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The field of quantum technology has been rapidly expanding in the past decades, yielding numerous applications, such as quantum information, quantum communication, and quantum cybersecurity. At the core of these applications lies the quantum emitter (QE), a precisely controllable generator of either single photons or photon pairs. Semiconductor QEs, such as perovskite nanocrystals and semiconductor quantum dots, have shown much promise as emitters of pure single photons, with the potential for generating photon pairs when hybridized with plasmonic nanocavities. In this study, we have developed a system in which individual quantum emitters and their ensembles can be traced before, during, and after the interaction with an external plasmonic metasurface in a controllable way. Upon coupling the external plasmonic metasurface to the QE array, the individual QEs switch from the single-photon emission mode to the multiphoton emission mode. Remarkably, this method preserves the chemical structure and composition of the QEs, allowing them to revert to their initial state after decoupling from the plasmonic metasurface. This significantly expands the potential applications of semiconductor QEs in quantum technologies.

[EN] Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal-polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity.

Upon illumination at the surface plasmon resonance, electron density of metallic nanoparticles oscillates at the frequency of incoming light. The decay of the plasmon band leads to heat generation, a phenomenon that gave rise to the field of thermoplasmonics, attracting much attention in the context of life science applications including cancer therapy and neuronal photostimulation. The latter is of particular interest since the local heat generation under pulsed laser excitation can induce an action potential in neurons. However, the measure of the local temperature in situ during neuronal photostimulation has yet to be shown. Here we propose a hybrid construct in which water-soluble conjugated polymers, apart from acting as fluorescent nanothermometer, serve as a scaffold for a monolayer of gold bipyramids as a heat source (Figure 1: (a) Chemical structure and (b) fluorescence spectra of the conjugated polymers, (c) scheme of the system comprising a monolayer of gold bipyramids and conjugated polymer matrix, (d) macroscopic image of the substrate under white light and the UV lamp, (e) SEM image of the substrate showing randomly distributed nanoparticles, (f) TEM image of gold bipyramids monolayer and (g) UV-Vis-NIR spectrum of the nanocrystals in the solution.(a) Chemical structure and (b) fluorescence spectra of the conjugated polymers, (c) scheme of the system comprising a monolayer of gold bipyramids and conjugated polymer matrix, (d) macroscopic image of the substrate under white light and the UV lamp, (e) SEM image of the substrate showing randomly distributed nanoparticles, (f) TEM image of gold bipyramids monolayer and (g) UV-Vis-NIR spectrum of the nanocrystals in the solution.). Using the Fluorescence Lifetime Imaging Microscopy (FLIM) one can measure the change of fluorescence lifetime of conjugate polymers matrix as a function of local temperature under infrared light irradiation. The biocompatibility and structural diversity of layer-by-layer nanoarchi

Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal–polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity.