Preparation method of nitrogen-sulfur co-doped carbon nanoparticles and application of nitrogen-sulfur co-doped carbon nanoparticles in detection of hydroxylamine hydrochloride

Abstract

The invention discloses a preparation method of nitrogen and sulfur co-doped carbon nanoparticles and application of hydroxylamine hydrochloride detection, dimethyl sulfoxide and dimethylamine hydrochloride are used as raw materials, and the nitrogen and sulfur co-doped carbon nanoparticles with the characteristics of high sensitivity, high selectivity and strong anti-interference capability in hydroxylamine hydrochloride detection are simply and conveniently synthesized by a one-step hydrothermal method. A potassium permanganate solution and ethyl acetate are mixed to prepare MnO2 nanosheets, a nitrogen and sulfur co-doped carbon nanoparticle solution is added into MnO2 nanosheet dispersion liquid to form a nitrogen and sulfur co-doped carbon nanoparticle / MnO2 nanosheet composite fluorescent sensing system, and the nitrogen and sulfur co-doped carbon nanoparticles are combined with the MnO2 nanosheets to design the fluorescent probe. NaCl, KCl, Na2HPO4 and KH2PO4 are dissolved with ultrapure water to obtain a phosphate buffer solution, the phosphate buffer solution and a hydroxylamine hydrochloride reference substance solution are added into the composite fluorescence sensing system, and hydroxylamine and MnO2 nanosheets are subjected to an oxidation-reduction reaction, so that fluorescence of nitrogen and sulfur co-doped carbon nanoparticles is recovered, and rapid detection of hydroxylamine hydrochloride is realized.

Description

Technical Field

[0001] The invention relates to the preparation of co-doped carbon nanoparticles and the technical field of fluorescence sensing, and in particular to a preparation method and application of nitrogen and sulfur co-doped carbon nanoparticles for detecting hydroxylamine hydrochloride. Background Art

[0002] Hydroxylamine hydrochloride is a commonly used reducing agent in drug synthesis and is often used as a starting material. It has been widely used in many fields, such as a reducing agent for the synthesis of antitumor drugs (hydroxyurea), sulfonamides (sulfamethoxazole) and pesticides (methoxazole), a raw material for the synthesis of hydroxyl compounds, and an inorganic catalyst for transamination. However, it is a known carcinogen, and excessive hydroxylamine hydrochloride is genotoxic and mutagenic to a variety of organisms. Similarly, from an environmental perspective, marine hydroxylamine produced during the production of nitrous oxide is considered a hazardous compound. Therefore, the detection of hydroxylamine hydrochloride is crucial to ensure the quality of drugs and pesticides, maintain ecological safety, and reduce harm to organisms. The detection methods for hydroxylamine hydrochloride reported in the literature mainly include HPLC, HPLC-MS, GC-MS, ion chromatography, electrochemical methods, etc. The above methods have certain limitations, such as either requiring expensive instruments and complex procedures, or low detection sensitivity, which limits the detection of hydroxylamine hydrochloride in practical applications.

[0003] Compared with traditional technologies, fluorescence detection technology has become an effective method in the field of analysis due to its simplicity, economy, fast response, high sensitivity and stable performance. So far, there are no reports on hydroxylamine sensing by nitrogen-sulfur co-doped carbon nanoparticles, nor on the reaction of hydroxylamine with MnO 2 Reports on nanosheet interactions.

[0004] The fluorescent probe disclosed in the document with Chinese patent publication number CN108218822A and titled "A ratiometric fluorescent probe for detecting hydroxylamine, its synthesis method and application" is a rhodamine derivative containing a biotin group, and is used to qualitatively determine hydroxylamine by the change in the ratio of fluorescence intensity at two wavelengths. However, the problems it has are: the fluorescent probe is a rhodamine derivative containing a toxic biotin group, and the synthesis steps of the fluorescent probe are cumbersome, and it is limited to detecting hydroxylamine in cells. The linear range of the detection concentration is 0 to 80 μmol / L, and the linear range is relatively narrow. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing nitrogen-sulfur co-doped carbon nanoparticles with a simple and efficient preparation process in view of the above existing detection problems of hydroxylamine hydrochloride, and based on the high fluorescence intensity of the nitrogen-sulfur co-doped carbon nanoparticles and MnO 2The strong absorption of the nanosheets was used to prepare a new type of fluorescent sensing probe with good chemical and optical stability, which was used to quickly and sensitively detect hydroxylamine hydrochloride and expand the application of nitrogen-sulfur co-doped carbon nanoparticles.

[0006] To achieve the above object, the preparation method of nitrogen-sulfur co-doped carbon nanoparticles of the present invention is implemented by the following technical scheme: comprising the following steps:

[0007] Step A): preparing a dimethylamine hydrochloride aqueous solution, adding dimethyl sulfoxide to the dimethylamine hydrochloride aqueous solution, and stirring to form a mixed solution;

[0008] Step B): first subjecting the mixed solution to a constant temperature reaction, then naturally cooling it to room temperature, and taking the upper clear liquid of the cooled mixed solution;

[0009] Step C): filtering the supernatant with a microporous filter membrane, dialyzing it, and finally freeze-drying it to obtain nitrogen-sulfur co-doped carbon nanoparticles.

