Luminescent nanobeads for optical sensing and imaging of dissolved oxygen

A variety of luminescent oxygen nanosensors were prepared by addressable staining of poly(styrene-block-vinylpyrrolidone) nanobeads with metal-ligand complexes whose luminescence is quenched by oxygen. They display optimal sensitivity in responding to dissolved oxygen in concentrations from 0 to 100% air saturation. The nanobeads based on cyclometallated iridium(III) complexes with coumarins are especially promising due to excellent brightnesses. The nanosensors respond virtually in real time to altering oxygen concentration and are capable of recording even very rapid changes in oxygen partial pressure. Signals are obtained by determination of luminescence lifetime in the frequency domain and in the time domain, and by ratiometric measurement of luminescence intensity. The nanosensors have been applied to sensing and imaging of dissolved oxygen, to monitor the consumption of oxygen during enzymatic oxidation of glucose, and to monitoring dissolved oxygen in a growing culture of E. coli.