OH Peak Research Articles

Infrared Spectroscopic Study on the Modified Mechanism of Aluminum-Impregnated Bone Charcoal

Fluoride contamination in drinking water is a prominent and widespread problem in many parts of the world. Excessive ingestion of fluoride through water can lead to the high risk of fluorosis in human body. Bone charcoal, with the principal active component of hydroxyapatite, is a frequently used adsorbent for fluoride removal. Many laboratory experiments suggest that the aluminum-impregnated bone charcoal is an effective adsorbent in defluoridation. However, the mechanisms underlying this modification process are still not well understood, which in turn greatly impedes the further studies on other different modified adsorbents. To address this issue, we used the infrared spectroscopy to examine the bone charcoal and the aluminum-impregnated bone charcoal, respectively. The comparative results show that the −OH peak of infrared spectroscopy has been intensified after modification. This significant change helped speculate the modified mechanism of the aluminum-impregnated bone charcoal. In addition, it is found that the hydroxide ion dissociates from hydroxyapatite in the modification process. Such finding implies that the tetrahydroxoaluminate can be combined with the hydroxyapatite and the aluminum ion can be impregnated onto the bone char surface.

Interfacial Segregation in Polymer Blends Driven by Acid–Base Interactions

Infrared-visible sum frequency generation spectroscopy (SFG) was used to measure the interfacial concentrations of poly(methyl methacrylate) (PMMA)/polystyrene (PS) blends next to a sapphire substrate. The acid-base interactions of carbonyl groups of PMMA with the hydroxyl groups on the sapphire drive the interfacial segregation of PMMA next to the sapphire substrate. Using the shift of sapphire surface OH peaks, we have determined the difference in interfacial energy between the PMMA/sapphire and the PS/sapphire to be ~44-45 mJ/m(2). These results highlight the importance of acid-base interactions and their role in controlling the interfacial segregation next to solid substrates in polymer blends.

Photoactivity of Poly(lactic acid) nanocomposites modulated by TiO2 nanofillers

ABSTRACTPhotoactivity of poly(lactic acid) (PLA) nanocomposites is of great interest for rational design of products for either short‐term/single‐use or long‐term/durable applications. We prepared PLA/TiO2 nanocomposite films through a solution mixing/film casting method. Results showed that photodegradability/photostability of PLA could be well modulated by selecting appropriate TiO2 nanofillers. TiO2 nanoparticles and nanowires were characterized using X‐ray diffraction, UV–Vis–NIR spectrophotometer, and scanning electron microscopy. Changes in color, weight, structure, thermal stability, and phase transitions of PLA and nanocomposite films before and after UV irradiation were evaluated to study photoactivity characteristics. Pure PLA exhibited moderate photodegradability, but the photodegradability and photostability of PLA nanocomposites (PNA) were significantly enhanced by NanoActive (NA) TiO2 nanoparticles and A type TiO2 nanowires, respectively. Pure PLA had a weight loss of 27% after 38 days of UV irradiation. The weight loss of photodegradable (PD) PNA (PNA = PLA with 1% NA TiO2) reached 38%, whereas that of photostable (PS) nanocomposites (P3AW) (P3AW = PLA with 3% A type TiO2 nanowire) was only 5%. PD PLA exhibited characteristic peaks of carboxylic acid OH stretching and CC double bond after UV irradiation in Fourier‐transform infrared spectra, whereas spectra of PS PLA remained almost the same. Thermal decomposition temperatures, glass transition temperatures, and melting temperatures of PD PLAs decreased dramatically after UV irradiation, but no obvious changes were observed for those of PS PLAs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40241.

Modification of tapioca starch by non-chemical route using jet atmospheric argon plasma

Non-chemical modification of tapioca starch was investigated using jet atmospheric argon plasma treatment. Two forms of starch slurry, i.e. granular starch (G) and cooked starch (C), were jet-treated by argon plasma generated by supplying input power of 50W (denoted as G50 and C50 samples) and 100W (denoted as G100 and C100 samples) for 5min. Physical, rheological, and structural characteristics of the modified starch were investigated. The G50 and C100 samples had lower paste clarity but higher thermal stability and performed stronger gels (G50 only) compared to their control counterparts. On the other hand, the analyzed properties of the G100 and C50 samples showed the opposite trend. FTIR and 1H NMR results revealed that the relative areas of COC and OH peaks were changed after the treatment. Cross-linking reaction seemed to predominantly take place for the G50 and C100 samples, whereas depolymerization predominated for the G100 and C50 samples.

