Carbon dots with aggregation-induced emission characteristics and multi-element detection of Hg 2+ , Cu 2+ and BSA

Abstract

The application discloses carbon dots with an aggregation-induced emission feature and a multi-element detection Hg 2+ , Cu 2+ and BSA, which is synthesized by a hydrothermal method with o-phenylenediamine (OPD) and thiourea (Tu) as precursors; trace Cu 2+ , Hg 2+ and BSA in environmental water samples and food samples can be detected through a fluorescence mode; a fluorescence enhancement mechanism of the carbon dot fluorescence probe is an AIE mechanism induced by Cu 2+ ; Hg 2+ quenches the fluorescence of the carbon dot fluorescence probe through a static quenching effect (SQE) mechanism; and the fluorescence recovery of the quenched carbon dot-Hg 2+ complex is based on the strong chelation ability of BSA to Hg 2+ , which takes away Hg 2+ , so that the fluorescence of the carbon dot is recovered; and the presence of Cu 2+ hardly influences the recognition ability of the SN-CDs fluorescence probe to Hg 2+ .

Description

Technical Field

[0001] This invention belongs to the field of nanotechnology and detection technology, specifically relating to a yellow fluorescent carbon dot SN-CDs with aggregation-induced emission characteristics and its use as a fluorescent probe to identify Cu in the environment. 2+ Hg 2+ And BSA. Background Technology

[0002] As is well known, heavy metal ions are among the most harmful pollutants. Heavy metals hardly degrade in nature and accumulate in higher organisms through the food chain, eventually entering the human body and harming human health. Even trace concentrations can cause irreversible damage to the environment and human health. Divalent mercury ions (Hg) 2+ Copper divalent ions (Cu) are among the most toxic heavy metal ions. They are non-degradable and can be converted into methylmercury by bacteria, eventually accumulating in the human body through the food chain. Even at extremely low doses, they can cause serious damage to our nervous system, brain, kidneys, and even endocrine system [YX Zhang, ZC Song, SJ Huang, P. Zhang, YM Peng, PP Wu, J. Gu, S.Dutkiewicz, HX Zhang, SL Wu, FY Wang, L. Chen, SX Wang, P. Li, Globalhealth effects of future atmospheric mercury emissions, Nat. Commun. 12(2021) 3035.]. 2+ Cu plays a crucial role in catalysis and maintaining the stability of the nervous system. However, due to bioaccumulation, excessive Cu... 2+ Cu can cause damage to the human body and may indirectly lead to some serious kidney or liver diseases [LC Zhang, YM Yang, L. Liang, YJ Jiang, CM Li, YF Li, L. Zhan, HYZou, CZ Huang, Lighting up of carbon dots for copper(II) detection using anaggregation-induced enhanced strategy, Analyst 147 (2022) 417–422.]. Therefore, it is necessary to develop effective analytical methods to selectively detect Cu in the environment. 2+ and Hg 2+It is extremely important. Bovine serum albumin (BSA) plays a vital role in various fields, including food, biochemistry, and immunology. It is widely used as a protein calibrator, a standard protein in the design of immunochemical assays, and as a ligand carrier for applications in the food and pharmaceutical industries. BSA is a central component of fetal bovine serum (FBS), which is commonly used as a culture medium for vaccine production. Excessive BSA can cause allergic reactions in humans. The World Health Organization (WHO) has stipulated that the residual BSA dose in vaccines should be less than 50 ng [A. Basu, GS Kumar, Thermodynamics of the interaction of the foodadditive tartrazine with serum albumins: a microcalorimetric investigation, Food Chem. 175 (2015) 137–142; A. Jahanban-Esfahlan, L. Roufegarinejad, R.Jahanban-Esfahlan, M. Tabibiazar, R. Amarowicz, Latest developments in the detection and separation of bovine serum albumin using molecularly imprinted polymers, Talanta 207 (2020) 12031.]. Therefore, the detection of BSA has attracted increasing attention.

