CN113466205B - Preparation method of surface enhanced Raman sensor based on metal organic framework structure - Google Patents

Abstract

The invention discloses a preparation method of a surface enhanced Raman sensor based on a metal organic framework structure, wherein the surface enhanced Raman sensor is prepared from a rod-shaped Ag-MOF material with silver as a metal coordination ion and 2-amino terephthalic acid as a ligand, the material is uniformly coated on the surface of a substrate during preparation, silver ions are reduced into uniform silver simple substance particles through high-temperature carbonization reduction, and an organic matter is carbonized, so that the interference of a functional group in a Raman spectrum of the functional group in a low-wave-number section is removed, and the sensor has a good surface enhanced Raman sensing effect. The sensor has the advantages of simple preparation process, low cost, uniform grid structure of MOF materials, fixed distance between silver particles, good surface enhanced Raman effect, high sensitivity and small background interference signal, and can be used for low-concentration detection of various organic matters in water.

Description

Preparation method of surface-enhanced Raman sensor based on metal-organic framework structure

technical field

The invention relates to the fields of aquaculture and sewage detection, in particular to a preparation method of a surface-enhanced Raman sensor based on a metal-organic frame structure (MOF).

Background technique

Methylene blue (MB), malachite green (MG), and crystal violet (CV) are three common organic dyes. They have good fungicidal, bactericidal, and parasitic effects at low doses. They are often used by aquatic products. Improve fish survival in farming and transportation. Among them, malachite green and crystal violet are triphenylmethane organic compounds. According to reports, they have high toxicity, high residues, and three harms. They are listed as banned veterinary drugs for edible animals in my country. The European Union requires them not to be detected. In addition, methylene blue is a phenothiazine organic compound with relatively low toxicity, so it replaces malachite green and crystal violet, but it still has certain toxicity and teratogenicity, and it is also banned from aquaculture in some countries.

The traditional detection methods include spectrophotometry, liquid chromatography, immunosorbent analysis and so on. Traditional methods often require complex pretreatment of samples, resulting in a slow detection process, high instrument cost, and poor portability. Surface-enhanced Raman is a low-cost, fast, portable, and non-invasive detection method with high sensitivity for trace detection. Methylene blue, malachite green and crystal violet molecules have large Raman cross sections, which are suitable for detection by surface-enhanced Raman method, and Raman fingerprint spectroscopy can distinguish different substances, and can also effectively detect their mixed solutions. However, it is difficult to control the gaps between the nanoparticles that constitute hot spots on the traditional surface-enhanced Raman substrate. When used for low-concentration detection of organic dyes in aquaculture and sewage, the Raman spectral signal intensity cannot be effectively improved. Silver nanoparticles are easily oxidized and do not It is beneficial for the sensor to be used for low-concentration detection of organic dyes in aquaculture and sewage.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a surface Raman-enhanced sensor in order to solve the above problems, which has high sensitivity and can be used for low-concentration detection of organic dyes in aquaculture and sewage.

The object of the present invention is achieved through the following technical solutions:

A preparation method of a surface-enhanced Raman sensor based on a metal-organic framework structure, comprising the following steps:

Step 1, dissolve silver nitrate in deionized water, dissolve 2-aminoterephthalic acid in DMF solution, then add DMF dissolved with 2-aminoterephthalic acid into deionized water dissolved with silver nitrate, The mixed solution is heated to reflux to obtain a dispersed liquid;

In step 2, the dispersion liquid is washed and dried to obtain Ag-MOF solid powder, the Ag-MOF solid powder is dispersed in the solution, and then coated on the surface of the substrate and dried;

In step 3, the spin-coated substrate is subjected to high-temperature carbonization reduction, and under the protection of an inert gas, the temperature is raised to a certain temperature, and after maintaining for a period of time, it is naturally cooled to room temperature to obtain a surface-enhanced Raman sensor.

