A number of cobalt complexes of substituted polypyridine ligands were synthesized and investigated as possible alternatives to the volatile and corrosive iodide/triiodide redox couple commonly used as an electron-transfer mediator in dye-sensitized solar cells (DSSCs). The extinction coefficients in the visible spectrum are on the order of 10(2) M(-1) cm(-1) for the majority of these complexes, diminishing competition with the light-harvesting dye. Cyclic voltammetric studies revealed a dramatic surface dependence of the heterogeneous electron-transfer rate, which is surprisingly different for gold, carbon, and platinum electrodes. DSSCs were assembled using a mediator that consisted of a mixture of Co(II) and Co(III) complexes in a 10:1 ratio. DSSCs containing these mediators were used to characterize incident photon-to-current conversion efficiency and photoelectrochemical responses. The best performing of these mediators were identified and subjected to further study. As suggested by electrochemical results, gold and carbon are superior cathode materials to platinum, and no evidence of corrosion on any cathode material was observed. Addition of lithium salts to the mediator solution resulted in a dramatic improvement in cell performance. The observed Li(+) effect is explained in terms of the recombination of injected electrons in the photoanode with the oxidized mediator. The best mediator, based on tris(4,4'-di-tert-butyl-2,2'-dipyridyl)cobalt(II/III) perchlorate, resulted in DSSCs exhibiting efficiencies within 80% of that of a comparable iodide/triiodide-mediated DSSC. Due to the commercial availability of the ligand and the simplicity with which the complex can be made, this new mediator represents a nonvolatile, noncorrosive, and practical alternative as an efficient electron-transfer mediator in DSSCs.

A series of dual polymer electrochromic devices (ECDs) based on 12 complementary pairs of conducting polymer films have been constructed using 3,4-ethylenedioxythiophenecontaining conducting polymers. Poly[3,)-N-methylcarbazole] (PBEDOT-NCH 3 Cz), poly [3,6-bis(2-(3,4-ethylenedioxythiophene))-N-eicosylcarbazole] (PBEDOT-NC 20 H 41 Cz), and poly [4,4′-bis(2-(3,4-ethylenedioxythiophene))biphenyl] (PBEDOT-BP) were utilized as anodically coloring polymers that electrochemically switch between an oxidized deep blue absorptive state and a transmissive (orange or yellow) reduced state. Poly(3,4-ethylenedioxythiophene) (PEDOT) and its alkyl derivatives (PEDOT-C 14 H 29 and PEDOT-C 16 H 33 ) have been used as high-contrast cathodically coloring polymers that switch between a deep blue absorptive state in the reduced form and a sky blue, highly transmissive state in the oxidized form. The dual polymer ECDs were constructed by separating complementary pairs of EC polymer films, deposited on ITO glass, with a gel electrolyte composed of a lithium salt and plasticized poly(methyl methacrylate) (PMMA). Device contrast ratios, measured as ∆%T, ranged from 27% to 63%, and subsecond switching times for full color change were achieved. These devices were found to exhibit extremely high coloration efficiencies of up to 1400 cm 2 /C over narrow (ca. 100 nm) wavelength ranges and to retain up to 60% of their optical response after 10 000 deep, double potential steps, rendering them useful for EC applications.

Chronically implanted neural multi-electrode arrays (MEA) are an essential technology for recording electrical signals from neurons and/or modulating neural activity through stimulation. However, current MEAs, regardless of the type, elicit an inflammatory response that ultimately leads to device failure. Traditionally, rigid materials like tungsten and silicon have been employed to interface with the relatively soft neural tissue. The large stiffness mismatch is thought to exacerbate the inflammatory response. In order to minimize the disparity between the device and the brain, we fabricated novel ultrasoft electrodes consisting of elastomers and conducting polymers with mechanical properties much more similar to those of brain tissue than previous neural implants. In this study, these ultrasoft microelectrodes were inserted and released using a stainless steel shuttle with polyethyleneglycol (PEG) glue. The implanted microwires showed functionality in acute neural stimulation. When implanted for 1 or 8 weeks, the novel soft implants demonstrated significantly reduced inflammatory tissue response at week 8 compared to tungsten wires of similar dimension and surface chemistry. Furthermore, a higher degree of cell body distortion was found next to the tungsten implants compared to the polymer implants. Our results support the use of these novel ultrasoft electrodes for long term neural implants.

New electrochromic materials (ECMs) must exhibit rapid response times, long‐term stability, and a large difference in percentage transmittance between the bleached and colored states. The design, fabrication, and characterization of fast, solid‐state, dual conducting polymer EC devices that utilize PEDOT (see Figure) as the cathodically coloring material are described, following background information on ECMs. magnified image

All these data indicate increasing Mn 2+ ±Mn 2+ interactions (S eff ) and decreasing w(y) with decreasing particle size. It can thus be concluded that the increase in depth of the bandgap variation minimum with composition is due to strong interactions between manganese ions and the conduction and valence band electrons, and the magnetic interactions increase markedly with decreasing particle size.That the magnetic interactions (Mn 2+ ±Mn 2+ and Mn 2+ ± electron bands of CdS) increase markedly with decreasing particle size is not easy to explain. To our knowledge, it is the first time such data have been obtained. Theoretical models may be useful in this respect, and this is a topic for future work. If these results extend to other magnetic semiconductors, it could be very important for quantum dots research.