Surface Molecular Structure Research Articles

Chemical and structural characterization of copper adsorbed on mosses (Bryophyta)

The adsorption of copper on passive biomonitors (devitalized mosses Hypnum sp., Sphagnum denticulatum, Pseudoscleropodium purum and Brachythecium rutabulum) was studied under different experimental conditions such as a function of pH and Cu concentration in solution. Cu assimilation by living Physcomitrella patents was also investigated. Molecular structure of surface adsorbed and incorporated Cu was studied by X-ray Absorption Spectroscopy (XAS). Devitalized mosses exhibited the universal adsorption pattern of Cu as a function of pH, with a total binding sites number 0.05–0.06mmolgdry−1 and a maximal adsorption capacity of 0.93–1.25mmolgdry−1 for these devitalized species. The Extended X-ray Absorption Fine Structure (EXAFS) fit of the first neighbor demonstrated that for all studied mosses there are ∼4.5 O/N atoms around Cu at ∼1.95Å likely in a pseudo-square geometry. The X-ray Absorption Near Edge Structure (XANES) analysis demonstrated that Cu(II)-cellulose (representing carboxylate groups) and Cu(II)-phosphate are the main moss surface binding moieties, and the percentage of these sites varies as a function of solution pH. P. patens exposed during one month to Cu2+ yielded ∼20% of Cu(I) in the form of Cu–S(CN) complexes, suggesting metabolically-controlled reduction of adsorbed and assimilated Cu2+.

Probing Shear Thinning Behaviors of IgG Molecules at the Air-Water Interface via Rheological Methods.

Shear thinning behavior, often observed in shear viscosity tests of IgG therapeutic molecules, could lead to significant disparities in the projections for the viscosity profile of a molecule. Despite its importance, molecular determinants of sheer thinning in protein suspensions are largely unknown. To better understand the factors influencing sheer thinning, viscosity profiles of IgG1 and IgG2 molecules were monitored over a wide range of bulk concentrations (0.007-70 mg/mL). The degree of shear-thinning of 70 and 0.007 mg/mL samples was minimal in comparison to the 0.7 mg/mL solution for both IgG molecules. These observations suggest that bulk concentration alone does not determine the degree of sheer thinning, and additional factors play a role. Additional data reveals, within a threshold range of concentrations, that a strong correlation exists between the degree of shear thinning and the surface area to volume (SA:V) ratio of an IgG sample exposed to the interface. The influence of the interface, however, diminishes when the bulk concentration falls outside this concentration window. Also revealed by interfacial oscillatory rheological testing, both IgG molecules showed solid-like behavior (G'i) at the air-water interface at 0.7 mg/mL, whereas liquid-like behavior (G″i) was dominant at 0.007 and 70 mg/mL concentrations. These observations imply that the lack of solid-like behavior was due to the absence of a network structure. Likewise the addition of polysorbate 20 (PS20) to the 0.7 mg/mL solutions decreased the degree of shear thinning by disrupting the network structure at the interface. Taken together, the results presented here suggest that, although shear thinning behavior is a manifestation of an interfacial, rather than a bulk, phenomenon, the extent of it depends on how susceptible the surface molecules are to the air-water interface, where the surface molecular structures are influenced by the bulk properties.

Feeder-free culture of mouse embryonic stem cells using ozone/UV surface-modified substrates

