Au NPs / MXene / WS2 composite material, preparation method thereof and sensor

Abstract

The invention belongs to the technical field of food safety detection, and particularly relates to an Au NPs / MXene / WS2 composite material, a preparation method thereof and a sensor. The Au NPs / MXene / WS2 composite material comprises an MXene matrix, the MXene matrix is of a multi-layer organ-shaped structure, wrinkled WS2 nanosheets are loaded between layers of the MXene matrix, and an MXene / WS2 substrate is formed; gold nanoparticles are loaded on the surface of the MXene / WS2 substrate; wherein the particle size of the gold nanoparticles ranges from 100 nm to 150 nm. The photoelectrochemical sensor prepared on the basis of the Au NPs / MXene / WS2 composite material has the advantages of separation of an input signal and an output signal, simplicity in operation and easiness in miniaturization, and meets the requirement of on-site rapid detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of food safety detection, and specifically relates to an Au NPs / MXene / WS2 composite material and a preparation method and a sensor thereof. Background Art

[0002] Staphylococcus aureus is a common foodborne pathogen that exists in cooked food and its processing stage. Ingestion of contaminated food can cause food poisoning and infection. Staphylococcus aureus can infect a variety of livestock (pigs, cattle, sheep, deer), poultry (chickens, ducks, geese) and even humans. Severe infections can also cause clinical symptoms such as sepsis, pneumonia, mastitis, endometritis, diarrhea, suppuration and toxin-induced shock in animals, and even cause food poisoning in humans, seriously endangering animal and human health. In recent years, there have been more and more reports on diseases caused by Staphylococcus aureus, so rapid and reliable detection of this bacterium is of great significance for the prevention and control of Staphylococcus aureus.

[0003] The national standard detection method for Staphylococcus aureus is the plate colony count method. Other common detection methods include polymerase chain reaction, hybridization chain reaction, rolling circle nucleic acid amplification technology, loop-mediated isothermal amplification technology, and enzyme-linked immunosorbent assay technology. These methods have limitations such as long time consumption, expensive equipment, and harsh reaction conditions. Many countries and organizations have strict regulations on the limit of Staphylococcus aureus in food. For example, in many food safety standards formulated by the Codex Alimentarius Commission and the World Health Organization, the limit of Staphylococcus aureus is stipulated as: no more than 100 (CFU / g) in food. Therefore, in order to ensure the safety of food, drugs and public health, it is urgent to establish a rapid, accurate and sensitive method for detecting Staphylococcus aureus.

[0004] The prior art also provides some sensors for detecting Staphylococcus aureus. For example, Chinese patent CN202410458222.1 provides a system and method for detecting Staphylococcus aureus based on nucleic acid aptamers and tree-like CRISPR signal amplification. The CRISPR / Cas12a system used is combined with a hyperbranched hybridization chain reaction to form a dual signal amplification system, thereby achieving highly sensitive detection of Staphylococcus aureus in food.

[0005] Chen Xiaomei et al. (Dai H, Yin M, Zhang S, et al. A paper-based photoelectrochemical aptsensor using near-infrared light-responsive AgBiS2 nanoflowers as probes for the detection of Staphylococcus aureus in pork [J]. Talanta, 2024, 266: 125128.) used amino-functionalized AgBiS2 nanoflowers (NH2–AgBiS2 NFs) modified carboxyl-functionalized aptamers for highly specific capture of Staphylococcus aureus. The sensor has a range of 20 CFU / mL to 2×10 7 The wide linear range of CFU / mL and the low detection limit of 4 CFU / mL. However, when the composite materials in the prior art including the above scheme are used to detect Staphylococcus aureus, their detection sensitivity still needs to be improved. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an Au NPs / MXene / WS2 composite material and a preparation method and sensor thereof to improve the sensitivity and stability of Staphylococcus aureus detection. The present invention uses MXene as a matrix, loads wrinkled WS2 nanosheets between layers of a MXene matrix with a multi-layer accordion-like structure to form a MXene / WS2 substrate; and loads gold nanoparticles on the surface of the MXene / WS2 substrate to obtain an Au NPs / MXene / WS2 composite material with excellent photoelectric properties, which is used to modify the sensing interface, enhance the photoelectric signal conversion efficiency and photoelectric signal response, and effectively solve the problems of low sensitivity and slow detection speed of traditional detection methods.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] The first object of the present invention is to provide an Au NPs / MXene / WS2 composite material, wherein the Au NPs / MXene / WS2 composite material includes a MXene matrix, the MXene matrix is ​​a multi-layer accordion-like structure, and the MXene matrix is ​​loaded with wrinkled WS2 nanosheets between layers to form a MXene / WS2 substrate; and gold nanoparticles are loaded on the surface of the MXene / WS2 substrate; wherein the particle size of the gold nanoparticles is 100nm to 150nm.

[0009] The second object of the present invention is to provide a method for preparing the above-mentioned Au NPs / MXene / WS2 composite material, comprising the following steps:

[0010] S1. Add MXene to sulfur source and tungsten source, and react by solvothermal method at 190℃~210℃ to make wrinkled WS2 nanosheets grow and load between MXene layers to obtain MXene / WS2 composite material.

[0011] S2. The MXene / WS2 composite material is dissolved in a solvent, a gold source is added and mixed, and then a self-reduction reaction is performed to make the gold nanoparticles grow evenly and load on the MXene / WS2 composite material to obtain the Au NPs / MXene / WS2 composite material.

[0012] Furthermore, the mass molar ratio of MXene / WS2 composite material to gold nanoparticles in the Au NPs / MXene / WS2 composite material is 1 mg:4×10 -5 mmol~2×10 -4 mmol, and the self-reduction reaction time is 10min~60min.

[0013] Furthermore, the mass ratio of MXene, sulfur source, and tungsten source is 1:0.5-2:0.3-1, the sulfur source is thioacetamide, and the solvothermal reaction time is 18h-24h.

[0014] Furthermore, the preparation method of the MXene comprises the following steps:

[0015] Lithium fluoride and hydrochloric acid are fully mixed at room temperature to form a mixture, Ti3AlC2 solution is added to the mixture, and the Al layer in Ti3AlC2 is etched by the mixture under stirring at 35°C. After etching, MXene powder is obtained by centrifugation, washing and drying.

[0016] Among them, the mass volume ratio of lithium fluoride and hydrochloric acid is 1g:20mL, the concentration of hydrochloric acid is 6M, and the mass ratio of lithium fluoride and Ti3AlC2 is 1:1.

[0017] The third object of the present invention is to provide a sensor prepared using the above-mentioned Au NPs / MXene / WS2 composite material.

[0018] Furthermore, the sensor is a photoelectrochemical sensor.

[0019] Furthermore, the photoelectrochemical sensor comprises:

[0020] A substrate and an electrode layer attached to the substrate, wherein the electrode layer comprises a working electrode layer.

[0021] The surface of the working electrode layer is coated with Au NPs / MXene / WS2 composite material, ssDNA, 6-mercaptohexanol and nucleic acid aptamer Apt-Fc in sequence.

[0022] Furthermore, the nucleotide sequence of the ssDNA is: 5'-GTA CCG TAC CATTGC TAG CGT CTTCCC GT-3'.

[0023] Furthermore, the nucleotide sequence of the nucleic acid aptamer Apt-Fc is: 5'-Fc-GCA ATG GTA CGG TACTTC CTC GGC ACG TTC TCA GTA GCG CTC GCT GGT CAT CCC ACA GCT ACG TCA AAA GTGCAC GCT ACTTTG CTA A-3'.

[0024] Furthermore, the method for detecting Staphylococcus aureus by the sensor comprises the following steps:

[0025] The photocurrent intensity of solution samples containing different known concentrations of Staphylococcus aureus was detected by a photoelectric sensor, and a detection linear response relationship between Staphylococcus aureus concentration and photocurrent intensity was constructed. The curve with the highest fitting degree was selected as the standard curve for Staphylococcus aureus detection.

[0026] The linear regression equation for the detection of Staphylococcus aureus concentration and photocurrent intensity is: y = 0.7796LgC + 0.636, C is the concentration of Staphylococcus aureus in the sample to be tested, y is the photocurrent intensity, and the detection range is 10 CFU / mL to 10 7 CFU / mL, and the detection limit was 2.9 CFU / mL.

[0027] The concentration of Staphylococcus aureus in the sample to be tested is obtained according to the obtained detection linear regression equation and the measured photocurrent intensity of the sample to be tested.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention uses a MXene matrix with a multi-layer accordion-like structure, and loads wrinkled WS2 nanosheets between the MXene matrix layers to form a MXene / WS2 substrate, and loads gold nanoparticles on the surface of the MXene / WS2 substrate to form an Au NPs / MXene / WS2 composite material, wherein WS2 is a transition metal sulfide compound with good light absorption ability, which can effectively inhibit the recombination of photogenerated carriers when used as a photoelectric active material; (2) MXene has a unique two-dimensional layered structure and high electron transport capacity; and due to its high light stability and absorption coefficient, it can effectively enhance the utilization rate of visible light. (3) The addition of MXene constructs a MXene / WS2 Schottky junction, which can improve the electron-hole separation efficiency and enhance the photoelectric conversion efficiency of WS2. (4) The LSPR effect of Au NPs can inject hot electrons into the conduction band of MXene / WS2, further promoting the enhancement of the photoelectric signal. The Au NPs / MXene / WS2 composite material was prepared with excellent photoelectric properties. It was used to modify the sensing interface, enhance the photoelectric signal conversion efficiency and photoelectric signal response, and effectively solve the problems of low sensitivity and slow detection speed of traditional detection methods.

[0030] (2) The present invention uses MXene as the substrate of the composite material, and synthesizes the Au NPs / MXene / WS2 composite material by solvothermal method and self-reduction reaction. The preparation method is simple and the reaction conditions are mild. The layered structure of the edge of the MXene material is complete and has a multi-layer accordion-like structure, which provides favorable conditions for loading WS2. The gold nanoparticles (Au NPs) are uniformly dispersed on the surface of MXene / WS2 through the self-reduction reaction. The growth size of Au NPs is relatively uniform, which can further improve the photoelectric performance of the composite material. The photoelectrochemical sensor based on the Au NPs / MXene / WS2 composite material has the advantages of separation of input signal and output signal, simple operation, and easy miniaturization, which meets the needs of rapid on-site detection.

