CN111766230B - Disposable SERS sensor, preparation method thereof and application thereof in fast detection of diquat - Google Patents

Disposable SERS sensor, preparation method thereof and application thereof in fast detection of diquat Download PDF

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CN111766230B
CN111766230B CN202010697168.8A CN202010697168A CN111766230B CN 111766230 B CN111766230 B CN 111766230B CN 202010697168 A CN202010697168 A CN 202010697168A CN 111766230 B CN111766230 B CN 111766230B
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molybdenum disulfide
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CN111766230A (en
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曹玥
蒋巧艳
陈�峰
俞尤嘉
李开
毛征生
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Nanjing Medical University
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    • G01—MEASURING; TESTING
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    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
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Abstract

The invention relates to a preparation method of a SERS sensor, a disposable SERS sensor prepared by the preparation method and application of the SERS sensor. The preparation method comprises the following steps: uniformly mixing the gold nanometer bipyramid aqueous solution and the flaky molybdenum disulfide aqueous solution to obtain a mixed solution; dropwise adding the mixed solution onto the tinfoil, evaporating the solvent, drying and covering a transparent film to obtain an SERS substrate; and assembling the plurality of layers of SERS substrates in a preset container to obtain a finished product of the SERS sensor. The SERS sensor can be used for rapidly detecting diquat with the detection limit as low as 10‑ 15mol·L‑1And the disposable operation can be realized, and the portable field rapid detection device is particularly suitable for portable field rapid detection scenes.

Description

Disposable SERS sensor, preparation method thereof and application thereof in fast detection of diquat
Technical Field
The invention relates to a disposable SERS sensor, in particular to a preparation method of the sensor and application of the sensor in fast detection of diquat, belonging to the technical field of a preparation method of a novel nano functional material and SERS sensing.
Background
As far as the applicant knows, the diquat is a high-efficiency, cheap and conductive nonselective contact type pyridine herbicide, and has the advantages of quick response, good stability and long half-life. The diquat has strong water solubility, and if the diquat is used in an excessive amount and in a large scale for a long time, the diquat can be gradually gathered into a water body through the processes of soil leakage, rainwater rinsing and the like to cause water source pollution, and the United States Environmental Protection Agency (United States Environmental Protection Agency) stipulates that: the content of diquat in drinking water is not higher than 5.52 × 10-8mol/L. The diquat has moderate toxicity, and oral administration, skin, mucosa, respiratory tract and the like are toxic routes, wherein the oral administration is the most common toxic route and the most serious toxic route (the oral lethal dose is 6-12 g). There are cases of fast pesticide poisoning of diquat in clinic, andthe cases (A) have already been subjected to forensic dissection, but no consensus on the fast-acting enemy poisoning has been made, no specific treatment method exists, and no clear treatment consensus exists. Therefore, paraquat poisoning is basically referred to as treatment for diquat poisoning, so that the key of treatment is to discover and treat diquat poisoning as early as possible, reduce the absorption of poisons and increase the excretion. While the pollution of the diquat in the environment (particularly water sources) seems to be negligible, the diquat is finally accumulated in the human body through the biological enrichment effect, and the diquat causes chronic harm to the human body. At present, the common analysis methods of the pesticide diquat are mainly High Performance Liquid Chromatography (HPLC) or liquid chromatography-mass spectrometry (LC-MS), physicochemical analysis, electrochemical analysis and the like. However, these methods have some disadvantages, such as long or complicated sample pretreatment time, long analysis time, low sensitivity, inconvenience for rapid detection on site, etc.
At present, the fast field detection of the diquat mainly depends on surface-enhanced Raman scattering (SERS), the SERS is an analysis technology for characterizing substances adsorbed on the surface of a rough precious metal on a molecular level, and is mainly an abnormal optical enhancement effect of a nanoscale rough surface, and the method has the advantages of high sensitivity, short detection time, small water interference, direct in-situ analysis, wide detection range and the like, does not need a complex pretreatment process, and has wide interest of scholars in many fields such as biomedicine, food safety, environmental analysis and the like. In recent years, with the development of optical fiber sensing technology and the miniaturization of Raman spectrometers, rapid on-site detection by using the SERS technology becomes possible, and the SERS technology has the advantages of high sensitivity, good signal light stability and the like for the detection capability of extremely small-volume samples, so that the SERS technology is gradually developed into one of the most promising technologies in the field of environmental analysis.
