A simple route for manufacturing highly dispersed silver nanoparticles
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Highly dispersed uniform silver nanoparticles were prepared by reducing silver diamine ions [Ag(NH3)2]+ with D-glucose in the presence of a stabilizing agent. Along with the nature of the dispersing agent, the pH and the temperature of the reaction had the most pronounced effect on the reduction rate, the nucleation of the metallic phase, and ultimately the size and dispersion of the resulting particles. Through suitable manipulations of these parameters, it was possible to prepare uniform Ag nanoparticles ranging in size from 30 to 120 nm. A rapid and complete reduction of the silver species was possible only at elevated pH and temperatures above 50 °C. The reduction of silver diamine ions in these conditions caused the complete cleavage of the C–C bond, resulting in the release of 12 electrons per molecule of D-glucose. It was also found that the addition of ammonia to an already acidified silver nitrate solution leads to the formation of a much more stable and safe-to-handle diamine complex.
I. INTRODUCTION
Due to its unique properties, colloidal silver is widely used in catalysis,1 chemical sensing and biosensing,2,3 photonics,4 electronics,5,6 optics,7 DNA sequencing,8 surface-enhanced Raman spectroscopy,9,10 and pharmaceuticals.11,12 The diversity and importance of these applications has generated a great deal of interest in developing versatile methods to synthesize silver nanoparticles with well-defined and controlled properties. The list of approaches used to date includes reduction in solutions13,14; chemical and photochemical reactions in reverse micelles15; thermal decomposition of silver compounds16; radiation-assisted,17,18 electrochemical,19 sonochemical,20 and microwave-assisted21,22 processes; and, recently, biosynthesis using living plant systems.23,24 The reduction in homogeneous solutions has been for a long time the most attractive method for preparing highly dispersed metallic particles,25–27 with the reducing agents most widely used being formaldehyde,28 alkali metals in ammonia,29 inorganic and organic borohydrides, 30 ascorbic acid, 31 free radicals, 32 monoalcohols,33,34 polyols,35,36 acetonitrile,37 hydrazine,38 citrate, or ethylenediaminetetraacetic acid.39 Because many of the reducing agents, solvents, and additives used in the reduction process often pose severe environmental and biological risks, it is important to develop “ecofriendly” precipitation processes especially for the largea)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0308 2488 J. Mater. Res., Vol. 22, No. 9, Sep 2007 http://journals.cambridge.org Downloaded: 01 Sep 2014
scale production of these materials. Considering the rather limited choices of water-soluble precursor silver compounds, most attempts to provide “green” chemistries have been focused on selecting benign solvents, reductants, and stabilization agents. Following this strategy, Raveendran et al.40 have described an environmentally friendly procedure for preparing silver nanoparticles using water as a sol
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