Dynamic Disorder and Stepwise Deactivation in a Chymotrypsin Catalyzed Hydrolysis Reaction

In situ observation of the catalytic activity of individual α-chymotrypsin enzymes reveals a novel pathway for spontaneous deactivation. Rather than deactivating abruptly in a one-step process, the enzyme seems to struggle for life; the activity decreases stepwise with intermittent inactive periods before deactivating irreversibly. During the active periods, dynamic disorder and memory effects are observed, originating from conformational fluctuations within the enzyme's structure

Exploration of Single Molecule Events in a Haloperoxidase and Its Biomimic: Localization of Halogenation Activity

Exploration of Single Molecule Events in a Haloperoxidase and Its Biomimic: Localization of Halogenation Activit

Relating Pore Structure to Activity at the Subcrystal Level for ZSM-5: An Electron Backscattering Diffraction and Fluorescence Microscopy Study

Relating Pore Structure to Activity at the Subcrystal Level for ZSM-5: An Electron Backscattering Diffraction and Fluorescence Microscopy Stud

Determination and Optimization of the Luminescence External Quantum Efficiency of Silver-Clusters Zeolite Composites

We have measured for the first time the external quantum efficiency (EQE) of silver clusters containing zeolites (henceforth referred to as silver-clusters zeolite composites). These materials, fabricated by silver cation exchange followed by a thermal autoreduction process, have EQEs up to 69%. Because of their unique spectral features such as large Stokes shift and high EQE, these materials could be potentially used as phosphors for the fabrication of fluorescent lamps and as wavelength convertors in solar cells. An EQE comparison between less pure commercial silver-loaded zeolites and self-synthesized silver-zeolites showed the importance of the chemical and optical purity of the starting host material. Besides this, the zeolite topology and silver content play an important role on the luminescent performance of such materials. The ability to reliably measure the EQE enabled us to further optimize the synthesis of silver-zeolite composites. A new reduction–oxidation cycle is demonstrated not only to improve the luminescent performance of the silver-zeolite composites but also to enhance their water stability

Characterization of Fluorescence in Heat-Treated Silver-Exchanged Zeolites

Thermal treatment of Ag+-exchanged zeolites yields discrete highly photostable luminescent clusters without formation of metallic nanoparticles. Different types of emitters with characteristic luminescence colors are observed, depending on the nature of the cocation, the amount of exchanged silver, and the host topology. The dominant emission bands in LTA samples are situated around 550 and 690 nm for the samples with, respectively, low and high silver content, while in FAU-type materials only a broad band around 550 nm is observed, regardless of the degree of exchange. Analysis of the fluorescent properties in combination with ESR spectroscopy suggests that a Ag6+ cluster with doublet electronic ground state is associated with the appearance of the 690-nm emitter, having a decay of a few hundred microseconds. Tentatively, the nanosecond-decaying 550-nm emitter is assigned to the Ag3+ cluster. This new class of photostable luminescent particles with tunable emission colors offers interesting perspectives for various applications such as biocompatible labels for intracellular imaging