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您的检索式：作者名="Thomas RTH"
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| 1 | Particle-size-dependent upconversion luminescence of NaYF4:Yb,Er nanoparticles in organic solvents and water at different excitation power densities显示文摘A systematic study of the luminescence properties of monodisperse β-NaYF4: 20%Yb^3+,2%Er^3+ upconversion nanoparticles (UCNPs)with sizes ranging from 12--43nm is presented utilizing steady-state and time-resolved fluorometry. Special emphasis was dedicated to the absolute quantification of size-and environment-induced quenching of upconversion luminescence (UCL)by highenergy O-H and C-H vibrations from solvent and ligand molecules at different excitation power densities (P).In this context,the still-debated population pathways of the 4F9/2 energy level of Er^3+ were examined.Our results highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12nm UCNPs,which outweighs the red Er^3+emission under 'strongly quenched'conditions and accounts for over 50% of total UCL in water.Because current rate equation models do not include such emissions,the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed.Furthermore,we postulate population pathways for the 4F9/2energy level of Er3.,Which correlate with the size-,environment-,and P-dependent quenching states of the higher Er^3+ energy levels. | Marco Kraft Christian Würth Verena Muhr Thomas Hirsch Ute Resch-Genger | 2018 | Nano Research2018，11，12： | 8 |
| 2 | Multiband emission from single β-NaYF_(4)(Yb,Er) nanoparticles at high excitation power densities and comparison to ensemble studies显示文摘Ensemble and single particle studies of the excitation power density (P)-dependent upconversion luminescence (UCL) of core and core-shell β-NaYF_(4):Yb,Er upconversion nanoparticles (UCNPs) doped with 20% Yb^(3+) and 1% or 3% Er^(^(3+)) performed over a P regime of 6 orders of magnitude reveal an increasing contribution of the emission from high energy Er^(3+) levels at P > 1 kW/cm^(2). 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/cm^(2), the increasing population of higher Er^(^(3+)) 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 Er^(3+) levels. | Florian Frenzel Christian Würth Oleksii Dukhno Frédéric Przybilla Lisa MWiesholler Verena Muhr Thomas Hirsch Yves Mély Ute Resch-Genger | 2021 | Nano Research2021，14，11： | 3 |
| 3 | Longitudinal and repeated cross sectional cluster-randomization designs using mixed effects regression for binary outcomes bias and coverage of frequentist and Bayesian methods 显示文摘 | A Russell Localio Jesse AB Thomas RTH | 2006 | Statistics in Medicine2006，25，： | 1 |
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