Activators Confined Upconversion Nanoprobe with Near-Unity Förster Resonance Energy Transfer Efficiency for Ultrasensitive Detection

Tong Chen; Yunfei Shang; Yuyan Zhu; Shuwei Hao; Chunhui Yang

doi:10.1021/acsami.2c00604

Activators Confined Upconversion Nanoprobe with Near-Unity Förster Resonance Energy Transfer Efficiency for Ultrasensitive Detection

ACS Appl Mater Interfaces. 2022 May 4;14(17):19826-19835. doi: 10.1021/acsami.2c00604. Epub 2022 Apr 19.

Authors

Tong Chen¹, Yunfei Shang¹, Yuyan Zhu¹, Shuwei Hao^{1

2}, Chunhui Yang^{1

2}

Affiliations

¹ MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China.
² Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China.

PMID: 35438973
DOI: 10.1021/acsami.2c00604

Abstract

Lanthanide-doped upconversion nanoparticles (UCNPs) as energy donors for Förster resonance energy transfer (FRET) are promising in biosensing, bioimaging, and therapeutic applications. However, traditional FRET-based UC nanoprobes show low efficiency and poor sensitivity because only partial activators in UCNPs possessing suitable distance with energy acceptors (<10 nm) can activate the FRET process. Herein, a novel excited-state energy distribution-modulated upconversion nanostructure is explored for highly efficient FRET. Integration of the optimal 4% Er³⁺ doped shell and 100% Yb³⁺ core achieves ∼4.5-fold UC enhancement compared with commonly used NaYF₄:20%Yb³⁺,2%Er³⁺ nanoparticles, enabling maximum donation of excitation energy to an acceptor. The spatial confinement strategy shortens significantly the energy-transfer distance (∼4.5 nm) and thus demonstrates experimentally a 91.9% FRET efficiency inside the neutral red (NR)-conjugated NaYbF₄@NaYF₄:20%Yb³⁺,4%Er³⁺ nanoprobe, which greatly outperforms the NaYbF₄@NaYF₄:20%Yb³⁺,4%Er³⁺@SiO₂@NR nanoprobe (27.7% efficiency). Theoretical FRET efficiency calculation and in situ single-nanoparticle FRET measurement further confirm the excellent energy-transfer behavior. The well-designed nanoprobe shows a much lower detection limit of 0.6 ng/mL and higher sensitivity and is superior to the reported NO₂^- probes. Our work provides a feasible strategy to exploit highly efficient FRET-based luminescence nanoprobes for ultrasensitive detection of analytes.

Keywords: Monte Carlo simulation; core/shell nanoprobe; highly efficient FRET; single-nanoparticle FRET measurement; ultrasensitive detection; upconversion luminescence.