Foremanclements3091

Among molecular building blocks, metal oxide cluster anions and their countercations provide multiple options for the self-assembly of functional materials. Currently, however, rational design concepts are limited to electrostatic interactions with metal or organic countercations or to the attachment and subsequent reactions of functionalized organic ligands. We now demonstrate that bridging μ-oxo linkages can be used to string together a bifunctional Keggin anion building block, [PNb2Mo10O40]5- (1), the diniobium(V) analogue of [PV2Mo10O40]5- (2). Induction of μ-oxo ligation between the NbV═O moieties of 1 in acetonitrile via step-growth polymerization gives linear polymers with entirely inorganic backbones, some comprising over 140 000 repeating units, each with a 3- charge, exceeding that of previously reported organic or inorganic polyelectrolytes. As the chain grows, its flexible μ-oxo-linked backbone, with associated countercations, coils into a compact 270 nm diameter spherical secondary structure as a result of electrostatic interactions not unlike those within ionic lattices. More generally, the findings point to new options for the rational design of multidimensional structures based on μ-oxo linkages between NbV═O-functionalized building blocks.Few studies aiming to develop a glue with an underwater reversible adhesive property have been reported because combining the two properties of reversible adhesion and underwater adhesion into a single glue formulation is a challenging issue. Herein, preparation of a simple mixture of polyvinyl alcohol (PVA) and a well-known phenolic compound, namely, tannic acid (TA), results in an underwater glue exhibiting reversible adhesion. We named the adhesive VATA (PVA + TA). Using VATA, two stainless-steel objects (0.77 kg per each) are able to be instantly attached. In addition to the high adhesive strength, surface applied VATA in water retains its adhesive capability even after 24 hours. In contrast, a cyanoacrylate applied in the same water condition rapidly loses its adhesive power. Another advantage is that VATA's adhesion is reversible. Bonded objects can be forcibly detached, and then, the detached ones can be reattached by the residual VATA. VATA maintains nearly 100% of its initial adhesive force, even after 10 repetitions of attach-detach cycles. HDM201 VATA bonds various materials ranging from metals and polymers to ceramics. Particularly, we first attempt to test the toxicity of the underwater adhesives using an invertebrate nematode, Caenorhabditis elegans, and goldfish (vertebrate) due to potential release to the environment.Construction of carbon-carbon bonds is one of the most important tools in chemical synthesis. In the previously established cross-coupling reactions, prefunctionalized starting materials were usually employed in the form of aryl or alkyl (pseudo)halides or their metalated derivatives. However, the direct use of arenes and alkanes via a 2-fold oxidative C-H bond activation strategy to access chemoselective C(sp2)-C(sp3) cross-couplings is highly challenging due to the low reactivity of carbon-hydrogen (C-H) bonds and the difficulty in suppressing side reactions such as homocouplings. Herein, we present the new development of a copper-catalyzed cross-dehydrogenative coupling of polyfluoroarenes with alkanes under mild conditions. Relatively weak sp3 C-H bonds at the benzylic or allylic positions, and nonactivated hydrocarbons could be alkylated by the newly developed catalyst system. A moderate-to-high site selectivity was observed among various C-H bonds present in hydrocarbon reactants, including gaseous feedstocks and complex molecules. Mechanistic information was obtained by performing combined experimental and computational studies to reveal that the copper catalyst plays a dual role in activating both alkane sp3 C-H bonds and sp2 polyfluoroarene C-H bonds. It was also suggested that the noncovalent π-π interaction and weak hydrogen bonds formed in situ between the optimal ligand and arene substrates are key to facilitating the current coupling reactions.Efficient energy transfer is a promising strategy in overcoming the inherent limits of a narrow band and weak absorption of lanthanide ions due to the nature of 4f-4f transitions. Herein, we introduce a nanoparticle-sensitized nanoparticle system where a near-infrared-emitting quantum dot (QD) is used as a sensitizer with broadband photon absorption for a lanthanide-doped nanoparticle (LNP) to generate second near-infrared (NIR-II) emission. The NIR-II luminescence of Er3+-doped LNP by Ag2S QD sensitization displays an enhancement of ∼17-fold in intensity and ∼10-fold in brightness over bare LNP because of increased absorptivity and overall broadening of the absorption spectrum of LNP. Furthermore, a QD-sensitized LNP system exhibits excellent photostability and is able to improve the signal-to-noise ratio of tumor NIR-II imaging via in situ cross-linking of QD and LNP. The QD-sensitized LNP system for luminescence enhancement opens a potential avenue for efficient energy transfer in complex nanoparticle-nanoparticle systems.We investigated the impact of a series of hole transport layer (HTL) materials such as Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOTPSS), NiOx, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA), and polytriarylamine (PTA) on photostability of thin films and solar cells based on MAPbI3, Cs0.15FA0.85PbI3, Cs0.1MA0.15FA0.75PbI3, Cs0.1MA0.15FA0.75Pb(Br0.15I0.85)3, and Cs0.15FA0.85Pb(Br0.15I0.85)3 complex lead halides. Mixed halide perovskites showed reduced photostability in comparison with similar iodide-only compositions. In particular, we observed light-induced recrystallization of all perovskite films except MAPbI3 with the strongest effects revealed for Br-containing systems. Moreover, halide and β FAPbI3 phase segregations were also observed mostly in mixed-halide systems. Interestingly, coating perovskite films with the PCBM layer spectacularly suppressed light-induced growth of crystalline domains as well as segregation of Br-rich and I-rich phases or β FAPbI3. We strongly believe that all three effects are promoted by the light-induced formation of surface defects, which are healed by adjacent PCBM coating.