Optimizing the Optical Properties of Functionalized Silver Nanoparticles by Size

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Many studies have focused on harnessing the extraordinary optical properties of noble metal nanoparticles for the development of biological and chemical nanosensors. Metallic nanoparticles emulate surface roughness, facilitating the coupling of light to surface plasmon polaritons. The excitation of the plasmons enhances the electromagnetic field near the surface so that minute changes in the surrounding nanoenvironment’s index of refraction induces a measurable change in the nanoparticles response to the optical field. This study endeavors to quantify the general correlation between the nanoparticle sensitivity and the aspect ratio, specified as the in-plane-width over out-of-plane height. The antidinitrophenyl (antiDNP) immunoassay was used as a model for ligand-receptor systems. The fabrication of silver triangular nanoparticles of three different out-of-plane heights was performed by nanosphere lithography (NSL). The binding of antiDNP to dinitrobenzoic acid (DNBA)- functionalized self-assembled monolayers (SAMs) upon the nanoparticle surfaces was measured with localized surface plasmon resonance (LSPR) spectroscopy. Results demonstrated that increasing the aspect ratio of nanoparticles increased extinction shift. Larger LSPR shifts correspond to greater sensitivity of the nanoparticles to adsorption of molecular analytes. LSPR measurements will allow us to develop model systems for approximating the physical properties of the optical nanosensor conducive to optimal performance.

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  • 07/17/2018
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