[0031] (3) The present invention is based on the photoelectrochemical sensor prepared from the Au NPs / MXene / WS2 composite material. The photoelectrochemical sensor has the advantages of separation of input and output signals, simple operation, and easy miniaturization, which meets the needs of rapid on-site detection. It can quickly, accurately and reliably detect trace amounts of Staphylococcus aureus in food, effectively solving the problem of poor timeliness of traditional detection methods, providing convenience for the rapid sale of short-shelf-life food in the market, helping to ensure food safety and protect public health. This method has broad application prospects and can provide simple, economical, rapid and effective technical support for food safety detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1Schematic diagram of the principle of the photoelectric chemical sensor of the present invention for detecting Staphylococcus aureus.

[0033] Figure 2 This is a morphology and structure diagram of MXene in Example 2 of the present invention.

[0034] Figure 3 This is a morphology structure diagram of the composite material of MXene / WS2 in Example 2 of the present invention.

[0035] Figure 4 This is the morphology and structure diagram of the Au NPs / MXene / WS2 composite material of Example 2 of the present invention.

[0036] Figure 5 This is a photoelectric response curve of the Au NPs / MXene / WS2 composite material in Example 2 of the present invention.

[0037] Figure 6 This is the X-ray photoelectron energy spectrum of the Au NPs / MXene / WS2 composite material of Example 2 of the present invention.

[0038] Figure 7 It is the time-current curve diagram of the sensor corresponding to different concentrations of Staphylococcus aureus of the present invention.

[0039] Figure 8 It is a linear fitting curve diagram of the concentration value of Staphylococcus aureus with different concentrations and the photocurrent of the present invention.

[0040] Fig. 9 This is a graph showing the stability test results of the photoelectrochemical sensor provided by the present invention.

[0041] Fig.10 This is a diagram showing the selectivity test results of the photoelectrochemical sensor provided by the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0044] In recent years, there have been more and more reports on diseases caused by Staphylococcus aureus. In order to ensure the safety of food, medicine and public health, there is an urgent need to establish a rapid, accurate and sensitive method for detecting Staphylococcus aureus.

[0045] Existing technologies such as Chen Xiaomei et al. (Dai H, Yin M, Zhang S, et al. A paper-based photoelectrochemical aptsensor using near-infrared light-responsive AgBiS2 nanoflowers as probes for the detection of Staphylococcus aureus in pork [J]. Talanta, 2024, 266: 125128.) use amino-functionalized AgBiS2 nanoflowers (NH2–AgBiS2 NFs) modified carboxyl-functionalized aptamers for highly specific capture of Staphylococcus aureus. The sensor has a range of 20 CFU / mL to 2×10 7 The wide linear range of CFU / mL and the low detection limit of 4 CFU / mL. However, the sensitivity of the composite material in the above scheme for detecting Staphylococcus aureus still needs to be improved.

[0046] Based on the above problems, on the one hand, the present invention provides an Au NPs / MXene / WS2 composite material, wherein the AuNPs / MXene / WS2 composite material includes a MXene matrix, wherein the MXene matrix is ​​a multi-layer accordion-like structure, and the MXene matrix is ​​loaded with wrinkled WS2 nanosheets between layers to form a MXene / WS2 substrate; and gold nanoparticles are loaded on the surface of the MXene / WS2 substrate; wherein the particle size of the gold nanoparticles is 100nm to 150nm.

[0047] Among them, the Au NPs / MXene / WS2 composite material provided by the present invention has a MXene matrix with a multi-layer accordion-like structure, and wrinkled WS2 nanosheets are loaded between the layers of the MXene matrix to form a MXene / WS2 substrate, and gold nanoparticles are loaded on the surface of the MXene / WS2 substrate to form an Au NPs / MXene / WS2 composite material, which has the following advantages: (1) WS2 is a transition metal sulfide compound with good light absorption ability, which can effectively inhibit the recombination of photogenerated carriers when used as a photoelectric active material; (2) MXene has a unique two-dimensional layered structure and high electron transport capacity; and due to its high light stability and absorption coefficient, it can effectively enhance the utilization rate of visible light. (3) The addition of MXene constructs a MXene / WS2 Schottky junction, which can improve the electron-hole separation efficiency and enhance the photoelectric conversion efficiency of WS2. (4) The LSPR effect of Au NPs can inject hot electrons into the conduction band of MXene / WS2, further promoting the enhancement of photoelectric signals.

[0048] On the other hand, the present invention provides a method for preparing the above-mentioned Au NPs / MXene / WS2 composite material, comprising the following steps:

[0049] S1. Add MXene to sulfur source and tungsten source, and perform solvothermal reaction at 190℃~210℃ to make wrinkled WS2 nanosheets grow and load between MXene layers. After the solvothermal reaction, centrifuge and dry to obtain MXene / WS2 composite material.

[0050] S2. The MXene / WS2 composite material is dissolved in a solvent, a gold source is added and mixed, and then a self-reduction reaction is performed to make the gold nanoparticles grow evenly and load on the MXene / WS2 composite material to obtain the Au NPs / MXene / WS2 composite material.