The surface-enhanced Raman sensor is prepared from a rod-shaped Ag-MOF material with silver as the metal coordination ion and 2-aminoterephthalic acid as the ligand. During preparation, the material is uniformly coated on the surface of the substrate, and then carbonized at high temperature. Reduction, the silver ions are reduced to relatively uniform silver particles, and the organic matter is carbonized, thereby removing the interference of functional groups in its Raman spectrum in the low wave number range, so that the sensor has a good surface-enhanced Raman sensing effect. The sensor of the invention is simple in preparation process and low in cost, takes advantage of the uniform grid structure of MOF material, has high sensitivity and small background interference signal, and can be used for low concentration detection of organic dyes in aquaculture and sewage.

Preferably, the molar ratio of silver nitrate and 2-aminoterephthalic acid in step 1 is 1:0.5-2, so that silver nitrate and 2-aminoterephthalic acid are fully reacted.

Preferably, in the first step, the mixed solution is heated to reflux at 125° C. for 2 hours.

Preferably, in step 2, the dispersion liquid is washed with DMF and ethanol by centrifugation for several times, and vacuum-dried at 60° C. to make the residual solvent in the voids more volatile.

Preferably, the substrate described in step 2 includes glass, silicon wafer, ITO glass, etc., and the surface of the substrate is flat, which can make the sensitive material more uniformly distributed.

Preferably, magnetron sputtering is used on the surface of the substrate to sputter a metal element with a thickness of 100-1500 nanometers, which has few Raman characteristic peaks and is unlikely to cause background interference.

Preferably, the metal element includes gold, silver, copper, aluminum, nickel, and chromium.

Preferably, the surface of the substrate is ultrasonically cleaned with acetone, isopropanol and ethanol before use to remove impurities and organic substances on the surface of the silicon wafer.

Preferably, the coating method in step 2 includes drop coating, spin coating, liquid phase epitaxy, etc., which can make the sensitive material evenly distributed and control the thickness of the material.

Preferably, the high temperature carbonization reduction temperature range in step 3 is 200-450°C, and the time is 1 to 3 hours, which can carbonize the Ag-MOF solid powder without completely collapsing the structure.

In the present invention, silver with higher sensitivity is selected as the precious metal ion to construct MOF, 2-aminoterephthalic acid is used as the organic ligand, dense and uniform elemental silver nanoparticles are formed on the rod-shaped surface of Ag-MOF, and the heat treatment makes the organic matter carbonize, The functional groups are destroyed, the characteristic peaks of these functional groups in the Raman spectrum are removed, the interference to the sensor is reduced, and the adsorption of carbon materials and the hot spot effect of silver nanoparticles are effectively combined to obtain a surface-enhanced Raman effect. sensor, which can be used for low-concentration detection of organic dyes in aquaculture and sewage.

The MOF of the present invention is composed of metal ions and organic ligands, and has an ordered grid structure. By adjusting the types of metal ions and organic ligands, the metal ions are replaced, the distance between the metal ions is controlled, and finally particles can be obtained by high-temperature reduction. Uniform size and tightly arranged structure can produce better surface-enhanced Raman effect.

The advantages of the invention are that the preparation method is simple and fast, and the cost is low. With the help of the ordered grid structure of the MOF material, the distance between the hot spots can be controlled, and the interference of the use of organic reagents in the preparation process is treated at high temperature, and the obtained silver nanoparticles have regular morphology. , uniform in size, close arrangement, good hot spot effect, can effectively improve the intensity of Raman spectrum signal, and silver nanoparticles contain some carbon elements, which can slow down the oxidation of silver nanoparticles, so that the sensor can be stably stored in the air for a period of time time, thereby facilitating the sensor to be used for low-concentration detection of organic dyes in aquaculture and sewage.

