Measurement of photoneutron doses in and out of high-energy X-ray beam of a SATURNE-20 medical linear accelerator by ECE polycarbonate detectors

Photoneutron contaminations in and out of high energy X-ray beams of the medical linear accelerator SATURNE 20 (CGR) of the Radiotherapy Department of Omeed Hospital in Isfahan, Iran, have been determined using 250 μm polycarbonate (PC) dosimeters, in strips or in sheets, processed by electrochemical etching (ECE) using specially designed ECE chambers to etch larger sheets. A two dimensional or topographical distribution of neutron contamination was also determined in a full size beam. The neutron dose equivalents (Hn) in the beam of 18 MV X-rays at 80 cm FSD were determined to be linear functions of X-ray dose equivalents (Hx) up to 1400 cSv. The distribution of the Hn at different X-ray doses showed bell-shape profiles with maxima at the isocenter. The ratios of dose equivalents of neutrons to those of X-rays increased as the field size increased having values of 0.22%, 0.28%, 0.31% and 0.37% for field sizes of 10×10, 20×20, 30×30, and 40×40 cm² respectively. Although such neutron dose equivalents can be corrected for patient treatment, it can cause radiation protection problems for workers where the design of the facility is not well planned.     

Electrocatalytic reactions involving the NiII—ZnII—2,2"-bipyridine system

Factors determining the effect of Zn^II ions on the catalytic activity of the Ni^II complexes with 2,2"-bipyridine (bpy) in the reduction of organohalides were elucidated by cyclic voltammetry and electrolysis. The mechanism proposed involves the reduction of the Ni^IIbpy complex to Ni⁰bpy, the oxidative addition of organohalides to the Ni⁰bpy complex, and nickel transmetallation with the cathode-generated Zn⁰ to form an organozinc compound.     

Synthesis and Characterization of CdS Nanoparticles with Strong Electrolyte Behavior

The CdS nanoparticles whose structure is similar to a strong electrolyte were synthesized by the colloidal chemical method. The CdS nanoparticles with Cd²⁺-rich surface are capped by the electrically neutral ligand of 2,2-bipyridine (bpy), and the counterion, BPh₄ ^-, is adsorbed around the particle as balance charge. The donation from 2,2-bipyridine at 2-position to the Cd²⁺-rich surface of the CdS nanoparticles was characterized by X-ray photoelectron spectroscopy (XPS). These CdS nanoparticles can redisperse in pyridine (py) or DMF, and have high stability. The determination of electroconductivity and the electrophoresis deposition in dilute solution containing the CdS nanoparticles further prove the rationality of the above electrolyte structure of the CdS nanoparticles.     

Band‐gap engineering of polythiophenes via dithienophosphole doping

A series of polythiophenes doped with dithieno[3,2‐b:2′,3′‐d]phosphole units at varying levels (0–17%) were synthesized and characterized. Polymer work up provided two series of polymers from chloroform (C) and hexanes (H) for each doping level, respectively. Systematic structure–property studies revealed that the C‐series polymers generally had higher molecular weights than the H‐series, but also slightly higher relative dithienophosphole concentrations, both having a significant impact on the photophysical and electrochemical properties of the polymers. Furthermore, the presence of the dithienophosphole units also stabilizes the LUMO levels, whereas the HOMO levels remain dominated by the thiophene units, resulting in desirable electronics for an interaction with acceptor materials, such as 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl[6,6]C₆₁. Importantly, increasing amount of dithienophosphole doping results in increased conductivities for the polymers in their oxidized state, while concurrently significantly stabilizing the neutral polythiophenes toward oxidation under environmental conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A Theory of Electron Transfer in Bridged and Supramolecular Systems

Expressions are derived for the tunnel electric current between two metals produced by the adiabatic transitions of the electrons through a bridge electron level. A new possible physical phenomenon is discussed, viz. electronically driven oscillations of the electron bridge level between two molecular wires.     

Anchoring of sulfur‐containing alkylphosphonic and semifluorinated alkylphosphonic molecules on a polycrystalline aluminum substrate

Self‐assembly on a polycrystalline aluminum substrate of two sulfur‐containing alkylphosphonic acids, CH₃? (CH₂)₁₁? S? (CH₂)₂? PO(OH)₂, and CF₃? (CF₂)₇? (CH₂)₂? S? (CH₂)₂? PO(OH)₂, has been compared with CH₃? (CH₂)₁₅? PO(OH)₂. The reaction of the phosphonic head groups with the hydroxyls at the alumina surface to form phosphonates was studied with X‐ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection‐absorption spectroscopy (PM‐IRRAS). Barrier effects of the resulting layers was assessed by electrochemical polarization curves. With the conditions used in the present work for the self‐assembly reaction, it appears that the sulfur‐containing molecules do not perform as well as CH₃? (CH₂)₁₅? PO(OH)₂ in terms of film quality. Questions are raised about the possibility that the sulfur‐containing molecules could undergo cleavage during surface modification. Copyright © 2008 John Wiley & Sons, Ltd.     

Study of Oxidation-Reduction Properties and NO-Donor Ability of Dienediamines in the Indole, Pyrrole, and Thiophene Series

We have conducted an electrochemical study of the oxidation-reduction properties of synthesized dienediamines: derivatives of indole, pyrrole, and thiophene. We have established that reduction of the indicated compounds occurs with successive transfer of two electrons, the first transfer being reversible. We consider the effect of structural factors and the nature of the heterocycle on the ease of reduction of the given compounds. We present the results of an initial study of the NO-donor ability of the compounds upon oxidation.     

A Silicon Nanowire‐Based Electrochemical Sensor with High Sensitivity and Electrocatalytic Activity

A new kind of silicon nanowire (SiNWs)‐based nanoelectrode assembly, a gold‐nanoparticle‐decorated silicon nanowire array (AuNPs@SiNWsAr), is employed for the construction of high‐performance electrochemical sensors. Significantly, the electrochemical nanosensors are capable of sensitive detection of various electroactive molecules (e.g., dopamine (DA), ascorbic acid (AA), hydrogen peroxide (H₂O₂), and glucose). Further, DA molecules loaded on the surface of AuNPs@SiNWsAr preserve stable high electroactivity overnight without special protection, while free DA molecules may lose their biological activity due to severe oxidization in ambient environment. These findings may offer new opportunities for the design of high‐performance electrochemical nanosensors with high sensitivity and robust stability.     

Self‐Assembly of Ag6 Clusters into Nanowires for Nonenzymatic Electrochemical Sensing of Glucose

Self‐assembly of metal nanoclusters into 3D ordered superstructures and the exploration of their electrochemical properties are highly significant for fundamental research and practical application. In this study, atomically precise Ag₆(NALC)₅ nanoclusters are successfully synthesized and their structure is determined carefully. It is interesting that the prepared Ag₆(NALC)₅ nanoclusters can be self‐assembled into ultrafine nanowires, long ribbons, and finally 3D porous network in the mixed solution of water and ethanol, which can be attributed to the solvent polarity, static electricity interaction between ligands, and the possible Van der Waals attractions. Such assembly phenomenon lays a foundation for the future fabrication of silver clusters‐based nanodevices. In addition, the synthesized silver nanoclusters can be used for electrochemical sensing of glucose with high detection sensitivity, selectivity, and low limit of detection. This work is expected to be helpful for the synthesis of atomically precise metal nanoclusters and their applications in fabrication of nanodevices for chemical sensors.