Nitrogen-doped carbon quantum dots derived from periplaneta americana dregs as well as preparation method and application of nitrogen-doped carbon quantum dots

Abstract

The invention discloses nitrogen-doped carbon quantum dots derived from American cockroach dregs as well as a preparation method and application of the nitrogen-doped carbon quantum dots, and belongs to the technical field of nitrogen-doped carbon quantum dots. The nitrogen-doped carbon quantum dots are prepared from the American cockroach dregs by a one-step hydrothermal method, optimal synthesis parameters are obtained through experimental optimization of synthesis conditions, and the prepared nitrogen-doped carbon quantum dots have excellent optical characteristics and stability; the invention also provides an application of the nitrogen-doped carbon quantum dot in Ag < + > detection, the nitrogen-doped carbon quantum dot has good selectivity, sensitivity and anti-interference performance on Ag < + >, a detection mechanism is an internal filtering effect and light-induced electron transfer, and the nitrogen-doped carbon quantum dot can be used as a preferred fluorescent material of an Ag < + > fluorescent sensor. The nitrogen-doped carbon quantum dots synthesized by the method not only have an Ag < + > sensing function, but also realize high-valued utilization of medicine residues, and also provide a new thought for self-doping of heteroatoms.

Description

Technical Field

[0001] This invention belongs to the field of carbon doping technology, specifically relating to nitrogen-doped carbon quantum dots derived from American cockroach residue, their preparation method, and applications. Background Technology

[0002] The American cockroach (Periplaneta americana) is a traditional Chinese medicine with medicinal value in wound healing, anti-tumor, anti-fibrotic, and anti-inflammatory applications. Currently, extracts from American cockroaches have been developed into various new drugs and are widely used clinically. However, the residue produced after extracting the active ingredients is mostly discarded as waste. The residual components in this residue still have potential for resource utilization, and can be processed into chitin, chitosan feed additives, and fertilizers. However, existing conversion technologies suffer from drawbacks such as low energy efficiency, high cost, and difficulty in storage. A one-step hydrothermal method converts traditional Chinese medicine waste into carbon materials, avoiding these problems.

[0003] Carbon quantum dots possess excellent photostability, low cytotoxicity, chemical inertness, ease of surface modification, and superior biocompatibility, leading to their widespread application in fields such as bioimaging, cancer therapy, drug delivery, and photocatalytic degradation. In recent years, the synthesis of carbon dots has also attracted considerable attention. Traditional synthesis methods typically require chemical reagents such as citric acid, p-phenylenediamine, urea, and glucose. While traditional methods are highly effective, allowing for the adjustment of the optical and physical properties of carbon dots based on reagents, achieving homogeneous production, and maintaining high yields and purity, they also face challenges such as high raw material costs, poor sustainability, and the potential generation of toxic byproducts during synthesis. Currently, the synthesis of carbon dots using waste biomass is increasingly common. Compared to carbon dots synthesized from pure chemicals, the use of waste biomass successfully combines environmental friendliness, sustainability, low toxicity, and high performance. Therefore, the use of green sources for carbon dot synthesis is a growing trend. Furthermore, existing technologies document that nitrogen atoms have similar radii to carbon atoms, and nitrogen atoms can partially replace and embed themselves in the carbon framework, thereby affecting its internal electronic environment, altering the electronic state of carbon dots, regulating band structure, increasing the possibility of radiative transitions, and improving the quantum yield of carbon dots. Using medicinal herb residue as a precursor for carbon dot preparation not only enables the high-value utilization of medicinal herb residue but also has a significant advantage: it promotes atomic self-doping or modification without the need for additional reagents.

