Surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide as well as preparation method and application of surface enhanced Raman probe

Abstract

The invention belongs to the technical field of SERS (Surface Enhanced Raman Scattering) detection, and particularly relates to a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide as well as a preparation method and application of the surface enhanced Raman probe. An oxygen vacancy doped plasmon WO3-x nanowire is prepared by utilizing a solvothermal method, and then a ZIF-8 coated WO3-x composite structure is prepared by utilizing electrostatic self-assembly. The composite structure is used as a Raman probe for detecting 4 '-mercaptobiphenyl nitrile molecules, on one hand, the molecular adsorption capacity of MOF is fully utilized, target molecules are effectively enriched, Raman signals of the target molecules are remarkably amplified through a strong local field of plasmon WO3-x, and then high-sensitivity detection of the target molecules is achieved; on the second aspect, an electron transmission channel is formed by utilizing the structural characteristics of the MOF to promote WO3-x hot electron transfer, so that adsorption molecules are efficiently catalytically degraded, and green self-cleaning and reutilization of the probe are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of SERS detection, and in particular relates to a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide, and a preparation method and application thereof. Background Art

[0002] Surface-Enhanced Raman Scattering (SERS) is a very promising trace detection and analysis technology with the advantages of fast detection speed, strong anti-interference ability and non-destructiveness. This technology uses probes with SERS activity to enhance the characteristic Raman signals of adsorbed molecules to achieve ultra-sensitive detection of target molecules, and has important application prospects in environmental monitoring, biomedicine, food safety and other fields. To achieve high-sensitivity detection of probes, three logical key nodes need to be achieved: the first is the specific adsorption enrichment of the target, the second is the use of physical mechanisms to enhance the original signal, and the third is that the target can be controlled to degrade or desorb to ensure the self-stability of the probe, that is, the performance of the Raman probe itself is not destroyed due to the detection behavior. Current Raman probe technology often only focuses on the first two nodes. For example, SERS probes are often micro-nano structures, and their optical properties are heavily dependent on the optical structure and dielectric constant of the medium. Once adsorption occurs, it is equivalent to causing surface contamination, and the design performance of the Raman probe itself will be greatly reduced, and the repeatability of the results is out of the question. The currently reported SERS probe technology usually does not have efficient catalytic degradation capabilities to achieve self-cleaning, which makes it impossible to guarantee the repeatability and stability of the detection effect, and also makes the probe non-reusable. Therefore, it is very necessary to design and develop a new type of green Raman probe that can achieve high selectivity, ultra-sensitivity and efficient catalytic degradation of target molecules.

[0003] The new porous metal organic framework zeolite imidazole framework-8 (ZIF-8) material has the advantages of diverse structures, high specific surface area, easy design and control of pore structure, and abundant reactive sites, which can achieve molecular adsorption enrichment. Tungsten oxide nanomaterials are formed by oxygen vacancy doping to form non-stoichiometric tungsten oxide WO 3-x , which can significantly increase the free electron concentration and generate surface plasmon resonance in the visible-near infrared region, thereby enhancing the molecular detection signal. At the same time, its hot electrons can effectively catalyze and degrade the target molecules. 3-xThe material is not conducive to the adsorption of target molecules, and the LSPR hot electrons recombine quickly, resulting in low utilization, which seriously affects its SERS and photocatalytic degradation activity. The ZIF-8 structure can provide an electron transmission channel, effectively promote the charge separation and transfer of LSPR tungsten oxide, and improve the utilization of hot electrons. Therefore, the design and development of a new type of SERS probe combining tungsten oxide and ZIF-8 can overcome the shortcomings of the current SERS technology. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned existing SERS technology, the present invention constructs a surface enhanced Raman probe based on ZIF-8-coated surface plasmon tungsten oxide, which synergistically utilizes the LSPR effect of tungsten oxide and the strong adsorption ability of the ZIF-8 structure, and is based on multiple mechanisms such as electromagnetic field enhancement, thermal electron transfer and molecular enrichment, thereby achieving ultra-sensitive SERS detection and efficient catalytic degradation of target molecules, and making the Raman probe reusable.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The invention provides a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide. The plasmon tungsten oxide has an elongated linear morphology with a length of 300-1000nm and a width of 5-50nm, and has an obvious surface plasmon resonance absorption effect in the 500-1400nm band. The size of the ZIF-8 shell particles is 20-70nm, and the composite structure of the ZIF-8 coated plasmon tungsten oxide is in a short chain shape, and the composite structure of the ZIF-8 coated plasmon tungsten oxide also shows an obvious surface plasmon resonance absorption effect in the 500-1400nm band.

