Zinc nitride quantum dots and their application as fluorescent nanosensors in the detection of Cu 2+ and / or Mn 2+ detection

Abstract

The present invention discloses a zinc nitride quantum dot and its application as a fluorescent nanosensor in the detection of Cu<supgt;2+< / supgt> and Mn<supgt;2+< / supgt>. The complexation of blue fluorescent quantum dots containing rich functional groups with metal ions Cu<supgt;2+< / supgt> and Mn<supgt;2+< / supgt> results in a strong quenching of the blue fluorescence, thereby realizing the change of the fluorescence color of this probe from blue to colorless for the detection of Cu<supgt;2+< / supgt> and Mn<supgt;2+< / supgt>. This method has good visualization effects, high selectivity, high sensitivity, and low detection limits. In addition, the chemicals and technologies used have less economic harm, stable materials, and high quantum yields. It has been successfully coated on paper strips and can be used as a mobile detector for on-site local sensing of heavy metal ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescence visualization detection, and particularly relates to a zinc nitride quantum dot and its application as a fluorescent nanosensor for highly sensitive fluorescence visualization detection of Cu 2+ and Mn 2+ ions. It quenches sharply when Cu 2+ and Mn 2+ are added. It is found that the quenching potential of Cu 2+ is about 57%, and the quenching potential of Mn 2+ is about 70%, as shown in Figure 6b and c. Background Art

[0002] Heavy metals are naturally occurring and are popular for their large mass and density, but their negative impacts outweigh their beneficial aspects; Cu 2+ is the third most essential trace element in the human body and plays a crucial role in various basic physiological processes of the human body. Heavy metal pollution has become a serious environmental and human health problem due to its high toxicity and accumulation ability in the ecosystem. In particular, excessive intake of Cu 2+ can have many negative impacts on the human body, including digestive problems, liver or kidney damage, etc. Therefore, it is very important to quantify the amount of Cu 2+ in the environment and drinking water. The main risk factor associated with diseases caused by Cu 2+ is soluble copper salts in drinking water. Therefore, it is very important to develop a technology for quickly, economically and accurately measuring Cu 2+ in water. Manganese ions (Mn 2+ ) are another important component of the human body and have a significant impact on several biological processes including metabolism. However, excessive exposure to Mn 2+ is dangerous, especially to the nervous system, which can have a negative impact on the central nervous system and cause diseases such as Parkinson's disease. In addition, a lack of Mn 2+ ions can lead to hypercholesterolemia and delayed blood coagulation. Manganese and copper are essential trace elements for many important functions of the human body, including enzyme activity, bone development and fat metabolism. However, excessive exposure to these metal ions during biological processes can be harmful to health and even lead to fatal diseases.

[0003] Optical signal-based biochemical sensors have proven to be a promising detection method due to their simplicity, high sensitivity, and good selectivity. Early studies have shown that nanomaterials can sense metal ions even at very low concentrations. These nanostructures include quantum dots, organic molecules, and metal oxide nanomaterials; however, these substances are also harmful to living cells. Therefore, recent research has mainly focused on creating inorganic nanoparticles as sensing probes with high stability and minimal toxicity; developing affordable sensors as alternatives to precious noble metals has become an emerging research area in the scientific community. Summary of the Invention

[0004] An object of the present invention is to provide a zinc nitride quantum dot and its application as a fluorescent nanosensor for highly sensitive fluorescence visualization detection of Cu 2+ and Mn 2+ ions. This sensing visualization detection strategy can construct a reliable, convenient, and on-site Cu 2+ and Mn 2+ ion analysis platform. Specifically, the present invention is achieved by the following technical solutions:

[0005] A zinc nitride quantum dot of the present invention has blue fluorescence, reaches a peak at 408 nm when excited at 320 nm, has a quantum yield of 29.56%, and an average size of 2 - 3 nm.

[0006] A zinc nitride quantum dot of the present invention is obtained by the following preparation method:

[0007] Add zinc nitrate hexahydrate and ammonia solution, mix the solution in clarified distilled water and stir to obtain a clear solution; then pour the obtained mixture into a stainless steel lined with polytetrafluoroethylene, fix the temperature at 150 - 180 °C for 15 - 18 hours; here, the injected ammonia solution serves as a nitrogen source. Subsequently, separate the reaction chamber and keep it outside to cool to room temperature, then dialyze the solution (the molecular weight cut-off of the dialysis bag is 12 - 14 kDa) for 1 - 3 hours to remove any unwanted substances, and refrigerate the obtained solution for later use. The zinc nitrate hexahydrate should be dissolved sufficiently, and the stirring time should not be less than 1 hour. The amount of substance of zinc nitrate hexahydrate is 3 - 6 mmol, the concentration of the ammonia solution is 20 - 30 wt%, and the dosage is 2 - 5 mL. The fluorescence is the strongest when the amount of substance of zinc nitrate hexahydrate is 5 mmol.

