Waste PET Bottle Derived, Hierarchical Core–Shell Activated Charcoal Reinforced PET Nanofiber: A Sustainable and Scalable Closed Carbon Loop Solution for Formaldehyde Sensing

Formaldehyde (HCHO) and PET disposal are significant environmental issues. Synthesizing activated charcoal and electrospun PET nanofiber mats using waste plastic bottles as carbon precursors has potential for formaldehyde sensing. Solvent-based electrospinning produces recycled PET nanofibers, with varying amounts of AC loading (0–1.25 Wt%). The material properties of these NF mats were determined by Scanning Electron Microscopy (SEM), Transmission Electron Spectroscopy (TEM), Infrared spectroscopy (IR), Tensile testing, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), and Water Contact Angle (WCA). The NF film mat with an AC content of 0.75 Wt% exhibited the best current response, which in turn was fabricated to form a resistive sensor of HCHO by Electrochemical Impedance Spectroscopy (EIS). The prepared sensor exhibited an extensive dynamic response range (1–300 ppm) with low limit of detection (0.352 ppm), ultrasensitivity, excellent selectivity, and reproducibility. The electrospinning technique to generate PET nanofiber mats and ionothermal synthesis of N-doped AC, from used PET bottles, other than being an easy and ultrasensitive platform for formaldehyde sensing, will also achieve maintaining a closed carbon loop. The flexible sensing platform has the capability to function as a suitable carrier for immobilizing other biological or harmful chemical entities as recognition elements on the surface of electrospinning nanofibers, paving the way for the development of additional electrospun nanofibers to establish ultrasensitive sensors with favorable sensitivity and analytical performance. Other than that, this sensor can be utilized for detecting HCHO in adulterated milk samples, juices, and other liquid food products.