Raman probe based on reduced graphene oxide enhanced semiconductor plasma as well as preparation method and application of Raman probe

Abstract

The invention belongs to the technical field of SERS (Surface Enhanced Raman Scattering) detection, and particularly relates to a Raman probe based on reduced graphene oxide enhanced semiconductor plasma as well as a preparation method and application of the Raman probe. A composite structure of semiconductor plasma tungsten oxide nanowire in-situ loaded reduced graphene oxide is prepared by using a solvothermal method, and the composite structure is used as a Raman probe to realize dual functions of methylene blue (MB) molecule quantitative detection and photocatalytic degradation. After WO3-x with an SPR effect is compounded with reduced graphene oxide, on one hand, target aromatic pollutant molecules are efficiently adsorbed through pi-pi stacking interaction, the SERS activity of the probe is improved, on the other hand, surface oxygen vacancies of a semiconductor WO3-x can be effectively stabilized, continuous generation of hot electrons is promoted, and the SERS activity of the probe is improved. More reaction active sites are provided, the photocatalytic degradation performance of the probe is improved, and meanwhile, molecular chemical bond breakage priority information is obtained through SERS in-situ monitoring.

Description

Technical Field

[0001] The invention belongs to the technical field of SERS detection, and in particular relates to a Raman probe based on reduced graphene oxide enhanced semiconductor plasma and a preparation method and application thereof. Background Art

[0002] Trace detection and catalytic degradation of pollutant molecules are crucial for environmental protection. A deeper understanding of the catalytic degradation mechanism of pollutants will help explore and develop new technology systems to improve degradation efficiency and further optimize environmental protection solutions. However, traditional pollutant detection methods have bottleneck problems such as low sensitivity, susceptibility to interference, and inability to perform in-situ detection.

[0003] The surface plasmon resonance (SPR) effect is a phenomenon in which free electrons on the surface of noble metal nanostructures oscillate collectively under light irradiation, which can localize the light field and energy on a subwavelength scale, thereby further significantly enhancing various interactions between light and matter (such as Raman scattering, photochemical reactions, etc.). Currently, various noble metal nanostructures have been developed as emerging Raman probes to achieve ultra-sensitive surface enhanced Raman scattering (SERS) sensing of biochemical molecules. However, since it is difficult for noble metal Raman probes to simultaneously achieve efficient degradation of pollutant molecules, and the preparation cost is high and the price is expensive, it cannot be applied on a large scale. Studies have found that in addition to noble metals, when the free carrier concentration in semiconductors increases to a certain level, it will also oscillate with the incident light, thereby producing a metal-like SPR phenomenon. For example, self-doped semiconductors (Cu 2-x S.WO 3-x In the visible-near infrared band, it can produce a wide range of strong SPR absorption, and the abundant surface vacancies can also provide active sites for chemical reactions, so it also has broad application prospects in the fields of SERS sensing and photocatalysis. However, in a single semiconductor material system, due to the instability of oxygen vacancies and the rapid non-radiative decay of hot carriers, its SERS detection and photocatalytic degradation performance are severely restricted. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the present invention proposes a Raman probe based on reduced graphene oxide enhanced semiconductor plasma, which uses a semiconductor (such as WO) with SPR effect to 3-x ) and the ultra-thin two-dimensional material reduced graphene oxide (rGO), such as SPR local field enhancement, charge transfer, and molecular enrichment, thereby achieving ultra-sensitive SERS detection and efficient catalytic degradation of target molecules, so that the Raman probe can be reused while SERS in situ monitoring can be used to obtain the molecular chemical bond breakage priority information.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a Raman probe of reduced graphene oxide enhanced semiconductor plasma, wherein the Raman probe is a composite structure of semiconductor plasma tungsten oxide nanowires loaded with reduced graphene oxide, and the composite structure exhibits obvious plasma resonance absorption in the wavelength region of 500-1400 nanometers, the diameter of the plasma tungsten oxide nanowires is 5-10 nm, the length is 100-400 nm, the size of the reduced graphene oxide is 1-5 μm, and the thickness is 2-6 nm.

