Two-Dimensional Nanostrips of Hydrophobic Copper Tetradecanoate for Making Self-Cleaning Glasses

We report a simple, solution-based technique for coating arbitrary surfaces with thin layers of self-assembled copper tetradecanoate (CTD) nanostrips, resulting in an optically transparent, superhydrophobic coating. The nanostrip-coated surfaces show water contact angles close to 150° and roll-off angles as small as 2°-3°. Importantly, CTD retains its hydrophobic nature even after annealing the self-assembled nanostrips at 200°C, which does not alter the crystal structure but “melts” the surface microstructure. This clearly indicates that the hydrophobicity in CTD is likely to be intrinsic in nature and not induced by the surface microstructure (as has been suggested earlier). Strong hydrophobicity in CTD over a relatively wide temperature range presumably results from the presence of the long aliphatic (tetradecanoate) chains in its structure. Importantly, the self-assembled copper tetradecanoate nanostrips can be dip-coated on glass to render it hydrophobic and at the same time retain a significant level of transparency over the entire visible region. Such nanostructured thin films may be expected to find applications not only as a self-cleaning glass, but also as a corrosion resistant coating, in gas storage (due to the layered structure), and as an active catalyst because of the visible absorbance

Structural and electronic properties of anisotropic ultrathin organic films from dichroic resonant soft x-ray reflectivity

We developed a quantitative approach for the determination of molecular arrangement and electronic structure in anisotropic organic ultrathin films based on the measurement of polarized reflectivity at the carbon K-edge. The reflectivity spectra were fitted to a parameterized model calculation. The method was applied to a self-assembled monolayer of 1,4-benzenedimethanethiol on gold. To simulate reflectivity, the organic anisotropic film was described by a dielectric tensor, obtained by ab initio calculations for the single molecule and suitable rotations to describe the molecular organization in film domains. Film structure was obtained though the best fit of the simulation to the experiment. Results were consistent with a monolayer-thick film composed of domains of molecules with in-plane isotropic distribution of orientations. In each domain, molecules adopted a standing configuration, with a tilt of 28° relative to the substrate normal. Information on the modification of the molecular electronic states due to chemical bonding was derived

Lying-Down to Standing-Up Transitions in Self Assembly of Butanedithiol Monolayers on Gold and Substitutional Assembly by Octanethiols

Self-assembly of butanedithiol (C4DT) mono- layers (SAMs) on gold and substitutional assembly by octanethiols from a lying-down doubly tethered phase of butane dithiol, were investigated in a vacuum evaporation experiment by high-resolution photoemission. The intent was to address the question of transitions from a lying-down to a standing-up phase in dithiol self-assembly and whether a standing-up phase of short chain dithiol can be formed. The lying-down doubly tethered dithiol phase, with both sulfur atoms attached to gold, was formed by evaporation and then exposed to octanethiol molecules. A mixed SAM composed of standing-up octanethiol and dithiol molecules is found to be formed. The degree of dithiol replacement, as evidenced by the increasing thickness of the SAM, is found to augment slowly with increasing exposure to octanethiol. A standing-up C4DT phase was found to be formed upon rapid very large exposure to C4DT vapors. Differences in valence band photoemission between the standing-up and lying-down phases were noted and accounted for theoretically. In all cases, measurements indicate more than one possible adsorption configuration as evidenced by different sulfur binding energies

Polarized X-ray scattering measures molecular orientation in polymer-grafted nanoparticles

