The Effect of Ag Concentration of Core-Shell Fe₃O₄@Ag Nanoparticles for Sensitivity Enhancement of Surface Plasmon Resonance (SPR) - Based Biosensor

Abstract

The objective of this research is to advance the affectability of Surface Plasmon Resonance (SPR) biosensor utilizing core-shell Fe3O4@Ag nanoparticles (Fe3O4@Ag NPs) with a variation of Ag concentration (20, 40, 60, 80, 100) mM. Fe3O4@Ag NPs were synthesized by the aqueous solution method. The characterization by utilizing X-ray Diffractometer (XRD) depicts that the crystal structure of Fe3O4 compares to the cubic inverse spinel structure and based on Transmission Electron Microscopy (TEM) estimation, the particle size average of Fe3O4@Ag NPs is 14.45 nm. The magnetic properties of Fe3O4@Ag NPs were evaluated by Vibrating Sample Magnetometer (VSM), the result appears that the more concentration of Ag increases, the more remanent magnetization (Mr), saturation magnetization (Ms), and coercitivity field (Hc) diminishes. In this research, a Fe3O4@Ag NPs, a spherical nanoparticle consisting of a spherical Fe3O4 core covered by an Ag shell, was used as an active material to enhance the signal detection of SPR, with a wavelength of 632.8 nm in the Kretschmann configuration. The system consists of a four-layer material, i.e., prism/Au film/ Fe3O4@Ag NPs. The results show that the SPR angle shifted to the larger angle of incident light by using Fe3O4@Ag NPs. However, the effect of Ag concentration appears that the more concentration of Ag extends, the lower angle of SPR shifts. The addition of a core-shell in the conventional SPR-based biosensor leads to the enhancement of the SPR biosensor sensitivity if the fractional volume of the core-shell is large.

Magneto-optic surface plasmon resonance properties of core-shell Fe3O4@Ag nanoparticles

“…The sensitivity of SPR sensor could be investigated by the shift phenomenon in the SPR angle. The SPR angle shift for core-shell Fe 3 O 4 @Ag NPs is greater than that of the deposition of Fe 3 O 4 and Ag NPs [37]. By using Fe 3 O 4 @Ag, the SPR angle shifts are much greater due to the higher dielectric constant [38].…”

“…The solution type of core-shell Fe 3 O 4 @Ag NPs-ethanol with the concentration of 2.5 mg ml −1 was prepared. The core-shell Fe 3 O 4 @Ag NPs were deposited on the Au thin film surface using the spray method [36,37,[47][48][49][50]. The thickness of Au film and nanoparticle was obtained by fitting in the Winspall software [50][51][52].…”

“…The magneto-optical behaviour of sample prism/Au/ Fe 3 O 4 @Ag/air in the Kretschmann configuration was investigated using the hand-made SPR spectroscopy tool [14,20,36,37,53], as shown in figure 1(a). The SPR system consists of mechanical and optical instruments, main unit (microcontroller), and computer sets [36,37].…”

“…The magneto-optical behaviour of sample prism/Au/ Fe 3 O 4 @Ag/air in the Kretschmann configuration was investigated using the hand-made SPR spectroscopy tool [14,20,36,37,53], as shown in figure 1(a). The SPR system consists of mechanical and optical instruments, main unit (microcontroller), and computer sets [36,37]. The optical instrument in the system consists of a He-Ne laser beam with the wavelength of 632.8 nm, beam splitter, a half-cylinder prism, and a pair light detector.…”

“…We recently reported the microstructural, optical properties, magnetic properties, and SPR properties of core-shell Fe 3 O 4 @Ag NPs [36,37]. The variation of Ag concentration in core-shell Fe 3 O 4 @Ag NPs leads to the modification of the SPR sensor sensitivity.…”