Hydrogels of polyaniline with graphene oxide for highly sensitive electrochemical determination of lead ions.

Conducting polymers with graphene/graphene oxide hydrogels represent a unique class of electrode materials for sensors and energy storage applications. In this article, we report a facile in situ method for the polymerisation of aniline resulting in the decoration of 1D conducting polyaniline (PANI) nanofibers onto the surface of 2D graphene oxide (GO) nanosheets followed by hydrogel formation at elevated temperature. The synthesized nanomaterial exhibits significant properties for the highly sensitive electrochemical determination as well as removal of environmentally harmful lead (Pb2+) ions. The square wave anodic stripping voltammetry (SWASV) determination of Pb2+ ions showed good electroanalytical performance with two linear ranges in 0.2-250 nM (correlation coefficient = 0.996) and 250-3500 nM (correlation coefficient = 0.998). The developed protocol has shown a limit of detection (LOD) of about 0.04 nM, which is much lower than that of the World Health Organization (WHO) threshold limits. The prepared electrode showed an average of ∼99.4% removal of Pb2+ ions with a relative standard deviation (RSD) of 3.4%. Selectivity of the electrode towards Pb2+ ions were tested in presence of potential interferences such as Na+, K+, Ca2+, Mg2+, Cu2+, Cd2+, Hg2+, Zn2+, Co2+, Ni2+, Fe2+ and Fe3+ of similar and higher concentrations. The sensor showed good repeatability and reproducibility. The developed protocol was used to analyse samples from industrial effluents and natural water samples. The results obtained were correlated with atomic absorption spectroscopy (AAS).

Mutually ordered self-assembly of discotic liquid crystal-graphene nanocomposites.

The room temperature anthraquinone discotic 1,5-dihydroxy-2,3,6,7-tetrakis(3,7-dimethyloctyloxy)-9,10-anthraquinone (RTAQ) self-assembles in the presence of octadecylamine functionalized graphene (f-graphene) into an ordered sandwich like structure, where the discotic molecules form columnar structures on graphene sheets. Cryo-SEM and SEM images provide evidence for this ordering. This behaviour is also supported by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and conductivity studies of nanocomposites.