A novel electrochemical sensor based on graphene nanosheets and ethyl 2-(4-ferrocenyl-1,2,3triazol-1-yl) acetate for electrocatalytic oxidation of cysteine and tyrosine

A novel electrochemical sensor based on ethyl 2-(4-ferrocenyl-1,2,3triazol-1-yl) acetate (EFTA) and graphene has been developed for electrocatalytic oxidation and determination of cysteine. The electrochemical behavior of cysteine at the EFTAGCPE was investigated by voltammetric techniques. The EFTAGCPE showed efficient electrocatalytic activity for the oxidation of cysteine in 0.1 M phosphate buffer solution (pH 7.0). The oxidation overpotential of cysteine decreased significantly compared with the bare electrode and its oxidation peak currents increased dramatically at EFTAGCPE. The potential utility of the sensor was demonstrated by applying it to the analytical determination of cysteine concentration. The results showed that the electrocatalytic current increased linearly with the cysteine concentration in the range of 4.0�2300.0 μM and the detection limit was 0.9 μM. Also the prepared modified electrode exhibits a very good resolution between the voltammetric peaks of cysteine and tyrosine. The sensor was applied to determine cysteine and tyrosine in human fluids samples. © 2019 Elsevier Lt

Role of Heterojunctions of Core Shell Heterostructures in Gas Sensing

Heterostructures made from metal oxide semiconductors MOS are fundamental for the development of high performance gas sensors. Since their importance in real applications, a thorough understanding of the transduction mechanism is vital, whether it is related to a heterojunction or simply to the shell and core materials. A better understanding of the sensing response of heterostructured nanomaterials requires the engineering of heterojunctions with well defined core and shell layers. Here, we introduce a series of prototypes CNT nMOS, CNT pMOS, CNT pMOS nMOS, and CNT nMOS pMOS hierarchical core shell heterostructures CSHS permitting us to directly relate the sensing response to the MOS shell or to the p n heterojunction. The carbon nanotubes are here used as highly conductive substrates permitting operation of the devices at relatively low temperature and are not involved in the sensing response. NiO and SnO2 are selected as representative p and n type MOS, respectively, and the response of a set of samples is studied toward hydrogen considered as model analyte. The CNT n,pMOS CSHS exhibit response related to the n,pMOS shell layer. On the other hand, the CNT pMOS nMOS and CNT nMOS pMOS CSHS show sensing responses, which in certain cases are governed by the heterojunctions between nMOS and pMOS and strongly depends on the thickness of the MOS layers. Due to the fundamental nature of this study, these findings are important for the development of next generation gas sensing device