[0010] The technical solution adopted by the application of nitrogen-sulfur co-doped carbon nanoparticles in the detection of hydroxylamine hydrochloride of the present invention comprises the following steps:

[0011] Step 1: Preparation of MnO 2 Nanosheets

[0012] Weigh potassium permanganate solid, add purified water, stir and dissolve to obtain potassium permanganate solution, mix the potassium permanganate solution with an appropriate amount of ethyl acetate to obtain a mixed solution, reflux the mixed solution to fade, separate with a separatory funnel after colloid is produced, take the dark brown liquid at the bottom layer, wash with purified water and ethanol to obtain MnO 2 Nanosheets, MnO 2 Nanosheet drying;

[0013] Step 2: Preparation of MnO 2 Nanosheet dispersion

[0014] The MnO 2 Nanosheets were added to ultrapure water to obtain MnO 2 Nanosheet solution, MnO 2 The nanosheet solution was ultrasonically treated to obtain uniform MnO 2 Nanosheet dispersion;

[0015] Step 3: Prepare phosphate buffer solution

[0016] Use ultrapure water to dissolve NaCl, KCl, Na 2 HPO 4 and KH 2 PO 4, obtain a phosphate buffer solution, adjust the pH value of the phosphate buffer solution to 4.0-8.0, and then add ultrapure water to make up to volume;

[0017] Step 4: Detection of Hydroxylamine Hydrochloride

[0018] Step 4: Detection of Hydroxylamine Hydrochloride

[0019] The nitrogen-sulfur co-doped carbon nanoparticles are dissolved in ultrapure water to prepare a nitrogen-sulfur co-doped carbon nanoparticle solution; the MnO 2 Nanosheet dispersion, forming nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Nanosheet composite fluorescence sensing system;

[0020] Then, in the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 The 1-10 mmol / L phosphate buffer and different concentrations of hydroxylamine hydrochloride reference solution (concentration of 0.2-200 μmol / L) are added to the nanosheet composite fluorescence sensing system, and a series of reference solutions are obtained after sufficient mixing. The series of reference solutions are placed in the sample pool of the fluorescence spectrophotometer to detect the fluorescence intensity, and the concentration of the hydroxylamine hydrochloride reference solution and the fluorescence enhancement efficiency (F t -F s ) / F s The linear equation between t and F s Respectively represent the fluorescence intensity tested in the presence and absence of hydroxylamine hydrochloride reference substance;

[0021] When measuring the actual sample, first filter it with a 0.22 μm microfiltration membrane to remove impurities, and collect the filtrate as the test solution; replace the hydroxylamine hydrochloride reference solution with the same volume of the test solution, and detect the fluorescence intensity of the actual sample solution under the same conditions, and bring the fluorescence intensity of the actual sample solution into the linear equation to calculate the concentration of hydroxylamine hydrochloride in the actual sample solution.

[0022] The beneficial effects of the present invention after adopting the above technical solution are:

[0023] 1. The present invention uses dimethyl sulfoxide and dimethylamine hydrochloride as raw materials and a one-step hydrothermal method to simply synthesize novel nitrogen-sulfur co-doped carbon nanoparticles. The novel nitrogen-sulfur co-doped carbon nanoparticles have the advantages of excellent optical properties, good water solubility, resistance to photobleaching, and stable optical properties in a high-salt environment, and have the characteristics of high sensitivity, high selectivity, and strong anti-interference ability in the detection of hydroxylamine hydrochloride.

[0024] 2. The present invention utilizes the synthesized novel nitrogen-sulfur co-doped carbon nanoparticles combined with manganese dioxide (MnO2 ) nanosheets are designed as "off-on" fluorescent probes using MnO 2 Nanosheets act as quenchers and recognition agents, and MnO 2 Nanosheets have good light absorption properties, oxidase-like activity, large specific surface area, good water solubility, good chemical stability, and simple synthesis methods, and are widely used in the construction of optical sensor platforms. 2 Nanosheets have strong absorption at 200-600nm and can be used as quenchers for various fluorescent materials. 2 Nanosheets quench the fluorescence of nitrogen-sulfur co-doped carbon nanoparticles due to hydroxylamine and MnO 2 The redox reaction between the nanosheets can make MnO 2 Nanosheets decompose to generate Mn 2+ , thereby restoring the fluorescence of nitrogen-sulfur co-doped carbon nanoparticles, and using the concentration of hydroxylamine hydrochloride reference solution and the fluorescence enhancement efficiency (F t -F s ) / F s A linear relationship is shown, so hydroxylamine hydrochloride in water samples can be detected. When the new nitrogen-sulfur co-doped carbon nanoparticles are used as fluorescent probes for hydroxylamine hydrochloride detection, they have the advantages of good selectivity and high sensitivity, short response time, and real-time detection.

[0025] 3. Hydroxylamine detection based on fluorescence sensing analysis has the characteristics of stable signal, strong anti-interference ability, long service life and no pollution, which realizes the rapid detection of hydroxylamine hydrochloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a transmission electron microscope (TEM) image of nitrogen-sulfur co-doped carbon nanoparticles prepared by the present invention;

[0027] Figure 2 is the particle size distribution diagram of nitrogen-sulfur co-doped carbon nanoparticles;

[0028] Figure 3 This is an infrared image of nitrogen-sulfur co-doped carbon nanoparticles;

[0029] Figure 4 X-ray photoelectron spectroscopy characterization diagram of nitrogen-sulfur co-doped carbon nanoparticles: overall spectrum;

[0030] Figure 5 UV-visible spectra (left), fluorescence excitation spectra (middle) and emission spectra (right) of nitrogen-sulfur co-doped carbon nanoparticles (the inset is the irradiation of the solution under a fluorescent lamp (left) and a 365nm UV lamp (right));

[0031] Figure 6 MnO 2 TEM image of nanosheets;

[0032] Figure 7 MnO 2 Fourier transform infrared spectra of nanosheets;

[0033] Figure 8 Mn 2p X-ray photoelectron spectroscopy;

[0034] Fig. 9 MnO 2 X-ray diffraction pattern of nanosheets;

[0035] Fig.10 MnO 2 Raman spectra of nanosheets;

[0036] Fig.11 The effect of different concentrations of NaCl solution on the stability of nitrogen and sulfur co-doped carbon nanoparticles;

[0037] Fig.12 for the photostability of nitrogen-sulfur co-doped carbon nanoparticles;

