阅读说明：本技术 可增强碳点荧光的还原氧化石墨烯薄膜的制备方法 (Preparation method of reduced graphene oxide film capable of enhancing carbon dot fluorescence ) 是由 孙向英 翁文婷 何维 刘斌 于 2020-06-30 设计创作，主要内容包括：本发明公开了可增强碳点荧光的还原氧化石墨烯薄膜、制备方法和应用,采用循环伏安法及恒电电位法快速制备还原氧化石墨烯薄膜ErGO。本发明在基底膜表面组装聚电解质分子层,精确调控ErGO与碳点的间隔距离,可增强自组装膜外层碳点的荧光信号。本发明制得的石墨烯基底具有贵金属纳米增强基底所不能比拟的廉价和环保的优点,可解决荧光传感膜的荧光信号弱、检测灵敏度低的问题。(The invention discloses a reduced graphene oxide film capable of enhancing carbon dot fluorescence, a preparation method and application thereof, and the reduced graphene oxide film ErGO is rapidly prepared by adopting a cyclic voltammetry method and a constant-potential method. According to the invention, the polyelectrolyte molecular layer is assembled on the surface of the basement membrane, the spacing distance between ErGO and the carbon point is accurately regulated and controlled, and the fluorescence signal of the carbon point on the outer layer of the self-assembled membrane can be enhanced. The graphene substrate prepared by the invention has the advantages of low price and environmental protection which cannot be compared with a noble metal nano enhanced substrate, and can solve the problems of weak fluorescence signal and low detection sensitivity of a fluorescence sensing film.)

1. The preparation method of the reduced graphene oxide film capable of enhancing carbon dot fluorescence is characterized by comprising the following steps of: the method comprises the following steps:

1) depositing graphene oxide on the conductive FTO slide by adopting a cyclic voltammetry method to prepare an FTO/GO film;

2) reducing the graphene oxide by combining a constant potential method to prepare an FTO/ErGO film;

3) the FTO/ErGO membrane is sequentially put into a PDDA solution and a PSS solution, and is alternately and repeatedly carried out, and a self-assembly membrane FTO/ErGO/[ PDDA/PSS ] is prepared in a self-assembly mode]_nSAMs, wherein n is 1-5;

4) soaking the self-assembled film in a fluorescent carbon dot solution to prepare the FTO/ErGO/[ PDDA/PSS ]]_n/CDs SAMs。

2. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 1, wherein the method comprises the following steps: in step 1), the cyclic voltammetry comprises the following steps:

a three-electrode system with a conductive FTO slide as a working electrode, an Ag-AgCl electrode as a reference electrode and a platinum wire electrode as a counter electrode is controlled at 0.02 g.L^-1And (3) in HAc-NaAc buffer solution with the pH value of GO being 5.0, carrying out cyclic voltammetry curve scanning at the scanning speed of 50mV/s and the voltage of-0.6-1.0V, wherein the number of scanning circles is 8, and preparing the FTO/GO film in one step.

3. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 1, wherein the method comprises the following steps: in the step 2), the constant potential method comprises the following steps:

a three-electrode system with an FTO/GO film as a working electrode, an Ag-AgCl electrode as a reference electrode and a platinum wire electrode as a counter electrode is placed in a range of 0.1 mol.L^-1And (3) carrying out constant potential reduction in KCl electrolyte, wherein the potential is-1.4V, and the time is 1000s, so as to prepare the FTO/ErGO film.

4. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 1, wherein the method comprises the following steps: the step 3) comprises the following steps:

putting the FTO/ErGO membrane into a PDDA solution with the volume fraction of 1% to assemble for 1h, taking out, cleaning with ultrapure water, and putting into a constant temperature and humidity box to dry; then placing at 1 g.L^-1In the PSS solution of (1)Assembling for 1h, taking out, cleaning with ultrapure water, and air drying in a constant temperature and humidity box; the above processes are alternately repeated to prepare the self-assembled film FTO/ErGO/[ PDDA/PSS ]]₃SAMs；

Wherein the PDDA solution and the PSS solution contain NaCl with the volume fraction of 1 percent.

5. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 1, wherein the method comprises the following steps: the step 4) comprises the following steps:

soaking the self-assembled film in the fluorescent carbon dot solution for 3h, taking out the self-assembled film, and drying the self-assembled film by using nitrogen to obtain the enhanced carbon dot fluorescent self-assembled film FTO/ErGO/[ PDDA/PSS ]]_n/CDs SAMs。

6. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 1, wherein the method comprises the following steps: and also comprising 0) pretreatment, wherein the pretreatment comprises preparation of a graphene oxide mother solution and cleaning of the conductive FTO glass slide.

7. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 6, wherein the method comprises the following steps: the preparation method of the graphene oxide mother liquor comprises the following steps:

uniformly dispersing graphene oxide powder in ultrapure water, dissolving in ultrasonic wave at a temperature of not higher than 40 ℃ for 1h to prepare 0.2 g.L^-1The clarified graphene oxide solution is a mother liquor.

8. The method for preparing a reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 6, wherein the method comprises the following steps: the cleaning of the conductive FTO glass slide comprises the following steps:

and (3) enabling the conductive surface of the conductive FTO slide to face upwards, washing the conductive surface of the conductive FTO slide for 30min by using ultrapure water, then washing the conductive surface of the conductive FTO slide for 10min by using absolute ethyl alcohol under an ultrasonic condition, then ultrasonically washing the conductive surface of the conductive FTO slide for 30min in a Piranha solution which is prepared currently, finally ultrasonically cleaning the conductive surface of the conductive FTO slide for multiple times by using the ultrapure water, and drying the conductive surface of.

9. The reduced graphene oxide film capable of enhancing fluorescence of carbon dots prepared by the method according to any one of claims 1 to 8, wherein: the reduced graphene oxide film is an enhanced carbon point fluorescence self-assembled film FTO/ErGO/[ PDDA/PSS ]]_nthe/CDsSAMs are shown in the specification, wherein n is 1-5.

10. The use of the reduced graphene oxide film capable of enhancing fluorescence of carbon dots according to claim 9 in fluorescence analysis and detection, wherein: used as a substrate film for enhancing the signal of the fluorescent probe.

Technical Field

The invention relates to a reduced graphene oxide film capable of enhancing carbon dot fluorescence, a preparation method and application.

Background

The Surface Enhanced Fluorescence (SEF) effect refers to a technique for enhancing the fluorescence emission of a fluorescent substance by using the Surface plasma oscillation and electromagnetic field cutting effect of a special substance Surface or a nanostructure. The problem of low sensitivity of fluorescence analysis can be solved essentially.

Many of the studies on the fluorescence enhancement of metal nanoparticles have been verified to be based on the Surface Plasmon Resonance (SPR) effect. Research has shown that the formation of MEF on the surface of metal nanomaterials is influenced by three main factors: (1) the degree of spectral overlap of the two; (2) the distance between the fluorophore and the metal; (3) nanoparticles that enhance the structure and properties of the substrate (with tips, edges and corners) can enhance fluorescence more efficiently. In addition, the fluorescence intensity depends on the degree of polarization of the fluorescence molecules and the number and density of the fluorophores deposited on the surface of the metal particles. Studies on the enhanced fluorescence of metal surfaces of various types of metal nanometers have been reported successively. However, the fluorescence enhancement systems established based on the metal nano-substrate have the defects of easy oxidation and instability of substrate raw materials, relatively high cost, environmental pollution and the like. In addition, when the metal nano is used as a SPR research material, the optical loss ratio of the metal nano is large, the electromagnetic property of the metal nano is difficult to change, and the regulation of SP propagation and resonance is not facilitated.

It is reported that graphene has a characteristic that plasmon polariton enhances a near-field fluorescence signal, and SPs is mostly generated in a graphene lattice structure within 5 layers formed on the SiC surface by a solid-phase growth method. The graphene sheets mechanically exfoliated from the highly oriented pyrolytic graphite can induce a resonant plasma to enhance the fluorescence signal of the adjacent zinc oxide nanolayers. However, physically exfoliated graphene is stable in properties and poor in solubility, and a suspended aqueous solution thereof is easily agglomerated and precipitated, which is not favorable for forming a uniform film formation process on a solid substrate. The graphene has to be coated by chitosan and then deposited on a glass substrate, and the fluorescence enhancement effect on carbon dots is researched, so that the structure of few-layer graphene is difficult to keep in the preparation process of the film substrate. The Graphene Oxide (GO) serving as a graphene oxidized derivative has good solubility, and the reduced graphene can be prepared by a polyelectrolyte PDDA (polymer dispersed data acquisition) coating synchronous chemical reduction method, so that the enhancement effect on a carbon dot fluorescence signal is realized. However, the whole process of preparing the thin film substrate involves a plurality of synthesis steps, is cumbersome, and introduces chemical substances into the graphene substrate. The most ideal method for reducing graphene oxide should be green, safe and simple, minimizing the introduction of impurities and defects.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides the reduced graphene oxide film capable of enhancing the carbon dot fluorescence, and the preparation method and the application thereof, and solves the problems in the background art.

