Issue 27, 2021

Breaking the diffraction limit in absorption spectroscopy using upconverting nanoparticles

Abstract

We employ a single optically trapped upconverting nanoparticle (UCNP) of NaYF4:Yb,Er of diameter about 100 nm as a subdiffractive source to perform absorption spectroscopy. The experimentally expected mode volume of 100 nm of the backscatter profile of the nanoparticle matches well with a numerical simulation of the dominant backscattering modes to confirm our assertion of achieving a source dimension considerably lower than the diffraction limit set by the excitation wavelength of 975 nm for the UCNP. We perform absorption spectroscopy of several diverse entities such as the dye Rhodamine B in water, a thin gold film of thickness 30 nm, and crystalline soft oxometalates micro-patterned on a glass substrate using the UCNP as a source. The initial results lead to unambiguous utility of UCNPs as single nanoscopic sources for absorption spectroscopy of ultra-small sample volumes (femtolitres), and lead us to hypothesize a possible Resonance Energy Transfer mechanism between the UCNP and the molecules of the ambient medium, which may even lead to single molecule absorption spectroscopy applications.

Graphical abstract: Breaking the diffraction limit in absorption spectroscopy using upconverting nanoparticles

Article information

Article type
Paper
Submitted
04 Apr 2021
Accepted
25 Jun 2021
First published
25 Jun 2021
This article is Open Access
Creative Commons BY-NC license

Nanoscale, 2021,13, 11856-11866

Breaking the diffraction limit in absorption spectroscopy using upconverting nanoparticles

S. Kumar, G. M., R. Vaippully, A. Banerjee and B. Roy, Nanoscale, 2021, 13, 11856 DOI: 10.1039/D1NR02103F

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