[0038] Fig.13 Nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Selectivity of nanosheet composite fluorescence sensing system for hydroxylamine hydrochloride;

[0039] Fig.14 Nitrogen-sulfur co-doped carbon nanoparticles / MnO under the action of different concentrations of hydroxylamine hydrochloride 2 Fluorescence spectrum of nanosheet composite fluorescence sensing system;

[0040] Fig.15 For (F t -F s ) / F s Linear graph with hydroxylamine hydrochloride concentration. DETAILED DESCRIPTION

[0041] In order to further explain the present invention, the following specific embodiments and implementation examples are provided. The following specific embodiments and examples are only preferred examples of the present invention and do not limit the present invention. Professionals in the field can make improvements and changes to them according to the spirit of the present invention. These improvements and changes, etc., should all be deemed to be included in the protection scope of the present invention. The reagents, drugs, instruments and equipment used in the specific embodiments of the present invention are all known products and can be obtained by purchasing commercial products. Specifically as follows:

[0042] The preparation method of nitrogen-sulfur co-doped carbon nanoparticles of the present invention is specifically as follows:

[0043] First, a certain amount of dimethylamine hydrochloride is weighed, and an appropriate amount of water is added, and the dimethylamine hydrochloride aqueous solution is prepared after stirring and dissolving. The concentration range of the dimethylamine hydrochloride aqueous solution is 0.001-1 g / mL.

[0044] Then, slowly add a proper amount of dimethyl sulfoxide (DMSO) to the prepared dimethylamine hydrochloride aqueous solution, wherein the molar ratio of dimethylamine hydrochloride to dimethyl sulfoxide is 1:1 to 1:20, and stir evenly with a glass rod to form a mixed solution.

[0045] Next, the mixed solution is divided into a polytetrafluoroethylene-lined autoclave, and placed in an electric heating blast drying oven for constant temperature reaction, the temperature of the constant temperature reaction is constant at 100°C to 220°C, and the constant temperature reaction time is 1 to 20 hours. Then it is naturally cooled to room temperature, and the large particle impurities in the cooled solution are removed, and the supernatant is taken. The present invention can use a desktop high-speed centrifuge to centrifuge at a speed of 12000 rpm for 15 minutes to remove large particle impurities.

[0046] The supernatant liquid is filtered with a microporous membrane, and the present invention preferably uses a microporous membrane with a pore size of 0.22 μm. The filtered solution is then placed in a dialysis bag for dialysis, and the molecular retention capacity of the dialysis bag is required to be MWCO=500. The dialysis is performed for 24 hours, during which the ultrapure water is replaced every 4 hours. Finally, the dialyzed solution is placed in a freeze dryer for freeze drying, and a brown solid is obtained, which is the prepared nitrogen-sulfur co-doped carbon nanoparticles. The obtained nitrogen-sulfur co-doped carbon nanoparticles are placed in a refrigerator and stored at 4°C, and the solid is redissolved in ultrapure water according to experimental needs.

[0047] The morphology and particle size of the prepared nitrogen-sulfur co-doped carbon nanoparticles were observed using a transmission electron microscope (TEM). Figure 1 As shown, from Figure 1 It can be judged that the morphology of the prepared nitrogen-sulfur co-doped carbon nanoparticles is approximately spherical and has good dispersibility.

[0048] like Figure 2 The particle size distribution diagram of the prepared nitrogen-sulfur co-doped carbon nanoparticles is shown, and the average particle size of the nitrogen-sulfur co-doped carbon nanoparticles is about 25 nm.

[0049] like Figure 3 The infrared spectrum of the prepared nitrogen-sulfur co-doped carbon nanoparticles is shown at 3408 cm -1 and 3010cm -1 The broad peaks at 2930 cm-1 are attributed to the stretching vibrations of -OH and -NH. -1 and 1431cm -1 The absorption peak at is attributed to -CH 3 Stretching vibration, 1675 and 1647 cm-1 The peak at 1340 cm is attributed to the stretching vibrations of C=C, C=O and C=N in the conjugated structure. -1 and 1174cm -1 The peaks at 948 and 773 cm are attributed to the stretching vibrations of CN and CS. -1 The absorption peaks at 551 and 524 cm are attributed to the stretching vibration of SO. -1 The absorption peak at 20° is attributed to the bending vibration of the CS bond. All these results also prove the successful doping of nitrogen and sulfur atoms in N, S-CNP. These results also show that there are many functional groups on the surface of N, S-CNP, such as -OH, -NH 2 and -SH, which is conducive to its high hydrophilicity and stability in aqueous solution.

[0050] X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition of nitrogen-sulfur co-doped carbon nanoparticles, such as Figure 4 As shown, the four binding energy peaks at 165.47, 284.32, 398.95, and 529.82 eV are attributed to S 2p , C 1s , N 1s and O 1s The nitrogen-sulfur doped carbon nanoparticles are mainly composed of 14.12% S, 51.76% C, 2.13% N and 31.98% O.

[0051] like Figure 5 The spectral characteristics shown include UV-visible absorption and fluorescence spectra. Figure 5 As can be seen from the black line in the figure, nitrogen-sulfur co-doped carbon nanoparticles show a shoulder peak at 265nm due to the C=C bond (π-π*). Nitrogen-sulfur co-doped carbon nanoparticles are well dispersed, appear brown-yellow under visible light, and show strong blue fluorescence under ultraviolet light ( Figure 5 Inset). The optimal excitation peak (λex, red line) and emission peak (λem, blue line) are located at 380 nm and 458 nm, respectively.

[0052] The fluorescence stability of nitrogen-sulfur co-doped carbon nanoparticles was investigated in NaCl solutions with different concentrations. Figure 6 It can be seen that with the increase of NaCl solution concentration, the fluorescence intensity of nitrogen-sulfur co-doped carbon nanoparticles did not decrease significantly, indicating that the prepared nitrogen-sulfur co-doped carbon nanoparticles have strong salt resistance.

