Chiral composite nanoprobe for hydrogen sulfide dual signal sensing and preparation method thereof

Abstract

The application discloses a high-selectivity and high-sensitivity chiral composite nanoprobe for hydrogen sulfide double-signal sensing and a preparation method thereof, and belongs to the technical field of sensors. 3+ The energy transfer distance is shortened by limiting ions in a surface layer, and the energy transfer efficiency is improved; and the chiral Cu x The upconversion nanoparticles and the chiral Cu x OS are encapsulated by taking ZIF-8 as a shell layer to construct the composite nanoprobe. The small pore diameter of ZIF-8 can effectively exclude some macromolecular interferents (such as glutathione, cysteine and lysine), thereby directly improving the specificity of detection. The reduction of hydrogen sulfide to Cu x OS leads to the recovery of the upconversion luminescence intensity, so that the composite nanoprobe can generate an upconversion luminescence / circular dichroism double-signal specific response to hydrogen sulfide. x The absorption of the composite nanoprobe and the decrease of the circular dichroism signal, and further the recovery of the upconversion luminescence intensity, enable the composite nanoprobe to generate an upconversion luminescence / circular dichroism double-signal specific response to hydrogen sulfide.

Description

Technical Field

[0001] This invention belongs to the field of sensing technology, specifically relating to a chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide and its preparation method. This sensor can achieve highly selective and highly sensitive dual-signal sensing of hydrogen sulfide. Background Technology

[0002] Most biomolecules are chiral, such as DNA, amino acids, peptides, and proteins. Due to the excellent safety and biocompatibility of these naturally occurring chiral compounds, many artificial chiral nanomaterials are increasingly being constructed, including chiral nanoparticles, chiral nanocomposites, and two-dimensional chiral nanofilms. Circular dichroism, one of the most representative optical properties of these chiral nanomaterials, is an ideal and powerful sensing technique with the potential for non-destructive cell analysis. In recent years, research on biosensing using circular dichroism spectroscopy has yielded many excellent results, demonstrating higher sensitivity compared to other analytical methods. Nevertheless, the time-consuming process of sample pretreatment, signal acquisition, and analysis makes real-time, in-situ sensing and analysis of cells and living tissues difficult, which is crucial for biomonitoring in rapidly changing physiological environments.

[0003] To broaden their applications in the biological field, scientists have combined chiral materials with other materials, giving these chiral nanocomposites more diverse biological functional properties. However, some chiral nanocomposites assembled through electrostatic adsorption or other methods exhibit poor structural stability and are prone to dissociation and destruction in complex physiological environments, leading to performance deviations. Furthermore, some chiral composite sensing materials struggle to distinguish between interfering substances with similar properties to the analyte, resulting in poor detection selectivity. Therefore, developing structurally stable and high-performance chiral composite nanomaterials to meet the needs of biomedical diagnostics and detection remains a challenging task. Summary of the Invention

[0004] The purpose of this invention is to provide a chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide and its preparation method. This invention aims to improve the selectivity of detection by utilizing the screening properties of the zeolite imidazole salt framework-8 (ZIF-8), the upconversion nanoparticles in ZIF-8, and Cu. x OS nanoparticles provide both fluorescence and circular dichroism signals, enabling the sensor to achieve highly selective and sensitive dual-signal sensing of hydrogen sulfide.

[0005] In this application, we constructed chiral UCNPs / Cu x OS@ZIF nanoprobes are used for highly selective dual-signal sensing of hydrogen sulfide in vitro and in vivo tumor imaging. The designed NaYbF4@NaYF4 contains 20% Yb. 3+ 2% Er3+ The upconversion nanoparticles were obtained by adding 100% activator Yb to the core. 3+ Ions are used to maximize the collection of near-infrared excitation energy and by using the luminescent center Er 3+ Ions are confined to the surface to shorten energy transfer distances, thereby maximizing energy transfer efficiency. Chiral Cu is employed. x OS nanoparticles serve as energy acceptors and circular dichroism signal sources; then, upconversion nanoparticles and chiral Cu are encapsulated in a zeolite imidazolium framework-8 (ZIF-8) shell. x OS is used to construct nanoprobes. The small pore size of ZIF-8 can effectively exclude some large molecular interferences (such as glutathione, cysteine, and lysine), thereby directly improving the specificity of detection. Hydrogen sulfide affects Cu x OS restoration leads to Cu x The changes in OS absorption and circular dichroism signal enable the designed nanoprobe to produce a highly selective and sensitive response to the upconversion luminescence / circular dichroism dual signal for hydrogen sulfide.

