Method for detecting nano plastic based on photon MOFs photo-induced enhanced SERS (Surface Enhanced Raman Scattering)

Abstract

The invention relates to a method for detecting nano-plastics based on photon MOFs (Metal Organic Frameworks) photoinduction enhanced SERS (Surface Enhanced Raman Scattering), which comprises the following steps: assembling photoresponsive metal (cluster) and an organic ligand, and packaging a specific photon object unit by utilizing a pore structure of MOFs. Selected photonic units comprise rare earth metal, photosensitive organic ligands, optical switch molecules and the like, and a series of MOFs structures which are different in size, thickness (layer number), exposed active sites and composed of the photonic units are prepared by accurately controlling synthesis conditions such as the proportion of central metal to the organic ligands, the reaction temperature and the reaction time. Compared with the prior art, the SERS substrate is constructed through a photon MOFs structure, good general applicability and light adjusting performance are shown, and optimization is particularly conducted on external disturbance such as a light field applied in situ, so that interaction between the substrate and organic molecules in nano-plastic is enhanced, and the SERS substrate is prepared. The SERS sensitivity of nano plastic detection is obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental pollutant identification, and particularly relates to a method for detecting nanoplastics based on photoinduced enhanced SERS of photon MOFs. Background Art

[0002] There are various detection methods for microplastics, including visual inspection, Fourier transform-infrared spectroscopy, Raman spectroscopy, pyrolysis gas chromatography-mass spectrometry, etc. However, due to the action of environmental factors, microplastics can be broken into nanoplastics, which can easily cross cell membranes and enter various organs of the human body due to their smaller size, leading to metabolic disorders and toxic effects. The existing technology for detecting nanoplastics is not yet sufficient, so its detection has become a major challenge in the environmental field.

[0003] Surface-enhanced Raman scattering (SERS), as a highly sensitive, rapid, and non-destructive technique, can achieve detection at the single-molecule level. By amplifying Raman signals through specific substrate materials, the detection becomes more precise. Traditional SERS substrates are divided into noble metals (such as Au, Ag) and semiconductor materials (such as W18O49, CuO2). Although the former provides a strong signal enhancement effect, it is costly; the latter is more economical, but its performance modulation space is limited.

[0004] In view of this, it is particularly important to develop a new type of SERS substrate based on photon metal-organic frameworks (MOFs). By making full use of the high tunability of MOF materials themselves and combining the excellent light response characteristics of photon units, this innovative substrate is expected to overcome the limitations of the existing technology and thus accelerate the progress of nanoplastics detection technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for detecting nanoplastics based on photoinduced enhanced SERS of photon MOFs.

[0006] To achieve the above technical purposes and reach the above technical effects, the present invention is realized through the following technical solutions: A preparation method of an SERS substrate based on photon MOFs, comprising: At least mixing and reacting a metal salt, an organic ligand, and a photon unit in a solvent at a reaction temperature of 20-180°C for a reaction time of more than 0.5 h to form an SERS substrate based on photon MOFs.

[0007] Further, the photon unit includes a rare earth metal, a photosensitive organic ligand, and a light-switching molecule, wherein: The rare earth metal includes any one element or a combination of two or more elements selected from europium, terbium, cerium, dysprosium, and gadolinium; The photosensitive organic ligands include any one or a combination of two or more of phthalocyanine and porphyrin; The photoswitch molecules include any one or a combination of two or more of azobenzene, spiropyran / spirooxazine, Schiff base, and fulgide.

[0008] Furthermore, the reaction time is 0.5 h to 24 h.

[0009] Furthermore, the SERS substrate based on photon MOFs is irradiated with light, and the wavelength used for the light irradiation is 280 nm - 2500 nm, and the light irradiation time is 5 min to 3 h.

[0010] Furthermore, the light band of the light irradiation includes any one or a combination of two or more of the ultraviolet band, visible band, and near-infrared band, and the light intensity range is 1000–10000 cd.

[0011] Application of the SERS substrate based on photon MOFs prepared by the preparation method provided by the present invention in detecting nanoplastics.

[0012] The present invention provides a method for detecting nanoplastics, including: The SERS substrate based on photon MOFs prepared by the preparation method provided by the present invention; Using the SERS substrate, nanoplastics are detected by a surface-enhanced Raman detection method.

[0013] The beneficial effects of the present invention are: 1) By using photon MOFs to construct the SERS substrate, the present invention covers photon MOFs of various different material systems; this not only increases the diversity of the existing SERS substrates, makes up for the deficiencies in traditional SERS technologies, but also provides more possibilities for the detection of nanoplastics due to its excellent general applicability, tunability, and light responsiveness.

