This review focuses on the synthesis and improvement of two types of N-containing conducting polymers – polypyrrole and polyindole – as well as an in-depth analysis of their binary and ternary nanocomposites in the treatment of contaminants, sensing, and green chemistry.

Simultaneous actuation and sensing properties of a triple layer actuator interchanging cations are presented for the first time. Thick polypyrrole (pPy)/dodecylbenzenesulfonate (DBS) films (36 μm) were electrogenerated on stainless steel electrodes. Sensing characteristics of pPy-DBS/tape/pPy-DBS triple layer artificial muscle were studied as a function of electrolyte concentration, temperature and driving current using lithium perchlorate (LiClO₄) aqueous solution as electrolyte. The chronopotentiometric responses were studied by applying consecutive square waves of currents to produce angular movements of ±45° by the free end of the triple layer. The evolution of the muscle potential (anode film versus cathode film) during current flow is a function of the studied chemical and physical variables. The electrical energy consumed to describe a constant angle is a linear function of the working temperature or of the driving electrical current, and a double logarithmic function of the electrolyte concentration. Those are the sensing functions. The cation exchanging bending triple layer actuator senses the working conditions. Similar sensing functions were described in the literature for devices interchanging anions. Irrespective of the reaction mechanism, a single electrochemo–mechanical device comprised of two reactive polymer electrodes (oxidation film and reduction film) works simultaneously as both sensor and actuator (self-sensing actuators). These are the general sensing properties of dense and biomimetic reactive gels of conducting polymers. Thus, any reactive device based on the same type of materials and reactions (batteries, smart windows, actuators, electron–ion transducers) is expected to sense surrounding conditions, as biological organs do.

Flexible, controllable, and stable electrochemical supercapacitors serving as actuators at low operating voltage combining the advantages of the high power of the dielectric capacitors and the high specific energy of rechargeable batteries are important in artificial muscle technology, hybrid electric vehicles, and in short-term power sources for mobile electronic devices [ Baughman , Science , 300 , 268 (2003) ; Winter and Brodd , Chem. Rev. (Washington, D.C.) , 104 , 4245 (2004) ; Ebron , et al. , Science , 311 , 1580 (2006) ]. High capacitance, a surprising 99% inner charge contribution and actuation in the hydrogel-assisted actuatable electrochemical supercapacitor (HAES) microfiber fabricated through wet spinning of a chitosan solution, followed by the in situ chemical polymerization of aniline was made possible through the perfect utilization of the large surface area provided by the nanostructured polyaniline grown inside as well as on the surface of the fiber. The HAES electrodes with an actuation strain of 0.33% showed <mml:math display="inline"><mml:mrow><mml:mn>703</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">F</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow></mml:math>703F∕g specific capacitance in <mml:math display="inline"><mml:mrow><mml:mn>1</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">M</mml:mi></mml:mrow></mml:math>1M methane sulfonic acid, and more than <mml:math display="inline"><mml:mrow><mml:mn>3000</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>cycles</mml:mtext></mml:mrow></mml:math>3000cycles durability. The change in impedance as well as capacitance was achieved by the controlled strain as a function of applied stress, which can establish a direct relationship between the actuation strain and specific capacitance of electrochemical supercapacitors.