Composite Electrospun Fibers Based on Sustainable and Biodegradable Polymers for Monitoring Air Pollution

Environmental monitoring is a growing concern in both developed and non-developed countries across the globe, because of the strong impact of several anthropogenic activities on both human and planet health. Air quality monitoring is usually performed with specialized equipment and analytical methods by regulatory agencies and researchers. However, in order to obtain more realistic and continuous results on the situation of pollutants distribution, EU projects guidelines report the need to involve also citizens in environmental monitoring, thus low-cost and easy-to-use technologies are required. To achieve this aim, novel sensors for environmental monitoring have been designed and developed to date to obtain reliable values comparable to those provided by standard methods and technologies. Currently, electrospinning is considered as one of the most versatile and inexpensive manufacturing technologies to design and develop nanostructured sensors to detect gases and volatile organic compounds (VOCs) in the air [1]. Sensors based on polymeric fibers look extremely attractive for the low cost and great versatility of the raw materials that can be easily tunable, according to the transducer used and the application of interest, taking part to the resulting sensing features (selectivity and sensitivity). Therefore, electrospun nanofibrous and environmentally friendly materials have been designed and fabricated for detecting some atmospheric pollutants. The attention has been focused on the challenging goal of obtaining conductive sensors for the monitoring of air pollutants employing suitable scaffolds of eco-friendly (polyhydroxybutyrate) [2] and sustainable (recycled) nanomaterials. Indeed biodegradability is a noteworthy feature to obtain sensing tools environmentally friendly and safe for health. However, sensors for gas monitoring must also be able to both persist intact for a useful shelf life and to preserve their sensing features over time, depending on the specific application and the working period. There are operative conditions where biodegradable polymers cannot be reasonably used. In these cases, some recycled plastics (as PS) can be used to develop more durable sensing materials suitable and selective for optically/electrically active molecules/particles, according to a sustainable approach. Finally, the selectivity of fibers can be tuned by introducing differently functionalized macromolecules that are sensitive to several classes of gas and VOCs. Therefore, some heterocyclic compounds (Me-tetraphenylporphyrins) [3] that resembles naturally occurring porphyrins, have been synthesized and solubilized within selected polymer blends solutions and subjected to electrospun deposition on interdigitated metal electrodes. The conductivity of the planned sensors has been implemented by adding conductive nanoparticles (e.g. graphene's flakes) in the ES-solution. The novel sensors resulted sensitive to several gas (i.e. NH3, NO2) and VOCs (i.e. aromatic hydrocarbons) with different selectivity, reporting promising sensing features potentially useful for environmental pollution monitoring.