Preparation of Free-Standing PZT and Gold Nanoparticles
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Preparation of Free-Standing PZT and Gold Nanoparticles 1
R. N. Das
Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India 1 Cornell University, Materials Science and Engineering, Ithaca, NY-14850 ABSTRACT Free-standing PZT (Lead Zirconate Titanate ) and Gold nanoparticles (ceramic and metal) have been prepared by complex process. In case of PZT, the process involves the preparation of metal ion complex (ligand) solution followed by evaporation. Complete evaporation results in fluffy dried mass. Calcination of dried mass at low temperature produces free-standing PZT nanoparticles. The concept of the process involves choice of correct metal ion complex, stoiochiometry and drying conditions to produce free-standing individual nanoparticles. Similar process has been used to prepare free-standing gold nanoparticles where individual gold form complex with the ligands (complexing agents) to produce free-standing nanoparticles. INTRODUCTION In recent years, there has been an increasing interest in the synthesis of free-standing nanoparticles [1-5]. These materials are important due to their variety of opto and electronic properties. For example, piezoelectrics such as PZT in free-standing nanocrystalline form can act as memory bits in two- and three-dimensional information storage devices. Similarly, ZnO or other semiconductor freestanding nanoparticles have potential applications in optical devices and optical storage. Many methods have already been developed to synthesize free-standing nanoparticles and each of which have their own advantages and disadvantages. For example, colloidal chemistry [5] has been used widely to produce nanoparticles with narrow size distributions; however, from a production standpoint the yields are small. Although several methods are available for the preparation of a variety of free-standing nanoparticles, the author believes that there is scope for improvement of the existing methods, so that less cumbersome, more versatile and cost effective methods can be developed for large scale production. An effort in this direction is presented in the present paper. New strategies have been used here to produce free standing nanoparticles with narrow size distributions. In case of ceramics, rapid evaporation of metal-ion complex precursor solution followed by calcination under air atmosphere produces freestanding ceramic nanoparticles. The decomposition of complexes generates large amount of gases and the corresponding gas pressure is sufficient to separate particles from each other to produce discrete nanoparticle. For metals, nanoparticles readily form complex with the ligand (complexing agent) to avoid agglomeration. Considering the bulk of the work involved, the present investigation was restricted to the preparation of PZT (multicomponent oxides and piezoelectric materials) and gold nanoparticles .
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EXPERIMENTAL PROCEDURE Preparation of PZT nanoparticles : Free-standing nanoparticles of PZT are obtained from a binary complex mixture at
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