Abstract Polymer thin films in wearable electronics undergo creep recovery during operation as on-body devices, resulting in unrecoverable strain that subsequently induces mechanical instability in the films. However, the creep recovery behavior of polymer thin films has not been investigated due to their intrinsic fragility and the difficulty in controlling ultralow loads for the films. We evaluate the creep recovery behavior of pseudo-free-standing polymer thin films as a function of creep stress, developing direct creep recovery testing with a feedback-based ultralow-load control system. Polystyrene (PS) thin films exhibit a sharp increase in unrecoverable strain with the onset of crazing. While poly(3-butylthiophene) (P3BT) thin films show a linear increase in the relative ratio of unrecoverable strain with increasing creep stress, poly(3-hexylthiophene) (P3HT) thin films exhibit a viscoelastic strain larger than unrecoverable strain. This work reveals the creep recovery behavior of polymer thin films and proposes a direct creep recovery testing method.
Abstract Stereochemistry underlies structure–function relationships across biology and materials science. Here, we investigate electron transport in oligopeptide stereoisomers using single-molecule experiments and computational modeling. Our results show that stereochemical modifications in tyrosine-based peptides lead to significant variations in molecular conductance and transport distance along the peptide backbone, associated with changes in aromatic side-chain interactions and electronic coupling. In alanine-based peptides, stereochemical modifications alter molecular conductance through secondary-structure interactions associated with β-turn conformations. Molecular dynamics simulations and quantum mechanical calculations reveal the molecular origins of these stereochemistry-dependent structural and electronic properties. Overall, this work shows that stereochemical modification of nonterminal amino acids provides a means to control electron transport through distinct mechanisms involving aromatic side-chain interactions and secondary structure. These results establish stereochemistry as a molecular design parameter for controlling electron transport in peptide-based electronic materials.
Abstract Lanthanide-doped nanoparticles with near-infrared-II (NIR-II, 1000–1700 nm) emission hold great promise for deep-tissue bioimaging, yet their luminescence efficiency is often limited by conventional sensitization pathways. Herein, we go beyond this conventional paradigm by introducing a Ca2+-formed band structure modulation in the host lattice to dramatically boost the NIR-II emission of lanthanide-doped nanoparticles. Rational doping of Ca2+ ions restructures the energy levels, enabling the probe to efficiently capture excitation energy and channel it toward NIR-II-emitting lanthanide activators. This Ca2+-induced band structure modulation mechanism not only enhances the absorption cross section but also accelerates energy transfer to the NIR-II-emitting states. As a result, the designed nanoprobes exhibit excellent photostability and a high quantum yield. In vivo bioimaging demonstrates that the resulting nanoprobes enable deep-tissue visualization with an improved signal-to-background ratio. This work establishes a sensitization strategy that goes beyond conventional approaches, positioning lanthanide-based NIR-II probes as promising candidates for advanced biological imaging.
Abstract Dense TiO2 thin-film electrodes suffer from limited electrolyte penetration and restricted Li-ion transport, making the electrode architecture a critical parameter for efficient charge storage. Herein, glancing-angle deposition (GLAD) combined with reactive magnetron sputtering is used to engineer ion-accessible TiO2 nanocolumnar architectures without compositional modification or postprocessing. Kinetic Monte Carlo simulations guided the selection of substrate tilt and azimuthal rotation conditions to control the column orientation, intercolumnar spacing, and open porosity. The predicted morphologies were subsequently validated by electron microscopy for the experimentally deposited thin films. Electrochemical measurements show that GLAD-engineered electrodes deliver up to approximately 4-fold higher areal capacitance than dense TiO2 films. ToF-SIMS depth profiling further reveals that Li species remain largely concentrated near the surface of dense films. In contrast, the GLAD-engineered nanocolumnar architecture allows for a more uniform Li distribution throughout the electrode depth. These results establish morphology-controlled ion accessibility as the primary origin of the enhanced electrochemical response.
Abstract Accessing crystal phases under nonequilibrium conditions is a central challenge for expanding the landscape of materials. Simple-cubic (sc) structures are considered energetically unfavorable in elemental solids and have previously been confirmed only in polonium. Here, we report the direct observation of a previously unrecognized sc-Ag formed under far-from-equilibrium conditions. Using electron beam irradiation inside a high-resolution transmission electron microscope as a trigger, we induced the radiolytic decomposition of silver iodide (AgI) and tracked the in situ formation of silver crystals in real time. Continuous imaging revealed that sc-Ag formation strongly depends on the polymorph of the precursor and occurs selectively from metastable γ-AgI. The sc-Ag exhibited unusually high chemical reactivity, undergoing gradual oxidation into silver oxide under high-vacuum conditions where conventional fcc-Ag remains stable. These findings demonstrate that irreversible crystal formation pathways can kinetically stabilize crystal structures inaccessible under near-equilibrium conditions and extend a previously inaccessible structural limit of metallic bonding.
