| Noble metal nanoparticles exhibit unique localized surface plasmon resonance(LSPR) properties, which exhibit strong absorption band in the spectrum in the Vis-NIRspectra. The frequencies and intensities of LSPR are affected not only by the dielectricproperties of the surrounding media but also by the composition, size and shape of thenanoparticles. For gold nanorods, two LSPR bands could be observed, one associatedwith the transverse mode (510-535nm) and the other with the longitudinal mode. Thelongitudinal plasmon wavelength of gold nanorods is more sensitive to the changes in thedielectric properties of the surroundings. Therefore, the synthetic and analysis applicationof LSPR of nanorods have attracted much attention. In this paper, we mainly researchnanorods self-assembled on glass, by changing the way the assembly, aspect ratio ofnanorods and the thickness of the silver shell on the gold core and examining thebehavior of nanorods self-assembled on glass, to tune sensitivity of the nanorodsimmobilized on glass. We develop LSPR biosensors with high sensitivity, good stability,simple and rapid method for label-free bioanalytical based on nanorods self-assembledon glass.The main contents and results are as follows:The first section, develop nanorods self-assembled on glassNanorods are immobilized on glass substrates using direct growth method andself-assembly method. In the experiment, the morphology and the behavior of LSPR ofnanorods was characterized by transmission electron microscopy, scanning electronmicroscopy and extinction spectra. Experimental results show that nanorods consistently well separate from each other and the yield of nanorods is lower. However, taking theadvantages of self-assembly manner, the nanorods are randomly distributed onto thesubstrates. Moreover, these nanorods consistently well separately from each other andrarely coupled between adjacent particles. Therefore, the LSPR band in extinctionspectrum should be sharper and more intense. The LSPR peak of Au NRs on glasssubstrates was red-shifted with increasing aspect ratio by comparing the aspect ratio of2.8and4.5of gold nanorods. Also, we examined the effect of thickness of silver shell onthe behavior of LSPR of the Au@Ag NRs on glass substrates. The LSPR band inextinction spectrum was blue-shifted with the increasing thickness of Ag shell. Theresearch results have laid a good foundation for nanorods used in biosensors.The second section, the research and compare of the performance of LSPRsensor based on nanorods immobilized on glassGold nanorods and Au-Ag core-shell nanorods self-assembled on glass was used tobuild biosensors and the effect of BSA on the behavior of LSPR was examined. Also, thebiotin–streptavidin scheme was used as a model system to investigate the affinity assaysfor nanorods on glass. We examine the effect of materials and aspect ratio on the LSPRperformance.The research results are as follows:(1)Nanorods self-assembled on glass have agood LSPR response for protein molecules;(2)The RI sensitivity of Au@Ag NRs onglass substrate of287nm/RIU was enhanced almost30per cent than that of Au NRs (Aucore) on glass substrate, which indicates the RI sensitivity of noble bimetallicnanoparticles is higher than single metal nanoparticles;(3)The biotin-NRs on glasssubstrates have a high sensitive response to streptavidin and the red-shift of the LSPRpeak linearly increased with increasing SA concentration. The linear range of Au@AgNRs to SA concentration is from9.46×1011to1.72×10-6mol·L-1with a detection limit(S/N=3) of3.5×10-11mol·L-1. The results show bimetallic core-shell structure has asynergistic effect, which can effectively improve the LSPR sensitivity response to thesurrounding medium and get a good performance of the biosensor. The research results have laid a good foundation for nanorods of gold and silverself-assembled on glassapplied in LSPR biosensors. |
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