Abstract
Optically-assisted large-scale assembly of nanoparticles have been of recent interest owing to their potential in applications to assemble and manipulate colloidal particles and biological entities. In the recent years, plasmonic heating has been the most popular mechanism to achieve temperature hotspots needed for extended assembly and aggregation. In this work, we present an alternative route to achieving strong thermal gradients that can lead to non-equilibrium transport and assembly of matter. We utilize the excellent photothermal properties of graphene oxide to form a large-scale assembly of silica beads. The formation of the assembly using this scheme is rapid and reversible. Our experiments show that it is possible to aggregate silica beads (average size 385 nm) by illuminating thin graphene oxide microplatelet by a 785 nm laser at low intensities of the order of 50–100 µW/µm2. We further extend the study to trapping and photoablation of E. coli bacteria using graphene oxide. We attribute this aggregation process to optically driven thermophoretic forces. This scheme of large-scale assembly is promising for the study of assembly of matter under non-equilibrium processes, rapid concentration tool for spectroscopic studies such as surface-enhanced Raman scattering and for biological applications.
Highlights
Optically-assisted large-scale assembly of nanoparticles have been of recent interest owing to their potential in applications to assemble and manipulate colloidal particles and biological entities
The authors showed that extended assembly of colloidal particles by optically-induced thermal gradients is an interplay between the convective forces and thermophoresis
In order to extend the capability of the scheme, we used the thermal gradient generated by graphene oxide (GO) illuminated by laser to trap and aggregate E. coli bacteria on the GO leading to their photothermal destruction
Summary
Optically-assisted large-scale assembly of nanoparticles have been of recent interest owing to their potential in applications to assemble and manipulate colloidal particles and biological entities. Garcés-Chávez et al have reported the use of optical and plasmonic forces to create thermal gradients that lead to large scale assembly of colloidal p articles[26]. Plasmonic heating by illumination of noble metals can be harnessed to induce a temperature gradient for trapping and colloidal assembly applications.
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