10.1021/acsomega.8b01813.s001 Changyou Zhu Changyou Zhu Manling Huang Manling Huang Jialing Lan Jialing Lan Lung Wa Chung Lung Wa Chung Xin Li Xin Li Xiaojiang Xie Xiaojiang Xie Colorimetric Calcium Probe with Comparison to an Ion-Selective Optode American Chemical Society 2018 probe colorimetric calcium ion-exchange process dimer forms Computational studies tunable detection range Ion-Selective Optode Design strategies ion-selective optodes Colorimetric Calcium Probe ionophore-based ion-selective optode 2018-10-03 08:13:36 Journal contribution https://acs.figshare.com/articles/journal_contribution/Colorimetric_Calcium_Probe_with_Comparison_to_an_Ion-Selective_Optode/7159646 Design strategies for small molecular probes lay the foundation of numerous synthetic chemosensors. A water-soluble colorimetric calcium molecular probe inspired by the ionophore-based ion-selective optode is presented here with a tunable detection range (around micromolar at pH 7). The binding of Ca<sup>2+</sup> resulted in the deprotonation of the probe and thus a significant spectral change, mimicking the ion-exchange process in ion-selective optodes. The 1:1 exchange between Ca<sup>2+</sup> and H<sup>+</sup> was confirmed with Job’s plot. Computational studies revealed possible monomer and dimer forms of the probe–Ca<sup>2+</sup> complexes.