Ahmed B. Soliman

The potential of a graphene-supported porous-organic polymer (POP) for CO2 electrocatalytic reduction

A one-pot, bottom-up assembly of a pyrimidine-containing porous-organic polymer (PyPOP) was conducted to homogenously deposit the PyPOP atop unmodified graphene sheets, affording a composite material PyPOP@G. The PyPOP demonstrated an appreciable affinity toward CO2 capture but was found to be largely insulating, hindering its usage in potential electrochemical conversion of CO2. However, its composite with graphene was found to be microporous, with maintained affinity toward CO2 and furthermore demonstrated significant electrochemical activity toward CO2 reduction (5 mA cm-2 at -1.6 V), not observed in either of its two components separately.

Multiband Printed Metamaterial Inverted-F Antenna (IFA) for USB Applications

A printed multiband coplanar waveguide (CPW)-fed inverted-F antenna (IFA) is presented in this letter. The concept of loading a printed-IFA with composite right/left-handed (CRLH) unit cells is theoretically and experimentally investigated by using electromagnetic simulators, Advanced Design System (ADS) and High Frequency Structure Simulator (HFSS), for universal serial bus (USB) applications. The proposed USB antenna structure consists of a CPW printed-IFA with two arms loaded by two CRLH unit cells to achieve two extra operating bands in addition to the two fundamental resonant frequencies of two IFA arms. The structure is designed to operate at GSM 1.8 GHz, Bluetooth 2.4 GHz, WiMAX 3.5 GHz, and WLAN 5.2 GHz. Measured and simulated results are in good agreement with the theoretical predictions.

Tuning surface accessibility and catalytic activity of Au nanoparticles through immobilization within porous-organic polymers

Herein, we outline a facile and promising approach in which microporous organic polymer matrices were constructed from their molecular building blocks, in the presence of surface-functionalized Au nanoparticles (AuNPs) as one component of the system. This approach permitted the construction of microporous networks around AuNPs and consequently allowed controlling access of small guest molecules to the surface of the AuNPs. Gas sorption measurements confirmed the permanent microporosity of the composites, and furthermore demonstrated interdependence between the size and degree of connectivity of the molecular linkers, the amount of AuNPs added to the initial reaction mixture, and porosity of the composites. A clear electrocatalytic activity dependence on the molecular size of the substrate and pore system of the host matrix is demonstrated. Of special significance is the enhanced catalytic activity of the investigated composites towards borohydride oxidation (mass activity of 8.8–12 mA mg−1) as compared to flat Au electrode (1.6 mA mg−1). These results show a versatile pathway to utilize decorated AuNPs, as functionalized building units, in construction of porous solids with hybrid composition and tunable properties.

Surface functionality and electrochemical investigations of a graphitic electrode as a candidate for alkaline energy conversion and storage devices.

Graphite is a typical electrocatalyst support in alkaline energy conversion and storage devices such as fuel cells, supercapacitores and lithium ion batteries. The electrochemical behaviour of a graphite electrode in 0.5 M NaOH was studied to elucidate its surface structure/electrochemical activity relationship. Graphite voltammograms are characterized by an anodic shoulder AI and a cathodic peak CI in addition to the oxygen reduction reaction plateaus, PI and PII. AI and CI were attributed to oxidation and reduction of some graphite surface function groups, respectively. Rotating ring disk electrode (RRDE) study revealed two different oxygen types assigned as inner and outer oxygen. The inner oxygen was reduced via the more efficient 4-electron pathway. The outer oxygen reduction proceeded with a lower efficient 2-electron pathway. The calculated percentages of the 4-electron pathway were ranged from 70% to 90%. A full mechanism for the graphite surface function groups changes over the studied potential window was suggested through the combination between the voltammetric, FT-IR and Raman results.

Microporous cobaloxime–graphene composite: a reloadable non-noble metal catalyst platform for the proton reduction reaction

A heterogeneous catalyst for the proton reduction reaction was constructed through immobilization of cobaloxime, in a microporous solid, atop unmodified graphene sheets through a one-pot reaction. This approach afforded a true heterogeneous catalyst to circumvent the known poor stability of cobaloximes in aqueous solutions. The composite demonstrated significant electrochemical activity and ability to reload the Co ions and with enhanced activity toward proton reduction (an onset of ∼−11 mV and a current density of 9 mA cm−2 at −0.88 V vs. RHE).

Tailoring the Oxygen Reduction Activity of Hemoglobin through Immobilization within Microporous Organic Polymer–Graphene Composite

A facile one-pot, bottom-up approach to construct composite materials of graphene and a pyrimidine-based porous-organic polymer (PyPOP), as host for immobilizing human hemoglobin (Hb) biofunctional molecules, is reported. The graphene was selected because of its excellent electrical conductivity, while the PyPOP was utilized because of its pronounced permanent microporosity and chemical functionality. This approach enabled enclathration of the hemoglobin within the microporous composite through a ship-in-a-bottle process, where the composite of the PyPOP@G was constructed from its molecular precursors, under mild reaction conditions. The composite-enclathrated Fe-protoporphyrin-IX demonstrated electrocatalytic activity toward oxygen reduction, as a functional metallocomplex, yet with a distinct microenvironment provided by the globin protein. This approach delineates a pathway for platform microporous functional solids, where fine-tuning of functionality is facilitated by judicious choice of the active host molecules or complexes, targeting specific application.

Chest ultrasound versus chest computed tomography for imaging assessment before medical thoracoscopy

Background and objective The aim of this work was to assess the concordance between chest ultrasound (US) and chest computed tomography (CT) findings before medical thoracoscopy (MT) and the impact of the findings on the conduct and outcome of MT. Materials and methods The study was conducted prospectively on 52 patients referred for MT. All patients received chest X-ray (CXR), chest US, and chest CT before the procedure. Images were evaluated and findings were correlated with thoracoscopic findings. Results US findings were discordant with CT findings regarding consistency, septation, and loculation of effusion in 24/52 patients, with US detecting the findings in 24/24 patients. None of these findings was detectable on CT. US was superior to CT in detection of diaphragmatic nodules (16/52, 3/52, respectively). US findings affected MT conduct in 20/52 cases and outcome in 5/40 cases, and they were consistent with MT findings in 39/40 cases; US and CT missed septation in one case. US findings were concordant with CT findings regarding site and size of effusion and pleural masses, sizable nodules, and thickening. US missed discrete small parietal nodules in 10/52, consolidation in 2/52, mediastinal lymphadenopathy in 6/52, and mediastinal shift in 42/52 cases. CXR could identify mediastinal shift but none of other CT findings were missed by US. None of US-missed abnormalities directly altered MT management. Conclusion US identifies more explicitly the imaging information relevant to MT compared with chest CT. Pre-MT imaging workup can be limited to CXR and US, reserving chest CT for cases in which US is technically unrevealing.