[0053] The photostability of the nitrogen-sulfur co-doped carbon nanoparticles was evaluated by irradiating the solution under UV light (365 nm) for different time periods. Figure 7It can be seen that after the solution of nitrogen-sulfur co-doped carbon nanoparticles was continuously irradiated under ultraviolet light for 60 minutes, its fluorescence intensity did not decrease significantly, indicating that the obtained nitrogen-sulfur co-doped carbon nanoparticles have good photostability.

[0054] The application steps of the prepared nitrogen-sulfur co-doped carbon nanoparticles in hydroxylamine detection are as follows:

[0055] Step 1: Preparation of MnO 2 Nanosheets

[0056] MnO 2 The preparation method of the nanosheet is: accurately weigh an appropriate amount of potassium permanganate solid, add an appropriate amount of purified water, stir and dissolve to obtain a potassium permanganate solution, wherein the concentration range of the potassium permanganate solution is preferably 0.001 to 0.41 mol / L. The potassium permanganate solution is then mixed with an appropriate amount of ethyl acetate to obtain a mixed solution, and the volume ratio of the potassium permanganate solution to ethyl acetate is preferably 1:0.001 to 1:100. The mixed solution is then refluxed to fade and produce a colloid. The present invention preferably refluxes the mixed solution at 85°C until the color fades. After the colloid is produced, a separatory funnel is used for separation, the dark brown liquid of the lower layer is taken, and then it is washed more than three times with purified water and ethanol each, and the obtained precipitate is MnO 2 Nanosheets, and finally MnO 2 The nanosheets were placed in an oven for drying.

[0057] like Figure 6 As shown, the prepared MnO 2 The nanosheets show a characteristic two-dimensional sheet-like morphology with occasional wrinkles, wrinkles, and curled edges. Figure 7 As shown, MnO 2 The Fourier transform infrared spectrum of the nanosheets showed the presence of -1 The peaks are related to the stretching vibrations of OH, C=O and Mn-O. XPS analysis is further used to identify the valence states of Mn and O elements. Figure 8 As shown in Figure 2, according to XPS analysis, the binding energies of Mn 2p3 / 2 and Mn 2p1 / 2 were found to be 642.5 and 654.5 eV, respectively, indicating the presence of tetravalent Mn ions and MnO in the oxide. 2 .like Fig. 9 As shown, XRD results show that the product can be labeled as layered amorphous δ-MnO 2 .like Fig.10 As shown, MnO 2 The Raman spectrum of the nanosheets is at 631 cm -1 A peak appears at , which is attributed to the Mn-O vibration.

[0058] Step 2: Preparation of MnO 2Nanosheet dispersion

[0059] A certain amount of MnO obtained in step 1 2 Add appropriate amount of ultrapure water to obtain MnO 2 Nanosheet solution, preferably MnO 2 The concentration range of the nanosheet solution is 0.001-2 mg / mL MnO 2 Nanosheet solution, and then MnO 2 The nanosheet solution was ultrasonically treated for 0.5 h to obtain uniform MnO 2 Nanosheet dispersion.

[0060] Step 3: Prepare phosphate buffer solution

[0061] Weigh 0.08-0.8 g NaCl, 0.002-0.02 g KCl, 0.0144-0.144 g Na 2 HPO 4 0.0024~0.024g KH 2 PO 4 , dissolve with 80 mL of ultrapure water to obtain a phosphate buffer solution. Then adjust the pH value of the phosphate buffer solution to 4.0-8.0 with HCl solution or NaOH solution, and finally add ultrapure water to make up the volume. The present invention can make up the volume to 100 mL to prepare a phosphate buffer solution of 1-10 mmol / L.

[0062] Step 4: Detection of Hydroxylamine Hydrochloride

[0063] First, the prepared freeze-dried nitrogen-sulfur co-doped carbon nanoparticles are dissolved in an appropriate volume of ultrapure water to prepare a nitrogen-sulfur co-doped carbon nanoparticle solution. The concentration of the nitrogen-sulfur co-doped carbon nanoparticle solution is preferably in the range of 0.001 to 2 mg / mL.

[0064] Then, accurately measure an appropriate volume of nitrogen-sulfur co-doped carbon nanoparticle solution and add an appropriate volume of MnO prepared in step 2. 2 Nanosheet dispersion, wherein nitrogen-sulfur co-doped carbon nanoparticle solution and MnO 2 The volume ratio of the nanosheet dispersion is 1:1, forming nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Nanosheet composite fluorescence sensing system.

[0065] Subsequently, the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2The nanosheet composite fluorescence sensing system is added with an appropriate volume of 1-10 mmol / L phosphate buffer solution with a pH of 4.0-8.0 prepared in step 3 and an appropriate volume of hydroxylamine hydrochloride reference solution with a concentration range of 0.2-200 μmol / L. 2 The volume ratio of the nanosheet composite system: phosphate buffer: hydroxylamine hydrochloride reference solution is 2:5:13. After thorough mixing, a series of reference solutions are obtained. The series of reference solutions are placed in the sample cell of the fluorescence spectrophotometer to test their fluorescence intensity. With 380nm as the excitation wavelength, the fluorescence spectrum of the above series of reference solutions is tested, and the fluorescence intensity at 458nm is recorded. Then, according to the known concentration of hydroxylamine hydrochloride and the fluorescence enhancement efficiency (F t -F s ) / F s The relationship between the linear equation is obtained, where F t and F s The nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Fluorescence intensity of the nanosheet composite fluorescence sensing system. All experiments were performed in triplicate at room temperature.

