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Silver Nanoparticle Surface Enabled Self-Assembly of Organic Dye Molecules

Department of Chemistry, School of Computer, Mathematical and Natural Sciences, Morgan State University, Baltimore, MD 21251, USA
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Materials 2019, 12(16), 2592; https://doi.org/10.3390/ma12162592
Received: 30 July 2019 / Revised: 9 August 2019 / Accepted: 13 August 2019 / Published: 14 August 2019
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Abstract

Fluorescence titration of methylene blue, rhodamine B and rhodamine 6G (R6G) by silver nanoparticle (AgNP) all resulted in an initial steep quenching curve followed with a sharp turn and a much flatter quenching curve. At the turn, there are about 200,000 dye molecules per a single AgNP, signifying self-assembly of approximately 36-layers of dye molecules on the surface of the AgNP to form a micelle-like structure. These fluorescence-quenching curves fit to a mathematical model with an exponential term due to molecular self-assembly on AgNP surface, or we termed it “self-assembly shielding effect”, and a Stern-Volmer term (nanoparticle surface enhanced quenching). Such a “super-quenching” by AgNP can only be attributed to “pre-concentration” of the dye molecules on the nanoparticle surface that yields the formation of micelle-like self-assembly, resulting in great fluorescence quenching. Overall, the fluorescence quenching titration reveals three different types of interactions of dye molecules on AgNP surface: 1) self-assembly (methylene blue, rhodamine B and R6G), 2) absorption/tight interaction (tryptamine and fluorescein), and 3) loose interaction (eosin Y). We attribute the formation of micelle-like self-assembly of these three dye molecules on AgNP to their positive charge, possession of nitrogen atoms, and with relatively large and flat aromatic moieties. View Full-Text
Keywords: silver nanoparticle; self-assembly; fluorescence quenching; self-assembly shielding effect; fluorescent organic molecules silver nanoparticle; self-assembly; fluorescence quenching; self-assembly shielding effect; fluorescent organic molecules
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Deng, H.; Yu, H. Silver Nanoparticle Surface Enabled Self-Assembly of Organic Dye Molecules. Materials 2019, 12, 2592.

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