Functionalized nanostructures with liquid-like behavior: Expanding the gallery of available nanostructures

Recently, we have developed a novel family of functionalized nanostructures that exhibit liquid-like behavior in the absence of solvents and preserve their nanostructure in the liquid state. The gallery of nanostructures developed so far includes functionalized silica and magnetic iron oxide nanoparticles, layer-like organosilicate nanoparticles, polyoxometalate clusters, and organic-inorganic hybrid networks. In an effort to demonstrate the wider applicability of this concept and to provide a deeper insight into this class of materials, the present work cites additional paradigms of functionalized nanostructures with similar behavior as above. In one case, surface functionalization of anatase nanoparticles (TiO2, an inorganic nanostructure) with a quaternary ammonium organosilane leads to ionically modified nanoparticles that, when electrostatically combined with a poly(ethylene glycol) (PEG)-tailed sulfonate anion, exhibit liquid-like behavior in the absence of solvents. In a different but quite interesting case of a bionanostructure, ion-exchange functionalization of a DNA oligonucleotide with a PEG-tailed quaternary ammonium cation leads to an easily separable liquid derivative with attractive features. These examples show the versatility of this concept over a range of nanostructures.