Kinetics of low pressure ammonia oxidation over Rh(111)

The kinetics of the NH3 + O2 reaction over a Rh(111) single crystal catalytic surface was explored in the 10-6 mbar pressure range at tempera-tures between 300-900 K. Selectivity towards N2 and NO products, and reactive sticking coefficients were monitored in situ using differentially pumped quad-rupole mass spectroscopy (QMS). © 2018, Latin American Applied Research

Traveling interface modulations in the NH 3 + O 2 reaction on a Rh(110) surface

A new type of traveling interface modulation has been observed in the NH 3 + O 2 reaction on a Rh(110) surface. A model is set up which reproduces the effect, which is attributed to diffusional mixing of two spatially separated adsorbates causing an excitability which is strictly localized to the vicinity of the interface of the adsorbate domains. © 2012 the Owner Societies

Metal-organic frameworks meet polymer brushes: enhanced crystalline film growth induced by macromolecular primers

We used poly-(3-sulfopropylmethacrylate) brushes as macromolecular 3D primers to promote heterogeneous nucleation and growth of archetypal ZIF-8 MOF thin films. The enhancement can be understood in terms of a high preconcentration of Zn2+ ions in the polymer brush; this leads to a rapid increase of nucleation sites in the primer.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Síntesis y caracterización de nanopartículas constituidas por polímeros microporosos de coordinación : Autoensamblado de films electroactivos con micro y mesoporosidad controlada

En este trabajo se estudió el efecto de la modificación post-sintética de nanopartículas de polímeros microporosos de coordinación, en particular de ZIF-8, con cisteamina (ZIF-8+Cis) sobre el tamaño, índice de polidispersidad, morfología y estructura cristalina de las ZIF-8 y se comparó el comportamiento de adsorción de ZIF-8+Cis sobre un sustrato de oro con el de nanopartículas de ZIF-8. Se encontró que la cisteamina reduce el tamaño e incrementa la polidispersidad de ZIF-8 pero la morfología y la estructura cristalina no son afectadas significativamente, por lo que es factible anclar cristales de ZIF-8+Cis a sustratos de oro a través de interacción S-Au.Facultad de Ciencias Exacta

Review of biosensing with whispering-gallery mode lasers

This is the final version. Available from Springer Nature via the DOI in this record. Lasers are the pillars of modern optics and sensing. Microlasers based on whispering-gallery modes (WGMs) are miniature in size and have excellent lasing characteristics suitable for biosensing. WGM lasers have been used for label-free detection of single virus particles, detection of molecular electrostatic changes at biointerfaces, and barcode-type live-cell tagging and tracking. The most recent advances in biosensing with WGM microlasers are described in this review. We cover the basic concepts of WGM resonators, the integration of gain media into various active WGM sensors and devices, and the cutting-edge advances in photonic devices for micro- and nanoprobing of biological samples that can be integrated with WGM lasers.Engineering and Physical Sciences Research Council (EPSRC)Engineering and Physical Sciences Research Council (EPSRC)Biotechnology and Biological Sciences Research Council (BBSRC

Effect of acid oxidation treatment on adsorption properties of arc-discharge synthesized multiwall carbon nanotubes

The effect of nitric/sulfuric acid oxidation treatment on commercial arc-discharge multiwall carbon nanotubes was studied. Purification and structure modifications were assessed via Transmission Electron Microscopy and Thermogravimetric Analysis; while changes in adsorption properties were monitored by nitrogen and methane adsorption isotherms. After treatment, nitrogen isotherms present hysteresis loop and an increased BET surface area; while adsorption energies obtained from isosteric heat profiles revealed a marked decrease. We propose an explanation for these findings and use macroscopic experimental data to gain insight on acid oxidation effect on the material.Se estudió el efecto de la oxidación ácida por medio de mezclas sulfúrico/nítrico, de nanotubos comerciales de pared múltiple sintetizados por el método de la descarga de arco. Para evaluar el grado de pureza y las modificaciones estructurales se utilizaron las técnicas de Microscopía Electrónica de Transmisión y Termogravimetría; mientras que los cambios en las propiedades de adsorción fueron monitoreados por medio de la realización de isotermas a distintas temperaturas utilizando gases simples como Nitrógeno y Metano. Luego del tratamiento oxidativo, se observó la aparición de ciclos de histéresis en las isotermas al mismo tiempo que el área superficial según BET se incrementó. Por otro lado, los calores isostéricos obtenidos evidenciaron una disminución importante. Proponemos una explicación posible para estos hallazgos y hacemos uso de la información experimental obtenida para revelar detalles del mecanismo de oxidación de los Nanotubos.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasCentro de Química Inorgánic

