Lead-free halide perovskite nanocrystal and its application in detecting peroxide value of oils and fats

Abstract

The invention discloses a lead-free halide perovskite nanocrystal and its application in detecting the peroxide value of oils and fats. The lead-free halide perovskite nanocrystal is prepared according to the following steps: a precursor substance, oleylamine, and oleic acid are stirred in N,N-dimethylformamide to obtain a clarified precursor solution; an ammonia solution is added to the precursor solution, and the mixture is vigorously stirred at 1500 rpm for 1-5 minutes to obtain a precursor solution to which ammonia water is added; the precursor solution to which ammonia water is added is quickly added to a dry solvent, centrifuged 1-3 times, and a precipitate obtained from the final centrifugation is collected to obtain the lead-free halide perovskite nanocrystal. The invention utilizes low-toxic, green lead-free halide perovskite nanocrystal to measure the peroxide value of edible oil in a solvent capable of improving fluorescence quantum efficiency, thereby improving the environmental friendliness of the detection method and achieving advantages such as visualization, high sensitivity, and a low detection limit for the detection of the peroxide value of edible oil.

Description

(1) Technical field

[0001] The invention relates to a lead-free halide perovskite nanocrystal and application thereof in detecting the peroxide value of oils and fats. (2) Background technology

[0002] Edible oil is a kind of natural organic compound that not only provides calories to the human body, but also provides some essential fatty acids and fat-soluble vitamins (V A 、V D 、V E 、V K ) and possess indispensable nutritional value. However, edible oils often undergo oxidation and deterioration during processing, transportation, and storage, significantly impacting their nutritional value, flavor, safety, storage, and economic benefits. Therefore, identifying the degree of oxidation in edible oils is crucial.

[0003] Currently, methods for measuring the peroxide value of edible oils primarily include titration, chromatography, spectroscopy, and rapid detection. To achieve in situ, rapid, and visual detection of edible oil peroxide value, rapid colorimetric detection methods have garnered significant attention. Colorimetric detection methods based on perovskite quantum dots offer advantages such as low detection limits and strong visualization. However, their fluorescence stability relies heavily on highly toxic heavy metal lead salts and highly toxic solvents such as toluene or chloroform. Consequently, these methods suffer from numerous drawbacks, including low sensitivity, low accuracy, and environmental and operator-unfriendly detection systems. (3) Summary of the invention

[0004] The present invention aims to provide a lead-free halide perovskite nanocrystal and its application in detecting the peroxide value of oils and fats. The lead-free halide perovskite nanocrystal has the advantages of being green, having high fluorescence quantum efficiency, and having a stable fluorescence signal. It is used to detect the peroxide value of oils and fats, and has the advantages of being sensitive, rapid, and highly visual. The detection method is flexible and can detect both characteristic fluorescence absorption and maximum fluorescence absorption peak shift. In addition, instant visual detection can be achieved by detecting the colorimetric value of the solution.

[0005] The technical solution adopted in the present invention is:

[0006] The invention provides a lead-free halide perovskite nanocrystal. The lead-free halide perovskite nanocrystal is prepared according to the following steps: a precursor substance, oleylamine and oleic acid are stirred in N,N-dimethylformamide (DMF) to obtain a clear precursor solution; an ammonia solution is added to the precursor solution, and the mixture is vigorously stirred at 1500 rpm for 1-5 minutes (preferably 3 minutes) to obtain a precursor solution to which ammonia water is added; the precursor solution to which ammonia water is added is quickly added to a dry solvent, centrifuged 1-3 times repeatedly, and a precipitate obtained by the final centrifugation is collected to obtain the lead-free halide perovskite nanocrystal. The precursor substance is a combination of one of BiBr3, SnBr2 or CuBr and CsBr; and the dry solvent comprises n-pentane, ethyl acetate, ether, acetonitrile, n-hexane, cyclohexane, butyl acetate, n-heptane, n-octane and petroleum ether.

[0007] Preferably, the mass ratio of CsBr to BiBr3, SnBr2 or CuBr is 1:0.1-2; more preferably, the mass ratio of CsBr to BiBr3 is 1:0.45, the mass ratio of CsBr to SnBr2 is 1:1.3, and the mass ratio of CsBr to CuBr is 1:0.85.

