scholarly journals Multiband emission from single β-NaYF4(Yb,Er) nanoparticles at high excitation power densities and comparison to ensemble studies

Nano Research ◽  
2021 ◽  
Author(s):  
Florian Frenzel ◽  
Christian Würth ◽  
Oleksii Dukhno ◽  
Frédéric Przybilla ◽  
Lisa M. Wiesholler ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Single Particle ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Excited State Absorption ◽  
High Energy ◽  
Excitation Power ◽  
Relaxation Processes ◽  
Excitation Power Density ◽  
Radiative Relaxation

AbstractEnsemble and single particle studies of the excitation power density (P)-dependent upconversion luminescence (UCL) of core and core-shell β-NaYF4:Yb,Er upconversion nanoparticles (UCNPs) doped with 20% Yb3+ and 1% or 3% Er3+ performed over a P regime of 6 orders of magnitude reveal an increasing contribution of the emission from high energy Er3+ levels at P > 1 kW/cm2. This changes the overall emission color from initially green over yellow to white. While initially the green and with increasing P the red emission dominate in ensemble measurements at P < 1 kW/cm2, the increasing population of higher Er3+ energy levels by multiphotonic processes at higher P in single particle studies results in a multitude of emission bands in the ultraviolet/visible/near infrared (UV/vis/NIR) accompanied by a decreased contribution of the red luminescence. Based upon a thorough analysis of the P-dependence of UCL, the emission bands activated at high P were grouped and assigned to 2–3, 3–4, and 4 photonic processes involving energy transfer (ET), excited-state absorption (ESA), cross-relaxation (CR), back energy transfer (BET), and non-radiative relaxation processes (nRP). This underlines the P-tunability of UCNP brightness and color and highlights the potential of P-dependent measurements for mechanistic studies required to manifest the population pathways of the different Er3+ levels.

scholarly journals Volume and surface effects on two-photonic and three-photonic processes in dry co-doped upconversion nanocrystals

Nano Research ◽  
2021 ◽  
Author(s):  
Bettina Grauel ◽  
Christian Würth ◽  
Christian Homann ◽  
Lisa Krukewitt ◽  
Elina Andresen ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Near Infrared ◽  
Surface Passivation ◽  
Upconversion Luminescence ◽  
Three Dimensional ◽  
Solid Core ◽  
Excitation Power Density ◽  
Surface Protection ◽  
Upconversion Nanocrystals ◽  
Co Doped

AbstractDespite considerable advances in synthesizing high-quality core/shell upconversion (UC) nanocrystals (NC; UCNC) and UCNC photophysics, the application of near-infrared (NIR)-excitable lanthanide-doped UCNC in the life and material sciences is still hampered by the relatively low upconversion luminescence (UCL) of UCNC of small size or thin protecting shell. To obtain deeper insights into energy transfer and surface quenching processes involving Yb3+ and Er3+ ions, we examined energy loss processes in differently sized solid core NaYF4 nanocrystals doped with either Yb3+ (YbNC; 20% Yb3+) or Er3+ (ErNC; 2% Er3+) and co-doped with Yb3+ and Er3+ (YbErNC; 20% Yb3+ and 2% Er3+) without a surface protection shell and coated with a thin and a thick NaYF4 shell in comparison to single and co-doped bulk materials. Luminescence studies at 375 nm excitation demonstrate back-energy transfer (BET) from the 4G11/2 state of Er3+ to the 2F5/2 state of Yb3+, through which the red Er3+4F9/2 state is efficiently populated. Excitation power density (P)-dependent steady state and time-resolved photoluminescence measurements at different excitation and emission wavelengths enable to separate surface-related and volume-related effects for two-photonic and three-photonic processes involved in UCL and indicate a different influence of surface passivation on the green and red Er3+ emission. The intensity and lifetime of the latter respond particularly to an increase in volume of the active UCNC core. We provide a three-dimensional random walk model to describe these effects that can be used in the future to predict the UCL behavior of UCNC.

scholarly journals Spectroscopy and Near-Infrared to Visible Upconversion of Er3+ Ions in Aluminosilicate Glasses Manufactured with Controlled Optical Transmission

2021 ◽  
Vol 11 (3) ◽  
pp. 1137
Author(s):  
Daniel Sola ◽  
Adrián Miguel ◽  
Eduardo Arias-Egido ◽  
Jose I. Peña
Keyword(s):  
Energy Transfer ◽  
Spectral Range ◽  
Optical Transmission ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Excited State Absorption ◽  
Visible Spectral Range ◽  
Excitation Spectra ◽  
Aluminosilicate Glasses ◽  
Energy Transfer Upconversion

In this work we report on the spectroscopic properties and the near-infrared to visible upconversion of Er3+ ions in aluminosilicate glasses manufactured by directionally solidification with the laser floating zone technique. Glasses were manufactured in a controlled oxidizing atmosphere to provide them with high optical transmission in the visible spectral range. Absorption and emission spectra, and lifetimes were assessed in both the visible and the near infrared spectral range. Green upconversion emissions of the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions at 525 nm and 550 nm attributed to a two-photon process were observed under excitation at 800 nm. Mechanisms responsible for the upconversion luminescence were discussed in terms of excited state absorption and energy transfer upconversion processes. Excitation spectra of the upconverted emission suggest that energy transfer upconversion processes are responsible for the green upconversion luminescence.

