Red‐ and Green‐Emitting Iridium(III) Complexes for a Dual Barometric and Temperature‐Sensitive Paint

Abstract

A new dual luminescent sensitive paint for barometric pressure and temperature (T) is presented. The green-emitting iridium(III) complex [Ir(ppy)(2)(carbac)] (ppy=2-phenylpyridine; carbac=1-(9H-carbazol-9-yl)-5,5-dimethylhexane-2,4-dione) was applied as a novel probe for T along with the red-emitting complex [Ir(btpy)(3)], (btpy=2-(benzo[b]thiophene-2-yl)pyridine) which functions as a barometric (in fact oxygen-sensitive) probe. Both iridium complexes were dissolved in different polymer materials to achieve optimal responses. The probe [Ir(ppy)(2)(carbac)] was dispersed in gas-blocking poly(acrylonitrile) microparticles in order to suppress any quenching of its luminescence by oxygen. The barometric probe [Ir(btpy)(3)], in turn, was incorporated in a cellulose acetate butyrate film which exhibits good permeability for oxygen. The effects of temperature on the response of the oxygen probe can be corrected by simultaneous optical determination of T, as the poly(acrylonitrile) microparticles containing the temperature indicator are incorporated into the film. The phosphorescent signals of the probes for T and barometric pressure, respectively, can be separated by optical filters due to the approximately 75 nm difference in their emission maxima. The dual sensor is applicable to luminescence lifetime imaging of T and barometric pressure. It is the first luminescent dual sensor material for barometric pressure/T based exclusively on the use of Ir(III) complexes in combination with luminescence lifetime imaging.

Oxygen and temperature sensitivity of blue to green to yellow light-emitting Pt(ii) complexes

“…A more detailed description of the chamber and the imaging setup is described in a previous publication. 5 The response of the luminescence of the studied complexes to increasing temperature is shown in Fig. 3.…”

“…The latter can be further suppressed by incorporation in gas-blocking polymer materials. 5,6 In terms of optical sensor applications, the complex 3 is interesting as a temperature-sensitive probe. Its temperature coefficient is almost as high as that of typical luminescent indicators for T such as ruthenium and europium complexes.…”

“…In contrast to luminescent indicators for temperature based on ruthenium, 41,47 europium, 9,48 or iridium 5,6 complexes, the emission of 3 is comparably short-wave, enabling a combination with a second red emitting indicator such as platinum(II)-porphyrins for simultaneous detection of oxygen in dual sensors.…”

“…Generally, triplet emitting transition metal complexes are the probes of choice applied in optical oxygen sensors. Oxygen indicators such as polypyridyl ruthenium(II) 4 and iridium(III) complexes [5][6][7] have successfully been used as an alternative to the widely used platinum(II)-or palladium(II)-porphyrins. 8,9 However, some of these oxygen-sensitive probes have rather long luminescence decays up to milliseconds.…”

Indicators for optical oxygen sensors

“…However, similarly to other cyclometallated complexes the absorption is very efficient only in the UV region (ε as high as 60,000 M −1 cm −1 at 292 nm Table 4). Ir(btpy) 3 has been used, along with a green-emitting iridium dye, in a dual pressure and temperature sensitive paint [77]. The barometric dye 70 was incorporated in a cellulose acetate butyrate film and the crosssensitivity to temperature was efficiently corrected by simultaneous optical determination of the temperature.…”