Chemical Binding Effects Research Articles

Analytical Description of the Neutron Up-Scattering in the Resonance Range

The double-differential scattering cross section for a nucleus with pronounced resonances can be calculated using the stochastic method called Doppler Broadening Rejection Correction (DBRC). Its analytical formulation was developed by Rothenstein and Dagan. Both methodologies are based on the Free Gas Model (FGM), so they exclude chemical binding effects. The numerical instability of including chemical bounds can be balanced by the uncoupled phonon approximation (UPA). However, Courcelle showed that the UPA does not asymptotically resume the FGM and proposed an alternative model for correcting the asymptotic form. Preliminary tests on the Courcelle model showed inconsistent results in differential cross sections compared with the DBRC option of Monte Carlo codes in the framework of the FGM. In this work, a corrected version of Courcelle’s model is presented and applied in the FGM to 238U cross sections. The double-differential scattering cross sections calculated at 300 and 1474 K are in good agreement with those provided by the DBRC. The corrected model is consistent with angle-integrated scattering cross sections calculated with NJOY. The introduction of the effective temperature via the Short Collision Time approximation demonstrates the need to use a more complex S ( α , β ) model to account for crystalline effects.

Fe-MOFs/graphene oxide-derived magnetic nanocomposite for enhanced adsorption of As(V) in aqueous solution

The urgent need to remove arsenic from groundwater stems from the irreversible damage it causes to aquatic systems and biological health. In this study, unique magnetic Fe3O4/graphene oxide (GO) nanocomposites derived from MIL-100(Fe)/GO precursor were rationally and precisely developed by combination of solvothermal synthesis and pyrolysis methods. The optimized MIL-100(Fe)/1%GO-400 magnetic nanocomposite (where 1% and 400 represent the mass ratio of GO to MIL-100(Fe) and pyrolysis temperature, respectively) exhibited exceptional adsorption capacity for As(V) and possessed magnetic separation properties. The novel nanocomposite had complete MOF morphology and crystal structure, as well as good resistance to interference from ions and could be used effectively over a wide pH range (2–9) for adsorption of As(V). The As(V) adsorption on the nanocomposite was found to follow the pseudo-second-order (PSO) kinetic model and Temkin adsorption isotherm model, as well as a spontaneous endothermic process dominated by chemisorption. The incorporation of GO and pyrolysis of the Fe-MOFs was proven to enhance the adsorption capacity of nanocomposite, water stability, and magnetic recovery ability. The adsorption mechanism was attributed to the synergistic effect of chemical complexation, hydrogen binding and electrostatic interaction. This work not only presents a feasible strategy for the development of Fe-MOFs-based derivatives, but also offers a promising approach to expanding the application of functional Fe-MOFs-based derivatives in arsenic-contaminated wastewater treatment.

Effect of operating conditions on release and transformation of sodium during CFB gasification of Zhundong coal

To provide some useful suggestions to the operation of circulating fluidized bed (CFB) gasifier, the effect of gasification temperature, residence time and agent on the release and transformation of sodium was studied by using a fixed bed reactor combined with Factsage software. The results indicated that gasification temperature was the significant factor to the release and transformation of sodium. For the promoting effect of sodium release, it was ascribed to the intense of sodium volatilization and competitive reaction between lime and meta-kaolin. Meanwhile, the high temperature promoted the formation of nepheline and slag. The threshold temperature of latter was near 950 °C. It was interesting to find that the release of sodium could be divided into two stages: coal pyrolysis and char gasification. In coal pyrolysis, part of organic and water-soluble sodium was released. The remainder either combined with char structure, or reacted with minerals. In char gasification, sodium, combined with char structure, was released along with char gasification. Due to the decrease of melting temperature and the formation of NaOH, steam showed a promoting effect on the sodium release. Oppositely, oxygen and nitrogen presented an inhibiting effect. The former was ascribed to the formation of Na2SO4, while the latter was caused by the chemical binding and physical wrapping effect of char.

Improving Mechanical, Electrical and Thermal Properties of Fluororubber by Constructing Interconnected Carbon Nanotube Networks with Chemical Bonds and F-H Polar Interactions.

