Excellent electromagnetic interference shielding effectiveness of chemically reduced graphitic oxide paper at 101 GHz*

Graphitic oxide (GO) was synthesized by oxidation of graphite powder using Hummer’s method and the formed GO is solution processed into paper-like macroscopic form. Subsequently, chemically reduced graphitic oxide paper (CRGOP) is prepared by hydrazine vapours induced reduction of formed GO precursor based paper. The formation of GO and its successful reduction to RGO phase is confirmed by FTIR, Raman Spectroscopy and X-ray diffraction. It has been observed that due to high electrical conductivity ~200 micron thick CRGOP display excellent EMI shielding performance at very high frequency of 101 GHz frequency with total shielding effectiveness (SE) value of ?35.49 dB (i.e. >99.97% blocking of incident EM radiation) which is much higher compared to pristine GO paper (?1.55 dB) or comparable to expanded graphite (EG) sheet (?35.61 dB). Due to their lightweight nature, these freestanding CRGOPs display average specific SE value of ?221.8 dB cm³/g. Besides, their excellent flexibility and makes them potential candidate for lightweight EMI gasketing material compared to other forms of flexible carbons like EG.     

Cobalt and magnesium ferrite nanoparticles: preparation using liquid foams as templates and their magnetic characteristics

An easy and convenient method for the synthesis of cobalt and magnesium ferrite nanoparticles is demonstrated using liquid foams as templates. The foam is formed from an aqueous mixture of an anionic surfactant and the desired metal ions, where the metal ions are electrostatically entrapped by the surfactant at the thin borders between the foam bubbles and their junctions. The hydrolysis is carried out using alkali resulting in the formation of desired nanoparticles, with the foam playing the role of a template. However, in the formation of ferrites with the formula MFe(2)O(4), where the metal ion and iron possess oxidation states of +2 and +3, respectively, forming a foam from a 1:2 mixture of the desired ionic solutions would lead to a foam composition at variance with the original solution mixture because of greater electrostatic binding of ions possessing a greater charge with the surfactant. In our procedure, we circumvent this problem by preparing the foam from a 1:2 mixture of M(2+) and Fe(2+) ions and then utilizing the in situ conversion of Fe(2+) to Fe(3+) under basic conditions inside the foam matrix to get the desired composition of the metal ions with the required oxidation states. The fact that we could prepare both CoFe(2)O(4) and MgFe(2)O(4) particles shows the vast scope of this method for making even multicomponent oxides. The magnetic nanoparticles thus obtained exhibit a good crystalline nature and are characterized by superparamagnetic properties. The magnetic features observed for CoFe(2)O(4) and MgFe(2)O(4) nanoparticles are well in accordance with the expected behaviors, with CoFe(2)O(4) particles showing higher blocking temperatures and larger coercivities. These features can easily be explained by the contribution of Co(2+) sites to the magnetocrystalline anisotropy and the absence of the same from the Mg(2+) ions.     

On the convergence of difference schemes for the approximation of solutionsu ∈ W 2 m (m>0.5) of elliptic equations with mixed derivatives

Summary The paper deals with such estimates of the rate of convergence of difference methods, which are compatible with the smoothness of the exact solutionu W ₂ ^m (),m>0.5, of elliptic equations with mixed derivatives: The error in the norm of the discrete Sobolev spaceW ₂ ^s (), denoting the set of grid points, is shown to be of the orderO(|h| ^m–s), 0s<m.     

Efficient electrocatalytic oxidation of NADH at gold nanoparticles self-assembled on three-dimensional sol-gel network

It is demonstrated that gold (Au) nanoparticles self-assembled on a sol-gel derived three-dimensional silicate network efficiently catalyze the oxidation of NADH in the absence of any electron transfer mediators with a decrease in overpotential of 780 mV in neutral solution.     

Mösbauer chemical phase characterization of iron aerosols

⁵⁷Fe Mössbauer spectroscopy has been employed to characterize the chemical composition of iron aerosols collected from three distinct groups of sites representing remote, urban and industrially active areas. The Mössbauer spectra clearly show this environmental difference. The fact that the spectra of the samples collected from the remote areas are quite similar to those of clay minerals corroborates the view that iron aerosols are soil derived. Similarly the predominant presence of -Fe₂O₃ and Fe₃O₄ in the close vicinity of industrial activities suggests that the Mössbauer spectroscopy can help identify the anthropogenic processes against the natural ones.Work performed under the Punjab States Research Scheme NPC-5.     

Aqueous solution properties of amphiphilic triblock copolymer poly(p-dioxanone-co-l-lactide)-block-poly(ethylene glycol)

A poly(ethylene glycol) (PEG)-based new amphiphilic block copolymer bearing the poly(p-dioxanone-co-l-lactide) (PPDO/PLLA) hydrophobic moieties was prepared. Depending on the copolymer composition and molecular weights, solubility of the polymeric samples in water was varied. Its diluted aqueous solution properties were studied by viscometry, dye solubilization, ¹H-NMR and dynamic light scattering. 1,6-Diphenyl-1,3,5-hexatriene solubilization and ¹H-NMR spectra carried out in CDCl₃ and D₂O were used to prove the existence of hydrophobic domains as the core of micelle. Average particle size of 60-165 nm with low polydispersity and lower negative zeta (ξ) potential of −3 to −14 mV were observed on the aqueous copolymer dispersion.     