[0006] The present invention discloses a method for preparing a chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide, comprising the following steps:

[0007] (1) Synthesis of core-shell structured NaYbF4@NaYF4:Yb,Er upconversion nanoparticles (UCNP-OA): 1.00 mmol YbCl3·6H2O, 14 mL 1-octadecene and 6 mL oleic acid were mixed in a flask and stirred for 20-40 minutes. The resulting solution was heated to 150-160℃ and stirred continuously for 20-40 minutes until the solid in the solution dissolved. After naturally cooling to 45-55℃, 10 mL of a methanol solution containing 2.50 mmol sodium hydroxide and 4.00 mmol ammonium fluoride was added, and the mixture was heated to 65-75℃ and stirred for 20-40 minutes until the methanol was completely removed. The mixture was then heated to 300-320℃ and reacted for 60-90 minutes. After the reaction, the solution was allowed to cool naturally to 45-55℃, and NaYbF4 bare core upconversion nanoparticles were obtained by centrifugation with acetone and ethanol. Finally, the obtained bare core upconversion nanoparticles were dissolved in 4... The raw core upconversion nanoparticles were prepared in mL of cyclohexane and the concentration was 125 mM. Throughout the experiment, nitrogen gas was kept circulating to remove oxygen from the reaction system.

[0008] A mixture of 0.50 mmol YCl3·6H2O, 10 mL 1-octadecene, and 5 mL oleic acid was mixed in a flask and stirred for 20–40 minutes. The resulting solution was heated to 150–160 °C and stirred continuously for 20–40 minutes until the solid dissolved. After naturally cooling to 45–55 °C, 4 mL of a pre-synthesized cyclohexane solution containing the naked NaYbF4 core was added, and the mixture was heated to 80–90 °C and stirred for 20–40 minutes until the cyclohexane was completely removed. After naturally cooling to 45–55 °C, 5 mL of a methanol solution containing 1.25 mmol sodium hydroxide and 2.00 mmol ammonium fluoride was added, and the mixture was heated to 65–75 °C and stirred for 20–40 minutes until the methanol was completely removed. The solution was then heated to 300–320 °C and reacted for 60–90 minutes. After the reaction, the solution was allowed to cool naturally to 45–55 °C, washed with acetone and ethanol, and centrifuged to obtain NaYbF4@NaYF4. Yb, Er core-shell upconversion nanoparticles were used. Finally, the obtained core-shell upconversion nanoparticles were dissolved in 4 mL of cyclohexane for later use, and the concentration of the core-shell upconversion nanoparticles was 125 mM. Throughout the experiment, nitrogen gas was kept circulating to remove oxygen from the reaction system.

[0009] (2) Preparation of polyvinylpyrrolidone-modified NaYbF4@NaYF4:Yb,Er upconversion nanoparticles (UCNP-PVP): First, 2 mL of NaYbF4@NaYF4:Yb,Er cyclohexane solution was added to 2 mL of 0.1 M dilute hydrochloric acid solution and stirred for 8-12 hours to remove oleic acid ligands; then, acetone was added to precipitate ligand-free upconversion nanoparticles, which were collected by centrifugation and dispersed in 2 mL of ethanol, with a ligand-free upconversion nanoparticle concentration of 125 mM; then, 1 mL of ethanol solution containing ligand-free upconversion nanoparticles was mixed with 5 mL of ethanol solution containing 0.3 g polyvinylpyrrolidone (Mw=40000) and stirred at room temperature for 18-24 hours to obtain polyvinylpyrrolidone-modified upconversion nanoparticles. The nanoparticles were precipitated with n-hexane, collected by centrifugation and dispersed in 1 mL of ethanol. A methanol solution of polyvinylpyrrolidone-modified upconversion nanoparticles was obtained by dissolving the polyvinylpyrrolidone-modified upconversion nanoparticles in 1 mL of methanol. The concentration of the polyvinylpyrrolidone-modified upconversion nanoparticles was 125 mM.

