Alexander D. Modestov

Bio: Alexander D. Modestov is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Catalysis & Proton exchange membrane fuel cell. The author has an hindex of 22, co-authored 69 publications receiving 1743 citations. Previous affiliations of Alexander D. Modestov include D. Mendeleev University of Chemical Technology of Russia & Hebrew University of Jerusalem.

Sol−Gel Materials in Electrochemistry

Abstract: The subject of sol−gel electrochemistry is introduced, starting with a brief account of milestones in its evolution. Then, the types of sol−gel materials that are useful for electrochemistry are presented, followed by a description of recent advances in the various fields of sol−gel electrochemistry. Modified electrodes, solid electrolytes, electrochromic devices, and corrosion protection coatings are described. Emerging fields such as RuO2 supercapacitors and electrochemical synthesis of sol−gel precursors are also addressed.

Synergistic Effect of Superhydrophobicity and Oxidized Layers on Corrosion Resistance of Aluminum Alloy Surface Textured by Nanosecond Laser Treatment

Abstract: We report a new efficient method for fabricating a superhydrophobic oxidized surface of aluminum alloys with enhanced resistance to pitting corrosion in sodium chloride solutions The developed coatings are considered very prospective materials for the automotive industry, shipbuilding, aviation, construction, and medicine The method is based on nanosecond laser treatment of the surface followed by chemisorption of a hydrophobic agent to achieve the superhydrophobic state of the alloy surface We have shown that the surface texturing used to fabricate multimodal roughness of the surface may be simultaneously used for modifying the physicochemical properties of the thick surface layer of the substrate itself Electrochemical and wetting experiments demonstrated that the superhydrophobic state of the metal surface inhibits corrosion processes in chloride solutions for a few days However, during long-term contact of a superhydrophobic coating with a solution, the wetted area of the coating is subjected to corrosion processes due to the formation of defects In contrast, the combination of an oxide layer with good barrier properties and the superhydrophobic state of the coating provides remarkable corrosion resistance The mechanisms for enhancing corrosion protective properties are discussed

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...

A review of water treatment membrane nanotechnologies

Abstract: Nanotechnology is being used to enhance conventional ceramic and polymeric water treatment membrane materials through various avenues. Among the numerous concepts proposed, the most promising to date include zeolitic and catalytic nanoparticle coated ceramic membranes, hybrid inorganic–organic nanocomposite membranes, and bio-inspired membranes such as hybrid protein–polymer biomimetic membranes, aligned nanotube membranes, and isoporous block copolymer membranes. A semi-quantitative ranking system was proposed considering projected performance enhancement (over state-of-the-art analogs) and state of commercial readiness. Performance enhancement was based on water permeability, solute selectivity, and operational robustness, while commercial readiness was based on known or anticipated material costs, scalability (for large scale water treatment applications), and compatibility with existing manufacturing infrastructure. Overall, bio-inspired membranes are farthest from commercial reality, but offer the most promise for performance enhancements; however, nanocomposite membranes offering significant performance enhancements are already commercially available. Zeolitic and catalytic membranes appear reasonably far from commercial reality and offer small to moderate performance enhancements. The ranking of each membrane nanotechnology is discussed along with the key commercialization hurdles for each membrane nanotechnology.

Enzymatic biofuel cells for implantable and microscale devices.

Abstract: Introduction Technology for electrical power generation using enzyme catalysts, established four decades ago, has recently received increased attention associated with demand for micro-scale and implantable power supplies. The main challenges, namely the fragility of enzyme molecules, characteristic low current density, and poor fundamental understanding of redox biocatalysis, are currently being addressed from a variety of research perspectives, to take advantage of enzyme selectivity, low temperature and moderate pH activity, and manufacturability in small-scale devices. Such an effort benefits from four decades of multidisciplinary research in biosensors and related bioelectrochemical fields. This review paper summarizes the current state of enzymatic biofuel cell research in the context of foreseeable applications and assesses the future prospects of the technology. Emphasis is placed on device performance and engineering aspects, with a view toward practical portable power devices based on enzymatic biofuel cells. Research in biocatalytically modified electrodes, particularly for sensor applications, has provided a significant technological underpinning for current biofuel cell development. There exists significant overlap in technical requirements between sensors and biofuel cells, including chemical and mechanical stability, selectivity, and cost of materials. However, these two technologies diverge in the areas of current density, cell potential and stability. There exists extensive review literature in the area of biological fuel cells. Notably, Palmore and Whitesides summarized biological fuel cell concepts and performance up until about 1992. More recently, Katz and Willner discussed recent progress in novel electrode chemistries for both microbial and enzymatic fuel cells. We do not duplicate these valuable contributions, but instead focus on the strengths and weaknesses of state-of-art materials in the context of specific classes of applications, and point to areas where additional knowledge is currently needed to exploit biological fuel cells. With some exceptions, we focus on contributions made after 1992. Biofuel cells have traditionally been classified according to whether the catalytic enzymes were located inside or outside of living cells. If living cells are involved the system is considered to be microbial, and if not it is considered enzymatic. Although microbial fuel cells posses unique features unmatched by enzymatic cells, such as long-term stability and fuel efficiency, the power densities associated with such devices are typically much lower owing to resistance to mass transfer across cell membranes. Thus, microbial fuel cells are expected to find limited application in smallscale electronic devices. This review will focus on enzymatic biofuel cells. While such cells typically demonstrate reduced stability due to the limited lifetime of extracellular enzymes, and are typically unable to fully oxidize fuels, they allow for substantial concentration of catalysts and removal of mass transfer barriers and provide higher current and power densities, approaching the range of applicability to microand mini-scale electronics applications. Applications and Requirements The range of possible applications for biofuel cells may be broken down into three main subclasses: 1. Implantable power, such as micro-scale cells implanted in human or animal tissue, or larger cells implanted in blood vessels. 2. Power derived from ambient fuels or oxidants, mainly plant saps and juices, but extending to sewage and other waste streams. 3. Power derived from conventional fuels including hydrogen, methanol or higher alcohols. Classes 1 and 2 are closely related. The fuels available for implantable power, such as blood borne glucose or lactate, are ambient in the sense that they are present in a physiological environment in the absence of a fuel cell device. One major distinction between these two classes is that the ambient-fueled cell need not be implanted, and focuses on plantor waste-derived fuels, whereas the implantable cell focuses on animal-derived fuels and is present within the physiological system. Class 3 is unique in that this class competes with well-established conventional fuel cell technology. To a greater or lesser extent, all three classes share the fundamental technical requirements of high power density and high activity.