PQDs-coated UiO-66-based ciprofloxacin ratio-dependent fluorescence sensor as well as preparation method and application of PQDs-coated UiO-66-based ciprofloxacin ratio-dependent fluorescence sensor

Abstract

The invention belongs to the technical field of composite material preparation and food safety detection, and particularly relates to a PQDs-coated UiO-66-based ciprofloxacin ratiometric fluorescence sensor as well as a preparation method and application of the PQDs-coated UiO-66-based ciprofloxacin ratiometric fluorescence sensor. According to the method provided by the invention, a perovskite quantum dot (PQDs) is embedded in a zirconium-based metal organic framework (UiO-66), and a molecular imprinting technology is combined, so that the perovskite quantum dot UiO-66 molecular imprinting fluorescent probe (PQDs (at) UiO-66 (at) MIP) is constructed. The prepared composite material can be directly applied to detection and analysis work of CIP in complex aquatic product samples, and the high-specificity and high-sensitivity analysis and detection target of CIP in aquatic products is achieved; the operation process is simple and convenient, the detection period is short, and the detection time is greatly shortened; according to the technical scheme, the detection sensitivity is high, and the lowest detection limit is 0.014 mg / L.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material preparation and food safety detection, and particularly relates to a ciprofloxacin ratiometric fluorescent sensor based on a perovskite quantum dot-zirconium-based metal organic framework (UiO-66) as well as a preparation method and application thereof. BACKGROUND

[0002] Under the background of the continuous increase of global food safety concerns, the accurate screening of antibiotic residues is a key link to ensure food safety and public health. Ciprofloxacin, as a commonly used fluoroquinolone antibiotic, may be left in the environment, food and water sources due to its extensive use, which poses a potential threat to the ecological environment and human health.

[0003] Therefore, it is of great practical significance to develop a ciprofloxacin detection technology with high sensitivity, high selectivity and convenient operation. The existing CIP detection methods mainly include traditional methods such as high performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA). Although these methods have high detection accuracy, they cannot meet the requirements of sensitive and efficient detection in food safety detection due to their complex operation steps, expensive instruments and equipment, and long detection time. SUMMARY

[0004] In view of the problems in the prior art, the application provides a ciprofloxacin ratiometric fluorescent sensor based on PQDs@UiO-66, which improves the detection sensitivity and selectivity of CIP. This new type of molecular imprinting fluorescent probe can not only efficiently and quickly identify and detect CIP residues, but also overcome the defects in traditional methods, and has a wide application prospect.

[0005] Another object of the application is to provide a preparation method of the above-mentioned ciprofloxacin ratiometric fluorescent sensor.

[0006] The application also provides an application of the above-mentioned ciprofloxacin ratiometric fluorescent sensor in CIP sensing and detection. Based on the blue fluorescence of CIP itself and the green fluorescence of PQDs, the method uses a ratio enhancement factor (REF = R / R0) as an analysis signal instead of directly using an absolute ratio value (R = F CIP / F PQDs ), and constructs a CIP detection method with high sensitivity and high selectivity. The linear range of the method is 0.03-20 mg / L, and the lowest detection limit is 0.014 mg / L. The method is used for the determination of CIP in various aquatic products.

[0007] The technical scheme adopted by the application to achieve the above-mentioned purposes is as follows: The application provides a preparation method of a ciprofloxacin ratio type fluorescent sensor, comprising the following steps: (1) Preparation of UiO-66 Zirconium oxychloride (ZrOCl2) and terephthalic acid (PTA) are dispersed in N,N-dimethylformamide (DMF), formic acid (FA) is added, and reaction is carried out; after the reaction is completed, the precipitate is collected by centrifugation, and after drying, UiO-66 is obtained; (2) Preparation of PQDs@UiO-66 a. Cesium carbonate (CsCO3), oleic acid (OA) and octadecene (ODE) are moved to a heating jacket, and under a nitrogen (N2) atmosphere, stepwise heating is carried out, and incubation reaction is carried out, to obtain a cesium oleate precursor; b. Lead bromide (PbBr2) and octadecene (ODE) are mixed, vacuum is applied, nitrogen is introduced, heating is carried out to a certain temperature, OA, APTES and UiO-66 are added, heating is continued, the cesium oleate precursor is rapidly added, an ice water bath is used for cooling, hydrolysis treatment is carried out, centrifugation, washing and drying are carried out, and PQDs@UiO-66 is obtained; (3) Preparation of PQDs@UiO-66@MIP The template molecule is dispersed in octadecene, functional monomers and PQDs@UiO-66 are added, pre-polymerization is carried out, a crosslinking agent is added and stirred overnight, the product is collected by centrifugation, eluent is washed, and finally PQDs@UiO-66@MIP is dried.

