Parasuraman Selvam

A visible-light active catechol–metal oxide carbonaceous polymeric material for enhanced photocatalytic activity

Designing new materials for sustainable energy and environmental applications is one of the prime focuses in chemical science. Here, an unprecedented visible-light active catechol–TiO2 carbonaceous polymer based organic–inorganic hybrid material was synthesized by a photosynthetic route. The visible light induced (>400 nm) photosynthetic polymerization of catechol led to the formation of carbonaceous polymeric deposits on the surface of TiO2. The band gap energy of hybrids was shifted to the visible region by orbital hybridization between 3d(Ti) of TiO2 and 2p(O), π(C) of catechol. The Tauc plot clearly revealed that 1.0 wt% catechol–TiO2 carbonaceous polymer remarkably tailored the optical band gap of TiO2 from 3.1 eV to 1.9 eV. The synthesized hybrid materials were thoroughly characterized and their photocatalytic activity was evaluated towards toxic Cr(VI) to relatively less toxic Cr(III) reduction under visible light irradiation (>400 nm), and solar light-driven H2 production through water splitting. Very interestingly, the hybrid material showed 5- and 10-fold enhanced activity for photocatalytic Cr(VI) reduction and solar light-driven H2 production respectively compared with pure TiO2. Moreover, the hybrid materials showed enhanced stability during photocatalysis. Thus, the simple photosynthetic strategy for developing light harvesting organic–inorganic hybrid materials can open up potential applications in energy and environmental remediation.

Mesoporous γ-Iron Oxide Nanoparticles for Magnetically Triggered Release of Doxorubicin and Hyperthermia Treatment.

Mesoporous iron-oxide nanoparticles (mNPs) were prepared by using a modified nanocasting approach with mesoporous carbon as a hard template. mNPs were first loaded with doxorubicin (Dox), an anticancer drug, and then coated with the thermosensitive polymer Pluronic F108 to prevent the leakage of Dox molecules from the pores that would otherwise occur under physiological conditions. The Dox-loaded, Pluronic F108-coated system (Dox@F108-mNPs) was stable at room temperature and physiological pH and released its Dox cargo slowly under acidic conditions or in a sudden burst with magnetic heating. No significant toxicity was observed in vitro when Dox@F108-mNPs were incubated with noncancerous cells, a result consistent with the minimal internalization of the particles that occurs with normal cells. On the other hand, the drug-loaded particles significantly reduced the viability of cervical cancer cells (HeLa, IC50 =0.70u2005μm), wild-type ovarian cancer cells (A2780, IC50 =0.50u2005μm) and Dox-resistant ovarian cancer cells (A2780/AD, IC50 =0.53u2005μm). In addition, the treatment of HeLa cells with both Dox@F108-mNPs and subsequent alternating magnetic-field-induced hyperthermia was significantly more effective at reducing cell viability than either Dox or Dox@F108-mNP treatment alone. Thus, Dox@F108-mNPs constitute a novel soft/hard hybrid nanocarrier system that is highly stable under physiological conditions, temperature-responsive, and has chemo- and thermotherapeutic modes of action.

Acid‐Mediated Synthesis of Ordered Mesoporous Aluminosilicates: The Challenge and the Promise

A new intrinsic hydrolysis method was employed, for the first-time, to synthesize well-ordered H-AlSBA-15 with trivalent aluminium exclusively in the tetrahedral framework structure of SBA-15. Unlike other methods, which involve incorporation of aluminium ions in both the framework (Brønsted) and non-framework (Lewis) sites of the silicate matrix, the intrinsic hydrolysis method isomorphously substitutes aluminium ions in the tetrahedral network even at high aluminium content. This unique approach relies mainly on the hydrolysis rates of the inorganic (silicon and aluminium) precursors used for the preparation in such a way that the condensation occurs simultaneously so as to overcome the usually encountered difficulties in stabilizing aluminium ions in the silicate matrix. In this way, we could successfully synthesize high quality Brønsted acidic H-AlSBA-15, hitherto not reported. The synthesized materials were systematically characterized by various analytical, spectroscopic, and imaging techniques, including XRD, Brunauer-Emmett-Teller (BET) surface area measurements, TEM, SEM, 29 Si and 27 Al magic angle spinning NMR spectroscopy, X-ray fluorescence (XRF), and NH3 temperature-programmed desorption (TPD). The characterization results reveal the presence of a highly porous structure (with narrow pores) and tetrahedrally coordinated trivalent aluminium in the silicate matrix with more medium to strong Brønsted acid sites. The resulting high quality catalysts exhibit excellent activity for tert-butylation of phenol with high selectivity towards para-tert-butyl phenol and 2,4-di-tert-butyl phenol.

Development of the bifunctional catalyst Mn—Fe—Beta for selective catalytic reduction of nitrogen oxides*

The catalytic properties of the Mn-Fe-Beta system with Mn contents in the range 0.1–16 wt.% were studied in the selective catalytic reduction (SCR) of NOx with ammonia. The catalyst structure was investigated using IR spectra of adsorbed NO, temperature-programmed reduction with hydrogen (H2-TPR), X-ray diffraction analysis, and ESR. The use of manganese as a promoter substantially increases the activity of iron-containing catalysts in the SCR of NOx with ammonia. At low contents (<2 wt.%), Mn exists in the cation form and the catalytic activity of the Mn-Fe-Beta system does not increase. At a higher content of Mn, clusters MnOx begin to form, which are highly active in the oxidation of NO to NO2 and the low-temperature catalytic activity of the Mn-Fe-Beta system increases. The observed increase in the low-temperature catalytic activity in the process of SCR of NOx with ammonia is related to a change in the reaction route. The MnOx clusters favor the oxidation of NO and the iron cations facilitate the reaction of “fast” SCR.