However, due to the complexity of contaminants in water, the use of SERS techniques in environmental sample analysis has remained hindered. Firstly, the SERS effect is mainly derived from the enhancement of a local electromagnetic field generated by the surface of a noble metal nanostructure such as gold and silver or the chemical action between the surface of the nanostructure and an adsorbed molecule, and one of the important prerequisites for realizing the application of the SERS technology in environmental analysis is to construct a high-performance SERS sensing nano active substrate and to require that the substrate of the sensor has good anti-interference capability to cope with a changing multi-terminal water environment. Secondly, pure nanoparticles cannot be enriched and cannot amplify the SERS signal to the utmost, so that the detection sensitivity is improved, and the method is well applied to actual environmental detection.
According to the existing reports, although the detection limit of the sample of the diquat in the environment well meets the detection requirement of the diquat in drinking water, along with the attention of people on the environment, the ecology and the body health, the quick detection of the diquat in the environmental water body needs to have a lower detection limit, and the occurrence of the pollution and poisoning events of the diquat is restrained as early as possible at the source.
The invention patent application with the application number of CN201611046690.X and the application publication number of CN106596501A, found by retrieval, discloses a magnetic movable Raman enhancement chip, which comprises an array formed by gold nanoparticles and ferroferric oxide microspheres embedded in the array, wherein the gold nanoparticles are orderly arranged except the part contacted with the ferroferric oxide microspheres in the array, and the chip has no substrate load. The preparation method comprises the following steps: preparing aqueous solution containing gold nanoparticles and sulfhydryl polyethylene glycol compounds, adding ferroferric oxide microspheres, dripping the obtained mixed solution onto the surface of a hydrophobic substrate coated with perfluoropolyether oil with proper viscosity, and drying by a solvent evaporation method to obtain the chip. The chip can be used for detecting diquat, but the detection concentration can be only as low as 1ppb (the level is equivalent to about 10–9M), there is also room for lift.
The invention patent application with the application number of CN201610841261.5 and the application publication number of CN106618577A discloses an optical fiber respiration sensor, and a sensing head of the optical fiber respiration sensor is provided with a sensor based on MoS2An optical fiber sensor of a nano-sheet. However, there is no description of MoS therein2The nanosheet is applied to an SERS sensor.
Disclosure of Invention
The invention aims to: aiming at the problems in the prior art, the preparation method of the SERS sensor and the prepared disposable SERS sensor are provided, the SERS sensor can be used for rapidly detecting diquat, and the detection limit is low.
The technical scheme for solving the technical problems of the invention is as follows:
a preparation method of the SERS sensor is characterized by comprising the following steps:
step one, uniformly mixing a gold nanometer bipyramid aqueous solution and a flaky molybdenum disulfide aqueous solution according to a preset volume ratio to obtain a mixed solution;
secondly, dropwise adding the mixed liquid obtained in the first step onto the tinfoil loaded in a preset container, evaporating the solvent, drying and covering a transparent film to obtain a layer of SERS substrate borne by the tinfoil;
and thirdly, repeating the second step to obtain a plurality of layers of SERS substrates carried by the tinfoil, and assembling the SERS substrates in a preset container in the second step to obtain a finished product of the SERS sensor.
The preparation method is characterized in that a gold nanometer bipyramid (AuBP) material and flaky molybdenum disulfide (MoS) are fixed on a tinfoil (tinfoil) bearing body2) The mixture is used as a SERS substrate (AuBPs @ MoS2@ tinfoil), and after the transparent film is covered, a plurality of layers of SERS substrates can be assembled in the same preset container to obtain a finished SERS sensor (AuBPs @ MoS2@ tinfoil @ box). The SERS sensor can be used for rapidly detecting diquat and has low detection limit; meanwhile, the disposable operation can be realized, the used SERS substrate on the upper layer is taken out and discarded under the condition that the container is not replaced, the unused SERS substrate on the lower layer can be used for next detection, and the disposable SERS substrate is particularly suitable for portable field rapid detection scenes.
The technical scheme of the invention is further perfected as follows:
preferably, in the first step, the preset volume ratio is gold nano bipyramid aqueous solution: 1-2 parts of flaky molybdenum disulfide aqueous solution: 1; the concentration of the gold nanometer bipyramid aqueous solution is 2.5 multiplied by 10-4～8.0×10-4mol·L-1(ii) a The concentration of the flaky molybdenum disulfide aqueous solution is 0.06-1 mg/ml;
in the second step, when the solvent is evaporated, an evaporation environment with the temperature of 25 +/-5 ℃ and the humidity of 50 +/-5% RH is adopted, and the evaporation time is 10 +/-5 minutes; the transparent film is a plastic preservative film.
With this preferred embodiment, the specific parameters of both the first and second critical steps can be further optimized.
