Issue 18, 2019

Upconversion nanoparticles for sensing pH

Abstract

Upconversion nanoparticles (UCNPs) can provide a vehicle for chemical imaging by coupling chemically sensitive dyes and quenchers. The mechanism for coupling of two anthraquinone dyes, Calcium Red and Alizarin Red S, was investigated as a function of pH. The green emission band of the UCNPs was quenched by a pH-dependent inner filter effect (IFE) while the red emission band remained unchanged and acted as the reference signal for ratiometric pH measurements. Contrary to previous expectation, there was little evidence for a resonance energy transfer (RET) mechanism even when the anthraquinones were attached onto the UCNPs through electrostatic attraction. Since the UCNPs are point emitters, only emitters close to the surface of the UCNP are within the expected Förster distance and UC-RET is <10%. The theoretical and experimental analysis of the interaction between UCNPs and pH-sensitive quenchers will allow the design of UCNP pH sensors for determination of pH via IFE.

Graphical abstract: Upconversion nanoparticles for sensing pH

Supplementary files

Article information

Article type
Paper
Submitted
02 Feb 2019
Accepted
07 Aug 2019
First published
09 Aug 2019

Analyst, 2019,144, 5547-5557

Upconversion nanoparticles for sensing pH

E. S. Tsai, S. F. Himmelstoß, L. M. Wiesholler, T. Hirsch and E. A. H. Hall, Analyst, 2019, 144, 5547 DOI: 10.1039/C9AN00236G

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