A dual-functionalized graphene oxide nonlinear optical nanohybrid material and its preparation and application

Abstract

The present invention relates to a bifunctionalized graphene oxide nonlinear optical nanohybrid material and its preparation and application. First, the carbonyl group at the edge of the graphene oxide is converted into dicyanomethylene through a Knoevenagel condensation reaction, and then porphyrin molecules are covalently grafted on the surface of the graphene oxide through a free radical addition reaction, thereby achieving bicovalent functionalization of the graphene oxide. By chemically bonding the electron-donating porphyrin and the dicyanomethylene with strong electron-pulling properties to the graphene surface, the electron and energy transfer process between the porphyrin and the graphene oxide is strengthened, thereby enhancing the third-order nonlinear optical properties of the organic-inorganic hybrid material. The present invention enriches the chemical modification methods of graphene oxide, and the obtained materials have broad application prospects in optoelectronic fields such as nonlinear optical devices.

Description

Technical Field

[0001] The invention belongs to the technical field of organic-inorganic functional composite materials and military high-intensity laser protection materials, and relates to a dual-functionalized graphene oxide nonlinear optical nano-hybrid material and its preparation and application. Background Art

[0002] In 2004, Novoselov and his colleagues first used tape to separate sp-based 2 Graphene is a single-layer honeycomb network of hybrid carbon atoms. Since then, graphene has attracted widespread attention from researchers due to its unique physical and chemical properties. Graphene has a high specific surface area (theoretically 2,630m2 for a single-layer graphene). 2 / g), excellent thermal conductivity, electrical conductivity, excellent mechanical strength and electron transport ability (the mobility of electrons and holes at room temperature is as high as 15,000 cm 2 / (V·s)). Therefore, it is considered the most promising carbon allotrope for nanostructures. However, despite its promising prospects, large-scale production of high-quality graphene products is currently difficult, which to some extent limits its promotion in practical applications. Among the methods reported to date, wet chemical exfoliation of bulk graphite is recognized as the best way to achieve large-scale production of single- to few-layer graphene due to its high efficiency and scalability.

[0003] Porphyrins are versatile molecular building blocks abundant in nature, and their optical properties are highly sensitive to structural modifications, particularly the degree of π-electron conjugation. Covalent functionalization of graphene with organic porphyrins is an effective approach to modulate its physical and electronic properties, enabling the synthesis of nanoconjugates with diverse applications, such as catalysts, photonic synapses, light harvesting, and, most notably, optical limiters. Porphyrins have been successfully covalently bonded to graphene using solution-processed wet chemical methods. This process typically involves more dispersible graphene forms such as graphene oxide (GO), reduced GO, and exfoliated few-layer graphene. Free radical addition reactions, "click" reactions, 1,3-dipolar cycloaddition reactions, and acylation reactions have been used to generate a range of covalently linked products between porphyrin units and graphene. These porphyrin-graphene nanohybrids exhibit remarkable nonlinear optical properties compared to their individual components. Among them, efficient electron and energy transfer between the two components plays a key role in enhancing the nonlinear optical properties of porphyrin-graphene hybrids. Past research has focused on modifying the bonding mode between porphyrin and graphene to control the electronic and energy interactions between the two. However, in all reported porphyrin-graphene covalent hybrids, almost all graphene is monocovalently functionalized, meaning that only a single porphyrin molecule is attached to the graphene. To further expand the performance and application range of these hybrids, the introduction of multiple functional molecules with different properties into graphene is a promising strategy. This would integrate groups with different properties into a whole, providing opportunities for the realization of functional nanocomposites with tailored properties. In this regard, the development of functionalized graphene hybrid structures with two or more molecules covalently linked is very promising. Summary of the Invention

[0004] The purpose of the present invention is to provide a bifunctionalized graphene oxide nonlinear optical nanohybrid material and its preparation and application, so as to improve the nonlinear optical absorption performance of the material and broaden the nonlinear application range of the material.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a bifunctionalized graphene oxide nonlinear optical nanohybrid material, which is obtained by converting the carbonyl groups on the edges of graphene oxide into dicyanomethylene through a Knoevenagel condensation reaction, and then covalently grafting porphyrin molecules on the surface of graphene oxide through a free radical addition reaction.

