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One-Step Controlled Synthesis of Size-Tunable Toroidal Gold Particles for Biochemical Sensing

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journal contribution
posted on 05.12.2019, 19:33 by Phuong-Diem Nguyen, Xuanru Zhang, Judith Su
Controlling the size and shape of nanoparticles is a major goal in materials science. Here we show the fast, 30 min, controlled one-step synthesis of gold particles (tAUPs) with sizes tunable from 350 nm to 1.7 μm by using a mixture of surfactant scaffolds made from sodium dodecyl sulfate (SDS) and cetyltrimethyl­ammonium bromide (CTAB). The as-synthesized tAUPs have nanospikes that protrude either inward or outward from the ring cavity. The number of nanospikes can be tuned by a two-step temperature change process to create so-called rough tAUPs. The toroidal gold particle structures exhibit surface plasmon extinction peaks in the near-infrared region and demonstrate a high surface-enhanced Raman scattering (SERS) sensitivity for the detection of 4-mercaptobenzoic acid (4-MBA) molecules. The protruding nanospikes significantly enhance the electromagnetic field oscillating inside the ring cavity. This is confirmed through sensitive detection of 4-MBA molecules as well as by simulation. Rough tAUP structures generate the highest sensitivity with an estimated total enhancement (TE) factor of 3.33 × 106, which is 2 orders of magnitude greater than reported by gold nanostars. A variety of different gold structures such as gold nanodendrites, nanowires, and nanochains can be obtained by changing the SDS to CTAB concentration ratios. The unique structures and plasmonic properties of tAUPs hold promise for ultrasensitive biochemical sensing.