1 research outputs found
Molecular Tuning of the Vibrational Thermal Transport Mechanisms in Fullerene Derivative Solutions
Control
over the thermal conductance from excited molecules into
an external environment is essential for the development of customized
photothermal therapies and chemical processes. This control could
be achieved through molecule tuning of the chemical moieties in fullerene
derivatives. For example, the thermal transport properties in the
fullerene derivatives indene-C<sub>60</sub> monoadduct (ICMA), indene-C<sub>60</sub> bisadduct (ICBA), [6,6]-phenyl C<sub>61</sub> butyric acid
methyl ester (PCBM), [6,6]-phenyl C<sub>61</sub> butyric acid butyl
ester (PCBB), and [6,6]-phenyl C<sub>61</sub> butyric acid octyl ester
(PCBO) could be tuned by choosing a functional group such that its
intrinsic vibrational density of states bridge that of the parent
molecule and a liquid. However, this effect has never been experimentally
realized for molecular interfaces in liquid suspensions. Using the
pump–probe technique time domain thermotransmittance, we measure
the vibrational relaxation times of photoexcited fullerene derivatives
in solutions and calculate an effective thermal boundary conductance
from the opto-thermally excited molecule into the liquid. We relate
the thermal boundary conductance to the vibrational modes of the functional
groups using density of states calculations from molecular dynamics.
Our findings indicate that the attachment of an ester group to a C<sub>60</sub> molecule, such as in PCBM, PCBB, and PCBO, provides low-frequency
modes which facilitate thermal coupling with the liquid. This offers
a channel for heat flow in addition to direct coupling between the
buckyball and the liquid. In contrast, the attachment of indene rings
to C<sub>60</sub> does not supply the same low-frequency modes and,
thus, does not generate the same enhancement in thermal boundary conductance.
Understanding how chemical functionalization of C<sub>60</sub> affects
the vibrational thermal transport in molecule/liquid systems allows
the thermal boundary conductance to be manipulated and adapted for
medical and chemical applications