The specific detection of Cu(II) using an AIE-active alanine ester

Within a series of metal cations, only Cu(II) can catalyze the hydrolyzation of tetraphenylethene-modified alanine ester. The released TPE-methanol exhibits lower solubility and higher fluorescence intensity than the ester, which allows Cu(II) to be detected by fluorescence enhancement. Cu(II) detection is important because it plays crucial role in several biological processes and ecological systems. Fluorescent techniques have attracted more and more attention in Cu(II) detection. In this report, we contribute a novel strategy to use fluorescence spectroscopy for Cu(II) specific detection. The specificity relies on the fact that, of the many metal cations, only Cu(II) can catalyze the hydrolyzation of α-amino acid ester. The novelty originates from the unique aggregation-induced emission (AIE) property of the fluorescent label. We designed a model α-amino acid ester (TPE-Ala) constructed with alanine and tetraphenylethene-functionalized methanol (TPE-methanol). In comparison with the precursor TPE-Ala, TPE-methanol has lower solubility and is easy to form aggregates in water, thereby displaying a higher fluorescent response. Thus, the Cu(II) catalyzed hydrolyzation can be monitored by recording the fluorescence enhancement and fluorescent detection Cu(II) is rationally achieved.