Method for detecting rhodamine b by using solvent-induced fluorescence enhancement and application thereof

Abstract

The application discloses a method for detecting rhodamine B by using solvent-induced fluorescence enhancement. The method synthesizes up-conversion nanoparticles NaYF4:20%Yb,2%Er@NaYF4:30%Nd (UCNPs) with small particle size, uniform size and good water solubility by a thermal decomposition method, and the up-conversion nanoparticles can emit 541 nm fluorescence under the excitation of 808 nm light and the fluorescence is absorbed by rhodamine B. A simple, stable, rapid and high-sensitivity method for detecting rhodamine B based on fluorescence enhancement of the up-conversion nanoparticles is established by changing the medium environment of the UCNPs by using a mixed solvent of N,N dimethylformamide and water. The method is simple in operation, high in selectivity and fast in response speed, and is successfully applied to tomato sauce actual samples.

Description

Technical Field

[0001] This invention belongs to the field of analytical detection technology, specifically relating to a method for detecting the dye Rhodamine B using upconversion nanoparticles and its application. Background Technology

[0002] Fluorescent nanomaterials are nanoscale materials with special optical properties, mainly including carbon nanotubes, organic fluorescent dyes, quantum dots, semiconductor polymers, metal nanoclusters, and rare earth nanoparticles. They can absorb external energy and emit fluorescence at specific wavelengths, showing broad application prospects in detection and biosensing. However, their further development is limited by factors such as the easy photobleaching of organic dyes and their broad emission spectra, the toxicity and poor chemical stability of carbon nanotubes and quantum dots, and the low quantum yield of semiconductor polymers and metal nanoclusters.

[0003] Upconversion luminescence of rare-earth nanoparticles is a complex process involving the absorption of (at least) two photons, multiple energy transfer and energy shift steps, and the final emission of high-energy photons. Compared to traditional fluorescent materials, fluorescent materials with two-photon absorption exhibit less photobleaching and higher selectivity. However, rare-earth nanoparticles possess surface defects, and their fluorescence intensity is affected by the high-energy vibrational coupling between them and the dispersion medium. The more hydroxyl groups in the solvent, the stronger the high-energy vibrations of the hydroxyl groups caused by energy transfer to the surface of the rare-earth nanoparticles, and the more severe the fluorescence quenching of the rare-earth nanoparticles.

[0004] Currently, methods for detecting Rhodamine B include ultra-high performance liquid chromatography (UHPLC), ultraviolet-visible spectrophotometry (UV-Vis), electrochemical methods, and surface-enhanced Raman spectroscopy (SMR). While these methods offer many advantages, they still require time-consuming sample preparation, complex instruments, and long detection times, and are significantly affected by sample matrix interference. Therefore, providing a rapid and reliable method for detecting Rhodamine B is crucial for ensuring food safety. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for detecting Rhodamine B that is simple to operate, highly selective, fast-responding, and highly sensitive. A small, uniform, and water-soluble upconversion nanoparticle, NaYF4:20%Yb,2%Er@NaYF4:30%Nd (UCNPs), is synthesized via thermal decomposition. This upconversion nanoparticle emits fluorescence at 541 nm under 808 nm excitation light, which is absorbed by Rhodamine B. By utilizing a mixed solvent of N,N-dimethylformamide and water to modify the medial environment of the UCNPs, a simple, stable, rapid, and highly sensitive method for detecting Rhodamine B based on fluorescence enhancement by the upconversion nanoparticles is established.

[0006] This invention is achieved through the following scheme:

[0007] A method for detecting rhodamine B using solvent-induced fluorescence enhancement, characterized by comprising the following steps:

[0008] (1) Establishment of fluorescence detection system: A buffer solution was prepared by mixing N,N-dimethylformamide aqueous solution with Tris and HCl. Standard RhB solutions with different concentrations were prepared using the buffer solution. Upconversion nanoparticles were added to the standard RhB solution to form the test solution. The test solution was irradiated with an 808nm laser, and the fluorescence intensity F values ​​at 541nm and 655nm were recorded to obtain the RhB concentration and Lg(F). 655nm / F 541nm The standard curve of ) is used as the fluorescence detection system;

[0009] The upconversion nanoparticles are NaYF4:Yb,Er@NaYF4:Nd;

[0010] (2) Detection of RhB concentration in the sample: The sample was added to the buffer solution of step (1), and upconversion nanoparticles were added to obtain the test solution. The sample was irradiated with an 808nm laser and the fluorescence intensity F values ​​at 541nm and 655nm were recorded to obtain the Lg(F) concentration of the test solution. 655nm / F 541nm The RhB concentration of the test solution is obtained by corresponding to the standard curve in step (1).