[0008] Preferably, in step (1), the mass ratio of ZrOCl2 and PTA is 1.5-3:1; the concentration of ZrOCl2 in DMF is 0.04-0.06 g / mL; and the volume ratio of DMF and FA is 2-3:1.

[0009] Preferably, in step (1), the reaction is incubation reaction at 130-150 DEG C for 2-3 h under the condition of vigorous stirring; and the product is collected by centrifugation, and dried under vacuum for 8-12 h.

[0010] Preferably, in step (a), the ratio of CsCO3, OA and ODE is 0.8-0.9 g:2.5-3 mL:20-30 mL; in step (b), the ratio of PbBr2, ODE, OA and APTES is 0.138 g:10 mL:50-100 μL:1 mL; the mass ratio of UiO-66 and PbBr2 is 100:0.13~0.14; and the ratio of the cesium oleate precursor and PbBr2 is 1 mL:0.13-0.14 g.

[0011] Preferably, in step (a), the incubation is first heated to 110-130 DEG C at a rotation speed of 500 r / min for 1 h, and then heated to 130-150 DEG C for 2 h; in step (b), after adding OA, APTES and UiO-66, the reaction temperature is increased to 110-130 DEG C at a rotation speed of 500 r / min for 1 h, and then heated to 140-160 DEG C; the hydrolysis is stirred at 25 DEG C for 2-3 h; and the drying is vacuum drying at 40-60 DEG C.

[0012] Preferably, in step (3), the molar ratio of the template molecule, the functional monomer and the crosslinking agent is 1:3-5:8-20; the ratio of the template molecule and PQDs@UiO-66 is 1 mmol:200-400 mg; and the eluent is composed of n-hexane and acetic acid in a volume ratio of 9:1.

[0013] Preferably, the template molecule is CIP; the functional monomer is APTES; the crosslinking agent is TMOS; the prepolymerization is performed at 25-28 DEG C for 30-40 min; and the vacuum drying temperature is 40-60 DEG C.

[0014] The application further provides application of the UiO-66 prepared by the preparation method in enhancing the quantum confinement fluorescence effect of CIP.

[0015] Another object of the application is to provide application of the ciprofloxacin ratiometric fluorescent sensor prepared by the preparation method in analyzing and detecting CIP, wherein the analysis and detection utilize a fluorescence enhancement factor to quantitatively analyze a ratiometric fluorescent probe; and the application specifically comprises the following steps: (1) adding the prepared polymer PQDs@UiO-66@MIP into a sample extraction liquid according to a material-liquid ratio, and oscillating at room temperature for analysis and detection; (2) detecting and analyzing the sample to be tested by using a fluorescence spectrophotometer.

[0016] Preferably, the ratio of the PQDs@UiO-66@MIP and the sample extraction liquid is 1 mg:1-5 mL; the oscillation time at room temperature is 15-30 min; and the fluorescence spectrophotometer detection and analysis conditions are as follows: the excitation wavelength is 365 nm, the emission wavelength is 400-600 nm, and the slit width is 5 nm.

