Intense Orange Emission Research Articles

Temperature-dependent photoluminescence properties of porous silicon nanowire arrays

Luminescent porous silicon nanowire arrays are prepared through metal-assisted chemical etching. Photoluminescence (PL) and cathodoluminescence (CL) reveal that both the nanowire arrays and individual nanowire exhibit intense orange emission around 1.9 eV at room temperature. The emission linewidth increases monotonously and significantly with decreasing temperature. Combined with PL decay measurements, the results indicate that there are two transitions contributing to the broad emission at low temperatures. In addition, negative thermal quenching of the PL intensity due to surface states is observed. A multi-level transition model is proposed to interpret the experimental results.

Photoluminescence and Cathodoluminescence Properties of NanocrystallineCa2Gd8Si6O26:Sm3+Phosphors

NanocrystallineCa2Gd8Si6O26(CGS):Sm3+phosphors were synthesized by solvothermal reaction method. The structural and morphological properties of the samples were evaluated by X‐ray diffraction and scanning electron microscopy. The photoluminescence excitation and emission spectra along with decay properties were investigated as a function ofSm3+concentration. Under 405 nm excitation wavelength, the photoluminescence spectra showed three emission peaks at 565 nm (4G5/2 → 6H5/2) and at 650 nm (4G5/2 → 6H9/2), and with an intense orange emission at 600 nm (4G5/2 → 6H7/2).Based on the orange emission performance, the Sm3+concentration was optimized to be at 2 mol%. The low voltage cathodoluminescence (CL) properties were also performed for 2 mol%Sm3+‐dopedCGSphosphors as a function of accelerating voltage (1–5 kV). From theCLspectra, the reddish‐orange emission was observed. The calculated Commission International De I‐Eclairage chromaticity coordinates are in close proximity to the chromaticity coordinates of Nichia corporation developed amber light emitting diodes.

Optically stimulated luminescence (OSL) and laser excited photo luminescence of electron beam treated (EBT) diamonds: Radiation sensitization and potential for tissue equivalent dosimetry

We report the first optically stimulated luminescence (OSL; blue light stimulated luminescence (BLSL) and infrared light stimulated luminescence (IRSL)) results on colored diamonds and present experimental evidence that electron beam treatment (EBT) increases the radiation sensitivity of diamonds to a level that makes them suitable for low level radiation dosimetry. A suite of seven samples was examined. These comprise a white, three brown and three yellow diamond pieces. The FT-IR spectra of these diamonds revealed the nature and concentration of nitrogen impurity. The white diamond was kept as a control. The brown and yellow (with varied saturation) diamonds were irradiated by a 1.7 MeV electron beam. These turned blue/dark green; three of them were then heated in vacuum in the temperature range of 850–900 °C for two hours. Heating turned the irradiated diamonds to lemon yellow, pink, and purple colors. The irradiated and unheated blue samples were designated as 2C and 2D. The control sample, an un-irradiated white type Ia diamond, did not yield any significant IRSL/BLSL with doses up to 100 Gy. The BLSL/IRSL sensitivity of irradiated and heat treated diamonds was very poor, and depended on the heat cycle and hence were not pursued. Sample 2C exhibited significant BLSL and negligible IRSL sensitivity. Sample 2D gave an intense orange red emission under IR excitation as also responded to BLSL. The dose response of the BLSL signal in 2C suggested a minimum detectable dose of ~ 0.1 Gy and its use as a tissue equivalent dosimeter. Based on supporting experiments such as laser excited photoluminescence, we suggest that the BLSL process in 2C is primarily driven by carbon vacancies, which release a mobile hole when excited by GR2 band in the blue region. BLSL intensity exhibited a maximum around 285 °C. Given that TL glow peak also occurs near this temperature and that the nitrogen–interstitial carbon (N–Ci) complex also forms at this temperature (as reported in the literature), and it appears that the e–h recombination at sites with N–Ci complex could be involved in BLSL production. Laser excited photoluminescence (PL) at wavelengths 325, 514 and 785 nm and absorption spectra in UV–Visible range gave insights into the contrasting BLSL/IRSL responses of 2C and 2D. These differences were due to differences in nitrogen impurity complexes and the concentration of carbon vacancies produced by EBT in 2C and 2D. In 2D, the presence of Ni as NE8 center (four nitrogens coordinated to Ni) giving 800 nm emission on 785 nm excitation, appeared to suppress BLSL and sensitize IRSL in the orange window.

Orange Emission in Eu3+-Activated Mg2M (PO4)2(M = Sr and KNa) and KSrPO4 Phosphors

This work concerns the photoluminescence (PL) studies of intense orange emission in phosphate based phosphors doped with trivalent europium. The present compounds were prepared by combustion synthesis, and the completion of the synthesis was confirmed by X-ray diffraction (XRD) pattern. The PL emission spectrum of Eu3+ in Mg2M(PO4)2 (M = Sr and KNa) and KSrPO4 phosphors was observed at around 590 nm orange region. The spectrum is due to 5D0 → 7F1 transitions at near UV excitation, i.e., 391 nm. The 300–400 nm is Hg free excitation (Hg excitation is 85% 254 nm wavelength of light and 15% are other wavelengths), which is characteristic of solid-state lighting phosphors. Hence, intense orange PL emissions suggest the possibility of the potential of phosphate based phosphors in warm white LED phosphors.

