Hybrid plasmonic nano-emitters based on the combination of quantum dot emitters (QD) and plasmonic nanoantennas open up new perspectives in the control of light. However, precise positioning of any active medium at the nanoscale constitutes a challenge. Here, we report on the optimal overlap of antenna’s near-field and active medium whose spatial distribution is controlled via a plasmon-triggered 2-photon polymerization of a photosensitive formulation containing QDs. Au nanoparticles of various geometries are considered. The response of these hybrid nano-emitters is shown to be highly sensitive to the light polarization. Different light emission states are evidenced by photoluminescence measurements. These states correspond to polarization-sensitive nanoscale overlap between the exciting local field and the active medium distribution. The decrease of the QD concentration within the monomer formulation allows trapping of a single quantum dot in the vicinity of the Au particle. The latter objects show polarization-dependent switching in the single-photon regime.

Fabrication of freestanding, three-dimensional microstructures having gold nanoparticles as building blocks has been achieved using two-photon lithography. The reported constructions hold structural coherence without the need of a polymeric network to embed the nanoparticles. The Au nanoparticles are produced by radical-mediated photoreduction and immediately self-arrange in micrometre-sized cylinders, which are used as the building units of the 3D structure writing. The manufactured structures present plasmonic activity, as well as excellent properties as substrates for Surface-Enhanced Raman Spectroscopy, in key issues such as reproducibility in intensity or enhancement factor. Such is calculated to be above 8 × 10⁶ for the non-resonant probe molecule trans-1,2-bis-4-pyridylethylene. The option of repeated use of the substrates is confirmed, and they are successfully applied for detection of the fungicide thiabendazole.

The integration of nanoparticles (NPs) into photonic devices and plasmonic sensors requires selective patterning of these NPs with fine control of their size, shape, and spatial positioning. In this article, we report on a general strategy to pattern different types of NPs. This strategy involves the functionalization of photopolymers before their patterning by two-photon laser writing to fabricate micro- and nanostructures that selectively attract colloidal NPs with suitable ligands, allowing their precise immobilization and organization even within complex 3D structures. Monolayers of NPs without aggregations are obtained and the surface density of NPs on the polymer surface can be controlled by changing either the time of immersion in the colloidal solution or the type of amine molecule chemically grafted on the polymer surface. Different types of NPs (gold, silver, polystyrene, iron oxide, colloidal quantum dots, and nanodiamonds) of different sizes are introduced showing a potential toward nanophotonic applications. To validate the great potential of our method, we successfully demonstrate the integration of quantum dots within a gold nanocube with high spatial resolution and nanometer precision. The promise of this hybrid nanosource of light (plasmonic/polymer/QDs) as optical nanoswitch is illustrated through photoluminescence measurements under polarized exciting light.

We report on the realization of functional infrared light concentrators based on a thick layer of air-polymer metamaterial with controlled pore size gradients. The design features an optimum gradient index profile leading to light focusing in the Fresnel zone of the structures for two selected operating wavelength domains near 5.6 and 10.4 μm. The metamaterial which consists in a thick polymer containing air holes with diameters ranging from λ/20 to λ/8 is made using a 3D lithography technique based on the two-photon polymerization of a homemade photopolymer. Infrared imaging of the structures reveals a tight focusing for both structures with a maximum local intensity increase by a factor of 2.5 for a concentrator volume of 1.5 λ³, slightly limited by the residual absorption of the selected polymer. Such porous and flat metamaterial structures offer interesting perspectives to increase infrared detector performance at the pixel level for imaging or sensing applications.

High-throughput, simple nanofabrication methods are essential keys for involving plasmonic materials with large electric fields for practical applications. We demonstrate in this paper a facile route for fabricating multifunctional metallic nanomaterials for sensing, which is particularly relevant to SERS spectroscopy. A simple deposition of a polymer dispersion doped with metallic precursor onto a conducting substrate allows a spontaneous formation of SERS-active substrates via vapor induced phase separation. The process enables the fabrication of several kinds of SERS chips with an original combination of fast throughput, low cost, reproducibility and high sensitivity. Our SERS results show significant enhancement factors exceeding 10¹³, which match the largest value (10¹⁴) of metallic nanoparticle aggregates found until now. We quantify these enhancements by depositing bipyridine ethylene (BPE) on the substrate and spatially mapping their Raman intensities using confocal micro-Raman spectroscopy. Both the sensitivity threshold and reproducibility of all substrates were estimated by SERS measurements at variable concentrations of BPE. Our approach is new in fabricating high-throughput and reproducible SERS substrates over a large surface (on the whole substrate) by a one-step technique. As a result, we demonstrate a novel class of SERS substrates for which no patterning is necessary as in lithography, which provide a quick, simple and cheap way to fabricate highly sensitive SERS substrates.