Physical and Thermal Properties of <i>Zingiber officinale</i> Rosc. (Ginger) Rhizome Fine Particle as a Function of Grinding System

In this study,Zingiber officinale(ginger) rhizome fine particles were prepared by using food processor, hammer mill and planetary ball mill and tested for their physical and thermal properties. The physical changes by means of particle size, surface morphology, FT-IR and thermal stability (TGA) were investigated. The size reduction method had a distinct effect on physical and thermal properties of ginger rhizome tested. Average particle size of ginger rhizome after using food processor and hammer mill was around 50µm and 20µm respectively while after using planetary ball mill the ginger rhizome was successfully reduced to nanoscale (222.3 nm). Higher degree of granule surface fractured was observed as a result of a planetary ball milling process based on FESEM images. There were also some notable differences of FT-IR spectra detected. By comparing the spectra, the stretching vibration peak of OH at 3292 cm-1[U1]and the symmetric stretching vibration peak of the NO2and C=C at 1369 – 1639.51cm-1 for ginger rhizome ground using food processor were disappeared. Yet, presence of possibly strong alkenes group (in the range 2850 – 2970cm-1) were observed in all samples tested. Ginger rhizome particles obtained from hammer milling process were found to be more stable to thermal effect where the decomposed temperature was 276.64°C as compared to samples milling using food processor and planetary ball mill. These results would provide useful insight for exploring the potential applications of ginger rhizome fine powder as functional food ingredient as well as in pharmaceutical applications. [U1]Check typing of superscript.

Sodium Dodecyl Sulfate Adsorption onto Positively Charged Surfaces: Monolayer Formation With Opposing Headgroup Orientations

The adsorption and structure of sodium dodecyl sulfate (SDS) layers onto positively charged films have been monitored in situ with vibrational sum-frequency-generation (SFG) spectroscopy and surface plasmon resonance (SPR) sensing. Substrates with different charge densities and polarities used in these studies include CaF2 at different pH values as well as allylamine and heptylamine films deposited onto CaF2 and Au substrates by radio frequency glow discharge deposition. The SDS films were adsorbed from aqueous solutions ranging in concentration from 0.067 to 20 mM. In general the SFG spectra exhibited well resolved CH and OH peaks. However, at SDS concentrations between 1 and 8 mM the SFG CH and OH intensities decreased close to background levels. Combined data sets from molecular conformation, orientation, and order sensitive SFG with mass sensitive SPR suggest that the observed changes in SFG intensities above 0.2 mM are related to structural arrangements in the SDS layer. A model is proposed where the SFG intensity minimum between 1 and 8 mM is associated with a monolayer containing two headgroup orientations, one pointing toward the substrate and one pointing toward the solution phase. The SFG peaks observed at concentrations below 0.2 mM are dominated by the presence of adsorbed contaminants such as fatty alcohols (e.g., dodecanol), which are more surface active than SDS. As SDS solution concentration is increased above 1 mM SDS molecules are incorporated in the surface layer, with dodecanol continuing to be present in the surface layer for solution concentrations up to at least the critical micelle concentration.

Study of the Microcharacter of Ultrastable Aqueous Foam Stabilized by a Kind of Flexible Connecting Bipolar-Headed Surfactant with Existence of Magnesium Ion

In this paper, ultrastable aqueous foam stabilized by a kind of flexible connecting bipolar-headed surfactant alkyl polyoxyethylene sulfate (AE3S) with coexisting Mg(2+) was reported. Detailed molecular behaviors of AE3S in foam film with coexisting divalent cationic Ca(2+) or Mg(2+) were investigated by molecular dynamic simulation, comparing with the traditional surfactant sodium dodecyl sulfate (SDS), to find out how the microcharacter and array behavior of molecules in the foam film determined by molecular interaction effect the foam stability. It was found that the ultrastable foam film obtained by the cooperation of magnesium ions and AE3S was driven from two aspects: one is the favorable arrangement of surfactant molecules, and the other is the increase of capacity of foam films for resolutely holding water molecules deduced by a dipolar pair formed by the flexible connecting head groups of AE3S and hydrated Mg(2+) via intermolecular coactions, both related to the presence of magnesium ions. Foam lamella stability measurement and foam decay method were both used to evaluate the stability of foam. Fourier transform infrared (FT-IR) was used to detect the composition variation of foam film in the drainage process; the vibration peak of OH for water molecule shifted from the 3390 cm(-1) (being assigned to the bulk water integrated by hydrogen bonds) to 3685 cm(-1) (being assigned to the vibration of isolated water molecules) for the ultrastable foam film after complete drainage, which agreed very well with the molecular simulation results.

