Current Nanoscience

Polymers play an important role in the development of materials for energy conversion and sensoristic applications because of their low cost and appealing electronic, catalytic and mechanical properties. Their nanostructuring is becoming a hot topic due to the possibility to enhance the performance of sensors and energy conversion devices where polymers are active components [1, 2]. The aim of this special issue is to focus on current research efforts in the development of nanostructured polymer materials for energy conversion and sensoristic applications with particular attention to novel materials or synthetic strategies. In a critic and comprehensive review on the nanostructuring of conducting polypyrrole (PPy) [3], a vast collection of related papers is provided for the consideration of the interested readers. Attention is paid to the electrochemical methods for deposition of polypyrrole (PPy), nanostructures and potential applications by analyzing the effect of different physico-chemical parameters, electro-oxidative conditions including template-based or template-less depositions and cathodic polymerization. Diverse interfaces and morphologies of polymer nanodeposits are addressed and discussed. The collected and discussed literature demonstrates that a simple combination between the intrinsic properties of polypyrrole, the advantages of the electropolymerization process [4] and potentiality of nanostructuring can produce high-performance PPy electrodes for technological devices, such as fuel cell, lithium batteries and supercapacitors. This review revealed that up to now, few papers deal with the performance evaluation of nanostructured polypyrrole electrodes prepared via electrodeposition, and further works are required to be published including results about real application of PPy electrodes besides the characterization. The review is aimed to encourage future research studies on these topics in order to cover the still present literature lacking in the direct application of electrodeposited PPy nanostructures as electrode. More data of energy devices employing PPy nanostructures from electrodeposition are required to build a robust database and baseline performances to compare the prospective effectiveness of the synthesis methods and to suggest the most convenient setup. An important theme is the electrochemical synthesis of conducting polymers [5] by using green solvents, such as deep eutectic solvents (DESs), a new generation of ionic liquids, promoted as “green solvents” due to their negligible volatility and inflammability, environmental benignity and wide electrochemical stability. A commonly used quaternary ammonium salt is choline chloride and hydrogen bond donors are exemplified by ethylene glycol, urea, malonic acid or glycerol. The use of these ionic media as solvents for electrochemical synthesis of conducting polymers could influence the polymer properties and reduce their economic cost. Therefore, the most recent results regarding the electropolymerization of common conductive polymers such as polypyrrole, polyaniline and poly(3,4-ethylenedioxythiophene) involving choline chloride-based ionic liquids are presented and deeply discussed. The use of these low cost eutectic mixtures based on readily available components is expected to contribute to the promotion of more sustainable technological processes easier to be developed at a larger scale. Finally, a review of thirty-six articles is dedicated to molecular imprinted photonic polymeric hydrogels/films for sensing applications devoted to a variety of analytes, such as cinchonie, melanine, estradiol [6], amino acids, glucose, caffeine, atropine, cholesterol, bisphenol A and cholic acid. The combination of artificial recognition material such as molecular imprinted polymer with highly ordered photonic crystals leads to the formation of efficient colorimetric sensors working with a visual color change. This makes them very cost effective and reduces the use of expensive analytical instruments for target recognition. A lot of work has been done in this field, but the increase of sensitivity for specific analytes and the response time are still challenging. I am grateful to the staff of Current Nanoscience for the opportunity to present this Special Issue and to the authors who contributed with their papers to the dissemination of this research theme.