Correction: Rational synthesis of 10GDC electrolyte through a microwave irradiation GNP facile route for SOFC applications.

[This corrects the article DOI: 10.1039/C9RA09476H.].

Synthesis of indeno-[1,2-b]-quinoline-9,11(6H,10H)-dione and 7,7-dimethyl-10-aryl-7,8-dihydro-5H-indeno[1,2-b]quinoline-9,11(6H,10H)-dione derivatives in presence of heterogeneous Cu/zeolite-Y as a catalyst.

A simple method for the synthesis of indeno-[1,2-b]-quinoline-9,11-(6H,10H)-dione derivatives and 7,7-dimethyl-10-aryl-7,8-dihydro-5H-indeno[1,2-b]quinoline-9,11(6H,10H)-diones through the reaction of aromatic aldehydes, indan-1,3-dione, dimedone, and p-toluidine/ammonium acetate in the presence of heterogeneous CuO supported on a zeolite-Y catalyst has been investigated in ethanol under reflux conditions. By this method, the reaction time has been reduced, giving an excellent yield of the product. The catalyst was prepared by a hydrothermal method followed by a wet impregnation method. The catalyst had shown Brønsted acid sites and Lewis acid sites. The used catalyst could be actively recycled with a marginal decrease in yield up to five recycles. The prepared catalyst was characterized by FT-IR, pyridine FT-IR, XRD, SEM, EDS, XPS, TEM, and BET surface area analysis. The synthesized compounds were characterized by FT-IR, 1H NMR, 13C NMR and GC-MS spectroscopy.

Rational synthesis of 10GDC electrolyte through a microwave irradiation GNP facile route for SOFC applications.

The gadolinium-doped ceria Gd0.1Ce0.9O1.95 (10GDC) powder was synthesized using a microwave-synthesized glycine nitrate process (MS-GNP). The powder was subsequently pressed into circular pellets and sintered at various temperatures viz. 800, 900, 1000 and 1200 °C, in a microwave, high temperature furnace for 4 h so as to investigate the effect of the sintering temperature and sintering environment on the structural, morphological, thermal and electrical properties. The crystallite size and particle size as observed from X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) are found to be in the range of 15-28 nm and 12-20 nm, respectively. The electrochemical impedance spectroscopy (EIS) analysis was carried out to study the electrochemical properties during the cooling cycle from 400 °C to 800 °C. The highest value of ionic conductivity (3.55 × 10-1 S cm-1) is observed at an operating temperature of 800 °C and O2 gas partial pressure of 1 atm. Further, it is observed that the sintering temperature has a significant effect on the surface morphology and crystallite size, thereby improving the electrical performance of the samples. Though 20GDC was used as an electrolyte in the authors' previous study, the novelty of the present work is the synthesis of 10GDC using a microwave-assisted glycine nitrate process and the size (thickness) of the prepared electrolyte for use in a Solid Oxide Fuel Cell (SOFC), which plays a major role in enhancing the structural, morphological and electrochemical properties with respect to different sintering temperatures as compared to the reported data. Hence, the prepared 10GDC electrolyte may be treated as one of the promising candidates as an electrolyte for SOFC for intermediate as well as high temperature applications.

Synthesis of silver nanoparticles colloids in imidazolium halide ionic liquids and their antibacterial activities for gram-positive and gram-negative bacteria.

Four 1-butyl-3-methylimidazolium halide ionic liquids were synthesized via metathesis and anion exchange reactions. Silver nanoparticles (AgNPs) colloids were synthesized in four ionic liquids in the pressurized reactor by reduction of silver nitrate with hydrogen gas, without adding solvents or stabilizing agents. Antibacterial activities of base ionic liquids and AgNPs colloids in ionic liquids were reviewed by well-diffusion method for gram-positive Bacillus cereus (NCIM-2155) and gram-negative Escherichia coli (NCIM-2931) bacteria. Antibacterial activities of ionic liquids and AgNPs colloids in ionic liquids were observed to be controlled by ionic liquids anions and AgNPs particle size. The 1-butyl-3-methylimidazolium iodide ionic liquid exhibited higher antibacterial activities among the studied ionic liquids. Further, the presence of AgNPs in 1-butyl-3-methylimidazolium iodide, ionic liquid enhanced its antibacterial activity for Bacillus cereus and Escherichia coli bacteria.

Valorization of Oceanic Waste Biomass: A Catalytic Perspective.

Efficacious waste utilization is vital in context of sustainability. The past decade has witnessed attempts of usage of land biomass and wastes for various applications, contributing towards a sustainable society. Exploitation of the marine biomass, which does not compete with habitation and food production like land biomass has been largely unnoticed and therefore not being utilized judiciously. Researchers have mainly exploited these resources as functional materials having significant potential applications. However, a catalytic perspective for the valorisation of these polymers arising from oceanic waste widens their scope and ameliorates its use. The objective of the present review is to demonstrate the effectiveness of chitin/chitosan as a catalyst and as a feedstock for deriving important fuels and chemicals. It displays all the reactions heterogeneously catalyzed by them along with the strategic methodology. Their important catalytic organic transformations attempted so far, have also been discussed. The future perspectives are also presented which if inculcated would improve the value addition of the waste, paving a way for greener and imperishable world.

Fluorescent Carbon-Dots Thin Film for Fungal Detection and Bio-labeling Applications.

