4,7-Disubstituted benzothiadiazoles containing 1-arylethynyl and 4-methoxyphenyl groups are selective photoluminescent “light up” probes to duplex DNA with unprecedented sensibility in both spectrophotometric and spectrofluorimetric measurements. ... These molecules possess the geometry and electronic properties desirable for DNA duplex intercalators. Here, we demonstrate that new neutral and highly polar BTD are outstanding light up probes for human DNA.