Event Abstract Back to Event Feeder-free culture of mouse embryonic stem cells using ozone/UV surface-modified substrates Kohei Kasai1*, Hideo Nakata2* and Shogo Miyata3* 1 Keio University, Graduate School of Science and Technology, Japan 2 Ebara Jitsugyo Corp., Japan 3 Keio University, Faculty of Science and Technology, Japan Introduction: Culturing pluripotent stem cells effectively requires feeder cell layers or coating by specially conditioned extracellular matrixes (ECM). However, to apply the pluripotent stem cells as resources for regenerative medicine, feeder cell layers or animal-derived factors have to be removed for to establish of xeno-free culture condition. To enable the xeno-free culture system, we focused on Ozone/UV surface treatment of polystyrene substrates to improve adhesion and proliferation of pluripotent stem cells. The ozone/UV treatment modifies the hydrophilic property and molecular structure of polystyrene surface by ozone oxidation. In this study, as a fundamental research for the xeno-free culture system of embryonic stem cells (ESCs), mouse ESCs (mESCs) were cultured on the modified polystyrene substrates without the feeder cell layers. The adhesion, proliferation, and pluripotency were evaluated. Materials and Methods: The polystyrene substrates were modified by ozone/UV radiation. The wavelength of UV lamps was 185 nm and 254 nm. Virgin polystyrene, ozone/UV surface-modified polystyrene, and polystyrene with feeder cell layer were used as culturing substrate. The mESCs were cultured on the substrates during 2 days. The microscopic images of the cells were acquired during the culture. Also the DNA amount of the cells per dish at the time point of 2 days after cell seeding was measured to evaluate the adhesion and proliferation. Results: The microscopic images of the cells are showed in Figure 1. Also the DNA amount per dish is shown in Figure 2. While the cells on the virgin polystyrene were not adhered, the adhesion and proliferation rate of mESCs on the ozone/UV surface-modified polystyrene showed similar values to those on feeder cell layer. And the cells on both substrates formed colonies which were positive for alkaline phosphatase staining stained. Discussion: The cell proliferation rate on ozone/UV surface-modified polystyrene were significantly greater than the number of cells on the virgin polystyrene. It is considered that the molecular structure modified by ozone/UV treatment promoted the adhesion of the ESCs and kept their pluripotency. Then, it could be considered that the modified surface played the similar role to feeder cell layer. Conclusion: In conclusion, it was suggested that the ozone/UV surface-modified polystyrene substrates made it possible to culture mESCs in feeder-free condition without any chemical treatment for substrates. Keywords: Cell Proliferation, stem cell, Surface modification, Polymeric material Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Cellular migration and biomaterials Citation: Kasai K, Nakata H and Miyata S (2016). Feeder-free culture of mouse embryonic stem cells using ozone/UV surface-modified substrates. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01845 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. * Correspondence: Dr. Kohei Kasai, Keio University, Graduate School of Science and Technology, Yokohama, Kanagawa, Japan, k.kasai@keio.jp Dr. Hideo Nakata, Ebara Jitsugyo Corp., Kawasaki, Japan, Email1 Dr. Shogo Miyata, Keio University, Faculty of Science and Technology, Yokohama, Japan, miyata@mech.keio.ac.jp Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Kohei Kasai Hideo Nakata Shogo Miyata Google Kohei Kasai Hideo Nakata Shogo Miyata Google Scholar Kohei Kasai Hideo Nakata Shogo Miyata PubMed Kohei Kasai Hideo Nakata Shogo Miyata Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Evidence of a molecular boundary lubricant at snakeskin surfaces

During slithering locomotion the ventral scales at a snake's belly are in direct mechanical interaction with the environment, while the dorsal scales provide optical camouflage and thermoregulation. Recent work has demonstrated that compared to dorsal scales, ventral scales provide improved lubrication and wear protection. While biomechanic adaption of snake motion is of growing interest in the fields of material science and robotics, the mechanism for how ventral scales influence the friction between the snake and substrate, at the molecular level, is unknown. In this study, we characterize the outermost surface of snake scales using sum frequency generation (SFG) spectra and near-edge X-ray absorption fine structure (NEXAFS) images collected from recently shed California kingsnake (Lampropeltis californiae) epidermis. SFG's nonlinear optical selection rules provide information about the outermost surface of materials; NEXAFS takes advantage of the shallow escape depth of the electrons to probe the molecular structure of surfaces. Our analysis of the data revealed the existence of a previously unknown lipid coating on both the ventral and dorsal scales. Additionally, the molecular structure of this lipid coating closely aligns to the biological function: lipids on ventral scales form a highly ordered layer which provides both lubrication and wear protection at the snake's ventral surface.

