CN111157595B

CN111157595B - Composite nano material and preparation method thereof, and electrochemical detection method of chrysophanol

Info

Publication number: CN111157595B
Application number: CN201911373700.4A
Authority: CN
Inventors: 石玲; 王泽锋; 杨光明; 刘卫; 吴娜; 陈显兰
Original assignee: Honghe University
Current assignee: Honghe University
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2023-02-07
Anticipated expiration: 2039-12-26
Also published as: CN111157595A

Abstract

The invention discloses a preparation method of a composite nano material, which comprises the following steps: and mixing the ZnO nano-rod loaded with the nano-noble metal with the N-doped graphene. In another aspect, the present invention provides a composite nanomaterial prepared by the above-described preparation method. In another aspect, the invention provides an electrochemical sensor, which comprises the glassy carbon electrode modified by the composite nano material. In another aspect, the present invention provides a method for electrochemically detecting chrysophanol, comprising using the above electrochemical sensor. The method successfully prepares the composite nano material, the prepared composite nano material is used for constructing an electrochemical sensor to detect chrysophanol, and the result shows that the composite nano material has good electrochemical activity and can realize the detection of chrysophanol, the linear range of the detection is 1.57-27.53 mu M, and the detection limit is 0.49 mu M, and the sensor provided by the invention can successfully detect the chrysophanol in the rheum officinale medicinal material.

Description

Composite nano material and preparation method thereof, and electrochemical detection method of chrysophanol

Technical Field

The invention relates to the technical field of traditional Chinese medicine detection, in particular to a composite nano material and a preparation method thereof, and an electrochemical detection method of chrysophanol.

Background

The radix et rhizoma Rhei is dry root and rhizome of Rheum palmatum L., rheum tanguticum Maxim. Or Rheum officinale Baill. Of Polygonaceae, is bitter in taste and cold in nature, and has effects of clearing heat and purgation, resisting bacteria, removing blood stasis and resolving food stagnation, diminishing inflammation and hemostasis, and resisting tumor. Has effects of clearing away heat and toxic materials, and purging. The composition contains total anthraquinone derivatives such as rhein, aloe-emodin, chrysophanol and physcion, wherein chrysophanol is the main effective component for generating pharmacological action. Therefore, the determination of the content of chrysophanol in the rhubarb medicinal material is particularly important for the application of the rhubarb medicinal material in the pharmaceutical field. At present, chrysophanol is mainly detected by adopting a gas chromatography-mass spectrometry method, a high performance liquid chromatography method and a capillary electrophoresis analysis method, but the methods involve expensive instruments, complex sample pretreatment methods, complex instrument use and the like. At present, the electrochemical analysis method has been widely applied to the field of sample detection due to its advantages of simple equipment, simple operation, low cost, high analysis speed, high sensitivity, and the like. According to the relevant data, no report is found on the detection of the chrysophanol content in the rhubarb medicinal material by an electrochemical method at present.

Disclosure of Invention

The invention aims to provide a composite nano material, a preparation method thereof and a chrysophanol detection method, and solves one or more of the problems in the prior art.

In one aspect, the present invention provides a method for preparing a composite nanomaterial, comprising the steps of:

and mixing the ZnO nano-rod loaded with the nano-noble metal with the N-doped graphene.

In some embodiments, the nano noble metal has a particle size of 5 to 100nm.

In some embodiments, the nano noble metal has a particle size of 25 to 30nm.

In some embodiments, illustrative examples of noble metals that can be used in the present invention are not limited to Au, pt, ag, or Pd.

In some embodiments, illustrative examples of noble metals that can be used in the present invention are not limited to Au.

In some embodiments, the ZnO nanorods are 10 to 100nm in length.

In some embodiments, the ZnO nanorods are 15 to 30nm in length.

In some embodiments, illustrative examples of graphene that can be used in the present invention are, but not limited to, reduced graphene oxide or graphene oxide.

In some embodiments, the weight ratio of the nano noble metal-loaded ZnO nanorods to the N-doped graphene is 20:1 to 50:1.

In some embodiments, the weight ratio of the nano noble metal-loaded ZnO nanorods to the N-doped graphene is 30:1.

In some embodiments, a post-mixing sonication step is also included.

In some embodiments, the ultrasonic power is 100 to 500W.

