Presence Of OH Groups Research Articles

Nanoscale Studies of Organic Radicals: Surface, Interface, and Spinterface.

In the last decade technology has brought significant changes to our lives, including new habits and a new view on social relationships. These technological innovations are based on several factors, one of which is miniaturization. This was made possible also due to the discovery and synthesis of new materials with characteristics at the nanoscale that are designed for specific purposes. This "on purpose" approach, joined to the development of preparation and growth methods, has led to use of thin films rather than bulk materials in devices. Using thin films makes devices easier to produce, and using films for coating protects the devices and gives specific properties to surfaces. For several decades thin films, surfaces, and interfaces have been intensively investigated. Indeed, device performances rely on the optimized match of thin films of different natures, such as organic and inorganic semiconductors and metals for contacts. Surprisingly, in comparison, little attention has been devoted to the deposition of organic radicals on a substrate. This might be because these materials are considered not stable enough for evaporation. In this work, we demonstrate that it is possible to evaporate and deposit organic radicals onto well-defined surfaces under controlled conditions, without degradation. Using soft X-ray spectroscopies, performed also at synchrotrons, we investigate thin film processes, surfaces, and interfaces at the nanoscale, when organic radicals are deposited on metal and metal oxide surfaces. We suggest how to design organic radicals bearing in mind the thermodynamic factors that govern thin film stability, with the purpose of obtaining not only a chemically stable radical, but also stable thin films. We investigate the thermal and air stability of the deposited films, and we explore the influence of the surface/radical chemical bond and the role of surface defects on the magnetic moment at the interface. We find that organic radicals are physisorbed and keep their magnetic moment on inert and passivated surfaces such as Au(111) and Al2O3(112̅0) single crystals, SiO2, and ideal TiO2(110) single crystals, while defective sites such as oxygen vacancies or the presence of OH groups lead to chemisorption of the organic radicals on the surface with quenching of their magnetic moment. Our work shows that the use of X-ray based techniques represents a powerful approach to reveal the mechanisms governing complex interfaces, such as radical/metal and radical/metal-oxide, where it is important to describe both charge and spin behavior (spinterfaces). It also makes it possible to conceive new experiments to investigate the magnetic character of the thin films versus their structural properties, toward tuning the arrangement of the molecules in films. Controlling the molecular arrangement will give the opportunity to tune the mutual position and orientation of the molecules, that is, of the single magnetic moments in the films, "imprinting" their magnetic properties. A deep understanding of stable radical/inorganic spinterfaces may open the way to use radicals in solid state devices or as quantum bits with dedicated configurations, as proposed for other molecular quantum bits, and in spin-based electronics.

Zincovelesite-6N6S, Zn3(Fe3+,Mn3+,Al,Ti)8O15(OH), a new högbomite-supergroup mineral from Jacupica mountains, Republic of Macedonia