[0010] (3) Chiral Cu x Synthesis of OS nanoparticles: 100 µL of 0.2 mol / L copper chloride aqueous solution, 100 µL of 0.4 mol / L sodium hydroxide aqueous solution, 150 µL of 0.4 mol / L D-penicillamine aqueous solution, and 300 µL of 1 mmol hydroxylamine hydrochloride aqueous solution were added to 3 mL of deionized water and stirred for 4–6 minutes to form Cu. xOS nanoparticles; after the reaction, Cu was precipitated with ethanol. x OS nanoparticles were collected by centrifugation and then dispersed in 3 mL of deionized water.

[0011] (4) UCNPs / Cu x Preparation of OS@ZIF-8: First, mix 4 mL of methanol solution containing 0.015191 g Zn(NO3)2•6H2O with 4 mL of methanol solution containing 0.007125 g 2-methylimidazole and stir for 1-3 minutes. Then, inject 50 µL of polyvinylpyrrolidone-modified upconversion nanoparticles obtained in step (2) and stir for 4-8 minutes until the solution turns white. Then, add 200 µL of Cu x OS nanoparticles were allowed to stand for 30-40 minutes; after the reaction was complete, the chiral composite nanoprobe UCNPs / Cu described in this invention was obtained. x OS@ZIF-8, collected by centrifugation, and dissolved in 1 mL of methanol;

[0012] (5) The chiral composite nanoprobe UCNPs / Cu prepared in step (4) x Add 1 mL of known hydrogen sulfide aqueous solutions of different concentrations (hydrogen sulfide aqueous solutions are produced by the hydrolysis of sodium sulfide in water) to OS@ZIF-8 to prepare 2 mL of test solution; react the test solution at room temperature for 10-20 minutes, and then measure the upconversion emission spectrum and circular dichroism spectrum of the test solution respectively; establish the "relationship curve between hydrogen sulfide concentration and upconversion emission intensity" and the "relationship curve between hydrogen sulfide concentration and circular dichroism signal intensity". The integration wavelength range of the upconversion emission intensity is 500-700 nm, and the circular dichroism signal intensity is obtained by subtracting the circular dichroism signals at 481 nm and 411 nm.

[0013] (6) The chiral composite nanoprobe UCNPs / Cu prepared in step (4) of the present invention x 1 mL of an aqueous solution of hydrogen sulfide of unknown concentration was added to OS@ZIF to obtain 2 mL of the test solution. The test solution was reacted at room temperature for 10-20 minutes, and then the upconversion emission spectrum and circular dichroism spectrum of the test solution were measured. The upconversion fluorescence intensity and the circular dichroism signal intensity were substituted into the "relationship curve between hydrogen sulfide concentration and upconversion emission fluorescence intensity" and the "relationship curve between hydrogen sulfide concentration and circular dichroism signal intensity" respectively to calculate the concentration of hydrogen sulfide.

[0014] The chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide described in this invention is prepared by the above method.

[0015] Working principle:

[0016] This invention utilizes Cux OS nanoparticles provide circular dichroism signals while simultaneously quenching the upconversion luminescence generated by NaYbF4@NaYF4:Yb,Er under 980nm excitation light. Hydrogen sulfide reduces Cu. x OS weakens the circular dichroism signal while restoring fluorescence. Hydrogen sulfide is quantitatively detected based on the linear relationship between the intensity of the circular dichroism signal, the change in upconversion luminescence intensity, and the concentration of hydrogen sulfide.