[0006] The second aspect of the present invention also provides a method for preparing the reduced graphene oxide enhanced semiconductor plasma Raman probe described in the first aspect, specifically: adding graphene oxide to an ethylene glycol solution of tungsten hexachloride, stirring it into a uniform solution and then performing a solvothermal reaction, and after the reaction, washing and drying to prepare a reduced graphene oxide / plasma tungsten oxide composite structure.

[0007] Preferably, the concentration of the tungsten hexachloride in the ethylene glycol solution is 2-10 mg / mL, and the mass ratio of the tungsten hexachloride to graphene oxide is (50-150):1.

[0008] Preferably, the temperature of the solvent thermal reaction is 160-200° C. and the time is 18-30 hours.

[0009] Preferably, the washing is centrifugal washing with water and ethanol, the centrifugal speed is 5000-9000r / min, and the time is 5-15min.

[0010] The third aspect of the present invention further provides the use of the Raman probe of reduced graphene oxide enhanced semiconductor plasma described in the first aspect in quantifying the concentration of methylene blue (MB) molecules.

[0011] The research found that, with MB as the target molecule, the detection concentration limit of the Raman probe based on reduced graphene oxide enhanced semiconductor plasma provided by the present invention is as low as 10 -10 moles per liter, for a concentration of 10 -6 The MB molecules of M can complete efficient catalytic degradation within 5 minutes, showing ultrasensitive SERS detection capability and efficient catalytic degradation activity.

[0012] Preferably, the method for quantifying the concentration of methylene blue molecules comprises the following steps:

[0013] S1, dispersing the reduced graphene oxide enhanced semiconductor plasma Raman probe described in the first aspect in an ethanol solution, then drop-coating the solution on a substrate, and drying naturally;

[0014] S2, immersing the substrate in methylene blue molecular solutions of different concentrations, and collecting Raman spectra after adsorption for more than 30 minutes;

[0015] S3. Draw a curve showing the regular variation of the intensity of the characteristic Raman peak of methylene blue with the concentration, complete the standard curve fitting, and then measure the concentration of the methylene blue molecules to be tested according to the standard curve.

[0016] More preferably, the concentration of the reduced graphene oxide enhanced semiconductor plasma Raman probe in the ethanol solution is 0.5-3 mg / mL.

[0017] More preferably, the methylene blue molecular solutions of different concentrations are 10 -10 M-10 -6 Methylene blue molecular solution.

[0018] More preferably, the excitation wavelength of the Raman spectrum is 633 nm, and the power is 0.01-1 mW.

[0019] More preferably, the method used to disperse the Raman probe of reduced graphene oxide enhanced semiconductor plasma in the ethanol solution is ultrasonic dispersion method, the power of ultrasound is 400-800W, and the time is 1-10min.

[0020] The fourth aspect of the present invention further provides the use of the Raman probe of reduced graphene oxide enhanced semiconductor plasma described in the first aspect in in-situ Raman monitoring of photocatalytic degradation of methylene blue molecules.

[0021] The present invention constructs a Raman probe based on reduced graphene oxide enhanced semiconductor plasma by in-situ growth of a composite structure of plasma semiconductor on ultra-thin two-dimensional material reduced graphene oxide (rGO). Among them, rGO has a strong affinity with aromatic ring molecules through π-π stacking interaction, can effectively enrich the target aromatic pollutant molecules, and can stabilize the surface oxygen vacancies of the composite structure, promote the generation of hot electrons, and provide more active sites, thereby improving the photocatalytic degradation performance of the probe. At the same time, in the catalytic degradation process, the Raman probe based on reduced graphene oxide enhanced semiconductor plasma synergistically enhances the Raman signal of the pollutant molecules through multiple physical effects such as SPR local field enhancement, charge transfer, and molecular enrichment, thereby realizing SERS in-situ monitoring of the molecular degradation process, and obtaining chemical bond breakage priority information. Therefore, the Raman probe based on reduced graphene oxide enhanced semiconductor plasma proposed in the present invention has the dual functions of quantitative SERS analysis of target molecules and self-tracking photocatalytic degradation, which provides a new way to deeply understand the catalytic degradation mechanism of pollutants.