[0008] The present invention also provides the application of the zinc nitride quantum dot as a fluorescent nanosensor in the detection of Cu 2+ and Mn 2+ And when coupling Cu 2+ and Mn 2+ ions to the probe, the emission signal is significantly reduced, and for Cu 2+ and Mn2+ The corresponding detection limits obtained for the ions were 21.78 and 63.82 nM, respectively.

[0009] The sensor was also successfully coated on a paper strip and can be used as a portable detector for on-site local sensing of heavy metal ions.

[0010] Preferably, in the application, 1 mL of the prepared zinc nitride quantum dot solution was taken as the fluorescence sensing system. The prepared quantum dots were used directly, and it was determined that the fluorescence was the strongest when the molar concentration of zinc nitrate hexahydrate was 5 mM.

[0011] Preferably, in the application, a metal ion solution containing Cu 2+ and / or Mn 2+ was added to the fluorescent nanosensor, and the fluorescence spectrum in the range of 350 - 550 nm was recorded with an excitation light of 320 nm. When Cu 2+ and / or Mn 2+ was added, the blue fluorescence of the fluorescent nanosensor was quenched sharply.

[0012] Preferably, in the application, solutions of different concentrations of Cu 2+ or Mn 2+ were added to the fluorescent nanosensor respectively. By recording the corresponding fluorescence spectra with an excitation light of 320 nm, the relationship between the fluorescence intensity and the concentration of Cu 2+ or Mn 2+ was established.

[0013] Preferably, in the application, the fluorescent nanosensor was made into a paper-based sensor.

[0014] Preferably, in the application, the paper-based sensor used cellulose paper and was made into a strip, circular or square shape. Specifically, cellulose paper was taken and soaked in a Zn3N2 quantum dot solution, and after drying, it was used for the detection of Cu 2+ and Mn 2+ . More specifically, for the preparation of the fluorescent paper-based sensor of the present invention, circular cellulose sheets of equal diameter were taken and treated with the prepared Zn3N2 quantum dot solution to activate the surfaces of the sheets with their respective functions. Then the strips were dried under ambient conditions for 24 hours and cut into strips for further use.

[0015] In the present invention, the principle of using the fluorescent sensor to detect Cu 2+ and Mn 2+ is based on the fluorescence quenching strategy. Specifically, it is because the blue fluorescent quantum dot Zn3N2 has rich functional groups that complex with the metal ions Cu 2+ and Mn 2+ , and the blue fluorescence shows strong quenching, thereby realizing the detection of Cu 2+ and Mn by this probe.2+ The fluorescence color changes from blue to colorless. The entire fluorescence signal response can be completed within 2 seconds. By establishing the relationship between the fluorescence intensity and Cu 2+ and Mn 2+ , quantitative detection of Cu 2+ and Mn 2+ can be achieved.

[0016] In the present invention, by continuously increasing the concentrations of Cu 2+ and Mn 2+ , based on the gradual quenching of the blue fluorescence, a series of changes in fluorescence intensity are presented under ultraviolet light, thereby enabling visual detection of Cu 2+ and Mn 2+ .

[0017] Compared with the existing detection techniques, the beneficial effects of the present invention are as follows:

[0018] 1. The present invention uses single-color fluorescence to detect Cu 2+ and Mn 2+ . The single-color fluorescence intensity is relatively stable, enabling visual detection. This probe can simultaneously detect Cu 2+ and Mn 2+ , which is different from the previous probes that separately detect Cu 2+ or Mn 2+ . Moreover, it has good selectivity for Cu 2+ and Mn 2 + , achieving qualitative detection of multiple heavy metal ions with one probe.

[0019] 2. The response time of the fluorescence sensor of the present invention is completed within two seconds, enabling rapid detection.

[0020] 3. The detection limit of the fluorescence sensor of the present invention for Cu 2+ is 21.78 nM, and the detection limit for Mn 2+ is 63.82 nM.

[0021] 4. The fluorescence paper-based sensor of the present invention is safe, stable, and portable, breaking the limitations of time and space.

[0022] 5. The fluorescence quenching type system of the blue quantum dot sensor prepared in the present invention has good selectivity and sensitivity for Cu 2+ and Mn 2+ . The fluorescence nanosensor of the present invention can be used for highly sensitive fluorescence visual detection applications of Cu 2+ and Mn 2+ ions. As shown in Figure 6c , it quenches sharply when adding Cu 2+ and Mn 2+ , and it is found that Cu2+ The quenching potential is about 57% for Mn 2+ and about 70% for Mn. In addition, the fluorescent nanosensor of the present invention can also effectively avoid the interference of other impurities and has a rapid response, as shown in Figure 6a and 6b . BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the transmission electron microscope image of the fluorescent sensor.

