Unidentified Infrared Discrete Emission Bands

Unidentified Infrared emission bands (UIBs) are infrared discrete emissions from circumstellar regions, interstellar media (ISM), star-forming regions, and extragalactic objects for which the identity of the emitting materials is unknown. The main infrared features occur around peaks at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with the photon’s rest energy at the peaks 0.376, 0.200, 0.161, 0.144, 0.111, and 0.098 eV, respectively. The UIB emission phenomenon has been studied for about forty five years. The prevailing hypothesis is that the materials responsible for UIB are polycyclic aromatic hydrocarbon (PAH) molecules. PAHs are thought to be one of the main forms in which carbon exists in space. And yet, not a single member of this group of compounds had been identified in space definitively until now [1]. In frames of Hypersphere World-Universe Model (WUM), we introduced Dark Matter (DM) particles, named DIONs, with the rest energy 0.199 eV and an energy density of 68.8% of the total energy density of the World. DIONs compose Outer shells of DM Supercluster’s Cores—the main objects of the World [2]. In this paper, we give an explanation of UIB emission based on the self-annihilation of DM particles DIONs and biDIONs (DIONs pairs) with a rest energy about 0.38 eV that depends on the binding energy. To the best of our knowledge, WUM is the only cosmological model in existence that is consistent with UIB emission phenomenon.

Band Edge Emission Improvement by Energy Transfer in HybridⅢ-Nitride/Organic Semiconductor Nanostructure

GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-（2-ethyl）hexoxy-l,4-phenylenevinylene] （MEH-PPV）/GaN-nanorod hybrid structure is fabricated by depositing the MEH-PPV film on the GaN nanorods by using the spin-coating process. In the hybrid structure, the spatial separation is minimized to achieve high-emciency non-radiative resonant energy transfer. Optical properties of a novel device consisting of MEH-PPV/GaN-nanorod hybrid structure is studied by analyzing photoluminescenee （PL） spectra. Compared with the pure GaN nanorods, the PL intensity of the band edge emission of GaN in the MEH-PPV/GaN-nanorods is enhanced as much as three times, and the intensity of the yellow band is suppressed slightly. The obtained results are analyzed by energy transfer between the GaN nanorods and the MEH-PPV. An energy transfer model is proposed to explain the phenomenon.

Origion of Band-like and Atom-like Features of the Valence Band Auger Emission from Thansition Metals

The occurrence of both band-like and atom-like Auger spectra involving valence band electron of d-transition metals is discussed based on the two-step model of the Auger electron emission, i.e.an initial core-hole is first generated and the Auger transition occurs between the core-hole andthe valence states, The occupied vaIence states relax to screen the core-hole which results in a redistribution of the valence electrons, The electronic states concerned by the Auger transitionare calculated by the FLAPW method. There is a clear relation between band-like and atom-like features of the spectra and the different responses of these metals to the existence of a core-hole.

A novel narrow band UV-B emitting phosphor-YPO_4:Sb^(3+),Gd^3

YPO4 phosphors single-doped with Sb3+ or Gd3+ and co-doped with Sb3+ and Gd3+were prepared by a solid-state reaction method. The phase purity, morphology, photoluminescence excitation and emission properties of the prepared phosphors were inves-tigated. The results showed that Sb3+ could sensitize Gd3+ in the co-doped phosphors which made the phosphors excitable by short-wave ultraviolet (UV) at a wavelength between 220 and 260 nm. Under 253.7 nm excitation, the co-doped phosphors Y1–x–yPO4: Sb3+x,Gd3+yshowed strong emission of Gd3+ at a wavelength of 312 nm whose intensity changed with the doping concentrations of Gd3+ and Sb3+. The optimized Y0.77PO4:Sb3+0.07,Gd3+0.16 phosphor showed an intensity comparable to commercial LaPO4:Ce phosphor (UVB-315), making it a potential candidate for mercury low-pressure discharge narrow-band UV-B emitting lamps.

Photoluminescence and structural analysis of wurtzite(ZnO)1-x(V2O5)x composite

This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction(XRD) studies show that(ZnO)(VO)composites have the poly crystalline wurtzite structure of hexagonal Zn O. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increase in doping concentration. The existence of E1(TO) and E2(high) Raman modes show that the Zn O still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence(PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of VOup to a certain concentration(x < 9). Moreover, the optical band gap increase with doping, which is accompanied by the blue shift of the NBE emission.

Impact of surface coating on morphological, optical and photoluminescence properties of YF3：Tb^3＋ nanoparticles

A simple polyol and sol–gel Stober process were employed for synthesis of YF_3：Tb~＋（core）, YF_3：Tb~＋@LaF_3（core/shell） and YF_3：Tb~＋@LaF_3@SiO_2（core/shell/SiO_2） nanoparticles（NPs）. The phase purity, crystalinity,morphology, optical and photoluminescence properties were investigated and discussed with the help of various analytical techniques including X-ray diffraction pattern,FE-transmission electron microscopy（TEM）,FTIR, UV/vis absorption, energy band gap and emission spectra. XRD andFE-TEM studies indicate the formation of core/shell nanostructure and ~10 nm thick amorphous silica surface coating surrounding the core-NPs, which is also confirmed byFTIR spectral results. The surface modifications of core-NPs significantly affect the optical features in the form of energy band gap, which were correlated with particle size of the nanomaterials. The comparative emission spectral results show that after inert layer coating the luminescent core-NPs display stronger emission intensity in respect to core and silica coated core/shell/SiO_2-NPs. The solubility character along with colloidal stability was improved after silica surface modification, whereas luminescent intensity was suppressed causing the surface functionalized with high energy silanol（Si-OH） molecules. These novel luminescent nanomaterials with enhanced emission intensity and excellent solubility in aqueous solvents would be potentially useful for fluorescence bioimaging/optical bio-probe etc.