A new mineral species zincovelesite-6N6S with the simplified formula Zn3(Fe3+,Mn3+,Al,Ti)8O15(OH) was discovered in the orogenetic zone related to the “Mixed Series” metamorphic complex near the Nežilovo village, Jacupica Mountains, Pelagonia mountain range, Republic of Macedonia. In oxide Zn-Fe-Mn ore, zincovelesite-6N6S forms lenticular aggregates up to 2 × 2 × 0.5 mm consisting of thin near-coplanar platelets up to 70 × 70 × 1 µm3 and associated with franklinite, gahnite, hetaerolite, zincochromite, ferricoronadite, baryte, As-rich fluorapatite, dolomite, Zn-bearing talc, almeidaite, hydroxycalcioromeite, zircon, quartz, and scheelite. In silicate-baryte zones of the metasomatic rock, uniaxial intergrowths of zincovelesite-6N6S with nežilovite are observed. The new mineral is opaque, black, with brownish-black streak. The lustre is strong submetallic to metallic. The micro-indentation hardness is 1118 kg/mm2 which corresponds to Mohs’ hardness ca. 6½. Zincovelesite-6N6S is brittle, with uneven fracture. No cleavage or parting is observed. The density calculated from the empirical formula is 5.158 g/cm3. In reflected light zincovelesite-6N6S is light grey. The reflectance values [Rmax/Rmin, % (λ, nm)] are: 17.1/13.4 (470), 16.5/12.8 (546), 16.2/12.6 (589), 15.6/12.2 (650). The IR spectrum shows the presence of OH groups. According to the Mossbauer spectrum, all iron is trivalent. The Mn K-edge XANES spectroscopy shows that Mn is predominantly or completely trivalent. The average chemical composition is (wt%; electron microprobe, H2O determined by gas chromatography of ignition products): MgO 0.97, CuO 0.50, ZnO 30.80, Al2O3 8.17, Mn2O3 21.31, Fe2O3 29.44, TiO2 5.28, Sb2O5 3.74, H2O 1.1, total 101.31. The empirical formula based on 16 O atoms is H1.05Zn3.26Mg0.21Cu0.05Fe3+3.18Mn3+2.32Al1.38Ti0.57Sb0.20O16. Zincovelesite-6N6S is trigonal, probable space group P-3m1, a = 5.902(2) A, c = 55.86(1) A, V = 1684.8(9) A3, Z = 6. The strongest lines of the powder X-ray diffraction pattern [d, A (I, %) (hkl)] are: 2.952 (62) (110), 2.881 (61) (1.0.16), 2.515 (100) (204), 2.493 (88) (1.1.12), 2.451 (39) (1.0.20), 1.690 (19) (304, 2.1.16), 1.572 (19) (2.0.28), 1.475 (29) (221). Zincovelesite-6N6S is the first Fe3+-dominant member of the hogbomite supergroup and, thus, can be considered as a parent species of a new mineral group. The rootname velesite is given for the discovery locality near the city of Veles.

Ultrasound, microwave and Box-Behnken Design amalgamation offered superior yield of gum from Abelmoschus esculentus: Electrical, chemical and functional peculiarity

Background and objectiveIn present investigation, ultrasonic assisted followed by microwave irradiation involving extraction process was developed under the umbrella of Box-Behnken design for gaining superior yield of gum from okra fruit, Abelmoschus esculentus. Methods and resultsStationed on single factor layout, Box-Behnken design was employed to calculate the optimized conditions for isolating the okra fruit gum (OFG) using ultrasonic waves and microwave radiations. The extracted gum was further characterized for particle size, zeta-potential, surface morphology, thermal stability, functional groups, and polymorphism. The optimized conditions like water to raw material ratio of 44.98 ml/g, extraction time of 40 min and ultrasonic power of 60 W provided the uppermost extraction yield of 31.52% ± 0.22% that was analogous to the predicted value. The average mean diameter of OFG was measured to be 256.3 ± 18.4 nm in addition to the zeta potential of −9.85 ± 0.12 mV. SEM image of OFG powder revealed irregular, rough surfaced and amorphous structure of OFG powder. The degree of esterification was measured to be 7.8 with high thermal stability, as exposed by DSC. The FT-IR spectrum of OFG displayed a broad peak at 3405.20 cm−1 announcing presence of OH group and hydrophilicity attribute. The spectrum also presented the small peak at 1605.20 cm−1 (CO) owing to the presence of galacturonic acid besides galactose and rhamnose. ConclusionIn conclusion, ultrasound and microwave irradiation assisted extraction process under the shed of Box-Behnken design offered superior yield of OFG that may be used as a pharmaceutical excipient for designing medicated or health products.

Antioxidant and Total Phenolic Content of Breadfruit (Artocarpus altilis) Leaves

This work aims to determine antioxidant, total phenolic content and Fourier transform infrared spectroscopy (FTIR) analysis of breadfruit leaves which are essential in management of diabetes. The methanolic extracts of breadfruit leaves was used to analyze for total phenolic content and antioxidant. Total phenolic content of the extracts was measured using the Folin–Ciocalteu assay while the antioxidant activity of plant extracts was measured by the 1, 1-diphenyl-2-picryhyradrazyl (DPPH) radical scavenging assay. FTIR analysis was used to determine the chemical components in the leaves. Total phenolic content in fresh breadfruit leaves (144.16 mg/g ± 17.98) was comparable to those of green tea. The results showed the breadfruit leaves extracts exhibited potent antioxidant activity. The presence of OH group also suggests antioxidant capacity of breadfruit leaves to deactivate free radicals as glucose itself could react with hydrogen peroxide in the presence of iron and copper ions to form hydroxyl radical.

Hidroksiapatit dari Tulang Ikan Tuna Sirip Kuning (Tunnus albacores) dengan Metode Presipitasi

Indonesia as one of the biggest tuna fish produsers in the world, produce tuna fish bones large enough. Since tuna fish bone contain high calcium it is potentially to be the raw material of hydroxyapatite. Hydroxyapatite are inorganic compounds constituent of bones and teeth has the moleculer formula Ca5(PO4)3OH. Synthesis of hydroxyapatite can be done with precipitation method through tuna fish bone calcination process at the temperature 900°C for 5 hours to obtain calcium compounds in the form of calcium oxide. Calcium wich has been obtained added phosphoric acid 0,6 M with flow rate/rapid 1 mL/minute. Controlled synthesis process parameters are pH 10 of solution. Yield of hydroxyapatite generated after synthesis with of the precipitation time 12 hours are of 91.15%. hydroxyapatite product obtained was analyzed by FTIR(Fourier Transform Infrared) and XRD (X-Ray Diffraction). FTIR analysis indicate the presence of OH groups, PO4 and CO3. Based on the resulting diffraction of XRD analysis, crystallite size obtained each of 211.29 nm structure is hexagonal. Scherrer method was used to obtain crystallite size.

Isolation and Identification of Compounds from the Leaf Extract of Melaleuca alternifolia

Introduction: Melaleuca alternifolia also known as Tea tree oil belonging to family Myrtaceae. This plant has diverse and therapeutic uses in traditional herbal medicine for treating Skin care, First Aid, Household Cleaning, Hair care, Aromatherapy, Feminine care, Chronic illness, and Dental care in Australia. Method: The methanolic extract of Melaleuca alternifolia family Myrtaceae was subjected for Soxhlet extraction in round bottomed flask with petroleum ether. The petroleum ether extracted leaf powder was dried and once again subjected to Soxhlet extraction successively with different solvents viz, chloroform, ethyl acetate and methanol. Result: The IR spectra showed characteristic absorption bands at 3421 cm-1 indicating the presence of a OH group, at 1691cm-1 for C=O group, 2848 cm-1. The 1HNMR spectra showed a triplet signal at δ 10.44, 9.48, 13.21 showing the presence of OH group and Carboxylic acid. The 13C NMR spectra showed signals at δ 16.28 for a methyl carbon, δ 29.89 for a methylene carbon, The ESI-negative mode mass spectrum showed pseudo molecular ions at m/z 515 for [M+] ion. Conclusion: Based on spectral analysis and comparison of the spectral data with literature values, the compounds were identified as 3,3’dimethylellagic acid and its aglycone portion with some little impurity.

Determination of Trap Density in Hafnium Oxide Films Produced by Different Atomic Layer Deposition Techniques

