A green fluorescent carbon quantum dot-based material, preparation method and application thereof

Abstract

The application discloses a kind of based on green fluorescent carbon quantum dots and preparation method and application, the present application with o-phenylenediamine and 3-amino-1,2,4-triazole as precursor, by hydrothermal synthesis method obtains a green fluorescent carbon quantum dots, the carbon quantum dots synthesized not only have strong fluorescence intensity and show excellent fluorescence stability, and carbon quantum dots to Fe 3+ Have good fluorescent response, to Fe 3+ High selectivity and high sensitivity.The carbon quantum dots prepared in the application have high selectivity and high sensitivity. 3+ Concentration is 0.01-100 µmol / L, the detection lower limit is 6.7nmol / L, and the recovery rate is between 98.64%~102.01%, which solves the problem of high detection limit and low sensitivity of existing carbon quantum dots in the process of Fe 3+ Concentration detection.

Description

Technical Field

[0001] This invention relates to the field of carbon quantum dot preparation technology, and more specifically, to a method for preparing green fluorescent carbon quantum dots and their applications. Background Technology

[0002] Carbon quantum dots (CDs) are common fluorescent nanomaterials, consisting of spherical nanoparticles with a diameter of less than 10 nm, formed by carbon as a framework. Due to their unique photoluminescence properties, high stability, excellent hydrophilicity, biocompatibility, and low toxicity, CDs are used in photoelectrocatalysis, bioimaging, and drug delivery, and show great promise for applications in ion and drug detection.

[20] This includes research on its application in metal ion detection. The electrostatic adsorption and coordination of metal ions with CDs in solution both affect the fluorescence properties of CDs, which provides a promising application prospect for using CDs as fluorescent probes to detect metal ions.

[0003] Iron ions (Fe) 3+ Fe is a common metal ion found in water bodies in nature and is widely present in people's daily drinking water. Meanwhile, Fe... 3+ Fe is one of the essential elements for the survival of most plants and animals, and also one of the essential trace elements for the human body. Therefore, Fe 3+ Concentration detection is an important indicator for soil, water, and food. How to quickly and accurately detect Fe? 3+ These are important indicators for CDs fluorescent probes. CN120870079A, a method for rapid detection of ferric ions in water, discloses the use of copper nitrate trihydrate (Cu(NO3)2·3H2O) and tryptophan (C... 10 H 12 Carbon quantum dots (CuCDs) were prepared using N2 as a raw material, resulting in copper-doped carbon quantum dots. When Fe was added to CuCDs... 3+ Subsequently, its blue fluorescence was quenched. With Fe... 3+ As the concentration increases, the fluorescence color gradually fades from an initial blue to nearly colorless. Utilizing this property, this patented technology enables the fluorescence detection of Fe in aqueous media. 3+ Rapid on-site detection is possible. However, CuCDs have relatively high detection limits, such as in the range of 200 μM to 500 μM, as Fe... 3+ As the concentration decreases, the error gradually increases; therefore, the sensitivity of CuCDs prepared by this method is not high at extremely low concentrations. Summary of the Invention

[0004] The main technical problem to be solved by this invention is the application of existing technologies to prepare carbon quantum dots in Fe... 3+The concentration detection process has shortcomings such as high detection limit and need to improve sensitivity. Therefore, a method based on green fluorescent carbon quantum dots is proposed.

[0005] Another technical problem solved by the present invention is to provide a method for preparing the carbon quantum dot.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing green fluorescent carbon quantum dots, comprising the following steps: o-phenylenediamine and 3-amino-1,2,4-triazole were dissolved in water at a mass ratio of 2:1~10, and then reacted at 100~180℃ for 1~6h to obtain a suspension. After filtration and elution, green fluorescent carbon quantum dots were obtained.

[0008] Furthermore, the mass ratio of o-phenylenediamine to 3-amino-1,2,4-triazole is 1:2.

[0009] Furthermore, the reaction temperature is 140°C and the reaction time is 4 hours.

