Ratio-type red fluorescent silver nanoparticles as well as preparation method and application thereof

Abstract

The invention discloses ratio type red fluorescent silver nanoparticles as well as a preparation method and application thereof, and belongs to the technical field of metal nanoparticles. According to the preparation method, the ratio type red fluorescent silver nanoparticles are prepared by taking polyethyleneimine as a reducing agent, polyvinylpyrrolidone as a protective agent and 2-mercaptobenzothiazole as an aggregation inducer. The invention further discloses the ratio type red fluorescent silver nanoparticles prepared by the preparation method and application of the ratio type red fluorescent silver nanoparticles in ratio fluorescence detection of sulfur ions. The preparation method disclosed by the invention is simple to operate and mild and rapid in reaction condition; the prepared silver nanoparticles can be applied to ratiometric fluorescence detection of sulfur ions.

Description

Technical Field

[0001] The invention belongs to the technical field of metal nanoparticles, and in particular relates to ratiometric red fluorescent silver nanoparticles and a preparation method and application thereof. Background Art

[0002] Sulfide ion (S 2- ) is an important raw material in industrial production and can be used in papermaking, petroleum, electroplating, leather making and pharmaceutical synthesis. However, excessive accumulation of sulfur-containing waste will seriously threaten human health and the ecological environment. Studies have shown that S in the human body 2- Abnormal levels of S can induce Alzheimer's disease, Down syndrome, diabetes, cardiovascular diseases and other diseases. It should also be noted that a certain concentration of S 2- It can bind to hemoglobin in the blood, causing breathing difficulties, loss of consciousness and cardiac arrest. Therefore, it is necessary to develop a novel, simple, sensitive and efficient S 2- The detection method is of great significance.

[0003] Currently used to detect S 2- The main methods for sulfur ion detection are chromatography, electrochemical method, ultraviolet-fluorescence spectroscopy and inductively coupled plasma mass spectrometry. However, most of them have limitations such as cumbersome sample preparation, expensive equipment, time-consuming and labor-intensive, and special operation. Therefore, it is necessary to develop a fast-response, sensitive, accurate, and cost-effective sulfur ion detection technology. Fluorescence colorimetry has attracted widespread attention due to its advantages of sensitivity, simplicity, and low cost. Fluorescent nanomaterials have been widely used in food testing, environmental monitoring, cancer identification, cell imaging, and other fields in recent years due to their high sensitivity, rapid response, and real-time detection. Metal nanoparticles are favored as functional luminescent nanomaterials due to their unique optical and electrochemical properties. Among them, silver nanoparticles not only have the advantages of small size, good photostability, adjustable fluorescence properties, and low toxicity, but also have excellent fluorescence properties, catalytic properties, chirality, and antibacterial activity. They have become one of the materials with good development prospects in the field of nanoparticles. However, most of the silver nanoparticles reported so far are single-emission fluorescence, which is easily disturbed by the environment, instruments, background signals, or concentrations in applications, resulting in a decrease in accuracy.

[0004] Ratiometric fluorescent nanomaterials can utilize the change in the ratio of fluorescence intensity to improve the dynamic response range and effectively avoid interference from internal and external factors to achieve accurate determination of the detected substance. In addition, compared with single-wavelength fluorescent nanomaterials, ratiometric fluorescent nanomaterials are more sensitive, and their visualized detection results are more reliable and easier to distinguish. However, currently, ratiometric red fluorescent silver nanoparticles that can be used for high-sensitivity and accurate detection of sulfide ions are still scarce.

[0005] Therefore, how to provide a ratiometric red fluorescent silver nanoparticle with strong stability and good fluorescence performance for environmental monitoring is a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a ratiometric red fluorescent silver nanoparticle and a preparation method and application thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing ratio-type red fluorescent silver nanoparticles comprises taking polyethyleneimine as a reducing agent, polyvinyl pyrrolidone as a protecting agent and 2-mercaptobenzothiazole as an aggregation inducing agent to prepare the ratio-type red fluorescent silver nanoparticles.

