Amphiphilic hemicyanine dyes were obtained by coupling unpolar derivatives of aniline and naphthylamine, respectively, to polar derivatives of pyridinium and isoquinolinium, respectively. These dyes have no free double bond that is prone to photoisomerization. They are effective voltage-sensitive probes in biomembranes. The dyes were characterized by their spectra of absorption and by the spectra, the quantum yields, and the lifetimes of ...