To improve the properties of fluororubber (FKM), aminated carbon nanotubes (CNTs-NH2) and acidified carbon nanotubes (CNTs-COOH) were introduced to modulate the interfacial interactions in FKM composites. The effects of chemical binding and F-H polar interactions between CNTs-NH2, CNTs-COOH, and FKM on the mechanical, electrical, thermal, and wear properties of the FKM composites were systematically investigated. Compared to the pristine FKM, the tensile strength, modulus at 100% strain, hardness, thermal conductivity, carbon residue rate, and electrical conductivity of CNTs-NH2/CNTs-COOH/FKM were increased by 112.2%, 587.5%, 44.2%, 37.0%, 293.5%, and nine orders of magnitude, respectively. In addition, the wear volume of CNTs-NH2/CNTs-COOH/FKM was reduced by 29.9%. This method provides a new and effective way to develop and design high-performance fluororubber composites.

In vitro binding capacities, physicochemical properties and structural characteristics of polysaccharides fractionated from Passiflora edulis peel

This study aimed to determine structural characteristics, physical properties and binding effects of polysaccharide and its fractions from Passiflora edulis peel on lipid, cholesterol and bile acids. The crude polysaccharide (WPEP) was extracted using hot water extraction method, fractionated using DEAE-52 cellulose column, and purified by Sepharose CL-6B column to obtain four polysaccharide fractions (WPEP-F1, WPEP-F2, WPEP-F3, and WPEP-F4). The physicochemical properties and structural characteristics were analyzed using several methods. The chemical-binding effects were also determined. Among all polysaccharide samples, WPEP-F2 had the highest total sugar content (77.63%). The viscosity of all polysaccharide samples was increased. Among the four polysaccharide fractions, WPEP-F2 showed the best emulsifying activity. WPEP-F1 was mainly composed of glucose, galactose, mannose, and arabinose, whereas WPEP-F2, WPEP-F3, and WPEP-F4 were principally composed of galacturonic acid. SEM analysis showed that the four fractions had different microstructures. Among the polysaccharide components, WPEP-F2 had the highest lipid-binding effect (9.3 g/g). It also had the best binding effect on taurocholic acid, deoxycholic acid, glycocholic acid, and cholesterol (50.87%, 69.12%, 30.22%, and 78.68%, respectively), but WPEP-F3 had the best binding effect on cholic acid (53.99%). The lipid, cholesterol, and bile acid-binding activities of WPEP-F2 could be attributed to its high viscosity, porous appearance structure, and sugar content in addition to its triple helix structure. The findings lay a theoretical foundation for developing Passiflora edulis peel polysaccharide-related foods and promoting application of the peel polysaccharide in functional food industries.

Chemically etched CeO2-x nanorods with abundant surface defects as effective cathode additive for trapping lithium polysulfides in Li-S batteries

The commercialization of Li-S batteries has been seriously hindered by the notorious polysulfides shuttling and sluggish redox kinetics. To effectively address these technical issues, in this work, oxygen-deficient CeO2-x nanorods (NR) decorated on free-standing carbon cloth (CeO2-x NR@CC) were used as a promising dual-functional cathode host material to enhance the electrochemical and cycling performance of Li-S batteries. The oxygen-deficient CeO2-x NR were prepared in a facile processing route by tuning the surface structures of pristine CeO2 NR in strong reducing NaBH4 solution. In contrast to the pristine CeO2NR@CC control sample, chemically etched CeO2-x NR@CC with abundant implanted oxygen vacancies effectively trapped the polysulfides and dramatically accelerated electron charge transfer, leading to faster redox kinetics. The main working mechanism of CeO2-x NR@CC on the improved electrochemical performance was attributed to chemical binding effect on trapping lithium polysulfides and even promoting the conversion of polysulfides, thanks to reversible Ce3+/Ce4+ transformation, oxygen vacancies, and other surface defects. Hence, the CeO2-x NR@CC electrode delivered an outstanding initial capacity of 1358 mAh g−1 at 0.2C for the 1st cycle and a superb sulfur utilization of 81%, compared to an initial capacity of 1176 mAh g−1 at 0.2C and a sulfur utilization of 70% for the CeO2 NR@CC electrode. The improved electrochemical performances of the CeO2-x NR@CC electrode can be mainly attributed to the successful adsorption of more dissolvable polysulfides by the dual-functional cathode host materials that combine the physical confinement of conductive CC and the chemical binding of CeO2-x NR with ample surface defects.

