Preparation and application of ratiometric polystyrene-based microspheres as oxygen sensors.

Mono-dispersed polystyrene-based microspheres with diameters about 1 μm encapsulating rhodamine moieties as oxygen insensitive internal reference probes and platinum octaethylporphyrin units as oxygen sensitive probes were synthesized as new ratiometric oxygen sensors (Rhod-PtOEP-PS). The dual luminophors of rhodamines and platinum porphyrin moieties exhibited emissions maxima at 585 nm and 644 nm, respectively. The microspheres showed good oxygen sensing properties in different oxygen partial pressures (pO) and dissolved oxygen (DO) concentrations. It was found the oxygen probes and reference probes in microspheres showed higher photo-stability than their corresponding free fluorophores in solution. The microspheres also showed good sensitivity for air-pressure and cellular oxygen in cell culture medium. These microspheres were used to detect DOs in a few kinds of liquids including some daily drinks and it was found the measured errors were within positive/negative 11% as compared with the measured results using traditional oxygen electrodes.