CN112961392A

CN112961392A - Preparation method of bionic layered material based on microbial mineralization

Info

Publication number: CN112961392A
Application number: CN202110262491.7A
Authority: CN
Inventors: 竹文坤; 陈涛; 何嵘; 杨帆; 雷佳; 刘欢欢; 周莉; 白文才
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2021-03-10
Filing date: 2021-03-10
Publication date: 2021-06-15
Anticipated expiration: 2041-03-10
Also published as: CN112961392B

Abstract

The invention discloses a preparation method of a bionic layered material based on microbial mineralization, which comprises the following steps: firstly, preparing an insoluble chitosan layered framework by taking chitosan as a raw material, and screening high-efficiency mineralized bacteria; preparing high-concentration somatic cells by using the optimized mineralized culture medium, and constructing a micro-nano layered framework-mineralized bacterium system; and then, periodically dropwise adding a mineralization culture solution in the constructed micro-nano layered framework-mineralization bacterium system to perform a mineralization experiment, and carrying out microorganism induction on calcium carbonate mineralization to prepare the biomimetic layered material based on microorganism mineralization. The invention utilizes the microorganism to induce the mineralization of calcium carbonate in the nacre-like micro-nano layered framework to prepare the nacre-like composite structure material with three-dimensional macro scale, realizes the composite of organic and inorganic components and the construction of a multilevel structure, and has the characteristics of simplicity, mildness, high efficiency and universality compared with the traditional physical and chemical methods.

Description

Preparation method of bionic layered material based on microbial mineralization

Technical Field

The invention relates to the field of preparation of bionic materials, in particular to a preparation method of a bionic layered material based on microbial mineralization.

Background

Of the many biological structural materials, the nacre layer of seashells has received extensive attention from researchers due to its unique "brick-mud" microstructure, extremely high strength and good toughness. Inspired by the mechanical properties and structural models of natural shells, researchers at home and abroad have made an important progress in the preparation of high-performance shell-like pearl layer composite structural materials. At present, the preparation of the shell-like pearl layer structure material mainly adopts two strategies: one is a bottom-up strategy, namely the construction of a cross-scale multi-level complex structure is realized by assembling nano structure units from a micro-nano scale to a macro-scale step by step. According to the strategy, researchers have utilized different self-assembly technologies such as an alternate growth method, a layer-by-layer assembly method, a framework mineralization method and the like to prepare a series of high-performance shell-like pearl layer structure materials from micro-nano units such as alumina, graphene oxide, layered double hydroxide, nano clay, carbon nano tubes and the like. For example, the Shushu book macro topic group is obtained by simulating the growth process of natural mother-of-pearlAn artificial bionic structure material has chemical components and microstructures which are highly similar to natural mother-of-pearl, and has strength and toughness, the achievement is published in journal of science published in 10.7.10.354.107-110. furthermore, the Shushu Macro subject group uses calcium phosphate as an inorganic member block and sodium alginate polymer to self-evaporate and form a film, the shell-like material is prepared by hot pressing, the clay sheet is used as a structural unit, the shell-like artificial thin film material with the tensile strength reaching 400MPa is prepared by a method of alternately depositing the clay sheet and the polymer, but the preparation process of the strategy is complicated, the experimental condition requirement is high, the obtained thin film material is usually a thin film material, and some defects exist for realizing the macro-scale preparation of the shell-like pearl layer structure material, the other strategy is a top-down strategy, namely, a large number of nano construction units are assembled to form a large bulk block with a macro-scale oriented structure, then the inorganic or organic phase is introduced. Researchers have utilized construction methods such as ice templates and magnetic field induced arrangement, and assembled and prepared large-volume ordered framework structures by using aluminum oxide, hydroxyapatite, micro-nano plates loaded with superparamagnetic nano particles and the like as construction units, and then filled with organic or inorganic phases to prepare a series of high-performance shell-like pearl layer structure materials. For example, mixing Al₂O₃And hydroxyapatite is arranged into a layered framework structure by an ice template method, and then a polymer or an inorganic metal is filled into the framework to form the shell-like structure nano composite material with the fracture toughness of 30Mpam 1/2. The strategy can generally process samples with large quantity and obtain large-scale materials, but the high-temperature and other harsh post-processing processes are required, and the problems of difficult assembly preparation of a layered frame, difficult control of an ordered micro-nano structure and the like exist.

