A zeolite-based SERS composite substrate material, a preparation method and application thereof

Abstract

The application relates to a zeolite-based SERS composite substrate material and a preparation method and application thereof, wherein the SERS composite substrate material is a double-layer structure, the lower layer is a zeolite with a porous structure, and the upper layer is a metal nano structure; the specific surface area of the zeolite is 400 m 2 / g-1100 m 2 / g; the nano layer thickness of the metal nano structure is 50 nm-300 nm, wherein the nano metal includes any one of metal gold, silver or a gold-silver alloy. The SERS composite substrate material can be used for detecting gas-phase system asphalt VOCs, and based on the SERS technology, the detection lower limit of typical pollutants, toluene and acetone, in the asphalt VOCs can reach 8 ppm, and the detection lower limit of 2-methylpentane can reach 6 ppm, so that the detection sensitivity is relatively high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas-phase molecule detection, and more particularly to a zeolite-based SERS composite substrate material and a preparation method and application thereof. BACKGROUND

[0002] Asphalt material is an organic cementitious material composed of complex organic hydrocarbons and their derivatives. It has been widely used in waterproofing engineering, road construction and other fields. However, due to the high molecular polymer properties of asphalt material, it will release volatile organic compounds (VOCs) under the influence of environmental factors such as temperature and light, becoming an important precursor of fine particulate matter (PM2.5) and ozone (O3), which poses a great threat to human health and the atmospheric environment. The types of compounds in asphalt VOCs can be as high as several hundred. The target calibration compounds selected in patent CN 114019074A mainly include aliphatic hydrocarbons, aromatic hydrocarbons, oxygen-containing hydrocarbons and halogenated hydrocarbons. Typical pollutant components include toluene, acetone, 2-methylpentane, etc. However, the content of asphalt VOCs is usually low. Studies have shown that the VOCs concentration range of asphalt pavement is 46.69-2179 μg / m 3 , in which aromatic hydrocarbons are the main pollutants, accounting for more than 70% of the total concentration.

[0003] The existing detection and analysis method for asphalt VOCs is gas chromatography-mass spectrometry analysis. Although it has the advantages of strong separation ability, high sensitivity, rich structural information, etc., due to the complexity and high cost of the instrument equipment, long analysis time, complicated process, high cost, and susceptibility to human operation, gas samples need to be transported to a professional laboratory for detection and analysis, which is difficult to realize on-site real-time rapid detection, and will also increase the secondary pollution of the sample to be tested during the transportation process, which greatly limits its application in the actual detection and analysis of road engineering asphalt VOCs pollutant emissions.

[0004] Surface-enhanced Raman scattering (SERS) technology is a "fingerprint identification" technology that uses substrate materials such as metal nanostructures to enhance Raman signals and provide structural information about the analyzed substance by giving its vibrational spectrum. However, this detection technology requires the analyzed substance to be adsorbed on the metal surface through chemical or physical action and to be located within a specific electromagnetic field enhancement range. The selection of the substrate material also has a significant impact on the detection effect and application scenarios of SERS technology.

[0005] Currently, the research based on SERS technology at home and abroad mainly aims at detecting organic pollutants in liquid samples. Commonly used metal nanostructures such as gold nanoparticles and silver nanoparticles are mainly used for detecting and analyzing molecules with thiol and amino groups in water systems. However, weakly adsorbed molecules such as benzene, toluene and polycyclic aromatic hydrocarbons are difficult to adsorb on the metal surface. The composite substrate material in patent CN104749161B is a double-layer structure (the lower layer is a gold film with gold nanoparticle structure, and the upper layer is a polydimethylsiloxane film). Based on the adsorption performance of polydimethylsiloxane (PDMS), the Au-PDMS composite substrate is prepared by covering PDMS on the surface of the gold film. The physical adsorption of the PDMS film is used to fix and enrich weakly adsorbed molecules, and then the detection of toluene, benzene and nitrobenzene and other substances in water systems is realized.

[0006] However, compared with water systems, gas molecules have lower concentration and shorter adsorption equilibrium time on solid surfaces, which are difficult to capture, resulting in slow progress of SERS technology in the field of gas-phase molecule detection. Although the substrate material MOF@Au / Ag can be used for gas-phase SERS detection research, the MOF material has an organic framework structure, and its own Raman peak is easy to overlap with the characteristic peak position of the asphalt VOCs component, causing interference and affecting the test effect and precision. In addition, the preparation process of MOF is complex and high in cost, which is not conducive to practical popularization and application. In fact, there is no relevant report on the research of asphalt VOCs detection based on surface-enhanced Raman scattering effect. Therefore, the research of a SERS substrate material suitable for asphalt VOCs detection can promote the application of SERS technology in asphalt VOCs detection, and is conducive to realizing the in-situ rapid detection of VOCs in the field environment of asphalt pavement. SUMMARY

