This invention relates to a facile heteroepitaxial method for growing conductive zinc-catecholate frameworks on bio-fibers with biomimetic connections, which is beneficial to fabricate biocompatible and high-performance photodetectors and chemiresistors. In this method, a conductive layer was first introduced on the surface of polysaccharide bio-fibers, and then well-aligned zinc oxide nanoarrays was densely constructed on the bio-fibers by physiological coagulation mechanism. Employing fractional surface of zinc oxide nanoarrays as sacrifice, zinc-catecholate frameworks with hierarchical structure were prepared by low-temperature hydrothermal method. Benefiting from amplification effect of in-situ formed heterojunctions, promoted interfacial charge transfer is achieved, which enables the prepared material with stimuli-responsive properties, such as photoelectric and gas sensing. The obtained fibrous electronics have the advantages of good stability, environmental-friendly, flame retardancy, and high response.
Metal-organic frameworks (MOFs) are crystalline microporous materials in which metal ions or clusters are coordinated with organic linkers to form long-range ordered crystal structures. Owing to their structural and chemical tunability, the MOFs have been widely used in adsorption, energy storage, gas separation, catalysis. However, most MOFs are inherently insulated due to low-energy barriers for charge transfer, restricting their further application in electronics, such as sensors. With the emergence of new design and synthesis strategies, the preparation of electrically conductive MOFs has become current research hotspots. Conductive 2D MOFs based on through-space or through-bond mechanisms have emerged, the most prominent of which is M3(C18H6X6)2, where M=Cu, Ni or Fe; X=O or NH (C18H6O6=2,3,6,7,10,11-hexahydroxytriphenylene (HHTP); C18H6NH6=2,3,6,7,10,11-hexaiminotriphenylene (HITP)). These metal-catecholate frameworks with graphene-like honeycomb structure are atomically thin organic 2D materials with in-plane x-x conjugation.
Traditional growth of MOFs is based on solution reactions via the coordination between soluble metal salts and organic ligands. The resulting MOFs in the form of powders can drop-casted or spin-coated onto substrates for electronic applications, while the non-uniformity of MOFs and their significant mismatch with substrates inevitably affects the reliability of electronics. Therefore, in recent years, obtaining MOFs films on different material substrates has become a mainstream trend in MOFs synthesis and applications. Wang et al. (CN107602474A) reported a method for preparing metal-organic skeleton films (ZIF-8, ZIF-67) with specific orientation by a template method, in which metal oxide were electrodeposited on the surface of rigid substrates such as titanium sheets, conductive glass, stainless steel mesh, etc., and metal nitrates and organic ligands were used as resources. Liu et al. (CN110806430B) reported a method for in-situ synthesis of MOF films on permeable films of gas sensors, which improved sensor selectivity by the filtration of obtained MOF films. Gu et al. (CN114369252A) reported a method for preparing MOF films based on self-sacrificing crystallize metal oxide templates, but high temperature annealing treatment were required. Up to now, the development of organized 2D conductive MOFs is still limited by the use of completely rigid substrates such as silicon wafers, conductive glass, etc., thereby limiting their flexible or wearable applications. As well known, soft electronics will become a mainstream trend in the future. Mirica et al. (US20210230191A1) reported a method for oxidation of zero-oxidation state metal atoms on cotton to metallic ions, and then reaction with ligands to form MOFs. However, the current method using zero-oxidation metal sources may lead fast growth kinetics, resulting in nonuniform films on substrates and relatively poor stability of flexible electronics.
Compared with substrates such as titanium sheet, ITO glass, stainless steel mesh and traditional synthetic polymers (e.g., polyester, polyamide, polyurethane, and Kevlar), bio-fibers substrates based on polysaccharides are environmentally friendly, biodegradable and recyclable, which is important for achieving energy saving and low carbon development. To date, the growth of conductive MOFs on biofiber is crucial and highly desirable but remains a prodigious challenge, especially for fiberous soft electronics. For example, alginate fiber (AF) is a kind of polysaccharide fiber prepared by dissolving seaweed-derived sodium alginate in water through wet spinning technology, possessing excellent characteristics such as flame retardant, antibacterial, bacteriostasis, etc. Owing to easy availability of raw materials, low cost and environmental-friendly characteristics, AF has become a new favorite in textile industry in recent years. However, the polysaccharide bio-fibers are easy to swell and are not resistant to high temperature, which makes the growth of functional nanomaterials on the nonplanar organisms harsh and easy to fall off. Therefore, how to achieve shape plasticity and scale preparation of conductive MOFs materials on the surface of polysaccharide bio-fibers is the key to achieve their future application. Rational interfacial design between functional nanomaterials and nonplanar organisms will revolutionize the paradigm and future direction of device durability and user experience. The conventional solution method is cumbersome and the reaction solution conditions are relatively harsh, which is not conducive to large-scale preparation of MOFs on bio-fibers, and the final prepared materials are mostly hard substrate films without flexibility, which limits the application of such materials in the field of next-generation information materials and technologies.
A facile method of biomimetic precipitation and heteroepitaxial growth is demonstrated to grow crystalline catecholate MOFs with honeycomb lattice on biocompatible bio-fibers, which is expected to form biomimetic connections and maintain durable stability. The MOFs prepared by this method are tightly bonded between the bio-fiber/metal oxide/MOFs due to chemical bonding, which facilitates the interlayer electron transfer and makes the fiber devices equipped with this material good photoelectric and gas-sensing performance.