[0008] Preferably, the volume amount of oleylamine is 1-5 mL / g, the volume amount of oleic acid is 5-15 mL / g, and the volume amount of N,N-dimethylformamide is 40-100 mL / g based on the total mass of the precursor.

[0009] Preferably, the volume concentration of the ammonia solution is 2.8%, the volume ratio of the precursor solution to the ammonia solution is 1:0.01-1, preferably 1:0.02; the volume ratio of the precursor solution to which ammonia solution is added to the dry solvent is 1:50.

[0010] Preferably, the precursor solution is obtained by stirring at 75-120° C. for 1-3 hours.

[0011] The present invention also provides a method for rapidly visually detecting the peroxide value of edible oils using lead-free halide perovskite nanocrystals. The method comprises dispersing the lead-free halide perovskite nanocrystals in an organic solvent (a) to form a dispersion, adding a solution of oleylamine iodine in an organic solvent (b) and the edible oil to be tested, measuring the colorimetric value or the fluorescence emission spectrum of the mixed solution at an excitation wavelength, extracting the fluorescence emission peak intensity or the maximum absorption peak shift value, and obtaining the peroxide value of the edible oil to be tested based on a standard curve of peroxide value versus colorimetric value, fluorescence intensity, or maximum absorption peak shift value. The organic solvent (a) includes ethyl acetate, cyclohexane, n-heptane, toluene, n-hexane, petroleum ether, ether, and chloroform; the organic solvent (b) is the same as the organic solvent (a). The lead-free halide perovskite nanocrystals are dispersed in the organic solvent (a) at a concentration of 1 mg / mL; the oleylamine iodine is added in the form of 0.135 mM oleylamine iodine in the organic solvent (b) at a volume ratio of 1:1 to the dispersion; and the volume ratio of the dispersion to the edible oil to be tested is 1:0.22.

[0012] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0013] The present invention provides lead-free halide perovskite nanocrystals and their application in detecting the peroxide value of oils and fats, addressing the environmental pollution issues associated with conventional lead halide perovskite nanocrystals. By utilizing these low-toxic, green lead-free halide perovskite nanocrystals in solvents that enhance fluorescence quantum efficiency (such as ethyl acetate, n-hexane, and cyclohexane), the peroxide value of edible oils is measured, enhancing the environmental friendliness of the detection method and achieving advantages such as visualization, high sensitivity, and a low detection limit for edible oil peroxide value detection. For example, the detection limit for Cs3BiBr6 is 0.01g / 100g, significantly lower than the national standard limit of 0.25g / 100g and the iodine titration limit of 0.02g / 100g, representing a significant improvement. (IV) Description of the accompanying drawings

[0014] Figure 1 This is a comparison of the fluorescence intensities of CsPbBr3 perovskite nanocrystals dispersed in different solvents.

[0015] Figure 2 This is a visual diagram of the reaction system of ethyl acetate dispersion of CsPbBr3 perovskite nanocrystals and oils with different peroxide values.

[0016] Figure 3 This is a fluorescence intensity detection diagram of ethyl acetate dispersion of CsPbBr3 perovskite nanocrystals to edible oils with different peroxide values ​​(0.02-0.4g / 100g).

[0017] Figure 4 This is the standard curve of the color value of edible oils with different peroxide values ​​detected by ethyl acetate dispersion of CsPbBr3 perovskite nanocrystals.

[0018] Figure 5 This is the standard curve of fluorescence intensity of ethyl acetate dispersion of CsPbBr3 perovskite nanocrystals for detecting edible oils with different peroxide values.

[0019] Figure 6 This is the standard curve of the maximum fluorescence absorption wavelength shift value of edible oils with different peroxide values ​​detected by ethyl acetate dispersion of Cs3PbBr6 perovskite nanocrystals.

[0020] Figure 7 This is the ultraviolet absorption spectrum of the Cs3BiBr6 perovskite nanocrystals prepared in Example 2.

[0021] Figure 8 This is a fluorescence intensity diagram of ethyl acetate dispersion of Cs3BiBr6 perovskite nanocrystals versus edible oil peroxide value (0.02-0.33 g / 100 g).

[0022] Figure 9 This is the standard curve of the fluorescence intensity of ethyl acetate dispersion of Cs3BiBr6 perovskite nanocrystals versus the peroxide value of edible oil.

