Photoluminescence and Scintillation Modulation Upon UV/X‐ray‐Induced Photochromism in Europium Tungstate Phosphors

Abstract

Rare earth (RE) tungstates with general formula REW2O6(OH)3 (RE = YIII or EuIII) were synthesized by hydrothermal method by using different citric acid contents. The prepared samples exhibit both UV and X‐ray‐induced photochromism at room temperature, as well as photomodulated luminescence. The presence of citric acid residues improves the photochromism when the samples are UV‐irradiated, but has a secondary effect when the material is exposed to X‐ray, evidencing particular mechanisms of action in each case. The emission profiles, in its turn, are similar independently of irradiation source. The continuous irradiation leads to color changes of samples concomitantly to the suppression of EuIII emission, without variations in the point symmetry of EuIII, but showing differences in the quenching behaviour according the excitation energy. The observed photochromic effect is stable and persists for several hours, which can be reversed by heating the irradiated material in air for a few minutes, when the restitution of emission intensity takes place. The observed properties make these materials promising for ionizing radiation detection and optical data storage.

Selective Photochromic Response to Low-Dose X-ray Radiation Detection in One-Dimensional Cadmium-Viologen Complexes

“…Ionizing radiations, especially X-ray radiation from natural and artificial sources, pose a variety of potential health risks if inappropriately used, which has aroused extensive attention from our society. − As such, the precise detection of X-ray radiation is highly desirable in the radiation biological study, environmental and cosmic radiation detection, and medical radiation treatment. − For these applications, the important requirements are high sensitivity, strong chemical, thermal and radiolytic stabilities, good X-ray absorption, outstanding resistance to fatigue, excellent detection performance, and mild operating conditions. − The currently used commercial detectors mainly focus on radio-photoluminescence (RPL) materials, scintillators, and semiconductors, which still face severe limitations in practical application due to their inherent vice. − For example, many radio-photoluminescence materials display limited luminescent stability after continuous high-dose X-ray radiation and scintillators can only record the instantaneous radiation, both of which require spectrophotometers to indirectly read the radiation signal when they are applied for X-ray detection, ,− while the semiconductors used as X-ray detection materials display several other disadvantages such as poor X-ray absorptivity, low detection efficiency, and harsh operating conditions. , Thus, these limitations call for the continued search for new efficient X-ray radiation detection materials.…”

A photochromic and scintillation Eu-MOF with visual X-ray detection in bright and dark environments

“…9–11 X-ray-induced photochromic (XP) compounds have been extensively studied due to their higher X-ray sensitivity than commercial silver salt-based radiographic films. 12,13 XP inorganic materials that can be realized by X-ray induction include manganite, 14 spinel, 15 tungstates, 16 oxometallates with impurities (such as LiNbO 3 :Cu), 17 Prussian blue analogs, 18 Fe II spin-crossover complexes, 19 and cobalt dioxolene. 20 Organic materials include spiropyran-based composites, 6,21 naphthalenediimide (NDI) derivatives, 22 metal complexes bearing nonionic N-heterocyclic aromatic ligands, 23 and N-substituted bipyridinium-containing compounds.…”

Photoluminescence Induced in Mineral Oil by Ionizing Radiation

“…Our studies also demonstrated the versatility of the fluorescence spectroscopy approach to assessment of the mechanism and degree of mineral oil degradation during radiative exposure. With proper calibration, this method may be used as a simple diagnostic tool for online monitoring of oil aging or for non-destructive optical diagnostics of condition/quality of various materials (or constructions) in some industrial processes as demonstrated in Nasieka et al [42] and Sobrinho et al [43]. Other methods such as colorimetric measurement, spectroscopy or viscometry are much less sensitive to chemical and especially physical changes in oil lubricants, require multiple sample preparation steps, are time consuming and/or require a larger volume of sample for such analyses.…”