[0009] Preferably, the method comprises the following steps:

[0010] The silver nitrate solution, the polyvinyl pyrrolidone solution, the polyethyleneimine solution and the 2-mercaptobenzothiazole solution are mixed, the pH is adjusted, and the obtained mixed solution is heated for reaction. After the reaction is completed, the solution is post-treated to obtain a ratiometric red fluorescent silver nanoparticle solution.

[0011] Beneficial effect: The present invention uses polyethyleneimine and polyvinylpyrrolidone as ligands, and the lone pair electrons in the amine and carbonyl groups contained in them can react with Ag in silver nitrate. + The empty orbitals of the Ag nanoparticles were combined to form a chelate with a highly concentrated area, and then 2-mercaptobenzothiazole as an aggregation inducer was able to form Ag-S bonds to obtain silver nanoparticles with red fluorescence emission.

[0012] Preferably, in the mixed solution, the concentration of silver nitrate is 0.1-0.5 mmol / L.

[0013] Beneficial effects: If the concentration is lower than the above, the silver nanomaterial solution cannot be formed. If the concentration is higher than the above, the silver nanoparticle solution will aggregate to form large-sized nanoparticles, which will quench the fluorescence.

[0014] Preferably, in the mixed solution, the concentration of polyvinyl pyrrolidone is 0.01-0.1 mmol / L.

[0015] Beneficial effects: If the concentration is lower than the above, the stability of the silver nanoparticle solution will decrease, and it will be easily oxidized by air, causing the fluorescence to weaken. If the concentration is higher than the above, the silver nanoparticle solution will aggregate to form large-sized nanoparticles, which will quench the fluorescence.

[0016] Preferably, in the mixed solution, the concentration of polyethyleneimine is 2-40 mmol / L.

[0017] Beneficial effects: If the concentration is lower than the above, Ag(I) cannot be reduced to Ag(0). If the concentration is higher than the above, the silver nanoparticle solution will aggregate to form large-sized nanoparticles, which will quench the fluorescence.

[0018] Preferably, in the mixed solution, the concentration of 2-mercaptobenzothiazole is 0.2-4.0 mmol / L.

[0019] Beneficial effects: If the concentration is lower than the above, Ag-S bonds cannot be formed to obtain silver nanoparticles with red fluorescence emission. If the concentration is higher than the above, the silver nanoparticle solution will aggregate to form large-sized nanoparticles, which will quench the fluorescence.

[0020] Preferably, the pH is adjusted to 9.0-10.0 using concentrated nitric acid.

[0021] Beneficial effects: If the pH is lower than the above, the polyethyleneimine will be protonated and unable to play a reducing role, and no silver nanoparticles will be obtained. If the pH is higher than the above, silver hydroxide precipitation will be formed, and no silver nanoparticles will be obtained.

[0022] Preferably, the heating reaction is carried out at a temperature of 40-90°C and a time of 0.1-8h.

[0023] Beneficial effects: If the temperature or time is lower than the above, the reduction reaction cannot proceed and no silver nanoparticles can be obtained. If the temperature or time is higher than the above, the silver nanoparticles will aggregate to form large-sized nanomaterials, causing fluorescence quenching.

[0024] More preferably, the post-treatment includes centrifugal purification.

[0025] After the centrifugal purification, the concentration of the ratiometric red fluorescent silver nanoparticles in the solution was 0.3 mM.

[0026] A ratiometric red fluorescent silver nanoparticle prepared by the preparation method.

[0027] Application of ratiometric red fluorescent silver nanoparticles in ratiometric fluorescence detection of sulfide ions.

