Composite particles with magnetic properties, near-infrared excitation, and far-red emission for luminescence-based oxygen sensing

Abstract

Oxygen sensing, magnetic, and upconversion luminescence properties are combined in multi-functional composite particles prepared herein by a simple mixing, baking, and grinding procedure. Upconverting nanocrystals are used as an excitation source and an oxygen indicator with far-red emission. The composite particles are excited with near infrared (NIR) laser light (980 nm). The visible upconversion emission is converted into an oxygen concentration-dependent far-red emission (<750 nm) using an inert mediator dye and a platinated benzoporphyrin dye. This concept combines the advantages of NIR excitation and far-red emissive indicator dyes, offering minimized auto-fluorescence and enhanced membrane permeability. Additional functionality is obtained by incorporating magnetic nanoparticles into the composite particles, which enables easy manipulation and separation of the particles by the application of an external magnetic field.