Post-Synthesis Crystallinity Tailoring of Water-Soluble Polymer Encapsulated CdTe Nanoparticles using Rapid Thermal Anne

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1207-N03-08

Post-Synthesis Crystallinity Tailoring of Water-Soluble Polymer Encapsulated CdTe Nanoparticles using Rapid Thermal Annealing Steven Rutledge1, Abdiaziz A. Farah1, Jordan Dinglasan2, Darren Anderson2, Anjan Das2, Jane Goh3, Cynthia Goh3, and Amr S. Helmy1* 1

The Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, 10 Kings College, Toronto, Ontario M5S 3G4 (Canada), 2 Vive Nano Incorporated, 80 St. George St, Toronto, Ontario M5S 3H6 (Canada), 3 Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario M5S 3H6 (Canada) ABSTRACT The crystallinity of colloidal CdTe nanoparticles has been enhanced post synthesis. This control over the nanoparticles’ properties has been achieved using non-adiabatic thermal processing. The technique preserves the polymer capping and hence introduces no adverse effects on the nanoparticles’ optical properties. The crystallinity is probed primarily through Raman spectroscopy in a hollow core photonic crystal fiber and x-ray diffraction powder studies. INTRODUCTION The process of rapid thermal annealing (RTA) has been applied extensively in semiconductor processing and has been demonstrated to provide numerous benefits in semiconductor systems [1]. RTA has been used to influence the photoluminescence (PL) efficiency, size dispersion and compositional intermixing for epitaxial grown or implanted quantum dots (QDs) [1,2]. However, its influence on the properties of polymer capped nanostructures has not yet been investigated. If characterized, the influence of RTA on colloidal nanostructures can present an attractive processing technique. It can be a particularly enabling processing technology as shown in the case of PEDOT-PSS thin films to influence morphological and microstructural change of this semiconducting polymer while preserving its molecular integrity [3]. NPs of numerous shapes, sizes, and compositions have been reported over the past two decades and continue to exhibit exciting optical and electrical characteristics [4]. In particular, II-VI semiconductor CdTe NPs have been demonstrated suitable for use in applications involving efficient solar cells, ultrafast electron transfer, and negative refractive index materials [5-7]. This study reports on the ability to influence the degree of crystallinity of polymer stabilized CdTe NPs using RTA. Raman spectroscopy, PL, UV-visible absorption, Xray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), have been utilized to analyze the crystalline changes in the polymer capped CdTe NPs. DISCUSSION Dried carboxylate functionalized CdTe NPs obtained from Vive Nano are annealed in inert Argon gas conditions for 30 seconds before a cool off period. The annealing temperature ranges from 200ºC to 600ºC in 100ºC increments with the ramping temperature maintained at a constant 50ºC/s gradient in all cases. All annealing is performed in an AnnealSys AS-One rapid thermal annealing system. The sample is then reweighed and dispersed in water to achieve NP concent

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