[0004] Silver (Ag) + Ag, as an important precious metal, can bind to the sulfhydryl groups (-SH) in bacteria, inactivating bacterial proteases and effectively inhibiting the growth and spread of bacteria and viruses. When the human body is exposed to high concentrations of Ag for a long period... + In the environment, it can cause DNA damage, organ damage and failure, alginate (silver deposits), and even cancer. Ag is typically detected. +Atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and electrochemical methods are employed. However, these methods are limited by the high cost of equipment, long detection times, complex procedures, and intricate sample pretreatment processes, making them unsuitable for rapid Ag detection. + In comparison, fluorescence methods have emerged as a promising alternative, offering advantages such as rapid response, high sensitivity, and convenience. Therefore, increasing research is focusing on utilizing carbon dots for Ag detection. + . Summary of the Invention

[0005] Based on the above needs, the purpose of this invention is to provide nitrogen-doped carbon quantum dots derived from American cockroach residue, their preparation method, and applications. The nitrogen-doped carbon quantum dots provided by this invention possess excellent optical properties and stability, and are suitable for use with Ag... + The detection exhibits good selectivity, sensitivity, and anti-interference capabilities, with a method detection limit of 5.54 μM. The detection mechanism is a synergistic effect of internal filtering and photoinduced electron transfer, and it has broad application prospects.

[0006] To achieve the above objectives, the present invention is implemented through the following solution:

[0007] This invention provides a method for preparing nitrogen-doped carbon quantum dots derived from American cockroach residue. The nitrogen-doped carbon quantum dots are prepared by a one-step hydrothermal method, and the specific preparation steps are as follows:

[0008] (1) Add the American cockroach residue powder to ultrapure water and stir to obtain a mixture;

[0009] (2) The mixture is transferred to a reaction vessel for carbonization reaction. After carbonization is completed, it is cooled to room temperature to obtain a brownish-yellow solution;

[0010] (3) The brownish-yellow solution was filtered, centrifuged, and then filtered again. Dialysis was performed using a dialysis membrane to remove fluorescent small molecules and unreacted substances, and finally a yellow solution of nitrogen-doped carbon quantum dots was obtained, which is nitrogen-doped carbon quantum dots derived from American cockroach residue.

[0011] Furthermore, in step (1), the mass-volume concentration of the American cockroach residue powder in the mixture is 0.005-0.01 g / mL.

[0012] Furthermore, the carbonization temperature in the carbonization reaction is 200-250℃, and the carbonization time is 210-250 min.

[0013] Furthermore, the filtration is performed using a 0.1-0.3 μm microporous membrane, the dialysis membrane has a cutoff molecular weight of 500-1000 Da, and the dialysis time is 20-30 h.

[0014] Furthermore, the optimized American cockroach residue powder has a mass-volume concentration of 0.006 g / mL in the mixture, a carbonization temperature of 210℃, and a carbonization time of 240 min.

[0015] The present invention also provides nitrogen-doped carbon quantum dots, wherein the nitrogen-doped carbon quantum dots excite fluorescence in a λ-wave. Ex The average size of the nitrogen-doped carbon quantum dots is 350-370 nm. The average particle size is 2-3 nm and the average fluorescence lifetime is 16-18 ns.

[0016] Furthermore, the nitrogen-doped carbon quantum dots contain 69.82% C atoms and 10.02% N atoms.

[0017] Furthermore, the nitrogen-doped carbon quantum dots and Ag + There is electrostatic interaction.

[0018] This invention also provides the nitrogen-doped carbon quantum dots used in the preparation of Ag. + Applications of fluorescence sensors.

[0019] Furthermore, the nitrogen-doped carbon quantum dots are used in the detection of Ag. + Its LOD at the concentration was 5.54 μM.

[0020] This invention also provides the application of the nitrogen-doped carbon quantum dots in the preparation of materials for the rapid detection of Ag in wastewater or solvents. + Its application in material formulations.

[0021] Furthermore, the nitrogen-doped carbon quantum dots exhibit blue fluorescence under a 350-370 nm ultraviolet light.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. This invention converts waste materials from traditional Chinese medicine into carbon materials via a one-step hydrothermal method, solving the problems of raw material costs and toxic byproducts. Furthermore, it optimizes the preparation method, achieving the highest biofluorescence intensity for nitrogen-doped carbon quantum dots prepared under the following conditions: a mass-volume concentration of the residue in the mixture of 0.006 g / mL, a carbonization time of 240 min, and a carbonization temperature of 210℃. This invention converts American cockroach residue into fluorescent nanomaterials via a hydrothermal method, optimizing the reuse of waste resources and providing an effective strategy for the high-value-added utilization of traditional Chinese medicine residue. It also provides theoretical guidance for its large-scale production and has significant reference value.

