Super-capacitors interfaced with quantum dots at the electrolyte/electrode interface: capacitance gain and fluorescence line-width narrowing

Quantum dots (QDs), embedded in supercapacitors (S-C) cells exhibited capacitance amplification that peaked at certain QD concentration. More than 2.5 peak amplification was demonstrated with cyclic voltammetry (C-V) at a scan rate of 0.1 V/s. The mass ratio of the dots to that of the active-carbon electrode (A-C) was less than 1:5000. Fluorescence signals from dry (without electrolyte) and wet (with electrolyte) samples, exhibited a correlated, substantial peak enhancement vs QD concentration, as well. In the case of wet samples, fluorescence line narrowing was demonstrated, which indicates a substantial fluorescence gain. Both effects are attributed to local field effects through formation of a colloidal array at the electrode/electrolyte interface. Embedding QDs at the electrolyte/electrode interface has an added value that it may be further enhanced by white light and indeed this is the case here. Probing the electrolyte/electrode interface with fluorescing materials adds to our basic knowledge of the interface and could be useful for light-sensitive S-C cells.