Preferably, in the first step, the gold nanopyramids are prepared by a seed-mediated growth method in an aqueous solution by using cetyl trimethyl ammonium bromide as a stabilizer;
the flaky molybdenum disulfide is prepared from LiCl-KCl- (NH)4)6Mo7O24-on the Mo electrode of the KSCN reaction system and prepared by a constant current electrolysis process;
the preparation process of the flaky molybdenum disulfide aqueous solution comprises the following steps: adding the flaky molybdenum disulfide into deionized water, and carrying out ultrasonic treatment for at least 4 hours to obtain the molybdenum disulfide.
By adopting the preferred scheme, the preparation method of the gold nanometer bipyramid used in the first step, the preparation method of the flaky molybdenum disulfide used in the first step and the preparation method of the flaky molybdenum disulfide aqueous solution can be further optimized.
More preferably, the gold nanopyramid aqueous solution is prepared by the following specific steps:
s1, fresh preparation 0.01 mol. L-1Sodium borohydride (NaBH)4) Pre-cooling the solution at 2-6 ℃;
s2, mixing 0.01 mol/L of 0.1-0.15 mL-1Chloroauric acid (HAuCl)4) 0.01 mol. L of 0.2mL to 0.3mL of the solution-1Trisodium citrate (Na)3C6H5O7·2H2O) solution and 9-10 mL deionized water are mixed;
s3, 0.1-0.2 mL of sodium borohydride (NaBH) obtained from S14) The solution is quickly injected into the mixed water solution prepared by S2 to prepare a seed solution;
s4, storing the seed solution prepared in the S3 at room temperature for 2 hours; the room temperature is 10-35 ℃;
s5, mixing 35-45 mL of 0.1 mol/L-1Cetyl Trimethyl Ammonium Bromide (CTAB) solution, 1-3 mL of 0.01 mol/L-1Chloroauric acid (HAuCl)4) 0.01 mol. L of 0.3mL to 0.5mL of the solution-1Silver nitrate (AgNO)3) Solution, 0.7mL to 0.9mL of 1 mol. L-1Hydrochloric acid (H)Cl), 0.25mL to 0.40mL of 0.1 mol/L-1Ascorbic acid (C)6H8O6) Mixing the solutions to prepare a growth solution;
s6, injecting 0.1-0.3 mL of seed solution of S4 into the growth solution of S5, and carrying out mild inversion and uniform mixing for 10-15 seconds;
s7, standing the reaction solution of S6 at room temperature overnight to obtain a gold nanopyracle (AuBP) aqueous solution.
By adopting the preferred scheme, the specific preparation process of the gold nanometer bipyramid aqueous solution can be further optimized.
More preferably, the specific preparation process of the flaky molybdenum disulfide is as follows:
w1, taking LiCl-KCl mixed solution as electrolyte, and adding KSCN, (NH) into positive and negative electrodes respectively4)6Mo7O24The solution and the electrode are made of glass carbon material, the reaction temperature is 800 +/-10 ℃, and the current density is 2.0 +/-0.2A cm-2Preparing nano flaky molybdenum disulfide on a Mo electrode by a constant current electrolysis method;
w2, washing and purifying the black precipitate obtained by electrolysis for multiple times by using distilled water and absolute ethyl alcohol, and finally drying the black precipitate for 1.5 to 3 hours in vacuum at the temperature of 60 +/-5 ℃ to obtain a flaky molybdenum disulfide material;
the specific preparation process of the flaky molybdenum disulfide aqueous solution comprises the following steps:
adding the flaky molybdenum disulfide into deionized water, and carrying out ultrasonic treatment at 25 +/-5 ℃ for at least 4 hours to obtain the molybdenum disulfide.
By adopting the preferred scheme, the specific preparation process of the flaky molybdenum disulfide and the flaky molybdenum disulfide aqueous solution can be further optimized.
Preferably, the preset container in the second step is a self-made box element; the self-made box element comprises a base and a cover plate, wherein one side edge of the base is fixedly connected with one side edge of the cover plate through a hinge, a first buckling edge is arranged on the other side edge of the base, a second buckling edge is arranged on the other side edge of the cover plate, and the first buckling edge is matched with the second buckling edge; the cover plate is a grating plate with a group of sampling holes, and the sampling holes are uniformly distributed on the grating plate;
in the second step, the mixed solution is dripped into the tinfoil from each sample adding hole;
and thirdly, paving a plurality of layers of SERS substrates borne by tinfoil in a base of the self-made box element layer by layer to finish assembly.
By adopting the preferred scheme, the specific structure of the preset container, the dripping process in the second step and the specific assembling process in the third step can be further optimized. The self-made box element can be paved with a plurality of layers of SERS substrates, and the number of samples which can be detected by one box can be greatly increased.