[0011] Preferably, the volume ratio of N,N-dimethylformamide to water in the N,N-dimethylformamide aqueous solution in step (1) is 1:1.

[0012] Preferably, the concentration range of RhB in the test solution in step (1) is 0.02-35µg / mL, including 10 or more test solutions with different RhB concentrations.

[0013] Preferably, the concentration of the upconversion nanoparticles in the test solution in steps (1) and (2) is 5 ± 0.2 μg / mL.

[0014] Preferably, the pH of the test solution in steps (1) and (2) is 8.2 to 8.6.

[0015] Preferably, the upconversion nanoparticles NaYF4:Yb, Er@NaYF4:Nd are prepared by the following method:

[0016] (a) Inorganic salts containing Y, Yb and Er were added to a mixture of oleic acid and octadecene. The mixture was heated and stirred under an inert gas atmosphere until the inorganic salts were completely dissolved to obtain a transparent solution. NaOH and NH4F were added to the transparent solution and the mixture was heated under an inert gas atmosphere. After cooling, the mixture was washed with ethanol and cyclohexane to obtain nanoparticles NaYF4:Yb, Er.

[0017] (b) Inorganic salts containing Y and Nd were added to a mixed solution of oleic acid and octadecene, and heated and stirred under an inert gas atmosphere until the inorganic salts were completely dissolved to obtain a transparent solution. NaOH, NH4F and the nanoparticles NaYF4:Yb,Er obtained in step (a) were added to the transparent solution, and the reaction was carried out under an inert gas atmosphere. After cooling, the nanoparticles NaYF4:Yb,Er@NaYF4:Nd were obtained.

[0018] Preferably, the inorganic salt containing Y, Yb and Er in step (a) is a chloride salt, and the molar ratio of Y, Yb and Er metal ions is 78%:20%:2%; the inorganic salt containing Y and Nd in step (b) is a chloride salt, and the molar ratio of Y and Nd metal ions is 70%:30%.

[0019] Preferably, the heating reaction in steps (a) and (b) refers to first heating to 80±5°C and stirring for 20-40 min, then raising the temperature to 120±5°C and stirring for 20-40 min; and finally heating to 315±5°C and reacting for 60±10 min.

[0020] The above method is used in the detection of Rhodamine B in food.

[0021] Preferably, it is used to detect the concentration of Rhodamine B in tomato sauce.

[0022] This invention eliminates the need for excessive modification of upconversion nanoparticles when detecting Rhodamine B, simplifying the detection process and facilitating future widespread application. Compared with existing technologies, it offers the following advantages:

[0023] 1. This invention employs an active shell to coat rare-earth luminescent central ions, with Nd in the active shell... 3+ It exhibits broad absorption at 808 nm, while water molecules primarily absorb light at 980 nm and convert it into heat. Using 808 nm excitation light effectively avoids the thermal effect of traditional 980 nm excitation upconversion luminescence, reducing the impact of DMF solvent evaporation on detection. Simultaneously, Nd... 3+ It exhibits a relatively broad absorption at 808 nm, with Nd doping. 3+ Then it can be excited by an 808nm laser, avoiding interference from the system's autofluorescence, reducing light loss, and significantly enhancing the upconversion luminescence of rare earth ions.

[0024] 2. This invention primarily utilizes the fluorescence enhancement effect induced by a binary solvent, thereby significantly improving the photobleaching resistance and fluorescence intensity of upconversion nanoparticles. No modification of the upconversion nanoparticles is required, making the detection process simpler and more efficient. Simultaneously, DMF is miscible with water and most common organic solvents, and can dissolve most organic compounds, even some inorganic salts. It can essentially dissolve most components in tomato sauce, making the entire system more stable during detection and improving the radiative energy transfer efficiency between the upconversion nanoparticles and Rhodamine B, resulting in higher accuracy.