[0024] 2. This invention successfully prepared nitrogen-doped carbon quantum dots using a one-step hydrothermal method with American cockroach residue as a precursor. Given that nitrogen-doped carbon quantum dots possess good water solubility, excellent thermal stability and salt resistance, and superior anti-interference ability, they can meet the practical requirements of Ag... + The need for rapid detection and highly sensitive sensing. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the synthesis of nitrogen-doped carbon quantum dots.

[0026] Figure 2 This is a single-factor experimental optimization diagram of the fluorescent probe prepared in Example 1 of the present invention, where a is the amount of residue added, b is the carbonization time, and c is the carbonization temperature.

[0027] Figure 3 These are transmission electron microscope (TEM) images and high-resolution TEM images of the nitrogen-doped carbon quantum dots prepared in Example 1 of this invention.

[0028] Figure 4 This is a particle size distribution diagram of nitrogen-doped carbon quantum dots prepared in Example 1 of the present invention.

[0029] Figure 5 This is an X-ray diffraction pattern of nitrogen-doped carbon quantum dots prepared in Example 1 of this invention.

[0030] Figure 6 This is the infrared spectrum (4000 cm⁻¹) of the nitrogen-doped carbon quantum dots prepared in Example 1 of this invention. -1 -400cm -1 ).

[0031] Figure 7 This is the full X-ray photoelectron spectrum of the nitrogen-doped carbon quantum dots prepared in Example 1 of this invention.

[0032] Figure 8 This is a fine X-ray photoelectron spectrum of the nitrogen-doped carbon quantum dots prepared in Example 1 of this invention with respect to C1s.

[0033] Figure 9 This is a fine X-ray photoelectron spectrum of the nitrogen-doped carbon quantum dots prepared in Example 1 of this invention with respect to N1s.

[0034] Figure 10 This is a fine X-ray photoelectron spectrum of the nitrogen-doped carbon quantum dots prepared in Example 1 of this invention with respect to O1s.

[0035] Figure 11 This is a fluorescence intensity diagram of nitrogen-doped carbon quantum dots prepared in Example 1 of the present invention at different temperatures.

[0036] Figure 12This is a fluorescence intensity diagram of nitrogen-doped carbon quantum dots prepared in Example 1 of the present invention at different salt concentrations.

[0037] Figure 13 This is a fluorescence intensity diagram of nitrogen-doped carbon quantum dots prepared in Example 1 of the present invention after sensing different metal ions.

[0038] Figure 14 The nitrogen-doped carbon quantum dots prepared in Example 1 of this invention are used to sense different concentrations of Ag. + Fluorescence emission spectrum after ionization.

[0039] Figure 15 The nitrogen-doped carbon quantum dots prepared in Example 1 of this invention are used in low-concentration fluorescence sensing Ag. + Linear fitting plot of ions.

[0040] Figure 16 It is the nitrogen-doped carbon quantum dots and Ag prepared in Example 1 of this invention. + The relationship between them is shown in the graph, where 'a' represents the presence or absence of Ag. + Fluorescence lifetime plot of nitrogen-doped carbon quantum dots; b represents Ag. + UV-Vis absorption spectra and excitation and emission spectra of nitrogen-doped carbon quantum dots; c represents the addition of different concentrations of Ag. + UV-Vis absorption spectrum of nitrogen-doped carbon quantum dot solution.

[0041] Figure 17 It is the nitrogen-doped carbon quantum dots and Ag prepared in Example 1 of this invention. + and nitrogen-doped carbon quantum dots + Ag + Zeta potential of the solution. Detailed Implementation

[0042] The following embodiments are for illustrative purposes only and are not intended to limit the technical solutions described in this invention. Although this specification has described the invention in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the invention, and all technical solutions and improvements that do not depart from the spirit and scope of the invention should be covered within the scope of the claims of this invention.

[0043] Unless otherwise specified, the experimental methods described in the embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0044] The mass-volume concentration of the American cockroach residue powder described in this invention is the ratio of the mass of the American cockroach residue powder to the volume of pure water, wherein the mass unit is g and the volume unit of the pure water is mL.

