Dual-emission ratiometric probe combining carbon dots and CdTe quantum dots for fluorometric and visual determination of H2O2

In this work, blue-emitting carbon quantum dots and distinctly sized CdTe semiconductor quantum dots were combined to implement a ratiometric probe for the monitoring of H2O2. By implementing a sensing scheme that combines multiple nanoprobes, excited at the same wavelength and emitting at different ones, which exhibit also dissimilar reactivity, it was possible to minimize detrimental factors associated with the use of a single photoluminescence wavelength such as fluctuations in excitation source or measured signal, fluorophore concentration, matrix effects and background fluorescence. The developed ratiometric probe was applied on the implementation of a conventional fluorometric assay and on a visual assay relying on the red, green and blue (RGB)-based colour changes promoted by increasing H2O2 concentrations. For the fluorometric determination assay, a good linear relationship between the fluorescence intensity ratio (FI(CD)434/FI(MPA)587) and H2O2 concentration within the range of 0.0100-0.2125% (w/w) was obtained (R = 0.9994, n = 7). The detection limit was about 0.00793% (w/w). The obtained results in the determination of H2O2 in contact lens solutions were in agreement with those provided by the reference procedure, with relative deviations between -4.71 and 1.89%. Regarding the RGB-visual assay, a linear working range for hydrogen peroxide concentrations up to 0.150% (w/w) was verified (n = 9) with a correlation coefficient of 0.9966, which confirms its potential as valuable analytical tool for on-the-spot semi-quantitative detection of H2O2.