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Your search keyword '"Lei, Lei"' showing total 8 results
Start Over Author "Lei, Lei" Topic luminescence Topic nanoparticles
8 results on '"Lei, Lei"'

1. Amplifying Upconversion by Engineering Interfacial Density of State in Sub-10 nm Colloidal Core/Shell Fluoride Nanoparticles

Author

Shiqing Xu, Youjie Hua, Rundong Mao, Enyang Liu, Lei Lei, Guohua Jia, Junjie Zhang, Jiayi Chen, and Yubin Wang

Subjects
Luminescence, Materials science, Phonon, Shell (structure), Nanoparticle, Bioengineering, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Ion, Fluorides, General Materials Science, Photons, business.industry, Mechanical Engineering, Doping, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Photon upconversion, 0104 chemical sciences, Density of states, Nanoparticles, Optoelectronics, Metals, Rare Earth, 0210 nano-technology, business
Abstract

Achieving bright photon upconversion under low irradiance is of great significance and finds many stimulating applications from photovoltaics to biophotonics. However, it remains a daunting challenge to significantly intensify upconversion luminescence in small nanoparticles with a simple structure. Herein, we report the amplification of photon upconversion through engineering interfacial density of states between the core and the shell layer in sub-10 nm colloidal rare-earth ions doped fluoride nanocrystals. Through tuning of the metal cations in the shell layer of alkaline-earth-based core/shell nanoparticles, both the interfacial phonon frequency and the density of state are evidently decreased, resulting in the luminescence intensification of up to 8224 times. The generality of this upconversion enhancement strategy has been verified through expansion of this approach to alkali-based core/shell nanoparticles. The engineering of photon density of state in such core/shell nanoparticles enables dynamic display and high-level security information storage.

Published
2021

2. Spectral Manipulation of X‐Ray Excited Optical/Persistent Luminescence by Constructing Metal–Organic Framework@Fluoride Nanoparticles Composites.

Author

Xu, Weixin, Lei, Lei, Wang, Yubin, Prasad, Paras N., Chen, Liang, and Xu, Shiqing

Subjects
*LUMINESCENCE, *X-rays, *NANOPARTICLES, *METAL-organic frameworks, *MOLECULAR spectra, *SMALL-angle X-ray scattering
Abstract

Lanthanide doped fluoride nanoparticles (NPs) possess superior X‐ray excited optical luminescence (XEOL) and persistent luminescence (XEPL), which attracts great attention in many fields. Manipulating profiles of XEOL and XEPL spectra is of siginificance for new emerging applications, however, the intrinsic sharp 4f–4f transitions of trivalent lanthanide ions only generate narrow emission profiles. Here, a convenient and versatile strategy is demonstrated to greatly modulate the emission spectrum in a broad wavelength range by constructing a new class of metal–organic framework (MOF)@NPs composites which involves electrostatic binding of positively charged various rare‐earth containing fluoride nanoparticles with the same negatively charged surface of a MOF. The emission profile can be facile designed through controlling the attached NPs composition and their relative contents on the MOF crystals. For the first time, the MOF@NPs composites are employed to realize full XEOL spectrum for multiple organic molecules sensing using the matching of their absorption profiles with the XEOL of a specific NP to effect energy transfer. In addition, time and temperature dependent multicolor XEPL evolution provides advanced information encryption. These findings can promote the exploration of a new type of nanoscintillators with innovative XEOL and XEPL performances. [ABSTRACT FROM AUTHOR]

Published
2023
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3. Modulating electron population pathways for time-dependent dynamic multicolor displays

Author

Shiqing Xu, Lei Lei, Enyang Liu, Liang Chen, Yubin Wang, and Xu Weixin

Subjects
Lanthanide, Materials science, Luminescence, business.industry, Process Chemistry and Technology, X-Rays, Nanoparticle, Electrons, Laser, Lanthanoid Series Elements, Photon upconversion, law.invention, Afterglow, Mechanics of Materials, law, Activator (phosphor), Optoelectronics, Nanoparticles, General Materials Science, Irradiation, Electrical and Electronic Engineering, business
Abstract

Multicolor luminescent nanoparticles (NPs) show several potential emerging applications. In this work, we provide a new route that integrates the afterglow and upconversion (UC) that originate in a single activator to achieve color variations without the modulation of any other parameters. The Er3+ ions in Na3HfF7:Yb/Er NPs exhibit bright green afterglow upon X-ray irradiation and single-band red UC under 980 nm laser excitation, which are attributed to the significantly different electron population pathways. The UC intensity is stable and the afterglow decreases gradually over time, thus the output color is clearly changed from green to red naturally via illuminating the pre-X-ray-irradiated NPs with a 980 nm laser. Furthermore, the fine emission profiles of Er3+, Ho3+ and Tm3+ are achieved upon X-ray irradiation. Our results develop a new approach for time-dependent dynamic color displays and a simple route to revealing the electronic fine structures of lanthanide activators at room temperature.

Published
2021

4. Impact of High Ytterbium(III) Concentration in the Shell on Upconversion Luminescence of Core-Shell Nanocrystals

Author

Yuansheng Wang, Lei Lei, Wenjuan Zhu, Ju Xu, and Daqin Chen

Subjects
Ytterbium, Luminescence, Upconversion luminescence, Organic Chemistry, Shell (structure), chemistry.chemical_element, Nanotechnology, General Chemistry, engineering.material, Crystallography, X-Ray, Biochemistry, Molecular physics, Photon upconversion, Core shell, Core (optical fiber), Microscopy, Electron, Transmission, chemistry, Coating, Nanocrystal, engineering, Nanoparticles
Abstract

After coating 20 Yb/2 Er:NaGdF4 core nanocrystals with a NaYbF4 shell, upconversion emission of the rare earth ions weakens. So far, the exact reason for this phenomenon is still unclear due to lack of the direct evidence. In this report, a core@shell@shell sandwich-like structure is designed and fabricated to investigate this phenomenon. We find that high Yb(3+) concentration in the shell has mainly two adverse impacts: it promotes not only the deleterious back energy transfer from Er(3+) in the core to Yb(3+) in the shell but also the energy transfer from Yb(3+) in the core to Yb(3+) in the shell. To obtain nanocrystals with high upconversion efficency, appropriate Yb(3+) concentration should be introduced into the shell or the transition layer.

