By Gary Thomas
Researchers at University of California, Los Angeles (UCLA) in conjunction with researchers from the Pennsylvania State University and University of Washington have found that molecules are capable of sensing curvature at the nanoscale and hence differ in their reactions on curved surfaces and flat surfaces.
The researchers employed photochemical reactions on the surface to analyze the impact exerted on self-assembly and ligand setting by the substrate morphology. The team found that molecules exhibit a wider range of orientations on curved surfaces vis-à-vis flat surfaces and hence undergo slower reactions on the former.
There are numerous approaches developed by researchers for introducing molecules individually, in a line, in pairs and in clusters on flat surfaces. However, there has been no validation of these approaches with respect to curved and faceted surfaces typical of nanorods, nanostructures and porous materials. Molecules in solution are known to react differently than molecules on surfaces as their placement in solution enables them to rotate freely as opposed to the rigid and adjacent placements on surfaces.
The current study involved the placement of pairs of molecules on both flat and curved surfaces by means of an innovative technique that enables the introduction of pairs of identical reactants on different types of surfaces. The result of the study was that molecules on curved surfaces possess a greater degree of orientation. Though this level of freedom is lesser than that allowed in solutions, it is definitely better than that allowed on flat surfaces where the molecules are held tightly.
The study results have significance for systems employing multifunctional nanoparticles in which different molecules are placed on the nanoparticles.