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Metallic nanostructures can be used to manipulate light on the subwavelength scale to create tailored optical material properties. Next to electric responses, artificial optical magnetism is of particular interest but difficult to achieve at visible wavelengths. DNA-self-assembly has proved to serve as a viable method to template plasmonic materials with nanometer precision and to produce large quantities of metallic objects with high yields. We present here the fabrication of self-assembled ring-shaped plasmonic metamolecules that are composed of four to eight single metal nanoparticles with full stoichiometric and geometric control. Scattering spectra of single rings as well as absorption spectra of solutions containing the metamolecules are used to examine the unique plasmonic features, which are compared to computational simulations. We demonstrate that the electric and magnetic plasmon resonance modes strongly correlate with the exact shape of the structures. In particular, our computations reveal the magnetic plasmons only for particle rings of broken symmetries, which is consistent with our experimental data. We stress the feasibility of DNA self-assembly as a method to create bulk plasmonic materials and metamolecules that may be applied as building blocks in plasmonic devices.

The development of remotely controlled nanoscopic sources of heat is essential for investigating and manipulating temperature sensitive processes at the nanoscale. Here, we use single gold nanoparticles to rapidly deposit controlled amounts of heat in nanoscopic regions of defined size. This allows us to induce and control nanoscale reversible gel-fluid phase transitions in phospholipid membranes. We exploit the optical control over the phase transition to determine the velocity of the fluid phase front into the gel phase membrane and to guide the nanoparticles to specific locations. These results illustrate how single gold nanoparticles enable local thermodynamic investigation and manipulation on nanoscale (bio-) systems.

Noble-metal particles feature intriguing optical properties, which can be utilized to manipulate them by means of light. Light absorbed by gold nanoparticles, for example, is very efficiently converted into heat, and single particles can thus be used as a fine tool to apply heat to a nanoscopic area. At the same time, gold nanoparticles are subject to optical forces when they are irradiated with a focused laser beam, which renders it possible to print, manipulate, and optically trap them in two and three dimensions. Here, we demonstrate how these properties can be used to control the polymerization reaction and thermal curing of polydimethylsiloxane (PDMS) at the nanoscale and how these findings can be applied to synthesize polymer nanostructures such as particles and nanowires with subdiffraction limited resolution.

We report on the deposition of individual gold nanorods from an optical trap using two different laser wavelengths. Laser light, not being resonant to the plasmon resonances of the nanorods, is used for stable trapping and in situ alignment of individual nanorods. Laser light, being resonant to the transversal mode of the nanorods, is used for depositing nanorods at desired locations. The power and polarization dependence of the process is investigated and discussed in terms of force balances between gradient and scattering forces, plasmonic heating, and rotational diffusion of the nanorods. This two-color approach enables faster printing than its one-color equivalent and provides control over the angular orientation (±16°) and location of the deposited nanorods at the single-nanorod level.

We propose and demonstrate a new method of an all-optical, contactless, one-step injection of single gold nanoparticles through phospholipid membranes. The method is based on the combination of strong optical forces acting on and simultaneous optical heating of a gold nanoparticle exposed to laser light tuned to the plasmon resonance of the nanoparticle. A focused laser beam captures single nanoparticles from the colloidal suspension, guides them towards a phospholipid vesicle and propels them through the gel-phase membrane, resulting in the nanoparticle internalization into the vesicle. Efficient resonant optical heating of the gold nanoparticle causes a pore to form in the gel-phase membrane, a few-hundred nanometers in size, which remains open for several minutes. Keywordsgold; nanoparticle; phospholipid; membrane; vesicle; injection; drug-delivery The delivery of hydrophilic biological molecules, such as proteins, DNA and RNA, to the interior of living cells is of extreme importance for biocellular research, gene therapy and drug development. 1 The cellular membrane, which is impermeable to most hydrophilic substances, is a barrier shielding the interior of a cell from its surrounding. To pass through this barrier a number of advanced biological, chemical and physical methodologies have been developed in the last three decades, including lipoplex 2 and polyplex 3 injection, a "gene gun", 4 electroporation, 5 photoporation 6 and liposomal release. 7,8,9,10 Each of these methods has its advantages and disadvantages, which must be considered carefully taking into account the delivery purpose and the cell type. 11 Among others the photoporation or optical injection has increasingly attracted attention as it is a contactless, all-optical and therefore aseptic technique. It relies on the transient increase of a phospholipid membrane permeability induced by a laser beam, allowing hydrophilic substances to diffuse across the membrane. Although the effect of photoporation has been extensively studied and employed for DNA and RNA delivery, the mechanism of the membrane permeability increase upon illumination by light has still not been completely understood. Often the photoporation mechanism is discussed as a combination of several processes, depending on the laser source used: heating, thermoelastic stress, multi-photon absorption and generation of a free electron plasma. 12 Occurrence of these processes requires extremely high peak laser powers 13 and therefore poses a danger of inducing photochemical damage to cell regions illuminated by out-of-focus light. 14,15 In this regard, * Corresponding author: andrey.lutich@physik.lmu.de. Europe PMC Funders GroupAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2013 November 25. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts novel, less harmful approaches to the optical poration of phospholipid membranes and injection of hydrophilic substances through membranes are in strong demand.Here we introduce a novel strategy for ac...

We discuss methods for coherently controlling mesoscopic atomic ensembles where the number of atoms varies randomly from one experimental run to the next. The proposed schemes are based on adiabatic passage and Rydberg blockade and can be used for implementation of a scalable quantum register formed by an array of randomly loaded optical dipole traps.

We present schemes for geometric phase compensation in an adiabatic passage which can be used for the implementation of quantum logic gates with atomic ensembles consisting of an arbitrary number of strongly interacting atoms. Protocols using double sequences of stimulated Raman adiabatic passage (STIRAP) or adiabatic rapid passage (ARP) pulses are analyzed. Switching the sign of the detuning between two STIRAP sequences, or inverting the phase between two ARP pulses, provides state transfer with well-defined amplitude and phase independent of atom number in the Rydberg blockade regime. Using these pulse sequences we present protocols for universal single-qubit and two-qubit operations in atomic ensembles containing an unknown number of atoms.