A Review on Metal Oxide Nanoparticles: Bridging Chemical Synthesis Strategies to Emerging Applications

Abstract

Metal oxide nanoparticles (MONPs) exhibit size-dependent properties that drive advances in catalysis, energy storage, sensing, remediation, and biomedicine. Chemical synthesis routes allow precise control over structure, composition, and crystallinity, typically yielding 5–100 nm particles. Sol-gel offers molecular-level mixing and uniformity; hydrothermal/solvothermal methods operate at 100–250 °C and 1–10 MPa; thermal decomposition yields highly crystalline oxides at 300–750 °C; and microwave-assisted synthesis achieves uniform nanoparticles within minutes. Unlike prior reviews that focus separately on methods or applications, this article uniquely bridges synthesis strategies with application-driven property requirements, mapping how reaction conditions govern morphology, defect states, and surface reactivity. Representative case studies highlight enhanced catalytic activity from high surface areas, improved Li-ion battery cycling stability, ppm-level gas sensing, pollutant degradation via photocatalysis, and targeted drug delivery using functionalized oxides. Finally, we critically assess challenges in scalability, reproducibility, and biocompatibility, and outline future directions in hybrid architectures and continuous-flow synthesis.