Surface Treatment of Glass by Microplasma

Microplasma technology was used in many applications from biomedical to surface treatment of polymers. A new application could be the surface treatment of glass panels for the electronic industry in order to improve the surface wettability. The remote microplasma method is proposed for the surface treatment of glass. It can be easily applied as an industrial process due to the relatively low discharge voltage around 1 kV and small size of the reactor. This paper presents the surface treatment of glass by microplasma using Ar and mixtures of Ar with N2 and O2. A microplasma process was analyzed by the emission spectroscopy method. A Marx generator with MOSFET switches, a neon transformer, and a pulsed power supply were used to energize the electrodes. The emission spectrum was measured by an intensified charge-coupled device camera and a spectrometer. An optic fiber was used to have an accurate measurement of a small part of the microplasma discharge. Surface wettability of glass was confirmed, measuring the contact angle before and after the microplasma treatment. The surface of glass was modified due to the action of the radicals and active species generated by microplasma. The emission spectrum of the microplasma discharge in Ar and mixtures of Ar with and showed ArI peaks, OH peaks, second positive band system peaks, and first positive band system peaks.

Ultrasound-assisted degradation for preparing soluble melanin from squid ink and its anti-oxidant activity

We developed a new method using ultrasound-assisted degradation under alkaline condition for preparation of solution squid ink melanin.The squid ink melanin was mixed with NaOH solvent in brown glass tubes.The melanin-solvent suspension was treated by ultrasound for 1 h and then divided into three different molecular weight(Mw)fractions by membrane separation(below 10 ku,among 10-50 ku and over 50 ku).The result showed that the mean diameter of the squid ink melanin was decreased from 17.34 μm.to 1.467 μm after ultrasound process.UV,IR and solid13C NMR spectra indicated that the basic structure of melanin fraction was still retained after ultrasound process.The fraction with Mw below 10 ku showed more severe degree of oxidation on active groups(DHI and DHICA)than those above 10 ku.Further in vitro analysis showed soluble melanin fractions obtained in 0.5 and 1 mol/L NaOH,with Mw above 10 ku which had greater characteristic absorption peak of-OH and-NH structure exhibited much higher antioxidant potency.The IC50 of these fractions(among 19-80 μg)on scavenging O-2· is more efficient than carnosine(IC50=355 μg/mL.),a commercialized antioxidant.And they(IC50 among 115-180 μg/mL)are as efficient as carnosine(IC50=110 μg/mL)on scavenging ·OH in free radical scavenge assay.In conclusion,our results showed that soluble squid melanin is a natural pigment and a new free radical scavenger with a promising prospect.The excellent solubility can increase absorption and enhance utilization rate in vivo,providing a potential prospect for squid ink melanin product as a natural antioxidant.

Spatial Distribution of Light Emission in Microplasma under 100 µm Gaps

Emission spectroscopy analysis was used to study the microplasma phenomena. The microplasma discharge in Ar, N2/Ar, and O2/Ar was analyzed in the discharge gap area, and the spatial distribution of active species was also measured outside the electrodes. The spatial distribution in the discharge gap showed a higher intensity of the N2 second positive band system (N2 SPS) peak towards the grounded electrode (anode). The measurement of OH peak at 308.9 nm proved the existence of this excited species 1 mm outside the electrodes area. Images of the discharges at various gaps showed that the diameter of streamers derived from microdischarges was about 10 µm at the 100 µm gap, then decreased relative to the decrease in gap width. For gas mixtures containing N2 in Ar, a more diffuse discharge was observed with the decrease in the amount of N2 in Ar. The results are necessary for optimizing microplasma processes such as surface treatment and biomedical applications.