[0007] In a second aspect, the present invention provides a method for preparing a bifunctionalized graphene oxide nonlinear optical nanohybrid material, comprising the following steps:

[0008] (1) Graphene oxide and malononitrile are sequentially added to a pyridine solution, and then the entire reaction system is sealed and heated to reflux. After the reaction, dicyanomethylene-functionalized graphene oxide is separated and recorded as CN-GO;

[0009] (2) 5-(4-aminophenyl)-10,15,20-triphenylporphyrin and the CN-GO obtained in step (1) are dispersed in a tetrahydrofuran solution, uniformly dispersed by ultrasonication, and then isoamyl nitrite is added thereto, heated under reflux, and separated to obtain a bifunctionalized graphene oxide product, which is the target product.

[0010] Furthermore, in step (1), the ratio of the added amounts of graphene oxide, malononitrile and pyridine is (20-50) mg: (200-500) mg: (50-100) mL.

[0011] Furthermore, in step (1), the heating reflux temperature is 60-100°C.

[0012] Furthermore, in step (1), the heating reflux time is 1 to 2 days.

[0013] Furthermore, in step (2), the ratio of the added amounts of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, CN-GO and isoamyl nitrite is: (200-500) mg: (20-50) mg: (0.5-1) mL.

[0014] Furthermore, in step (2), the heating reflux temperature is 40 to 60°C.

[0015] Furthermore, in step (2), the heating reflux time is 2 to 3 days.

[0016] In a third aspect, the present invention provides an application of a bifunctionalized graphene oxide nonlinear optical nanohybrid material in the field of optical limiting.

[0017] Furthermore, the nonlinear optical nanohybrid material has enhanced nonlinear absorption performance under 532 and 1064 nm nanosecond laser irradiation.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The bifunctionalized graphene oxide nonlinear optical nanohybrid material prepared in the present invention comprises an electron donor porphyrin, an electron acceptor dicyanomethylene and a bridging component, which enriches the preparation method of graphene oxide hybrid materials.

[0020] 2. The fluorescence quenching phenomenon of the bifunctionalized graphene oxide nonlinear optical nanohybrid material Por-CN-GO prepared by the present invention is more significant, indicating that there is a more efficient electron and energy transfer process in the system.

[0021] 3. The bifunctionalized graphene oxide nonlinear optical nanohybrid material Por-CN-GO prepared in the present invention has enhanced nonlinear absorption under 532 and 1064nm nanosecond laser irradiation than the parent material GO, porphyrin and the monofunctionalized product Por-GO, indicating that the introduction of dicyanomethylene plays an important role in the nonlinear optical properties of the material. This design idea provides ideas for the future synthesis and preparation of more flexible nonlinear light-responsive materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the preparation route and synthesis of the Por-CN-GO nanohybrid material prepared in the present invention;

[0023] Figure 2 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the Por-CN-GO nanohybrid material prepared in the present invention are shown;

[0024] Figure 3 This is the infrared spectrum of the Por-CN-GO nanohybrid material prepared in the present invention;

[0025] Figure 4 This is the UV absorption graph of the Por-CN-GO nanohybrid material prepared in the present invention;

[0026] Figure 5 Steady-state fluorescence and transient fluorescence spectra of the Por-CN-GO nanohybrid material prepared in the present invention;

[0027] Figure 6 This is the nonlinear optical absorption spectrum of the Por-CN-GO nanohybrid material prepared in the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0029] In the following examples, unless otherwise specified, raw materials, products or processing techniques are conventional commercially available products or conventional processing techniques in the art.

[0030] Example 1:

[0031] Reference Figure 1The process flow shown in FIG. 1 is a process for preparing a bifunctionalized graphene oxide nonlinear optical nanohybrid material.

[0032] (1) GO was prepared by a modified Hummers method. At 0°C, 1 g of graphite powder was added to 23 mL of concentrated sulfuric acid (with a concentration of 98 wt%). After 30 minutes, 3 g of potassium permanganate was added to the reaction system in small amounts and multiple times. The above process was completed within 2 hours. After the addition of potassium permanganate, the reaction system was heated to 35°C. After 1 hour, 100 mL of deionized water and 10 mL of 30 wt% H2O2 were added to the reaction solution, and the solution was filtered while hot. The reaction solution was washed with 5 wt% hydrochloric acid and deionized water until neutral, and the GO sample was obtained after freeze-drying.