[0017] The chiral composite nanoprobe UCNPs / Cu prepared in this invention for highly selective and sensitive dual-signal sensing of hydrogen sulfide x OS@ZIF-8 has the following advantages:

[0018] 1. The designed NaYbF4@NaYF4: 20% Yb 3+ 2% Er 3+ Upconversion nanoparticles employ the activator Yb in the core 3+ The near-infrared excitation energy is maximized by using ion-doped (100% molar ratio) methods, and by using the luminescent center Er 3+ Ions are confined to the surface to shorten the distance between the Cu and the outside. x This maximizes the energy transfer efficiency by reducing the energy transfer distance between OS receptors.

[0019] 2. Cu as an energy acceptor x While quenching upconversion luminescence, OS nanoparticles possess a powerful circular dichroism signal, which has the potential for non-destructive cell analysis. They also exhibit high sensitivity, thus improving the detection sensitivity of chiral composite nanoprobes.

[0020] 3. A zeolite-type imidazole framework-8 (ZIF-8) was introduced as the shell of the nanoprobe to encapsulate upconversion nanoparticles and Cu. x OS nanoparticles improve the stability of the composite material, while the unique screening properties of ZIF-8 can effectively eliminate some macromolecular interferences (such as glutathione, cysteine ​​and lysine), thereby directly improving the specificity of detection. Attached Figure Description

[0021] Figure 1 : A schematic diagram of the preparation process of a highly selective and highly sensitive chiral composite nanoprobe for hydrogen sulfide dual-signal sensing according to the present invention;

[0022] like Figure 1As shown, NaYbF4 bare-core upconversion nanoparticles were first prepared. To improve their luminescence properties, an inert shell of NaYF4:Yb,Er was coated on their surface, forming lipophilic NaYbF4@NaYF4:Yb,Er core-shell structured upconversion nanoparticles. Then, the surface of these nanoparticles was modified with polyvinylpyrrolidone to transform them into hydrophilic upconversion nanoparticles. In an alkaline environment, copper ions and penicillamine ligands were added, and Cu was formed under the action of hydroxylamine hydrochloride. x OS nanoparticles; next, the ZIF-8 shell is coated using a self-assembly method of metal clusters and organic ligands to form the final chiral composite nanoprobe UCNPs / Cu. x OS@ZIF-8. Cu x OS nanoparticles provide circular dichroism signals while simultaneously quenching the upconversion fluorescence generated by NaYbF4@NaYF4:Yb,Er under 980nm excitation light. Hydrogen sulfide reduces Cu. x OS weakens the circular dichroism signal while restoring fluorescence, thus establishing a relationship between hydrogen sulfide and the intensity of the circular dichroism signal and the upconversion luminescence intensity for hydrogen sulfide detection.

[0023] Figure 2 Detection of chiral composite nanoprobes UCNPs / Cu in Example 1 x The curves showing the upconversion luminescence spectrum of OS@ZIF-8 under 980 nm laser excitation as a function of hydrogen sulfide concentration (0~70 μM).

[0024] Figure 3 Detection of chiral composite nanoprobes UCNPs / Cu in Example 1 x Linear relationship between upconversion luminescence intensity of OS@ZIF-8 under 980 nm laser excitation and hydrogen sulfide concentration (0~70 μM).

[0025] Figure 4 Detection of chiral composite nanoprobes UCNPs / Cu in Example 1 x The circular dichroism spectrum of OS@ZIF-8 varies with hydrogen sulfide concentration (0~100 μM).

[0026] Figure 5 Detection of chiral composite nanoprobes UCNPs / Cu in Example 1 x Linear relationship between the circular dichroism signal intensity of OS@ZIF-8 and hydrogen sulfide concentration (0~100 μM).

[0027] Figure 6 Statistical analysis of the interference detection results for the upconversion luminescent signal and circular dichroism signal in Example 2. Figure 6 A represents the detection result of interference in the upconversion luminous signal. Figure 6 B represents the detection result of interference from the circular dichroic signal. Detailed Implementation

[0028] Example 1: Synthesis of core-shell structured NaYbF4@NaYF4:Yb,Er upconversion nanoparticles.

