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Updated: Jan 21, 2026

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Evaline S Tsai1, Sandy F Himmelstoß, Lisa M Wiesholler
1Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK. lisa.hall@biotech.cam.ac.uk.
Upconversion nanoparticles (UCNPs) were studied for pH sensing. A pH-dependent inner filter effect, not resonance energy transfer, was found to be the primary mechanism for quenching UCNP emission, enabling ratiometric pH measurements.
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