[0014] 2) The present invention also provides a method for reducing the detection limit by using a single photon metal-organic framework material as the SERS substrate; this method includes using specific light irradiation to adjust the surface properties and structure of the photon MOFs, thereby significantly reducing the Raman response detection limit of nanoplastics during the Raman detection process; this method is simple to operate and easy to implement, greatly enhancing the feasibility of highly sensitive detection of nanoplastics. Description of the Drawings

[0015] Figure 1 is the transmission electron microscope image of the SERS substrate (Eu-MIL-125-NH2) in Example 1 of the present invention; Figure 2Surface - enhanced Raman spectroscopy of nanoplastics by the SERS substrate (Eu - MIL - 125 - NH2) in Example 1 of the present invention; Figure 3 Are the experimental results of the repeatability and uniformity of the SERS substrate (Eu - MIL - 125 - NH2) in Example 1 of the present invention; Figure 4 Surface - enhanced Raman spectroscopy of nanoplastics by the SERS substrate (MIL - 125 - NH2 containing fulgide) in Example 2 of the present invention; Figure 5 Are the enhanced Raman spectra of nanoplastics by the SERS substrate (after photo - activation) in Examples 3, 4 and 5. Detailed implementation manners

[0016] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments. The following will further explain and illustrate the technical solution, its implementation process and the underlying principles. It should be noted that within the scope of the present invention, the above - mentioned technical features and the technical details described in detail in the following (embodiment part) can be combined with each other to form new or optimized technical solutions. Due to space limitations, all possible technical combinations cannot be described in detail herein, but these combinations and their potential advantages and applications are all regarded as part of the present invention.

[0017] As an aspect of the technical solution of the present invention, it relates to a preparation method of a SERS substrate based on photon MOFs, including: At least mixing and reacting metal salts, organic ligands, and photon units in a solvent at a reaction temperature of 20~180 °C for a time of more than 0.5 h to form a SERS substrate based on photon MOFs; The photon units include rare - earth metals, photosensitive organic ligands, and light - switch molecules, where: the rare - earth metals include any one element or a combination of two or more elements selected from europium, terbium, cerium, dysprosium, and gadolinium; the photosensitive organic ligands include any one or a combination of two or more of phthalocyanine - based and porphyrin - based; the light - switch molecules include any one or a combination of two or more of azobenzene, spiropyran / spiropoxazine - based, Schiff - base - based, and fulgide.

[0018] Among them, the organic ligands coordinate with the central metal ions to form a porous coordination polymer, and the photon units provide light - responsive properties.

[0019] In some embodiments, the SERS substrate based on photon MOFs is irradiated with light, and the wavelength of the light irradiation is 280 nm - 2500 nm, and the light - irradiation time is 5 min~3 h.

[0020] In some embodiments, the light band of the light irradiation includes any one or a combination of two or more of the ultraviolet band, visible band, and near-infrared band; the light intensity is about 1000–10000 cd In some embodiments, the reaction time is 0.5 h to 24 h.

[0021] Thus, photon MOFs with different sizes and structures can be obtained.

[0022] In some specific embodiments, after the mixed reaction fully reacts, the lower-layer precipitate is taken, washed, and dried to obtain a SERS substrate based on photon MOFs.

[0023] Its purpose is to detect nanoplastics.

[0024] The embodiment of the present invention also provides a SERS substrate based on photon MOFs prepared by the foregoing method.

[0025] The embodiment of the present invention also provides an application of a SERS substrate based on photon MOFs in detecting nanoplastics.

[0026] The embodiment of the present invention also provides a method for detecting nanoplastics, including: Preparing a SERS substrate based on photon MOFs by the foregoing method; Using the SERS substrate to detect nanoplastics by surface-enhanced Raman detection method.

[0027] Among them, the method for preparing the photon MOFs substrate includes: selecting a central metal ion, an organic ligand, and a photon unit, continuously designing the metal-organic ligand topological structure to prepare different photon MOFs, finding the most suitable photon MOFs substrate, and greatly enhancing the Raman signal of nanoplastics; based on the same photon MOFs, by light field perturbation, the detection limit is reduced. Compared with similar substrates, the photon MOFs after light irradiation as a SERS substrate have excellent tunability and enhanced SERS activity.