[0007] The present invention also provides a method for preparing the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide, comprising the following steps:

[0008] S1. Using tungsten hexachloride ethanol solution as a precursor, oxygen vacancy-doped tungsten oxide nanowires were prepared by solvothermal method. After drying, WO 3-x Powder samples;

[0009] S2, dispersing the zinc compound in methanol to form a uniform solution A;

[0010] S3. Will WO 3-x The powder sample and 1,2-dimethylimidazole were dispersed in methanol to form a homogeneous solution B;

[0011] S4. After mixing solutions A and B, stir evenly at room temperature, centrifuge, wash three times with ethanol, and vacuum dry to obtain WO 3-x@ZIF-8 sample.

[0012] Preferably, in S1, the concentration of the tungsten hexachloride ethanol solution is 2-10 mg / ml; the temperature of the solvothermal method is 160-200 degrees Celsius, and the time is 18-30 hours.

[0013] Preferably, in S2, the zinc compound includes zinc nitrate hexahydrate, zinc chloride, and zinc acetate; and the mass volume ratio of the zinc compound to methanol is (20-40) mg:1 mL.

[0014] Preferably, in S3, the WO 3-x The mass ratio of the powder to 1,2-dimethylimidazole is 1:(2-4); the WO 3-x The mass volume ratio of powder to methanol is (10-30) mg:1 mL.

[0015] Preferably, in S4, the zinc compound and WO 3-x The molar ratio of the powder is (0.25-1):1; the stirring rate is 500-1000 r / min, and the stirring time is 1-3 h; the centrifugal speed is 5000-9000 r / min, and the time is 5-15 min.

[0016] The present invention also provides the use of the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide in detecting 4'-mercaptobiphenylnitrile (BPTCN) molecules.

[0017] Preferably, the detection method is specifically as follows: the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide is mixed with an acetone solution, and then an acetone solution of 4'-mercaptobiphenylnitrile (BPTCN) molecules is added after ultrasonic dispersion. After mixed adsorption for more than 12 hours, the resulting mixed solution is dropped on a silicon wafer, and a confocal Raman spectrometer (Renishaw InVia Reflex) is used for Raman spectrum measurement, wherein the Raman spectrum excitation wavelength is 785 nanometers and the power is 1 to 5 milliwatts.

[0018] More preferably, the volume ratio of the ZIF-8 coated plasmonic tungsten oxide to the acetone solution is 0.5 to 3 mg / ml; the power of the ultrasound is 400 to 800 watts, and the time is 1 to 10 minutes.

[0019] The present invention also provides the use of the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide in the photocatalytic degradation of 4'-mercaptobiphenylnitrile (BPTCN) molecules.

[0020] Experimental results show that, with BPTCN as the target molecule, the detection limit of the Raman probe based on MOF-coated surface plasmon tungsten oxide provided by the present invention is as low as 10-10 mol / L, for a concentration of 10 -5 The BPTCN molecules of M can complete efficient catalytic degradation within 12 minutes, showing ultrasensitive SERS detection capability and efficient catalytic degradation activity.

[0021] Preferably, the specific application method is: mixing the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide with an acetone solution, adding an acetone solution of 4'-mercaptobiphenylnitrile (BPTCN) molecules after ultrasonic dispersion, and mixing and adsorbing for more than 12 hours, dropping the obtained mixed solution on a silicon wafer, and then placing the substrate under a full-spectrum xenon lamp for irradiation, and using a confocal Raman spectrometer to monitor the Raman spectrum signal until the Raman signal of the molecule can no longer be detected, indicating that the adsorbed molecule has been completely degraded, the spectral wavelength of the xenon lamp is 190-1100 nanometers, and the irradiation power density is 100-300mW·cm -2 .

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention discloses a method for preparing ZIF-8 coated plasmon tungsten oxide, firstly using a solvent thermal method to prepare oxygen vacancy doped plasmon WO 3-x Nanowires, and then ZIF-8 coated WO was prepared in methanol solution by electrostatic self-assembly 3-x Composite structure. Using this composite structure as a Raman probe for the detection of 4'-mercaptobiphenylnitrile (BPTCN) molecules can make full use of the strong local field formed by the surface plasmon resonance effect of tungsten oxide and the molecular enrichment ability of MOF, which can effectively amplify the Raman signal of the target molecule and thus achieve highly sensitive detection of the target molecule. At the same time, the unique structural characteristics of ZIF-8 provide more electron transmission channels, promote the transfer of hot electrons from tungsten oxide, improve its utilization rate, further promote the efficient catalytic degradation of adsorbed molecules, and then achieve efficient photocatalytic degradation integration, so that the Raman probe can be reused, and realize the green self-cleaning and reuse of the probe. At the same time, the metal oxide WO with LSPR effect 3-x It can replace high-cost precious metals, reduce the cost of probe preparation, and is expected to be applied on a large scale. In addition, the synthesis conditions of the probe are relatively mild, the cost is low, and it is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 WO is a surface plasmon 3-x Transmission electron microscopy images of nanowires;

