A surface-enhanced raman probe based on zif-8 coated surface plasmonic tungsten oxide and a preparation method and application thereof

Abstract

The present invention belongs to the field of SERS detection technology, and specifically relates to a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide and its preparation method and application. The present invention uses a solvothermal method to prepare oxygen vacancy doped plasmon WO 3‑x Nanowires, and then ZIF-8 coated WO prepared by electrostatic self-assembly 3‑x The composite structure is used as a Raman probe for the detection of 4'-mercaptobiphenyl nitrile molecules. On the one hand, it fully utilizes the molecular adsorption capacity of MOF to effectively enrich the target molecules, and at the same time, it can effectively enrich the target molecules through the plasmon WO 3‑x The strong local field significantly amplifies the Raman signal of the target molecule, thereby achieving high-sensitivity detection of the target molecule; secondly, the structural characteristics of MOF are used to form an electron transmission channel to promote WO 3‑x Thermal electron transfer, followed by efficient catalytic degradation of adsorbed molecules, enables green self-cleaning and reuse of the probe.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of SERS detection, and particularly relates to a surface-enhanced Raman probe based on ZIF-8 coated surface plasmonic tungsten oxide and a preparation method and application thereof. BACKGROUND

[0002] Surface-enhanced Raman scattering (SERS) is a very promising trace detection and analysis technology, which has the advantages of fast detection speed, strong anti-interference ability and non-destructive effect. The technology uses a SERS-active probe to enhance the characteristic Raman signal of an adsorbed molecule to realize ultra-sensitive detection of a target molecule, and has important application prospects in the fields of environmental monitoring, biomedicine and food safety. To realize high-sensitivity detection of the probe, three logical key nodes need to be realized: first, specific adsorption and enrichment of the target; second, use of a physical mechanism to realize enhancement of the original signal; and third, controllable degradation or desorption of the target to ensure the self-stability of the probe, i.e., the performance of the Raman probe itself is not damaged due to the detection behavior. Current Raman probe technologies usually only focus on the first two nodes. For example, a SERS probe is usually a micro-nano structure, and its optical properties are seriously dependent on the optical structure and the dielectric constant of the medium. Once adsorption occurs, it is equivalent to causing surface contamination, and the designed performance of the Raman probe itself will be greatly reduced, and the repeatability of the results is even more difficult to talk about. The currently reported SERS probe technologies usually do not have high-efficiency catalytic degradation ability to realize self-cleaning, which leads to the inability to guarantee the repeatability and stability of the detection effect, and also makes the probe not reusable. Therefore, it is necessary to design and develop a new type of green Raman probe, while realizing high selectivity, ultra-sensitivity and efficient catalytic degradation of the target molecule.

[0003] The new porous metal organic framework zeolitic imidazolate framework-8 (ZIF-8) material has the advantages of structural diversity, high specific surface area, easy design and control of pore structure, and rich reaction active sites, and can realize molecular adsorption enrichment. The tungsten oxide nanomaterial is doped with oxygen vacancies to form non-stoichiometric tungsten oxide WO 3-x , which can significantly increase the concentration of free electrons, produce surface plasmon resonance in the visible-near infrared region, and realize enhancement of the molecular detection signal. Meanwhile, the thermal electrons of the tungsten oxide nanomaterial can realize efficient catalysis and degradation of the target molecules. However, single WO 3-xThe material is not conducive to the adsorption of target molecules, and the LSPR hot electron recombination is fast, resulting in low utilization, which seriously affects the SERS and photocatalytic degradation activity. The structure of ZIF-8 can provide an electron transport channel, effectively promote the charge separation and transfer of LSPR tungsten oxide, and improve the utilization rate of hot electrons. Therefore, a new type of SERS probe is designed and developed by combining tungsten oxide and ZIF-8, which can overcome the shortcomings of the current SERS technology. SUMMARY