[0028] The technical solution of the present invention will be further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. The implementation conditions adopted in the following embodiments can be further adjusted according to actual needs, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0029] Example 1 During the synthesis of MIL-125-NH2, the doped rare earth metal: titanium(IV) isopropoxide, 2-aminoterephthalic acid, and europium nitrate are used to obtain a SERS substrate of Eu-MIL-125-NH2. Among them, the reaction time of Eu-MIL-125-NH2 is 18 h, and the reaction temperature is 160 °C. Figure 1It is the transmission electron microscope image of the SERS substrate (Eu-MIL-125-NH2). Figure 2 It is the enhanced Raman spectrum of the SERS substrate (Eu-MIL-125-NH2) for nanoplastics. Taking the detection of bisphenol A in nanoplastics as an example, the laser wavelength is 532 nm and the detection concentration is 10-5 M. As Figure 3 shown, it is the experimental results of the repeatability and homogeneity of the SERS substrate (Eu-MIL-125-NH2), indicating that the SERS substrate has good repeatability and homogeneity. In the figure, RSD refers to the relative standard deviation.

[0030] Example 2 During the synthesis of MIL-125-NH2, the doped photosensitive organic molecules: titanium(IV) isopropoxide, 2-aminoterephthalic acid, and fulgide were used to obtain the SERS substrate of MIL-125-NH2 containing fulgide. Among them, the reaction time of MIL-125-NH2 containing fulgide was 24 h and the reaction temperature was 120 °C. Figure 4 It is the enhanced Raman spectrum of the SERS substrate (MIL-125-NH2 containing fulgide) for nanoplastics. Taking the detection of bisphenol A in nanoplastics as an example, the laser wavelength is 532 nm and the detection concentration is 10-5 M.

[0031] Example 3 The Eu-MIL-125-NH2 in Example 1 was irradiated under high-energy light in the visible light band with a light intensity of 10000 cd for 10 min to obtain the SERS substrate of photoactivated Eu-MIL-125-NH2.

[0032] Example 4 The Eu-MIL-125-NH2 in Example 1 was irradiated under high-energy light in the visible light band with a light intensity of 10000 cd for 20 min to obtain the SERS substrate of photoactivated Eu-MIL-125-NH2.

[0033] Example 5 The Eu-MIL-125-NH2 in Example 1 was irradiated under high-energy light in the visible light band with a light intensity of 10000 cd for 30 min to obtain the SERS substrate of photoactivated Eu-MIL-125-NH2.

[0034] Figure 5 It is the enhanced Raman spectrum of the SERS substrate after photoactivation in Examples 3, 4, and 5 for nanoplastics. Taking bisphenol A in nanoplastics as an example, the laser wavelength is 532 nm.

[0035] In summary, by means of the above technical solution of the present invention, a SERS substrate is constructed through photon MOFs, which involves a variety of metal-organic framework materials and has good general applicability, tunability and light responsiveness. By irradiating the photon MOFs with light, the Raman response detection limit of the detected nanoplastics can be greatly reduced in Raman detection.

[0036] In addition, corresponding tests were carried out by using other process conditions listed above to replace the corresponding process conditions in Examples 1-5, and the content to be verified was close to that of the products in Examples 1-5. Therefore, the verification content of each example will not be described one by one here, and only Examples 1-5 are taken as representatives to illustrate the excellent features of the present invention application.

[0037] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a SERS substrate based on photonic MOFs, characterized in that: include: At least metal salt, organic ligand and photon unit are mixed and reacted in a solvent, the reaction temperature is 20-180° C., and the reaction time is more than 0.5 h to form a SERS substrate based on photon MOFs.

2. The preparation method according to claim 1, characterized in that: The photon unit comprises a rare earth metal, a photosensitive organic ligand and a photo-switch molecule, wherein: Rare earth metals include any one element or a combination of two or more elements of europium, terbium, cerium, dysprosium and gadolinium; The photosensitive organic ligand includes any one or a combination of two or more of phthalocyanines and porphyrins; The optical switch molecules include any one or a combination of two or more of azobenzene, spiropyran / spirooxazines, Schiff bases and fulgide.

3. The preparation method according to claim 1, characterized in that: The reaction time is 0.5h~24h.

4. The preparation method according to claim 1, characterized in that: The photon MOFs-based SERS substrate is subjected to light irradiation, wherein the wavelength of the light irradiation is 280nm-2500nm and the irradiation time is 5min-3h.

5. The preparation method according to claim 4, characterized in that: The light band of the light irradiation includes any one of the ultraviolet band, the visible band, and the near-infrared band, or a combination of two or more thereof, and the light intensity ranges from 1000 to 10000 cd.

6. Application of the SERS substrate based on photonic MOFs prepared by the preparation method according to any one of claims 1 to 5 in detecting nanoplastics.

7. A method for detecting nanoplastics, characterized in that: include: A SERS substrate based on photonic MOFs prepared by the preparation method according to any one of claims 1 to 5; The SERS substrate is used to detect nano plastic substances through a surface enhanced Raman detection method.

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