Zinc(II) perchlorate as a new and highly efficient catalyst for formation of aldehyde 1,1-diacetate at room temperature and under solvent-free conditions

Zinc(II) perchlorate efficiently catalysed the conversion of aromatic, heteroaromatic, and aliphatic aldehydes to 1,1-diacetates under solvent-free conditions at room temperature. It was compatible with other functional groups (e.g., ether, ester, nitro, and cyano) likely to interfere by complex formation with the catalyst. Other anhydrides such as isobutyric, pivalic, and benzoic anhydrides afforded the corresponding 1,1-dicarboxylates and established the generality. The reaction rate was influenced by the steric and electronic nature of the anhydride. The rate of 1,1-dicarboxylate formation was found to follow the order Ac₂O > (i-PrCO)₂O > (t-BuCO)₂O > (PhCO)₂O and no 1,1-dicarboxylate formation took place with (ClCH₂CO)₂O, and (F₃CO)₂O. During inter- and intra-molecular competition between a ketone and an aldehyde group with Ac₂O, 1,1-diacetate formation took place exclusively with the aldehyde group. An 88:12 selectivity was observed for 1,1-diacetate formation in favour of 1-naphthaldehyde during competition with 2-methoxy-1-naphthaldehyde.     

Neurotrope und psychotrope Substanzen, 6. Mitt.: Synthese neuer Aminoderivate von 6,11-Dihydrodibenzo[b,e]thiepin

Zusammenfassung Ausgehend vom 6,11-Dihydrodibenzo[b,e]thiepin-11-on (II) wurde über den Alkohol III das Chlorid V gewonnen, das durch übliche Umsetzungen die Amine VI–VIII, das Phthalimidoderivat IX, das primäre Amin X und das Nitril XI lieferte. Bei der Reaktion mit 3-Dimethylaminopropylmagnesiumchlorid ergab es das antireserpin-wirksame 11-(3-Dimethylaminopropyl)-6,11-dihydrodibenzo[b,e]thiepin (XII), das zum ebenfalls antireserpin-aktiven sekundären Amin XIV partiell demethyliert wurde.

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The preparation of 11-chloro-6,11-dihydrodibenzo[b,e]thiepine (V) from the ketone II via III is described. Usual transformations gave amines VI–VIII, the phthalimido derivative IX, the primary amine X, and the nitrile XI. Treatment of V with 3-dimethylaminopropylmagnesium chloride resulted in 11-(3-dimethylaminopropyl)-6,11-dihydrodibenzo[b,e]thiepine (XII), having antireserpine activity. Partial demethylation of XII gave the secondary amine XIV, which had the same type of pharmacodynamic activity.

     

Syntheses and properties of arenediazonium and anilinium cation lariat ether complexes: an “ostrich molecule” complex and evidence for intramolecular sidearm - macroring interaction

The preparation of several novel lariat ethers (macrocyclic crown polyethers having sidearms bearing pendant donor groups) is reported, These compounds are ethers derived from known 2-hydroxymethyl-15-crown-5 or -21-crown-7. The sidearms Include 2-aminophenyl, 2,4-diaminophenyl, 2-nitrophenyl, 2-(3'-nitrobiphenyl), and 2-(3'-aminobiphenyl). In several cases, the amino groups were converted into ammonium salts which showed substantial stabilization by intramolecular hydrogen bonding. Likewise, an -NH₂^+.,BF₃^- complex showed evidence of intramolecular hydrogen bonding. Diazotization of the aminobiphenyl residue produced an arenediazonium cation which underwent intramolecular crown complexation, as judged by infrared spectroscopic studies to form what we call an “ostrich molecule” complex. Addition of N,N-dimethylaniline to the intramolecular arenediazonium cation complex afforded an azo compound, but europium shift reagent studies showed clearly that the diazonium cation reacted outside the macroring.     

Synthesis and structural characterization of 2,6-bis-(N-methylenemorpholino)-4-ter-butylphenol

The crystal and molecular structure of the title compound, C₂₀H₃₂N₂O₃, has been determined from X-ray diffraction data using CuK radiation (=1.5418 Å). The compound crystallizes in triclinic space groupP1^¯ with a=8.828(1),b=18.680(1),c=6.272(2)Å, =93.42(1), =0.24(2), =77.93(1)°,V=1009.4(2)ų, andZ=2. The structure was solved by direct methods and the full-matrix least-squares refinement leads the finalR-factor to 0.065 for 3481 observed reflections withI3(I). The phenyl ring is planar and the morpholino rings assume perfect chair conformation. The molecules are held together by van der Waals forces.DCB Contribution No. 810.