More preferably, the home-made box element has dimensions of: length × width × height ═ 6cm × 6cm × 0.6 cm; the sampling hole is a square hole and the size of the sampling hole is 0.8cm multiplied by 1.0 cm; the number of the sampling holes is 16; the size of the tinfoil loaded in the homemade box element is as follows: length × width is 5cm × 5 cm;
in the second step, when the mixed solution is dripped into the tinfoil, the volume of the mixed solution dripped into each sample adding hole is 10 mu l.
By adopting the preferred scheme, the sizes of all the components and the volume of the mixed solution dropwise added in the second step can be further optimized. Wherein, the SERS substrate layer number of the self-made box element can reach 40 or more.
The invention also proposes:
the disposable SERS sensor is prepared by the preparation method of the SERS sensor.
The sensor can be used for rapidly detecting the diquat and has low detection limit; and can realize the formula operation of can throwing, under the condition of not changing the container, take out the used SERS base of upper story and throw away, can be used for next detection with the SERS base that next floor has not used yet, be particularly useful for portable scene short-term test scene.
The invention also proposes:
the use of the aforementioned disposable SERS sensor for detecting a contaminant in an environmental sample, wherein the contaminant in the environmental sample is aquacide in a water body.
The invention also proposes:
a method for detecting diquat with non-diagnostic purpose is characterized in that the above-mentioned disposable SERS sensor is adopted; the adopted detection method comprises the following steps: dropwise add target sample solution to jettisonable SERS sensor, stand and carry out Raman spectrum after presetting time and detect, detect the parameter and be: the laser wavelength is 785nm, the laser power is 250-300 mw, the integration time, namely the laser action time, is 5-10 s, and each sample is repeatedly tested for 3 times.
The method for developing the synthesis method of the novel nano material and the preparation method of the SERS sensor have important research significance and application value. Gold nanoparticles are particularly concerned compared with other materials, and have the advantages of excellent physical and chemical properties, easily modified surface, lower cytotoxicity and the like. Currently, gold nanospheres (aunps), gold nanorods (aunrs) have been widely used in the field of environmental sensing and biosensing, but researchers found that the tips of gold nanopyramids (aubps) have better SERS enhancement effect. The gold nanometer bipyramid not only has a local electromagnetic field which can be modulated in a near infrared region, but also greatly enhances the strength of a surrounding electromagnetic field by a 'Hot spot' (Hot Spots) with a sharp tip, so that the SERS enhancement effect is better. MoS2The novel nano electronic and optoelectronic properties of a typical layered two-dimensional (2D) chalcogenide material show the feasibility of decorating noble metal nanoparticles on a molybdenum disulfide sheet, and experiments prove that the novel nano electronic and optoelectronic properties of the chalcogenide material can improve the enhanced Raman effect. Tinfoil, an economical and common material, has the main component of metallic aluminum, which has the characteristics of high specific strength, good corrosion resistance, high heat resistance and the like, and aluminum is the most abundant metal in the earth crust, thus making it a potential low-cost and sustainable candidate metal for many plasma applications.
Compared with the prior art, the invention has the following beneficial effects:
(1) the preparation method is simple and convenient to operate. The method is based on the disposable SERS sensor prepared by layer-by-layer self-assembly, can realize high-selectivity and high-sensitivity detection on the actual sample of the aquacide, is green and environment-friendly, has low cost, can be applied to portable field rapid detection, and has potential application prospect.
(2) The self-made box element is adopted, 40 or more layers of SERS substrates can be loaded, the carrying is convenient, a box can measure a large number of samples, the box can be reused, the cost is saved, and the environmental pollution is reduced.
(3) The reproducibility and stability of the SERS sensor are remarkably improved by controlling the mixing ratio, the evaporation temperature, the humidity and the time and covering a protective film, namely the specific parameters of the first step and the second step.
(4) The invention constructs the surface enhanced Raman substrate for diquat detection by combining the gold nano bipyramid material, the flaky molybdenum disulfide material and the tinfoil, can enhance the detection sensitivity and reduce the detection limit (10)-15mol·L-1) And a new platform with huge potential is provided for the detection and analysis of the diquat molecules in the environmental sample.
Drawings
Fig. 1 is a schematic main flow chart of embodiment 1 of the present invention.
FIG. 2 shows a mixed solution (AuBPs @ MoS) prepared in example 1 of the present invention2(Mixing)) electron microscopy scanning of the images.
FIG. 3 is a schematic view showing the developed state of the homemade box member in example 1 of the present invention.
FIG. 4 is a Raman spectrum of example 2 of the present invention.
