Comparative analysis of energy-level splitting of Pr^(3+) doped in LiYF_4 and LiBiF_4 crystals:a complete energy matrix calculation

Based on the combination of Racah＇s group-theoretical consideration with Slater＇s wavefunction, a 91 ×91 complete energy matrix is established in tetragonal ligand field D2d for Pr3＋ ion. Thus, the Stark energy-levels of Pr3＋ ions doped separately in LiYF4 and LiBiF4 crystals are calculated, and our calculations imply that the complete energy matrix method can be used as an effective tool to calculate the energy-levels of the systems doped by rare earth ions. Besides, the influence of Pr3＋ on energy-level splitting is investigated, and the similarities and the differences between the two doped crystals are demonstrated in detail by comparing their several pairs of curves and crystal field strength quantities. We see that the energy splitting patterns are similar and the crystal field interaction of LiYF4：Pr3＋ is stronger than that of LiBiF4：Pr3＋.

Enhancing light yield of Tb^(3+)-doped fluoride nanoscintillator with restricted positive hysteresis for low-dose high-resolution X-ray imaging

Developing scintillators with high light yield(LY),superior irradiation stability,and weak afterglow is of significance for the realization of low-dose high-resolution X-ray excited optical luminescence(XEOL)imaging.Lanthanide doped fluoride nanoparticles possess low toxicity,superior environmental stability,facial fabrication process,and tunable emissions,which are appropriate candidates for the next generation nanoscintillators(NSs).However,the low LY and strong positive hysteresis greatly restrict their practical application.Here,we propose an effective strategy that engineers energy gap to significantly enhance the LY.Our results verify that the tetragonal LiLuF4 host benefits the crystal level splitting of Tb^(3+)ions,which greatly promotes the electrons population on the Tb^(3+):5D4 level followed by the enhanced LY.The LY of LiLuF4:Tb@LiLuF4 NSs is calculated to be~31,169 photons/MeV,which is much higher than the lead halide perovskite colloidal CsPbBr3(~21,000 photons/MeV)and LuAG:Ce(~22,000 photons/MeV)scintillators.Moreover,the positive hysteresis is remarkably restricted after coating a thin shell.The X-ray detection limit and spatial resolution are measured to be~21.27 nGy/s and~7.2 lp/mm,respectively.We further verify that this core/shell NS can be employed as scintillating screen to realize XEOL imaging under the low dose rate of 13.86μGy/s.Our results provide an effective route to develop high performance NSs,which will promote great opportunities for the development of low-dose high-resolution XEOL imaging devices.

Interfacial thermodynamics-inspired electrolyte strategy to regulate output voltage and energy density of battery chemistry

The electrochemical behaviors of battery chemistry,especially the operating voltage,are greatly affected by the complex electrode/electrolyte interface,but the corresponding basis understanding is still largely unclear.Herein,the concept of regulating electrode potential by interface thermodynamics is proposed,which guides the improvement of the energy density of Zn-MnO_(2) battery.A cationic electrolyte strategy is adopted to adjust the charge density of electrical double layer,as well as entropy change caused by desolvation,thus,achieving an output voltage of 1.6 V(vs.Zn^(2+)/Zn)and a capacity of 400 mAh g^(-1).The detailed energy storage behaviors are also analyzed in terms of crystal field and energy level splitting.Furthermore,the electrolyte optimization benefits the efficient operation of Zn-MnO_(2) battery by enabling a high energy density of 532 Wh kg^(-1) based on the mass of cathode and a long cyclic life of more than 500 cycles.This work provides a path for designing high-energy-density aqueous battery via electrolyte strategy,which is expected to be extended to other battery systems.