A method for in-situ synthesis of carbonized polymer dot@few-layer black phosphorus 0D-2D heterojunction

Abstract

The application relates to a preparation method of a 0D-2D heterojunction of "quasi-egg" carbonized polymer point@few-layer black phosphorus nanosheet, which only needs one step and specifically comprises the following steps: after a mixture of bulk black phosphorus and N-methylpyrrolidone is heated in a microwave oven for 10-14 minutes, the upper clear liquid is collected by centrifugation to obtain the 0D-2D heterojunction of "quasi-egg" carbonized polymer point@few-layer black phosphorus nanosheet. The preparation method simultaneously comprises a "top-down" and "bottom-up" synthesis strategy. The "top-down" refers to the peeling of bulk multi-layer black phosphorus into few-layer black phosphorus nanosheet; the "bottom-up" refers to the polymerization, dehydration and carbonization of N-methylpyrrolidone to form carbonized polymer points. Compared with the prior art, the preparation process is simple and the preparation efficiency is high. The FLBP defect repairing technology provides a new idea for improving the stability of FLBP, and the intelligent wireless portable electrochemical sensor constructed by the prepared N-CPDs@FLBP heterojunction has an ultra-low detection limit and a wide detection range for rutin detection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterial preparation, and relates to a preparation method of a 0D-2D heterojunction of an in-situ synthesized "quasi-egg-in-egg" carbonized polymer dot (N-CPD) @ few-layer black phosphorus (FLBP) nanosheet. BACKGROUND

[0002] Black phosphorus (BP) is a newly researched layered two-dimensional semiconductor material. It has unique properties such as good direct band gap adjustment, large on-off ratio and structural anisotropy. Few-layer black phosphorus nanosheet (FLBP) and its composite materials have been widely used in the fields of solar cells, sensors, field effect transistors and energy storage devices. However, due to the high reactivity of the lone pair electrons on the surface and edge of FLBP under environmental conditions to form phosphate, the inherent defects of FLBP not only lead to environmental instability, but also destroy its conductivity and electrochemical activity.

[0003] FLBP usually needs to be prepared by liquid phase exfoliation, and surface defects are inevitably generated in the preparation process, which is an important factor leading to oxidation and affecting the performance. How to repair the surface defects of FLBP is a key problem that needs to be solved at present. Although a lot of work has been done to solve this problem, it is still a challenge to design new simple and efficient strategies to overcome these defects. SUMMARY

[0004] The purpose of the application is to overcome the shortcomings of the prior art by in-situ exfoliating black phosphorus and growing carbonized polymer dots by a simple microwave-assisted solvent heating method. The application simultaneously contains a "top-down" and "bottom-up" synthesis strategy. "Top-down" refers to the exfoliation of bulk multi-layer black phosphorus into few-layer black phosphorus nanosheet; "bottom-up" refers to the process of polymerization, dehydration and carbonization of N-methylpyrrolidone to form "quasi-egg-in-egg" polymer dots (N-CPDs). The high chemical activity at the defect sites of FLBP in-situ adsorbs N-CPDs produced by dehydration, polymerization and carbonization of organic solvent N-methylpyrrolidone, thereby forming N-CPDs@FLBP heterojunction. Benefiting from the filling of defect sites, the stability and conductivity of the heterojunction are significantly improved; at the same time, N-CPDs provide high-activity electrocatalytic sites. Compared with FLBP, the 0D-2D heterojunction N-CPDs@FLBP has more stable and superior electrochemical performance. This FLBP defect repair technology provides a new idea for improving the stability of FLBP, and the microwave solvent heating assisted method for constructing the heterojunction of FLBP and 0D nanomaterials will promote the design and synthesis of new BP composites; the application of N-CPDs@FLBP in intelligent wireless portable electrochemical sensors will effectively expand the application of BP in the field of electrochemical sensors.

[0005] The purpose of the application can be achieved by the following technical solutions.

