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The charge redistribution that occurs within dipolar molecules as they self-assemble into organized organic monolayer films is studied. It is shown that charge transfer acts to reduce the dipole-dipole interaction between the molecules but may either decrease or increase the molecule-to-surface dipole moment.

The comprehensive analysis of the air-sensitive products of the reaction between cesium and oxygen is presented. Both direct lattice image and electron diffraction modes of transmission electron microscopy (TEM) indicate that a mixture of oxides was obtained in this reaction.

A quantitative study of substrate-quantum particles (QPs) charge-transfer channels is provided by laser-intensity dependent contact potential difference (CPD) measurements. The extracted electron-transfer rate constants exhibit marked differences in electron transfer from the film towards the substrate versus the backward process, and the charging of the hybrid films was found to be either negative or positive depending on the intensity of the laser that photoexcites the OPs.

The increased global demand for energy and the environmental concerns associated with fossil fuels highlight the need for alternative approaches. Fossil fuel combustion, particularly coal and oil shale, contributes to greenhouse gas emissions and generates large amounts of ash residues, posing environmental challenges. This study focuses on the potential of thermal treatment to upgrade oil shale bottom ash (OSBA) for use as a cement replacement in concrete, addressing both the economic viability of oil shale combustion and the environmental issue of ash waste management. The findings have significant implications for improving the economics and environmental sustainability of oil shale combustion in construction. By enhancing the properties of OSBA, this study contributes to the advancement of greener energy solutions and waste management practices in the energy and construction sectors., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Oil shale is a rock that contains organic matter in a concentration that allows it to be used as an energy source. As a result of the shale combustion process, large amounts of two types of ash are formed: fly ash (∼10%) and bottom ash (∼90%). At present, in Israel, only fly oil shale ash is used, which constitutes a minority of the oil shale burn products, whereas bottom oil shale ash is accumulated as waste. Bottom ash contains a high percentage of calcium in the form of anhydrite (CaSO 4 ) and calcite (CaCO 3 ). Thus, it can be used to neutralize acidic waste and to fix trace elements. This study examined the process of scrubbing the acid waste by the ash, its characterization pre- and post-upgrade treatment, to test its suitability as a partial substitute for aggregates, natural sand, and cement in concrete mixtures. In the current study, we compared the chemical and physical characterization of oil shale bottom ash before and after upgrading the ash via chemical treatment. In addition, its utilization as a scrubbing reagent for acidic wastes from the phosphate industry was studied., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Antibiotic-resistant bacterial infections have increased the prevalence of sepsis and septic shock mortality worldwide and have become a global concern. Antimicrobial peptides (AMPs) show remarkable properties for developing new antimicrobial agents and host response modulatory therapies. A new series of AMPs derived from pexiganan (MSI-78) were synthesized. The positively charged amino acids were segregated at their N- and C-termini, and the rest of the amino acids created a hydrophobic core surrounded by positive charges and were modified to simulate the lipopolysaccharide (LPS). The peptides were investigated for their antimicrobial activity and LPS-induced cytokine release inhibition profile. Various biochemical and biophysical methods were used, including attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, microscale thermophoresis (MST), and electron microscopy. Two new AMPs, MSI-Seg-F2F and MSI-N7K, preserved their neutralizing endotoxin activity while reducing toxicity and hemolytic activity. Combining all of these properties makes the designed peptides potential candidates to eradicate bacterial infection and detoxify LPS, which might be useful for sepsis treatment., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Coal is at present a major fuel source for power generation worldwide and will remain as such in the near future. The most important property of coal that determines its price is its calorific value. However, volatiles, ash, and moisture content are also very important properties needed for the quality control (QC) of the coal used to maintain an optimal operation of coal combustion in a boiler. The determination of these properties is carried out via well-established ASTM/DIN methods, which are slow and time-consuming. This study uses combined thermogravimetric analysis (TGA)/differential thermal calorimetry (DSC) instrumentation as a tool to evaluate the reactivity patterns of the aliphatic versus aromatic content of coals, which is correlated to the volatile content of coals. Two coals, bituminous (American Baily Pittsburgh No. 6) used in Israeli utilities and lignite (brown coal Hambach) used in German power plants, have been investigated in this study. The results show that the combined TG/DSC method can provide a much better understanding of the chemical reactivity of coals in the combustion process., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Coal is intensively used worldwide as a main fuel source. However, it may undergo oxidation processes [i.e., low-temperature oxidation (LTO)] when stored under an air atmosphere in piles post-mining at low temperatures ranging from 300 to 425 K, specifically, a surface gas/solid reaction with molecular oxygen. Therefore, it is of major importance to prevent or appreciably slow down such reactions, which result in a loss in the energy content (calorific value) of coal. Previously, we showed that radicals are formed during the LTO process. In this work, the dependence of radical formation on coal rank as a function of heating (temperature) and the presence of oxygen gas were studied using electron paramagnetic resonance spectroscopy. It was shown that lignite coals are more sensitive than bituminous coals to the atmospheric environment (i.e., molecular oxygen and nitrogen content) and to temperature, as reflected by the formation of surface carbon-centered radicals. Moreover, this is the first publication showing the effects of LTO on micro- and macro-pores by assessing how these structures affect O 2 diffusion. The LTO process blocks the micro-pores, such that radicals form mainly at the surface of the coal macromolecules, in both bituminous and lignite coals., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The redox chemistry of Ce III DOTA in cage in carbonate solutions was studied using electrochemistry and radiolysis techniques (continuous radiolysis and pulse radiolysis). Spectroscopic measurements point out that the species present in the solutions at high bicarbonate concentrations are [Ce III DOTA(CO 3 )] 3- (or less plausible [Ce III DOTA(HCO 3 )] 2- ) with the carbonate (bicarbonate) anion as the ninth ligand versus [Ce III DOTA(H 2 O)] - present in the absence of bicarbonate. Electrochemical results show a relatively low increase in the thermodynamic stabilization of the redox couple Ce IV/III in the presence of carbonate versus its aqueous analogue. [Ce IV DOTA(CO 3 )] 2- and [Ce IV DOTA(H 2 O)], prepared electrochemically, decompose photolytically. However, kept in the dark, both are relatively long lived; [Ce IV DOTA(H 2 O)], though, is orders of magnitude kinetically more stable (a considerably longer half-life). Thus, one concludes that the carbonate species have a different mechanism of decomposition depending also on the presence of dioxygen after its preparation (in deaerated/aerated solutions). The [Ce IV DOTA(CO 3 )] 2- species is produced radiolytically by oxidation of the trivalent species by CO 3 •- with a rate constant, measured using pulse radiolysis, of 3.3 × 10 5 M -1 s -1 . This rate constant is at least 1 order of magnitude smaller than most of the rate constants so far reported for the reaction of CO 3 •- with transition metal/lanthanide (cerium)/actinide complexes. This result together with the bulkiness of the reactants might suggest an outer-sphere electron transfer rather than the inner-sphere one so far proposed. The lifetime of the tetravalent cerium species obtained radiolytically in the presence of carbonate is shorter than the electrochemical one, suggesting a different conformer involved.

