Probing metastable Sm2+ and optically stimulated tunnelling emission in YPO4: Ce, Sm

Prasad, Amit Kumar; Kook, Myungho; Jain, Mayank

doi:10.1016/j.radmeas.2016.11.012

Cited by 10 publications

(6 citation statements)

References 25 publications

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“…Here the trapped electrons in the Sm 2+ metastable state (formed by ionising radiation: Sm 3 + e − → Sm 2+ ) may be measured non-destructively by resonant excitation, while a higher energy excitation results in electron detrapping and subsequent transfer to the Ce 4+ hole centre (also formed by ionising radiation: Ce 3+ + h + → Ce 4+ ). Prasad et al 14 used this system to obtain insights into excited-state tunnelling recombination from Sm 2+ to Ce 4+ . The RPL from Sm 2+ , unfortunately, quenches at around 180 K, severely restricting the investigations and applications.…”

Section: Introductionmentioning

confidence: 99%

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A novel coupled RPL/OSL system to understand the dynamics of the metastable states

Jain

Kumar

Kook

2020

Sci Rep

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Metastable states form by charge (electron and hole) capture in defects in a solid. They play an important role in dosimetry, information storage, and many medical and industrial applications of photonics. Despite many decades of research, the exact mechanisms resulting in luminescence signals such as optically/thermally stimulated luminescence (OSL or TL) or long persistent luminescence through charge transfer across the metastable states remain poorly understood. Our lack of understanding owes to the fact that such luminescence signals arise from a convolution of several steps such as charge (de)trapping, transport and recombination, which are not possible to track individually. Here we present a novel coupled RPL(radio-photoluminescence)/OSL system based on an electron trap in a ubiquitous, natural, geophotonic mineral called feldspar (aluminosilicate). RPL/OSL allows understanding the dynamics of the trapped electrons and trapped holes individually. We elucidate for the first time trap distribution, thermal eviction, and radiation-induced growth of trapped electron and holes. The new methods and insights provided here are crucial for next generation model-based applications of luminescence dating in Earth and environmental sciences, e.g. thermochronometry and photochronometry.

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Section: Introductionmentioning

confidence: 99%

“…One example of such a system is the Sm 2+ defect in YPO4: Sm, Ce. This shows both RPL and OSL behavior (Poolton et al, 2010Prasad et al, 2017aDorenbos et al, 2003Dorenbos et al, , 2011. Prasad et al (2017) used this system to obtain insights into excited state tunneling induced recombination (Sm 2+  Ce 4+ ) in YPO4.…”

Section: Introductionmentioning

confidence: 99%

A novel coupled RPL/OSL system to understand the dynamics of the metastable states

Jain

Kumar

Kook

2020

Sci Rep

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“…The decrease in the Ce 3+ intensity was due to ionisation to Ce 4+ , where Ce 3+ acts as a hole-trapping site. Ce 3+ hole trapping has been reported in other materials such as YPO4:Ce,Sm [300] and MgO:Li,Ce,Sm [244].…”

Section: Resultsmentioning

confidence: 85%

“…It was anticipated that UV excitation into Ce 3+ would result in energy transfer to Sm 3+ ions, enhancing the latter's luminescence. Ce 3+ → Sm 3+ energy transfer has been reported in other Ce,Sm co-doped compounds including YPO4:Ce,Sm [300], CaSrSiO4:Ce,Sm [137],…”

Section: %(Cesm) Co-doped Namgf3 Bulk Materials and Nanoparticles Int...mentioning

confidence: 80%

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The Luminescence of Lanthanide-doped NaMgF3 Nanoparticles: Radioluminescence, Radiophotoluminescence and Optically Stimulated Luminescence