[0028] Beneficial effect: The present invention detects S 2- The ratio fluorescence detection mechanism is used. Silver nanoparticles have two fluorescence emission signals, located at 610nm and 435nm respectively. 2- The F 610 / F 435 Fluorescence ratio belongs to the ratio fluorescence detection mechanism. Compared with the single emission fluorescence detection mechanism, the ratio fluorescence has the following advantages: self-calibration function, avoiding the interference of the detection environment background, avoiding the influence of probe concentration and instrument detection parameters, and improving sensitivity; PEI and MBT as ligands do not react with S2- The reaction can be used as a reference signal, and the monovalent silver on the surface of AgNPs can react with S 2- The reaction forms Ag2S, which causes fluorescence quenching and can be used as a detection response signal, thus forming a new type of fluorescence sensor for ratiometric detection of sulfide ions, which can be used in the fields of food testing and environmental monitoring.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] The present invention provides a ratiometric red fluorescent silver nanoparticle and a preparation method and application thereof, which has fluorescence with dual emission peaks. Compared with the prior art, the present invention adopts a one-pot method to prepare the product, which has the excellent characteristics of short time and simple operation. The operation only requires standing, and no tedious operations such as stirring and ultrasound are required. There is no need to introduce other nanomaterials to prepare dual-emission fluorescent silver nanoparticles through chemical forces. It has the characteristics of being green, environmentally friendly, economical and easy to operate. At the same time, the fluorescent silver nanoparticles prepared by the present invention have ratiometric characteristics. Compared with single-emission fluorescent nanoparticles, they have a self-calibration function, which can effectively avoid interference and improve the stability and accuracy of detection. The fluorescent silver nanoparticle material prepared by the present invention is used as a probe, and the change of the solution value is converted into an optical signal, which is convenient for naked eye observation and instrument measurement. It has high sensitivity and strong selectivity for sulfur ions and can be used to construct a ratiometric fluorescence detection S 2- The invention provides a chemical sensing system for ions, and the detection method is simple and the detection result is accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0032] Figure 1 Schematic diagram of the synthesis and application of ratiometric red fluorescent silver nanoparticles in Example 1 of the present invention;

[0033] Figure 2 The photo of the ratiometric red fluorescent silver nanoparticles obtained in Example 1 under a fluorescent lamp (left) and a photo of the ratiometric red fluorescent silver nanoparticles under a 365 nm ultraviolet lamp (right);

[0034] Figure 3 The UV-visible absorption spectrum (A) and fluorescence spectrum (B) of the ratiometric red fluorescent silver nanoparticles and the reaction raw materials obtained in Example 1;

[0035] Figure 4 The UV-visible absorption spectrum, fluorescence excitation and emission spectrum of the ratiometric red fluorescent silver nanoparticles obtained in Example 1;

[0036] Figure 5TEM image of the ratiometric red fluorescent silver nanoparticles obtained in Example 1;

[0037] Among them, A is the TEM image, and B is the HRTEM image;

[0038] Figure 6 is a SEM image of the ratiometric red fluorescent silver nanoparticles obtained in Example 1;

[0039] Figure 7 The stability test results of the silver nanoparticles in Example 1;

[0040] Among them, A is the storage time stability influence diagram, B is the pH effect influence diagram, and C is the temperature effect influence diagram;

[0041] Figure 8 This is a diagram showing the selectivity of the ratiometric red fluorescent silver nanoparticles obtained in Example 1 for detecting sulfide ions;

[0042] Wherein, A is the test result of the amino acid solution, and B is the test result of the ion solution;

[0043] Fig. 9 This is a graph showing the time response of the ratiometric red fluorescent silver nanoparticles obtained in Example 1 to detect sulfide ions;

[0044] Fig.10 This is a graph showing the sensitivity of the ratiometric red fluorescent silver nanoparticles obtained in Example 1 to detect sulfide ions;

[0045] A is a fluorescence spectrum of silver nanoparticles after the reaction with different concentrations of sulfur ions, B is a graph showing the relationship between the fluorescence intensity of silver nanoparticles and the change of sulfur ions at different concentrations, C is a linear relationship graph between silver nanoparticles and sulfur ions in the concentration range of 50-350 nM, and D is a linear relationship graph between silver nanoparticles and sulfur ions in the concentration range of 720-920 nM.