[0003] Currently, there are many traditional methods for detecting these heavy metal ions and biomacromolecules, such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), voltammetry, and high-performance liquid chromatography (HPLC) [H. Bagheri, M. Naderi, Immersed single-drop microextraction-electrothermal vaporization atomic absorption spectroscopy for the trace determination of mercury in water samples, J. Hazard. Mater. 165 (2009) 353–358; XP Chen, C. Han, HY Cheng, YC Wang, JH Liu, ZG Xu, L. Hu, Rapid speciation analysis of mercury in seawater and marine fish by cation exchange chromatography hyphenated withinductively coupled plasma mass spectrometry, J. Chromatogr. A 1314 (2013) 86–93.]. However, these techniques often require complex operation and expensive equipment, demand certain technical skills from operators, and the detection process is time-consuming. Therefore, it is crucial to develop simple, rapid, reliable, and low-cost detection methods. Fluorescence methods have advantages such as convenient detection, fast response, high sensitivity, and the ability to perform in-situ monitoring in various environments, and have been widely studied and applied in the detection of food and biological samples [H. He, DW Sun, Z. Wu, H. Pu, Q. Wei, On-off-on fluorescent nanosensing: Materials, detection strategies and recent food applications, Trends Food Sci. Tech. 119 (2022) 243–256.].

[0004] Carbon dots (CDs) are a novel type of nanomaterial, first discovered in 2004. They are typically smaller than 10 nm in size and have a quasi-spherical structure. CDs can be prepared using a variety of simple methods, such as hydrothermal / solvothermal methods, carbonization, pyrolysis, and microwave methods. CDs are inexpensive to produce, have abundant surface functional groups, and excellent optical properties, making them suitable as fluorescent probes for analyte detection. Furthermore, CD-based fluorescent probes offer advantages such as in-situ and real-time detection of target analytes [V. Sharma, P. Tiwari, N. Kaur, SM Mobin, Optical nanosensors based on fluorescent carbon dots for the detection of water contaminants: areview, Environ. Chem. Lett. 19 (2021) 3229–3241.]. Photoluminescence is one of the most attractive features of carbon dots (CDs). However, most CDs have short emission wavelengths, and yellow to red emitting CDs with emission wavelengths above 550 nm are difficult to synthesize, which greatly hinders the application of CDs, especially CDs with aggregation-induced emission (AIE). AIE is different from general fluorescence. In AIE, molecular aggregation causes a decrease in the energy of nonradiative transitions, resulting in enhanced fluorescence. Since the discovery of AIE, researchers have applied its unique fluorescence properties to many fields, including analytical detection, bioimaging, optoelectronic devices, room temperature phosphorescence, and photothermal therapy [F. Yan, X. Sun, T. Ma, Y. Zhang, Y. Jiang, R. Wang, C. Ma, J. Wei, L. Chen, Y. Cui, A viscosity-dependent carbon dots with anti-VEGF properties for monitoring and promoting apoptosis in cancerous cell, Chem. Eng. J. 407 (2021) 127801.]. Doping is a general and convenient functionalization technique that modifies the inherent structure of carbon dots (CDs) by inserting heteroatoms into them. It can further improve the chemical composition and structural properties of CDs, and is one of the important methods for controlling their optical and sensing properties. In this study, a yellow fluorescent carbon dot with AIE characteristics was designed and prepared through co-doping of sulfur and nitrogen elements, and it is capable of simultaneously detecting multiple heavy metal ions (Cu). 2+ Hg 2+ And the properties of biomolecule BSA. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by providing an SN-CD with aggregation-induced emission characteristics exhibiting yellow fluorescence emission and its application in the detection of Cu. 2+ Hg 2+ Applications related to BSA.

[0006] The SN-CDs exhibiting aggregation-induced emission with yellow fluorescence were synthesized via a hydrothermal method using o-phenylenediamine OPD and thiourea Tu as precursors.

[0007] The aforementioned yellow fluorescent SN-CDs exhibiting aggregation-induced emission characteristics are prepared by the following method, comprising:

[0008] 1) Disperse 0.1081~0.2162 g o-phenylenediamine and 0.0761~0.1522 g thiourea in 10 mL of ultrapure water, then transfer the mixture to a high-pressure reactor and heat at 120~200 °C for 2~8 h;

[0009] 2) After cooling to room temperature, SN-CDs were obtained by dialysis purification;

[0010] In step 1), the o-phenylenediamine is 0.1622 g and the thiourea is 0.0761 g.

[0011] The temperature in step 1) is 180 ℃; the heating time is 4 h.

