Mechanisms of Photoluminescence in Copper-Containing Fluoride Borate Crystals

Abstract

Mechanisms of photoluminescence in antizeolite fluoride borates (AFBs) doped by copper ions are interpreted based on a comparison between experimental and computational approaches. Doped AFBs demonstrate the effect of thermally stimulated photoluminescence and hold a promise for the use as radiation detectors. AFBs are built of porous framework [Ba 12 (BO 3 ) 6 ] 6+ with channels along the c axis. Lattice channels can accommodate various guest anionic groups. In this study, we present the results of modeling the electronic and optical properties of Cu-containing fluoride borates with [Cu(OH) 4 ] 3− (monovalent Cu) and [Cu(OH) 6 ] 4− (divalent Cu) as anionic groups. It is found that monovalent Cu + ions create occupied Cu-3d states near the top of the valence band, whereas divalent Cu 2+ ions create vacant Cu-3d states near the bottom of the conduction band. These states can serve as traps for electronic excitations and affect both the linear absorption and photoluminescent (PL) properties. PL spectra calculations were performed using two ab initio methodologies: (i) molecular dynamics (MD) sampling and (ii) time integration along with the progression of subsequently occupied excited states. The results show that the theoretical PL spectra calculated at a temperature of 10 K are instrumental in interpretation of experimental data obtained at 77 K. This effect is due to the strong dependence of Cu−OH distances in anionic groups along MD trajectories at given temperatures, which, in addition, manifests itself in the temperature dependence of the times and relaxation paths of electronic excitations. The results obtained open the way to designing new materials with predetermined properties for applications in radiation detectors based on thermally stimulated photoluminescence.

Photoluminescence in Cerium-Doped Fluoride Borate Crystals

“…(iii) To consider the influence of F-centers, we employed the simplest case of the LBBF structure, in which one fluorine atom was removed. In this case, PL spectra were calculated using a spin-polarized approach, as in the study of Cu-doped LBBF …”

“…Luminescent properties of LiBa 12 (BO 3 ) 7 F 4 doped with Eu 3+ , Tb 3+ , and Ce 3+ in different combinations were recently studied . PL processes of copper-containing borates were studied using ab initio calculation methods …”

First-Principles Study on Optoelectronic Properties of Fe-Doped Montmorillonite Clay

“…In the case of HS, intensities of transitions are weak except for LU → HO transition, since hot carriers relax much faster to frontier orbitals than those of LS and IS. Note that a recent study reveals that Redfield PL tends to narrow down the line widths and blueshifts transition energies …”

“…Note that a recent study reveals that Redfield PL tends to narrow down the line widths and blueshifts transition energies. 56 In summary, the ground state electronic properties of Fe-MMT under various spin multiplicities are explored by utilizing spin-polarized DFT calculations with PBE functionals. HS is found with the lowest total energy in agreement with Hund's rule.…”

A Lewis acid–base paired InBO3 catalyst: synthesis and high selectivity for isopropanol dehydrogenation

“…Metal borates possess great structural diversity, which is due to the abundant modes of connectivity between the BO 3 and BO 4 anion groups as well as their combinations with metal cations that have different valence states and radii. [1][2][3] This diverse structural chemistry leads to various applications for metal borates, particularly in nonlinear optics and photoluminescence, [4][5][6][7] while their application as solid catalysts has been insufficiently investigated. This great structural diversity may allow the existence of exposed metal cations with an unsaturated coordination environment, sites which are usually active in heterogeneous catalysis, for example by adsorbing substrate molecules or activating oxidative species.…”