2,089 publications from this institution
The chain length of the surfactant and the solvent composition are two of the factors that determine whether the lamellar or the hexagonal form of mesoporous SiO2(or ZrO2) is formed by the neutral amine route; a lamellar–hexagonal transformation occurs on removal of the amine from the former.
No abstract is provided for this article.
No abstract is provided for this article.
α-Tocopherol is found to interact with the stable free radical DPPH orders of magnitude faster than ordinary phenols. It is suggested that the high reactivity arises from the coplanarity of the C-O-C framework with the aromatic ring. The rate constant of the reaction of α-tocopherol with DPPH increases progressively with solvent polarity and can be quantitatively related to Kosower's Z parameter. Fatty acid derivatives slow down the reaction with DPPH due to binding with α-tocopherol.
No abstract is provided for this article.
Mixed valency in CePd3 has been examined by a study of the LIII (Ce) absorption edge in this compound as well as other model compounds. In CePd3, peaks characteristic of 3+ and 4+ states of Ce are found to be separated by 2 eV.
A novel solvothermal route for the preparation of organic soluble CdS nanocrystals, involving the reaction of cadmium stearate with sulfur in the presence of tetralin has been described. Tetralin in the presence of S gives H2S, getting aromatized to naphthalene. By using trioctylphosphineoxide as the capping agent, nanocrystals of 4 nm are obtained. Use of dodecanethiol cap results in 5 nm as well as 10 nm nanocrystals which can be separated readily. The nanocrystals have the cubic zinc blende structure and exhibit blue shifts of the absorption maximum.
S. Ayyappan and C. N. R. Rao, Chem. Commun., 1997, 575 DOI: 10.1039/A607782J
X-ray and UV photoemission along with Auger spectroscopic studies show the formation of surface alloys in the Pd/Ag and Cu/Au overlayers on polycrystalline substrates. Surface alloy formation also occurs in the Ni/Au overlayers although Au and Ni do not form bulk alloys over the entire range of compositions.
Electron transport and magnetic properties of three series of manganates of the formula (La1−xLnx)0.7Ca0.3MnO3 with Ln = Nd, Gd and Y, wherein only the average A-site cation radius ⟨rA ⟩ and associated disorder vary, without affecting the Mn4+/Mn3+ ratio, have been investigated in an effort to understand the nature of phase separation. All three series of manganates show saturation magnetization characteristic of ferromagnetism, with the ferromagnetic Tc decreasing with increasing x up to a critical value of x, xc (xc = 0.6, 0.3, 0.2 respectively for Nd, Gd, Y). For x > xc, the magnetic moments are considerably smaller, showing a small increase around TM, the value of TM decreasing slightly with increase in x or decrease in ⟨rA ⟩. The ferromagnetic compositions (x ≤ xc) show insulator–metal transitions, while the compositions with x > xc are insulating. The magnetic and electrical resistivity behaviour of these manganates is consistent with the occurrence of phase separation in the compositions around xc, corresponding to a critical average radius of the A-site cation, ⟨rAc ⟩, of 1.18 Å. Both Tc and TIM increase linearly when ⟨rA ⟩ > ⟨rAc ⟩ or x ≤ xc, as expected of a homogeneous ferromagnetic phase. Both Tc and TM decrease linearly with the A-site cation size disorder as measured by the variance σ2. Thus, an increase in σ2 favours the insulating AFM state. Percolative conduction is observed in the compositions with ⟨rA ⟩ > ⟨rAc ⟩. Electron transport properties in the insulating regime for x > xc conform to the variable-range hopping mechanism. More interestingly, when x > xc, the real part of dielectric constant (ε') reaches a high value (104 –106) at ordinary temperatures dropping to a very small (∼ 500) value below a certain temperature, the value of which decreases with decreasing frequency.
Mittels der CNDO/2‐Methode und der EHT werden annehmbare Werte für die Barrieren der Rotation um die C‐N‐Bindung für Formamid und N;Methyl‐acetamid" ermittelt.
Polyoctasilsesquioxane (POSS) has been employed to covalently functionalize nanostructures of TiO2, ZnO and Fe2O3 as well as carbon nanotubes, nanodiamond and graphene to enable their dispersion in polar solvents. Covalent functionalization of these nanostructures with POSS has been established by electron microscopy, EDAX analysis and infrared spectroscopy. On heating the POSS-functionalized nanostructures, silica-coated nanostructures are obtained. POSS-functionalized nanoparticles of TiO2, Fe2O3 and graphite were utilized to prepare polymer-nanostructure composites based on PVA and nylon-6,6.
