A carbon quantum dot (CQD) fluorescent probe for traditional Chinese medicine residue, its preparation method and application

Abstract

This invention belongs to the field of nanomaterials technology, specifically relating to a carbon quantum dot (CQD) fluorescent probe made from traditional Chinese medicine residue, its preparation method, and its application. Nitrogen-doped carbon quantum dots (CQDs) are synthesized at high temperatures using Alisma plantago-aquatica residue as a carbon and nitrogen source via a hydrothermal method. The abundant surface active sites and excellent fluorescence properties of the CQD fluorescent probe are then utilized to detect Fe... 3+ This method enables rapid and accurate specific identification of TCH (tetracycline hydrochloride), and also exhibits strong anti-interference capabilities, a low detection limit, and good reproducibility.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and in particular relates to a carbon quantum dot (CQD) fluorescent probe made from traditional Chinese medicine residue, its preparation method, and its application. Background Technology

[0002] With increasing metal and antibiotic pollution in aquatic environments, the detection of these pollutants in water bodies has become a research hotspot. Tetracycline hydrochloride (TCH) is a multifunctional broad-spectrum antibiotic with excellent antibacterial effects, but its overuse has led to its accumulation in the food chain and negative impacts on aquatic environments. It can threaten human health through chronic toxicity, allergic symptoms, and even liver damage, with TCH being the most common culprit. Simultaneously, water pollution by metal ions is also a serious problem. Iron (Fe) is the fourth most abundant element and the second most abundant metal ion in the Earth's crust, widely used in various industrial fields. However, in recent years, people have begun to pay attention to Fe... 3+ The toxicity of this substance is causing increasing concern. Increased utilization of it is considered a potential contributing factor to diseases such as cirrhosis, diabetes, cardiovascular disease, and even cancer.

[0003] Traditional detection techniques, including high-performance liquid chromatography (HPLC), inductively coupled plasma mass spectrometry (ICP-MS), ultraviolet spectrophotometry (UV), atomic absorption spectrometry (AAS), enzyme-linked immunosorbent assay (ELI), and electrochemical methods, are limited in practical applications due to expensive equipment, high costs, complex operation, and poor portability, making them unsuitable for timely and effective detection of water pollution. Fluorescence sensing, a rapidly developing detection technology in recent years, has been extensively studied for its relatively simple operation, technical simplicity, and wide applicability, particularly in the detection of metal ions and antibiotics. Carbon quantum dots (CQDs) possess unique properties such as good biocompatibility, excellent fluorescence characteristics, photoluminescence, high water solubility, and low toxicity, and are widely available, thus rapidly becoming a novel fluorescent nanomaterial widely used in fluorescence sensing. Therefore, the invention of a rapid, accurate, and effective method for detecting Fe... 3+ The fluorescent probe materials of TCH are of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for treating Fe 3+ The paper presents a highly selective carbon quantum dot fluorescent probe (CQD) for traditional Chinese medicine residues, along with its preparation method and application, which effectively solves the problems of low efficiency, time consumption, susceptibility to interference, and poor portability in traditional testing methods.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing carbon quantum dots (CQDs) from traditional Chinese medicine residue includes the following steps: Alisma plantago-aquatica residue is ultrasonically dispersed in ultrapure water as a carbon and nitrogen source. After standing for 12 hours, it is placed in a polytetrafluoroethylene-lined reactor and reacted at 100-200℃ for 12 hours. A brown solution is obtained after cooling to room temperature. The solution is then vacuum filtered, filtered through a 0.22 μm organic filter membrane, and finally freeze-dried to obtain carbon quantum dots (CQDs).

[0007] Furthermore, the ratio of the amount of Alisma plantago-aquatica residue to the amount of ultrapure water is 1g:10mL.

[0008] The fluorescent probe prepared using the above-mentioned method for preparing carbon quantum dots (CQDs) from traditional Chinese medicine residue has spherical particles with a size distribution range of 1-7 nm. It exhibits good dispersibility and a relatively uniform distribution without obvious aggregation. Clearly visible ordered lattice fringes are observed, and it possesses a crystalline core and an amorphous outer shell structure. Furthermore, the CQDs have a quantum yield as high as 62% and abundant active sites on their surface. The presence of carbonyl, carboxyl, and amino groups was confirmed using Fourier transform infrared spectroscopy. The hydrophilic surface functional groups give the carbon quantum dots excellent water solubility and good dispersibility in water.

