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Flexible screen-printing technology combined with the use of a nano/material coating for improving electrode functionalities boosted the manufacturing of highly sensitive electrochemical sensors addressing the need for fast and easy-to-handle tests in different application fields. However, due to the large-scale production and disposable and single-use nature of these devices, their environmental footprint should be taken into careful consideration. Herein, the innovative reuse of post-consumer polyethene terephthalate (PET) plastics as an alternative substrate coupled with biochar as an environmentally friendly and cost-effective modifier is described as a sustainable alternative for the production of robust electrochemical sensors. The good printability of reused plastics with graphite inks despite the chemical heterogeneity, different crystallinity, and surface roughness was demonstrated using atomic force microscopy and attenuated total reflection Fourier transform infrared spectroscopy. Functionalization with brewers' spent grain biochar enabled the fabrication of highly performing electrochemical sensors for nitrite detection in water having a limit of detection and a limit of quantification of 3.3 nM and 10.3 nM, respectively, with a linear range spanning from 0.01 to 500 μM, and good reproducibility (RSD% 8%). The innovative intervention of the biochar-multilayer system markedly enhanced the electron transfer process at the electrode interface while simultaneously serving as an absorptive material for the investigated analyte. This work lays a foundation for repurposing end-of-life plastics for the electronics industry and presents a customizable reuse strategy aimed to keep the value of plastics in the economy and reduce waste and leakage into the natural environment. [ABSTRACT FROM AUTHOR]

Chiral mesoscopic structures were obtained by Langmuir–Blodgett (LB) deposition of two tetrasteroid-porphyrins differing by the number of hydroxy groups functionalizing the steroid rings. The morphology of the porphyrin aggregates was characterized by spectroscopy (UV-Vis absorption, steady-state fluorescence, circular dichroism) and microscopy (fluorescence, scanning electrons, atomic force) techniques. Molecular Mechanics calculations were also carried out to analyze the hierarchical self-assembly process leading to the propagation of the structural properties of the tetrasteroid-porphyrin building blocks to the mesoscopic scale of the imaged chiral architectures. It has been found that, while the transfer of chiral information from the molecular to the nanoscale is determined by the winding of the tetrasteroid chains functionalizing the porphyrin scaffold, the morphology of the mesoscopic aggregates (rods or twisted ribbons) is determined by the amphiphilic (rods) or hydrophobic (ribbons) character of the outer surface of the interacting porphyrin nanostructures. [ABSTRACT FROM AUTHOR]