Soft-graphoepitaxy using nanoimprinted polyhedral oligomeric silsesquioxane substrates for the directed self-assembly of PS-b-PDMS

We report here the fabrication of periodic sub-25 nm diameter size cylinder structures using block copolymer (BCP) directed self-assembly on nanoimprinted topographically patterned substrates. Tailored polyhedral oligomeric silsesquioxanes (POSSs) films were spin coated onto silicon substrates and were patterned by nanoimprint lithography to produce topographies commensurable with the BCP domain spacing. The chemistry of the POSS was tuned to control the alignment and orientation of the BCP films. The substrates were used to direct the microphase separation (following toluene solvent annealing) of a hexagonal structure forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) having a domain spacing of 42.6 nm and PDMS cylinder widths of 23.7 nm. On more hydrophilic POSS substrates the cylinders were obtained parallel to the substrate plane and aligned with the topography. In contrast, in more hydrophobic POSS patterns, the cylinders align perpendicular to the substrate plane. The use of these methods for the nanofabrication of vias, nanofluidic devices or interconnect structures of sub-25 nm feature size is discussed.     

Characterization and crystal structure study of a new Cu(II) complex of pyridine-2,6-dicarboxylic acid and aniline containing a water cluster

A new monoclinic Cu(II) salt complex (C₆H₆N₂) ₂ ⁺ [Cu(2,6-dipico)₂]^2?·6H₂O, (2,6-dipico=pyridine-2,6-dicarboxylic acid) is synthesized and characterised by CHN analyses, IR, UV-Vis, magnetic susceptibility measurements, and single crystal X-ray crystallography. The structure contains two pyridine-2,6-dicarboxylate species as tridentate ligands with protonated aniline acting as a counter cation and six uncoordinated water molecules. The complex crystallizes in the monoclinic space group C2/c with unit cell parameters a = 20.9393(4) Å, b = 7.94330(10) Å, c = 19.9093(4) Å, V(ų) = 2932.32(9), Z = 4. Crystal packing is stabilized by N-H…O, O-H…O intermolecular hydrogen bonds and weak π…π interactions. The water molecules are trapped by a cooperative association of coordination interactions forming water clusters as well as by a hydrogen bond to the Cu (II) complex.     

Synthesis of some novel spiro substituted pyrido[2,3-c]coumarins by exploring ‘tertiary amino effect’ reaction strategy

Some novel spiro substituted pyrido[2,3-c]coumarin derivatives were synthesized from 4-hydroxycoumarin by exploring ‘tertiary amino effect’ reaction strategy.     

Imidazole-Catalyzed Henry Reactions in Aqueous Medium

2-Nitroalkanols can be efficiently synthesized using imidazole as a mild Lewis basic catalyst in aqueous medium as well as in organic solvents. The products have been found in good yields without purification (> 95% purity by ¹H NMR) for aromatic aldehydes. Additionally, the very mild reaction conditions prevent the particular side reactions such as aldol condensation, Cannizzaro reaction, or dehydration of the 2-nitro alcohols into nitro alkenes even if aromatic aldehydes are used. This report satisfies the criteria for green synthesis in terms of reaction medium and recycling of the catalyst (imidazole).     

Cramer-Rao lower bounds on estimation of laser system pointing parameters by use of the return photon signal

Cramer-Rao lower bounds (CRLBs) on the estimation of the pointing parameters of a laser system using the return signal are obtained. A maximum likelihood estimator is found to obtain an estimation performance close to the CRLB in most scenarios considered.     

