Photoluminescence behaviors of organic soluble DNA bearing carbazole and pyrene derivatives as side-chain substituents and effect of the copolymer structure on the förster energy transfer process

Organic soluble DNA bearing two different fluorophores in the side chain was prepared by reacting purified DNA with the cationic molecules 9-(12-bromododecyl)-9H-carbazole and (E)-l-(4-(12-bromododecyloxy)styryl)pyrene in water. Two homopolymers (CzDNA and PyDNA) and random copolymers (CzDNA-co-PyDNA) were prepared successfully. The absorption and photoluminescence (PL) behavior of CzDNA-co-PyDNA with pyrene derivative concentrations was investigated. As reference, we employed a guest-host system and polymer blends using DNA homopolymers. The Förster energy transfer process was investigated in three different DNA systems. The DNA copolymer system showed much better energy transfer efficiency than the other DNA systems. The copolymers were mixed with 2-{2-[2-(4-diethylamino-phenyl)-vinyl]-6-methyl- pyran-4-ylidene}-malononitrile (DCM) at an optimum, concentration. At low DCM concentration (0.3 wt %), undesired emissions were observed due to an incomplete energy transfer process from excited pyrene moieties. At high DCM concentration (5.0 wt %), red emissions were predominant; this is attributed to an efficient Förster energy transfer process.