02891nas a2200217 4500008004100000022001400041245016300055210006900218260007100287300001400358490000800372520204400380100001402424700001802438700001502456700001302471700002102484700001402505700002302519856013102542 2009 eng d a1932-744700aComparing ultraviolet and chemical reduction techniques for enhancing photocatalytic activity of silver oxide/silver deposited nanocrystalline anatase titania0 aComparing ultraviolet and chemical reduction techniques for enha a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR a6243-62550 v1133 a

Silver oxide/silver have been deposited, with varying silver concentration (0.01-10 mol %), on the surface of sol-gel derived nanocrystal line anatase titania using two different techniques, namely the ultraviolet reduction and chemical reduction (using stannous ions). The pure and silver oxide/silver-deposited nanocrystalline anatase titania have been characterized for their morphology, average nanocrystal lite size, specific surface area, phases involved, surface chemistry, band gap, and photoluminescence using various analytical techniques, such as scanning electron microscopy, transmission electron microscopy, Brunauer, Emmett, and Teller surface-area measurement, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectrophotometry, and spectrofluorometry, respectively. The photocatalytic activity of pure and silver oxide/silver-deposited nanocrystalline anatase titania has been measured by monitoring the degradation of methylene blue dye in an aqueous solution under ultraviolet-radiation exposure. Within the investigated Ag-concentration range, the maximum photocatalytic activity has been observed for 0.1 and 10 mol % Ag for the chemical-reduction (using stannous ions) and ultraviolet-reduction methods with the corresponding apparent first-order reaction-rate constant (k(app)) values of 0.228 and 0.151 min(-1), which are 3.5 and 2.3 times larger than that of pure nanocrystalline anatase fitania (0.065 min(-1)). The chemical-reduction method (using stannous ions), hence, appears to be more effective than the ultraviolet-reduction method for enhancing the photocatalytic activity of nanocrystalline anatase titania. Various factors such as the surface concentration of superoxide ions, oxygen-ion vacancies, and stannous ions as well as the amount of silver oxide/silver and tin oxide are observed to control the surface-adsorption of methylene blue and photoinduced electron/hole lifetime and, hence, variation in the photocatalytic activity as a function of silver concentration.

1 aPriya, R.1 aBaiju, K., V.1 aShukla, S.1 aBiju, S.1 aReddy, M., L. P.1 aPatil, K.1 aWarrier, K., G. K. uhttps://library.ncl.res.in/content/comparing-ultraviolet-and-chemical-reduction-techniques-enhancing-photocatalytic-activity-001736nas a2200289 4500008004100000022001400041245011300055210006900168260005700237300001200294490000800306520078800314653002001102653001901122653001101141653001201152653001201164653001701176100001401193700001801207700001501225700001301240700002101253700001801274700002301292856013101315 2009 eng d a1011-372X00aEnhanced solar-radiation induced photocatalytic activity of surface-modified nanocrystalline anatase-titania0 aEnhanced solarradiation induced photocatalytic activity of surfa a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcMAR a137-1430 v1283 a

Sol-gel derived pure nanocrystalline (similar to 20-30 nm) anatase-titania has been surface-modified by depositing silver(I) oxide and silver (predominantly the former) via UV-reduction process. The pure and surface-modified nanocrystalline anatase-titania have been characterized using different analytical techniques for determining the average nanocrystallite size, phase-contents, surface-chemistry, as well as the absorption and photoluminescence characteristics. It is demonstrated that, the latter exhibits an enhanced solar-radiation induced photocatalytic activity as compared to that of the former as a result of the absorption in the visible-region and enhanced photo-induced e(-)/h(+) life-time, both caused by the surface-deposition of silver(I) oxide and silver.

10aNanocrystalline10aPhotocatalysis10aSilver10asol-gel10atitania10aUV-reduction1 aPriya, R.1 aBaiju, K., V.1 aShukla, S.1 aBiju, S.1 aReddy, M., L. P.1 aPatil, K., R.1 aWarrier, K., G. K. uhttps://library.ncl.res.in/content/enhanced-solar-radiation-induced-photocatalytic-activity-surface-modified-nanocrystalline-002352nas a2200265 4500008004100000022001400041245011700055210006900172260007300241300001400314490000800328520145300336653001101789653001601800653001101816653001901827653001201846653001201858100001701870700001801887700001501905700001401920700002301934856012901957 2009 eng d a0169-433200aNovel electroless process for copper coating of flyash using titania/ultraviolet-radiation/metal catalyst-system0 aNovel electroless process for copper coating of flyash using tit aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAPR a6696-67040 v2553 a

A novel electroless process has been demonstrated in this investigation to coat the surface of flyash particles with a conducting metal such as copper. The conventional electroless process has been modified for this purpose by replacing the tin-palladium catalyst-system with the titania/ultraviolet-radiation/metal catalyst-system, where the metal is either copper or silver as demonstrated here. The mechanism of copper coating of flyash particles in an electroless bath, using the novel methods of surface-sensitization and surface-activation, has been systematically studied by monitoring changes in the surface-morphology, surface-chemistry, and surface-structure of flyash particles using the scanning electron microscope, energy dispersive analysis of X-rays, X-ray photoelectron spectroscope, and X-ray diffraction. It has been revealed that the novel electroless method involves coating the flyash particles with titania photocatalyst via sol-gel, which acts as a surface-sensitizer under the ultraviolet-radiation exposure for the subsequent surface-activation with the copper- or silver-clusters. The latter in turn acts as surface-catalyst for the subsequent Cu-coating in an electroless bath. The proposed mechanism of surface-sensitization and surface-activation of flyash particles using the novel catalyst-system has been compared with that using the conventional catalyst-system. (C) 2009 Elsevier B. V. All rights reserved.

10aCopper10aElectroless10aFlyash10aPhotocatalysis10asol-gel10atitania1 aShijitha, T.1 aBaiju, K., V.1 aShukla, S.1 aPatil, K.1 aWarrier, K., G. K. uhttps://library.ncl.res.in/content/novel-electroless-process-copper-coating-flyash-using-titaniaultraviolet-radiationmetal-0