Although various high-performance shell-like nacreous layer structure materials are prepared by the two strategies, the perfect structure of a natural shell nacreous layer cannot be achieved; how to construct a multi-scale ordered structure spanning multiple scales and a shell-like nacreous layer structure material with excellent performance under mild conditions still remains a great challenge in the field. The existing research results show that the growth process of the shell pearl layer mainly relates to insoluble organic framework and soluble pearl layerSexual biomacromolecule, nucleation site and orientation growth, mineral bridge, amorphous precursor crystallization transformation and other factors. Especially, the insoluble framework composed of chitin, fibroin and the like plays an important role in forming a brick-mud structure in the pearl layer and improving the mechanical property. Recently, a multi-step biomimetic mineralization route is designed for the first time by secondary professor of ginger source at Xiamen university, a mineral seed layer stabilized by polyelectrolyte is successfully constructed under the condition of normal temperature and liquid phase, and a prismatic layer structure of calcium carbonate is constructed by an epitaxial mineralization method on the basis. This study has a great hint to understand the biomineralization mechanism. Besides the small molecule regulation, one of the most important reasons for the growth of aragonite crystals in the nacreous layer is that the framework is a layered structure, and the insoluble framework is mainly used as a hard template for crystal growth to control the aragonite crystals to grow in two-dimensional directions to form a plate structure. In the construction process of the shell pearl layer, a plurality of organic frameworks are formed firstly, and then the strategy of mineralization is carried out, so that important inspiration is provided for the synthesis of artificial materials. Microorganism-induced calcium carbonate deposition is a biomineralization that is widely present in nature, and is mainly achieved through the metabolic processes of three types of microorganisms: 1) photosynthetic microorganisms such as cyanobacteria; 2) sulfate reducing bacteria; 3) and microorganisms associated with nitrogen circulation, such as Bacillus, halophilic bacteria, Bacillus mucilaginosus, carbonate mineralized bacteria, Alternaria alternata, etc. In the three microorganisms for inducing the mineralization of calcium carbonate, the research on the microorganisms related to nitrogen circulation is more, and particularly, the microorganisms catalyze the hydrolysis and deposition of urea to obtain calcium carbonate. During mineralization, the negatively charged groups on the microbial cell wall can attract Ca²⁺As CaCO₃And (3) the precipitated nucleation sites, and simultaneously, the soluble protein generated by microbial metabolism regulate the crystal form and the morphology of the calcium carbonate. At present, the contents of researches on mineralization of calcium carbonate induced by microorganisms at home and abroad mainly focus on: screening various high-efficiency carbonate mineralization bacteria, and developing the research on the physiological and biochemical characteristics and growth and propagation rules of the carbonate mineralization bacteria, the influence of environmental factors (ion concentration, temperature, time, pH and the like) and a culture medium on the mineralization process; bacterial cells and metabolitesHow to regulate the nucleation growth, phase structure, micro-morphology and the like of calcium carbonate crystals; the method utilizes the microorganism to induce the mineralization of calcium carbonate to carry out material repair and environmental management, such as cement crack repair, stone cultural relic repair, heavy metal or radionuclide consolidation, foundation reinforcement, slope maintenance, desert solidification and the like. However, the application of the microorganism-induced calcium carbonate deposition to the preparation of the bionic structure material, particularly the preparation of the multi-scale and multi-level ordered structure macroscopic block material by combining the method with the assembly technology, has been reported.

In summary, many reports are made at home and abroad about shell-like layered structure materials and microbial induced calcium carbonate mineralization, but the combination of biomineralization and an assembly method for preparing a multi-scale multi-level ordered structure macroscopic block material is only reported. Aiming at the problems of complex preparation process, difficult control of ordered micro-nano structure, incapability of realizing macro-scale and large-scale preparation and the like of the current shell-like pearl layer structure material. The applicant is inspired by the growth mechanism of a natural pearl layer and combines the construction of an ordered micro-nano frame and the growth of induced crystals on the frame in combination with the assembling process of different dimensions based on the research foundation of the construction of a microbe-induced calcium carbonate mineralization and a bionic micro-nano structure material, proposes to construct a micro-nano layered frame-carbonate mineralization bacterium system, develops the research of microbe-induced calcium carbonate mineralization in the micro-nano frame structure, and aims to realize the composite of organic and inorganic components and the construction of a multi-level structure and prepare a macroscopic size pearl shell-like bionic composite structure material under mild conditions. However, the following scientific problems to be solved exist:

1) the micro-nano layered framework-mineralized thallus system multi-phase interface is to be further researched for microorganism-induced calcium carbonate crystal nucleation, growth regulation and control and a nano-scale interaction mechanism between a mineral crystal and the interface;

2) how the micro-nano layered space regulates and controls the nucleation, the oriented growth, the phase structure and the micro-morphology of the calcium carbonate crystal induced by the microorganism through the confinement effect needs to be deeply discussed;

3) the relationship between the interaction between the calcium carbonate induced and deposited by the microorganisms and the micro-interface of the micro-nano layered framework and the strength of the macroscopic material needs to be deeply analyzed.

Therefore, the construction of a nacre-like micro-nano layered framework-carbonate mineralization bacterium system and the development of microorganism-induced calcium carbonate mineralization in the micro-nano layered framework and mechanism research thereof become necessary.

Disclosure of Invention

Aiming at the problems, the invention provides a preparation method of a biomimetic layered material based on microbial mineralization, which utilizes microorganisms to induce calcium carbonate mineralization in a nacre-like micro-nano layered framework to prepare a nacre-like composite structure material with a three-dimensional macro scale, realizes the compounding of organic and inorganic components and the construction of a multi-level structure, and has the characteristics of simplicity, mildness, high efficiency and universality compared with the traditional physical and chemical methods.

The technical scheme adopted by the invention is as follows:

a preparation method of a bionic layered material based on microbial mineralization comprises the following steps:

s1, preparing an insoluble chitosan layered framework by taking chitosan as a raw material;

s2, determining an optimal mineralization culture medium and culture conditions, and screening high-efficiency mineralization bacteria;

s3, preparing high-concentration thallus cells by adopting the optimal mineralization culture medium, and constructing a micro-nano layered frame-mineralized bacteria system by using the chitosan layered frame and the high-concentration thallus cells;

s4, periodically dripping a mineralization culture solution into the constructed micro-nano layered framework-mineralization bacterium system to carry out a mineralization experiment, and carrying out microorganism induction on calcium carbonate mineralization to prepare the biomimetic layered material based on microorganism mineralization.

In a further embodiment, in step S1, the method for preparing the insoluble chitosan layered framework is as follows:

s11, under the condition of rapid magnetic stirring, adding chitosan powder into deionized water solution of glacial acetic acid with a certain volume percentage, continuously stirring, freezing and storing the sample after ultrasonic treatment, and preparing chitosan solution;

s12, assembling and fixing a steel plate, a PDMS mold and a plastic plate according to requirements, placing the steel plate, the PDMS mold and the plastic plate in a refrigerator at 4 ℃ for precooling, then precooling a chitosan solution to zero without freezing, placing the steel plate into the PDMS mold for flattening, inserting the lower end 1/3 of the steel plate into liquid nitrogen, enabling a temperature gradient to exist along the X direction and the Z direction, enabling ice crystals to grow along the XOZ direction to form a multilayer planar crystal, dividing solutes, namely chitosan, into multiple layers, placing the frozen material in a freeze dryer for drying, and observing the layered structure and the spatial scale of a chitosan block material through a scanning electron microscope;

s13, drying the dried chitosan layered frame under normal pressure, putting the dried chitosan layered frame into a methanol-acetic anhydride mixed solution, performing acetylation, washing to remove acid and the like, and immersing the chitosan layered frame into sterile water to obtain the insoluble chitosan layered frame.