[0045] Example 1: Synthesis of nitrogen-doped carbon quantum dots

[0046] American cockroach residue is the residue after alcohol extraction of American cockroaches. It is dried in a forced-air drying oven at 50°C, ground, and sieved through a 100-mesh sieve to obtain American cockroach residue powder, which is stored at room temperature for later use. This example provides the synthesis of nitrogen-doped carbon quantum dots using a hydrothermal method, the specific operation of which is as follows:

[0047] (1) Add 0.1200 g of American cockroach residue powder to 20 mL of ultrapure water and stir for 15 min.

[0048] (2) The mixture was transferred to a 25 mL Teflon-lined reactor for carbonization at a temperature of 210 °C for 240 min and then cooled to room temperature.

[0049] (3) The obtained brownish-yellow solution was filtered and centrifuged (20 min, 10000 rpm). The obtained yellow solution was then filtered (0.22 μm microporous membrane) and dialyzed for 24 h using a dialysis membrane (cutoff molecular weight 1000 Da) to remove fluorescent small molecules and unreacted substances. Finally, a yellow solution of nitrogen-doped carbon quantum dots was obtained, which is nitrogen-doped carbon quantum dots derived from American cockroach residue.

[0050] Specifically, such as Figure 1 As shown, the nitrogen-doped carbon quantum dots prepared were used in subsequent experiments.

[0051] Example 2: Single-factor optimization experiment

[0052] To obtain nitrogen-doped carbon quantum dots with excellent detection performance, three single factors were optimized: the amount of residue added, carbonization time, and carbonization temperature.

[0053] Except for the amount of residue added, under the same reaction conditions, the fluorescence intensity of the synthesized nitrogen-doped carbon quantum dots reached its maximum at 0.1200 g. When the amount of residue added was between 0.0600 and 0.1200 g, the fluorescence intensity gradually increased. When the amount of residue added exceeded 0.1200 g, the fluorescence intensity showed a decreasing trend. This is because excessive raw materials accumulated in the reactor, resulting in incomplete carbonization, with only a small portion undergoing the carbonization reaction. Therefore, the fluorescence intensity basically no longer changed with the increase of raw material amount and began to stabilize or even decrease. Subsequently, the effect of different carbonization times on the fluorescence intensity of nitrogen-doped carbon quantum dots was evaluated. With the increase of carbonization time, the fluorescence intensity continuously increased and then tended to stabilize.

[0054] Finally, the effect of carbonization temperature on the fluorescence intensity of nitrogen-doped carbon quantum dots was evaluated. Figure 2As can be seen from Figure c, when the carbonization temperature is below 210℃, the American cockroach residue is not completely carbonized due to the low temperature. However, after the carbonization temperature reaches 210℃, the fluorescence intensity tends to stabilize. When the amount of residue added for preparing nitrogen-doped carbon quantum dots derived from American cockroach residue is 0.1200 g, the carbonization time is 240 min, and the carbonization temperature is 210℃, the strongest emission (λ) occurs at 413 nm. Ex =356 nm), at which point the fluorescence intensity is at its maximum.

[0055] Example 3: Characterization information of nitrogen-doped carbon quantum dot structure

[0056] (I) Morphological Analysis

[0057] The nitrogen-doped carbon quantum dots prepared in Example 1 were analyzed, and their TEM images were compared as follows: Figure 3 As shown, the prepared nitrogen-doped carbon quantum dots exhibit good dispersion and are relatively uniform. In high-resolution transmission electron microscopy (HR-TEM) images, clear lattice fringes with a d-spacing of 0.31 nm were observed, corresponding to the (203) crystal plane of carbon, indicating that the nitrogen-doped carbon quantum dots underwent a certain degree of graphitization during preparation. The average particle size of the nitrogen-doped carbon quantum dots is 2.41 ± 0.12 nm. Figure 4 (As shown). Furthermore, Figure 5 As shown, the peak at 2θ = 21.3° in the XRD pattern is an amorphous diffraction peak, which corresponds to the (002) plane of graphite carbon, indicating that the synthesized nitrogen-doped carbon quantum dots are amorphous structures.

