Jacek Gurgul

Photocatalytic Activity of Titanium Dioxide Modified by Silver Nanoparticles

Photocatalytic activity of Ag/TiO(2) composites obtained by photoreduction treatment (PRT) was investigated. The composite materials, containing various ratio of silver nanoparticles (0.6-3.7 wt %) were obtained by depositing silver on the Evonic-Degussa P25 titania surface. Selected samples whose color varied between light rose and purple brown were examined by SEM, TEM, XPS, DRS, and BET techniques. Flat band potential was determined using Roy method. TEM analysis showed spherically shaped silver nanoparticles of the diameter 4-12 nm. The XPS measurements revealed that silver particles were obtained mainly in metallic form. DRS spectra and photovoltage measurements showed that silver nanoparticles modified the P25 spectral properties but they changed neither the band gap nor the location of flat band potential. The photocatalytic activity of Ag/P25 composite was compared to the photocatalytic activity of pure P25 in the photooxidation reaction of an important potable water contaminant humic acid (HA) and two model compounds, oxalic acid (OxA) and formic acid (FA). The photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that a small amount of silver nanoparticles deposited on the titania surface triggers the increase in photocatalytic activity; this increase depends, however, on the decomposed substance.

Structure, magnetic properties and {sup 119}Sn Mossbauer spectroscopy of PrRhSn

AbstractPrRhSnwassynthesizedinpolycrystallineformbyareactionofpraseodymium,rhodium,andtininanarc-meltingfurnace.Thesample was investigated by powder and single crystal X-ray diffraction: ZrNiAl type, space group P¯62 m; a ¼ 742:49ð7Þ,c ¼ 415:05ð5Þpm, wR 2 ¼ 0.0737, 353F 2 values and 14 variables. The PrRhSn structure has two crystallographically independentrhodiumsiteswithatricappedtrigonalprismaticcoordination,i.e.[Rh1Sn 3 Pr 6 ]and[Rh2Sn 6 Pr 3 ].Therhodiumandtinatomsbuildup a three-dimensional [RhSn] network with short Rh–Sn contacts (278 and 285pm), in which the praseodymium atoms filldistorted hexagonal channels. The magnetic and electronic properties of PrRhSn have been studied by means of AC and DCmagnetic susceptibility measurements as well as 119 Sn Mo¨ssbauer spectroscopy. A transition from a paramagnetic to aferromagneticstatewasfoundatT C ¼ 3:0K.r 2005ElsevierInc.Allrightsreserved. Keywords: Intermetalliccompound;Magnetism;Mo¨ssbauerspectroscopy 1. IntroductionThe rare-earth metal based stannides RERhSn(RE ¼ rare-earthelement)havethoroughlybeeninves-tigated in recent years [1–5, and references therein].A detailed literature overview is given in [1] and [5].Especially, the valence fluctuations of CeRhSn andthe heavy fermion behavior of YbRhSn are of greatinterest.The crystal chemistry and the physical propertiesof the RERhSn stannides with the early rare-earthelementshavecontroversiallybeendiscussed.ThelatticeparametersforCeRhSn,PrRhSn,andNdRhSnreportedbyRoutsietal.[6]aredifferentfromthosereportedbyMishra et al. [1]. A recent single crystal study of theNdRhSnstructure[7]clearlyconfirmedtheX-raypowderdatagivenin[1].Thetwodifferentstudiesalsorevealedadiscrepancyconcerningthemagneticordering.Whilenohint for magnetic ordering was evident in the originalwork [6], ferromagnetic ordering at T

Electronic and Magnetic Properties of Ternary Stannides RERhSn (RE = Tb, Dy and Ho)

The results of magnetic studies and Mössbauer investigations made with 119Sn source are reviewed for the series of RERhSn (RE = Tb, Dy and Ho) compounds crystallizing in the same hexagonal ZrNiAl-type of structure. The role of crystalline electric field effects in the establishing of magnetic moment orientations observed in these compounds and their influence on the observed magnitudes of magnetic moments are discussed.