In-Situ Versus Post-Synthetic Stabilization of Metal Oxide Nanoparticles

Abstract

Within the last two decades, the synthesis and application of nanoparticles has evolved as one of the most active fields of research and development, promising solutions to some of humanity’s most pressing needs in cases as diverse as cancer therapy, water purification, or energy storage (Duget et al., 2006; Bazito & Torresi, 2006; Centi & Perathoner, 2009; Feldmann & Goesmann, 2010; Goyal et al., 2011; Kim & van der Bruggen, 2010; Li et al., 2008; Moghimi et al., 2005; Prandeep & Anshup, 2009; Sanvicens & Pilar, 2008; Sides et al., 2002; Theron et al., 2007). Today, nanoparticles are predominantly being applied as particulate materials with enhanced properties as compared to the standard bulk material. One however envisions nanotechnology already in the near future to strongly increase in complexity, leading to the development of hierarchical nanosystems being capable of computing and robotic or even self-replicating tasks (Mallouk & Sen, 2009; Rasmussen et al., 2003; Requicha, 2003; Sanchez & Pumera, 2009). Most future applications are expected to be eventually realised via the so-called bottom-up approach, emanating from nanoparticles as tiny building blocks that self-assemble in a controlled and organised manner to a higher level of hierarchy (Shenhar & Rotello, 2003; Dong et al., 2007). The primary prerequisite for the realisation of this strategy is the availability of high-quality nanoparticles that can act as such building blocks, possessing a predefined and uniform size and shape. Consequently, research on the controlled preparation of nanoparticles has greatly intensified within the last two decades, mainly focusing on carbon-based nanostructures (Mostofizadeh et al., 2011), metals (Cushing et al., 2004; Guo & Wang, 2011), metal oxides (Cushing et al., 2004; Chen & Mao, 2007; Pinna & Niederberger, 2008), semiconductor nanostructures (Trindade et al., 2001) and organic or hybrid nanostructures (Biswas & Ray, 2001; Ballauff, 2003). Remarkable progress has been made in the synthesis of nanoparticles with defined and even complex shape for certain materials (Jun et al., 2006), although a general unterstanding of the formation processes of nanostructured materials appears to remain a long way off.