[0033] (2) Under nitrogen atmosphere, 50 mg of GO and 500 mg of malononitrile were added to 50 mL of pyridine solution in sequence, and then the entire reaction system was sealed and reacted at 80 ° C for two days. After the reaction solution was cooled to room temperature, it was filtered using a 0.22 μm filter membrane. The filter cake obtained by filtration was repeatedly washed with organic solvents such as ethanol, DMF and dichloromethane to remove unreacted organic matter and reaction by-products. Finally, 58 mg of dicyanomethylene functionalized product (CN-GO) was obtained by vacuum drying;

[0034] (3) Under nitrogen atmosphere, 20 mg of CN-GO was dispersed in 50 mL of tetrahydrofuran solution and the solution was ultrasonically treated for 30 minutes. Then, 150 mg of porphyrin and 0.5 mL of isoamyl nitrite were quickly added thereto. The reaction system was sealed and heated to 50 ° C and refluxed for 48 hours. After the reaction was completed and cooled to room temperature, the reaction solution was filtered with a filter membrane with a pore size of 0.22 μm. The resulting black solid was dispersed in DMF and subjected to multiple ultrasonic-filtration-redispersion processes to ensure that unreacted organic small molecules and other reaction by-products were completely removed. The final product (Por-CN-GO) was obtained by drying at 80 ° C in a vacuum drying oven for 24 hours.

[0035] Comparative Example 1

[0036] Synthesis of Por-GO:

[0037] The synthesis process is the same as that of Por-CN-GO, except that the starting material is GO instead of CN-GO.

[0038] Product characterization and performance testing

[0039] Figure 2Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the various samples prepared in this invention show that the original GO samples exhibit a wrinkled and transparent structure, with some of the folded regions formed by stacked multilayer graphene sheets. After modification with organic molecules, the morphologies of CN-GO and Por-CN-GO did not change significantly, indicating that the functionalization process did not disrupt the GO structure.

[0040] Figure 3 The infrared spectra of each group of samples prepared in the present invention are given. Figure 3 a shows the infrared spectra of GO and CN-GO. From the infrared spectrum of GO, we can see that the -1 The broadband absorption peak centered at 1722 cm corresponds to the stretching vibration of OH. -1 The absorption peak at 1640 cm-1 can be attributed to the C=O stretching vibration mode. -1 The absorption peak at 1042 cm is derived from the CC stretching vibration of the graphite domain in GO. -1 The signal at 2205 cm is caused by CO stretching vibration. -1 A new absorption peak signal appeared at 1722cm, which comes from the stretching vibration of C≡N. -1 The signal intensity of the absorption peak attributed to C=O is slightly weakened, indicating that part of the C=O in GO is converted into dicyanomethylene groups. Figure 3 b shows the infrared spectra of Porphyrin, Po-GO, and Por-CN-GO. For Porphyrin, the -1 The sharp peak at 968 and 794 cm-1 can be attributed to the C=N stretching vibration mode of the porphyrin skeleton, while the -1 The absorption peak at 1278 cm can be attributed to the stretching vibration of NH, and the stretching vibration peak of CN is located at 1278 cm -1 In the spectra of Por-GO and Por-CN-GO, the -1 Some characteristic absorption peaks of porphyrin appeared in the region, indicating that porphyrin was covalently grafted to GO and CN-GO. It is worth noting that the infrared spectrum of Por-CN-GO also showed characteristic peaks belonging to C≡N, indicating that the dicyanomethylene groups were introduced into the GO edge through covalent bonds rather than non-covalent interactions.

