Luminescence and scintillation characteristics of four selected material systems, namely CsI:Tl(Na), CeF 3 , PbWO 4 and Ce-doped aluminium perovskites XAIO 3 :Ce (X=Y, Lu, Y-Lu) are reviewed. The progress in their physical understanding and related optimisation of their characteristics and technology are demonstrated. The important role of various defect states in the scintillator performance of these materials is stressed, which has led to the need for a deeper study of the processes of energy transfer and storage to achieve their intrinsic limits and full exploitation in scintillation detectors.

Wide Band Gap Scintillation Materials: Progress in the Technology and Material Understanding

A silver halide photographic material is disclosed, comprising a support having provided thereon at least one silver halide emulsion layer, wherein the silver halide emulsion layer contains, in the dispersion medium phase of the emulsion, one or more kinds of inorganic fine particles having a refractive index the total weight of the fine particles contained in the unit volume of the dispersion medium phase is from 1.0 to 95 wt %, the dispersion medium phase containing the fine particles is substantially transparent to the photosensitive peak wavelength light of the emulsion layer, and the photographic material is exposed and processed in the development process comprising at least a developing step and a fixing step.

Silver halide photographic material.

J-aggregates are fascinating fluorescent nanomaterials formed by highly ordered assembly of organic dyes with the spectroscopic properties dramatically different from that of single or disorderly assembled dye molecules. They demonstrate very narrow red-shifted absorption and emission bands, strongly increased absorbance together with the decrease of radiative lifetime, highly polarized emission and other valuable features. The mechanisms of their electronic transitions are understood by formation of delocalized excitons already on the level of several coupled monomers. Cyanine dyes are unique in forming J-aggregates over the broad spectral range, from blue to near-IR. With the aim to inspire further developments, this review is focused on the optical characteristics of J-aggregates in connection with the dye structures and on their diverse already realized and emerging applications.

https://iopscience.iop.org/article/10.1088/2050-6120/aa8d0d/pdf

Fluorescent J-aggregates of cyanine dyes: basic research and applications review

Coordination and organometallic chemistry of metal-NO complexes.

The DNA region encoding biphenyl dioxygenase, the first enzyme in the biphenyl-polychlorinated biphenyl degradation pathway of Pseudomonas species strain LB400, was sequenced. Six open reading frames were identified, four of which are homologous to the components of toluene dioxygenase from Pseudomonas putida F1 and have been named bphA, bphE, bphF, and bphG. From this comparison, biphenyl dioxygenase was found to be a multicomponent enzyme containing a two-subunit iron-sulfur protein, a ferredoxin, and a reductase. Comparison of the large subunit of the iron-sulfur protein and the ferredoxin with other multicomponent dioxygenases identified amino acid sequences similar to Rieske iron-sulfur proteins for binding a [2Fe-2S] cluster. Sequences have also been identified in the reductase component that match the consensus sequence for FAD or NAD binding. Transcription of the biphenyl dioxygenase region was examined, and three transcription initiation sites were identified. Transcription initiating at the site furthest upstream is greatly increased when the LB400 cells are grown on biphenyl as the sole carbon source.

Nucleotide sequencing and transcriptional mapping of the genes encoding biphenyl dioxygenase, a multicomponent polychlorinated-biphenyl-degrading enzyme in Pseudomonas strain LB400.

Experimental and computational studies of photophysical processes in silver halide imaging materials are presented. Recent investigations that have refined our understanding of carrier recombination paths, exciton behavior, quantum confinement effects, and the structure and function of small surface silver clusters are detailed. The theory and mechanism of electron and hole injection from photoexcited surface-adsorbed dye molecules are outlined. The carrier trapping properties and subsequent photophysics of transition-metal dopant complexes are presented. Particular emphasis is given to the role of relaxation processes in electron and hole trapping events.

The photophysics of silver halide imaging materials

The temperature dependence of the luminescence from Eu 2+ activators in BaFBr:Eu2+ photostimulated between 10 and 300 K in the optical absorptions of F centres produced by room temperature X-irradiation, revealed two thermally-activated processes. The photostimulated luminescence (PSL) increases sharply in intensity when excited between 60 and 100 K. After the low-temperature PSL is exhausted by continuous F centre excitation, it can be almost entirely regained by warming the crystal to 300 K. This thermal cycle can be repeated several times. It is shown by EPR that no Eu3+ is formed upon X-irradiation at 300 K. These results are explained with a model for the PSL mechanism which involves a loose aggregate of Eu2+, F, and hole centres.

https://iopscience.iop.org/article/10.1088/0953-8984/2/32/013/pdf

Temperature dependence of the photostimulated luminescence of X-irradiate BaFBr:Eu2+

Oxygen in oxide form is a common contaminant of BaFBr and BaFCl crystals. Upon x-irradiation of oxide-containing crystals of both materials, ${\mathrm{O}}_{\mathrm{F}}^{\mathrm{\ensuremath{-}}}$ centers are formed, as has been shown previously by electron paramagnetic resonance (EPR) methods. It is shown here by EPR that upon x-irradiation ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ centers are also formed on the ${\mathrm{Br}}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{Cl}}^{\mathrm{\ensuremath{-}}}$ sites, respectively. With electron nuclear double resonance spectroscopy, hyperfine interactions with the nearest $^{19}\mathrm{F}$ neighbors have been determined for ${\mathrm{O}}_{\mathrm{Br}}^{\mathrm{\ensuremath{-}}}$ in BaFBr. Their interpretation leads to the conclusion that the ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ ion is displaced along the c axis from the ${\mathrm{Br}}^{\mathrm{\ensuremath{-}}}$ site by about 1 \AA{}, in qualitative agreement with previous theoretical calculations. The EPR hyperfine data for ${\mathrm{O}}_{\mathrm{Cl}}^{\mathrm{\ensuremath{-}}}$ centers in BaFCl indicate that a similar displacement occurs. Also by EPR, (${\mathrm{O}}_{2}$${)}_{\mathrm{Cl}}^{\mathrm{\ensuremath{-}}}$ centers could be identified in x-irradiated BaFCl crystals containing ${\mathrm{O}}^{2\mathrm{\ensuremath{-}}}$ enriched with the magnetic $^{17}\mathrm{O}$ isotope.

Oxygen defects in BaFBr and BaFCl.

An O- centre formed upon hole trapping by O2- in X-irradiated BaFBr is long-lived at room temperature and has been detected by EPR below 30 K. It can also be produced in low concentrations by exposure of BaFBr to sub-bandgap (200-300 nm) radiation. The formation of F(Br-) centres at a charge-compensating bromide ion vacancies is a corollary of the photoionization of O2-. High concentrations of oxide have been successfully introduced into this material by doping with anhydrous BaO, including Ba17O for unambiguous identification of the O- defect. Oxide addition and the formation of O- produces a series of optical bands that have been assigned using a combination of optical and magneto-optical techniques. The influence of the material preparation conditions on the concentration of O2- is discussed and possible mechanisms for the formation of O- are proposed.

Radiation-produced electron and hole centres in oxygen-containing BaFBr. I. EPR and ODEPR studies

The Photochemistry and Photophysics of the Silver Halides

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