In a further technical scheme, in step S2, the method for screening and obtaining the high-efficiency mineralized bacteria is as follows:

s21, transferring the preserved strain to a fresh test tube slant culture medium, culturing for 24h at 30 ℃, preserving for later use in a 4 ℃ refrigerator, selecting 5-ring lawn from the preserved slant culture medium by using an inoculating ring, inoculating into a triangular flask filled with a liquid seed culture medium, performing shake cultivation for 24h at 30 ℃, and preserving for later use in a 4 ℃ refrigerator;

s22, observing the physiological and biochemical characteristics and the morphology of bacterial colonies, optimizing the components of a thallus culture medium and culture conditions through single factor and orthogonal tests, increasing the number of viable bacteria per unit volume to achieve high-density culture, culturing thallus by using the optimized culture medium and culture conditions, sampling every 3 hours, counting samples, drawing a growth curve, and determining the optimal culture time;

s23, dissolving 20g/L glucose, 5g/L soyabean peptone and 0.5mol/L calcium nitrate in deionized water, packaging with a triangular flask, sterilizing, cooling, adding 20g/L urea into the triangular flask by a microporous filter membrane filtration sterilization method, and preparing a urea-calcium nitrate mineralization culture medium;

s24, inoculating liquid strain by using the urea-calcium nitrate mineralization, carrying out shake culture, standing, carrying out suction filtration, washing for 3 times by using distilled water and absolute ethyl alcohol, and carrying out vacuum drying to obtain a calcium carbonate mineralization powder sample.

In a further technical scheme, in step S3, the method for constructing the micro-nano layered framework-mineralized bacteria system comprises the following steps:

firstly, preparing high-concentration thallus cells, then taking out a chitosan micro-nano layered frame stored in sterile water on a hyperstatic table, pressing to remove water, immersing into high-concentration mineralized thallus cell liquid, placing in a shaking table at 200r/min for oscillation for 2h, taking out again, pressing to remove the thallus cell liquid, then placing in new high-concentration mineralized thallus cell liquid, repeating the operation for 3 times, observing the distribution uniformity of thallus in the frame by using an Olympus inverted microscope, and constructing a micro-nano layered frame-mineralized thallus system.

In a further technical scheme, the method for preparing the high-concentration somatic cells comprises the following steps:

preparing the optimal mineralized culture medium determined in the step S2, sterilizing, cooling, inoculating liquid seeds, performing shake culture at 30 ℃ for 24 hours, contrasting a bacterial growth standard curve, taking out bacterial liquid, performing high-speed freezing and centrifugal concentration on thalli, and cleaning for 3 times by using sterile water to obtain high-concentration thalli cell sap.

In a further embodiment, the mineralizing bacterial strain is bacillus pasteurii.

In a further technical scheme, in step S4, the method for preparing the biomimetic layered material based on microbial mineralization is as follows:

s41, placing the constructed micro-nano layered frame-mineralized bacteria block in a culture dish, then dropwise adding a urea-calcium nitrate mineralized culture solution, infiltrating, periodically dropwise adding the mineralized culture solution, placing the culture dish in an incubator at 30 ℃ after each treatment, repeating the steps for a plurality of times, taking out a sample, respectively cleaning 3 times with absolute ethyl alcohol and deionized water, and performing vacuum drying;

and S42, according to the steps, optimizing external factors by adopting a single-factor and orthogonal experiment method, and preparing the bionic layered material which is excellent in structure and performance and based on microbial mineralization by adopting the optimized factors.

The invention has the beneficial effects that:

1. the invention provides a new idea of combining assembly and mineralization by dividing the preparation process of the bionic material into two steps of ordered layered framework synthesis and crystal growth induction in the framework;

2. the invention applies the microorganism-induced calcium carbonate mineralization to the preparation of the nacre-like structure macroscopic block material, and solves a plurality of problems in constructing the multilevel ordered composite bionic structure macroscopic block material spanning multiple scales under mild conditions;

3. constructing a micro-nano layered framework-mineralized bacteria system, developing the research on the mineralization of microorganisms in the micro-nano layered framework with macroscopic scale, finding out the behaviors of the micro-nano layered confinement space, a multiphase interface and metabolites on the induction of the mineralization of calcium carbonate by the microorganisms and the action mechanism of the behaviors, butting the existing theoretical knowledge with the experimental research by combining a computer simulation method, and revealing the relation between the interaction of the micro interface and the strength of a macroscopic material;

4. the invention utilizes the microorganism to induce the mineralization of calcium carbonate in the nacre-like micro-nano layered framework to prepare the nacre-like composite structure material with three-dimensional macro scale, realizes the composite of organic and inorganic components and the construction of a multilevel structure, and has the characteristics of simplicity, mildness, high efficiency and universality compared with the traditional physical and chemical methods.

