Alternative Metallic Fillers for the Preparation of Conductive Nanoinks for Sustainable Electronics

The development of electronics with net zero carbon emissions through more efficient and environmentally friendly materials and processes is still a challenge. Here, alternative chemical synthesis routes of metal conductive nanoparticles, based on biodegradable materials are explored, such as nickel, iron–nickel alloy and iron nanoparticles, to be used, in the long term, as fillers in inks for inject printing. Thus, Ni and FeNi metal nanoparticles of 25–12 nm, forming aggregates of 614–574 nm, respectively, are synthesized in water in the presence of a polyol and a reducing agent and under microwave heating that enables a more uniform and fast heating. Iron nanoparticles of 120 ± 40 nm are synthesized in polyol that limits the aggregation and the oxidation degree. Commercial metal nanoparticles of iron and nickel, are coated with ethylene glycol and used for comparison. The conductivity of nanoparticles when pressed into pellets remains similar for both commercial and synthesized samples. However, when deposited on a strip line and heated, synthesized Ni, FeNi, and Fe nanoparticles show significant conductivity and interesting magnetic properties. It is demonstrated that the nanosize facilitates sintering at reduced temperatures and the capping agents prevent oxidation, resulting in promising conductive fillers for printed electronic applications.
B.C.P. and C.D.U. contributed equally to this work. This research wasfunded by the Spanish Ministry of Science, grant number PID2020-13480RB-I00 and TED2021-130191B-C43, and by the EU-commission,HORIZON-CL4-2021-DIGITAL-EMERGING-01 (HyPELignum), PROJECTNo.101070302 (2022-26). M.S. was supported by a Margarita Salas fel-lowship financed by the European Union-NextGenerationEU and thePlan for Recovery, Transformation and Resilience. Authors also acknowl-edge the Servicio Interdepartamental de Investigación at the Universi-dad Autónoma de Madrid, the TEM Service at the Centro de BiologíaMolecular Severo Ochoa (CBMSO, CSIC-UAM), SEM at MiNa Labora-tory (IMN, funding from CM (project S2018/NMT-4291 TEC2SPACE),MINECO (project CSIC13-4E-1794) and EU (FEDER, FSE)) and XRD, FTIR,the elemental and thermal analysis, and the characterization and growthof thin films service at ICMM/CSIC.