradiation and vibration shaking. The higher the TEPA concentration, the more cycles it could have. Figure 4 As shown, the fluorescence wavelength of eight N-CDs / TEPA solutions with different concentrations did not change before and after the first UV irradiation and before and after the second UV irradiation, and the fluorescence intensity remained almost unchanged, showing excellent reversibility.

[0026] Figure 5 The UV-visible absorption spectra of N-CDs / TEPA solutions with different concentrations before and after UV irradiation are shown. The changes in the UV-visible absorption spectra before and after irradiation were analyzed by taking the N-CDs / TEPA solution with a concentration of 1:1 as an example. Before UV irradiation, N-CDs / TEPA showed three absorption peaks at 229 nm, 368 nm and 390 nm. After continuous UV irradiation, the absorption peak near 229 nm was slightly enhanced, the absorption peaks at 368 nm and 390 nm became weaker, and new absorption peaks appeared in the range of 400-500 nm. After UV irradiation, the UV absorption weakened and the visible light absorption increased, indicating that free radical anions were generated. The new absorption peak generated in the range of 400-500 nm is similar to the absorption peak of the naphthalene imide radical anion generated by photoinduced electron transfer, which further illustrates that after the addition of TEPA to modify the surface of N-CDs, a naphthalene imide structure that can respond to light after UV irradiation is generated on N-CDs. The UV-visible absorption spectra of N-CDs / TEPA at other different concentrations were also characterized, showing similar changes to that of N-CDs / TEPA at a concentration of 1:1. The UV-visible absorption spectra before and after UV irradiation showed that a naphthylimide structure was formed on the surface of the carbon dots after UV irradiation, providing conditions for the occurrence of photoresponsive behavior.

[0027] N-CDs / TEPA materials with different concentrations show reversible multicolor fluorescence with different colors after ultraviolet light irradiation. Based on the time dependence of the photoresponsive fluorescence, a dynamic information encoding model with repeatable function is designed, which has potential application prospects in the field of repeatable dynamic information encryption. Figure 6As shown in the figure, four different concentrations of N-CDs / TEPA materials, 1:1, 10:1, 300:1 and 1500:1, were selected to design a repeatable dynamic information coding strip. Red and yellow fluorescence are defined as the "-" signal in Morse code, orange and blue fluorescence are defined as the "." signal in Morse code, and green fluorescence is defined as the pause " / " signal in Morse code. When the ultraviolet light is just turned on, the four materials show green and blue fluorescence, and the information stored at this time is "E". After continuous ultraviolet light irradiation for 60 s, the four concentrations of N-CDs / TEPA all undergo light-responsive fluorescence color change, showing red, orange, yellow and green fluorescence, and the information encoded "K" is obtained. This system can realize repeatable and cyclic dynamic information encoding applications through vibration shaking and continuous ultraviolet light irradiation.

Claims

1. A method for preparing a reversible fast-response multicolor fluorescent CDs material, characterized in that: The following steps are involved: (1) Synthesis of N-CDs Naphthalene-1,4,5,8-tetracarboxylic acid, urea, diethylamine and deionized water were ultrasonically mixed and then the mixture was subjected to microwave heating reaction. After the reaction was completed, the mixture was cooled to room temperature to obtain CDs powder, which was then washed and purified with deionized water to obtain N-CDs. (2) Preparation of N-CDs / tetraethylenepentamine (N-CDs / TEPA) solutions of different concentrations N-CDs were dissolved in tetraethylenepentamine solutions of different concentrations to obtain N-CDs / tetraethylenepentamine solutions of different concentrations.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass volume ratio of the naphthalene-1,4,5,8-tetracarboxylic acid, urea, diethylamine and deionized water is 0.3 g:3 g:1 mL:10 mL.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the microwave heating is carried out at a power of 275-285 W for 10 min.

4. The preparation method according to claim 1, characterized in that: In step (2), in the tetraethylenepentamine solution, the volume ratio of tetraethylenepentamine to deionized water is 1:0-1500.

5. The preparation method according to claim 1 or 4, characterized in that: In step (2), the mass volume ratio of the N-CDs to the tetraethylenepentamine solution is 40 mg: 1-16 mL.

6. A multicolor fluorescent CDs material prepared by the preparation method according to any one of claims 1 to 5.

7. An application of the multicolor fluorescent CDs material as claimed in claim 6 in the field of repeatable dynamic information encryption.

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