In this invention, the dense thin layer of ZnO was constructed on the surface of bio-fibers by a simple hydrothermal method. A series of MOFs were synthesized by a self-sacrificing metal oxide template strategy, and the type and morphology of MOFs were strictly controlled by changing the metal oxides or MOF organic ligands.
In situ synthesis of Zn-HHTP for UV detection and TEA chemoresistive sensing when the organic ligand is 2,3,6,7,10, 11-hexahydroxybenzophenanthrene (HHTP);
The specific steps are as follows:
The cleaned bio-fibers are immersed in a metal ion solution, so that the fiber surface adsorbs metal ions and is reduced in situ to form a thin conductive layer.
Wherein said bio-fibers are alginate fibers, bamboo pulp fibers, Lyocell fibers, chitin fibers, etc. and their composite fibers.
Said bio-fibers in the form of single fibers, fiber bundles, fabric, fiber aerogel, etc.
Said metal ions are Ag+, Cu2+, Ni2+, etc., with a mass concentration of 10 to 35%.
Said immersion time of 10 to 60 s.
Said reduction process is: placing the fiber into 0.03-0.5% dimethylamine borane (DMAB) aqueous solution until the surface of the fiber appears metallic luster.
Bio-fibers loaded with conductive thin layer were placed in seed layer precursor solution with continuous stirring and pH adjustment to deposit oxide nanocrystalline seeds; mussel-like structure oxide nanoarrays were grown in a solution of metal salts/organic amines using low temperature hydrothermal method; bio-fiber/conductive thin layer/metal oxide nanocrystalline seed composite was obtained
Wherein said seed layer precursor solution: 5 mM ethanol solution of (Zn(CH3COO)2.
Said method of depositing oxide nanocrystal seeds: placing the bio-fiber loaded with conductive thin layer in the seed layer precursor solution for 5˜60 s, fishing out and drying at 100° C. for 10˜20 min, repeated 2˜10 times.
Said low temperature hydrothermal method: the deposited metal oxide nanocrystalline species of biomass fibers placed in the hydrothermal solution, 80˜120° C. at the reaction of 2˜18 h, to be cooled and removed, deionized water and ethanol alternately washed 2˜3 times.
The bio-fiber/conductive thin layer/metal oxide nanocrystal species composite obtained from the step was immersed in a mixed aqueous solution containing organic ligands (HHTP or 2-methylimidazole or BTC) and N, N-dimethylformamide (DMF) to react to obtain a bio-fiber based metal-organic framework material with a hierarchical structure.
Wherein, the total mass percentage concentration of the organic ligand and DMF in said mixed aqueous solution is 0.2 to 0.5%; the mass ratio of the organic ligand and DMF is 1:12.5.
Said reaction temperature is from 50˜80° C. and said reaction time is from 5˜80 min.
Said metal oxide nanoarray acts as a sacrificial agent, both as a metal source partially involved in the composition of the MOFs, while confining the synthesis process to a specific region, resulting in a better multilevel structure.
Further, said bio-fiber based metal-organic framework compound material has a porous array structure and bendable properties.
The present invention also provides the application of the bio-fiber based metal-organic framework compound material for photoelectric sensing, and the resulting Zn-HHTP material is made into a fiber-like photodetector with the best response to 365 nm wavelength light at an applied bias voltage of 0.5 V, with a maximum response of 0.18 A. Moreover, the material has a good response to light in the wavelength range of 300˜900 nm.
The present invention also provides the gas sensing application of the said bio-fiber based metal-organic framework compound material, which is made into a flexible gas-sensitive device with good response to hazardous gases such as TEA at room temperature, with a response of about 1.65 to TEA.
The bio-fiber based metal-organic framework compound material described in the present invention can be made into a variety of forms of fibrous, paper-based and other photoelectric sensor devices, flexible gas-sensitive devices for highly sensitive detection of different wavelengths of light as well as toxic and harmful gases.
The advantages and beneficial effects of the present invention are.
The method described in the present invention is general and the process is simple and reproducible, which is suitable for large-scale preparation. The prepared materials have a variety of physical signal responses such as photoelectricity and gas sensitivity, and the fabricated flexible sensor devices have the advantages of high responsiveness, good stability, environmental protection and flame retardancy, flexibility and bendability, which realize the functionalized application of biomass fibers.
This embodiment relates to a method of constructing a metal-organic framework compound material on the surface of bio-fibers in the following steps.
The obtained products were characterized as follows.
Scanning electron microscopy (SEM) was used to observe the surface morphology of alginate fiber/ZnO before and after the synthesis of Zn-HHTP, as shown in
X-ray powder diffraction (XRD) was used to characterize the physical phase structure and crystalline shape of the synthesized Zn-HHTP, and the results are shown in
This embodiment relates to a method for constructing a metal-organic framework compound material on the surface of biomass fibers in the following steps.
The surface morphology of the Lyocell fabric/ZnO before and after the synthesis of Zn-HHTP was observed by scanning electron microscopy (SEM) as shown in
The photodetectors made from Zn-HHTP fibers in Embodiment 1 were subjected to a single-order constant voltage output system in Keithley dual-channel source meter integrated measurement software to determine their photovoltaic performance for different wavelengths of light.
The specific application results are shown in
The ends of the Zn-HHTP fabric made in Embodiment 2 were wrapped with double-sided copper tape to be used as electrodes; the fabric was put into the vacuum chamber of the gas-sensitive test apparatus, and the electrodes were connected and detected for TEA.
The specific application results are shown in
Number | Date | Country | Kind |
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202111050075.7 | Sep 2021 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2022/058467 | 9/8/2022 | WO |