[0029] (1) YbCl3·6H2O (1.00 mmol), 14 mL of 1-octadecene, and 6 mL of oleic acid were mixed in a 50 mL flask and stirred for 30 minutes. The solution was heated to 160 °C and held for 30 minutes. After cooling to 50 °C, 10 mL of a methanol solution containing sodium hydroxide (2.50 mmol) and ammonium fluoride (4.00 mmol) was added, and the mixture was heated to 70 °C and stirred for 30 minutes until the methanol was removed. The mixture was then heated to 315 °C and held for 60 minutes. After the reaction was completed, the solution was allowed to cool naturally to 50 °C. After centrifugation with acetone and ethanol, NaYbF4 bare core upconversion nanoparticles with an average size of 16.38 ± 0.78 nm were obtained. Finally, the obtained bare core upconversion nanoparticles were dissolved in 8 mL of cyclohexane for later use (the concentration of bare core upconversion nanoparticles was 125 mM). Throughout the experiment, nitrogen gas was kept circulating to remove oxygen from the reaction system.

[0030] (2) Mix 0.50 mmol YCl3·6H2O, 10 mL 1-octadecene and 5 mL oleic acid in a flask and stir for 20-40 minutes. Heat the solution to 160°C and continue for 30 minutes. After cooling to 50°C, add 4 mL of the NaYbF4 naked core cyclohexane solution (125 mM) prepared in step (1) and heat to 85°C and stir for 30 minutes until the cyclohexane is removed. After cooling to 50°C, add 5 mL of methanol solution containing sodium hydroxide (1.25 mmol) and ammonium fluoride (2.00 mmol) and heat to 70°C and continue for 30 minutes until the methanol is removed. Then heat the solution to 315°C and continue for 60 minutes. After the reaction is complete, allow the solution to cool to 50°C and wash with acetone and ethanol. After centrifugation, the average size of the lipophilic sample is (18.08 ± 0.19) * (24.91 ± 1.57). NaYbF4@NaYF4:Yb,Er core-shell upconversion nanoparticles were prepared. Finally, the obtained core-shell upconversion nanoparticles were dissolved in 4 mL of cyclohexane for later use (concentration of core-shell upconversion nanoparticles: 125 mM). Throughout the experiment, nitrogen gas was continuously supplied to remove oxygen from the reaction system.

[0031] Example 2: Preparation of polyvinylpyrrolidone-modified upconversion nanoparticles

[0032] (1) First, 2 mL of cyclohexane solution (125 mM) containing 0.25 mmol NaYbF4@NaYF4:Yb,Er was added to 2 mL of dilute hydrochloric acid solution (0.1 M) and stirred for 12 hours to remove oleic acid ligands; then acetone was added to precipitate ligand-free upconversion nanoparticles, and the ligand-free upconversion nanoparticles were collected by centrifugation and dispersed in 2 mL of ethanol (concentration of 125 mM).

[0033] (2) Then, 1 mL of ethanol solution (125 mM) containing ligand-free upconversion nanoparticles was mixed with 5 mL of ethanol solution containing polyvinylpyrrolidone (0.3 g, Mw=40000) and stirred at room temperature for 24 hours. The obtained polyvinylpyrrolidone-modified upconversion nanoparticles were precipitated with an appropriate amount of n-hexane, collected by centrifugation, and then dispersed in 1 mL of methanol to obtain a methanol solution of polyvinylpyrrolidone-modified upconversion nanoparticles (concentration of 125 mM).

[0034] Example 3: Chiral Cu x Preparation of OS nanoparticles

[0035] 100 µL of copper chloride (0.2 mol / L), 100 µL of sodium hydroxide (0.4 mol / L), 150 µL of D-penicillamine (0.4 mol / L), and 300 µL of hydroxylamine hydrochloride (1 mmol) were added to 3 mL of deionized water and stirred for 5 minutes to form Cu. x OS nanoparticles. After the reaction, Cu was precipitated with ethanol. x OS nanoparticles were collected by centrifugation. Then, the prepared Cu... x OS nanoparticles were dispersed in 3 mL of water.