[0004] In order to overcome the shortcomings of the above-mentioned existing SERS technology, the present application constructs a surface enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide, which cooperatively utilizes the LSPR effect of tungsten oxide and the strong adsorption capacity of ZIF-8 structure, and based on the multiple mechanisms of electromagnetic field enhancement, hot electron transfer and molecular enrichment, and then realizes the super-sensitive SERS detection and efficient catalytic degradation of target molecules, and the Raman probe can be reused.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

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

[0007] The present application also provides a preparation method of 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 precursor, adopting solvent thermal method to prepare oxygen vacancy doped tungsten oxide nanowire, and obtaining WO 3-x powder sample;

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

[0010] S3, dispersing WO 3-x powder sample and 1,2-dimethyl imidazole in methanol to form uniform solution B;

[0011] S4, after mixing A and B solutions, uniformly stirring at room temperature, centrifuging, washing with ethanol for three times, and vacuum drying to obtain WO 3-xZIF-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 DEG C, and the time is 18-30 h.

[0013] Preferably, in S2, the zinc compound includes zinc nitrate hexahydrate, zinc chloride, zinc acetate; 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 the powder to methanol is (10-30) mg: 1 mL.

[0015] Preferably, in S4, the zinc compound and the 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 application further provides application of the surface-enhanced Raman probe based on ZIF-8 coated surface plasmonic tungsten oxide in detection of 4'-mercaptobiphenyl cyanide (BPTCN) molecules.

[0017] Preferably, the detection method specifically comprises the following steps: mixing the surface-enhanced Raman probe based on ZIF-8 coated surface plasmonic tungsten oxide with an acetone solution, adding an acetone solution of 4'-mercaptobiphenyl cyanide (BPTCN) molecules after ultrasonic dispersion, mixing and adsorbing for more than 12 hours, dropping the obtained mixed solution on a silicon wafer, and performing Raman spectrum measurement by using a confocal Raman spectrometer (Renishaw InVia Reflex), wherein the Raman spectrum excitation wavelength is 785 nm, and the power is 1-5 mW.

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

[0019] The application further provides application of the surface-enhanced Raman probe based on ZIF-8 coated surface plasmonic tungsten oxide in photocatalytic degradation of 4'-mercaptobiphenyl cyanide (BPTCN) molecules.

[0020] Experiments show that, when BPTCN is a target molecule, the detection limit of the Raman probe based on MOF coated surface plasmonic tungsten oxide provided by the application is as low as 10-10 Moles per liter, for a concentration of 10 -5 The BPTCN molecules of M can be efficiently catalytically degraded within 12 minutes, showing super-sensitive SERS detection capability and high catalytic degradation activity.

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

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

[0023] The application discloses a preparation method of ZIF-8 coated plasmonic tungsten oxide. 3-x The composite structure is prepared by using a solvent thermal method to prepare oxygen vacancy doped plasmonic WO 3-x nanowires, and then using electrostatic self-assembly to prepare a ZIF-8 coated WO 3-x The composite structure is used as a Raman probe for detection of 4'-mercaptobiphenyl cyanide (BPTCN) molecules, and the strong local field formed by the surface plasmon resonance effect of tungsten oxide and the molecular enrichment capacity of MOF can be fully utilized to effectively amplify the Raman signal of the target molecules, and then high-sensitivity detection of the target molecules is realized. 3-x Meanwhile, the unique structural characteristics of ZIF-8 provide more electron transmission channels, promote the transfer of hot electrons of tungsten oxide, improve the utilization rate, further promote the efficient catalytic degradation of the adsorbed molecules, and then realize the integration of efficient photocatalytic degradation, so that the Raman probe can be reused, realizing green self-cleaning and reuse of the probe. 3-x In addition, the synthesis conditions of the probe are relatively mild and the cost is relatively low, and the probe is suitable for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The transmission electron microscope image of the surface plasmonic WO 3-x nanowires;

[0025] Figure 2 The transmission electron microscope image of the surface plasmonic WO 3-xElectron paramagnetic resonance spectroscopy of nanowires;

[0026] Figure 3 Coating ZIF-8 with WO 3-x Transmission electron microscopy 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 The ZIF-8 coated WO was repeated for four times in a row. 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 following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may 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) 150 mg of tungsten hexachloride was dissolved in 30 mL of anhydrous ethanol and stirred until the solution was yellow and clear. Then, the solution was placed in a 50 mL Teflon reactor and heated in an oven at 180 ° C for 24 h. After cooling to room temperature naturally, the solution was centrifuged at 8000 r / min for 10 min. The solution was then washed three times with anhydrous ethanol and dried in vacuum to obtain WO 3-x Powder sample.