[0046] Fig.11 This is a diagram showing the temperature effect mechanism of the ratiometric red fluorescent silver nanoparticles obtained in Example 1 for detecting sulfide ions;

[0047] Fig.12 is a fluorescence spectrum of ratiometric red fluorescent silver nanoparticles obtained in Example 1-34;

[0048] Wherein, A is the fluorescence spectrum of Example 1 and Examples 2-5, B is the fluorescence spectrum of Example 1 and Examples 6-9, C is the fluorescence spectrum of Example 1 and Examples 10-13, D is the fluorescence spectrum of Example 1 and Examples 14-17, E is the fluorescence spectrum of Example 1 and Examples 18-23, F is the fluorescence spectrum of Example 1 and Examples 24-27, and G is the fluorescence spectrum of Example 1 and Examples 28-31;

[0049] Fig.13 The fluorescence spectra of the ratiometric red fluorescent silver nanoparticles obtained in Example 1 and Examples 32-34 are shown;

[0050] Fig.14 is the fluorescence spectrum of the silver nanoparticle solution obtained in Comparative Example 1;

[0051] Fig.15 is the fluorescence spectrum of the silver nanoparticle solution obtained in Comparative Example 2;

[0052] Fig.16 is the fluorescence spectrum of the silver nanoparticle solution obtained in Comparative Example 3;

[0053] Fig.17 is a fluorescence spectrum of the silver nanoparticle solution obtained in Comparative Example 4;

[0054] Fig.18 is a fluorescence spectrum of the silver nanoparticle solution obtained in Comparative Example 5;

[0055] Fig.19 This is the fluorescence spectrum of the silver nanoparticle solution obtained in Comparative Example 6. DETAILED DESCRIPTION

[0056] 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.

[0057] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0059] Silver nitrate (AgNO3, molecular weight 169.873) was produced by Tianjin Jinbei Fine Chemical Co., Ltd.;

[0060] 2-Mercaptobenzothiazole (C7H5NS2, molecular weight 167.251) was produced by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0061] Polyvinylpyrrolidone ((C6H9NO) n , molecular weight 58000) was produced by Shanghai MacLean Biochemical Technology Co., Ltd.;

[0062] Polyethyleneimine ((C2H8N 2.C2H5N)x, molecular weight 1800) was produced by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0063] Sodium sulfide (Na2S, molecular weight 78.045) was produced by Tianjin Komiou Chemical Reagent Co., Ltd.;

[0064] The water used was 18.2 MΩ ultrapure water.

[0065] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present invention refers to 25±3°C.

[0066] Example 1

[0067] A method for preparing ratio-type red fluorescent silver nanoparticles, using a complex formed by combining polyvinyl pyrrolidone and polyethyleneimine as a ligand and 2-mercaptobenzothiazole as an aggregation inducer, a new method for preparing ratio-type red fluorescent silver nanoparticles, the reaction schematic diagram is shown in Figure 1 As shown, the specific steps include:

[0068] (1) using ultrapure water to prepare a 0.001M AgNO3 aqueous solution, a 0.0001M polyvinyl pyrrolidone solution, and a 0.1M polyethyleneimine solution, and dissolving them in a 1.0M NaOH solution to prepare a 0.01M 2-mercaptobenzothiazole solution;

[0069] (2) 1.5 mL of the silver nitrate solution, 2.0 mL of the polyvinyl pyrrolidone solution, and 0.3 mL of the polyethyleneimine solution were sequentially pipetted into a clean, dry 10.0 mL threaded transparent reaction bottle, and 0.3 mL of the 2-mercaptobenzothiazole solution was added, followed by dilution to 5.0 mL and the pH was adjusted to 9.0 with concentrated nitric acid to obtain a slightly yellow mixed solution;

[0070] (3) The yellowish mixed solution obtained in step (2) was reacted in a 50° C. digital heating magnetic stirrer for 2.0 h, and then the mixed solution was centrifuged and purified using an ultrafiltration centrifuge tube with a molecular weight cutoff of 50,000, and then stored in a -20° C. refrigerator away from light to obtain a ratiometric red fluorescent silver nanoparticle solution, which was recorded as PVP / PEI-AgNPs solution.