Hafnia-based high-κ dielectrics are used in MOS devises as gate dielectrics [J.Robertson Rep.Prog.Phys.69,327(2006)]. The electronic properties of HfO2, including leakage currents, are defined by traps and defects [V.A.Gritsenko Phys.Rep.613,1(2016)]. Traps play different roles in different HfO2-based devices. When hafnia is used as a gate dielectric, traps increase its conductance. Electron or hole localization on traps shifts the threshold voltage and leads to the MOSFET degradation. In active layers of RRAM, traps act as precursors of the filament during the switch from a high-resistance state to a low-resistance state. In this case, the traps are used for device switching and information storing. The trap density in RRAM ranges as N~1019-1022cm-3. On the one hand, this is a huge defect concentration, which corresponds to the degeneration in semiconductors. On the other hand, such density is very low for modern analytical methods of analysis. Recently, it was reported that the charge transport in HfO2 is limited by the phonon-assisted tunneling between traps [D.R.Islamov Appl.Phys.Lett.105,222901(2014)]. The theory of phonon-assisted tunneling between traps allows defining the traps density from the slope of log J-V dependences. [K.A.Nasyrov J.Appl.Phys.109,097705(2011)]. In the study, we demonstrate the described approach and define the trap density in HfO2films after annealing in the inert atmosphere for two different ALD synthesis technologies. The HfO2 films with the thickness of 40nm were deposited on Si(100) substrates in a hot-wall Picosun Sunale R-200 ALD reactor (Finland) at an evacuation to ~1mbar. Pure nitrogen was used as a carrier gas and for purging the reactor after each reagent pulse. The well-known TEMAH+H2O precursor system was used. TEMAH was delivered into the reactor from the heated source at 100°C. The substrate temperature was 250°C. To compare the film quality of the TEMAH+H2O system, we studied a novel ALD precursor system Hf(thd)4+O2. Hf(thd)4 was delivered into the reactor from a heated source at 240°С. The substrate temperature was 440°C. The samples were annealed in the N2 flow for 1 hour at different temperatures. Annealing was performed directly in the reaction chamber at T ann=440, 550 and 700°C for TEMAH+H2O samples and T ann=550, and 700°C for the samples deposited from the Hf(thd)4+O2 system. The samples were taken out from the reactor after cooling to room temperature. For transport measurements, top Al electrode with the area of 0.5mm2, was deposited. The current-voltage characteristics were measured at room temperature. A set of the experimental current-voltage characteristics (log J-F) of n-Si/HfO2/Al structures from TEMAH+H2O series is shown by characters in Fig.1. The slope of log J-F curves depends on the temperature annealing. The experimental data are described by phonon-assisted tunneling between traps with the thermal (W t=1.25eV) and optical (W opt=2.5eV) trap energies (lines in Fig.1). These values are equal to that obtained from the literature [D.R.Islamov (2014)]. Annealing leads to a trap density decrease. After annealing at 700°C, the trap density value is N=1.2×1020cm-3. A set of experimental log J-F of n-Si/HfO2/Al structures from Hf(thd)4+O2 series is shown by characters in Fig.2. These curves can be described by the phonon-assisted tunneling theory with the same values of trap parameters as that obtained for TEMAH+H2O series. The trap density rises with the annealing temperature increase to 1.2×1020cm-3. The trap density dependences on the annealing temperature are shown in Fig.3. The HfO2 films from TEMAH+H2O series have more defects (and traps) than those from Hf(thd)4+O2series. After high-temperature annealing, the amount of the defects is the same for both series. We explain the obtained traps density values by the presence of hydrogen in HfO2 precursor. The presence of OH-groups in such films was also confirmed by infrared spectroscopy, wherein the sharp reduction in their concentration during annealing in the nitrogen atmosphere at 700°C was recorded. Since the hydroxyl groups are a fixture of the H2O-based ALD process, then a certain amount of hydroxyl groups unreacted with TEMAH will be integrated into the film structure. High temperatures in an inert atmosphere can lead to the destruction of OH-groups. The scheme could look like (≡Hf–OH–Hf≡)+→≡Hf–O–Hf≡+H+, with the subsequent hydrogen removal from HfO2 bulk due to low pressure annealing. Thus, we assume that reverse process has been observed in comparison with [S.Kim Nanotechnology23,325702(2012)] where high-pressure H2-annealing was performed for oxygen vacancies generation and the great influence of mobile OH-groups on the film conductivity was noted. The OH-groups are missing in the precursors of Hf(thd)4+O2 system, and their formation is unlikely during ALD. Therefore, annealing leads to the generation of a small number of additional oxygen vacancies in the HfO2film. The work was supported by the Russian Science Foundation, grant #16-19-00002. Figure 1

An imidazole based ESIPT molecule for fluorescent detection of explosives

A bright blue emitting excited-state intramolecular proton transfer (ESIPT) molecule, 2-(4,5-bis(4-chlorophenyl)-1H-imidazol-2-yl)-4-chlorolphenol (HPICl) has been designed and synthesized, whose solvent-dependent PLQY is up to 0.53 in EtOH, and 0.46 as solid state. Fluorescence quenching experiments manifest the selective detection of picric acid (PA) and p-nitrophenol (p-NP) over other nitroaromatic explosive compounds, which is closely related with the presence of OH groups on these two molecules that affect the ESIPT-based luminescence character of HPICl.