In some embodiments, the ultrasound power is 200W.

In some embodiments, the sonication time is from 1 to 24h.

In some embodiments, the sonication time is 6h.

In some embodiments, the ZnO nanorods are prepared by:

dissolving zinc acetate in an alcohol solvent and pure water to obtain an alcoholic solution of the zinc acetate;

dissolving KOH in an alcohol solvent, and adding the alcoholic solution of zinc acetate;

volatilizing nitrogen and concentrating to obtain a concentrated solution;

aging the concentrated solution at 40 to 60 ℃ for 10 to 24 hours;

standing and separating to obtain the ZnO nano rod.

In some embodiments, the nano-precious metal-loaded ZnO nanorods are prepared by:

dispersing the ZnO nano-rod in trisodium citrate solution to obtain ZnO nano-rod dispersion liquid;

adding a chloric acid solution of noble metal, and reacting for 10 to 24 hours;

and carrying out centrifugal separation to obtain the nano precious metal loaded ZnO nano rod.

In some embodiments, illustrative examples of noble metal chloric acid solutions that can be used in the present invention are not limited to HAuCl ₄ And (3) solution.

In some embodiments, the molar ratio of ZnO nanorods to the chloric acid solution of the noble metal is 1: 10 to 1: 50.

In another aspect, the present invention provides a composite nanomaterial prepared by the above-described preparation method.

In another aspect, the invention provides an electrochemical sensor, which comprises the glassy carbon electrode modified by the composite nano material.

In some embodiments, the amount of composite nanomaterial is 2 to 7 μ L.

In some embodiments, the amount of composite nanomaterial is 7 μ L.

On the other hand, the invention provides an electrochemical detection method of chrysophanol, which comprises the following steps:

pulverizing radix et rhizoma Rhei to obtain medicinal powder;

dissolving the medicinal material powder in ethanol, and performing ultrasonic extraction to obtain medicinal material extract

The medicinal material extracting solution is detected by the electrochemical sensor.

In some embodiments, the method further comprises the step of diluting the herbal extract with ethanol.

In some embodiments, the herbal extract is diluted 2 to 10 times.

In some embodiments, the herbal extract is diluted 5-fold.

In some embodiments, further comprising adding an acetic acid buffer solution.

In some embodiments, the pH of the acetic acid buffer solution is from 2 to 5.

In some embodiments, the pH of the acetic acid buffered solution is 3.6.

In some embodiments, the enrichment time of the electrode is 1 to 6min.

In some embodiments, the enrichment time of the electrode is 6min.

Has the advantages that:

the composite nano material is successfully prepared by adopting the method, the prepared composite nano material is used for constructing an electrochemical sensor to detect chrysophanol, and the result shows that the composite nano material has better electrochemical activity and can realize the detection of the chrysophanol, the linear range of the detection is 1.57-27.53 mu M, the detection limit is 0.49 mu M, and the sensor provided by the invention can successfully detect the chrysophanol in the rheum officinale medicinal material.

Drawings

FIG. 1 is TEM (A) and HRTEM (B) images of ZnO nanorods;

FIG. 2 is TEM (A) and HRTEM (B) images of ZnO/Au nanoparticles;

FIG. 3 is TEM (A) and HRTEM (B) images of N-rGO-ZnO/Au composite nanomaterial;

FIG. 4 is XRD patterns of (a) ZnO nanorods, (b) ZnO/Au nanoparticles, and (c) N-rGO-ZnO/Au;

FIG. 5 is XPS spectrum of (A) N-rGO-ZnO/Au full spectrum, (B) C1 s, (C) N1s, (D) O1 s, (E) Zn 2p, (F) Zn 3p and Au 4F high resolution spectrum;

FIG. 6 is a cyclic voltammogram of ZnO (a), znO/Au (b), and N-rGO-ZnO/Au (c) modified electrodes in 0.1M pH =3.6 acetic acid buffer solution containing 10.18 μ M chrysophanol, with a scan rate of 20mV s ^-1 ；

FIG. 7 is a cyclic voltammogram of (A) N-rGO-ZnO/Au/GCE in 10.18 μ M chrysophanol in acetic acid buffer solution with pH =3.6, with scan rates of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200 and 250mV · s, respectively ^-1 (ii) a (B) Calibration plot of peak current versus square root of scan rate; (C) calibration plot of peak potential versus log scan rate;