[0012] Step 1) The dialysis purification is performed by filtration through a 0.22 μm microporous membrane and dialysis purification through a dialysis bag with a molecular weight cutoff of 1000.

[0013] SN-CDs-Hg 2+ The sensor comprises: carbon dots with aggregation-induced emission characteristics as described in claim 1 and Hg 2+ .

[0014] The carbon dots with aggregation-induced emission characteristics simultaneously detect Cu 2+ Hg 2+ Applications related to BSA.

[0015] This invention provides carbon dots with aggregation-induced emission characteristics and a multi-element detection method for Hg2+, Cu2+, and BSA. It is synthesized via a hydrothermal method using o-phenylenediamine OPD and thiourea Tu as precursors. Trace amounts of Cu in environmental water and food samples can be detected using fluorescence mode. 2+ Hg 2+ And BSA, the fluorescence enhancement mechanism of carbon dot fluorescent probes is Cu 2+ Induced AIE mechanism, Hg 2+The fluorescence of the carbon dot fluorescent probe is quenched through the static quenching effect (SQE) mechanism, while BSA-induced quenching of the carbon dot-Hg... 2+ The fluorescence recovery of the complex was based on the BSA reaction with Hg. 2+ Its strong chelating ability carried away Hg 2+ To restore the fluorescence of carbon dots, Cu 2+ The presence of Hg has almost no effect on the SN-CDs fluorescent probe's response to Hg. 2+ Its recognition capabilities.

[0016] This invention uses sulfur and nitrogen as doping atoms, and the synthesis method employed is based on the work of Fan [PF Fan, C.Liu, CC Hu, FF Li, X. Lin, FB Xiao, H. Liang, L. Li, SY Yang, Orange-emissive N,S-co-doped carbon dots for label-free and sensitive fluorescence assay of vitamin B]. 12 , New J. Chem. 46 (2022) 877–882.] and Liu [QL Liu, XYNiu, KX Xie, YM Yan, BR Ren, RR Liu, YX Li, L. Li, FluorescentCarbon Dots as Nanosensors for Monitoring and Imaging Fe 3+ and [HPO4] 2− According to the research of Ions, ACS Appl. Nano Mater. 4 (2021) 190–197., a Cu-type polymer with AIE characteristics was synthesized by studying the reaction temperature, reaction time, and reactant ratio. 2+ Hg 2+ Yellow fluorescent sulfur-nitrogen-doped carbon dots (SN-CDs) with BSA have unique sensing properties.

[0017] The present invention has the following advantages:

[0018] 1. The carbon dots of the present invention exhibit yellow fluorescence and have obvious aggregation-induced emission (AIE) characteristics.

[0019] 2. The carbon dot fluorescent probe constructed in this invention can directly detect Cu. 2+ and Hg 2+ Simultaneous detection of Cu 2+To enhance the fluorescence of the carbon dot probe, Hg 2+ Fluorescence quenching of carbon dot probes, detection of Cu based on different mechanisms 2+ and Hg 2+ They can be performed simultaneously without interference. (In Hg) 2+ Based on the quenching of SN-CDs, and utilizing the ability of BSA to restore the fluorescence of quenched carbon dots, a fluorescence recovery model based on fluorescent carbon dots-Hg was constructed. 2+ A probe for the complex enables the detection of BSA.

[0020] 3. The fluorescent detection probe provided by this invention has high sensitivity and good selectivity, and can simultaneously detect Cu. 2+ Hg 2+ And the detection of BSA, in which the probe targets Hg 2+ The detection limit was 25.77 nM, which is lower than the maximum allowable Hg level in drinking water set by the World Health Organization. 2+ Concentration (30 nM). Simultaneously, for Cu... 2+ The detection limits for BSA were 0.46 μM and 1.52 μM, respectively.

[0021] 4. This invention is simple to operate, and the detection results are intuitive and easy to read, enabling rapid detection of analytes. Attached Figure Description

[0022] Figure 1 Fluorescence spectra of SN-CDs at (a) different reaction temperatures, (b) normalized fluorescence intensity at different reaction temperatures, (c) fluorescence spectra at different reaction times, (d) normalized fluorescence intensity at different reaction times, (e) fluorescence spectra of SN-CDs synthesized with different amounts of OPD and Tu, and (f) normalized fluorescence intensity of SN-CDs synthesized with different amounts of OPD and Tu.

