Single-Step Plasmonic Dimer Printing by Gold Nanorod Splitting with Light.

Optical printing is a flexible strategy to precisely pattern plasmonic nanoparticles for the realization of nanophotonic devices. However, the generation of strongly coupled plasmonic dimers by sequential particle printing can be a challenge. Here, we report an approach to generate and pattern dimer nanoantennas in a single step by optical splitting of individual gold nanorods with laser light. We show that the two particles that constitute the dimer can be separated by sub-nanometer distances. The nanorod splitting process is explained by a combination of plasmonic heating, surface tension, optical forces, and inhomogeneous hydrodynamic pressure introduced by a focused laser beam. This realization of optical dimer formation and printing from a single nanorod provides a means for dimer patterning with high accuracy for nanophotonic applications.

Optical and Thermophoretic Control of Janus Nanopen Injection into Living Cells.

Devising strategies for the controlled injection of functional nanoparticles and reagents into living cells paves the way for novel applications in nanosurgery, sensing, and drug delivery. Here, we demonstrate the light-controlled guiding and injection of plasmonic Janus nanopens into living cells. The pens are made of a gold nanoparticle attached to a dielectric alumina shaft. Balancing optical and thermophoretic forces in an optical tweezer allows single Janus nanopens to be trapped and positioned on the surface of living cells. While the optical injection process involves strong heating of the plasmonic side, the temperature of the alumina stays significantly lower, thus allowing the functionalization with fluorescently labeled, single-stranded DNA and, hence, the spatially controlled injection of genetic material with an untethered nanocarrier.

Optofluidic transport and manipulation of plasmonic nanoparticles by thermocapillary convection.

Optothermal control of fluid motion has been suggested as a powerful way of controlling nanomaterials in micro- or nanofluidic samples. Methods based on merely thermal convection, however, often rely on high temperature for achieving fluid velocities suitable for most practical uses. Here, we demonstrate an optofluidic approach based on Marangoni or thermocapillary convection to steer and manipulate nano-objects with high accuracy at an air/liquid interface. By experiments and numerical simulations, we show that the fluid velocities achieved by this approach are more than three orders of magnitude stronger compared to natural convection and that it is possible to control the transport and position of single plasmonic nanoparticles over micrometer distances with high accuracy.