Hydrogen diffusivity in oxide layers formed in Zr alloy in air or steam

The effect of the oxidation conditions on hydrogen diffusion in oxide layers in Zr alloy was experimentally studied. Samples of GNF-Ziron (high-iron Zircaloy-2-type alloy) sheets were oxidized in air or steam and then exposed to deuterium plasma to charge them with deuterium. Deuterium depth profiles in each sample were observed by nuclear reaction analysis during plasma exposure, and the deuterium diffusion coefficient D was estimated. The results showed that the D values of the steam-oxidized samples were high, whereas that of a steam-oxidized sample that was subsequently heated in vacuum was as low as those of air-oxidized samples. The difference in D was not attributed to the structure but is probably due to the presence of OH groups absorbed during steam oxidation.

Characterization of PECVD a-C:H:Si:O:Cl films

Thin films were produced by plasma enhanced chemical vapor deposition of tetramethylsilane, chloroform, and argon mixtures. The partial pressure of chloroform in the chamber feed, CCl, was varied from 0% to 40%. Amorphous hydrogenated carbon films also containing silicon, oxygen, and small amounts of chlorine, a-C:H:Si:O:Cl, were produced at deposition rates of up to about 220 nm min−1 (for a CCl of 40%). Transmission infrared analyses revealed the presence of OH groups in chlorinated films, along with, among others, CH, C=C, Si-CH, Si-CH2, and Si-O-Si groups. As revealed by energy dispersive x-ray spectroscopy, the films could be doped with chlorine to a maximum of about 3 at. %. Surface morphology and roughness were examined using scanning electron microscopy and atomic force microscopy. Tauc band gaps, calculated from transmission ultraviolet–visible near infrared spectra, tend to decrease from ∼3.4 eV for unchlorinated films to around 2.5 eV for those doped with chlorine.

Luminescence switching in Ce3+ ion sensitized YPO4:Tb3+ through Redox reaction

Ce3+ sensitized Tb3+ ion doped YPO4 nanophosphor is synthesized by simple polyol method using ethylene glycol as capping agent as well as reaction medium. Green emission from Tb3+ ion doped YPO4 nanophosphor has been enhanced with incorporation of Ce3+ ion into the matrix of YPO4:Tb3+. XRD of YPO4:Tb3+ annealed at 900°C reveals crystalline tetragonal structure without any impurity phase. Morphology of YPO4:Tb3+ nanophosphor was also studied. Homogenous incorporation of rare earth, RE (RE=Tb3+, Ce3+) ion into the host matrix were given in EDAX spectra. TGA/DTA analysis shows phase transformation of the as-prepared sample. Also, it is found that the as-prepared sample were readily re-dispersible in water due to presence of OH group. By using an alternate oxidising and reducing agent, behaviour of luminescence switching (ON and OFF) can be examined. Lifetime decay of Tb3+ ion doped YPO4 nanophosphor was also studied.

A multimethodic approach for the characterization of manganiceladonite, a new member of the celadonite family from Cerchiara mine, Eastern Liguria, Italy

