Role Of Chemical Interactions Research Articles

Development and Application of Surface-Enhanced Raman Scattering (SERS).

Since the discovery of the phenomenon of surface-enhanced Raman scattering (SERS), it has gradually become an important tool for the analysis of material compositions and structures. The applications of SERS have been expanded from the fields of environmental and materials science to biomedicine due to the extremely high sensitivity and non-destructiveness of SERS-based analytical technology that even allows single-molecule detection. This article provides a comprehensive overview of the surface-enhanced Raman scattering (SERS) phenomenon. The content is divided into several main sections: basic principles and the significance of Raman spectroscopy; historical advancements and technological progress in SERS; and various practical applications across different fields. We also discuss how electromagnetic fields contribute to the SERS effect, the role of chemical interactions in enhancing Raman signals, a modeling and computational approaches to understand and predict SERS effects.

Thermal stability and flame retardancy of cotton fabric coated with PVA-boric acid-cellulose nanofiber hybrid: Role of chemical interactions

An ecofriendly, polymer coating to impart fire retardancy to cotton fabric is introduced in the current study. Polyvinyl alcohol-boric acid-cellulose nanofiber (PVA-BA-CNF) hybrid coating with different compositions of boric acid and 2.5 wt% cellulose nanofiber (CNF) were coated over cotton fabric. The CNF used in the study was extracted from onion skin, an agricultural waste. The nanofibrous morphology of extracted CNF was confirmed from Transmission Electron Microscopic (TEM) images. The surface morphology of treated cotton was compared with that of bare cotton using scanning electron microscope (SEM) and optical microscope (OM). The dispersion of the coating formulation over the cotton fabric and the porosity after coating were confirmed. Chemical interactions developed in the coating formulations were characterized by Fourier transform infrared spectroscopy (FTIR). In addition to hydrogen bonding established between the coating formulation and cotton fabric, the existence of chemical bonding (B-O-C) between the components of the coating formulation and between the crosslinked coating and cotton fabric has been evident. The thermal stability of the coated cotton fabrics was evaluated using thermogravimetric analysis (TGA). The high char residue recorded for PVA-BA-CNF coated fabric, especially with 17phr BA content indicated the efficiency of crosslinked coating matrix in enhancing the thermal stability of the cotton fabric. The coated cotton degraded in two stages and with a different degradation kinetics than that of uncoated cotton fabric. Flame retardant performance of the coated fabric has been evaluated by vertical flammability tests and pyrolysis combustion flow calorimetry (PCFC). The peak temperature of heat release rate (pHRR) showed 32 % reduction for PVA-BA-CNF coating with 17phr BA content compared with pure cotton indicating a decreasing flame spreading rate due to the inhibition of oxygen diffusion by chemically crosslinked PVA-BA-CNF coating.

Probing the thermal resistance of solid-liquid interfaces in nanofluids with molecular dynamics.

The significance of interfacial thermal resistance in the thermal conductivity of nanofluids is not well understood, in part because of the absence of measurements of this quantity. Here, we study the interfacial thermal resistance for metal-oil nanofluids of interest as heat transfer fluids for concentrating solar power, using density functional theory and molecular dynamics simulations. Insights on the role of chemical interactions in determining the interfacial thermal resistance are revealed. The results presented here showcase a general picture in which the stronger the chemical interactions between species at the interface, the lower the associated interfacial thermal resistance. The implications toward nanofluid design are discussed. We show that, for this important family of metal-oil nanofluids, the interfacial thermal resistance values are low enough so that it is possible to afford a reduction in particle size, minimizing stability and rheological issues while still offering enhancement in the effective thermal conductivity with respect to the base fluid.

Attractant Activity of Host-Related Chemical Blends on the Poultry Red Mite at Different Spatial Scales

Many blood-feeding arthropods use volatile organic compounds (VOCs) to detect their vertebrate hosts. The role of chemical interactions in mediating the behavior of hematophagous insects and ticks has been investigated before but remains poorly understood in hematophagous mesostigmatic mites. The poultry red mite Dermanyssus gallinae is an obligatory blood-sucking mesostigmatic mite that feeds on birds and causes damage in poultry farms. We characterized the attractive response of D. gallinae to candidate VOCs previously reported from the odor emitted by living hens. We performed in-vitro choice-test bioassays as well as semi-field and field trials using baited and unbaited traps, in the presence and absence of hens. Among different tested combinations of VOCs, a blend of 5 VOCs (mix1.0) was significantly attractive to our reference population of D. gallinae in vitro, whereas the same individual compounds tested alone were not attractive. Ammonia was attractive on its own and increased the mix1.0 attractiveness. The attractiveness of mix1.0 was confirmed at 'natural' spatial scales in the absence of hens both at the lab and on the farm that provided the reference population. The presence of hens inhibited the mix1.0 attractiveness. The attractive power of mix1.0 was not found in other farms. This research is an important step to advance our understanding of host-parasite interactions in hematophagous mesostigmatic mites and paves the way for developing alternative control tools against D. gallinae by interfering with chemical interactions. Moreover, it underlines the importance of assessing kairomonal activity on different pest populations when developing attract-and-kill systems.