[0006] The application relates to a preparation method of a 0D-2D heterojunction of a "pocket-egg-like" carbon polymer dot (CPD) @ few-layer black phosphorus (FLBP) synthesized in situ, and specifically comprises the following steps.

[0007] (1) quickly adding bulk BP into a glass sample bottle containing N-methyl pyrrolidone, sealing, and ultrasonic treatment for 10 minutes.

[0008] (2) placing the sample bottle after ultrasonic treatment into a microwave oven, heating with medium-high fire and then heating with medium-low fire to obtain a yellow solution.

[0009] (3) centrifuging the yellow solution to collect supernatant to obtain a solution containing N-CPDs@FLBP.

[0010] In step (1), the bulk BP is quickly added into the glass sample bottle containing N-methyl pyrrolidone, and the operation is carried out in a glove box filled with nitrogen to prevent the few-layer BP from being oxidized.

[0011] In step (1), the N-methyl pyrrolidone can also be one of N-cyclohexyl-2-pyrrolidone, isopropyl alcohol, propylene carbonate and dimethylformamide or a mixture of two or more thereof.

[0012] In step (1), the sample bottle after ultrasonic treatment is placed into the microwave oven, the sample bottle is first placed into a glass surface dish containing water, the sample bottle cover is opened, and the sample bottle and the surface dish are placed into the microwave oven filled with argon or nitrogen to prevent the few-layer BP precursor from being oxidized.

[0013] In step (1), the microwave oven has an output power of 700 W.

[0014] In step (1), the heating with medium-high fire is followed by heating with medium-low fire, wherein the heating with medium-high fire is performed for 7-11 minutes, and the heating with medium-low fire is performed for 3 minutes.

[0015] In step (1), the yellow solution is centrifuged to collect supernatant to obtain N-CPDs@FLBP, the centrifugation is performed at a speed of 7000-10000 r / min for 20-30 minutes.

[0016] In step (1), the supernatant is collected, and 60%-70% of the supernatant is collected.

[0017] In step (1), the solution containing N-CPDs@FLBP is obtained, the sample bottle is filled with argon or nitrogen to prevent the few-layer black phosphorus from being oxidized, and the sample bottle is stored at-20 DEG C.

[0018] The application mainly peels off the multi-layer BP by microwave-assisted solvent heating to prepare the FLBP while doping the carbonized polymer dots in situ.

[0019] Compared with the prior art, the application has the following innovations.

[0020] (1) A novel 0D-2D heterostructure of (N-CPD) "pocket-egg-like" nitrogen-doped carbonized polymer dots grown in situ on few-layer black phosphorus nanosheets (FLBP) is synthesized in situ by one-step method. N-methylpyrrolidone acts as both a solvent for peeling off bulk black phosphorus and a carbon source for generating carbonized polymer dots in the process of microwave assistance. The preparation process is simple: only one step, and the preparation efficiency is high: only 11 minutes.

[0021] (2) The preparation method simultaneously contains "top-down" and "bottom-up" synthesis strategies. "Top-down" refers to the peeling of bulk multi-layer black phosphorus into few-layer black phosphorus nanosheets; "bottom-up" refers to the polymerization, dehydration and carbonization process of carbonized polymer dots from N-methylpyrrolidone.

[0022] (3) The intelligent wireless portable electrochemical sensor based on 0D-2D heterostructure N-CPDs@FLBP and gold nanoparticles (AuNPs) has an ultra-low detection limit and a wide linear range for the detection of rutin. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 AFM image of N-CPDs@FLBP prepared in Example 1.

[0024] Figure 2 XRD image of N-CPDs@FLBP prepared in Example 1.

[0025] Figure 3 TEM image of N-CPDs@FLBP prepared in Example 1.

[0026] Figure 4 TEM image of the sample prepared in Examples 2-5.

[0027] Figure 5 TEM image of the "pocket-egg-like" carbonized polymer dots prepared in Example 6.

[0028] Figure 6 Raman spectrum of N-CPDs@FLBP prepared in Example 1.