[0025] 3. This invention selects upconversion luminescence at two wavelengths with significantly different absorption coefficients for characterization, which is independent of absolute luminescence intensity and can effectively improve detection sensitivity. Because the addition of Rhodamine B only affects the fluorescence at 541 nm, while the fluorescence at 655 nm remains essentially unchanged, the ratio of the two effectively eliminates interference from other factors, thereby improving detection sensitivity and selectivity.

[0026] 4. This invention can provide a rapid response to Rhodamine B within 1 minute, without requiring a long incubation time.

[0027] 5. This invention can quantitatively detect the harmful substance Rhodamine B in tomato sauce, while excluding other substances such as Na. + Cl - Zn 2+ K + Ca 2+ The interference from isoleucine (Ile), lysine (Lys), etc., greatly improves the accuracy of this method. Attached Figure Description

[0028] Figure 1 This is a transmission electron microscope (TEM) image of upconversion nanoparticles UCNPs.

[0029] Figure 2 This is the X-ray powder diffraction (XRD) pattern of upconversion nanoparticles UCNPs.

[0030] Figure 3 The fluorescence spectrum of upconversion nanoparticles NaYF4:20%Yb,2%Er@NaYF4:30%Nd (UCNPs) is shown.

[0031] Figure 4 The graph shows the double logarithmic curves of fluorescence intensity versus excitation power at upconversion wavelengths of 523nm, 541nm, and 655nm under 808nm laser excitation.

[0032] Figure 5 The images show the fluorescence spectra of the upconversion nanoparticles in different solvents in Example 2 of this invention.

[0033] Figure 6The diagram shows the kinetic results of the upconversion nanoparticles in different solvents in Example 2 of this invention.

[0034] Figure 7 This is a diagram of the energy transfer mechanism in Embodiment 2 of the present invention.

[0035] Figure 8 Er under different RhB concentrations in Example 2 of this invention 3+ The upconversion emission spectrum.

[0036] Figure 9 This is a linear range graph of the detection of Rhodamine B by upconversion nanoparticles (UCNPs) in Example 3 of the present invention.

[0037] Figure 10 This is a linear fitting graph of the upconversion nanoparticles UCNPs used in Example 3 of the present invention to detect Rhodamine B.

[0038] Figure 11 This is a statistical chart of interference detection results in Example 4 of the present invention.

[0039] Figure 12 This is a response time diagram for Rhodamine B in Example 5 of the present invention. Detailed Implementation

[0040] Unless otherwise specified, the technical means used in the following embodiments are all conventional means in this technical field. Unless otherwise specified, the reagents, equipment and methods used in this invention are conventional reagents, equipment and methods in this technical field.

[0041] Main reagents and instruments: Anhydrous yttrium chloride (YCl3, 99.99%), anhydrous erbium chloride (ErCl3, 99.99%), anhydrous ytterbium chloride (YbCl3, 99.99%), anhydrous neodymium chloride (NdCl3, 99.99%), ammonium fluoride (NH4F, 97%), cyclohexane (Cyclohexane, 90%), and 1-octadecene (1-Octadecene, 90%) were purchased from Energy Chemical (Shanghai, China). Rhodamine B (RhB, C 28 H 31 ClN2O3 (80%) was purchased from J&K Scientific (Beijing, China). Cyclohexane (C6H2O3) was also purchased. 12N,N-dimethylformamide (C3H7NO, 99.5%) was purchased from ALaddin Reagsent Corporation (Shanghai, China). Ethanol (C2H6O, 99.9%) and sodium hydroxide (NaOH, 97%) were purchased from Fuyu Chemical (Tianjin, China). All chemicals used in this invention are analytical grade reagents and can be used without further purification. The ultrapure water used in the experiments was purified using a Milli-Q purification system (Millipore, USA) with a resistivity of 18.2 MΩ.