[0023] Figure 10 This is the ultraviolet absorption spectrum of the lead-free CsSnBr3 perovskite nanocrystals prepared in Example 3.

[0024] Figure 11 This is a fluorescence intensity diagram of the lead-free CsSnBr3 perovskite nanocrystals prepared in Example 3.

[0025] Figure 12 This is the ultraviolet absorption spectrum of the lead-free CsCu2Br3 perovskite nanocrystals prepared in Example 4.

[0026] Figure 13 This is a fluorescence intensity graph of the ethyl acetate dispersion of the lead-free CsCu2Br3 perovskite nanocrystal prepared in Example 4 versus the peroxide value of edible oil (0.06-0.33 g / 100 g).

[0027] Figure 14 This is a standard curve of the fluorescence intensity of the ethyl acetate dispersion of the lead-free CsCu2Br3 perovskite nanocrystal prepared in Example 4 versus the peroxide value of edible oil. (V) Specific implementation methods

[0028] The present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0029] The microplate reader used in the embodiment of the present invention is a multifunctional microplate reader (Synergy H1, Bioteck, Vermont, USA).

[0030] The room temperature is 25-30°C.

[0031] Example 1: Preparation of CsPbBr3 perovskite nanocrystals and screening of dispersing solvents for determining the peroxide value of edible oils

[0032] 1. CsPbBr3 perovskite nanocrystals

[0033] 0.1468g of PbBr2, 0.0851g of CsBr, 0.6mL of oleylamine (OAm), and 1.8mL of oleic acid (OA) were weighed and evenly dispersed in 10mL of N,N-dimethylformamide (DMF). The mixture was stirred at 120°C for 2 hours to obtain a clear precursor solution. To 2mL of the precursor solution, 40μL of a 2.8% aqueous ammonia solution was added. After vigorous stirring at 1500rpm for 3 minutes, the ammonia-doped precursor solution was obtained. 0.2mL of the ammonia-doped precursor solution was quickly added to 10mL of ethyl acetate and centrifuged at 8000rpm for 5 minutes at room temperature. The precipitate was centrifuged twice in ethyl acetate. The precipitate from the final centrifugation was collected and dried with nitrogen. This was the CsPbBr3 perovskite nanocrystal, which was weighed and had a yield of approximately 95%.

[0034] CsPbBr3 perovskite nanocrystals were prepared with ethyl acetate to prepare a CsPbBr3 perovskite nanocrystal dispersion with a concentration of 1 mg / mL.

[0035] Under the same conditions, ethyl acetate was replaced with cyclohexane, n-heptane, toluene, n-hexane, petroleum ether, ethyl ether, and chloroform to prepare 1 mg / mL CsPbBr3 perovskite nanocrystal dispersions in different solvents.

[0036] 2. Fluorescence spectrum detection

[0037] The dispersion of CsPbBr3 perovskite nanocrystals prepared in step 1 was transferred to a microplate reader and excited at 365 nm to measure its fluorescence spectrum at 400-700 nm. The results are as follows: Figure 1 As shown, the results show that the fluorescence emission intensity of CsPbBr3 perovskite nanocrystals in ethyl acetate is the highest, so ethyl acetate is selected as the dispersion solvent.

[0038] 3. Preparation of FI, FS, and RGB standard curves

[0039] (1) Test solution

[0040] 1 mL of 1 mg / mL CsPbBr3 perovskite nanocrystal ethyl acetate dispersion, 1 mL of 0.135 mM oleylamine iodine ethyl acetate solution, and 0.22 mL of edible oil with different peroxide values ​​(0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5 g / 100 g) were taken and evenly mixed in a reaction tube and allowed to stand at room temperature for 5 minutes to obtain the test solution. The photos of each reaction tube are shown in Figure 2 As shown, as the peroxide value increases, the color of the mixed system changes from red to orange and finally to green, indicating that the color of the system can be seen by the naked eye and reversed to the peroxide value. If the color is green, the peroxide value is high; if the color is red, the peroxide value is low.

[0041] (2) Fluorescence spectrum detection

[0042] Step (1) The solution to be tested is placed in an enzyme-labeled instrument, excited at 365 nm, and its fluorescence spectrum at 400-700 nm is measured. The results are as follows: Figure 3 As shown, Figure 3 It shows that as the peroxide value of edible oil (0.02-0.5g / 100g) increases, the fluorescence emission peak wavelength of CsPbBr3 perovskite nanocrystals gradually decreases and the emission peak intensity also decreases accordingly.

