Nanosized silver powder via reduction of silver nitrate by sodium formaldehydesulfoxylate in acidic pH medium

Nanosized silver powder is prepared by using sodium formaldehydesulfoxylate (SFS) as reducing agent in acidic pH, typically between 1 and 5. The use sodium formaldehydesulfoxylate of (SFS, HOCH2SO2Na.2H(2)O)is attempted for the first time in aq. formaldehyde (HCHO). The oxidation of formaldehyde to formate ion by silver ion is thought to be the key to control the reduction of silver ion to zero valent silver particles. The entire reaction is completed at pH less than 5, while final silver powder is precipitated, the pH of the reaction medium is measured to be less than 2. The powder is flaky, amorphous or crystalline depending upon the experimental conditions and ratio between the silver nitrate and reducing agent. The powder is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)/EDAX. SEM indicates the nanosized powder with majority in the range of 100 nm and EDAX analysis indicate the theoretical silver percentage. (C) 2002 Elsevier Science B.V. All rights reserved.