FIG. 8 is a cyclic voltammogram of (A) N-rGO-ZnO/Au/GCE in acetic acid buffer solutions at pH 3.0, 3.6, 4.0, 4.6, 5.0 and 5.6, respectively, with a scan rate of 20mV s-1; (B) Calibration curve graphs between anode peak potential and cathode peak potential and pH of chrysophanol;

FIG. 9 is a graph showing the effect of (A) the amount of N-rGO-ZnO/Au on chrysophanol detection; (B) a graph of the effect of enrichment time on chrysophanol detection;

FIG. 10 is (A) a differential pulse voltammogram of N-rGO-ZnO/Au/GCE at different concentrations (1.57, 2.36, 3.93, 5.51, 7.08, 8.65, 11.80, 15.73, 21.63, 27.53 μ M) of chrysophanol under optimal conditions; and (B) calibrating the graph.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Example 1

1. Preparation of Zinc oxide nanorods (ZnO)

In a round bottom flask, 4.45mmol of zinc acetate was dissolved in 42mL of methanol and 250. Mu.L of ultrapure water, stirred vigorously at 60 ℃ and 9.62mmol of 82.0% KOH in 23mL of methanol was added to the solution over 10-15 min. And after the obtained reaction mixture continuously reacts for 135min, cooling to room temperature, volatilizing nitrogen to concentrate the reaction solution to 10mL, aging the obtained concentrated solution in a water bath at 60 ℃ for 12h, standing for 30min, removing supernatant, adding 50mL of methanol, stirring for 5min, continuously standing for 30min, removing supernatant, repeating the steps twice, adding 50mL of methanol, stirring for 5min, standing overnight, removing supernatant, and dispersing the obtained sample solution in methanol.

2. Preparation of Au-Supported ZnO nanorods (ZnO/Au)

The ZnO nanorods obtained above were dispersed in trisodium citrate solution to obtain 50mL of 0.4mmol/L ZnO dispersion, 10mL of 0.39mM of chloroauric acid was added dropwise with stirring to react at room temperature for 12 hours, and the solution was centrifugally washed with ultrapure water.

3. Preparation of N-doped reduced graphene oxide supported ZnO nanorod-loaded Au nanoparticle multifunctional composite nanomaterial (N-rGO-ZnO/Au)

50mL of 3.0mg/mL ZnO/Au and 10mL of 0.5mg/mL N-doped reduced graphene oxide are mixed and subjected to ultrasonic treatment at 200W for 6 hours to obtain the N-rGO-ZnO/Au composite nano material.

Wherein, the raw material purchasing manufacturer list is as follows:

the ZnO, au/ZnO and N-rGO-ZnO/Au composite nano-materials in the embodiment 1 are subjected to TEM, HRTEM, XRD and XPS detection.

Wherein TEM and HRTEM adopt high-resolution transmission electron microscope of JEM-2100 of JEOL company;

XRD was carried out using PANALYTICAL CORPORATION model X' Pert ³ The powder diffractometer of (1);

XPS adopts the model K-Alpha of Thermo fisher Scientific of America Seimer Feishell science ⁺ The vacuum degree of the analysis chamber during working: 2X 10-7mba, X light source: monochromated Al K α source (Mono Al K α), energy: 1486.6eV,6mA × 12KV (72W), beam spot size: 400 μm; scanning mode: CAE (fixed analyzer energy), full spectrum scan: the flux energy is 100eV, and the step size is 1eV; narrow spectrum scanning: the pass energy was 30eV, with a step size of 0.1eV.

The characterization results were as follows:

as shown in FIG. 1A, znO has a good rod-like structure, and most of ZnO is arranged together in parallel, and ZnO nanorods are about 25nm long;

as clearly shown in FIG. 1B, it can be seen that 0.25 and 0.19nm interplanar spacings correspond to the crystalline forms of ZnO nanorods of 101 and 102, respectively.

ZnO nano-rod is prepared by using zinc acetate and KOH as raw materials, and Zn (OH) is obtained at the beginning ₂ Intermediate product, but Zn (OH) ₂ The instability can be transformed into ZnO, and after a period of reaction, the solution is volatilized by using nitrogen to facilitate the generation of ZnO nano-rods.