Nalumaga¹

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NaMgF3 is a host material that has demonstrated luminescent properties suitable for radiation dose measurements when doped with lanthanide (Ln) ions. NaMgF3 has a response to ionising radiation similar to that of tissue, and hence it has potential application in radiotherapy where a high level of accuracy is required. This thesis focused on investigations into the suitability of NaMgF3 nanoparticles for radiation dose measurements. Nanoparticles display advantages that can be exploited to increase spatial resolution in two-dimensional dosimetry. Additionally, nanoparticles exhibit new and different distributions of optically active traps, and their luminescence can be sensitised to increase the signal to noise. Hence, this thesis presents results obtained from the synthesis and characterisation of Ln-doped NaMgF3 nanoparticles. The nanoparticles were synthesised via the hydrothermal, reverse micelle and thermolysis techniques. Structural studies were carried out, followed by investigations on the effect of X-ray irradiation on the luminescent properties of the nanoparticles. It was observed that compared to the bulk materials, the nanoparticles exhibited increased oxygen (O2-)-related defect luminescence and favoured substitution of trivalent ions over the divalent ions. The behaviour was attributed to the stability of trivalent ions in aqueous solutions during nanoparticle synthesis, which encouraged increased incorporation of O2--related defects to create charge neutrality. O2--related defects allowed for O2- → Yb3+ charge transfer process, hence Yb3+ emission in the infrared region. X-ray stimulation resulted in Yb3+ → Yb2+ radiophotoluminescence (RPL), but the increase in Yb-dopant concentration revealed no significant effect on the structural and luminescent properties. Most of the studied materials exhibited multiple luminescence properties for monitoring radiation doses, which would increase the dose accuracy. Ce-doped nanoparticles exhibited the first reported optically stimulated luminescence (OSL) in Ln-doped near tissue-equivalent NaMgF3 nanoparticles suitable for total radiation measurements. OSL occurred through a series of processes, including the creation of F-centres through X-ray irradiation and optical stimulation to release electrons that recombined with holes trapped at Ce4+ sites, followed by Ce3+ emission. In addition, the Ce3+ → Ce4+ RPL effect suitable for cumulative radiation monitoring was observed from isolated and aggregated Ce3+ sites in the Ce-doped nanoparticles, providing an additional method to increase dose accuracy. Furthermore, the Ce,Sm co-doped NaMgF3 nanoparticles demonstrated suitability for real-time and cumulative radiation dose monitoring via Sm radioluminescence after a priming dose and multiple Ce3+ → Ce4+, Sm3+ → Sm2+, and O2- → O- RPL signals through which cumulative radiation doses can be determined. Finally, the applicability of singly doped oleic acid-capped NaMgF3:Eu and NaMgF3:Sm nanoparticles for radiation monitoring via the Eu3+ → Eu2+ and Sm3+ → Sm2+ RPL effects were demonstrated. The studies were followed by investigations of the sensitisation of Eu3+ and Sm3+ luminescence signals using 2-thenoyltrifluoroacetone (TTFA). The first successful sensitisation of NaMgF3 nanoparticles was demonstrated through remarkable TTFA → Eu3+ energy transfer. However, minimal TTFA → Sm3+ sensitisation was observed, attributable to a non-optimal energy difference between the TTFA triplet state and the Sm3+ resonance energy level, encouraging back energy transfer. TTFA → O2- sensitisation was additionally observed in the NaMgF3:Sm nanoparticles. Furthermore, enhancement of Sm3+ luminescence was additionally demonstrated in the Ce,Sm co-doped nanoparticles via energy transfer from the Ce3+ fully allowed 4f → 5d transitions. The studies resulted in a wealth of information, and where possible, detailed schematic models are presented to explain the observations, which will guide future research. Ultimately, nanoparticles display luminescent properties suitable for dosimetry applications, and the results encouraged further research into the application of nanoparticles as dosimeter materials.

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Chemical stabilization of Eu2+ in LuPO4 and YPO4 hosts and its peculiar sharp line luminescence

Zeler

Sulollari

Meijerink

et al. 2020

Journal of Alloys and Compounds

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Probing metastable Sm2+ and optically stimulated tunnelling emission in YPO4: Ce, Sm

Cited by 10 publications

References 25 publications

A novel coupled RPL/OSL system to understand the dynamics of the metastable states

A novel coupled RPL/OSL system to understand the dynamics of the metastable states

The Luminescence of Lanthanide-doped NaMgF3 Nanoparticles: Radioluminescence, Radiophotoluminescence and Optically Stimulated Luminescence

Chemical stabilization of Eu2+ in LuPO4 and YPO4 hosts and its peculiar sharp line luminescence

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