[0043] (3) Chromaticity value standard curve

[0044] Step (1) Take a picture of the solution to be tested and use Image J software to extract the color value of the picture (Image J). Draw the RGB standard curve with the color value (RGB) as the horizontal axis and the peroxide value as the vertical axis. Figure 4 As shown in the figure, it shows that: as the peroxide value of edible oil increases, the G / R value of the photo decreases, and the G / R value of the photo is negatively correlated with the peroxide value of edible oil (R 2 =0.962), the linear detection range of this method is 0.02-0.5g / 100g, and the detection limit is 0.02g / 100g.

[0045] (4) Maximum fluorescence absorption intensity standard curve

[0046] The peroxide value in the test solution is taken as the vertical axis and the maximum fluorescence absorption intensity (FI) at 365nm is taken as the horizontal axis to draw the FI standard curve. The results are shown in Figure 5 As shown in the figure, it shows that: as the peroxide value of edible oil increases, FI gradually decreases, and FI and peroxide value of edible oil have a good negative correlation linear relationship (R 2 =0.998), the linear detection range of this method is 0.02-0.2g / 100g, and the detection limit is 0.02g / 100g.

[0047] (5) Standard curve of maximum fluorescence absorption wavelength shift value (FS)

[0048] The FS standard curve is drawn with the peroxide value in the solution to be tested as the vertical axis and the fluorescence emission spectrum emission peak wavelength shift value (FS) of the solution after 365nm excitation as the horizontal axis. The results are shown in Figure 6 As shown in the figure, it shows that: as the peroxide value of edible oil increases, FS gradually increases, and FS and edible oil peroxide value have a good positive correlation linear relationship (R 2 =0.986), the linear detection range of this method is 0.02-0.25 g / 100 g, and the detection limit is 0.0034 g / 100 g.

[0049] 4. Comparison of different methods for the detection of peroxide value of edible oil

[0050] Edible oils: soybean oil (first-grade refined soybean oil, Q / BBAH0019S), camellia oil (GB / T 11765), olive oil (extra virgin olive oil, GB / T 23347), and linseed oil (first-pass cold-pressed, winterized, and dewaxed, GB / T 8235). Two replicate samples were collected for each edible oil.

[0051] CsPbBr3 perovskite nanocrystals: Take 1 mL of 1 mg / mL CsPbBr3 perovskite nanocrystals ethyl acetate dispersion, 1 mL of 0.135 mM oleylamine iodide ethyl acetate solution and 0.22 mL of different edible oils and mix them evenly. Let them stand at room temperature for 5 minutes. Use the method in step 3 to detect FI, FS, and RGB values. Figure 4 、 5 , 6 standard curves to obtain the peroxide value. The results are shown in Table 1.

[0052] Cs3BiBr6 perovskite nanocrystals: Take 1 mL of 1 mg / mL ethyl acetate dispersion of Cs3BiBr6 perovskite nanocrystals prepared in Example 2, 1 mL of 0.135 mM oleylamine iodine ethyl acetate solution and 0.22 mL of different edible oils and mix them evenly. Let them stand at room temperature for 5 minutes. Detect the FI value using the method in step 3. Figure 9 The FI standard curve was used to obtain the peroxide value. The results are shown in Table 1.

[0053] CsCu2Br3 perovskite nanocrystals: Take 1 mL of 1 mg / mL ethyl acetate dispersion of CsCu2Br3 perovskite nanocrystals prepared in Example 4, 1 mL of 0.135 mM oleylamine iodine solution in ethyl acetate, and 0.22 mL of different edible oils and mix them evenly. Let them stand at room temperature for 5 minutes. Detect the FI value using the method in step 3. Figure 14 The FI standard curve was used to obtain the peroxide value. The results are shown in Table 1.

[0054] Iodine titration: 1 mL of a 1 mg / mL ethyl acetate dispersion of CsPbBr3 perovskite nanocrystals was used to test the peroxide value of the edible oil using the iodine titration method (GB 5009.227-2016). The results are shown in Table 1.

