title: Speciation and site occupancy of uranium in strontium orthosilicate by photoluminescence and X-ray absorption spectroscopy: A combined experimental and theoretical approach.
abstract: Identifying the oxidation state and coordination geometry of radioactive element like uranium is important to fully understand its toxicology and other harmful effect in environment. Strontium orthosilicate is taken as a model compound for that. Strontium silicate doped with 1.0 mol% of U has been synthesized using sol-gel method and characterized using X-ray diffraction (XRD), time resolved fluorescence spectroscopy (TRFS) and extended X-ray absorption fine structure (EXAFS). Uranium exhibits multiple oxidation state and each one of them is having characteristics luminescence is an interesting dopant from structural point of view. TRFS is used to investigate the oxidation state and coordination behavior of uranium in Sr2SiO4. From TRFS measurement it was observed that uranium stabilizes in +6 oxidation state in the form of uranyl ion. Based on luminescence lifetime and EXAFS studies it was inferred that uranyl is stabilized on both 9- and 10-coordinated strontium polyhedra but majority occupies relatively asymmetric 9-coordinated Sr sites. This is further confirmed using theoretical measurement.
authors.affiliation: Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India. Electronic address: santoshg@barc.gov.in.
authors.forename: Santosh K
authors.initials: SK
authors.lastname: Gupta
authors.affiliation: Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Yadav
authors.affiliation: Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Nigam
authors.affiliation: Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: S N
authors.initials: SN
authors.lastname: Jha
authors.affiliation: Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: C
authors.initials: C
authors.lastname: Mazumder
authors.affiliation: Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: D
authors.initials: D
authors.lastname: Bhattacharya
authors.affiliation: Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Thulasidas
keywords: EXAFS; Photoluminescence; Speciation; Sr(2)SiO(4); Uranium