A trimethine cyanine dye for copper (II) detection based on the transformation between monomers and J-aggregates via G-quadruplex regulation

A trimethine cyanine dye (MTC) was developed for Cu 2+ detection. MTC can exhibit different aggregation modes, such as monomers, dimers, H- and J-aggregates. Here, G-quadruplex (G2) with modification of an alkyne at the 5′ end could regulate J-aggregates of MTC to monomers. Upon addition of Cu 2+ , sodium ascorbate, and another sequence (G1) with azide modification at the 3′ end, a new sequence was ligated by click chemistry of azide-alkyne cycloaddition, accompanied by MTC monomers assembling into J-aggregates again. The colors of the solution turned pink to blue. This strategy shows high specificity and selectivity and can realize monitoring Cu 2+ in tap water. This simple method uses only a Uv-vis instrument to finish Cu 2+ detection. Graphical abstract A cyanine dye transformation between J-aggregates and monomers was applied to monitor the Cu 2+ level via Cu + -promoted azide-alkyne cycloaddition of two rich guanine sequences.