We report on the quantitative characterization of the plasmonic optical near-field of a single silver nanoparticle. Our approach relies on nanoscale molecular molding of the confined electromagnetic field by photoactivated molecules. We were able to directly image the dipolar profile of the near-field distribution with a resolution better than 10 nm and to quantify the near-field depth and its enhancement factor. A single nanoparticle spectral signature was also assessed. This quantitative characterization constitutes a prerequisite for developing nanophotonic applications.

This article is aimed at demonstrating that physicochemical parameters can be used to control the spatial extent (length, width, and shape) of polymer objects in view of micro-and nano-fabrication applications. In particular, we showed that oxygen quenching and internal filter effects could be turned to advantage to modulate the response of the material by controlling the threshold energy of polymerization and/or the shape of the light into the photopolymerizable medium. The experimental configuration used in this study is based on light-induced polymerization at the extremity of an optical fiber that produces polymer micro-objects after development. Spectroscopic approaches and polymerization threshold measurements were performed to quantitatively evaluate the influence of the physicochemical parameters on the micropatterning of photopolymerizable material. Interestingly, fluorescence that is usually regarded as a process competing with photopolymerization reaction, was used for controlling the fabrication process. By this means, it was possible to better understand the impact of a nonhomogeneous irradiation on photopolymerization process and thus, to tune the shape and the size of the final polymer objects.

The efficiency of 11 cleavable photoinitiators in polymerization reactions was determined in various media, such as oligomer, acrylate, and methacrylate monomers in solution or in poly(methyl methacrylate). It was found that the efficiency of the photoinitiator strongly depends on the polymerized medium. The results are explained and discussed on the basis of the viscosity effect on the rate constants of the processes involved, resulting in good efficiency/reactivity relationships. Quantum yields of initiation were calculated for an acrylate photopolymerization in solution. The efficiency in viscous bulk media is quite well reflected in the dissociation quantum yields of the photoinitiators measured in solution. The role of the other low-viscosity media is also explained. Kinetic treatments were used to examine the influence of the monomer structure on the propagation and termination rate constants of the reaction. These results allowed to shed some light on the influence of the medium on the initiation efficiency and to provide a better knowledge of the key parameters for practical applications.