Biosensors Based On Carbon Nanotubes And Graphene

This work introduces two hybrid electrodes including NiO/carbon nanotube（CNT）/poly（3,4-ethylenedioxythiophene）（PEDOT）/glassy carbon electrode（GCE）and AuPt-vertical graphene（VG）/GCE.The properties of the two electrodes are investigated respectively.The NiO/CNT/PEDOT electrode was successfully constructed by electrodeposition.The NiO/CNT/PEDOT composite has a one-dimensional coaxial nanostructure,which exhibits a low liquid-solid interface resistance and high electrocatalytic activity.Dopamine（DA）,serotonin（5-HT）,and tryptophan（Trp）are simultaneously present in human bodily fluids that affect human health.The response characteristics of DA,5-HT,and Trp were investigated using the NiO/CNT/PEDOT/GCE-based biosensors.For the oxidation of DA,5-HT,and Trp,the electrode exhibited high selectivity,stability,and excellent reproducibility.The NiO/CNT/PEDOT/GCE-based electrochemical sensor is an attractive candidate for the simultaneous determination of multiple electroactive species in the bodily fluids.Graphene nanosheets were vertically grown on GCE using a direct-current arc plasma jet CVD method.Next,AuPt hybrid nanoparticles were deposited on the graphene sheets using the multi-potential step method.Thus,AuPt-VG/GCEs were produced.The AuPt hybrid nanoparticles are uniformly embedded in the surface of the graphene sheets.The AuPt hybrid nanoparticles not only increase the specific surface area,but also enrich the electroactive sites.The alpha fetoprotein（AFP）is a key tumor marker for the early diagnosis of patients with liver cancer.Furthermore,the sandwich-type and label-free electrochemical immunosensors were constructed for the detection of AFP.This work suggested that the sensitivity under the sandwich-type strategy was higher than that under the label-free strategy.The sandwich-type electrochemical immunosensor had a low detection limit of 0.7 fg mL^-1.The sensors based on the two strategies exhibited a linear range from 1 fg mL^-1 to 100 ng mL^-1 for AFP detection.The AuPt-VG/GCE-based immunosensors are a promising tool for the clinical monitoring of AFP and other tumor markers.The innovation point of this paper:First,the NiO/CNT/PEDOT composite with a coaxial tubular nanostructure was successfully deposited on a GCE through electrochemical processes.The outer PEDOT matrix has a high affinity for biomolecules,while the CNT inner layer has a strong electron transport capacity.Thus,the electrode was used for the simultaneous detection of DA,5-HT,and Trp.Second,the graphene sheets are grown vertically on the surface of the GCE,and AuPt nanoparticles are deposited on the VG/GCE.AuPt nanoparticles have good biocompatibility and excellent conductivity and were used to immobilize primary antibodies;VG sheets helped accelerate the electron transfer.Sandwich-type and label-free electrochemical immunosensors were designed for AFP detection.