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Poly(aspartic acid) (PASP) is a biodegradable, biocompatible water-soluble synthetic anionic polypeptide. PASP has shown a strong affinity and thus robust complexation with heavy and alkaline earth metal ions, from which several applications are currently benefiting, and several more could also originate. This paper discusses different areas where the ion chelation ability of PASP has thus far been exploited. Due to its calcium chelation ability, PASP prevents precipitation of calcium salts and hence is widely used as an effective scale inhibitor in industry. Due to potassium chelation, PASP prevents precipitation of potassium tartrate and is employed as an efficient and edible stabilizer for wine preservation. Due to iron chelation, PASP inhibits corrosion of steel surfaces in harsh environments. Due to chelation, PASP can also enhance stability of various colloidal systems that contain metal ions. The chelation ability of PASP alleviated the toxicity of heavy metals in Zebrafish, inhibited the formation of kidney stones and dissolved calcium phosphate which is the main mineral of the calcified vasculature. These findings and beyond, along with the biocompatibility and biodegradability of the polymer could direct future investigations towards chelation therapy by PASP and other novel and undiscovered areas where metal ions play a key role., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

In this paper, we presented the fabrication and properties of new ammonia (NH 3 ) sensors with sensitive layer of nickel nanoparticles decorated on three-dimensional nitrogen-doped graphene-based frameworks/polyaniline (NiNPs@3D-(N)GFs/PANI) hybrid. The hybrid are synthesized through in-situ oxidative polymerization on flexible thin substrate. Synergetic behavior between both components manifested outstanding sensitivity (750.2 at 1000 ppm NH 3 ) and quick response (95 s) and recovery (25 s) times and a lower limit of detection (~ 45 ppb) at room temperature. The sensitivity of NiNPs@3D-(N)GFs/PANI hybrid sensor was shown to be about 14 times more than its of pure PANI sensor at 1000 ppm of NH 3 . The excellent sensitivity of the as-prepared hybrid is mainly originated from the substantial rise of hole-like carriers by NiNPs@3D-(N)GFs as well as improved inter-molecule interactions via π- π electron networks. The obtained results revealed significant advantages for the synthesized hybrid sensor, making it a suitable choice for real-world applications of NH 3 detection., (Copyright © 2019 Elsevier B.V. All rights reserved.)