Low-Temperature Sintering of l-Alanine-Functionalized Metallic Copper Particles Affording Conductive Films with Excellent Oxidative Stability

Abstract

Here, the alpha amino acid l -alanine is employed as both a capping and stabilizing agent in the aqueous synthesis of submicron-sized metallic copper particles under ambient atmospheric conditions. The reduction of the copper(II) precursor is achieved using l -ascorbic acid (vitamin C) as the reducing agent. The nature of the complex formed between l -alanine and the copper(II) precursor, pH of the medium, temperature, and the relative proportion of capping agent are found to play a significant role in determining the size, shape, and oxidative stability of the resulting particles. The adsorbed l -alanine is shown to act as a barrier imparting excellent thermal stability to capped copper particles, delaying the onset of temperature-induced aerial oxidation. The stability of the particles is complemented by highly favorable sintering conditions, rendering the formation of conductive copper films at significantly lower temperatures ( T ≤ 120 °C) compared to alternative preparation methods. The resulting copper films are well-passivated by residual surface l -alanine molecules, promoting long-term stability without hindering the surface chemistry of the copper film as evidenced by the catalytic activity. Contrary to the popular belief that ligands with long carbon chains are best for providing stability, these findings demonstrate that very small ligands can provide highly effective stability to copper without significantly deteriorating its functionality while facilitating low-temperature sintering, which is a key requirement for emerging flexible electronic applications.

Reprogramming Filamentous fd Viruses to Capture Copper Ions

“…Moreover, C and N peaks were detected on these whitish areas showing the co‐existence of phage organic material. It is well known that Cu(II) ions can be easily oxidized under ambient conditions in the presence of moisture and oxygen [39] . These mineralized structures are most probably an oxidized form of Cu which were grown on engineered phage filaments due to the presence of Cu5 peptide variants on virus surfaces.…”

“…It is well known that Cu(II) ions can be easily oxidized under ambient conditions in the presence of moisture and oxygen. [39] These mineralized structures are most probably an oxidized form of Cu which were grown on engineered phage filaments due to the presence of Cu5 peptide variants on virus surfaces. Presumably, the peptides acted as nucleation points to trigger the mineralization process.…”

Study on the preparation of ascorbic acid reduced ultrafine copper powders in the presence of different protectants and the properties of copper powders based on methionine protection

“…Y. Shun et al 18 synthesized nanoscale (Cu NPs) and micrometer-sized Cu particles (Cu MPs) with narrow size distributions using ascorbic acid as a reductant and citric acid as a complexing agent and discussed their growth mechanisms; N. Kumar et al 19 synthesized copper nanoparticles in aqueous media using l -cysteine as a capping and functionalizing agent; H. J. Pereira et al 20 used l -alanine as a capping layer and stabilizer for the aqueous synthesis of submicron-sized copper metal particles under ambient conditions and found the nature of complex formation between l -alanine and the copper( ii ) precursor and demonstrated that l -alanine acted as an effective barrier on the surface of the copper particles conferring good thermal stability and delaying the onset of oxidation.…”