Aqueous Sodium Borohydride Chemistry. The Colnage Metals, Copper, Silver, and Gold.

Abstract

Sir: A previous publication describes procedures for the quantitative separation of lead and barium, of cadmium and mercury, of lead and zinc, and the semiquantitative separation of cadmium and zinc (3). Since this technique is simple and rapid and does not require elaborate equipment, the investigation was continued to develop procedures for the reduction of the coinage metals.EXPERIMENTAL Apparatus and Reagents. The pH of the solutions was determined with a Beckman Zeromatic pH meter.Sodium Borohydride.Approximately 1% aqueous solution was prepared just before use from 98+% sodium borohydride purchased from Metal Hydrides, Inc. Solution concentrations were approximated on a weight basis-for example, 1% Na-I3H4 was made by dissolving 1 gram of NaBH4 in 100 ml. of solution.Gold(III) Chloride. Stock solutions of gold chloride, approximately 0.06 7, were prepared by dissolving pure metallic gold in chlorine water and diluting to 1 liter. The 0.1 A7 solutions of copper chloride, copper nitrate, copper sulfate, and silver nitrate were standardized using established procedures described in the literature {2).Procedure.

Role of Surfactant in the Formation of Gold Nanoparticles in Aqueous Medium

“…Surfactants are used in the synthesis of gold nanoparticles when the reducing agent is not able to stabilize the particles [6]. The standard reducing agents which stabilize the gold nanoparticles in absence of any surfactant are sodium borohydride [7] and sodium citrate [8]. But for in-vivo applications these nanoparticles are of little use since the oxidised products of the reducing agents themselves show cytotoxicity [9,10].…”

Synthesis and Characterization of Silver Nanoparticles for an Undergraduate Laboratory

“…To this mixture, students were told to slowly add 25 mL of 2 mM sodium borohydride solution, taking care to add NaBH 4 slowly, where the time frame was typically of the order 1−2 min. Should a large amount of NaBH 4 be added too rapidly, one can expect a large increase in pH to occur; this has been found to cause coinage metals to precipitate from solution 15 and will prevent the formation of nanoparticles from occurring. The solution color rapidly changed from a clear solution to a light yellow, then dark yellow, brown, and then black color (Supporting Information).…”

“…Further to this, the concept of solubility of metal ions and pH can be explored, as there is reference given to the fact that sodium borohydride was once touted as a reactant that may be able to separate coinage metals based on pH. 15 …”

Synthesis of New Metallized Polyimide Films with High Optical and Physical Performances

“…The reaction of sodium borohydride with silver results in the formation of pure metal, independent of the acidity of the reduction medium and presence of ligands [26,27]. According to reaction (4) metallic copper can be formed in the film under conditions of large excess of BH 4 − ions (α = 0.1 to 0.25).…”