Precise Surface Imprinting Controllable Construction Of 2D Nanosheet Composite Sorbents And Study On The Selective Seperation Of Nucleoside Compound

The newly discovered risks of emerging contaminants to the environment or human health have raised widespread concern at home and abroad.Nucleoside compounds,as important components of antibiotics,appear as new pollutants in environmental water samples,causing environmental pollution and endangering human health.Therefore,the development of efficient methods of separating and enriching nucleosides in environmental water samples and complex biological samples is one of the important tasks in the field of environmental science and engineering,and the related research is of great significance for environmental safety,prevention and control of major diseases and improve national health.Surface molecular imprinting technology（SMIT）,in which molecular imprinted polymers（MIPs）are grafted onto the surface of substrate materials,effectively avoids the problems of deep encapsulation,difficult elution of templates,weak imprinting force and slow mass transfer efficiency of traditional imprinted materials.Nanosheet substrate materials are ideal for surface blotting due to their high aspect ratio and large specific surface area.In this work,we propose three strategies to precisely control the imprinting process and improve the separation and recognition performance of nucleoside compounds.First,through the chemical design and synthesis of functional monomers specific for matching nucleoside compounds,the affinity of functional monomers to template molecules is improved and the effect of imprint recognition is enhanced.Second,we are based on the strategies of continuous assembly and sequential grasping,where sequential assembly is proposed to improve the fidelity of multiple assemblies and precisely control the orientation recognition of template molecules.Third,we explore post-imprint modification strategies that perform site-specific modifications within the imprinted recognition hole,optimize the recognition sites,and improve the affinity between the sites and the target molecule.This work has prepared six types of surface imprinted nanosheet sorbents for the highly selective separation of2’-deoxyadenosine（dA）and 5′-monophosphate（AMP）following three strategies.The morphology,crystal structure,elemental composition,magnetic properties,and surface properties of the six sorbents were analyzed by means of systematic characterization tests.The selective separation behavior of six adsorbents for nucleoside compounds was investigated in combination with static and dynamic adsorption experiments.The precise imprinting recognition mechanism has been discussed in detail,and the equilibrium and kinetic properties of the adsorption and separation processes have been elucidated,providing new ideas for the selective separation of nucleoside compounds from complex biomass products.The main research contents of this thesis are as follows:1.Construction of surface imprinted adsorbent based on Janus nanosheets and its application for selective recognition of 2′-deoxyadenosine（1）Based on the adenine group of dA and the complementary base pairing,synthesized 5-（2-Carbomethoxyvinyl）-2′-deoxyuridine（Acr U）was synthesized as functional monomer.An ester group was introduced to reduce the spatial hindrance of complementary base pairing and enhance the assembly effect of Acr U on dA.Janus SiO₂ nanosheets（J-SNs）with chlorine on one side and amino on the other were prepared by the emulsion template method.The MIPs and magnetically responsive particles of dA were modified on both sides of the J-SNs by atom transfer radical surface polymerization（SI-ATRP）and amidation reactions,respectively.Janus-MIPs magnetic sorbents（J-SNs-MMIPs）were synthesized,which realized the separate design of the magnetic separation function and the molecular dA recognition function,effectively reduced the masking of recognition sites by magnetic particles,introduced specific matching monomers that enhanced site affinity and enhancing molecular recognition and separation effects.The J-SNs-MMIPs displayed the ability to specifically recognize and fast separate dA,the equilibrium time was 70 min,the maximum monolayer adsorption was calculated to be 61.22μmol/g at 25°C.By evaluating the selective recognition of dA from spiked human urine samples,the J-SNs-MMIPs could be used for selective separation and analysis of target dA in complex biological samples（2）Traditional surface imprinted sorbents on nanosheets are prone to agglomeration and stack,resulting in site loss and collection difficulties,and hampering application in target separation in complex samples.Therefore,Janus nanosheets surface imprinting are used as solid particles to stabilize the Pickering emulsion,and the internal phase is an aqueous solution of alginate（Alg^-）or divalent cation(Ca²⁺)with magnetic particles.After gentle mechanical mixing of the two emulsions,two sets of emulsion coalesced to trigger the gelation of Alg-Ca²⁺yielding J-SNs-MIPs immobilized the mosaic type magnetic Alg-Ca²⁺Pickering（J-SNs-MMIPs-Pickering）.J-SNs-MMIPs-Pickering is expected to possess the advantages of excellent adsorption capacity,fast uptake kinetics,simple separation,and acceptable affinity towards dA.The equilibrium time and maximum adsorption capacity of J-SNs-MMIPs-Pickering are 1.0 h and 73.04μmol/g at 298 K,respectively,and the dispersed