Layer-by-layer integration of conducting polymers and metal organic frameworks onto electrode surfaces: enhancement of the oxygen reduction reaction through electrocatalytic nanoarchitectonics

In this work we explore a nanoarchitectonics approach to construct functional composite nanomaterials with enhanced electrocatalytic properties. Functional electrodes were designed in order to combine two key elements: high surface area and porosity with electroactivity, thus enabling their application to the enhancement of the electrochemical oxygen reduction reaction (ORR). We propose a simple, yet unexplored, layer-by-layer (LbL) method which makes use of sequential assembly of colloidal suspensions of polyaniline/polystyrene sulfonate (Pani-PSS), and polyallylamine hydrochloride-coated ZIF-8 metal organic framework nanocrystals (PAH-ZIF-8). The Pani-PSS/PAH-ZIF-8 nanoarchitecture thus obtained benefits from the synergy between the electroactivity provided by the negatively charged conducting polymer component (Pani-PSS), and the high-surface area porous environment provided by the positively charged MOF counterpart (PAH-ZIF-8). LbL-assembled films were found to be electrically connected and feature promising increases in the electrocatalytic currents obtained for the ORR in neutral pH aqueous environments.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Rape with Extreme Violence: The New Pathology in South Kivu, Democratic Republic of Congo

Cathy Nangini and Denis Mukwege describe their work at the Panzi Hospital in the Democratic Republic of Congo, which treats women victims of rape with extreme violence that are often perpetrated at the hands of armed groups

Bromelain Inhibits Allergic Sensitization and Murine Asthma via Modulation of Dendritic Cells

The incidence of atopic conditions has increased in industrialized countries. Persisting symptoms and concern for drug side-effects lead patients toward adjunctive treatments such as phytotherapy. Previously, we have shown that Bromelain (sBr), a mixture of cysteine proteases from pineapple, Ananas comosus, inhibits ovalbumin (OVA)-induced murine model of allergic airway disease (AAD). However, sBr’s effect on development of AAD when treatment is administered throughout OVA-alum sensitization was unknown and is the aim of the present study. C57BL/6J mice were sensitized with OVA/alum and challenged with 7 days OVA aerosol. sBr 6 mg/kg/0.5 ml or PBS vehicle were administered throughout sensitization. Lung, bronchoalveolar lavage (BAL), spleen, and lymph nodes were processed for flow cytometry and OVA-specific IgE was determined via ELISA. sBr treatment throughout OVA-alum sensitization significantly reduced the development of AAD (BAL eosinophils and lymphocytes). OVA-specific IgE and OVA TET+ cells were decreased. sBr reduced CD11c+ dendritic cell subsets, and in vitro treatment of DCs significantly reduced CD44, a key receptor in both cell trafficking and activation. sBr was shown to reduce allergic sensitization and the generation of AAD upon antigen challenge. These results provide additional insight into sBr's anti-inflammatory and antiallergic properties and rationale for translation into the clinical arena

Effect of acid oxidation treatment on adsorption properties of arc-discharge synthesized multiwall carbon nanotubes

The effect of nitric/sulfuric acid oxidation treatment on commercial arc-discharge multiwall carbon nanotubes was studied. Purification and structure modifications were assessed via Transmission Electron Microscopy and Thermogravimetric Analysis; while changes in adsorption properties were monitored by nitrogen and methane adsorption isotherms. After treatment, nitrogen isotherms present hysteresis loop and an increased BET surface area; while adsorption energies obtained from isosteric heat profiles revealed a marked decrease. We propose an explanation for these findings and use macroscopic experimental data to gain insight on acid oxidation effect on the material.Se estudió el efecto de la oxidación ácida por medio de mezclas sulfúrico/nítrico, de nanotubos comerciales de pared múltiple sintetizados por el método de la descarga de arco. Para evaluar el grado de pureza y las modificaciones estructurales se utilizaron las técnicas de Microscopía Electrónica de Transmisión y Termogravimetría; mientras que los cambios en las propiedades de adsorción fueron monitoreados por medio de la realización de isotermas a distintas temperaturas utilizando gases simples como Nitrógeno y Metano. Luego del tratamiento oxidativo, se observó la aparición de ciclos de histéresis en las isotermas al mismo tiempo que el área superficial según BET se incrementó. Por otro lado, los calores isostéricos obtenidos evidenciaron una disminución importante. Proponemos una explicación posible para estos hallazgos y hacemos uso de la información experimental obtenida para revelar detalles del mecanismo de oxidación de los Nanotubos.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasCentro de Química Inorgánic