Estimating specific surface area: Incorporating the effect of surface roughness and probing molecule size

AbstractThe pore–solid interface and its characteristics play a key role in chemical interactions between minerals in the solid soil matrix and the liquid in pore space and, consequently, solute transport in soils. Specific surface area (SSA), typically measured to characterize the pore–solid interface, depends not only on the particle size distribution (PSD) but also on particle shapes and surface roughness. In this note, we investigate the effects of surface roughness and probing molecule size on SSA estimation, use concepts from fractals, and theoretically estimate SSA from PSD and the water retention curve (WRC). The former is used to characterize the particle sizes and the latter to approximately quantify the pore–solid interface roughness by determining the surface fractal dimension. To evaluate our approach, we use five Washington and 21 Arizona soils for which both PSDs and WRCs were accurately measured over a wide range of particle sizes and matric potentials. Comparison with the experiments show that the proposed method estimates the SSA reasonably well, with RMSE = 16.8 and 30.1 m2 g–1 and average relative error = –56 and –35% for the Washington and Arizona datasets, respectively.

Interfacial molecular layering enhances specific heat of nanofluids: Evidence from molecular dynamics

It is well known that the specific heat of a heat transfer fluid can be significantly improved by the addition of nanoparticles to form a so-called nanofluid, but the origin of the effect is not completely understood yet. Here, we use molecular dynamics simulations in a nanofluid consisting of palladium nanoparticles in a commercial heat transfer fluid, to demonstrate that a significant fraction (nearly half) of the specific heat enhancement associated to the presence of the nanoparticles is due to strong chemisorption interaction of the fluid molecules at the nanoparticle surfaces. This insight opens new avenues for the nanofluid research community by providing sufficient understanding on the role of chemical interactions in the specific heat of nanofluids, helping on the discussion of what materials and base fluids to be chosen for the optimisation of the thermophysical properties of nanofluids and promoting the transition from basic research to actual application in energy conversion and thermal management processes.

Role of chemical interaction between MgH2 and TiO2 additive on the hydrogen storage behavior of MgH2

The present study explores how the additive titania chemically reacts with magnesium hydride and influences the dehydrogenation of MgH2. Quantitative X − ray diffraction study of ball milled MgH2+xTiO2 (x=0.25, 0.33, 0.5 and 1) suggests that Ti substituted MgO is the main reaction product in all the product powders. Convincing evidence is obtained to conclude that Ti dissolution in MgO makes a dramatic behavioral change to MgO; passive MgO turns as an active in-built catalyst. The analysis correlating the dehydrogenation kinetics, composition of in-situ catalyst and sample durability suggests that effectiveness of Ti substituted MgO (MgxTiyOx+y) as a catalyst for MgH2 depends on the concentration of Ti in MgxTiyOx+y rock salt. These observations are immensely helpful for understanding the hydrogen desorption mechanism of metal oxide additives loaded MgH2 system.

PTFE Tribology and the Role of Mechanochemistry in the Development of Protective Surface Films

The wear and friction behavior of ultralow wear polytetrafluoroethylene (PTFE)/α-alumina composites first described by Burris and Sawyer in 2006 has been heavily studied, but the mechanisms responsible for the 4 orders of magnitude improvement in wear over unfilled PTFE are still not fully understood. It has been shown that the formation of a polymeric transfer film is crucial to achieving ultralow wear on a metal countersurface. However, the detailed chemical mechanism of transfer film formation and its role in the exceptional wear performance has yet to be described. There has been much debate about the role of chemical interactions between the PTFE, the filler, and the metal countersurface, and some researchers have even concluded that chemical changes are not an important part of the ultralow wear mechanism in these materials. Here, a “stripe” test allowed detailed spectroscopic studies of PTFE/α-alumina transfer films in various stages of development, which led to a proposed mechanism which accounts ...

Impairment of benthic diatom adhesion and photosynthetic activity by allelopathic compounds from a green alga: involvement of free fatty acids?