[0023] Figure 2 (a) TEM image of SN-CDs, with the corresponding HRTEM image in the inset; (b) particle size distribution histogram; (c) Ex, Em fluorescence spectra and UV-Vis absorption spectra, with the insets showing images under natural light (left) and UV lamp (right), respectively; (d) fluorescence emission spectra at excitation wavelengths of 390–450 nm.

[0024] Figure 3 Fluorescence spectra of SN-CDs mixed with different types of metal ions, with the inset showing the corresponding images under ultraviolet light.

[0025] Figure 4 (a) Adding different concentrations of Cu 2+The fluorescence spectra of the SN-CDs are shown in the inset, with the corresponding images under a UV lamp. (b) The fluorescence intensity ratio of the SN-CDs (I / I0, where I and I0 are the fluorescence intensities of the SN-CDs at 560 nm in the presence and absence of the analyte, respectively) is compared with Cu. 2+ (c) Linear relationship of concentrations (1~100 μM). 2+ Fluorescence spectra of SN-CDs, with the inset showing the corresponding images under a UV lamp. (d) Fluorescence intensity ratio (I / I0) of SN-CDs versus Hg. 2+ Linear relationship of concentrations (0.08~1.0 μM).

[0026] Figure 5 1: SN-CDs, 2: SN-CDs+Cu 2+ -Hg 2+ 3: SN-CDs+Hg 2+ +Cu 2+ 4: SN-CDs+Cu 2+ +Hg 2+ 5: SN-CDs+Hg 2+ , and 6: SN-CDs+Cu 2+ The fluorescence spectrum.

[0027] Figure 6 Schematic diagram of multivariate detection using SN-CD fluorescent probes.

[0028] Figure 7 (a) SN-CDs+Hg 2+ (a) Fluorescence spectra of SN-CDs mixed with different biomolecules (200 μM), with insets showing images under the corresponding UV lamps. (b) Fluorescence spectra of SN-CDs mixed with different samples, with insets showing images under the corresponding UV lamps (1: SN-CDs, 2: SN-CDs + Hg). 2+ 3: BSA, 4: BSA+Hg 2+ , 5: SN-CDs+BSA, 6: SN-CDs-Hg 2+ +BSA). (c) SN-CDs-Hg 2+ Fluorescence spectra after mixing with different concentrations of BSA (0–200 μM). (d) SN-CDs-Hg 2+ The linear relationship between the fluorescence intensity ratio (I / I0) and the BSA concentration (2~40 μM). Detailed Implementation

[0029] Example 1: Preparation of carbon dots

[0030] SN-CDs were prepared via a hydrothermal method. 0.1081–0.2162 g of o-phenylenediamine and 0.0761–0.1522 g of thiourea were dispersed in 10 mL of ultrapure water, and the mixture was then transferred to a 20 mL high-pressure reactor. The mixture was heated at 120–200 °C for 2–8 h and then cooled to room temperature to obtain a yellow solution containing SN-CDs. After purification by filtration through a 0.22 μm microporous membrane and dialysis using a dialysis bag with a molecular weight cutoff of 1000 Da, the SN-CDs were obtained. The fluorescence intensity of the carbon dots synthesized under different conditions was measured by fluorescence spectroscopy. Figure 1 The preferred synthesis conditions were: 0.1622 g of o-phenylenediamine, 0.0761 g of thiourea, a hydrothermal reaction temperature of 180 °C, and a reaction time of 4 h. The product obtained was SN-CDs prepared under the optimized conditions.

[0031] Characterization of carbon dots

[0032] (1) Transmission electron microscope (TEM)

[0033] The morphology of the synthesized SN-CDs was characterized using TEM. Figure 2 As can be seen from a, the prepared SN-CDs are spherical and monodisperse, with an average particle size of 3.59 ± 0.07 nm. Figure 2 b). HRTEM images of SN-CDs ( Figure 2 High-resolution lattice fringes with a lattice spacing of 0.21 nm were found in the illustration (a), corresponding to the (100) plane of graphitic carbon, indicating that SN-CDs have a highly crystalline carbon structure.

