Construction And Application Of Electrochemical Biomimetic Sensing Platform Based On Submicro-Channel Heterogeneous Membrane

Biomimetic solid nanochannel has attracted much attention due to the stable physical and chemical property,controllable pore size and similar ion transport characteristics to biological ion channel.The submicro/micron channel in the heterogeneous membrane has larger pore size and versatility of heterogeneous membrane,the generation of ion current rectification（ICR）characteristic in submicron/micron channel is expected to overcome the shortcoming of high nanochannel resistance,low switching current and narrow detection range,broadening the biosensor development.Therefore,based on the above solution,the hydrophobic conducting polymers,poly（4,4’-bis（4-vinylphenyl）triphenylamine）（PTPA）and poly（9-（4’-vinyl-[1,1’-biphenyl]-4-yl）-3-（4-vinylphenyl）-9H-carbazole）（PPhCz）are combined with porous anodic aluminum oxide（AAO）channel membrane at submicron aperture using simple drop-coating and thermal crosslinking,a novel electrochemical biomimetic sensing platform with ICR characteristic is designed,the main contents of research are as follows.1)The AAO/PTPA submicro-channel heterogeneous membrane with ICR characteristic is preliminarily constructed.AAO/PTPA as a submicro-channel heterogeneous membrane with asymmetrical composition,charge and wettability distribution is constructed by the simple drop-coating and in-situ thermal crosslinking of a volatile organic small molecule solution containing triphenylamine and styrene groups on cylindrical AAO channels（D≈319 nm）.Under the pH gradient stimulation,this heterogeneous membrane has typical ICR characteristic dominated by channel surface charge,and the rectification ratio is up to 36.9,which can effectively regulate the transport of electrolyte ions and performed well in the stability study.This work provides an effective strategy for the construction of submicro-channel heterogeneous membrane,and also broadens the application range of biomimetic ion channels.2)The AAO/PPhCz submicro-channel heterogeneous membrane with better ICR characteristic is further constructed at a lower thermal crosslinking temperature using an optimized hydrophobic conducting polymer precursor,and the mechanism of ICR in submicron channel is also discussed.AAO/PPhCz,one kind of heterogeneous membrane with asymmetric composition,geometry and wettability is prepared by simple drop-coating of the neutral hydrophobic conducting polymer precursor and in-situ thermal polymerization on cylindrical submicron scale AAO channels（D≈269 nm）at 150℃.ICR in the submicro-channel heterogeneous membrane is successfully achieved due to the asymmetric charge distribution induced by asymmetric pH gradient.Furthermore,the rectification ratio(R_ic:1.6～42.8)could be effectively regulated by multiple drop-coating,the electrolyte concentration（0.01 mM～1 M）and pH gradient（3～11）.Finally,through the permeation experiment of anionic dye and cationic dye,the mechanism of the synergistic effect of surface charge and electrophoresis on the ion selectivity and ICR is discussed,and it is successfully applied to the directional and on-demand transport of anionic and cationic ions under the regulation of pH gradient and voltage driving.3)AAO/PPhCz as a submicro-channel heterogeneous membrane with asymmetric geometry is prepared as the base by combining thermally crosslinked hydrophobic conducting polymer and AAO channels with submicron pore size（269 nm）.After the polydopamine-Au multilayer assembly,a large number of Au nanoparticles with adjustable size（～10 and 89 nm）and density are in situ generated and fixed on the inner wall of AAO.Then 4-mercapto phenylboric acid with high density is grafted through Au-S bond to construct the submicro-channel heterogeneous membrane with the characteristic of ICR in response to pH and saccharide.Benefit from the blocking effect of hydrophobic conducting polymer and the multilayer assembly of polydopamine-Au,the current of background response by the membrane device is effectively reduced,the ICR strength can be effectively regulated in the range of pH 3-9,and the response to ultra-low glucose concentration without enzyme is achieved in the linear range of 1 p M-0.1μM.A universal substrate platform is provided for the construction of solid nanochannel-based biosensor with submicron pore size.4)Based on polydopamine-Au modified AAO/PPhCz submicro-channel heterogeneous membrane,the temperature-sensing switch with near-infrared light response was realized.Sulfhydryl and carboxyl terminated poly-N-isopropyl acrylamide with thermosensitivity is synthesized by reversible addition-fragmentation chain transfer polymerization and amolysis reaction,it is further grafted at the Base end of polydopamine/Au nanoparticle-modified photothermal responsive heterogeneous membrane via Au-S bond to achieve the thermosensitive polymer modification.After the asymmetric 808 nm near-infrared light irradiation,the"on"or"off"status of submicron channel can be realized stably and reversibly for the reasons that the thermosensitive poly-N-isopropyl acrylamide reversibly changes from the extended hydrophilic state to the contracted hydrophobic state under the photothermal effect of three polydopamine-Au layers.The conductance of submicro-channel heterogeneous membrane with ICR characteristic increases at the asymmetric pH gradient,the rectification ratio maximally decreases by 11.4,and the photoresponsive current reaches 26.6μA（0.1 mM KCl）.At the same time,the ICR effect is also achieved at the high salt concentration of 1 M KCl,and the photoresponsive current can reach 183.7μA;the intensity of ICR and photoresponsive current can be effectively regulated by the power density,salt concentration and pH,then the temperature-sensing switch with near-infrared light response is successfully constructed.This work provides a new way to improve the photoresponsive current,and shows great potential in the fields of solar desalination and power generation.In summary,by constructing submicro-channel heterogeneous membranes with ICR characteristic,this thesis has successfully realized the directional and on-demand transport of anionic and cationic ions,non-enzymatic glucose sensing detection at ultra-low concentration and temperature-sensing switch by the remote near-infrared light control,which provides a new approach and strategy for the diversified application of biomimetic solid nanochannel at the submicron aperture.