and Fridkin, V.M., "Nanoscale polarization manipulation and conductance switching in ultrathin films of a ferroelectric copolymer" (2003). Peter Dowben Publications. 11.

Surface structure of ultrathin copolymer films of ferroelectric vinylidene fluoride (70%) with trifluoroethylene (30%) on graphite" (2004 The structure and local structural distortions, through the polarization manipulation, of crystalline films of ferroelectric vinylidene fluoride (70%) with trifluoroethylene (30%) [P(VDF-TrFE)] copolymer on graphite were studied by scanning tunneling microscopy (STM). A quasispiral twist in C u C bonds with rotations about the polymer chain axis was observed by high-resolution STM, indicating a surface relaxation of the strained copolymer films. Such a relaxation behavior appears to be linked to the observed local dipole rotations accompanied by the reversal of the local polarization with biasing the STM tip. A structure model is proposed based upon the observations.

No abstract

Sodium (Na) is predicted to be an ideal plasmonic material with ultralow optical loss across visible to near-infrared (NIR). However, there has been limited research on Na plasmonics. Here we develop a scalable fabrication method for Na nanostructures by combining phase-shift photolithography and a thermo-assisted spin-coating process. Using this method, we fabricated Na nanopit arrays with varying periodicities (300–600 nm) and with tunable surface plasmon polariton (SPP) modes spanning visible to NIR. We achieved SPP resonances as narrow as 9.3 nm. In addition, Na nanostructures showed line width narrowing from visible toward NIR, showing their prospect operating in the NIR. To address the challenges associated with the high reactivity of Na, we designed a simple encapsulation strategy and stabilized the Na nanostructures in ambient conditions for more than two months. As a low-cost and low-loss plasmonic material, Na offers a competitive option for nanophotonic devices and plasmon-enhanced applications.

By exploiting the benefits of bimetallic platinum–nickel (Pt–Ni) alloy nanosphere and an ionic liquid (IL) (i.e., 1-butyl-1-methyl­pyrrolidinium bis­(trifluoro­methylsulfonyl)­imide (BmpyNTf2), an organic–inorganic hybrid interface of IL/Pt–Ni was designed and characterized for electrochemical sensing of oxygen and hydrogen gases for miniaturized electrochemical gas sensor development. The spherical Pt–Ni alloy nanoparticles (NPs) were synthesized through template-free, one-pot solvothermal method. The morphology, crystal structure, and chemical composition of Pt–Ni alloy NPs were thoroughly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained Pt–Ni alloy NPs were used to fabricate the planar sensor devices and tested for oxygen and hydrogen sensing. The oxygen-sensing performance of the resulting planar electrochemical sensor was investigated over a low concentration range of 500–5000 ppm of O2 at room temperature by using constant potential amperometry. The planar electrochemical sensor device exhibited a high sensitivity to O2 ((3.04 ± 0.18) × 10–5 mA cm–2 ppm–1) compared to commercial Pt/C-based sensor ((2.57 ± 0.22) × 10–5 mA cm–2 ppm–1). The planar electrochemical sensor device also showed good reproducibility and selectivity for oxygen detection during sensing tests. Moreover, the sensor device based on the obtained Pt–Ni alloy NPs was investigated for hydrogen detection with excellent analytical performance in hydrogen sensing. The outstanding gas sensing properties were attributed to unique interface properties and highly efficient catalytic reaction of gas species of oxygen and hydrogen at the interface of IL/Pt–Ni alloy NPs. This work demonstrated that the integration of Pt–Ni alloy NPs with ILs enabled beneficial electrode interface for O2 and H2 gases sensing with high sensitivity, rapid gas response, and superior reproducibility based on a novel planar electrochemical sensor platform.