Hybrid plasmonic nanoemitters 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.

In the present work, the standard monometallic localized surface plasmon resonance (LSPR) biosensing sensitivity is highly improved when using a new system based on glass substrates modified with high-temperature annealed gold/silver bimetallic nanoparticles (Au/Ag bimetallic NPs) coated with polydopamine films before biomolecule specific immobilization. Thus, different zones of bimetallic NPs are spatially created onto a glass support thanks to a commercial transmission electron microscopy (TEM) grid marker in combination with two sequential evaporations of continuous films of gold (4 nm) and silver (2 nm) and followed by annealing at 500 °C for 8 h. By using the scanning electron microscopy (SEM), it is found that annealed Au/Ag bimetallic NPs have uniform size and shape distribution that exhibited a sharper well-defined LSPR resonant peak when compared with that of monometallic Au NPs and thereby contributing to an improved sensitivity in LSPR biosensor application. The controlled micropatterns consisting of bimetallic particles are used in the construction of LSPR biochips for high-throughput detection of different concentrations of a model antigen named bovine serum albumin (BSA) on a single glass sample, with a lower limit of detection of 0.01 ng/mL under the optimized conditions.

Silicon nanocrystals offer huge advantages compared to other semi-conductor quantum dots as they are made from an abundant, non-toxic material and are compatible with silicon devices. Besides, among a wealth of extraordinary properties ranging from catalysis to nanomedicine, metal nanoparticles are known to increase the radiative emission rate of semiconductor quantum dots. Here, we use gold nanoparticles to accelerate the emission of silicon nanocrystals. The resulting integrated hybrid emitter is 5-fold brighter than bare silicon nanocrystals. We also propose an in-depth analysis highlighting the role of the different physical parameters in the photoluminescence enhancement phenomenon. This result has important implications for the practical use of silicon nanocrystals in optoelectronic devices, for instance for the design of efficient down-shifting devices that could be integrated within future silicon solar cells.

We propose an improved version of variable-angle total internal reflection fluorescence microscopy (vaTIRFM) adapted to modern TIRF setup. This technique involves the recording of a stack of TIRF images, by gradually increasing the incident angle of the light beam on the sample. A comprehensive theory was developed to extract the membrane/substrate separation distance from fluorescently labeled cell membranes. A straightforward image processing was then established to compute the topography of cells with a nanometric axial resolution, typically 10-20 nm. To highlight the new opportunities offered by vaTIRFM to quantify adhesion process of motile cells, adhesion of MDA-MB-231 cancer cells on glass substrate coated with fibronectin was examined.