Highly Doped Upconversion Nanoparticles for In Vivo Applications Under Mild Excitation Power
Authors: Xiangyang Shi
Shihui Wen
Du Li
Wei Hu
Bingyang Shi
Yongtao Liu
Mengya Kong
Dayong Jin
Journal: Analytical Chemistry (2020)
Discipline: CHEMISTRY
Keywords: upconversion nanoparticles; brightness improvement; NaYF4:Yb0.8,Er0.06; excitation power; Yb3+ sensitizer ions
Affiliations: Institute for Biomedical Materials and Devices (IBMD), Faculty of Science, University of Technology Sydney, Sydney, New South Wales 2007, Australia, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, People’s Republic of China, Department of Chemistry, Fudan University, Shanghai 200433, China, Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China, State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200438, China, Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, Sydney, New South Wales 2109, Australia, UTS-SUStech Joint Research Centre for Biomedical Materials & Devices and Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China

Abstract:  One of the major challenges in using upconversion nanoparticles (UCNPs) is to improve their brightness. This is particularly true for in vivo studies, as the low power excitation is required to prevent the potential photo toxicity to live cells and tissues. Here, we report that the typical NaYF4:Yb0.2,Er0.02 nanoparticles can be highly doped, and the formula of NaYF4:Yb0.8,Er0.06 can gain orders of magnitude more brightness, which is applicable to a range of mild 980 nm excitation power densities, from 0.005 W/cm2 to 0.5 W/cm2. Our results reveal that the concentration of Yb3+ sensitizer ions plays an essential role, while increasing the doping concentration of Er3+ activator ions to 6 mol % only has incremental effect. We further demonstrated a type of bright UCNPs 12 nm in total diameter for in vivo tumor imaging at a power density as low as 0.0027 W/cm2, bringing down the excitation power requirement by 42 times. This work redefines the doping concentrations to fight for the issue of concentration quenching, so that ultrasmall and bright nanoparticles can be used to further improve the performance of upconversion nanotechnology in photodynamic therapy, light-triggered drug release, optogenetics, and night vision enhancement. 

Retracted: No

PubPeer comments:
 Figure 1 and Figure S5. * Blue boxes: the NaYF4@NaYF4:Yb0.8,Er0.06 panel in Figure 1b right looks similar to panel c in Figure S5, which is NaYF4@NaYF4:Yb0.8,Er0.08 * Yellow boxes: the NaYF4@NaYF4:Yb0.8,Er0.06@NaYF4 panel in Figure 1c right looks similar to panel c in Figure S5, which is NaYF4@NaYF4:Yb0.8,Er0.08@NaYF4 Could the authors please check? ![file] , 
 thank you for picking this up. It was a mistake (as so many raw images). we are in the process of contacting the journal and make the correction. , 
 Correction, August 2021, found here: https: pubs.acs.org doi 10.1021 acs.analchem.1c03065  In our original Letter, (1) an error was found in the Supporting Information. By mistake, the TEM images of NaYF4@NaYF4:Yb0.8,Er0.08 and NaYF4@NaYF4:Yb0.8,Er0.08@NaYF4 in Figure S5c,k had been repeated from the TEM images of NaYF4@NaYF4:Yb0.8,Er0.06 and NaYF4@NaYF4:Yb0.8,Er0.06@NaYF4 in Figure 1b,c of the published Letter. (1) The Supporting Information file has been revised with the corrected TEM images in Figure S5 and is included as Supporting Information for this Addition and Correction. This correction does not affect any conclusions reported in the original Letter. We apologize for this unwanted mistake. I thank the authors and the journal for correcting this error. ,