Domestic lighting using white light-emitting diodes (WLEDs) requires a choice of materials to be eco-friendly as well as economically viable.

The luminescence of Fluorescein, an inexpensive dye, ought to be interesting for lighting application devices such as commercial LEDs. However, the molecule suffers from severe instability, making it inappropriate for such applications. As previously studied, fluorescein molecules may be hosted in a layered double hydroxide (LDH), and the role of such an inorganic material in stabilizing the dye has been underlined. However, a deep understanding of the resulting optical properties is still required. Using extremely small amounts of fluorescein, it is demonstrated here that Zn 2 Al cation-based LDH tethering acts as a «solid solvent» for the dye, enabling its luminescence even in powder form, whereas fluorescein molecules on their own emit no luminescence at all in the solid state. However, aggregations of the dye occur in the interlamellar space, leading to non-radiative emission. Emission and excitation spectra, as well as fluorescence decays, are studied to explain the difference between the hybrid LDH-Fluorescein material and an aqueous solution of fluorescein. Additionally, LDH platelets are found to help the dispersion of the intercalated fluorescein in silicone to obtain a homogeneous composite film, which exhibits luminescent properties. Finally, an accelerated photoaging study demonstrates that the LDH-fluorescein filler has a pro-degradant effect on polymer aging under UV radiation.

When sulforhodamine B (SRB) is entrapped in a tightly packed hybrid material composed of dodecylsulfate anions interleaved in layered double hydroxide, the organic dye is considered as a possible red-emitting phosphor for white light-emitting diodes (WLEDs). To confirm such promising potential, a reliability study is here undertaken and the materials and their associated silicone films are subjected to different thermal and photonic stresses. Optical properties, photoluminescence quantum yields and emission spectra are recorded after photo-aging studies. Interestingly, the composite silicone film is found to be completely stable under blue LED excitation, while in the absence of the hybrid LDH the emission of SRB decays rapidly, thus underlining the protective role of the LDH hybrid cargo. At this stage, these results confirm the potential offered by a system consisting of such an emitter film and a blue LED. This system also opens up new possibilities for interesting organic dyes that are sensitive to photonic and/or thermal stresses.

A pyrazino-1,3a,6a-triazapentalene dye-based molecule was intercalated by direct coprecipitation method into the galleries of negatively charged layered double hydroxide (LDH) to form a new luminescent LDH filler. The materials of cation composition Zn/Al = 2 lead to well-defined organic inorganic assemblies. The structure of the hybrid materials was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR) and UVvisible spectra. Optical properties of the materials, at both solid state and slurry state, were also recorded and absolute photoluminescent quantum yields (PLQY) were determined showing that the nanohybrid LDH slurry exhibited higher luminescence properties under UV excitation than the corresponding LDH powder. LDH fillers were used to prepare composite films by dispersion in both hydrophobic or hydrophilic polymer matrix such as poly(dimethyl siloxane) (PDMS) and poly(ethylene oxide) (PEO), respectively. Composite films were 3 characterized by Small Angle X-ray Scattering (SAXS) and PLQY were recorded in order to compare the behaviour of the nanohybrid LDH filler in both polymer matrices. It was found that the aggregation of particles is still observed by SAXS.

Diffraction is the main physical effect involved in the imaging process of holographic displays. In the application of near-eye displays, it generates physical limits that constrain the field of view of the devices. In this contribution, we evaluate experimentally an alternative approach for a holographic display based mainly on refraction. This unconventional imaging process, based on sparse aperture imaging, could lead to integrated near-eye displays through retinal projection, with a larger field of view. We introduce for this evaluation an in-house holographic printer that allows the recording of holographic pixel distributions at a microscopic scale. We show how these microholograms can encode angular information that overcomes the diffraction limit and could alleviate the space bandwidth constraint usually associated with conventional display design.

The optical properties of sulforhodamine B (SRB) hosted in surfactant-modified layered double hydroxide (LDH) are explored using quantum yield efficiencies and temporal variations in luminescence. The effect of the spacer,...

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