[0034] (2) Ultraviolet-visible absorption spectrum

[0035] UV-Vis absorption spectra of SN-CDs ( Figure 2 (c Purple portion) A strong absorption peak was observed at 290 nm, attributed to the π–π* transition of aromatic groups. Meanwhile, a broad and weak absorption peak near 415 nm was attributed to the n–π* transition of nitrogen- or oxygen-containing functional groups (C=O, C−N, etc.) on the surface of SN-CDs.

[0036] (3) Fluorescence spectrum

[0037] The fluorescence excitation and emission spectra of SN-CDs show that, at the optimal excitation wavelength of 420 nm, the strongest emission peak is observed at 560 nm. Figure 2 c), and at the same time exhibits strong yellow fluorescence under a 365 nm ultraviolet light source ( Figure 2 c illustration). Figure 2The d-axis shows that the position of the fluorescence emission peak does not change with the excitation wavelength, indicating that SN-CDs are not excitation-dependent, which suggests that the carbon dots have a uniform size distribution and surface state distribution.

[0038] The above results of optical property and morphology studies all prove the successful preparation of SN-CDs and their excellent optical properties.

[0039] Example 2 Cu 2+ Hg 2+ And BSA detection

[0040] Direct detection of Cu using SN-CDs as fluorescent probes 2+ and Hg 2+

[0041] Using SN-CDs as fluorescent probes to detect Cu 2+ The synthesized SN-CDs were diluted 120 times and used as a fluorescent detection probe. Then, an equal volume of the sample solution to be tested was added, and the fluorescence change was observed under a UV lamp. Figure 4 As shown in the illustration, when Cu 2+ In the presence of these substances, the fluorescence of the SN-CDs probe solution is significantly enhanced, and the increase in fluorescence intensity of SN-CDs can be observed from the fluorescence spectrum. Figure 4 a) When Cu is present in the solution 2+ At that time, the fluorescence spectral intensity of the solution was related to Cu. 2+ The ion concentration (1–100 μM) showed a reliable dependence. This is a typical characteristic of aggregation-induced emission enhancement, confirming the AIE properties of SN-CDs. When Hg is present... 2+ In the presence of Hg, the fluorescence of the SN-CDs probe solution is quenched. Observations of the fluorescence spectrum show that the fluorescence intensity of SN-CDs changes with the presence of Hg in the solution. 2+ As the concentration of Hg in the solution increases, the fluorescence intensity of the solution decreases. Furthermore, when the concentration of Hg in the solution increases... 2+ At higher concentrations (≥60 μM), SN-CD fluorescent probes will exhibit complete quenching. Figure 4 (c illustration). To cope with complex detection environments, SN-CDs fluorescent probes were combined with Cu... 2+ and Hg 2+ The priority of the reactions was investigated, and the specific reactions of SN-CDs with two metal ions under different conditions were tested. When the SN-CDs probe solution reacted with 100 μM Cu... 2+ ( Figure 5 Curve 6) or concentration of 100 μM Hg 2+ ( Figure 5 During the reaction shown in curve 5), the fluorescence intensity exhibited significant increases and decreases, respectively, further demonstrating the responsiveness of the SN-CDs fluorescent probe to Cu.2+ and Hg 2+ Its specific recognition capability. However, as Figure 5 As shown in curve 2, when the SN-CDs probe solution reacts with Cu 2+ and Hg 2+ Mixed solution (Cu) 2+ and Hg 2+ When the concentration of Hg was 100 μM, the intensity change of the fluorescence emission peak at 560 nm was due to the reaction. 2+ Dominant. Whether it's the SN-CDs probe solution or 100 μM Hg... 2+ After the reaction is complete, add an equal volume of Cu of the same concentration. 2+ ( Figure 5 Curve 3) is still related to 100 μM Cu 2+ After the reaction is complete, add an equal volume of Hg of the same concentration. 2+ ( Figure 5 Curve 4) shows fluorescence intensities similar to Hg. 2+ The effects on the SN-CDs probe solution were quite similar, indicating that Cu 2+ The presence of Hg has almost no effect on the SN-CDs fluorescent probe's response to Hg. 2+ Its recognition capabilities.

