Increasing the Sensitivity to Short-Lived Species in a Modulated Excitation Experiment.

The combination of spectroscopic and diffraction methods to study chemical transformations is fundamental for the understanding of reaction mechanisms. The identification of short-lived species, likely active species, is often hindered by the contribution of spectator species not directly involved in the reaction. The present study considers two different approaches to obtain increased sensitivity to transient species for experiments obeying the modulated excitation paradigm and exploiting phase sensitive detection (PSD).

An operando emission spectroscopy study of Pt/AlO and Pt/CeO/AlO.

In situ time-resolved spectroscopic examination of catalysts based on well dispersed nanoparticles on metal oxides under transient conditions significantly facilitates the elucidation of reaction mechanisms. In this contribution, we demonstrate the level of structural information that can be obtained using high-energy resolution off-resonant spectroscopy (HEROS) to study 1.3 wt% Pt/AlO and 1.

Kinetic Studies of the Pt Carbonate-Mediated, Room-Temperature Oxidation of Carbon Monoxide by Oxygen over Pt/AlO Using Combined, Time-Resolved XAFS, DRIFTS, and Mass Spectrometry.

The kinetics involved in a recently revealed ambient-temperature mechanism for the catalytic oxidation of carbon monoxide by oxygen over a 5 wt % Pt/AlO catalyst are evaluated within a periodic, plug flow, redox operation paradigm using combined mass spectrometry (MS), diffuse reflectance infrared spectroscopy (DRIFTS), and time-resolved Pt L-edge XAFS. The species that are the most active at room temperature are shown to be a high-wavenumber (ca. 1690 cm) carbonate that we associate directly with a room-temperature redox process occurring in a fraction of the Pt atoms present in the catalyst.

Twisted and tubular silica structures by anionic surfactant fibers encapsulation.

Organic molecules imprinting can be used for introducing specific properties and functionalities such as chirality to mesoporous materials. Particularly organic self-assemblies can work as a scaffold for templating inorganic materials such as silica. During recent years chiral imprinting of anionic surfactant for fabrication of twisted rod-like silica structures assisted by co-structuring directing agent were thoroughly investigated.

Room-temperature carbon monoxide oxidation by oxygen over Pt/Al2O3 mediated by reactive platinum carbonates.

Room-temperature carbon monoxide oxidation, important for maintaining clean air among other applications, is challenging even after a century of research into carbon monoxide oxidation. Here we report using time-resolved diffuse reflectance infrared spectroscopy, X-ray absorption fine structure spectroscopy and mass spectrometry a platinum carbonate-mediated mechanism for the room-temperature oxidation of carbon monoxide. By applying a periodic reduction-oxidation mode of operation we further show that this behaviour is reversible and can be formed into a catalytic cycle that requires molecular communication between metallic platinum nanoparticles and highly dispersed oxidic platinum centres.

Adding diffuse reflectance infrared Fourier transform spectroscopy capability to extended x-ray-absorption fine structure in a new cell to study solid catalysts in combination with a modulation approach.

We describe a novel cell used to combine in situ transmission X-ray absorption spectroscopy (XAS) with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in a single experiment. The novelty of the cell design compared to current examples is that both radiations are passed through an X-ray and IR transparent window in direct contact with the sample. This innovative geometry also offers a wide surface for IR collection.

Subsecond and in situ chemical speciation of Pt/Al(2)O(3) during oxidation-reduction cycles monitored by high-energy resolution off-resonant X-ray spectroscopy.

We report an in situ time-resolved high-energy resolution off-resonant spectroscopy study with subsecond resolution providing insight into the oxidation and reduction steps of a Pt catalyst during CO oxidation. The study shows that the slow oxidation step is composed of two characteristic stages, namely, dissociative adsorption of oxygen followed by partial oxidation of Pt subsurface. By comparing the experimental spectra with theoretical calculations, we found that the intermediate chemisorbed O on Pt is adsorbed on atop position, which suggests surface poisoning by CO or surface reconstruction.

Synchrotron high energy X-ray methods coupled to phase sensitive analysis to characterize aging of solid catalysts with enhanced sensitivity.

X-ray absorption spectroscopy and X-ray diffraction are suitable probes of the chemical state of a catalyst under working conditions but are limited to bulk information. Here we show in two case studies related to hydrothermal aging and chemical modification of model automotive catalysts that enhanced detailed information of structural changes can be obtained when the two methods are combined with a concentration modulated excitation (cME) approach and phase sensitive detection (PSD). The catalysts are subject to a modulation experiment consisting of the periodic variation of the gas feed composition to the catalyst and the time-resolved data are additionally treated by PSD.

Muscle activity around the knee and gait performance in unicompartmental knee arthroplasty patients: a comparative study on fixed- and mobile-bearing designs.

Purpose: Unicompartmental knee arthroplasty (UKA) offers clinical and functional advantages over total knee arthroplasty. The aim of this study was to compare the functional recovery of patients with mobile UKA versus fixed-bearing designs by state-of-the-art gait analysis and, in particular, by assessing muscular activity.

Methods: Ten patients with the Oxford (mobile bearing) and ten patients with Optetrak (fixed bearing) UKA were evaluated at a minimum follow-up of 1 year post-operatively by gait analysis, which includes the main time-distance parameters, kinematics and kinetics of the replaced knee, and muscular activity of the main relevant muscles.