Olive oil adulteration detection method based on fluorescent perovskite nanocrystals

Abstract

The invention discloses an olive oil adulteration detection method based on fluorescent perovskite nanocrystals. CsPbBr3NCs is used as a fluorescent probe to detect adulterated oil in different proportions in adulterated olive oil, a relation curve of fluorescence intensity and the adulteration proportion of the adulterated oil is further obtained, and when the adulteration proportion of peanut oil and soybean oil is 10%-50%, the change of the fluorescence intensity and the adulteration proportion have a good linear relation (R2 = 0.988). The invention provides a novel, simple, efficient and low-cost rapid detection method for the olive oil adulteration phenomenon, the application range of the perovskite quantum dots is expanded, and a basis is provided for application of the perovskite quantum dots in the field of food safety. The design and establishment of the invention can provide a new thought and a new method for edible oil quality detection, and have important theoretical significance and research value.

Description

Technical Field

[0001] The invention belongs to the field of spectral analysis, and in particular relates to an olive oil adulteration detection method based on fluorescent perovskite nanocrystals. Background Art

[0002] Perovskite materials generally refer to materials with a perovskite crystal structure. All-inorganic perovskites and organic-inorganic hybrid perovskites, as semiconductor materials, have attracted much attention due to their novel optical properties. + Located in the center of the cubic structure, the metal ion Pb 2+ The halogen ions (Cl, Br, I) are located at the vertices of the cubic structure. + With suitable ionic radius, all-inorganic perovskite nanomaterial Cs bX3 (X=Cl, Br, I) has higher structural stability than organic-inorganic hybrid perovskite. As an emerging fluorescent material, all-inorganic perovskite nanocrystals have high photoluminescence quantum yield, narrow emission peak, adjustable emission wavelength across the entire visible spectrum, and high photoelectric conversion efficiency. They are widely used in optoelectronic devices such as light-emitting diodes (LEDs), solar cells, and photodetectors.

[0003] Although the all-inorganic perovskite nanomaterial CsPbX3 has excellent photoelectric properties, it has poor fluorescence stability when exposed to water, oxygen, and long-term exposure to ultraviolet light, which also hinders the practical application of CsPbX3 quantum dots in the fields of bioanalysis and sensor detection. Therefore, perovskite quantum dots coated with inorganic oxide shells such as SiO2 and TiO2, ligand protective layers, and organic polymer protective layers came into being, effectively improving their fluorescence stability. In addition, researchers are also constantly exploring the preparation methods of water-soluble perovskite nanomaterials and the phase transition methods of oil-soluble perovskite quantum dots.

[0004] Due to the poor stability in the aqueous phase, all-inorganic perovskite nanomaterials have unexpected application prospects in the detection and analysis of non-aqueous phases (including gas phase sensing and oil phase peroxide value detection). As a high-end edible oil, olive oil enjoys a good reputation in the international market, but at the same time it is also one of the most chaotic edible oil varieties in the Chinese food oil market. There are unscrupulous manufacturers who use cheaper seed oils to dilute olive oil to increase profits, or pass off inferior products as good ones. Adulterated olive oil may be mixed with other oils, such as soybean oil, corn oil, etc., or chemicals such as pigments and flavors may be added. This may lead to a decline in the quality of olive oil and even bring potential health risks, such as affecting cardiovascular health and causing allergic reactions. Identifying and detecting adulterated olive oil is a technical challenge, and it is necessary to develop efficient, accurate and rapid detection methods. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a simple and efficient method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals.

[0006] Technical solution: A method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals, comprising the following steps:

[0007] (1) adding different volumes of adulterated oil to olive oil to obtain a series of olive oils containing adulterated oil at gradient concentrations;

[0008] (2) adding CsPbBr3 NCs as fluorescent probes to a series of olive oils containing gradient concentrations of adulterated oil in step (1) to obtain test solutions, measuring the fluorescence intensity of the test solutions to obtain a standard curve related to the fluorescence intensity and the amount of adulterated oil;

[0009] (3) CsPbBr3 NCs were added to the olive oil sample to be tested as a fluorescent probe, and the fluorescence intensity was measured. The obtained fluorescence intensity was compared with the standard curve to obtain the adulteration amount in the olive oil sample to be tested.

[0010] In the above technical solution, the gradient concentration of adulterated oil refers to the concentration of adulterated oil in olive oil calculated by the volume ratio of adulterated oil added to olive oil. The amount of adulterated oil refers to the volume ratio of adulterated oil in olive oil.

[0011] Furthermore, in step (1), the adulterated oil is soybean oil or peanut oil. The adulterated oil in olive oil is a single adulterated oil.

[0012] Furthermore, in step (1), the test solution is placed in the dark at room temperature (20° C.) for 30 minutes to measure the fluorescence spectrum.

