Indicators for optical oxygen sensors

Abstract

Continuous monitoring of oxygen concentration is of great importance in many different areas of research which range from medical applications to food packaging. In the last three decades, significant progress has been made in the field of optical sensing technology and this review will highlight the one inherent to the development of oxygen indicators. The first section outlines the bioanalytical fields in which optical oxygen sensors have been applied. The second section gives the reader a comprehensive summary of the existing oxygen indicators with a critical highlight on their photophysical and sensing properties. Altogether, this review is meant to give the potential user a guide to select the most suitable oxygen indicator for the particular application of interest.

Exceptional Oxygen Sensing Properties of New Blue Light‐Excitable Highly Luminescent Europium(III) and Gadolinium(III) Complexes

“…The emission was recorded using a combination of an OG-580 filter (Schott) and Calflex X filter from Linos. The modulation frequencies were 2.5, 2 kHz and 1.5 kHz for Eu(HPhN) 3 phen, Eu(HPhN) 3 dpp and Eu(HPhN) 3 DDXPO, respectively and 205, 180 and 145 Hz for the Gd(HPhN) 3 phen, Gd(HPhN) 3 dpp and Gd(HPhN) 3 DDXPO, respectively. The intensity-based quenching plots were obtained at the modulation frequencies of 165 Hz and 21 Hz for the Eu(III) and Gd(III) complexes, respectively.…”

“…The crude product was used without further purification. Yield: 760 mg (78 %) for Eu(HPhN) 3 (74.3 mg, 0.1 mmol), respectively, in hot toluene (5 mL, 100 °C). The heating was continued for 1h, the resulted solution was rapidly cooled to room temperature and centrifuged to remove the remaining sediment.…”

“…The lanthanide salts used for complexes represent low cost materials which compare favourably with the price of platinum group metals used in most oxygen indicators. The intermediate complexes europium(III) and gadolinium(III) tris-[9-(hydroxy-kO)-1H-phenaleno-1-onatokO] (Eu(HPhN) 3 and Gd(HPhN) 3 , respectively) are poorly soluble in common solvents and their thorough purification was not performed. Instead, the crude materials were introduced in the second step in which a quaternary complex was formed (Scheme 1).…”

“…The materials used in optical oxygen sensors are quite established. [1][2][3][4] Most oxygen sensors employ such widespread indicators as ruthenium(II) polypyridyl complexes, [5][6][7] platinum(II) and palladium(II) porphyrins [8][9][10][11] and their analogues. [12][13][14] Other luminescent indicators are less popular which is explained by their inferior photophysical properties (low absorption coefficients and luminescence quantum yields, short luminescence decay times, poor photostability etc.)…”

“…[12][13][14] Other luminescent indicators are less popular which is explained by their inferior photophysical properties (low absorption coefficients and luminescence quantum yields, short luminescence decay times, poor photostability etc.) [3]or by complicated multistep synthesis. Such indicators as cyclometalated iridium(III) and platinum(II) complexes, [15][16][17] osmium(II), [18] rhenium(I) [19] and copper(I) [20,21] complexes should also be mentioned.…”