As shown in fig. 2A and B, the Au nanoparticles with nanometer size are uniformly dispersed on the surface of the ZnO nanorod, and it can be seen from HRTEM that the average particle size of the Au nanoparticles is about 18nm, the interplanar spacing of 0.23nm corresponds to the Au nanoparticles with cubic crystal form, the interplanar spacing of 0.25nm corresponds to the ZnO with 101 lattice, and further, from a Fast Fourier Transform (FFT) diagram (inset in fig. 2B), it can be seen that the ZnO nanorod obtained is of a single crystal structure.

As shown in FIG. 3A, N-rGO has a transparent film-like structure, and ZnO/Au nanoparticles which are rarely aggregated are dispersed on the surface of the N-rGO.

As shown in fig. 3B, the interplanar spacing of Au nanoparticles is 0.23nm corresponding to cubic crystal Au nanoparticles, and the interplanar spacing of ZnO is 0.25nm corresponding to 101 crystal faces thereof, which indicates that the introduction of N-rGO does not change the crystal forms of Au nanoparticles and ZnO.

TEM and HRTEM results show that example 1 has successfully prepared the N-rGO-ZnO/Au composite nano-material.

As shown in figure 4 of the drawings,

the curve a is the XRD pattern of the ZnO nanorod, and it can be seen from the diagram that the positions of diffraction peaks are respectively 31.80 °, 34.46 °, 36.36 °, 47.64 °, 56.56 °, 62.86 °, 68.04 °, 72.43 ° and 77.07 ° corresponding to the (100), (002), (101), (102), (110), (103), (112), (004) and (004) crystal planes of ZnO, and this result well corresponds to the Wurtzite structure of ZnO according to JCPDS card No.36-1451.

Curve b is the XRD spectrum of ZnO/Au, and it can be seen that the diffraction peaks at 38.25 ° and 44.42 ° correspond to the Au nanoparticles with (111) and (200) crystal planes.

The curve c is an XRD spectrogram of N-rGO-ZnO/Au, and a diffraction peak near 22.64 degrees is a characteristic peak of graphene with a (002) crystal face, and in addition, corresponding diffraction peaks of ZnO and Au also appear.

The XRD result shows that the N-rGO-ZnO/Au multifunctional composite nano material with a better crystal structure is successfully prepared in the example 1.

As shown in FIG. 5A, the prepared N-rGO-ZnO/Au contains five elements of Au, C, N, O and Zn;

FIG. 5B shows the high resolution spectrum of C1 s, and as shown in FIG. 5B, C1 s has four bonding modes: c = C, C-C/C-N, C = O, O-C = O correspond to a binding energy of 284.5eV, 285.8eV, 287.0eV and 289.0eV, respectively.

FIG. 5C is a spectrum of N1s, which shows significant peaks corresponding to-NH-and-N at 399.1eV and 400.4eV as shown in FIG. 5C ⁺ -signal peak of (a).

FIG. 5D is a high resolution spectrum of O1 s, with the peak at 530.0eV corresponding to O as shown in FIG. 5D ^2- And the spectral peak of the metal ion in ZnO, the peak at 531.0eV corresponding to the peak of O at the acupuncture point, the peak at C-O at the peak position of 532.2eV, and the peak of oxygen in chemisorbed and dissociated state at the peak position of 533.2 eV.

FIG. 5E is a high resolution spectrum of Zn 2p, as shown in FIG. 5E, the binding energies are 1022.2eV and 1045.3eV, respectivelyZn 2p _3/2 And Zn 2p _1/2 The separation of the binding energy is 23.1eV, which is a typical peak characteristic of ZnO.

FIG. 5F is a high resolution spectrum of Zn 3p and Au 4F, as shown in FIG. 5F, peaks at 84.2 and 87.8eV correspond to 4F of Au nanoparticles _7/2 And 4f _5/2 Spectral peaks, secondly, two strong peaks appear next to gold, which correspond to Zn 3p, respectively _3/2 And 3p _1/2 Spectrum peak of (2).

XPS results show that the N-rGO-ZnO/Au of example 1 has been successfully prepared.

