We designed and synthesized 2-[6-(4-hydroxy)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (HPF) and 2-[6-(4-amino)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (APF) as novel fluorescence probes to detect selectively highly reactive oxygen species (hROS) such as hydroxyl radical ( ⅐ OH) and reactive intermediates of peroxidase. Although HPF and APF themselves scarcely fluoresced, APF selectively and dose-dependently afforded a strongly fluorescent compound, fluorescein, upon reaction with hROS and hypochlorite ( ؊ OCl), but not other reactive oxygen species (ROS). HPF similarly afforded fluorescein upon reaction with hROS only. Therefore, not only can hROS be differentiated from hydrogen peroxide (H 2 O 2 ), nitric oxide (NO), and superoxide (O 2 . ) by using HPF or APF alone, but ؊ OCl can also be specifically detected by using HPF and APF together. Furthermore, we applied HPF and APF to living cells and found that HPF and APF were resistant to light-induced autoxidation, unlike 2,7-dichlorodihydrofluorescein, and for the first time we could visualize ؊ OCl generated in stimulated neutrophils. HPF and APF should be useful as tools to study the roles of hROS and ؊ OCl in many biological and chemical applications.

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We found the specific activities of Pt/Sn0.96Nb0.04O2−δ for the oxygen reduction reaction increased with increasing conductivity of the support.

In polymer electrolyte fuel cells, it is essential to minimize Pt loading, particularly at the cathode, without serious loss of performance. From this point of view, we will report an advanced concept for the design of high performance catalysts and membrane-electrode assemblies (MEAs): first, the evaluation of Pt particle distributions on both the interior and exterior walls of various types of carbon black (CB) particles used as supports with respect to the "effective surface (ES)"; second, control of both size and location of Pt particles by means of a new preparation method (nanocapsule method); and finally, a new evaluation method for the properties of MEAs based on the Pt utilization (UPt), mass activity (MA), and effectiveness of Pt (EfPt), based on the ES concept. The amounts of Pt catalyst particles located in the CB nanopores were directly evaluated using the transmission electron microscopy, scanning electron microscopy and corresponding three-dimensional images. By use of the nanocapsule method and optimization of the ionomer, increased MA and EfPt values for the MEA were achieved. The improvement in the cathode performance can be attributed to the sharp particle-size distribution for Pt and the highly uniform dispersion on the exterior surface of graphitized carbon black (GCB) supports.

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