[0036] Example 4: Chiral composite nanoprobes UCNPs / Cu x Preparation of OS@ZIF-8

[0037] 4 mL of a methanol solution containing Zn(NO3)2·6H2O (0.015191 g) was mixed with 4 mL of a methanol solution containing 2-methylimidazole (0.007125 g) and stirred for 1 minute. Then, 50 µL of polyvinylpyrrolidone-modified upconversion nanoparticles (125 mM) were injected. After 5 minutes, the solution turned white, and 200 µL of the prepared Cu was added. x OS nanoparticles were left to stand for 30 minutes. After the reaction, a chiral composite nanoprobe UCNPs / Cu was formed. x OS@ZIF-8, collected by centrifugation, and the product was dissolved in 1 mL of methanol (the concentration of the converted nanoparticles was calculated to be 6.25 mM).

[0038] Detection Example 1: Chiral Composite Nanoprobe UCNPs / Cu x Dual-signal sensing of hydrogen sulfide in aqueous solution using OS@ZIF-8

[0039] To 1 mL of chiral composite nanoprobe UCNPs / Cu x 1 mL of hydrogen sulfide solution of different concentrations was added to OS@ZIF-8 (6.25 mM) to prepare a series of 2 mL test solutions. The resulting mixtures were reacted at room temperature for 10 minutes, and the upconversion emission spectrum and circular dichroism spectrum of the test solutions were measured. The results of the upconversion emission spectrum test are shown in […]. Figure 2 As the hydrogen sulfide concentration increases, the upconversion luminescence gradually recovers. Furthermore, the hydrogen sulfide concentration and the upconversion luminescence intensity exhibit a good linear relationship between 0 and 70 μM. Figure 3 As shown; the results of the circular dichroism spectroscopy test are shown below. Figure 4 As the concentration of hydrogen sulfide increases, the circular dichroism signal gradually weakens. Meanwhile, the hydrogen sulfide concentration and the circular dichroism signal intensity exhibit a good linear relationship between 0 and 100 μM, such as... Figure 5 As shown.

[0040] Example 2: Chiral composite nanoprobe UCNPs / Cu x OS@ZIF-8 for the specific detection of hydrogen sulfide content

[0041] To 1 mL of chiral composite nanoprobe UCNPs / Cu x In OS@ZIF-8 (6.25 mM), 1 mL of each of the following aqueous solutions were added to prepare 2 mL test solutions for specific detection: sodium sulfide, L-cysteine, D-cysteine, L-lysine, glutathione, glutamic acid, glycine, phenylalanine, alanine, glucose, ascorbic acid, hydrogen peroxide, potassium chloride, sodium chloride, and sodium sulfate. The final concentration of each analyte in the test solution was 1 mM. As a control group, UCNP and Cu were used... x OS was simply mixed without ZIF-8 coating, and the same 15 analytes were added to demonstrate the screening effect of ZIF-8. The test results are as follows: Figure 6 As can be seen from the figure, the chiral composite nanoprobe UCNPs / Cu encapsulated in ZIF-8... x OS@ZIF-8 only responded to hydrogen sulfide; while the control group, which was not encapsulated with ZIF-8, also responded to cysteine, lysine and glutathione, demonstrating that ZIF-8 plays a crucial role in improving probe selectivity.

[0042] Example 3: Chiral composite nanoprobes UCNPs / Cu xOS@ZIF-8 dual-signal detection of aqueous solutions with unknown hydrogen sulfide concentration

[0043] To 1 mL of chiral composite nanoprobe UCNPs / Cu x 1 mL of an aqueous solution of hydrogen sulfide of unknown concentration was added to OS@ZIF-8 (6.25 mM) to prepare a series of 2 mL test solutions. The resulting mixtures were reacted at room temperature for 10 minutes, and the upconversion fluorescence spectrum and circular dichroism spectrum of the test solutions were measured. The upconversion fluorescence intensity and circular dichroism signal intensity were substituted into the "relationship curve between hydrogen sulfide concentration and upconversion fluorescence intensity" and the "relationship curve between hydrogen sulfide concentration and circular dichroism signal intensity", respectively, to calculate the concentration of hydrogen sulfide, as shown in Table 1.

