Advanced Materials

Guillermo Bazan and Huaping Li show on p. 964 that a range of optical reporters can be prepared by electrostatic interactions between a cationic conjugated oligoelectrolyte (COE) and dye-labeled single-stranded DNAs (ssDNA). Proteins perturb the optical properties of these aggregates and generate unique fluorescence resonance energy transfer (FRET) patterns that allow protein discrimination. Two different signatures can be obtained, depending on whether the fluorescence intensity of the COE or the ssDNAbound dye is observed.

Eun Chul Cho, Unyong Jeong, and co-workers demonstrate on p. 968 the programmable release of multiple agents by using polymeric core-sheath nanofibers consisting of arrays of colloids in the core and polymeric sheath. The fibers were produced by one-step single nozzle electrospinning. Loading different species of active agents in each colloid can provide independent control over the release of each agent.

Infiltration of a porous yttria-stabilized zirconia scaffold provides for a high degree of flexibility in the choice of active materials used in the cathode of a solid oxide fuel cell. In this paper we review the infiltration method and how it is being used to produce high-performance cathodes.

Bernd Tieke and co-workers (p. 959) have created incredibly thin films that change color in response to an electric current. The electrochromic films were self-assembled with zinc ions and polytopic polyiminofluorene-tpy ligands and can be switched between yellow, red, and blue; they exhibit switching times of 450 ms, and display high contrast and high stability. The cover shows the process of coordinative self-assembly and electrochromic switching, the background indicates the film surface.

Coordinative self-assembly of zinc(II) ions and polytopic polyiminofluorene-tpy ligands is used to prepare electrochromic films with thickness in the nanometer range. The films can be switched between yellow, red, and blue, and exhibit switching times of 500 ms, high contrast, and high stability.

A range of optical reporters is prepared by electrostatic interactions between a cationic conjugated oligoelectrolyte (COE) and dye-labeled single-stranded DNAs (ssDNA). Proteins perturb the optical properties of these aggregates, and generate unique fluorescence resonance energy transfer (FRET) patterns that allow protein discrimination. Two different signatures can be obtained, depending on whether the fluorescence intensity of the COE or the ssDNA-bound dye is observed.

Polymeric core-sheath nanofibers consisting of polymeric sheath and arrays of colloids in the core are produced by one-step single-nozzle electrospinning. Loading different species of active agents in each colloid provides control over the release of each of the agents independently, which enables a programmed release pattern for multiple agents.

A broad-band and omnidirectional antireflection coating consisting of semiconductor nanowires is fabricated. The reflection is reduced due to a graded refractive index, which is achieved by a certain nanorod-length distribution of cylindrical and conically shaped rods. An increased transmission and, accordingly, a reduced reflection are demonstrated for the visible and near-infrared parts of the spectrum.

A large-scale integration technology for MEMS based on the optoelectrothermic control of a temperature-sensitive hydrogel is described and exemplified using an imaging array system, a so-called artificial skin. The hydrogel itself acts as active functional unit, i.e., as actuator. The artificial skin comprises more than 4 000 individual actuators and provides both, visual and palpable artificial impressions of a surface.

Electrode-imposed signals are used to assemble proteins without the need for reactive reagents. The two-step assembly approach uses i) cathodic signals to electrodeposit the amino-polysaccharide chitosan and ii) anodic signals to activate the chitosan film for protein assembly. Proteins are shown to assemble at individual electrode addresses, with spatial selectivity and quantitative control.

Dispersion of ultranarrow ZnS nanorods of molecular dimensions encapsulated by a fluid-like soft organic layer in the nematic liquid crystal (LC ZLI-4792) results in a novel soft-matter-type blend with previously unachieved electro-optic properties. The local ordering of the nanorods significantly affects the global ordering of the blend, allowing a more rapid response.

Highly efficient nanoporous TiO₂-polythiophene hybrid solar cells are reported. A metal-free organic dye (D102) is employed to modify the TiO₂/polythiophene interface. Results indicate dye and interfacial engineering are crucial for highly efficient TiO₂/P3HT hybrid solar cells.

Nanocomposite films are prepared by layer-by-layer (LBL) assembly of cationic genetically engineered rodlike nontoxic viruses and anionic spherical Au nanoparticles. The cationic viruses electrostatically interact with the anionic Au nanoparticles to drive the LBL assembly. The nanocomposite films exhibit humidity-dependent surface plasmon resonance spectra (see figure).

The chemical structures and electronic structures at conjugated polyelectrolyte/Au interfaces demonstrate that conjugated polyelectrolytes with identical backbones but different pendant charges and charge-compensating ions exhibit different electronic properties. This finding shows that counterions and backbone charges enable control of the electronic and chemical nature of critical device interfaces.

Ultrathin nanowires, especially in colloidal form, represent a new material platform in the study of materials' behaviour, at the border between nanostructures and polymers. We here discuss some of the recent breakthroughs in the field and the synthetic methodologies they have introduced, their pros and cons, and some future directions of the field.