3 research outputs found
Energetics of Forced Thermal Ratchet
Molecular motors are known to have the high efficiency of energy
transformation in the presence of thermal fluctuation.
Motivated by the surprising fact, recent studies of thermal ratchet models
are showing how and when work should be extracted from non-equilibrium
fluctuations.
One of the important finding was brought by Magnasco where he studied the
temperature dependence on the fluctuation-induced current in a ratchet
(multistable) system and showed that the current can generically be maximized
in a finite temperature.
The interesting finding has been interpreted that thermal fluctuation is not
harmful for the fluctuation-induced work and even facilitates its efficiency.
We show, however, this interpretation turns out to be incorrect as soon as we
go into the realm of the energetics
[Sekimoto,J.Phys.Soc.Jpn.66,1234-1237(1997)]: the efficiency of energy
transformation is not maximized at finite temperature, even in the same system
that Magnasco considered. The maximum efficiency is realized in the absence of
thermal fluctuation. The result presents an open problem whether thermal
fluctuation could facilitate the efficiency of energetic transformation from
force-fluctuation into work.Comment: 3pages, 4sets of figure
Deep Blue Asymmetrical Streptocyanine Dyes: Synthesis, Spectroscopic Characterizations, and Ion-Specific Cooperative Adsorption at the Surface of TiO<sub>2</sub> Anatase Nanoparticles
Various
triflate (TfO<sup>–</sup>), tetrafluoroborate (BF<sub>4</sub><sup>–</sup>), and perchlorate (ClO<sub>4</sub><sup>–</sup>) salts of (<i>E</i>)-9-(3-(4-(diphenylamino)phenyl)allylidene)-9<i>H</i>-carbazol-9-ium chromophores, asymmetrical streptocyanine
blue dyes, were synthesized, and their structures and photochemical
and electrochemical properties were characterized. Displaying a high
absorption band in the wavelength range 620–640 nm in acidified
benzonitrile, the dyes provide an intense absorption at longer wavelength
thanks to their oxidized π-conjugated systems. The π-electronic
structure underwent twisting and bending, counteracting the electron-donating/withdrawing
induction of its different substituents with a propensity to cancel
its dipole moment and HOMO–LUMO charge-transfer coefficient.
Zeta potential measurements of colloidal suspensions of sensitized
TiO<sub>2</sub> anatase nanoparticles outlined the difference in electric
behavior of the organic ionic pairs at the surface of the nanoparticles:
The noncoordinating or coordinating characters of the counterions
were found governing the molecular density at the surface and the
adsorption/desorption kinetics of the ionic pairs. Dye-sensitized
solar cell (DSSC) measurements performed with I<sup>–</sup>/I<sub>3</sub><sup>–</sup> as redox shuttle outlined the availability
of the dyes for solar cell sensitization and the conditions for best
stability/efficiency of such π-conjugated structures according
to the nature of the counterion