Showing papers in "ECS Journal of Solid State Science and Technology in 2018"

Spectroscopy of Mn4+ in Double Perovskites, La2LiSbO6 and La2MgTiO6: Deep Red Photon Generators for Agriculture LEDs

Abstract: aGE Global Research, One Research Circle, Niskayuna, New York 12309, USA bCollege of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065, People’s Republic of China cInstitute of Physics, University of Tartu, Tartu 50411, Estonia dInstitute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa, Poland eCurrent & Lighting, Current Powered by GE, Cleveland, Ohio 44112, USA fLighting Enabled Systems & Applications ERC, Rensselaer Polytechnic Institute, Troy, New York 12180, USA

Critical Review—A Review of the Electronic Structure and Optical Properties of Ions with d3 Electron Configuration (V2+, Cr3+, Mn4+, Fe5+) and Main Related Misconceptions

Abstract: Tetravalent manganese ions with the 3d3 electronic configuration have recently began to play a major role as a red photon generator in the LED based lighting and display devices. The goal of this article is to tutorize the fundamental optical properties of Mn4+ and to clear up some common misconceptions that we have encountered in the archival literature that pertains to the spectroscopic properties of this ion and other ions with the same electron configuration. The methods to properly interpret the optical spectra of these systems are also discussed. This is accomplished by presenting a discussion on the electronic properties of the free d3 ions and the changes which occur when the ion is introduced in a crystalline lattice. It is hoped that such systematic presentation of spectroscopic properties of the d3 ions and their variation from the free state to the crystalline solids will be useful for many researchers – mainly experimentalists – actively working in the field and will help them avoiding many mistakes when presenting their experimental results.

Silver-doped titania modified carbon electrode for electrochemical studies of furantril

Abstract: An electrochemical method for the determination of an antrallinic acid derivative based on nanoparticles modified electrode was studied through cyclic and differential pulse voltammetry. Modification of electrode with silver-doped titania nanoparticles enhanced the peak current for the electro-oxidation of Furantril. The silver-doped titania nanoparticles were prepared by simple wet chemical methods and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffractometer (XRD). Silver-doped TiO2 voltamogramms suggested that pH 5.0 was suitable for electrochemical investigation of furantril. Rate constant, diffusion coefficient, electrode process and number of electrons involved were calculated. Based on these investigations a feasible mechanism for electrode reaction was presented. Limit of detection and quantification were found to be 1.98 nM and 6.6 nM respectively.

Thermal Effect of Sulfur Doping for Luminescent Graphene Quantum Dots

Abstract: This work presents a comprehensive study of quantum yield in doped graphene quantum dots with a series of sulfur containing compounds ( S-GQDs). The facile hydrothermal method was used to synthesize S-GQDs at different temperatures (similar to 80 degrees C-140 degrees C) with ZnSO4.7H(2)O containing sulfur powder as a reducing agent. High Resolution Transmission Electron Microscope images suggest that the size of S-GQDs vary as a function of temperature during synthesis. Powdered X-Ray Diffraction confirms the crystallinity of all samples. Raman spectroscopy study reveals that the intensity ratio increases with an increase in temperature due to the presence of additional sulfur related defects that create enhanced elastic scattering. Removal of oxygen functional groups was maximized at 140 degrees C and reached to a ID/IG value of similar to 1.14. The photoluminescence measurements of doped GQDs having sulfur containing compounds at temperature of similar to 140 degrees C attributes to violet shift at lower excitation energy and a blueshift at higher excitation energy within the energy gap of S-GQDs due to the strong interaction of GQDs with high defect concentration of sulfur. The S-GQDs formed at similar to 140 degrees C demonstrated a superior fluorescence quantum yield of 51%. This is, therefore, expected to make S-GQDs more suitable for bioimaging and optoelectronic applications. (C) 2018 The Electrochemical Society.

Local, temperature-dependent trapping and detrapping in the LiGa5O8:Cr infrared emitting persistent phosphor

Abstract: The near-infrared emitting persistent phosphor LiGa5O8:Cr3+ (LGO:Cr) has promising applications in bioimaging. In order to improve the persistent luminescence of LGO:Cr and other Cr-doped persistent phosphors, a better understanding of trapping and detrapping mechanisms is necessary. In this work, we study the afterglow and thermoluminescence via a thermal fading experiment. The results show that there is a broad trap distribution present in LGO:Cr. The emission spectrum of chromium changes during the afterglow, which indicates that different Cr ions experience a varying crystal field in the LGO host, due to different defect configurations, and that the detrapping process occurs locally. The results of thermoluminescence and spectral decay measurements show that chromium ions residing near deep traps are subject to a smaller crystal field. Vacancies formed during the synthesis are most probably causing this effect. Codoping LGO with Si4+ or Ge4+ significantly improves the persistent luminescence and increases the number of deep-lying traps in the phosphor.