[0007] In view of the above defects or improvement needs of the prior art, the present application provides a zeolite-based SERS composite substrate material and a preparation method and application thereof. The purpose is to find a SERS composite substrate material that can be used for detecting asphalt VOCs in gas-phase systems. The SERS composite substrate material is a double-layer structure, wherein the lower layer is a zeolite with a specific surface area of 400m 2 / g-1100m 2 / g, and the upper layer is a metal nano-layer structure with a thickness of 50nm-300nm. The detection lower limit of the SERS composite substrate material for typical pollutants such as toluene and acetone in asphalt VOCs can reach 8ppm, and the detection lower limit for 2-methylpentane can reach 6ppm. Thus, the technical problem that the existing metal nanostructure substrate material cannot be used for detecting asphalt VOCs in gas-phase systems is solved.

[0008] To achieve the above object, according to one aspect of the present application, there is provided a SERS composite substrate material based on zeolite, wherein the composite substrate material is a double-layer structure, the lower layer is a porous zeolite, and the upper layer is a metal nanostructure.

[0009] The zeolite has a specific surface area of 400 m 2 / g to 1100 m 2 / g.

[0010] The metal nanostructure has a nano-layer thickness of 50 nm to 300 nm, and the nano-metal includes any one of gold, silver or gold-silver alloy.

[0011] Preferably, the SERS composite substrate material, the zeolite is an acid-pretreated zeolite, the specific surface area of which is 700 m 2 / g to 1100 m 2 / g, and the pore size is 0.5 nm to 2 nm.

[0012] The nano-metal has a size of 30 nm to 100 nm and a shape of any one of spherical, rod-like and flower-like.

[0013] Preferably, the SERS composite substrate material, the metal nanostructure thereof has a nano-metal of nano-silver and a nano-layer thickness of 150 nm to 200 nm.

[0014] According to another aspect of the present application, there is also provided a preparation method of the SERS composite substrate material as described in the present application, which comprises the following steps:

[0015] The zeolite with a specific surface area of 400 m 2 / g to 1100 m 2 / g is used as a substrate, a metal nano-sol with a size of 30 nm to 100 nm is coated on the surface of the zeolite, and the SERS composite substrate material is obtained through drying and solidification, wherein the metal nano-layer thickness of the upper layer of the substrate material is 50 nm to 300 nm.

[0016] The metal nano-sol includes a silver nano-sol with a concentration of 0.1 M to 0.5 M.

[0017] Preferably, the preparation method, the zeolite is an acid-pretreated zeolite, and the pretreatment is as follows:

[0018] The zeolite is added to an acid solution in a predetermined proportion, and reacted at 20°C to 100°C for 6 h to 24 h, and the suspension after reaction is filtered, washed with deionized water until neutral, and dried to obtain the pretreated zeolite.

[0019] The acid solution has a concentration of 0.1M-5M, and is one or a combination of hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid, and citric acid.

[0020] Preferably, the preparation method, the acid pretreated zeolite has a specific surface area of 700m 2 / g-1100m 2 / g, a zeolite crystal grain size of 1-3μm, and a pore size of 0.5-2nm.

[0021] According to another aspect of the present application, there is also provided a use of the SERS composite substrate material as described in the present application, which is used for detecting organic matters in a gas phase system by surface enhanced Raman spectroscopy; the organic matters include one or more typical pollutants in asphalt VOCs, such as toluene, acetone, and 2-methylpentane; preferably, the use is for detecting asphalt VOCs by surface enhanced Raman spectroscopy.

[0022] Preferably, the use is for detecting a gas phase system with a toluene concentration of 8ppm or above by surface enhanced Raman spectroscopy.

[0023] Preferably, the use is for detecting a gas phase system with an acetone concentration of 8ppm or above by surface enhanced Raman spectroscopy, and / or for detecting a gas phase system with a 2-methylpentane concentration of 6ppm or above by surface enhanced Raman spectroscopy.

[0024] Preferably, the use is for in-situ rapid detection of asphalt VOCs.