Description of the drawings:

FIG. 1 is a graph of the preparation and morphological features of the anisotropic cellular biomass-derived carbonaceous aerogel of example 1;

FIG. 2 is a macroscopic digital photographic image of the unique layered mineral bridge structures KA and KGA at different concentrations of GO in example 1;

FIG. 3 is a schematic diagram of the two-way freezing of the layered structure of the chitosan bulk in example 1;

FIG. 4 is a microscopic digital photographic image of the unique layered mineral bridge structures KA and KGA at different concentrations of GO in example 1;

FIG. 5 is a graph of the physicochemical characterization of the anisotropic cellular biomass-derived carbonaceous aerogel of example 1;

FIG. 6 is a high resolution XPS spectrum of example 1;

FIG. 7 is a graph of structural design and compressive elasticity characterization of the anisotropic cellular biomass carbonaceous aerogel of example 1;

FIG. 8 is a SEM image of the three-dimensional network structure of KGA-3 in example 1 (disorder);

FIG. 9 is an SEM image of KGA-3 after 80% compression recovery in example 1;

FIG. 10 is a graph comparing the electrical conductivity of the unique mineral bridge structure KGA-3 of example 1 with a prior art material;

FIG. 11 is a graph of the relationship between the frequency response and the output signal of a KGA-3 based strain sensor of example 1;

FIG. 12 is a graph of the electrochemical performance of KGA-3 measured in the three-electrode system of example 1;

FIG. 13 is a graph showing the effect of absorbing tall oil from KA and KGAs carbon aerogels in example 1.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Example 1:

firstly, preparing an insoluble chitosan layered framework:

s13, drying the dried chitosan layered frame under normal pressure, putting the dried chitosan layered frame into methanol-acetic anhydride mixed solution prepared according to different volume ratios, performing acetylation treatment at a certain temperature, performing post-treatment such as cleaning and deacidification, and immersing the chitosan layered frame in sterile water to obtain the insoluble chitosan layered frame. Adopting a soaking method to represent the swelling property by the mass and volume change of the material; FI-IR and Raman tests are carried out to test the acetylation reaction degree and surface groups; observing structural changes before and after reaction by a scanning electron microscope; zeta potential analyzer tests the surface potential of the material.

Secondly, screening high-efficiency mineralized bacteria (the mineralized bacteria strain selected in this example is bacillus pasteurii):

s22, observing physiological and biochemical characteristics and morphology of bacterial colonies, optimizing components (carbon sources, nitrogen sources, inorganic salts and the like) of a thallus culture medium and culture conditions (temperature, pH, rotating speed, inoculation amount and the like) through single-factor and orthogonal tests, increasing the number of viable bacteria in unit volume to achieve high-density culture, culturing thallus by using the optimized culture medium and culture conditions, sampling every 3 hours, counting samples, drawing a growth curve and determining the optimal culture time;

the method for observing the shape of the thallus comprises the following steps: washing the bacteria with 2% phosphate buffer solution, centrifuging, fixing 2.5% glutaraldehyde in a refrigerator at 4 deg.C for 4h, cleaning, and centrifuging; adding 100% ethanol, standing in a refrigerator at 4 deg.C for 4h, performing gradient dehydration for 15 min/time, centrifuging, tabletting, drying, spraying gold, and observing thallus morphology by scanning electron microscope; the enzymatic property of the pasteur bacillus is detected by a urea-phenol red method, and the enzymatic activity is tested by a urease kit.

Thirdly, constructing a micro-nano layered framework-mineralized bacterium system:

s31, preparing the optimal mineralization culture medium, sterilizing, cooling, inoculating liquid seeds, performing shake culture at 30 ℃ for 24 hours, contrasting a bacterial growth standard curve, taking out bacterial liquid, performing high-speed freezing and centrifugal concentration on the bacteria, and cleaning for 3 times by using sterile water to obtain high-concentration bacterial cell liquid, wherein the bacteria are in a stable stage at the moment and have the highest bacterial quantity and activity;

s32, taking out the chitosan micro-nano layered frame stored in sterile water on a hyperstatic table, pressing to remove water, immersing into high-concentration mineralized bacteria cell sap, placing in a shaking table at 200r/min for oscillation for 2h, taking out again, pressing to remove the bacteria cell sap, placing in new high-concentration mineralized bacteria cell sap, repeating the operation for 3 times, observing the distribution uniformity of bacteria in the frame by using an Olympus inverted microscope, and constructing a micro-nano layered frame-mineralized bacteria system.

Fourthly, preparing the bionic layered material based on microbial mineralization:

s42, adopting single-factor and orthogonal experimental method to treat external factors (Ca in mineralized culture medium) according to the steps²⁺And urea concentration, temperature, time and pH) and adopting the optimized factors to prepare the bionic layered material which has excellent structure and performance and is based on microbial mineralization.

The structural morphology, phase, porosity and distribution of the calcium carbonate crystal are characterized by adopting testing means such as TEM, SEM, XRD, X-CT and the like, and the mechanical properties of the material are tested by utilizing a nano-indenter and a three-point bending method.

In this embodiment, in step S21, the formula of the slant medium is: 3g/L beef extract, 10g/L, NaCl5 g/5 g/L peptone, 15g/L agar and 8.0 pH value.

In this embodiment, in step S21, the formula of the liquid seed culture medium is: 20g/L glucose, 10g/L, NaCl5 g/5 g/L peptone and pH 8.0.

This example designs a superelastic, ultra-lightweight konjac glucomannan/graphene oxide (KGM/GO) carbon aerogel (denoted KGAs) composed of many unique mineral bridge microscale structures arranged in parallel stacks. This unique hierarchical mineral bridge structure is obtained by applying a two-way freezing method to KGM/GO composites consisting of parallel plates. KGAs were obtained by carbonizing the composite at 1200 ℃ in an NH3 atmosphere. Unlike most previously reported biomass-derived carbon aerogels, the KGAs prepared have a combination of arbitrary shape and size, high surface area ratio, ultra-low density, ultra-recoverable compressibility, high electrical conductivity, high adsorption capacity, and excellent electrochemical performance.

