Green-synthesized superparamagnetic and biocompatible Fe₃O₄ nanoparticles for memristive and synaptic bioelectronics

Iron oxide nanoparticles (IONPs) have garnered significant attention in various fields as they exhibit interesting physical, chemical, and biological properties. This work demonstrates the green synthesis of IONPs using Averrhoa carambola leaf extract as a reducing agent. The IONPs were characterized using various spectroscopic and imaging techniques. Superparamagnetic IONPs with sizes in the range of 10-20 nm were obtained through this green synthesis approach. Furthermore, the IONPs were also found suitable for bioelectronics applications, as they showed biocompatibility towards the normal cell line (HEK293) and can be used as potential anticancer agents since they exhibited cytotoxicity against the MDA-MB-231 cell line, with an IC₅₀ of 979.78 µg/mL. The Ag/Fe₃O₄/FTO memristor device was fabricated using the synthesized IONPs, which demonstrated a good bipolar resistive switching effect with good non-volatile memory performance (endurance: 2 × 10⁴ cycles and retention: 1.5 × 10⁴ s). Different statistical measures and techniques were utilized for the reliability assessment of the Ag/Fe₃O₄/FTO memristor. Interestingly, the Ag/Fe₃O₄/FTO device mimics various synaptic properties, including potentiation, depression, excitatory postsynaptic current (EPSC), and paired-pulse facilitation (PPF). These results demonstrate that these superparamagnetic and biocompatible IONPs are suitable for non-volatile memory and synaptic learning applications.