[0044] Table 1: Results of calculating the hydrogen sulfide concentration in an unknown hydrogen sulfide solution based on the upconversion luminescence signal intensity and the circular dichroism signal intensity.

[0045] Sample number Upconversion luminous intensity (au) Hydrogen sulfide concentration (calculated value in μM) Hydrogen sulfide concentration (actual value μM) Accuracy (calculated value / actual value) 1 2097.28966 5.82 5.00 116.49% 2 3856.77825 23.14 25.00 92.56% 3 6907.65388 53.17 50.00 106.34% Sample number Circular dichroism signal strength (au) Hydrogen sulfide concentration (calculated value in μM) Hydrogen sulfide concentration (actual value μM) Accuracy (calculated value / actual value) 1 23.55696 5.16 5.00 103.26% 2 21.10681 26.10 25.00 104.41% 3 18.19143 51.02 50.00 102.04%

[0046] It should be noted that, unlike the direct detection principle of circular dichroism signals, upconversion luminescence signals are affected by the energy transfer efficiency between the donor and acceptor. Therefore, the accuracy of hydrogen sulfide concentration calculated from the intensity of upconversion luminescence signals is slightly lower than that calculated from circular dichroism signals. However, since the upconversion luminescence signal of this probe mainly plays a localization role in bioimaging, the lower detection accuracy in solution will not affect the performance of this probe in biological applications.

Claims

1. A method for preparing a chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide, comprising the following steps: (1) Synthesis of core-shell structured NaYbF4@NaYF4:Yb,Er upconversion nanoparticles: 1.00 mmol YbCl3·6H2O, 14 mL 1-octadecene and 6 mL oleic acid were mixed in a flask and stirred for 20-40 minutes. The resulting solution was heated to 150-160℃ and stirred continuously for 20-40 minutes until the solid in the solution dissolved. After naturally cooling to 45-55℃, 10 mL of methanol solution containing 2.50 mmol sodium hydroxide and 4.00 mmol ammonium fluoride was added, and the mixture was heated to 65-75℃ and stirred for 20-40 minutes until the methanol was removed. Then the mixture was heated to 300-320℃ and reacted for 60-90 minutes. After the reaction, the solution was allowed to cool naturally to 45-55℃, and NaYbF4 bare core upconversion nanoparticles were obtained by centrifugation with acetone and ethanol. Finally, the obtained bare core upconversion nanoparticles were dissolved in 4 The raw core upconversion nanoparticles were prepared in mL of cyclohexane and the concentration was 125 mM. Throughout the experiment, nitrogen gas was kept circulating to remove oxygen from the reaction system. A mixture of 0.50 mmol YCl3·6H2O, 10 mL 1-octadecene, and 5 mL oleic acid was mixed in a flask and stirred for 20–40 minutes. The resulting solution was heated to 150–160 °C and stirred continuously for 20–40 minutes until the solid dissolved. After naturally cooling to 45–55 °C, 4 mL of a pre-synthesized cyclohexane solution containing the naked NaYbF4 core was added, and the mixture was heated to 80–90 °C and stirred for 20–40 minutes until the cyclohexane was completely removed. After naturally cooling to 45–55 °C, 5 mL of a methanol solution containing 1.25 mmol sodium hydroxide and 2.00 mmol ammonium fluoride was added, and the mixture was heated to 65–75 °C and stirred for 20–40 minutes until the methanol was completely removed. The solution was then heated to 300–320 °C and reacted for 60–90 minutes. After the reaction, the solution was allowed to cool naturally to 45–55 °C, washed with acetone and ethanol, and centrifuged to obtain NaYbF4@NaYF4. Yb, Er core-shell upconversion nanoparticles were used. Finally, the obtained core-shell upconversion nanoparticles were dissolved in 4 mL of cyclohexane for later use, and the concentration of the core-shell upconversion nanoparticles was 125 mM. Throughout the experiment, nitrogen gas was kept circulating to remove oxygen from the reaction system. (2) Preparation of polyvinylpyrrolidone-modified NaYbF4@NaYF4:Yb,Er upconversion nanoparticles: First, 2 mL of NaYbF4@NaYF4:Yb,Er cyclohexane solution was added to 2 mL of 0.1 M dilute hydrochloric acid solution and stirred for 8-12 hours to remove oleic acid ligands; then acetone was added to precipitate ligand-free upconversion nanoparticles, which were collected by centrifugation and dispersed in 2 mL of ethanol, with a concentration of 125 mM for ligand-free upconversion nanoparticles; then 1 mL of ethanol solution containing ligand-free upconversion nanoparticles was mixed with 5 mL of ethanol solution containing 0.3 g of polyvinylpyrrolidone with Mw=40000, and stirred at room temperature for 18-24 hours to obtain polyvinylpyrrolidone-modified upconversion nanoparticles. The nanoparticles were precipitated with n-hexane, collected by centrifugation and dispersed in 1 mL of methanol to obtain a methanol solution of polyvinylpyrrolidone-modified upconversion nanoparticles with a concentration of 125 mM. (3) Chiral Cu x Synthesis of OS nanoparticles: 100 µL of 0.2 mol / L copper chloride aqueous solution, 100 µL of 0.4 mol / L sodium hydroxide aqueous solution, 150 µL of 0.4 mol / L D-penicillamine aqueous solution, and 300 µL of 1 mmol hydroxylamine hydrochloride aqueous solution were added to 3 mL of deionized water and stirred for 4–6 minutes to form Cu. x OS nanoparticles; after the reaction, Cu was precipitated with ethanol. x OS nanoparticles were collected by centrifugation and then dispersed in 3 mL of deionized water. (4) UCNPs / Cu x Preparation of OS@ZIF-8: First, mix 4 mL of methanol solution containing 0.015191 g Zn(NO3)2•6H2O with 4 mL of methanol solution containing 0.007125 g 2-methylimidazole and stir for 1-3 minutes. Then, inject 50 µL of polyvinylpyrrolidone-modified upconversion nanoparticles and stir for 4-8 minutes until the solution turns white. Then, add 200 µL of Cu. x OS nanoparticles were allowed to stand for 30–40 minutes; after the reaction, a chiral composite nanoprobe UCNPs / Cu for hydrogen sulfide dual-signal sensing was obtained. x OS@ZIF-8, collected by centrifugation, dissolved in 1 mL of methanol.