[0055] Table 1. Comparison of peroxide values ​​in edible oils detected by ethyl acetate dispersions of CsPbBr3 and Cs3BiBr6

[0056]

[0057]

[0058] FI, fluorescence intensity; FS, fluorescence peak shift, maximum fluorescence absorption peak shift.

[0059] The results in Table 1 demonstrate that, compared to the iodine titration method (GB 5009.227-2016), the present invention, based on the determination of peroxide value using FI, FS, and RGB for CSPbBr3, or the FI determination of lead-free Cs3BiBr6 and CsCu2Br3, can effectively characterize the peroxide value of actual oil samples. Furthermore, the detection accuracy of lead-free Cs3BiBr6 and CsCu2Br3 is essentially consistent with that of the lead-containing and national standard iodine titration methods. This present invention achieves a lead-free system with excellent detection performance while being lead-free and solvent-safe.

[0060] Example 2: Detecting the peroxide value of edible oil using lead-free Cs3BiBr6 perovskite nanocrystals

[0061] 1. Lead-free Cs3BiBr6 perovskite nanocrystals

[0062] Weigh 0.038g BiBr3, 0.0851g CsBr, 0.6mL oleylamine (OAm), 1.8mL oleic acid (OA), and evenly disperse them in 10mL DMF. Stir the mixture at 90°C for 2 hours to obtain a clear precursor solution. Take 2mL of the precursor solution, add 40μL of ammonia solution with a volume concentration of 2.8%, and vigorously stir at 1500rpm for 3min to obtain a precursor solution with ammonia added. Take 0.2mL of the precursor solution with ammonia added and quickly add it to 10mL of dry ethyl acetate. Centrifuge at 8000rpm for 5min at room temperature. Repeat the centrifugation twice with dry ethyl acetate to precipitate. Take the final precipitate and blow it dry with nitrogen to obtain lead-free Cs3BiBr6 perovskite nanocrystals. Weigh it. The yield is above 95%. See the UV spectrum. Figure 7 As shown, it was shown that the above method successfully obtained the crystal.

[0063] 2. Fluorescence intensity of lead-free Cs3BiBr6 perovskite nanocrystals

[0064] The lead-free Cs3BiBr6 perovskite nanocrystals were prepared with ethyl acetate to prepare a lead-free Cs3BiBr6 perovskite nanocrystal dispersion with a concentration of 1 mg / mL.

[0065] Take 1mL of 1mg / mL Cs3BiBr6 perovskite nanocrystal ethyl acetate dispersion, 1mL of 0.135mM oleylamine iodine ethyl acetate solution and 0.22mL of edible oil with different peroxide values ​​(0.02, 0.11, 0.22, 0.33g / 100g) and mix them evenly. Let it stand at room temperature for 5min to obtain the test solution. Place it in a microplate reader, excite it at 365nm, and measure its fluorescence spectrum at 400-700nm. The results are shown in Figure 2. Figure 8 As shown, the maximum fluorescence absorption intensity was obtained at 455 nm.

[0066] Maximum fluorescence absorption intensity standard curve: With the peroxide value in the test solution as the ordinate and the maximum fluorescence absorption intensity (FI) at 455nm as the abscissa, draw the standard curve of the peroxide value. The results are shown in Figure 9 As shown in the figure, it shows that as the peroxide value of edible oil increases, FI gradually decreases, and there is a good linear relationship between FI and peroxide value of edible oil (R 2 =0.9717), the linear detection range of this method is 0.02-0.33 g / 100 g, and the detection limit is 0.01 g / 100 g.

[0067] 3. Detect the peroxide value of edible oil

[0068] The results in Table 1 demonstrate that, compared to the iodine titration method (GB 5009.227-2016), the present invention's determination of peroxide value based on the FI of lead-free Cs3BiBr6 effectively characterizes the peroxide value of actual oil samples. Furthermore, the accuracy of lead-free Cs3BiBr6 detection is essentially consistent with that of the lead-containing, national standard iodine titration method. This present invention achieves a lead-free system with excellent detection performance, while maintaining lead-free and solvent-safe properties.

