Photochromic Free MOF‐Based Near‐Infrared Optical Switch

We demonstrate herein an all‐optical switch based on stimuli‐responsive and photochromic‐free metal–organic framework (HKUST‐1). Ultrafast near‐infrared laser pulses stimulate a reversible 0.4 eV blue shift of the absorption band with up to 200 s^?1 rate due to dehydration and concomitant shrinking of the structure‐forming [Cu₂C₄O₈] cages of HKUST‐1. Such light‐induced switching enables the remote modulation of intensities of photoluminescence of single crystals of HKUST‐1 as well visible radiation passing through the crystal by 2 order of magnitude. This opens up the possibility of utilyzing stimuli‐responsive MOFs for all‐optical data processing devices.     

Water-based route to colloidal Mn-doped ZnSe and core/shell ZnSe/ZnS quantum dots

Relatively monodisperse and highly luminescent Mn(2+)-doped zinc blende ZnSe nanocrystals were synthesized in aqueous solution at 100 °C using the nucleation-doping strategy. The effects of the experimental conditions and of the ligand on the synthesis of nanocrystals were investigated systematically. It was found that there were significant effects of molar ratio of precursors and heating time on the optical properties of ZnSe:Mn nanocrystals. Using 3-mercaptopropionic acid as capping ligand afforded 3.1 nm wide ZnSe:Mn quantum dots (QDs) with very low surface defect density and which exhibited the Mn(2+)-related orange luminescence. The post-preparative introduction of a ZnS shell at the surface of the Mn(2+)-doped ZnSe QDs improved their photoluminescence properties, resulting in stronger emission. A 2.5-fold increase in photoluminescence quantum yield (from 3.5 to 9%) and of Mn(2+) ion emission lifetime (from 0.62 to 1.39 ms) have been observed after surface passivation. The size and the structure of these QDs were also corroborated by using transmission electron microscopy, energy dispersive spectroscopy, and X-ray powder diffraction.     

Photochromic Free MOF-Based Near-Infrared Optical Switch

We demonstrate herein an all-optical switch based on stimuli-responsive and photochromic-free metal–organic framework (HKUST-1). Ultrafast near-infrared laser pulses stimulate a reversible 0.4 eV blue shift of the absorption band with up to 200 s⁻¹ rate due to dehydration and concomitant shrinking of the structure-forming [Cu₂C₄O₈] cages of HKUST-1. Such light-induced switching enables the remote modulation of intensities of photoluminescence of single crystals of HKUST-1 as well visible radiation passing through the crystal by 2 order of magnitude. This opens up the possibility of utilyzing stimuli-responsive MOFs for all-optical data processing devices.     

Aluminium substitution in iron(II-III)-layered double hydroxides: Formation and cationic order

The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula (OH)₁₂ SO₄, 8H₂O are followed by pH titration curves, Mössbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO₄²⁻), i.e. y=0, in which a bilayer of sulphate anions points to the Fe³⁺ species. A cationic order is proposed to occur in both GR(SO₄²⁻) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO₄²⁻) is preceded by the successive precipitation of Fe^III and Al^III (oxy)hydroxides. Adsorption of more soluble Al^III species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y∼0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive Fe^II species of the material.