[0009] This probe is used for trace or micro-scale detection of Fe. 3+ Ions, which in aqueous solution affect Fe 3+ The detection limit is as low as 0.88 μM.

[0010] This probe is used for trace or ultra-trace detection of TCH, with a detection limit as low as 0.83 μM for TCH in aqueous solution.

[0011] Mechanism: This invention synthesizes nitrogen-doped carbon quantum dots (CQDs) using a hydrothermal method with Alisma plantago-aquatica residue as the carbon and nitrogen source. Alisma plantago-aquatica residue is widely available, and its main components include alkaloids, polysaccharides, cellulose, and hemicellulose, providing a good foundation for CQD preparation. Preliminary characterization of the CQDs confirmed the presence of carbonyl, carboxyl, and amino groups. These hydrophilic functional groups provide excellent water solubility and biocompatibility for the CQDs, enabling the CQD nanofluorescent sensing materials to detect Fe in aqueous solutions. 3+ Ions and TCH exhibit rapid and accurate specific recognition capabilities, strong anti-interference ability, and low detection limits. The fluorescent probe CQD material provided by this invention shows that it can detect Fe in aqueous solution. 3+ The detection limit for ions can be as low as 0.88 μM and the detection limit for TCH can be as low as 0.83 μM.

[0012] The advantages of this invention are: the fluorescent probe CQD material of this invention itself has a high quantum yield, and it is effective against Fe... 3+Ions and TCH have highly selective fluorescence detection capabilities, are less affected by other interfering substances, and have high sensitivity. They are also simple to operate and easy to synthesize using both hydrothermal and direct synthesis methods, making them suitable for large-scale industrial production and possessing high research and application value. Attached Figure Description

[0013] Figure 1 These are the fluorescence emission spectra of the fluorescent probes CQD100, CQD120, CQD140, CQD160, CQD180, and CQD200 prepared in Examples 1-6 of this invention.

[0014] Figure 2 This is a transmission electron microscope image of the fluorescent probe CQD200 prepared in Example 1 of this invention.

[0015] Figure 3 This is a particle size distribution diagram of the fluorescent probe CQD200 prepared in Example 1 of this invention.

[0016] Figure 4 This is a high-resolution transmission electron microscope image of the fluorescent probe CQD200 prepared in Example 1 of this invention.

[0017] Figure 5 This is the infrared spectrum (4000 cm⁻¹) of the fluorescent probe CQD200 prepared in Example 1 of this invention. -1 -400cm -1 ).

[0018] Figure 6 This is the full X-ray photoelectron spectrum of the fluorescent probe CQD200 prepared in Example 1 of this invention.

[0019] Figure 7 This is a fine X-ray photoelectron spectrum of the fluorescent probe CQD200 prepared in Example 1 of this invention with respect to N1s.

[0020] Figure 8 This is a fine X-ray photoelectron spectrum of the fluorescent probe CQD200 prepared in Example 1 of this invention with respect to C1s.

[0021] Figure 9 This is a fine X-ray photoelectron spectrum of the fluorescent probe CQD200 prepared in Example 1 of this invention with respect to O1s.

[0022] Figure 10 This is a fluorescence intensity diagram of the fluorescent probe CQD200 prepared in Example 1 of this invention after sensing different metal ions.

[0023] Figure 11 This is a fluorescence intensity diagram of the CQD200 fluorescent probe prepared in Example 1 of this invention after sensing different antibiotics.

[0024] Figure 12 The fluorescent probe CQD200 prepared in Example 1 of this invention is used to sense different concentrations of Fe. 3+ Fluorescence emission spectrum after ionization.

[0025] Figure 13 The fluorescent probe CQD200 prepared in Example 1 of this invention is used in low-concentration fluorescent sensing of Fe. 3+ Linear fitting plot of ions.

[0026] Figure 14 This is the fluorescence emission spectrum of the fluorescent probe CQD200 prepared in Example 1 of this invention after sensing different concentrations of antibiotics.