Published
2014

5. Highly intensified upconversion luminescence of Ca(2+) -doped Yb/Er:NaGdF(4) nanocrystals prepared by a solvothermal route

Author

Daqin Chen, Yuansheng Wang, Rui Zhang, Ju Xu, and Lei Lei

Subjects
Luminescence, Dopant, Chemistry, Surface Properties, Organic Chemistry, Doping, Sodium, Temperature, Nanoparticle, Nanotechnology, Gadolinium, General Chemistry, Biochemistry, Photon upconversion, Crystallinity, Fluorides, Nanocrystal, Chemical engineering, Nanoparticles, Nanorod, Calcium, Particle Size, Ytterbium, Erbium
Abstract

Upon introducing Ca(2+) dopants into the grain lattices by substituting Gd(3+) ions, irregular Yb/Er:NaGdF4 nanocrystals prepared through a simple solvothermal route convert into highly uniform nanorods. Meanwhile, their upconversion luminescence intensifies by about 200 times, probably due to a modification of the crystal structure of NaGdF4 and an improvement in the crystallinity of the nanophase.

Published
2013

6. The enhanced 1830 nm emission in Yb/Tm:NaYF4@NaYF4 active-core/inert-shell nanocrystals.

Author

Lei, Lei, Wu, Ruozhen, Zhou, Jiajia, Zhang, Shengjun, Xiao, Zhen, Zhang, Junjie, and Xu, Shiqing

Subjects
*NANOCRYSTALS, *ELECTRON emission, *METAL ions, *LUMINESCENCE, *NANOPARTICLES, *SODIUM compounds
Abstract

The strong 1830 nm emission is realized in Yb/Tm:NaYF 4 @Yb:NaYF 4 core/shell nanocrystals for the first time. The optimal Tm 3+ concentration, shell thickness and composition respectively are 2 mol%, 6.5 nm and inert NaYF 4 . In comparison with Yb/Tm:NaYF 4 nanocrystals, the luminescence intensity of Yb/Tm:NaYF 4 @NaYF 4 core/shell nanocrystals enhances about 160 times. [ABSTRACT FROM AUTHOR]

Published
2017
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7. Optimizing crystallinity to enhance X-ray excited persistent luminescence intensity of NaLuF4: Gd/Tb nanoparticles.

Author

Yang, Haolin, Zhang, Anshuo, Xu, Shiqing, and Lei, Lei

Subjects
*TERBIUM, *CRYSTALLINITY, *LUMINESCENCE, *RARE earth metals, *X-rays, *NANOPARTICLES, *OPTICAL images
Abstract

Lanthanide doped fluoride nanoparticles (NPs) exhibit tunable X-ray excited persistent luminescence (XEPL), which show promising applications in optical imaging, cancer therapy and information storage. Although a few progresses have been achieved in enhancing the XEPL of lanthanide activators, there is no report about the influence of crystallinity on the XEPL intensity. In this work, we verify that the XEPL intensity can be improved by optimizing the NP crystallinity. Our results reveal that better crystallinity benefit the lower non-radiative relaxation possibility but also the restriction of the formation of Frenkel defects. This work provides important information for the development of lanthanide doped fluoride nanoparticles with superior XEPL performances. • The influence of crystallinity on the XEPL intensity was studied for the first time. • Better crystallinity inhibits the formation of Frenkel defects. • It exists optimal crystallinity for stronger XEPL. [ABSTRACT FROM AUTHOR]

Published
2023
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8. Improved X-ray excited optical luminescence of divalent manganese ion in LiLuF4 nanoparticles via introducing energy transfer pathways.

Author

Xu, Weixin, Wang, Yubin, Deng, Degang, Chen, Liang, and Lei, Lei

Subjects
*X-rays, *LUMINESCENCE, *IONS, *NANOPARTICLES, *MANGANESE
Abstract

Trivalent lanthanide ions are widely used for the realization of scintillation, while the narrow transition lines do not benefit the overall integral intensity. In this work, Mn2+ doped LiLuF 4 NPs are employed to realize strong broad emission for the first time. Upon X-ray irradiation, the strong broad emission from 500 to 700 nm corresponding to the Mn2+: 4T 1 →6A 1 transition is observed. Through incorporating Ce3+ and Gd3+ ions, the X-ray excited optical luminescence (XEOL) intensity is greatly improved owing to the introduce of energy transfer pathways of Gd3+→Mn2+ and Ce3+→Gd3+→Mn2+. After coating a LiLuF 4 shell, both the XEOL intensity and X-ray irradiation stability are improved. Our results may promote the exploration of new kinds of scintillators with broad band emissions. • Mn: LiLuF 4 NPs are employed to realize strong broad emission for the first time. • Gd3+ ions are used to improve the XEOL intensity via Gd3+.→Mn2+ energy transfer. • Ce3+ ions are used to improve the XEOL intensity via Ce3+.→Gd3+→Mn2+ energy transfer. • A LiLuF 4 shell is used to improve both the XEOL intensity and X-ray irradiation stability. [ABSTRACT FROM AUTHOR]

Published
2022
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