[0042] Main characterization instruments: X-ray powder diffractometer (XRD, Bruker D8 Advance, Cu-Kα (λ=1.5405Å)), transmission electron microscope (JEM-2100F), Fluoromax-4 fluorescence spectrometer (HORIBA, Co., USA), 808nm laser (INFRARED DIODE LASERAT 808nm).

[0043] The NaYF4:20%Yb,2%Er@NaYF4:30%Nd (UCNPs) rare earth nanoparticles used in Example 1 below were prepared according to the following method:

[0044] Preparation of oleic acid-encapsulated upconversion nanoparticle cores:

[0045] a) First, add 0.0055g ErCl3, 0.0559g YbCl3, and 0.1523g YCl3 to a 100mL three-necked flask, then add 6mL oleic acid and 15mL octadecene; heat to 50℃ and stir for 20min under a nitrogen atmosphere, then raise the temperature to 180℃ and react for 15min to completely dissolve the rare earth chlorides and form a transparent clear solution. Then stop heating and cool to room temperature.

[0046] b) Next, add 0.1 g NaOH and 0.1481 g NH4F to the clear solution, heat to 80 °C and stir for 30 min under nitrogen protection, then heat to 120 °C and stir for 30 min; finally, heat to 315 °C and react for 60 min under nitrogen atmosphere. After the reaction is complete, cool naturally to room temperature; add an appropriate amount of ethanol, centrifuge at 8000 r / min for 10 min, and remove the supernatant; add an appropriate amount of cyclohexane to the solid and disperse by ultrasonication, then add an appropriate amount of ethanol and centrifuge again; repeat the above steps, and wash several times with cyclohexane and ethanol to obtain nanoparticles NaYF4:20%Yb,2%Er. The final product is dispersed and stored in 10 mL of cyclohexane.

[0047] Preparation of oleic acid-coated upconversion nanoparticle shells:

[0048] a) First, add 0.1367g YCl3 and 0.0752g NdCl3 to a 100mL three-necked flask, then add 6mL oleic acid, 15mL octadecene and 1mL pure water; heat to 50℃ and stir for 20min under nitrogen atmosphere, then raise the temperature to 180℃ and react for 15min to completely dissolve the rare earth chlorides and form a transparent clear solution. Then stop heating and cool to room temperature.

[0049] b) Next, 0.1 g NaOH, 0.1481 g NH4F, and 10 mL of cyclohexane-dispersed NaYF4:20%Yb,2%Er nanoparticles were added to the clear solution. The mixture was heated to 80 °C and stirred for 30 min under nitrogen protection, then heated to 120 °C and stirred for 30 min. Finally, the mixture was heated to 315 °C and reacted for 60 min under nitrogen atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. An appropriate amount of ethanol was added, and the mixture was centrifuged at 8000 r / min for 10 min to remove the supernatant. An appropriate amount of cyclohexane was added to the solid, and the mixture was ultrasonically dispersed. An appropriate amount of ethanol was added again, and the mixture was centrifuged again. The above steps were repeated, and the mixture was washed several times with cyclohexane and ethanol to obtain NaYF4:20%Yb,2%Er@NaYF4:30%Nd nanoparticles (UCNPs). The final product was dispersed and stored in 10 mL of cyclohexane.

[0050] Removal of oleic acid from the surface of upconversion nanoparticles:

[0051] 5 mL of UCNPs cyclohexane dispersion was mixed with 2 mL of (0.2 M) HCl and sonicated at 30 °C for 20 min. Then, the mixture was stirred at room temperature for 12 h and centrifuged at 12000 r / min for 20 min. The supernatant was removed, and the obtained UCNPs were washed three times with ethanol and dried at 60 °C under vacuum for 12 h. The final product was dispersed in 50 mL of pure water (1 mg / mL) for later use.

[0052] Transmission electron microscope image attached Figure 1 As shown, the product exhibits a regular hexagonal shape, good dispersion, and a size of approximately 42 nm. The X-ray diffraction pattern is attached. Figure 2 As shown, all diffraction peaks correspond one-to-one with standard PDF card JCPDS 16-0334, and there are no redundant diffraction peaks, indicating that the product obtained by this invention is a pure hexagonal phase crystal.