Example 2

Firstly, using a proper amount of Al for a Glassy Carbon Electrode (GCE) ₂ O ₃ The powder was polished to a mirror surface on a chamois leather, rinsed clean with distilled water and then blown dry with nitrogen. And then, taking 7 mu L of ZnO, znO/Au and N-rGO-ZnO/Au nano materials prepared in the embodiment 1 to modify the glassy carbon electrode, airing at room temperature, and storing for later use, wherein the materials are respectively marked as ZnO/GCE, znO/Au/GCE and N-rGO-ZnO/Au/GCE.

Example 3

The electrochemical sensor prepared in example 2 was used to detect 10.18 μ M chrysophanol in 0.1m acetic acid buffer solution with ph =3.6, and the scanning rate was 20mV s ^-1 。

The results were as follows:

as shown in figure 6, znO/GCE and ZnO/Au/GCE have poor response to chrysophanol, while N-rGO-ZnO/Au/GCE has a pair of good redox peaks in response to chrysophanol, and the result shows that the prepared N-rGO-ZnO/Au/GCE can well detect chrysophanol, and the prepared N-rGO-ZnO/Au has the excellent properties of N-rGO, znO and Au.

The electrochemical sensor prepared in example 2 has cyclic voltammograms at 10.18 μ M chrysophanol in acetic acid buffer solution with pH =3.6, in which the scan rates are 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, and 250mV · s, respectively ^-1 The results are as follows:

as shown in FIG. 7, as the scan rate increased, the oxidation-reduction peak current of chrysophanol further increased, and the oxidation of chrysophanol occurredThe reduction peak current has a good linear relation with the square root of the scanning rate, and the linear equation is Ipa =5.7927 v 1/2+13.8739 (R) ₂ = 0.9913) and Ipc =6.2841 ν 1/2-3.6267 (R) ₂ = 0.9967), the results showed that the reaction of chrysophanol at the electrode surface was diffusion-controlled.

It can also be seen from the graph a that the oxidation peak potential is negatively shifted and the reduction front potential is positively shifted as the scan rate increases, and the graph C is a plot of the oxidation-reduction peak potential versus the log of the scan rate (ln v) with linear equations of Epa =0.01514ln υ -0.4037, R2=0.9988 and Epc = -0.02069ln υ -0.3558, and R2=0.9975. From the lavironon equation, the electron transfer rate constant (ks), the number of electron transfers (n), and the charge transfer coefficient (α) can be calculated. The slope value of the relation curve between the anode peak potential and ln upsilon corresponds to the RT/(1-alpha) nF value, and the slope value of the relation curve between the cathode peak potential and ln upsilon corresponds to the RT/alpha nF value.

Wherein Ep is a peak potential, E0' is a standard electrode potential, and R is a molar gas constant (R =8.314J · mol) ^-1 ·K ^-1 ) T is the thermodynamic temperature (T = 298K), ffaraday constant (F =96485C mol) ^-1 ) And υ is the scan rate. According to the above equation, n, α and ks are 2, 0.42 and 0.36s, respectively ^-1 . Thus, experimental results indicate that the transfer of two electrons occurs during the reaction.

Example 4

The electrochemical sensor pairs prepared in example 2 were added with acetic acid buffer solutions having pH =3.0, 3.6, 4.0, 4.6, 5.0, and 5.6, respectively, and subjected to cyclic voltammetry,wherein the scanning rate is 20mV s ^-1 。

The results are as follows:

as shown in fig. 8A, for the constructed sensor cyclic voltammograms at different pH, it can be seen from the figure that the peak current increased first and then decreased with increasing pH, with the best redox peak current at pH = 3.6.

Furthermore, as the pH increases, the oxidation-reduction peak potential shifts negatively, as shown in FIG. 8B, and it is seen that there is a good linear relationship between the peak potential and the pH, and the linear equations are: epa = -0.057pH-0.12 (R = 0.9916) and Epc = -0.045pH-0.23 (R = 0.9964). The slopes of the calibration curves were-0.057V and-0.045V, respectively, which are close to the theoretical value of-0.0592V, indicating that the electron transfer number and the proton transfer number during the reaction are consistent. According to d _Ep /d _pH =2.303mRT/nF equation, the ratio of m/n can be calculated to be 0.95 and 0.75 for the oxidation process and the reduction process, respectively, further illustrating that the electron transfer number and the proton transfer number are equal during the reaction.