[0069] Example 3: Detection of edible oil peroxide value using lead-free CsSnBr3 perovskite nanocrystals

[0070] 1. Lead-free CsSnBr3 perovskite nanocrystals

[0071] Weigh 0.1114g SnBr2, 0.0851g CsBr, 0.6mL oleylamine (OAm), 1.8mL oleic acid (OA), and evenly disperse them in 10mL DMF. Stir the mixture at 75°C for 2 hours to obtain a clear precursor solution. Take 2mL of the precursor solution, add 40μL of 2.8% volume concentration ammonia solution, and vigorously stir at 1500rpm for 3min to obtain a precursor solution with ammonia added. Take 0.2mL of the precursor solution with ammonia added and quickly add it to 10mL of dry ethyl acetate. Centrifuge at 8000rpm for 5min at room temperature. Repeat the centrifugation twice with dry ethyl acetate to precipitate. Take the final precipitate and blow it dry with nitrogen to obtain lead-free CsSnBr3 perovskite nanocrystals. Weigh it. The mass yield is more than 95%. The ultraviolet absorption spectrum shows Figure 10 As shown, it was shown that the crystals were successfully obtained.

[0072] 2. Detect the peroxide value of edible oil

[0073] Lead-free CsSnBr3 perovskite nanocrystals were prepared with ethyl acetate to prepare a 1 mg / mL lead-free CsSnBr3 perovskite nanocrystal dispersion. The peroxide value was determined using the method of Example 2. The results showed that the fluorescence emission peak of the lead-free CsSnBr3 perovskite was located near 900 nm (see Figure 11 ).

[0074] Example 4: Detection of edible oil peroxide value using lead-free CsCu2Br3 perovskite nanocrystals

[0075] 1. Lead-free CsCu2Br3 perovskite nanocrystals

[0076] Weigh 0.073g CuBr, 0.0851g CsBr, 0.6mL oleylamine (OAm), 1.8mL oleic acid (OA), and evenly disperse them in 10mL DMF. Stir the mixture at 105°C for 2 hours to obtain a clear precursor solution. Take 2mL of the precursor solution, add 40μL of ammonia solution with a volume concentration of 2.8%, and vigorously stir at 1500rpm for 3min to obtain a precursor solution with ammonia added. Take 0.2mL of the precursor solution with ammonia added and quickly add it to 10mL of dry ethyl acetate. Centrifuge at 8000rpm for 5min at room temperature. Repeat the centrifugation twice with dry ethyl acetate to precipitate. Take the final precipitate and blow it dry with nitrogen to obtain lead-free CsCu2Br3 perovskite nanocrystals. Weigh it. The mass yield is more than 95%. The ultraviolet absorption spectrum shows Figure 12 As shown, the results showed that the crystals were successfully obtained.

[0077] 2. Fluorescence intensity of lead-free CsCu2Br3 perovskite nanocrystals

[0078] Lead-free CsCu2Br3 perovskite nanocrystals were prepared with ethyl acetate to prepare a 1 mg / mL lead-free CsCu2Br3 perovskite nanocrystal dispersion. 1 mL of 1 mg / mL CsCu2Br3 perovskite nanocrystal ethyl acetate dispersion, 1 mL of 0.135 mM oleylamine iodide ethyl acetate solution, and 0.22 mL of edible oils with different peroxide values ​​(0.06, 0.14, 0.25, and 0.33 g / 100 g) were mixed evenly and allowed to stand at room temperature for 5 minutes to obtain the test solution. UV characterization was performed as follows. Figure 12 The fluorescence emission wavelength of the lead-free CsCu2Br3 perovskite nanocrystals was found to be around 400nm when the ultraviolet spectrum was measured in a microplate reader at 365nm for excitation. The fluorescence intensity of the ethyl acetate dispersion of the lead-free CsCu2Br3 perovskite nanocrystals to the peroxide value of edible oil (0.06-0.33g / 100g) was shown in the figure. Figure 13 , with the increase of peroxide value, the fluorescence intensity of CsCu2Br3 perovskite nanocrystals decreases.

[0079] Maximum fluorescence absorption intensity standard curve: With the peroxide value in the test solution as the ordinate and the maximum fluorescence absorption intensity (FI) at 400nm as the abscissa, draw the standard curve of the peroxide value. The results are shown in Figure 14 As shown in the figure, it shows that as the peroxide value of edible oil increases, FI gradually decreases, and there is a good linear relationship between FI and peroxide value of edible oil (R 2 =0.960), the linear detection range of this method is 0.06-0.33 g / 100 g, and the detection limit is 0.06 g / 100 g.

