Origin Of Emission Bands Research Articles

Dual emissive cyclometallated iridium complexes: Synthesis, structure and photophysical properties

Herein, we present a new set of dual emissive heteroleptic cationic cyclometallated iridium complexeDepartment of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal By-pass Road, Bhauri, Bhopal, 462 066, Madhya Pradesh, Indias [(L)2Ir(N^N)]+ ([1]+ - [3]+) using extended π-conjugated 1-isopentyl-2-phenyl-1H-naphtho [2,3-d] imidazole (L) as C^N chelating ligand. The complexes were characterized using various analytical techniques including single crystal X-ray crystallography. The complexes exhibit dual emission behavior (560 nm, 610 and 670 nm) at ambient condition (298 K). The photophysical properties along with DFT results indicate that the origin of emission bands is not only from the lowest energy T1 state but also there is involvement of other higher energy excited triplet states. The DFT study further reveals that the lowest excited triplet state (T1) has 3MLLCT character, whereas the closely lying other higher excited triplet states are predominately of 3LLCT/3ILCT character which could be responsible for such dual emission.

Radio-photoluminescence properties of silver-doped cesium chloride transparent ceramics

We discovered and reported that 0.01, 0.1 and 1% Ag-doped CsCl transparent ceramics by spark plasma sintering technique showed radiophotoluminescence (RPL). All the samples showed high transmittance (50–70%) in the visible range. Under 340 nm ± 40 nm excitation, the PL emission was observed around 450 nm before X-ray irradiation while PL emission peaks appeared around 450 and 610 nm after X-ray irradiation. Judged from excitation and emission spectra and lifetimes, the origins of emission bands around 450 and 610 nm would be Ag0/Ag2+ and Ag2+ centers, respectively. The RPL signal was confirmed to be stable over 3 min under an excitation of 340 nm ± 40 nm. Among the synthesized samples, the lowest detectable sensitivity for the 1% Ag-doped CsCl samples was 3 mGy for the emission range of 400–550 nm.

Characterization of DC N2O Plasma Discharge Using Optical Emission Spectroscopy

We report in this article the optical emission spectroscopy (OES) measurements for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O dc discharge in the pressure range between 0.1 and 0.6 mbar. The emission bands were observed and measured in the wavelength range of 200-1100 nm. The intensity of the principal species observed for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , NO, and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> was investigated as a function of pressure and discharge power. The origin of emission bands and lines was discussed. N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> were observed to be the dominant emission lines, on one hand, while no emission lines were observed for atomic oxygen and nitrogen.

Synthesis, structures and optical properties of CdS:Cd/Si multi-interface nanoheterojunction

CdS/Si multi-interface nanoheterojunction is synthesized through depositing nanocrystals CdS (nc-CdS) on the silicon nanoporous pillar array (Si-NPA) using a chemical bath deposition method. p-type nanocrystals Si in Si-NPA and n-type nc-CdS construct the multi-interface nanoheterojunction. Due to the reducibility of Si-NPA, a portion of Cd2+ in the interface of Si-NPA and solution are deoxidized and nanocrystals Cd are simultaneously incorporated into the interface of Si–CdS, namely, CdS:Cd/Si-NPA. Through decomposing the resolution XPS spectrum of Cd 3d, the ratio of Cd0 and Cd2+ is about 0.7:1. Three primary color emissions from CdS:Cd/Si-NPA are observed at the room temperature. Optical band gap obtained by the Tauc’s relation and origins of emission bands are studied.

LUMINESCENCE MECHANISM STUDY OF A POTENTIAL SCINTILLATION CRYSTAL YBa3B9O18

The luminescence mechanisms of a potential scintillation crystal YBa 3 B 9 O 18 were investigated by experimental methods. As a first step, the optical band gap energy Eg was estimated to be 7.3 eV from the optical absorption spectrum and vacuum ultraviolet excited luminescence spectra. The X-ray photoelectron spectroscopy measured in the valence region coincided with the first principle energy band calculation. Based on the analysis of valence band structure and vacuum ultraviolet excited luminescence spectra the origins of emission bands of YBa 3 B 9 O 18 were studied. The intrinsic luminescence of YBa 3 B 9 O 18 was attributed to the radiative decay of self-trapped excitons. The elucidation of the luminescence mechanism provides a physical picture on the property-structure correlation and may help to accelerate the applications of the potential scintillation crystal.

Life-time resolved emission spectra in CdBr 2 crystals

Decay curves of the Y-emission were measured at 60, 100 and 140 K by varying emission energy in the range of the Y-emission. The observed decay curves were decomposed into three or four exponential decay components. These decay components were named τ 1, τ 2, τ 4 and τ 5. The emission spectrum for each decay component, i.e., life-time resolved emission spectrum, was obtained by analyzing the observed decay curves. At 60 K, three bands at 1.95, 2.24 and 2.47 eV are obtained for the τ 5, τ 4 and τ 1 components, respectively. For the τ 2 component, sharp peaks appear around 2.30–2.50 eV. At 100 K, a dominant band of the τ 4 component is seen at 2.25 eV. In the low-energy side, a weak band of the τ 5 component is located at 1.95 eV. At 140 K, only a single band of the τ 4 component is observed at 2.27 eV. The origin of emission bands in life-time resolved emission spectra is discussed.

Thermoluminescence of gamma-irradiated CsBr:Ba 2+ and CsCl:Ba 2+ crystals and its application to dosimetry

Thermoluminescence (TL), optical absorption and thermoluminescence emission of undoped and Ba 2+ -doped CsBr and CsCl crystals have been studied. The formation of the Z center during irradiation is confirmed by both TL and optical absorption studies. Glow peaks due to various centers such as Z 1 and F are identified. Undoped CsBr and CsCl give thermoluminescence emission bands at 425 nm. Ba 2+ -doped CsBr and CsCl crystals give emission bands at 420, 425, 440, 450 and 475 nm. The origin of emission bands in pure and doped CsBr and CsCl is discussed.

Special luminescence properties of BaF 2 crystals

On the basis of analysing excitation spectra of intrinsic luminescence in BaF 2 crystals, the origin of emission bands at 220, 195, 178 nm and the temperature dependence of luminescence intensities under Ba ++ 5p core excitation have been studied. New information is also obtained concerning the nature of the 300 nm emission.