[0010] Furthermore, after the reaction is complete, silica gel powder is added to the suspension, and the water in the suspension is dried by rotary evaporator to prepare carbon quantum dots into powder. The powdered sample is then loaded into a silica gel column for elution to obtain green fluorescent carbon quantum dots.

[0011] A carbon quantum dot based on green fluorescent carbon, prepared according to the above method, is used for Fe... 3+ The detection.

[0012] Furthermore, the green fluorescent carbon quantum dot-based method for detecting Fe... 3+ The method, including the following steps: S1. Prepare Fe at different concentrations 3+ The solution consisted of 100 μL of a green fluorescent carbon quantum dot-based solution and 900 μL of Fe. 3 + Mix the solutions and react them in a water bath at 10~45℃ for 5~40 min; S2. Excite the light source with a wavelength of 414 nm, and record its fluorescence spectrum and fluorescence intensity using a fluorescence spectrophotometer. Plot a fitting line on the spectrum as a reference standard. S3. Mix the green fluorescent carbon quantum dot solution with the Fe2+ target. 3+ The solutions were mixed, and their fluorescence intensity was measured. The results were compared with a reference standard to obtain Fe. 3+ concentration.

[0013] Furthermore, Fe 3+ The solution concentration range is 0.01~100μmol / L.

[0014] Furthermore, the water bath reaction temperature was 25℃, and the reaction time was 20 min.

[0015] Furthermore, based on green fluorescent carbon quantum dot solution and Fe 3+ The solution mixture also includes adjusting the pH to neutral.

[0016] Compared with existing technologies, the beneficial effects are: This invention uses o-phenylenediamine and 3-amino-1,2,4-triazole as precursors to prepare a carbon quantum dot exhibiting bright green fluorescence under ultraviolet light via a high-temperature hydrothermal synthesis method. The synthesized carbon quantum dots have a stable structure, uniform particle size, and good water solubility. In addition, the carbon quantum dots prepared by this invention have optical properties, with an optimal excitation wavelength of 414 nm and an optimal emission wavelength of 556 nm. They not only have strong fluorescence intensity but also exhibit excellent fluorescence stability and superior fluorescence performance.

[0017] The carbon quantum dots prepared in this invention are paired with Fe 3+ It exhibits good fluorescence response, Fe 3+ It can significantly reduce the fluorescence intensity of GCDs, exhibiting high selectivity and high sensitivity, in Fe... 3+ The solution concentration was measured between 0.01 and 100 µmol / L. The detection limit of this invention was 6.7 nmol / L, and the recovery rate was between 98.64% and 102.01%. Attached Figure Description

[0018] Figure 1 This is a TEM image of GCDs; Figure 2 These are Fourier transform infrared (FT-IR) spectra; A is the FT-IR plot of GCDs, and B is the UV-Vis plot of GCDs. Figure 3 A is the wavelength with the highest fluorescence intensity; A is the optimal excitation and emission spectrum of GCDs; B is the fluorescence spectrum of GCDs at different excitation wavelengths. Figure 4 This is a line graph showing the fluorescence intensity of GCDs at different reaction temperatures; Figure 5 This is a line graph showing the fluorescence intensity of GCDs with different raw material ratios; Figure 6 This is a line graph showing the fluorescence intensity of GCDs at different reaction times; Figure 7 It represents the fluorescence quenching rate of GCDs at different salt concentrations; Figure 8 The fluorescence quenching rate of GCDs at different pH values; Figure 9It is the fluorescence quenching rate of GCDs after being left to stand for different times; Figure 10 The fluorescence intensity of different metal ions using GCDs normalization method; Figure 11 This is a graph showing the fluorescence quenching rate at different water bath times; Figure 12 The fluorescence quenching rate at different water bath temperatures; Figure 13 It represents the fluorescence quenching rate at different solution pH values; Figure 14 GCDs are in different Fe 3+ Relationship between fluorescence intensity at different concentrations.

[0019] Figure 15 It is the fluorescence anti-interference property of GCDs.

[0020] Detailed implementation method.

[0021] The following examples further explain and illustrate the invention, but the specific examples do not limit the invention in any way.

