**3.5 Summary and perspectives**

With the development of nanotechnology, CP nanostructures integrated into advanced electronics have pursuit of better sensing systems during the past decade for fabricating miniaturizing state-of-the-art sensor devices, due to their continuously discovered unique chemical and physical characteristics, such as reversible signal transduction processes, low operating temperature, tunable sensitivity, and design flexibility. However, sensing technologies based on CPs still require significant incubation and device development. From the viewpoint of sensing activity, control over CP characteristics is necessary to improve sensitivity, selectivity, and stability to design advanced detection sensors. The desired set of physicochemical properties can be introduced into the CPs through the rational molecular design of specific receptors or judicious functionalization of the CP surface with a molecular recognition, leading to enhanced specificity via covalent attachments and reproducibility in response. Also, for large-scale synthesis, it is important to develop reliable routes to synthesize CP nanostructures and nanocomposites with controlled morphology. Of the exciting synthetic methods, the soft template approach is somewhat advantageous in both large-scale synthesis and size/shape control. Such improvements in their molecular structure and crystallinity and an increase in conjugation length are crucial for increasing room temperature conductivity. Another concern is that CPs are also susceptible to environmental perturbations such as moisture, heat, and light, which may degrade over time, even in dry, oxygen-free environments, and thus much attention must be paid to improving their long-term stability that is considered to be an important factor in pursuing high sensor reliability for an ever-increasing role in online environmental monitoring, industrial safety control, and security. Since the fabrication of nanostructured CPs, response time and sensitivity have experienced impressive improvements with great advances in sensor nanotechnology. However, selectivity is still a challenging task for detecting specific target analyte in a multi-analyte environment which hindered the widespread application of CP-based sensors. Besides, the demand for miniaturization has encouraged for designing portable sensor devices, lower power dissipation, and better device integration. In this sense, nanostructured CPs have considerable potential for fabricating miniaturized multi-sensing arrays by using microcontact printing, surface-directed assembly, site-specific polymerization, inkjet printing, etc. Interestingly, CPs are highly compatible with a flexible substrate, which opens up the possibility of realizing all-polymer electronics. From viewpoint, we believe that nanostructured CPs still have many unexplored potentials and will definitely play an expanding role in future sensor technology for exclusively designing of next-generation sensors involving high sensitivity, high reliability, multi-analyte determination, miniaturization, and structural flexibility due to their fascinating chemical/physical properties that are not available in other materials. Thus, it is anticipated that extensive future research studies into the development of flexible high-performance sensors by utilizing CPs will be expected in the near future.

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**Author details**

Nagy L. Torad1

and Mohamad M. Ayad1,2\*

Technology (E-JUST), New Borg El-Arab City, Alexandria, Egypt

\*Address all correspondence to: mohamad.ayad@ejust.edu.eg

and mohamed.ayad@science.tanta.edu.eg

provided the original work is properly cited.

1 Chemistry Department, Faculty of Science, University of Tanta, Tanta, Egypt

2 Institute of Basic and Applied Sciences, Egypt-Japan University of Science and

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Gas Sensors Based on Conducting Polymers DOI: http://dx.doi.org/10.5772/intechopen.89888* *Gas Sensors Based on Conducting Polymers DOI: http://dx.doi.org/10.5772/intechopen.89888*

*Gas Sensors*

**3.5 Summary and perspectives**

Novel low-humidity sensors were investigated by the in situ photopolymerization of PPY/Ag/TiO2 nanoparticle composite thin film coating on QCM [224]. Room temperature highly sensitive sensors with short response/recovery time for humidity based on GO/SnO2/PANI and PANI-GO coating on QCM were explored by Zhang et al. [225, 226]. The adsorption process of water molecules on QCM senor was carefully discussed using Langmuir adsorption isotherm model.

With the development of nanotechnology, CP nanostructures integrated into advanced electronics have pursuit of better sensing systems during the past decade for fabricating miniaturizing state-of-the-art sensor devices, due to their continuously discovered unique chemical and physical characteristics, such as reversible signal transduction processes, low operating temperature, tunable sensitivity, and design flexibility. However, sensing technologies based on CPs still require significant incubation and device development. From the viewpoint of sensing activity, control over CP characteristics is necessary to improve sensitivity, selectivity, and stability to design advanced detection sensors. The desired set of physicochemical properties can be introduced into the CPs through the rational molecular design of specific receptors or judicious functionalization of the CP surface with a molecular recognition, leading to enhanced specificity via covalent attachments and reproducibility in response. Also, for large-scale synthesis, it is important to develop reliable routes to synthesize CP nanostructures and nanocomposites with controlled morphology. Of the exciting synthetic methods, the soft template approach is somewhat advantageous in both large-scale synthesis and size/shape control. Such improvements in their molecular structure and crystallinity and an increase in conjugation length are crucial for increasing room temperature conductivity. Another concern is that CPs are also susceptible to environmental perturbations such as moisture, heat, and light, which may degrade over time, even in dry, oxygen-free environments, and thus much attention must be paid to improving their long-term stability that is considered to be an important factor in pursuing high sensor reliability for an ever-increasing role in online environmental monitoring, industrial safety control, and security. Since the fabrication of nanostructured CPs, response time and sensitivity have experienced impressive improvements with great advances in sensor nanotechnology. However, selectivity is still a challenging task for detecting specific target analyte in a multi-analyte environment which hindered the widespread application of CP-based sensors. Besides, the demand for miniaturization has encouraged for designing portable sensor devices, lower power dissipation, and better device integration. In this sense, nanostructured CPs have considerable potential for fabricating miniaturized multi-sensing arrays by using microcontact printing, surface-directed assembly, site-specific polymerization, inkjet printing, etc. Interestingly, CPs are highly compatible with a flexible substrate, which opens up the possibility of realizing all-polymer electronics. From viewpoint, we believe that nanostructured CPs still have many unexplored potentials and will definitely play an expanding role in future sensor technology for exclusively designing of next-generation sensors involving high sensitivity, high reliability, multi-analyte determination, miniaturization, and structural flexibility due to their fascinating chemical/physical properties that are not available in other materials. Thus, it is anticipated that extensive future research studies into the development of flexible high-performance sensors by utilizing CPs will be expected

**140**

in the near future.
