# Application of Organic-Inorganic Hybrids in Chemical Analysis, Bio- and Environmental Monitoring
## 2 Classification and Synthesis of Organic-Inorganic Hybrids (OIH)
### Synthesis
#### 2.2.4 Combined Method  
The last approach is an integrative approach that combines all the above-mentioned methods. Among these methods, which can generate hybrid materials with hierarchical or other types of structures in a single stage, one may include nano-molding, reactive extrusion, electrospinninging [54]. Recently, hybrid synthesis approach based on the combination of atomic layer deposition (ALD) and electrospinninging (Figure 2) has been reported [55; 56; 57].  
Electrospinning is a low-cost powerful technique that can deposit 1D organic nanofibers, such as collagen, polylactic acid (PLA), gelatine, and hyaluronic acid (HA) [54]. These materials are widely used in tissue engineering and medicine as 3D scaffolds for cell growth [56]. At the same time, these nanofibers can be a template for optical biosensor via ALD coating with photonic material [57; 58]. ALD is a method that enables to deposit a broad class of materials with controlled properties. ALD provides the capability of introducing self-limited chemical reactions which lead to the formation of an ultrathin film even for complex morphologies, such as porous structures, nanoparticles, nanotubes etc., [40].  
As recently reported, 1D electrospun polyacrylamide(PAN) nanofibers coated with a 30 nm ZnO ALD layer showed 1000-fold higher signal response versus planar ZnO nanolayers. The developed 1D ZnO hybrid nanostructures have been applied for optical gas sensing [57]. The obtained structures demonstrated high photoluminescence and great sensitivity to low ethanol concentration. ALD deposited ZnO/Al\({}_{2}\)O\({}_{3}\) nanolaminates onto the organic polymer nanofibers are a new class of photonic materials with advanced structural and optical properties [57]. ALD technology has been improved to deposit ZnO/Al\({}_{2}\)O\({}_{3}\) nanolaminate with a total thickness in the range of 20-40 nm by varying the single layer thickness from 0.5 nm to 10 nm. This methodology allowed to fabricate robust composites with high surface area and possess enhanced optical properties, which was applied for the development of biosensing photoluminescence transducers [50; 57; 58].  
The same strategy can be applied for other materials to develop OIH for the bone tissue engineering (Figure 3). However, instead of using metal oxides, as an inorganic component, and PAN, as an organic one, we have used ALD boron nitrides (BN) and a biodegradable biopolymer, i.e., gelatin [56]. It has been demonstrated that BN effectively reinforces the gelatin matrix and increases the Young's modulus. It has been also shown that the obtained hybrid is a promising nontoxic, biocompatible material for orthopedic applications [56].  
Figure 2: Schematic representation of core-shell (PAN-ZnO) fibers synthesis and results of scanning electron microscopy (SEM) analysis (original image). Note: the SEM images were obtained in the laboratory of the presented authors (SEM JEOL JSM—7001F, operating voltage—15 kV).  
Regardless of the synthesis method, wide spectra of OIH have found a great application in biosensors development with different rate of success. In this regard, it is worth to provide an overview and to classify OIH for biosensing application.