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Studies of optical properties of lanthanide upconversion nanoparticles for emerging applications.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Royal Institute of Technology.
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

YTTERBY, a small village very close to Stockholm where I live, is the place in the world which has lent its name to the largest number of elements in the periodic table, namely four - YTTRIUM, YTTERBIUM, ERBIUM and TERBIUM. Three more lanthanide elements were discovered from the now empty quarry located in this village. By the time of their discoveries in the 19th century little could be known about their fantastic properties, the versatility of their use and functionality in what we now call nanotechnology. This is a circumstance that motivated me to rather recently enter lanthanide research, in particular studies of their outstanding optical properties for the purpose of information technology and energy harvesting.

So far, upconversion nanoparticles (UCNPs) have been much explored as unique spectral converters for various applications, like biotechnology, information technology and photovoltaic devices due to properties like sharp emission profiles, low autofluorescence and large anti-Stoke shifts. Still, there is much to explore and to understand in order to fully utilize the very unique properties of UCNPs. The kinetic dynamics of the upconversion process is one such aspect that is not well understood, and a deeper understanding of the kinetic dynamics of lanthanide upconversion systems could thus broaden their applications. Therefore, the work of this thesis is focused on investigating the kinetic dynamics of upconversion processes mainly based on systems with NaYF4 as host material, and Yb3+/Er3+ or Yb3+/Tm3+ embedded as sensitizer/activator. Through rate equation models, the kinetic dynamics of upconversion are comparatively investigated with numerical simulations and analytical derivation. The temporal response regarding upconverted luminescence and quantum yield power density dependence, excitation duration response and excitation frequency response of the upconversion systems are investigated and the corresponding applications for multicolor imaging, optical encoding, photovoltaics, IR photodetectors are explored and analyzed in the thesis, taking advantage of the kinetic properties.

Abstract [sv]

YTTERBY, en liten by nära Stockholm där jag bor, är den plats i världen som har lånat sitt namn till det högsta antalet element i det periodiska systemet, nämligen fyra - YTTRIUM, YTTERBIUM, ERBIUM och TERBIUM. Ytterligare tre lantanidelement upptäcktes från det nu tomma stenbrottet som ligger i denna by. Vid deras upptäckter på 1800-talet kunde man inte ana deras fantastiska egenskaper, mångsidigheten i deras användning och deras funktionalitet i det vi nu kallar nanoteknologi. Detta är en omständighet som motiverade mig ganska nyligen att intressera mig för lantanidforskning, i synnerhet studier av deras enastående optiska egenskaper och deras energitillämpningar och användning inom informationsteknik.

Hittills har uppkonverterande nanopartiklar (UCNPs) utforskats mycket som unika spektralkonverterare för olika applikationer, som bioteknik, informationsteknologi och fotovoltaiska enheter på grund deras egenskaper som skarpa emissions profiler, låg autofluorescens och stora anti-Stoke skift. Det finns fortfarande mycket att utforska och förstå för att utnyttja de mycket unika egenskaperna hos dessa partiklar. Den kinetiska dynamiken i upkonverteringsprocessen är en sådan aspekt som inte är väl undersökt ännu, och en djupare förståelse av den kinetiska dynamiken i uppkonverterande lantanid system kan bredda deras tillämpningar. Därför har jag fokuserat arbetet med den här avhandlingen på att undersöka den kinetiska dynamiken i upkonverterings processen huvudsakligen baserat på system med NaYF4 som värdmaterial och Yb3+/Er3+ eller Yb3+/Tm3+ inbäddat som sensibilisator/aktivator. Genom simuleringar av ekvationsmodeller har jag undersökt den kinetiska dynamiken i uppkonversionen jämförande numerisk simulering och analytisk härledning. Det temporära svaret med avseende på uppkonverterad luminescens, det s.k. täthetsberoendet av kvantutbytet och excitation frekvens responsen för olika upkonversionssystem har studerats. Motsvarande tillämpningar för flerfärgs avbildning, optisk kodning, fotovoltaik och IR fotodetektorer undersöks och analyseras i avhandlingen, med speciell fokus på de kinetiska egenskaperna.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. , p. 73
Series
TRITA-CBH-FOU ; 2020:18
Keywords [en]
Upconversion nanoparticles, solar cells sensitization, near infrared photodetector, multiplex imaging, optical encoding, information technology, bioimaging, rate equation models
National Category
Nano Technology
Research subject
Theoretical Chemistry and Biology
Identifiers
URN: urn:nbn:se:kth:diva-273038ISBN: 978-91-7873-500-6 (print)OAI: oai:DiVA.org:kth-273038DiVA, id: diva2:1429054
Public defence
2020-06-04, https://kth-se.zoom.us/webinar/register/WN_E0ALwYOFS-mP-vAFhp2QQw, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2020-05-14

