High-efficiency energy transfer in the strong orange-red-emitting phosphor CeO2:Sm3+, Eu3.

High-efficiency energy transfer (ET) from Sm3+ to Eu3+ leads to dominant red emission in Sm3+, Eu3+ co-doped single-phase cubic CeO2 phosphors. In this work, a series of Sm3+ singly and Sm3+/Eu3+ co-doped CeO2 cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at 800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm excitation, the Sm3+ singly doped CeO2 phosphor emitted strong yellow-red light at 573 nm (4G5/2-6H5/2) and 615 nm (4G5/2-6H7/2). Meanwhile, the CeO2:Sm3+, Eu3+ phosphors showed the emission characteristic of both Sm3+ and Eu3+, with the highest emission intensity at 631 nm. The emission intensity of Sm3+ decreased with increasing Eu3+ content, suggesting the ET from Sm3+ to Eu3+ in the CeO2:Sm3+, Eu3+ phosphors. The decay kinetics of the 4G5/2-6H5/2 transition of Sm3+ in the CeO2:Sm3+, Eu3+ phosphors were investigated, confirming the high-efficiency ET from Sm3+ to Eu3+ (reached 84%). The critical distance of energy transfer (RC = 13.7 Å) and the Dexter theory analysis confirmed the ET mechanism corresponding to the quadrupole-quadrupole interaction. These results indicate that the high-efficiency ET from Sm3+ to Eu3+ in CeO2:Sm3+, Eu3+ phosphors is an excellent strategy to improve the emission efficiency of Eu3+.

Firing-Associated Recycling of Coal-Fired Power Plant Fly Ash.

Coal-fired power plant fly ash is a global environmental concern due to its small particle size, heavy metal content, and increased emissions. Although widely used in concrete, geopolymer, and fly ash brick production, a large amount of fly ash remains in storage sites or is used in landfills due to inadequate raw material quality, resulting in a waste of a recoverable resource. Therefore, the ongoing need is to develop new methods for recycling fly ash. The present review differentiates the physiochemical properties of fly ash from two coal combustion processes: fluidized bed combustion and pulverized coal combustion. It then discusses applications that can consume fly ash without strict chemical requirements, focusing on firing-associated methods. Finally, the challenges and opportunities of fly ash recycling are discussed.

Characterization of structural and optical properties of Mn2+ -doped Zn2 GeO4 nanorods as an efficient green phosphor for solid-state lighting.

A series of Mn2+ -doped zinc germinate ZGO:xMn2+ (x = 0-0.05) nanorods was synthesized successfully using a hydrothermal method. XRD revealed that crystal phases of the ZGO:xMn2+ were rhombohedral and in the R-3 space group. The Williamson-Hall equation was also used to explain the strain, nanocrystalline size, and stacking fault. Green LEDs were successfully fabricated by coating ZGO:Mn2+ nanorods onto UV-LED chips. For high color purity, CIE of the fabricated green LEDs were (0.2404, 0.5428), which made this material a promising candidate for fabrication of UV-based green LEDs.

A label-free and highly sensitive DNA biosensor based on the core-shell structured CeO2-NR@Ppy nanocomposite for Salmonella detection.

A core-shell cerium oxide nanorod@polypyrrole (CeO2-NR@Ppy) nanocomposite-based electrochemical DNA biosensor was studied for Salmonella detection. The core-shell CeO2-NR@Ppy nanocomposite was prepared by in situ chemical oxidative polymerization of pyrrole monomer on CeO2-NRs, which provided a suitable platform for electrochemical DNA biosensor fabrication. The immobilization of ss-DNA sequences onto nanocomposite-coated microelectrode was performed via covalent attachment method. DNA biosensor electrochemical responses were studied by cyclic voltammetry and electrochemical impedance spectroscopy with [Fe (CN)6]3-/4- as redox probe. Under optimal conditions, DNA biosensor response showed good linearity in the range of 0.01-0.4 nM with sensitivity of 593.7â€¯Ω·nM-1·cm-2. The low limit of detection and limit of quantification for the DNA biosensor were 0.084 and 0.28 nM, respectively. The proposed DNA biosensor also showed good results when used in detecting actual Salmonella samples.

Luminescence of lemon-derived carbon quantum dot and its potential application in luminescent probe for detection of Mo6+ ions.

This article reports on the first attempt of a systematic study on the synthesis of carbon dots (C-dots) for the potential applications in labeling and detection of molybdenum ion (Mo6+ ). Carbon dots (C-dots) were synthesized directly via a simple hydrothermal method using lemon juices as carbon precursor with different temperatures to control the luminescence of C-dots. The obtained C-dots had strong green light emission and the ability to use its luminescence properties as probes for Mo6+ detection application, which is based on Mo6+ induced luminescence quenching of C-dots. This analysis system exhibits strong sensitivity and good selectivity for Mo6+ ion, and a detection limit as low as 20 ppm is achieved. These results suggest that the present C-dots have potential application in optoelectronic, labeling and luminescent probing of Mo6+ ions.

Enhancing the luminescence of Eu3+ /Eu2+ ion-doped hydroxyapatite by fluoridation and thermal annealing.

This paper reports a novel way for the synthesis of a europium (Eu)-doped fluor-hydroxyapatite (FHA) nanostructure to control the luminescence of hydroxyapatite nanophosphor, particularly, by applying optimum fluorine concentrations, annealed temperatures and pH value. The Eu-doped FHA was made using the co-precipitation method followed by thermal annealing in air and reducing in a H2 atmosphere to control the visible light emission center of the nanophosphors. The intensities of the OH- group decreased with the increasing fluorine concentrations. For the specimens annealed in air, the light emission center of the nanophosphor was 615 nm, which was emission from the Eu3+ ion. However, when they were annealed in reduced gas (Ar + 5% H2 ), a 448 nm light emission center from the Eu2+ ion of FHA was observed. The presence of fluorine in Eu-doped FHA resulted in a significant enhancement of nanophosphor luminescence, which has potential application in light emission and nanomedicine.

Improving osseointegration of Co-Cr by nanostructured titanium coatings.

This study reports the deposition of nanostructured Ti films on Co-Cr substrates to improve their surface characteristics and biocompatibility. The microstructure of the Ti films was controlled by application of negative substrate bias voltages. The surface roughness of Co-Cr implants was increased significantly after Ti coatings. The nanostructured Ti films are found to improve osteointergration of Co-Cr implants as indicated by enhancing cellular attachment, proliferation and differentiation, which was attributed mainly to the application of a biocompatible Ti coating, possessed a higher surface area for cell attachments and growth.

Deposition of TiN films on Co-Cr for improving mechanical properties and biocompatibility using reactive DC sputtering.

This study reports the deposition of TiN films on Co-Cr substrates to improve the substrates' mechanical properties and biological properties. In particular, the argon to nitrogen (Ar:N(2)) gas flow ratio was adjusted to control the microstructure of the TiN films. A Ti interlayer was also used to enhance the adhesion strength between the Co-Cr substrate and TiN films. A series of TiN films, which are denoted as TiN-(Ar/N(2))1:1, Ti/TiN-(Ar/N(2))1:1, and Ti/TiN-(Ar:N(2))1:3, were deposited by reactive DC sputtering. All the deposited TiN films showed a dense, columnar structure with a preferential orientation of the (200) plane. These TiN films increased the mechanical properties of Co-Cr, such as the critical load during scratch testing, hardness, elastic modulus and plastic resistance. In addition, the biological properties of the Co-Cr substrates, i.e. initial attachment, proliferation, and cellular differentiation of the MC3T3-E1 cells, were improved considerably by deposition of the TiN films. These results suggest that TiN films would effectively enhance both the mechanical properties and biocompatibility of biomedical Co-Cr alloys.