Coal is one of the major fuels for power generation, and it will continue in this capacity for the next several decades. Two types of coal are mainly used: lignite and bituminous coals. When exposed to air, post-mining, the coal surface undergoes LTO (low-temperature oxidation) at RT-150 °C according to the atmospheric oxygen level. The LTO process decreases the calorific value of the coal, and consequently, different gases are released [mainly carbon oxides (CO, CO 2 ), water vapor, hydrogen (H 2 ), and also some low molecular-weight organic gases (C 1-5 )]. Some of these gases are toxic and flammable. In extreme cases, fires erupt. The mechanism by which the molecular oxygen oxidizes the coal macromolecule at the temperature range of 30-150 °C (LTO process) is complex and also involves a chain of radical reactions that take place; however, the exact underlying mechanism is not yet clear. The LTO process was studied in detail by simulating the processes occurring in the coal piles by using two coal types: an American Bailey coal, used in Israeli coal-fired utilities and a German Hambach lignite, used in German utilities. The mechanism underlying the LTO process and the radical reactions that are involved are discussed in detail., Competing Interests: The authors declare no competing financial interest.

Redox reactions play key roles in fundamental biological processes. The related spatial organization of donors and acceptors is assumed to undergo evolutionary optimization facilitating charge mobilization within the relevant biological context. Experimental information from submolecular functional sites is needed to understand the organization strategies and driving forces involved in the self-development of structure-function relationships. Here we exploit chemically resolved electrical measurements (CREM) to probe the atom-specific electrostatic potentials (ESPs) in artificial arrays of bacteriochlorophyll (BChl) derivatives that provide model systems for photoexcited (hot) electron donation and withdrawal. On the basis of computations we show that native BChl's in the photosynthetic reaction center (RC) self-assemble at their ground-state as aligned gates for functional charge transfer. The combined computational and experimental results further reveal how site-specific polarizability perpendicular to the molecular plane enhances the hot-electron transport. Maximal transport efficiency is predicted for a specific, ∼5 Å, distance above the center of the metalized BChl, which is in remarkably close agreement with the distance and mutual orientation of corresponding native cofactors. These findings provide new metrics and guidelines for analysis of biological redox centers and for designing charge mobilizing machines such as artificial photosynthesis.

