Retraction: A study on the luminescence properties of gamma-ray-irradiated white light emitting Ca2Al2SiO7:Dy3+ phosphors fabricated using a combustion-assisted method.

[This retracts the article DOI: 10.1039/C6RA04913C.].

Correction and removal of expression of concern: A study on the luminescence properties of gamma-ray-irradiated white light emitting Ca2Al2SiO7:Dy3+ phosphors fabricated using a combustion-assisted method.

[This corrects the article DOI: 10.1039/C6RA04913C.].

Ca2 Al2 SiO7 :Ce3+ phosphors for mechanoluminescence dosimetry.

A series of Ce3+ ion single-doped Ca2 Al2 SiO7 phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca2 Al2 SiO7 :Ce3+ phosphor showed the characteristic emission of Ce3+ peaking at 400 nm (UV-violet) and originating from the Ce3+ transitions of 5d-4f (2 F5/2 and 2 F7/2 ). The photoluminescence (PL) emission spectra for Ca2 Al2 SiO7 :Ce3+ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca2 Al2 SiO7 :Ce3+ phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Photoluminescence and thermoluminescence properties of Eu2+ doped and Eu2+ ,Dy3+ co-doped Ba2 MgSi2 O7 phosphors.

In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu2+ -doped and Eu2+ ,Dy3+ -co-doped Ba2 MgSi2 O7 (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid-state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba2 MgSi2 O7 :Eu2+ showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba2 MgSi2 O7 :Eu2+ Dy3+ showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f6 5d1 to 4f7 transition of Eu2+ . TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu2+ doping in Ba2 MgSi2 O7 phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy3+ ions were co-doped in Ba2 MgSi2 O7 :Eu2+ and maximum TL intensity was observed for 2 mol% of Dy3+ . TL emission spectra of Ba1.95 MgSi2 O7 :0.05Eu2+ and Ba1.93 MgSi2 O7 :0.05Eu2+ ,0.02Dy3+ phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co-doping. The trap depths were calculated to be 0.54 eV for Ba1.95 MgSi2 O7 :0.05Eu2+ and 0.54 eV and 0.75 eV for Ba1.93 MgSi2 O7 :0.05Eu2+ ,0.02Dy3+ phosphors. It was observed that co-doping with small amounts of Dy3+ enhanced the thermoluminescence properties of Ba2 MgSi2 O7 phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication: The following parts of the abstract have been edited for consistency. '4f65d1' has been corrected to '4f6 5d1 ', '4f7' has been corrected to '4f7 ', 'Ba1.95' has been corrected to 'Ba1.95 ' and 'Ba1.93' has been corrected to 'Ba1.93 ' respectively.].

Fracto-mechanoluminescence and thermoluminescence properties of UV and γ-irradiated Ca2Al2SiO7:Ce³âº phosphor.

Ce(3+)-doped calcium aluminosilicate phosphor was prepared by a combustion-assisted method at an initiating temperature of 600°C. Structural characterization was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The absorption spectra of Ca2Al2SiO7:Ce(3+) showed an absorption edge at 230 nm. The optical characterization of Ca2Al2SiO7:Ce(3+) phosphor was investigated in a fracto-mechanoluminescence (FML) and thermoluminescence (TL) study. The peak of ML intensity increased as the height of impact of the moving piston increased. The TL intensity of Ca2Al2SiO7:Ce(3+) was recorded for different exposure times of UV and γ-irradiation and it was observed that TL intensity was maximum for a UV irradiation time of 30 min and for a γ-dose of 1180 Gy. The TL intensity had three peaks for UV irradiation at temperatures 82°C, 125°C and 203°C. Also the TL intensity had a single peak at 152°C for γ-irradiation. The TL and ML emission spectra of Ca2Al2SiO7:Ce(3+) phosphor showed maximum emission at 400 nm. The possible mechanisms involved in the TL and ML processes of the Ca2Al2SiO7:Ce(3+) phosphor are also explained.

Genetic Evidence for Modifying Oceanic Boundaries Relative to Fiji.

We present the most comprehensive genetic characterization to date of five Fijian island populations: Viti Levu, Vanua Levu, Kadavu, the Lau Islands, and Rotuma, including nonrecombinant Y (NRY) chromosome and mitochondrial DNA (mtDNA) haplotypes and haplogroups. As a whole, Fijians are genetically intermediate between Melanesians and Polynesians, but the individual Fijian island populations exhibit significant genetic structure reflecting different settlement experiences in which the Rotumans and the Lau Islanders were more influenced by Polynesians, and the other Fijian island populations were more influenced by Melanesians. In particular, Rotuman and Lau Islander NRY chromosomal and mtDNA haplogroup frequencies and Rotuman mtDNA hypervariable segment 1 region haplotypes more closely resemble those of Polynesians, while genetic markers of the other populations more closely resemble those of the Near Oceanic Melanesians. Our findings provide genetic evidence supportive of modifying regional boundaries relative to Fiji, as has been suggested by others based on a variety of nongenetic evidence. Specifically, for the traditional Melanesia/Polynesia/Micronesia scheme, our findings support moving the Melanesia-Polynesia boundary to include Rotuma and the Lau Islands in Polynesia. For the newer Near/Remote Oceania scheme, our findings support keeping Rotuma and the Lau Islands in Remote Oceania and locating the other Fijian island populations in an intermediate or "Central Oceania" region to better reflect the great diversity of Oceania.

Genetic structure among Fijian island populations.

We examined nine Y chromosome short tandem repeats (Y-STRs) and the mitochondrial DNA (mtDNA) hypervariable segment 1 region in the Fijian island populations of Viti Levu, Vanua Levu, Kadavu, the Lau islands and Rotuma. We found significant genetic structure among these populations for the Y-STRs, both with and without the Rotumans, but not for the mtDNA. We also found that all five populations exhibited the sex-biased admixture associated with areas settled by Austronesian-speaking people, with paternal lineages more strongly associated with Melanesian populations and maternal lineages more strongly associated with Polynesian populations. We also found that the Rotumans in the north and the Lau Islanders in the east were genetically more similar to Polynesian populations than were the other Fijians, but only for the mtDNA. For the Y-STRs, the Rotumans and the Lau Islanders were genetically as similar to Melanesian populations as were the other three populations. Of the five populations, the Rotumans were the most different in almost every regard. Although past genetic studies treated the Fijians as being genetically homogenous despite known geographic, phenotypic, cultural and linguistic variation, our findings show significant genetic variation and a need for a closer examination of individual island populations within Fiji, particularly the Rotumans, in order to better understand the process of the peopling of Fiji and of the surrounding regions.