scholarly journals Upconversion Luminescence of Silica–Calcia Nanoparticles Co-doped with Tm3+ and Yb3+ Ions

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 937
Author(s):  
Katarzyna Halubek-Gluchowska ◽  
Damian Szymański ◽  
Thi Ngoc Lam Tran ◽  
Maurizio Ferrari ◽  
Anna Lukowiak
Keyword(s):  
Energy Transfer ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Sol Gel ◽  
Emission Spectra ◽  
Transmission Electron ◽  
Characteristic Emission ◽  
Diffraction Patterns ◽  
Size Of Particles ◽  
Average Size

Looking for upconverting biocompatible nanoparticles, we have prepared by the sol–gel method, silica–calcia glass nanopowders doped with different concentration of Tm3+ and Yb3+ ions (Tm3+ from 0.15 mol% up to 0.5 mol% and Yb3+ from 1 mol% up to 4 mol%) and characterized their structure, morphology, and optical properties. X-ray diffraction patterns indicated an amorphous phase of the silica-based glass with partial crystallization of samples with a higher content of lanthanides ions. Transmission electron microscopy images showed that the average size of particles decreased with increasing lanthanides content. The upconversion (UC) emission spectra and fluorescence lifetimes were registered under near infrared excitation (980 nm) at room temperature to study the energy transfer between Yb3+ and Tm3+ at various active ions concentrations. Characteristic emission bands of Tm3+ ions in the range of 350 nm to 850 nm were observed. To understand the mechanism of Yb3+–Tm3+ UC energy transfer in the SiO2–CaO powders, the kinetics of luminescence decays were studied.

Effect of excitation power density on the upconversion luminescence of LaF3:Yb3+, Er3+ nanocrystals

2009 ◽  
Vol 485 (1-2) ◽  
pp. 493-496 ◽  
Author(s):  
Yuqiu Qu ◽  
Xianggui Kong ◽  
Yajuan Sun ◽  
Qinghui Zeng ◽  
Hong Zhang
Keyword(s):  
Power Density ◽  
Upconversion Luminescence ◽  
Excitation Power ◽  
Excitation Power Density

Phase-Selective Hydrothermal Preparation and Upconversion Luminescence of NaYF4:Yb3+,Tm3+

2016 ◽  
Vol 690 ◽  
pp. 120-125 ◽  
Author(s):  
Thanataon Pornpatdetaudom ◽  
Karn Serivalsatit
Keyword(s):  
Reaction Time ◽  
Near Infrared ◽  
Hexagonal Phase ◽  
Upconversion Luminescence ◽  
Upconversion Emission ◽  
High Energy ◽  
Lanthanide Ions ◽  
Cubic Phase ◽  
Good Efficiency ◽  
Hydrothermal Temperature

Upconversion luminescence materials have been proved to have a good efficiency on converting low energy light to high energy light. These materials have received considerable attentions for many applications such as bio-labels, sensors, using for developing solar cells and photocatalytic applications under sunlight. Among many inorganic host materials, NaYF4 has been proved to be the best for doping lanthanide ions and have a good upconversion emission due to its low phonon energy, chemical stability, and transparency in the near infrared to ultraviolet range. In this study, NaYF4:Yb3+,Tm3+ upconversion luminescence materials were synthesized by hydrothermal method at temperature of 90 to 200 °C for period between 1 to 24 hours. The synthesized NaYF4:Yb3+,Tm3+ were characterized by X-ray diffraction, scanning electron microscopy, and fluorescence spectroscopy. The hydrothermal temperature and reaction time have strongly influence on phases and upconversion emission of the synthesized NaYF4:Yb3+,Tm3+. At 90 °C for 1 hour of reaction time, the pure cubic phase of NaYF4:Yb3+,Tm3+ was found. After increasing temperature and reaction time, the NaYF4:Yb3+,Tm3+ converted from cubic phase to hexagonal phase. Under excitation of 980 nm diode laser, the hexagonal NaYF4:Yb3+,Tm3+ exhibited the emission wavelength at about 656 nm (3F2 → 3H6), 469, 492, 552 nm (1G4 → 3H6), 537 nm (1D2 → 3H5), 450, 461 nm (1D2 → 3F4), 362 nm (1D2 → 3H6) and 345 nm (1I6 → 3F4). The upconversion emission intensity of the hexagonal NaYF4:Yb3+,Tm3+ was much stronger, compared with that of the cubic NaYF4:Yb3+,Tm3+.

scholarly journals Photon upconversion through triplet exciton-mediated energy relay

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sanyang Han ◽  
Zhigao Yi ◽  
Jiangbin Zhang ◽  
Qifei Gu ◽  
Liangliang Liang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
High Performance ◽  
Technology Development ◽  
Upconversion Luminescence ◽  
Excitation Power ◽  
Host Lattice ◽  
Energy Migration ◽  
Triplet Exciton ◽  
Long Distance ◽  
Experimental Conditions

