Visualization of stress distribution has been realized by a nondestructive mechanoluminescence (ML) from SrAl2O4:Eu, which can emit three magnitudes higher visible light than that of well-known ML substance of quartz. A simulation result confirms that such a ML image successfully reflects the stress distribution. A kinetic model for ML of SrAl2O4:Eu is proposed.

We report the realization of the dynamic image of stress distribution by developing a remarkably strong mechanoluminescence (ML) material of Sr0.975Al2O3.985:Eu0.01, which can emit four orders of magnitude larger intensity than that of the reported strong ML material of quartz crystal. This ML material can be mixed in the target composite or coated on the surface to sense stress by emitting visible light. This method is applicable to the dynamic visualization of stress distribution in a solid not only in the atmosphere but also in an aqueous environment.

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...

Elastico-deformation luminescence in strontium aluminates was investigated systematically using precisely controlled pure-phase Eu-doped strontium aluminates of SrAl12O19, Sr4Al14O25, SrAl4O7, α-SrAl2O4, β-SrAl2O4, Sr3Al2O6 and their mixed phases. This study revealed that only the α-SrAl2O4 phase produces strong elastico-deformation luminescence; other strontium aluminates show no deformation luminescence. Correlation of deformation luminescence and crystal structure was found. The α-SrAl2O4 has the lowest symmetry, crystallizing in a monoclinic structure. This finding can be applied in designing strong elastico-deformation-luminescent materials.

One of the present intensive concerns about the high-temperature superconductors is whether charge stripes are a key to superconductivity. Here we report observation of charge stripes in the simplest copper oxide, CuO, by real-space images obtained by electron microscopy. Charge-ordered domains and normal-lattice domains exist alternatively in the vapor-grown single crystal of CuO. Since CuO consists of the Cu-O bonding, which is a basic material feature for high- T(c) cuprates, the discovery of charge stripes in this basic compound has important implications for discussing the mechanism of superconductivity in complex cuprates.

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