[0053] As attached Figure 3As shown, under 808 nm laser excitation, the product exhibits bright upconversion luminescence in the green and red light regions. By varying the excitation power of the semiconductor laser, the luminescence intensity of the sample at 523 nm, 541 nm, and 655 nm was measured at different excitation powers. Then, a double logarithmic plot of the luminescence intensity and excitation power was obtained, as shown in the attached figure. Figure 4 As shown. By Figure 4 It can be seen that the slopes at 523nm, 541nm and 655nm are 1.84, 1.77 and 1.70 respectively, all close to 2, which indicates that both green and red light emission are two-photon processes.

[0054] The following description of the binary mixed solvent detection system in Example 2:

[0055] The fluorescence spectra of the product were measured by changing the solvents N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol (EtOH), methanol (MeOH), and n-butanol (1-Butanol), as shown in the attached figure. Figure 5 As shown, the fluorescence intensity of the product in other solvents is significantly higher than that in water. This is because the rare earth nanoparticles dispersed in water have a large number of hydroxyl groups on their surface, leading to fluorescence quenching. DMF, however, does not contain hydroxyl groups, and when used as a solvent, the fluorescence intensity of the upconversion nanoparticles increases significantly by approximately 16 times. Furthermore, with increasing DMF content (DMF to H2O volume ratios of 4:0, 3:1, 2:2, 1:3, and 0:4), the photostability of UCNPs first increases and then decreases, as shown in the attached figure. Figure 6 As shown, this is because the increase of organic solvents reduces the solubility of UCNPs, thereby causing the material to settle and resulting in a decrease in the photostability of upconversion nanoparticles. Figure 6 The results showed that the nanoparticles exhibited optimal stability when the system pH was 8.6 and the volume ratio of DMF to H2O was 2:2.

[0056] From the appendix Figure 7 The rare earth element Er shown 3+ The upconversion emission spectrum of the doped dye and the absorption spectrum of the fluorescent dye show that, under 808 nm laser excitation, the main emission peaks located at ~523 nm, ~541 nm, and ~655 nm correspond to Er, respectively. 3+ Ionic 2 H 11 / 2 → 4 I 15 / 2 , 4 S 3 / 2 → 4 I 15 / 2 and 4 F 9 / 2 →4I 15 / 2 Three types of energy transitions. And rare earth element Er...3+ The green upconversion luminescence of RhB largely overlaps with its absorption spectrum, as shown in the attached figure. Figure 8 As shown, the green light emission intensity of UCNPs in pure aqueous dispersions decreases with increasing RhB concentration (0-150 µg / mL), while the red light emission intensity remains essentially constant due to the lack of interference. Furthermore, an RhB emission peak is observed at 560-600 nm, indicating that rare earth Er... 3+ Efficient radiative energy transfer is possible between ions and RhB fluorescent molecules. We eliminate errors by using the ratio of fluorescence intensity at 655 nm to 541 nm, thus reducing the impact on sensitivity caused by the low efficiency of the radiative energy transfer process.

[0057] The following Example 3 describes the detection of Rhodamine B concentration using UCNPs:

[0058] a) Prepare the solutions used in the experiment:

[0059] Preparation of binary mixed solution A: Mix 200 mL of DMF with 200 mL of pure water evenly and cool to room temperature before use.

[0060] Preparation of Tris-HCl (pH=8.6) buffer solution: Weigh 0.6058g Tris into beaker a and add 50mL of solution A to dissolve it; then weigh 0.3765g HCl into beaker b and add 100mL of solution A to dissolve it; take the solution from beaker b to adjust the pH of the solution in beaker a to 8.6, and then use binary mixed solution A to make up to 100mL to prepare a 50mM Tris-HCl buffer solution for later use.

[0061] Preparation of standard RhB solutions: Disperse 2 mg of RhB in 10 mL of solution A as a high-standard solution. Dilute different volumes of RhB high-standard solutions with solution A to 2 mL to prepare RhB standard solutions with concentrations of 0.08 µg / mL, 0.2 µg / mL, 0.6 µg / mL, 1 µg / mL, 2 µg / mL, 3 µg / mL, 4 µg / mL, 5 µg / mL, 10 µg / mL, 15 µg / mL, 20 µg / mL, 30 µg / mL, 50 µg / mL, 60 µg / mL, 80 µg / mL, 100 µg / mL, and 140 µg / mL for later use.

[0062] b) Plotting the standard curve:

[0063] 10 µL of UCNP dispersion was added to 1500 µL of Tris-HCl buffer solution, and then mixed with 500 µL of standard RhB solutions of different concentrations. The mixture was ultrasonically vibrated for 3 min to ensure homogeneity. The final test solution contained UCNPs at a concentration of 5 µg / mL and RhB in the range of 0.02–35 µg / mL. The solution was then transferred to a quartz cuvette, and the fluorescence spectrum of the mixture was measured under 808 nm near-infrared laser irradiation. The data were processed to obtain a linear fluorescence spectrum, and the concentration of the RhB solution (C0) was determined. R ) and Lg(I 655nm / I 541nm (IR) standard curve. From the attached Figure 9 It can be seen that the standard chromatogram exhibits good linearity within the concentration range of 0.15-35 µg / mL, with a correlation coefficient R1 of 0.9993 and a detection limit of 0.039 µg / mL (S / N=3). The formula is: LgIR=0.0204C. R -0.5293. From Figure 10 The upconversion luminescence intensity ratio I shown 655nm / I 541nm (IR) and RhB concentration (C R The fitting curve between the intensity ratio IR and C shows that... R The concentrations satisfy IR = 1.1007exp(0.0014C). R The coefficient of determination R² for the fit is 0.9994, indicating that Er 3+ The green upconversion luminescence intensity ratio exhibits excellent RhB concentration sensing characteristics.

[0064] The specificity of UCNPs for the detection of Rhodamine B in Example 4 below:

[0065] A 2 mL test solution was prepared by adding sodium sulfate, sodium chloride, zinc chloride, potassium carbonate, potassium chloride, calcium chloride, isoleucine (Ile), lysine (Lys), valine (VaL), threonine (Thr), tryptophan (Trp), phenylalanine (Phe), leucine (Leu), histidine (His), and rhodamine B aqueous solution to the UCNPs dispersion for specific detection (the concentration of UCNPs in the test solution was 5 μg / mL, and the concentration of other test substances was 100 μM). These substances are common in tomato sauce. The test results are attached. Figure 11 The red upconversion fluorescence enhancement ratio of the sample with added Rhodamine B was much higher than that of the sample with added other substances, therefore the ratiometric fluorescence nanosensor has high selectivity for RhB.

[0066] The response speed of UCNPs to RhB detection in Example 5 below:

[0067] Add 500 μL of RhB solution (UCNP concentration 5 µg / mL) at a concentration of 35 µg / mL to 1500 μL of UCNP dispersion, and then immediately record its fluorescence intensity under continuous excitation with an 808 nm laser, as shown in the attached figure. Figure 12 As shown, the present invention can respond rapidly to Rhodamine B within 1 minute without requiring a long incubation time.

[0068] The concentration of RhB in tomato sauce samples was detected using UCNPs in Example 6 below:

[0069] Pretreatment of tomato sauce samples: Select a certain brand of tomato sauce sample, weigh 5g of tomato sauce (accurate to 0.01g) and place it in a beaker. Add 25mL of ethyl acetate and 25mL of cyclohexane solution, and extract by sonication for 30min at room temperature. Transfer the resulting mixture to a centrifuge tube and centrifuge at 8000rpm for 10min. Filter the supernatant through a 0.45µm filter membrane and evaporate to dryness by rotary evaporation at 40℃. Dissolve the residue in 5.0mL of binary mixed solution A and store at 4℃ for later use.

[0070] Selective detection of RhB in tomato sauce sample solution: 1500 μL of Tris-HCl buffer solution was mixed with 500 μL of sample solution, and 10 μL of UCNPs dispersion was added. The mixture was then sonicated for 3 min to ensure homogeneity. The solution was then transferred to a quartz cuvette, and the fluorescence spectrum of the mixture was measured under 808 nm near-infrared laser irradiation.