[0042] (1) SN-CDs as fluorescent probes for the detection of Cu 2+ and Hg 2+ Selectivity

[0043] Using SN-CDs as fluorescent probes to detect Cu 2+ and Hg 2+ It is necessary to examine its effect on Cu in other similar heavy metals. 2+ and Hg 2+ Selectivity. Under the same conditions, Ag at a concentration of 100 µM... + Ba 2+ Ca 2+ Cd 2+ Co 2+ , Cr 3+ Cu 2 + Fe 2+ Hg 2+ Mg 2+ , Mn 2+ Ni 2+ , Pb 2+ Zn 2+ The solutions were mixed with fluorescent probes, and the experimental phenomena were observed and the fluorescence spectra of the samples were measured. Fluorescence spectra ( Figure 3 This indicates that, except for Cu 2+Other ions, except Hg, could not significantly enhance the fluorescence of SN-CDs. 2+ Other ions cannot significantly quench the fluorescence of SN-CDs, especially Cu. 2+ and Hg 2+ Different responses can directly and simultaneously distinguish Cu 2+ Hg 2+ From photos taken under ultraviolet light ( Figure 3 As can be seen in the illustration, Cu 2+ This significantly enhances the fluorescence of the SN-CDs fluorescent detection probe under ultraviolet light, Hg 2+ The fluorescence of SN-CDs was completely quenched under ultraviolet light, while the colors of other samples were almost identical to those of the blank sample under ultraviolet light. This result is consistent with the fluorescence spectroscopy results, proving that the SN-CDs fluorescence detection probe is effective for Cu. 2+ and Hg 2+ It has high selectivity and different response modes, enabling simultaneous multivariate detection.

[0044] (2) SN-CDs as fluorescent probes for the detection of Cu 2+ and Hg 2+ Sensitivity

[0045] Using SN-CDs as fluorescent probes to detect Cu 2+ and Hg 2+ At that time, Cu 2+ and Hg 2+ The concentrations of the solution samples ranged from 0.01 µM to 100 µM and from 0.08 µM to 100 µM, respectively. The fluorescence spectra of these samples were then measured to verify the probe's sensitivity. The fluorescence spectra show that as Cu... 2+ As the concentration increases, the fluorescence intensity gradually increases. Figure 4 a) Fluorescence intensity and Cu 2+ The fluorescence intensity of the mixed solution is directly proportional to the concentration, as can be observed in the corresponding experimental phenomena images; the fluorescence intensity increases with Cu concentration. 2+ The fluorescence intensity increases with increasing concentration; the fluorescence intensity ratio (I / I0) of SN-CDs is related to Cu. 2+ There is a good linear relationship between the concentrations (1~100 μM). Figure 4 (b) The calculated detection limit is 0.46 μM. However, with Hg... 2+ As the concentration increases, the fluorescence intensity of the fluorescence emission peak of the mixed solution gradually decreases. Figure 4 c), the fluorescence of the corresponding mixed solution gradually quenches, and the fluorescence intensity ratio (I / I0) of SN-CDs is related to Hg. 2+ There is a good linear relationship between the concentrations (0.08~1.0 μM). Figure 4d), the calculated detection limit is 25.77 nM.

[0046] BSA was indirectly detected using SN-CDs as fluorescent probes.

[0047] (1) Methods for detecting BSA

[0048] SN-CD fluorescent probes can achieve the detection of Cu based on fluorescence enhancement and fluorescence quenching phenomena, respectively. 2+ and Hg 2+ The detection of SN-CDs-Hg. 2+ The weak fluorescence of the complex provides a basis for the construction of a fluorescence-activated sensor. For example... Figure 6 As shown, add Hg 2+ After SN-CDs are quenched, BSA is added again, and the fluorescence of the quenched system is restored. Furthermore, the fluorescence recovery intensity is positively correlated with the increase of BSA concentration. Therefore, SN-CDs-Hg 2+ The complex can be used as a fluorescence-activated sensor for the selective determination of BSA.