[0013] Furthermore, in step (1), the volume ratio of the adulterated oil added to the olive oil is 5%-50%. Specifically, a series of olive oils containing gradient concentrations of adulterated oils are respectively, soybean oil volume / olive oil volume: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% and peanut oil volume / olive oil volume: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, a total of 20 mixed samples.

[0014] Furthermore, in step (2), the preparation method of CsPbBr3 NCs is:

[0015] 1) weighing raw materials of a perovskite nanocrystal precursor solution, and dissolving the raw materials together in an organic solvent to prepare a precursor solution;

[0016] 2) After the mixed solution in step 1) is completely dissolved, a stabilizer is added;

[0017] 3) dropping the mixed solution of step 2) into the rapidly stirred toluene solution, and then stirring for 3-5 minutes to obtain a bright green emitting solution;

[0018] 4) The product obtained in step 3) is centrifuged and washed to obtain CsPbBr3 NCs as a fluorescent probe.

[0019] Preferably, in step 1), the raw materials include cesium bromide and lead bromide.

[0020] Preferably, in step 1), the organic solvent is N,N-dimethylformamide.

[0021] Preferably, in step 2), the stabilizer comprises oleic acid and oleylamine.

[0022] Furthermore, in step (2), the scanning conditions of the test solution are determined as follows: the excitation wavelength is 365 nm, the emission wavelength scanning range is 450-580 nm, and the step length is 1 nm.

[0023] Preferably, in step (2), in the scanning condition, scanning is performed every 1 nm, and the slit width is set to 1.5 / 1.5 nm.

[0024] The present invention provides a method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals. The method adopts a ligand post-exchange strategy to mix the synthesized CsPbBr3 NCs with various common edible oils (olive oil, corn oil, soybean oil, palm oil and peanut oil). According to the characterization of the photoluminescence spectrum, it is found that olive oil can quench the fluorescence signal of CsPbBr3 NCs. Based on the unique quenching response mechanism of CsPbBr3 NCs to olive oil, a method for detecting olive oil adulteration using perovskite nanocrystals is established. CsPbBr3 NCs are used as fluorescent probes to detect different proportions of adulterated oil in adulterated olive oil. The relationship curve between the fluorescence intensity and the adulteration ratio of peanut oil is further obtained. When the adulteration ratio of peanut oil and soybean oil is in the range of 10% to 50%, the change in fluorescence intensity has a good linear relationship with the adulteration ratio (R 2 =0.988). This result broadens the application prospects of perovskite nanomaterials in food analysis and provides new ideas for the development of oil-phase food safety testing.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0026] 1) The olive oil adulteration detection method based on fluorescent perovskite nanocrystals of the present invention does not require pretreatment and complicated reaction processes. The fluorescence spectrum is measured by a spectrometer, characteristic parameters are extracted, and a relationship equation between the degree of fluorescence quenching and the adulteration ratio of adulterated oil is obtained by using a mapping software, thereby realizing the detection of adulterated olive oil;

[0027] 2) The method of the present invention uses CsPbBr3 nanocrystals as fluorescent probes for the first time to detect olive oil adulteration, and this method is simple, rapid, safe, and suitable for routine analysis. Based on the fluorescence quenching principle of quantum dots, the reaction has high sensitivity, higher precision, and good reproducibility. In the range of 10% to 50% of adulterated oil, there is a good linear relationship between the change in fluorescence intensity and the adulteration ratio. This method broadens the application prospects of perovskite nanomaterials in food analysis and provides new ideas for the development of oil-phase food safety detection; BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The photoluminescence spectra of the test solutions in Examples 1 to 5 and the perovskite nanocrystal solution prepared in Example 1;

[0029] Figure 2 are photos of samples under sunlight (a) and 365 nm ultraviolet light (b), wherein 1 to 5 correspond to the test solutions in Examples 1 to 5, respectively, and 6 corresponds to the perovskite nanocrystal in Example 1;

[0030] Figure 3 The time-resolved spectrum of the perovskite nanocrystal prepared in Example 1;

[0031] Figure 4 The time-resolved spectrum of the test solution prepared in Example 1;

[0032] Figure 5 The fluorescence spectrum of the adulterated peanut oil in the reaction system in Example 6 is 5%-50%;

[0033] Figure 6 This is the relationship curve between the adulteration ratio of peanut oil in the reaction system in Example 6 and the fluorescence intensity at 515 nm.