[0027] Figure 15 This is a linear fitting diagram of the fluorescent probe CQD200 prepared in Example 1 of this invention at a low concentration of fluorescent sensing TCH. Detailed Implementation

[0028] Example 1

[0029] Weigh 5.0 g of Alisma plantago-aquatica residue and disperse it in 50 mL of ultrapure water. Stir for 10 min, sonicate for 5 min, and let stand for 12 h. Transfer the solution to a 100 mL polytetrafluoroethylene reactor and place it in an electrically heated constant-temperature drying oven. Raise the temperature from room temperature to 200 °C in 30 min and maintain it at 200 °C for 12 h. Allow it to cool naturally to room temperature to obtain a brown solution. Vacuum filter the solution, then filter it through a 0.22 μm organic filter membrane. Finally, freeze dry the filtrate to obtain carbon quantum dots, denoted as CQD200.

[0030] Example 2

[0031] Weigh 5.0 g of Alisma plantago-aquatica residue and disperse it in 50 mL of ultrapure water. Stir for 10 min, sonicate for 5 min, and let stand for 12 h. Transfer the solution to a 100 mL polytetrafluoroethylene reactor and place it in an electrically heated constant-temperature drying oven. Raise the temperature from room temperature to 180 °C in 30 min and maintain it at 180 °C for 12 h. Allow it to cool naturally to room temperature to obtain a brown solution. Vacuum filter the solution, then filter it through a 0.22 μm organic filter membrane. Finally, freeze dry the filtrate to obtain carbon quantum dots, denoted as CQD180.

[0032] Example 3

[0033] Weigh 5.0 g of Alisma plantago-aquatica residue and disperse it in 50 mL of ultrapure water. Stir for 10 min, sonicate for 5 min, and let stand for 12 h. Transfer the solution to a 100 mL polytetrafluoroethylene reactor and place it in an electrically heated constant-temperature drying oven. Raise the temperature from room temperature to 160 °C in 30 min and maintain it at 160 °C for 12 h. Allow it to cool naturally to room temperature to obtain a brown solution. Vacuum filter the solution, then filter it through a 0.22 μm organic filter membrane. Finally, freeze dry the filtrate to obtain carbon quantum dots, denoted as CQD160.

[0034] Example 4

[0035] Weigh 5.0 g of Alisma plantago-aquatica residue and disperse it in 50 mL of ultrapure water. Stir for 10 min, sonicate for 5 min, and let stand for 12 h. Transfer the solution to a 100 mL polytetrafluoroethylene reactor and place it in an electrically heated constant-temperature drying oven. Raise the temperature from room temperature to 140 °C in 30 min and maintain it at 140 °C for 12 h. Allow it to cool naturally to room temperature to obtain a brown solution. Vacuum filter the solution, then filter it through a 0.22 μm organic filter membrane. Finally, freeze dry the filtrate to obtain carbon quantum dots, denoted as CQD140.

[0036] Example 5

[0037] Weigh 5.0 g of Alisma plantago-aquatica residue and disperse it in 50 mL of ultrapure water. Stir for 10 min, sonicate for 5 min, and let stand for 12 h. Transfer the solution to a 100 mL polytetrafluoroethylene reactor and place it in an electrically heated constant-temperature drying oven. Raise the temperature from room temperature to 120 °C in 30 min and maintain it at 120 °C for 12 h. Allow it to cool naturally to room temperature to obtain a brown solution. Vacuum filter the solution, then filter it through a 0.22 μm organic filter membrane. Finally, freeze dry the filtrate to obtain carbon quantum dots, denoted as CQD120.

[0038] Example 6

[0039] Weigh 5.0 g of Alisma plantago-aquatica residue and disperse it in 50 mL of ultrapure water. Stir for 10 min, sonicate for 5 min, and let stand for 12 h. Transfer the solution to a 100 mL polytetrafluoroethylene reactor and place it in an electrically heated constant-temperature drying oven. Raise the temperature from room temperature to 100 °C over 30 min and maintain it at 100 °C for 12 h. Allow it to cool naturally to room temperature to obtain a brown solution. Vacuum filter the solution, then filter it through a 0.22 μm organic filter membrane. Finally, freeze dry the filtrate to obtain carbon quantum dots, denoted as CQD100.

[0040] Performance testing:

[0041] (I) Fluorescence properties and quantum yield analysis

[0042] Fluorescence experiments were conducted on carbon quantum dots CQD100, CQD120, CQD140, CQD160, CQD180, and CQD200 synthesized at different temperatures at room temperature. Figure 1 It can be seen that, under the experimental conditions, the reaction temperature has a significant impact on the fluorescence intensity of the synthesized carbon quantum dots, and the fluorescence intensity of the synthesized carbon quantum dots gradually increases with increasing reaction temperature. When the reaction temperature is 200℃, strong emission (λ) is generated at 430 nm. Ex =361nm), at which point the fluorescence intensity is the highest, therefore CQD200 was chosen as the optimal carbon quantum dot.