[0017] The method provided by the application grows perovskite quantum dots (PQDs) in situ into high-stability UiO-66, embeds in a zirconium-based metal organic framework (UiO-66) in a way, combines a molecular imprinting technology, adopts a sol-gel method, and constructs a novel ratio type fluorescent probe, i.e., a perovskite quantum dot UiO-66 molecular imprinting fluorescent probe (PQDs@UiO-66@MIP). The enrichment and limited effect of UiO-66 on ciprofloxacin make the blue fluorescent emission signal of ciprofloxacin itself amplified, and meanwhile, the enriched ciprofloxacin also reacts with perovskite quantum dots, so that the green fluorescence of the perovskite quantum dots is quenched. Based on the above phenomenon, a high-sensitivity ratio type fluorescent detection method of ciprofloxacin in aquatic products is constructed. The composite material prepared in the application can be directly applied to the detection and analysis of CIP in complex aquatic product samples, so that the high specificity and high sensitivity analysis and detection of CIP in aquatic products are achieved; the operation process is simple, the detection period is short, and the detection time is greatly reduced; the detection sensitivity of the technical scheme is high.

[0018] The beneficial effects of the application are: (1) The preparation method of the perovskite quantum dot-UiO-66 ratio type fluorescent probe provided by the application is simple, the synthesis conditions are relatively mild, and a complex synthesis environment is not needed. By combining the molecular imprinting technology and the characteristics of the fluorescent material, the material has high selectivity, high sensitivity, rapid response and other excellent characteristics to CIP.

[0019] (2) The PQDs@UiO-66@MIP material prepared in the application can be directly applied to the detection and analysis of CIP in a complex matrix, and the selectivity and sensitivity of CIP in food, environment and other samples are significantly improved. The material has the characteristics of high selectivity, low interference and rapid response, and can complete efficient and accurate detection in a short time, and the lowest detection limit is 0.014 mg / L, and the operation is simple and easy to popularize and apply. Through the ratio type fluorescent signal response, the application technology can effectively reduce the influence of interfering substances in the sample on the detection result, and ensure the accuracy and reliability of the detection. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a synthesis ratio optimization diagram of the PQDs@UiO-66@MIP material; Figure 2 It is a diagram of the fluorescence enhancement effect of UiO-66 on CIP in the PQDs@UiO-66@MIP composite material; Figure 3 It is a scanning electron microscope diagram of the synthesized material UiO-66 (A), PQDs@UiO-66 (B) and PQDs@UiO-66@MIP (C) in Example 1; Figure 4The infrared spectra of PQDs, UiO-66, PQDs@UiO-66 and PQDs@UiO-66@MIP are as follows: Figure 5 The fluorescence selective diagram of PQDs@UiO-66@MIP and PQDs@UiO-66@NIP to CIP and its structural analogues, including pefloxacin, fleroxacin, levofloxacin, ofloxacin and enrofloxacin, with different concentrations are as follows: Figure 6 The standard curve diagram of fluorescence response of PQDs@UiO-66@MIP and PQDs@UiO-66@NIP to CIP with different concentrations is as follows. DETAILED DESCRIPTION

[0021] In order to make the above features and advantages of the present application more clear and easy to understand, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0022] The reagents involved in the following implementation examples are commercially available without special instructions and are not subjected to any treatment before use.

[0023] Example 1 The preparation method of the PQDs@UiO-66@MIP material is as follows: (1) 1.6 g of ZrOCl2 and 0.80 g of PTA were dispersed in 30 mL of DMF, 15 mL of FA was added, and the mixture was stirred vigorously at 140°C for 2 h. After the reaction was completed, the white precipitate was collected by centrifugation and dried in vacuum for 12 h to obtain UiO-66.

[0024] (2) 0.8 g of CsCO3, 2.5 mL of OA and 30 mL of ODE were added into a 100 mL three-necked round-bottom flask, and a double-tube was connected. First, the double-tube was screwed to the vacuum tube and vacuumized for 10 min, then screwed to the N2 tube, and the subsequent reaction needed to maintain N2 atmosphere. The reaction temperature was raised to 120°C at a rotation speed of 500 r / min for 1 h, then raised to 150°C for 2 h to obtain cesium oleate precursor. The obtained cesium oleate precursor was sealed and dried for storage.

