15,334 research outputs found

    Adsorption assisted translocation of a chain molecule through a pore in a spherical vesicle

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    We analyze the free energy for translocation of a polymer from the outside of a spherical vesicle to the inside. The process is assumed to be driven by the adsorption of the polymer on the inner surface of the vesicle. We argue that in the case where the polymer is adsorbed on the outer surface too, the entropic barrier for translocation is absent. We analyze the adsorption energy and find the free energy profile for the process. We argue that the motion corresponds to a polymer crossing a region with a change in free energy per segment. Based upon our earlier analsis of the behaviour of kinks in such a problem, we conclude that the translocation can occur with a crossing time tcrossNt_{cross}\sim N

    Excitation energy transfer from dye molecules to doped graphene

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    Recently, we have reported theoretical studies (J. Chem. Phys. 129, 054703, 2008 and J. Chem. Phys. 130, 086101, 2009) on the rate of energy transfer from an electronically excited molecule to graphene. It was found that graphene is a very efficient quencher of the electronically excited states and that the rate \propto (distance)4(distance)^{-4}. The process was found to be effective up to 30  nm30\;nm which is well beyond the traditional FRET limit. In this report, we study the transfer of an amount of energy Ω\hbar \Omega from a dye molecule to doped graphene. We find a crossover of the distance dependence of the rate from (distance)4(distance)^{-4} to exponential as the Fermi level is increasingly shifted into the conduction band, with the crossover occurring at a shift of the Fermi level by an amount Ω/2\hbar \Omega/2.Comment: This paper was submitted to J. Chem. Phys. on 20/05/201
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