TiO2 nanotube/RGO modified separator as an effective polysulfide-barrier for high electrochemical performance Li-S batteries

The “shuttle effect” in lithium-sulfur cell causes the terrible cycles stability, that hinders the Li-S batteries served as the next generation high energy density batteries. To address the issue, we investigated that anatase/bate crystal phase titanium dioxide nanotubes (TiO2 NTs) combined with reduced graphene oxide (RGO) to modify the initial polypropylene separator. The TiO2 NTs/RGO film not only localizes the migrating polysulfides by the common effects of chemical binding and physical adsorption but also enhances the lithium-ion migration by reducing the electrochemical resistance. The excellent chemical and physical adsorption ability were proved by the measurement of the X-ray photoelectron spectroscopy and adsorption experiments. The fast lithium-ion migration was analyzed by the diffusion experiment and electrochemical impedance systems. The outstanding initial discharge capacity of 1303.3 mAhg−1 at 0.2 C, which was 78% of the theoretical capacity. Over 100 cycles, the cell with TiO2 NTs/RGO coating separator still retained 620.6 mAhg−1 discharge capacity. The TiO2 NTs/RGO modifying separator exhibits great promise to develop the high energy Li-S batteries.

Determining the domain-level reaction-diffusion properties of an actin-binding protein transgelin-2 within cells

Proteins in cells undergo repeated binding to other molecules, thereby reducing the apparent extent of their intracellular diffusion. While much effort has been made to analytically decouple these combined effects of pure diffusion and chemical binding, it is difficult with conventional approaches to attribute the measured quantities to the nature of specific domains of the proteins. Motivated by the common goal in cell signaling research aimed at identifying the domains responsible for particular intermolecular interactions, here we describe a framework for determining the local physicochemical properties of cellular proteins associated with immobile scaffolds. To validate this new approach, we apply it to transgelin-2, an actin-binding protein whose intracellular dynamics remains elusive. We develop a fluorescence recovery after photobleaching (FRAP)-based framework, in which comprehensive combinations of domain-deletion mutants are created, and the difference among them in FRAP response is analyzed. We demonstrate that transgelin-2 in actin stress fibers (SFs) interacts with F-actin via two separate domains, and the chemical properties are determined for the individual domains. Its pure diffusion properties independent of the association to F-actin is also obtained. Our approach will thus be useful, as presented here for transgelin-2, in addressing the signaling mechanism of cellular proteins associated with SFs.

Coupled Transport of Sulfate and Chloride Ions With Adsorption Effect: A Numerical Analysis

In the marine environment, reinforced concrete will suffer from chloride ion erosion and sulfate ion erosion at the same time. However, most scholars only study the interaction mechanism between chloride ion and sulfate ion, and the consideration of physical adsorption and chemical combination caused by hydration products is not perfect. Based on the law of conservation of mass, this study integrates the relationship between porosity and hydration time, the weakening of chemical binding of sulfate ions to chloride ions into the mathematical model, establishes the coupling transport model of sulfate and chloride, and verifies the rationality of the model by comparing with the measured data. And then, the physical adsorption and chemical binding of chloride ions under the action of sulfate ions were quantitatively analyzed. It is found that chemical binding is dominant and sulfate ion will reduce the chemical binding effect of chloride ion. With the decrease of the initial water/cement ratio, the diffusion depth of free chloride ion will also decrease.

On the relationship between bond correction factors and elemental mean excitation energies

We have investigated the relationship between two methods to obtain mean excitation energies of large samples using a modified Bragg rule, one method using Bragg’s rule to determine elemental mean excitation energies from experimental stopping power data, and another method going the opposite way, that is determining compound mean excitation energies from theoretical elemental mean excitation energies and bond correction factors. We show how to obtain bond correction factors from elemental mean excitation energies and vice versa. The comparison leads to insight into the importance of the effect of chemical binding on the experimentally determined elemental mean excitation energies. We also introduce the concept of atomic correction factor that links theoretical, gas phase atomic mean excitation energies to elemental mean excitation energies.

Bond correction factors and their applications to the calculation of molecular mean excitation energies

We report bond correction factors that can be used to calculate molecular mean excitation energies including the effects of chemical bonding. The calculations are based on an extension of Bragg’s rule. We report results for several bonds – neutral and charged - involving gas phase atoms in the first, second and third row of the periodic system. The bond correction factors are dimensionless and turn out to be nearly constant and of the order 1–2. The method is applied to the calculations of mean excitation energies of linear hydrocarbons, amino acids and molecules and molecular ions of astrophysical interest. Examples show that chemical binding effects increase the molecular mean excitation energies with between 4% and 15 %, smallest for linear, unsaturated molecules and largest for molecules with longer aliphatic chains.