[0025] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects due to the SERS composite substrate material provided by the present application:

[0026] The SERS composite substrate material provided by the present application has a double-layer structure, the lower layer is a zeolite with a specific surface area of 400m 2 / g-1100m 2 / g, and the upper layer is a metal nano-layer structure with a thickness of 50-300nm, and experiments show that the specific surface area is 400m 2 / g-1100m 2The zeolite with a thickness of 50-300 nm metal nanostructure distributed on the surface can not only enhance the Raman effect, but also increase the roughness of the zeolite surface, which is conducive to further enhancing the adsorption and fixation of the zeolite on the VOCs of asphalt. Experiments show that the SERS composite substrate material can be used for detecting VOCs of asphalt, and can detect typical substances such as toluene, 2-methylpentane and acetone in VOCs of asphalt. The detection lower limit of gaseous toluene and acetone can reach 8 ppm, and the detection lower limit of gaseous 2-methylpentane can reach 6 ppm, which can realize in-situ rapid detection of VOCs of asphalt. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 XRD diagram of Ag-zeolite composite SERS substrate material;

[0028] Figure 2 Schematic diagram of detecting VOCs of asphalt based on SERS technology;

[0029] Figure 3 Raman spectrum of VOCs of asphalt on different treatment prepared substrate materials;

[0030] Figure 4 Nano-silver SERS substrate and its Raman spectrum on VOCs of asphalt;

[0031] Figure 5 Comparison diagram of the influence of ZIF-8@-Ag substrate material on Raman detection of VOCs of asphalt;

[0032] Figure 6 Influence of different metal nanostructures on detection effect of VOCs of asphalt;

[0033] Figure 7 Raman spectrum of different concentration toluene gas;

[0034] Figure 8 Raman spectrum of detection limit of acetone and 2-methylpentane. DETAILED DESCRIPTION

[0035] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object of the application, the specific embodiments, structures, features and effects thereof according to the present application are described in detail as follows in combination with the drawings and preferred embodiments.

[0036] Surface-Enhanced Raman Scattering (SERS) detection is a technique for improving the Raman scattering signal by using specific substrate materials to enhance the Raman signal, so that lower concentrations of molecules can be detected. Among them, the commonly used substrate materials for water system pollutant detection are gold nanoparticles and silver nanoparticles. However, compared with water system, the concentration of gas molecules is lower, and it takes a short time to reach adsorption equilibrium on the solid surface, which is difficult to capture, resulting in that SERS technology is difficult to apply to the detection of gas phase system asphalt VOCs.

[0037] The present application finds that a SERS composite substrate material can be used for effective detection of gas phase system asphalt VOCs, and the detection lower limit of the typical pollutants toluene and acetone gas in asphalt VOCs can reach 8 ppm, and the detection lower limit of the typical pollutants 2-methylpentane gas in asphalt VOCs can reach 6 ppm. The SERS composite substrate material is a double-layer structure, wherein the lower layer is a zeolite with a specific surface area of 400 m 2 / g-1100m 2 / g; the upper layer is a metal nanostructure with a thickness of 50 nm-300 nm, and the metal nanostructure includes any one of nano-gold, nano-silver or nano-gold-silver alloy.

[0038] Based on this, the present application provides a SERS composite substrate material prepared based on zeolite, which is a double-layer structure, wherein the lower layer is a porous zeolite, and the upper layer is a metal nano-layer structure, wherein the metal nano-layer is uniformly dispersed on the surface of the zeolite; the zeolite has a specific surface area of 400 m 2 / g-1100m 2 / g; the metal nanostructure has a nano-layer thickness of 50 nm-300 nm, and the nano-metal includes any one of metal gold, silver or gold-silver alloy.

[0039] The SERS composite substrate material has a specific surface area of 400 m 2 / g-1100m 2 / g; the upper layer is a metal nanostructure with a thickness of 50 nm-300 nm, and the metal nanostructure includes any one of nano-gold, nano-silver or nano-gold-silver alloy.

[0040] The metal nanostructure is composed of many longitudinal and transverse intersecting nanosheets, the surface electromagnetic fields of adjacent nanosheets are coupled with each other, a strong local electromagnetic field enhancement is generated, so that it shows very strong SERS performance. For example, nano-gold or nano-silver or alloy of the two can play a Raman enhancement effect.

[0041] In some embodiments, the size of the nanometal is 30nm-100nm, the zeolite has a specific surface area of 700m 2 / g-1100m 2 / g, a grain size of 1μm-3μm, and a pore size of 0.5nm-2nm.

[0042] In some embodiments, the nanometal structure has a nanolayer thickness of 150nm-200nm, and the nanometal is nanosilver, wherein the nanosilver has a size of 30nm-100nm and a shape selected from the group consisting of spherical, rod-like, and flower-like, for example, the nanosilver has a size of 70-80nm and a flower-like shape.

[0043] Further, the zeolite is an acid-treated zeolite, and the acid treatment is performed as follows:

[0044] The zeolite is added to an acid solution in a predetermined ratio, and reacted at 20℃-100℃ for 6h-24h. The reaction suspension is filtered, washed with deionized water until neutral, and dried to obtain the acid-treated zeolite. Preferably, the reaction is performed at 50-100℃ for 6-24h.

[0045] The acid treatment removes impurities in the zeolite, making the pore structure more complete, and further increases the specific surface area of the zeolite, which is beneficial to improving the adsorption effect of the composite substrate material on VOCs in bitumen.

