Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

The ability to precisely control nanoparticle-enabled electrical devices for applications involving conformal wrapping/bending adaptability in various complex sensing environments requires an understanding of the electrical correlation with the device strain and exposure to the molecular environment. This report describes novel findings of an investigation of molecularly mediated thin film assembly of gold nanoparticles on flexible chemiresistor devices under different device strains and exposure molecules. Both theoretical and experimental data have revealed that the electrical conductivity of the nanoparticle assembly depends on a combination of the device strain and the exposure molecules. Under no device strain, the electrical conductivity is sensitive to the molecular nature in the exposure environment, revealing a clear increase in electrical conductivity with the dielectric constant of vapor molecules. Under small device strains, the electrical conductivity is shown to respond sensitively to the strain directions (tensile vs compressive strain) and also to the dielectric constant of the vapor molecules in a way resembling the characteristic under no device strain. Under large device strains, the electrical conductivity is shown to respond to the difference in dielectric constant of the vapor molecules but, more significantly, to the device tensile and compressive strains than those under small device strains. This combination of device strain and dielectric characteristic is also dependent on the orientation of the microelectrode patterns with respect to the device strain direction, a finding that has important implications to the design of flexible arrays for a complex sensing environment.

A portable litmus‐type chemosensor is developed for the effective detection of environmentally hazardous volatile organic compounds (VOCs) using polydiacetylene (PDA) and graphene stacked within a composite film. The graphene is exploited as a transparent and efficient supporter for the highly ordered PDA monolayer. This colorimetric sensor exhibits a sensitive response to low concentrations of VOCs (∼0.01%), including tetrahydrofuran (THF), chloroform (CHCl3), methanol (CH3OH), and dimethylformamide (DMF). The color change that is caused by relatively high concentrations of VOCs can be perceived by the naked eye, and it is noteworthy that a logarithmic relationship is observed between the chromatic response and the VOC concentration in the range of ∼0.01%–10%. The structural conformation changes of the PDA molecules, caused by interactions with VOCs, are directly observed by scanning tunneling microscopy (STM), which reveals the intrinsic mechanism of the chromatic variety at the molecular level.

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