Nanoscale heterostructures comprised of silicon nanowires and gold nanoparticles encapsulated in graphitic shells for DN
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Nanoscale heterostructures comprised of silicon nanowires and gold nanoparticles encapsulated in graphitic shells for DNA immobilization Yuan Li1 and Nitin Chopra1,2 1 Metallurgical and Materials Engineering Department, Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, AL 35487, U.S.A. 2 Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, U.S.A. *Corresponding Author E mail: [email protected], Tel: 205-348-4153, Fax: 205-348-2164 ABSTRACT Deoxyribonucleic acid (DNA) immobilization on nanoscale architectures is critical for developing bio-compatible devices and clinical diagnoses. In this study, silicon nanowires (SiNWs) were combined with gold nanoparticles encapsulated in graphitic shells (GNPs). The resulting SiNWs-GNPs heterostructures were plasma oxidized to create carboxylic (-COOH) functionality on the surface of the graphitic carbon shell. These heterostructures and their surface chemistries were studied using electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. The –COOH terminated graphitic shells in heterostructures were covalently linked with DNA. The DNA molecules on these heterostructures were detected by linking with fluorescent streptavidin and observed under a fluorescence microscope. Such inorganic heterostructure-biomolecule assemblies can be very useful in the development of biomolecule analysis and detection devices. INTRODUCTION Sensitive, selective, rapid, and cost-effective analysis of biomolecules has become necessary due to an increasing demand for lab-on-chip-type analytical devices [1-3]. Deoxyribonucleic acid (DNA) can be potentially used as a building block for the assembly of nanoscale electronic devices, clinical testing, environmental monitoring, and food safety [4]. However, DNA purification and yield remains a major limitation for such applications. In addition, high cost, low efficiency, and poor repeatability of DNA binding substrates or detection devices is a challenge. This necessitates detailed study of immobilization of DNA on sensitive and selective substrates. Chemical absorption, covalent binding, electrostatic attraction, copolymerization, and streptavidin-biotin affinity systems are frequently reported methods for DNA detection [5]. Carbon nanotubes (CNTs) and graphene, the fundamental carbon-based onedimensional nanostructures, have been widely used as the backbone for DNA immobilization [69] due to their interesting properties and surface chemistries. Silicon nanowires (SiNWs) are promising one-dimensional materials for nanoscale devices and bio-nano architectures. These can be chemically-modified, have large surface-to-volume ratio, faster response, and good reproducibility [10-12]. In this study, complex heterostructures comprised of SiNWs decorated with gold nanoparticles (AuNPs) or graphene encapsulated AuNPs were fabricated. The former are referred to as SiNWs-AuNPs heterostructures and the latter are referred to as SiNWs-GNPs heterostructures. The
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