[0071] Technical effect:

[0072] 1. Performance Characterization

[0073] (1) Figure 2 As shown, the prepared silver nanoparticles are light yellow in color under fluorescent light and red under 365nm ultraviolet light.

[0074] (2) In order to confirm whether the red fluorescent silver nanoparticles, namely PVP / PEI-AgNPs, were successfully prepared, the corresponding UV spectra and fluorescence spectra of PVP / PEI-AgNPs solution and control samples PVP, MBT and PEI were measured in quartz cuvettes. The results are shown in Figure 3 and Figure 4 The UV absorption spectrum shows that PVP / PEI-AgNPs have UV absorption peaks at around 310nm and 365nm, and the fluorescence spectrum shows that under the excitation of 365nm, there are two emission peaks, located at 435nm and 610nm respectively.

[0075] (3) In order to confirm the morphology and size of PVP / PEI-AgNPs, the PVP / PEI-AgNPs solution was dropped on a copper grid to prepare a sample, and the sample was observed using a transmission electron microscope after the solvent evaporated. Figure 5 This is the transmission electron microscopy analysis spectrum of the prepared PVP / PEI-AgNPs. It can be seen that the prepared PVP / PEI-AgNPs are evenly dispersed and spherical, with an average size of about 15.0 nm.

[0076] (4) In order to confirm the constituent elements of PVP / PEI-AgNPs in this example, the prepared liquid sample was freeze-dried to obtain a solid, which was characterized by scanning electron microscopy. The results are shown in Figure 6 . Figure 6 This is the SEM image of PVP / PEI-AgNPs. It can be seen from the figure that the obtained PVP / PEI-AgNPs have a spherical structure and are composed of five elements: C, N, O, S, and Ag.

[0077] 2. Stability test

[0078] In order to explore the effects of storage time, pH and temperature on the fluorescence intensity of PVP / PEI-AgNPs prepared in this example, the original solution was placed for different time periods and under different pH and temperature conditions, and its fluorescence spectra were measured at 365nm excitation wavelength, 435nm and 610nm emission wavelengths. Figure 7 As shown, the fluorescence intensity did not change significantly, indicating that the silver nanoparticles of the present invention have good stability.

[0079] 3. Fluorescence study of the interaction between various ions and the PVP / PEI-AgNPs synthesized in this example

[0080] Prepare 17 ion solutions (P2O7 4- ,HPO4 2- ,C2O4 2- ,F - ,Cl - ,Br - ,I- ,PO4 3- ,Ac - ,SO3 2- ,HCO3 - ,HSO3 - ,H2PO4 - ,CO3 2- ,SO4 2- ,Cit 3- and S 2- ) and 11 kinds of amino acid solutions (Cys, Hcy, GSH, Trp, Arg, Gly, Ser, Phe, His, Met, Lys), take 1.95mL of the prepared PVP / PEI-AgNPs solution into 28 EP tubes, and add 0.05mL of the above ion solution and amino acid solution respectively. Set the parameters of the fluorescence spectrometer to λ ex =365nm, λ em =385nm-700nm, scan the sample and record the data. The experimental results are as follows Figure 8 As shown, the results show that only S 2- It can change the fluorescence of PVP / PEI-AgNPs, while other anions and amino acids have almost no effect on the fluorescence of PVP / PEI-AgNPs.

[0081] 4. Determination of detection time

[0082] An excellent fluorescence sensor is inseparable from a fast detection time, so the detection time was also tested. Fig. 9 It can be seen that when S 2- After 3 minutes of interaction with PVP / PEI-AgNPs, the fluorescence was no longer quenched, so the optimal detection time of PVP / PEI-AgNPs was determined to be 3 minutes.

