André Del Guerzo

Femtosecond laser inscription in a ytterbium-doped silver-containing phosphate glass is demonstrated by achieving 3D highly localized laser-induced silver photochemistry. The produced fluorescent silver nanoclusters lead to high optical contrast in the visible range, showing that the coinsertion of Yb³⁺ ions is not detrimental to the silver-based photochemistry. We demonstrate efficient energy transfer from these silver nanoclusters to the rare-earth Yb³⁺ ions, leading to near-IR background-free fluorescence emission. Indeed, we demonstrate the 3D-localized near-IR emission of homogeneously distributed Yb³⁺ ions thanks to their spatially selective excitation by colocalized silver nanoclusters. This creation of hybrid donor/acceptor systems, composed of coupled laser-inscribed silver nanoclusters and Yb³⁺ ions, respectively, allows for the 3D-distribubed creation of a laser-active gain medium. The reported effective laser gain results from the silver nanocluster-mediated excitation of the Yb³⁺ lasing ions, demonstrating the energy-transfer-based achievement of inversion population and optically induced transparency of the material. This opens the route for the all-optical fabrication of near-IR micron-scale multiscale architectures compatible with the development of new laser-active media especially for integrated waveguides and active photonic integrated circuits. This includes perspectives of versatile 3D laser-integrated architectures allowing for evanescent coupling under lasing operation with their environment, to achieve enhanced photonic sensing abilities beyond those offered by usual conventional planar of unidirectional architectures.

Circularly polarized (CP) light generated from photoluminescence (PL) has great potential for the transmission of diverse forms of optical information including light intensity (brightness), spectral profile (color), and polarization (left-handed (LH)/right-handed (RH)), as well as temporal information corresponding to the PL lifetime of the CP light source. However, a systematic approach to the design of CP light-generating materials for the conveyance of time-multiplexed chiroptical information has not yet been reported. Herein, we demonstrate a novel approach to time-multiplexing chiroptical information using multilayered luminescence-based CP convertors comprising two linearly polarized luminescence (LPL) films with different PL lifetimes and a quarter-wave retardation film. We prepared LPL films with short and long PL lifetimes by stretching films comprising poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and CdSe/CdS core/shell quantum rod (QR) luminogens, respectively. We then fabricated four types of multilayered luminescence-based CP convertors by laminating the LPL_MEH-PPV and LPL_QR films with quarter-wave retardation films, so that the azimuthal angles between the polarization axes of the LPL films and the fast axes of the quarter-wave films differed in each case. The resulting CP light comprised short- and long-lifetime components. Subsequently, we used a time-resolved spectroscopic technique to extract time-multiplexed chiroptical information from changes in the time-course of the spectral profile of the LH- and RH-CP light. The time-varying of CP light profiles were thereby read-out as time-multiplexed chiroptical information. Our findings will pave the way for the design of CP light-generating materials for conveying time-multiplexed chiroptical information.

Narcissistic self-sorting of n-acenes led to their self-assembly into separated nanoribbons despite identical side-chains and growth kinetics, due to discrepant dipolar vs. quadrupolar characters. Electroluminescence is switched-on at p–n junctions.

Radio-photoluminescence in silver-doped phosphate glasses has been extensively used for X-ray dosimetry. In this paper, we present the potential of silver clusters for X-ray spatially resolved dosimetry. Those clusters are generated in phosphate glasses containing a high concentration of silver oxide by femtosecond direct laser writing technique. Two phosphate glasses of different compositions were investigated. First, the spectroscopic properties of the pristine glasses were studied after X-ray irradiation at different doses to assess their dosimetry potential. Second, the impact of X-rays on the three-dimensional inscribed silver clusters has been analyzed using several spectroscopies methods. Our analysis highlights the resilience of embedded silver clusters acting as local probes of the deposited doses. We demonstrate that these inscribed glasses can define the range and sensitivity of X-ray doses and consider the realization of spatially-resolved dosimeters.

We report an anthracene-based Ni-MOF [Ni(II) metal–organic framework, {[Ni(μ₂-L)₂Cl₂]·x(C₆H₆)·y(MeOH)}_n (1), L = anthracene-9,10-diylbis(methylene)diisonicotinate] whose crystal structure reveals the presence of hexagonal channels with a pore size of 1.4 nm that can accommodate guests such as C₆₀ and C₇₀. Both confocal fluorescence and Raman microscopy results are in agreement with a homogeneous distribution of fullerenes throughout the single crystals of 1. Efficient energy transfer from 1 to the fullerenes was observed, which emitted partially polarized fluorescence emission. Stronger binding between 1 and C₇₀ versus C₆₀ was confirmed from HPLC analysis of the dissolved material and provides a basis for the selective retention of C₇₀ in liquid chromatography columns packed with 1.

Supramolecular engineering is employed to spontaneously generate sub-micron-sized vesicles from TADF chromophores for OLED applications.

We report on the 3D precipitation, using a direct laser writing approach, of highly fluorescent silver clusters in a Eu³⁺-doped silver-containing zinc phosphate glass. Micro-spectroscopy of fluorescence emission shows the ability to continuously adjust the local tri-chromatic coordinates in the CIE (Commission Internationale de l’Éclairage) chromaticity diagram between red and white colors, thanks to the laser-deposited dose and resulting tunable combination of emissions from Eu³⁺ and silver clusters. Moreover, continuous-wave and time-resolved FAST-FLIM spectroscopies showed a significant enhancement of the fluorescence emission of Eu³⁺ ions while being co-located with UV-excited laser-inscribed silver clusters. These results demonstrate the ability to perform efficient resonant non-radiative energy transfer from excited silver clusters to Eu³⁺, allowing such energy transfer to be highly localized on demand thanks to laser inscription. Such results open the route to 3D printing of the rare earth ions emission in glass.

The design of organic self-assembled nanomaterials requires a more complete understanding of all mechanisms leading to anisotropic and low-defect growth in solvent-processing, in particular in the vast case of polyaromatic compounds. 2,3-Dihexadecyloxy-9,10-diphenylanthracene (DPA16) self-assembles from solution into fluorescent nanoribbons without the addition of surfactants or polymers. These very high aspect-ratio anisotropic objects display a deep-blue emission with a remarkable linear polarisation P reaching a value of 0.6. The emission colour of ribbons can be further tuned by doping with a tetracene analogue. Crystallography, spectroscopy, atomic force and fluorescence polarisation microscopy techniques reveal that the growth mechanism not only involves a common ‘Ostwald ripening’, but also two commonly unforeseen features. First, an ‘oriented attachment’ mechanism contributes to the growth of the ribbons preventing packing mismatches. This mechanism has so far solely been demonstrated for inorganic nanoparticles. Second, a thermally activated dipole in less stable asymmetric conformations of DPA16 is proposed to contribute majorly to directional intermolecular interactions determining the main growth axis of the ribbons. These dipole–dipole interactions would contribute to explain the very high anisotropy of growth, in the absence of directional H-bonds predominating in many reported studies. This work provides new insights into the design of self-assembled nanoobjects with very high aspect ratios.

We report the first study dealing with the self-assembly of an α-amino acid derivative in perfluorocarbons. Rheology, microscopy, and spectroscopy studies reveal that the fluorous sodium L-prolinate derivative 1 self-assembles in perfluorocarbons to form a three-dimensional network of left-handed nano-helices resulting in solvent gelation. Singlet oxygen lifetime measured in a gel of perfluorodecalin is about 1000 times longer than in pure water.