Determination of the molecular weight of the cationic polythiophenes was performed on a Waters 515 GPC equipped with a SynChropak CATSEC 100 and 300 column (250 mm 4.6 mm) mounted in series. The columns were heated at 50 C to prevent aggregation of the polyelectrolyte during elution. A Waters 441 UV detector was fixed at 254 nm. Data acquisition and processing were performed using the Astra software program. SynChropak CATSEC columns were calibrated by injecting different samples of monodisperse poly(vinylpyridinium) salts. The eluent was a solution of 0.05 M NaCl and 0.1 % trifluoroacetic acid and the flow rate was set to 0.4 mL min ±1. The polymeric samples were dissolved in water (0.3 mg mL ±1 ), autoclaved for 60 min, and injected. The results were M n = 11 ± 1 kDa and M w = 22 ± 2 kDa for polymer 1; M n = 7.5 ± 0.8 kDa and M w = 17 ± 2 kDa for polymer 2 (M n : numberaverage molecular weight; M w : weight-average molecular weight; 1 Da = 1 g mol ±1 ). Monolayer Preparation: Before each use, the gold electrodes (BAS, 1.6 mm diameter) were polished with wet 0.05 lm alumina slurry (Buehler Gamma Micropolish deagglomerated alumina, Lake Bluff, IL, USA) on a felt pad, rinsed with distilled water and then sonicated for about 60 min. The freshly cleaned electrodes were placed upside down under argon in a polypropylene tube and then exposed to various HS-PNA solutions (concentrations ranging from 10 ±6 to 10 ±4 M). The best results were obtained by depositing 1 lL of the aqueous probe solution of concentration 4 lM. The tube was sealed to prevent water evaporation and kept at room temperature for about 60 min. All the electrodes were immediately used after washing with distilled water.Hybridization and Transduction: After modification with the probe monolayer, the gold electrodes were ready for hybridization by incubation at room temperature in various concentrations of different single-stranded (ss) oligonucleotides (from 10 ±6 M to 10 ±9 M) diluted with a specific hybridization solution (6X SSPE (Omnipur), 0.03 % poly(vinylpyrrolidone) (PVP), and 30 % formamide) [10]. The incubation time in 200 or 10 lL solutions was 30 min for all analyte concentrations and this period was prolonged to 45 min for concentrations lower than 10 ±8 M. To make the hybridization electrochemically detectable, the resulting modified electrodes were then soaked for 10 min in a 10 ±5 M (based on the monomeric unit) solution of polymer 1 or 2.Electrochemical Measurements: A conventional three-electrode cell enclosed in a grounded Faraday cage was used with an Epsilon (BAS) electrochemical potentiostat. All experiments were conducted in an electrolyte solution of 0.1 M LiClO 4 (Aldrich) in water at room temperature (23 C). The pseudo-reference electrode was constructed by sealing an Ag/AgCl wire into a glass tube containing a 3 M KCl aqueous solution, capped with a Vycor tip. The counter electrode was a platinum wire. SWV was performed to reveal the electrode surface. The potential was scanned from 0 to 1100 mV in potential steps of 4 mV, wit...

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Stress and piezoelectric properties of aluminum nitride thin films deposited onto metal electrodes by pulsed direct current reactive sputtering

Fluorescence Fluorescence D 6540Electro-Mechano-Optical Conversions in Pr 3+ -Doped BaTiO 3 -CaTiO 3 Ceramics. -Ba1-x-yCaxPryTiO3 ceramics (x = 0.2, 0.23, 0.25, 0.30, 0.40, 0.50; y = 0.002) are synthesized by solid state reactions of mixtures of BaCO3, CaCO3, Pr2O3, and TiO2 (1400°C, 4 h). The samples exhibit simultaneously electrostrictive, mechanoluminescent, and electroluminescent properties. An electrical-voltage input induces mechanical strain and light emission, while a mechanical-stress input induces an electrical signal and light emission. For example, red-light emission is produced upon compression. This multifunctional material is promising for complicated sensing-and actuating-system applications in which a material can respond simultaneously to applied electrical, mechanical, and optical signals. -(WANG, X.; XU*, C.-N.; YAMADA, H.; NISHIKUBO, K.; ZHENG, X.-G.; Adv. Mater. (Weinheim, Ger.) 17 (2005) 10, 1254-1258; PRESTO, Japan Sci. Technol. Agency, Saitama 332, Japan; Eng.) -W. Pewestorf 28-008

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