[0025] In a 100 mL three-necked round-bottom flask, 0.138 g of PbBr2and 10 mL of ODE were added, and a double-tube was connected. First, the double-tube was screwed to a vacuum tube, vacuumized for 10 min, and then screwed to an N2tube, so that the reaction was kept in an N2atmosphere. The reaction temperature was raised to 120°C at a rotation speed of 500 r / min, and maintained for 1 h. Then, 50 μL of OA and 1 mL of APTES were injected, and 100 mg of UiO-66 was added, and then the temperature was raised to 140°C, 1 mL of cesium oleate precursor (preheated to 100°C in advance) was quickly injected, and the reaction was cooled to room temperature with an ice water bath after 5 s. Finally, hydrolysis was carried out in a water bath at 25°C for 2.5 h, after which hydrolysis was completed, centrifugation was carried out at 8000 r / min for 8 min, the supernatant was removed, and the product was washed with n-hexane three times, vacuum dried at 60°C for 12 h, and finally ground using a jade mortar.

[0026] (3) Using a sol-gel technique, 1 mmol of template molecule CIP was dispersed in 10 mL of ODE, then 4 mmol of functional monomer APTES and 300 mg of fluorescent response material PQDs@UiO-66 were added, pre-polymerization was carried out at 25°C for 30 min, then 16 mmol of crosslinking agent TMOS was added, and stirring was carried out at 25°C overnight, the product was collected by centrifugation at 8000 r / min for 8 min, the product needed to be washed multiple times with eluent n-hexane:acetic acid (9:1, v:v), and finally vacuum dried at 60°C to obtain PQDs@UiO-66@MIP. In the absence of template molecule CIP, the above steps were repeated to obtain PQDs@UiO-66@NIP.

[0027] Example 2 The ratio of template molecule, functional monomer and crosslinking agent was optimized and analyzed, and the ratio of the fluorescence quenching intensity of PQDs@UiO-66@MIP and PQDs@UiO-66@NIP to CIP solution (imprinting factor) was used as a measure, and the specific dosage relationship and imprinting factor are shown in Table 1. Figure 1 .

[0028] From Figure 1 As can be seen from Table 1, when the CIP:APTES:TMOS ratio is adjusted from 1:3:16 to 1:4:16, the fluorescence quenching intensity of the MIP and the imprinting factor IF are both significantly increased; when the ratio is adjusted to 1:5:16, the fluorescence quenching intensity of the MIP and the imprinting factor IF are both decreased. Figure 1As shown in FIG. B, when the CIP:APTES:TMOS ratio is adjusted from 1:4:8 to 1:4:16, the fluorescence quenching intensity and imprint factor IF of the MIPs increase significantly; when the ratio is further adjusted to 1:4:20, the fluorescence quenching intensity and imprint factor IF of the MIPs decrease. Therefore, when the ratio of CIP:APTES:TMOS is 1:4:16, the fluorescence quenching effect of PQDs@UiO-66@MIP is the strongest, and the imprint factor IF reaches a peak, indicating that this ratio is the optimal ratio of the molecularly imprinted material.

[0029] Example 3 The fluorescence enhancement effect of UiO-66 on CIP in the PQDs@UiO-66@MIP composite material prepared in Example 1 was studied. As shown in FIG. 2, a 10 mg / mL CIP solution exhibits weak intrinsic fluorescence emission at 433 nm, with an intensity of 365, indicating that its quantum yield in solution state is low. In comparison, the UiO-66 material suspension alone shows almost no fluorescence emission due to the inhibition of the radiative recombination process by its band structure defects. However, when the two are mixed, i.e., the mixed suspension of CIP and UiO-66 at the same concentration, a higher fluorescence emission intensity (1831) is exhibited at 433 nm, which is about 5.0 times higher than that of the pure CIP solution, thus confirming the fluorescence enhancement confinement effect of UiO-66 on CIP.

[0030] Effect Example 1 (1) Characteristic study based on PQDs@UiO-66@MIP material In order to further understand the characteristics of the prepared material, a characteristic study was conducted on the prepared PQDs@UiO-66@MIP material (PQDs@UiO-66 material prepared based on UiO-66, 30 mg, template molecule, functional monomer and crosslinking agent, 0.1 mmol:0.4 mmol:1.6 mmol, respectively).

