This study demonstrates the enhanced Cu2+ adsorption capability of polyaniline nanofibers (PAni NFs) by doping of phytic acid. The PAni NFs were synthesized by radical polymerization process using acidic solutions of hydrochloric and phytic acid, yielding chlorinated (Cl-) and phytic acid-doped (Ph-) PAni NFs. The Ph-PAni NFs showed remarkably higher Cu2+-adsorption efficiency than Cl-PAni NFs, presumably owing to high capacity and/or high ionic affinity of the doped phytic acid in Ph-PAni NFs. The pH-dependent adsorption capability exhibited increasing Cu2+ adsorption trend as increasing aqueous pH because of spontaneous deprotonation of the doped phytic acid in a basic environment. Furthermore, Ph-PAni NFs showed stable, high Cu2+ adsorption capability, irrespective of Co2+ concentration in the bimetallic Cu and Co aqueous solution. Surface morphologies of PAni NFs were investigated using electron microscopy, and molecular structures were identified using X-ray photoemission and Fourier transform infrared spectroscopies. The ability of PAni NFs to capture aqueous Cu2+ is discussed in terms of surface functional groups doped to NFs. Surface modification and/or doping to enhance the adsorption capability of Cu­(II) introduced in this study will provide a great venue for expanding the use of many other polymeric nanostructures for reclamation in metal mining as well as the conventional environmental applications such as water purification.

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We report the tailoring of the electronic structure of poly(N-vinylcarbazole) (PVK) using a mixture layer of polyaniline:poly(p-styrenesulfonic acid) (PANI:PSS) in organic multilayer PVK/PANI:PSS/poly(3,4-ethylenedioxythiophene):PSS heterojunctions. The overall electronic structure of the PVK overlayer was systematically down-shifted while the work function of PANI:PSS increased as a function of the PSS-to-PANI weight ratio for the ratio range from 1 to 11 in the PANI:PSS film. The down-shift in the highest occupied molecular orbital of PVK markedly reduced the hole injection barrier from PVK to quantum-dot (QD) layers in QD-light emitting diode (QD-LED) structures, resulting in superior electrical and electroluminescent characteristics for QD-LEDs. The influences of PANI:PSS thickness on the electronic structure of PVK and the performance of QD-LEDs are also discussed.