The role of chemical interactions in shaping microbial communities has raised increasing interest over the last decade. Many benthic microorganisms are known to develop chemical strategies to overcome competitors, but the real importance of chemical interactions within freshwater biofilm remains unknown. This study focused on the biological and chemical mechanisms of an interaction involving two benthic microorganisms, an allelopathic filamentous green alga, Uronema confervicolum, and a common diatom, Fistulifera saprophila. Our results showed that functions critical for benthic phototrophic microorganisms were inhibited by U. confervicolum extracts. Growth, cell motility, adhesion, and photosynthetic activity were impaired at extract concentrations ranging between 5 and 20 μg ml(-1). The adhesion inhibition was mediated by intracellular nitric oxide (NO) induction. A bioassay-guided fractionation of the extract with HPLC helped to identify two C18 fatty acids present in the growth-inhibiting fractions: linoleic (LA) and α-linolenic (LNA) acids. These compounds represented 77% of the total free fatty acids of U. confervicolum and were present in the culture medium (1.45 μg l(-1) in total). Both could inhibit the diatom growth at concentrations higher than 0.25 μg ml(-1), but had no effect on cell adhesion. The discrepancy between the effective concentrations of fatty acids and the concentration found in culture medium may be explained by the presence of high-concentration microenvironments. The compounds involved in adhesion inhibition remain to be identified. Though further experiments with complex biofilms are needed, our results suggest that U. confervicolum may participate to the control of biofilm composition by inhibiting diatom adhesion.

H<sub>2</sub>-공기와 CO-공기의 예혼합화염의 화염소화에 있어서 화학적 상호작용의 효과

Important role of chemical interaction in flame extinction was numerically investigated in downstream inte- raction among lean(rich) and lean(rich) premixed as well as partially premixed H2-air and CO-air flames. The strain rate varied from 30 to 5917 s -1 until interacting flame could not be sustained anymore. Flame stability diagrams mapping lower and upper limit fuel concentrations for flame extinction as a function of strain rate are presented. Highly stretched interacting flames were survived only within two islands in the flame stability map where partially premixed mixture consisted of rich H2-air flame, extremely lean CO-air flame, and a diffusion flame. Further increase in strain rate finally converges to two points. Appreciable amount of hydrogen in the side of lean H2-air flame also oxidized the CO penetrated from CO-air flame, and this reduced flame speed of the H2-air flame, leading to flame extinction. At extremely high strain rates, interac- ting flames were survived only by a partially premixed flame such that it consisted of a very rich H2-air flame, an extremely lean CO-air flame, and a diffusion flame. In such a situation, both the weaker H2-air and CO-air flames were parasite on the stronger diffusion flame such that it could lead to flame extinction in the situation of weakening the stronger diffusion flame. Particular concerns are focused on important role of chemical interaction in flame extinction was also discussed in detail.

The Role of Chemical Interactions Between Thorium, Cerium, and Lanthanum in Lymphocyte Toxicity

ABSTRACT. Thorium, cerium, and lanthanum are metals present in several types of minerals, the most common of which is monazite. Cerium and lanthanum are elements in the lanthanides series. Thorium, an actinide metal, is a hazardous element due to its radioactive characteristics. There is a lack of information describing the possible chemical interactions among these elements and the effects they may have on humans. Toxicological analyses were performed using cell viability, cell death, and DNA damage assays. Chemical interactions were evaluated based on the Loewe additivity model. The results indicate that thorium and cerium individually have no toxic effects on lymphocytes. However, thorium associated with lanthanum increases the toxicity of this element, thereby reducing the viability of lymphocytes at low concentrations of metals in the mixture.

The role of chemical interactions and epitaxy during nucleation of organic crystals on crystalline substrates

A tandem strategy to control polymorphism through epitaxial relationships with crystalline substrates reveals the importance of chemical interactions at the nucleation surface compared with the periodic surface potential associated with epitaxy.

Chemically Driven Microstructure Evolution in Cobalt–Fullerene Mixed System

We report on the formation of Co–C60 nano‐composite prepared by simultaneous deposition of cobalt and C60 fullerene on sapphire or NaCl at room temperature. The composite includes fcc‐Co single‐crystals with size of order 10 nm separated by C60‐based matrix. Detailed characterization of the composite by electron diffraction and Raman spectrometry revealed the existence of small amount of diamond and cobalt carbides (orthorhombic Co2C and Co3C) in the composite matrix. According to electron diffraction analysis diamond nucleates epitaxialy on facets of fcc‐Co crystals. The proposed model shows the role of chemical interaction in Co–C60 mixture in the nano‐composite structure formation.

Role of chemical interactions in bacterial adhesion to polymer surfaces

Development of biomaterial-related infections is attracting an increasing interest due to the significant percentage of implant failure in the hospital care. Recent literature puts in evidence the dependence of the infection risk on the different biomaterials used, because of the different interactions between material surface and micro-organisms. Despite this, the mechanisms underlying the adhesion of bacteria to the biomaterial surface are still unclear. Aim of this work is to study the initial events of the processes responsible for the bacterial adhesion on polymers in order to prevent the development of bacterial infections and the consequent failure and replacement of biomedical devices. Electrostatic and Lifshitz–van der Waals forces are usually considered responsible for the interactions at the biomaterial interface. A new term that involves Lewis acid–base interactions is here introduced to better describe the bacterial adhesion to the polymer surface. Two requirements are needed to test this hypothesis: the development of an ideal polymeric surface in terms of chemical and morphological properties and the choice of a specific bacterial strain to be utilized as “probe”. Experiments were worked out using an Escherichia coli (Gram−) strain that represent one of the principal isolates from infected biomaterial implants and its adhesion was investigated on polymers having different acid/basic character. The findings indicate that the bacterial adhesion is influenced by the chemical properties of the polymeric surface. These results may be interpreted taking into account a mechanism in which the acid/base (Lewis) interaction plays an important role.