[0031] Figure 3 FIG. 1 is a scanning electron microscope image of UiO-66, FIG. 2 is a scanning electron microscope image of PQDs@UiO-66, and FIG. 3 is a scanning electron microscope image of PQDs@UiO-66@MIP. As can be seen from FIGS. 1-3, Figure 3 It can be seen that UiO-66 is composed of octahedral crystals (120-160 nm), and after the introduction of PQDs, the surface of the generated PQDs@UiO-66 particles becomes rough and the size slightly increases (160-200 nm), which is consistent with the silica layer generated by APTES. After molecular imprinting, the PQDs@UiO-66@MIP particles are converted into irregular aggregated structures, which indicates that the polymer layer has completely coated the PODs@UiO-66.

[0032] Figure 4 are the infrared spectra of PQDs, UiO-66, PQDs@UiO-66 and PQDs@UiO-66@MIP. The characteristic peaks of PQDs and PQDs@UiO-66 at 1030 cm -1 and 1130 cm -1 correspond to the symmetric and asymmetric stretching vibration of Si-O-Si, which confirms that APTES is hydrolyzed and condensed to form a silica layer; the presence of this characteristic peak in PQDs@UiO-66@MIP indicates that APTES and TMOS successfully participate in the construction of the composite material. The characteristic peaks of PQDs@UiO-66@MIP at 2830 cm -1 and 2930 cm -1 correspond to the stretching vibration of C-H bond on the organic silane chain, which is derived from PQDs. The asymmetric vibration characteristic peak of the terephthalic acid ligand carboxyl group appears at 1410 cm -1 for UiO-66, PQDs@UiO-66 and PQDs@UiO-66@MIP, which confirms that PQDs is successfully loaded on the UiO-66 matrix.

[0033] Figure 5 are the fluorescence selective experiments of PQDs@UiO-66@MIP and PQDs@UiO-66@NIP for different concentrations of CIP and its structural analogs, including pefloxacin, fleroxacin, levofloxacin, ofloxacin and enrofloxacin. As shown in the figure, when the concentration of CIP rises to 15 mg / L, the REF of CIP reaches the highest value of 3.22 for PQDs@UiO-66@MIP, while the REF of CIP for PQDs@UiO-66@NIP is 2.21, and the REF of other structural analogs under the same concentration is only between 1.0-1.3, which is much lower than the REF of CIP. The results show that the fluorescence response of PQDs@UiO-66@MIP to CIP is stronger than that of PQDs@UiO-66@NIP, and PQDs@UiO-66@MIP can specifically recognize CIP, and the detection method has good selectivity.

[0034] Figure 6 is the fluorescence response standard curve of PQDs@UiO-66@MIP material for different concentrations of CIP. As shown in the figure, in the range of 0.03-20 mg / L, the REF of PQDs@UiO-66@MIP and PQDs@UiO-66@NIP shows a good linear relationship with the concentration of CIP, and the linear equation of PQDs@UiO-66@MIP is: REF = 0.1391 C CIP + 1.11 (R 2= 0.997), Linear equation of PQDs@UiO-66@NIP: REF = 0.0828 C CIP + 0.974 (R 2 = 0.994), The fluorescence response of PQDs@UiO-66@MIP is more obvious than that of PQDs@UiO-66@NIP, which can be attributed to the specific binding of PQDs@UiO-66@MIP with ciprofloxacin leading to better fluorescence quenching efficiency, and the lowest detection limit of this method is 0.014 mg / L.

[0035] (II) Application of PQDs@UiO-66@MIP material in CIP analysis and detection The prepared polymer PQDs@UiO-66@MIP was added into the sample extract solution at a ratio of 1 mg:1 mL of feed liquid, and oscillated at room temperature for 30 min, and then used for fluorescence spectrophotometer analysis and detection. This method was applied to the determination of CIP in actual samples, and the results were compared with those of high performance liquid chromatography, as shown in Table 1.

