Upconversion nanoparticles for sensing pH. Issue 18 (12th August 2019)

• Record Type: Journal Article
• Authors: Tsai, Evaline S.; Himmelstoß, Sandy F.; Wiesholler, Lisa M.; Hirsch, Thomas; Hall, Elizabeth A. H.
• Is Part Of: Analyst. Volume 144:Issue 18(2019)
• Page Start: 5547
• Page End: 5557
• Publication Date: 2019-08-12
• Subjects: Chemistry, Analytic -- Periodicals; 543
• DOI: 10.1039/c9an00236g
• Languages: English
• ISSNs: 0003-2654

Abstract

Abstract : pH sensing IR-excited dye-linked upconversion nanoparticles, via inner field effect quenching at 540 nm referenced to emission at 650 nm. 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.