[0024] Figure 2 (b, c) are the transmission electron microscope images of the fluorescent sensor with the addition of Cu 2+ and Mn 2+ respectively. Scale bar: 5 nm.

[0025] Figure 3 (a, b) are the fluorescence spectra and color change diagrams of blue quantum dots with different concentrations of Cu 2+ and Mn 2+ . As the concentrations of Cu 2+ and Mn 2+ increase, the fluorescence color of the Cu 2+ (2.5, 5, 10, 25, 50, 70, 100, 300, 500, 700, 1000 μM) and Mn 2+ (0.05, 0.1, 1, 2.5, 5, 10, 25, 50, 75, 100, 300, 500, 700, 1000 μM) solutions gradually changes from blue to colorless.

[0026] Figure 4 a) Cu 2+ and b) Mn 2+ cellulose paper-based Zn3N2 quantum dot strips.

[0027] Figure 5 Calibration curves between I0 / I and the concentrations of a) Cu 2+ (2.5 - 50 μM) and b) Mn 2+ (0.05 - 5 μM).

[0028] FIG. 6 shows the interference study of cations (Pb 2+ , Zn 2+ , Mg 2+ plasma, 1000 μM), anions (NO3 - , Br - , SO4 2- , 1000 μM) and pesticides (corresponding to malathion, thiamethoxam, fenvalerate, cypermethrin in English names respectively, 1000 μM), a). With Cu 2+ , b). Containing Mn 2+; and the Zeta potential measurements of zinc nitride quantum dots, zinc nitride quantum dots + Cu 2+ and zinc nitride quantum dots + Mn 2+ . Detailed implementation mode

[0029] The following embodiments are further explanations of the content of the present invention to illustrate the technical content of the present invention. However, the substantial content of the present invention is not limited to the following embodiments. Those of ordinary skill in the art can and should know that any simple changes or substitutions based on the substantial spirit of the present invention should fall within the protection scope required by the present invention.

[0030] Example 1:

[0031] Preparation of blue quantum dots

[0032] Add zinc nitrate hexahydrate in an amount of substance (5 mM) and 2.5 mL of ammonia solution (25 wt%) and mix the solution in 30 mL of clarified distilled water and stir to obtain a clear solution; then pour the obtained mixture into a stainless steel with a polytetrafluoroethylene liner and fix the temperature at 160 °C for 16 hours; here, the injected ammonia solution serves as a nitrogen source. Subsequently, separate the reaction chamber and keep it outside to cool to room temperature, and then dialyze the solution for 2 hours (the molecular weight cut-off of the dialysis bag is 12 - 14 kDa) to remove any unwanted substances, and refrigerate the obtained Zn3N2 quantum dot solution for later use.

[0033] Example 2:

[0034] Preparation of fluorescent paper-based sensor

[0035] Take circular cellulose sheets of equal diameter and treat these cellulose sheets with the Zn3N2 quantum dot solution prepared in Example 1 to activate the surfaces of the sheets with their respective functions. Then dry the strips under ambient conditions for 24 hours and cut them into strips for further use.

[0036] Example 3:

[0037] Cu 2+ and Mn 2+ Ion probe solution detection: Add 0.5 mL of different concentrations of Cu 2+ (2.5, 5, 10, 25, 50, 70, 100, 300, 500, 700, 1000 μM) and Mn 2+ (0.05, 0.1, 1, 2.5, 5, 10, 25, 50, 75, 100, 300, 500, 700, 1000 μM) to the fluorescent nanosensor probe system respectively and add them to different vials of 1 mL of zinc nitride quantum dots, and record the corresponding fluorescence spectra by orderly exciting at 320 nm as the concentration increases. AsFigure 3 Cu 2+ When the concentration is about 700 μM, the fluorescence quenching is complete, and for Mn 2+ When the concentration is about 500 μM, the fluorescence quenching is complete.

[0038] Drawing of the standard curve: Different concentrations of Cu 2+ (Mn 2+ ) ion solutions were added to the blue quantum dots. After mixing, the fluorescence intensity was measured. The results showed that the blue fluorescence emission peak at 408 nm (400 nm) gradually weakened. According to the calibration graph of I0 / I, the fluorescence intensity ratios were proportional to the logarithms of the concentrations of Cu 2+ (2.5 - 50 μM) and Mn 2+ (0.05 - 5 μM) respectively. Linear regression curves of y = 0.1231x + 0.949 and y = 0.0628x + 1.1453 were respectively fitted, providing a correlation for quantitative detection of Cu 2+ (Mn 2+ ) solutions. When the excitation light was 320 nm, the fluorescence spectra of the mixed system in the wavelength range of 350 - 550 nm were recorded, as shown in Figure 3 Figures a and 3b.

