Bright-red light-emitting diodes (LEDs) with a narrow emission line width that emit between 620 and 635 nm are needed to meet the latest industry color standard for wide color gamut displays, Rec. 2020. CsPbI 3 perovskite quantum dots (QDs) are one of the few known materials that are ideally suited to meet these criteria. Unfortunately, CsPbI 3 perovskite QDs are prone to transform into a non-redemitting phase and are subject to further degradation mechanisms when their luminescence wavelength is tuned to match that of the Rec. 2020 standard. Here, we show that zwitterionic lecithin ligands can stabilize the perovskite phase of CsPbI 3 QDs for long periods in air for at least 6 months compared to a few days for control samples. LEDs fabricated with our ultrastable lecithin-capped CsPbI 3 QDs exhibit an external quantum efficiency (EQE) of 7.1% for electroluminescence centered at 634 nm�a record for all-inorganic perovskite nanocrystals in Rec. 2020 red. Our devices achieve a maximum luminance of 1391 cd/m 2 at 7.5 V, and their operational half-life is 33 min (T 50 ) at 200 cd/m 2 �a 10-fold enhancement compared to control samples. Density functional theory results suggest that the surface strain in CsPbI 3 QDs capped with the conventional ligands, oleic acid and oleylamine, contributes to the instability of the perovskite structural phase. On the other hand, lecithin binding induces virtually no surface strain and shows a stronger binding tendency for the CsPbI 3 surface. Our study highlights the tremendous potential of zwitterionic ligands in stabilizing the perovskite phase and particle size of CsPbI 3 QDs for various optoelectronic applications.

In the present work, we provide evidence for visible light irradiation of the Au/TiO2 nanoparticles’ surface plasmon resonance band (SPR) leading to electron injection from the Au nanoparticles to the conduction band of TiO2. The Au/TiO2 SPR band is shown to greatly enhance the light absorption of TiO2 in the visible region. Evidence is presented for the light absorption by the Au/TiO2 plasmon bands leading to the dissolution of Au nanoparticles. This dissolution occurs concomitantly with the injection of the hot electrons generated by the Au plasmon into the conduction band of TiO2. The electron injection from the Au nanoparticles into TiO2 was followed by femtosecond spectroscopy. The formation of Au ions was further confirmed by the spectral shift of the transient absorption spectra of Au/TiO2. The spectral changes of the SPR band of Au/TiO2 nanoparticles induced by visible light were detected by spectrophotometer, and the morphological transformation of Au/TiO2 was revealed by electron microscopy techniques as well. Subsequently, the fate of the Au ions was sorted out during the growth and biofilm formation for some selected Gram-negative bacteria. This study compares the bactericidal mechanism of Au ions and Ag ions, which were found to be substantially different depending on the selected cell used as a probe.

Reversible photochromic hybrid organicinorganic films containing nanocrystalline cellulose as a matrix and tungsten oxide as a photochromic component (CNC/WO 3 ) were obtained via a simple and quick solvent casting method. The films were studied by scanning electron microscopy, together with element mapping, FT-IR spectroscopy and X-ray diffraction, confirming successful incorporation of WO 3 nanoparticles into a nanocellulose matrix.Thermal analysis data indicated that the modification of a nanocellulose matrix with WO 3 increases its thermal stability. The CNC/WO 3 films showed a quick coloration-bleaching transition with good reversibility within 20 min, without notable degradation of photochromic properties after 10 cycles. The synthetic method proposed allows for scalable preparation of highly efficient low-cost WO 3 -based photochromic materials.

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