6 research outputs found
Interlayer Resistance and Edge-Specific Charging in Layered Molecular Crystals Revealed by Kelvin-Probe Force Microscopy
Organic field-effect
transistors (OFETs) having an active channel
of solution-processed 2,7-dioctyl[1]benzothieno[3,2-<i>b</i>][1]benzothiophene (C<sub>8</sub>–BTBT) were investigated
by Kelvin-probe force microscopy (KFM). We found step-like potential
distributions in a channel region, suggesting that the interlayer
resistance between the conjugated BTBT core layers is quite high and
each conjugated layer is electrically isolated from one another by
insulating alkyl chain layers. We also found a noticeable positive
charging in the channel region especially at the step edges after
the device operation. The observed charging was explained by long-lived
positive charges on the trap sites, and the trap density at the step
edge was estimated to be on the order of 10<sup>11</sup> cm<sup>–2</sup>. The KFM measurements suggest that the device performance of the
staggered C<sub>8</sub>–BTBT OFETs could deteriorate due to
the considerably high access resistance, which stems from the high
interlayer resistance and/or by the site-specific charge trapping
at the contact/semiconductor interface which originates from step
edge structures
A feasibility study of predictable and unpredictable surf-like sounds for tinnitus therapy using personal music players
<p><b>Objective:</b> To evaluate the feasibility of predictable or unpredictable amplitude-modulated sounds for tinnitus therapy.</p> <p><b>Design:</b> The study consisted of two parts. (1) An adaptation experiment. Loudness level matches and rating scales (10-point) for loudness and distress were obtained at a silent baseline and at the end of three counterbalanced 30-min exposures (silence, predictable and unpredictable). (2) A qualitative 2-week sound therapy feasibility trial. Participants took home a personal music player (PMP).</p> <p><b>Study sample:</b> Part 1: 23 individuals with chronic tinnitus and part 2: seven individuals randomly selected from Part 1.</p> <p><b>Results:</b> Self-reported tinnitus loudness and annoyance were significantly lower than baseline ratings after acute unpredictable sound exposure. Tinnitus annoyance ratings were also significantly lower than the baseline but the effect was small. The feasibility trial identified that participant preferences for sounds varied. Three participants did not obtain any benefit from either sound. Three participants preferred unpredictable compared to predictable sounds. Some participants had difficulty using the PMP, the average self-report hours of use were low (less <1 h/day).</p> <p><b>Conclusions:</b> Unpredictable surf-like sounds played using a PMP is a feasible tinnitus treatment. Further work is required to improve the acceptance of the sound and ease of PMP use.</p
Atomic-Scale 3D Local Hydration Structures Influenced by Water-Restricting Dimensions
Hydration
structures at solid–liquid interfaces mediate
between the atomic-level surface structures and macroscopic functionalities
in various physical, chemical, and biological processes. Atomic-scale
local hydration measurements have been enabled by ultralow noise three-dimensional
(3D) frequency-modulation atomic force microscopy. However, for their
application to complicated surface structures, e.g., biomolecular
devices, understanding the relationship between the hydration and
surface structures is necessary. Herein, we present a systematic study
based on the concept of the structural dimensionality, which is crucial
in various scientific fields. We performed 3D measurements and molecular
dynamics simulations with silicate surfaces that allow for 0, 1, and
2 degrees of freedom to water molecules. Consequently, we found that
the 3D hydration structures reflect the structural dimensions and
the hydration contrasts decrease with increasing dimension due to
the enlarged water self-diffusion coefficient and increased embedded
hydration layers. Our results provide guidelines for the analysis
of complicated hydration structures, which will be exploited in extensive
fields
Molecular-Resolution Imaging of Interfacial Solvation of Electrolytes for Lithium-Ion Batteries by Frequency Modulation Atomic Force Microscopy
Solvation
structures formed by ions and solvent molecules
at solid/electrolyte
interfaces affect the energy storage performance of electrochemical
devices, such as lithium-ion batteries. In this study, the molecular-scale
solvation structures of an electrolyte, a solution of lithium bis(trifluoromethanesulfonyl)imide
(LiTFSI) in propylene carbonate (PC) at the electrolyte–mica
interface, were measured using frequency-modulation atomic force microscopy
(FM-AFM). The spacing of the characteristic force oscillation in the
force versus distance curves increased with increasing ion concentration,
suggesting an increase in the effective size of molecules at the interface.
Molecular dynamics simulations showed that the effective size of molecular
assemblies, namely, solvated ions formed at the interface, increased
with increasing ion concentrations, which was consistent with the
experimental results. Knowledge of molecular-scale structures of solid/electrolyte
interfaces obtained by a combination of FM-AFM and molecular dynamics
simulations is important in the design of electrolytes for future
energy devices and in improving their properties
Beyond the Helix Pitch: Direct Visualization of Native DNA in Aqueous Solution
The DNA double helix was first elucidated by J.D. Watson and F.H.C. Crick over a half century ago. However, no one could actually “see” the well-known structure ever. Among all real-space observation methods, only atomic force microscopy (AFM) enables us to visualize the biologically active structure of natural DNA in water. However, conventional AFM measurements often caused the structural deformation of DNA because of the strong interaction forces acting on DNA. Moreover, large contact area between the AFM probe and DNA hindered us from imaging sub-molecular-scale features smaller than helical periodicity of DNA. Here, we show the direct observation of native plasmid DNA in water using an ultra-low-noise AFM with the highly sensitive force detection method (frequency modulation AFM: FM-AFM). Our micrographs of DNA vividly exhibited not only overall structure of the B-form double helix in water but also local structures which deviate from the crystallographic structures of DNA without any damage. Moreover, the interaction force area in the FM-AFM was small enough to clearly discern individual functional groups within DNA. The technique was also applied to explore the synthesized DNA nanostructures toward the current nanobiotechnology. This work will be essential for considering the structure–function relationship of biomolecular systems <i>in vivo</i> and for <i>in situ</i> analysis of DNA-based nanodevices