In addition, this example shows the unique mineral bridge structure of KGAs observed by scanning electron microscopy (Zeiss, Germany). The TEM image was operated at an accelerating voltage of 100kV on H-7650 (Hitachi, Japan). The crystal structure of KGAs was further characterized by X-ray diffraction (PANalytical, the netherlands). Fourier transform infrared spectroscopy (Nicolet, u.s.a) and X-ray photoelectron spectroscopy (XPS) analysis (Kratos Analytical, Manchester, UK) were used to detect functional changes in KGAs. The resistance of KGAs was measured using a digital multimeter. Compression testing of KGAs was carried out on a materials testing machine (Instron 5565A, England). Raman spectroscopy (Renishaw & Lexel, Inc, UK) was used to determine the degree of graphitization of the KGA. The results of the correlation were analyzed as follows:

a schematic diagram of the synthesis of KGAs is shown in FIG. 1. To obtain the desired excellent biomimetic layered structure, dispersed GO was first added to dispersed KGM as a starting material under vigorous stirring. The KGM/GO homogeneous suspension was then frozen using a freeze casting technique. The oriented layered 3D structure is formed by ice crystal growth from bottom to top and the KGM/GO homogeneous suspension is discharged to the boundaries between ice crystals during freeze casting (as shown in fig. 2). KGM/GO nanocomposites were formed by freeze-drying the frozen KGM/GO, which were finally carbonized in flowing NH3 to provide KGA (as shown in figure 3). KGA can be formed in any size and shape by a silica gel mold, such as eiffel tower, cherry blossom, unicorn, windmill, round, pyramid, heart, cone, triangle, etc. (as shown in fig. 1b, 1 f). The feature of shape and size controllability allows the KGA to be used as a flexible sensor and electrode in the future.

From Scanning Electron Microscope (SEM) images of KGA (as shown in fig. 1 c-e), aligned lamellar three-dimensional structures can be observed with interconnected bridges parallel to the direction of ice crystal growth, which can greatly reduce capillary forces. The unique mineral bridge structure is very similar to the stem structure of natural water arrowroot, which is very helpful for improving mechanical properties. During compression, the stress may spread throughout the layer to avoid stress concentrations. The interconnecting bridges act as a number of "springs" between each of the laminar layers and are predominantly elastically deformed during the compression cycle. After compression, the unique mineral bridge aerogel can be fully restored to the original state without significant damage. The results of poplar et al indicate that the final compressive properties of the carbon aerogel depend on the weakest link in the random porous structure. Cracking at the weakest point during compression is most likely, resulting in no elastic deformation and poor elasticity, consistent with our experimental results. The above analysis results show that unique mineral bridge aerogels are more elastic than disordered aerogels because they have unique layered mineral bridges.

To further investigate the microstructure of KGA, Transmission Electron Microscopy (TEM) was used to characterize the samples. KGA showed a lamellar microstructure (as shown in fig. 1 g), which is consistent with the SEM results. High Resolution Transmission Electron Microscopy (HRTEM) analysis (as shown in fig. 1h,1 i) showed that KGA had a continuous porous structure. Furthermore, fig. 1h,1i show some lattice fringes in KGA, which correspond to graphite (002) planes, indicating a partially graphitic structure. The scanning electron microscope is combined with the TEM, and the KGA has a good layered three-dimensional mineral bridge structure. This feature is very suitable for increasing the specific surface area and the mechanical properties as well as the electrical conductivity. The prepared KA and KGAs have the ultralow density of 4.2-11.2mg/cm3, which is equivalent to that of refractory Carbon Nanofiber (CNF) aerogel [207] (4-6mg/cm3) and graphene sponge [208] (12mg/cm3), but slightly larger than that of ultralight aerogel [209] (UFA) (0.16mg/cm 3). A piece of square KGA-3(d ═ 1cm) can be stood on green asparagus (as shown in fig. 1 b). The density of the KGAs can be further reduced by adjusting the ratio of the aqueous GO and KGM solutions.

The crystal structures of KA and KGA were further characterized by X-ray diffraction (XRD). As shown in fig. 5a, the characteristic peaks for KA and KGAs appear at 25.9 ° and 43.8 °, due to the (002) and (101) planes of hexagonal graphite, respectively, and indicate diffraction from graphitic carbon. As shown in FIG. 5b, Raman spectroscopy was used to detect the defect levels of KA and KGAs. It can be seen that KA and KGAs clearly show two characteristic peaks near 1598.3cm-1 and 1349.1cm-1, corresponding to the G and D bands, respectively. The number of sp2 hybridized carbon atoms in KA and KGA is indicated by the G band (IG). In general, the defect density of a carbon material can be clearly reflected by the D/G intensity ratio (ID/IG). It is clearly observed that the value of ID/IG rises with increasing GO, revealing chemical cross-linking of the KGM molecules and GO nanoplates, leading to a decrease in order.

The chemical structures of KA and KGA were studied using FT-IR, as shown in FIG. 5 c. Many typical KGAs functional groups are, for example, CO (1037.9cm-1), C-O-C (1147.7cm-1), C ═ C (1593.3cm-1), CH (2920.3 and 1388.2cm-1) and-OH (3435.8 cm-1). The FTIR spectrum of KGA is very similar to KA. In addition, the absorption characteristic bands of 1037.9cm-1(C-O stretching vibration) and 2920.3cm-1 and 1388.2cm-1(C-H bending vibration) become very weak in strength due to the thermal decomposition of KGA.

The surface atomic composition and chemical functionality of KA and KGA-3 were further analyzed by XPS, as shown in fig. 5 d. Broad scan XPS spectra of KA and KGA-3 showed peaks of O1s, C1s and N1s at 531.1,286.1 and 398.3eV, respectively (FIG. 5 d). As shown in fig. 6b, the C1s spectrum of KA is broken down into four peaks at 283.9,284.7,285.1 and 285.9eV, corresponding to C-O, C-C, O ═ C-N and O-C ═ O fig. 6(a, b) shows that the C content changes dramatically with the C-C ratio as GO loading increases. The spectrum of N1s decomposed into three peaks at 398.9eV (pyridine-N), 399.9eV (pyrrole-N) and 401.5eV (graphite-N) (FIG. 6(c, d)). Due to electronic defects, pyridine-N donates its p-electrons to the graphene layer, which may improve the initial potential and electrochemical properties of other N species in the carbon material, and this property plays a decisive role in KGA-3. pyridine-N is an N atom that donates two p electrons to the graphene pi system, which is formed by the pyridine-N contribution; graphite-N is derived from substituting the C atom in the graphene honeycomb ring, indicating that the N atom is bound to the C-C bond of graphene. Therefore, KGA-3 can effectively introduce nitrogen-containing groups on the surface of the carbon material after carbonization, and the carbon material is doped with a proper amount of N, so that more chemically active sites can be provided, and the power density of the supercapacitor is promoted. The N doping process provides more electrochemically active area to facilitate a fast reversible faradaic reaction.

