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2 Materials Science

2 2002

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Preparation and properties of colloidal nanosize silica dioxide for polishing of monocrystalline silicon wafers

Gaishun V. E., Tulenkova O. I., Melnichenko I. M., Baryshnin S. A., Potapenok Y. A., Xlebokazov A. P., Stręk W.

Materials Science

2002

Vol. 20, No. 2

19-22

Colloidal silica can be used for final general metallographic polishing. It is used to polish single crystal silicon for electronic applications and, subsequently, polycrystalline silicon for solar cells, gallium arsenide, indium phosphide, titanium, gadolinium gallium garnet and sapphire. The silica dioxide are dispersed in water with alkaline compound added to obtain the desired pH.

Determination of the photodynamic activity of porphyrins: Potential photosensitizers for treatment of age-related macular degeneration

Neri C. R., Maestrin Prado A. P. J., Ribeiro A. O., Serra O. A., Iamamoto Y.

Materials Science

2002

Vol. 20, No. 2

97-103

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in people between 65 and 74 years. Recently, the photodynamic therapy (PDT) is used as experimental treatment for exudative AMD. In a PDT process, a reaction takes place when a photosensitiser (PS), light of appropriated wavelength, and oxygen are present at the same time. In general, the PS are porphyrins and related systems. The aim of this study was to evaluate the photodynamic activity (PA) of the Benzoporphyrin (BPH2), Protophorphyrin-IX (Proto), Tetrakis(phydroxyphenyl) porphyrin (THPPH2) and Tetrakis(2-hydroxy-5-nitrophenyl)porphyrin (T2H5NPPH2). The PA is related to quantum yields (??) for the singlet oxygen (1O2.) production. Uric acid, a known singlet oxygen scavenger, is utilised as a chemical dosimeter in the PDT. When the uric acid (UA) and PS solution is irradiated with laser light the UA band absorbance at 293 nm decreases as a rapid evaluation of relative PA of the PS.