Nurul Hidayat, Arif Hidayat, Latifatul Aisyah Nabila, Siti Azimatul Luthfiyyah, Ahmad Taufiq, Muhammad Safwan Abd Aziz, Hazri Bakhtiar
The integration of localized surface plasmon resonance (LSPR) effects with tapered optical fibers has significantly improved refractive index (RI) sensing performance. This study introduces an optimized RI sensor using gold nanospheres (AuNSs) coated on tapered coreless termination fibers (TCTFs), which demonstrate a remarkable improvement in sensitivity. The TCTFs were optimized in terms of their taper waist diameter through the variation of CO2 laser power. Subsequently, 11.26 nm average-sized AuNSs synthesized by citrate reduction method were strongly attached to the optimized TCTF surface via thiol-functionalization. The LSPR peak of AuNSs, recorded by ultraviolet visible spectroscopy (UV-Vis), was ∼522 nm. The face-centered cubic crystal structure and nanospherical shapes of AuNSs were respectively obtained from X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) data. Furthermore, from the field emission scanning electron microscopy (FE-SEM) image, the average thickness of the attached AuNSs on the TCTF was 88 nm. The sensitivity of the unmodified CTF sensor was 50.97 ± 4.68 nm/RIU and the AuNSs-coated TCTF was 254.42 ± 20.75 nm/RIU. In other words, it exhibited a ∼400 % improvement in RI sensitivity. Five repetitive measurements indicated that fluctuation of sensitivity was ±3.93 nm/RIU, indicating good repeatability. The stability test for 20 min showed that the sensor experienced small wavelength shift variations of ±0.362 nm for refractive indices of 1.33 and 1.39, and ±0.726 nm for refractive index of 1.43. These results established AuNSs-coated TCTFs as a promising platform for high-performance RI sensing applications. © 2025 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, Jl. Semarang 5, Malang, 65145, Indonesia; Center for Instrumentation and Sensing Technology, Universitas Negeri Malang, Jl. Semarang 5, Malang, 65145, Indonesia; Laser Center, Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, Johor, Skudai, 81310, Malaysia; Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, Johor, Skudai, 81310, Malaysia
