Optical Emission Based Oxygen Sensing by ZnO Nanoparticles

TL;DR

This study demonstrates that ZnO nanoparticles' visible photoluminescence intensity decreases with reduced oxygen pressure, enabling optical oxygen sensing, with sensitivity influenced by particle size and surface vacancies.

Contribution

It reveals the dependence of ZnO nanoparticles' PL response on oxygen pressure and surface properties, introducing a novel optical oxygen sensing method.

Findings

PL intensity decreases with oxygen pressure reduction

Sensitivity is higher for smaller nanoparticles

Surface oxygen vacancies are key to PL emission

Abstract

ZnO nanoparticles (NP) of size less than around 20 nm inside a chamber exhibits complete reduction in their visible photoluminescence (PL) intensity when partial pressure of oxygen in the surrounding gaseous environment is decreased by evacuation. However the visible PL from ZnO nanoparticles are insensitive to the gases like N2, He and Ar. The rate of change of PL intensity with pressure (or the sensitivity) is inversely proportional to the ambient air pressure. Sensitivity increases when surface to volume ratio increases for lower particle size. The charged oxygen vacancies are attributed as the responsible candidates for surface related visible PL from ZnO NP.