[0034] (2) 110 mg of zinc nitrate hexahydrate was ultrasonically dispersed in 4 mL of methanol to form a homogeneous 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 A and B solutions in a 20 mL glass bottle, stirring at a rate of 800 r / min for 2 h at room temperature, centrifuging at a speed of 8000 r / min for 10 min, then washing with anhydrous ethanol for three times, and vacuum drying, ZIF-8 coated surface plasmonic tungsten oxide (WO 3-x @ZIF-8) samples were obtained.

[0037] As shown in FIG. 1, the morphology of the prepared plasmonic tungsten oxide is in the shape of an elongated line, with oxygen vacancy doping, a length of 300-1000 nm, and a width of 5-50 nm. The oxygen vacancy doping has a significant surface plasmon resonance absorption effect in the visible-near infrared region. Figure 1 As shown in FIG. 2, the size of the zeolitic imidazolate framework-8 (ZIF-8) shell particles is 20-70 nm, and the ZIF-8 coated plasmonic tungsten oxide composite structure is in the shape of a short chain, and the ZIF-8 coated plasmonic tungsten oxide composite structure also shows a significant surface plasmon resonance absorption effect in the range of 500-1400 nm (as shown in FIG. 3). 2 Figure 3 Figure 4

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

[0039] The WO 3-x @ZIF-8 prepared in Example 1 was dispersed in acetone at a concentration of 1 mg / mL, and different concentrations (10 -10 ~ 10 -6 mol / L) of 4'-mercaptobiphenyl nitrile (BPTCN, CAS No. 64409-12-7) molecules were added, mixed and adsorbed for 12 hours, and then the treated solution was dropped on a cleaned silicon wafer. A confocal Raman spectrometer was used for Raman spectrum measurement, with an excitation wavelength of 785 nm and a power of 2 mW. The results show that the limit concentration of the BPTCN molecules that can be detected is as low as 10 -10 mol / L. Figure 5

[0040] At the same time, the WO 3-x @ZIF-8 Raman probe substrate prepared by adsorbing BPTCN molecules was placed under a full-spectrum xenon lamp (190-1100 nm) for irradiation, and a confocal Raman spectrometer was used for Raman spectrum measurement every 2 min. Figure 6 The curves of the Raman peak intensity changing with the degradation time in the four repeated experiments are shown in FIG. 4. As can be seen from the figure, the BPTCN molecules have a characteristic Raman peak at 1083 cm -1 ​​​​The Raman intensity of BPTCN decreases with the extension of irradiation time, and the Raman signal of BPTCN can hardly be detected after irradiation for 12 minutes, indicating that the BPTCN molecules have been completely degraded, and a self-cleaning process is completed.

[0041] In summary, in the ZIF-8 coated surface plasmonic tungsten oxide, the ZIF-8 shell layer can promote the effective enrichment of molecules, and further enhance the Raman signal of the target molecules by the strong local field formed by the surface plasmon resonance effect of the tungsten oxide, to realize the ultra-sensitive SERS detection, on the other hand, it can provide an electron transport channel to improve the utilization rate of hot electrons, and then realize the integration of high-efficiency photocatalytic degradation, so as to realize the repeated use of the Raman probe.

[0042] The above describes the embodiments of the present application in detail, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments without departing from the principles and spirits of the present application still fall within the protection scope of the present application.