[0051] The present invention uses MXene as the substrate of the composite material, and synthesizes the AuNPs / MXene / WS2 composite material by solvothermal method and self-reduction reaction. The preparation method is simple and the reaction conditions are mild. The layered structure at the edge of the MXene material is complete and has a multi-layer accordion-like structure, which provides favorable conditions for loading WS2. The Au NPs are uniformly dispersed on the surface of the MXene / WS2 through the self-reduction reaction. The growth size of the Au NPs is relatively uniform, which can further improve the photoelectric performance of the composite material and be used to modify the sensing interface and enhance the photoelectric signal conversion efficiency and photoelectric signal response.

[0052] It should be noted that the MXene / WS2 prepared in the present invention is solid powder, Au NPs are gold nanoparticles, and the source of AuNPs is not limited, for example, it can be prepared using gold acid or salt solution as a raw material. The solvent is only used to make the MXene / WS2 composite material form a uniform solution and then undergo a self-reduction reaction with the gold source, and the solvent does not participate in the reaction. Preferably, the solvent is water, more preferably ultrapure water.

[0053] In some specific embodiments, the gold source is chloroauric acid, and the gold source is a chloroauric acid solution with a molar concentration of 10 mM.

[0054] In some specific embodiments, the mass molar ratio of the MXene / WS2 composite material to the AuNPs in the AuNPs / MXene / WS2 composite material is 1 mg:4×10 -5 mmol~2×10 -4 mmol, and the self-reduction reaction time is 10min to 60min. Preferably, the composite material is composed of MXene / WS2 and Au NPs at a ratio of 4mg:4×10 -4 The composite material is prepared by a reaction ratio of 100 mmol, and the average length of the tungsten sulfide nanosheets is about 200 nm, and the average particle size of Au NPs is about 120 nm.

[0055] In some specific embodiments, the mass ratio of MXene, sulfur source and tungsten source is 1:0.5-2:0.3-1, the sulfur source is thioacetamide, and the solvent thermal reaction time is 18h-24h. Preferably, the tungsten source is tungsten hexachloride, and the solvent used in the solvent thermal reaction is dimethylformamide.

[0056] In some specific embodiments, the structure of MXene includes a multi-layer accordion shape. It should be noted that the MXene structure used in the present invention is usually a multi-layer accordion shape, and the MXene structure can also be other structures, the purpose of which is to provide favorable conditions for loading WS2 and uniformly grow a large number of dense, wrinkled WS2 nanosheets between MXene layers.

[0057] In some specific embodiments, the method for preparing MXene comprises the following steps:

[0058] After lithium fluoride and hydrochloric acid are fully mixed at room temperature for 1 hour to form a mixture, Ti3AlC2 solution is added to the mixture, and the Al layer in Ti3AlC2 is etched by the mixture under stirring at 35°C for 24 hours. The black solid powder is thoroughly washed with deionized water and anhydrous ethanol until the pH value of the liquid supernatant is greater than 6, and dried in a vacuum oven at 60°C for 12 hours to obtain MXene powder.

[0059] Among them, the mass volume ratio of lithium fluoride and hydrochloric acid is 1g:20mL, the concentration of hydrochloric acid is 6M, and the mass ratio of lithium fluoride and Ti3AlC2 is 1:1.

[0060] In addition, the present invention provides a novel photoelectrically active material as a sensing substrate modification, based on a nucleic acid aptamer as a recognition unit, to design a sensor, which is prepared using the above-mentioned Au NPs / MXene / WS2 composite material, and the sensor is a photoelectrochemical sensor. The photoelectrochemical sensor prepared based on the Au NPs / MXene / WS2 composite material of the present invention has the advantages of separation of input and output signals, simple operation, and easy miniaturization, which meets the needs of rapid on-site detection. It can quickly, accurately and reliably detect trace amounts of Staphylococcus aureus in food, effectively solving the problem of poor timeliness of traditional detection methods, and providing convenience for the rapid sale of food with a short shelf life in the market, which helps to ensure food safety and protect public health. This method has broad application prospects and can provide simple, economical, fast and effective technical support for food safety detection.

[0061] In some specific embodiments, the photoelectrochemical sensor comprises:

[0062] A substrate and an electrode layer attached to the substrate, wherein the electrode layer includes a working electrode layer;

[0063] The surface of the working electrode layer is coated with Au NPs / MXene / WS2 composite material, ssDNA, 6-mercaptohexanol and nucleic acid aptamer Apt-Fc in sequence.

[0064] In some specific embodiments, the working electrode layer is based on indium tin oxide, and the Au NPs / MXene / WS2 composite material, ssDNA, 6-mercaptohexanol and Apt-Fc are sequentially coated on the surface of the indium tin oxide electrode.

[0065] In some specific embodiments, the electrode layer further comprises a counter electrode and a reference electrode. More preferably, the counter electrode is made of platinum and the reference electrode is made of Ag / AgCl.

[0066] In some specific embodiments, the nucleotide sequence of the ssDNA is: 5'-GTA CCG TAC CAT TGCTAG CGT CTT CCC GT-3'.

[0067] In some specific embodiments, the nucleotide sequence of the acid aptamer Apt-Fc is: 5'-Fc-GCA ATGGTA CGG TAC TTC CTC GGC ACG TTC TCA GTA GCG CTC GCT GGT CAT CCC ACA GCT ACGTCA AAA GTG CAC GCT ACT TTG CTA A-3'.

[0068] In some specific embodiments, the steps include:

[0069] The photocurrent intensity of solution samples containing different known concentrations of Staphylococcus aureus was detected by a photoelectric sensor, and a detection linear response relationship between Staphylococcus aureus concentration and photocurrent intensity was constructed. The curve with the highest fitting degree was selected as the standard curve for Staphylococcus aureus detection.

[0070] The linear regression equation for the detection of Staphylococcus aureus concentration and photocurrent intensity is: y = 0.7796LgC + 0.636, C is the concentration of Staphylococcus aureus in the sample to be tested, y is the photocurrent intensity, and the detection range is 10 CFU / mL to 10 7 CFU / mL, and the detection limit was 2.9 CFU / mL.

[0071] The concentration of Staphylococcus aureus in the sample to be tested is obtained according to the obtained detection linear regression equation and the measured photocurrent intensity of the sample to be tested.

[0072] The photoelectric chemical sensor provided by the present invention has the following mechanism for detecting Staphylococcus aureus: Figure 1 As shown in the figure, the details are as follows: under the condition of light irradiation, the photogenerated electrons of WS2 jump from the valence band to the conduction band. The Schottky heterojunction formed at the WS2 / MXene interface promotes the directional transfer of electrons from WS2 to the MXene surface, effectively enhancing the efficiency of photogenerated electron / hole separation and photoelectric signal enhancement. In addition, Au NPs generate high-energy hot electrons due to the plasma resonance effect, and these hot electrons can be quickly transferred to the conduction band of WS2, further improving the photoelectric signal response.

[0073] When Staphylococcus aureus was not present, Apt-Fc combined with ssDNA through DNA hybridization to form a double-stranded structure, and the photocurrent signal was greatly weakened due to the inhibitory effect of Fc on the photoelectric signal.

[0074] When Staphylococcus aureus is present, the target specifically binds to Apt-Fc, Apt-Fc is released from the modified electrode, the inhibitory effect of Fc is weakened, and the photocurrent signal is restored. Finally, by comparing the relationship between the change in the photoelectric signal and the concentration of the target, the quantitative detection of Staphylococcus aureus is achieved.

[0075] The present invention uses Au NPs / MXene / WS2 composite materials to make photoelectrochemical sensors. On the one hand, compared with traditional analytical methods, the photoelectrochemical sensor has the advantages of low background signal and high sensitivity due to the different modes of excitation signal (light) and detection signal (electricity). It is easy to integrate and has a fast detection speed, which effectively solves the problems of low sensitivity and slow detection speed of traditional detection methods, and provides an effective solution to the problem that the pre-prepared food industry needs to quickly detect and market it as soon as possible. On the other hand, the detection range of the AuNPs / MXene / WS2 photoelectrochemical sensor for detecting Staphylococcus aureus constructed by the present invention is 10CFU / mL~10 7 CFU / mL, with a low detection limit of 2.9 CFU / mL, it provides a new method for on-site application of rapid detection technology for foodborne pathogens, will help reduce large-scale outbreaks of foodborne diseases, and has good application prospects in food safety testing.

[0076] The invention is further described below through specific examples.

[0077] Example 1

[0078] The present invention provides a method for preparing an Au NPs / MXene / WS2 composite material, comprising the following steps:

[0079] S1. Preparation of MXene: 1 g of lithium fluoride (LiF) was added to 20 mL of 6 M hydrochloric acid (HCl) solution and mixed thoroughly at room temperature for 1 h. After that, 1 g of titanium aluminum carbide (Ti3AlC2) solution was added, and the mixture was heated to 35 ° C and stirred for 24 h to etch the Al layer in Ti3AlC2. The obtained black solid powder was thoroughly washed with deionized water and anhydrous ethanol by centrifugation at 7000 rpm until the pH value of the liquid supernatant was greater than 6. After drying in a vacuum oven at 60 ° C for 12 h, MXene powder was obtained.

[0080] S2, Preparation of MXene / WS2: Dissolve 150 mg of MXene in 60 mL of dimethylformamide solution, stir for 30 min, and ultrasonically vibrate for 30 min to completely dissolve it; then dissolve 150 mg of thioacetamide and 80 mg of tungsten hexachloride in the prepared MXene solution, stir for 1 h, and ultrasonically vibrate for 1 h, and completely dissolve it in the dimethylformamide solution again. Heat the mixture to 200 ° C for 24 h, dry it in a vacuum oven at 60 ° C for 12 h, and grind it thoroughly to obtain MXene / WS2 powder.

[0081] S3. Preparation of Au NPs / MXene / WS2 composite material: 40 mg MXene / WS2 powder was placed in a reaction container, and then 20 μL of 10 mM chloroauric acid solution was added and stirred for 10 min to allow it to undergo a self-reduction reaction; the mixture was washed with ultrapure water and anhydrous ethanol for 3 times, and the solid product was collected by centrifugation. Finally, the obtained composite material Au NPs / MXene / WS2 was dried in a vacuum oven at 60°C for 12 h, and then fully ground to obtain the Au NPs / MXene / WS2 composite material with a high gold loading, wherein the particle size of the gold nanoparticles in the prepared composite material was about 120 nm.