sorbents take about30 s to be captured by the external magnetic field.2.Sequential assembly and precise construction of dual receptors surface imprinting sorbents on nanosheets for highly specific separation of adenosine 5′-monophosphate（1）This work combines the dual receptor and sequential assembly to precisely control the imprint assembly process and refine imprint recognition sites from the perspective of precise orientation matching.Janus polymer nanosheets（J-PNs）with different wettabilities on two sides were synthesized by self-polymerizing dopamine（DA）based on octa-decylamine（ODA）lamellae with a bilayer structure,followed by a sequential imprinting assembly of low p K_a boronic acid and pyrimidine base monomers on the hydrophilic side of J-PNs to prepare Janus imprinting sorbents（J-MIPs）for highly specific separation of adenosine AMP.The sequential assembly strategy integrated two different functional monomers together to simultaneously interact with the surrounding template AMP molecule and to precisely control the imprinting site orientation,enabling the resulting J-MIPs with strong and specific binding towardAMP.Janus amphiphilic J-MIPs can be well fixed at the dodecane/water interface,which was benefit for their fast recycle and simple regeneration,and the uptake amount of the fifth adsorption/elution cycle was 86.08%of the first one.Taking the advantage of cooperative multi-point interaction,binding sites with high affinity to AMP accounted for about 76.71%of the total sites,and the high imprinting factor（2.182）of the J-MIP against non-imprinted counterpart was observed.In addition,61.30%of AMP in spiked human serum sample can be selectively extracted by J-MIPs,due to the highly specific receptor sites from sequential imprinting assembly.（2）In this work,hydrophilic dual receptor molecularly imprinted polymers（D-MIPs）were prepared by using hydrophilic Zr-MOFs nanosheets as substrate and grafting through sequential and precise assembly for highly specific separation of adenosine AMP.The t_1/2 and the maximum adsorption capacity of D-MIPs are 0.578 h and 286.7μmol/g at 298 K,and the high imprinting factor（2.764）,and under different temperature environments,AMP is adsorbed as a monolayer on the sorbent surface.The results of dynamic adsorption experiments show that at low flow rates,AMP has a higher adsorption capacity,has sufficient contact with the sorbent,and has more active sites.When at least 97%of the AMP is adsorbed in the D-MIPs separation of a sample spiked with a bio-fermentation broth.It has a high recognition and separation effect in complex biological samples and has promising application prospects in the field of environmental technology.3.Dual receptors post imprinting modification based on nanosheets for highly specific separation of adenosine 5’-monophosphate（1）In this work,the dual covalent receptors and post-imprinting modifications（D-PMIPs）were applied to the specific adsorption and separation of 5’-Monophosphate（AMP）.These modifications manipulate the orientation and arrangement of the AMP molecules on the mesoporous silica nanosheets by covalently assembling disulfide bonds with monomers containing NHS ester group（DS-FM1）and physiologically active boric acid（PBA-FM2）respectively.After imprinting polymerization,the disulfide bonds were reduced by tris（2-carboxyethyl）phosphine（TCEP）,and the AMP was removed along with the breaking of the covalently bound boronate affinity chain under acidic conditions.Finally,the residual sulfhydryl group in the reactive sites was introduced as a more specific affinity group through the sulfhydryl-disulfide bonding compound.The D-PMIPs against non-imprinted,single affinity integrated MIPs nanosheets S-BMIPs and S-FMIPs with high imprinting factors（2.634,2.690,1.969）were observed.The affinity binding sites for AMP were evaluated to be 70.9%by the Scatchard model.Over 80%of the capacity remained after six adsorption/desorption cycles,implying a satisfactory adsorption and regeneration capability.Additionally,D-PMIPs could selectively separate more than 52.70%of the AMP from the spiked deproteinized calf blood injection.These results demonstrated that D-PMIPs was an effective way to accurately recognize and separate AMP.（2）This work exploits the NHS ester of DS-FM1 and the ionic affinity of hydrophilic Zr-MOFs nanosheets to sequentially assemble with AMP molecules to precisely control the molecular orientation and arrangement.After thermally initiated imprinting polymerization,the disulfide bonds were reduced by tris（2-carboxyethyl）phosphine（TCEP）,and the AMP was removed along with ionic affinity breaking under acidic conditions.Finally,the residual sulfhydryl group in the reactive sites was introduced as a more specific affinity group through the sulfhydryl-disulfide binding compound to prepare dual receptor hydrophilic post imprinted modified nanosheet adsorbent（D-MOFs@PMIPs）.The maximum adsorption capacity of D-MOFs@PMIPs was increased from 120.4μmol/g at 288K to 143.6μmol/g at 308K,and under different temperature environments,AMP is adsorbed as a monolayer on the sorbent surface.The selective adsorption results show that the k_d value of D-MOFs@PMIPs for AMP is 219.0 L/g,which is significantly larger than 19.48,18.88,37.13,49.17 and 45.71 L/g for dC,dG,dA,ADP,andATP.It has a high recognition and separation effect in complex biological samples and promising application prospects in the field of environmental technology.