[0058] (ii) Infrared spectroscopy analysis

[0059] To verify the functional groups on the surface of nitrogen-doped carbon quantum dots and the self-doping of nitrogen, the synthesized samples were characterized by FT-IR and XPS in this embodiment. Figure 6 As shown, 3405 cm -1 The characteristic absorption band at this point belongs to the stretching vibration of NH / OH, while the stretching vibration of CH is at 2962 cm⁻¹. -1 There is a significant absorption peak at 1659 cm⁻¹, and the C=O / C=N ratio also shows a peak at 1659 cm⁻¹. -1 It exhibits a significant absorption peak at [value missing], while the plane bending vibration of NH / OH and the stretching vibrations of CO, CN, and COC are 619, 1450, 1398, and 1112 cm⁻¹, respectively. -1 It has absorption peaks on both sides.

[0060] (III) XPS Analysis

[0061] Furthermore, XPS was used to further analyze the chemical composition and elements of nitrogen-doped carbon quantum dots. In the full-spectrum XPS of nitrogen-doped carbon quantum dots, three different characteristic peaks could be observed. Figure 7 (As shown). The center positions are 284.81, 399.77, and 531.52 eV, respectively, attributed to C1s, N1s, and O1s, with atomic proportions of 69.82%, 10.02%, and 20.16%, confirming the presence of carbon, nitrogen, and oxygen in the material. In XPS, C atoms are relatively abundant (69.82%), while N atoms are relatively abundant (10.02%).

[0062] This further demonstrates that in the process of preparing nitrogen-doped carbon quantum dots using American cockroach residue, the residue provides C and N to the nitrogen-doped carbon quantum dots, achieving a functionalized result of atomic self-doping. For example... Figure 8 As shown, in the high-resolution C1s band, it can be decomposed into three peaks, with binding energies of 284.58, 285.33, and 287.91 eV attributable to CC / C=C, CO / CN, and C=N / C=O, respectively. In the high-resolution N1s band, it can be decomposed into two peaks, with binding energies of 399.69 eV and 400.04 eV corresponding to pyrrole nitrogen and graphitic nitrogen, respectively. Figure 9 As shown). The high-resolution band of O1s can be decomposed into two peaks, with binding energies of 531.05 eV and 531.99 eV corresponding to C=O and C-OH / COC, respectively. Figure 10 As shown in the figure. Based on the results of XPS and FT-IR, it was confirmed that a nitrogen-self-doped carbon dot was successfully prepared by a one-step hydrothermal method.

[0063] Example 4: Investigation into the stability of nitrogen-doped carbon quantum dots

[0064] This embodiment evaluated the thermal stability and salt resistance of the nitrogen-doped carbon quantum dots prepared in Example 1 based on temperature and NaCl concentration. Figure 11 As shown, the fluorescence intensity remained relatively stable at different temperatures as the temperature gradually increased from 25℃ to 50℃, demonstrating that nitrogen-doped carbon quantum dots possess good thermal stability. The fluorescence intensity remained stable at NaCl concentrations of 0–1000 μM. Figure 12 When the fluorescence intensity remained almost unchanged, it indicated that the synthesized nitrogen-doped carbon quantum dots exhibited good salt resistance.

[0065] Example 5: Ag based on nitrogen-doped carbon quantum dots + Construction of fluorescence sensor

[0066] 1. Ag based on nitrogen-doped carbon quantum dots + Selectivity and anti-interference

[0067] Ag + The ability to be selectively recognized among various ions is one of the criteria for evaluating the practical application capability of nitrogen-doped carbon quantum dots. This study aimed to evaluate the detection of Ag using fluorescent probes. + To investigate the selectivity of the nitrogen-doped carbon quantum dots prepared in Example 1, 11 analytes were screened and selected for selectivity experiments.

[0068] 200 μL of nitrogen-doped carbon quantum dots were added to a 3 mL centrifuge tube, followed by 100 μL of AgNO3 solution of varying concentrations. The volume was then adjusted to 1 mL with PBS buffer (pH = 7.4). After incubation at room temperature for 3 min, fluorescence intensity was recorded at 413 nm using an excitation wavelength of 356 nm. AgNO3 was then added using the same method. + Replaced with other metal ions (Cd) at a concentration of 200 μM. 2+ Cu 2+ Pb 2+ Hg 2+ Ni 2+ Fe 2+ Fe 3+ Zn 2+ Co 2+ Cr 3+ To verify the selectivity of nitrogen-doped carbon quantum dots.

