Stimuli-responsive photoluminescent copper(Ⅰ) halides for scintillation, anticounterfeiting, and light-emitting diode applications

Highly sensitive stimuli-responsive luminescent materials are crucial for appli-cations in optical sensing,security,and anticounterfeiting.Here,we report two zero-dimensional(0D)copper(I)halides,(TEP)_(2)Cu_(2)Br_(4),(TEP)_(2)Cu_(4)Br_(6),and 1D(TEP)_(3)Ag_(6)Br_(9),which are comprised of isolated[Cu_(2)Br_(4)]^(2-),[Cu_(4)Br_(6)]^(2-),and[Ag_(6)Br_(9)]3-polyanions,respectively,separated by TEP^(+)(tetraethylphosphonium[TEP])cations.(TEP)_(2)Cu_(2)Br_(4) and(TEP)_(2)Cu_(4)Br_(6) demonstrate greenish-white and orange-red emissions,respectively,with near unity photoluminescence quantum yields,while(TEP)_(3)Ag_(6)Br_(9) is a poor light emitter.Optical spectroscopy mea-surements and density-functional theory calculations reveal that photoemissions of these compounds originate from self-trapped excitons due to the excited-state distor-tions in the copper(I)halide units.Crystals of Cu(I)halides are radioluminescence active at room temperature under both X-andγ-rays exposure.The light yields up to 15,800 ph/MeV under 662 keVγ-rays of ^(137)Cs suggesting their potential for scintillation applications.Remarkably,(TEP)_(2)Cu_(2)Br_(4) and(TEP)_(2)Cu_(4)Br_(6) are inter-convertible through chemical stimuli or reverse crystallization.In addition,both compounds demonstrate luminescence on-off switching upon thermal stimuli.The sensitivity of(TEP)_(2)Cu_(2)Br_(4) and(TEP)_(2)Cu_(4)Br_(6) to the chemical and thermal stimuli coupled with their ultrabright emission allows their consideration for applications such as solid-state lighting,sensing,information storage,and anticounterfeiting.

Serrated flow in NaI:Tl scintillator crystals

The serrated-flow behavior is an important phenomenon that unveils material-deformation mechanisms,as reported for various kinds of materials.NaI doped with Tl(NaI:Tl)is unique among scintillation ma-terials in that the structure contains glide planes that are linked to serration behavior.In the present work,single crystals of NaI:Tl were subjected to room-temperature compression experiments at different strain rates.The serrated flow was observed,and complexity and multifractal analyses were performed to analyze the serration behavior.The findings revealed that the strain rate had a pronounced effect on the complexity and multifractality of the serrated flow,similar to what has been found in other alloy systems.The results also indicate that there may be a strong link between the complexity of the serrated flow behavior and the heterogeneity of the underlying dynamics.It is expected that the present work could be a step toward a better understanding of the deformation behavior and forgeability of NaI:Tl single crystals.

Tuning the melting point and phase stability of rare-earth oxides to facilitate their crystal growth from the meltv

The challenge of growing rare-earth(RE)sesquioxide crystals can be overcome by tailoring their structural stability and melting point via composition engineering.This work contributes to the advancement of the field of crystal growth of high-entropy oxides.A compound with only small REs(Lu,Y,Ho,Yb,Er)_(2)O_(3)maintains a cubic C-type structure upon cooling from the melt,as observed via in-situ high-temperature neutron diffraction on aerodynamically levitated samples.On the other hand,a compound with a mixture of small and large REs(Lu,Y,Ho,Nd,La)_(2)O_(3)crystallizes as a mixture of a primary C-type phase with an unstable secondary phase.Crystals of compositions(Lu,Y,Ho,Nd,La)_(2)O_(3)and(Lu,Y,Gd,Nd,La)_(2)O_(3)were grown by the micro-pulling-down(mPD)method with a single monoclinic B-type phase,while a powder of(Lu,Y,Ho,Yb,Er)_(2)O_(3)did not melt at the maximum operating temperature of an iridium-rhenium crucible.The minimization of the melting point of the two grown crystals is attributed to the mismatch in cation sizes.The electron probe microanalysis reveals that the general element segregation behavior in the crystals depends on the composition.