Highly sensitive biological and chemical sensors based on reversible fluorescence quenching in a conjugated polymer.
The fluorescence of a polyanionic conjugated polymer can be quenched by extremely low concentrations of cationic electron acceptors in aqueous solutions. We report a greater than million-fold amplification of the sensitivity to fluorescence quenching compared with corresponding "molecular excited states." Using a combination of steady-state and ultrafast spectroscopy, we have established that the dramatic quenching results from weak complex formation [polymer(-)/quencher(+)], followed by ultrafast electron transfer from excitations on the entire polymer chain to the quencher, with a time constant of 650 fs. Because of the weak complex formation, the quenching can be selectively reversed by using a quencher-recognition diad. We have constructed such a diad and demonstrate that the fluorescence is fully recovered on binding between the recognition site and a specific analyte protein. In both solutions and thin films, this reversible fluorescence quenching provides the basis for a new class of highly sensitive biological and chemical sensors.
Chen
L
L
Center for Material Science, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
McBranch
D W
DW
Wang
H L
HL
Helgeson
R
R
Wudl
F
F
Whitten
D G
DG
D015374:Biosensing Techniques; D005453:Fluorescence; D011108:Polymers / Q000737:chemistry*
D011108:Polymers