Devices that respond to negligibly small fluctuations in environmental conditions will be of great value for the realization of more sustainable, low-power-consumption actuators and electronic systems. Herein we report an unprecedented film actuator that seemingly operates autonomously, because it responds to the adsorption and desorption of a minute amount of water (several hundred nanograms per 10 mm(2)) possibly induced by fluctuations in the ambient humidity. The actuation is extremely rapid (50 ms for one curl) and can be repeated >10,000 times without deterioration. On heating or light irradiation, the film loses adsorbed water and bends quickly, so that it can jump vertically up to 10 mm from a surface or hit a glass bead. The film consists of a π-stacked carbon nitride polymer, formed by one-pot vapour-deposition polymerization of guanidinium carbonate, and is characterized by a tough, ultralightweight and highly anisotropic layered structure. An actuator partially protected against water adsorption is also shown to walk unidirectionally.

The thermal decomposition of hydrogen peroxide, H(2)O(2), was determined in aqueous suspensions of SiO(2), Al(2)O(3), TiO(2), CeO(2), and ZrO(2) nanometer-sized particles. First-order kinetics were observed for the decomposition in all cases. Temperature dependence studies found that the activation energy was 42 +/- 5 kJ/mol for the overall decomposition of H(2)O(2) independent of the type of oxide. Oxide type had a strong effect on the pre-exponential rate term with increasing rate in the order of SiO(2) < Al(2)O(3) < TiO(2) < CeO(2) < ZrO(2). The rate coefficient for H(2)O(2) decomposition increases with increasing surface area of the oxide, but the number or efficiency of reactive sites rather than the total surface area may have the dominant role. Very efficient scavengers for OH radicals in the bulk liquid are not able to prevent formation of molecular oxygen, the main H(2)O(2) gaseous decay product, suggesting that decomposition occurs on the oxide surfaces. The decomposition of H(2)O(2) in the gamma-radiolysis of water is enhanced by the addition of ceramic oxides, possibly due to excess formation of hydrated electrons from energy deposited in the solid.

Brilliance usually refers to the light reflected by the facets of a gemstone such as diamond due to its high refractive index. Nowadays, high‐refractive‐index materials find application in many optical and photonic devices and are mostly of inorganic nature. However, these materials are usually obtained by toxic or expensive production processes. Herein, the synthesis of a thin‐film organic semiconductor, namely, polymeric carbon nitride, by thermal chemical vapor deposition is presented. Among polymers, this organic material combines the highest intrinsic refractive index reported so far with high transparency in the visible spectrum, even reaching the range of diamond. Eventually, the herein presented deposition of high quality thin films and their optical characteristics open the way for numerous new applications and devices in optics, photonics, and beyond based on organic materials.

We present an innovative method for the synthesis of boron carbon nitride thin film materials in a simple furnace setup, using commonly available solid precursors and relatively low temperature compared to previous attempts. The as-prepared structural and optical properties of thin films are tuned via the precursor content, leading to a sp 2 -conjugated boron nitride− carbon nitride mixed material, instead of the commonly reported boron nitride−graphene phase segregation, with tunable optical properties such as band gap and fluorescence.

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We found unprecedented reverse relationships in anion-exchange membranes (AEMs) for Pt-free alkaline fuel cell systems, i.e., the increase in hydrophobicity increased water uptake and susceptibility to hydrolysis. AEMs with graft copolymers that composed of anion-conducting 2-methyl-N-vinylimidazolium (Im) and hydrophobic styrene (St) units were employed. We characterized two new structures in these AEMs using a small-angle neutron scattering with a contrast variation method. (1) The distribution of graft polymers in conducting (ion channel) or non-conducting (hydrophobic amorphous poly(ethylene-co-tetrafluoroethylene) (ETFE)) phase was evaluated in a quantitative manner. High fraction in conducting layer for AEMs having high grafting degrees was found using the proposed structural model of "conducting/non-conducting two-phase system". (2) Assuming a hard-sphere fluid model, we found AEMs having high St contents and low alkaline durability possessed nanophase-separated water puddles with diameters of 3-4 nm. The AEM having a low St content and the best alkaline durability did not show evident nanophase separation. The above hierarchical structures elucidate the unexpected reverse relationships that the AEM having highly hydrophobic graft polymers was subjected to the morphological transition to give water puddles at nanoscale. The imidazolium groups that were located at the boundary between graft polymers and water puddles should be susceptible to hydrolysis.

A fully hydrated Nafion membrane is generally treated as a three-component system comprising the tetrafluoroethylene-like main chain, the fluorinated side chain ending with a sulfonic acid group, and absorbed water. We applied the contrast variation small-angle neutron scattering technique to decompose scattering intensity profiles to partial scattering functions (PSFs) of each component in Nafion quantitatively. In the large scale (>30 nm), structural heterogeneities were observed in the main-and side-chain domains but not in water domains. In the middle scale (5−30 nm), a bicontinuous-like structure of crystalline and amorphous phases with a mean separation distance of 11 nm was observed, as a result of the main-chain semicrystalline templating effect. In the small scale (<5 nm), another bicontinuouslike structure exists in the amorphous phase with a mean separation distance of about 4 nm, indicating a well-connected water network responsible for the good membrane conductivity. Cross-term analysis of PSFs for two components suggested the location of each component that the main-chain domains tends to phase-separate from either the side-chain or water domains, but the sidechain and water domains are closely attached through sulfonic acid groups.

The radiation chemical yields of hydrogen peroxide formed in the γ-radiolysis of water with scavengers for oxidizing and/or reducing radicals were measured to examine initial water decomposition pathways to oxidizing species. Hydrogen peroxide yields were found to decrease toward zero with increasing concentration of OH radical scavenger in all solutions, suggesting that the OH radical is the sole precursor to hydrogen peroxide. The yields of hydrogen peroxide in nitrate and selenate solutions are closely associated with the scavenging capacity of the precursor to the hydrated electron, suggesting that its reactions have a significant role in hydrogen peroxide formation. Observed hydrogen peroxide yields at high nitrate concentrations coupled with model calculations show that the molecular cation of water, H2O+, is the dominant precursor of the oxidizing species leading to hydrogen peroxide. Proton-transfer reactions of the water molecular cation give 79% of the oxidizing species, whereas other reactions such as dissociative recombination reactions account for the rest. There is a significant additional production of OH radicals in the radiolysis of selenate solutions due to the production of •O- and the scavenging of low-level excited water molecules.