Test of the validity of Bragg’s rule for mean excitation energies of small molecules and ions

The purpose of this paper is to identify the fragmentation patterns of molecules and ions that give the best fulfilment of a Bragg’s rule estimation of the mean excitation energy of the molecules and ions. We investigate the effect of chemical binding on the validity of Bragg’s rule for the calculation of stopping cross sections and mean excitation energies. As test cases we use a series of small molecules and molecular ions, primarily carbon and nitrogen hydrides. We are using several nuclear fragments of the same molecule or ion to test the dependence of Bragg’s rule on the binding energy of the molecules/ions. The mean excitation energies of the molecules/ions and their fragments are computed with the same method. We find that neglect of chemical binding nearly always results in an underestimation of the mean excitation energies. We also find that the fully atomic decomposition of any molecule, but a diatomic molecule never gives the best fulfilment of Bragg’s rule. The best fulfilment of Bragg’s rule is obtained when using a fragmentation pattern with as few bonds as possible broken and when the choice of fragments is guided by chemical knowledge and intuition. By investigating several alternative fragmentation patterns for a molecule/ion, guidelines for choice of optimal Bragg rule fragmentation are suggested. Using the best fragmentation pattern for the tested molecules and ions, the error in the mean excitation energy is of the order of 5% or less, implying an error of not more than 1% in the pure Bethe stopping power because of applying Bragg’s rule.

Concentration dependence of in vitro biotransformation rates of hydrophobic organic sunscreen agents in rainbow trout S9 fractions: Implications for bioaccumulation assessment.

In vitro biotransformation studies were performed to support the bioaccumulation assessment of 3 hydrophobic organic ultraviolet filters (UVFs), 4-methylbenzylidene camphor (4-MBC), 2-ethylhexyl-4-methoxycinnamate (EHMC), and octocrylene. In vitro depletion rate constants (kdep ) were determined for each UVF using rainbow trout liver S9 fractions. Incubations performed with and without added cofactors showed complete (4-MBC) or partial (EHMC and octocrylene) dependence of kdep on addition of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH), suggesting that hydrolysis of EHMC and octocrylene by NADPH-independent enzymes (e.g., carboxylesterases) is an important metabolic route. The concentration dependence of kdep was then evaluated to estimate Michaelis-Menten parameters (KM and Vmax ) for each UVF. Measured kdep values were then extrapolated to apparent whole-body biotransformation rate constants using an in vitro-in vivo extrapolation (IVIVE) model. Bioconcentration factors (BCFs) calculated from kdep values measured at concentrations well below KM were closer to empirical BCFs than those calculated from kdep measured at higher test concentrations. Modeled BCFs were sensitive to in vitro binding assumptions employed in the IVIVE model, highlighting the need for further characterization of chemical binding effects on hepatic clearance. The results suggest that the tested UVFs are unlikely to accumulate to levels exceeding the European Union Registration, Evaluation, Authorisation, and Restriction regulation criterion for bioaccumulative substances (BCF > 2000 L kg-1 ). However, consideration of appropriate in vitro test concentrations and binding correction factors are important when IVIVE methods are used to refine modeled BCFs. Environ Toxicol Chem 2019;38:548-560. © 2018 SETAC.

Carbon Quantum Dots–Modified Interfacial Interactions and Ion Conductivity for Enhanced High Current Density Performance in Lithium–Sulfur Batteries

AbstractSignificant progress has achieved for developing lithium–sulfur (Li–S) batteries with high specific capacities and excellent cyclic stability. However, some critical issues emerge when attempts are made to raise the areal sulfur loading and increase the operation current density to meet the standards for various industrial applications. In this work, polyethylenimine‐functionalized carbon dots (PEI‐CDots) are designed and prepared for enhancing performance of the Li–S batteries with high sulfur loadings and operation under high current density situations. Strong chemical binding effects towards polysulfides and fast ion transport property are achieved in the PEI‐CDots‐modified cathodes. At a high current density of 8 mA cm−2, the PEI‐CDots‐modified Li–S battery delivers a reversible areal capacity of 3.3 mAh cm−2 with only 0.07% capacity decay per cycle over 400 cycles at 6.6 mg sulfur loading. Detailed analysis, involving electrochemical impedance spectroscopy, cyclic voltammetry, and density functional theory calculations, is done for the elucidation of the underlying enhancement mechanism by the PEI‐CDots. The strongly localized sulfur species and the promoted Li+ ion conductivity at the cathode–electrolyte interface are revealed to enable high‐performance Li–S batteries with high sulfur loading and large operational current.

Enhanced Cycling Performance for Lithium-Sulfur Batteries by a Laminated 2D g-C3 N4 /Graphene Cathode Interlayer.

