| Carbon and its composites have been widely applied in researches,industry and medical fields.Various carbon materials have outstanding chemical stability,excellent mechanical properties,good electron transfer capability,distinctive optical property and environment friendly.In particular,carbon nanomaterials have been extensively applied in semiconductor devices,energy storage,biomedical treatment,drug release and biosensing fields.Hence synthesis,modification,construction of carbon-based nanostructructure and application of various carbon composites have become the hotest research topic.Recently the application of carbon nanomaterials such as carbon nanotubes,graphene,active carbon and carbon hydrogels in sensors have attracted more and more attentions due to their great electrical conductivity and catalytic capability.These nanomaterials have been widely applied for the fabrication of electrochemical sensors for the detection of gas molecular,biological molecular,proteins,DNA,cells and disease diagnosis.In this work,we focus on the development of novel carbon composites and application for the preparation of electrochemical sensors for the detection of small biological molecules.The specific contents are as follows:?1?This work fabricated different hierarchical 3D Nafion enhanced carbon aerogels?CAGs?via a fast freeze drying method for sensing applications.Graphene oxide,multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by removal of ice crystals with freeze drying.The unique layered structure of graphene oxide provides a skeleton for the formation of three dimentional carbon aerogels.The addition of MWCNTs mainly increases the specific surface area and electrical conductivity of the CAGs.Meanwhile,the addition of Nafion enhances the mechanical strength of CAGs and effectively control the pore sizes and the cellular morphology.The resultant CAGs have high strength,low density and high specific surface area.Therefore,CAGs monoliths perform well as a gas sensor and as a biosensor with high sensitivity and selectivity.These outstanding properties make the CAGs a promising electrode candidate for sensing biological small molecule such as DA and organic gas.Further in-depth investigations are being undertaken to probe the structure-property relationship of CAGs monoliths prepared under various conditions.This research demonstrates a method to prepare controlled internal pore sized CAGs by controlling the content of Nafion.This method is environment-friendly,inexpensive,convenient,and can avoid aggregation in the process of building electrode.?2?A sensitive amperometric sensor is developed for selective determination of dopamine based on electrocatalytic activity of graphene-based macroporous carbon aerogel microelectrode.Three-dimensional carbon aerogel electrode was synthesized by freeze drying of graphene and multi-wall carbon nanotubes with the assistance of Nafion.We further improved and optimized the experimental conditions,the new hydroiodic acid steam reduction method was used to prepare CAGs electrodes,and examined the influence of the hydroiodic acid vapor reduction method and hydrazine vapor reduction method for CAGs.The experimental results confirmed that the CAGs reduced by both methods displayed excellent electrical conductivity and strong electro-catalytic activity towards dopamine oxidation.Moreover,the electrochemical DA sensor prepared with the latter mothod displays more rapid and higher sensitivity to the detection of DA with a detection limit of 20 nM?S/N=3?.This may be due to the fact that the hydrazine vapor reduction method is more thorough in the reduction of GO components in CAGs.The remarkable sensitivity was obtained in DA detection is two orders of magnitude better than the literature reported values using graphene aerogel electrodes made from a porous Ni template.Meanwhile,the results of DA determination in real samples verify the feasibility of the porous carbon aerogel and potential application in biosensing and medical diagnosis.In brief,this research work provides a general method for building carbon-based biomolecular electrochemical sensors,which can be widely used in basic research,drug treatment effect screening and clinical diagnosis.?3?In this work,we successfully fabricate a rapid,sensitive sensor for the detection of superoxide anions O2·-based on a sandwich structure,Graphene/DNA/Mn3?PO4?2biomimetic enzyme.It is important to real time detect O2·-for investigation of various critical biological processes,but the current researches are mostly drop catalytic factors directly on the surface of carbon materials,the connection between them is not close,this greatly hindered the effective transfer of electrons between them,thus greatly limits the detection sensitivity and selectivity of sensors.In this work,graphene is served as excellent carrier to improve the catalysis of Mn3?PO4?2 nanoparticals;and DNA adsorbed on graphene acts as medium to assist the growth of Mn3?PO4?2 on graphene.ThefabricatedGraphene/DNA/Mn3?PO4?2compositesexhibitexcellently electrochemical activity,significantly decrease the response time and increase the sensitivity of the sensor towards O2·-.The successful detection of O2·-released from cancer cell demonstrated its potential applications in biology and medicine.This work provides an effective material modification method which has great application prospect in construction of a highly catalytic activity and selectivity sensor platform.?4?Carbon nanofiber/manganese oxide?CNF-MnO?hybrid nanofibers were synthesized by calcination of KMnO4 loaded bacterial cellulose?BC?hydrogels.As early as manganese was reported possessing an effective catalytic effect in vivo protection against superoxide toxicity.In recent years,further study found that manganese phosphate has the ability to catalyze the dismutation of O2·-compared with free Mn2+ion that only stoichiometrically reacts with O2·-.Therefore Mn3?PO4?2 was usually selected as a substitute for enzyme to detect O2·-.As far as we know,there are no studies on the use of MnO nanoparticles as biomimetic enzymes for cancer cell release O2·-detection.The chemical structure,morphology,performance and application of CNF-MnO aerogels were characterized and studied.The results revealed that MnO nanoparticles were uniformly deposited on the surface of CNF which derived from BC hydrogels.An amperometric superoxide anions(O2·-)sensor was fabricated by the immobilization of the CNF-MnO aerogels on glassy carbon electrode?GCE?,which displayed a linear amperometric response with a high sensitivity of 76.2?A·cm-2·mM-1and a low detection limit of 1.2 nM in the concentration range of 5.0 nM2.5?M.The successful detection of O2·-released from cancer cells verifies the potential application in biomedical field.This experiment provides a new method of synthesis of CNF-MnO nanocomposite materials,which is low cost,simple,high catalytic activity.In brief,several carbon-based nanocomposites were synthesized and applied for the detection of biomecules including dopamine and superoxides anion.These experiments results demonstrate that carbon-based nanocomposites could facilitate interfacial electron transfer and enhance the catalytic activity.For the fabrication of biosensor,carbon nanocomposites efficiently improves the sensitivity and stability of sensor,display potential application in biological system.This research provides some new ideas and methods for the development of multifunctional carbon materials,preparation of carbon-based biomimetic enzyme and modification of carbon nanomaterials.Meanwhile,it offers valuable knowledge in the preparation of carbon-based electrochemical sensors and biomedical research. |
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