Electrodeposition as a Synthesis Strategy for Controlled Morphologies and Alloy Compositions

Abstract

The research work aims at developing controlled morphologies, compositions and crystallinity of bismuth and tin-bismuth (Sn-Bi) alloys by electrodeposition. Nano- and micro-structured bismuth morphologies have been synthesized for ultratrace detection of lead, cadmium, and zinc. Controlled compositions and smooth morphologies of Sn-Bi alloys have been electrodeposited for potential application as lead-free solder alloys for integrated circuit packaging. Hexagon-shaped bismuth nano- and micro-architectures have been electrodeposited onto polycrystalline copper electrodes from a nitrate bath at both constant current and constant potential conditions. Hexagonal geometries of varying sizes are obtained by tuning the deposition rate vis-à-vis that of a competing reaction, nitrate reduction. Nano-hexagons (100 nm to 1 and#956;m) have been obtained at 10 mA cmand#8722;2 when the HNO3 concentration is 0.2 M or less, and with 0.4 M HNO3, hexagons of sizes up to 20 and#956;m have been deposited. The ability of the obtained bismuth morphologies to detect ultratrace levels of lead has been studied. Only the nanohexagons and crystallites are able to detect lead at 1 ppb. The nanohexagons show good sensitivity towards the detection of lead (Sensitivity: ~0.75 and#956;A ppband#8722;1) with a detection limit of 0.05 ppb using Square-Wave Anodic Stripping Voltammetry (SWASV), and clearly distinct peaks for Pb2+, Zn2+, and Cd2+, indicating the usefulness of this morphology as an electrode material for simultaneous detection of analytes. A systematic examination has been carried out regarding the effects of bath additives and deposition conditions on the rates of electrodeposition of bismuth, obtained morphologies, and the ability of the bismuth films to detect trace concentrations of lead. Novel morphologies of bismuth are reported for the first time. The bath comprises bismuth nitrate, HNO3, and a set of additives, viz., citric acid (complexant), poly(vinyl alcohol) (surface inhibitor), and betaine (grain refiner). ...