Synthesis of Citrate-Capped Sn Nanoparticles with Excellent Oxidation Resistance for High-Performance Electrically Conductive Adhesives

Tin (Sn) metallic material is one of the best-known metals and has been extensively studied due to its ease of processing, low melting point, and low cost. However, it is still challenging to synthesize high-processing performance and antioxidant Sn nanoparticles with tunable sizes. This research reported a facile, easy-to-scale-up polyol-mediated synthesis of Sn nanoparticles assisted by sodium citrates as a capping agent. The presence of citrate capping facilitated uniform nucleation of Sn nanoparticles and enhanced their antioxidant capacity and dispersion properties. These nanoparticles can remain stable against oxidation for more than 270 days in an ambient atmosphere, even under continuous heating at 200 °C for over 12 h. The citrate capping also inhibits interparticle agglomeration and allows the preparation of high-quality suspensions in water and many conventional organics. Moreover, efficient size tuning over a wide range (60 nm–1 μm) can be achieved simply by changing the Sn2+ precursor concentrations. The above-mentioned antioxidant capacity and processability allow them to combine with silver flakes in thermosetting epoxy resin as complementary conductive fillers effectively, creating conductive pathways among the silver flakes to obtain high-performance electrically conductive adhesives (ECAs). By adding Sn nanoparticles as complementary conductive fillers, the resistivity of the ECAs can be reduced to 1/6000 of that of the ECAs filled with only the same mass ratio of silver flakes, exhibiting its great potential in future electronics.