The use of FT-IR imaging as an analytical tool for the characterization of drug delivery systems

FT-IR imaging spectroscopy is well suited for studying dynamic processes occurring in multi-component systems. Each component is resolved spatially based on the spectral response at each detector element. Additionally, the sequential collection of images tracks the movement of each component over time. In this study, the delivery characteristics of the drug, testosterone, suspended in a poly(ethylene oxide) (PEO) matrix was observed using this technique. Drug release occurred as the hydrophilic, erodible polymer underwent controlled dissolution, exposing the drug to the aqueous environment. The subsequent conversion of the drug into the therapeutic aqueous form completed the delivery process. Qualitative evaluation of the false color composite infrared images led to the elucidation of two distinct delivery mechanisms, dependent on the degree of drug loading. The spatially embedded spectral features led to the quantification of the drug release rates as well as the rates of polymer dissolution. The rates for both polymer dissolution and drug release were evaluated using well-established models. Additionally, the homogeneity of the drug dispersion for different loadings was characterized. The roles of chemical interactions across the solvent interface of species were also investigated. Changes in each component from the bulk to the solvated region were investigated, revealing changes in concentration and polymer orientation as well as inter-species interactions.

Interfacial trap states in junctions of molecular semiconductors

Interfacial states that were established in contacts of molecular semiconductors with aqueous electrolytes or in contacts with another organic semiconductor as a solid film were analyzed by photoelectrochemical experiments and by photoelectron spectroscopy. A crucial role of such states was indicated in the interfacial charge transfer and recombination kinetics of light-induced charge carriers and also in the energetic alignment in the solid contacts. Unsubstituted zinc-phthalocyanine (PcZn) served as model compound. The role of chemical interactions in the establishment of these interfacial states was investigated by use of different reaction partners, i.e., different redox couples in the electrolyte contacts and molecular semiconductors of different ionization potential in the solid contacts. Implications of these results for the use of organic semiconductor thin films in devices of molecular electronics and of dye molecules in dye-sensitized solar cells were also discussed.

Contribution of chemical and physical processes to the formation of alkaline silicate suspensions and their properties

The mechanism of the formation of alkaline silicate suspensions was proposed based on the role of chemical interactions of hydroxides, silicates, carbonates, and polyphosphates of alkali metals, soluble in dispersion medium, with one another and with the surfaces of natural disperse minerals. The experimental data indicating that these interactions in alkaline silicate suspensions proceed mainly in the pH 10–11 range were summarized. Based on developed notions, practical recommendations taking into account chemical interactions were suggested for preparing the alkaline silicate suspensions with predetermined properties.

Diversity and variability of plant secondary metabolism: a mechanistic view

AbstractBased upon a brief historical view, the typical features of plant secondary metabolism and its role in chemical interactions between plants and their environment are discussed. Facts and arguments are presented favouring the hypothesis that secondary metabolism evolved under the selection pressure of a competitive environment. The high ‘degree of chemical freedom’ of secondary metabolism which, in contrast to primary metabolism, allows structural modifications with almost no restrictions, is stressed as mechanistic basis for the generation of chemical diversity. Biochemical and physiological properties of secondary metabolism are in accordance with such a view. It is suggested that the great chemical diversity and intraspecific variability of secondary metabolism is the result of processes of natural selection which act upon highly variable chemical structures. This view is exemplified by the pyrrolizidine alkaloids, a typical class of secondary compounds.

Mössbauer study of primary crystallization in amorphous (Co77Si13.5B9.5)93Fe4Nb3

Abstract The behavior of (Co77Si13.5B9.5)93Fe4Nb3 and (Co77Si13.5B9.5)99.3Fe0.7 amorphous alloys during primary crystallization was studied using Mossbauer spectroscopy and X-ray diffraction. The data obtained clearly demonstrate a key role of chemical interactions in the structural evolution of amorphous alloys and further clarify some mechanisms underlying the evolution.

Chemical effects during solute-atom segregation at grain boundaries in the mean field approximation

The role of chemical interaction in impurity segregation on grain boundaries is considered in the framework of a model that takes into account diffuse distribution of impurities near the grain boundary. The possibility of segregation phase transitions of first and second order is predicted and criteria for determining the order of the phase transition are suggested.