[0022] Example 1 This embodiment provides a method for preparing green fluorescent carbon quantum dots, the preparation steps of which include: First, accurately weigh 0.0108 g of o-phenylenediamine and 0.0150 g of 3-amino-1,2,4-triazole and dissolve them in 10 mL of water. After stirring thoroughly, pour the solution into a reaction vessel and place the reaction vessel in a 140 ℃ constant temperature oven for heating and reaction for 4 h.

[0023] After the reaction was complete, the mixture was cooled to room temperature to obtain a yellow-brown suspension. 5 g of silica gel powder was added to the suspension, and the moisture was dried using a rotary evaporator to prepare the carbon quantum dots into a powder state.

[0024] Next, equip the chromatography column with silica gel powder and compact it. Pour the powdered sample into the prepared silica gel column and elute with eluent (methanol and ethyl acetate in a volume ratio of 3:1). Start collecting when the eluent shows green fluorescence under UV light and stop collecting when the eluent no longer shows obvious green fluorescence under UV light. The collected liquid is the green fluorescent carbon quantum dot (GCD) solution.

[0025] (1) The morphology of GCDs was observed using a transmission electron microscope (TEM). For example... Figure 1 As shown in the TEM image, the synthesized GCDs on the surface are spherical and have good monodispersity in aqueous solution. This may be because the surface of GCDs is rich in carboxyl and hydroxyl groups, which makes them well dispersible in aqueous solution.

[0026] (2) The characterization spectrum is obtained by Fourier transform infrared spectroscopy (FT-IR) detection, as shown in the figure. Figure 2 As shown in A, at 3440 cm -1 The peak at 1640 cm⁻¹ may be the stretching vibration peak of O-H and N-H. -1 The absorption peak at 1380 cm⁻¹ is caused by the C=O stretching vibration. -1 There may be -CH3 at 1060cm. -1 The location is likely due to the C-O stretching vibration. FT-IR analysis showed that the synthesized GCDs contained carboxyl and amino groups on their surface, indicating that N was well doped into the GCDs. Relevant information was obtained using UV-Vis, such as... Figure 2 As shown in Figure B, the absorption peak in the ultraviolet region is attributed to the π-phase of the conjugated C=C structure. The π* transition, and the broader absorption peak in the visible region are related to the more complex surface states of the carbon quantum dots themselves.

[0027] (3) The optimal excitation and emission wavelengths of GCDs were investigated. By repeatedly measuring their excitation and emission wavelengths, the wavelengths with the highest fluorescence intensity were screened. For example... Figure 3 As shown, the optimal excitation wavelength for GCDs is 414 nm, and the optimal emission wavelength is 556 nm. Fluorescence emission spectra of GCDs were obtained by exciting them with light sources of different wavelengths. As the excitation wavelength increases, the emission wavelength of the GCDs' fluorescence emission spectra remains unchanged, indicating that the fluorescence emission of GCDs is excitation-independent.

[0028] Example 2 This embodiment provides a method for preparing green fluorescent carbon quantum dots. Specifically, this embodiment optimizes the raw material ratio and hydrothermal reaction temperature and time in Example 1. (1) Carbon quantum dots were prepared by using 0.0108 g o-phenylenediamine and 0.0150 g 3-amino-1,2,4-triazole as precursors and setting hydrothermal temperatures of 100 ℃, 120 ℃, 140 ℃, 160 ℃ and 180 ℃ respectively. Depend on Figure 4 It can be seen that the fluorescence intensity of GCDs increases with increasing reaction temperature, and the fluorescence intensity is relatively high at 140 °C. However, the fluorescence intensity decreases with further increases in temperature. Therefore, the optimal temperature for preparing GCDs is determined to be 140 °C.

