We demonstrate that alkylthiol‐capped gold nanoclusters doped into nematic liquid crystals (N‐LCs) with positive dielectric anisotropy give rise to an unprecedented dual alignment mode and electro‐optical response, which has a potential impact on current liquid crystal (LC) display technologies and N‐LC optical‐biosensor design. By fine‐tuning experimental conditions (temperature, electric field, and alignment), N‐LCs doped with gold nanoclusters can be aligned and electrically reoriented either like N‐LCs with a positive dielectric anisotropy in a planar cell or, alternatively, as N‐LCs with a negative dielectric anisotropy in a homeotropic cell, both at lower threshold voltages than the pure N‐LC.

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Nickel-based metallic foams are commonly used in electrochemical energy storage devices (rechargeable batteries) as both current collectors and active mass support. These materials attract attention as tunable electrode materials because they are available in a range of chemical compositions, pore structures, pore sizes, and densities. This contribution presents structural, chemical, and electrochemical characterization of Ni-based metallic foams. Several materials and surface science techniques (transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), focused ion beam (FIB), and X-ray photoelectron spectroscopy (XPS)) and electrochemical methods (cyclic voltammetry (CV)) are used to examine the micro-, meso-, and nanoscopic structural characteristics, surface morphology, and surface-chemical composition of these materials. XPS combined with Ar-ion etching is employed to analyze the surface and near-surface chemical composition of the foams. The specific and electrochemically active surface areas (As, Aecsa) are determined using CV. Though the foams exhibit structural robustness typical of bulk materials, they have large As, in the range of 200-600 cm(2) g(-1). In addition, they are dual-porosity materials and possess both macro- and mesopores.

Against the rule: Liquid crystal hosts (5CB and 8CB) are doped with different thiol decorated gold nanoparticles (see figure). The "simple" hexanethiol and dodecanethiol capped nanoparticles (Au1 and Au2) are more compatible to the nematic cyanobiphenyl liquid crystals than nanoparticles capped simultaneously with alkylthiols and a nematic cyanobiphenyl thiol (Au3 and Au4).This study focuses on the miscibility of liquid crystal (LC) decorated gold nanoparticles (NPs) in nematic LCs. To explore if LC functional groups on the gold NP corona improve the compatibility (miscibility) with structurally related LC hosts, we examined mixtures of two LC hosts, 5CB and 8CB, doped at 5 wt % with different types of gold NPs. Four alkanethiol-capped NPs were synthesized; two homogeneously coated with alkanethiols (Au1 with C(6)H(13)SH and Au2 with C(12)H(25)SH), and two that were additionally capped at a different ratio with a mesogenic cyanobiphenyl end-functionalized alkanethiol HS10OCB (C(6)H(13)SH + HS10OCB for Au3 and C(12)H(25)SH + HS10OCB for Au4). Investigating these mixtures in the bulk for settling of the NPs, and in thin films using polarized optical microscopy (POM) between untreated glass slides as well as POM studies and electro-optic tests in planar ITO/polyimide test cells, reveal that the alkanethiol capped NPs Au1 and Au2 are more compatible with the two polar cyanobiphenyl hosts in comparison to the NPs decorated with the cyanobiphenyl moieties. All NPs induce homeotropic alignment in 5CB and 8CB between untreated glass slides, with Au1 and Au2 showing characteristic birefringent stripes, and Au3 and A4 exhibiting clear signs of aggregation. In rubbed polyimide cells, however, Au3 and Au4 fail to induce homeotropic alignment and show clear signs of macroscopic aggregation.

High surface area platinum electrodes with an ordered porous structure (Pt-OP electrodes) have been prepared and characterized by electrochemical methods. This study builds a foundation upon which we can seek an in-depth understanding of the limitations and design considerations to make efficient and stable Pt-OP electrodes for use in electrochemical applications. A set of Pt-OP electrodes were prepared by controlled electrodeposition of Pt through a self-assembled array of spherical particles and subsequent removal of the spherical templates by solvent extraction. The preparation method was shown to be reproducible and the resulting electrodes were found to have clean Pt surfaces and a large electrochemical surface area (A ecsa) resulting from both the porous structure, as well as the nano-and micro-scale surface roughness. Additionally, the Pt-OP electrodes exhibit a surface area enhancement comparable to commercially available electrocatalysts. In summary, the Pt-OP electrodes prepared herein show properties of interest for both gaining fundamental insights into electrocatalytic processes and for use in applications that would benefit from enhanced electrochemical response.

To capitalize on the unique size and shape-dependent optical and electronic properties of nanoscale particles for liquid crystal (LC) applications, detailed structure and size-property relationship studies are critical. To enhance our understanding of the thermal, optical and electro-optic effects of nanoparticles in nematic LCs we produced numerous different nematic LC mixtures containing small quantities of dispersed metal nanoparticles (i.e. gold and silver nanoclusters) or semiconductor quantum dots (i.e. CdTe nanocrystals) and studied their optical (texture, alignment, defect formation, luminescence) and electro-optic properties. Depending on several experimental parameters such as nanoparticle functionalization and concentration, as well as thermal history in combination with an applied electric field, these nanoparticle/LC mixtures with the nanoparticles differing in surface functionality, size, and core material gave rise to unique alignment effects and electro-optic responses in the two investigated nematic LC (N-LC) hosts.

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It is known that a small fraction of nanoparticles dispersed in a liquid crystal can alter the electrooptic response, completely. The present study on gold nanoparticles dispersed in 5-n-heptyl-2-(4-n-octyloxy-phenyl)-pyrimidine shows that the contrast inversion observed earlier is initiated by a change from parallel to homeotropic anchoring, thereby causing an instability, which in turn leads to the appearance of convection rolls. After rapid cooling from the isotropic phase, the nanoparticle dispersion shows a regular field-induced Fréedericksz transition, like the pure liquid crystal. The electrohydrodynamic instability is presumably an example for the behavior of (+, -) systems that was predicted by de Gennes, and only recently observed experimentally for the first time.