Graphene Oxide Based Two-Dimensional Optical Tweezers for Low Power Trapping of Quantum Dots and E. coli Bacteria

Optical trapping has become an important noninvasive tool to manipulate and immobilize microscopic particles. In particular, plasmonic tweezers provide sufficient gradient force with much lower laser powers that are capable of trapping subwavelength particles. However, the expensive and time-consuming fabrication techniques used in making plasmonic nanostructures often hinders direct application of such optical tweezers. Here, we demonstrate a novel trapping scheme using the optical and electronic properties of graphene oxide layers. First, we demonstrate the trapping of polystyrene beads on the graphene oxide-based substrate with a multimode laser illumination at very low intensity. We then present the trapping of silica-shelled quantum dots on graphene oxide layers thereby allowing the study of the quenching behavior of quantum dots on graphene oxide. The technique is then extended to live biological specimens (Escherichia coli bacteria) wherein bacteria is trapped and immobilized on graphene oxide in a noninvasive way. This scheme will be useful for studying biomolecular processes such as cell metabolism, cytotoxicity, and cell stimuli. This system will also be an inexpensive but effective replacement of plasmonically enhanced optical tweezers.