[0029] (2) Using 0.02 g of o-phenylenediamine as a precursor, a certain amount of 3-amino-1,2,4-triazole was added. The mass of 3-amino-1,2,4-triazole was 0.01 g, 0.02 g, 0.03 g, 0.04 g and 0.05 g respectively. The reaction was carried out at the optimal synthesis temperature of 140 °C for 4 h to prepare carbon quantum dots. Depend on Figure 5 It was found that as the amount of 3-amino-1,2,4-triazole added gradually increased, the fluorescence intensity of GCDs showed a significant increasing trend. When the mass ratio of o-phenylenediamine to 3-amino-1,2,4-triazole was adjusted to 1:2, the fluorescence intensity of GCDs reached its peak. However, further increasing the amount of 3-amino-1,2,4-triazole resulted in a decreasing fluorescence intensity. Therefore, the optimal feed ratio of o-phenylenediamine to 3-amino-1,2,4-triazole was determined to be 1:2.

[0030] (3) Carbon quantum dots were prepared by using the optimal ratio of o-phenylenediamine and 3-amino-1,2,4-triazole as precursors and setting hydrothermal time to 1 h, 2 h, 3 h, 4 h, 5 h and 6 h at the optimal synthesis temperature.

[0031] Depend on Figure 6 It can be seen that the fluorescence intensity of GCDs shows a significant increasing trend with the increase of hydrothermal time. When the hydrothermal time is 4 h, the fluorescence intensity of GCDs reaches its peak. Further increasing the hydrothermal time, the fluorescence intensity shows a decreasing trend. Therefore, the optimal reaction time is set to 4 h.

[0032] Example 3 This embodiment tests the salt resistance, acid and alkali resistance, and stability of carbon quantum dots, specifically as follows: (1) Prepare NaCl solutions of 0.5, 1, 1.5, 2 and 2.5 mol / L respectively. Then, mix 100 μL of GCDs solution with 900 μL of solutions of different NaCl concentrations. Finally, excite the GCDs mixed solutions containing different NaCl concentrations with light of wavelength 414 nm and record their fluorescence spectra and fluorescence intensities using a fluorescence spectrophotometer.

[0033] like Figure 7 As shown, when the salt concentration is in the range of 0-2.5 mol / L, the fluorescence intensity of GCDs decreases continuously but the change is small, indicating that GCDs have good salt resistance.

[0034] (2) Solutions with pH values ​​of 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, and 14.0 were prepared using NaOH and HCl solutions, respectively. Then, 100 μL of GCDs solution and 900 μL of solutions with different pH values ​​were mixed. Finally, the GCDs solutions with different pH values ​​were excited with a light source with a wavelength of 414 nm, and their fluorescence spectra and fluorescence intensities were recorded using a fluorescence spectrophotometer.

[0035] like Figure 8 As shown, the fluorescence intensity of GCDs changes little with pH in the solution range of 4.0–13.0, indicating that GCDs have good adaptability to different acid and alkaline environments and are suitable for Fe in different acid and alkaline ranges. 3+ Testing.

[0036] (3) Take 100 μL of the GCDs solution synthesized under optimal conditions and mix it precisely with 900 μL of ultrapure water. Next, inject the prepared solution into a 5 mL sealed centrifuge tube, ensuring the tube is completely sealed. Then, repeat this operation five times, marking specific time points for each sample group, namely day 0, day 3, day 5, day 7, and day 9, for standing treatment. Finally, excite the GCDs solutions placed for different times with a light source of 414 nm, and record their fluorescence spectra and fluorescence intensities using a fluorescence spectrophotometer.

[0037] like Figure 9 As shown in the figure, the experiment revealed that the fluorescence intensity of GCDs changed gradually within 0-9 days, indicating that GCDs have good fluorescence stability.

[0038] Example 4 This embodiment measures the fluorescence intensity of GCDs after interaction with different metal ions to determine the effect of other cations on Fe. 3+ The selective effect.

[0039] Add 10 μmol / L of metal ions (Ca) to 100 μL of GCDs solution. 2+ Fe 2+ Fe 3+ Cu 2+ Mg 2+ Co 2+ Cd 2+ Bi 3+ Hg 2+ Mn 2+ 、Sr 2+ Cr 3+ Sn 2+ Zn 2+ Al 3+K + ), and test its emission spectrum. For example Figure 10 As shown, only Fe 3+ This can cause a significant decrease in the fluorescence of the probe solution, indicating that GCDs affect Fe. 3+ It exhibits high selectivity. Furthermore, it was observed that only the probe reacted with Fe. 3 + After the reaction, the solution color changed significantly from pale yellow to yellow. These results indicate that GCDs have a significant effect on Fe... 3+ It has high selectivity and can be used for the detection of Fe. 3+ .

