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

In the past, we have observed an overall capacitance enhancement in super capacitors (S-C) when placing small amount of conductive colloids at the electrolyte/electrode interface with a mass ratio of 1:5000 to the electrode mass. The capacitance peaked at particular colloid concentration and the enhancement was attributed to local field effects by formation of an array of colloids at the interface. Here we show that fluorescing semiconductor quantum dots (QDs) at the interface exhibit similar effects on the cell capacitance with a capacitance amplification, measure by cyclic voltammetry (C-V), of more than 2.5 at a scan rate of 100 mV/s. 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. The effect was also correlated with resonating effect (large signal enhancement) and in the case of wet samples, with line narrowing of the dots' fluorescence; the latter indicates a substantial fluorescence gain. 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.