2. A chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide, characterized in that: It is prepared by the method described in claim 1.

3. The chiral composite nanoprobe for dual-signal sensing of hydrogen sulfide as described in claim 2, characterized in that: Chiral composite nanoprobes UCNPs / Cu x Add 1 mL of known hydrogen sulfide aqueous solutions of different concentrations to OS@ZIF-8 to prepare 2 mL of test solution; react the test solution at room temperature for 10-20 minutes, and then measure the upconversion emission spectrum and circular dichroism spectrum of the test solution respectively; establish the "relationship curve between hydrogen sulfide concentration and upconversion emission intensity" and the "relationship curve between hydrogen sulfide concentration and circular dichroism signal intensity". The integration wavelength range of the upconversion emission intensity is 500-700 nm, and the circular dichroism signal intensity is obtained by subtracting the circular dichroism signals at 481 nm and 411 nm.

4. The chiral composite nanoprobe for hydrogen sulfide dual-signal sensing as described in claim 3, characterized in that: Chiral composite nanoprobes UCNPs / Cu x 1 mL of an aqueous solution of hydrogen sulfide of unknown concentration was added to OS@ZIF-8 to obtain 2 mL of the test solution. The test solution was reacted at room temperature for 10-20 minutes, and then the upconversion emission spectrum and circular dichroism spectrum of the test solution were measured. The upconversion fluorescence intensity and the circular dichroism signal intensity were substituted into the "relationship curve between hydrogen sulfide concentration and upconversion emission fluorescence intensity" and the "relationship curve between hydrogen sulfide concentration and circular dichroism signal intensity" respectively to calculate the concentration of hydrogen sulfide.

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