[0040] Example 5 This embodiment provides a method for detecting Fe based on green fluorescent carbon quantum dots. 3+ The method, including the following steps: (1) Prepare 100 μL of GCDs solution and 900 μL of Fe with 10 μmol / L using the optimal process. 3+ The solutions were thoroughly mixed. Then, they were placed in a constant-temperature water bath at 25 °C and allowed to stand for 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, and 40 min, respectively. Finally, the GCDs solutions with different water bath times were excited with a light source at a wavelength of 414 nm, and their fluorescence spectra and fluorescence intensities were recorded using a fluorescence spectrophotometer.

[0041] (2) Take 100 μL of GCDs solution and 900 μL of 10 μmol / L Fe 3+ The solutions were placed in water baths at temperatures of 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, and 45 ℃ for optimal durations. Finally, the GCDs solutions at different incubation temperatures were excited with a light source of 414 nm, and their fluorescence spectra and fluorescence intensities were recorded using a fluorescence spectrophotometer.

[0042] (3) Prepare solutions with pH values ​​of 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, and 14.0 using NaOH and HCl solutions. Add 10 μmol / L Fe to each solution. 3+ Solution. Take 100 μL of LGCDs solution and Fe at different pH values. 3+ 900 μL of the solution was incubated in a water bath at the optimal incubation time and temperature. Finally, GCDs solutions with different pH values ​​were excited with a light source at a wavelength of 414 nm, and their fluorescence spectra and fluorescence intensities were recorded using a fluorescence spectrophotometer.

[0043] like Figures 11-13 As shown, investigations revealed that when the incubation time was 20 min and the incubation temperature was 25 ℃, Fe... 3+ fluorescence quenching rate ( F 0- F ) / F Reaching 0 at its maximum ensures both detection efficiency and accuracy. F 0 represents the fluorescence intensity of GCDs without changing external conditions. F This indicates the fluorescence intensity of GCDs after changing external conditions. Because pH value has a certain influence on the fluorescence intensity of GCDs, detection was performed at different pH values. For example, at pH=7.0, Fe... 3+ fluorescence quenching rate ( F 0- F ) / F The optimal pH value is 7.0, which maximizes the detection efficiency and achieves the best results. Therefore, the optimal pH value is chosen to ensure that Fe... 3+ The detection effect and accuracy.

[0044] Take 100 μL of GCDs solution and 900 μL of Fe at different concentrations 3+ Solution mixing, Fe 3+ The solution concentrations were 0.01, 1, 3, 5, 8, 10, 30, 80, and 100 μmol / L. Finally, under optimal conditions, the fluorescence intensity was measured. A fitted curve was then plotted.

[0045] like Figure 14 As shown, Fe 3+ The equation relating concentration to fluorescence intensity of GCDs is as follows: y = -1.1677x + 255.05878 y represents the fluorescence intensity of GCDs, and x represents Fe. 3+ The concentration, linear correlation coefficient R 2 =0.99, σ=0.12 (standard deviation calculated from 3 blank solution determinations), detection range is 1~100 μmol / L, detection limit is 0.67 μmol / L.

[0046] Example 6 This embodiment measures the fluorescence intensity of GCDs after interaction with different metal ions to determine the effect of other cations on Fe. 3+ The selective effect. Adding 5 μmol / L Fe to 100 μL of GCDs solution. 3+ and with added Fe concentration 3+ Metal ions (Fe) at a concentration 20 times higher 2+ Cu 2+ Mg2+ Co 2+ Bi 3+ Mn 2+ Sn 2+ Pb 2+ Al 3+ K + The fluorescence quenching efficiency of ) was compared.

