Search

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 2 ) 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. [ABSTRACT FROM AUTHOR]

Abstract: A scheme for the simultaneous determination of oxygen and temperature using quantum dots and a ruthenium complex is demonstrated. The luminescent complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)]2+ is immobilized in a non-hydrolytic sol–gel matrix and used as the oxygen sensor. The temperature information is provided by the luminescent emission of core–shell CdSe–ZnS semiconductor nanocrystals immobilized in the same material. Measurements of oxygen and temperature could be performed with associated errors of ±2% of oxygen concentration and ±1°C, respectively. In addition, it is shown that while the dye luminescence intensity is quenched both by oxygen and temperature, the nanocrystals luminescent emission responds only to temperature. Results presented demonstrate that the combined luminescence response allows the simultaneous assessment of both parameters using a single optical fiber system. In particular, it was shown that a 10% error in the measured oxygen concentration, induced by a change in the sample temperature, could be compensated using the nanocrystals temperature information and a correction function. [Copyright &y& Elsevier]

Accurately measuring dissolved oxygen concentrations in fresh and salt water environments has long been an interdisciplinary priority. Many methodologies exist, including two very promising new ones, optical fluorescence quenching optrodes (or optodes) and solid-state voltammetric electrodes. In this study we compare the responsiveness of these two techniques to dynamic changes in dissolved oxygen concentrations, using traditional methods of polarographic oxygen sensors and Winkler’s chemical titrations to corroborate the measurements. Advantages of the optrode system include simplicity of operation and high sensitivity when changes in oxygen concentrations are small (<Δ10 μM O2 min-1). Advantages of voltammetry include equally high sensitivity, independent of rate of change of oxygen concentration, and the capability of simultaneously measuring other chemical species. Both systems have the capability of producing high-resolution, continuous oxygen profiles by collecting and reporting real-time data. Kinetic estimates of the binding and dissociation constants for the ruthenium–oxygen complex in the optrode revealed a relatively long half-life of the Ru2+–O2 complex for dissociation (t1/2 of 43.2 s to equilibrate from a 100 to 0% O2 saturation change). In contrast, the Ru2+–O2 association constant was 5.0 times faster (t1/2 of 8.6 s to equilibrate from a 0 to 100% O2 saturation change). Therefore, because of these differential kinetics, researchers should take care when using a ruthenium-based optrode to measure real-time dissolved oxygen concentrations undergoing temporal variability. [Copyright &y& Elsevier]