Therefore, the pH of the acetic acid buffer solution was 3.6, which is the optimum value.

Example 5

Firstly, using a proper amount of Al for a Glassy Carbon Electrode (GCE) ₂ O ₃ The powder was polished to a mirror surface on a chamois leather, rinsed clean with distilled water and then blown dry with nitrogen. 2, 3, 4, 5, 6, 7, 8 and 9 μ L of the N-rGO-ZnO/Au nano-material prepared in the embodiment 1 are respectively taken to modify the glassy carbon electrode, dried at room temperature and stored for later use.

Chrysophanol was detected at a concentration of 1.0mg/mL using the electrochemical sensor prepared in example 5.

The results are as follows:

as shown in fig. 9A, when the amount of N-rGO-ZnO/Au is increased from 2 μ L to 7 μ L, the oxidation peak current gradually increases, and the peak current is not significantly increased when the amount of the nanomaterial is continuously increased, which may be because the amount of the nanomaterial is increased, the ability of capturing chrysophanol is effectively improved, and when the amount of the nanomaterial is increased to a certain extent, the active sites of the nanomaterial on the surface of the electrode are already substantially captured by chrysophanol, so that the peak current is not increased when the amount of the nanomaterial is continuously increased.

Therefore, the dosage of the N-rGO-ZnO/Au nano material is 7 mu L.

Secondly, we also investigated the effect of enrichment time on chrysophanol detection.

As shown in fig. 9B, the peak current increases first and then remains substantially unchanged with the increase of the enrichment time, a large amount of chrysophanol is enriched on the surface of the electrode with the increase of the enrichment time, the enrichment reaches saturation at 6min, the enrichment time is continued to be prolonged, and the current value of the oxidation peak is not increased, so the enrichment time is selected to be 6min.

Example 6

Firstly, using a proper amount of Al for a Glassy Carbon Electrode (GCE) ₂ O ₃ The powder was polished to a mirror surface on a chamois leather, rinsed clean with distilled water and then blown dry with nitrogen. And (3) taking 7 mu L of the N-rGO-ZnO/Au nano material prepared in the embodiment 1 to modify the glassy carbon electrode, airing at room temperature, and storing for later use.

The chrysophanol with different concentrations (1.57, 2.36, 3.93, 5.51, 7.08, 8.65, 11.80, 15.73, 21.63 and 27.53 mu M) is detected by adopting N-rGO-ZnO/Au/GCE, and the enrichment time is selected to be 6min.

The results were as follows:

as shown in fig. 10A, the oxidation peak current increased with increasing chrysophanol concentration;

as can be seen from FIG. 10B, the oxidation peak current of chrysophanol has a good linear relationship with the concentration of chrysophanol, and the linear equation is Ipa = -1.09c-1.47 (R) ₂ = 0.9968), the linear range is 1.57 to 27.53 μ M, the detection limit is 0.49 μ M (S/N = 3), and the result shows that the constructed sensor can well detect chrysophanol.

Example 7

Drying and pulverizing radix et rhizoma Rhei, weighing 50mg medicinal powder, adding 25mL ethanol, and ultrasonic extracting for 30min. Centrifuging to obtain extractive solution, and diluting with ethanol to 50.0 mL.

In order to evaluate the feasibility of the method, a sensor constructed by a standard addition method is adopted to detect and research chrysophanol in the rhubarb medicinal material, and the extracting solution is diluted by 5 times.

Chrysophanol was detected using the electrochemical sensor prepared in example 2, the enrichment time was selected to be 6min, and the pH of the added acetic acid buffer solution was 3.6.

The actual sample is analyzed by adopting a standard addition method, and the specific operation method is as follows: measuring the content of chrysophanol in the rhubarb extract by adopting a differential pulse voltammetry method, then adding 5 mu M chrysophanol standard solution, measuring the total chrysophanol content in the solution again, and calculating the recovery rate of the sample according to the following formula: recovery = (measured amount-sample content)/addition, 3 times in parallel. According to the method, 10.0 μ M and 15.0 μ M chrysophanol standard solutions are respectively added for measurement and the recovery rate is calculated. The results are shown in Table 1, and the chrysophanol content in the rhubarb is 3.85 mg/g ^-1 And the recovery rate is between 98.8 and 102.6 percent, which shows that the electrochemical sensor constructed in the embodiment can be applied to the detection of chrysophanol in the rhubarb medicinal material.