AbstractIn the manganesiferous ores associated with the metacherts of the ophiolitic sequences at the Cerchiara mine, Eastern Liguria (Italy), a new Mn-bearing mineral belonging to the mica group has been recently found and characterized. High resolution transmission electron microscopy and electron diffraction tomography studies confirm that the mineral belongs to the mica group. Unit-cell parameters from the powder diffraction pattern are:a= 5.149(1),b= 8.915(1),c= 10.304(1) Å, β = 102.03(1)°, space groupC2 orC2/m. On the basis of the electron paramagnetic resonance spectroscopic results, the Mn4+content represents a very subordinate fraction of the total Mn, the remaining occurring as Mn3+. The Raman spectrum clearly indicates the presence of OH groups in the structure. Laser-ablation inductively-coupled-plasma mass-spectrometry measurements assess the presence of considerable amounts of Li.Assuming all Mn as Mn3+and 22 negative charges, the empirical formula can be expressed as: (K0.83□0.17)(Mn1.143+Mg0.80Li0.20Fe0.023+)(Si3.89Al0.10)O10[(OH)1.92F0.08] with the sum of the octahedral cations indicating a 'transitional' character between a di- and a tri-octahedral structure. This formula corresponds ideally to the Mn3+analogue of celadonite, thus expanding the range of solid solution in the celadonite family. The ideal end-member formula KMn3+MgSi4O10(OH)2can be easily related to celadonite by the homovalent substitutionVIMn3+→VIFe3+. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, (IMA 2015-052).

Ab initio study of the trimethylaluminum atomic layer deposition process on carbon nanotubes—An alternative initial step

Electronic applications of carbon nanotubes (CNTs) require the deposition of dielectric films on the tubes while conserving their excellent electronic properties. In our density functional theory study we use the trimethylaluminum (TMA) atomic layer deposition (ALD) as a model process for a CNT-functionalization. Since this functionalization relies on the presence of OH-groups, the CNTs are exposed to a water or oxygen pre-treatment. We show that only CNTs with a single-vacancy defect are able to react with H$_{2}$O or O$_{2}$. Further, the defect is preferably saturated by oxygen. This leaves the CNT without the necessary hydroxyl groups for the first TMA addition. Therefore, we propose an alternative initial step after which a classical TMA ALD process can be performed on the CNT.

Identify OH groups in TiOF2 and their impact on the lithium intercalation properties

A detailed investigation on the chemical composition of the cubic form of titanium oxyfluoride-based compound reveals the presence of OH groups substituting the oxide/ fluoride sublattice. The substitution of oxide by hydroxyl groups induces the presence of titanium vacancies (□) which were characterized by 1H and 19F solid-state NMR. 1H NMR shows that OH groups are present as bridging Ti-OH-Ti or terminal OH groups, i.e. sitting close to a titanium vacancy Ti-OH-□. The electrochemical properties vs. Li+/Li indicates that the presence of OH groups prevents the intercalation of lithium in the upper voltage region (1.2–3V vs. Li+/Li). Indeed, a partial dehydroxylation of the framework enables to improve the reversibility of the lithium insertion/de-insertion processes. Since the presence of OH groups in this type of compounds is usual and depends on the synthesis method employed, this work enables to rationalize the different electrochemical behaviors reported in the literature and further highlights the importance of a good knowledge of the chemical composition with regard to the physico-chemical properties.

Water Affinity and Surface Charging at the z-Cut and y-Cut LiNbO3 Surfaces: An Ambient Pressure X-ray Photoelectron Spectroscopy Study

Polarization dependence of water adsorption and desorption on LiNbO3 surfaces was demonstrated using X-ray photoelectron spectroscopy (XPS) carried out in situ under near-ambient conditions. Positive and negative (0001) faces (z-cut) of the same crystal were compared for the same temperature and pressure conditions. Our results indicate a preferential adsorption on the positive face of the crystal with increasing water pressure and also higher desorption temperature of the adsorbed molecular water at the positive face. Adsorption measurements on the (1100) face (y-cut) showed also strong affinity to water, as observed for the z-cut positive surface. We found a direct relation between the capacity of the surface to discharge and/or to screen surface charges and the affinity for water of each face. XPS spectra indicate the presence of OH groups at the surface for all the conditions and surfaces measured.

Honeycomb-like S = 5/2 Spin-Lattices in Manganese(II) Vanadates.

