Richard Landers

Bio: Richard Landers is an academic researcher from State University of Campinas. The author has contributed to research in topics: X-ray photoelectron spectroscopy & Catalysis. The author has an hindex of 33, co-authored 260 publications receiving 4401 citations. Previous affiliations of Richard Landers include Universidade Federal de Minas Gerais & University of São Paulo.

Aniline Polymerization into Montmorillonite Clay: A Spectroscopic Investigation of the Intercalated Conducting Polymer

Abstract: The polymerization of aniline intercalated into montmorillonite clay was monitored by in situ UV−vis−NIR and resonance Raman spectroscopies and in situ small-angle X-ray scattering. In the initial stages of the polymerization, it is observed the PANI−ES polaronic band at 750 nm in the UV−vis−NIR spectrum and also the characteristic PANI-ES resonance Raman spectrum (excited at 632.8 nm), which indicate that the head-to-tail coupling reactions between anilinium radical cations are occurring. Nevertheless, the resonance Raman spectrum excited at 488.0 nm presents bands at 1211, 1370, 1455, and 1608 cm-1, assigned to the benzidine dication species, which suggests that tail-to-tail coupling reactions are also occurring. In the final stages of polymerization, the presence of electronic absorption bands at 670 and 620 nm indicates the formation of new chromophoric species, which is also confirmed by its peculiar resonance Raman spectrum at 632.8 nm wavelength. The in situ SAXS results show that, during the anili...

Enhanced photocatalytic properties of core@shell SiO2@TiO2 nanoparticles

Abstract: SiO2@TiO2 core@shell nanoparticles (CSNs) have recently attracted great attention due to their unique and tunable optical and photocatalytic properties and higher dispersion of the supported TiO2. Thus, development of facile, reproducible and effective methods for the synthesis of SiO2@TiO2 CSNs and a fundamental understanding of their improved properties, derived from combination of different core and shell materials, is of great importance. Here we report a very facile and reproducible method for the synthesis of CSNs with a control of particle morphology, crystallinity and phase selectivity, and provide important insight into the effect of core@shell configuration on the photocatalytic and optical properties of SiO2@TiO2 CSNs. For this purpose, synthesis of highly dispersed anatase nanocrystals (∼5 nm) of high surface area was carried out by supporting these nanocrystals on silica sub-micron spheres in the form of a porous shell of controlled thickness (10–30 nm). The amorphous TiO2 shell was crystallized into anatase using a low temperature (105 °C) hydrothermal treatment. The resulting CSNs were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray photoelectron spectroscopy, X-ray diffraction, vibrational spectroscopy, zeta-potential measurements, BET surface area and electron paramagnetic resonance measurements. Both experimental data and theoretical simulations showed that due to the size of the complete particle (SiO2@TiO2), the general optical response of the system is regulated by Rayleigh scattering, exhibiting a red-shift of the extinction spectra as shell-thickness increases. The SiO2@TiO2 configuration leads to efficient light harvesting by increasing the optical path inside the core@shell particles. An enhanced photoactivity and good recyclability of SiO2@TiO2 CSNs was demonstrated compared to unsupported TiO2. Together with BET surface area measurements, direct assessment of the density of photocatalytic sites probed by electron paramagnetic resonance measurements was used to provide insight into the enhanced photocatalytic activity of CSNs, which is also understood as a consequence of Rayleigh scattering, relative enhancement of the adsorption of organic molecules on the core@shell photocatalyst surface and increased optical path inside the SiO2@TiO2 particles. All these aspects are directly influenced by the core@shell configuration of SiO2@TiO2 samples.

X-ray photoemission and Auger energy shifts in some gold-palladium alloys.

Abstract: La comparaison des resultats avec les previsions de la version de l'atome excite du modele quasiatomique, montre que les corrections de transfert de charge au deplacement de l'energie cinetique d'Auger de l'or sont petites. Les resultats sont aussi coherents avec l'interpretation du deplacement du parametre d'Auger de l'or et avec l'analyse de la contribution de l'electron de valence a l'energie de liaison de cœur de l'or

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Magnetically recoverable nanocatalysts.

Abstract: We gratefully acknowledge funding and support from King Abdullah University of Science and Technology (KAUST). Thanks are also due to the KAUST communication department for designing several images for this Review.

Magnetically Separable Nanocatalysts: Bridges between Homogeneous and Heterogeneous Catalysis

Abstract: Recovery and reuse of expensive catalysts after catalytic reactions are important factors for sustainable process management. The aim of this Review is to highlight the progress in the formation and catalytic applications of magnetic nanoparticles and magnetic nanocomposites. Directed functionalization of the surfaces of nanosized magnetic materials is an elegant way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation.

Bimetallic Nanocrystals: Syntheses, Properties, and Applications

Abstract: Achieving mastery over the synthesis of metal nanocrystals has emerged as one of the foremost scientific endeavors in recent years. This intense interest stems from the fact that the composition, size, and shape of nanocrystals not only define their overall physicochemical properties but also determine their effectiveness in technologically important applications. Our aim is to present a comprehensive review of recent research activities on bimetallic nanocrystals. We begin with a brief introduction to the architectural diversity of bimetallic nanocrystals, followed by discussion of the various synthetic techniques necessary for controlling the elemental ratio and spatial arrangement. We have selected key examples from the literature that exemplify critical concepts and place a special emphasis on mechanistic understanding. We then discuss the composition-dependent properties of bimetallic nanocrystals in terms of catalysis, optics, and magnetism and conclude the Review by highlighting applications that h...