[0066] The concentration of hydroxylamine hydrochloride and the fluorescence enhancement efficiency (F t -F s ) / F s After the linear equation of the relationship between is obtained, the actual sample can be measured. When measuring the actual sample, first filter it with a 0.22μm microfiltration membrane to remove impurities, and collect the filtrate as the test solution. Then, replace the hydroxylamine hydrochloride reference solution in the composite fluorescence sensing system with the same volume of the test solution, and measure it under the same conditions, that is, the excitation wavelength is 380nm, and the fluorescence intensity at 458nm is recorded. All measurements were performed three times in parallel at room temperature. Finally, the fluorescence intensity Ft of the actual sample solution is substituted into the above linear equation to calculate the concentration of hydroxylamine hydrochloride in the actual sample solution.

[0067] To verify the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 The specific fluorescence response of the nanosheet composite fluorescence sensing system to hydroxylamine was studied by adding various inorganic ions or organic small molecules (1000 μmol / L) to the detection system to study the selectivity of the determination method. 2+ Mg 2+ , Mn 2+ , Fe 3+ , Fe 2+ 、Al 3+ 、Ni 2+ , Pb 2+Cr 3+ 、Co 2+ 、Ag + , Hg 2+ 、Zn 2+ , Cu 2+ , Cl - 、NO 2 - 、NO 3 - , HSO 3 - , S 2 O 3 2- 、SO 4 2- And the effects of some small molecules such as glucose, cysteine, sodium ascorbate, dopamine and formalin on the determination of hydroxylamine (200μmol / L). Figure 8 As shown in the figure, nitrogen-sulfur co-doped carbon nanoparticles have almost no specific fluorescence response to most anions and cations and organic small molecules. The experimental results show that the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 The nanosheet composite fluorescence sensing system only has a high fluorescence response to hydroxylamine.

[0068] like Fig. 9 As shown, nitrogen and sulfur co-doped carbon nanoparticles / MnO 2 The fluorescence intensity of the nanosheet composite fluorescence sensing system gradually changes with the increase of hydroxylamine concentration. As the concentration of hydroxylamine increases, the fluorescence of nitrogen-sulfur co-doped carbon nanoparticles gradually recovers. Fig.10 It can be seen that the fluorescence recovery efficiency value (F t -F s ) / F s ) showed a good linear relationship with hydroxylamine concentration in the range of 0.2-200 μmol / L, and the linear regression equations were (F t -F s ) / F s =0.000542C+0.0533(R 2 =0.985). In addition, this method does not use any precious metals, heavy metals or toxic organic fluorescent dyes, and has the advantages of simple operation, low cost and environmental protection. The above experimental results show that nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 The nanosheet composite fluorescence sensing system is an ideal fluorescent probe for detecting hydroxylamine content.

[0069] To verify the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2The feasibility of the nanosheet composite fluorescence sensing system in real samples, the sensor was tested in tap water samples. First, the concentration of hydroxylamine in tap water was determined, and then different concentrations of hydroxylamine hydrochloride reference solution were added to the tap water (the spike levels were 5.0, 40.0, and 100.0 μmol / L, respectively), and the spike recovery experiment was tested according to the experimental method. The recovery rates ranged from 98.0% to 102.3%, and the relative standard deviations (RSDs) were all less than 2%, confirming that the proposed method can be applied to real samples with high precision, as shown in Table 1 below. ND in Table 1 is not detected or below the detection limit (0.05 μmol / L), and RSD is the relative standard deviation:

[0070] Table 1 Detection results and recovery rate experiment of hydroxylamine in tap water

[0071]

[0072] Three embodiments of the present invention are provided below:

[0073] Example 1

[0074] Weigh dimethylamine hydrochloride, add water and stir to dissolve, and prepare a dimethylamine hydrochloride aqueous solution with a concentration of 0.001g / mL. Slowly add dimethyl sulfoxide to the prepared dimethylamine hydrochloride aqueous solution, so that the molar ratio of dimethylamine hydrochloride to dimethyl sulfoxide is 1:1, and stir evenly with a glass rod to form a mixed solution. The mixed solution is divided into a polytetrafluoroethylene-lined high-pressure reactor and placed in an electric heating blast drying oven at 100°C for constant temperature reaction for 20 hours. Then cool naturally to room temperature, centrifuge the cooled solution at 12000rpm for 15 minutes in a desktop high-speed centrifuge to remove large particle impurities, and take the supernatant. Filter the supernatant taken out with a microporous filter membrane with a pore size of 0.22μm, and then place the filtered solution in a dialysis bag for 24 hours. The molecular retention capacity of the dialysis bag is required to be MWCO=500. During this period, ultrapure water is replaced every 4 hours. Finally, the dialyzed solution was freeze-dried to obtain nitrogen-sulfur co-doped carbon nanoparticles. The obtained nitrogen-sulfur co-doped carbon nanoparticles were stored in a refrigerator at 4°C.

[0075] Preparation of MnO 2 Nanosheets: Potassium permanganate solid and purified water were stirred and dissolved to obtain a potassium permanganate solution with a concentration range of 0.001 mol / L. The 0.001 mol / L potassium permanganate solution was mixed with ethyl acetate (volume ratio of 1:0.001) to obtain a mixed solution. The mixed solution was refluxed at 85°C until the color faded and a colloid was produced. A separatory funnel was used for separation, and the dark brown liquid at the bottom layer was taken. Then, it was washed with purified water and ethanol for more than three times to obtain MnO 2 Nanosheets, MnO 2 The nanosheets were placed in an oven for drying.

[0076] Preparation of MnO 2 Nanosheet dispersion: MnO 2 The nanosheets were mixed with ultrapure water to obtain a MnO solution with a concentration of 0.001 mg / mL. 2 Nanosheet solution, and then MnO 2 The nanosheet solution was ultrasonically treated for 0.5 h to obtain uniform MnO 2 Nanosheet dispersion.