[0047] like Figure 15 As shown, only Fe 3+ This can cause a significant decrease in the fluorescence of the probe solution, indicating that other metal ions affect the probe and Fe. 3+ The fluorescence response generated by the binding showed no significant interference, indicating that GCDs have a positive effect on Fe. 3+ It exhibits high selectivity. Furthermore, it was observed that only the probe reacted with Fe. 3+ After the reaction, the solution color changed significantly from pale yellow to yellow. These results indicate that GCDs have a significant effect on Fe... 3+ It has high selectivity and can be used for the detection of Fe. 3+ .

[0048] Example 7 This embodiment uses a spiking method to determine the iron ion content, verifying the application value of GCDs as fluorescent probes in iron ion determination. Fe content was measured using water from a lake on campus. 3+ The content of Fe in the sample was analyzed using an optimized detection method, and the recovery rate of iron ions was determined. 3+ The measurement results are shown in Table 1 below: Table 1

[0049] As shown in Table 1 above, the detected Fe 3+ The concentration was 4.20 μmol / L, and the concentration of iron ions in surface water was below 5.37 μmol / L, which meets the standard. Experimental results show that the recovery rate of spiked samples ranged from 98.64% to 102.01%, with a small relative standard deviation. This method is accurate and precise, and can be used for the analysis of Fe in actual water bodies. 3+ The detection.

[0050] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing green fluorescent carbon quantum dots, characterized in that, The preparation steps include: o-phenylenediamine and 3-amino-1,2,4-triazole were dissolved in water at a mass ratio of 2:1~10, and then reacted at 100~180℃ for 1~6h to obtain a suspension. After filtration and elution, green fluorescent carbon quantum dots were obtained.

2. The preparation method based on green fluorescent carbon quantum dots according to claim 1, characterized in that, The mass ratio of o-phenylenediamine to 3-amino-1,2,4-triazole is 1:

2.

3. The preparation method based on green fluorescent carbon quantum dots according to claim 1, characterized in that, The reaction temperature was 140℃ and the reaction time was 4 hours.

4. The preparation method based on green fluorescent carbon quantum dots according to claim 1, characterized in that, After the reaction was completed, silica gel powder was added to the suspension, and the water was dried by rotary evaporator to prepare carbon quantum dots into powder. The powdered sample was then loaded into a silica gel column for elution to obtain green fluorescent carbon quantum dots.

5. A method based on green fluorescent carbon quantum dots, characterized in that, Prepared according to any one of claims 1 to 4.

6. The green fluorescent carbon quantum dot-based quantum dot according to claim 5, characterized in that, The carbon quantum dots are used for Fe 3+ The detection.

7. The method for detecting Fe based on green fluorescent carbon quantum dots according to claim 6 3+ The method, characterized in that, the steps include: S1. Prepare Fe at different concentrations 3+ The solution consisted of 100 μL of a green fluorescent carbon quantum dot-based solution and 900 μL of Fe. 3+ Mix the solutions and react them in a water bath at 10~45℃ for 5~40 min; S2. Excite the light source with a wavelength of 414 nm, and record its fluorescence spectrum and fluorescence intensity using a fluorescence spectrophotometer. Plot a fitting line on the spectrum as a reference standard. S3. Mix the green fluorescent carbon quantum dot solution with the Fe2+ target. 3+ The solutions were mixed, and their fluorescence intensity was measured. The results were compared with a reference standard to obtain Fe. 3+ concentration.

8. The method for detecting Fe based on green fluorescent carbon quantum dots according to claim 7 3+ The method is characterized by, Fe 3+ The solution concentration range is 0.01~100μmol / L.

9. The method for detecting Fe based on green fluorescent carbon quantum dots according to claim 7 3+ The method is characterized by, The water bath reaction temperature was 25℃, and the reaction time was 20 min.

10. The method for detecting Fe based on green fluorescent carbon quantum dots according to claim 7 3+ The method is characterized by, Based on green fluorescent carbon quantum dot solution and Fe 3+ The solution mixture also includes adjusting the pH to neutral.

Images