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Invited editorial in Chem: Harnessing entropy in single-molecule force spectroscopy with semiconducting polymers

last modified Feb 09, 2018 11:46 AM
Dr A. Zaccone

An invited editorial by CEB's Dr Alessio Zaccone has been published in the leading chemistry journal Chem, launched in 2016 by Cell Press as the chemistry niece of the journal Cell. The editorial by Dr Zaccone addresses a recent experimental breakthrough obtained in the group of Joris Sprakel at the University of Wageningen, the Netherlands. Sprakel et al. devised a new method which allows, for the first time, the measurement of femtonewton forces at the molecular level. The mechanism is based on the light-emitting properties of semiconducting polymers, as explained in the Figure. The method allows the measurement of elusive ultra-weak entropic forces in the molecular domain, and also was used by Sprakel et al. to confirm earlier theoretical predictions by Dr Zaccone on the dynamics of polymers under deformation at the molecular scale.

Harnessing Entropy in Single-Molecule Force Spectroscopy with Semiconducting Polymers Alessio Zaccone, Chem, Volume 4, Issue 2, p191–193, 8 February 2018.


illustration chem
Figure caption: A conductive conjugated polymer chain is doped with acceptor/donor monomers and stimulated with light. Transition to a higher energy level of a donor monomer is excited by the applied radiation. If the donor is surrounded by other donors only, the excited state decays via an internal photon emission process within the donor monomer, with rate kD. When an acceptor monomer is sufficiently close to a donor monomer, instead, the excitation energy can be transferred from the donor to the acceptor which then emits a photon, via Förster resonant energy transfer, with rate kET. Differences due to the chain conformation can thus be recorded in the grayscale emission spectrum which can be used to quantitatively infer back the mechanical force acting on the polymer molecule.