Sensors phosphorescence quenching

Following the discovery that the fluorescence of metalloporphyrins is strongly quenched by oxygen57, optical sensor membranes were developed that are suitable for phosphorescent sensing of oxygen58. Table 1 summarizes fundamental articles on optical sensors for oxygen until the year 2000. 

Kautsky 1931 first oxygen sensor (non-fiber optic) based on dynamic quenching of the phosphorescence of adsorbed dyes... 

In addition to the sensors dealt with in Section 3.3.1.1, which could equally have been included in this Section as they use consumable immobilized reagents and regenerable fluorophores, Frei et al. developed a sensor for HPLC determinations based on the solid-state detection cell depicted in Fig. 3.38.B, where they immobilized 1-bromonaphthalene for measuring phosphorescence quenchers. Experiments demonstrated the sensor s usefulness for determining nitrate with a detection limit of ca. 10" M and an RSD of 4% for an analyte concentration of M. However, the scope of application of this sensor to chromatographically separated anions is rather narrow owing to the low sensitivity of the quenched phosphorescence detection for iodide and other halides [268]. 

The OLED-based sensors were tested in the 23-60°C temperature range. The values of t are expected to generally decrease with increasing temperature, as the PL quenching is enhanced at elevated temperatures [47]. However, in the 23-60°C studied range, the phosphorescence of porphyrins is only slightly dependent on the temperature [68]. Indeed, the temperature effect on the SV plots was minimal small reductions in tq and t (100% O2) were observed as the temperature increased, e.g., for one film, tq decreased from 91 to 84 js with Sg varying from 36.5 to 37.5. 

The phosphorescence of the 2-benzothienylpridine iridium cation 9.52 was significantly quenched by molecular oxygen in living cells, demonstrating that 2-benzothienylpridine iridium cation 9.52 can be used as a mitochondria-specific oxygen sensor as shown in Fig. 9.9 [102]. 

Fig. 17 Fluorescent sensors based on displacement of fluorophores. (a) Chiral boronate 56 containing a fluorophore which is quenched upon displacement (b) CdSe/ZnS quantum dot (QD) modified with a spacer and a boronic acid unit bound to a fluorophore-containing P-cyclodextrin 57, which, upon interaction with the analyte, releases the fluorophOTe, thus pievtaiting energy transfer (ET) from QD (c) guest-induced phosphorescence of CD-l-hromonaphthalene complex...

---