Decay in electrochemical performance resulting from the "shuttle effect" of dissolved lithium polysulfides is one of the biggest obstacles for the realization of practical applications of lithium-sulfur (Li-S) batteries. To meet this challenge, a 2D g-C3 N4 /graphene sheet composite (g-C3 N4 /GS) was fabricated as an interlayer for a sulfur/carbon (S/KB) cathode. It forms a laminated structure of channels to trap polysulfides by physical and chemical interactions. The thin g-C3 N4 /GS interlayer significantly suppresses diffusion of the dissolved polysulfide species (Li2 Sx ; 2<x≤8) from the cathode to the anode, as proven by using an H-type glass cell divided by a g-C3 N4 /GS-coated separator. The S/KB cathode with the g-C3 N4 /GS interlayer (S/KB@C3 N4 /GS) delivers a discharge capacity of 1191.7 mAh g-1 at 0.1 C after 100 cycles, an increase of more than 90 % compared with an S/KB cathode alone (625.8 mAh g-1 ). The S/KB@C3 N4 /GS cathode shows good cycling life, delivering a discharge capacity as high as 612.4 mAh g-1 for 1 C after 1000 cycles. According to XPS results, the anchoring of the g-C3 N4 /GS interlayer to Li2 Sx can be attributed to a coefficient chemical binding effect of g-C3 N4 and graphene on long-chain polysulfides. Generally, the improvement in electrochemical performance originates from a coefficient of the enhanced Li+ diffusion coefficient, increased charge transfer, and the weakening of the shuttle effect of the dissolved Li2 Sx as a result of the g-C3 N4 /GS interlayer.

Effect of Chemical Binding of Doxorubicin Hydrochloride to Gold Nanoparticles, Versus Electrostatic Adsorption, on the In Vitro Drug Release and Cytotoxicity to Breast Cancer Cells.

The selective delivery of chemotherapeutic agent to the affected area is mainly dependent on the mode of drug loading within the delivery system. This study aims to compare the physical method to the chemical method on the efficiency of loading DOX.HCl to GNPs and the specific release of the loaded drug at certain tissue. Bifunctional polyethylene glycol with two different functionalities, the alkanethiol and the carboxyl group terminals, was synthesized. Then, DOX·HCl was covalently linked via hydrazone bond, a pH sensitive bond, to the carboxyl functional group and the produced polymer was used to prepare drug functionalized nanoparticles. Another group of GNPs was coated with carboxyl containing polymer; loading the drug into this system by the means of electrostatic adsorption. Finally, the prepared system were characterized with respect to size, shape and drug release in acetate buffer pH5 and PBS pH7.4 Also, the effect of DOX.HCl loaded systems on cell viability was assessed using MCF-7 breast cancer cell line. The prepared nanoparticles were spherical in shape, small in size and monodisperse. The release rate of the chemically bound drug in the acidic pH was higher than the electrostatically adsorbed one. Moreover, both systems show little release at pH7.4. Finally, cytotoxicity profiles against human breast adenocarcinoma cell line (MCF-7) exhibited greater cytotoxicity of the chemically bound drug over the electrostatically adsorbed one. Chemical binding of DOX·HCl to the carboxyl group of PEG coating GNPs selectively delivers high amount of drug to tumour-affected tissue which leads to reducing the unwanted effects of the drug in the non-affected ones.

Fluorinated, Sulfur-Rich, Covalent Triazine Frameworks for Enhanced Confinement of Polysulfides in Lithium-Sulfur Batteries.

Lithium-sulfur battery represents a promising class of energy storage technology owing to its high theoretical energy density and low cost. However, the insulating nature, shuttling of soluble polysulfides and volumetric expansion of sulfur electrodes seriously give rise to the rapid capacity fading and low utilization. In this work, these issues are significantly alleviated by both physically and chemically restricting sulfur species in fluorinated porous triazine-based frameworks (FCTF-S). One-step trimerization of perfluorinated aromatic nitrile monomers with elemental sulfur allows the simultaneous formation of fluorinated triazine-based frameworks, covalent attachment of sulfur and its homogeneous distribution within the pores. The incorporation of electronegative fluorine in frameworks provides a strong anchoring effect to suppress the dissolution and accelerate the conversion of polysulfides. Together with covalent chemical binding and physical nanopore-confinement effects, the FCTF-S demonstrates superior electrochemical performances, as compared to those of the sulfur-rich covalent triazine-based framework without fluorine (CTF-S) and porous carbon delivering only physical confinement. Our approach demonstrates the potential of regulating lithium-sulfur battery performances at a molecular scale promoted by the porous organic polymers with a flexible design.