[0077] Prepare phosphate buffer solution: weigh 0.08 g NaCl, 0.002 g KCl, 0.0144 g Na 2 HPO 4 , 0.0024g KH 2 PO 4 , dissolve with 80 mL ultrapure water to obtain a phosphate buffer solution. Then adjust the pH value of the phosphate buffer solution to 4.0 with HCl solution or NaOH solution, and finally add ultrapure water to make up the volume. The present invention can make up the volume to 100 mL to prepare a 1 mmol / L phosphate buffer solution.

[0078] Detection of hydroxylamine hydrochloride: Dissolve the prepared freeze-dried nitrogen-sulfur co-doped carbon nanoparticles in an appropriate volume of ultrapure water to prepare a nitrogen-sulfur co-doped carbon nanoparticle solution with a concentration range of 0.001 mg / mL. Then, accurately measure 100 μL of the nitrogen-sulfur co-doped carbon nanoparticle solution and add 100 μL of MnO 2 Nanosheet dispersion, forming nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Nanosheet composite fluorescence sensing system. In this nitrogen-sulfur co-doped carbon nanoparticle / MnO 2 1300 μL of 1 mmol / L phosphate buffer solution with pH 4.0 and 500 μL of hydroxylamine hydrochloride reference solution (the concentration range of hydroxylamine hydrochloride reference solution is 0.2-200 μmol / L) were added to the nanosheet composite fluorescence sensing system, and a series of reference solutions were obtained after thorough mixing. The series of reference solutions were placed in the sample pool of the fluorescence spectrophotometer respectively. The fluorescence spectrum of the series of reference solutions was tested with 380 nm as the excitation wavelength, and the fluorescence intensity at 458 nm was recorded. A linear equation was obtained based on the known relationship between the concentration of the hydroxylamine hydrochloride reference solution and the fluorescence enhancement efficiency.

[0079] When measuring the actual sample, first filter it with a 0.22μm microfiltration membrane to remove impurities, collect the filtrate, and use it as the test solution. Replace the hydroxylamine hydrochloride reference solution with the same volume of the test solution and test it under the same conditions. Substituting the fluorescence intensity of the actual sample solution into the linear equation can calculate the concentration of hydroxylamine hydrochloride in the actual sample solution. All experiments were performed three times in parallel at room temperature.

[0080] Example 2

[0081] Weigh dimethylamine hydrochloride, add water and stir to dissolve to prepare a dimethylamine hydrochloride aqueous solution with a concentration of 0.05g / mL, slowly add an appropriate amount of dimethyl sulfoxide to the prepared dimethylamine hydrochloride aqueous solution, the molar ratio of dimethylamine hydrochloride to dimethyl sulfoxide is 1:10, and stir evenly with a glass rod to form a mixed solution. The mixed solution is divided into a polytetrafluoroethylene-lined high-pressure reactor, placed in an electric heating blast drying oven with a constant temperature of 160°C for constant temperature reaction for 10 hours, and then naturally cooled to room temperature. The cooled solution is centrifuged at 12000rpm for 15 minutes in a desktop high-speed centrifuge to remove large particle impurities therein, and the supernatant is taken. The supernatant is filtered with a microporous membrane with a pore size of 0.22μm. The filtered solution is then placed in a dialysis bag for dialysis for one day, and the molecular retention capacity of the dialysis bag is required to be MWCO=500. During this period, ultrapure water is replaced every 4 hours. Finally, the dialyzed solution was freeze-dried to obtain a brown solid, which was the prepared nitrogen-sulfur co-doped carbon nanoparticles. The obtained nitrogen-sulfur co-doped carbon nanoparticles were stored in a refrigerator at 4°C, and the solid was redissolved in ultrapure water according to experimental needs.

[0082] Preparation of MnO 2 Nanosheets: Take an appropriate amount of potassium permanganate solid, add an appropriate amount of purified water, stir and dissolve to obtain a potassium permanganate solution with a concentration of 0.2 mol / L. Then mix the potassium permanganate solution with ethyl acetate to obtain a mixed solution, wherein the volume ratio of potassium permanganate solution to ethyl acetate is 1:50. The mixed solution is then refluxed and decolorized at 85°C to produce a colloid until the color fades. After the colloid is produced, use a separatory funnel to separate it, take the dark brown liquid of the lower layer, and then use purified water and ethanol to wash more than three times each. The resulting precipitate is MnO 2 Nanosheets, and finally MnO 2 The nanosheets were placed in an oven for drying.

[0083] Preparation of MnO 2 Nanosheet dispersion: The obtained MnO 2 The nanosheets were added with an appropriate amount of ultrapure water to obtain a concentration of 0.1 mg / mL MnO 2 Nanosheet solution, and then MnO 2 The nanosheet solution was ultrasonically treated for 0.5 h to obtain uniform MnO 2 Nanosheet dispersion.

[0084] Prepare phosphate buffer solution: weigh 0.4 g NaCl, 0.01 g KCl, 0.072 g Na 2 HPO 4 , 0.012gKH2 PO 4 , dissolve with 80 mL ultrapure water to obtain a phosphate buffer solution. Then adjust the pH value of the phosphate buffer solution to 6.0 with HCl solution or NaOH solution, and finally add ultrapure water to make up the volume. The present invention can make up the volume to 100 mL to prepare a 5 mmol / L phosphate buffer solution.