[0022] Preferably, the method for in-situ Raman monitoring of photocatalytic degradation of methylene blue molecules is:

[0023] S1, dispersing the reduced graphene oxide enhanced semiconductor plasma Raman probe described in the first aspect in an ethanol solution, then drop-coating the solution on a substrate, and drying naturally;

[0024] S2, immersing the substrate in methylene blue molecule solutions of different concentrations, irradiating the substrate adsorbed with methylene blue molecules with a xenon lamp after adsorption for more than 30 minutes, collecting Raman spectra at the same position every 1 minute during this process until the Raman signal of MB can no longer be detected;

[0025] S3. Make a fitting curve of the natural logarithm of the ratio of the characteristic peak Raman intensity of the methylene blue molecule to the initial Raman intensity at reaction time t versus reaction time, determine the degradation rate constant of the chemical bond corresponding to the characteristic peak from the slope of the curve, and analyze the priority order of molecular chemical bond breakage.

[0026] More preferably, the xenon lamp has a spectral wavelength of 190-1100 nm and an irradiation power density of 100-300 mW·cm -2 .

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention discloses a method for preparing reduced graphene oxide enhanced semiconductor plasma, wherein a composite structure of semiconductor plasma tungsten oxide nanowires in situ loaded with reduced graphene oxide is prepared by a solvothermal method, and the composite structure is used as a Raman probe to realize the dual functions of quantitative detection of methylene blue (MB) molecules and photocatalytic degradation. 3-x ) is combined with the ultra-thin two-dimensional material reduced graphene oxide (rGO). On the one hand, rGO can efficiently adsorb the target aromatic pollutant molecules through π-π stacking interaction, thereby improving the SERS activity of the probe. On the other hand, rGO can effectively stabilize the semiconductor WO 3-x The probe uses surface oxygen vacancies to solve the instability problem of the semiconductor SPR effect, promote the continuous generation of hot electrons, and provide more reactive sites to improve the photocatalytic degradation performance of the probe. At the same time, SERS in situ monitoring is used to obtain the molecular chemical bond breakage priority information. 3-x ) can replace high-cost precious metals, effectively reduce the cost of probe preparation, and can realize integrated detection and degradation, and is expected to achieve large-scale reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Transmission electron microscopy image of the reduced graphene oxide / plasma tungsten oxide composite structure;

[0030] Figure 2The electron paramagnetic spectrum of the reduced graphene oxide / plasma tungsten oxide composite structure;

[0031] Figure 3 UV-visible-near-infrared diffuse reflectance spectra of reduced graphene oxide / plasmonic tungsten oxide composite structures;

[0032] Figure 4 The linear fitting curve of the Raman peak intensity of MB molecules detected by WO / rGO Raman probe versus concentration;

[0033] Figure 5 The linear fitting curve of the ratio of the Raman intensity / initial intensity of the characteristic peak of MB molecules at time t monitored in situ by the WO / rGO Raman probe and the catalytic degradation time. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0036] Example 1: Preparation of a reduced graphene oxide enhanced semiconductor plasma

[0037] 150 mg of tungsten hexachloride powder was dissolved in 30 mL of ethylene glycol solution and stirred until the solution was a yellow clear liquid. Then, 0.75 mL of graphene oxide ethylene glycol solution (rGO, 2 mg / mL) was added to the above solution and stirred for 10 minutes. After a uniform solution was formed, the resulting solution was transferred to a 50 mL Teflon reactor and heated at 180 ° C for 24 hours. After cooling, it was centrifuged at a speed of 9000 r / min for 5 minutes, and washed with deionized water and anhydrous ethanol in turn, and finally dried in a vacuum oven at 60 ° C for 12 hours to obtain a reduced graphene oxide / plasma tungsten oxide (WO / rGO) powder sample.