[0043] (II) Morphological Analysis

[0044] like Figure 2 and 3 As shown, TEM characterization of the CQD microstructure reveals that the prepared CQD particles are spherical with a size distribution ranging from 1 to 7 nm, exhibiting good dispersibility and relatively uniform distribution without obvious aggregation. Ordered lattice fringes are clearly visible in the high-resolution TEM images. Figure 4 This indicates that CQDs possess a crystalline core and an amorphous outer shell structure. Therefore, CQDs are amorphous carbon lattices, consisting of small, uniformly sized particles with spherical morphology. The aforementioned microstructure conforms to the definition of CQDs, proving that CQDs have been successfully prepared.

[0045] (III) Infrared Spectroscopy Analysis

[0046] To determine the binding mode of each element in the carbon quantum dot, we performed FT-IR tests on the synthesized carbon quantum dot CQD200. Figure 5 As can be seen from the figure, at 3440cm -1 The absorption peak is due to the stretching vibration of NH and OH, at 1630 cm⁻¹. -1 The absorption peak at 1400 cm⁻¹ is due to the stretching vibrations of C=O and C=C. -1 The absorption peak at 1100 cm⁻¹ is due to the stretching vibration of CN. -1 The absorption peak at 1030 cm⁻¹ corresponds to the CO bending vibration and the COC stretching vibration. -1 The absorption peak at the point is due to the CO stretching vibration. Fourier transform infrared spectroscopy confirmed that the prepared carbon quantum dots have abundant hydrophilic groups. The hydrophilic surface functional groups give the carbon quantum dots excellent water solubility and good dispersibility in water.

[0047] (iv) XPS Analysis

[0048] To further analyze the structure of CQD200, the elemental types and chemical environment of CQD200 were characterized by XPS. Figure 6 The full spectrum of CQD200 shows that it contains C, N, and O elements, with characteristic peaks at 284.8, 400.2, and 531.9 eV, respectively. It is mainly composed of carbon, nitrogen, and oxygen. Calculations of the integral area of ​​the elements reveal that the relative atomic contents of carbon, nitrogen, and oxygen are 68.5%, 10.5%, and 19.6%, respectively. Analysis of the fine spectrum of CQD200 shows that the N 1s fine spectrum can be divided into two peaks, located at 399.3 and 401.5 eV, corresponding to CN and NH (…). Figure 7 The C1s spectrum of CQD200 can be fitted to three characteristic peaks located at 284.5, 285.8, and 287.5 eV, corresponding to CC / C=C, CO / CN, and C=O, respectively. Figure 8 The O 1s fine spectrum can be fitted to two characteristic peaks, belonging to CO and C=O, respectively, with these two functional groups located at 530.6 eV and 531.5 eV. Figure 9 The above results, combined with FTIR spectroscopy, further demonstrate that the carbon quantum dots were successfully prepared by functional group modification and confirm that the prepared carbon quantum dots have abundant hydrophilic groups, providing a solid chemical basis for their sensing applications in aqueous systems.

[0049] (V) Fluorescence Selectivity Analysis

[0050] Based on the good fluorescence properties of CQD200, this study investigated the effect of the fluorescent probe CQD200 on different metal ions, specifically As. 3+ Al 3+ As 5 + Zn 2+ Cd 2+ Zr 4+ Ag + Cu 2+ Cr 3+ Hg 2+ Fe 3+ fluorescence sensing performance such as Figure 10 As shown. The fluorescence sensing performance of the fluorescent probe CQD200 for different antibiotics, including sulfadiazine (SD), norfloxacin (NOR), penicillin (PG), erythromycin (EM), oxytetracycline (OTC), and tetracycline hydrochloride (TCH), was also investigated. Figure 10 As shown. By Figure 10 and 11 It can be seen that CQD200 affects Fe 3+TCH exhibits superior selectivity compared to other metal ions and antibiotics. The quenching efficiency (Q) can be calculated using the formula Q = (1 - I / I0) × 100%, where I0 is the fluorescence intensity before the addition of the analyte, and I is the fluorescence intensity after the addition of the analyte. When different types of metal ions and antibiotics of the same concentration are added dropwise to CQD200 solutions of the same concentration, Fe... 3+ TCH and Fe showed the highest quenching efficiencies of 94.9% and 99.9%, respectively, indicating that CQD200 effectively quenches Fe. 3+ TCH has extremely high specificity recognition ability and can be used in Fe 3+ And TCH in fluorescence sensing applications.