Evaluation of the potentials of humic acid removal in water by gas phase surface discharge plasma

Degradation of humic acid (HA), a predominant type of natural organic matter in ground water and surface waters, was conducted using a gas phase surface discharge plasma system. HA standard and two surface waters (Wetland, and Weihe River) were selected as the targets. The experimental results showed that about 90.9% of standard HA was smoothly removed within 40 min's discharge plasma treatment at discharge voltage 23.0 kV, and the removal process fitted the first-order kinetic model. Roles of some active species in HA removal were studied by evaluating the effects of solution pH and OH radical scavenger; and the results presented that O3 and OH radical played significant roles in HA removal. Scanning electron microscope (SEM) and FTIR analysis showed that HA surface topography and molecular structure were changed during discharge plasma process. The mineralization of HA was analyzed by UV–Vis spectrum, dissolved organic carbon (DOC), specific UV absorbance (SUVA), UV absorption ratios, and excitation-emission matrix (EEM) fluorescence. The formation of disinfection by-products during HA sample chlorination was also identified, and CHCl3 was detected as the main disinfection by-product, but discharge plasma treatment could suppress its formation to a certain extent. In addition, approximately 82.3% and 67.9% of UV254 were removed for the Weihe River water and the Wetland water after 40 min of discharge plasma treatment.

Using the Inverse Maximum Ratio-Λ as a Technique to Quantify Surface Uniformity

Techniques used in variability assessment are subsequently used to draw conclusions regarding the “spread”/uniformity of data curves. Due to the limitations of these techniques, they are not adequate for circumstances where data manifest with multiple peaks. Examples of these manifestations (in three-dimensional space) include under-foot pressure distributions recorded for different types of footwear (Becerro-de-Bengoa-Vallejo et al., 2014; Cibulka et al., 1994; Davies et al., 2003), surface textures and interfaces designed to impact friction, and and and molecular surface structures such as viral epitopes (Torras and Garcia-Valls, 2004; Pacejka, 1997; Fustaffson, 1997). This article proposes a technique for generating a single variable – Λ that will quantify the uniformity of such surfaces. We define and validate this technique using several mathematical and graphical models.

Plasma Treatment Effects on Molecular Structures at Dense and Porous Low-k SiCOH Film Surfaces and Buried Interfaces

The effects of oxygen plasma treatment on molecular structures at low-k organosilicate (SiCOH) film surfaces and buried interfaces were investigated using sum frequency generation (SFG) vibrational spectroscopy and Raman spectroscopy. SFG and Raman spectra were acquired from pristine and plasma-treated low-k SiCOH films to characterize the interfacial and bulk molecular structures of the films before and after plasma treatment. Two SiCOH films with similar molecular structures but different porosities were investigated to correlate the effects of plasma treatment to the porosity of low-k films. SFG spectra indicated that the surface molecular structure of dense SiCOH films was more resistant to plasma damage than the surface molecular structure of porous SiCOH films. Furthermore, the ratio of SFG peak intensities before and after plasma treatment enabled quantification of methyl depletion at the surface of SiCOH films after plasma treatment. The molecular structure at buried Si/SiCOH interfaces was charac...

Multireflection sum frequency generation vibrational spectroscopy.

We developed a multireflection data collection method in order to improve the signal-to-noise ratio (SNR) and sensitivity of sum frequency generation (SFG) spectroscopy, which we refer to as multireflection SFG, or MRSFG for short. To achieve MRSFG, a collinear laser beam propagation geometry was adopted and trapezoidal Dove prisms were used as sample substrates. An in-depth discussion on the signal and SNR in MRSFG was performed. We showed experimentally, with "m" total internal reflections in a Dove prism, MRSFG signal is ∼m times that of conventional SFG; SNR of the SFG signal-to-background is improved by a factor of >m(1/2) and <m. MRSFG also improved the SFG sensitivity to resolve weak vibrational signals. Surface molecular structures of adsorbed ethanol molecules, polymer films, and a lipid monolayer were characterized using both MRSFG and conventional SFG. Molecular orientation information on lipid molecules with a 9% composition in a mixed monolayer was measured using MRSFG, which showed a good agreement with that derived from 100% lipid surface coverage using conventional SFG. MRSFG can both improve the spectral quality and detection limit of SFG spectroscopy and is expected to have important applications in surface science for studying structures of molecules with a low surface coverage or less ordered molecular moieties.