[0025] Figure 2 WO is a surface plasmon 3-xElectron paramagnetic resonance spectroscopy of nanowires;

[0026] Figure 3 Coating ZIF-8 with WO 3-x TEM image of the composite structure;

[0027] Figure 4 For WO 3-x and ZIF-8 coated WO 3-x Absorption spectra of composite structures;

[0028] Figure 5 Coating ZIF-8 with WO 3-x The Raman probe detects the Raman spectra of BPTCN molecules with different concentrations;

[0029] Figure 6 Four consecutive repeated experiments were performed to coat WO with ZIF-8 3-x The curve of the Raman peak intensity of BPTCN molecules adsorbed by the Raman probe changing with the catalytic degradation time. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] Example 1: Preparation of ZIF-8 coated surface plasmon tungsten oxide

[0033] (1) Take 150 mg of tungsten hexachloride and dissolve it in 30 mL of anhydrous ethanol. Stir until the solution is yellow and clear. Then put it into a 50 mL Teflon reactor and heat it in an oven at 180 ° C for 24 hours. After cooling naturally to room temperature, centrifuge it at a speed of 8000 r / min for 10 minutes, wash it with anhydrous ethanol three times, and vacuum dry it to obtain WO 3-x Powder samples.

[0034] (2) 110 mg of zinc nitrate hexahydrate was ultrasonically dispersed in 4 mL of methanol to form a uniform solution A;

[0035] (3) 85 mg WO 3-x The powder sample and 240 mg of 1,2-dimethylimidazole were ultrasonically dispersed in 4 mL of methanol to form a homogeneous solution B;

[0036] (4) After mixing solutions A and B in a 20 mL glass bottle, the mixture was stirred at 800 r / min for 2 h at room temperature, and then centrifuged at 8000 r / min for 10 min. The mixture was then washed three times with anhydrous ethanol and dried in vacuo to obtain surface plasmon tungsten oxide (WO) coated with ZIF-8. 3-x @ZIF-8) sample.

[0037] like Figure 1 and 2 As shown in FIG. 1 , the morphology of the prepared plasmon tungsten oxide is in the form of a thin and long line with oxygen vacancy doping, a length of 300-1000nm, and a width of 5-50nm. Due to the oxygen vacancy doping, it has an obvious surface plasmon resonance absorption effect in the visible-near infrared region; Figure 3 As shown, the size of the zeolite imidazole framework-8 (ZIF-8) shell particles is 20-70nm, the composite structure of ZIF-8 coated plasmon tungsten oxide is in the form of a short chain, and the composite structure of ZIF-8 coated plasmon tungsten oxide also shows obvious surface plasmon resonance absorption effect at 500-1400nm (such as Figure 4 shown).

[0038] Example 2: SERS detection ability and catalytic degradation activity of ZIF-8 coated surface plasmon tungsten oxide

[0039] The WO prepared in Example 1 3-x @ZIF-8 was dispersed in acetone at a concentration of 1 mg / ml, and then different concentrations (10 -10 ~10 -6 mol / L) of 4'-mercaptobiphenylnitrile (BPTCN, CAS No. 64409-12-7) molecules, mixed and adsorbed for 12 hours, then the treated solution was dropped on a clean silicon wafer, and Raman spectroscopy was measured using a confocal Raman spectrometer. The excitation wavelength of the Raman spectrum was 785 nanometers and the power was 2 milliwatts. The results showed that the limit concentration of BPTCN molecules that can be detected is as low as 10 -10 Mole / liter ( Figure 5 ).

[0040] At the same time, the prepared WO adsorbed with BPTCN molecules 3-x The ZIF-8 Raman probe substrate was placed under a full-spectrum xenon lamp (190-1100 nm) for irradiation, and Raman spectra were measured every 2 minutes using a confocal Raman spectrometer. Figure 6 The curve of Raman peak intensity changing with degradation time in four consecutive repeated experiments. It can be seen from the figure that BPTCN molecules have a Raman characteristic peak of 1083cm -1The Raman intensity at the site weakened with the extension of irradiation time. After 12 minutes of irradiation, the Raman signal of BPTCN could hardly be detected, indicating that the BPTCN molecules had been completely degraded and completed a self-cleaning process.