[0085] Detection of hydroxylamine hydrochloride: First, the prepared freeze-dried nitrogen-sulfur co-doped carbon nanoparticles were dissolved in an appropriate volume of ultrapure water to prepare a nitrogen-sulfur co-doped carbon nanoparticle solution, the concentration of which was 0.1 mg / mL. Then, 100 μL of the nitrogen-sulfur co-doped carbon nanoparticle solution was accurately measured and 100 μL of the MnO prepared in step 3 was added. 2 Nanosheet dispersion, forming nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Nanosheet composite fluorescence sensing system. Subsequently, in the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 1300 μL of 5 mmol / L phosphate buffer solution with pH 6.0 and 500 μL of hydroxylamine hydrochloride reference solution (the concentration range of hydroxylamine hydrochloride reference solution is 0.2-200 μmol / L) were added to the nanosheet composite fluorescence sensing system, and a series of reference solutions were obtained after thorough mixing. The series of reference solutions were placed in the sample pool of the fluorescence spectrophotometer respectively. The fluorescence spectrum of the series of reference solutions was tested with 380 nm as the excitation wavelength, and the fluorescence intensity at 458 nm was recorded. A linear equation was obtained based on the known relationship between the concentration of the hydroxylamine hydrochloride reference solution and the fluorescence enhancement efficiency.

[0086] When measuring the actual sample, first filter it with a 0.22μm microfiltration membrane to remove impurities, collect the filtrate and use it as the test solution. Replace the hydroxylamine hydrochloride reference solution with the same volume of the test solution and test under the same conditions. All experiments were performed three times in parallel at room temperature.

[0087] Example 3

[0088] Weigh dimethylamine hydrochloride, add water and stir to dissolve, prepare a dimethylamine hydrochloride aqueous solution with a concentration of 1g / mL, then slowly add an appropriate amount of dimethyl sulfoxide to the prepared dimethylamine hydrochloride aqueous solution, the molar ratio of dimethylamine hydrochloride to dimethyl sulfoxide is 1:20, stir evenly with a glass rod to form a mixed solution. Then, the mixed solution is divided into a polytetrafluoroethylene-lined high-pressure reactor and placed in an electric heating blast drying oven for constant temperature reaction. The temperature of the constant temperature reaction is a constant temperature of 220°C and the constant temperature reaction time is 1 hour. Then cool naturally to room temperature, remove large particle impurities from the cooled solution, and take the supernatant. A desktop high-speed centrifuge can be used to centrifuge at a speed of 12000rpm for 15 minutes to remove large particle impurities. The supernatant taken out is filtered with a microporous filter membrane with a pore size of 0.22μm. The filtered solution is then placed in a dialysis bag for dialysis, with the molecular cutoff of the dialysis bag being MWCO = 500, and the dialysis is performed for 24 hours, during which the ultrapure water is replaced every 4 hours. Finally, the dialyzed solution is placed in a freeze dryer for freeze drying to obtain nitrogen-sulfur co-doped carbon nanoparticles. The obtained nitrogen-sulfur co-doped carbon nanoparticles are placed in a refrigerator and stored at 4°C.

[0089] Preparation of MnO 2 Nanosheets: Weigh an appropriate amount of potassium permanganate solid, add an appropriate amount of purified water, stir and dissolve to obtain a potassium permanganate solution, wherein the concentration of the potassium permanganate solution is 0.41 mol / L. The potassium permanganate solution is then mixed with an appropriate amount of ethyl acetate to obtain a mixed solution, and the volume ratio of the potassium permanganate solution to ethyl acetate is 1:100. The mixed solution is then refluxed to fade and produce a colloid. The present invention refluxes at 85°C until the color fades. After the colloid is produced, a separatory funnel is used to separate it, the dark brown liquid of the lower layer is taken, and then it is washed with purified water and ethanol for more than three times each, and the resulting precipitate is MnO 2 Nanosheets, and finally MnO 2 The nanosheets were placed in an oven for drying.

[0090] Preparation of MnO 2 Nanosheet dispersion: MnO 2 The nanosheets were added with an appropriate amount of ultrapure water to obtain a MnO concentration of 2 mg / mL. 2 Nanosheet solution, and then MnO 2 The nanosheet solution was ultrasonically treated to obtain uniform MnO 2 Nanosheet dispersion.

[0091] Prepare phosphate buffer solution: weigh 0.8 g NaCl, 0.02 g KCl, 0.144 g Na 2 HPO 4 , 0.024gKH 2 PO 4, dissolve with 80 mL ultrapure water to obtain a phosphate buffer solution. Then adjust the pH value of the phosphate buffer solution to 8.0 with HCl solution or NaOH solution, and finally add ultrapure water to make up the volume. The present invention can make up the volume to 100 mL to prepare a 10 mmol / L phosphate buffer solution.

[0092] Detection of hydroxylamine hydrochloride: Dissolve the prepared freeze-dried nitrogen-sulfur co-doped carbon nanoparticles in an appropriate volume of ultrapure water to prepare a nitrogen-sulfur co-doped carbon nanoparticle solution with a concentration of 2 mg / mL. Then, accurately measure 100 μL of the nitrogen-sulfur co-doped carbon nanoparticle solution and add 100 μL of MnO 2 Nanosheet dispersion, forming nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 Nanosheet composite fluorescence sensing system. Subsequently, in the nitrogen-sulfur co-doped carbon nanoparticles / MnO 2 1300 μL of 10 mmol / L phosphate buffer solution at pH 8.0 and 500 μL of hydroxylamine hydrochloride reference solution (the concentration range of hydroxylamine hydrochloride reference solution is 0.2-200 μmol / L) were added to the nanosheet composite fluorescence sensing system, and a series of reference solutions were obtained after thorough mixing. The series of reference solutions were placed in the sample pool of the fluorescence spectrophotometer respectively. The fluorescence spectrum of the series of reference solutions was tested with 380 nm as the excitation wavelength, and the fluorescence intensity at 458 nm was recorded. A linear equation was obtained based on the known relationship between the concentration of the hydroxylamine hydrochloride reference solution and the fluorescence enhancement efficiency.