FIG. 5 is a Raman spectrum and a line-fit chart of example 3 of the present invention.
FIG. 6 is a Raman spectrum of example 4 of the present invention.
Detailed Description
The invention is described in further detail below with reference to embodiments and with reference to the drawings. The invention is not limited to the examples given.
Example 1
The embodiment is a method for preparing a SERS sensor, as shown in fig. 1, and the method includes the following steps:
firstly, uniformly mixing a gold nanometer bipyramid (AuBP) aqueous solution and a flaky molybdenum disulfide aqueous solution according to a preset volume ratio to obtain a mixed solution (AuBPs @ MoS)2(Mixing)); wherein the preset volume ratio is gold nanometer bipyramid water solution: 1, flaky molybdenum disulfide aqueous solution: 1; the concentration of the gold nanometer bipyramid aqueous solution is 5.0 multiplied by 10-4mol·L-1(ii) a The concentration of the flaky molybdenum disulfide aqueous solution is 0.08 mg/ml. The scanning image of the mixture in the electron microscope is shown in FIG. 2.
Secondly, dropwise adding the mixed liquid obtained in the first step onto tinfoil (tinfoil) loaded in a preset container, evaporating the solvent, drying and covering a transparent film to obtain a layer of SERS substrate (AuBPs @ MoS2@ tinfoil) borne by the tinfoil; wherein, when the solvent is evaporated, an evaporation environment with the temperature of 25 ℃ and the humidity of 50% RH is adopted, and the evaporation time is 10 minutes; the transparent film is a plastic preservative film.
And thirdly, repeating the second step to obtain a plurality of layers of SERS substrates carried by the tinfoil, and assembling the SERS substrates in a preset container in the second step to obtain a finished SERS sensor (AuBPs @ MoS2@ tinfoil @ box).
Specifically, in the first step, the gold nanopyramid is prepared by a seed-mediated growth method in an aqueous solution by using hexadecyl trimethyl ammonium bromide as a stabilizer; the flaky molybdenum disulfide is prepared from LiCl-KCl- (NH)4)6Mo7O24-on the Mo electrode of the KSCN reaction system and prepared by a constant current electrolysis process; the preparation process of the flaky molybdenum disulfide aqueous solution comprises the following steps: adding the flaky molybdenum disulfide into deionized water, and carrying out ultrasonic treatment for 4 hours to obtain the molybdenum disulfide.
For example, the specific preparation process of the gold nanopyramids is as follows:
s1, fresh preparation 0.01 mol. L-1Sodium borohydride (NaBH)4) Pre-cooling the solution at 4 ℃;
s2, mixing 0.125mL of 0.01 mol. L-1Chloroauric acid (HAuCl)4) 0.25mL of 0.01 mol. L-1Trisodium citrate (Na)3C6H5O7·2H2O) solution and 9.625mL deionized water are mixed;
s3, 0.15mL of sodium borohydride (NaBH) obtained in S14) Quickly injecting the mixture into the mixed aqueous solution prepared in S2 to prepare a seed solution;
s4, storing the seed solution prepared in the S3 at room temperature for 2 hours; the room temperature is 10-35 ℃;
s5, mixing 40mL of 0.1 mol. L-1Hexadecyl radicalTrimethyl Ammonium Bromide (CTAB) solution, 2mL of 0.01 mol. L-1Chloroauric acid (HAuCl)4) 0.4mL of 0.01 mol. L solution-1Silver nitrate (AgNO)3) Solution, 0.8mL of 1 mol. L-1Hydrochloric acid (HCl) solution, 0.32mL of 0.1 mol. L-1Ascorbic acid (C)6H8O6) Mixing the solutions to prepare a growth solution;
s6, injecting 0.2mL of S4 seed solution into the growth solution of S5, and carrying out gentle inversion and uniform mixing for 10 seconds;
s7, standing the reaction solution of S6 at room temperature overnight to obtain a gold nanopyracle (AuBP) aqueous solution.
For another example, the specific preparation process of the flaky molybdenum disulfide comprises the following steps:
w1, taking LiCl-KCl mixed solution as electrolyte, and adding KSCN, (NH) into positive and negative electrodes respectively4)6Mo7O24The solution, the electrode are glass carbon material, the reaction temperature is 800 ℃, and the current density is 2.0A cm-2Preparing nano flaky molybdenum disulfide on a Mo electrode by a constant current electrolysis method;
w2, washing the black precipitate obtained by electrolysis with distilled water and absolute ethyl alcohol for multiple times, purifying, and finally drying in vacuum at 60 ℃ for 2 hours to obtain the flaky molybdenum disulfide material.
