Polymers are widely used in many areas, but often their individual properties are not sufficient for use in certain applications. One of the solutions is the creation of polymer-based composites and nanocomposites. In such materials, in order to improve their properties, nanoscale particles (at least in one dimension) are dispersed in the polymer matrix. These properties include increased mechanical strength and durability, the ability to create a developed inner surface, adjustable thermal and electrical conductivity, and many others. The materials created can have a wide range of applications, such as biomimetic materials and technologies, smart materials, renewable energy sources, packaging, etc. This article reviews the usage of composites as a matrix for the optical sensors and biosensors. It highlights several methods that have been used to enhance performance and properties by optimizing the filler. It shows the main methods of combining indicator dyes with the material of the sensor matrix. Furthermore, the role of co-fillers or a hybrid filler in a polymer composite system is discussed, revealing the great potential and prospect of such matrixes in the field of fine properties tuning for advanced applications.

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This paper highlights advances made using the 4-bora-3a,4a-diaza-s-indacene (BODIPY) as a fluorophore in design and application of fluorescent sensors for microenvironment polarity. Sections of the paper cover broad analysis of a range of fluorescent indicators immobilized in ethyl-and methyl cellulose matrices. The present study demonstrates that BODIPYbased fluorescent materials could be successfully utilized for ratiometric detection of ethanol and acetone in gas phase. The achieved limit of detection value equals 0.02 mg/ml for acetone and 0.08 mg/ml for ethanol, whereas obtained sensoric materials are reusable without regeneration required.

Hybrid materials based on organically modified silica with immobilized boron-dipyrrins (BODIPY) dyes were obtained. Spectral characteristics of the dyes were measured during the matrix formation and in obtained materials. It was stated, that immobilization does not affect the character of the absorption and fluorescence spectra of the dye, but due to the effect of fluorescent molecular rotor observed for meso-substituted BODIPY, the fluorescent quantum yields were found to increase during the matrix sealing. Quantum yield increase is linear for all of the investigated matrices except phenyl-substituted one, where the π-π interactions of the dye molecule with matrix could be observed. This effect could be used for fine control of the matrix formation process and leads to increase of the dye emission in the final material for further practical applications. All obtained hybrid materials were found to be stable upon UV light irradiation, hence immobilization enhance the stability of the dye in comparison with the BODIPY in organic solvents.

Silicon dioxide thin films with organic fluorescent dyes with different amount of matrix layers were prepared by sol-gel spin coating and dripping technique, synthetic and subsequent treatment parameters were proposed for obtaining materials with high homogeneity and dye stability. The structural, morphological and optical properties of obtained materials have been studied by X-ray diffraction, atomic force microscopy and ultraviolet-visible spectroscopy. Immobilisation of the dye increases the degree of film amorphousness. Immobilisation greatly affects the spectral properties of coumarin 6 and BODIPY due to the dye protonation by acid catalyst, this effect is reversible in case of coumarin 6. Rhodamine 6G spectral characteristics are not influenced by immobilisation. In the hybrid materials monomeric form of the dyes retained at higher concentration compared with solutions. Dye immobilisation was found to increase dyes photostability.