[0046] The acid solution has a concentration of 0.1M-5M, and is selected from the group consisting of hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid, and citric acid.

[0047] The mass-to-volume ratio of the zeolite to the acid solution is 1g:10mL-25mL, and the acid treatment is performed until the specific surface area of the zeolite no longer increases.

[0048] In addition, the present application also provides a preparation method of the SERS composite substrate material, which comprises the following steps:

[0049] The zeolite has a specific surface area of 400m 2 / g-1100m 2 / g, and the metal nanosol is coated on the surface of the zeolite, so that the thickness of the metal nanolayer on the surface of the zeolite is 50-300nm after drying and curing, to obtain the SERS composite substrate material. Preferably, the thickness of the metal nanolayer is 150-200nm.

[0050] The metal nanosol includes gold nanosol, silver nanosol, or gold-silver alloy nanosol.

[0051] Preferably, the zeolite is an acid pretreated zeolite with a specific surface area of 700 m 2 / g-1100 m 2 / g, a zeolite grain size of 1 μm-3 μm, and a pore size of 0.5 nm-2 nm.

[0052] In some embodiments, a nano-metal sol with a concentration of 0.1 M-0.5 M is used, and the coating amount is (10 μL-50 μL) / 15 g of zeolite; for example, a nano-Ag sol with a concentration of 0.1 M is used, and the total coating amount is 30 μL by one or more times of drop coating, so that the SERS composite substrate material with an Ag nano-layer thickness of 150-200 nm is obtained.

[0053] The application further provides a use of the SERS composite substrate material as described in the application, which is used for detecting organic matter in a gas phase system by surface enhanced Raman spectroscopy; the organic matter includes one or more typical gaseous pollutants such as toluene, acetone and 2-methylpentane; more preferably, the application is used for in-situ detecting asphalt VOCs by surface enhanced Raman spectroscopy, and the asphalt VOCs include toluene, acetone and 2-methylpentane.

[0054] In some embodiments, the application is used for detecting a gas phase system with a toluene concentration of more than 8 ppm by surface enhanced Raman spectroscopy.

[0055] In some embodiments, the application is used for detecting a gas phase system with an acetone concentration of more than 8 ppm by surface enhanced Raman spectroscopy.

[0056] In some embodiments, the application is used for detecting a gas phase system with a 2-methylpentane concentration of more than 6 ppm by surface enhanced Raman spectroscopy.

[0057] In some embodiments, the application is used for in-situ rapid detection of asphalt VOCs; for example, based on the SERS composite substrate material provided in the application, a gas phase system with asphalt VOCs at a concentration of 112 mg / m 3 can be detected by surface enhanced Raman spectroscopy.

[0058] The following are examples

[0059] Example 1: Effect of zeolite substrate materials prepared by different treatments on detection of asphalt VOCs

[0060] (1) Zeolite pretreatment: 15 g of zeolite (zeolite size: 1 μm-3 μm, specific surface area: 325 m 2g) adding to 150 mL of a hydrochloric acid solution with a concentration of 1 mol / L, setting the temperature at 25 °C, 50 °C, 75 °C and 100 °C respectively, soaking for 24 h, removing the supernatant, washing with deionized water until neutral, and drying in an oven at 60 °C under vacuum to obtain the acid-treated zeolite. In this embodiment, the hydrochloric acid solution can also be replaced by one or more of phosphoric acid, sulfuric acid, formic acid, acetic acid, citric acid in combination, with a concentration of 0.1 M-5 M.

[0061] The pore size of the acid-treated zeolite is 0.5 nm-2 nm, and the specific surface area and porosity of the zeolite pretreated under different conditions in Example 1 are compared, and the test results are shown in the following table:

[0062] Table 1 Specific surface area and pore volume of zeolite under different acid treatment conditions

[0063]

[0064] (2) Preparation of silver nanosol: At room temperature, 0.1 g of silver nitrate and 0.15 g of trisodium citrate were weighed and added to 50 mL of deionized water, stirred until completely dissolved, and prepared into solution A; 0.5 g of ascorbic acid was weighed and added to a mixture of 50 mL of water and ethylene glycol (volume ratio 1:1), stirred until completely dissolved, and prepared into solution B; then under the stirring of a magnetic stirrer, solution B was quickly added to solution A, and the reaction was carried out for 1 hour. After washing with deionized water and anhydrous ethanol several times, it was dispersed in deionized water to obtain Ag nanosol.

