# Application of Organic-Inorganic Hybrids in Chemical Analysis, Bio- and Environmental Monitoring
## 4 The Role of Nanoanalytics and Nanometrology in Biosensors/Nanobiosensors Development  
The unique properties of OIH make this class of materials popular in various application fields, including chemical analysis, SERS, biosensors, nanobiosensors, electrochemical sensors, spectroscopic sensor development, ELISA, immunoassay, molecular imprinted polymers (MIPs), etc. Meanwhile, there is still a great gap between nanohybrids development and their applications in the laboratory and industry. The reason for this situation is the absence of standardization procedures, poor validation, and metrology of the nano-based hybrid materials utilized for chemical analysis and biosensors development. \"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be\" ([PERSON], 1883) [78]. Today this concept can be summarized as follows: \"To measure is equal to know.\" In this regard, metrology as a global science of measurements and nanometrology as a part of metrology related to measurements at the nanoscale can directly affect our understanding of novel analytical systems. Unfortunately, the analysis of the literature data for the last two decades indicates a clear lack of metrology at the nano-scale as a scientific standardization approach, see Figure 5A,B. However, the literature search related to the simple term \"nanohybrids\" revealed more than 16,600 scientific papers (Figure 5C) published during the same time evidencing the importance and significant impact of this research field in modern science. Remarkably, the term nanometrology was already introduced in 2007 but the general guidelines toward nanomaterials validation and standardization in general and organic-inorganic nanohybrids (OInH) as a case study still do not exist. Moreover, the current challenges in nanometrology can be summarized as follows: (i) absence of new measurement platforms, test analytical methods, and methodologies working at the nanoscale; (ii) lack of analytical reference materials and documentation standards; (iii) lack of metrological traceability of the measurement that reduces confidence in the accuracy of our analyses and predictions; (iv) measurements in complex environments, i.e., biological matrices, presence of buffers, detergents, or other compounds interfering with a measured signal species (in case of biosensors-electrochemical species). Obviously, the standardization of nanohybrids is necessary not only to improve our scientific understanding of the underlying fundamental processes responsible for the generated analytical signals, but is also closely linked to the quality control concepts of the systems to promote their  
Figure 5: The number of cited papers related to the terms highlighted above per year: (**(A)** Organic-inorganic hybrids metrology; (**B**) Nanometrology in hybrid materials; (**C**) Nanohybrids). Preliminary figures for the present decades indicate the relevance of the research field. (_Compiled from the Web of Knowledge database search (www.webofknowledge.com), Nov. 2019_). industrial applications. Thus, the general role of nanometrology can be summarized by the following formula [79; 80; 81; 82; 83; 84; 85]:  
\[\text{NM}=\text{SU}+\text{QC}+\text{Ap},\]  
where NM--nanometrology; SU--improved scientific understanding on the object; QC--quality control; Ap--application. Nanometrology plays a crucial role in the production process of nanomaterials and devices with a high degree of accuracy and reliability for different applications. Not accepting this fact can lead to serious mistakes in evaluating results. A current challenge in nanometrology is to establish the criteria for reliability and accuracy of nanomaterials in general and OInH as a case study followed by protocols and approaches to measure them.