[0038] Figure 1The transmission electron microscope image of the reduced graphene oxide / plasma tungsten oxide composite structure prepared by the solvothermal method shows that the plasma tungsten oxide nanowires with a diameter of 5-10nm and a length of 100-400nm are evenly dispersed on the rGO layer, and the thickness of the rGO layer is 2-6nm. At the same time, oxygen vacancy doping can increase the free electron concentration on the surface of plasma tungsten oxide, so that it exhibits SPR resonance absorption in the wavelength region of 500-1400 nanometers. When it is composited with rGO, rGO can stabilize oxygen vacancies and thus enhance SPR ( Figure 2 ). In addition, the UV-visible-near-infrared diffuse reflectance spectrum of the reduced graphene oxide / plasmonic tungsten oxide composite structure also shows enhanced SPR resonance absorption intensity, such as Figure 3 shown.

[0039] Example 2: Quantification of methylene blue (MB) molecule concentration and photocatalytic degradation of methylene blue molecules using reduced graphene oxide enhanced semiconductor plasma as Raman probe (WO / rGO Raman probe)

[0040] After the reduced graphene oxide / plasma tungsten oxide powder sample prepared in Example 1 was ultrasonically dispersed in an anhydrous ethanol solution (concentration 1 mg / mL), the resulting solution was evenly drop-coated on a silicon wafer and dried naturally. The silicon wafer was then immersed in methylene blue (MB) molecular solutions of different concentrations (10 -10 M-10 -6 M) for 30 minutes, followed by Raman spectrum collection, the excitation wavelength of Raman spectrum collection was 633nm, and the laser power was 0.085mW. Figure 4 ), as the molecular concentration decreases, the Raman peak intensity also gradually decreases. And the logarithm of the Raman peak intensity I and the molecular concentration (log 10 [C]) follows a good linear dependence, and the correlation coefficient is greater than 0.99. The above results show that the reduced graphene oxide / plasma tungsten oxide probe can be used for quantitative analysis of low-concentration molecules.

[0041] At the same time, the adsorption concentration of 10 -6 The Raman probe substrate of MMB molecules was irradiated with a xenon lamp (the spectral wavelength of the xenon lamp was 190-1100 nm and the irradiation power density was 200 mW cm -2 ), during which Raman spectra were collected at the same position every 1 min to monitor the degradation reaction kinetics of MB molecules. After 5 min of irradiation, MB at 1398 cm -1 and 1630cm -1 The intensities of the two Raman characteristic peaks at α and β dropped sharply, and no obvious signals could be observed, indicating that the molecular structure of MB had been completely destroyed at this time. Figure 5It shows that ln(Raman intensity at time t / Raman initial intensity) and catalytic degradation time present a good linear relationship. The degradation rate constants of the corresponding chemical bonds CH and CC can be determined from the slope of the linear fitting curve [ln(I t / I0)=-kt, the slope of the fitting line is the degradation rate constant】, the results show that the CH bond of MB breaks preferentially over the CC aromatic ring. Therefore, the plasma WO / rGO heterostructure can effectively photocatalytically degrade organic pollutants, and the order of chemical bond cleavage can be displayed by quantitative SERS analysis, thus clearly showing the information of the molecular catalytic mechanism.

[0042] In summary, the Raman probe based on reduced graphene oxide enhanced semiconductor plasma provided by the present invention can, on the one hand, efficiently adsorb the target aromatic pollutant molecules through π-π stacking interaction to improve the SERS activity of the probe, and on the other hand, rGO can effectively stabilize the semiconductor WO 3-x The surface oxygen vacancies of the probe can solve the instability problem of the semiconductor SPR effect, promote the continuous generation of hot electrons, and provide more reactive sites to improve the photocatalytic degradation performance of the probe. At the same time, the SERS in-situ monitoring can be used to obtain the molecular chemical bond breakage priority information, which is helpful for a deeper understanding of the catalytic degradation mechanism of pollutants. The probe preparation method is simple, low-cost, and can achieve efficient detection and catalytic degradation integration, which is expected to achieve large-scale reuse.