[0065] (3) Preparation of Ag-zeolite composite substrate material: untreated and treated zeolites were respectively laid on a clean substrate as a VOCs gas adsorption layer. A drop coating method was used to add 30 μL of Ag nanosol (prepared as in step (2) above) with a concentration of 0.1 M on the zeolite adsorption layer, which can be added once or more times, and after drying, a uniform layer of nano-silver structure was formed on the zeolite surface, wherein the nano-silver structure formed on the zeolite surface has a nano-layer thickness of 180 nm, and the nano-silver is a flower-shaped structure with an average diameter of 80 nm.

[0066] These composite substrate materials were placed in a 60 °C oven to dry, and 5 different series of SERS substrate materials-Ag-zeolite composite substrate materials were prepared. The XRD pattern of the Ag-zeolite composite SERS substrate material is shown in Figure 1 .

[0067] As can be seen from Figure 1 , the characteristic diffraction peaks of zeolite and Ag can be detected, and the peak shape is sharp, indicating that the Ag-zeolite composite SERS substrate is successfully prepared.

[0068] The adding method of the Ag nanosol in the present embodiment is not limited, and other existing methods that can make the metal nanostructure meet the requirements of the present application can be used.

[0069] (4) Detection of asphalt VOCs based on SERS technology: as shown in Figure 2 , respectively, the above-mentioned 5 kinds of SERS substrate horizontally placed in a volume of 1L quartz airtight box (the top is a glass cover plate that can be opened and closed, and a sealing ring is installed between the cover plate and the box body, which is convenient for replacing the SERS substrate material), one end of the airtight box is connected with the asphalt VOCs generator, and the other end is connected with the gas sampling pump; wherein the gas inlet is connected with the connecting pipe and the field environment through the metal gas conduit, and the gas outlet is connected with the gas sampling pump, which can collect asphalt VOCs in the airtight box in real time by generating negative pressure.

[0070] Take 200g of matrix asphalt and put it into a volume of 1L asphalt VOCs generator, heat to 165℃ and keep warm; open the gas sampling pump, the sampling rate is 5mL / min-200mL / min, the sampling time is 10min-2h, such as the sampling rate is 5mL / min and the sampling time is 2h in this embodiment; close the gas control valve of the gas inlet and outlet, so that the asphalt VOCs gas molecules can fully react with the SERS substrate material in the airtight box, and the incubation time is 30min.

[0071] ATR3110-633nm type Raman spectrometer is used to detect and analyze the above-mentioned SERS substrate material, wherein the Raman laser wavelength represents different excitation energy, and the smaller the wavelength, the stronger the energy. One of the laser wavelengths of 532nm, 633nm, 785nm and 1064nm can be selected, and the signal collection time is 2-10min, wherein 532nm and 633nm are commonly used excitation wavelengths, and for some fluorescent organic compounds, a longer wavelength and lower energy laser is generally required. In this embodiment, the excitation wavelength is 633nm, the signal collection time is 8min, and the corresponding Raman spectrum of each group is obtained, as shown in Figure 3 .

[0072] The obtained spectrum is compared with the standard Raman spectrum of typical substances in asphalt VOCs, such as toluene, 2-methylpentane and acetone, and it is found that the untreated zeolite substrate almost cannot detect the characteristic substances in asphalt VOCs, and after acidification, the specific surface area of the zeolite increases, the adsorption effect of asphalt VOCs is enhanced, and the characteristic peaks of toluene, 2-methylpentane and acetone begin to appear (among them, 789cm -1 is the C-C symmetric stretching vibration peak of acetone, 815cm -1 is the C-C stretching vibration peak of 2-methylpentane CH3-CH3, and 1003cm -1is the toluene mononuclear aromatic ring breathing vibration peak, 1026 cm -1 is the toluene C-CH stretching vibration peak.

[0073] As the specific surface area of the zeolite in the SERS composite substrate material increases, the detection effect is more obvious, and is not affected by the Ag-zeolite substrate material. It is shown that using the above SERS composite substrate material, the SERS technology can be used to effectively detect VOCs in asphalt.

[0074] Comparative Example 1: Detection effect of silver nanometer substrate material on asphalt VOCs

[0075] (1) Preparation of silver nanometer sol: at room temperature, 0.1 g of silver nitrate and 0.15 g of trisodium citrate were weighed and added to 50 mL of deionized water, and stirred until completely dissolved to prepare solution A; 0.5 ascorbic acid was weighed and added to 50 mL of water and ethylene glycol mixture (volume ratio 1:1), and stirred until completely dissolved to prepare solution B; then under the stirring of a magnetic stirrer, solution B was quickly added to solution A, and reacted for 1 hour. After washing with deionized water and anhydrous ethanol for several times, it was dispersed in deionized water to obtain Ag nanometer sol.

[0076] (2) The Ag nanometer sol prepared in step (1) above was configured into a solution with a concentration of 0.1 M, and 30 μL was directly added on a clean quartz substrate, and was placed in a 60°C oven to dry to obtain an Ag nanometer substrate material.

[0077] (3) Detection of asphalt VOCs based on SERS technology: the Ag nanometer substrate material obtained in step (2) was used for detection, and the other operations were the same as in Example 1, and the obtained Raman spectrum is shown in Figure 4 .

[0078] It can be seen from Figure 4 that the Raman signal of the corresponding composition of asphalt VOCs was not detected, and the reason for the analysis may be that asphalt VOCs are gas molecules, which have poor interaction with the surface of nanometer metal materials and cannot be stably on the nanometer silver SERS substrate, so the Raman signal of the corresponding composition in asphalt VOCs cannot be detected.

[0079] Comparative Example 2: Detection of asphalt VOCs using SERS technology with MOF-Ag as a substrate material

[0080] (1) Preparation of MOF-Ag substrate material: with a specific surface area of 1200 m 2ZIF-8 as a substrate; it is laid on the clean substrate as a VOCs gas adsorption layer. Drop coating method is used to drop 0.1M Ag nanosol on the surface of the MOF material, the amount is the same as that in Example 1, and then the substrate material is placed in a 60℃ oven for drying to obtain a ZIF-8-Ag substrate material.

[0081] (2) Detection of asphalt VOCs based on SERS technology: the ZIF-8-Ag substrate material obtained in step (2) is used for detection, except that the substrate material used is different, the other operations are the same as those in Example 1, and the effects of zeolite, ZIF-8 and ZIF-8-Ag on the Raman detection of asphalt VOCs are compared and analyzed, and the results are shown in Figure 5 .

[0082] Taking toluene, a characteristic pollutant in asphalt VOCs, as an example, the characteristic peak of toluene is 1026cm -1 C-CH stretching vibration peak, which is the basis for determining the detection of toluene in asphalt VOCs. However, Figure 5 It can be seen that ZIF-8 also has Raman characteristic peaks at similar wave numbers, which will affect the determination of the detection results. This is mainly because ZIF-8 is a metal-organic framework material (MOFs) composed of metal ions and organic ligands. The organic structure features result in a large number of Raman vibration characteristic peaks, especially the similar organic ring framework structure and the aromatic ring structure of benzene series, which leads to the overlapping of part of the characteristic peaks and brings interference to the detection of benzene series. Zeolite is an inorganic substance, and its Raman characteristic peaks are quite different from those of organic substances, so it has little interference to the detection of asphalt VOCs.

[0083] Example 2 Influence of different thicknesses of metal nanostructures on the detection effect of asphalt VOCs

[0084] Aromatic hydrocarbons, as the main component of asphalt VOCs, are the key control objects of asphalt VOCs due to their irritancy and harmfulness to the human body. In this embodiment, toluene standard solution is used as the detection object to study the influence of different silver nanostructures on the detection effect of asphalt VOCs, as follows:

[0085] The pretreated zeolite obtained at 50℃ in Example 1 is used as a substrate to prepare an Ag-zeolite composite substrate material, which is prepared according to the following method:

[0086] (1) Zeolite pretreatment: 15g of zeolite is added to 150mL of 1mol / L hydrochloric acid solution, the temperature is set to 50℃, and after soaking for 24h, the supernatant is removed, and the zeolite is washed with deionized water until it is neutral, and then it is placed in an oven and dried at 60℃ under vacuum to obtain pretreated zeolite.

[0087] (2) Preparation of Ag nanosol: At room temperature, weigh 0.1g silver nitrate and 0.15g trisodium citrate, add 50mL deionized water, stir until completely dissolved, and prepare solution A; weigh 0.5g ascorbic acid, add it to 50mL water and ethylene glycol mixture (volume ratio 1:1), stir until completely dissolved, and prepare solution B; then, under the stirring of a magnetic stirrer, quickly add solution B to solution A, react for 1 hour, wash repeatedly with deionized water and anhydrous ethanol by centrifugation, and disperse in deionized water to obtain Ag nanosol.

[0088] (3) Preparation of Ag-zeolite composite substrate materials: The treated zeolite was spread on a clean substrate as a VOCs gas adsorption layer. Ag nanosol with a concentration of 0.1M was dropped onto the zeolite adsorption layer using a drop-coating method, with amounts of 10μL, 20μL, 30μL, 40μL and 50μL respectively. The drop-coating could be done once or multiple times to prepare surface functional layers with different Ag contents. These composite substrate materials were dried in a 60℃ oven to prepare five Ag-zeolite SERS composite substrate materials with different nanometal thicknesses.