In addition to the unique biomimetic layered structure, KA and KGA were also found to form micropores in the biomimetic layered wall, indicating that KA and KGA are layered porous materials. The microporosity of KA and KGA was quantitatively characterized by a nitrogen adsorption-desorption isotherm. As shown in fig. 5e, the BET curve can be derived from different lines corresponding to relative pressures (P/P0) from 0 to 1.0. The BET specific surface area of KA was 611m2 g-1, however, as the GO content increased, the specific surface area of the KGAs increased to 873m2 g-1(KGA-1), 941m2 g-1(KGA-2) and 1009m2 g-1(KGA-3), respectively (FIG. 5 e). The pore size distribution of KA and KCA calculated by Barret-Joyner-Halenda model is shown in FIG. 5 b. The results show that KA and KGA consist mainly of micropores from 2.1 to 4.9nm (FIG. 5 f). The ultrahigh specific surface area is beneficial to improving the adsorption performance of the material.

The excellent mechanical properties are very important for KGA-3 in order to achieve the application of the material in various fields. Unordered KGA-3 has little resistance to compression and shows large energy dissipation in 1000 compression cycles (as shown in fig. 7a and 8), indicating that the carbon aerogel component used to construct these unordered KGA-3 is actually very brittle. Interestingly, KGA-3 with a mineral bridge structure has highly compressible mechanical properties perpendicular to the lamellar direction and can withstand large deformations without collapsing (as shown in fig. 8). Fig. 7b shows typical compressive stress-strain curves for layered KGA-3 with different strains (20%, 30%, 40%, 50%, 60% and 80%). There are two distinct stages in the overall loading process. KGA-3 with a mineral bridge structure exhibits linear elastic deformation at high compressive strains after inelastic hardening and densification shortly after low compressive strains. When the strain is less than 30%, the compressive stress gradually increases with the strain due to the elastic bending of the layered frame. The compressive strain further increased to over 60% due to the collision between the layered frames, thus showing a densified region with a rapidly increasing slope. More importantly, KGA-3 with a mineral bridge structure can withstand up to 80% compression and recover its original appearance after release of the compressive force (as shown in fig. 9). Furthermore, the load remains above zero and returns almost to the original position throughout the compression process, indicating the high elasticity and structural stability of KGA-3 with a mineral bridge structure.

The unique mineral bridge structure KGA-3 underwent continuous cyclic compression testing over 1000 load-unload cycles at 80% strain (as shown in fig. 7 b). After 1000 load-unload cycles, the unique mineral bridge structure KGA-3 still recovered its original appearance without cracking or collapsing. Only 0.03% deformation after 1000 cycles, much lower than most biomass-derived carbon aerogels and polymer foams. Furthermore, there was little reduction in the maximum compressive stress after 1000 load-unload cycles at 80% strain (as shown in fig. 7 b). The above results show the excellent mechanical properties of KGA-3, which are attributed to the unique mineral bridge structure. It is worth noting that the unique mineral bridge structure KGA-3 has more stable mechanical properties than other carbon aerogels. In addition, we tested the modulus of the unique mineral bridge structure KGA-3 at different compression ratios. The results show that the modulus of the unique mineral bridge structure KGA-3 reaches a maximum at a compression ratio of about 0.5. Furthermore, the modulus of the unique mineral bridge structure KGA-3 was reduced by only 5.71% after 1000 load-unload cycles at 50% strain (as shown in fig. 7 d). Analysis of the above results shows that the uniquely oriented mineral bridge structure provides a great improvement in the compressive properties of the carbon aerogel. The bridges between the layers give the carbon aerogel the ability to withstand large geometric deformations without collapsing. The above results are consistent with high experimental results.

The properties of mechanically robust unique mineral bridge structures KGAs can be further demonstrated by the promising elastic response conductivities. The conductivity of unique mineral bridge structure KGA-3 with a density of 4.2mg cm-3 was measured to be 12.9S m-1, which is superior to other biomass-derived carbon aerogels (as shown in FIG. 10). Notably, the KGAs obtained for the unique mineral bridge structure exhibited anisotropic conductivity (12.9 Sm "1 in the flake direction and 4.9S m" 1 perpendicular to the flake direction), which was attributable to the unique anisotropic unique mineral bridge structure.

KGA is expected to be used as an elastic conductor due to excellent high conductivity and compression property. When connected to a circuit using KGA, the LED lamp can be very bright. The brightness fluctuation of the LED lamp can be achieved by the compression and release of the KGA (as shown in fig. 11 a). Fig. 11a shows that the brightness of the LED lamp will increase with increasing KGA deformation. At the same time, the resistance has a sensitive response to the compressive strain of the KGA. The relationship between the change in resistance of KGA and the compressive strain was studied systematically. As shown in fig. 11b, the normalized resistance (R/R0) drops almost linearly to 9.3% by increasing the loading pressure on the KGA until the compressive strain increases to 50%. This phenomenon is attributed to the increase in contact points between the layered nanoplatelets during loading. When the load is removed, the contact area between the layered nanoplatelets is slightly smaller than the contact area of the original nanoplatelets due to slight depressions on the surface of the layered nanoplatelets, resulting in a mild increase in electrical resistance. Furthermore, after 20 compression tests at 50% strain, the R/R0 of KGA remained extremely stable, which means that KGA has a long service life and reliability as an elastic conductor (as shown in fig. 11 c).

