Laser Beams Turn Gold Nanoparticles into Filaments

Research conducted at the Center for Nanoscale Materials and Argonne's Biosciences Division has discovered a user-friendly and cost-effective method, by which nanoparticles can be fitted into bigger constructions of any customized shape through a process known as ‘optically directed assembly’ (ODA).

Gold and carbon nanoparticles are suspended in water. A nano-drop of the suspension is kept on a glass slide. A laser of low power is beamed onto a tiny spot inside the drop close to its surface. The nanoparticles are first trapped visually, heated and evaporated. A Convective fluid is passed through them to test their chemical reactions. This makes them bind near the laser focus. The focus of the laser is moved through the drop, a constant filament of the bound material ensues. These materials remain intact even after the fluid is allowed to flow out completely.

Filaments of any customized shape measuring millimeters in length and 10-60 times wider than the original particles can thus be created. These hierarchical designs can be used in applications such as biological sensing, electronics, optics, and energy technologies.