Criteria for development of high sensitivity surface plasmon resonance (SPR) sensor depends on several factors such as types of metals, light polarization modes, light coupling techniques and thicknesses of metal film. This paper discussed the effect of light excitation wavelength ranging from ultra violet (UV) region to infrared (IR) region on SPR. Three regions have been classified such as UV region (from lambda=200nm to lambda 380nm), visible region (from lambda=400nm to lambda=633nm) and IR region (from lambda=870nm to lambda=1550nm). Noble metal gold thin film with thickness of 50nm and refractive index of n=0.1759+3.3104k was deposited on top of BK7 triangular prism (n=1.51). Very weak SPR signal was generated as the excitation wavelength was set in UV region. The signal's strength increased about 26.63% with the increment of wavelength from lambda=200nm until lambda=380nm, resulting the blue-shifting of SPR angle from 54.03 degrees to 43.48 degrees. The greatest excitation of SPP was significantly observed as the visible light region was incident through the thin film gold-coated prism represented by the abrupt decreased of R-min to 96.50% at lambda=633nm. The SPR angle was red-shifted about 0.30 degrees throughout this region. The SPR signal getting weaker as light excitation wavelength entered the IR region (from lambda=870nm to lambda=1550nm) indicated by the 64.34% inclination of R-min. In this region, the SPR angle was remain red-shifted from theta(SPR)=44.97 degrees until theta(SPR)=46.18 degrees with the average increment of 0.31 degrees for each wavelength. It can be concluded that the usage of red laser, lambda=633nm able to enhance the maximum excitation of SPP. The remarkable outcome of this work shows the vital role of light excitation wavelength in generating strong SPR signal for various application such as sensor and optoelectronic device.

This study proposed the development of hybrid Au-GO-GNP films for the enhancement of plasmon absorption in SPR sensing. Several thicknesses of Au at t=40nm, t=50nm and t=300nm were sputtered on the glass substrate. The hybridization of bilayer and trilayer films were formed by depositing GO-GNP layers and GNP-GO layers on top of various thicknesses of Au coated substrates. UV-Vis spectra analysis was conducted to characterize the plasmon absorption for each configuration. The plasmon absorption was successfully amplified by employing hybrid trilayer AuGO- GNP with the thickness of Au film was fixed at t=50nm. It is noteworthy to highlight that the employment of bilayer and trilayer configurations are the key success to enhance the SPP excitation. Au-GNP and Au-GNP-GO results no significant outcome in comparison with Au-GO and Au-GO-GNP. A redshift of the absorbance wavelength evinces the presence of GO on Au-GO sample and GNP on Au-GO-GNP sample due to the surface reconstruction. It is important to emphasize that not all bilayer and trilayer configurations able to enhance the plasmon absorption where no significant output was obtained with the hybridization order of Au-GNP and Au-GNP-GO.

Gold nanoparticles (GNPs) have been known as an excellent characteristic for Local Surface Plasmon Resonance (LSPR) sensors due to their sensitive spectral response to the local environment of the nanoparticle surface and ease of monitoring the light signal due to their strong scattering or absorption. Prior the technologies, GNPs based LSPR has been commercialized and have become a central tool for characterizing and quantifying in various field. In this review, we presented a brief introduction on the history of surface plasmon, the theory behind the surface plasmon resonance (SPR) and the principles of LSPR. We also reported on the synthetization as well of the properties of the GNPs and the applications in current LSPR sensors.