scholarly journals Synthesis and Surface Characterization ofγ-MnO2Nanostructures

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Chengxiang Liu ◽  
Jing Wang ◽  
Jiarui Tian ◽  
Lan Xiang
Keyword(s):  
Surface Properties ◽  
Electron Density ◽  
Surface Potential ◽  
Surface Characterization ◽  
Hydroxyl Groups ◽  
Surface Oxygen ◽  
Initial Ph ◽  
Oxygen Atoms

A facile method was developed to synthesizeγ-MnO2with different structures and surface properties in this paper.γ-MnO2was prepared by oxidation of MnSO4with Na2S2O8at90°C for 2.0 h.γ-MnO2formed at initial pH 1.0 (M1) and 8.5 (M2) was composed of MnO1.93·0.23H2O and MnO1.96·0.18H2O, respectively. The higher ratio of pyrolusite in M2 (Pr=43.90%) than that in M1 (Pr=24.86%) indicated that compared with M1, M2 would absorb more protons since the planar oxygen atoms in pyrolusite were incompletely coordinated and liable to absorb the protons. Meanwhile, the higher oxidation valence of Mn in M2 than that in M1 revealed that the Mn atoms in M2 were more liable to draw the electron density from the surface oxygen atoms in hydroxyl groups. The structural and compositional differences between M1 and M2 were the major reasons why M2 possessed a higher surface potential and a weaker ability to absorb Zn2+ions.

The surface chemistry of kaolinite. II. Catalysis of n-butane decomposition

1972 ◽  
Vol 25 (9) ◽  
pp. 1843 ◽  
Author(s):  
AS Buchanan ◽  
RC Oppenheim
Keyword(s):  
Catalytic Activity ◽  
Lone Pair ◽  
Acid Leaching ◽  
Hydroxyl Groups ◽  
Surface Oxygen ◽  
Hydrogen Atoms ◽  
Before And After ◽  
Hydrocarbon Reactions ◽  
Lone Pair Electrons ◽  
Oxygen Atoms

The catalytic activity of kaolinite before and after acid leaching for the decomposition of n-butane between 669 and 727 K has been compared with that of alumina natural and precipitated, and silica. The catalysis of hydrocarbon reactions on oxide surfaces appears to involve oxygen atoms which may be attached to the solid surface either physically adsorbed as the gas, as part of the lattice, or possibly as attached hydroxyl groups. Dehydrogenation of the hydrocarbon appears to be the first important step, suggesting that adsorption of the reactant involves interaction of the hydrogen atoms with lone pair electrons of surface oxygen atoms.

119Sn, 13C and 1H NMR Spectra of Tris(1-butyl)stannyl D-Glucuronate

1997 ◽  
Vol 62 (8) ◽  
pp. 1169-1176 ◽  
Author(s):  
Antonín Lyčka ◽  
Jaroslav Holeček ◽  
David Micák
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
1H Nmr ◽  
Equatorial Plane ◽  
Title Compound ◽  
Nmr Spectra ◽  
Hydroxyl Groups ◽  
Carboxylic Group ◽  
H Nmr ◽  
Oxygen Atoms

The 119Sn, 13C and 1H NMR spectra of tris(1-butyl)stannyl D-glucuronate have been measured in hexadeuteriodimethyl sulfoxide, tetradeuteriomethanol and deuteriochloroform. The chemical shift values have been assigned unambiguously with the help of H,H-COSY, TOCSY, H,C-COSY and 1H-13C HMQC-RELAY. From the analysis of parameters of 119Sn, 13C and 1H NMR spectra of the title compound and their comparison with the corresponding spectra of tris(1-butyl)stannyl acetate and other carboxylates it follows that in solutions of non-coordinating solvents (deuteriochloroform) the title compound is present in the form of more or less isolated individual molecules with pseudotetrahedral environment around the central tin atom and with monodentately bound carboxylic group. The interaction of tin atom with oxygen atoms of carbonyl group and hydroxyl groups of the saccharide residue - if they are present at all - are very weak. In solutions in coordinating solvents (hexadeuteriodimethyl sulfoxide or tetradeuteriomethanol), the title compound forms complexes with one molecule of the solvent. Particles of these complexes have a shape of trigonal bipyramid with the 1-butyl substituents in equatorial plane and the oxygen atoms of monodentate carboxylic group and coordinating solvent in axial positions.

