2 research outputs found
Mesophase in a Thiolate-Containing Diacyl Phospholipid Self-Assembled Monolayer
Maintaining
the intrinsic features of mesophases is critically
important when employing phospholipid self-assemblies to mimic biomembranes.
Inorganic solid surfaces provide platforms to support, guide, and
analyze organic self-assemblies but impose upon them a tendency to
form well-ordered phases not often found in biomembranes. To address
this, we measured mesophase formation in a thiolate self-assembled
monolayer (SAM) of diacyl phospholipid, 1,2-dipalmitoyl-<i>sn</i>-glycero-3-phosphothioethanol (DPPTE) on Au(111), and provide thermodynamic
analysis on the mixing behavior of inequivalent DPPTE acyl chains.
Our work has uncovered three fundamental issues that enable mesophase
formation: (1) Elimination of templating effects of the solid surface,
(2) Weakening intermolecular and molecule–substrate interactions
in adsorbates, and (3) Equilibrium through entropy-driven self-assembly.
Thus, our work provides a more holistic understanding of phase behavior,
from liquid phases to mesophases to highly crystalline phases, in
organic self-assemblies on solid surfaces, which may extend their
applications in nanodevices and to the wider fields of biology and
medicine
Micromachined Chip Scale Thermal Sensor for Thermal Imaging
The
lateral resolution of scanning thermal microscopy (SThM) has
hitherto never approached that of mainstream atomic force microscopy,
mainly due to poor performance of the thermal sensor. Herein, we report
a nanomechanical system-based thermal sensor (thermocouple) that enables
high lateral resolution that is often required in nanoscale thermal
characterization in a wide range of applications. This thermocouple-based
probe technology delivers excellent lateral resolution (∼20
nm), extended high-temperature measurements >700 °C without
cantilever
bending, and thermal sensitivity (∼0.04 °C). The origin
of significantly improved figures-of-merit lies in the probe design
that consists of a hollow silicon tip integrated with a vertically
oriented thermocouple sensor at the apex (low thermal mass) which
interacts with the sample through a metallic nanowire (50 nm diameter),
thereby achieving high lateral resolution. The efficacy of this approach
to SThM is demonstrated by imaging embedded metallic nanostructures
in silica core–shell, metal nanostructures coated with polymer
films, and metal–polymer interconnect structures. The nanoscale
pitch and extremely small thermal mass of the probe promise significant
improvements over existing methods and wide range of applications
in several fields including semiconductor industry, biomedical imaging,
and data storage