Spatial Distribution of Light Emission in Microplasma under 100 µm Gaps

Emission spectroscopy analysis was used to study the microplasma phenomena. The microplasma discharge in Ar, N2/Ar, and O2/Ar was analyzed in the discharge gap area, and the spatial distribution of active species was also measured outside the electrodes. The spatial distribution in the discharge gap showed a higher intensity of the N2 second positive band system (N2 SPS) peak towards the grounded electrode (anode). The measurement of OH peak at 308.9 nm proved the existence of this excited species 1 mm outside the electrodes area. Images of the discharges at various gaps showed that the diameter of streamers derived from microdischarges was about 10 µm at the 100 µm gap, then decreased relative to the decrease in gap width. For gas mixtures containing N2 in Ar, a more diffuse discharge was observed with the decrease in the amount of N2 in Ar. The results are necessary for optimizing microplasma processes such as surface treatment and biomedical applications.

UV–visible light absorption by hydroxyl and formaldehyde and knocking combustion in a DME-HCCI engine

Experiments were conducted in a compression–expansion test engine to investigate the combustion characteristics in a homogeneous charge compression ignition (HCCI) engine fuelled with dimethyl ether. Two types of analyses were performed. In the first, ultraviolet–visible (UV–Vis) light absorbance was investigated to identify the formation behaviour of HCHO and OH during HCCI combustion. In the second, knocking combustion was investigated by analysing the spatially integrated flame luminosity and in-cylinder pressure oscillations. The time-resolved HCHO and OH profiles at different equivalence ratios showed that HCHO absorbance increased in the low-temperature reaction (LTR) and thermal-preparation regions and gradually decreased as the combustion approached the high-temperature reaction (HTR) region. The in-cylinder temperature in the LTR region had little effect on the rate of the maximum pressure rise, and this did not change much at different equivalence ratios. The results demonstrated that there was a marked difference between the intensity of the flame emissions of non-knocking and knocking events. The time-resolved integrated absorbance spectra of HCHO with peaks at 328, 340, and 354nm that occurred before the OH peaks appeared suggested that when a certain threshold ratio of (dP/dθLTR)/(dP/dθHTR) was reached, the amount of HCHO decreased due to reactions in the thermal-preparation region while the tendency to knock increased.

Hybrid Silica–PVA Nanofibers via Sol–Gel Electrospinning

We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.

Extruded tellurite glass and fibers with low OH content for mid-infrared applications

Heike Ebendorff-Heidepriem, Kevin Kuan, Michael R. Oermann, Kenton Knight, and Tanya M. Monro

Stimulated Raman scattering from ice-VIII by shock-induced compression in liquid water

Stimulated Raman scattering (SRS) from ice-VIII was investigated using shock-induced compression (SIC) generated by laser-induced breakdown in liquid water. Three backward SRS peaks of OH stretching vibrations and one backward SRS characteristic peak of lattice translation were observed. The SRS spectra indicated that the ice-VIII structure is formed by SIC, as the trajectory of the SIC passes through the stable pressure-temperature range of ice-VIII. The static electric field generated by electron jets protects proton-ordered structure. The laser-induced shock wave mechanism is also discussed.

Investigation of the interfacial water structure on poly[2-(dimethylamino)ethyl methacrylate] at the air/water interface by sum frequency generation vibrational spectroscopy

The effect of pH on the conformation of surface alkyl groups and the structure of interfacial water molecules on poly[2-(dimethylamino)ethyl methacrylate] (PDEM) at the air/water interface were investigated with sum frequency generation vibrational spectroscopy (SFG-VS). At pH 4.1, the hydrogen bonding SFG spectra were similar to that of the air/pure water interface. As the pH increased from 5.4 to 9.6, the SFG intensities of both highly ordered hydrogen bonding (3200 cm−1 band) and less-ordered hydrogen bonding (3400 cm−1 band) were enhanced because of the charge-induced effect of deprotonated PDEM. The free OH peak disappeared completely because it was replaced by interfacial PDEM molecules. At pH 11.5, a new spectral band appeared at about 3580 cm−1 in the ppp and sps spectra, and this could be assigned to the C 2v asymmetric stretching mode of the water molecules through molecular symmetry simulation. These hydrogen bonding structures are fully consistent with the conformational change of PDEM alkyl groups, and PDEM molecules act as a Hofmeister solvent. PDEM molecules are kosmotropic when they are charged and become more chaotropic as the pH increases.