For another example, the specific preparation process of the flaky molybdenum disulfide aqueous solution comprises the following steps: adding 0.8mg of flaky molybdenum disulfide into 10ml of deionized water, and placing the mixture in water at 25 ℃ for ultrasonic treatment for 4 hours to obtain the molybdenum disulfide.
Specifically, the preset container in the second step is a self-made box element; as shown in fig. 3, the self-made box element comprises a base 01 and a cover plate 02, wherein one side edge of the base 01 is fixedly connected with one side edge of the cover plate 02 through a hinge 03, the other side edge of the base 01 is provided with a first buckle edge 04, the other side edge of the cover plate 02 is provided with a second buckle edge 05, and the first buckle edge 04 is matched with the second buckle edge 05; the cover plate 02 is a grid plate with a group of sampling holes 06, and the sampling holes 06 are uniformly distributed on the grid plate. In the second step, the mixed solution is dripped into the tinfoil from each sample adding hole; and thirdly, paving a plurality of layers of SERS substrates borne by tinfoil in a base of the self-made box element layer by layer to finish assembly.
For example, the dimensions of the homemade box element are: length × width × height ═ 6cm × 6cm × 0.6 cm; the sampling hole is a square hole and the size is 0.8cm multiplied by 1.0 cm; the number of the sampling holes is 16; the size of the tinfoil loaded in the homemade box element is as follows: length × width is 5cm × 5 cm. In the second step, when the mixed solution is dripped into the tinfoil, the volume of the mixed solution dripped into each sample adding hole is 10 mu l.
During detection, 5 mul of target sample solution is dripped into the box through the sample adding hole, the box is kept stand for 5min, and then the Raman spectrum is detected, wherein the detection parameters are as follows: the laser wavelength was 785nm, the laser power was 300mw, the integration time (laser action time) was 10s, and the test was repeated 3 times for each sample.
Example 2
This example is to verify the feasibility and specificity of the rapid detection of the disposable SERS sensor prepared in example 1 in diquat.
Example a: this example is the finished disposable SERS sensor made in example 1.
Example b: this example used the preparation method of example a, only the tinfoil in the second step was changed to a silicon wafer, and finally the finished product of this example for comparison was obtained.
Example c: this example used the preparation of example a, except that the mixed liquor in the first step was changed to an aqueous AuBPs solution with deionized water at a volume ratio of 1: 1, and finally the final product of this example was prepared for comparison.
Example d: in this example, the preparation method of example a was used, and only the mixed solution in the first step was changed to a flaky aqueous solution of molybdenum disulfide and deionized water in a volume ratio of 1: 1, and finally the final product of this example was prepared for comparison.
Example e: this example used the preparation of example a, eliminating the first and second steps, and assembling only the tinfoil into a box element without any liquid adhering to the tinfoil, and finally making the finished product of this example for comparison.
And (3) respectively dripping 5 mu l of the same target sample solution into the box through a sample adding hole by adopting the finished products of the examples a to e, standing for 5min, and then detecting the Raman spectrum, wherein the detection parameters are as follows: the laser wavelength was 785nm, the laser power was 300mw, the integration time (laser action time) was 10s, and the test was repeated 3 times for each sample. The obtained raman spectra are shown in fig. 4 a to e.
Example f: the raman spectrum was directly detected using the finished product of example a without any sample, with the following detection parameters: the laser wavelength was 785nm, the laser power was 300mw, the integration time (laser action time) was 10s, and the examination was repeated 3 times. The obtained raman spectrum is shown in f of fig. 4.
Example g: the raman spectrum was directly measured using the finished product of example c without any sample, with the same measurement parameters as in example f. The obtained Raman spectrum is shown in g of FIG. 4.
Example h: the raman spectrum was directly measured using the finished product of example d without any sample, with the same measurement parameters as in example f. The obtained Raman spectrum is shown in h of FIG. 4.
Example i: the raman spectrum was directly measured using the finished product of example e without any sample, with the same measurement parameters as in example f. The obtained raman spectrum is shown as i in fig. 4.
From the above results, the disposable SERS sensor of example 1 has feasibility and specificity for rapid detection in diquat, and the Raman characteristic peak (Raman Shift) of the diquat sample is: 733cm-1，1071cm-1，1178cm-1，1320cm-1，1523cm-1，1570cm-1。
Example 3
In this embodiment, the disposable SERS sensor prepared in embodiment 1 is used to detect the concentration gradient of the diquat molecules, thereby verifying the sensitivity of the disposable SERS sensor in detecting the diquat molecules.
