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Disordered proteins often undergo a stimuli-responsive, disorder-to-order transition which facilitates dynamic processes that modulate the physiological activities and material properties of cells, such as strength, chemical composition, and reflectance. It remains challenging to gain rapid and spatiotemporal control over such disorder-to-order transitions, which limits the incorporation of these proteins into novel materials. The reflectin protein is a cationic, disordered protein whose assembly is responsible for dynamic color camouflage in cephalopods. Stimuli-responsive control of reflectin's assembly would enable the design of biophotonic materials with tunable color. Herein, a novel, multivalent azobenzene photoswitch is shown to be an effective and non-invasive strategy for co-assembling with reflectin molecules and reversibly controlling assembly size. Photoisomerization between the trans and cis (E and Z) photoisomers promotes or reduces Coulombic interactions, respectively, with reflectin proteins to repeatedly cycle the sizes of the photoswitch-reflectin assemblies between 70 nm and 40 nm. The protein assemblies formed with the trans and cis isomers show differences in interaction stoichiometry and secondary structure, which indicate that photoisomerization modulates the photoswitch-protein interactions to change assembly size. Our results highlight the utility of photoswitchable interactions to control reflectin assembly and provide a tunable synthetic platform that can be adapted to the structure, assembly, and function of other disordered proteins.

Cation-π interactions drive the self-assembly and cohesion of many biological molecules, including the adhesion proteins of several marine organisms. Although the origin of cation-π bonds in isolated pairs has been extensively studied, the energetics of cation-π-driven self-assembly in molecular films remains uncharted. Here we use nanoscale force measurements in combination with solid-state NMR spectroscopy to show that the cohesive properties of simple aromatic- and lysine-rich peptides rival those of the strong reversible intermolecular cohesion exhibited by adhesion proteins of marine mussel. In particular, we show that peptides incorporating the amino acid phenylalanine, a functional group that is conspicuously sparing in the sequences of mussel proteins, exhibit reversible adhesion interactions significantly exceeding that of analogous mussel-mimetic peptides. More broadly, we demonstrate that interfacial confinement fundamentally alters the energetics of cation-π-mediated assembly: an insight that should prove relevant for diverse areas, which range from rationalizing biological assembly to engineering peptide-based biomaterials.

Organic solar cells that are transparent to visible light are highly desirable for applications such as window treatments or solar greenhouse panels. A key challenge is to simultaneously transmit most photons between 400 and 700 nm while retaining a high short‐circuit current and power conversion efficiency (PCE). Here, organic bulk heterojunction (BHJ) solar cells consisting of a donor polymer (PM2) is reported and the non‐fullerene acceptor ITIC‐Th achieves a PCE of 9.3%, and the BHJ thin films exhibit an average visible transmittance over 40%. This value is achieved primarily due to a very high open‐circuit voltage (VOC) of 0.93 V, which represents a voltage loss of only 0.50 V relative to the material optical bandgap, Eopt. In PM2:PC61BM devices, this voltage loss increases to 0.62 V (VOC = 0.82 V). It is found that this difference in VOC is due to higher nonradiative recombination in the fullerene‐based solar cell, suggesting that non‐fullerene acceptors may lead to better performance in semi‐transparent devices. The optoelectronic properties associated with PM2:ITIC‐Th and PM2:PC61BM blends are further corroborated by different morphological features and local structures at the donor‐acceptor interfaces characterized by atomic force microscopy, X‐ray scattering, and solid‐state NMR spectroscopy techniques. [ABSTRACT FROM AUTHOR]

Solid-state NMR and infrared (IR) measurements are combined with computational analysis to examine the structures of major sites formed by grafting C[H.sub.3]Re[O.sub.3] onto amorphous silica-alumina and their relationships with olefin metathesis activity of this material. The results have suggested simple modifications in catalyst preparation, which has led to higher selectivity, less leaching and efficient use of the Re complex.

Hadamard-based pulse sequences are used to determine (super 1)H{(super 13)C}-resolved diffusion coefficients and spin-relaxation time constants for the chemically similar components of an aqueous solution, which exhibit significant spectral overlap in their (super 1)H NMR spectra. The resulting resolved signal decay curves can be used with existing postacquisition analysis techniques to increase significantly the resolution of similar or, in the case of complete spectral resolution, identical decay constants.

The use of transparent silica-block copolymer composites as host matrices for optically limiting dye molecules is studied. The resulting increase in dye solubility and photophysical stability is examined.

A combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction, and quantum chemical and empirical force field modeling is used to establish the structure of a novel molecularly ordered two-dimensional (2D) silicate framework in a surfactant-templated mesophase. The intraframework structure of a novel non-3D-crystalline lamellar silicate-C16NMe2Et(super+) surfactant mesophase is determined by the 2D DQ29Si NMR.

A simple and flexible procedure to synthesis thermally stable, order large-pore mesoporous metal oxides is reported. Amphiphilic poly(alkylene oxide) block copolymers were used as structure-directing agents. The mesoporous oxides contained nanocrystalline domains in the comparatively thick amorphous walls, formed via a combination of block copolymer self-assembly and complexation of the inorganic species.

The synthesis of new mesoporous silica structures using low molecular weight nonionic ethylene oxide surfactants and poly(alkylene oxide) block copolymers in acid media is described. Results showed that the selected surfactant species not only influence the structure of ordered mesoporous silica, each surfactant type also plays a role in the formation of a specific mesostructured silica phase. It was also observed that the silica formed were highly ordered and thermally stable even in boiling water.

Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500 ° C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35 ° to 80 ° C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The black copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140 ° C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water., Large pore-size molecular sieves are much in demand for reactions or separations involving large molecules (1, 2). Since mesoporous molecular sieves such as hexagonally ordered MCM-41 were discovered by Mobil [...]

Synchrotron x-ray and neutron powder diffraction studies of the crystal structures of siliceous zeolite ferrierite reveal the presence of a Si-O-Si unit with a bond angle of 170 degrees. Crystal structures predicted by lattice energy minimization method agree with the experimental observations. A bond angle correlation helps assign the well-resolved 29Si magic angle spinning NMR spectrum. This assignment helps determine Si/Al ratios in the multiple T-site system and analyze the complex spectra of various aluminosilicate ferrierite samples.

By analogy to heat and mass transfer film theory, a general approach is introduced for determining hyperpolarization transfer rates between dilute electron spins and a surrounding nuclear ensemble. These analyses provide new quantitative relationships for understanding, predicting, and optimizing the effectiveness of hyperpolarization protocols, such as Dynamic Nuclear Polarization (DNP) under magic-angle spinning conditions. An empirical DNP polarization-transfer coefficient is measured as a function of the bulk matrix 1H spin density and indicates the presence of two distinct kinetic regimes associated with different rate-limiting polarization transfer phenomena. Dimensional property relationships are derived and used to evaluate the competitive rates of spin polarization generation, propagation, and dissipation that govern hyperpolarization transfer between large coupled spin ensembles. The quantitative analyses agree closely with experimental measurements for the accumulation, propagation, and dissipation of hyperpolarization in solids and provide evidence for kinetically-limited transfer associated with a spin-diffusion barrier. The results and classical approach yield general design criteria for analyzing and optimizing polarization transfer processes involving complex interfaces and composite media for applications in materials science, physical chemistry and nuclear spintronics. [ABSTRACT FROM AUTHOR]

Even though significant breakthroughs with over 18% power conversion efficiencies (PCEs) in polymer:non‐fullerene acceptor (NFA) bulk heterojunction organic solar cells (OSCs) have been achieved, not many studies have focused on acquiring a comprehensive understanding of the underlying mechanisms governing these systems. This is because it can be challenging to delineate device photophysics in polymer:NFA blends comprehensively, and even more complicated to trace the origins of the differences in device photophysics to the subtle differences in energetics and morphology. Here, a systematic study of a series of polymer:NFA blends is conducted to unify and correlate the cumulative effects of i) voltage losses, ii) charge generation efficiencies, iii) non‐geminate recombination and extraction dynamics, and iv) nuanced morphological differences with device performances. Most importantly, a deconvolution of the major loss processes in polymer:NFA blends and their connections to the complex BHJ morphology and energetics are established. An extension to advanced morphological techniques, such as solid‐state NMR (for atomic level insights on the local ordering and donor:acceptor ππ interactions) and resonant soft X‐ray scattering (for donor and acceptor interfacial area and domain spacings), provide detailed insights on how efficient charge generation, transport, and extraction processes can outweigh increased voltage losses to yield high PCEs. [ABSTRACT FROM AUTHOR]