[0034] Figure 7 The fluorescence spectrum of the reaction system in Example 7 when the adulteration ratio of soybean oil is 5%-50%;

[0035] Figure 8 This is the relationship curve between the adulteration ratio of soybean oil in the reaction system in Example 7 and the fluorescence intensity at 515 nm. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0037] The perovskite nanocrystals (CsPbBr3 NCs) used in the embodiment of the present invention are prepared by the following steps:

[0038] 1) Weigh 0.4 mmol of cesium bromide and 0.48 mmol of lead bromide into a clean beaker;

[0039] 2) Weigh 10 ml of N,N-dimethylformamide (DMF) and dissolve the raw materials in step 1) in DMF;

[0040] 3) After the mixed solution in step 2) is completely dissolved, add 1 ml of oleic acid and 0.6 ml of oleylamine;

[0041] 4) taking 1 ml of the mixed solution of step 2) and adding it to a toluene solution under vigorous rotation to obtain a bright green emitting solution in the toluene solution;

[0042] 5) The product obtained in step 4) is centrifuged and washed at a speed of 10000 r / min using a high-speed centrifuge, and the supernatant is discarded. The precipitate is collected and redispersed in a toluene solution to obtain a perovskite nanocrystal solution.

[0043] Example 1

[0044] This embodiment provides a method for preparing a perovskite nanocrystal fluorescent probe based on a ligand post-treatment method, which specifically includes the following steps:

[0045] 1) Weigh 0.4 mmol of cesium bromide and 0.48 mmol of lead bromide into a clean beaker;

[0046] 2) Weigh 10 ml of N,N-dimethylformamide (DMF) and dissolve the raw materials in step 1) in DMF;

[0047] 3) After the mixed solution in step 2) is completely dissolved, add 1 ml of oleic acid and 0.6 ml of oleylamine;

[0048] 4) taking 1 ml of the mixed solution of step 2) and adding it to a toluene solution under vigorous rotation to obtain a bright green emitting solution in the toluene solution;

[0049] 5) The product obtained in step 4) is centrifuged and washed at a speed of 10000 r / min using a high-speed centrifuge, and the supernatant is discarded. The precipitate is collected and redispersed in a toluene solution to obtain a perovskite nanocrystal solution (CsPbBr3 NCs); the perovskite nanocrystals obtained in this step are used as fluorescent probes in subsequent steps;

[0050] 6) vortex 1 ml of olive oil and 3 ml of toluene for five minutes to mix thoroughly to prepare an oil sample to be tested;

[0051] 7) 2 ml of the nanocrystal solution obtained in step 5) and 2 ml of the oil sample to be tested obtained in step 6) were vortexed for five minutes to mix them evenly; a test solution was obtained.

[0052] Determine the fluorescence spectrum: Scanning conditions: excitation wavelength is 365nm, emission wavelength scanning range is 450-580nm, scanning is performed every 1nm, and the slit width is set to 1.0 / 1.0nm (excitation slit / emission slit); determine the corresponding fluorescence spectrum, see Figure 1 ; All results were measured three times and the average values ​​were used for data processing.

[0053] Example 2

[0054] The only difference between this embodiment and embodiment 1 is that olive oil is replaced by peanut oil in step 6), and the product is dispersed in n-hexane solution for fluorescence detection. Under the excitation of ultraviolet light at 365 nm, its photoluminescence spectrum is as follows: Figure 1 shown.

[0055] Example 3

[0056] The only difference between this embodiment and embodiment 1 is that in step 6), olive oil is replaced by soybean oil, and the product is dispersed in n-hexane solution for fluorescence detection. Under the excitation of ultraviolet light at 365 nm, its photoluminescence spectrum is as follows: Figure 1 shown.

[0057] Example 4

[0058] The only difference between this embodiment and embodiment 1 is that olive oil is replaced by corn oil in step 6), and the product is dispersed in n-hexane solution for fluorescence detection. Under the excitation of ultraviolet light at 365 nm, its photoluminescence spectrum is as follows: Figure 1 shown.

[0059] Example 5

[0060] The only difference between this embodiment and embodiment 1 is that in step 6), olive oil is replaced by palm oil, and the product is dispersed in n-hexane solution for fluorescence detection. Under the excitation of 365 nm ultraviolet light, its photoluminescence spectrum is as follows: Figure 1 shown.

[0061] Depend on Figure 1 It can be seen that only the fluorescence intensity of the test solution of Example 1 after mixing with olive oil was significantly quenched, while the fluorescence intensity of Examples 2-5 did not change significantly;

[0062] Figure 2 The following are photos of samples under sunlight and 365nm ultraviolet light (from right to left, the test solutions of Examples 1-5 and the perovskite nanocrystals in Example 1). It can be seen that the fluorescence of the test solution in Example 1 is significantly quenched;

[0063] Figure 3 and Figure 4These are the time-resolved spectra of the prepared perovskite nanocrystal solution in Example 1 and the test solution in Example 1, and it can be seen that the fluorescence lifetime of the test solution has been significantly attenuated.