[0049] (2) Selectivity of BSA detection

[0050] In Hg 2+ Under the quenching effect, the fluorescence of SN-CDs disappears, and the fluorescence of SN-CDs-Hg is lost. 2+ The complex was used as a probe (SN-CDs diluted 120 times were mixed with 100 µM Hg). 2+ Equal volumes of the mixture were prepared, and 19 different biomolecules (bovine serum albumin (BSA), tryptophan (Trp), methionine (Met), histidine (His), phenylalanine (Phe), uric acid (UA), glucose (Glu), glutathione (GSH), lysine (Lys), serine (Ser), aspartic acid (Asp), citrulline (Cit), threonine (Thr), urea (Urea), leucine (Leu), dopamine (DA), glutamate (GA), ascorbic acid (AA), and cysteine ​​(Cys)) were added to investigate their selectivity. Under the same conditions, solutions of BSA, Trp, Met, His, Phe, UA, Glu, GSH, Lys, Ser, Asn, Cit, Thr, Urea, Leu, DA, GA, AA, and Cys at a concentration of 200 µM were respectively mixed with fluorescent probes (SN-CDs-Hg). 2+ After the mixture reaction, observe the experimental phenomena and test the fluorescence spectrum of the sample. Figure 7 Fluorescence spectroscopy indicates that, except for BSA, no other molecules can cause SN-CDs-Hg. 2+ The fluorescence of the complex was restored. From Figure 7The photograph corresponding to the illustration also shows that the fluorescence of the sample after mixing with BSA is enhanced, and the fluorescence color changes from yellow to green in SN-CDs, indicating that SN-CDs-Hg 2+ The complex fluorescent detection probe exhibits high selectivity for BSA. This green color is due to the weak blue fluorescence inherent in BSA itself, such as... Figure 7 As shown in b, SN-CDs+BSA and SN-CDs-Hg 2+ +BSA exhibits the same fluorescent color and the fluorescence emission peak is located at the same position. The presence of BSA can make Hg... 2+ The fluorescence of quenched SN-CDs is restored, and the degree of fluorescence restoration increases with increasing BSA concentration, thus enabling quantitative detection of BSA.

[0051] (3) Sensitivity of BSA detection

[0052] Using SN-CDs-Hg 2+ When the complex was used as a fluorescent probe to detect BSA, BSA solution samples with concentrations ranging from 2 µM to 200 µM were reacted with the probe, and the fluorescence spectra of the samples were then measured to verify the detection sensitivity. The fluorescence spectra showed that as the BSA concentration increased, the fluorescence intensity of the mixed solution's fluorescence emission peak gradually increased, and the fluorescence emission peak blue-shifted from 560 nm to 550 nm. Figure 7 c), as can be observed in the corresponding experimental image, the fluorescence of the mixed solution gradually recovers with increasing BSA concentration. For ease of calculation, fluorescence intensity at 560 nm was used for all samples. A good linear relationship was found between the fluorescence intensity ratio (I / I0) and the BSA (2~40 μM) concentration. Figure 7 d), the detection limit was calculated to be 1.52 μM, thus confirming that it has good sensitivity for the detection of BSA.

Claims

1. A type of SN-CDs exhibiting aggregation-induced emission (AIE) characteristics and yellow fluorescent emission for simultaneous detection of Cu 2+ Hg 2+ Applications related to BSA, characterized in that, The SN-CDs mentioned above are synthesized via a hydrothermal method using o-phenylenediamine OPD and thiourea Tu as precursors. The specific steps are as follows: 1) 0.1081–0.2162 g of o-phenylenediamine and 0.0761–0.1522 g of thiourea were dispersed in 10 mL of ultrapure water, and then the mixture was transferred to a high-pressure reactor and heated at 120–200 °C for 2–8 h. 2) After cooling to room temperature, SN-CDs were obtained by dialysis purification; The aforementioned SN-CDs exhibit aggregation-induced emission characteristics and react with Cu. 2+ Fluorescence is enhanced upon contact with Hg 2+ Fluorescence quenching, BSA can quench Hg 2+ Fluorescence recovery of quenched SN-CDs, Cu 2+ The presence of Hg does not affect the fluorescence probe's response to Hg. 2+ Its recognition capabilities.

2. The application according to claim 1, characterized in that: In step 1), the o-phenylenediamine is 0.1622 g and the thiourea is 0.0761 g.

3. The application according to claim 2, characterized in that: The temperature mentioned in step 1) is 180 degrees; heating for 4 hours.

4. The application according to claim 3, characterized in that: Step 2) describes dialysis purification by filtration through a 0.22 μm microporous membrane and dialysis purification using a dialysis bag with a molecular weight cutoff of 1000.

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