Nanoscale materials synthesis. 1. Solvent effects on hydridoborate reduction of copper ions

The reduction of CuBr2 by NaBH4 in a variety of solvents yields nanoscale m etallic copper as the primary product. Although the product of this reactio n is largely solvent independent, the studies show that reaction times, the total volume of gaseous products, and nanoscale particle sizes are depende nt on solvent properties. The reaction occurred instantaneously in polar, p rotic, and acidic solvents such as methanol and ethanol. In contrast, in po lar, aprotic, and coordinating solvents such as tetrahydrofuran and acetoni trile, the reaction was slow. Particle sizes increased as the rate of react ion decreased. For solvents in which similar reaction times were observed, the reaction carried out in polar, aprotic, and coordinating solvents yield ed copper samples with larger particle sizes. The acid propel-ties of the s olvent controlled the amount of gas evolved in these experiments.