[0039] Example 4:

[0040] Cu 2+ and Mn 2+ Detection of ions by fluorescence paper-based sensors

[0041] 0.5 mL of different concentrations of different concentrations of Cu 2+ (2.5, 25, 50, 100, 500 μM) and Mn 2+ (0.05, 1, 50, 100, 500 μM) were respectively added to different vials of 1 mL of zinc nitride quantum dots. Circular cellulose sheets of equal diameter were taken and treated with Zn3N2 quantum dot solution to activate the surface of the sheets with their respective functions and then dried for 24 hours under ambient conditions. Then, the strips were further used for the practical application of Cu 2+ (2.5, 25, 50, 100, 500 μM) and Mn 2+ (0.05, 1, 50, 100, 500 μM) ion determination. The paper strips were immersed in ion solutions of different concentrations of Cu 2+ and Mn 2+ or fluorescence sensing test strips with different concentrations of Cu 2+ (Mn 2+ ) ions were dropped, and then placed on the detection platform to obtain fluorescence phenomena under a 365 nm ultraviolet lamp in a dark environment, as shown in Figure 4As shown. When the color intensity decreases with the increase of metal ion concentration, the strip shows obvious changes.

[0042] Example 5:

[0043] Selectivity and Interference Testing of Fluorescent Nanoprobes

[0044] To explore the interference determination of Zn3N2 quantum dots, the selectivity of the quantum dots was studied by analyzing the fluorescence properties of these quantum dots to determine Cu 2+ and Mn 2+ , to determine whether common species (cations, anions, and pesticides) in different water sources would interfere with these quantum dots. Thereafter, different interference categories were studied, namely cations (Pb 2+ , Zn 2+ and Mg 2+ , 1000 μM), anions (NO 3- , Br - and SO4 2- , 1000 μM) and pesticides (malathion, thiamethoxam, fenvalerate, cypermethrin, 1000 μM.) on the fluorescence signal of Zn3N2 quantum dots. Introducing the above complementary interfering species into Zn3N2 quantum dots did not show any spectral changes. Adding Cu 2+ and Mn 2+ resulted in an obvious change in the fluorescence intensity ratio of blue fluorescence quenching, indicating that the system has good selectivity and anti-interference ability for Cu 2+ and Mn 2+ .

[0045] It should be noted that the above technical content of the present invention is only for explaining and clarifying so that those skilled in the art can understand the technical essence of the present invention. Therefore, the above technical content is not used to limit the substantive protection scope of the present invention. The substantive protection scope of the present invention shall be subject to what is described in the claims. Those skilled in the art should know that any modifications, equivalent substitutions, and improvements made based on the substantive spirit of the present invention shall be within the substantive protection scope of the present invention.

Claims

1. Application of zinc nitride quantum dots as a fluorescent nanosensor in the detection of Cu 2+ and / or Mn 2+ The application is characterized in that the zinc nitride quantum dots exhibit bright fluorescence, peak at 408 nm when excited at 320 nm, have a quantum yield of 29-30%, and an average size of 2-3 nm; the preparation method of the zinc nitride quantum dots comprises the following steps: Zinc nitrate hexahydrate and ammonia solution were mixed in distilled water and stirred to obtain a clear solution; then the obtained mixture was poured into a stainless-steel reactor lined with polytetrafluoroethylene and reacted at 150 - 180 °C for 15 - 18 hours; subsequently, it was cooled to room temperature, and then the solution was dialyzed for 1 - 3 hours: the obtained solution was refrigerated, and the molecular weight cut-off of the dialysis bag was 12 - 14 kDa.

2. The application according to claim 1, characterized in that: The amount of substance of zinc nitrate hexahydrate was 3 - 6 mmol, the concentration of ammonia solution was 20 - 30 wt%, and the dosage was 2 - 5 mL.

3. The application according to claim 1, characterized in that 1 mL of the prepared zinc nitride quantum dot solution was taken as the fluorescence sensing system.

4. The application according to claim 1, characterized in that Add a metal ion solution containing Cu 2+ or Mn 2+ to the fluorescent nanosensor, and record the fluorescence spectrum in the range of 350 - 550 nm with 320 nm excitation light.

5. The application according to claim 1, characterized in that, Add different concentrations of Cu to the fluorescent nanosensor 2 + or Mn 2+ solution. Record the corresponding fluorescence spectra under 320 nm excitation light to establish the relationship between the fluorescence intensity and the concentration of Cu 2+ or Mn 2+ concentration.

6. The application according to any one of claims 1 to 5, characterized in that, The fluorescent nanosensor was made into a paper-based sensor.

7. The application according to claim 6, characterized in that, The paper-based sensor used cellulose paper and was made into a strip shape, circular shape or square shape.

8. The application according to claim 7, characterized in that, Take cellulose paper, soak it in Zn3N2 quantum dot solution, dry it, and use it for the detection of Cu 2+ and / or Mn 2+ .

Images