AbstractExploration of upconversion luminescence from lanthanide emitters through energy migration has profound implications for fundamental research and technology development. However, energy migration-mediated upconversion requires stringent experimental conditions, such as high power excitation and special migratory ions in the host lattice, imposing selection constraints on lanthanide emitters. Here we demonstrate photon upconversion of diverse lanthanide emitters by harnessing triplet exciton-mediated energy relay. Compared with gadolinium-based systems, this energy relay is less dependent on excitation power and enhances the emission intensity of Tb3+ by 158-fold. Mechanistic investigations reveal that emission enhancement is attributable to strong coupling between lanthanides and surface molecules, which enables fast triplet generation (<100 ps) and subsequent near-unity triplet transfer efficiency from surface ligands to lanthanides. Moreover, the energy relay approach supports long-distance energy transfer and allows upconversion modulation in microstructures. These findings enhance fundamental understanding of energy transfer at molecule-nanoparticle interfaces and open exciting avenues for developing hybrid, high-performance optical materials.

scholarly journals On the decay time of upconversion luminescence

Nanoscale ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 4959-4969 ◽  
Author(s):  
Jan Bergstrand ◽  
Qingyun Liu ◽  
Bingru Huang ◽  
Xingyun Peng ◽  
Christian Würth ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Numerical Simulations ◽  
Rate Equation ◽  
Decay Time ◽  
Upconversion Luminescence ◽  
Luminescence Decay ◽  
Cross Relaxation ◽  
Relaxation Processes ◽  
Intermediate States

Numerical simulations based on rate-equation models were performed to investigate how the upconversion luminescence decay is affected by the lifetimes of intermediate states, energy transfer, and cross-relaxation processes.

scholarly journals The IR Emission Features and Hydrogenated Amorphous Carbon (HAC) Particles

1989 ◽  
Vol 135 ◽  
pp. 141-146
Author(s):  
W. W. Duley
Keyword(s):  
Amorphous Carbon ◽  
Interstellar Dust ◽  
Near Infrared ◽  
High Energy ◽  
Radiative Relaxation ◽  
Hydrogenated Amorphous Carbon ◽  
Nir Emission ◽  
Extended Red Emission ◽  
Ir Emission ◽  
Hydrogenated Amorphous

Various sources of non-equilibrium radiation from interstellar dust are discussed. It is shown that the existence of cirrus emission at 12 and 25 μm is consistent with the presence of amorphous carbon dust and arises from thermal spikes within ≃ 10å subvolumes of normal (0.01-0.1 μm radius) dust grains. The 3.28 μm unidentified infrared (UIR) feature also arises in this way, as the radiative relaxation of high energy vibrational modes accompanying a thermal spike in hydrogenated amorphous carbon. Extended red emission (ERE) and near-infrared (NIR) emission are also discussed and are postulated to originate as edge and defect luminescence from HAC solids with bandgaps Eg ≲ 2.5eV.

scholarly journals Ultra-stable near-infrared Tm3+-doped upconversion nanoparticles for in vivo wide-field two-photon angiography with a low excitation intensity

2019 ◽  
Vol 12 (03) ◽  
pp. 1950013 ◽  
Author(s):  
Wen Liu ◽  
Runze Chen ◽  
Sailing He
Keyword(s):  
Power Density ◽  
Near Infrared ◽  
Multilayer Coating ◽  
Excitation Power ◽  
Whole Body ◽  
Upconversion Nanoparticles ◽  
Excitation Power Density ◽  
Two Photon ◽  
Coating Method

Two-photon luminescence with near-infrared (NIR) excitation of upconversion nanoparticles (NPs) is of great importance in biological imaging due to deep penetration in high-scattering tissues, low auto-luminescence and good sectioning ability. Unfortunately, common two-photon luminescence is in visible band with an extremely high exciation power density, which limits its application. Here, we synthesized NaYF4:Yb[Formula: see text]Tm@NaYF4 upconversion NPs with strong two-photon NIR emission and a low excitation power density. Furthermore, NaYF4:Yb[Formula: see text]Tm@NaYF4@SiO2@OTMS@F127 NPs with high chemical stability were obtained by a modified multilayer coating method which was applied to upconversion NPs for the first time. In addition, it is shown that the as-prepared hydrophillic upconversion NPs have great biocompatibility and kept stable for 6 hours during in vivo whole-body imaging. The vessels with two-photon luminescence were clear even under an excitation power density as low as 25[Formula: see text]mW[Formula: see text]cm2. Vivid visualizations of capillaries and vessels in a mouse brain were also obtained with low background and high contrast. Because of cheaper instruments and safer power density, the NIR two-photon luminescence of NaYF4:Yb[Formula: see text]Tm@NaYF4 upconversion NPs could promote wider application of two-photon technology. The modified multilayer coating method could be widely used for upconversion NPs to increase the stable time of the in vivo circulation. Our work possesses a great potential for deep imaging and imaging-guided treatment in the future.

Sign in / Sign up

Export Citation Format

Share Document