Competitive anion binding aptitude of benzimidazole and amide functionality of a non-symmetrical receptor in solid state and solution phase

A novel non-symmetric tripodal receptor (L) with benzimidazole and amide –NH functionalities has been synthesised and a comparative study for anion binding aptitude of those functionalities has been performed in solid state and solution phase. The protonated receptors in solid state tend to form a pseudo-cavity around the octahedral hexafluorosilicate anion whilst in second complex, binding of one sulphate and two bisulphates in unison by two protonated units arises. The benzimidazole –NHs are the strongest hydrogen bond donors in both the crystals controlling dominance over amide –NHs. The neutral receptor being selective towards fluoride anion induces a naked eye visible colorimetric change. The ¹H NMR studies with the neutral and protonated form of the receptor suggest the strong involvement of amide –NH in anion binding in solution phase.     

Influence of anions on the adsorption kinetics of salicylate onto alpha-alumina in aqueous medium

The adsorption kinetics of salicylate on alpha-alumina surfaces were studied at 25 degrees C and pH 6 in the presence of 0.05 mM concentration of different anions (Cl(-), Br(-), I(-), SCN(-), HCOO(-), CH(3)COO(-), S(2)O(2-)(3), CO(2-)(3), and SO(2-)(4)) as a function of time. The experimental data were significantly better fitted to a pseudo-second-order kinetics equation of nonlinear form in the entire time duration and are in excellent agreement with corresponding estimated values. Considering adsorption data for salicylate in the presence of Cl(-) as the face value, all the monovalent anions (Br(-), I(-), SCN(-), HCOO(-), CH(3)COO(-)) promote the adsorption of salicylate onto alpha-alumina surfaces while the divalent anions (S(2)O(2-)(3), CO(2-)(3), and SO(2-)(4)) have the reverse effect under similar conditions. DRIFT spectra of alpha-alumina treated with salicylate reveal that the symmetric peak nu(s)(COO(-)) is shifted by approximately 40 cm(-1) to a lower wavelength region, which implies that salicylate forms an inner-sphere complex with alpha-alumina surface in the presence of both mono- and divalent anions.     

Surface-modified carbon black for As(V) removal

This paper reports the results of the adsorption performance of As(V) removal by a commercial carbon black and its H2SO4-modified form in a single-ion situation. The influence of different process parameters and the physicochemical principles involved were studied in detail. Acid modification caused morphological changes in the virgin carbon black as evidenced by BET surface area measurements and SEM study. FTIR spectra showed the introduction of sulfonic acid group in the parent carbon due to H2SO4 treatment. TGA analysis revealed higher weight loss characteristics of the modified carbon, demonstrating the creation of functional groups. The point of zero charge (pH pzc) of the modified carbon black is highly acidic (3.5) compared to commercial carbon black (6.4). It directly infers the generation of acidic functional moieties in the carbon black. The adsorption experiments were carried out following batch equilibrium techniques. The kinetics and thermodynamics of adsorption were investigated to unveil the mechanism and nature of the adsorption process, respectively. The kinetic parameters of different models were calculated and discussed. The kinetics of adsorption can be expressed by a pseudo-second-order model and intraparticle diffusion was not the rate-determining step. Dependence of pH on adsorption showed maximum metal uptake in the range of 4-5 and inferred surface complexion as the principal mechanism of adsorption. The equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin-Kaganer-Radushkevich (DKR) isotherm equations and the corresponding isotherm parameters were calculated and discussed in detail.     

Design and Exploration of –SO<Subscript>3</Subscript>H Group Functionalized Brønsted Acidic Ionic Liquids (BAILs) as Task-Specific Catalytic Systems for Organic Reactions: A Review of Literature

For several decades various chemical industries are involved in environment pollution by using hazardous chemicals or excessive use of solvents or catalysts to get maximum amount of desired product. In this case acidic ionic liquids may act as safer substitute of volatile organic solvents/or traditional Brønsted or Lewis acid catalysts with their unique dual task-specific solvent-catalyst properties. Recent surge in the literature review clearly describes the importance, properties and applications of acidic ionic liquids as solvent and efficient reusable catalyst in organic reactions. This review presents an account of some recent reports indicating the synthesis and uses of –SO₃H functionalized ionic liquids(SFILs) as catalyst in organic synthesis.