Refereed journal article or data article (A1)
Glowing synthetic chlorohectorite: The luminescent features of a trioctahedral clay mineral
List of Authors: Hellen S. Santos, José M. Carvalho, Antti Viinikanoja, Iko Hyppänen, Tero Laihinen, Eric C. Romani, Dunieskys G. Larrudé, Marjukka Tuominen, Pekka Laukkanen, Hendrik C. Swart, Hermi F. Brito, Jorma Hölsä, Mika Lastusaari
Publisher: ELSEVIER SCIENCE BV
Publication year: 2017
Journal: Journal of Luminescence
Journal name in source: JOURNAL OF LUMINESCENCE
Journal acronym: J LUMIN
Volume number: 192
Start page: 567
End page: 573
Number of pages: 7
ISSN: 0022-2313
eISSN: 1872-7883
DOI: http://dx.doi.org/10.1016/j.jlumin.2017.07.017
Abstract
Clay minerals are versatile materials with numerous industrial applications. Their unique layered structure can act as a host for many optically active species. The synthesis and luminescence properties of chlorohectorite clays are now reported for the first time. The synthesized clays are composed of quasi-circular nanoparticles with diameters around 20-30 nm showing blue/green emission and persistent luminescence with a duration of ca. 5 s. The luminescence features are associated with titanium impurities in the chlorohectorite structure. It is shown that Ti can act as activator ion even at low concentrations: the XRF and ICP-MS measurements of the chlorohectorite materials indicate a Ti concentration around 60 ppm originating from the precursors. The XPS measurements of the clay materials showed the Ti 2p(3/2) signals at 457.8 and 458.9 eV associated with Ti3+ and Ti-IV, respectively. The excitation spectra confirm Ti3+ as the luminescent center in the chlorohectorites through the bands at 287 and 370 nm, related to the e(-)(O2-(2p))-Ti-IV charge transfer and the electronic transitions from the t(2g) to e(g) levels of Ti3+, respectively. The persistent luminescence properties are due to structural defects common for layered silicates.
Clay minerals are versatile materials with numerous industrial applications. Their unique layered structure can act as a host for many optically active species. The synthesis and luminescence properties of chlorohectorite clays are now reported for the first time. The synthesized clays are composed of quasi-circular nanoparticles with diameters around 20-30 nm showing blue/green emission and persistent luminescence with a duration of ca. 5 s. The luminescence features are associated with titanium impurities in the chlorohectorite structure. It is shown that Ti can act as activator ion even at low concentrations: the XRF and ICP-MS measurements of the chlorohectorite materials indicate a Ti concentration around 60 ppm originating from the precursors. The XPS measurements of the clay materials showed the Ti 2p(3/2) signals at 457.8 and 458.9 eV associated with Ti3+ and Ti-IV, respectively. The excitation spectra confirm Ti3+ as the luminescent center in the chlorohectorites through the bands at 287 and 370 nm, related to the e(-)(O2-(2p))-Ti-IV charge transfer and the electronic transitions from the t(2g) to e(g) levels of Ti3+, respectively. The persistent luminescence properties are due to structural defects common for layered silicates.
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