One of the technical schemes adopted by the invention for solving the technical problems is as follows: the preparation method of the reduced graphene oxide film capable of enhancing carbon dot fluorescence is provided, and comprises the following steps:

1) depositing graphene oxide on the conductive FTO slide by adopting a cyclic voltammetry method to prepare an FTO/GO film;

2) reducing the graphene oxide by combining a constant potential method to prepare an FTO/ErGO film;

3) the FTO/ErGO membrane is sequentially put into a PDDA solution and a PSS solution, and is alternately and repeatedly carried out, and a self-assembly membrane FTO/ErGO/[ PDDA/PSS ] is prepared in a self-assembly mode]_nSAMs, wherein n is 1-5.

4) Soaking the self-assembled film in a fluorescent carbon dot solution to prepare the FTO/ErGO/[ PDDA/PSS ]]_nthe/CDs SAMs are shown in the specification, wherein n is 1-5;

in a preferred embodiment of the present invention, n is 3, and step 3) is performed to obtain a self-assembled film FTO/ErGO/[ PDDA/PSS ]]₃SAMs, step 4) preparation to FTO/ErGO/[ PDDA >PSS]₃/CDs SAMs。

In a preferred embodiment of the present invention, in step 1), the cyclic voltammetry includes the following steps:

a three-electrode system with a conductive FTO slide as a working electrode, an Ag-AgCl electrode as a reference electrode and a platinum wire electrode as a counter electrode is controlled at 0.02 g.L^-1And (3) in HAc-NaAc buffer solution with the pH value of GO being 5.0, carrying out cyclic voltammetry curve scanning at the scanning speed of 50mV/s and the voltage of-0.6-1.0V, wherein the number of scanning circles is 8, and preparing the FTO/GO film in one step.

In a preferred embodiment of the present invention, in the step 2), the potentiostatic method includes the following steps:

a three-electrode system with an FTO/GO film as a working electrode, an Ag-AgCl electrode as a reference electrode and a platinum wire electrode as a counter electrode is placed in a range of 0.1 mol.L^-1And (3) carrying out constant potential reduction in KCl electrolyte, wherein the potential is-1.4V, and the time is 1000s, so as to prepare the FTO/ErGO film.

In a preferred embodiment of the present invention, step 3) comprises the following steps:

putting the FTO/ErGO membrane into a PDDA solution with the volume fraction of 1% to assemble for 1h, taking out, cleaning with ultrapure water, and putting into a constant temperature and humidity box to dry; then placing at 1 g.L^-1The PSS solution is assembled for 1h, is taken out and then is cleaned by ultrapure water, and is placed in a constant temperature and humidity box for airing; the above process is alternately repeated for 3 times to prepare the self-assembled film FTO/ErGO/[ PDDA/PSS]₃SAMs；

Wherein the PDDA solution and the PSS solution contain NaCl with the volume fraction of 1 percent.

In a preferred embodiment of the present invention, step 4) includes the following steps:

soaking the self-assembled film in the fluorescent carbon dot solution for 3h, taking out the self-assembled film, and drying the self-assembled film by using nitrogen to obtain the enhanced carbon dot fluorescent self-assembled film FTO/ErGO/[ PDDA/PSS ]]_n/CDs SAMs。

In a preferred embodiment of the invention, the method further comprises 0) pretreatment, wherein the pretreatment comprises preparation of a graphene oxide mother solution and cleaning of the conductive FTO glass slide.

In a preferred embodiment of the present invention, the preparation of the graphene oxide mother liquor includes the following steps:

uniformly dispersing graphene oxide powder in ultrapure water, dissolving in ultrasonic wave at a temperature of not higher than 40 ℃ for 1h to prepare 0.2 g.L^-1The clarified graphene oxide solution is a mother liquor.