[0051] (vi) Fluorescence sensitivity analysis

[0052] like Figure 12-15 As shown, with Fe 3+ With increasing ion and TCH concentrations, the relative fluorescence intensity I0 / I of the CQD200 material gradually increases. Within the low concentration range, the linear correlation between the two can be expressed by the equation I0 / I = K. SV • [C]+1 analysis, where I0 is the fluorescence intensity of the solution at 430 nm before the addition of the analyte, I is the fluorescence intensity of the solution at 430 nm after the addition of the analyte, and [C] represents the concentration of the analyte in μM, K. SV The quenching coefficient is the slope of the linear curve fitting at low concentrations. Analysis shows that, within the low concentration range, the fluorescence quenching response of CQD200 exhibits a good linear relationship with the analyte concentration (Fe). 3+ R 2 =0.9902; TCH, R 2 =0.9959), following the Stern-Volmer equation, calculate Fe. 3+ and TCH's K SV They are 1.89×10 4 M -1 2.02×10 4 M -1 The detection limit (LOD) was calculated using the 3δ method reported in the literature: LOD(Fe 3+ )=3δ / K SV =0.88μM, LOD(TCH) =3δ / K SV =0.83 μM, where δ represents the standard deviation of the fluorescence intensity measured in the CQD200 aqueous solution, indicating that Fe 3+ Ions and TCH exhibit a strong fluorescence quenching effect on CQD200 materials, with very high sensitivity, comparable to Fe. 3+ The detection of ions and TCH provides practical conditions, making the CQD200 a suitable instrument for detecting Fe in various applications.3+ Ideal candidate material for ions and TCH.

[0053] (VII) Practical Application Analysis

[0054] Table 1. Fe in water samples 3+ Quantitative

[0055]

[0056] Table 2. Quantitative analysis of tetracycline hydrochloride in water samples.

[0057]

[0058] To test the application potential of the fluorescent probe CQD200 and evaluate its detection characteristics in real water samples, this method was successfully used in the laboratory to detect Fe in local Longzihu Lake water (Zhengzhou, China) and tap water. 3+ And TCH content. As shown in Table 1, the Fe content in the actual sample... 3+ The recovery rate was 98.80%-102.00%, Fe 3+ The relative standard deviations (RSDs) of the determinations ranged from 0.07% to 0.23%. Table 2 shows that the recoveries of tetracycline hydrochloride in actual samples were 93.00%–114.00%, and the relative standard deviations (RSDs) of tetracycline hydrochloride determinations ranged from 0.01% to 0.46%. These results indicate that the prepared CQD200 can be effectively used for Fe in actual water samples. 3+ And TCH detection, and as a measure of Fe 3+ TCH is a fluorescent probe with high sensitivity and high selectivity.

Claims

1. Application of a fluorescent probe prepared by using traditional Chinese medicine residue carbon quantum dots (CQD), characterized in that: For trace detection of Fe 3+ Ion and TCH, which in aqueous solution to Fe 3+ The detection limit is as low as 0.88 muM; the detection limit of TCH in aqueous solution is as low as 0.83 muM; the carbon quantum dot CQD particles are spherical, the size distribution range is 1-7 nm, have a crystalline core and amorphous shell structure, the carbon quantum dot CQD quantum yield is not less than 62%, and the surface has active sites carbonyl, carboxyl and amino; the preparation method of the traditional Chinese medicine residue carbon quantum dot CQD comprises the following steps: the alisma orientalis residue is used as carbon and nitrogen source and is ultrasonically dispersed in ultrapure water, is placed in a polytetrafluoroethylene lined reaction kettle after being placed for 12 hours, is reacted at 100-200 DEG C for 12 hours, a brown solution is obtained after being cooled to room temperature, is vacuum filtered, is filtered through a 0.22 mu m organic filter membrane, and is finally freeze-dried to obtain the carbon quantum dot CQD.

2. Use according to claim 1, characterized in that: The ratio of the amount of the alisma orientalis residue to the amount of ultrapure water is 1 g:10 mL.

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