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Ultraviolet emission and electron spin characteristics of Th(C2O4)2·xH2O:Gd3+
New Journal of Chemistry ( IF 2.7 ) Pub Date : 2020-09-02 , DOI: 10.1039/d0nj03360j Santosh K. Gupta 1, 2, 3, 4 , B. Rajeshwari 1, 2, 3, 4 , S. N. Achary 2, 3, 4, 5, 6 , R. M. Kadam 1, 2, 3, 4, 6
New Journal of Chemistry ( IF 2.7 ) Pub Date : 2020-09-02 , DOI: 10.1039/d0nj03360j Santosh K. Gupta 1, 2, 3, 4 , B. Rajeshwari 1, 2, 3, 4 , S. N. Achary 2, 3, 4, 5, 6 , R. M. Kadam 1, 2, 3, 4, 6
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Ultraviolet emitting Gd3+ doped phosphors have recently attracted significant attention from the optical science community owing to their important applications in the areas of photothermal therapy, transilluminators and sensitizer based photoluminescent phosphors (PLPs). It was found in several previous studies that the annealing temperature and water content has a profound influence on the emission intensity and luminescence lifetime of PLPs. In this context, we have synthesized Th(C2O4)2·6H2O:Gd3+ (TOHG) and characterized it using photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy. Emission spectroscopy showed the presence of a singular peak at 311 nm due to an electric dipole transition, suggesting the extremely low symmetry around Gd3+ in TOHG. Luminescence lifetime measurements suggested two different local environments of Gd3+ in TOHG; the shorter lived one (S) is closer to oxygen vacancies and the longer lived one (L) is further away from the oxygen vacancies. The time resolved emission spectrum shows a slightly different peak profile for S and L. The EPR spectra of TOHG suggested that Gd3+ is situated in a nearly eight-fold coordination of oxygen (cubic coordination) at the Th4+ ion. Furthermore, we carried out thermal treatment of TOHG at 250 °C which led to Th(C2O4)2·2H2O:Gd3+(TODG) which on further annealing at 300 °C was converted into anhydrous thorium oxalate (TOAG). X-ray diffraction analysis suggested a triclinic lattice structure for TOHG and a monoclinic and orientationally disordered structure for TOAG. The PL emission intensity and excited state lifetime were found to be greater for TOAG due to the absence of the non-radiative transition provided by water molecules. The EPR spectra of TOAG suggested lowering of the site symmetry to rhombic symmetry in TOAG. This is in agreement with our structural analysis. Such a complete spectrum of work wherein the structure, excited state dynamics and spin properties of Gd3+ were investigated will open up a new avenue into gadolinium photophysics, particularly for researchers to explore actinide oxalate with a view to thermally tuning its properties.
中文翻译：
Th（C2O4）2·xH2O：Gd3 +的紫外发射和电子自旋特性
掺杂紫外线的Gd 3+掺杂磷光体由于在光热疗法，透射照明器和基于敏化剂的光致发光磷光体（PLP）领域的重要应用，最近引起了光学科学界的广泛关注。在先前的几项研究中发现，退火温度和水含量对PLP的发射强度和发光寿命具有深远的影响。在这种情况下，我们合成了Th（C 2 O 4）2 ·6H 2 O：Gd 3+（TOHG）并使用光致发光（PL）和电子顺磁共振（EPR）光谱对其进行了表征。发射光谱表明，由于电偶极跃迁，在311 nm处出现一个奇异峰，表明TOHG中Gd 3+周围的对称性极低。发光寿命的测量表明TOHG中Gd 3+的两个不同局部环境。寿命越短（S）越接近氧空位，寿命越长（L）越远离氧空位。时间分辨的发射光谱显示出S和L的峰轮廓略有不同。TOHG的EPR光谱表明，Gd 3+在Th 4+处的氧配位几乎是八倍（立方配位）。离子。此外，我们在250°C下进行了TOHG的热处理，导致产生了Th（C 2 O 4）2 ·2H 2 O：Gd 3+（TODG），将其在300°C下进一步退火，转化为无水草酸th（TOAG）。X射线衍射分析表明TOHG为三斜晶格结构，TOAG为单斜晶和定向无序结构。发现TOAG的PL发射强度和激发态寿命更长，这是因为不存在水分子提供的非辐射跃迁。TOAG的EPR谱表明，TOAG的位点对称性降低为菱形对称性。这与我们的结构分析是一致的。这样完整的工作光谱，其中Gd 3+的结构，激发态动力学和自旋特性 研究人员将为into光物理研究开辟一条新途径，尤其是对于研究人员探索act系草酸盐以热调节其性质而言。
更新日期：2020-09-28
中文翻译：
Th（C2O4）2·xH2O：Gd3 +的紫外发射和电子自旋特性
掺杂紫外线的Gd 3+掺杂磷光体由于在光热疗法，透射照明器和基于敏化剂的光致发光磷光体（PLP）领域的重要应用，最近引起了光学科学界的广泛关注。在先前的几项研究中发现，退火温度和水含量对PLP的发射强度和发光寿命具有深远的影响。在这种情况下，我们合成了Th（C 2 O 4）2 ·6H 2 O：Gd 3+（TOHG）并使用光致发光（PL）和电子顺磁共振（EPR）光谱对其进行了表征。发射光谱表明，由于电偶极跃迁，在311 nm处出现一个奇异峰，表明TOHG中Gd 3+周围的对称性极低。发光寿命的测量表明TOHG中Gd 3+的两个不同局部环境。寿命越短（S）越接近氧空位，寿命越长（L）越远离氧空位。时间分辨的发射光谱显示出S和L的峰轮廓略有不同。TOHG的EPR光谱表明，Gd 3+在Th 4+处的氧配位几乎是八倍（立方配位）。离子。此外，我们在250°C下进行了TOHG的热处理，导致产生了Th（C 2 O 4）2 ·2H 2 O：Gd 3+（TODG），将其在300°C下进一步退火，转化为无水草酸th（TOAG）。X射线衍射分析表明TOHG为三斜晶格结构，TOAG为单斜晶和定向无序结构。发现TOAG的PL发射强度和激发态寿命更长，这是因为不存在水分子提供的非辐射跃迁。TOAG的EPR谱表明，TOAG的位点对称性降低为菱形对称性。这与我们的结构分析是一致的。这样完整的工作光谱，其中Gd 3+的结构，激发态动力学和自旋特性 研究人员将为into光物理研究开辟一条新途径，尤其是对于研究人员探索act系草酸盐以热调节其性质而言。
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