Assembly of Ag@Au Nanoparticles Using Complementery Stranded DNA Molecules and Their Detection Using UV-Vis and RAMAN Sp
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Assembly of Ag@Au Nanoparticles Using Complementary Stranded DNA Molecules and Their Detection Using UV-Vis and Raman Spectroscopic Techniques. Derrick Mott, Nguyen T. B. Thuy, Yoshiya Aoki, and Shinya Maenosono. School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan ABSTRACT Silver nanoparticles coated by a layer of gold (Ag@Au) have received much attention because of their potential application as ultra sensitive probes for the detection of biologically important molecules such as DNA, proteins, amino acids and many others. However, the ability to control the size, shape, and monodispersity of the Ag@Au structure has met with limited success. In our own research we have addressed this challenge by creating an aqueous wet chemical synthesis technique towards size and shape controllable Ag@Au nanoparticles. These materials are highly interesting because of the tunable silver core size, and the tunable gold shell thickness, opening many avenues to the modification of the particle properties in terms of biomolecular sensing. The resulting nanoparticle probes were functionalized with two complementary stranded DNA oligonucleotides. When combined, the complementary strands hybridized, causing the Ag@Au nanoparticles to assemble into large nano-structures. The presence of the oligonucleotide was confirmed through a series of techniques including UV-Vis and Raman spectroscopy, as well as TEM, XPS, DLS, and many others. The results reflect the role that the nanoparticle physical properties play in the detection of the bio-molecules, as well as elucidate the characteristics of the bio-molecule/nanoparticle interaction. INTRODUCTION To date there have been several attempts to detect DNA using nanoparticles as sensitive probes [1]. Such detection techniques often rely on assembly of complementary stranded NPs (Ag, Au or Ag@Au NPs) and their subsequent hybridization which is detected by colorimetric techniques or by labeling of the nanoparticles with a reporter label which can then be detected using Raman Spectroscopy [1]. These techniques open the doors to the ultra-sensitive detection of DNA using nanoparticle probes, but there is still much work to be done in understanding the nanoparticle probe properties themselves. Both silver and gold nanoparticles (NPs) have received wide attention for their enhanced properties in a multitude of potential applications such as sensing, microelectronics, and catalysis, [2,3] because of the many desirable chemical and physical properties of the materials. In terms of bio-diagnostics and sensing, it is the optical properties that make Ag NPs exceptional, while for Au NPs it is the resistance to oxidation and enhanced thiol chemistry that is attractive [1,4]. The current trend in this area of research is the coupling of these two materials as a core@shell structure that takes advantage of the optical properties of silver and the stability/thiol chemistry of gold. These Ag@Au nanoparticles are expected to ha
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