Spongy chitosan composite material, preparation method thereof, SERS (Surface Enhanced Raman Scattering) substrate material and application thereof

Abstract

The invention discloses a spongy chitosan composite material, a preparation method of the spongy chitosan composite material, an SERS (Surface Enhanced Raman Scattering) substrate material and application of the SERS substrate material and belongs to the field of photoelectric devices. The spongy chitosan SERS substrate material is composed of chitosan nanofibers (CS-NFs), precious metal nanoparticles (NB-NPs), polydopamine (PDA) and physical crosslinking molecule DNA and is obtained through a layer-by-layer self-assembly method, due to the 3D porous structure, the spongy chitosan SERS substrate material has the characteristic of high specific surface area, the sensitivity and high repeatability of SERS signals can be ensured, the spongy chitosan SERS substrate material is superior to the raw material bio-based characteristics, and the spongy chitosan SERS substrate material has the advantages of being simple in preparation process, low in cost and good in application prospect. The method can be applied to the field of traditional Chinese medicinal material identification, the surface of the traditional Chinese medicinal material is wiped or the traditional Chinese medicinal material is put into a traditional Chinese medicinal material soaking solution for sampling, then Raman spectrum testing is carried out, and before use, an alkaline or acidic buffer solution can be sprayed on the spongy chitosan SERS substrate material; then, the capturing capacity of cationic or anionic dyes in the dyed traditional Chinese medicinal materials is further improved.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic devices, and in particular to a sponge-like chitosan composite material and a preparation method thereof, a SERS substrate material and applications thereof. Background Art

[0002] Traditional Chinese medicine is a treasure of Chinese civilization and plays an important role in the health of the whole people. Zhejiang ranks third in the country in terms of the total amount of authentic medicinal materials resources. However, fake and inferior Chinese medicinal materials have always been a "chronic disease" that hinders the development of the Chinese medicine industry, mainly concentrated in dyeing and adulteration. Traditional Chinese medicine dyeing mostly uses artificial synthetic pigments, which have side effects such as high toxicity, "three-cause" and high residue. Traditional Chinese medicine dyeing mostly uses artificial synthetic pigments, whose molecular structure contains chromophores such as azo, vinyl, benzene ring and acid / base auxochromophores, and has different hydrophilic and hydrophobic properties. In addition, it also contains some inorganic substances such as malachite green (lead chromate). At present, there are 83 methods for testing adulteration of traditional Chinese medicine dyeing approved and issued by the state. The relatively mature paths include: ① Physical and chemical identification method, which mainly refers to color change and precipitation reaction. For example, commercial rapid detection kits mainly use edible pigments and non-edible pigments to qualitatively identify the different adsorption forces of test cotton; ② High performance liquid chromatography (HPLC). HPLC has the advantages of high sensitivity and good separation effect. It is currently the most widely used and most studied method, and it is also a commonly used method in national standards. However, the current national standard for HPLC mainly targets 1 to 5 dyes in more than 10 single medicinal materials, and the HPLC test results need to be compared with the standard sample, which is not suitable for the determination of complex unknown samples. In addition, there have been reports in recent years on the use of infrared spectroscopy, mass spectrometry and its combined technology, fluorescence spectroscopy, immunoassay, etc. in the detection of artificial synthetic pigments. However, in view of the complex composition, random variability, and high timeliness requirements of the monitored objects, the commonly used technologies can no longer meet the testing needs due to the shortcomings of complex operation, time-consuming analysis, and high cost.

[0003] Surface enhanced Raman spectroscopy (SERS) is a qualitative and quantitative analysis method based on the principle of Raman scattering. In the past 50 years, it has gradually matured with the development of laser technology, inductively coupled detectors and nano-preparation technology, and has emerged in the fields of environmental, chemical and biological analysis. In view of the characteristics of SERS, its application in the detection of dyeing of Chinese herbal medicines has the following potential advantages: ① Simple pretreatment: solids, liquids, colloidal ointments, etc. can be directly measured, with less sampling, especially suitable for precious Chinese herbal medicine samples; ② Large amount of information: With fingerprint spectrum characteristics, it can realize rapid detection of unknown samples; ③ Low detection limit: It can realize ultra-trace component analysis and even single-molecule detection to avoid major drug safety accidents. At present, the research on dye detection using SERS technology at home and abroad has shown an increasing trend year by year. However, it is still challenging to prepare SERS substrates with high sensitivity and good signal reproducibility in batches and in a controllable manner.

