Abstract
AbstractOxygen 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.
Highlights
Oxygen is essential for most living systems, it is one of the most important chemical species on earth
MO, USA, www.sigmaaldrich.com); oleic acid and 1-octadecene purchased from Alfa Aesar (Ward Hill, MA, USA, www.alfa.com); poly(phenylsilsesquioxane) (PPSQ), 100% phenyl, 4.5–6.5% OH purchased from ABCR (Karlsruhe, Germany, www.abcr.de); Macrolex fluorescent red G (MFR) purchased from Simon und Werner GmbH (Flörsheim am Main, Germany, www.simon-und-werner.de); EMG1300 purchased from FerroTec (Santa Clara, CA, USA, www.ferrotec.com); ethanol and chloroform purchased from VWR (Radnor, PA, USA, www.vwr.com); nitrogen 5.0 purchased from Air Liquide (Paris, France, www.airliquide.com); and osmosis water and compressed air were used
After cooling to room temperature, the upconverting luminescent nanoparticles (UCLNPs) were precipitated by addition of approximately 20 mL of ethanol and isolated via centrifugation at a relative centrifugal force (RCF) of 1000 g for 5 min
Summary
Oxygen is essential for most living systems, it is one of the most important chemical species on earth. Optical sensor systems for oxygen are typically based on gas-permeable polymer matrices containing oxygen-sensitive probes. Such a design allows for the fabrication of sensor films or spots, which can be placed inside any optical transparent vessel, enabling a contactless and non-invasive readout for subsequent data processing and further analysis[3]. Another approach is the application of particles with micro- or nanometre dimensions and oxygensensing capabilities[4,5,6]. A promising class of materials for sensor development is upconverting crystals because of their near-infrared (NIR) excitation
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