A disposable SERS sensor was prepared using example 1; preparing a series of diquat molecular standard solutions, wherein the base solution is deionized water and has a concentration range of 10-6-10-15mol·L-1. During detection, 5 mu l of sample solution is dripped into the box through the sample adding hole, stands for 5min and then detects the Raman spectrum. The parameters in the detection of the Raman spectrum are set as follows: the laser wavelength is 785nm, the laser power is 300mw, and the integration time (laser action time) isThe test was repeated 3 times for each sample for 10 s. The Raman spectrum is shown in graph A of FIG. 5.
Drawing a working curve: different concentrations (10)-6-10-15mol·L-1) Recording the response Raman spectrum Intensity of the diquat molecular standard solution as Intensity, and drawing an I-LogC working curve, wherein the Intensity is in a linear relation with the mass concentration c of the diquat molecular standard solution; the parameters in the detection of the Raman spectrum are set as follows: the laser wavelength was 785nm, the laser power was 300mw, the integration time (laser action time) was 10s, and the test was repeated 3 times for each sample.
The results show that the disposable SERS sensor prepared in example 1 has a paraquat content of 10-6-10-15mol·L-1Has good linear relation in the range and the detection limit is 10-15mol·L-1And the detection sensitivity is high.
Wherein, the Raman characteristic peak (Raman Shift) is as follows:
733cm-1r of (A) to (B)20.9937 (concentration range 10)-6-10-15mol·L-1)，
1071cm-1R of (A) to (B)20.9929 (concentration range 10)-6-10-15mol·L-1)，
1178cm-1R of (A) to (B)20.9910 (concentration range 10)-6-10-15mol·L-1)，
1320cm-1R of (A) to (B)20.9928 (concentration range 10)-6-10-15mol·L-1)，
1523cm-1R of (A) to (B)20.9900 (concentration range 10)-6-10-15mol·L-1)，
1570cm-1R of (A) to (B)20.9903 (concentration range 10)-6-10-15mol·L-1) See, in particular, diagram B of fig. 5.
Example 4
This example illustrates the detection of an actual sample by the disposable SERS sensor of example 1.
When the disposable SERS sensor prepared in example 1 is used for SERS detection, 5 μ l of sample solution is dripped into a box through a sample adding hole, the box is kept stand for 5min, and then a Raman spectrum is detected. The parameters in the detection of the Raman spectrum are set as follows: the laser wavelength was 785nm, the laser power was 300mw, the integration time (laser action time) was 10s, and the test was repeated 3 times for each sample.
First, SERS detection was performed on the following samples to investigate possible presence of diquat molecules in water samples: deionized water prepared in a laboratory, tap water in a certain area, and an actual surface water sample in a certain lake. The results are shown in d, e and f in a diagram of fig. 6, and it can be seen that none of the 3 water samples has SERS response, which indicates that the concentration of diquat molecules in deionized water and actual water samples is low or even extremely low.
Then, the experiment was continued by adding the same concentration (10) to each sample-6mol·L-1) Respectively carrying out SERS detection on the samples of diquat. The results are shown in a, B and c in graph a of fig. 6 and graph B of fig. 6, and show that the detection results, such as SERS peak shift and peak intensity, of diquat molecules at the same concentration in different samples are not very different.
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.

Claims (7)

1. A preparation method of the SERS sensor is characterized by comprising the following steps:
step one, uniformly mixing a gold nanometer bipyramid aqueous solution and a flaky molybdenum disulfide aqueous solution according to a preset volume ratio to obtain a mixed solution;
secondly, dropwise adding the mixed liquid obtained in the first step onto the tinfoil loaded in a preset container, evaporating the solvent, drying and covering a transparent film to obtain a layer of SERS substrate borne by the tinfoil;
thirdly, repeating the second step to obtain a plurality of layers of SERS substrates carried by the tinfoil, and paving and assembling the SERS substrates in the preset container in the second step layer by layer to obtain a finished SERS sensor;
in the first step, the preset volume ratio is gold nanometer bipyramid water solution: flake disulfide1-2 parts of a molybdenum aqueous solution: 1; the concentration of the gold nanometer bipyramid aqueous solution is 2.5 multiplied by 10-4～8.0×10-4mol·L-1(ii) a The concentration of the flaky molybdenum disulfide aqueous solution is 0.06-1 mg/ml;
the gold nanometer bipyramid is prepared by a seed-mediated growth method in aqueous solution by using hexadecyl trimethyl ammonium bromide as a stabilizer;
the flaky molybdenum disulfide is prepared from LiCl-KCl- (NH)4)6Mo7O24-on the Mo electrode of the KSCN reaction system and prepared by a constant current electrolysis process; the specific preparation process of the flaky molybdenum disulfide comprises the following steps:
w1, using LiCl-KCl mixed solution as electrolyte, adding KSCN solution into positive pole, adding (NH) into negative pole4)6Mo7O24The solution, the anode electrode is a glass carbon material, the reaction temperature is 800 +/-10 ℃, and the current density is 2.0 +/-0.2A cm-2Preparing nano flaky molybdenum disulfide on a cathode Mo electrode by a constant current electrolysis method;
w2, washing and purifying the black precipitate obtained by electrolysis for multiple times by using distilled water and absolute ethyl alcohol, and finally drying the black precipitate for 1.5 to 3 hours in vacuum at the temperature of 60 +/-5 ℃ to obtain a flaky molybdenum disulfide material;
the specific preparation process of the flaky molybdenum disulfide aqueous solution comprises the following steps:
adding the flaky molybdenum disulfide into deionized water, and carrying out ultrasonic treatment at 25 +/-5 ℃ for at least 4 hours to obtain the molybdenum disulfide;
in the second step, when the solvent is evaporated, an evaporation environment with the temperature of 25 +/-5 ℃ and the humidity of 50 +/-5% RH is adopted, and the evaporation time is 10 +/-5 minutes; the transparent film is a plastic preservative film.
