Shaping and patterning gold nanoparticles via micelle templated photochemistry.

Shaping and positioning noble metal nanostructures are essential processes that still require laborious and sophisticated techniques to fabricate functional plasmonic interfaces. The present study reports a simple photochemical approach compatible with micellar nanolithography and photolithography that enables the growth, arrangement and shaping of gold nanoparticles with tuneable plasmonic resonances on glass substrates. Ultraviolet illumination of surfaces coated with gold-loaded micelles leads to the formation of gold nanoparticles with micro/nanometric spatial resolution without requiring any photosensitizers or photoresists. Depending on the extra-micellar chemical environment and the illumination wavelength, block copolymer micelles act as reactive and light-responsive templates, which enable to grow gold deformed nanoparticles (potatoids) and nanorings. Optical characterization reveals that arrays of individual potatoids and rings feature a localized plasmon resonance around 600 and 800 nm, respectively, enhanced photothermal properties and high temperature sustainability, making them ideal platforms for future developments in nanochemistry and biomolecular manipulation controlled by near-infrared-induced heat.

Charge distribution induced inside complex plasmonic nanoparticles.

We developed a versatile numerical technique to compute the three-dimensional charge distribution inside plasmonic nanoparticles. This method can be easily applied to investigate the charge distribution inside arbitrarily complex plasmonic nanostructures and to identify the nature of the multipolar plasmon modes involved at plasmonic resonances. Its ability to unravel the physical origin of plasmonic spectral features is demonstrated in the case of a single gold nanotriangle and of a gold nano-antenna. Finally, we show how the volume charge distribution can be used to define and compute the first terms of the multipolar expansion.

Temperature mapping near plasmonic nanostructures using fluorescence polarization anisotropy.

We report on a thermal imaging technique based on fluorescence polarization anisotropy measurements, which enables mapping the local temperature near nanometer-sized heat sources with 300 nm spatial resolution and a typical accuracy of 0.1 degrees C. The principle is demonstrated by mapping the temperature landscape around plasmonic nano-structures heated by near-infrared light. By assessing directly the molecules' Brownian dynamics, it is shown that fluorescence polarization anisotropy is a robust and reliable method which overcomes the limitations of previous thermal imaging techniques. It opens new perspectives in medicine, nanoelectronics and nanofluidics where a control of temperature of a few degrees at the nanoscale is required.