Molecular structure of ionic surfactant solution surface and effects of counter-ion therein—a joint investigation by simulation and experiment

The main goal of the current paper is to investigate the surface structure of ionic surfactant solutions at molecular level and the influences of the counter-ion in this course. The used methods are molecular dynamics simulation and neutral impact collision ion scattering spectroscopy. The surfactants are sodium dodecyl sulfate and cesium dodecyl sulfate. With Material Studio (MS), the concentration-depth profiles of all the components in the surface layer have been simulated. With those profiles, the surface pictures of the ionic surfactant solutions are mapped out in angstrom scale and the orientation of surface active dodecyl sulfate ion at the surface dependent on its surface density is derived. Simultaneously, neutral impact collision ion scattering spectroscopy is employed to investigate the same systems experimentally. The results indicate that the surface structure is profoundly influenced by surface density of the surfactant and specificity of the counter-ion; however, the orientation of the dodecyl sulfate ion on the surface is only subjected to its surface density but hardly affected by the properties of its counter-ion. The comparison between those simulated and experimental results reveals reasonable agreements, indicating the reliability of this investigation as well as the reliability of the simulation strategy applied in these systems.

Structural Evolution during Lithiation Cycles of the Li-Au System Observed By in-Situ High-Energy x-Ray Diffraction

Recent new Li-Ion Battery (LIB) developments include alloy anodes such as Si-Li, and a general trend towards nanostructured components. With technological development LIB were proposed to store energy for stationary applications as well as electromobility. Batteries need to become more robust achieving longer cycle lifetime in use to achieve this future goal. Therefore fundamental insight into the acting atomic-scale processes and structural evolution within the active materials during the charging, i.e. lithiation and delithiation cycles is required. Crystalline phases are often formed during cycling as well as amorphous phases which prominently form in alloy anodes based on Si or Ge. Due to its inert nature Au has been often used as a model material in electrochemical research including Li ion storage (1,2). Au was as well employed in composite LIB anodes for example as seed layers to further grow Si nanowires or as coatings. For gold model electrodes as well as gold contained in a LIB anode several studies have pointed to many intermediate metastable crystalline Li-Au phases. X-ray diffraction is a classical non-destructive method to characterize crystalline phases and synchrotron light has more recently facilitated the analysis of surfaces and thin films as well as in-situ or in-operando characterization. Using high-energy x-ray sources a complete reciprocal plain can be imaged on short time scales necessary to follow also quick structural changes on the time-scale of a few seconds. The huge benefit of high-energy x-rays has been demonstrated in-operando for detailed studies from catalytic surface reactions and molecular interface structures and layering to battery processes. We describe an in-situ high-energy x-ray diffraction study (3) following the alloying of Li (charging) and dealloying (de-charging) with a Au thin film and discuss the observations with the result of a theoretical screening of potential metastable phases. During the entire charging and discharging cycles we observed in total 6 different crystalline phases which are mainly so far unknown metastable intermediate phases leading in the here chosen end state to the known stable Li3Au phase. The detailed evolution of the different phases have been followed during cycling. Using a thin Au film grown on single crystalline Cu substrates we also observe the final crystalline cubic Li3Au to emerge in oriented relation to the below Cu substrate thus indicating this phase nucleates at the interface. 1. P. Bach, M. Stratmann, I. Valencia-Jaime, A. H. Romero, F. U. Renner, Lithiation and Delithiation Mechanisms of Gold Thin Film Model Anodes for Lithium Ion Batteries: Electrochemical Characterization, Electrochimica Acta (2015), 164, 81–89. 2. F.U. Renner, H. Kageyama, Z. Siroma, M. Shikano, S. Schöder, Y. Gründer, O. Sakata, Gold model anodes for Li-ion batteries: Single crystalline systems studied by in situ X-ray diffraction, Electrochim. Acta 53 (2008), 6064-6069. 3. P. Bach, I. Valencia-Jaime, U. Rütt, O. Gutowski, I. Valencia-Jaime, A. H. Romero, F. U. Renner, to be published. Figure 1

Multivalency as a chemical organization and action principle.