Investigation of Nano-Molybdenum Carbide Particle Produced by Wire-Explosion Process

Molybdenum carbide (MoC) nanoparticles were generated by exploding molybdenum conductor in methane gas ambience at different pressures. To enhance the level of carburization, exploding conductor was coated with graphite and paraffin mixtures. Various physico-chemical studies were employed to characterize the produced nano-carbide particles, viz., X-ray diffraction, optical emission spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was deduced from these investigations that the nano-MoC particles produced by a wire explosion process (WEP) are spherical in shape. The size of the particles formed by WEP can be controlled by varying the operating ambience pressure of the methane gas. The particle size produced follows a log-normal distribution. Optical emission results clearly indicates the presence of Mo-I, C-I, and C-II components during WEP. X-ray photoelectron spectroscopy confirms the formation of MoC.

Crystal structure of aquadioxido(2-{[(2-oxido-ethyl)-imino]-meth-yl}phenol-ato-κ(3) O,N,O')molybdenum(VI).

The mononuclear title complex, [Mo(C9H9NO2)O2(H2O)], contains an Mo(VI) atom in a distorted octahedral coordination sphere defined by an Mo=O and an Mo—(OH2) bond to the axial ligands and two Mo—O bonds to phenolate and alcoholate O atoms, another Mo=O bond and one Mo—N bond to the imino N atom in the equatorial plane. The five-membered metalla-ring shows an envelope conformation. In the crystal, individual molecules are connected into a layered arrangement parallel to (100) by means of O—H⋯O hydrogen bonds involving the water molecule as a donor group and the O atoms of neighbouring complexes as acceptor atoms. These interactions lead to the formation of a three-dimensional network.

Crystal structure of bis­(acetato-κO)di­aqua­(2,2′-bi­pyridine-κ2N,N′)manganese(II)

In the title monomeric manganese(II) complex, [Mn(CH3COO)2(C10H8N2)(H2O)2], the metal ion is coordinated by a bidentate 2,2′-bipyridine (bpy) ligand, two water molecules and two axial acetate anions, resulting in a highly distorted octahedral environment. The aqua ligands are stabilized by the formation of strong intramolecular hydrogen bonds with the uncoordinated acetate O atoms, giving rise to pseudo-bridging arrangement of the terminal acetate groups. In the crystal, the molecules form [010] zigzag chains via O—H⋯O hydrogen bonds involving the aqua ligands and acetate O atoms. Further, the water and bpy ligands are trans to each other, and are arranged in an off-set fashion showing intermolecular π–π stacking between nearly parallel bipy rings, the centroid–centroid separations being 3.8147u2005(12) and 3.9305u2005(13)u2005Å.

Fabrication of SPAEK-Cerium zirconium oxide nanotube composite membrane with outstanding performance and durability for vanadium redox flow batteries

Herein, an alternative sulfonated poly(arylene ether ketone) (SPAEK)–cerium zirconium oxide nanotube (Ce2Zr2O7NT) composite (SPAEK/Ce2Zr2O7) membrane has been proposed as a potential polymer electrolyte membrane for all vanadium redox flow batteries (VRFBs) performance. The as-prepared composite membrane showed higher ion selectivity and reduced vanadium ion crossover than the pristine SPAEK and NRE-212 (Nafion-212) membranes in VRFB operation. The vanadium ion permeability rate of SPAEK/Ce2Zr2O7 (2%) composite membrane was found to be 27-fold and 12-fold lower than that of commercial NRE-212 and pristine SPAEK membranes, respectively. VRFBs operated with SPAEK/Ce2Zr2O7 (441 h) were shown to have a lower self-discharge rate than pristine SPAEK (172 h) and NRE-212 (42 h) membranes, respectively. Finally, an electrochemical test of VRFB exhibited high retention capacity after 100 cycles for SPAEK/Ce2Zr2O7 membrane as compared to NRE-212 and pristine SPAEK, while the coulombic efficiency (99.42%) at 40 mA cm−2. The structure and morphology of Ce2Zr2O7NT and the composite membrane were investigated by means of XRD, SEM, and TEM, and a consistent chemical structure of SPAEK/Ce2Zr2O7 (2%) composite membrane before and after the chemical stability test was confirmed using 1H NMR. The composite with 2% filler exhibits improved thermal, mechanical, oxidative, and chemical stability with superior ion selectivity. Also, X-ray photoelectron spectroscopy (XPS) analysis of SPAEK/Ce2Zr2O7 (2%) composite membrane reveals the existence of a vanadium peak after 100 VRFB cycles.

Crystal structure of (2-formyl-phenolato-κ(2) O,O')oxido(2-{[(2-oxidoeth-yl)imino]-meth-yl}phenolato-κ(3) O,N,O')vanadium(V).

In the unsymmetrical title vanadyl complex, [V(C9H9NO2)(C7H5O2)O], one of the ligands (2-formylphenol) is disordered over two sets of sites, with an occupancy ratio of 0.55u2005(2):0.45u2005(2). The metal atom is hexacoordinated, with a distorted octahedral geometry. The vanadyl O atom (which subtends the shortest V—O bond) occupies one of the apical positions and the remaining axial bond (the longest in the polyhedron) is provided by the (disordered) formyl O atoms. The basal plane is defined by the two phenoxide O atoms, the iminoalcoholic O and the imino N atom. The planes of the two benzene rings are almost perpendicular to each other, subtending an interplanar angle of 84.1u2005(2)° between the major parts. The crystal structure features weak C—H⋯O and C—H⋯π interactions, forming a lateral arrangement of adjacent molecules.