[0041] In summary, in the ZIF-8-coated surface plasmon tungsten oxide provided by the present invention, the ZIF-8 shell can, on the one hand, promote the effective enrichment of molecules, and cooperate with the strong local field formed by the surface plasmon resonance effect of tungsten oxide to further enhance the Raman signal of the target molecule and realize ultra-sensitive SERS detection; on the other hand, it can provide an electron transmission channel, improve the utilization rate of hot electrons, and further realize the integration of efficient photocatalytic degradation, thereby realizing the reuse of Raman probes.

[0042] 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 protection scope of the present invention.

Claims

1. A surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide, characterized in that: The plasmon tungsten oxide has a slender linear morphology with a length of 300-1000nm and a width of 5-50nm, and has an obvious surface plasmon resonance absorption effect in the 500-1400nm band; the size of the ZIF-8 shell particles is 20-70nm, and the composite structure of ZIF-8 coated plasmon tungsten oxide is in the form of a short chain, and the composite structure of ZIF-8 coated plasmon tungsten oxide also shows an obvious surface plasmon resonance absorption effect in the 500-1400nm band.

2. The method for preparing a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide according to claim 1, characterized in that: The following steps are involved: S1. Using tungsten hexachloride ethanol solution as a precursor, oxygen vacancy-doped tungsten oxide nanowires were prepared by solvothermal method. After drying, WO 3-x Powder samples; S2, dispersing the zinc compound in methanol to form a uniform solution A; S3. Will WO 3-x The powder sample and 1,2-dimethylimidazole were dispersed in methanol to form a homogeneous solution B; S4. After mixing solutions A and B, stir evenly at room temperature, centrifuge, wash three times with ethanol, and vacuum dry to obtain WO 3-x @ZIF-8 sample.

3. The method for preparing a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide according to claim 2, characterized in that: In S1, the concentration of the tungsten hexachloride ethanol solution is 2-10 mg / ml; the temperature of the solvothermal method is 160-200 degrees Celsius, and the time is 18-30 hours.

4. The method for preparing a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide according to claim 2, characterized in that: In S2, the zinc compound includes zinc nitrate hexahydrate, zinc chloride, and zinc acetate; the mass volume ratio of the zinc compound to methanol is 20-40 mg:1 mL.

5. The method for preparing a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide according to claim 2, characterized in that: In S3, the WO 3-x The mass ratio of the powder to 1,2-dimethylimidazole is 1:2-4; the WO 3-x The mass volume ratio of powder to methanol is 10-30 mg:1 mL.

6. The method for preparing a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide according to claim 2, characterized in that: In S4, the zinc compound is reacted with WO 3-x The molar ratio of the powder is 0.25-1:1; the stirring rate is 500-1000 r / min, and the stirring time is 1-3 hours; the centrifugal speed is 5000-9000 r / min, and the time is 5-15 minutes.

7. Use of the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide as claimed in claim 1 in detecting 4'-mercaptobiphenylnitrile molecules.

8. The use according to claim 7, characterized in that: The detection method is specifically as follows: the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide described in claim 1 is mixed with an acetone solution, and then an acetone solution of 4'-mercaptobiphenylnitrile molecules is added after ultrasonic dispersion. After mixed adsorption for more than 12 hours, the resulting mixed solution is dropped on a silicon wafer, and a confocal Raman spectrometer is used to perform Raman spectrum measurement, wherein the Raman spectrum excitation wavelength is 785 nanometers and the power is 1 to 5 milliwatts.

9. Use of the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide as claimed in claim 1 in photocatalytic degradation of 4'-mercaptobiphenylnitrile molecules.

10. The use according to claim 9, characterized in that: The specific application method is: the surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide according to claim 1 is mixed with an acetone solution, and then an acetone solution of 4'-mercaptobiphenylnitrile molecules is added after ultrasonic dispersion. After mixed adsorption for more than 12 hours, the obtained mixed solution is dropped on a silicon wafer, and then the substrate is placed under a full-spectrum xenon lamp for irradiation, and a confocal Raman spectrometer is used to monitor the Raman spectrum signal until the Raman signal of the molecule can no longer be detected, indicating that the adsorbed molecule has been completely degraded. The spectrum wavelength of the xenon lamp is 190-1100 nanometers, and the irradiation power density is 100-300mW·cm -2 .

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