# Application of Organic-Inorganic Hybrids in Chemical Analysis, Bio- and Environmental Monitoring
## 1 Introduction  
Development of novel materials for chemical analysis and biosensor application is one of the most significant challenges in today's science and technology. Novel developed platforms applied for biosensors and chemical analyses are mostly produced from inorganic materials [1; 2; 3]. However, in some cases, where it is significantly important to use specific mechanical (e.g., flexibility) or optical (e.g., transmittance) properties, these developed materials should also include organic components, and as a consequence, specific polymeric and/or (bio)receptors are used. The possibility of combining properties of inorganic (e.g., high charge-carrier mobility, mechanical and thermal stability) and organic (e.g., low cost, flexibility, facile tuning of optical and electrical properties) components in a novel composite material with unique features has been a tremendous challenge for a long period. Organic-inorganic hybrids (OIH) consist of two or more different components, typically inorganic material (metal/semiconductor/dielectric particle or bulk component) and organic components which could be organic functional groups or molecules, biomolecules, polymers, etc., [4; 5; 6; 7; 8]. These components are attached together by specific interactions that result in the synergistic enhancement of their specific properties. OIH have attracted a lot of attention in the fields of ceramics [9], polymer chemistry [10], organic and inorganic chemistry [11], physics and material engineering [12; 13]. Interestingly, paint pigments, i.e., Prussian Blue (iron(III) hexacyanoferrate) dispersed in organic solvents can be readily considered to be the earliest representatives of organic-inorganic hybrids [14]. However, the \"organic-inorganic hybrid\" concept appeared only in the 1980s with the development of soft inorganic chemistry [14]. Since that time, the preparation, characterization, and applications of organic-inorganic hybrids have become a fast expanding area of research in materials and life science,nanotechnology, bio- and environmental monitoring. For instance, the above-mentioned Prussian Blue has been successfully employed in biosensor development because of its selective ability toward hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) reduction in the presence of O\({}_{2}\) as a product of enzymatic activity [15]. In the past years OIH were developed on a large scale with a lot of applications in analytical chemistry, and in bio- and environmental monitoring [16; 17; 18]. One may note the tremendous increase in the number of publications and patents relating to the development of novel OIH. Such composites may be casted into thin films [19; 20], nanofibers [21], nanoparticles [22], porous materials [23], and hierarchical nanostructures [24], which is extremely important, for instance, to design effective biosensing platforms with quick read-out capabilities for biomedicine and environmental applications. Recently, considerable efforts have been made toward the development of electrochemical transducers for glucose detection which finds applications for diagnostic purposes, viz., point of care or in the food and beverage industry. The possibility to use OIH based on gold (Au)-chitosan nanoparticles (NPs) [25], and nanofilms [26] was demonstrated for efficient detection of glucose at different concentration range. In these OIH, chitosan provides a biocompatible environment and temperature-related harsh physiological conditions. On the other hand, Au-NPs enhance the overall system stability, catalytic activity, and facilitate the electron transfer for hydrogen peroxide removal. The same effect was shown for another OIH based on polyaniline-Au-NPs [27]. Recently, Pt-porphyrin-encapsulated polylactic acid (PLA) NPs were synthesized and glucose biosensors with an improved detection range were developed [28]. Apart from glucose biosensors, OIH materials are widely used for the detection of cancer biomarkers [29], toxins [30], and ions of heavy metals [31].