Nitrogen and phosphorus codoped hierarchically porous carbon as an efficient sulfur host for Li-S batteries

For the first time, nitrogen and phosphorus codoped hierarchically porous carbon (NPHPC) has been explored as an efficient host for sulfur. The material is fabricated based on a scalable, one-step process involving the pyrolysis of melamine polyphosphate synthesized via a simple and versatile organic approach by using low cost industrial raw materials (melamine and polyphosphoric acid). The key features of NPHPC are the hierarchically porous structure and high surface area (1398m2g−1) that not only benefit for maximum sulfur loading but also capable of suppressing the dissolution of polysulfides through physisorption. Meanwhile, the N and P codopants together with the thermally stable functionalities are favorable for binding polysulfides via chemisorption. Benefitting from the synergistic effect of structural confinement (physisorption) and chemical binding (chemisorption), the NPHPC/S composite with a high sulfur content of 73wt% delivers high capacity (1580mAhg−1 at 0.02C) and long lifespan (200 cycles with 71% retention) for Li-S batteries. The present work highlights the importance of adopting heteroatom-doped hierarchically porous carbon for improving the performance of Li-S batteries, which may further stimulate more efforts in exploring advanced carbon-based hosts in the near future.

Influence of Ocean Acidification on the Organic Complexation of Iron and Copper in Northwest European Shelf Seas; a Combined Observational and Model Study

The pH of aqueous solutions is known to impact the chemical speciation of trace metals. In this study we conducted titrations of coastal seawaters with iron and copper at pH 7.91, 7.37 and 6.99 (expressed on the total pH scale). Changes in the concentration of iron and copper that complexed with the added ligands 1-nitroso-2-napthol and salicylaldoxime respectively were determined by adsorptive cathodic stripping voltammetry - competitive ligand equilibrium (AdCSV-CLE). Interpretation of the results, assuming complexation by a low concentration of discrete ligands, showed that conditional stability constants for iron complexes increased relative to inorganic iron complexation as pH decreased by approximately 1 log unit per pH unit, whilst those for copper did not change. No trend was observed for concentrations of iron and copper complexing ligands over the pH range examined. We also interpreted our titration data by describing chemical binding and polyelectrolytic effects using non-ideal competitive adsorption in Donnan-like gels (NICA-Donnan model) in a proof of concept study. The NICA-Donnan approach allows for the development of a set of model parameters that are independent of ionic strength and pH, and thus calculation of metal speciation can be undertaken at ambient sample pH or the pH of a future, more acidic ocean. There is currently a lack of basic NICA-Donnan parameters applicable to marine dissolved organic matter (DOM) so we assumed that the measured marine dissolved organic carbon could be characterized as terrestrial fulvic acids. Generic NICA-Donnan parameters were applied within the framework of the software program visual MINTEQ and the metal –added ligand concentrations [MeAL] calculated for the AdCSV-CLE conditions. For copper, calculated [MeAL] using the NICA-Donnan model for DOM were consistent with measured [MeAL], but for iron an inert fraction with kinetically inhibited dissolution was required in addition to the NICA-Donnan model in order to approximate the trends observed in measured [MeAL]. We calculated iron and copper speciation in Northwest European shelf water samples at ambient alkalinity and projected increased pCO2 concentrations as a demonstration of the potential of the approach.

Separation of Electromagnetic and Chemical Contributions to Surface-Enhanced Raman Spectra on Nanoengineered Plasmonic Substrates

Ramansignalsfrommoleculesadsorbedonanoblemetalsurfaceare enhanced by many orders of magnitude due to the plasmon resonances of the substrate.Additionally,theenhancedspectraaremodifiedcomparedtothespectra ofneatmolecules;manyvibrationalfrequenciesareshifted,andrelativeintensities undergo significant changes upon attachment to the metal. With the goal of devising an effective scheme for separating the electromagnetic and chemical effects, we explore the origin of the Raman spectra modification of benzenethiol adsorbed on nanostructured gold surfaces. The spectral modifications are attrib- uted to the frequencydependence of the electromagnetic enhancement and to the effect of chemical binding. The latter contribution can be reproduced computa- tionally using molecule-metal cluster models. We present evidence that the effect of chemical binding is mostly due to changes in the electronic structure of the molecule rather than to the fixed orientation of molecules relative to the substrate. SECTION Kinetics, Spectroscopy