[0071] Horizontal spiking: Rhodamine B at concentrations of 0.2 μg / mL, 2.3 μg / mL, and 23 μg / mL within the standard curve range was selected. Three aliquots of each concentration were processed in parallel. Each aliquot was treated with 500 μL of tomato paste sample solution and incubated overnight at room temperature to ensure thorough mixing of the spiked solution with the sample matrix. Extraction was performed the following day. The recovery results of the spiking concentrations in the samples are shown in Table 1. The average recoveries were 99.1%, 100.2%, and 102.2%, with corresponding RSDs of 1.3%, 1.9%, and 1.0%, respectively.

[0072] Table 1: Selective Detection of Rhodamine B in Tomato Sauce

[0073]

[0074] Table 2: Comparison of the detection method of the present invention with other methods:

[0075] .

Claims

1. A method for detecting Rhodamine B using solvent-induced fluorescence enhancement, characterized in that, Includes the following steps: (1) Establishment of fluorescence detection system: Standard RhB solutions with different concentrations were prepared using a buffer solution containing N,N-dimethylformamide; upconversion nanoparticles were added to the standard RhB solutions to form the test solution; the test solution was irradiated with an 808nm laser, and the fluorescence intensity F values ​​at 541nm and 655nm were recorded to obtain the relationship between RhB concentration and Lg(F). 655nm / F 541nm The standard curve of ) is used as the fluorescence detection system; The upconversion nanoparticles are NaYF4:Yb,Er@NaYF4:Nd; (2) Detection of RhB concentration in the sample: The sample was added to a buffer solution containing N,N-dimethylformamide, and upconversion nanoparticles were added to obtain the test solution. The sample was irradiated with an 808nm laser, and the fluorescence intensity F values ​​at 541nm and 655nm were recorded to obtain the Lg(F) concentration of the test solution. 655nm / F 541nm The RhB concentration of the test solution is obtained by corresponding to the standard curve in step (1); In steps (1) and (2), the volume ratio of N,N-dimethylformamide to water in the buffer solution containing N,N-dimethylformamide is 1:1, and the pH is 8.

6. The concentration range of RhB in the test solution in step (1) is 0.02-35µg / mL, including 10 or more test solutions with different RhB concentrations; The concentration of the upconversion nanoparticles in the test solution in steps (1) and (2) is 5 ± 0.2 μg / mL.

2. The method according to claim 1, characterized in that, The upconversion nanoparticles were prepared by the following method: (a) Inorganic salts containing Y, Yb and Er were added to a mixture of oleic acid and octadecene. The mixture was heated and stirred under an inert gas atmosphere until the inorganic salts were completely dissolved to obtain a transparent solution. NaOH and NH4F were added to the transparent solution and the mixture was heated under an inert gas atmosphere. After cooling, the mixture was washed with ethanol and cyclohexane to obtain nanoparticles NaYF4:Yb,Er. (b) Inorganic salts containing Y and Nd were added to a mixed solution of oleic acid and octadecene, and heated and stirred under an inert gas atmosphere until the inorganic salts were completely dissolved to obtain a transparent solution. NaOH, NH4F and the nanoparticles NaYF4:Yb,Er obtained in step (a) were added to the transparent solution, and the reaction was carried out under an inert gas atmosphere. After cooling, the solution was washed with ethanol and cyclohexane to obtain NaYF4:Yb,Er@NaYF4:Nd.

3. The method according to claim 2, characterized in that, The inorganic salt containing Y, Yb and Er in step (a) is a chloride salt, and the molar ratio of Y, Yb and Er metal ions is 78%:20%:2%; the inorganic salt containing Y and Nd in step (b) is a chloride salt, and the molar ratio of Y and Nd metal ions is 70%:30%.

4. The method according to claim 3, characterized in that, The heating reaction in steps (a) and (b) refers to first heating to 80±5℃ and stirring for 20-40 min, then raising the temperature to 120±5℃ and stirring for 20-40 min; and finally heating to 315±5°C and reacting for 60±10 min.

5. The application of the method according to any one of claims 1-4 in the detection of rhodamine B in food.

6. The application according to claim 5, characterized in that, Used to detect the concentration of Rhodamine B in tomato sauce.

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