Advanced perspectives on nanoparticle engineering: Green innovations, and characterization techniques

The physicochemical and functional characteristics of nanoparticles have size-dependent variations that can neither be attained nor demonstrated in bulk systems. Though there have been many reviews that reported independently on progress made either on synthesis or characterization of nanoparticles during the past few years, there is still room for development when synthesis routes are correlated systematically with identifiable physicochemical properties and functional characteristics. In this review, we offer an integrated review on the synthesis and characterization of nanoparticles with well-clarified synthesis routes correlated with structural and practical properties. The conventional synthesis routes, such as mechanical milling, lithography, laser ablation, and arc discharge processes, are dealt with from the point of size, morphological changes, crystallographic development, surface modifications, and porosity. The bottom-up synthesis routes include sol–gel processing, chemical vapor deposition, and hydro- and solvothermal synthesis. The comparison of conventional synthesis routes with green synthesis is further given. The complementary characterization for established synthesis traits includes many advanced characterization tools such as X-ray diffraction studies, scanning and transmission electron microscopy (SEM and TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR) spectroscopy, UV-Vis spectroscopy studies, Brunauer-Emmett-Teller (BET) surface area measurement technique, and energy dispersive spectroscopy. The comparison between conventional synthesis routes and green synthesis routes is further employed.