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Crystalline phase effect on the up-conversion processes and white emission of Yb3+/Er3+/Tm3+: Y2Si2O7 nanocrystals.
摘要： Yb3+, Er3+, Tm3+: Y2Si2O7 nano powders were fabricated by sol-gel method and then annealed at two different temperatures of 1050°C and 1480°C for 12 h to investigate the phase effect on the structural and optical properties. X-ray diffraction patterns (XRD) of all powders revealed that most of the peaks were in good harmony with the standard JCPDS cards of Y2Si2O7 (PDF#38-0223 and PDF#38-0440). SEM images of the powders were taken to examine the morphology and chemical analysis of the powders. Diffuse reflections spectra of Y2Si2O7 exhibited varying number of transitions depending on the dopant ion in all powders in the range of 400-1050 nm. Spectral properties of the powders were detailed to identify the possible up-conversion (UC) emission mechanism in the range between 400 - 900 nm under 975 nm excitation. The broadening white light emission was observed with increasing laser pumping power at room temperature as well. Spectral profiles of the transitions observed in both reflectance and up-conversion luminescence spectra were found to be crystalline phase depended.
关键词： Nanophosphors,Sol–gel process,Up-conversion,White emission
更新于2025-11-25 10:30:42
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Improved photovoltaic performance of perovskite solar cells by utilizing down-conversion NaYF <sub/>4</sub> :Eu <sup>3+</sup> nanophosphors
摘要： Perovskite solar cells assembled with titanium dioxide electron transport layer exhibited brilliant photovoltaic properties due to titanium dioxide having a high electron mobility, appropriate energy level alignment and easy fabrication procedure. However, inherent instability exists in titanium dioxide-based perovskite solar cells because of the ultraviolet photocatalytic activity of titanium dioxide. This results in recombination at the interface of titanium dioxide/perovskite. In this report, the down-conversion nanocrystals film made of europium-doped sodium yttrium fluoride was deposited on the non-conducting side of the conducting glass. The down-conversion nanocrystal layer could absorb high energy ultraviolet photons and converted them to visible light. The layer not only extended the spectral response range for perovskite solar cells but also alleviated the photocatalytic activity of titanium dioxide. The perovskite solar cells with the down-conversion nanocrystals film generated average power conversion efficiency yield of 19.99%, which is much better than that of the device without the down-conversion nanocrystals film (16.99%). The best power conversion efficiency for the device with the down-conversion nanocrystals film was 20.17%. In addition, perovskite solar cells with the down-conversion nanocrystals film showed a small hysteresis.
关键词： titanium dioxide,down-conversion,NaYF4:Eu3+ nanophosphors,photovoltaic performance,perovskite solar cells
更新于2025-11-14 17:04:02
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Highly efficient transparent nanophosphor films for tunable white light-emitting layered coatings
摘要： Bright luminescence in rare-earth (RE) nanocrystals, so-called nanophosphors, is generally achieved by choosing a host that enable the effective excitation of the RE activator through charge or energy transfer. Although tungstate, molybdate or vanadate compounds provide the aforementioned transfer, a comparative analysis of the efficiency of such emitters remains elusive. Herein we perform a combined structural and optical analysis, which reveals that the tetragonal GdVO4 matrix gives rise to the highest efficiency among the different transparent nanophosphor films compared. Then we demonstrate that by sequential stacking of optical quality layers made of Eu3+ and Dy3+ doped nanocrystals, it is possible to attain highly transparent white light emitting coatings of tunable shade with photoluminescence quantum yields above 35%. Layering provides precise dynamic tuning of the chromaticity based on the photoexcitation wavelength dependence of the emission of the nanophosphor ensemble without altering the chemical composition of the emitters or degrading their efficiency. Total extinction of incoming radiation along with the high quantum yields achieved make these thin layered phosphors one of the most efficient transparent white converter coatings ever developed.
关键词： rare-earth nanocrystals,transparent coatings,nanophosphors,phosphor materials,white-light emission
更新于2025-11-14 15:23:50
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Wide Spectrum Photocatalytic Activity in Lanthanide-doped Upconversion Nanophosphors Coated with Porous TiO2 and Ag-Cu Bimetallic Nanoparticles
摘要： Approaches towards maximum utilization of solar light spectrum for photocatalysis have currently attracted great interest. The combination of profoundly different properties, such as, upconversion, semiconducting and plasmonic properties can produce a favorable path in efficient utilization of the different regions of solar light reaching to earth. In this regard, design and fabrication of microstructures consisting of upconverting lanthanide doped nanophosphors coated with porous semiconducting material, TiO2 and decorated with plasmonic Ag-Cu bimetallic nanoparticles is presented in this work. These microstructures display great stability and exceptional photocatalytic activity by absorbing wide spectrum from ultraviolet to near infrared. The photocatalytic activity could be attributed to the synergistic effects between the different components and the efficient energy transfer between them. The development of such sort of hybrid microstructures could pave way for the development of new materials for the efficient utilization of the wide spectrum of sunlight.
关键词： bimetallic plasmonic nanoparticles,titania,wide spectrum utilization,photocatalysis,Upconversion nanophosphors
更新于2025-09-23 15:23:52
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Synthesis and Luminescence Properties of Nanostructured Gd3 –x – yYbxEryBWO9 Borate Tungstates
摘要： Using the Pechini process in the presence of citric acid and mannitol, followed by annealing in the range 800–1000°C, we have synthesized nanostructured rare-earth borate tungstates crystallizing in hexagonal symmetry (sp. gr. P63): undoped Gd3BWO9 and Gd3 – x – yYbxEryBWO9, containing Yb3+ and Er3+ active ions. We have measured upconversion luminescence spectra of the Er3+ ions in Gd3 – x – yYbxEryBWO9 for the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions under excitation by an IR laser (λ = 974 nm). The spectra consist of two groups of broadened bands in the red and green spectral regions. Brighter luminescence is observed in the green spectral region, which contains two bands corresponding to the Er3+ 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions. We have analyzed the effect of annealing temperature on the upconversion luminescence intensity of Gd3 – x – yYbxEryBWO9 and determined the energy yield of upconversion luminescence in the Gd3 – x – yYbxEryBWO9 borate tungstates. The highest value, Ben = 0.19%, has been obtained for the phosphor with Yb : Er = 7 : 1.
关键词： nanophosphors,rare-earth borate tungstates,upconversion phosphors
更新于2025-09-23 15:21:21
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Controlled synthesis and upconversion luminescence properties of Yb3+/Er3+ co-doped Bi2O3 nanospheres for optical and X-ray computed tomography imaging
摘要： Bi2O3 nanospheres co-doped with Yb3t/Er3t upconverting ions pair have been successfully synthesized via a facile hydrothermal method followed by a heat treatment. The resulting Bi2O3:Yb3t,Er3t nanospheres show a monodisperse spherical morphology with narrow size distribution (~180 nm) and display intense upconversion luminescence under 980 nm laser excitation. It is found that the crystal structure, morphology and upconversion luminescence properties of nanospheres have a direct relationship with the doping concentration of Yb3t and the subsequent calcination temperature. These Bi2O3:Yb3t,Er3t nanospheres can be prepared in large quantities and can be easily modified with a layer of biocompatible polyethyleneimine (PEI) molecules. The yielded nanospheres could not only maintain uniform size and morphological characteristics, but also show good water dispersibility and biocompatibility. Remarkably, these Bi2O3:Yb3t,Er3t upconversion nanophosphors could also act as an effective contrast agent for X-ray computed tomography (CT) imaging, which show higher contrast efficacy than commercial iodine-based contrast agent. The proposed facile synthetic route and inexpensive matrix materials pave the way for broad use of these Bi2O3:Yb3t,Er3t nanospheres as ideal dual-mode bio-imaging probes in biomedical field.
关键词： Hydrothermal synthesis,CT imaging,Bi2O3,Upconversion luminescence,Nanophosphors
更新于2025-09-23 15:19:57
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AIP Conference Proceedings [AIP Publishing DAE SOLID STATE PHYSICS SYMPOSIUM 2018 - Hisar, Haryana, India (18–22 December 2018)] DAE SOLID STATE PHYSICS SYMPOSIUM 2018 - Mixed fuel approach for the fabrication of TiO2:Dy3+(1-11?mol%) nanophosphors: Applications towards wLED and latent finger print detection
摘要： The pure and Dy3+(1-11 mol%) ions doped TiO2 nanophosphors (NPs) were prepared by solution combustion method using grouping of fuels; glycine and ammonium acetate. PXRD studies establishes that the pure and doped samples show rutile and anatase phases respectively. The Raman spectra illustrates that the absorption peaks noticed at ～ 142, 446 and 609 cm-1 were due to the active vibrational optical phonon modes pertaining to B1g, Eg and A1g respectively of the pure tetragonal rutile phase, whereas the peaks at ～ 395, 513 and 639 cm-1 were attributed due the active modes B1g, A1g and Eg respectively of anatase phase of TiO2. The active mode observed at ～ 142 cm-1 was a characteristic mode whereas the mode at ～ 229 cm-1 was attained due to second order effect [SOE] of pure rutile phase of TiO2. The Raman studies validate the PXRD studies. The CIE and CCT outcomes show that NPs can be used for wLED and household applications. The optimized product TiO2:Dy3+(9 mol% ) was utilized for the visualization of latent finger prints (LFPs). The results reveal that, all the levels (I to III) of ridge feature were clearly visualized under normal light indicating that the powder was a reliable and promising labeling agent for LFPs.
关键词： TiO2:Dy3+,latent finger print detection,wLED,solution combustion method,nanophosphors
更新于2025-09-19 17:13:59
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An effective emission of characteristic cool white light from Dy3+ doped perovskite type SrLa2Al2O7 nanophosphors in single-phase pc WLEDs
摘要： Characteristic cool white light emitting perovskite type SrLa2Al2O7: Dy3+ nanophosphors were fabricated by solution combustion route. Presence of tetragonal phase with 14/mmm space group was investigated. Spherical shape with their size in range of 45-52 nm was observed. Qualitative and quantitative elemental composition was examined. On near UV excitation, Photoluminescence emission spectra showed blue and yellow bands at 483 and 575 nm due to 4F9/2→6H15/2 and 4F9/2→6H13/2 transition respectively. CCT (8480 K) and CIE coordinates (0.302, 0.269) of SrLa1.94Dy0.06Al2O7 were found close to National Television System Committee white coordinates, thus proved them a potential candidate in single-phase phosphor converted WLEDs.
关键词： SrLa2Al2O7:Dy3+,Perovskite,Tetragonal,Nanophosphors
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Kerala, India (12–14 June 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Photoluminescence study of (Sm0.95 Ce0.05)2O3 nanoparticles for LED applications
摘要： Nanophosphors are a blazing area which has gained momentum in the present day research due to the fabulous unique properties of nanoparticles from their respective bulk. The rare earth doped sesquioxides have received considerable attention due to its unique properties like high chemical and thermal stabilities, intense UV absorption and also its use in solid state lightings, LASERS and so on. Here, we have synthesized (Sm0.95 Ce0.05)2O3 nanocrystalline powder using combustion method. Powder X-ray diffraction was used to study the structural characterization of the synthesized sample and the result confirmed that the synthesized nanoparticles had a nanocrystalline structure with a cubic phase and ? space group. The crystal structure and the shape of the particles have a tremendous effect on the photoluminescent properties. The surface morphology and the size of the particles were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM micrographs showed that the synthesized particles appear to be spherical. The TEM results confirmed that the particles formed were spherical and in nano regime. Phosphors with spherical morphology will surely enhance the photoluminescent properties of the materials. Hence the synthesized sample will have good luminescent characteristics. The optical properties of the sample were studied using ultraviolet –visible (UV-Vis) data analysis and photoluminescence (PL) studies. The absorption peaks obtained are at 364nm, 376, 405, 464 nm and 476nm which correspond to 6H5/2 → 4D3/2, 6H5/2 → 4D1/2, 6H5/2 → 6F7/2, 6H5/2 → 4I13/2 and 6H5/2 → 4I11/2 transitions respectively. On excitation, these particles showed a strong emission at 605 nm which corresponds to 4G5/2 →6H7/2 transition and other emissions at 563 nm and 647nm correspond to 4G5/2 →6H5/2 and 4G5/2 →6H5/2 transitions revealing that it is an orange-red emissive phosphor. This novel nanophosphor can offer new possibilities for the development of white light-emitting diodes (WLEDs) which can be excited by the near-UV chips and also in solid state lightings.
关键词： combustion method,LED applications,photoluminescence,Nanophosphors,(Sm0.95 Ce0.05)2O3
更新于2025-09-11 14:15:04
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Bioinspired crystallization, sensitized luminescence and cytocompatibility of citrate-functionalized Ca-substituted europium phosphate monohydrate nanophosphors
摘要： Biocompatible nanosystems exhibiting long-lifetime (~millisecond) luminescence features are particularly relevant in the field of bioimaging. In this study, citrate-functionalized calcium-doped europium phosphates nanophosphors of the rhabdophane type were prepared at different synthesis times by a bioinspired crystallization route, consisting in thermal decomplexing of Ca2+/Eu3+ /citrate/phosphate/carbonate solutions. The general formula of this material is Ca?Eu1-?(PO4)1-?(HPO4)?·nH2O, with ??ranging from 0 to 0.58 and n~1. A thorough characterization of the nanoparticles has been carried out by XRD (including data processing with Topas 6.0), HR-TEM, TEM, FTIR, TG/DTA, ICP, dynamic light scattering (DLS), electrophoretic mobility, and fluorescence spectroscopy. Based on these results a crystallization mechanism involving the filling of cationic sites with Ca2+ ions associated to a concomitant adjustment of the PO4/HPO4 ratio was proposed. Upon calcium doping, the aspect ratio of the nanoparticles as well as of the crystalline domains decreased and the relative luminescence intensity (R.L.I.) could be modulated. Neither the pH nor the ionic strength, nor the temperature (from 25 to 37 oC) affected significantly the R.L.I. of particles after resuspension in water, leading to rather steady luminescence features usable in a large domain of conditions. This new class of luminescent compounds has been proved to be fully cytocompatible relative to GTL-16 human carcinoma cells and showed an improved cytocompatibility as the Ca2+ content increased when contacted with the more sensitive m17.ASC murine mesenchymal stem cells. These biocompatible nanoparticles thus appear as promising new tailorable tools for biomedical applications as luminescent nanoprobes.
关键词： Nanophosphors,Citrate-functionalized,Luminescence,Bioimaging,Cytocompatibility,Calcium-doped europium phosphates
更新于2025-09-10 09:29:36