Six new rugged, high-temperature tolerant phosphine oxide-containing poly(4,4′-(p-phenylene)-bis(2,6-diphenylpyridinium)) polymers P-1, P-2, P-3, P-4, P-5, and P-6 are synthesized, characterized, and evaluated. Synthesis results in high yield and purity, as confirmed by elemental, proton (1H), and carbon 13 (13C) nuclear magnetic resonance (NMR) spectra analyses. High glass transition temperatures (Tg > 230 °C) and high char yields (>50% at 700 °C) are determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. These new ionic polymers exhibit excellent processability, thin-film forming, high-temperature resistance, fire-resistance and retardation, coating, adhesion, mechanical and tensile strength, and n-type (electron transport) properties. The incorporation of phosphine oxide and bis(phenylpyridinium) moieties in the polymer backbones leads to high glass transition temperatures and excellent fire retardant properties, as determined by microcalorimetry measurements. The use of organic counterions allows these ionic polymers to be easily processable from several common organic solvents. A large variety of these polymers can be synthesized by utilizing structural variants of the bispyrylium salt, phosphine oxide containing diamine, and the counterion in a combinatorial fashion. These results make them very attractive for a number of applications, including as coating and structural component materials for automobiles, aircrafts, power and propulsion systems, firefighter garments, printed circuit boards, cabinets and housings for electronic and electrical components, construction materials, mattresses, carpets, upholstery and furniture, and paper-thin coatings for protecting important paper documents.

Thin-film solar cells based on compound semiconductors consist of a multilayer structure with various interfaces and contain a multitude of elements and impurities, etc. A rapid progress of these photovoltaic technologies can only be achieved by an insight-driven optimization/development. Hence it is crucial to characterize and understand the relationship between the chemical and electronic properties of these components. This paper reviews some examples of our recent work characterizing compound semiconductor thin films using laboratory- and synchrotron-based electron and soft X-ray spectroscopic characterization methods. It is demonstrated how these different analytical techniques are extraordinarily powerful to reveal the material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of the related electronic and chemical properties. As examples, the paper will discuss the electronic surface structure of chalcopyrite thin-film solar cell absorbers, the chemical structure of the CdS/chalcopyrite interface, present the band alignment at the CdS/kesterite interface, and report on how post-deposition treatments cause chemical interaction/interdiffusion processes in CdTe/CdS thin-film solar cell structures. (C) 2012 Elsevier B.V. All rights reserved.

The preparation of free-standing polyimide/carbon (PI/Carbon) substrates and the electrochemical deposition of Pt to produce PI/Carbon/Pt electrodes are demonstrated to provide thermally stable and conductive PI composites. The conductivity of polyimide (PI)/Carbon composites is evaluated as a function of composition of a binary solvent involving DMSO (dimethyl sulfoxide) and highly volatile acetone, which enhances carbon dispersion (PI/Carbon) in the polymer precursor. The solution conditions have been optimized to provide the highest conductivity for the lowest relative carbon loading. The deposition of Pt metal on PI/Carbon composite electrodes is demonstrated using cyclic voltammetry. The conductivity of the PI/Carbon composite is sufficient that the metal precursor PtCl 4 2− is fully reduced and deposited without the need for additional chemical reduction processes. Thermal gravimetric analysis (TGA) shows that the thermal stability of PI is maintained with carbon incorporation and platinum deposition. Scanning electron microscopy (SEM) analysis shows that carbon aggregation at the PI surface is minimized and that Pt deposits are well dispersed. X-ray photoelectron spectroscopy (XPS) results indicate that the electrochemical reduction of PtCl 4 2− produces metallic Pt deposits on the PI/Carbon composite. Four-point probe measurements are utilized to assess the conductivity of the materials and highlight the influence of C and Pt on the electronic properties of modified PI. Finally, the electrochemical reactivity of PI/Carbon/Pt composite is examined using the redox properties for ferricyanide and the catalytic oxidation of methanol in acidic solution. The electrochemical experiments demonstrate that the free-standing PI/Carbon composites are sufficiently conductive to observe the electrodeposition of Pt metal that is stable and reactive on the organic substrate.

