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Key Parameter Controlling the Sensitivity of Plasmonic Metal Nanoparticles: Aspect Ratio

Research paper by Assad U. Khan, Shuqi Zhao, Guoliang Liu

Indexed on: 23 Aug '16Published on: 09 Aug '16Published in: Journal of Physical Chemistry C



Abstract

Currently the synthesis of plasmonic nanoparticles for sensing applications mostly focuses on their shape because it is believed that nanoparticles with sharp tips provide higher sensitivities than those without. Herein, by measuring and analyzing the sensitivities of more than 74 types of nanoparticles of various shapes, sizes, and compositions, we found that, contrary to this common belief, the correlation between shape and sensitivity is much weaker than that between aspect ratio and sensitivity. Among all the parameters investigated here, including size, shape, composition, aspect ratio, cross-sectional area, and initial plasmonic resonance frequency, the aspect ratio (R) is the key parameter that controls the nanoparticle sensitivity (S) following an empirical equation, S = 46.87R + 109.37. Other parameters have much less influence on the nanoparticle sensitivity to refractive index changes. The stronger dependence of the sensitivity on aspect ratio than on shape encourages us to reassess the current focus of nanoparticle synthesis chemistry. In addition, the S–R linear relationship determined here can be used as a design rule for future synthesis and fabrication of highly sensitive nanomaterials for chemical, biological, biomedical, and environmental sensing.

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