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- Bagheri, Niusha, et al.
(författare)
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Change in the emission saturation and kinetics of upconversion nanoparticles under different light irradiations
- 2019
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 97
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Tidskriftsartikel (refereegranskat)abstract
- Nd3+-sensitized upconversion nanoparticles (UCNPs) can be excited by both 980 and 808 nm light, which is regarded as a particularly advantageous property of these particles. In this work, we demonstrate that the nanoparticles can exhibit significantly different response when excited at these two excitation wavelengths, showing dependence on the intensity of the excitation light and the way it is distributed in time. Specifically, with 808 nm excitation saturation in the emitted luminescence is more readily reached with increasing excitation intensities than upon 980 nm excitation. This is accompanied by delayed upconversion luminescence (UCL) kinetics and weaker UCL intensities. The different luminescence response at 808 and 980 nm excitation reported in this work is relevant in a manifold of applications using UCNPs as labels and sensors. This could also open new possibilities for multi-wavelength excitable UCNPs for upconversion color display and in laser-scanning microscopy providing selective readouts and sub-sectioning of samples.
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| 2. |
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| 3. |
- Huang, Fuhua, et al.
(författare)
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Low-lying excited state energy trap induced by cross-relaxation - The main origin of concentration quenching in lanthanide upconversion nanoparticles
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 936
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Tidskriftsartikel (refereegranskat)abstract
- In lanthanide-doped upconversion nanoparticles (UCNPs), the concentration of emitter ions, also known as activator ions, is usually limited to 1 - 5 mol% due to concentration quenching effects. This circumstance limits the luminescent efficiency of UCNPs' and their use in a variety of application areas. Earlier studies have attributed the activator concentration quenching to migration of energy to the nanoparticle surface, while indicating that cross-relaxation between activator ions had a minor role therein. In this work, we carried out comparative studies on Er3+-doped and Yb3+-Er3+ codoped UCNPs and could, in contrast to this notion, prove a general adverse effect of cross-relaxation between activator ions, here Er3+ ions, on up -conversion luminescence (UCL). The direct result of the cross-relaxation is that the energy of the excitation light is accumulated into a low-lying excited state of Er3+ in the infrared region, so forming a "low-lying excited state energy trap ". As a result, the excitation energy is used for generating down-conversion lu-minescence or for indirectly facilitating UCL channels that are directly related to the low-lying excited state energy trap. The identified effect can be used to regulate UCL channels to achieve a concentrated UCL band that is more favorable for certain applications, e.g., biological imaging.
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| 4. |
- Huang, Fuhua, et al.
(författare)
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Suppression of Cation Intermixing Highly Boosts the Performance of Core-Shell Lanthanide Upconversion Nanoparticles
- 2023
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 145:32, s. 17621-17631
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Tidskriftsartikel (refereegranskat)abstract
- Lanthanide upconversion nanoparticles (UCNPs) have beenextensivelyexplored as biomarkers, energy transducers, and information carriersin wide-ranging applications in areas from healthcare and energy toinformation technology. In promoting the brightness and enrichingthe functionalities of UCNPs, core-shell structural engineeringhas been well-established as an important approach. Despite its importance,a strong limiting issue has been identified, namely, cation intermixingin the interfacial region of the synthesized core-shell nanoparticles.Currently, there still exists confusion regarding this destructivephenomenon and there is a lack of facile means to reach a delicatecontrol of it. By means of a new set of experiments, we identify andprovide in this work a comprehensive picture for the major physicalmechanism of cation intermixing occurring in synthesis of core-shellUCNPs, i.e., partial or substantial core nanoparticle dissolutionfollowed by epitaxial growth of the outer layer and ripening of theentire particle. Based on this picture, we provide an easy but effectiveapproach to tackle this issue that enables us to produce UCNPs withhighly boosted optical properties.
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