[0089] (4) Detection of gaseous toluene based on SERS technology: The five SERS substrate materials obtained in step (3) were placed horizontally in a sealed box, and 20 μL of toluene standard was added to the sealed box. After sealing, the boxes were left to stand at room temperature for 8 hours to allow volatilization. An ATR3110-633nm Raman spectrometer was used to detect and analyze the SERS substrate materials adsorbed with toluene gas. The excitation wavelength was 633nm and the signal acquisition time was 8 minutes. The corresponding Raman spectra of each group were obtained as follows: Figure 6 .

[0090] The obtained spectrum was compared with the spectrum of the toluene standard sample. Figure 6 As can be seen, the characteristic peak of toluene was detected in the Raman spectra of all groups of toluene standard gas: 785 cm⁻¹. -1 1003cm -1 And 1026cm -1 The other peaks are spectral peaks of zeolite in the SERS substrate material. Zeolite is an inorganic substance, and its Raman characteristic peaks are quite different from those of organic substances, so the interference is relatively small. Therefore, it does not affect the detection results of other organic substances in asphalt VOCs.

[0091] The characteristic peak of toluene at 785 cm⁻¹ was detected by adding 10 μL of 0.1 M Ag nanosol (with a 50 nm thick silver nanolayer on the SERS substrate). -1 1003cm -1 And 1026cm -1, with the increase of the amount of Ag nanosol, the SERS signal intensity showed a trend of first increasing and then decreasing. The possible reason was that when the amount of Ag nanosol was 10 μL, the Ag content on the surface of the zeolite was low, the nanosilver was sparse, and the distance between the particles was large, resulting in low SERS signal intensity. With the increase of the amount of Ag nanosol, the number of nanosilver gradually increased, the number of "hot spots" on the surface of the zeolite increased, the distribution density of nanosilver increased, and the distance between the particles decreased, showing uniform and moderate distribution, which could significantly enhance the electromagnetic effect and further improve the SERS signal intensity. When the amount of nanosilver sol increased to 40-50 μL, the nanosilver particles began to aggregate (metal nanolayer thickness 200-300 nm), forming larger clusters, thereby reducing the number of effective hot spots. This aggregation effect weakened the electromagnetic enhancement effect, resulting in a decrease in SERS signal intensity. It can be seen that the SERS signal intensity is not linearly positively correlated with the total amount of nanosilver. The metal nanolayer thickness in the SERS composite substrate material is in the range of 50 nm-300 nm, which can detect the typical pollutant toluene gas in asphalt VOCs, and the metal nanolayer thickness is preferably 150 nm-200 nm, which has better detection effect.

[0092] Example 3 Sensitivity of Ag-zeolite substrate material to detection of asphalt VOCs and its characteristic pollutants

[0093] Since the composition of asphalt VOCs is very complex, the present application takes toluene, 2-methylpentane and acetone as the research objects, and explores the sensitivity of the Ag-zeolite substrate material to the detection of asphalt VOCs and its characteristic pollutants.

[0094] 3.1 Sensitivity of Ag-zeolite substrate material to detection of toluene in asphalt VOCs

[0095] (1) The Ag-zeolite substrate material was prepared according to steps (1)-(3) in Example 2, wherein the recommended amount of 0.1 M nanosilver sol was 30 μL.

[0096] (2) The above SERS substrate material was placed horizontally in a sealed box, 1 μL, 10 μL, 20 μL, 200 μL and 1000 μL of toluene standard sample were added respectively in the sealed box, and after sealing, it was placed at room temperature for 8 h. After toluene standard sample was completely volatilized, the concentration of toluene gas corresponding to the toluene standard sample was calculated as 1 ppm-900 ppm by multiplying the volume of toluene by the density of toluene and then dividing by the volume of the sealed container. A Raman spectrometer of ATR3110-633 nm type was used to detect and analyze the SERS substrate adsorbed with different concentrations of toluene gas, wherein the excitation wavelength was 633 nm, the signal acquisition time was 8 min, and the corresponding Raman spectrum was obtained as shown in Figure 7 .

[0097] Depend on Figure 7 It can be seen that when the volume of the toluene standard sample is 1 μL, that is, the toluene gas concentration is 1 ppm, the Raman characteristic peak of toluene does not appear due to the low gas concentration. When the volume of the toluene standard sample increases to 10 μL, that is, the toluene gas concentration increases to 8 ppm, the peak at 785 cm⁻¹ is observed. -1 1003cm -1 and 1026cm -1 The Raman characteristic peak of toluene begins to appear at a certain concentration. Although the peak shape is weak, toluene can still be detected, indicating that the detection limit for toluene gas is 8 ppm. Further increasing the concentration of toluene results in a more pronounced characteristic peak and better detection.