[0082] Example 2

[0083] The present invention provides a method for preparing an Au NPs / MXene / WS2 composite material, comprising the following steps:

[0084] S1. Preparation of MXene: 1 g of LiF was added to 20 mL of 6 M HCl solution and mixed thoroughly at room temperature for 1 h. After that, 1 g of Ti3AlC2 was added to the solution, and the mixture was heated to 35 °C and stirred for 24 h to etch the Al layer in Ti3AlC2. The obtained black solid powder was thoroughly washed with deionized water and anhydrous ethanol by centrifugation at 7000 rpm until the pH value of the liquid supernatant was greater than 6. After drying in a vacuum oven at 60 °C for 12 h, MXene powder was obtained.

[0085] S2, Preparation of MXene / WS2: Dissolve 150 mg of MXene in 60 mL of dimethylformamide solution, stir for 30 min, and ultrasonically vibrate for 30 min to completely dissolve it; then dissolve 150 mg of thioacetamide and 80 mg of tungsten hexachloride in the prepared MXene solution, stir for 1 h, and ultrasonically vibrate for 1 h, and completely dissolve it in the dimethylformamide solution again. Heat the mixture to 200 ° C for 24 h, dry it in a vacuum oven at 60 ° C for 12 h, and grind it thoroughly to obtain MXene / WS2 powder.

[0086] S3. Preparation of Au NPs / MXene / WS2 composite material: 40 mg of MXene / WS2 powder was placed in a reaction container, and then 40 μL of 10 mM chloroauric acid solution was added and stirred for 10 min to allow it to undergo a self-reduction reaction; the mixture was washed with ultrapure water and anhydrous ethanol for 3 times, and the solid product was collected by centrifugation. Finally, the obtained composite material Au NPs / MXene / WS2 was dried in a vacuum oven at 60°C for 12 h, and then fully ground to obtain a nano-gold loaded Au NPs / MXene / WS2 composite material, wherein the particle size of the nano-gold in the prepared composite material was about 120 nm.

[0087] Example 3

[0088] The present invention provides a method for preparing an Au NPs / MXene / WS2 composite material, comprising the following steps:

[0089] S1. Preparation of MXene: 1 g of LiF was added to 20 mL of 6 M HCl solution and mixed thoroughly at room temperature for 1 h. After that, 1 g of Ti3AlC2 was added to the solution, and the mixture was heated to 35 °C and stirred for 24 h to etch the Al layer in Ti3AlC2. The obtained black solid powder was thoroughly washed with deionized water and anhydrous ethanol by centrifugation at 7000 rpm until the pH value of the liquid supernatant was greater than 6. After drying in a vacuum oven at 60 °C for 12 h, MXene powder was obtained.

[0090] S2, Preparation of MXene / WS2: Dissolve 150 mg of MXene in 60 mL of dimethylformamide solution, stir for 30 min, and ultrasonically vibrate for 30 min to completely dissolve it; then dissolve 150 mg of thioacetamide and 80 mg of tungsten hexachloride in the prepared MXene solution, stir for 1 h, and ultrasonically vibrate for 1 h, and completely dissolve it in the dimethylformamide solution again. Heat the mixture to 200 ° C for 24 h, dry it in a vacuum oven at 60 ° C for 12 h, and grind it thoroughly to obtain MXene / WS2 composite material powder.

[0091] S3. Preparation of Au NPs / MXene / WS2 composite material: 40 mg of MXene / WS2 composite material powder was placed in a reaction container, and then 60 μL of 10 mM chloroauric acid solution was added and stirred for 10 min to allow it to undergo a self-reduction reaction; the mixture was washed with ultrapure water and anhydrous ethanol for 3 times, and the solid product was collected by centrifugation. Finally, the obtained composite material Au NPs / MXene / WS2 was dried in a vacuum oven at 60°C for 12 h, and then fully ground to obtain a nano-gold loaded Au NPs / MXene / WS2 composite material, wherein the particle size of the nano-gold in the prepared composite material was about 120 nm.

[0092] Since the Au NPs / MXene / WS2 composite materials prepared in Examples 1 to 3 have similar structures, the Au NPs / MXene / WS2 composite material prepared in Example 2 was used as the object to illustrate the structures of MXene, MXene / WS2 composite material and Au NPs / MXene / WS2 composite material. The results are as follows.

[0093] Figure 2 This is the morphology and structure diagram of MXene in Example 2 of the present invention. Figure 1As shown, the layered structure at the edge of the MXene material is complete, and it can be seen that it has a multi-layer accordion-like structure, which provides favorable conditions for loading WS2.

[0094] Figure 3 This is a morphology structure diagram of the composite material of MXene / WS2 in Example 2 of the present invention. Figure 3 As shown, a large number of dense, wrinkled WS2 nanosheets grow uniformly between the MXene layers in the MXene / WS2 binary composite material.

[0095] Figure 4 The morphology and structure diagram of the Au NPs / MXene / WS2 composite material of Example 2 of the present invention. Figure 3 As shown in Figure 2, AuNPs / MXene / WS2 composites Figure 3 On this basis, growing gold nanoparticles with relatively uniform size can further improve the photoelectric properties of the material.

[0096] When the amount of chloroauric acid solution is 40 μL (i.e. 4×10 -4 mmol), Au NPs with a particle size of about 120 nm were uniformly dispersed on the surface of MXene / WS2, and no obvious agglomeration occurred. -4 The Au NPs / MXene / WS2 composite material prepared at 100 mmol / mol is a preferred example. Its performance is tested by time-current curve and compared with WS2 and WS2 / MXene materials. The results are shown in Figure 5 shown.