Polymer chains are attached to nanoparticle surfaces for many purposes, including altering solubility, influencing aggregation, dispersion, and even tailoring immune responses in drug delivery. The most unique structural motif of polymer-grafted nanoparticles (PGNs) is the high-density region in the corona where polymer chains are stretched under significant confinement, but orientation of these chains has never been measured because conventional nanoscale-resolved measurements lack sensitivity to polymer orientation in amorphous regions. Here, we directly measure local chain orientation in polystyrene grafted gold nanoparticles using polarized resonant soft X-ray scattering (P-RSoXS). Using a computational scattering pattern simulation approach, we measure the thickness of the anisotropic region of the corona and extent of chain orientation within it. These results demonstrate the power of P-RSoXS to discover and quantify orientational aspects of structure in amorphous soft materials and provide a framework for applying this emerging technique to more complex, chemically heterogeneous systems in the future.This article is published in Nature Communications. DOI: 10.1038/s41467-021-25176-4. Posted with permission.</p

Lying-Down to Standing-Up Transitions in Self Assembly of Butanedithiol Monolayers on Gold and Substitutional Assembly by Octanethiols

Self-assembly of butanedithiol (C4DT) monolayers (SAMs) on gold and substitutional assembly by octanethiols from a lying-down doubly tethered phase of butane dithiol, were investigated in a vacuum evaporation experiment by high-resolution photoemission. The intent was to address the question of transitions from a lying-down to a standing-up phase in dithiol self-assembly and whether a standing-up phase of short chain dithiol can be formed. The lying-down doubly tethered dithiol phase, with both sulfur atoms attached to gold, was formed by evaporation and then exposed to octanethiol molecules. A mixed SAM composed of standing-up octanethiol and dithiol molecules is found to be formed. The degree of dithiol replacement, as evidenced by the increasing thickness of the SAM, is found to augment slowly with increasing exposure to octanethiol. A standing-up C4DT phase was found to be formed upon rapid very large exposure to C4DT vapors. Differences in valence band photoemission between the standing-up and lying-down phases were noted and accounted for theoretically. In all cases, measurements indicate more than one possible adsorption configuration as evidenced by different sulfur binding energies

Prion-derived tetrapeptide stabilizes thermolabile insulin via conformational trapping

Summary: Unfolding followed by fibrillation of insulin even in the presence of various excipients grappled with restricted clinical application. Thus, there is an unmet need for better thermostable, nontoxic molecules to preserve bioactive insulin under varying physiochemical perturbations. In search of cross-amyloid inhibitors, prion-derived tetrapeptide library screening reveals a consensus V(X)YR motif for potential inhibition of insulin fibrillation. A tetrapeptide VYYR, isosequential to the β2-strand of prion, effectively suppresses heat- and storage-induced insulin fibrillation and maintains insulin in a thermostable bioactive form conferring adequate glycemic control in mouse models of diabetes and impedes insulin amyloidoma formation. Besides elucidating the critical insulin-IS1 interaction (R4 of IS1 to the N24 insulin B-chain) by nuclear magnetic resonance spectroscopy, we further demonstrated non-canonical dimer-mediated conformational trapping mechanism for insulin stabilization. In this study, structural characterization and preclinical validation introduce a class of tetrapeptide toward developing thermostable therapeutically relevant insulin formulations

The role of interfacial donor–acceptor percolation in efficient and stable all-polymer solar cells

Abstract Polymerization of Y6-type acceptor molecules leads to bulk-heterojunction organic solar cells with both high power-conversion efficiency and device stability, but the underlying mechanism remains unclear. Here we show that the exciton recombination dynamics of polymerized Y6-type acceptors (Y6-PAs) strongly depends on the degree of aggregation. While the fast exciton recombination rate in aggregated Y6-PA competes with electron-hole separation at the donor–acceptor (D–A) interface, the much-suppressed exciton recombination rate in dispersed Y6-PA is sufficient to allow efficient free charge generation. Indeed, our experimental results and theoretical simulations reveal that Y6-PAs have larger miscibility with the donor polymer than Y6-type small molecular acceptors, leading to D–A percolation that effectively prevents the formation of Y6-PA aggregates at the interface. Besides enabling high charge generation efficiency, the interfacial D–A percolation also improves the thermodynamic stability of the blend morphology, as evident by the reduced device “burn-in” loss upon solar illumination