[0093] When measuring the actual sample, first filter it with a 0.22μm microfiltration membrane to remove impurities, collect the filtrate and use it as the test solution. Replace the hydroxylamine hydrochloride reference solution with the same volume of the test solution and test under the same conditions. All experiments were performed three times in parallel at room temperature.

Claims

1. A method for preparing nitrogen-sulfur co-doped carbon nanoparticles, characterized in that The following steps are involved: Step A): preparing a dimethylamine hydrochloride aqueous solution, adding dimethyl sulfoxide to the dimethylamine hydrochloride aqueous solution, and stirring to form a mixed solution; Step B): first subjecting the mixed solution to a constant temperature reaction, then naturally cooling it to room temperature, and taking the upper clear liquid of the cooled mixed solution; Step C): filtering the supernatant with a microporous filter membrane, dialyzing it, and finally freeze-drying it to obtain nitrogen-sulfur co-doped carbon nanoparticles.

2. The method for preparing nitrogen-sulfur co-doped carbon nanoparticles according to claim 1, characterized in that: The concentration of the dimethylamine hydrochloride aqueous solution is 0.001-1 g / mL, the molar ratio of the dimethylamine hydrochloride to the dimethyl sulfoxide is 1:1-1:20, the temperature of the isothermal reaction is 100°C-220°C, and the time is 1-20 hours.

3. The method for preparing nitrogen-sulfur co-doped carbon nanoparticles according to claim 1, characterized in that: In step C), the supernatant is filtered using a microporous filter membrane with a pore size of 0.22 μm, and the filtered solution is placed in a dialysis bag with a molecular cutoff MWCO=500 for 24 hours.

4. The method for preparing nitrogen-sulfur co-doped carbon nanoparticles according to claim 1, characterized in that: In step B), the cooled solution is first centrifuged at 12000 rpm for 15 minutes using a desktop high-speed centrifuge to remove large particle impurities in the mixed solution, and then the supernatant is taken.

5. Use of the nitrogen-sulfur co-doped carbon nanoparticles as claimed in claim 1 in the detection of hydroxylamine hydrochloride, characterized in that The following steps are involved: Step 1: Preparation of MnO2 nanosheets Weigh potassium permanganate solid, add purified water, stir and dissolve to obtain potassium permanganate solution, mix the potassium permanganate solution with an appropriate amount of ethyl acetate to obtain a mixed solution, reflux the mixed solution to fade, separate with a separatory funnel after colloid is generated, take the dark brown liquid of the lower layer, wash with purified water and ethanol to obtain MnO2 nanosheets, and dry the MnO2 nanosheets; Step 2: Preparation of MnO2 nanosheet dispersion The MnO2 nanosheets are added into ultrapure water to obtain a MnO2 nanosheet solution, and the MnO2 nanosheet solution is subjected to ultrasonic treatment to obtain a uniform MnO2 nanosheet dispersion: Step 3: Prepare phosphate buffer solution Weigh 0.08-0.8 g NaCl, 0.002-0.02 g KCl, 0.0144-0.144 g Na2HPO4, and 0.0024-0.024 g KH2PO4 respectively, and dissolve them in 80 mL ultrapure water to obtain a phosphate buffer solution; then adjust the pH value of the phosphate buffer solution to 4.0-8.0, and finally add ultrapure water to make up to volume to prepare a 1-10 mmol / L phosphate buffer solution; Step 4: Detection of Hydroxylamine Hydrochloride Dissolving the nitrogen-sulfur co-doped carbon nanoparticles in ultrapure water to prepare a nitrogen-sulfur co-doped carbon nanoparticle solution; adding the MnO2 nanosheet dispersion to the nitrogen-sulfur co-doped carbon nanoparticle solution to form a nitrogen-sulfur co-doped carbon nanoparticle / MnO2 nanosheet composite fluorescence sensing system; Then, the 1-10 mmol / L phosphate buffer and different concentrations of hydroxylamine hydrochloride reference solution were added to the nitrogen-sulfur co-doped carbon nanoparticle / MnO2 nanosheet composite fluorescence sensing system, and a series of reference solutions were obtained after sufficient mixing. The series of reference solutions were placed in the sample cell of the fluorescence spectrophotometer to test their fluorescence intensity. The fluorescence enhancement efficiency (F t -F s ) / F s The relationship between the linear equation is obtained, where F t and F s Respectively represent the fluorescence intensity tested in the presence and absence of hydroxylamine hydrochloride reference substance; When measuring the actual sample, first filter it with a 0.22 μm microfiltration membrane to remove impurities, and collect the filtrate as the test solution; The hydroxylamine hydrochloride reference solution is replaced by the same volume of the test solution, and the fluorescence intensity of the actual sample solution is detected under the same conditions. The fluorescence intensity of the actual sample solution is substituted into the linear equation to calculate the concentration of hydroxylamine hydrochloride in the actual sample solution.

6. The use according to claim 5, characterized in that: In step 1, the concentration of the potassium permanganate solution is 0.001-0.41 mol / L, the volume ratio of the potassium permanganate solution to ethyl acetate is 1:0.001-1:100, and the mixed solution is refluxed at 85° C. until the color fades.

7. The use according to claim 5, characterized in that: In step 2, the concentration of the MnO2 nanosheet solution is 0.001-2 mg / mL.

8. The use according to claim 5, characterized in that: In step 3, ultrapure water is added to make the volume to 100 mL to prepare a 1-10 mmol / L phosphate buffer solution; in step 4, the concentration of the hydroxylamine hydrochloride reference solution is 0.2-200 μmol / L, and 380 nm is used as the excitation wavelength to detect the fluorescence spectra of the series of hydroxylamine hydrochloride reference solutions and the test solution, and the fluorescence intensity at 458 nm is recorded.

9. The use according to claim 5, characterized in that: In step 4, the concentration of the nitrogen-sulfur co-doped carbon nanoparticle solution is 0.001-2 mg / mL.

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