Available from: 2020-05-14 Created: 2020-05-07 Last updated: 2020-05-20Bibliographically approved
List of papers
1. Change in the emission saturation and kinetics of upconversion nanoparticles under different light irradiations
Open this publication in new window or tab >>Change in the emission saturation and kinetics of upconversion nanoparticles under different light irradiations
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2019 (English)In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 97, article id 109389Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Color tunability, Kinetics, Laser scanning microscopy, Saturation, Upconversion, Enzyme kinetics, Laser applications, Luminescence, Nanoparticles, Saturation (materials composition), Excitation intensity, Excitation wavelength, Multi-wavelengths, Up-conversion, Upconversion luminescence, Upconversion nanoparticles, Light
National Category
Theoretical Chemistry Atom and Molecular Physics and Optics
Research subject
Theoretical Chemistry and Biology; Physics, Theoretical Physics
Identifiers
urn:nbn:se:kth:diva-263500 (URN)10.1016/j.optmat.2019.109389 (DOI)000501396600023 ()2-s2.0-85072543021 (Scopus ID)
Funder
Swedish Research Council, 2016-03804Swedish Foundation for Strategic Research , SSF ITM17-0491ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 19-424
Note

QC 20191205

Available from: 2019-12-05 Created: 2019-12-05 Last updated: 2020-05-07Bibliographically approved
2. On the decay time of upconversion luminescence
Open this publication in new window or tab >>On the decay time of upconversion luminescence
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 11, p. 4959-4969Article in journal (Refereed) Published
Abstract [en]

In this study, we systematically investigate the decay characteristics of upconversion luminescence (UCL) under anti-Stokes excitation through numerical simulations based on rate-equation models. We find that a UCL decay profile generally involves contributions from the sensitizer's excited-state lifetime, energy transfer and cross-relaxation processes. It should thus be regarded as the overall temporal response of the whole upconversion system to the excitation function rather than the intrinsic lifetime of the luminescence emitting state. Only under certain conditions, such as when the effective lifetime of the sensitizer's excited state is significantly shorter than that of the UCL emitting state and of the absence of cross-relaxation processes involving the emitting energy level, the UCL decay time approaches the intrinsic lifetime of the emitting state. Subsequently, Stokes excitation is generally preferred in order to accurately quantify the intrinsic lifetime of the emitting state. However, possible cross-relaxation between doped ions at high doping levels can complicate the decay characteristics of the luminescence and even make the Stokes-excitation approach fail. A strong cross-relaxation process can also account for the power dependence of the decay characteristics of UCL.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-246212 (URN)10.1039/C8NR10332A (DOI)000462669600033 ()30839016 (PubMedID)2-s2.0-85062877182 (Scopus ID)
Note

QC 20190318

Available from: 2019-03-16 Created: 2019-03-16 Last updated: 2020-05-07Bibliographically approved
3. Microlens array enhanced upconversion luminescence at low excitation irradiance
Open this publication in new window or tab >>Microlens array enhanced upconversion luminescence at low excitation irradiance
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 29, p. 14070-14078Article in journal (Refereed) Published
Abstract [en]

