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Lookup NU author(s): Professor Gavin RichardsonORCiD, Dr Priscila MeloORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Glycine is the smallest nonessential amino acid in humans and animals, a basic building block with a crucial role on several physiological events. Despite its simplicity, glycine presents three polymorphs – α, β, and γ- with distinct functional properties. While α-glycine is widely used in pharmaceuticals, β- and γ-glycine have found a place in energy harvesting due to their non-centrosymmetric structure and therefore notable piezoelectricity. β-glycine polymorph shows remarkable out-of-plane piezoelectricity (d16 = 178 pm.V−1), comparable to traditional piezoceramics like barium titanate or lead zirconate, whereas γ-glycine demonstrates superior in-plane piezoelectricity (d33 = 10.4 pm.V−1) comparable to biological materials (0.1–10 pm.V−1). Advances in polymorph synthesis and stabilization enabled the fabrication of glycine-based piezoelectric (PENGs) and piezo-triboelectric nanogenerators (PTENGs) with favourable features such as enhanced flexibility, integrability, and electromechanical coupling. In this review, we delineate glycine polymorphism, relative stability, and crystallization methods, with a special focus on strategies to stabilize specific polymorphs in view of enhancing its piezoelectric activity. Furthermore, the interaction of glycine with hydrophilic polymers is explored to develop biodegradable nanogenerators. The development of glycine-based PENGs and PTENGs is presented, with detailed examination of the piezoelectric and triboelectric mechanisms illustrating the beneficial effects of incorporating glycine. These approaches bring the performance of organic-based PTENGs closer to ceramic-based nanogenerators. Emergent applications encompassing sensors for physiological processes and electromechanical energy conversion devices such as ultrasound-induced drug delivery and electrotherapy are reviewed along their performance in vitro and in vivo. Finally, we discuss the advantages,limitations, and future progresses forthese devices. Overall, this review provides a comprehensive overview of glycine research, offering a solid foundation to further its utilization in the field of green energy.
Author(s): Nascimento L, Richardson GD, Melo P, Barroca N
Publication type: Article
Publication status: Published
Journal: Chemical Engineering Journal
Year: 2025
Volume: 510
Print publication date: 01/04/2025
Online publication date: 14/03/2025
Acceptance date: 11/03/2025
Date deposited: 31/03/2025
ISSN (print): 1385-8947
ISSN (electronic): 1873-3212
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.cej.2025.161514
DOI: 10.1016/j.cej.2025.161514
Data Access Statement: No data was used for the research described in the article.
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