Pushing nanoparticles with light - A femtonewton resolved measurement of optical scattering forces

Optomechanical manipulation of plasmonic nanoparticles is an area of current interest, both fundamental and applied. However, no experimental method is available to determine the forward-directed scattering force that dominates for incident light of a wavelength close to the plasmon resonance. Here, we demonstrate how the scattering force acting on a single gold nanoparticle in solution can be measured. An optically trapped 80 nm particle was repetitively pushed from the side with laser light resonant to the particle plasmon frequency. A lock-in analysis of the particle movement provides a measured value for the scattering force. We obtain a resolution of less than 3 femtonewtons which is an order of magnitude smaller than any measurement of switchable forces performed on nanoparticles in solution with single beam optical tweezers to date. We compared the results of the force measurement with Mie simulations of the optical scattering force on a gold nanoparticle and found good agreement between experiment and theory within a few fN. (C) 2016 Author(s)

Supported Membranes Embedded with Fixed Arrays of Gold Nanoparticles

10.1021/nl202847tNano Letters11114912-491

Pripper: prediction of caspase cleavage sites from whole proteomes

Peer reviewe

Synthesis of quasi-hexagonal ordered arrays of metallic nanoparticles with tuneable particle size

Quasi-hexagonal ordered arrays of noble-metal nanoparticles are synthesized by block copolymer micelle nanolithography (BCML) and electroless deposition. Two approaches are discussed to uniformly grow surface-deposited gold, platinum, and palladium nanoparticles independent of interparticle spacing (see figure). The geometrical order of the particles is preserved by either embedding them into a monolayer of alkylsiloxane molecules or using micelles as a stabilizing template

Determination of transition dipole moments from time–resolved photoelectron spectroscopy

We show how to extract the energy- and coordinate dependence of dipole-moments for a neutral-to-ionic molecular transition from time-resolved photoelectron spectra. The procedure needs the potential surfaces of the neutral and the cationic state which are involved in the ionization process as an input. Given these potentials and the laser parameters it is possible to determine the functional form of the transition dipole moment from the measured time- and energy-resolved transient signals

Growth mechanisms of phthalocyanine nanowires induced by Au nanoparticle templates

We combine X-ray reflectivity and scanning electron microscopy measurements to investigate the mechanisms involved in the growth of vertical arrays of phthalocyanine nanowires directed by templates of Au nanoparticles. The study has been carried out for H(16)CuPc at different substrate temperatures. It is shown that three organic morphologies evolve during the growth: 1D nanostructures on top of the Au nanoparticles, a multilayer film on the substrate and a layer wetting the gold nanoparticles. For substrate temperatures below 100 °C there is a coexisting and competing growth of the three structures, whereas beyond this temperature the 1D growth on the nanoparticles is predominantly favored. The observance of two regimes with the temperature is characterized by two different activation energies. Both the length of the 1D structures and the thickness of the multilayer film can be precisely controlled by the substrate temperature which is of importance for application of vertical organic nanowires as donor/acceptor architecture in organic solar cells