Chalcogen Nanowires: Synthesis and Properties
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Chalcogen Nanowires: Synthesis and Properties Brian T. Mayers and Younan Xia Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA - [email protected] ABSTRACT We have demonstrated a variety of solution-phase approaches for the synthesis of 1dimensional nanostructures from chalcogens such as Se and Te. These nanostructures include uniform, single crystalline nanowires and nanorods (lateral dimensions from 10 to 1000 nm, and lengths ranging from 2 to >100 µm). These nanostructures grew via a solid-solution-solid transformation mechanism, in which Se and Te atoms were transported from the less stable source (amorphous colloids) into the more stable product (trigonal phase nanocrystallites). The nanocrystallites (or seeds) were formed either through temperature driven homogeneous nucleation or by sonochemical cavitation. As directed by the highly anisotropic crystal structure, the growth could be confined to one particular direction. These nanowires could be prepared both as dispersions in various solvents or as networked arrays on solid supports. INTRODUCTION One-dimensional (1D) nanostructures - such as nanowires, rods, and tubes – have recently been the focus of intense research for their potential use as active components and/or interconnects in nanoscale electronic and electromechanical devices.[1] A rich variety of nanostructures can be generated using advanced nanolithographic techniques (e.g., electronbeam writing, X-ray lithography, proximal probe patterning, and near-field optical lithography).[2] However, these techniques can be limiting when cost, complexity (multiple steps) and throughput are the major concerns. Alternatively, chemical methods, the so-called bottom-up approach, may provide a more effective approach to 1D nanostructures in terms of cost, versatility, and potential for large-scale production.[3] Most of these methods are based on vapor-solid (VS) and vapor-liquid-solid (VLS) reactions. Notable examples include carbon nanotubes and their derivatives,[4] nanowires of metals and semiconductors,[5] and whiskers of various inorganic substances.[6] Several solution-phase procedures have recently been demonstrated for generating nanostructures such as nanowires of silicon and III-V semiconductors.[7] Unfortunately, most solution-phase methods are constrained by to their tendency to produce zero-dimensional (0D) nanostructures such as nanocrystallites or colloids. Physical templates – for example, channels in porous materials, block- copolymers or selfassembled surfactant structures – are usually required to generate nanostructures with complex morphologies.[8] Our work has been directed towards the use of materials whose crystal structures directly control the morphology of nanostructures formed through solution-phase routes. To this end, we have studied the chalcogens Se and Te as an ideal system for the formation of 1D nanostructures.[9] The anisotropic morphology of these materials is determined by the nature of their crystal structure - infinite helical ch
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