NANOCRYSTALS – SYNTHESIS, CHARACTERIZATION AND APPLICATIONS pot

NANOCRYSTALS – SYNTHESIS, CHARACTERIZATION AND APPLICATIONS Edited by Sudheer Neralla Nanocrystals – Synthesis, Characterization and Applications http://dx.doi.org/10.5772/2560 Edited by Sudheer Neralla Contributors Noelio Oliveira Dantas, Ernesto Soares de Freitas Neto, Peter Petrik, P. Vengadesh, Ricardo Souza da Silva, Ernesto Soares de Freitas Neto, Noelio Oliveira Dantas, Igor Yu. Denisyuk, Julia A. Burunkova, Sandor Kokenyesi, Vera G. Bulgakova, Mari Iv. Fokina, Chengjun Zhou, Qinglin Wu, Anurag Srivastava, Neha Tyagi, Liang-Yih Chen, Hung-Lung Chou, Ching-Hsiang Chen, Chia-Hung Tseng, Xuejun Zhang, Fuxing Gan Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2012 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Dragana Manestar Typesetting InTech Prepress, Novi Sad Cover InTech Design Team First published August, 2012 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechopen.com Nanocrystals – Synthesis, Characterization and Applications, Edited by Sudheer Neralla p. cm. ISBN 978-953-51-0714-9 Contents Preface IX Chapter 1 Carrier Dynamics and Magneto-Optical Properties of Cd 1-x Mn x S Nanoparticles 1 Noelio Oliveira Dantas and Ernesto Soares de Freitas Neto Chapter 2 Characterization of Nanocrystals Using Spectroscopic Ellipsometry 29 Peter Petrik Chapter 3 Localized Nano-Environment for Integration and Optimum Functionalization of Chlorophyll-a Molecules 41 P. Vengadesh Chapter 4 Optical, Magnetic, and Structural Properties of Semiconductor and Semimagnetic Nanocrystals 61 Ricardo Souza da Silva, Ernesto Soares de Freitas Neto and Noelio Oliveira Dantas Chapter 5 Optical Nanocomposites Based on High Nanoparticles Concentration and Its Holographic Application 81 Igor Yu. Denisyuk, Julia A. Burunkova, Sandor Kokenyesi, Vera G. Bulgakova and Mari Iv. Fokina Chapter 6 Recent Development in Applications of Cellulose Nanocrystals for Advanced Polymer-Based Nanocomposites by Novel Fabrication Strategies 103 Chengjun Zhou and Qinglin Wu Chapter 7 Semiconductor Nanocrystals 121 Anurag Srivastava and Neha Tyagi Chapter 8 Surface Modification of CdSe and CdS Quantum Dots-Experimental and Density Function Theory Investigation 149 Liang-Yih Chen, Hung-Lung Chou, Ching-Hsiang Chen and Chia-Hung Tseng VI Contents Chapter 9 The Synthesis of Nano-Crystalline Metal Oxides by Solution Method 169 Xuejun Zhang and Fuxing Gan Preface This book provides an overview of the synthesis and characterization of nanocrystals. Nanocrystals, owing to their unique behavior with reduction in size, have been a significant part of the novel materials developed for applications such as biosensors, optics, catalysts to semiconductor devices. Over the years, various synthesis methods are discovered to develop nanostructures with tunable properties such as optical, electronic magnetic and mechanical properties. The chapters in this book cover a broad range of properties of nanocrystals synthesized for various applications. Chapter 1 discusses optical absorption and photoluminescence properties of Cd 1-xMnxS nanoparticles grown by the melting-nucleation synthesis approach. The difference in magneto-optical behavior of nanocrystals and quantum dots are discussed. A spectroscopic ellipsometry method used to characterize nanocrystals is described in chapter 2. The basics, measurable nanocrystal properties and range applications of spectroscopic ellipsometry are explained in this chapter. Chapter 3 presents an overview of the density function theory (DFT) software used for the calculations of different periodic and non-periodic systems. Density of crystal structures and spectroscopic properties of nanoparticles are evaluated. In chapter 4, fabrication of photovoltaic device using carboxymethyl cellulose and Chlorophyll-a nanocrystals and Bacteriorhodopsin is explained. Spectroscopic and photoelectric properties are analyzed to evaluate the material suitability. Chapter 5 presents an overview of optical, magnetic and structural properties Cd 1-xMnxS, Pb1-xMnxS, Zn1-xMnxO nanocrystals grown by fusion and co-precipitation methods. Effect of secondary phase on the properties of the nanocrystals is studied using x-ray diffraction and Raman spectroscopic analysis of the nanocrystals. Chapter 6 describes UV-curable nanocomposite materials with self-writing properties like light self-focusing and light induced nanoparticle redistribution. Mechanical, optical properties of these ZnO based nanocomposites are studied and explained in detail. The developments in the applications of cellulose nanocrystals (CNC) in nanocomposites prepared by gelation and electrospinning are reported in chapter 7. Nanocomposite fibers containing CNC are synthesized using electrospinning. Chapter 8 discusses various applications of semiconductor nanocrystals, their synthesis and electronic, structural, optical, magnetic and mechanical properties. Structural transformation of nanocrystals under pressure is studied. Chapter 9 presents an overview of surface modification of X Preface colloidal semiconductor CdS and CdSe quantum dots using organic ligands and their characterization using time-resolved photoluminescence (TRPL) spectroscopy and density function theory (DFT). I believe our contribution provides a significant value to the science and technology community resulting in more discoveries in diverse fields implementing nanotechnology. Dr. Sudheer Neralla NSF-Engineering Research Center North Carolina A&T State University Greensboro, USA [...]... unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited 2 Nanocrystals – Synthesis, Characterization and Applications Although the dot doped with impurities (metal and magnetic) are currently being synthesized by colloidal chemistry techniques [13,14], some possible applications require the nanoparticles (NPs) being embedded in robust and transparent host... differences in the quantum confinements of these QDs that would cause shifts in the OA band peaks Thus, it was concluded that the observed blue shift in OA band peak 4 Nanocrystals – Synthesis, Characterization and Applications (Fig 1a) was a consequence of the sp-d exchange interactions between electrons confined in dot states and those located in the partially filled Mn2+ states This explanation is reasonable... and (EB’) for the Mn2+ ions 14 Nanocrystals – Synthesis, Characterization and Applications The non-radiative energy transfers from NPs to Mn2+ions are related to the following activation energies: EC for the QDs; and EB’ for the bulk-like NCs In Table I, it can be seen that EC increases and EB decreases with rising x-concentration This opposite behavior between QDs and bulk-like NCs demonstrates that... the Eb emission from bulk-like NCs The non-radiative processes associated to the VCd – VS divacancies occurring in the structures are also indicated 18 Nanocrystals – Synthesis, Characterization and Applications The characteristic emissions 4T1 → 6A1 between levels of Mn2+ ions, labelled as E(Mn2+) in Figs 6b and 6c and with transition energy ~2.12 eV, also confirm that these magnetic impurities were... shape of the emission band around 480 nm at low temperatures confirms the presence of shallow virtual levels for the QDs, and evidently there is also for the bulk-like NCs, as depicted in Fig 2c However, this emission 6 Nanocrystals – Synthesis, Characterization and Applications band (480 nm) becomes symmetric with rising temperature, which demonstrates that the trapped carriers in the virtual levels... intensity of the bulk-like NCs 12 Nanocrystals – Synthesis, Characterization and Applications Figure 4 Experimental integrated PL intensity of Cd1-xMnxS NPs as a function of reciprocal temperature: (a) x = 0.000; (b) x = 0.005; (c) x = 0.050; and (d) x = 0.100 Each panel shows the fitting curves for the specified equations For the undoped NPs (x = 0), only a PL emission band associated with the bulk-like... represented by filled and opened symbols in Fig 8, respectively For QD emissions,  ( B) increases almost linearly up to B = 15 T, and reaches 25% polarization The 22 Nanocrystals – Synthesis, Characterization and Applications bulk-like NC emissions appear to increase quadratically with B and, at higher magnetic fields, show a saturation tendency near 35% However, the degree of polarization for CdS bulk-like... This shift can be ascribed to two possible annealing effects: (i) the size increase of the magnetic dot and thus, inducing weakening on the quantum confinement, and (ii) the decrease in the 16 Nanocrystals – Synthesis, Characterization and Applications effective concentration of Mn2+ ions incorporated into the dots during growth thus, inducing decreasing on the energy gap The dot size increase for... A, B, C, A’, and B’ In Eqs (1) and (2), both the radiative emissions from QDs and bulk-like NCs and all non-radiative energy transfers are QD and highlighted In steady-state conditions, the laser excitations are given by g  N1 0   r b g '  N1 0   rb for QDs and bulk-like NCs, respectively Moreover, there are no temporal changes in the carrier numbers, i.e.,  dN1 T  dt   0 and  dN b 1... increasing magnetic field values Notice that magnetic doping affects strongly the magnetic dependence of these intensities 20 Nanocrystals – Synthesis, Characterization and Applications Hence, in our samples is also expected that the electron-hole radiative recombinations (EQD and Eb) show increasing intensities while the E(Mn2+) emissions show decreasing change of intensities for increasing magnetic . NANOCRYSTALS – SYNTHESIS, CHARACTERIZATION AND APPLICATIONS Edited by Sudheer Neralla Nanocrystals – Synthesis, Characterization and Applications http://dx.doi.org/10.5772/2560. would cause shifts in the OA band peaks. Thus, it was concluded that the observed blue shift in OA band peak Nanocrystals – Synthesis, Characterization and Applications 4 (Fig. 1a) was. for the QDs, and evidently there is also for the bulk-like NCs, as depicted in Fig. 2c. However, this emission Nanocrystals – Synthesis, Characterization and Applications 6 band (480 nm)