Table 2.
Benefits and limitations of the MNP synthesis methods.
| MNP Synthesis Methods | Advantages | Disadvantages | References |
|---|---|---|---|
| Mechanical attrition | Simple; inexpensive equipment; adequate for scale-up. | Contamination from the materials in the media and/or atmosphere; difficulty to consolidate the powder core without coarsening the crystalline structure. | [35,36] |
| Thermal quenching | Up-scalable process; favorable composition control. | Elevated temperatures required; large size distribution; lack of homogeneity in microstructure. | [37] |
| Pyrolysis | Reduced reaction times; high purity. | High-pressure and temperature conditions; gas as adsorbent and carrier; large size distribution; aggregation phenomena. | [36,38] |
| Co-precipitation | Simple execution; adequate for the synthesis of complex metal oxide NPs; high reproducibility; inexpensive method. | Requires a nanoparticle separation step, for obtaining uniform size distribution; quasi-spherical NPs; risk of oxidation and aggregation phenomena. | [36,39] |
| Thermal decomposition | Size control; narrow size distribution; crystallinity; Easy scale-up process. | Dilatory process; uses organic solvents; requires further steps to obtain water-soluble MNPs. | [40] |
| Hydrothermal | Fine particles; no required organic solvents; no required post-treatment; Environmentally benign. | Long reaction times. | [36] |
| Microemulsification | Simple method; adequate for in vitro and in vivo applications; controllable size and MNP morphology. | Low scalability; reduced quantity of MNPs synthesized; difficult removal of surfactant. | [41] |
| Polyol-based | Uniform MNPs; size and shape control; simple and reproducible process. | May require high temperature and pressure environment for higher magnetization values. | [42] |
| Sol-gel | Controlled particle size and shape; production of oxide MNP by gel calcination; adequate for hybrid MNPs. | Requires thermal treatment at elevated temperatures; incomplete removal of matrix components from MNP surface. | [35] |
| Electrochemical | Ambient temperature environment; narrow size distribution; high purity; adequate for maghemite NPs. | Complicated and long process. | [40,43] |
| Biosynthesis | High crystallinity; prominent T2 relaxation reduction and contrast. | Reduced control in MNP specifications; mixture of cubic, octahedral and dodecahedral MNPs; low scalability potential. | [37,40] |