Hydrophilic redox-active polymer nanoparticles with different redox potentials and radii were synthesized via the dispersion polymerization to yield their stable dispersion in aqueous electrolyte media as promising catholytes and anolytes in redox flow batteries. Despite the small physical diffusion coefficient (10 −9 cm 2 /s) of the nanosized particles, the sufficiently large coefficient for charge transfer within the polymer particle dispersion (10 −7 cm 2 /s) was observed as a result of the fast electron propagation throughout the polymer particles. Redox flow cells were fabricated using TEMPO-, viologen-, or diazaanthraquinonesubstituted polymer nanoparticles as active materials. The reversible charge/discharge over 50 cycles was achieved even at a high concentration of the redox units (1.5 M), which exceeded the limitation of the solubility of the corresponding dissolved species.

An electrochemical molecular sensor based on a new principle is reported. Nereistoxin (NRT, 4-N,N-dimethylamino-1,2-dithiolane), a naturally occurring neurotoxin (nicotinic acetylcholine receptor agonist), was adsorbed on an Au electrode via Au-S covalent bonding and accelerated the electron transfer between the electrode and the marker, ferricyanide anion. The contrast between the electrochemical responses obtained with the bare and NRT-modified Au electrodes was more pronounced at a low ionic strength of the supporting electrolyte, KCl. In the presence of 1 mM KCl, almost a 0/1 contrast between the signals was obtained through electrostatic interaction between the protonated tertiary amino group of NRT and the anionic ferricyanide ion. No current was observed with an electrode modified with mercaptopropionic acid. An unusually low ionic strength thickened the electric double layer to the degree where current was not observed with the bare electrode. The effect of the electrostatic concentration of the marker ion becomes obvious under such conditions. Commercially available NRT-related pesticides such as Cartap and Bensultap were also detected using the same format after pretreatments by hydrolysis/reduction. The present sensing method was successfully applied to human serum with satisfactory sensitivity.