[0083] 5. Fluorescence test of the interaction between sulfide ions and PVP / PEI-AgNPs synthesized in Example 1

[0084] Take 1.9 mL of the prepared PVP / PEI-AgNPs solution and add 0.005 mL of S 2- Solution (0.002M), scan the sample, record the data, the result is as follows Fig.10 shown. Fig.10 Part A and Fig.10 The results of Part B show that with the increase of S 2- With the increase of solution concentration, the fluorescence intensity of 0.02M at the emission peak of 610nm gradually weakened, while the fluorescence intensity at the emission peak of 435nm did not change significantly, indicating that the red fluorescent silver nanoparticles prepared by the present invention can achieve S 2- Ratio detection. Fig.10 Part C and Fig.10 The results of part D in F 610 / F 435 Fluorescence intensity change ratio and S 2- The concentration showed a good linear relationship, showing two linear relationships, namely F 610 / F 435 =-0.00086[S 2- ]+0.46041(R 2 =0.9978) and F 610 / F 435 =-0.000082[S 2- ]+0.10682(R 2 =0.9969), the linear range was 50-350nM and 720-920nM, and the detection limit was 1.1nM, indicating that the obtained PVP / PEI-AgNPs had a strong affinity for S 2- It has better responsiveness and sensitivity.

[0085] 6. Sulfide ion detection mechanism test

[0086] The results of the experiment were respectively investigated at 25℃, 30℃ and 37℃ for different concentrations of S 2- The fluorescence quenching degree of PVP / PEI-AgNPs was measured by scanning the samples and recording the data. Fig.11 As shown. It can be seen that PVP / PEI-AgNPs and different concentrations of S 2- After the interaction, the slope of the curve increases with the increase of temperature, indicating dynamic quenching, which is mainly due to the soft base S 2- It can combine with the soft acid Ag(I) in PVP / PEI-AgNPs to form Ag2S, which leads to a large amount of quenching of the red fluorescence of PVP / PEI-AgNPs.

[0087] Embodiment 2-5

[0088] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that the concentrations of silver nitrate in the slightly yellow mixed solution obtained in step (2) are 100 μM, 200 μM, 400 μM and 500 μM, respectively, and the other steps and parameters are the same as those in Example 1.

[0089] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Example 2-5 at 610 nm were measured by fluorescence spectrometer. The results are as follows: Fig.12 As shown in part A, it can be seen that when the concentration of silver nitrate in the solution system is 300 μM, the fluorescence intensity of the synthesized PVP / PEI-AgNPs is the largest.

[0090] Embodiment 6-9

[0091] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that the concentrations of polyethyleneimine in the slightly yellow mixed solution obtained in step (2) are 2.0 mM, 12.0 mM, 20.0 mM and 40.0 mM, respectively, and the other steps and parameters are the same as those in Example 1.

[0092] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 6-10 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.12 As shown in part B, it can be seen that when the concentration of polyethyleneimine in the solution system is 6.0 mM, the fluorescence intensity of the synthesized PVP / PEI-AgNPs is the maximum at 610 mm.

[0093] Examples 10-13

[0094] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that the concentrations of polyvinyl pyrrolidone in the slightly yellow mixed solution obtained in step (2) are 10 μM, 20 μM, 60 μM and 100 μM, respectively, and the other steps and parameters are the same as those in Example 1.

[0095] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 10-13 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.12 As shown in part C, when the concentration of polyvinyl pyrrolidone in the solution system is 40 μM, the fluorescence intensity of the synthesized PVP / PEI-AgNPs is the highest.

[0096] Examples 14-17

[0097] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that the concentrations of 2-mercaptobenzothiazole in the slightly yellow mixed solution obtained in step (2) are 0.6 mM, 1.2 mM, 2.0 mM and 4.0 mM, respectively, and the other steps and parameters are the same as those in Example 1.

