City Research Online

Abstract

Ammonia sensing is important for environmental monitoring, industrial safety, and food spoilage detection, but achieving a stable and reliable sensing response at low concentrations remains challenging. This work reports the development and optimization of a gold nanoparticle (AuNP) layer stabilized with poly(diallyldimethylammonium chloride) (PDDA) for application in optical fiber ammonia sensing. To optimize the coating process, PDDA concentrations (0.5, 0.10, and 1 wt%), molecular weights (low and medium), and AuNP deposition times (5–20 min) were systematically varied. The optimum condition, identified as 1 wt% medium-molecular-weight PDDA with a 20 min AuNP deposition, produced uniform nanoparticle coverage, enhanced interfacial stability, and a strong plasmonic response. The homogeneous distribution and surface coverage of AuNPs, as well as the adsorption of NH₃ at the AuNP/PDDA interface, were verified by FE-SEM, AFM, and FTIR. The optimized layer was applied onto an optical fiber to demonstrate its structural stability and practical sensing capability, exhibiting concentration-dependent spectral shifts upon NH₃ exposure at 0.5, 1, 5, 10, 15, 20, and 25 ppm under room temperature conditions. A sensitivity of 0.023 nm/ppm with excellent linearity (R² = 0.97) was achieved, and nitrogen-assisted desorption enabled repeatable operation. This study demonstrates that systematic material optimization provides a stable, uniform, and robust interfacial layer, supporting the potential of the AuNP/PDDA-coated optical fiber for real-world ammonia detection in environmental, industrial, and healthcare applications.

Publication Type:	Article
Additional Information:	© 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/).
Publisher Keywords:	Gold nanoparticles; Poly(diallyldimethylammonium chloride) (PDDA); Optical fiber sensor; Ammonia detection; Localized surface plasmon resonances (LSPR)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TP Chemical technology
Departments:	School of Science & Technology School of Science & Technology > Department of Engineering
SWORD Depositor:	Symplectic Administrator

Preview

Text - Published Version
Available under License Creative Commons Attribution Non-commercial No Derivatives.
Download (9MB) | Preview

Export

Downloads