2. The method for preparing the SERS sensor according to claim 1, wherein the gold nano-bipyramid aqueous solution is prepared by the following steps:
s1, fresh preparation 0.01 mol. L-1Pre-cooling the sodium borohydride solution at 2-6 ℃;
s2, mixing 0.01 mol/L of 0.1-0.15 mL-10.2-0.3 mL of chloroauric acid solution.01mol·L-1Mixing trisodium citrate solution with 9-10 mL of deionized water;
s3, quickly injecting 0.1-0.2 mL of the sodium borohydride solution obtained from S1 into the mixed aqueous solution prepared from S2 to prepare a seed solution;
s4, storing the seed solution prepared in the S3 at room temperature for 2 hours; the room temperature is 10-35 ℃;
s5, mixing 35-45 mL of 0.1 mol/L-1Cetyl trimethyl ammonium bromide solution, 1-3 mL of 0.01 mol. L-10.01 mol/L of 0.3 mL-0.5 mL of chloroauric acid solution-1Silver nitrate solution, 0.7 mL-0.9 mL of 1 mol. L-10.1 mol. L of 0.25mL to 0.40mL of hydrochloric acid solution-1Mixing ascorbic acid solutions to prepare a growth solution;
s6, injecting 0.1-0.3 mL of seed solution of S4 into the growth solution of S5, and carrying out mild inversion and uniform mixing for 10-15 seconds;
and S7, standing the reaction solution of S6 at room temperature for one night to obtain the gold nano bipyramid aqueous solution.
3. The method of preparing a SERS sensor according to claim 1, wherein the predetermined container in the second step is a self-made box; the self-made box element comprises a base and a cover plate, wherein one side edge of the base is fixedly connected with one side edge of the cover plate through a hinge, a first buckling edge is arranged on the other side edge of the base, a second buckling edge is arranged on the other side edge of the cover plate, and the first buckling edge is matched with the second buckling edge; the cover plate is a grating plate with a group of sampling holes, and the sampling holes are uniformly distributed on the grating plate;
in the second step, the mixed solution is dripped into the tinfoil from each sample adding hole;
and thirdly, paving a plurality of layers of SERS substrates borne by tinfoil in a base of the self-made box element layer by layer to finish assembly.
4. The method for preparing a SERS sensor according to claim 3, wherein the home-made box element has the following dimensions: length × width × height ═ 6cm × 6cm × 0.6 cm; the sampling hole is a square hole and the size of the sampling hole is 0.8cm multiplied by 1.0 cm; the number of the sampling holes is 16; the size of the tinfoil loaded in the homemade box element is as follows: length × width is 5cm × 5 cm;
in the second step, when the mixed solution is dripped into the tinfoil, the volume of the mixed solution dripped into each sample adding hole is 10 mu l.
5. A disposable SERS sensor prepared by the method of preparing a SERS sensor as claimed in any one of claims 1 to 4.
6. Use of the disposable SERS sensor of claim 5 to detect a contaminant in an environmental sample that is diquat in a body of water.
7. A method of detecting diquat for non-diagnostic purposes, wherein the disposable SERS sensor of claim 5 is used; the adopted detection method comprises the following steps: dropwise add target sample solution to jettisonable SERS sensor, stand and carry out Raman spectrum after presetting time and detect, detect the parameter and be: the laser wavelength is 785nm, the laser power is 250-300 mw, the integration time, namely the laser action time, is 5-10 s, and each sample is repeatedly tested for 3 times.
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