[0097] Figure 5 This is a photoelectric response curve of the Au NPs / MXene / WS2 composite material of Example 2 of the present invention. Figure 5 As shown in the figure, compared with WS2 and WS2 / MXene, the Au NPs / MXene / WS2 composite material prepared in Example 2 shows better photoelectric signal response. This is because MXene has a unique two-dimensional layered structure. The addition of MXene can form a Schottky heterojunction with WS2 at the WS2 / MXene interface, so that electrons are transferred from WS2 to the MXene surface in a directional manner, effectively enhancing the photogenerated electron / hole separation efficiency. In addition, since the plasma resonance effect of Au NPs can generate high-energy hot electrons, these hot electrons can be quickly transferred to the conduction band of WS2, further improving the photoelectric signal response.

[0098] Figure 6 This is the X-ray photoelectron spectrum of the Au NPs / MXene / WS2 composite material of Example 2 of the present invention. Figure 6As shown in the figure, the main elements detected by the XPS full spectrum in the Au NPs / MXene / WS2 composite material include Ti, C, O, W, S, and Au. No Al element was found in the full spectrum, indicating that the etching process during preparation was very sufficient. The binding energy of the peak corresponding to O 1s is 530.77eV, the binding energy of the peak corresponding to C 1s is 284.97eV, the binding energy of the peak corresponding to Ti 2p is 459.27eV, the binding energy of the peak corresponding to S2p is 161.47eV, the binding energy of the peak corresponding to Au 4f is 83.77eV, and the binding energy of the peak corresponding to W 4f is 35.97eV.

[0099] The WS2 / MXene and Au NPs prepared in Example 2 were mixed at 4 mg: 4 × 10 -4 The AuNPs / MXene / WS2 composite material prepared by the reaction ratio of mmol is used for the photoelectrochemical mode sensor. The preparation method of the sensor is as follows:

[0100] Step 1: drop 10 μL of 2.00 mg / mL Au NPs / MXene / WS2 ultrapure aqueous solution onto the surface of the indium tin oxide working electrode layer, dry it at room temperature, rinse the electrode surface with ultrapure water, and dry it.

[0101] Step 2, continue to drop 10 μL of 1.0 μg / mL ssDNA solution on the surface of the working electrode layer modified with Au NPs / MXene / WS2; wherein the nucleotide sequence of the ssDNA is: 5'-GTA CCG TAC CAT TGC TAG CGT CTT CCCGT-3'.

[0102] Step 3, continue to add 5 μL of 6-mercaptohexanol (MCH) solution to the surface of the working electrode layer to block the nonspecific active sites on the electrode surface.

[0103] Step 4, continue to add 10 μL of 1.0 μg / mL Apt-Fc solution to the surface of the working electrode layer to bind to the ssDNA through DNA hybridization, wherein the nucleotide sequence of the nucleic acid aptamer Apt-Fc is: 5'-Fc-GCA ATG GTA CGG TAC TTCCTC GGC ACG TTC TCA GTA GCG CTC GCT GGT CAT CCC ACA GCT ACG TCA AAA GTG CACGCT ACT TTG CTA A-3'.

[0104] Step 5, after drying, a photoelectrochemical sensor for detecting Staphylococcus aureus is obtained.

[0105] 10 μL, 10 CFU / mL, 10 2CFU / mL, 10 3 CFU / mL, 10 4 CFU / mL, 10 5 CFU / mL, 10 6 CFU / mL and 10 7 Staphylococcus aureus solutions of different concentrations (CFU / mL) were dripped onto the surface of the photoelectrochemical sensor and reacted at room temperature for 40 minutes. Figure 7-Figure 8 shown.

[0106] Figure 7 : is the time-current curve diagram of the sensor corresponding to different concentrations of Staphylococcus aureus of the present invention. Figure 7 As shown, the photocurrent intensity of Staphylococcus aureus with different concentrations was obtained by photoelectrochemical signal detection through time-current curve.

[0107] The linear response relationship between the concentration of Staphylococcus aureus and the photocurrent intensity was established by using the photocurrent intensity of different concentrations of Staphylococcus aureus, and a fitting curve of the photocurrent intensity and the concentration value of Staphylococcus aureus was drawn. The curve with the highest fitting degree was selected as the standard curve for Staphylococcus aureus detection; Figure 8 : is a linear fitting curve diagram of the concentration value of Staphylococcus aureus of different concentrations and photocurrent of the present invention. Figure 8 As shown in the figure, the linear regression equation for the detection of Staphylococcus aureus concentration and photocurrent intensity is: y=0.7796LgC+0.636, C is the concentration of Staphylococcus aureus in the sample to be tested, y is the photocurrent intensity, the linear correlation coefficient is 0.995, and the detection range is 10CFU / mL~10 7 CFU / mL, and the detection limit was 2.9 CFU / mL.

[0108] In order to verify the effectiveness and reliability of the designed photoelectric chemical sensor for detecting the concentration of Staphylococcus aureus, the milk samples in the food were tested and the spike method (live bacteria addition method) was used to simulate the actual sample for detection. 3 CFU / mL, 7.0×10 4 CFU / mL, 7.0×10 5 The Staphylococcus aureus bacterial solution with a CFU / mL was used as the mother solution and added into milk to prepare the actual sample.

