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Afterglow and thermoluminescence of ZrO2 nanopowders

100%

Puust L., Kiisk V., Utt K., Mändar H., Sildos I.

Open Physics

2014

vol. 12

issue 6

415-420

A careful study of the phosphorescence afterglow and the thermoluminescence (TL) of sol-gel-prepared m-ZrO2 nanocrystalline powders in an extended temperature range −100 to 300 °C was carried out. Wavelength-resolved TL proved the existence of a single active luminescence centre in this temperature range. A TL method based on various heating rates was used to derive more reliable trap depths of 0.75, 0.95, 1.25, 1.46 and 1.66 eV whereas deconvolution methods provided somewhat lower values. The most intense room-temperature afterglows (that were easily observable beyond 1000 s) were obtained from samples annealed at 1250 and 1500 °C, and were attributed mainly to depopulation of the 1.25 eV traps.

Raman modes in transferred bilayer CVD graphene

86%

Niilisk A., Kahro T., Kiisk V., Rähn M., Alles H., Aarik J., Sammelselg V.

Open Physics

2015

vol. 13

issue 1

A systematic experimental Raman spectroscopic study of twisted bilayer graphene (tBLG) domains localized inside wide-area single layer graphene (SLG) produced by low-pressure CVD on Cu foil and transferred onto SiO2/Si substrate has been performed. According to the Raman characterization the tBLG domains had a great variety of twisting angles θ between the bottom and top graphene layers (6° < θ < 25°). The twisting angle θ was estimated from the spectral position of the rotating R and R' modes in the Raman spectrum.Under G band resonance conditions the breathing mode ZO' with a frequency of 95- 97 cm−1 was detected, and a breathing mode ZO was found in the spectra between 804 cm−1 and 836 cm−1, its position depending on the twisting angle θ. An almost linear relationship was found between the frequencies ωZO and ωR. Also a few other spectral peculiarities were found, e.g. a high-energy excitation of the G band resonance, the 2G overtone appearing at 3170-3180 cm−1 by the G band resonance, revealing a linear dispersion of 80 cm−1/eV of the 2D band in tBLG

Sensitizing of Sm3+ fluorescence by silver dopant in the TiO2 films

86%

Dolgov L., Kiisk V., Reedo V., Pikker S., Sildos I., Kikas J.

Open Physics

2011

vol. 9

issue 2

542-546

Composite material based on a TiO2 matrix doped with Sm3+ ions and co-doped with silver was investigated. Samarium ions together with nano- and micro-aggregates of silver were incorporated into the titanium alkoxide during the sol-gel process. Samarium ions were excited either directly (λ exc = 488 nm) or through the TiO2 host (λ exc = 355 nm). It was revealed that samarium fluorescence (λ exc = 488 nm) in gelled TiO2 films is enhanced by up to 20 times in the vicinity of silver inclusions. Sensitizing and plasmonic mechanisms of enhancement in Sm3+ fluorescence are discussed.

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3 Open Physics

1 2015

1 2014

1 2011

3 Kiisk V.

2 Sildos I.

1 Aarik J.

1 Alles H.

1 Dolgov L.

1 Kahro T.

1 Kikas J.

1 Mändar H.

1 Niilisk A.

1 Pikker S.

1 Puust L.

1 Reedo V.

1 Rähn M.

1 Sammelselg V.

1 Utt K.

Search results

Afterglow and thermoluminescence of ZrO2 nanopowders

Raman modes in transferred bilayer CVD graphene

Sensitizing of Sm3+ fluorescence by silver dopant in the TiO2 films