Ilia Shkrob

Bio: Ilia Shkrob is an academic researcher from Hebrew University of Jerusalem. The author has contributed to research in topics: Polyunsaturated fatty acid & Aphanizomenon. The author has an hindex of 9, co-authored 10 publications receiving 419 citations.

Studies on Charge Transport in Self-Assembled Gold−Dithiol Films: Conductivity, Photoconductivity, and Photoelectrochemical Measurements

Abstract: Electronic transport in gold−dithiol nanoparticle films was studied using conductivity, photoconductivity, and photoelectrochemical means. The films were characterized by SEM and optical spectroscopy. GC/MS was used for the analysis of the pyrolysis products during heat treatment. Films were assembled on glass substrates using gold sol and different alkanethiol spacers (1,2-ethanedithiol (C2), 1,5-pentanedithiol (C5), and 1,8-octanedithiol (C8)). Resistance−temperature measurements revealed that the effective activation energies for conduction were 0, 5, and 15 meV for films assembled using C2, C5, and C8 spacers, respectively. Light action spectra of photoconductivity of gold−dithiol nanoparticle films revealed 0.8−1.0 eV threshold photon energy. The difference between the observed threshold energies points to different mechanisms for conductivity and photoconductivity. The low effective activation energy for dark conduction is attributed to a mixed mechanism of conduction, tunneling between insulated pa...

Formation of Polysulfides in an Oxygen Rich Freshwater Lake and Their Role in the Production of Volatile Sulfur Compounds in Aquatic Systems

Abstract: We present the first observations on the occurrence of inorganic polysulfides in an oxygen rich aquatic system. Inorganic polysulfides were found both in the hypolimnion and the epilimnion of a freshwater lakeLake Kinneret. The presence of these compounds in oxic systems resolves the enigma concerning the mechanism of formation of dimethyl disulfide, dimethyltrisulfide, and dimethyltetrasulfide in oxygen rich aquatic systems and marine water. The abundance of low molecular weight organic and inorganic polysulfides relative to the a priori postulated dominance of the pentasulfide family is explained by the low level of polysulfides in oxygen-rich aquatic systems. Thermodynamic calculations show that for trace levels of reduced sulfur compounds, dimethyl disulfide becomes the dominant polysulfide form.

Branched alkanes and other apolar compounds produced by the cyanobacterium Microcoleus vaginatus from the Negev desert

Abstract: Gas chromatography–mass spectrometry on serially coupled capillary columns with different polarity of stationary phases showed that the soil cyanobacterium Microcoleusvaginatusfrom the Negev desert produces an unusual mixture of 4 normal and more than 60 branched alkanes, as well as a number of fatty acids, cyclic and unsaturated hydrocarbons, aldehydes, alcohols, and ketones. The dominant compounds were heptadecane (12%), 7-methylheptadecane (7.8%), hexadecanoic acid (6.5%), (Z)-9-hexadecenoic acid (5.6%), 4-ethyl-2,2,6,6-tetramethylheptane (2.8%), (Z)-9-octadecenoic acid (2.8%), and 4-methyl-5-propylnonane (2.7%).

Biogeochemistry of marine dissolved organic matter

Abstract: Marine dissolved organic matter (DOM) is a complex mixture of molecules found throughout the world's oceans. It plays a key role in the export, distribution, and sequestration of carbon in the oceanic water column, posited to be a source of atmospheric climate regulation. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, focuses on the chemical constituents of DOM and its biogeochemical, biological, and ecological significance in the global ocean, and provides a single, unique source for the references, information, and informed judgments of the community of marine biogeochemists. Presented by some of the world's leading scientists, this revised edition reports on the major advances in this area and includes new chapters covering the role of DOM in ancient ocean carbon cycles, the long term stability of marine DOM, the biophysical dynamics of DOM, fluvial DOM qualities and fate, and the Mediterranean Sea. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, is an extremely useful resource that helps people interested in the largest pool of active carbon on the planet (DOC) get a firm grounding on the general paradigms and many of the relevant references on this topic. * Features up-to-date knowledge of DOM, including five new chapters* The only published work to synthesize recent research on dissolved organic carbon in the Mediterranean Sea* Includes chapters that address inputs from freshwater terrestrial DOM

Nanoelectrochemistry: metal nanoparticles, nanoelectrodes, and nanopores.

Abstract: Nanois a big prefix-word. Much of contemporary chemistry focuses on small scale structures, and indeed, molecular science is intrinsically on the nanometer scale. Selecting material for this review of “nanoelectrochemistry” involved a necessary arbitrariness of defining what “nano” means. Here, it refers to a dimensional scale of electrodes and electrochemical events, as opposed to time or volume or mass. Still, most of molecular chemistry fits within the 1-1000 nm range of dimensions, as does a substantial body of charged or conducting substances, e.g., microand nanoparticles, colloids, emulsions, and aerosols. The topology of conducting substances can have nanoscopic dimensions, with mesoporous materials such as areogels and xerogels being contemporary examples. These are important topics, as are nanoparticle applications in bioanalysis, catalysis, and electrocatalysis, and nanomaterials such as fullerenes, carbon nanotubes and networks, semiconductor nanoparticles, and arrays of nanoelectrodes and nanopores. With apologies to those topics, I have chosen to whittle the scenery down to the electrochemistry of nanoparticles, and single nanoelectrodes and nanopores. Within these, attention will be biased toward metal nanoparticles having dimensions of only a small number of nanometers, because it is in the 10 nm and lower size range where many significant recent advances have been made. Similarly, I will focus mainly on single nanoelectrodes and nanopores, as opposed to arrays thereof. The literature cited here is predominantly not over a decade old; a lot has happened, and quickly. I hope the reader will find it an interesting decade. What has promoted the rapid advances in the 1-10 nm range of dimensions? For nanoparticles, progress has been stimulated by synthetic innovations; for single nanoelectrodes and single nanopores, similarly by advances in methods of fabrication. Further, while making something that is really small can be special, it does not push science forward unless one can demonstrate its size and shape and chemical composition. So some substantial attention will be given to developments in fabrication and characterization. Knowing what you have prompts the more interesting and burning questions of how do its properties (of any kind, spectroscopic, electron transfer, etc). depend on its size, on the dimensions of other substances and structures that it interacts with (as in a nanopore), on the particular geometry of the small size, and of course on the extent that the chemist and electrochemist can tailor the composition and/or surface of the small particle/electrode/pore object to further expand its range of properties and usefulness. The authors cited in this report are leaving the first trackssto some extent tentative trackssin the scientific sand in these areas of nanoscience.

Self-Assembled Gold Nanoparticle/Alkanedithiol Films: Preparation, Electron Microscopy, XPS-Analysis, Charge Transport and Vapor-Sensing Properties

Abstract: Gold nanoparticle/alkanedithiol films were prepared via layer-by-layer self-assembly. For the assembly process, dodecylamine-stabilized Au nanoparticles with an average size of 4 nm and alkanedithiols with different alkylene chain lengths (C6, C9, C12, C16) were used. The thickness of the films was determined by AFM and ranged between 26 and 34 nm. FE-SEM and TEM images indicate that the particle size within the film materials was similar to that of the dodecylamine-stabilized particles used for film preparation. The composition of the films was analyzed by XPS. The absence of the nitrogen signal indicated that the dodecylamine ligands were quantitatively exchanged by alkanedithiol molecules during film assembly. Two sulfur signals were observed, which could be assigned to sulfur bound to gold (S−Au) and to free thiol groups (S−H). As indicated by the relative signal intensities, about 60% of the alkanedithiol molecules were bound with both ends to the nanoparticles, whereas 40% were bound with only one t...