[0064] Example 6

[0065] This example provides a rapid detection method for olive oil adulterated with peanut oil, which specifically comprises the following steps:

[0066] Step 1, prepare the samples to be tested: vortex and shake the peanut oil and olive oil in different volume ratios for 10 minutes to mix them evenly to obtain a series of adulterated olive oil samples with different adulteration ratios (peanut oil volume / olive oil volume: 5% to 50%). There are 10 samples to be tested, including 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

[0067] Step 2, prepare a mixed standard sample solution: vortex the CsPbBr3 perovskite nanocrystal solution prepared in Example 1 and 10 samples to be tested for five minutes, and place them in the dark at room temperature (about 25°C) for 30 minutes to obtain a mixed system of different adulterated olive oils and fluorescent probes for measuring the fluorescence spectrum.

[0068] Step 3, determine the fluorescence spectrum: Scanning conditions: excitation wavelength is 365nm, emission wavelength scanning range is 450-580nm, scan once every 1nm, slit width is set to 1.5 / 1.5nm (excitation slit / emission slit); determine the corresponding fluorescence spectrum; all results are measured three times, and the average value is used for data processing.

[0069] Step 4: Construct a linear determination model: Construct a relationship curve between different adulteration ratios and the fluorescence intensity of the reaction system at 515 nm, such as Figure 5 The fitting curve of fluorescence intensity and peanut oil adulteration ratio is shown in Figure 6 As shown, when the adulteration ratio is in the range of 10%-50%, the fluorescence intensity is linearly related to the adulteration ratio of peanut oil. The linear regression equation is y=90327x-96500, and the correlation coefficient is R 2 =0.988.

[0070] Example 7

[0071] This example provides a rapid detection method for adulterating olive oil with soybean oil. The only difference between the steps of this method and those of Example 6 is that the peanut oil in step 1 is replaced with soybean oil, and the adulterated olive oil samples to be tested are obtained (soybean oil volume / olive oil volume: 5% to 50%): 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, a total of 10 samples to be tested. And the relationship curve between different adulteration ratios and the fluorescence intensity of the reaction system at 515nm is constructed, as shown in FIG. Figure 7 The fitting curve of fluorescence intensity and soybean oil adulteration ratio is shown in Figure 8 As shown, when the adulteration ratio is in the range of 10%-50%, the fluorescence intensity is linearly related to the adulteration ratio of peanut oil. The linear regression equation is y=97171x-211279, and the correlation coefficient is R 2 =0.996.

[0072] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals, characterized in that: The following steps are involved: (1) adding different volumes of adulterated oil to olive oil to obtain a series of olive oils containing adulterated oil at gradient concentrations; (2) adding CsPbBr3 NCs as fluorescent probes to a series of olive oils containing gradient concentrations of adulterated oil in step (1) to obtain test solutions, measuring the fluorescence intensity of the test solutions to obtain a standard curve related to the fluorescence intensity and the amount of adulterated oil; (3) CsPbBr3 NCs were added to the olive oil sample to be tested as a fluorescent probe, and the fluorescence intensity was measured. The obtained fluorescence intensity was compared with the standard curve to obtain the adulteration amount in the olive oil sample to be tested.

2. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 1, characterized in that: In step (1), the adulterated oil is soybean oil or peanut oil.

3. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 1, characterized in that: In step (1), the test solution is placed in the dark at room temperature for a period of time to measure the fluorescence spectrum.

4. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 1, characterized in that: In step (1), the volume ratio of the adulterated oil added to the olive oil is 5%-50%.

5. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 1, characterized in that: In step (2), the preparation method of CsPbBr3 NCs is: 1) weighing raw materials of a perovskite nanocrystal precursor solution, and dissolving the raw materials together in an organic solvent to prepare a precursor solution; 2) After the mixed solution in step 1) is completely dissolved, a stabilizer is added; 3) dropping the mixed solution of step 2) into the rapidly stirred toluene solution, and then stirring for 3-5 minutes to obtain a bright green emitting solution; 4) The product obtained in step 3) is centrifuged and washed to obtain CsPbBr3 NCs as a fluorescent probe.

6. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 5, characterized in that: In step 1), the raw materials include cesium bromide and lead bromide.

7. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 5, characterized in that: In step 1), the organic solvent is N,N-dimethylformamide.

8. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 5, characterized in that: In step 2), the stabilizer includes oleic acid and oleylamine.

9. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 1, characterized in that: In step (2), the scanning conditions of the test liquid are determined as follows: the excitation wavelength is 365 nm, and the emission wavelength scanning range is 450-580 nm.

10. The method for detecting olive oil adulteration based on fluorescent perovskite nanocrystals according to claim 9, characterized in that: In step (2), the scanning conditions are to scan once every 1 nm, and the slit width is set to 1.5 / 1.5 nm.

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