[0036] Table 1 Application of PQDs@UiO-66@MIP material in fluorescence sensing detection of CIP

Claims

1. A method for preparing a ciprofloxacin ratiometric fluorescence sensor, characterized in that, Includes the following steps: (1) Preparation of UiO-66 Zirconium oxychloride (ZrOCl2) and terephthalic acid (PTA) were dispersed in N,N-dimethylformamide (DMF), and formic acid (FA) was added to carry out the reaction. After the reaction was completed, the precipitate was collected by centrifugation and dried to obtain UiO-66. (2) Preparation of PQDs@UiO-66 a. Cesium carbonate (CsCO3), oleic acid (OA), and octadecene (ODE) are subjected to a staged heating reaction under a nitrogen (N2) atmosphere and kept at the temperature to obtain a cesium oleate precursor; b. Mix lead bromide (PbBr2) and octadecene (ODE), evacuate the vacuum, introduce nitrogen gas, heat to a certain temperature, add OA, APTES and UiO-66, continue to heat, quickly add cesium oleate precursor, cool with an ice-water bath, perform hydrolysis treatment, centrifuge, wash and dry to obtain PQDs@UiO-66; (3) Preparation of PQDs@UiO-66@MIP The template molecule was dispersed in octadecene, and the functional monomer and PQDs@UiO-66 were added. After prepolymerization, the crosslinking agent was added and the mixture was stirred overnight. The product was collected by centrifugation, washed with eluent, and finally dried.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of ZrOCl2 to PTA is 1.5-3:1; the concentration of ZrOCl2 in DMF is 0.04-0.06 g / mL; and the volume ratio of DMF to FA is 2-3:

1.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the reaction is carried out at 130-150℃ for 2-3 h under vigorous stirring; the product is collected by centrifugation and dried under vacuum for 8-12 h.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (a), the ratio of CsCO3, OA, and ODE is 0.8-0.9 g: 2.5-3 mL: 20-30 mL; in step (b), the ratio of PbBr2, ODE, OA, and APTES is 0.138 g: 10 mL: 50-100 μL: 1 mL; the mass ratio of UiO-66 to PbBr2 is 100: 0.13~0.14; and the ratio of the cesium oleate precursor to PbBr2 is 1 mL: 0.13-0.14 g.

5. The preparation method according to claim 1 or 4, characterized in that, In step (a), the heat preservation reaction is carried out by first heating to 110-130℃ at a rotation speed of 500 r / min and holding for 1 h; then continuing to heat to 130-150℃ and reacting for 2 h; in step (b), after adding OA, APTES and UiO-66, the reaction temperature is raised to 110-130℃ at a rotation speed of 500 r / min and held for 1 h; then the temperature is raised to 140-160℃; the hydrolysis is carried out by stirring in a water bath at 25℃ for 2-3 h; the drying is carried out by vacuum drying at a temperature of 40-60℃.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (3), the molar ratio of the template molecule, functional monomer and crosslinking agent is 1:3-5:8-20; the ratio of the template molecule and PQDs@UiO-66 is 1 mmol: 200-400 mg; the eluent is composed of n-hexane and acetic acid in a volume ratio of 9:

1.

7. The preparation method according to claims 1-6, characterized in that, The template molecule is CIP; the functional monomer is APTES; the crosslinking agent is TMOS; the prepolymerization is carried out at 25-28℃ for 30-40 min; and the vacuum drying temperature is 40-60℃.

8. The application of UiO-66 prepared by the preparation method according to any one of claims 1-7 in enhancing the quantum confinement fluorescence effect of CIP.

9. The application of a ciprofloxacin ratiometric fluorescence sensor prepared by the preparation method according to any one of claims 1-7 in the analytical detection of CIP, characterized in that, The analytical detection utilizes a fluorescence enhancement factor for ratiometric fluorescent probe quantitative analysis; specifically, it includes the following steps: (1) Add the prepared polymer PQDs@UiO-66@MIP to the sample extract according to the material-liquid ratio, shake at room temperature, and wait for analysis and detection; (2) The sample to be tested was detected and analyzed using a fluorescence spectrophotometer.

10. The application according to claim 8, characterized in that, The ratio of PQDs@UiO-66@MIP to sample extract is 1 mg: 1-5 mL; the shaking time at room temperature is 15-30 min; the detection and analysis conditions of the fluorescence spectrophotometer are: excitation wavelength of 365 nm, emission wavelength of 400-600 nm, and slit width of 5 nm.

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