In a preferred embodiment of the present invention, the cleaning of the conductive FTO slide comprises the following steps:

and (3) enabling the conductive surface of the conductive FTO slide to face upwards, washing the conductive surface of the conductive FTO slide for 30min by using ultrapure water, then washing the conductive surface of the conductive FTO slide for 10min by using absolute ethyl alcohol under an ultrasonic condition, then ultrasonically washing the conductive surface of the conductive FTO slide for 30min in a Piranha solution which is prepared currently, finally ultrasonically cleaning the conductive surface of the conductive FTO slide for multiple times by using the ultrapure water, and drying the conductive surface of.

The second technical scheme adopted by the invention for solving the technical problems is as follows: the reduced graphene oxide film capable of enhancing carbon dot fluorescence prepared by the method is a carbon dot fluorescence enhancement self-assembled film FTO/ErGO/[ PDDA/PSS ]]₃/CDs SAMs。

The third technical scheme adopted by the invention for solving the technical problems is as follows: the application of the reduced graphene oxide film capable of enhancing carbon dot fluorescence in fluorescence analysis and detection is provided, and the reduced graphene oxide film can be used as a substrate film for enhancing a fluorescent probe signal.

Compared with the background technology, the technical scheme has the following advantages:

1. the graphene oxide which is cheap and easy to obtain is selected as the material. Compared with gold, silver nanometer, rare metal nanometer materials and other nanometer materials, the material has the advantages of stable chemical property, large specific surface area, excellent photoelectric performance and the like. The complex synthesis steps are avoided, so the preparation process is green and environment-friendly, secondary pollution is not generated, and the production cost is saved.

2. The invention adopts a green and safe process for reducing graphene oxide by an electrochemical method. The requirements of high-performance and high-cost equipment of traditional methods such as mechanical stripping, chemical vapor deposition, epitaxial growth and the like are not required. The simple method for electrochemically reducing the graphene overcomes the defect that the defects of graphene sheets are increased in the preparation process by a thermal reduction method. Avoiding the operation of introducing toxic chemical substances and impurity atoms in the chemical reduction process. Makes up the defects of long time consumption and large radiation of the photo-reduction method.

3. The invention adopts the layer-by-layer self-assembly technology to construct the film. The method has the advantages that the spacing distance between the film substrate and the probe can be accurately controlled, and the charge state of the surface of the assembled film can be freely designed.

Drawings

FIG. 1 is a graph of the trend of the corresponding values of (a) cyclic voltammetry curves and (b) AC impedance curves (Nyquist plot) and (c) for FTO/GO membranes formed under different cyclic voltammetry conditions.

FIG. 2 shows a plot of (a) cyclic voltammetry curves, (b) AC impedance curves, (c) corresponding trend of values, (d) Raman spectra, (e) surface enhanced fluorescence spectra, and (f) corresponding trend of values for FTO/ErGO membranes formed at different reduction potentials.

FIG. 3 shows the cyclic voltammograms (a) and the AC impedance curves (b) and the corresponding trend plots (c) for the values, (d) the Raman spectra and (e) the surface-enhanced fluorescence spectra and (f) the corresponding trend plots for the values of FTO/ErGO films formed at different reduction times.

Fig. 4 is a graph showing (a) cyclic voltammetry curves, (b) alternating current impedance curves, (c) corresponding numerical value change trends, (d) raman spectra, (e) surface enhanced fluorescence spectra, and (f) corresponding numerical value change trends of FTO/ErGO films formed under different graphene oxide concentrations.

FIG. 5 shows FTO/GO/[ PDDA/PSS]_nPerCDs and FTO/ErGO/[ PDDA/PSS]_n(a) fluorescence spectrum, (b) fluorescence decay curve, (c) FTO/GO/[ PDDA/PSS ] of/CDs]_nConfocal laser microscopy of/CDs and (d) FTO/ErGO/[ PDDA/PSS]_nConfocal laser microscopy of/CDs and (e) comparison of luminescence signals at different sites.

FIG. 6 shows (a) cyclic voltammetry curves, (b) AC impedance curves, (c) Raman spectra and (d) surface enhanced fluorescence spectra of different types of FTO/ErGO membranes prepared by graphene oxide reduction.

Detailed Description