Multivalency is a key principle in nature to establish strong, but also reversible chemical interactions between two units, e.g., a receptor and a ligand, viruses and host cells, or between two cell surfaces. Multivalent binding is based on multiple simultaneous molecular recognition processes and plays an important role in the self-organization of matter, in biological recognition processes as well as in signal transduction in biological systems. The targeted development of multivalent molecules is not only used for the strong inhibition of proteins and prevention of pathogen infections, but also allows for the selective production of functional molecular architectures and surface structures as well as the controlled interaction of multivalent surfaces. The chemical and biological mechanisms and the influence of scaffold architectures with different dimensions for multivalent interactions have not been comprehensively explored. Thus, the experimental and theoretical understanding of defined oligovalent binding systems requires further detailed understanding in the gas phase, in solution and on surfaces. Frequently the interaction of a single ligand with an acceptor (monovalent interaction) in many cases can be quantitatively understood. This, however, is completely different, when several covalently linked ligands of the same or of a similar nature bind to an ensemble of acceptors (multivalent interactions) [1]. Due to the multiple additive (in some cases cooperative) interactions the equilibrium will shift and bond reinforcement occurs (Fig. 1). Also, the kinetically controlled dissociation can become very slow to almost non-existent. Multivalency is also dependent on the size, shape and flexibility of the scaffold architecture, especially for the interfacial interaction with biological systems. Figure 1 Multivalent interactions shift the equilibrium and enhance the binding strength. Reprinted with permission from [1]. Copyright 2012 Wiley-VCH. In order to obtain a deeper understanding of multivalent interactions this Thematic Series in the Beilstein Journal of Organic Chemistry puts its focus to unravel new cellular interactions that are highly relevant [2] and systematically combines theoretical exploration of defined multivalent supramolecular interactions [3] as well as new supramolecular designer systems [4–5]. The influence of spacer length and flexibility on the binding affinity of ligands [6] will be examined as well as the mechanical stability of complexes [7]. Furthermore, the Thematic Series covers the synthesis of various new glycoarchitectures for multivalent interactions [8–12] and studies the scope of multivalent lectin-glycointeractions in galectins [13], with iminosugars [14] and carbohydrate mimetics [15]. This Thematic Series in the Beilstein Journal of Organic Chemistry also investigates the enhanced multivalent binding of protein scaffolds [16], peptide–polymer interactions [17–20] tripodal-catecholates [21] and polycatechol–surface interactions [22] as well as multivalent organocatalyts [23]. Finally, multivalent dendritic poly(arginine/histidine)-siRNA complexes are evaluated regarding their transfection efficiency [24]. In the future a deeper understanding of multivalent interactions at all length scales from the nanometer to the micrometer range is crucial for solving important problems and for the development of new systems in the fields of life and materials science. In order to address this highly complex and long-term challenge, the interdisciplinary cooperation of scientists with different expertise ranging from biochemistry to theory is essential. Rainer Haag Berlin, May 2015

Nanoscale Heterogeneity of the Molecular Structure of Individual hIAPP Amyloid Fibrils Revealed with Tip‐Enhanced Raman Spectroscopy

Type 2 diabetes mellitus is characterized by the pathological deposition of fibrillized protein, known as amyloids. It is thought that oligomers and/or amyloid fibrils formed from human islet amyloid polypeptide (hIAPP or amylin) cause cell death by membrane damage. The molecular structure of hIAPP amyloid fibrils is dominated by β-sheet structure, as probed with conventional infrared and Raman vibrational spectroscopy. However, with these techniques it is not possible to distinguish between the core and the surface structure of the fibrils. Since the fibril surface crucially affects amyloid toxicity, it is essential to know its structure. Here the surface molecular structure and amino acid residue composition of hIAPP fibrils are specifically probed with nanoscale resolution using tip-enhanced Raman spectroscopy (TERS). The fibril surface mainly contains unordered or α-helical structures, in contrast to the β-sheet-rich core. This experimentally validates recent models of hIAPP amyloids based on NMR measurements. Spatial mapping of the surface structure reveals a highly heterogeneous surface structure. Finally, TERS can probe fibrils formed on a lipid interface, which is more representative of amyloids in vivo.

Effects of Surface Modificationon the Suspension Stability and Thermal Conductivity of Carbon Nanotubes Nanofluids

The composite carbon nanotubes (CCNTs) were synthesized by surface modification of the as-synthesized carboxyl-functionalized carbon nanotubes (f-CNTs) with the polyethylene glycol, and the composite carbon nanotubes-based nanofluids(CCNTs-based nanofluids) were prepared with the as-synthesized CCNTs and ethylene glycol. The surface molecular structure, surface morphology of the CCNTs were characterized by FourierTransform Infrared Spectroscopy, Field Emission Scanning Electron Microscope and Transmission Electron Microscopy. The suspension stability and thermal conductivity enhancement ratio of the CCNTs-based nanofluids were characterized viathe thermal conductivity variation method. The results show that suspension stability of the CCNTs-based nanofluids was greatly improved by surface modification of the carbon nanotubes; the thermal conductivity of the CCNTs-based nanofluids was further enhanced and became more stableby surface modification.