Description of drawings

Fig. 1 is the SEM image of the prepared sensor;

Figure 2 is a TEM image of the prepared sensor;

Fig. 3 is the X-ray spectrum of the prepared sensor;

Figure 4 is the EDX image of a single particle in STEM mode; A is the HAADF-STEM, B is the surface scan image of silver, and C is the surface scan image of carbon;

Figure 5 shows the Raman spectra of blank sensors treated at different temperatures; wherein, curve a is the group without high temperature treatment, curve b is the group treated with high temperature at 300°C, and curve c is the group treated with high temperature at 350°C;

Figure 6 shows the Raman spectrum of R6G detected by the sensor after being placed in the air for different days; in which, curve a is the detection result after the sensor is placed in the air for 1 day, curve b is the detection result after the sensor is placed in the air for 30 days, the curve c is the detection result after the sensor is placed in the air for 60 days;

Fig. 7 is the Raman spectrum of the R6G with different concentrations detected by the sensor and the blank sensor; in which, a is the Raman spectrum when the R6G concentration is 10 ^-6 M detected by the sensor, and b is the R6G concentration detected by the sensor at 10 ^-8 M The Raman spectrum at , c is the Raman spectrum when the R6G concentration is 10 ^-9 M detected by the sensor, and d is the Raman spectrum of the blank sensor;

Fig. 8 is the Raman spectrum of using the sensor to detect different concentrations of MB, MG and CV in lake water; in which, A is the detection of MB solutions of different concentrations, B is the detection of MG solutions of different concentrations, and C is the detection of CV solutions of different concentrations; in curve a The concentration of the solution to be tested is 10 ^-3 M, the concentration of the solution to be tested in b is 10 ^-5 M, the concentration of the solution to be tested in c is 10 ^-6 M, and the concentration of the solution to be tested in d is 10 ^-7 M.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

In this example, all chemical reagents are of analytical grade and above. 2-Aminoterephthalic acid, silver nitrate AgNO3, DMF, acetone, isopropanol, ethanol, rhodamine 6G (R6G) were purchased from Sigma Aldrich (Sigma, USA). The deionized water used in the experiment was prepared in real time by the Millipore-Q ultrapure water system (Millipore, USA), and the conductivity was not lower than 18.2 MΩcm.

Preparation of the sensor

Step 1, take 169.87mg (1mmol) of silver nitrate and fully dissolve it in 50mL deionized water, take by weighing 181.15mg (1mmol) of 2-aminoterephthalic acid and dissolve it in 5mL DMF, then use a syringe to dissolve 2- The DMF of aminoterephthalic acid was slowly added into deionized water dissolved with silver nitrate, and heated under reflux at 125° C. for 2 hours to obtain a dispersed black-gray liquid. The obtained solution was centrifuged and washed three times with DMF and ethanol, and vacuum-dried at 60 °C overnight to obtain Ag-MOF as a black-gray solid powder;

Step 2: Use acetone, isopropanol, and ethanol to ultrasonically clean the silicon wafer twice to remove impurities, organics, etc. on the surface of the silicon wafer. Use magnetron sputtering to sputter gold with a thickness of 300 nm on the silicon wafer, and use chromium as the transition layer. , after cutting to get 5mm*5mm gold sheet;

Step 3: Weigh 20mg Ag-MOF, ultrasonically disperse it in 1ml deionized water, take 10ul of the above dispersion, drop it on the surface of the plasma cleaned gold flakes, low speed 900r, high speed 3000r, place it on a 45 ℃ heating table to dry, repeat the above Step spin coat 3 times. The spin-coated substrate was carbonized and reduced at high temperature in a tube furnace, protected by argon gas, raised to 350 °C at a rate of 3 °C/min for 2 h, and cooled to room temperature naturally;

Step 4: Drop the liquid to be tested on the sensor surface, wait for it to dry, and then use the Renishaw inVia Qontor Raman spectrometer for detection. The conditions are: excitation light wavelength 532nm, laser power 1.25mw, and integration time 10s.

Figure 1 is the SEM image of the above sensor, and Figure 2 is the TEM image of the above sensor. It can be seen that it has a hollow nanorod structure, and a large number of dense and uniform particles are distributed on the surface, forming a hot spot, which is conducive to the generation of surface-enhanced Raman effect.