[0043] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A Raman probe for reduced graphene oxide enhanced semiconductor plasma, characterized in that: The Raman probe is a composite structure of semiconductor plasma tungsten oxide nanowires loaded with reduced graphene oxide, which exhibits obvious plasma resonance absorption in the wavelength region of 500-1400 nanometers. The diameter of the plasma tungsten oxide nanowires is 5-10 nm and the length is 100-400 nm. The size of the reduced graphene oxide is 1-5 μm and the thickness is 2-6 nm.

2. The method for preparing the Raman probe of reduced graphene oxide enhanced semiconductor plasma according to claim 1, characterized in that: Graphene oxide is added to an ethylene glycol solution of tungsten hexachloride, stirred into a uniform solution, and then a solvent thermal reaction is carried out. After the reaction, the reduced graphene oxide / plasma tungsten oxide composite structure is prepared by washing and drying.

3. The method for preparing a Raman probe for reduced graphene oxide enhanced semiconductor plasma according to claim 2, characterized in that: The concentration of the tungsten hexachloride in the ethylene glycol solution is 2-10 mg / mL, and the mass ratio of the tungsten hexachloride to graphene oxide is 50-150:

1.

4. The method for preparing a Raman probe for reduced graphene oxide enhanced semiconductor plasma according to claim 2, characterized in that: The temperature of the solvent thermal reaction is 160-200° C. and the time is 18-30 hours.

5. Use of the reduced graphene oxide enhanced semiconductor plasma Raman probe according to claim 1 in quantifying the concentration of methylene blue molecules.

6. The use according to claim 5, characterized in that: The method for quantifying the concentration of methylene blue molecules comprises the following steps: S1. Dispersing the reduced graphene oxide enhanced semiconductor plasma Raman probe according to claim 1 in an ethanol solution, then drop-coating the solution on a substrate, and drying the solution naturally; S2, immersing the substrate in methylene blue molecular solutions of different concentrations, and collecting Raman spectra after adsorption for more than 30 minutes; S3. Draw a curve showing the regular variation of the intensity of the characteristic Raman peak of methylene blue with the concentration, complete the standard curve fitting, and then measure the concentration of the methylene blue molecules to be tested according to the standard curve.

7. The use according to claim 6, characterized in that: The concentration of the Raman probe of the reduced graphene oxide enhanced semiconductor plasma in the ethanol solution is 0.5-3 mg / mL, and the methylene blue molecular solution of different concentrations refers to 10 -10 M-10 -6 The methylene blue molecular solution is 0.1 M, the excitation wavelength of the Raman spectrum is 633 nm, and the power is 0.01-1 mW.

8. Use of the reduced graphene oxide enhanced semiconductor plasma Raman probe according to claim 1 in in-situ Raman monitoring of photocatalytic degradation of methylene blue molecules.

9. The use according to claim 8, characterized in that: The method for in situ Raman monitoring of photocatalytic degradation of methylene blue molecules is: S1. Dispersing the reduced graphene oxide enhanced semiconductor plasma Raman probe according to claim 1 in an ethanol solution, then drop-coating the solution on a substrate, and drying the solution naturally; S2, immersing the substrate in methylene blue molecule solutions of different concentrations, irradiating the substrate adsorbed with methylene blue molecules with a xenon lamp after adsorption for more than 30 minutes, collecting Raman spectra at the same position every 1 minute during this process until the Raman signal of methylene blue can no longer be detected; S3. Make a fitting curve of the natural logarithm of the ratio of the characteristic peak Raman intensity of the methylene blue molecule to the initial Raman intensity at reaction time t versus reaction time, determine the degradation rate constant of the chemical bond corresponding to the characteristic peak from the slope of the curve, and analyze the priority order of molecular chemical bond breakage.

10. The use according to claim 9, characterized in that: The xenon lamp has a spectral wavelength of 190-1100 nm and an irradiation power density of 100-300 mW·cm -2 .

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