Controlling the thermal switching in upconverting nanoparticles through surface chemistry
authors Martinez, ED; Garcia-Flores, AF; Carneiro, AN; Brites, CDS; Carlos, LD; Urbano, RR; Rettori, C
nationality International
journal NANOSCALE
keywords UP-CONVERSION LUMINESCENCE; ION ENERGY-TRANSFER; TEMPERATURE-DEPENDENCE; ENHANCEMENT; EMISSION; NANOCRYSTALS; MECHANISMS; STRATEGY; EXCHANGE; DEFECT
abstract Photon upconversion taking place in small rare-earth-doped nanoparticles has been recently observed to be thermally modulated in an anomalous manner, showing thermal enhancement of the emission intensity. This effect was proved to be linked to the role of adsorbed water molecules as surface quenchers. The surface capping of the particles has a direct influence on the thermal dynamics of water adsorption and desorption, and therefore on the optical properties. Here, we show that the upconversion intensity of small-size (<25 nm) nanoparticles co-doped with Yb3+ and Er3+ ions, and functionalized with different capping molecules, presents clear irreversibility patterns upon thermal cycling that strongly depend on the chemical nature of the nanoparticle surface. By performing temperature-controlled luminescence measurements we observed the formation of a thermal hysteresis loop, resembling an optical switching phenomenon, whose shape and trajectory depend on the hydrophilicity of the surface. Additionally, an intensity overshoot takes place immediately after turning off the heating source, affecting each radiative transition differently. We performed numerical modelling to understand this effect considering non-radiative energy transfer from the surface defect states to the Er3+ ions. These findings are relevant for the comprehension of nanoparticle-based luminescence and the interplay between the surface and volume effects, and more generally, for applications involving UCNPs such as nanothermometry and bioimaging, and the development of optical encoding systems.
publisher ROYAL SOC CHEMISTRY
issn 2040-3364
isbn 2040-3372
year published 2021
volume 13
issue 38
beginning page 16267
ending page 16276
digital object identifier (doi) 10.1039/d1nr03223b
web of science category 10
subject category Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied
unique article identifier WOS:000698160900001
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journal analysis (jcr 2019):
journal impact factor 6.895
5 year journal impact factor 7.315
category normalized journal impact factor percentile 82.576
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