Architectures of YF3:Eu3+ solid and hollow sub-microspheres: a facile arginine-assisted hydrothermal synthesis and luminescence properties

Solid and hollow YF3:Eu3+ spheres assembled by nanorods have been successfully synthesized via a facile arginine-assisted hydrothermal method and followed by a subsequent heat-treatment process. The experimental results reveal that the as-prepared YF3:Eu3+ spheres are composed of the nanorods with a diameter of 20–50 nm and a length of 200–500 nm, the morphologies of YF3:Eu3+ have been changed from solid to hollow spheres assembled by nanorods. With increase of hydrothermal temperature and time, the diameter of YF3:Eu3+ spheres can be controlled from 300 to 800 nm. The solid and hollow spheres show an intense orange red emission peak near 595 nm, corresponding to the 5D0 → 7F1 transition of Eu3+. The possible formation mechanism for the hollow spheres has been presented in detail. This amine acid-assisted method is very simple, economic and environmental friendly for organic-free solvent, which would be potentially used in synthesizing other hollow materials.

STRUCTURAL AND OPTICAL PROPERTIES OF Eu3+ DOPED CERIUM OXIDE NANOPHOSPHORS

Europium (3%) doped ceria nanoparticles were successfully prepared by 72 h hydrolysis assisted co-precipitation method. The average grain size of the as-prepared sample was 11 nm. The grain sizes were 12 and 18 nm for samples annealed at 500°C and 800°C respectively. The grain size effect on optical bandgap is investigated from diffuse reflectance spectroscopy (DRS). The orange and red color emissions of europium doped ceria nanoparticles were investigated by photoluminescence (PL) spectra under excitation of 330 nm. The high intense orange emission peak was found at 591 nm for as-prepared and annealed nanoparticles. This is the characteristic peak of the Eu 3+ ion corresponding to the parity allowed magnetic dipole transition between the 5 D 0–7 F 1 states. Site occupancy of europium ions was estimated by Red (R)/Orange (O) intensity ratio using PL spectrum.

Synthesis and photoluminescent properties of two 2D and 3D iodocuprates modified by a protonated ligand

Two new cuprous iodides [Cu4I5(DABCOH+)CH3CN] (1) and [Cu7I8(DABCOH+)DABCO] (2) (DABCO = 1,4-diazabicyclo-[2.2.2]octane) have been prepared solvothermally and characterized by IR, TGA, elemental analysis, powder/single-crystal X-ray diffraction and photoluminescent properties. Compound 1 contains a 2D cuprous iodide layer Cu4I5−, while compound 2 exhibits a novel 3D open framework constructed from [Cu14I16]2−clusters with six-connected (412·63) net, and both of them are modified by monoprotonated DABCO ligand, which may be related with the high-dimensional iodocuprates. 1 and 2 display intense orange emission with maximum at 547 nm and 561 nm, respectively, which are rarely found in the most reported iodocuprates.

Aggregation-driven growth of well-oriented ZnO nanorod arrays

Here we report an aggregation-driven growth of highly oriented and densely packed ZnOnanorod arrays through a simple natural oxidation process of pure metal zinc informamide/water solution at low temperature. Very intense orange emission was observedin the resulting nanoparticle-built ZnO nanorods with numerous interfacial defects amongtheir primary nanoparticles.

Photoluminescence of Pt II(cyclooctatetraene)(CN) 2 originating from a MLCT triplet

The complex Pt II(cyclooctatetraene)(CN) 2 shows a longest-wavelength absorption ( λ max = 430 nm) which is assigned to a (Pt II → π ∗ C 8H 8) MLCT transition. At r.t. the solid complex displays an intense orange emission at 572 nm which originates from the MLCT triplet. The emission spectrum exhibits a vibrational structure which may indicate an IL contribution.

Novel Luminescent Mixed‐Metal PtTl‐Alkynyl‐Based Complexes: The Role of the Alkynyl Substituent in Metallophilic and η2(π⋅⋅⋅Tl)‐Bonding Interactions

A novel series of [PtTl(2)(C[triple chemical bond]CR)(4)](n) (n = 2, R = 4-CH(3)C(6)H(4) (Tol) 1, 1-naphthyl (Np) 2; n = infinity, R = 4-CF(3)C(6)H(4) (Tol(F)) 3) complexes has been synthesized by neutralization reactions between the previously reported [Pt(C[triple chemical bond]CR)(4)](2-) (R = Tol, Tol(F)) or novel (NBu(4))(2)[Pt(C[triple chemical bond]CNp)(4)] platinum precursors and Tl(I) (TlNO(3) or TlPF(6)). The crystal structures of [Pt(2)Tl(4)(C[triple chemical bond]CTol)(8)]4 acetone, 14 acetone, [Pt(2)Tl(4)(C[triple chemical bond]CNp)(8)]3 acetone1/3 H(2)O, 23 acetone 1/3 H(2)O and [[PtTl(2)(C[triple chemical bond]CTol(F))(4)](acetone)S](infinity) (S = acetone 3 a; dioxane 3 b) have been solved by X-ray diffraction studies. Interestingly, whereas in the tolyl (1) and naphthyl (2) derivatives, the thallium centers exhibit a bonding preference for the electron-rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt(2)Tl(4)(C[triple chemical bond]CR)(8)] clusters (with additional Tlacetone (1) or Tlnaphthyl (2) secondary interactions), in the C(6)H(4)CF(3) (Tol(F)) derivatives 3 a and 3 b the basic Pt(II) center forms two unsupported Pt-Tl bonds. As a consequence 3 a and 3 b form an extended columnar structure based on trimetallic slipped PtTl(2)(C[triple chemical bond]CTol(F))(4) units that are connected through secondary Tl(eta(2)-acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH(2)Cl(2) 1,2; acetone 3) are very different to those in solid state (orange), have been studied. Curiously, solid-state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3, or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm).