Abstract
Two cationic conjugated polyelectrolytes (CPs, P1i and P2i) were synthesized and examined as a fluorescence resonance energy transfer (FRET) donor to fluorescein (Fl)-labeled single-stranded DNA (ssDNA-Fl) using steady-state and time-resolved photoluminescence (PL) spectroscopy. The two polymers have the same π-conjugation with the main structural difference being the presence of the spiro-anthracenyl substituents orthogonal to the polymer backbone of P2i. These spiro-substituents can function as a molecular spacer that increases the intermolecular separation in the electrostatic complex with ssDNA-Fl. We measured almost complete PL quenching of the excited Fl* after electrostatic complexation with P1i (PL lifetime 4 ns → 78 ps) and relatively moderate quenching with P2i (PL lifetime 4 ns → 552 ps). A quenching efficiency (ΦeT) of 98% and 86% was obtained for P1i/ssDNA-Fl and for P2i/ssDNA-Fl, respectively. Both systems have same thermodynamic driving force for quenching as a result of them having the same electronic structures. This discrepancy can be explained in terms of the reduced quenching (via electron transfer, eT) by the increased D-A distance due to the existence of spiro-attached molecular spacers in P2i. It shows that thermodynamically favorable eT quenching can be controlled kinetically by modulating the D-A intermolecular distance using molecular spacers, which suggests an important molecular design guideline for efficient CPs-based DNA detection.
Original language | English |
---|---|
Pages (from-to) | 636-642 |
Number of pages | 7 |
Journal | Current Applied Physics |
Volume | 9 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2009 May |
Externally published | Yes |
Keywords
- Conjugated polyelectrolytes
- Energy transfer
- FRET
- Fluorescence
- Water-soluble conjugated polymers
ASJC Scopus subject areas
- Materials Science(all)
- Physics and Astronomy(all)