The superelasticity of the KGA imparts to the KGA a function as a flexible piezoresistive sensor. FIG. 11e shows the change in Δ R/R0 for vertical output pressures from 0 to 20 kPa. In practice, the pressure obtained by accumulating weight on the surface area coincides with the pressure on the sensor. We generally define the sensitivity as S ═ Δ R/R0)/Δ P, and obtain a slope of about 0.022k/Pa by performing a rough linear fit over the use pressure region of 0 to 20 kPa. The gradual increase in conductivity with increasing pressure is attributed to the reduction in effective voids by the application of force. It can be seen that by applying different strain forces in successive times, the resistance changes proportionally to KGA-3.

FIG. 11f shows the relationship between the frequency response and the output signal of a KGA-3 based strain sensor. It is noteworthy that the electrical response of the strain sensor has excellent stability durability with 50% strain in the frequency range of 0.05 to 5 Hz. The strong layered framework ensures that the peak of the electrical signal almost coincides with the increase in frequency. These extraordinary properties enable us to detect a wide variety of sensory signals from small deformations (vocalization) associated with various body movements to large-scale muscle movements.

In addition to the flexible piezoresistive sensor, the KGA may also be used as a supercapacitor. The electrochemical performance of the obtained KGA-3 in a three-electrode system in a 1.0M KOH electrolyte is discussed. FIG. 12a shows the CV curves of KGA-3 over a potential range of-1.0 to 0V for various scan rates ranging from 5 to 50 mV/s. As the scan rate increased, the CV showed no significant change and maintained a clear rectangle even at 50mV/s, indicating good rate performance of KGA-3. The GCD curves verify the capacitive performance at different current densities. At a current density of 1A/g, the specific capacitance of the KGA-3 electrode was 287.6F/g, consistent with the CV results (as shown in FIG. 12 b). KGA-3 has a higher specific capacitance than other materials. This is mainly due to the large specific surface area and nitrogen doping, which can alter the electronic properties of the carbon nanoplatelets and facilitate the transfer of electrolyte ions into the interior of the carbon material. Surprisingly, at this current density of 20A/g, the capacitance was still 129.4F/g, which corresponds to a capacity retention of about 44.993%, and showed excellent rate performance (shown in FIG. 12 c).

Electrochemical Impedance Spectroscopy (EIS) is a powerful means to study the resistance between the electrolyte and the electrodes and the internal resistance of the electrodes. FIG. 12d shows the Nyquist plot for KGA-3 over a frequency range of 0.01Hz to 1 MHz. The nyquist diagram is composed of straight lines, semicircles and high frequency regions in the low frequency region. KGA-3 has a unique layered structure and a high specific surface area, and promotes the migration and migration of ions in an electrolyte, thereby improving electrochemical performance.

KA and KGAs carbon aerogels are well suited for absorbing and recovering oils and organic solvents from wastewater due to their super-hydrophobicity/lipophilicity (CAwater-151.3, CAoil-0) and high surface area (see FIG. 13). Furthermore, the biomimetic layered structure of KGAs carbon aerogel provides a large volume for the storage of the absorbed liquid. KGA-3 carbon aerogel can be used to selectively absorb oil slick on water surface within 20 seconds (as shown in fig. 13 a). KGAs-3 carbon aerogel having an oil content remains floating on the water surface due to its super-hydrophobicity, ultra-low density, and thus can be easily removed from the water after the oil is completely absorbed, resulting in clean water. Furthermore, KGAs carbon aerogels can be used for efficient oil/water separation (as shown in fig. 13 b). In addition, KA and KGAs carbon aerogels can absorb various oils and organic solvents with absorption capacities of up to 54-360 times their own weight, depending on the density and viscosity of the oil (as shown in FIG. 13 d). Even in oil-water systems, the oil absorption capacity of KA and KGAs carbon aerogels hardly decreases due to competitive adsorption of water. The change in oil absorption capacity of these materials is consistent with the change in water contact angle (as shown in fig. 13c, 13 d). Compared with other biomass carbon materials, KGA-3 carbon aerogel shows better performance in oil absorption. In a batch experiment for oil-water separation, once the oil/water mixture was poured into the home-made injector apparatus, the oil was rapidly absorbed or permeated by the KGA-3 carbon aerogel and fell into the beaker below it (as shown in FIG. 13 b). At the same time, more and more water was collected on the surface of the KGA-3 carbon aerogel. After equilibrium absorption, the absorbed oil must be collected from the KGA-3 carbon aerogel in order to be used in the next cycle. At the same time, water was collected and drained on the surface of the KGA-3 carbon aerogel. The separation process is completely dependent on the gravity of the oil/water mixture without any external forces.

The recyclability of KA and KGAs and the recyclability of contaminants are key criteria for practical oil cleaning applications. After 10 cycles, the saturated adsorption of the pump oil was still maintained at about 272 g/g. The recoverability of KA and KGAs carbon aerogels by combustion of the pump oil is summarized in fig. 13 e. The results clearly demonstrate the good reusability of KA and KGAs carbon aerogels, indicating that KA and KGAs carbon aerogels can be used as efficient oil adsorbents for practical use.

In summary, this example draws inspiration from the unique structure of natural water arrowroot stems and uses low cost biomass as the main raw material, replicates this natural water arrowroot stem-like structure in anisotropic carbonaceous plants, i.e. a layered structure with mineral bridges, imparting many interesting properties to the carbonaceous gel, including light weight (4.2mg/cm3), super-elasticity (maximum strain 80%, almost no loss after 1000 compression cycles), high electrical conductivity (12.9S/m) and high oil absorption capacity (up to 360 g/g). . By collecting these characteristics in one body, KGA is able to detect pressure stimuli at different frequencies, indicating its potential application in flexible piezoresistive sensors. Furthermore, KGAs shows good electrochemical performance with a maximum specific capacitance of 287.6F/g at a current density of 1A/g. KGAs with a series of excellent characteristics is expected to be widely applied to the aspects of sensors, energy storage, adsorbents, elastic conductors and the like in the future.