[0109] The experimental results are shown in Table 1. The average recovery rate of the actual sample detection is between 98.4% and 102.7%, and the relative standard deviation (RSD) is between 1.43% and 2.17%, indicating that the sensor technology has good detection performance for Staphylococcus aureus in milk samples.

[0110] Table 1 Results of spike recovery experiments in milk samples

[0111]

[0112] To examine the periodic switching cycle stability of the photoelectrochemical sensor, the modified indium tin oxide electrode was incubated in a Staphylococcus aureus suspension, and then multiple consecutive time-current curve tests were performed under long-term light / no-light cycles. Fig. 9 This is a graph showing the stability test results of the photoelectrochemical sensor provided by the present invention. Fig. 9 As shown, the photocurrent signal of the sensor remains stable, and the peak and valley photocurrents are consistent, indicating that the performance stability of the sensor is good during multiple cycles, and the sensor responds quickly to changes in the light signal without an obvious downward trend.

[0113] Interfering foodborne pathogens that may exist in actual samples, such as Escherichia coli (E. coli), Listeria monocytogenes (L. monocytogenes), Salmonella typhimurium (S. typhimurium) and Vibrio parahemolyticus (V. parahemolyticus), were used to test the selectivity of the photoelectrochemical sensor. The results are shown in Figure 2. Fig.10 shown.

[0114] Fig.10 This is a diagram showing the selectivity test results of the photoelectrochemical sensor provided by the present invention. Fig.10 As shown in the figure, the signal response of the interfering foodborne pathogenic bacteria sample is consistent with that of the blank sample. When the target Staphylococcus aureus is present in the sample, the sensor shows an obvious photoelectric signal change, which shows that the sensor has good selectivity.

[0115] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0116] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An Au NPs / MXene / WS2 composite material, characterized in that: The Au NPs / MXene / WS2 composite material includes a MXene matrix, which is a multi-layer accordion-like structure, and wrinkled WS2 nanosheets are loaded between the layers of the MXene matrix to form a MXene / WS2 substrate; and gold nanoparticles are loaded on the surface of the MXene / WS2 substrate; wherein the particle size of the gold nanoparticles is 100nm to 150nm.

2. A method for preparing the Au NPs / MXene / WS2 composite material according to claim 1, characterized in that: The following steps are involved: MXene is added to a sulfur source and a tungsten source, and reacted by solvothermal method at 190°C to 210°C, so that wrinkled WS2 nanosheets grow and are loaded between MXene layers to obtain a MXene / WS2 composite material; The MXene / WS2 composite material is dissolved in a solvent, a gold source is added and mixed, and then a self-reduction reaction is carried out to make the gold nanoparticles grow evenly and load on the MXene / WS2 composite material to obtain the Au NPs / MXene / WS2 composite material.

3. The method for preparing the Au NPs / MXene / WS2 composite material according to claim 2, characterized in that: The mass molar ratio of MXene / WS2 composite material to gold nanoparticles in the Au NPs / MXene / WS2 composite material is 1 mg:4×10 -5 mmol~2×10 -4 mmol, and the self-reduction reaction time is 10min~60min.

4. The method for preparing the Au NPs / MXene / WS2 composite material according to claim 2, characterized in that: The mass ratio of MXene powder, sulfur source and tungsten source is 1:0.5~2::0.3~1, the sulfur source is thioacetamide, and the solvothermal reaction time is 18h~24h.

5. A sensor, characterized in that: It is prepared using the Au NPs / MXene / WS2 composite material described in claim 1.

6. The sensor according to claim 5, characterized in that The sensor is a photoelectrochemical sensor.

7. The sensor according to claim 6, characterized in that The photoelectrochemical sensor comprises: A substrate and an electrode layer attached to the substrate, wherein the electrode layer includes a working electrode layer; The surface of the working electrode layer is coated with Au NPs / MXene / WS2 composite material, ssDNA, 6-mercaptohexanol and nucleic acid aptamer Apt-Fc in sequence.

8. The sensor according to claim 7, characterized in that The nucleotide sequence of the ssDNA is: 5'-GTA CCGTAC CATTGC TAG CGT CTT CCC GT-3'.

9. The sensor according to claim 7, characterized in that The nucleotide sequence of the nucleic acid aptamer Apt-Fc is: 5'-Fc-GCA ATG GTA CGG TAC TTC CTC GGC ACG TTCTCA GTA GCG CTC GCT GGT CATCCC ACA GCT ACG TCA AAA GTG CAC GCTACTTTG CTAA-3'.

10. The sensor according to claim 6, characterized in that The method for detecting Staphylococcus aureus with the sensor comprises the following steps: The photocurrent intensity of the sample to be tested is detected, and the concentration of Staphylococcus aureus in the sample to be tested is obtained by using a linear regression equation between the concentration of Staphylococcus aureus and the photocurrent intensity; The linear regression equation for the detection of Staphylococcus aureus concentration and photocurrent intensity is: y = 0.7796LgC + 0.636, C is the concentration of Staphylococcus aureus in the sample to be tested, y is the photocurrent intensity, and the detection range is 10 CFU / mL to 10 7 CFU / mL, and the detection limit was 2.9 CFU / mL.

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