Romidepsin (FK228) and its analogs as HDAC/PI3K dual inhibitors. A molecular surface structure around FK‐A11 in the ATP‐binding pocket

Cancer ScienceVolume 106, Issue 2 p. February cover-February cover Cover ImageOpen Access Romidepsin (FK228) and its analogs as HDAC/PI3K dual inhibitors. A molecular surface structure around FK-A11 in the ATP-binding pocket Ken Saijo, Ken SaijoSearch for more papers by this authorJin Imamura, Jin ImamuraSearch for more papers by this authorKoichi Narita, Koichi NaritaSearch for more papers by this authorAkifumi Oda, Akifumi OdaSearch for more papers by this authorHideki Shimodaira, Hideki ShimodairaSearch for more papers by this authorTadashi Katoh, Tadashi KatohSearch for more papers by this authorChikashi Ishioka, Chikashi IshiokaSearch for more papers by this author Ken Saijo, Ken SaijoSearch for more papers by this authorJin Imamura, Jin ImamuraSearch for more papers by this authorKoichi Narita, Koichi NaritaSearch for more papers by this authorAkifumi Oda, Akifumi OdaSearch for more papers by this authorHideki Shimodaira, Hideki ShimodairaSearch for more papers by this authorTadashi Katoh, Tadashi KatohSearch for more papers by this authorChikashi Ishioka, Chikashi IshiokaSearch for more papers by this author First published: 20 February 2015 https://doi.org/10.1111/cas.12607AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume106, Issue2February 2015Pages February cover-February cover RelatedInformation

Molecular structure and thermal stability of the oxide-supported phosphotungstic Wells-Dawson heteropolyacid.

We present, for the first time in the literature, a systematic study of the molecular structure of the Wells-Dawson heteropolyacid H6P2W18O62·24H2O (HPA) dispersed on TiO2, SiO2, ZrO2 and Al2O3. The heteropolyacid-based materials were synthesized through a conventional impregnation method (in aqueous and ethanol media) at a loading that corresponds to the theoretical "monolayer" coverage (dispersion limit loading). The combination of Raman and infrared studies demonstrates the presence of crystals of HPA (regardless of the nature of the medium used during the synthesis) suggesting that the dispersion limit loading was greatly exceeded. In situ temperature programmed spectroscopy analyses demonstrated that the Raman shift of the distinctive W[double bond, length as m-dash]O Raman mode of the phosphotungstic Wells-Dawson heteropolyacid is sensitive to the local environment, that is, the amount of water molecules associated with the structure. Moreover, the aqueous based species associated with such structures are recognizable through infrared spectroscopy.

Quantitative sum-frequency generation vibrational spectroscopy of molecular surfaces and interfaces: lineshape, polarization, and orientation.

Sum-frequency generation vibrational spectroscopy (SFG-VS) can provide detailed information and understanding of the molecular composition, interactions, and orientational and conformational structure of surfaces and interfaces through quantitative measurement and analysis. In this review, we present the current status of and discuss important recent developments in the measurement of intrinsic SFG spectral lineshapes and formulations for polarization measurements and orientational analysis of SFG-VS spectra. The focus of this review is to present a coherent description of SFG-VS and discuss the main concepts and issues that can help advance this technique as a quantitative analytical research tool for revealing the chemistry and physics of complex molecular surfaces and interfaces.

Effects of Surface Modification on the Stability of Suspension and Thermal Conductivity Enhancement of Composite Fe Nanofluids

Composite Fe nanoparticles (CINPs) were synthesized by surface modification of Fe nanoparticles with silicon alkyl ethylenediamine triacetic acid, and the silicone oil-based composite Fe nanofluids (CINPs nanofluids) were prepared with the as-synthesized CINPs and silicone oil. The surface molecular structure, magnetic properties, and surface morphology of the CINPs were characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscope, and vibrating sample magnetometer. The stability and thermal conductivity enhancement of the CINPs nanofluids were characterized via a thermal conductivity method and using a thermal property analyzer. Results show that the suspension stability of the CINPs nanofluids was greatly improved by the surface modification of the Fe nanoparticles. The thermal conductivity enhancement became more stable, and further, it was demonstrated that thermal conductivity could be tuned by applying magnetic field.

