Self‐Assembly Silver Nanoparticles Decorated on Gold Nanoislands for Label‐Free Localized Surface Plasmon Resonance Biosensing

Abstract

scattering and unique surface plasmon absorption spectrum induced by the coherent oscillation form the basis of utilization of LSPR effect in surface-enhanced Raman spectroscopy, [1,3] photoelectronic devices, [4] biosensing, [5] thermoplasmonics, [6] plasmonic filter, [7,8] and photocatalysis. [9] Among the applications, LSPR biosensors as an efficient and reliable platform in clinical biomolecule detection have gained extensive interest due to their ability to conduct measurements in a labelfree and real-time manner. [10] In affinitybased target-specific LSPR biosensing, the local refractive index (RI) changes when diverse biological receptors immobilized on the surface of the nanostructure, e.g., aptamer, antibody, and enzyme react with the targets of interest, which leads to the variation of surface plasmon wave. In this way, LSPR biosensors are capable to detect specific analytes.It is reported that electromagnetic (EM) near-field enhancement due to coupling of EM wave can be induced by metal nanostructures with the configurations of narrow gaps [11][12][13][14] and structures with small radius of curvature, [15][16][17] such as nanoparticles, nanobranches, and nanodendrites. The intensified EM near-field enhanced by the coupling effect, also known as hot spots, has been intensively investigated in both experiments and computer simulations. [18] The hot spots are confined within only a tiny region of nanometer length scale near the surface of the nanostructure and decays exponentially thereafter. [19] It is reported that the hot spots possess higher sensitivity to local changes of RI and the presence of local binding events over other locations due to the coupled resonance effect. [11,18,20] In order to improve the sensitivity of the LSPR biosensor, one of the strategies is to make use of the hot spots and generate efficient overlap between localized nearfields and target. Kim and co-workers [21] have proved that the SPR detection limit (LOD) of sensing biotin-streptavidin can be improved by more than two orders of magnitude through selective functionalization at the hot spots. In our previous studies, the gold nanoislands (AuNIs) were developed as a promising LSPR nanostructure. [22][23][24] They provided better biosensing sensitivity, and with dielectric functionalization also possible at the gaps. It was also shown, through finite difference time domain A nanostructure of self-assembly silver nanoparticles decorated on gold nanoislands (SAM Ag@AuNIs) is proposed in this article as a sensitive sensing medium for localized surface plasmon resonance (LSPR) biosensing applications. A wide tunable plasmonic sensing range from 472 to 552 nm is found by adjusting the Au-Ag atomic ratio. Biotin is employed as an indicator to investigate the potential biosensing applicability and site-specific bioactivity of the SAM Ag@AuNIs. In virtue of a white light common-path sensing system, direct adsorption of biotin on the SAM Ag@AuNIs is measured in label-free manner with detection limit (LOD) of 2.9 pg mL −1 (11.87 × 10 ...

Smart Nanostructured Materials for SARS-CoV-2 and Variants Prevention, Biosensing and Vaccination

“…Plasmonic Au and Ag nanostructures have been used in biosensors due to their excellent optical properties and widely tunable LSPR positions from visible to near-infrared regions [ 130 , 131 , 132 ]. Compared with Au nanostructures, Ag nanomaterials have stronger LSPR and therefore are more favorable in developing high-performance biosensors [ 133 , 134 , 135 , 136 ]. However, Ag nanostructures are not stable compared to materials made of Au because Ag are susceptible to oxidizers and can be easily oxidized to cations at ambient conditions.…”

Triangular Silver Nanoparticles Synthesis: Investigating Potential Application in Materials and Biosensing

“…Due to their properties, AgNPs are recognized as efficient optical sensors for pesticide residues detection [41]. Moreover, the nanostructure of silver nanoparticles decorated on gold nanoparticles was reported as a sensitive medium for localized surface LSPR biosensing applications [42].…”