INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Analytical applications of electrochemical sensors based on carbon nanostructures
Autor/es:
G. A. RIVAS; N. F. FERREYRA; M. C. RODRÍGUEZ; M. D. RUBIANES; M. L. PEDANO; F. GUTIERREZ; P. DALMASSO; A. GASNIER; E. PRIMO; G. LUQUE; M. EGUÍLAZ-RUBIO
Lugar:
Buenos Aires
Reunión:
Encuentro; International Meeting in Chemical Sensors 2014; 2014
Institución organizadora:
Comisión Nacional de Energía Atómica
Resumen:
Carbon nanotubes (CNT) dispersed in different polymers were used to develop electrochemical (bio)sensors by drop-coating at glassy carbon electrodes (GCE). GCEs modified with CNT-polyhistidine were used for the sensitive and selective quantification of Cu(II). GCEs modified with CNT-dsDNA were used in two directions, as a platform for detecting promethazine through the intercalation of the drug, and as a platform to build supramolecular architectures for glucose biosensing. The simultaneous dispersion of copper microparticles and CNT in polyethylenimine made possible the development of stable and robust electrochemical sensors for the quantification of aminoacids, albumin and glucose through the complex formation. Graphene composite electrodes were successfully used for the quantification of NADH and for the construction of enzymatic electrodes for phenols and ethanol. Carbon nanotubes (CNTs) and graphene (Gr) have received enormous attention in the last years for the development of electrochemical (bio)sensors due to their outstanding mechanical, electronic and structural properties [1-2]. Here, we proposed two types of electrochemical (bio)sensors based on carbon nanostructures, one of them obtained by modification of glassy carbon electrodes (GCE) with CNT dispersed in different polymers and the other one prepared by dispersing graphene in mineral oil. 1. We present a critical comparison of the electrochemical behavior of GCE modified with CNT dispersed in polylysine (Polylys), calf-thymus double stranded DNA (dsDNA), polyethylenimine (PEI) and polyhistidine (Polyhis). The dispersions were obtained by mixing CNT with the given polymer (in general, prepared in 50% v/v ethanol/water solution), followed by sonication for a given time. The sensors were obtained by drop-coating at polished GCE and further evaporation of the solvent at room temperature. The comparison was focused on the analysis of the influence of sonication time, solvent, polymer/CNT ratio and nature of the polymer on the efficiency of the dispersions, on the electrochemical behavior of the resulting modified electrodes, and on the (bio)sensing applications for the quantification of biomarkers of clinical relevance like glucose, NADH, dopamine and DNA. Fig. 1A depicts the voltammetric response of GCE modified with CNT-Polyhis in acetate buffer solution pH 5.00 after interaction with different concentrations of Cu(II) and reduction of the preconcentrated copper after medium exchange while Fig.1B shows the corresponding calibration plot. The sensitivity was (3.6 ± 0.3) x 106 μAM-1 and the detection limit was 75nM. GCE/CNT-dsDNA was used as a platform to build a supramolecular architecture for glucose biosensing based on the self-assembling of poly(diallyldimethyl ammonium) and glucose oxidase. The resulting multistructure made possible the successful quantification of glucose in different samples. The analytical applications of graphene paste electrodes (GrPE) are also discussed in connection with the electrocatalytic activity towards the oxidation of NADH, either for detecting NADH in the presence of ascorbic acid using bare GrPE, or ethanol using GrPE modified with alcohol dehydrogenase (ADH) and NAD+. The resulting electrode was successfully used for the quantification of ethanol in different beverages with excellent correlation with the reported values. Figure 2 displays a SEM picture of the GrPE as well as the voltammetric behavior of the redox marker, ascorbic acid, clearly demonstrating the decrease in the overvoltage in the presence of Gr. In summary, the adequate selection of the dispersing agent of CNT and further modification of GCE and the incorporation of graphene in a composite material make possible to develop excellent electrochemical (bio)sensors for the quantification of different analytes of clinical and environmental interest.