In this work, poly(acrylic acid) (PAA) and PAA/multi-walled carbon nanotube (MWNTs) nanofibrous membranes are fabricated by electrospinning to immobilize acetylcholinesterase (AChE).3-Aminopropyltriethoxysilane (APTES) and glutaraldehyde are used for surface modification and PAA membrane stabilization in aqueous media. The structure of the nanofibrous membrane was studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, thermogravimetric and mechanical analyses. The AChE enzyme was immobilized on the PAA nanofibers with different amounts of MWNTs concentrations from 0 to 5 wt%. The SEM images revealed that the average diameter of the PAA nanofibers was 226 AE 25 nm which was increased by increasing the MWNTs concentration. The tensile strength and modulus of the nanofibrous membranes increased by 1.87 and 4.39 fold respectively after a crosslinking process. The results show that membranes containing MWNTs are a more appropriate support for enzyme immobilization. In comparison to pure PAA, the activity of the sample containing 4 wt% of MWNTs was increased by 5.07 fold. Also, the immobilized enzyme showed excellent reusability even after 10 cycles of washing and samples maintained more than 90% of their original activities. Moreover, the pH and thermal stability of the immobilized enzyme was improved compared to the free enzyme. The results show that a PAA/MWNTs nanofibrous membrane could be counted as a suitable support for AChE immobilization in addition to different applications such as biosensor manufacturing.
Electroactive actuators based on conductive polymers currently have attracted a great deal of attention. In this study, a nanofibrous structure of polypyrrole (PPy) was used to fabricate an electroactive bending actuator. For this purpose, polyurethane/PPy (PU/PPy) nanofibrous bending actuator was fabricated through the combined use of electrospinning and in-situ chemical polymerization. The response surface methodology (RSM) was considered to find the optimal electrospinning conditions for producing PU nanofibers with the minimum diameter. The in-situ chemical polymerization method was then used to prepare a conductive layer of PPy on the surface of optimum electrospun nanofibers with p-toluenesulfonate (pTS) as the dopant. The coated nanofibers were used in the fabrication of PU/PPy-pTS nanofibrous bending actuator. The morphology and electrical, thermal, electrochemical, and electrochemomechanical properties of the fabricated actuator were investigated. By using optimum conditions of electrospinning, PU nanofibers were obtained with a diameter of 221 nm. The results showed that the produced PU/PPy-pTS nanofibers enjoy good thermal stability and have an electrical conductivity of about 276.34 S/cm. The obtained cyclic voltammetric and dynamo-voltammetric responses showed that the dominant mechanism of actuation in the fabricated PU/PPy-pTS nanofibrous actuator is the exchange of perchlorate anions with a partial exchange of lithium cations in 1M lithium perchlorate electrolyte solution. The fabricated actuator was capable of undergoing 141°r eversible angular displacement during a potential cycle. The results demonstrated that, given high porosity, large specific surface area, flexibility, and desirable electrical properties, PU/PPy nanofibrous electroactive actuator provides a lot of potential for developing artificial muscle applications.
Electrochemical power tools are regarded as essential keys in a world that is becoming increasingly reliant on fossil fuels in order to meet the challenges of rapidly depleting fossil fuel...
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