Table 1 recovery experiments (n = 3).

The N-rGO-ZnO-Au multifunctional composite nanomaterial is successfully prepared by adopting the method disclosed by the embodiment of the invention, the prepared nanomaterial is characterized by adopting TEM, XPS and XRD, the prepared N-rGO-ZnO-Au nanomaterial is used for constructing an electrochemical sensor to detect chrysophanol, and the result shows that the N-rGO-ZnO-Au has better electrochemical activity and can realize the detection of chrysophanol, the linear range of the detection is 1.57-27.53 mu M, and the detection limit is 0.49 mu M, and the sensor disclosed by the invention can successfully detect chrysophanol in a rheum officinale medicinal material.

The above description is only a preferred form of the invention, and it should be noted that it is possible for a person skilled in the art to make several variations and modifications without departing from the inventive concept, and these should also be considered as within the scope of the invention.

Claims

1. The electrochemical detection method of chrysophanol is characterized by comprising the following steps:

pulverizing radix et rhizoma Rhei to obtain medicinal powder;

dissolving the medicinal material powder in ethanol, and performing ultrasonic extraction to obtain a medicinal material extracting solution;

detecting the medicinal material extracting solution by an electrochemical sensor, wherein,

the electrochemical sensor is a glassy carbon electrode modified by a composite nano material, and the composite nano material is formed by mixing an Au nano-loaded ZnO nanorod with N-doped graphene;

the detection method is differential pulse voltammetry or cyclic voltammetry, and the electrode enrichment time is 1-6 min.

2. The method according to claim 1, further comprising a step of diluting the extract with ethanol by 2 to 10 times.

3. The detection method according to claim 2, wherein the medicinal material extract is diluted by 5 times.

4. The method of claim 1, further comprising adding an acetic acid buffer solution, wherein the pH of the acetic acid buffer solution is from 3 to 5.6.

5. The method according to claim 4, wherein the pH of the acetic acid buffer solution is 3.6.

6. The detection method according to claim 1, wherein the enrichment time of the electrode is 6min.

7. The detection method according to claim 1, wherein the Au nanoparticles have a particle size of 5 to 100nm.

8. The detection method according to claim 7, wherein the Au nanoparticles have a particle size of 25 to 30nm.

9. The detection method according to claim 1, wherein the ZnO nanorods have a length of 10 to 100nm.

10. The detection method according to claim 9, wherein the ZnO nanorods are 15 to 30nm in length.

11. The detection method according to claim 1, wherein the graphene is selected from reduced graphene oxide, graphene oxide or a mixture thereof, and the weight ratio of the Au nano-loaded ZnO nanorods to the N-doped graphene is 20:1 to 50.

12. The detection method according to claim 11, wherein the weight ratio of the Au-loaded nano ZnO nanorods to the N-doped graphene is 30.

13. The method of claim 1, further comprising a post-mixing sonication step, wherein the sonication power is from 100 to 500W.

14. The detection method according to claim 13, wherein the ultrasonic power is 200W and the ultrasonic time is 1 to 24h.

15. The detection method according to claim 14, wherein the ultrasound time is 6h.

16. The detection method as claimed in claim 1, wherein the ZnO nanorods are prepared by the following steps:

dissolving KOH in an alcohol solvent, and adding the alcoholic solution of the zinc acetate;

volatilizing nitrogen and concentrating to obtain a concentrated solution;

aging the concentrated solution at 40-60 ℃ for 10-24 h;

standing and separating to obtain the ZnO nano rod.

17. The detection method as claimed in claim 1, wherein the Au nano-loaded ZnO nanorod is prepared by the following steps:

dispersing the ZnO nano-rod in a trisodium citrate solution to obtain a ZnO nano-rod dispersion liquid;

addition of a chloric acid solution of Au metal: HAuCl ₄ Reacting the solution for 10 to 24 hours;

and carrying out centrifugal separation to obtain the Au-loaded nano ZnO nanorod.

18. The detection method according to claim 1, wherein the amount of the composite nanomaterial used is 2 to 7 μ L.

19. The detection method according to claim 18, wherein the amount of the composite nanomaterial used is 7 μ L.