Nanowire formation is preceded by nanotube growth in templated electrodeposition of cobalt hybrid nanostructures

Fabrication of Co-Sb Junction Nanowires by Galvanostatic Electrodeposition

This work presents the synthesis of CoSb3 one-dimensional (1D) thermoelectric nanomaterials using electrodeposition under galvanostatic conditions and polycarbonate membranes as a template (50 nm diameter pores). Cyclic voltammetry measurements have been performed to get preliminary information on the electrochemical reduction process of the involved species. Different current density values in the range 1-4 mA cm-2 have been applied, leading to the formation of nanowires (NWs) and micro- and nanomushroom caps, as evidenced by the scanning electron microscopy and scanning transmission electron microscopy investigations. Through fine-tuning of the current density the desired Co/Sb atomic ratio could be achieved. Energy-dispersive X-ray spectroscopy analysis showed the formation of CoSb3 at 1.4 mA cm-2, and it has also been confirmed by high-resolution transmission electron microscopy and micro-Raman spectroscopy. In this work, we present for the first time the fabrication of a CoSb3-CoxSby heterojunction on the same NW exhibiting Sb-rich and Co-rich alloy segments, prepared by electrodeposition from the same electrolyte by simply varying the applied current density.

Removal of Heavy Metals from Wastewaters: A Challenge from Current Treatment Methods to Nanotechnology Applications

Removing heavy metals from wastewaters is a challenging process that requires constant attention and monitoring, as heavy metals are major wastewater pollutants that are not biodegradable and thus accumulate in the ecosystem. In addition, the persistent nature, toxicity and accumulation of heavy metal ions in the human body have become the driving force for searching new and more efficient water treatment technologies to reduce the concentration of heavy metal in waters. Because the conventional techniques will not be able to keep up with the growing demand for lower heavy metals levels in drinking water and wastewaters, it is becoming increasingly challenging to implement technologically advanced alternative water treatments. Nanotechnology offers a number of advantages compared to other methods. Nanomaterials are more efficient in terms of cost and volume, and many process mechanisms are better and faster at nanoscale. Although nanomaterials have already proved themselves in water technology, there are specific challenges related to their stability, toxicity and recovery, which led to innovations to counteract them. Taking into account the multidisciplinary research of water treatment for the removal of heavy metals, the present review provides an updated report on the main technologies and materials used for the removal of heavy metals with an emphasis on nanoscale materials and processes involved in the heavy metals removal and detection.