New complex manganese vanadate materials were synthesized as high-quality single crystals in multi-millimeter lengths using a high-temperature, high-pressure hydrothermal method. One compound, Mn5(VO4)2(OH)4, was grown from Mn2O3 and V2O5 in 3 M CsOH at 580 °C and 1.5 kbar. Changing the mineralizer to 1 M CsOH/3MCsCl leads to the formation of another product, Mn6O(VO4)2(OH). Both compounds were structurally characterized by single-crystal X-ray diffraction (Mn5(VO4)2(OH)4: C2/m, Z = 2, a = 9.6568(9) Å, b = 9.5627(9) Å, c = 5.4139(6) Å, β = 98.529(8)°; Mn6O(VO4)2(OH): P21/m, Z = 2, a = 8.9363(12) Å, b = 6.4678(8) Å, c = 10.4478(13) Å, β = 99.798(3)°), revealing interesting low-dimensional transition-metal features. Mn5(VO4)2(OH)4 possesses complex honeycomb-type Mn-O layers, built from edge-sharing [MnO6] octahedra in the bc plane, with bridging vanadate groups connecting these layers along the a-axis. Mn6O(VO4)2(OH) presents a more complicated structure with both octahedral [MnO6] and trigonal bipyramidal [MnO5] units. A different pattern of planar honeycomb sheets are formed by edge-shared [MnO6] octahedra, and these sublattices are connected through edge-shared dimers of [MnO5] trigonal bipyramids to form corrugated sheets. Vanadate groups again condense the sheets into a three-dimensional framework. Infrared and Raman spectroscopies indicated the presence of OH groups and displayed characteristic Raman scattering due to vanadate groups. Temperature-dependent magnetic studies indicated Curie-Weiss behavior above 100 K with significant anti-ferromagnetic coupling for both compounds, with further complex magnetic behavior at lower temperatures. The data indicate canted anti-ferromagnetic order below 57 K in Mn5(VO4)2(OH)4 and below 45 K in Mn6O(VO4)2(OH). Members of another class of compounds, K2M3(VO4)2(OH)2 (M = Mn, Co), also containing a honeycomb-type sublattice, were also synthesized to allow a comparison of the structural features across all three structure types and to demonstrate extension to other transition metals.

Electrochemical Analysis and Quantum Chemistry of Castor Oil-Based Corrosion Inhibitors

Background: Corrosion in industrial structures has generated much concern with regard to material loss, especially in the oil production. Organicmolecules can act as inhibitors because they can be adsorbed at the metal-solution interface, replacing the water molecules and thereby inhibiting the metal dissolution. In general the imidazoline derivatives have unique structure that make them efficient corrosion inhibitors in CO2 environments. Castor oil is the only unsaturated fatty acid occurring in natural vegetable oils with a functional hydroxyl group in the 12C. The presence of OH groups in the fatty acid chains makes the oil unusually polar. Therefore, based on its molecular structure, castor oil or its derivatives can be used as an effective corrosion inhibitor. Methods: Inhibitor used was a hydroxyethyl-imidazoline derivate based on castor oil. Concentrations of inhibitor used were 5, 10, 25, 50 and 100 ppm. Corrosivesolutionusedwasa CO2 saturated mixture (90:10, of 3% NaCl solution and diesel) at 50°C. Corrosion tests were carried out by real-time monitoring and EIS measurements. Results: Real-time monitoring showed that the castor oil-based imidazoline has an inhibition efficiency greater than 99%. From EIS measurementstwodifferentbehaviors were obtained. Evolution of the EIS spectra was similar for additions of 5, 10 and 25 ppm, and for 50 and 100 ppm it was different. For 5, 10 and 25 ppm the evolution of the spectrum in the high frequency region was the characteristic fingerprint of the self-assembled of the oil-based imidazolines. However, for 50 and 100 ppm after 9 hours, the time constant decreased as time passed. This behavior could be due to the presence of the functional groups in the oily-tail which tend to interact with the metallic surface forming a denser inhibitor film. The molecular reactivity (HOMO and LUMO) of the optimized molecule of inhibitor showed that LUMO is moved to unusual location the middle of the molecule due to the presence of double bond in 39C-41C and the hydroxyl group in 45C. Conclusion: Real-time corrosion measurements showed that the inhibition efficiency was greater than 99%. From EIS measurements two different behaviors are observed. Presence of the functional groups in the alkyl chain tend to interact with the metal surface. Quantum chemical calculations showed that LUMO is located in the alkyl chain, favoring a flat-adsorption process. Keywords: Castor oil, green inhibitor, imidazoline, electrochemical sweet corrosion.