Theoretical study on the difference of OH vibrational spectra between OH−(H2O)3 and OH−(H2O)4

Theoretical simulations are performed for the vibrational spectra of selected isomers of OH(-)(H(2)O)(3) and OH(-)(H(2)O)(4) clusters to understand the origin of the difference in the experimental OH stretching fundamental spectra between these clusters reported by Robertson et al. [Science, 2003, 299, 1367]. Vibrational excitation energies and intensities are calculated by combining the adiabatic separation treatment of water and OH(-) units, and the least order inter unit coupling correction. Moreover, to directly simulate the shape of the experimental spectra, both the homogeneous and inhomogeneous widths of the spectra are calculated using on-the-fly quasi-classical trajectories and rotational constants information. Through these simulations, we show that the dominant isomer of OH(-)(H(2)O)(4) should be the one with a second solvation shell water as suggested by Robertson et al. to explain the spectra in the 3200-3700 cm(-1) range. In particular, rather than the peaks of the second shell water OH bands themselves, the peak corresponding to the weakly hydrogen bonded OH of the first solvation shell water is essential for the assignment of the dominant isomer. We also discuss the power law relation between the homogeneous width and the red-shift by the hydrogen bond, the limitation of B3LYP for the accurate description of strong hydrogen bonded OH peak positions, and the dependence of the inter unit coupling effects on the structure and the size of the clusters.

Spatial and Temporal Analysis of Microplasma Light Emission

ABSTRACTEmission spectroscopy analysis was used to study the microplasma phenomena. The microplasma discharge in Ar, N2/Ar and O2/Ar was analyzed in the discharge gap area and spatial distribution of active species was measured also outside the electrodes. Spatial and temporal distribution showed the propagation of light emission from anode towards cathode within a time period of 190 ns. The measurement of OH peak at 308.9 nm proved the existence of this excited species 1 mm outside the electrodes area.

Nitrous acid (HONO) during polar spring in Barrow, Alaska: A net source of OH radicals?

[1] HONO was measured by a LOPAP instrument (LOng Path Absorption Photometer) for one month during the OASIS spring 2009 campaign in Barrow, Alaska. HONO concentrations between ≤ 0.4 pptv (DL) and ∼500 pptv were measured. The very high concentrations observed on several days were caused by local direct emissions and were highly correlated with the NOx and CO data. When only “clean days” were considered, average HONO concentrations varied between ≤ 0.4 - 10 pptv. Average HONO/NOx and HONO/NOy ratios of ∼6% and ∼1% were observed, respectively, in good agreement with other remote LOPAP measurement data, but lower than measured in most other polar regions by other methods. The strong correlation between sharp peaks of OH and HONO during daytime, which was not observed for any other measured radical precursor, suggested that HONO photolysis was a major source of OH radicals in Barrow. This was supported by calculated net OH radical production by HONO and O3 photolysis for which the contribution of O3 (2%) could be neglected compared to that of HONO (98%). A net extra HONO/OH source necessary to explain elevated HONO levels during daytime of up to 90 pptv/h was determined, which was highly correlated with the actinic flux. Accordingly, a photochemical HONO source is proposed here, in good agreement with recent studies. From the higher correlation of the net HONO source with and [NO2] compared to and [NO3−], photosensitized conversion of NO2 on humic acid containing snow surfaces may be a more likely source of HONO in the polar atmosphere of Barrow than nitrate photolysis.

Characterization of hydroxyl groups of highly crystalline β-chitin under static tension detected by FT-IR

► Two OHs of β-chitin were identified by FTIR with tensioning in chain direction. ► Both peaks shifted to higher wavenumbers by tension, but the shift amount differed. ► O3H is located in chain's backbone, and O6H is located in a side-branch of the chain. ► Both are hydrogen bonded, but that of O3H would be more affected by tension applied. ► Thus the peak that shifted more severely under tension could be assigned to O3H. The different behavior of the OH groups of a highly crystalline β-chitin from Lamellibrachia sp. was revealed by FT-IR spectroscopy with static tension applied in the direction of the chain. Both OH groups shifted to higher wavenumbers under the tension, possibly because the force constant of the OH vibration intensified due to the erosion of hydrogen bonds, but the shift in the OH peak occurring at 3435 cm −1 was 14% greater than that of the peak at 3470 cm −1 . The band at 3435 cm −1 was assigned to O(3)H and that at 3470 cm −1 to O(6)H, because the intramolecular hydrogen bond of O(3)H⋯O(5) occurs along the chitin chain's backbone and is likely to be more affected under tensile stress as a load carrier, than O(6)H⋯O(7) C, which is an intermolecular hydrogen bond located in a branch of the chain. Computation of an IR spectrum under stretching was conducted and supported the assignment of the two OH groups.