108 research outputs found
Two-dimensional perovskites with alternating cations in the interlayer space for stable light-emitting diodes
An embedded interfacial network stabilizes inorganic CsPbI<sub>3</sub> perovskite thin films
The black perovskite phase of CsPbI(3) is promising for optoelectronic applications; however, it is unstable under ambient conditions, transforming within minutes into an optically inactive yellow phase, a fact that has so far prevented its widespread adoption. Here we use coarse photolithography to embed a PbI(2)-based interfacial microstructure into otherwise-unstable CsPbI(3) perovskite thin films and devices. Films fitted with a tessellating microgrid are rendered resistant to moisture-triggered decay and exhibit enhanced long-term stability of the black phase (beyond 2.5 years in a dry environment), due to increasing the phase transition energy barrier and limiting the spread of potential yellow phase formation to structurally isolated domains of the grid. This stabilizing effect is readily achieved at the device level, where unencapsulated CsPbI(3) perovskite photodetectors display ambient-stable operation. These findings provide insights into the nature of phase destabilization in emerging CsPbI(3) perovskite devices and demonstrate an effective stabilization procedure which is entirely orthogonal to existing approaches
Relating Pore Structure to Activity at the Subcrystal Level for ZSM-5: An Electron Backscattering Diffraction and Fluorescence Microscopy Study
Single Molecule Nanospectroscopy Visualizes Proton-Transfer Processes within a Zeolite Crystal
Visualizing proton-transfer processes at the nanoscale is essential for understanding the reactivity of zeolite-based catalyst materials. In this work, the Brønsted-acid-catalyzed oligomerization of styrene derivatives was used for the first time as a single molecule probe reaction to study the reactivity of individual zeolite H-ZSM-5 crystals in different zeolite framework, reactant and solvent environments. This was accomplished via the formation of distinct dimeric and trimeric fluorescent carbocations, characterized by their different photostability, as detected by single molecule fluorescence microscopy. The oligomerization kinetics turned out to be very sensitive to the reaction conditions and the presence of the local structural defects in zeolite H-ZSM-5 crystals. The remarkably photostable trimeric carbocations were found to be formed predominantly near defect-rich crystalline regions. This spectroscopic marker offers clear prospects for nanoscale quality control of zeolite-based materials. Inter..
Spatial Heterogeneity of n-Phases Leads to Different Photophysical Properties in Quasi-Two-Dimensional Methylammonium Lead Bromide Perovskite
Simultaneous photocatalytic H<sub>2</sub> generation and organic synthesis over crystalline–amorphous Pd nanocube decorated Cs<sub>3</sub>Bi<sub>2</sub>Br<sub>9</sub>
Single Molecule Nanospectroscopy Visualizes Proton-Transfer Processes within a Zeolite Crystal
Visualizing proton-transfer
processes at the nanoscale is essential
for understanding the reactivity of zeolite-based catalyst materials.
In this work, the Brønsted-acid-catalyzed oligomerization of
styrene derivatives was used for the first time as a single molecule
probe reaction to study the reactivity of individual zeolite H-ZSM-5
crystals in different zeolite framework, reactant and solvent environments.
This was accomplished via the formation of distinct dimeric and trimeric
fluorescent carbocations, characterized by their different photostability,
as detected by single molecule fluorescence microscopy. The oligomerization
kinetics turned out to be very sensitive to the reaction conditions
and the presence of the local structural defects in zeolite H-ZSM-5
crystals. The remarkably photostable trimeric carbocations were found
to be formed predominantly near defect-rich crystalline regions. This
spectroscopic marker offers clear prospects for nanoscale quality
control of zeolite-based materials. Interestingly, replacing <i>n</i>-heptane with 1-butanol as a solvent led to a reactivity
decrease of several orders and shorter survival times of fluorescent
products due to the strong chemisorption of 1-butanol onto the Brønsted
acid sites. A similar effect was achieved by changing the electrophilic
character of the <i>para</i>-substituent of the styrene
moiety. Based on the measured turnover rates we have established a
quantitative, single turnover approach to evaluate substituent and
solvent effects on the reactivity of individual zeolite H-ZSM-5 crystals
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