[0029] Figure 7 Schematic diagram of the intelligent electrochemical sensing system constructed by N-CPDs@FLBP and Au NPs prepared in Example 1.

[0030] Figure 8 The DPV curve superimposition figure of the smart wireless portable electrochemical sensor constructed by N-CPDs@FLBP and Au NPs prepared in Example 1 in PBS solution containing different concentrations of rutin. DETAILED DESCRIPTION

[0031] The application will be described in detail below with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present application, and gives a detailed implementation and specific operation process, but the protection scope of the present application is not limited to the following examples.

[0032] Example 1

[0033] A preparation method of an in-situ synthesized "egg-like" carbon polymer dot@few-layer black phosphorus nanosheet 0D-2D heterojunction, which specifically comprises the following steps.

[0034] (1) 25 mg of blocky BP was quickly added to a glass sample bottle containing 5 mL of N-methylpyrrolidone, and the bottle was sealed. The above operation was carried out in a nitrogen-filled glove box to prevent BP from being oxidized. After being taken out of the glove box, it was ultrasonicated for 10 minutes.

[0035] (2) The sample bottle after ultrasonication was first placed in a glass surface dish containing water, the sample bottle cap was opened, and the sample bottle and surface dish were placed in an argon or nitrogen filled microwave oven to prevent the BP precursor from being oxidized. Put it in a microwave oven with an output power of 700 W, heat it with medium-high fire for 8 minutes, and then heat it with medium-low fire for 3 minutes to obtain a yellow solution.

[0036] (3) The above yellow solution was centrifuged at a speed of 10000 rpm for 20 minutes, and the supernatant containing N-CPDs@FLBP was collected. It was filled with argon or nitrogen to prevent FLBP from being oxidized, and stored at -20℃.

[0037] (4) The obtained N-CPDs@FLBP was constructed into an electrochemical sensor: N-CPDs@FLBP and AuNPs ethanol solution were sequentially self-assembled on a screen-printed electrode to obtain a modified electrode NF / AuNPs / N-CPDs@FLBP / SPE. It was used as a working electrode to construct an intelligent electrochemical sensing system, and the electrical signal was transmitted to the mobile phone software through wireless Bluetooth.

[0038] Figure 1 The AFM image of N-CPDs@FLBP. As can be seen from the figure, the FLBP layer structure obtained by exfoliating the blocky multi-layer BP is clear, and the average thickness is 2.54 ± 0.86 nm. This thickness indicates that the multi-layer BP has been exfoliated into 3-5 layer BP nanosheets.

[0039] Figure 2 XRD patterns of N-CPDs, FLBP and N-CPDs@FLBP. N-CPDs have a broad scattering peak at 2q = 26, which is due to the introduction of a large number of disordered polymer chains on the (002) plane of the carbon skeleton. This result proves the polymer / carbon hybrid structure of N-CPDs. The broad peaks of FLBP at ~20º and ~24º are considered to be the (111) plane of the typical simple cubic BP. The N-CPDs@FLBP spectrum further indicates that the N-CPDs@FLBP heterostructure is successfully prepared.

[0040] Figure 3 TEM images of N-CPDs@FLBP. As shown in the figure, a large number of carbonized polymer points with a diameter of 2-5 nm are uniformly grown on the FLBP nanosheet.

[0041] Figure 4 TEM images of samples prepared in Examples 2-5. As can be seen from the figure, the size of BP gradually decreases and the thickness gradually thins with the increase of microwave-assisted heating time.

[0042] Figure 5 TEM images of "egg-like" carbonized polymer points prepared in Example 6. As can be seen from the figure, N-methylpyrrolidone gradually grows into "egg-like" polymer points during microwave heating.

[0043] Figure 6 Raman spectra of N-CPDs, FLBP and N-CPDs@FLBP. The D-peak and G-peak at 1364 cm-1 and 1580 cm-1 are Raman characteristic peaks of C atomic crystals. The vibration peaks of the three characteristic Raman peaks of black phosphorus, Ag1, B2g and Ag2, can be clearly observed in FLBP and N-CPDs@FLBP. The appearance of D and G peaks in N-CPDs@FLBP also proves the successful synthesis of the composite material.

[0044] Figure 7 Schematic diagram of the electrochemical sensor constructed by N-CPDs@FLBP and Au NPs. Au NPs are signal amplification materials, and Nafion is an adhesive. The working electrode is a screen-printed electrode with PET as the substrate, the electrochemical workstation is an intelligent portable workstation, and the generated electrical signal is transmitted to the mobile phone through Bluetooth.

[0045] Figure 8The DPV curve superimposition plot of the smart wireless portable electrochemical sensor constructed for N-CPDs@FLBP and Au NPs in 0.1 M PBS solution in the range of 1.0 nM-20.0 μM and 20.0 μM-240.0 μM rutin.

[0046] Examples 2, 3, 4, 5:

[0047] The difference between Example 1 and Example 2 is that the heating time in step (2) is 7, 9, 10, 11 minutes respectively, and the other steps are the same as Example 1.

[0048] Example 6

[0049] The difference between Example 1 and Example 6 is that 5 mL N-methyl pyrrolidone is added into the glass sample bottle in step (1). There is no step (4), and the other steps are the same as Example 1.

[0050] The above description of the examples is for the purpose of enabling one of ordinary skill in the art to understand and use the invention. Various modifications to these examples can be made by those skilled in the art without departing from the scope of the invention, and the general principles described herein can be applied to other examples without resort to inventive faculty. Therefore, the present invention is not limited to the above examples, and the improvements and modifications made by those skilled in the art without departing from the scope of the invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing in-situ synthesized "egg-like" carbonized polymer dot@few-layer phosphorene nanosheet 0D-2D heterojunctions, characterized in that, The method specifically comprises the following steps: (1) quickly adding the bulk black phosphorus into a glass sample bottle containing N-methyl pyrrolidone, sealing, and ultrasonicating for 10 minutes; (2) placing the sample bottle after ultrasonicating into a microwave oven, heating with medium-high fire and then heating with medium-low fire to obtain a yellow solution; the sample bottle after ultrasonicating is placed into a microwave oven with an output power of 700 W, the sample bottle is first placed into a glass surface dish containing water, the cover of the sample bottle is opened, and the sample bottle and the surface dish are placed into the microwave oven filled with argon or nitrogen to prevent the multilayer black phosphorus precursor from being oxidized; the heating with medium-high fire is performed for 7-11 minutes, and the heating with medium-low fire is performed for 3 minutes; (3) centrifuging the yellow solution to collect the supernatant to obtain a solution containing carbonized polymer dot-doped few-layer black phosphorus nanosheets.

2. The method according to claim 1, wherein the method for in-situ synthesis of "egg-like" carbonized polymer dot@few-layer black phosphorus nanosheet 0D-2D heterojunction is characterized in that, The operation of placing the bulk black phosphorus into the glass sample bottle containing N-methyl pyrrolidone and sealing in step (1) is performed in a glove box filled with nitrogen.

3. The method according to claim 1, wherein the method is characterized by: The N-methyl pyrrolidone in step (1) is replaced by any one or a mixture of two or more of N-cyclohexyl-2-pyrrolidone, isopropyl alcohol, propylene carbonate and dimethylformamide.

4. The method according to claim 1, wherein the method for in-situ synthesis of "egg-like" carbonized polymer dot@few-layer black phosphorus nanosheet 0D-2D heterojunction is characterized in that, The centrifugation of the yellow solution in step (3) is performed at a speed of 7000-10000 rpm for 20-30 minutes.

5. The method according to claim 1, wherein the method is characterized in that, The supernatant in step (3) is collected to 60-70 %.

6. The method according to claim 1, wherein the method is characterized in that, The solution containing carbonized polymer dot-doped few-layer black phosphorus nanosheets in step (3) is filled with argon or nitrogen to prevent the few-layer black phosphorus from being oxidized and is stored at-20 ℃.

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