Through the X-ray energy spectrum (XPS) in Figure 3, it can be found that there are obvious C1S, Ag3d, Ag3p3/2, Ag3p1/2, indicating that the sensor has a large number of silver nanoparticles on the surface in addition to carbon.

In Figure 4, EDX elemental analysis in STEM mode is performed on a single particle of the sensor. It can be observed that the particle is composed of silver and a small amount of carbon, which can block the sensor signal attenuation caused by the oxidation of silver in the air.

Comparing Figure 5 with different high-temperature treatment temperatures in step 3, it can be seen that without high-temperature treatment, the blank sensor has more organic functional group peaks in the low-band part of the Raman spectrum. As the temperature of high-temperature treatment increases, the organic functional groups are destroyed. After carbonization and treatment at 350 °C, there are only obvious D peaks and G peaks in the Raman spectrum.

By comparing the detection of 10 ^-6 M R6G aqueous solution after the sensor is placed in the air for different days in Fig. 6, it can be known that the sensor can be stably stored in the air for a period of time.

In the Raman spectrum in Figure 7, it can be seen that the sensor is relatively clean, with less background interference signal, and can detect R6G solution with a concentration of 10-9M, indicating that it has a strong surface-enhanced Raman effect and has a high sensitivity.

From the detection of different concentrations of MB, MG and CV in lake water by the sensor in Figure 8, it can be seen that the sensor can detect MB, MG and CV solutions with a concentration of 10 ^-7 M, which can be used in aquaculture and organic dyes in sewage. Low concentration detection.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (9)

1. a preparation method of a surface-enhanced Raman sensor based on a metal-organic framework structure, is characterized in that, comprises the following steps: Step 1, dissolve silver nitrate in deionized water, dissolve 2-aminoterephthalic acid in DMF solution, then add DMF dissolved with 2-aminoterephthalic acid into deionized water dissolved with silver nitrate, The mixed solution is heated to reflux to obtain a dispersed liquid; In step 2, the dispersion liquid is washed and dried to obtain Ag-MOF solid powder, the Ag-MOF solid powder is dispersed in the solution, and then coated on the surface of the substrate and dried; Step 3, the spin-coated substrate is subjected to high-temperature carbonization reduction, and under the protection of an inert gas, the temperature is raised to a certain temperature, and after maintaining for a period of time, it is naturally cooled to room temperature to obtain a surface-enhanced Raman sensor; The high temperature carbonization reduction temperature range described in step 3 is 200-450 ℃, and the time is 1 to 3 hours. 2. The method for preparing a surface-enhanced Raman sensor based on a metal-organic framework structure according to claim 1, wherein the molar ratio of the silver nitrate and 2-aminoterephthalic acid in step 1 is 1 : 0.5-2. 3 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic framework structure according to claim 1 , wherein, in step 1, the mixed solution is heated and refluxed at 125° C. for 2 hours. 4 . 4 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic framework structure according to claim 1 , wherein in step 2, the dispersion liquid is washed by centrifugation with DMF and ethanol respectively, and vacuum dried at 60° C. 5 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic frame structure according to claim 1 , wherein the substrate in step 2 comprises glass, silicon wafer, and ITO glass. 6 . 6 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic frame structure according to claim 5 , wherein the substrate surface is sputtered by magnetron sputtering with a thickness of 100-1500 nanometers of metal element. 7 . . 7 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic frame structure according to claim 6 , wherein the metal element comprises gold, silver, copper, aluminum, nickel, and chromium. 8 . 8 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic frame structure according to claim 5 , wherein the substrate surface is ultrasonically cleaned with acetone, isopropanol and ethanol before use to remove silicon. 9 . Surface impurities and organic matter. 9 . The method for preparing a surface-enhanced Raman sensor based on a metal-organic frame structure according to claim 1 , wherein the coating method in step 2 comprises drop coating, spin coating, and liquid phase epitaxy. 10 .

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