[0041] Figure 4 The UV absorption graphs of the samples prepared in the present invention are given. Figure 4As shown in Figure 1a, the absorption spectrum of GO has a broad absorption peak centered at 266 nm, which can be attributed to the π-π* transition of the aromatic C=C bond. As for the absorption spectrum of CN-GO, the π-π* transition absorption peak of the C=C bond red-shifts to 273 nm, which may be due to the electron-withdrawing effect of the dicyanomethylene group affecting the electron distribution of GO. Figure 4 b shows the UV-visible-near-infrared absorption spectra of porphyrin, Por-GO, and Por-CN-GO nanohybrids. Porphyrin exhibits a strong Soret band absorption peak at 417 nm and four weaker Q band absorption peaks located in the 500 to 700 nm region. The Soret band absorption and Q band absorption of porphyrin are caused by singlet transitions of electrons from S0 to S2 and S0 to S1, respectively. Compared with porphyrin and GO, two spectral changes are observed in the absorption spectrum of Por-GO: the intensity of the Soret band absorption peak of porphyrin is weakened and red-shifted to 418 nm. This spectral change can be explained by charge transfer in the donor-acceptor system (porphyrin is generally considered an electron donor, while GO is an electron acceptor). The absorption spectra of Por-GO and Por-CN-GO differ in two significant ways: first, the Soret band absorption peak of Por-CN-GO is significantly broadened. On the other hand, the Soret band absorption peak in Por-CN-GO undergoes a more pronounced red shift (421 nm), indicating that the strong electron-withdrawing effect of the dicyanomethylene group enables more efficient charge transfer between porphyrin and GO. UV-visible absorption spectroscopy strongly demonstrates that the introduction of the dicyanomethylene group not only affects the electronic structure of GO but also promotes charge and energy transfer in the GO-based donor-acceptor system.

[0042] Figure 5 The steady-state fluorescence and transient fluorescence spectra of each group of samples prepared by the present invention are given. Figure 5As shown in a, under excitation at a wavelength of 417 nm, porphyrin exhibits a wide emission spectrum ranging from 630 to 700 nm, which corresponds to the S1→S0 radiative transition process of electrons. Compared with porphyrin, obvious fluorescence quenching occurs in Por-GO and Por-CN-GO. According to previous studies, fluorescence quenching is caused by the electron and / or energy transfer process in the donor-acceptor system. The fluorescence peak intensity in Por-CN-GO decreased by about 91.5%, which is significantly greater than the decrease in Por-GO (83.7%), indicating that a more efficient electron and / or energy transfer process occurred in Por-CN-GO. The strong electron-withdrawing ability of the dicyanomethylene group makes it easier for the electrons / energy on the singlet excited state of porphyrin to be transferred to the GO part through the covalent bond between the two, resulting in a significant quenching of the fluorescence of porphyrin. In order to further understand the electronic interaction between porphyrin and GO components, transient fluorescence spectroscopy gives the fluorescence lifetime curves of porphyrin, Por-GO, and Por-CN-GO. As shown in Figure 5 As shown in (b), the fluorescence lifetime of porphyrin is 10.88 ns after single exponential fitting, while the fluorescence lifetimes of Por-GO and Por-CN-GO are 9.58 ns and 4.91 ns, respectively. The shorter fluorescence lifetime of Por-CN-GO indicates a stronger electronic / energy interaction between porphyrin and CN-GO components.

[0043] Figure 6 The nonlinear optical absorption spectra of each group of samples prepared by the present invention are given. First, the nonlinear optical performance test results of several groups of samples at a wavelength of 532nm are shown in Figure 6 a. When the incident light energy is 120 μJ, the Z-scan curves of GO, Porphyrin, CN-GO, Por-GO, and Por-CN-GO all show a symmetrical trough shape, which means that the samples all exhibit typical anti-saturation absorption response under the test conditions. T min The calculated β values ​​are 24.13 cmGW for GO, 0.85 for Porphyrin, 0.80 for CN-GO, 0.71 for Por-GO, and 0.55 for Por-CN-GO. -1 、Porphyrin's 35.25cm GW -1 , CN-GO's 62.10cm GW -1 、Por-GO's 90.10cm GW -1 、Por-CN-GO's 110.52cm -1 It can be seen that under the same test conditions (linear transmittance and incident light energy), Por-CN-GO exhibits the smallest T minThe maximum value and the largest β value indicate that its anti-saturation absorption response is the strongest among several groups of samples. Next, the Z-scan curves of all samples at a wavelength of 1064nm were tested, and the results are shown in the figure below. Figure 6 As shown in b. Under the condition of 1064nm wavelength, porphyrin molecules do not show nonlinear optical response, which is consistent with the previous research results. However, GO, CN-GO, Por-GO, and Por-CN-GO show the same anti-saturation absorption response as under the condition of 532nm wavelength. The T min The values ​​are 0.89 for GO, 0.76 for CN-GO, 0.72 for Por-GO, and 0.49 for Por-CN-GO. For the β value obtained by fitting, GO is 16.40 cm GW -1 , CN-GO is 40.63cm GW -1 , Por-GO is 63.56cm GW -1 , Por-CN-GO is 195.73cm -1 Similarly, Por-CN-GO exhibited the strongest nonlinear optical properties among several groups of samples.

