Self-assembly of gold nanoparticles to silver microspheres as highly efficient 3D SERS substrates
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NANO EXPRESS
Open Access
Self-assembly of gold nanoparticles to silver microspheres as highly efficient 3D SERS substrates Shouhui Chen1,2†, Peng Huang2†, Zhihua Wang2, Zhe Wang2, Magdalena Swierczewska2, Gang Niu2, Daxiang Cui1* and Xiaoyuan Chen2*
Abstract Herein we report a simple, one-pot, surfactant-free synthesis of 3D Ag microspheres (AgMSs) in aqueous phase at room temperature. The 3D AgMSs act as supports to fix the gold nanoparticles (GNPs) in 3D space via the interaction between the carboxyl groups of GNPs and the Ag atoms of AgMSs. The ensemble of AgMSs@GNPs with high surface-enhanced Raman scattering (SERS) activity and sensitivity can be an ideal 3D substrate choice for practical SERS detection applications. The simple self-assembly strategy may be extended to other metallic materials with great potentials in SERS, catalysis, and photoelectronic devices. Keywords: Self-assembly, Gold nanoparticles, Silver microspheres, SERS
Background Ensembles of inorganic nanoparticles, which display unique collective properties that are different from those of both the individual nanoparticles and bulk materials, are of much scientific and technological interest [1-5]. The ensembles have the following potential advantages: (1) to display new electronic, magnetic, and optical properties as a result of interactions between the excitons, magnetic moments, or surface plasmons of individual nanoparticles; (2) to improve the mechanical properties of composite materials; and (3) to allow multiple tasks to be performed simultaneously or in sequence. Typically, the self-assembly of noble-metal nanoparticles has attracted much attention because of their unique plasmon resonance and their tremendous applications in the area of optical waveguides [6], superlensing [7], photon detection [8], and surfaceenhanced Raman scattering (SERS) [9-12]. Recently, the * Correspondence: [email protected]; [email protected] † Equal contributors 1 Department of Bio-Nano-Science and Engineering, National Key Laboratory of Nano/Micro Fabrication Technology, Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Institute of Micro-Nano Science and Technology, Shanghai JiaoTong University, Shanghai 200240, China 2 Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, MD 20892, USA
SERS effect based on noble-metal ensembles is of particular interest because of its extraordinary ability to detect a wide variety of chemical/biological species at extremely low concentrations even down to the singlemolecule level [9]. Gold nanoparticles (GNPs) have been widely used as Raman active substrates because of their good biocompatibility and strong SERS enhancement [13-18]. However, it should be mentioned that the particles tend to aggregate during aging, which results in an unwanted reduction of the active surface area [19,20]. To address this issue, the fixation of GNPs in one-dimensional (1D), 2D, or 3D spaces
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