the addition of Al3+ to C-dots-R6G solution results in
gradual decrease in the emission intensity at 410 nm with
concomitant increase in the emission at 560 nm, exhibiting the
blue-to-yellow emission color change. This could be clearly
observed by the naked-eye under UV illumination (inset photos
in Scheme 2). This phenomenon can be explained by the fact
that the introduction of Al3+ induced dual changes in emissions,
suggesting that the ratiometric detection of Al3+ was possible
(Figure 2a).