[0080] 3. Detect the peroxide value of edible oil

[0081] The results in Table 1 demonstrate that, compared to the iodine titration method (GB 5009.227-2016), the present invention's FI-based peroxide value determination based on lead-free CsCu2Br3 effectively characterizes the peroxide value of actual oil samples. Furthermore, the accuracy of lead-free CsCu2Br3 detection is slightly lower than that of the lead-containing perovskite material method and the national standard iodine titration method. This present invention achieves a lead-free system with excellent detection performance while maintaining lead-free and solvent-safe properties.

Claims

1. A method for preparing lead-free halide perovskite nanocrystals, characterized in that: The lead-free halide perovskite nanocrystals are Cs3BiBr6, CsSnBr3 or CsCu2Br3; the lead-free halide perovskite nanocrystals are prepared according to the following steps: a precursor substance, oleylamine and oleic acid are stirred in N,N-dimethylformamide to obtain a clear precursor solution; the precursor solution is taken, an ammonia solution is added, and vigorously stirred at 1500rpm for 1-5min to obtain a precursor solution with ammonia water added; the precursor solution with ammonia water is quickly added to a dry solvent, centrifuged 1-3 times repeatedly, and the precipitate from the last centrifugation is collected to obtain the lead-free halide perovskite nanocrystals; the precursor substance is a combination of one of BiBr3, SnBr2 or CuBr and CsBr; the dry solvent includes n-pentane, ethyl acetate, ether, acetonitrile, n-hexane, cyclohexane, butyl acetate, n-heptane, n-octane, and petroleum ether.

2. The method for preparing lead-free halide perovskite nanocrystals according to claim 1, wherein: The mass ratio of the CsBr to BiBr3, SnBr2 or CuBr is 1:0.1-2.

3. The method for preparing lead-free halide perovskite nanocrystals according to claim 1 or 2, wherein: The mass ratio of CsBr to BiBr3 is 1:0.45, the mass ratio of CsBr to SnBr2 is 1:1.3, and the mass ratio of CsBr to CuBr is 1:0.

85.

4. The method for preparing lead-free halide perovskite nanocrystals according to claim 1, wherein: The volume amount of oleylamine used is 1-5 mL / g based on the total mass of the precursor substances, the volume amount of oleic acid used is 5-15 mL / g based on the total mass of the precursor substances; and the volume amount of N,N-dimethylformamide used is 40-100 mL / g based on the total mass of the precursor substances.

5. The method for preparing lead-free halide perovskite nanocrystals according to claim 1, wherein: The volume concentration of the ammonia solution is 2.8%, the volume ratio of the precursor solution to the ammonia solution is 1:0.01-1; the volume ratio of the precursor solution to which ammonia solution is added to the dry solvent is 1:

50.

6. The method for preparing lead-free halide perovskite nanocrystals according to claim 1, wherein: The precursor solution is obtained by stirring at 75-120° C. for 1-3 hours.

7. Use of the lead-free halide perovskite nanocrystals prepared by the method of claim 1 in rapid visual detection of peroxide value of edible oil.

8. The use according to claim 7, characterized in that The application method comprises the following steps: dispersing lead-free halide perovskite nanocrystals in an organic solvent a to form a dispersion liquid, adding an organic solvent b solution of oleylamine iodine and an edible oil to be tested, measuring the color value of the mixed liquid or the fluorescence emission spectrum at an excitation wavelength, extracting the fluorescence emission peak intensity or the maximum absorption peak shift value, and obtaining the peroxide value of the edible oil to be tested based on a standard curve of the peroxide value and the color value, fluorescence intensity or maximum absorption peak shift value; the organic solvent a comprises ethyl acetate, cyclohexane, n-heptane, toluene, n-hexane, petroleum ether, ether, and chloroform; and the organic solvent b is the same as the organic solvent a.

9. The use according to claim 7, characterized in that The lead-free halide perovskite nanocrystals are dispersed in the organic solvent a at a concentration of 1 mg / mL; the oleylamine iodine is added in the form of 0.135 mM oleylamine iodine in the organic solvent b, with a volume ratio of 1:1 to the dispersion; and the volume ratio of the dispersion to the edible oil to be tested is 1:0.22.

Images