New Research in Physics

Concave-Tip Lab-on-Fiber Based on Localized Surface Plasmon Resonance for Simultaneous Refractive Index and Temperature Sensing

Authors

Mohammad Mahdi Babakhani fard
Mohammad Ismail Zibaii
Soroush Rostami

Shahid Beheshti University

https://doi.org/10.66224/jmrph.10.1.71
Abstract
Fiber optic biosensors are highly effective tools for early disease diagnosis due to their exceptional sensitivity and low detection limit of biological samples. Label-free sensors based on refractive index (RI) variation measurements exhibit enhanced sensitivity and selectivity when integrated with localized surface plasmon resonance (LSPR) technology. In this study, a dual LSPR fiber optic sensor based on a concave-tip structure combined with hybrid nanoparticles (NPs) of gold nanoparticles (AuNPs) and gold@silver core-shell NPs (CSNPs) is developed for simultaneous detection of RI and temperature. The RI sensitivity of sensors functionalized with AuNPs and CSNPs was measured at 1845.71 nm/RIU and 1984.58 nm/RIU within the RI range of 1.3332 to 1.3604 RIU, respectively. For the dual LSPR sensor incorporating hybrid NPs, the RI sensitivities corresponding to the two resonance wavelengths were found to be 1567.67 nm/RIU and 1787.73 nm/RIU. The slight reduction in sensitivity compared to single NP configurations is due to a decrease in surface NP density, which is negligible. A critical challenge in fiber optic sensor operation is the influence of temperature fluctuations on measurement accuracy. To address this issue, the temperature sensitivity of the dual LSPR sensor was measured in the range 20–50°C, resulting SAu = –1.2 nm/°C and SCS = –1.32 nm/°C for AuNPs and CSNPs, respectively. To mitigate cross-sensitivity, a sensitivity matrix was employed, enabling accurate simultaneous measurement of RI and temperature. These results demonstrate that the developed lab-on-fiber sensor is a promising candidate for dual-parameter monitoring in label-free fiber optic biosensing applications.

Keywords

Lab-on-fiber
label-free
refractive index
temperature
localized surface plasmon resonance (LSPR)
core-shell nanoparticle
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New Research in Physics
Volume 10, Issue 1 - Serial Number 18
September 2025
Pages 71-81

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