| The safety of agricultural products is related to the national economy and people’s livelihood,and is an important foundation for national security,social stability,and national health.The rapid and sensitive detection of harmful substances related to agricultural product safety is the key technology and challenge in this field.The difficulty lies in how to efficiently identify,enrich and detect harmful substances in complex agricultural products（sample pretreatment liquid）,which is the common core.The problem is to construct an adsorbent/recognition interface suitable for harsh environment,and then to develop highly robust pre-processing and detection devices.However,the currently used detection elements,included enzymes,antibodies,and other biological recognition molecules,are easy to inactivation in harsh environment;the enrichment of small molecule targets in the sample pretreatment process requires the use of complex conditions such as organic solvent extraction,and the application of conventional adsorbents capacity and efficiency need to be improved.Metal-organic frameworks（MOFs）are a new type of porous material formed by metal ions/clusters and organic ligands.It has a series of advantages such as high rigidity,strong adsorption capacity,and suitable for harsh environment.It has become one of the most promising emerging materials in the agricultural product safety field.However,MOFs are often in powder form and have poor moldability.It is difficult to develop MOFs film devices that are easy to integrate and operate with automated instruments.This dissertation focuses on the key aspects of the enrichment and detection of harmful substances in the safety inspection of agricultural products.Facing the lack of efficient and suitable adsorption/recognition functional devices for harsh environment,this dissertation learns the methods of preparing materials from nature,based on the biological mineralization concept（biomolecular regulation to generate inorganic minerals）,proposes a variety of new technologies for MOFs immobilization,and develops three MOFs composite membrane devices used for high-efficiency enrichment and detection of glucose and veterinary drugs.（1）Biomineralization-mimetic preparation of robust metal-organic frameworks biocomposites film with high enzyme load for glucose biosensingInspired by the phenomenon of biomineralization,a robust enzyme-MOFs biocomposite material is proposed for the manufacture of ultra-stable modified electrodes and used for small molecule biosensing.Glucose oxidase（Gox）and Zeolitic Imidazolate Frameworks-8（ZIF-8）are used as model enzymes and MOFs,respectively.The biomimetic mineralization-assisted in-situ embedding method promoted the formation of enzyme-MOFs biocomposite,and gave 89%enzyme loading rate.The prepared biocomposite is cast-coating on the surface of the gold electrode to obtain a biocomposite film modified electrode.The modified electrode produced a sensitivity of 21Μa cm-2 Mm-1for glucose,and a detection limit as low as 2.2Μm.Importantly,thanks to the biomimetic mineralization preparation method and the rigid framework characteristics of MOFs,the enzymes in the biocomposite membrane are strongly protected by the MOFs shell,and the modified electrode undergoes repeated electrochemical scanning（200 cycles）and high temperature treatment at 90°C,organic solvent（acetone）exposure and long-term storage（more than 50 days with almost no loss of detection performance）,both show excellent stability in harsh environments.Anti-interference test and actual sample detection test show that the biosensor is suitable for detecting glucose in red wine.The method proposed in this research based on biomimetic mineralization enzyme-MOFs composite membrane is expected to solve the difficulties of low enzyme loading rate and low robustness in the process of enzyme immobilization-based biosensing detection in agricultural product safety detection.（2）Biomineralization-mimetic growth of ultrahigh-load metal-organic frameworks on inert glass fibers to prepare hybrid membranes for collecting MG and TC in harsh environmentGF membrane is a kind of membrane material with high applicability and cost-effectiveness,and it is expected to serve as an excellent carrier for new MOFs functional membranes.Therefore,it is necessary to develop new surface engineering technology to realize functionalization.Inspired by biomineralization,this research proposes a strategy to grow ultra-high loading MOFs on the surface of inert GF by biomimetic mineralization to prepare GF@MOFs（ZIFs）composite membranes for collecting small organic molecules under conventional and unconventional conditions.Compared with the lower MOFs coverage of the traditional method,the new method achieves about 100%coverage and has a diverse and controllable morphology.The adsorption capacity of GF@ZIFs for the veterinary drug malachite green（MG）is as high as 3964.8 mg g-1,while the reported analogues’adsorption capacity for MG is only1667 mg g-1;the adsorption capacity for antibiotic tetracycline（TC）is 192.2 mg g-1.More importantly,thanks to the introduction of surface-inert GF,the stability of GF@ZIFs composite membrane has been significantly improved,and shows the synergistic stabilization effect of GF and ZIFs.GF@ZIFs composite membrane shows good performance in 70°C hot water,chloroform,and Ph 14 Na OH solutions.The GF@ZIFs membrane was further developed as a filter device,which can quickly collect more than 95%of MG(50 mg L-1,10 Ml)within 1 h.The method of biomimetic mineralization preparation of MOFs composite membrane based on the surface of inert GF membrane proposed in this research is expected to provide a new method for the preparation of membrane materials for the high-efficiency enrichment of small molecules under harsh conditions（high temperature,organic,and alkali）during the safe pretreatment of agricultural products.（3）Microwave-enabled all-in-one bioinspired synthesis of MOF fabrics for collection of TCA biologically inspired full microwave-assisted MOFs rapid growth method on the inert GF surface to prepare GF@PDA@ZIF-8 composite membrane was proposed.Firstly,the microwave method was used to accelerate the modification of dopamine on the surface of GF,and to realize rapid（1 min）polymerization on the surface of GF fiber to form a 20 nm thin layer of PDA.Subsequently,microwave was used again to accelerate the biomimetic growth of ZIF-8 on the PDA-modified GF surface,achieving a high loading of the ZIF-8 shell within 3 minutes.Compared with the conventional preparation time of 12-48 h,the full microwave method can be used to complete it in10 minutes,and the MOFs shell coverage is significantly improved.Based on the highly porous and covering MOFs shell layer,the composite membrane shows excellent adsorption performance for antibiotic TC,and under the action of microwave,it can adsorb 82%of TC(20 mg L-1)in 1 min.The all-microwave technology proposed in this research can provide efficient technical means for the rapid and simple preparation of MOFs modified membranes and the rapid collection of harmful substances in agricultural products. |
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