Example 2:

a micro-nano layered space microbe mineralization and an analysis method of an action mechanism thereof mainly comprise the following three aspects:

firstly, carrying out limited domain crystallization analysis on a micro-nano layered space, wherein the layered space has a limited domain effect in the microbial mineralization process of a micro-nano layered framework, and spatially regulating and controlling the oriented growth of a calcium carbonate crystal and the mass transfer of nutrient substances; the multiphase interface mainly regulates and controls crystal nucleation sites; the metabolite mainly regulates and controls crystal growth and phase structure, and the three synergistically regulate and control the mechanism of the whole mineralization process of microorganisms.

The specific method comprises the following steps:

selecting a constructed micro-nano layered frame-mineralized bacterium block as a test group, setting a control group, dropwise adding a urea-calcium nitrate mineralized culture medium on the test group and the control group block, periodically dropwise adding a mineralized culture solution, placing a culture dish in an incubator at 30 ℃ after each treatment for culturing for 3d, 6d, 9d, 12d and 15d, respectively taking out a sample, washing the sample for 3 times by using absolute ethyl alcohol and deionized water, performing vacuum drying, and analyzing and researching the microscopic morphology and size of the mineralized crystal at different times in a system by adopting SEM and TEM; analyzing the change condition of the crystal phase structure in a system by XRD; AFM is adopted to detect the crystal deposition form in the limited space in situ. And comparing the results of the test group and the control group, and analyzing a mechanism for regulating and controlling the orientation growth of the mineralized crystal by the lamellar confinement space.

Among them, the control group needs to be treated as follows:

the method comprises the steps of placing calcium carbonate mineralization induced by microorganisms in an open space, mineralizing the surface of an acetylated chitosan membrane, pouring a deaerated chitosan solution into a plastic culture dish, unfolding, naturally evaporating and drying at room temperature to form a membrane, performing acetylation treatment according to a micro-nano layered framework method, performing ultraviolet sterilization on the prepared membrane, placing the membrane in the culture dish, coating high-concentration thallus cell liquid on the surface of the membrane in a super clean bench, air-drying, repeating for 3 times, and observing the distribution uniformity of thallus on the surface of the membrane by using an optical microscope.

Secondly, multiphase interface mineralization reaction analysis, and exploring the multiphase interface as Ca in the process of microorganism-induced calcium carbonate mineralization²⁺The action site can effectively induce crystal nucleation and growth, and the chitosan interface, the cell membrane interface and the synergistic effect of the two interfaces.

The specific method comprises the following steps:

chitosan interface: coating a certain amount of urease solution on the surface of the acetylated chitosan membrane, air-drying, dropwise adding a mineralization culture solution on the surface of the membrane, inducing mineralization at 30 ℃ for 0.5h, 1h, 1.5h, 2h and 2.5h, cleaning a sample, and vacuum-drying;

cell membrane interface: inoculating mineralized bacteria to a mineralized culture medium, culturing for 6h, 12h, 18h, 24h and 30h in a biochemical incubator at the temperature of 30 ℃, respectively cleaning precipitates, and drying in vacuum;

the interface synergy is as follows: coating mineralized bacteria cells on the surface of an acetylated chitosan membrane, dropwise adding mineralized culture solution to perform a mineralization experiment, culturing for 6 hours, 12 hours, 18 hours, 24 hours and 30 hours in a biochemical incubator at the temperature of 30 ℃, cleaning a sample, and drying in vacuum;

characterization test:

discussion of Chitosan and cell multiphase interface Ca from molecular microstructure by XPS and XAFS²⁺The content of (2), the change of electron binding energy of the inner layer of the element and the occurrence state; AFM in-situ detection of multiphase interface crystal deposition morphology; SEM and TEM analyze the microscopic morphology and size of the interface mineralized crystal; XRD analysis is carried out on the change situation of the phase structure of the mineral crystal; chitosan, mineralized bacteria and Ca in FT-IR and Raman analysis system²⁺Radical changes before and after the action;and (5) analyzing the surface electrical property change condition by a Zeta potentiometer.

And analyzing the nucleation and growth mechanism of the multiphase interface induced mineralized crystal through result comparison.

And thirdly, the metabolic products are used for regulating and analyzing mineralization and exploring the influence of the metabolic products of the mineralized bacteria on the mineralization process.

The specific method comprises the following steps:

analyzing the influence of mineralized bacteria metabolites (such as exopolysaccharides, organic acids, proteins and the like) on the phase structure and growth of the crystal in the layered space and the membrane surface at different time by using a liquid chromatography mass spectrometer (HPLC-MS) and a full-automatic biochemical analyzer; carrying out thermogravimetric analysis on the content of organic matters in the crystal; XRF crystal chemical composition analysis; FT-IR and Raman analysis of the effect of the metabolite groups on the crystals.

The above-mentioned embodiments only express the specific embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A preparation method of a bionic layered material based on microbial mineralization is characterized by comprising the following steps:

2. The method for preparing a biomimetic layered material based on microbial mineralization of claim 1, wherein in step S1, the method for preparing the insoluble chitosan layered framework is as follows:

3. The method for preparing a biomimetic layered material based on microbial mineralization of claim 1, wherein in step S2, the method for obtaining high-efficiency mineralized bacteria by screening comprises the following steps:

4. The preparation method of the biomimetic layered material based on microbial mineralization of claim 1, wherein in step S3, the method for constructing the micro-nano layered framework-mineralized bacteria system comprises the following steps:

5. The preparation method of the biomimetic layered material based on microbial mineralization, according to claim 4, is characterized in that the method for preparing the high-concentration somatic cells is as follows:

6. The method for preparing a biomimetic layered material based on microbial mineralization of any one of claims 1-5, wherein the strain of mineralized bacteria is Bacillus pasteurii.

7. The method for preparing a biomimetic layered material based on microbial mineralization according to claim 1, wherein in step S4, the method for preparing the biomimetic layered material based on microbial mineralization is as follows: