Tunable multicolor and white emission NaLuF4:Yb, Nd, Ln (Ln = Er, Tm, Er/Tm) microstructures

Yang, Guixin; Wu, Zhenyu; Yang, Dan; Gai, Shili; Xu, Mengshu; Sun, Xiaojun; Yang, Piaoping

doi:10.1016/j.solidstatesciences.2019.03.010

Cited by 6 publications

(4 citation statements)

References 34 publications

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“…There have been quite a large number of synthetic attempts to fabricate white light-emitting agents like polymers, single molecules, organic light-emitting diodes, quantum dots, etc. − for vital technological applications like illumination and displays. − However, such agents mostly utilize the down-conversion of UV visible light into the respective white emissions through a Stokes shift. − On the contrary, there have been recent developments in the conversion of near-infrared (NIR) excitation sources into white light through a process known as upconversion (UC). − The capability of generating distinct and sharp emission bands simultaneously in blue, green, and red visible regions by a single monochromatic NIR source turns out to be advantageous for specialized purposes. Thus, white-emitting UC nanomaterials have found effective applications in phototheranostics, lasing, and display technologies. − Like their downconversion counterparts, UC-based white-emitting fluorophores also require smart designing and involve challenges of tailored crystal engineering. − …”

Section: Introductionmentioning

confidence: 99%

Local Disorder Affecting NIR-Upconverting White Light Emission Manifests in Lattice Strain

et al. 2021

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Dopant-induced intensity enhancement in the single-phase upconversion (UC) host lattice is a well-known method based on the facilitation of parity forbidden electronic transitions but lacks fundamental understanding at the atomic scale. Our study revealed that the extent of local disorder produced within the host lattice of β-NaYF4 crystals due to gradual insertion of Li+ dopant passes through a maximum, coinciding with the maximum intensity of the corresponding UC white emission. Interestingly, we found that at considerable Li+ doping, the variation of the local disorder could be assessed through experimentally measuring the changes in compressive lattice strain so generated. Herein, a systematic investigation was carried out by introducing a gradually increasing Li+ mol % within white-emitting NaYF4-based UC crystals. Rietveld refinement from synchrotron X-ray diffraction (SXRD) confirmed P6̅ space group of the samples with the localization Li+ in the octahedral voids and at lattice positions, along with other structural details including electron density mapping. Respective lattice strain values were determined from Williamson–Hall analysis of SXRD. A high-energy X-ray total scattering experiment using the atomic pair distribution function was used to investigate the local disorder at the atomic scale. The intensity of white emission was found to attain the highest value at 70 mol % (nominal) when the corresponding compressive lattice strain became least negative (−1.622 × 10–4) and the local disorder hit the highest point. The study may serve as an experimental basis for understanding the extent of crystal field symmetry distortion of UC crystals by connecting local disorder with lattice strain.

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Section: Introductionmentioning

confidence: 99%

Local Disorder Affecting NIR-Upconverting White Light Emission Manifests in Lattice Strain

et al. 2021

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“…It can be seen from Fig 5 that the migration of water to different depths of the loess column cause a sudden sharp decrease in the resistivity of the soil under different types of rainfall. The reason is that under the action of rainfall, the soil saturation gradually increases, the pores between soil particles are rapidly filled with water, and some ions in the soil dissolve into the pore water, which enhances the conductivity of soil, resulting in a sudden decrease in the resistivity of soil [25,26]. During the downward migration of water, the resistivity of loess at the depth Z = 3.2 cm of the first layer of the loess column is most sensitive.…”

Section: Analysis Of Variation Law Of Resistivity With Durationmentioning

confidence: 99%

Experimental study of water migration characteristics in compacted loess subjected to rainfall infiltration

Zhang

Han

et al. 2022

PLoS ONE

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In order to study the effect of the rainfall infiltration on water migration in compacted loess, a model device was developed for testing water migration in the soil under rainfall conditions. In this study, the volumetric water content and resistivity of soil were introduced into the model test device. This model test device was applied to the study of water migration characteristics in compacted loess under different rainfall conditions. The results show that the resistivity decreases with the increase of the volumetric water content at the same depth of the loess column. In this way, the characteristics of the water migration can also be reflected from the change of the resistivity. There is an intimate relationship between the resistivity and volumetric water content, dry density. The volumetric water content and dry density are normalized by saturation of loess, arriving the equation of saturation against the resistivity. The characteristics of rainfall infiltration in compacted loess show a particular pattern, which demonstrates that, with the increase of dry density of the loess column, the rainfall infiltration line present “Y”, “D” and “Λ” shape distribution respectively, under light rain, heavy rain and rainstorm.

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“…Besides, multicolor emission is generally achieved by doping a single nanomaterial with different cations. 41 , 42 Yet, activator codoping typically leads to unwanted cross-relaxation that results in UC quenching, along with a strong dependence of the color on the excitation power. 43…”

Section: Introductionmentioning

confidence: 99%

“…Along with the quest for stable, bright and efficient materials, scientists are lately concerned about their processing, required to achieve versatile UC coatings that can be readily integrated in devices that benefit from them. ,, Indeed, features beyond efficiency such as transparency, pliability or tailor-made chromaticity are sought after. − Thus, flexible and transparent polymer waveguides based on UC nanophosphors have been demonstrated by dispersing UCNPs in a polymer. , However, it is still challenging to increase nanophosphor filling fraction without compromising the stability of the composite. Besides, multicolor emission is generally achieved by doping a single nanomaterial with different cations. , Yet, activator codoping typically leads to unwanted cross-relaxation that results in UC quenching, along with a strong dependence of the color on the excitation power …”

Section: Introductionmentioning

confidence: 99%

Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films

Ngo

Cabello‐Olmo

Arroyo

et al. 2021

ACS Appl. Mater. Interfaces

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Fluoride-based compounds doped with rare-earth cations are the preferred choice of materials to achieve efficient upconversion, of interest for a plethora of applications ranging from bioimaging to energy harvesting. Herein, we demonstrate a simple route to fabricate bright upconverting films that are transparent, self-standing, flexible, and emit different colors. Starting from the solvothermal synthesis of uniform and colloidally stable yttrium fluoride nanoparticles doped with Yb 3+ and Er 3+ , Ho 3+ , or Tm 3+ , we find the experimental conditions to process the nanophosphors as optical quality films of controlled thickness between few hundreds of nanometers and several micrometers. A thorough analysis of both structural and photophysical properties of films annealed at different temperatures reveals a tradeoff between the oxidation of the matrix, which transitions through an oxyfluoride crystal phase, and the efficiency of the upconversion photoluminescence process. It represents a significant step forward in the understanding of the fundamental properties of upconverting materials and can be leveraged for the optimization of upconversion systems in general. We prove bright multicolor upconversion photoluminescence in oxyfluoride-based phosphor transparent films upon excitation with a 980 nm laser for both rigid and flexible versions of the layers, being possible to use the latter to coat surfaces of arbitrary shape. Our results pave the way toward the development of upconverting coatings that can be conveniently integrated in applications that demand a large degree of versatility.

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Tunable multicolor and white emission NaLuF4:Yb, Nd, Ln (Ln = Er, Tm, Er/Tm) microstructures

Cited by 6 publications

References 34 publications

Local Disorder Affecting NIR-Upconverting White Light Emission Manifests in Lattice Strain

Local Disorder Affecting NIR-Upconverting White Light Emission Manifests in Lattice Strain

Experimental study of water migration characteristics in compacted loess subjected to rainfall infiltration

Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films

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