Real-time conductance switching and place-exchange up and down substrate step edges have been measured for oligo(phenylene ethynylene) (OPE) molecules inserted into host dodecanethiolate ...self-assembled monolayers (SAM). These measurements were obtained by placing a scanning tunneling microscopy tip over individual nitro-functionalized OPE molecules and recording apparent height versus time. In addition, real-time measurements for the host SAM were acquired and indicated small motions for the monolayer−substrate system.
Photodynamic therapy: A novel supramolecular photosensitizer is efficiently fabricated based on a strong host–guest interaction, which shows an enhanced singlet oxygen generation ability of the ...porphyrin units and has thus a greatly improved antibacterial efficiency (see picture). The supramolecular photosensitizer is an adaptive system with switchable photophysical properties.
Ultraviolet photoemission spectra of monolayers of 4,4′-bis-(phenylethynyl)benzenethiol on Pt, Au, Cu, Ag.
Ultraviolet photoemission spectra have been used to study the interfacial electronic ...structure of self-assembled monolayers of 4,4′-bis-(phenylethynyl) benzenethiol, 2-naphthalenethiol, and 3-(naphthalen-2-yl)propane-1-thiol chemisorbed on Ag, Cu, Au, and Pt. The binding energy of the highest occupied
π-state and the work function of the modified surface, though dependant on the molecule, were nearly independent of the substrate.
Using ultrasound to 3D-print materials Yao, Yuxing; Shapiro, Mikhail G
Science (American Association for the Advancement of Science),
12/2023, Letnik:
382, Številka:
6675
Journal Article
Recenzirano
Ultrasound allows additive manufacturing to go deeper-potentially inside the body.
We have studied oligo(phenylene-ethynylene)s inserted into amide-containing alkanethiol self-assembled monolayers using scanning tunneling microscopy to demonstrate switching based on chemical ...functionality of the environment of the inserted molecules. The molecules show stability in two conductance states: an ON and an OFF state. We demonstrate bias-dependent switching due to hydrogen bonding between the inserted oligo(phenylene-ethynylene) and the matrix molecules. In addition, the inserted molecules exhibit fewer switching events than previously reported for alkanethiol matrixes, which we attribute to the rigidity of the hydrogen-bonded matrix.
Reliable and reproducible methods have been developed for the formation of self-assembled monolayers (SAMs) of thiolacetyl-terminated oligo(phenylene ethynylene)s on a Au surface. The thiolacetyl ...groups are deprotected in situ and transformed to the free thiol, which then spontaneously forms a SAM. The SAMs are characterized by ellipsometry and electrochemistry, while the solutions are characterized by UV−vis spectroscopy. The results indicate that the previously described NH4OH/THF mixture is a poor choice for deprotection of thiols bearing multiple nitro substituents. Conversely, use of the more polar system acetone/MeOH/NH4OH or acid conditions CH2Cl2/MeOH/H2SO4 permits the formation of SAMs with thicknesses that are consistent with the predicted length of the molecules. However, the latter acid mixture appears to be less destructive to the highly electron-deficient multinitro oligomers when analyzed by UV−vis spectroscopy. The potential-assisted assembly is 1−2 orders of magnitude faster than the chemical method. This technique can be directly used to assemble different conjugated oligomers on one electrode to the exclusion of a nearby electrode.
Energy devices such as rechargeable batteries, fuel cells, and solar cells are central to powering a renewable, mobile, and electrified future. To advance these devices requires a fundamental ...understanding of the complex chemical reactions, material transformations, and charge flow that are associated with energy conversion processes. Analytical in situ transmission electron microscopy (TEM) offers a powerful tool for directly visualizing these complex processes at the atomic scale in real time and in operando. Recent advancements in energy materials and devices that have been enabled by in situ TEM are reviewed. First, the evolutionary development of TEM nanocells from the open‐cell configuration to the closed‐cell, and finally the full‐cell, is reviewed. Next, in situ TEM studies of rechargeable ion batteries in a practical operation environment are explored, followed by applications of in situ TEM for direct observation of electrocatalyst formation, evolution, and degradation in proton‐exchange membrane fuel cells, and fundamental investigations of new energy materials such as perovskites for solar cells. Finally, recent advances in the use of environmental TEM and cryogenic electron microscopy in probing clean‐energy materials are presented and emerging opportunities and challenges in in situ TEM research of energy materials and devices are discussed.