Novel reactive polymerizable nonyl phenol ethoxylate surfactants as emulsifier in non-aqueous emulsion polymerization

In this work, new series of modified nonionic polymerizable nonyl phenol ethoxylates (NPEs) were synthesized as organic solvent-soluble surfactants. The nonyl, phenyl and propenyl groups were acted as solvophilic segment. The modified polyoxyethylene, maleate chains were behaved as solvophobic segment. The new bifunctional surfmers were prepared by reacting polyoxyethylene 4-nonyl-2-propylenephenol nonionic reactive surfactant with maleic anhydride followed by esterification with poly(ethylene glycol). The chemical structure of the prepared surfactants was determined by 13C and 1H NMR analyses. The surface activities of these surfactants were determined in organic solvents including formamide, toluene and aqueous water solvent from surface tension measurements. The relationship between the surface activity and molecular structure of the organic solvent-soluble polymerizable NPE surfactants as well as the type and structure of organic solvents were discussed. The results showed that the prepared polymerizable NPE surfactants have been reduced the surface tension of both polar and non-polar organic solvents. Surface parameters such as surface excess concentration (Γmax), the area per molecule at interface (Amin) and the effectiveness of surface tension reduction were determined from the adsorption isotherms of the prepared surfactants. The prepared polymerizable surfactant used to prepare crosslinked N-isopropylacrylamide (NIPAAm) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) copolymer microgel based on nonaqueous emulsion copolymerization.

Excitation wavelength dependent visible photoluminescence of CdO nanomorphotypes

We report the red-shifted photoluminescence (PL) band edge emission behavior as a function of subsequent increment in excitation wavelength on cadmium oxide (CdO) nanoflakes and nanoparallelepiped morphotypes prepared through the hydrothermal method. The unusual band edge PL emission lines in crystalline nanomaterials are explained as strong quantum size effect due to the size selective band gap widening in nanomaterials. This kind of excitation wavelength dependent PL emission behavior appears to be in violation of Kasha׳s rule of excitation wavelength independence of the emission spectrum. The surface morphology, particle size, molecular structure, chemical composition and chemical bonding of the samples are analyzed by SEM, TEM, XRD, EDS and FTIR spectroscopy. Direct optical band gap is calculated and found to be of 2.75eV for nanoflakes and 2.52eV for parallelepiped nanostructures.

Molecular structure of poly(methyl methacrylate) surface. I. Combination of interface-sensitive infrared-visible sum frequency generation, molecular dynamics simulations, and ab initio calculations.

The chemical composition and molecular structure of polymeric surfaces are important in understanding wetting, adhesion, and friction. Here, we combine interface-sensitive sum frequency generation spectroscopy (SFG), all-atom molecular dynamics (MD) simulations, and ab initio calculations to understand the composition and the orientation of chemical groups on poly(methyl methacrylate) (PMMA) surface as a function of tacticity and temperature. The SFG spectral features for isotactic and syndiotactic PMMA surfaces are similar, and the dominant peak in the spectra corresponds to the ester-methyl groups. The SFG spectra for solid and melt states are very similar for both syndiotactic and isotactic PMMA. In comparison, the MD simulation results show that both the ester-methyl and the α-methyl groups of syndiotactic-PMMA are ordered and tilted toward the surface normal. For the isotactic-PMMA, the α-methyl groups are less ordered compared to their ester-methyl groups. The backbone methylene groups have a broad angular distribution and are disordered, independent of tacticity and temperature. We have compared the SFG results with theoretical spectra calculated using MD simulations and ab initio calculations. Our analysis shows that the weaker intensity of α-methyl groups in SFG spectra is due to a combination of smaller molecular hyperpolarizability, lower ordering, and lower surface number density. This work highlights the importance of combining SFG spectroscopy with MD simulations and ab initio calculations in understanding polymer surfaces.