pH-stabilized polydiacetylenes achieved through sodium dodecyl benzenesulfonate doping: application in dopamine sensing

Abstract

Polydiacetylenes (PDAs), known for their distinct blue-to-red color transition, are widely applied in chemical and biological sensing, including point-of-care diagnostics. However, their high sensitivity to pH fluctuations—particularly under basic conditions—can lead to chromatic false positives, limiting reliability. In this study, we developed surfactant co-doped PDA self-assemblies that resolve this long-standing challenge by stabilizing PDA assemblies against alkaline pH while preserving their characteristic chromatic responsiveness. 10,12-Pentacosadiynoic acid (PCDA) was co-assembled with surfactants, including sodium dodecyl benzenesulfonate, sodium dodecyl sulfate, cetyltrimethylammonium bromide, Triton X-100, and Tween-20, yielding diverse morphologies such as vesicles and flower-like and rod-shaped structures, as observed by SEM and TEM. Notably, the PCDA : SDBS system formed Aloe polyphylla-like architectures and maintained remarkable chromatic stability at pH > 10, effectively addressing PDA instability in basic environments. Zeta potential analysis revealed a highly negative surface charge (–107 mV) for PCDA : SDBS, likely repelling anions from the polymer backbone and preserving chromatic integrity. Furthermore, PCDA : SDBS exhibited a selective blue-to-red transition upon interaction with the cationic surfactant CTAB. The system was further functionalized with phenyl boronic acid-modified PCDA (PDABA) for dopamine detection, achieving high selectivity and a low detection limit (1.5 ppb) under basic conditions. This co-doping strategy offers a robust route to enhance PDA stability and expand applicability in real-world sensing platforms across variable pH environments.