Removal of toxic aqueous ions using amorphous AlPO4

ABSTRACTAluminium phosphate (AlPO4) was characterized using X-ray diffractometry (XRD), Fourier Transform infrared (FTIR), point of zero charge (PZC) and dissolution studies. XRD showed the sample to be amorphous, FTIR confirmed the presence of OH groups on the surface and PZC was determined at pH 3.45. The dissolution study illustrated a decrease in dissolution with an increase in the pH. Potentiometric titration data were fit to the Gaines–Thomas equation, which showed that AlPO4 is a weakly acidic ion exchanger. Sorption studies were carried out at pH 4–6 and temperatures 293–323 K. The uptake of metal ions was observed to increase with an increase in the pH and temperature. The surface selectivity towards metal ions was found in the order Pb2+> Cu2+> Cd2+. Sorption data were fit to the new equation derived from the proposed mechanism for metal ion uptake. Various parameters such as stoichiometry of the surface H+ ion release, equilibrium constant, standard enthalpy, entropy and free energy changes were evaluated from the plots. The values of all these parameters were found to be closely related to the values reported in the literature.

“Synthesis, characterization and studies on antioxidant activity of silver nanoparticles using Elephantopus scaber leaf extract”

The simple, eco-friendly and cost effective method of green synthesis of silver nanoparticle in the leaf extract of medicinal plant Elephantopus scaber L. is illustrated in the present work. The synthesized silver nanoparticles (AgNPs) were characterized with UV–Vis-spectroscopy, nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The UV-spectra show maximum absorbance at 435nm, NTA analysis shows 78nm average sizes of nanoparticles, TEM analysis indicates spherical shape of the nanoparticles with the average diameter of 50nm. The XRD peaks at 2θ range of 30–80° correspond to (111), (200), (220), (311) reflection planes that indicate the structure of metallic silver. FTIR analysis reveals surface capping of phenolic groups. Existence of peaks in the range of 1611 to 1400cm−1 indicates the presence of aromatic rings in the leaf extract. The peak at 1109cm−1 is due to the presence of OH groups. The antioxidant activity of synthesized nanoparticles was evaluated performing DPPH assay and it is observed that the photosynthesized nanoparticle also possesses antioxidant potentials. Thus, it can be used as potential free radical scavenger. Silver particles have tremendous applications in the field of diagnostics and therapeutics. To this context, the surface coating of plant metabolite constituents has great potentials. Therefore, the present work has been undertaken to synthesize the AgNPs using leaf extract of medicinal plant, E. scaber, to characterize and access their antioxidant properties.

Study on the reaction of amines with internal epoxides

The reactivity of internal epoxides, as in epoxidized fatty acids, with primary amines was investigated using primary amines and a model epoxide compound, which was a mixture involving cis‐ and trans‐isomers of 9,10‐epoxyoctadecane.The reactions were carried out at 100, 170, and 200°C for 24 h. It was observed that the reaction of an amine with an internal epoxide does not proceed to any significant extent even at 200°C in the absence of catalysts.Practical applications: The model reaction of an amine with 9,10‐epoxyoctadecane is helpful to understand the reaction of amines with epoxidized vegetable oils. It revealed that the key step in the reaction of amine with epoxidized vegetable oils, in the absence of a catalyst, is amidation.Model compound, 9,10‐epoxyoctadecane (E‐OCD), was prepared and reacted with n‐octylamine and ehtanolamine without catalysts. GPC showed that in the absence of catalysts, ring opening of an internal epoxide with amine does not take place to any significant extent. While ring opening in the presence of OH groups happens to a higher extent. OH groups could act as reactants or catalysts.