[0044] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A bifunctionalized graphene oxide nonlinear optical nanohybrid material, characterized in that: It converts the carbonyl groups on the edge of graphene oxide into dicyanomethylene through Knoevenagel condensation reaction, and then covalently grafts porphyrin molecules on the surface of graphene oxide through free radical addition reaction. The nano hybrid material is prepared by the following steps: (1) Graphene oxide and malononitrile are added to a pyridine solution in sequence, and then the entire reaction system is sealed and heated to reflux. After the reaction, dicyanomethylene-functionalized graphene oxide is separated and recorded as CN-GO; (2) 5-(4-aminophenyl)-10,15,20-triphenylporphyrin and CN-GO obtained in step (1) are dispersed in a tetrahydrofuran solution and uniformly dispersed by ultrasonication. Then, isoamyl nitrite is added thereto, and the mixture is heated under reflux to separate and obtain a bifunctionalized graphene oxide product, which is the target product.

2. The method for preparing a bifunctionalized graphene oxide nonlinear optical nanohybrid material according to claim 1, wherein: The following steps are involved: (1) Graphene oxide and malononitrile are added to a pyridine solution in sequence, and then the entire reaction system is sealed and heated to reflux. After the reaction, dicyanomethylene-functionalized graphene oxide is separated and recorded as CN-GO; (2) 5-(4-aminophenyl)-10,15,20-triphenylporphyrin and CN-GO obtained in step (1) are dispersed in a tetrahydrofuran solution and uniformly dispersed by ultrasonication. Then, isoamyl nitrite is added thereto, and the mixture is heated under reflux to separate and obtain a bifunctionalized graphene oxide product, which is the target product.

3. The method for preparing a bifunctionalized graphene oxide nonlinear optical nano-hybrid material according to claim 2, wherein: In step (1), the ratio of the added amounts of graphene oxide, malononitrile and pyridine is (20-50) mg: (200-500) mg: (50-100) mL.

4. The method for preparing a bifunctionalized graphene oxide nonlinear optical nano-hybrid material according to claim 2, wherein: In step (1), the heating reflux temperature is 60-100°C.

5. The method for preparing a bifunctionalized graphene oxide nonlinear optical nano-hybrid material according to claim 2, wherein: In step (1), the heating reflux time is 1 to 2 days.

6. The method for preparing a bifunctionalized graphene oxide nonlinear optical nanohybrid material according to claim 2, wherein: In step (2), the ratio of the added amounts of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, CN-GO, and isoamyl nitrite is: (200-500) mg: (20-50) mg: (0.5-1) mL.

7. The method for preparing a bifunctionalized graphene oxide nonlinear optical nano-hybrid material according to claim 2, wherein: In step (2), the heating reflux temperature is 40-60°C.

8. The method for preparing a bifunctionalized graphene oxide nonlinear optical nano-hybrid material according to claim 2, wherein: In step (2), the heating reflux time is 2 to 3 days.

9. Application of the bifunctionalized graphene oxide nonlinear optical nanohybrid material according to claim 1 in the field of optical limiting.

10. The use of the bifunctionalized graphene oxide nonlinear optical nanohybrid material according to claim 9, characterized in that: This nonlinear optical nanohybrid material has enhanced nonlinear absorption properties under 532 and 1064 nm nanosecond laser irradiation.

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