[0004] Chitosan, as the biomass polymer with the largest reserves in the ocean, has natural advantages such as being renewable, insoluble in general solvents, thermally stable, biocompatible and degradable. At the same time, chitosan itself has a large number of functional groups, which facilitates chemical modification and is expected to achieve specific effects with different target molecules, thus having a wide range of potential applications. Summary of the invention

[0005] In view of the problems that the existing authenticity identification of traditional Chinese medicines has poor timeliness, complex pre-treatment, and is not convenient for large-scale detection, the present invention provides a sponge-like chitosan composite material and a preparation method thereof, a SERS substrate material and an application thereof. The sponge-like DNA / NB-NPs@PDA@CS-NFs composite material is obtained by a self-assembly method by utilizing the abundant hydroxyl and amino groups of chitosan and the adhesion capture effect of polydopamine. The capillary action and high specific surface capture ability of the sponge-like material can be utilized to identify the surface of the traditional Chinese medicine by wiping the surface of the traditional Chinese medicine or adding the water solution soaked in the traditional Chinese medicine to the surface of the sponge, and then performing a Raman spectrum test.

[0006] In order to achieve the above technical objectives, the present invention provides a sponge-like chitosan composite material and a preparation method thereof. The specific technical scheme is as follows:

[0007] A sponge-like chitosan composite material, which is composed of chitosan nanofibers CS-NFs, noble metal nanoparticles NB-NPs, polydopamine PDA, and physically cross-linked molecules DNA; the CS-NFs are 200 nanometers to 3 micrometers in length, the NB-NPs are 10 to 100 nanometers in particle size, PDA is coated on the surface of CS-NFs to form a PDA@CS-NFs structure, NB-NPs are coated on the outside of PDA@CS-NFs to form a NB-NPs@PDA@CS-NFs structure, and are cross-linked with DNA molecules to self-assemble into a sponge-like DNA / NB-NPs@PDA@CS-NFs composite material.

[0008] Furthermore, in the sponge-like DNA / NB-NPs@PDA@CS-NFs composite material, the mass proportion of NB-NPs is 5-10%, and the mass proportion of DNA is 1-3%.

[0009] A method for preparing the spongy chitosan composite material comprises the following steps:

[0010] Step 1, dispersing CS-NFs in a solution containing dopamine hydrochloride and a buffer solution of Tris-HCl, homogenizing by ultrasound, standing for 24 hours, and dialyzing to obtain a PDA@CS-NFs dispersion;

[0011] Step 2, silver nitrate or chloroauric acid is added to the PDA@CS-NFs dispersion alone, or is added to the PDA@CS-NFs dispersion in sequence, and then sodium borohydride is added for reduction, and dialyzed to obtain a NB-NPs@PDA@CS-NFs dispersion;

[0012] Step 3: Concentrate the NB-NPs@PDA@CS-NFs dispersion to a mass concentration of 15-25%, then add DNA, stir and let stand for self-assembly to obtain a DNA / NB-NPs@PDA@CS-NFs dispersion, and then freeze-dry to obtain a sponge-like DNA / NB-NPs@PDA@CS-NFs composite material.

[0013] Another object of the present invention is to provide a method for preparing a sponge-like chitosan SERS substrate material and its application. The specific technical scheme is as follows:

[0014] A sponge-like chitosan SERS substrate material is made of a sponge-like chitosan composite material.

[0015] Application of sponge-like chitosan SERS substrate material. The sponge-like chitosan SERS substrate material is used as a flexible SERS substrate material for identification of traditional Chinese medicines.

[0016] Furthermore, the surface of the Chinese medicinal materials is wiped by the flexible SERS substrate material or the Chinese medicinal materials soaking liquid is added to the surface of the flexible SERS substrate material, and then Raman spectroscopy is performed for identification.

[0017] Furthermore, before use, an alkaline or acidic buffer solution is sprayed on the sponge-like chitosan SERS substrate material to improve the capture ability of cationic or anionic dyes in dyed Chinese medicinal materials.

[0018] The raw materials used in the present invention are all bio-based, which has significant advantages in environmental protection and biosafety, and is very suitable for authenticity identification of precious medicinal materials to avoid contamination of Chinese medicinal materials during the detection process.

[0019] The base material used in the present invention is porous 3D sponge-like, and its main component is chitosan nanofiber. The material has good porosity, specific surface area, and flexibility, so that the base material can be directly wiped on the surface of Chinese medicinal materials for sampling, or the Chinese medicinal material extraction liquid is added to the base material for sampling, and then Raman spectroscopy is used for detection. The pre-treatment is simple and suitable for real-time monitoring of high-throughput and large-volume samples; the controllable preparation of the 3D high-density "hotspot" framework is realized, and the problem of signal reproducibility is solved while improving the detection limit. Based on the hot spots with high biocompatibility and no obvious toxicity of the material, it is particularly suitable for the authenticity identification of precious Chinese medicinal materials.

[0020] The base material used in the present invention is obtained through layer-by-layer self-assembly, and the high-density nanoparticles are evenly distributed in the sponge to ensure high sensitivity and good repeatability of the test results. At the same time, the hydroxyl, amino, and phosphate groups in the polydopamine, DNA, and chitosan nanofibers in the material are responsive to the acid-base environment, and the acidic or alkaline dyes can be selectively captured by changing the pH value of the test environment, thereby further improving the sensitivity of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The dispersion suspension of DNA / NB-NPs@PDA@CS-NFs and its TEM electron microscope image;

[0022] Figure 2 This is the SEM electron micrograph of DNA / NB-NPs@PDA@CS-NFs sponge aerogel;

[0023] Figure 3 Digital photo of DNA / NB-NPs@PDA@CS-NFs sponge aerogel;

[0024] Figure 4 This is the cyclic compression experiment diagram of DNA / NB-NPs@PDA@CS-NFs sponge aerogel;

[0025] Figure 5a is the SERS spectra of auramine O solutions with different concentrations;

[0026] Figure 5b is the linear fitting graph of SERS intensity plotted against log[auramine O (mg / ml)];

[0027] Figure 5c The SERS spectra of 10-3mg / ml auramine O solution obtained by randomly selecting 6 points;

[0028] Figure 5d At 1272cm -1 The SERS intensity observed at . DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] 0.15g Tris-HCl was added to the CS-NFs suspension, and 0.3g dopamine hydrochloride was added, and stirred for 12 hours. After dialysis, a PDA@CS-NFs suspension was obtained for later use; 0.2M AgNO3 solution was added to the PDA@CS-NFs suspension, and 0.01M NaBH4 solution was slowly added dropwise under stirring, and after dialysis, an Ag-NPs@PDA@CS-NFs dispersion was obtained; the Ag-NPs@PDA@CS-NFs dispersion was concentrated to 18% mass concentration, and then 0.01g / ml DNA was added, stirred and allowed to stand for self-assembly to obtain a DNA / NB-NPs@PDA@CS-NFs dispersion, the suspension was poured into a mold and placed in a -40℃ refrigerator overnight, and freeze-dried in a vacuum freeze dryer to obtain a DNA / NB-NPs@PDA@CS-NFs sponge aerogel.

[0031] like Figure 1-3 As shown, the nitrogen adsorption-desorption curve measured that the pore size of the sponge aerogel sample is mainly distributed in 1-5nm, partially distributed in 4-6nm, and the average pore size is 1.7nm.

[0032] like Figure 4 As shown in the figure, the mechanical properties of the aerogel were tested by testing the stress-strain curves of the sponge aerogel under different compression deformations. The DNA / NB-NPs@PDA@CS-NFs aerogel has strong recovery performance. In the process of 80% deformation compression, it still has good compression rebound ability under 33KPa pressure.

[0033] Different concentrations of R6G dye aqueous solution were added to DNA / NB-NPs@PDA@CS-NFs sponge aerogel, and then Raman spectroscopy was performed to detect that the enhancement factor of the substrate material was 5.4×10 7 , the detection limit reached 10 -8 The linear relationship between the signal peak intensity and concentration of R6G dye aqueous solution with different concentrations reached 0.9621.

[0034] Different concentrations of auramine O dye were used to dye the Chinese medicinal material Phellodendron chinense.

[0035] DNA / NB-NPs@PDA@CS-NFs sponge aerogel was used to wipe the surface of dyed Chinese medicinal materials, and then Raman test was performed, with a detection limit as low as 10 -5 mg / ml, the linear relationship between the signal peak intensity and concentration of auramine O dye at different concentrations reached 0.949, and the relative standard deviation of repeated tests reached 9.28%.

[0036] The selective detection of different charged dyes by the sponge aerogel substrate was not tested. Sunset yellow (SY, negative charge) and methylene blue (MB, positive charge) were selected as the research objects. -6 M. SY / MB aqueous solutions of equal concentrations were mixed, and the pH was adjusted to 4 and 11 by adding 0.1 M HCl or NaOH, respectively. It was found that at pH = 4 and pH = 11, the signal peak intensity of SY was 100 times that of the latter, and at pH = 11 and pH = 4, the signal peak intensity of MB was 50 times that of the latter.

Claims

1. A sponge-like chitosan composite material, which is composed of chitosan nanofibers CS-NFs, noble metal nanoparticles NB-NPs, polydopamine PDA, and physically cross-linked molecules DNA; characterized in that: The CS-NFs are 200 nanometers to 3 micrometers in length, the NB-NPs are 10 to 100 nanometers in size, PDA is coated on the surface of CS-NFs to form a PDA@CS-NFs structure, and NB-NPs are coated on the outside of PDA@CS-NFs to form a NB-NPs@PDA@CS-NFs structure, which are cross-linked with DNA molecules to self-assemble into a sponge-like DNA / NB-NPs@PDA@CS-NFs composite material.

2. The spongy chitosan composite material according to claim 1, characterized in that: In the sponge-like DNA / NB-NPs@PDA@CS-NFs composite material, the mass proportion of NB-NPs is 5-10%, and the mass proportion of DNA is 1-3%.

3. A method for preparing a spongy chitosan composite material as claimed in claim 1 or 2, characterized in that: The following steps are involved: Step 1, dispersing CS-NFs in a solution containing dopamine hydrochloride and a buffer solution of Tris-HCl, homogenizing by ultrasound, standing for 24 hours, and dialyzing to obtain a PDA@CS-NFs dispersion; Step 2, silver nitrate or chloroauric acid is added to the PDA@CS-NFs dispersion alone, or is added to the PDA@CS-NFs dispersion in sequence, and then sodium borohydride is added for reduction, and dialyzed to obtain a NB-NPs@PDA@CS-NFs dispersion; Step 3: Concentrate the NB-NPs@PDA@CS-NFs dispersion to a mass concentration of 15-25%, then add DNA, stir and let stand for self-assembly to obtain a DNA / NB-NPs@PDA@CS-NFs dispersion, and then freeze-dry to obtain a sponge-like DNA / NB-NPs@PDA@CS-NFs composite material.

4. A sponge-like chitosan SERS substrate material, characterized in that: The sponge-like chitosan composite material is prepared by using the sponge-like chitosan composite material according to claim 1 or 2.

5. The use of the sponge-like chitosan SERS substrate material as claimed in claim 4, characterized in that: The sponge-like chitosan SERS substrate material is used as a flexible SERS substrate material for identification of traditional Chinese medicines.

6. The use of the sponge-like chitosan SERS substrate material as claimed in claim 5, characterized in that: The surface of the Chinese medicinal materials is wiped with a flexible SERS substrate material or the Chinese medicinal materials soaked in water are dropped onto the surface of the flexible SERS substrate material, and then Raman spectroscopy is performed for identification.

7. The use of the sponge-like chitosan SERS substrate material as claimed in claim 5, characterized in that: Before use, an alkaline or acidic buffer solution is sprayed on the sponge-like chitosan SERS substrate material to improve the capture ability of cationic or anionic dyes in dyed Chinese medicinal materials.

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