Luminescence mechanism in doubly Gd, Nd-codoped fluoride crystals for VUV scintillators

Abstract

The Nd-doped, Gd-doped and doubly Nd,Gd-codoped BaLu1.2Y0.8F8 (BaLuYF) and LuF3 single crystals were grown by micro-pulling-down method. Their photoluminescence, radioluminescence and alpha-ray-excited pulse-height spectra were studied in the vacuum-ultra-violet (VUV) region to confirm their possible application as fast VUV scintillators. Complementary photoluminescence measurements in the ultra-violet/ visible spectral region were performed as well. The possibility of scintillation performance improvement by Gd codoping was tested. The overall scintillation efficiency of BaLuYF:Nd1% was comparable to that of the LaF3:Nd8% reference sample and only slight improvement was observed after Gd1% codoping. The positive effect of Gd codoping was confirmed for higher dopant concentrations. This was explained by an energy transfer from the high-energy Gd 3+ 4f 2 G(0)7/2 level to the Nd 3+ 5d state. On the other hand, pulse -height spectra showed degradation of the light yield under alpha-ray excitation, which was explained by introduction of slow components due to Gd codoping. On the other hand, no positive effect of Gd codoping was found for the overall scintillation efficiency of Nd-doped LuF3, despite the same energy transfer process was confirmed.Slight improvement of the light yield under alpha-ray excitation was confirmed.doped wide-band-gap fluorides emitting in the vacuum-ultra-violet (VUV) region were considered as the candidate materials [1][2][3]. Since the decay time of the rare earth 5d-4f emission is proportional to the emission wavelength as τ ~ λ 3 [7], the Nd 3+ 5d-4f VUV emission has the decay time of several nanoseconds. Other rare-earth luminescence ions emitting at even shorter wavelengths, such as Tm 3+ or Er 3+ , can be considered as well [4]. When coupled to the contemporary fast VUV photodetectors such as gas electron multiplier (GEM) with micro-pixel chamber or a photomultiplier (PMT) with CsIcoated photocathode [5,6], fast position-sensitive detection system can be obtained.The first studied VUV scintillator was the Nd-doped LaF3 [1-3] with the Nd 3+ 5d-4f luminescence at

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“…The mesopore size and volume were 3.5 nm and 0.215 cm 3 /g, respectively (Figure S7). An FDA-approved, water-soluble ophthalmic diagnostic agentrose bengalwith high 1 O 2 quantum yield (ø = 0.75) was chosen because of the excellent overlap between its absorption spectrum and the emission spectrum of CGT NPs (542 nm; Figure h). Fourier transform infrared (FTIR) spectra (Figure S8) also verified the amine functionalized silica coating through the presence of SiO– and NH 2 – peaks at 1078 and 1637 cm –1 , respectively.…”

“…Unfortunately, no previous work has been reported on this hypothesis. Moreover, the dominant, green emission peak of Tb 3+ at 543 nm also provides us with the opportunity to use a variety of photosensitizers, such as rose bengal (FDA-approved), , porphyrin, or MC540 . Any of these photosensitizers would allow for good spectral overlap, making this nanoplatform an efficient 1 O 2 generator with high clinical relevance.…”