The dearth of high upconversion luminescence (UCL) intensity at low excitation irradiance hinders the prevalent application of lanthanide-doped upconversion nanoparticles (UCNPs) in many fields ranging from optical bioimaging to photovoltaics. In this work, we propose to use microlens arrays (MLAs) as spatial light modulators to manipulate the distribution of excitation light fields in order to increase UCL, taking advantage of its nonlinear response to the excitation irradiance. We show that multicolored UCL from NaYF4:Yb3+,Er3+@NaYF4:Yb3+,Nd3+ and NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Nd3+ core/shell UCNPs can be increased by more than one order of magnitude under either 980 or 808 nm excitation, by simply placing a polymeric MLA onto the top of these samples. The observed typical green (525/540 nm) and red (654 nm) UCL bands from Er3+ and a blue (450/475 nm) UCL band from Tm3+ exhibit distinct enhancement factors due to their different multi-photon processes. Importantly, our ray tracing simulation reveals that the MLA is able to spatially confine the excitation light (980 and 808 nm) by orders of magnitude, thus amplifying UCL by more than 225-fold (the 450 nm UCL band of Tm3+) at low excitation irradiance. The proposed MLA method has immediate ramifications for the improved performance of all types of UCNP-based devices, such as UCNP-enhanced dye sensitized solar cells demonstrated here.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-256248 (URN)10.1039/c9nr03105g (DOI)000477704400039 ()31313798 (PubMedID)2-s2.0-85069640491 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2020-05-07Bibliographically approved
4. Cascade photon upconversion amplification for selective multispectral narrow-band near-infrared photodetection
Open this publication in new window or tab >>Cascade photon upconversion amplification for selective multispectral narrow-band near-infrared photodetection
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Facing the fact that selective detection of multiple narrow spectral bands in the near-infrared (NIR) region still poses a fundamental challenge, we have, in this work, developed NIR photodetectors (PDs) using photon upconversion nanocrystals (UCNCs) combined with perovskite films. In order to conquer the relatively high pumping threshold of UCNCs, we designed a novel cascade amplification strategy for upconversion luminescence (UCL) through cascading the superlensing effect of dielectric microlens arrays and the plasmonic effect of gold nanorods, which readily leads to a UCL enhancement by more than four orders of magnitude under weak light irradiation. By accommodating multiple optical active lanthanide ions in a core-shell-shell hierarchical architecture, the developed PDs on top can detect three well-separated narrow bands in the NIR region, i.e., 808, 980, and 1540 nm, respectively. Due to the large UCL enhancement, the obtained PDs demonstrate extremely high responsivity of 30.73, 23.15, 12.20 A/W and detectivity of 5.36, 3.45, 1.91x10^11 Jones for the 808, 980, and 1540 nm light detection, respectively, together with short response times in the range of 80-120 ms. Moreover, we demonstrate for the first time that the response to the excitation modulation frequency of a PD can be employed to discriminate the incident light wavelength. We believe that our work provides a novel insight for developing NIR PDs, and that it can spur the development of other applications using upconversion nanotechnology.

Keywords
upconversion nanoparticles, cascade amplification, multi-wavelength selective photodetection, dielectric superlensing effect, localized surface plasmon resonance, excitation modulation, frequency response
National Category
Nano Technology
Research subject
Materials Science and Engineering; Physics, Optics and Photonics
Identifiers
urn:nbn:se:kth:diva-273152 (URN)
Note

QC 20200603

Available from: 2020-05-07 Created: 2020-05-07 Last updated: 2020-06-03Bibliographically approved
5. High throughput decoding approach for luminescencekinetics-based optical encoding of lanthanide upconversion nanoparticles
Open this publication in new window or tab >>High throughput decoding approach for luminescencekinetics-based optical encoding of lanthanide upconversion nanoparticles
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Lanthanide upconversion nanoparticles (UCNPs) are increasingly explored to develop high-security-level anti-counterfeiting and multiplexing applications, due to the availability of ample encoding dimensions. Among other applications, upconversion luminescence(UCL) kinetics-based optical encoding is particularly attractive as it provides an almost unlimited encoding capacity due to the ease of manipulating the UCL kinetics by chemical engineering. However, current decoding methods limit its applications because of a typically low throughput and high cost of the system. In this Letter, we propose a novel decoding approach for UCL kinetics-based optical encoding, which utilizes a pulsed excitation source with adjustable pulse duration and a low time-resolution and large-area detector. We develop a theoretical fitting model and show how fingerprint time constants of the UCNPs (the encoding identities) can be extracted from the correlation between the averaged UCL intensity and the pulse duration. Our new approach provides a high-throughput and cost-effective solution to decode UCL kinetics.

Keywords
upconvesion nanoparticles, optical encoding, lanthanide, rate equation models, kinetics, high capacity, high throughput
National Category
Nano Technology
Research subject
Materials Science and Engineering; Physics, Optics and Photonics
Identifiers
urn:nbn:se:kth:diva-273149 (URN)
Note

QC 20200603

Available from: 2020-05-07 Created: 2020-05-07 Last updated: 2020-06-03Bibliographically approved

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