Amino(oligo)thiophene dyes useful for studying the electrophysiology of organelles, cells, and tissues are described. Compared to previously known dyes, the amino(oligo)thiophene dyes exhibit improved (faster) response to membrane potential changes, as well as the ability to be excited by 1064 nanometer femtosecond pulses. Methods of preparing the amino( oligo )thiophene dyes are also described.