Effect of Gamma-Ray Irradiation on the Growth of Au Nano-Particles Embedded in the Germano-Silicate Glass Cladding of the Silica Glass Fiber and its Surface Plasmon Resonance Response.

Seongmin Ju,Won-Taek Han

doi:10.3390/s19071666

Abstract

The effect of γ-ray irradiation on the surface plasmon resonance (SPR) sensing capability of refractive index (n = 1.418–1.448) of the silica glass optical fiber comprised of germano-silicate glass cladding embedded with Au nano-particles (NPs) was investigated. As the γ-ray irradiation increased from 1 h to 3 h with the dose rate of 1190 Gy/h, the morphology of the Au NPs and the SPR spectrum were found to change. The average diameter of Au NPs increased with the aspect ratio from 1 to 2, and the nano-particles became grown to the clusters. The SPR band wavelength shifted towards a longer wavelength with the increase of total dose of γ-ray irradiation regardless of the corresponding refractive indices. The SPR sensitivities (wavelength/refractive index unit, nm/RIU) also increased from 407 nm/RIU to 3553 nm/RIU, 1483 nm/RIU, and 2335 nm/RIU after the γ-ray irradiation at a total dose of 1190 Gy, 2380 Gy, and 3570 Gy, respectively.

Highlights

Transparent host materials embedded with noble metal nano-particles (NPs) such as Au and Ag are of great interest due to their unique characteristics of surface plasmon resonance (SPR) arising from the excitation of electron density oscillations around metal NPs [1,2,3,4,5,6,7,8,9]
The silica glass optical fiber incorporated with Au NPs in the germano-silicate glass cladding has been irradiated by 60 Co γ-rays with the dose rate of 1190 Gy/h for 1 h to 3 h at room temperature to investigate the enhancement of the SPR sensitivity and the enabling tunability of the operation range of sensing wavelength of the SPR for the refractive index sensing by controlling the size and shape of the incorporated crystalline Au NPs in the fiber cladding
As the total dose of the γ-ray irradiation increased to 1190 Gy, 2380 Gy and 3570 Gy, the average aspect ratio of the Au NPs increased from 1.0 to 1.05, 1.29, and 2.00, respectively

Summary

Introduction

Transparent host materials embedded with noble metal nano-particles (NPs) such as Au and Ag are of great interest due to their unique characteristics of surface plasmon resonance (SPR) arising from the excitation of electron density oscillations around metal NPs [1,2,3,4,5,6,7,8,9]. The localized SPR usually observed by confined colloidal, periodic, nano-systems gets resonantly excited when the wavelength of incident light is equal to the characteristic wavelength of metal NPs [10,11,12,13]. This comes from confined conduction electrons oscillating in resonance with the electromagnetic field.

Methods

Results

Discussion

Conclusion