Electroless Synthesis of 1.4 nm Pd and Pt Nanoparticles on Self-Assembled Rosette Nanotubes
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Electroless Synthesis of 1.4 nm Pd and Pt Nanoparticles on Self-Assembled Rosette Nanotubes Rahul Chhabra and Hicham Fenniri* National Institute for Nanotechnology, Department of Chemistry, University of Alberta Edmonton, AB, T6G 2M9 Canada ABSTRACT Electroless synthesis and hierarchical organization of 1.4 nm Pd and Pt nanoparticles (NPs) on self-assembled Rosette Nanotubes (RNTs) is described. The nucleated NPs are nearly monodisperse and reveal supramolecular organizations guided by RNT templates. Interestingly, the narrow size distribution is attributable to unique templating behavior of RNTs. The resulting metal NP-RNT composites were characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). X-ray Photoelectron Spectroscopy (XPS) was also performed to confirm the nature and composition of RNT-templated NPs. INTRODUCTION Owing to their unique optical, electronic and catalytic properties, metal nanoparticles have received significant interests from researchers worldwide [1]. These properties vary in large with size, shape and composition of metal NPs [2]. Therefore, effective strategies to build tailored NPs in reliable and predictable fashions are highly desirable. In general, methods including chemical reduction of metal salts are very prominent; however, lack of reproducibility and polydispersity of synthesized NPs limit their versatility [3]. Recently, molecular templates that control the dimensions of NPs in situ during chemical synthesis have shown huge potential in controlling the size of metal NPs [4]. Biomolecular templates like DNA [5], peptides [6], proteins [7] and virus [8] were also being investigated for their size-controlled synthesis. Biomolecular templates also offer additional advantage of organizing these NPs in orderly fashions due to their inherent molecular recognition properties [9]. We herein describe RNTs as guiding templates for one-pot electroless synthesis and hierarchical organization of 1.4 nm Pd and Pt NPs. RNTs, due to their unique templating nature, nucleate nearly monodisperse NPs of diverse metals. RNTs are new class of biocompatible nanomaterials obtained by the self-assembly of synthetic DNA hybrid, a G∧C base [10]. The G∧C base mimics the hydrogen bonding pattern of Guanine and Cytosine. Under physiological conditions, six G∧C bases self-assemble to form a supermacrocycle called a ‘rosette’ (figure 1B) which in turn stacks on each other to form helical RNTs (figure 1C). RNTs form tubular nanoarchitectures with an internal channel spanning a diameter of 1.1 nm. Previously, our group has demonstrated that RNTs self-assembled from twin G∧C base form stable and longer nanotubes due to enhanced hydrogen bonding capabilities and reduced electrostatic interactions [11]. Therefore, in present studies, RNTs self-assembled from twin G∧C base have been utilized (figure 1A). Due to supramolecular organization of the G∧C base, any functional group that is chemically anchored to the G∧C base will end up being displayed o
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