Substitutional and solvation effects on conformational equilibria. Effects on the interaction between opposing axial oxygen atoms

1969 ◽  
Vol 47 (23) ◽  
pp. 4441-4446 ◽  
Author(s):  
R. U. Lemieux ◽  
A. A. Pavia
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Hydroxyl Groups ◽  
Evidence Based ◽  
Electrostatic Repulsion ◽  
Hydrogen Bridge ◽  
Conformational Equilibria ◽  
Free Hydroxyl ◽  
Oxygen Atoms

Evidence based both on nuclear magnetic resonance and rotation data primarily obtained from methyl 3-deoxy-β-L-erythro-pentopyranoside and a number of its derivatives is interpreted to show that the electrostatic repulsion between the oxygen atoms at the 2 and 4 positions is substantially less when these oxygens are linked to acyl groups than when in the form of either methyl ethers or as hydroxyl groups hydrogen bonded to solvent. Also, experimental evidence is presented which requires the hydrogen bridge between two axially disposed hydroxyl groups to be substantially strengthened by hydrogen bonding of the free hydroxyl by solvent.

The relationship between inner surface potential and electrokinetic potential from an experimental and theoretical point of view

2017 ◽  
Vol 14 (5) ◽  
pp. 295 ◽  
Author(s):  
Tajana Preočanin ◽  
Danijel Namjesnik ◽  
Matthew A. Brown ◽  
Johannes Lützenkirchen
Keyword(s):  
Surface Properties ◽  
Surface Potential ◽  
Single Particle ◽  
Surface Reactions ◽  
Solid Particles ◽  
Theoretical Point ◽  
Surface Characterisation ◽  
Layer Potential ◽  
Average Surface ◽  
Inner Surface

Environmental contextInterfacial properties of colloid and nanoparticles are directly related to the reactivity and surface densities of existing surface sites. Surface characterisation of particles provides only some kind of average surface properties. Analysis of well-defined monocrystal surfaces, which form the surface of the single particle, leads to a better understanding of surface reactions and mutual interactions of adjacent crystal planes on average surface properties. AbstractThe contact of small solid particles and macroscopic flat planes with aqueous electrolyte solutions results in the accumulation of ions at the interface and the formation of the electrical interfacial layer. Analysis of well-defined monocrystal surfaces, which are the building blocks of a single particle, leads to a better understanding of surface reactions and mutual interactions of adjacent crystal planes on average surface properties of particles. We analyse inner surface potential (obtained by single-crystal electrode) and zeta-potential data (obtained by streaming potential measurements) that were obtained on identical samples. Among the systems for which comparable surface and zetapotentials are available, measured inner surface potential data for sapphire (0001), haematite (0001) and rutile (110) show the expected behaviour based on the face-specific surface chemistry model, whereas the slopes for rutile (110) and quartz (0001) do not. Isoelectric points for sapphire (0001), haematite (0001) and rutile (100) are in conflict with the standard model that implies consistent behaviour of surface potential and diffuse layer potential. For the two former systems, previous results from the literature suggest that the charge of interfacial water can explain the discrepancy. The water layer could also play a role for quartz (0001), but in this case, the discrepancy would simply not be noticed, because both point of zero potential and isoelectric point are low. Along with data on silver halides, it can be concluded that six-ring water structures on solids may generate the electrokinetic behaviour that is typical of inert surfaces like Teflon.

scholarly journals Zn(II) and Ag(I) complexes of N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids and products their proton- and iodocyclization

2019 ◽  
Vol 85 (3) ◽  
pp. 3-19
Author(s):  
Polina Borovyk ◽  
Mariia Litvinchuk ◽  
Anton Bentya ◽  
Svitlana Orysyk ◽  
Yurii Zborovskiy ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Metal Ion ◽  
Polymer Chains ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Polymer Complexes ◽  
Vis Spectroscopy ◽  
Polynuclear Coordination Compounds ◽  
Complexation Reactions ◽  
Oxygen Atoms

The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

Structure of TiO2 Rutile (110) (1 × 1) from Ion Scattering Measurements

1998 ◽  
Vol 05 (01) ◽  
pp. 309-313 ◽  
Author(s):  
B. Hird ◽  
R. A. Armstrong ◽  
J. A. Seel
Keyword(s):  
Surface Layer ◽  
Sample Preparation ◽  
Preliminary Analysis ◽  
Surface Oxygen ◽  
Ion Scattering ◽  
Oxygen Ion ◽  
Scattering Measurements ◽  
Low Incidence ◽  
Tio2 Rutile ◽  
Oxygen Atoms

9.22 keV oxygen ion scattering has been used to examine the (110) surface structure of TiO 2 rutile. Peaks in the spectrum of the emitted ions at 45° and at 77° are found at the energies expected for O +– Ti and O +– O collisions by surface atoms. Surface preoparation to optimize the 1 × 1 structure involved annealing a previously sputtered surface to 600°C, first in 10-6 Torr of O 2, and then in UHV. Azimuthal and elevation angular variations of the yields for low incidence angles show shadowing effects. Preliminary analysis seems to be consistent with the (1 × 1) model of a complete surface layer, with rows of oxygen atoms above on the titanium bridge sites. The data suggests that our sample preparation produces incomplete rows of above-surface oxygen atoms, or frequent steps.

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