Although the two sets of NPs gave almost identical LODs, initial position of the LSPR band was tuned in the cyan to green region (~500 nm) displayed a substantially more distinct color change from orange to red, as revealed by the by naked eye. Upon addition of SEA large red shifts of the LSPR band were observed spectroscopically and the limits of detection (LOD) were estimated to 0.2 nM and 0.4 nM for respectively. The two parti-cle systems were subsequently applied as transducers to spectroscopically and visually detect anti-SEA antibody – SEA interac-tions.
In this work, we aimed at synthesizing two types of NPs based on compositionally complex core-shell NPs – Ag shell on AuNPs and Ag inside gold nanoshell By controlling the thickness of the shells as well as their surface chemistry with anti-SEA antibody, the LSPR band was tuned to near 495 and 520 nm, respectively. Dual plasmonic AuCu2-x S core-shell nanorods (NRs) have been fabricated by using a hydrothermal method and plasmon-coupled effect between the Au core and Cu2-x S shell in the near-infrared (NIR) region.Finally, the enhanced photothermal effect of AuCu 2x S NRs has been demonstrated. If the initial position of the LSPR band is located in the cyan region, even a small red shift (~2 3 nm) induced by Refractive index (RI) change close to the surface of nanoparticles (NPs), could make the light absorp-tion transit from cyan to green and become visually detectable via a concomitant change in the complementary colors. The calculated coupled coefficients between SPR of the Cu 2x S shell and LSPR of the Au NRs is 180 meV, which is much stronger than that of TSPR of Au NRs of 55 meV. Herein, this unique feature was employed to build up a homogeneous optical biosensor to detect staphylococcal enterotoxin A (SEA) in solution down to very low levels by naked eye readout. The Localized Surface Plasmon Resonance (LSPR) phenomenon provides a versatile property for biodetection.
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