[0069] Combined with appendix Figure 13 As shown, Ag was obtained. + The fluorescence signal of nitrogen-doped carbon quantum dots can be significantly quenched, while the fluorescence intensity of nitrogen-doped carbon quantum dots does not change significantly after the addition of other metal ion solutions. In summary, the prepared nitrogen-doped carbon quantum dot fluorescent probe exhibits excellent selectivity.

[0070] 2. Fluorescence sensitivity analysis

[0071] Subsequently, in order to study the effect of nitrogen-doped carbon quantum dots on Ag + Detection performance in aqueous solution. Ag was observed. + The fluorescence intensity of nitrogen-doped carbon quantum dots decreases in the concentration range of 0–200 μM. Figure 14 (As shown). Furthermore, the fluorescence intensity ratio of F0 / F is related to Ag. + The concentration showed a good linear relationship within the linear range of 0-180 μM, and the linear regression equation was y = 0.0035x + 1.0028, with a correlation coefficient (R²). 2 The limit of detection (LOD) was 0.9991, and the limit of detection (LOD) was 5.54 μM. Figure 15 (As shown). In addition, Ag +In the concentration range of 0 to 200 μM, the fluorescence intensity of nitrogen-doped carbon quantum dots is concentrated between 17,000 and 40,000 au.

[0072] Example 6: Nitrogen-doped carbon quantum dot fluorescence detection of Ag +

[0073] Fluorescence quenching typically describes the interaction between the fluorophore and the quenching substance, driven by various mechanisms, including dynamic quenching, static quenching, internal filtering effects, photoinduced electron transfer, and fluorescence resonance energy transfer. To distinguish these mechanisms, observing changes in the UV-Vis absorption spectra and fluorescence lifetime decay between nitrogen-doped carbon quantum dots and the quenching group is an extremely important method.

[0074] Combination Figure 16 As shown, where the combination Figure 16 As shown in Figure a, adding and not adding Ag + The average lifetimes of the nitrogen-doped carbon quantum dots were 17.81 ns and 16.85 ns, respectively, and the average fluorescence lifetime did not change significantly, indicating that the main quenching mechanism is the internal filtering effect. It is worth noting that, combined with... Figure 16 As shown in b, Ag + The UV-Vis absorption peak of Ag partially overlaps with the fluorescence excitation peak of nitrogen-doped carbon quantum dots, but does not overlap with the emission peak. + The absorption of energy from part of the excitation wavelength of nitrogen-doped carbon quantum dots leads to a decrease in their emission intensity, which is a typical internal filtering effect. Furthermore, different Ag... + The UV-Vis absorption spectra of nitrogen-doped carbon quantum dots at different concentrations show that, with different Ag concentrations... + The addition of Ag did not result in any new absorption peaks in the UV-Vis absorption, indicating that nitrogen-doped carbon quantum dots and Ag... + No new compounds were formed between them. Figure 16 (as shown in c).

[0075] To further study Ag + The quenching mechanism of nitrogen-doped carbon quantum dots was investigated at a pH of approximately 6, by measuring the nitrogen-doped carbon quantum dots and Ag. + And the zeta potential after the two substances are mixed ( Figure 17 As shown in the figure, the potential of the mixture is significantly different from that of the two individual substances, indicating that Ag... + There is an electrostatic interaction between Ag and nitrogen-doped carbon quantum dots. In summary, Ag... + The fluorescence quenching mechanism of nitrogen-doped carbon quantum dots is a synergistic result of internal filtering effect and photoinduced electron transfer.

[0076] Example 7: Application of nitrogen-doped carbon quantum dots in detection of real samples

[0077] To investigate the feasibility of nitrogen-doped carbon quantum dots in actual samples, a spiked recovery method was used to analyze Ag in Xierhe River water, mineral water, and tap water. + Recovery was determined. All samples were first centrifuged at 4000 rpm for 10 min, then filtered through a 0.22 μm microporous membrane. The resulting filtrate was then diluted three times with deionized water. Ag was subsequently added to the treated samples. + The solution was prepared into spiked samples of different concentrations, and its fluorescence intensity was measured. The measurements were repeated three times, and the recovery rate and relative standard deviation were calculated.

