Green synthesis of CdSe/ZnS core-shell quantum dot nanophosphors and its Poly methyl methacrylate composite thin film in
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Green synthesis of CdSe/ZnS core-shell quantum dot nanophosphors and its Poly methyl methacrylate composite thin film in the visible spectral range Sneha Mohan 1,2, Theertha Soman2, Samuel. O. Oluwafemi1*, Soney. C. George 3, Patrice Miska 4, 5 , Didier Rouxel 4, 5, Nandakumar Kalarikkal 2, 6, Sabu Thomas2, 7 1
Department of Chemistry, Cape-Peninsula University of Technology, P.O. Box 652, Capetown, 8000, South Africa. E-mail: [email protected] 2 International and Interuniversity Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala- 686560, India. 3 Amal Jyothi College of Engineering, Kanjirappally, Kottayam, Kerala- 686560. 4 Université de Lorraine, Institut Jean Lamour, Vandoeuvre-lès-Nancy, F-54500, France. 5 CNRS, UMR 7198, Vandoeuvre-lès-Nancy, F-54500, France. 6 School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, Kerala 686560, India. 7 School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala-686560, India. ABSTRACT We herein report the synthesis of highly-fluorescent CdSe/ZnS core-shell quantum dots (QDs) nanophosphors via a simple, non-phosphine and one pot synthetic method in the absence of an inert atmosphere. The as-prepared nanocrystallites were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis) and photoluminescence spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The obtained CdSe/ZnS QDs were of high quality with sharp absorption peaks, bright luminescence, narrow emission width and high PL quantum yield (up to 74 %) without any size sorting. The structural analysis showed that the as-synthesised QDs are small and spherical in shape with narrow size distributions while the presence of the lattice fringe in the HRTEM image confirmed the crystallinity of the material. The dispersion of the obtained core-shell QDs in PMMA matrix resulted in the fabrication of highly fluorescent PMMA- CdSe/ZnS core shell QDs polymer nanocomposite film. INTRODUCTION Semiconductor nanocrystallites due to their quantum confinement effect possess unique physical and optical properties, which have attracted researchers since the last two decades. The interest in fluorescent semiconducting nanocrystals have increased due to their technological applications as absorption filters, chemical sensors, light emitting diodes and in biotechnology to mention a few [1-5]. Core-shell composite quantum dots exhibit novel properties which make them attractive from both an experimental and practical point of view. Over coating nanocrystallites with higher band gap inorganic materials passivate the surface nonradiative recombination sites and thus increase the quantum yield of the nanocrystals. Previous studies have shown that particles passivated in this way are more robust and have greater tolerance to processing conditions necessary for incorporation into solid state structures [6-7]. In CdSe /ZnS core-shell QDs, the band gap of the core lies energetically within the band gap of
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