Influence of Nanoscale Phase Separation in the Response of Ion-Selective Fluorescent/Colorimetric Probes

Fluorescent and colorimetric probes are widely used in analytical chemistry. A variety of fluorescent probes have been designed and synthesized, which can exhibit optical responses to various analytes (such as metal ions and disease biomarkers) and are widely applied in fields like cell imaging. However, many of these probes do not possess good water solubility. Therefore, it is common to see researchers using mixed solvents or adding surfactants to the solvent for characterization. But is this approach problematic? Taking the simplest pH probe as an example, we investigated the effects of molecular lipophilicity, mixed solvents, and molecular aggregation behavior on the probe response. We hope that our experimental findings can provide guidance for the design and research of nano- and molecular-scale fluorescent or colorimetric probes. Following the discussion, I will also show two chemical sensors based on lipophilized pH sensitive probes: one for ammonia detection in urine and the other for water hardness in fresh water.