[0098] 3.2 The effect of Ag-zeolite matrix materials on characteristic pollutants 2-methylpentane and... Figure 8 Sensitivity of Raman spectroscopy detection limits for acetone and 2-methylpentane

[0099] As described in section 3.1 above, for Ag-zeolite substrate materials, 10 μL of 2-methylpentane or acetone standard was added to a sealed chamber, sealed, and allowed to stand at room temperature for 8 hours to allow complete evaporation and absorption. An ATR3110-633nm Raman spectrometer was used to detect and analyze the SERS substrates that had adsorbed 2-methylpentane or acetone gas. The excitation wavelength was 633 nm, and the signal acquisition time was 8 minutes. The results are as follows. Figure 8 As shown.

[0100] Depend on Figure 8 It is evident that the SERS composite substrate material provided by this invention can detect 2-methylpentane at a gaseous concentration of 6 ppm and acetone at a gaseous concentration of 8 ppm. Therefore, the detection limit of this method for 2-methylpentane gas can be as low as 6 ppm, and the detection limit for acetone gas can be as low as 8 ppm.

[0101] 3.3 In-situ detection of VOCs in asphalt based on Ag-zeolite matrix materials

[0102] As described in 3.1 above, following step (4) of Example 1, 200g of matrix asphalt was weighed and placed in a 1L asphalt VOCs generator. The mixture was heated to 165℃ and kept warm. The gas sampling pump was turned on to collect asphalt VOCs gas samples at a sampling rate of 5mL / min for 2h. An ATR3110-633nm Raman spectrometer was used to detect and analyze the SERS substrate that adsorbed asphalt VOCs gas. The excitation wavelength was 633nm and the signal acquisition time was 8min. This method can effectively detect a variety of typical pollutants in asphalt VOCs, such as toluene, 2-methylpentane, and acetone.

[0103] With the same collection condition as above, in order to determine the actual concentration of the asphalt VOCs, the GC-MS detection is carried out, and the concentration of the asphalt VOCs is 112 mg / m 3 It can be seen that the Ag-zeolite composite SERS substrate material provided by the present application can realize in-situ rapid detection of asphalt VOCs.

[0104] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make slight changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution range of the present application. Any modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application, without departing from the technical solution content of the present application, still belong to the scope of the technical solution of the present application.

Claims

1. A SERS composite substrate material prepared on the basis of zeolite, characterized by The SERS composite substrate material for detecting asphalt VOCs in gas phase system is a double-layer structure, wherein the lower layer is a porous zeolite structure and the upper layer is a metal nanostructure. The zeolite is an acid pretreated zeolite having a specific surface area of 700 m 2 / g-1100 m 2 / g, and a pore size of 0.5 nm-2 nm. The metal nanostructure has a nano-layer thickness of 50-300 nm, wherein the nano-metal includes any one of metal gold, silver or gold-silver alloy.

2. The SERS composite substrate material of claim 1, wherein, The nano-metal has a size of 30-100 nm and a shape of any one of spherical, rod-like and flower-like.

3. The SERS composite substrate material of claim 2, wherein, The metal nanostructure has a nano-metal of nano-silver and a nano-layer thickness of 150-200 nm.

4. A method for preparing the SERS composite substrate material according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: The acid pretreated zeolite is used as a substrate, and a metal nano-sol with a size of 30-100 nm is coated on the surface of the zeolite, and the SERS composite substrate material is obtained by drying and curing, wherein the upper layer of the substrate material has a metal nano-layer thickness of 50-300 nm. said acid pretreated zeolite having a specific surface area of 700 m 2 / g - 1100 m 2 / g, a zeolite crystal size of 1 pm - 3 pm, a pore size of 0.5 nm - 2 nm; The metal nano-sol includes a silver nano-sol with a concentration of 0.1-0.5 M.

5. The production method according to claim 4, wherein The acid pretreated zeolite is pretreated as follows: The zeolite is added to an acid solution in a predetermined ratio, and the mixture is stirred at 20 o C-100 o The zeolite is added to an acid solution in a predetermined ratio, and the mixture is stirred at 20 o C-100 o The zeolite is added to an acid solution in a predetermined ratio, and the mixture is stirred at 20 The acid solution has a concentration of 0.1-5 M and includes one or more combinations of hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid and citric acid.

6. Use of the SERS composite substrate material according to any one of claims 1 to 3, characterized in that The method is applied to in-situ rapid detection of asphalt VOCs in gas phase system, and the asphalt VOCs include one or more typical gas pollutants such as toluene, acetone and 2-methylpentane.

7. Use according to claim 6, wherein The method is used for surface-enhanced Raman spectrum detection of a gas phase system with a toluene concentration of 8 ppm or more.

8. Use according to claim 7, wherein the compound is ###0002### The method is used for surface-enhanced Raman spectrum detection of a gas phase system with an acetone concentration of 8 ppm or more, and / or for surface-enhanced Raman spectrum detection of a gas phase system with a 2-methylpentane concentration of 6 ppm or more.

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