Preparation And Electrochemical Applications Of Hierarchically Porous PS-b-P4VP Film

Compared to conventional porous materials with uniform pore size distribution,hierarchical ones containing both interconnected macro-,meso-and microporous structures have greatly enhanced material performance due to the increased specific surface area and mass transport.Copolymer is a good candidate for preparation of such hierarchically porous material,resulting from its tunable segment composition,unique phase separation and self-assembly,etc.Hierarchically porous materials derived from copolymers can be served as a versatile support for many reactive molecules,which have promising applications in energy conversion and storage.In present work,a block copolymer film was prepared via spinodal-decomposition-induced macro-and meso-phase separation plus extraction by rinsing(SIM2PLE);The resulting copolymer film was used as immobilization matrix in electrochemistry.Moreover,several electrochemical applications were developed based on this material:(1)Hierarchically porous copolymer film was prepared with amphiphilic diblock copolymers poly(styrene-b-4-vinylpyridine)(PS-b-P4VP)via SIM2PLE.The film exhibited an interconnected porous structure including macropores and mesopores.The diameters of mesopores were higher than 1 ?m and the nanopores were ranging from 20?100 nm.Moreover,the average diameter of mesopores was 60 nm.The hierarchically porous copolymer film exhibited large specific surface area and mass transfer.The morphologies of copolymer film,which were affected by the concentration of polymer solution,molecular weight of polymer,matrix,temperature,moisture et al.,were studied with scanning electron microscopy(SEM).The experiments showed that mesopores disappeared and the value of contact angle became large with increasing the concentration of polymer solution.Furthermore,the diameter of nanopores decreased while the mesopores increased with increasing the molecular weight of polymer.When the temperature was increased,the structure of the film will change and mesopores became larger.In addition,matrix and moisture both would pose an effect on the structure of the film and the pores in the film cannot be connected if the polymer solution containing water.(2)Hierarchically porous copolymer film was prepared with amphiphilic diblock copolymers PS-b-P4VP via SIM2PLE.The obtained film with half-dry status was used as immobilization matrix to immobilize tyrosinase(Tyr)with glutaraldehyde as crosslinking agent.The obtained Tyr/PS-b-P4VP/GCE was developed to construct high performance electrochemical biosensor for detection of phenolic compounds.The as-developed phenol biosensor exhibited a high sensitivity(3.0 × 103 mA M-1·cm-2),quick response(<5 s)and extremely low detection limit(7.0 nM at an S/N ratio of 3).Moreover,a decent linear range(0.02?35 ?M)was also observed The value of apparent Michaelis-Menten constant and apparent activation energy were 0.17 mM and 23 kJ mol-1,respectively.In addition,the biosensor exhibited excellent selectivity,repeatability,reproducibility and long-term stability.(3)Hierarchically porous copolymer film was prepared with amphiphilic diblock copolymers PS-b-P4VP via SIM2PLE.The resulting film with half-dry status was used as immobilization matrix to immobilize glucose oxidase(GOx)with glutaraldehyde as crosslinking agent.The obtained GOx/PS-b-P4VP/Pt was developed to construct high performance electrochemical biosensor for detection of glucose.The as-developed glucose biosensor displayed a long linear range(0.01 × 103?4.5 × 103 ?M),a low detection limit(0.05 ?M)and quick response(2 s).Moreover,a decent sensitivity(55 mA·M-1·cm-2)was also observed.The value of apparent Michaelis-Menten constant and apparent activation energy were 3.0 mM and 34 kJ·mol-1,respectively.In addition,the biosensor exhibited excellent selectivity,repeatability,reproducibility and long-term stability.(4)Hierarchically porous copolymer film was prepared with amphiphilic diblock copolymers PS-b-P4VP via SIM2PLE.Through cyclic voltammetry(CV)test,the results showed that the PS-b-P4VP film has a pH-sensitive response to the potassium ferricyanide probe:when the pH value of electrolyte was 3.0,the CV curve has a pair of redox peaks at about 0.2 V,which revealed that the electrochemical switch response of the PS-b-P4VP film to potassium ferricyanide was in the "ON" state;when the pH value of electrolyte was 7.0,the CV curve has no redox peak at about 0.2 V,indicating that the electrochemical switch response of the PS-b-P4VP film to potassium ferricyanide was in the "OFF" state.When GOx and laccase(Lac)were loaded on the hierarchically porous copolymer film,GOx/PS-b-P4VP/GCE and Lac/PS-b-P4VP/GCE were obtained and served as anode and cathode of enzymatic fuel cell,respectively.The results showed that:At a pH of 3.0,the open circuit potential was 0.46 V and the maximum output power of the cell was 4.8 ?W·cm-2.At a pH of 7.0,the open circuit potential was 0.32 V and the maximum output power of the cell was 0.04 ?W·cm-2.The power density ratio was up to 119 times in the ON-OFF state.