This paper reports the electronic and organogelation properties of novel T-shaped bisphenazines functionalized with alkyl side groups and small peripheral cyano (CN) or aldehyde (CHO) substituents. UV-vis spectroscopy and cyclic voltammetry show the effect of the position, type, and number of the peripheral substituents on the electronic properties of the entire system. Interesting organogelation properties including a thixotropic behavior were observed from these T-shaped bisphenazines. We describe important findings from an in-depth characterization on the fibers formed by organogelation: (i) The position of the peripheral substituents influences the fiber morphology by modulating the intermolecular CN (or CHO) interaction and the pi-pi stacking. (ii) Compounds with CHO groups form islands of fiber aggregates, which is not the case for compounds with CN groups. (iii) Decyl-substituted compounds show higher gelation temperatures (i.e., produce stronger gels) than hexadecyl-substituted ones. (iv) The thixotropic behavior originates from an extensive three-dimensional entanglement of very thin, flexible fibers.

Soft x-ray spectroscopy has been used to follow the effects of postdeposition steps (CdCl(2) activation and back contact treatment) on surfaces and interfaces in CdTe-based superstrate solar cells. We find that the CdCl(2) activation drives sulfur atoms from the CdS layer toward the back contact but not to its surface. Using atomic force microscopy, we find that both treatments strongly influence the morphology of the Au/Cu back contact. The spectroscopic results, in contrast, suggest that CdCl(2) activation exhibits a larger impact on the surface composition and chemical structure of the interfaces involved in CdTe solar cells. (C) 2010 American Institute of Physics. [doi:10.1063/1.3505155]

An electrochemical sensor for the detection of dopamine (DA) was designed using a modified Nafion membrane on a glassy carbon electrode. The electrochemical signals from dopamine were enhanced more than 10-fold on a Nafion membrane coated electrode relative to a bare electrode. The hypothesis that the origin of the signal enhancement was due to the accumulation of cationic dopamine in the Nafion was tested using Pd ions as an analog which undergo a two electron reduction similar to dopamine. Electroless deposition of palladium was used to deposit palladium on a highly oriented pyrolytic graphite surface with and without the Nafion membrane. Using scanning electron microscopy (SEM) significantly greater deposits of metallic Pd were observed on the Nafion coated surfaces than in the absence of Nafion and energy dispersive X-ray spectroscopy (EDS) confirmed quantitatively greater Pd deposition on the Nafion coated surfaces.

We deposit Pt particles electrochemically on an electrode covered with a Nafion membrane. Platinum ions travel through the hydrophilic channels of the membrane, and platinum deposits are formed at the place where the channels make contact with the planar electrode. This procedure deposits the catalyst only at the end of the hydrophilic channels that cross the membrane; no catalyst is placed under the hydrophobic domains, where it would not be in contact with the electrolyte. By performing a series of cyclic voltammograrns with this system, we show that deposition of the platinum through the membrane achieves better platinum utilization than deposition of platinum oil the naked electrode followed by the placement of the membrane on top.

Evaluation of indium(III) tris(8-quinolinolato) (Inq(3)) chelate crystals grown slowly from the vapor phase under vacuum (similar to10(-6) Torr) was compared to the aluminum analogue, Alq(3). In both cases, a previously unidentified close pi-pi interaction is identified, which likely impacts charge conduction. In the case of Inq3, we observe a mixture of both meridianal (mer) and facial (fac) crystals. The larger pseudohexagon mer-Inq(3) crystals were analyzed by single-crystal X-ray diffraction and showed average In-N and In-O bond lengths significantly longer (0.22 and 0.26 Angstrom, respectively) than Alq(3) and bond angles about the In3+ ion more distorted from an ideal octahedral geometry. The crystalline packing of mer-Inq(3) is found to closely resemble the beta-Alq(3) phase, where both metal chelates are characterized by pairing of symmetry-related mer-optical isomers in three-dimensional pi-pi stacking interactions (similar to3.5 Angstrom or less). The smaller needlelike crystals were determined to be pure fac-Inq(3) by powder X-ray diffraction studies. An equivalent is not observed when Alq(3) is processed in an identical manner.