[0098] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 14-17 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.12 As shown in part D, when the concentration of 2-mercaptobenzothiazole in the solution system is 0.2 mM, the fluorescence intensity of the synthesized PVP / PEI-AgNPs is the highest.

[0099] Examples 18-23

[0100] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that in step (2), the pH is adjusted to 2.0, 6.0, 8.0, 10.0, 12.0 and 14.0 respectively with concentrated nitric acid, and the other steps and parameters are the same as those in Example 1.

[0101] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 18-23 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.12 As shown in part E, when the pH of the solution system in step (3) is 9.0, the fluorescence intensity of the synthesized PVP / PEI-AgNPs solution is the highest.

[0102] Examples 24-27

[0103] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that in step (3), the temperatures of the digital heating magnetic stirrer are set to 40°C, 60°C, 80°C and 90°C respectively, and the other steps and parameters are the same as those in Example 1.

[0104] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 24-27 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.12 As shown in part F. It can be seen from the figure that the fluorescence intensity of PVP / PEI-AgNPs prepared at 50℃ is the strongest.

[0105] Examples 28-31

[0106] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that in step (3), the reaction time of the digital heating magnetic stirrer is set to 0.1h, 0.5h, 4.0h and 8.0h respectively, and the other steps and parameters are the same as those in Example 1.

[0107] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 28-31 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.12 As shown in part G. It can be seen from the figure that the fluorescence intensity of PVP / PEI-AgNPs prepared after 2.0h of reaction is the strongest.

[0108] Examples 32-33

[0109] A method for preparing ratiometric red fluorescent silver nanoparticles, which is different from Example 1 in that when ultrapure water is used to make up the volume in step (2), the added volume of ultrapure water is 5.9 mL and 10.9 mL respectively, and the other steps are the same as Example 1, and PVP / PEI-AgNPs are prepared respectively.

[0110] The fluorescence intensity values ​​of the PVP / PEI-AgNPs solutions obtained in Example 1 and Examples 32-33 at 610 nm were measured using a fluorescence spectrometer. The results are as follows: Fig.13 As shown in the figure, it can be seen that the added volume of ultrapure water is 0.9 mL, that is, the fluorescence intensity is strongest when the concentration of PVP / PEI-AgNPs in Example 1 is 0.3 mM.

[0111] Each of the above examples is a single-factor experiment. In the process of comparing Example 1 with each single-factor experiment, the product obtained in Example 1 was re-prepared and tested. The fluorescence intensity detection data is affected by factors such as different product batches and equipment life during the detection process. Therefore, Fig.12 The AG part and Fig.13 The fluorescence intensity data of each embodiment 1 are different, which is a normal phenomenon and is within the allowable error range.

[0112] Comparative Example 1

[0113] A method for preparing silver nanoparticles, which is different from Example 1 in that no polyethyleneimine reducing agent is added.

[0114] The fluorescence intensity of the obtained solution was measured, and the fluorescence spectrum was shown in FIG. Fig.14 As shown, it can be seen that without the presence of polyethyleneimine reducing agent, a silver nanoparticle solution with red fluorescence properties cannot be successfully prepared. This is because without the presence of reducing agent, silver ions cannot be reduced to silver atoms, resulting in the failure to successfully prepare a silver nanoparticle solution with red fluorescence properties.

[0115] Comparative Example 2

[0116] A method for preparing silver nanoparticles, which is different from Example 1 in that no polyethyleneimine reducing agent and 2-mercaptobenzothiazole inducing agent are added.

[0117] The fluorescence intensity of the solution was measured and the fluorescence spectrum was shown in Fig.15 As shown, it can be seen that due to the absence of polyethyleneimine reducing agent and 2-mercaptobenzothiazole inducing agent, silver ions cannot be reduced to silver atoms and Ag-S bonds cannot be formed, resulting in the inability to successfully prepare a silver nanoparticle solution with red fluorescence properties.