The most recent developments in in situ transmission electron microscopy for studying green‐energy materials and devices such as rechargeable ion batteries, chemical fuel cells, and perovskite solar cells are reviewed. A critical view on the application of this technology on the long road toward a green‐energy future is provided.
NanoCell Electronic Memories Tour, James M; Cheng, Long; Nackashi, David P ...
Journal of the American Chemical Society,
10/2003, Letnik:
125, Številka:
43
Journal Article
Recenzirano
NanoCells are disordered arrays of metallic islands that are interlinked with molecules between micrometer-sized metallic input/output leads. In the past, simulations had been conducted showing that ...the NanoCells may function as both memory and logic devices that are programmable postfabrication. Reported here is the first assembly of a NanoCell with disordered arrays of molecules and Au islands. The assembled NanoCells exhibit reproducible switching behavior and two types of memory effects at room temperature. The switch-type memory is characteristic of a destructive read, while the conductivity-type memory features a nondestructive read. Both types of memory effects are stable for more than a week at room temperature, and bit level ratios (0:1) of the conductivity-type memory have been observed to be as high as 104:1 and reaching 106:1 upon ozone treatment, which likely destroys extraneous leakage pathways. Both molecular electronic and nanofilamentary metal switching mechanisms have been considered, though the evidence points more strongly toward the latter. The approach here demonstrates the efficacy of a disordered nanoscale array for high-yielding switching and memory while mitigating the arduous task of nanoscale patterning.
Living cilia stir, sweep and steer via swirling strokes of complex bending and twisting, paired with distinct reverse arcs
. Efforts to mimic such dynamics synthetically rely on multimaterial designs ...but face limits to programming arbitrary motions or diverse behaviours in one structure
. Here we show how diverse, complex, non-reciprocal, stroke-like trajectories emerge in a single-material system through self-regulation. When a micropost composed of photoresponsive liquid crystal elastomer with mesogens aligned oblique to the structure axis is exposed to a static light source, dynamic dances evolve as light initiates a travelling order-to-disorder transition front, transiently turning the structure into a complex evolving bimorph that twists and bends via multilevel opto-chemo-mechanical feedback. As captured by our theoretical model, the travelling front continuously reorients the molecular, geometric and illumination axes relative to each other, yielding pathways composed from series of twisting, bending, photophobic and phototropic motions. Guided by the model, here we choreograph a wide range of trajectories by tailoring parameters, including illumination angle, light intensity, molecular anisotropy, microstructure geometry, temperature and irradiation intervals and duration. We further show how this opto-chemo-mechanical self-regulation serves as a foundation for creating self-organizing deformation patterns in closely spaced microstructure arrays via light-mediated interpost communication, as well as complex motions of jointed microstructures, with broad implications for autonomous multimodal actuators in areas such as soft robotics
, biomedical devices
and energy transduction materials
, and for fundamental understanding of self-regulated systems
.
We report excellent correlations between the first negative threshold potentials (V THs) for electric conduction, electrochemical potentials, and computed lowest unoccupied molecular orbital energies ...in a series of phenylene−ethynylene oligomers bearing a sulfur-based anchoring unit and different electroactive substituents on the central benzene ring. The theoretical and electrochemical results strongly suggest that the peaks observed in the i − V curves have a true molecular origin and are associated with distinct unoccupied molecular levels of the compounds that are strongly localized on the central ring (except for compound I). This localization might account for the existence of a long-lived radical−anion state that permits lateral electron hopping and leads to charge trapping and storage.
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