[0078] To verify the practicality of this method in actual sample detection, nitrogen-doped carbon quantum dot fluorescent probe technology was used to detect Ag in water samples. + Ag was detected in Xierhe River water, mineral water, and tap water using a spiked recovery method. + As can be seen from Table 1, the Ag content in the samples of Xier River water, mineral water, and tap water... + The recoveries were 93.4%–100.2%, 99.0%–104.7%, and 94.2%–100.3%, respectively, with relative standard deviations all below 5.0%. This method is effective for Ag... + The recoveries were all within a reasonable range, with small relative standard deviations. This indicates that nitrogen-doped carbon quantum dots can effectively detect Ag in real samples. + The enormous potential for Ag in environmental samples, and for the discovery of Ag in environmental samples + This provides a new strategy for rapid detection.

[0079] Table 1 Ag in different water samples + Measurement

[0080] In summary, this invention successfully prepared nitrogen-doped carbon quantum dots using American cockroach residue as a precursor via a simple and environmentally friendly one-step hydrothermal method. The prepared nitrogen-doped carbon quantum dots exhibit good sensitivity, water solubility, selectivity, anti-interference ability, and stability, and blue fluorescence can be observed under a 365 nm UV lamp. The established method has a linear range of 0–180 μM and a detection limit of 5.54 μM, successfully constructing a "turn-off" type fluorescent nanosensor for Ag… + The sensitivity and selectivity of the detection were assessed. The detection mechanism mainly involves internal filtration effect and photoinduced electron transfer. Subsequently, nitrogen-doped carbon quantum dots were used to detect Ag in actual water samples. + Satisfactory results were obtained. This invention not only provides for Ag... + The development of nitrogen-doped carbon quantum dots with sensing function provides a new approach and a new research direction for the high-value utilization of traditional Chinese medicine residue.

[0081] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing nitrogen-doped carbon quantum dots derived from American cockroach residue, characterized in that, The nitrogen-doped carbon quantum dots were prepared using a one-step hydrothermal method. The specific preparation steps are as follows: (1) Add the American cockroach residue powder to ultrapure water and stir to obtain a mixture; (2) The mixture is transferred to a reaction vessel for carbonization reaction. After carbonization is completed, it is cooled to room temperature to obtain a brownish-yellow solution; (3) The brownish-yellow solution was filtered, centrifuged, and then filtered again. The solution was dialyzed with a dialysis membrane to remove fluorescent small molecules and unreacted substances, and finally a yellow solution of nitrogen-doped carbon quantum dots was obtained, which is nitrogen-doped carbon quantum dots derived from American cockroach residue.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass-volume concentration of the American cockroach residue powder in the mixture is 0.005-0.01 g / mL.

3. The preparation method according to claim 1, characterized in that, The carbonization temperature in the carbonization reaction is 200-250℃, and the carbonization time is 210-250 min.

4. The preparation method according to claim 1, characterized in that, The filtration is performed using a 0.1-0.3 μm microporous membrane, the cutoff molecular weight of the dialysis membrane is 500-1000 Da, and the dialysis time is 20-30 h.

5. The preparation method according to claim 1, characterized in that, The optimized American cockroach residue powder had a mass-volume concentration of 0.006 g / mL in the mixture, a carbonization temperature of 210℃, and a carbonization time of 240 min.

6. The nitrogen-doped carbon quantum dots prepared by the method according to any one of claims 1-5, characterized in that, The nitrogen-doped carbon quantum dots excited by λ fluorescence Ex The average size of the nitrogen-doped carbon quantum dots is 350-370 nm. The average particle size is 2-3 nm and the average fluorescence lifetime is 16-18 ns.

7. The nitrogen-doped carbon quantum dot according to claim 6, characterized in that, The nitrogen-doped carbon quantum dots and Ag + There is electrostatic interaction.

8. The nitrogen-doped carbon quantum dots of claim 6 in the preparation of Ag + Applications of fluorescence sensors.

9. The nitrogen-doped carbon quantum dots of claim 6 in the preparation of materials for rapid detection of Ag in wastewater or solvents. + Its application in material formulations.

10. The application according to claim 8 or claim 9, characterized in that, The nitrogen-doped carbon quantum dots exhibit blue fluorescence under a 350-370 nm ultraviolet light.

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