A review on synthesis, capping and applications of superparamagnetic magnetic nanoparticles

Magnetic nanoparticles (MNPs) have garnered significant attention from researchers due to their numerous technologically significant applications in diverse fields, including biomedicine, diagnostics, agriculture, optics, mechanics, electronics, sensing technology, catalysis, and environmental remediation. The superparamagnetic nature of MNP is exploited for many applications and remains fascinating to study many fundamental phenomena. The uniqueness of this review is that it gives an in-depth review of different synthesis approaches adopted for preparing magnetic nanoparticles and nanoparticle formation mechanisms, functionalizing them with different capping agents, and applying different functionalized magnetic nanoparticles. The important synthesis techniques covered include coprecipitation, microwave-assisted, sonochemical, sol-gel, microemulsion, hydrothermal/solvothermal, thermal decomposition, and mechano-chemical synthesis. Further, the advantages and disadvantages of each technique are discussed, and tables show important results of prepared particles. Other aspects covered in this review are the dispersion of magnetic nanoparticles in the continuous matrix, the influence of surface capping on high-temperature thermal stability, the long-term stability of ferrofluids, and applications of functionalized magnetic nanoparticles. For effective utilization of the ferrite nanoparticles, it is essential to formulate thermally and colloidally stable magnetic nanoparticles with desired magnetic properties. Capping enhances the phase transition temperature and long-term colloidal stability. Magnetic nanoparticles capped or functionalized with specific binding species, specific components like drugs, or other functional groups make them suitable for applications in biotechnology/biomedicine. Recent studies reveal the tremendous scope of MNPs in therapeutics and theranostics. The requirements for nanoparticle size, morphology, and physio-chemical properties, especially magnetic properties, functionalization, and stability, vary with applications. There are also challenges for precise size control and the cost-effective production of nanoparticles in large quantities. The review should be an ideal material for researchers working on magnetic nanomaterials and an excellent reference for freshers.