In situ space- and time-resolved sorption kinetics of anionic dyes on individual LDH crystals

Fluorescence spectroscopy is employed to follow the ion exchange of an emissive dye - a carboxylated perylene imide - on a layered double hydroxide. The exchange of the carboxylate ions starts at the edges of the layered double hydroxide crystals and is followed by diffusion to the basal plane. Such space-resolved observations provide a solid basis for modelling and studying the mechanisms of exchange

Highly Photoluminescent Sulfide Clusters Confined in Zeolites

© Copyright 2018 American Chemical Society. The design, synthesis and photoluminescence characterization of sulfide cluster-based zeolitic materials with the general formula Na8[SiAlO4]6SxCl2-2x is presented in this report. The employed experimental conditions, which included the thermal treatment of sodium Linde type A (Na-LTA) zeolites in the presence of Na2SO4 and NaCl, yielded highly photoluminescent sulfur-zeolites with remarkably large Stokes shifts. An emission band at 650 nm for samples with low sulfur contents is observed when excited at 380 nm, which is fully consistent with S2- clusters as light-emitting centers. These orange emitting materials display external quantum efficiencies (EQEs) reaching 53% with peculiar high temperature photoluminescence stability up to 450 °C. For higher S/Cl molar ratios, a gradual conversion to near-infrared (NIR) light-emitting centers is observed with a maximum at 780 nm. This novel NIR luminescent species with EQEs of about 10% are attributed to polysulfide clusters (tentatively S42- species). Given the high EQE values, large Stokes shifts, and thermal stability, the materials presented in this report can find applications in light down-conversion systems or as phosphors in lighting devices.status: publishe

X-Ray-Induced Growth Dynamics of Luminescent Silver Clusters in Zeolites

Herein, AlKα X-rays are used to drive the growth of luminescent silver clusters in zeolites. The growth of the silver species is tracked using Auger spectroscopy and fluorescence microscopy, by monitoring the evolution from their ions to luminescent clusters and then metallic, dark nanoparticles. It is shown that the growth rate in different zeolites is determined by the mobility of the silver ions in the framework and that the growth dynamics in calcined samples obeys the Hill-Langmuir equation for noncooperative binding. Comparison of the optical properties of X-ray-grown silver clusters with silver clusters formed by standard heat treatment indicates that the latter have a higher specificity toward the formation of luminescent clusters of a specific (small) nuclearity, whereas the former produce a wide distribution of cluster species as well as larger nanoparticles.status: publishe

Hot π-electron tunneling of metal–insulator–cof nanostructures for efficient hydrogen production

202308 bcvcAccepted ManuscriptOthersNSFC; the Natural Science Foundation of Fujian Province of P.R. China; the Science and Technology Project of Education Office of Fujian Province of P.R. China; the State Key Laboratory of Photocatalysis on Energy and EnvironmentPublishe

Air-based photoelectrochemical cell capturing water molecules from ambient air for hydrogen production

A system is demonstrated that autonomously produces hydrogen gas using sunlight and outside air as the only inputs. Oxygen and hydrogen formation reactions occur on either side of a monolithic "solar membrane" inserted in a two-compartment photoelectrochemical cell. A surface film of Nafion (R) serves as a solid electrolyte. This proof of concept invites further development of air-based cells

Giant Electron-Phonon Coupling and Deep Conduction Band Resonance in Metal Halide Double Perovskite

The room-temperature charge carrier mobility and excitation–emission properties of metal halide perovskites are governed by their electronic band structures and intrinsic lattice phonon scattering mechanisms. Establishing how charge carriers interact within this scenario will have far-reaching consequences for developing high-efficiency materials for optoelectronic applications. Herein we evaluate the charge carrier scattering properties and conduction band environment of the double perovskite Cs2AgBiBr6 via a combinatorial approach; single crystal X-ray diffraction, optical excitation and temperature-dependent emission spectroscopy, resonant and nonresonant Raman scattering, further supported by first-principles calculations. We identify deep conduction band energy levels and that scattering from longitudinal optical phonons—via the Fröhlich interaction—dominates electron scattering at room temperature, manifesting within the nominally nonresonant Raman spectrum as multiphonon processes up to the fourth order. A Fröhlich coupling constant nearing 230 meV is inferred from a temperature-dependent emission line width analysis and is found to be extremely large compared to popular lead halide perovskites (between 40 and 60 meV), highlighting the fundamentally different nature of the two “single” and “double” perovskite materials branches

Visualization of molecular fluorescence point spread functions via remote excitation switching fluorescence microscopy

The enhancement of molecular absorption, emission and scattering processes by coupling to surface plasmon polaritons on metallic nanoparticles is a key issue in plasmonics for applications in (bio)chemical sensing, light harvesting and photocatalysis. Nevertheless, the point spread functions for single-molecule emission near metallic nanoparticles remain difficult to characterize due to fluorophore photodegradation, background emission and scattering from the plasmonic structure. Here we overcome this problem by exciting fluorophores remotely using plasmons propagating along metallic nanowires. The experiments reveal a complex array of single-molecule fluorescence point spread functions that depend not only on nanowire dimensions but also on the position and orientation of the molecular transition dipole. This work has consequences for both single-molecule regime-sensing and super-resolution imaging involving metallic nanoparticles and opens the possibilities for fast size sorting of metallic nanoparticles, and for predicting molecular orientation and binding position on metallic nanoparticles via far-field optical imaging