[0118] Comparative Example 3

[0119] A method for preparing silver nanoparticles, which is different from Example 1 in that no polyvinyl pyrrolidone protective agent is added.

[0120] The fluorescence intensity of the solution was measured and the fluorescence spectrum was shown in Fig.16As shown, it can be seen that without the presence of polyvinyl pyrrolidone protective agent, it is impossible to successfully prepare a silver nanoparticle solution with strong red fluorescence performance. This is because without the presence of the protective agent, the formed silver nanoparticles are easily oxidized in the air to form silver oxides, thereby losing some of their fluorescence properties.

[0121] Comparative Example 4

[0122] A method for preparing silver nanoparticles, which is different from Example 1 in that no polyvinyl pyrrolidone protective agent and 2-mercaptobenzothiazole inducing agent are added.

[0123] The fluorescence intensity of the solution was measured and the fluorescence spectrum was shown in Fig.17 As shown, it can be seen that without the presence of polyvinyl pyrrolidone protective agent and 2-mercaptobenzothiazole inducer, a silver nanoparticle solution with red fluorescence properties cannot be successfully prepared. This is because without the presence of the inducer, the Ag-S bond cannot be formed.

[0124] Comparative Example 5

[0125] A method for preparing silver nanoparticles, which is different from Example 1 in that no polyethyleneimine reducing agent and no polyvinyl pyrrolidone protecting agent are added.

[0126] The fluorescence intensity of the solution was measured and the fluorescence spectrum was shown in Fig.18 As shown, it can be seen that without the presence of polyethyleneimine reducing agent and polyvinylpyrrolidone protecting agent, it is impossible to successfully prepare a silver nanoparticle solution with ratiometric red fluorescence performance. This is because without the presence of polyethyleneimine and polyvinylpyrrolidone, the Ag-N bond cannot be formed and the fluorescence emission peak at 435nm will not appear.

[0127] Comparative Example 6

[0128] A method for preparing silver nanoparticles, which is different from Example 1 in that no 2-mercaptobenzothiazole inducer is added.

[0129] The fluorescence intensity of the solution was measured and the fluorescence spectrum was shown in Fig.19 As shown, it can be seen that without the presence of 2-mercaptobenzothiazole inducer, the silver ions cannot form Ag-S bonds after being reduced to silver atoms, and the fluorescence emission peak at 610 nm will not appear, resulting in the inability to successfully prepare a silver nanoparticle solution with red fluorescence properties.

[0130] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing ratiometric red fluorescent silver nanoparticles, characterized in that: The ratiometric red fluorescent silver nanoparticles are prepared by using polyethyleneimine as a reducing agent, polyvinyl pyrrolidone as a protecting agent and 2-mercaptobenzothiazole as an aggregation inducing agent.

2. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: The following steps are involved: The silver nitrate solution, the polyvinyl pyrrolidone solution, the polyethyleneimine solution and the 2-mercaptobenzothiazole solution are mixed, the pH is adjusted, and the obtained mixed solution is heated for reaction. After the reaction is completed, the solution is post-treated to obtain a ratiometric red fluorescent silver nanoparticle solution.

3. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: In the mixed solution, the concentration of silver nitrate is 0.1-0.5 mmol / L.

4. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: In the mixed solution, the concentration of polyvinyl pyrrolidone is 0.01-0.1 mmol / L.

5. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: In the mixed solution, the concentration of polyethyleneimine is 2-40 mmol / L.

6. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: In the mixed solution, the concentration of 2-mercaptobenzothiazole is 0.2-4.0 mmol / L.

7. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: The pH is adjusted to 9.0-10.0 using concentrated nitric acid.

8. The method for preparing ratiometric red fluorescent silver nanoparticles according to claim 1, characterized in that: The heating reaction temperature is 40-90°C and the time is 0.1-8h.

9. Ratio-type red fluorescent silver nanoparticles prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the ratiometric red fluorescent silver nanoparticles as claimed in claim 9 in ratiometric fluorescence detection of sulfide ions.

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