Claims

1. A surface-enhanced Raman probe based on ZIF-8 coated surface plasmon tungsten oxide, characterized in that, The plasmonic tungsten oxide has an elongated linear shape, a length of 300-1000 nm, a width of 5-50 nm, and an obvious surface plasmon resonance absorption effect in a 500-1400 nm wave band; the ZIF-8 shell particle has a size of 20-70 nm, the ZIF-8 coated plasmonic tungsten oxide composite structure has a short chain shape, and the ZIF-8 coated plasmonic tungsten oxide composite structure also shows an obvious surface plasmon resonance absorption effect in a 500-1400 nm wave band; The preparation method of the ZIF-8 coated surface plasmonic tungsten oxide based surface enhanced Raman probe comprises the following steps: S1, using tungsten hexachloride ethanol solution as precursor, adopting solvothermal method to prepare oxygen vacancy doped tungsten oxide nanowire, drying to obtain WO 3-x powder sample; the concentration of the tungsten hexachloride ethanol solution is 2-10 milligrams per milliliter; the temperature of the solvothermal method is 160-200 degrees Celsius, and the time is 18-30 hours; S2, dispersing a zinc compound in methanol to form a uniform solution A; the zinc compound includes zinc nitrate hexahydrate, zinc chloride or zinc acetate; the mass-volume ratio of the zinc compound to methanol is 20-40 mg: 1 mL; S3, WO 3-x The powder sample and 1,2-dimethylimidazole were dispersed in methanol to form a homogeneous solution B; S4, After mixing A, B solution, stirring uniformly at room temperature, centrifugation, washing with ethanol three times, vacuum drying to obtain WO 3-x @ZIF-8 samples.

2. The ZIF-8 coated surface plasmon polariton tungsten oxide based surface- enhanced Raman probe of claim 1, wherein, In S3, the WO 3-x The mass ratio of powder and 1,2-dimethylimidazole is 1:2~4; the WO 3-x The mass volume ratio of powder and methanol is 10~30mg:1mL.

3. The ZIF-8 coated surface plasmon polariton tungsten oxide based surface- enhanced Raman probe of claim 1, wherein, In S4, the zinc compound is combined with WO 3-x The molar ratio of the powder is 0.25-1:1; the stirring rate is 500-1000 r / min, the stirring time is 1-3 h; the centrifugal speed is 5000-9000 r / min, and the time is 5-15 min.

4. Application of the ZIF-8 coated surface plasmonic tungsten oxide based surface enhanced Raman probe in detecting 4'-mercaptobiphenylurea molecules according to any one of claims 1-3.

5. Use according to claim 4, characterized in that, The detection method is specifically as follows: mixing the ZIF-8 coated surface plasmonic tungsten oxide based surface enhanced Raman probe according to any one of claims 1-3 with an acetone solution, ultrasonic dispersion, then adding a 4'-mercaptobiphenylurea molecule acetone solution, mixing and adsorbing for more than 12 hours, then dropping the obtained mixed solution on a silicon wafer, and measuring a Raman spectrum by using a confocal Raman spectrometer; the Raman spectrum excitation wavelength is 785 nm, and the power is 1-5 mW.

6. Application of the ZIF-8 coated surface plasmonic tungsten oxide based surface enhanced Raman probe in photocatalytic degradation of 4'-mercaptobiphenylurea molecules according to any one of claims 1-3.

7. Use according to claim 6, characterized in that, The specific application method is: mixing the surface-enhanced Raman probe based on ZIF-8 coated surface plasmonic tungsten oxide according to any one of claims 1-3 with an acetone solution, ultrasonic dispersion, then adding an acetone solution of 4'-mercaptobiphenyl cyanide molecules, mixing and adsorbing for more than 12 hours, then dropping the obtained mixed solution on a silicon wafer, then placing the substrate under a full-spectrum xenon lamp for irradiation, and monitoring the Raman spectrum signal by using a confocal Raman spectrometer until the Raman signal of the molecules can no longer be detected, indicating that the adsorbed molecules have been completely degraded, and the spectral wavelength of the xenon lamp is 190-1100 nanometers, and the irradiation power density is 100-300 mW·cm -2 .

Images