Ni(I)(1,4,8,11-tetraazacyclotetradecane)(+) reduces ethylene quantitatively to ethane plus butane (and hexane traces) in neutral aqueous solutions. A radical mechanism is proposed.

Light-induced chemically resolved electrical measurements (CREM) under controlled electrical conditions are used to study photovoltaic effects at selected regions in nanocrystalline CdSe-based films. The method, based on X-ray photoelectron spectroscopy (XPS), possesses unique capabilities for exploring charge trapping and charge transport mechanisms, combining spectrally filtered input signals with photocurrent detection and with a powerful, site-selective, photovoltage probe.

A series of p- and n-GaAs-S-C(n)H(2n+1) || Hg junctions are prepared, and the electronic transport through them is measured. From current-voltage measurements, we find that, for n-GaAs, transport occurs by both thermionic emission and tunneling, with the former dominating at low forward bias and the latter dominating at higher forward bias. For p-GaAs, tunneling dominates at all bias voltages. By combining the analysis of the transport data with results from direct and inverse photoemission spectroscopy, we deduce an energy band diagram of the system, including the tunnel barrier and, with this barrier and within the Simmons tunneling model, extract an effective mass value of 1.5-1.6m(e) for the electronic carriers that cross the junctions. We find that transport is well-described by lowest unoccupied and highest occupied states at 1.3-1.4 eV above and 2.0-2.2 eV below the Fermi level. At the same time, the photoemission data indicate that there are continua of states from the conduction band minimum and the valence band maximum, the density of which varies with energy. On the basis of our results, it appears likely that, for both types of junctions, electrons are the main carrier type, although holes may contribute significantly to the transport in the p-GaAs system.

High-resolution scanning tunneling microscopy (STM) imaging of single double-stranded poly(G)-poly(C) DNA molecules, made by a novel synthesis method, shows the molecules morphology. The STM images reveal a periodic structure of approximately 4 nm, seen as repeating "bulbs" along the molecules. These "bulbs" are associated with the molecule helix (the major grooves). "Nicks", two per 100 nm on the average, are observed along the DNA as well. The STM measurements were supported by a morphological statistics of the DNA molecule groove length and apparent height relative to the surface.

Submolecular electrical information is successfully derived by applying element-specific, chemically resolved electrical measurements to a covalently bound stilbazole-based monolayer on a silicon substrate. Pronounced affinity effects are found in the response of adjacent atomic sites to external charge injection, accompanied by intramolecular polarization variations. These noncontact electrical read-out capabilities may provide a first entry toward the realization of organic devices based on submolecular electrical units.

Diodes made by (indirectly) evaporating Au on a monolayer of molecules that are adsorbed chemically onto GaAs, via either disulfide or dicarboxylate groups, show roughly linear but opposite dependence of their effective barrier height on the dipole moment of the molecules. We explain this by Au-molecule (electrical) interactions not only with the exposed end groups of the molecule but also with its binding groups. We arrive at this conclusion by characterizing the interface by in situ UPS-XPS, ex situ XPS, TOF-SIMS, and Kelvin probe measurements, by scanning microscopy of the surfaces, and by current-voltage measurements of the devices. While there is a very limited interaction of Au with the dicarboxylic binding groups, there is a much stronger interaction with the disulfide groups. We suggest that these very different interactions lead to different (growth) morphologies of the evaporated gold layer, resulting in opposite effects of the molecular dipole on the junction barrier height.

If a thin film (tens of nm) of CdSe quantum dots (4 nm diameter) is deposited by chemical bath deposition onto various substrates, the films, although essentially intrinsic, behave as if they were n-type with respect to charge separation. However, films deposited under certain deposition conditions on Si (both n(+)- and p(+)-type) behave as if they were p-type. In this case, we show that it is possible to switch this p-type photoresponse by either light illumination intensity or injection of electrons from an external filament. Using both surface photovoltage spectroscopy and a novel adaptation of X-ray photoelectron spectroscopy, we show how this behavior results from a Cd(OH)(2) layer adsorbed at the Si surface at the beginning of the deposition. This response is explained by a competition between a high concentration of relatively shallow hole traps in the CdSe and a lower concentration of deeper electron traps in the Cd(OH)(2). The relative occupancies of these traps determine the fields in the film and their response to external parameters.