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Eu3+/Yb3+ co-doped gadolinium oxysulfide upconverting nanorods: Morphological, physicochemical and optical evaluation
摘要： In this study, we introduce a novel route to produce down and upconverting Eu3t/Yb3t co-doped oxysul?de nanorods, which display strong red emission at 620 nm under Vis (460 nm) or NIR (976 nm) wavelength excitation. An in-depth analysis of the synthesis parameters such as lanthanides concentration, type of nucleating agent, reaction temperature, and the reaction pressure was performed to determine their in?uence in the morphology and photoluminescence properties. It was demonstrated that as a nucleating agent, ethanolamine is a good substitute of the commonly used triethylamine providing the advantage of using lower toxicity reagents. The Transmission Electron Microscopy (TEM), Infrared (FTIR) and Zeta Potential analysis showed that the chemical surface of nanorods evolve during thermal and sul?dation processes without producing morphological changes. The intensity of light emission during downconversion (DC) and upconversion (UC) phenomena was found to be doping ions concentration dependent. The highest DC light emission was found at a Yb3t/Eu3t concentration ratio of 0.25, while the most intense UC luminescence was found at 4. Conversely, quenching of DC and UC was observed when using Yb3t/Eu3t concentration ratios of 4 and 0.25 respectively, indicating that luminescent centers are strongly affected in both processes by the chemical environment but also for the ions doping ratio. It was demonstrated that two-photon absorption is the primary mechanism for the red emission in the UC process.
关键词： Nanorods,Rare earth alloys and compounds,Upconversion,Oxysul?de
更新于2025-11-19 16:56:35
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Ordered langasites La3Ga5MO14:Eu3+ (M = Zr, Hf, Sn) as red-emitting LED phosphors
摘要： The temperature-dependent luminescence behavior of three ordered langasites La3Ga5ZrO14 (LGZr), La3Ga5HfO14 (LGHf) and La3Ga5SnO14 (LGSn) doped with up to 20% Eu3+ were investigated. Band gap energies of 4.32 eV (LGZr), 4.43 eV (LGHf), and 4.46 eV (LGSn) were determined by diffuse reflection measurements of the undoped compounds. The influence of the structural differences on the luminescence properties of the three langasites were investigated by means of excitation, emission (77-500 K) and luminescence lifetime measurements (77-300 K). The quenching temperatures of the three langasites do vary. They were attained using different excitation wavelengths in the charge transfer band (300 nm) and in the 4f levels (394 nm). LGSn:Eu 20% Eu3+ showed the best temperature performance with intensities at 500 K of 85% (300 nm) and 67% of the intensity measured at 77 K. At room temperature and with an excitation wavelength of 394 nm, maximum quantum efficiencies of 41% for LGZr:Eu 20% Eu3+, 58% for LGHf:Eu 20% Eu3+ and 68% for LGSn:Eu 20% Eu3+ were reached. The quenching behavior observed is explained by semi-quantitative configurational coordinate diagrams. Based on these results and the high red color purity, the langasites were built into LEDs with (In,Ga)N chips emitting at 394 nm, to test the applicability of the materials as red LED phosphors.
关键词： inorganic materials,optical properties,rare earth alloys and compounds,phosphors,oxide materials,luminescence
更新于2025-09-11 14:15:04