Indicators for long-wave excitable luminescent sensors

The project is aimed to design luminescent sensors which can be interrogated with long-wave emitting light sources. Most luminescent sensors described in the literature rely on indicators which are excitable in the blue and green parts of the spectrum ( < 550 nm) or even require excitation with the UV light. The established systems used for practical applications also make use of such indicators. It is well known that short-waved excitation is accompanied by many practical difficulties which become increasingly pronounced with decreasing of the excitation wavelength. Those include interferences from the probed medium such inner filter effect, autofluorescence and light straying. Instrumental aspects should also be considered. Cheap and high qualitative optical and optoelectronic components are mostly available for the wavelength > 600 nm. Long-wave excitable sensors are thus highly advantageous; their successful development is however hindered by lack of indicators with desirable properties. The long-wave excitable state-of-the-art indicators do not fully meet the requirements for their application in luminescent sensors (such as brightness, photostability, solubility, sensitivity and suitability for immobilization). The project is focused on synthesis and characterization of novel long-wave excitable luminescent indicators with defined properties. These should be used to design sensors for dissolved oxygen, pH, as well as acidic and basic gases, which is the aim of the second part of the project. The new materials will make possible to extend the optical sensing technology to so far not realizable applications (such as subcutaneous sensing of the analytes), but also to increase the reliability of the established methods.

Optical sensors for chemical and biological parameters become increasingly popular particularly due to their simplicity and multitude of potential applications. The common formats include small microsensors for biological applications and planar optodes which can be used for imaging on surfaces. Analyte-sensitive nano- and microparticles which rely on the same principles become more and more widespread. Most optical chemosensors rely on a dye (which interacts with the analyzed species) and a matrix in which the dye is immobilized. The dye shows analyte-dependent optical properties such as coloration or luminescence, the luminescent sensors being the most common ones. Measurements with optical chemosensors are influenced by the properties of the analyzed medium which can be the source of undesired interferences by the detection of the signal. Typical optical interferences include coloration, autofluorescence and scattering. They compromise the measurements in such media as tissues or blood. The optical interferences are particularly strong if the read-out is performed in UV or visible part of the spectrum. Much less interferences are observed if the measurements are performed in the near-infrared part of the spectrum (650-1000 nm). Unfortunately, indicators which operate in this region are rare and even fewer of them are suitable for practical applications. The project was aimed at preparation and characterization of new near-infrared indicators for oxygen and acidity (pH) which belong to most important parameters. Particularly, phosphorescent platinum(II) and palladium(II) porphyrins were shown to be one of the most promising indicator dyes which now find application in several follow-up projects such as optical glucose measurements in diabetic patients and monitoring of oxygen concentration in ocean.