The fluorescence properties of CDs, such as high quantum yield, tunability of emission color, and so on, make a strong potential material in various fields. These applications are mainly derived from in situ formation of surface functional groups, high chemical stability, biocompatibility, and easy interaction with substrates, etc. Mostly, the research applications of CDs concentrate on the labeling of biological species, drug delivery, and sensing in consequent biomedical applications. However, the detection of the fungal species/spores present in the environment by using CDs is rarely reported. Herein, we demonstrate CDs-based thin film as a sensor for detection of fungal spores from the environment. The procedure of detection is based on fluorescence, observed in the film of carbon dots deposited on quartz plates by using the Blodgett technique. It is observed that the CDs film shows quenching in the fluorescence intensity by the substrate, namely, fungal spores' (Aspergillus niger, Penicillium chrysogenum, Alternaria alternata). The effective features of the present detector system are easy fabrication, low cost, high stability, and a green and economical procedure of synthesis. The process of detecting fungal spores even at low concentration from the atmosphere is relatively fast when compared to presently used methods. Finally, real-world feasibility of the sensor film is tested by its successful application for the determination of the presence fungal spores in the environment. Furthermore, CDs have been also successfully applied for the bio-labeling of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacterial systems.

Friedel-Crafts Alkylation over Zr-Mont Catalyst for the Production of Diesel Fuel Precursors.

Heterogeneous Zr-Mont catalyst prepared by a simple protocol was employed for the production of diesel fuel precursors via Friedel-Crafts (FC) alkylation of petroleum-derived arenes (e.g., mesitylene, xylene, and toluene) with biomass-derived 5-(hydroxymethyl)furfural (HMF), HMF derivatives, and carbohydrates. Initially, several acidic catalysts were screened for the FC alkylation of mesitylene with HMF in nitroethane solvent. Among all, Zr-Mont catalyst gave an exceptionally high yield (80%) of mesitylmethylfurfural (MMF). The catalytic activity of Zr-Mont was also evaluated for the alkylation of different petroleum-derived arenes with ester/halogen derivatives of HMF. Suitable acid strength and high surface area of Zr-Mont were its major attributes to make it the most efficient solid acid catalyst for this FC reaction. Even after several reuses, the catalytic activity of Zr-Mont was found to be consistent, which was also evidenced by the acidity measurements of fresh and reused Zr-Mont catalysts by temperature-programmed desorption of ammonia and pyridine Fourier transform infrared spectroscopy techniques. Direct conversion of glucose to diesel fuel precursors was also attempted over Zr-Mont catalyst in mesitylene and polar nonacidic solvents at 150 °C. However, the activity of Zr-Mont catalyst was limited for glucose dehydration to HMF and MMF did not form. When the same experiment was performed in formic acid medium, MMF was produced in 34% yield. After the addition of formic acid, the reaction becomes biphasic which contains mesitylene as an organic phase and formic acid as an aqueous phase. Formic acid worked as a solvent, reactant, and cocatalyst, whereas mesitylene worked as a reactant and product extraction phase to enable easy product isolation. With this strategy, other diesel fuel precursors were also produced in 26-30% yields from glucose and different arenes. Similar strategy was successfully extended for the conversion of sucrose to diesel fuel precursors.

Single-Pot Reductive Rearrangement of Furfural to Cyclopentanone over Silica-Supported Pd Catalysts.

Direct one-pot hydrogenation of furfural (FFR) to cyclopentanone (CPO) was investigated over different silica-supported Pd catalysts. Among these, 4% Pd on fumed silica (4%Pd/f-SiO2) showed remarkable results, achieving almost 98% furfural (FFR) conversion with ∼89% selectivity and 87% yield to cyclopentanone at 165 °C and 500 psig H2 pressure. More interestingly, the fumed-silica-supported catalyst tuned the selectivity toward the rearrangement product, i.e., cyclopentanone, whereas all of the other supports were found to give ring hydrogenation as well as side chain hydrogenation products due to their parent Brönsted acidity and specific support properties. X-ray diffraction data revealed the presence of different phases of the face-centered cubic lattice of metallic Pd along with lowest crystallite size of 15.6 nm in the case of the silica-supported Pd catalyst. However, Pd particle size was found to be in the range of 5-13 nm with even dispersion over the silica support, confirmed by high-resolution transmission electron microscopy analysis. While studying the effect of reaction parameters, it was observed that lower temperature gave low furfural conversion of 58% with only 51% CPO selectivity. Similarly, higher H2 pressure lowered CPO selectivity with subsequent increase in 2-methyl furan and ring hydrogenation product 2-methyl furan and 2-methyl tetrahydrofuran. Thus, as per the requirement, the product selectivity can be tuned by varying the type of support and/or the reaction parameters suitably. With the help of several control experiments and the characterization data, a plausible reaction pathway was proposed for the selective formation of cyclopentanone.

Mixed bacterial culture mediated direct conversion of bio-glycerol to diols.

Direct and economic transformation of biodiesel derived crude glycerol is gaining more significance. During screening of bacterial cultures Klebsiella pneumoniae and Enterobacter aerogenes were able to convert crude bio-glycerol to 2,3-butanediol (2,3-BDO) and 1,3-propanediol (1,3-PDO), as major compounds, ethanol and acetoin as minor compounds, with a conversion of 69% and 79% respectively. Process optimization could achieve maximum conversion at pH 7.0, 37 °C, 30-40 g/L glycerol and 1.5 g of inoculum until 120 h. Mixed cultures led to complete glycerol conversion with optimal yield and productivity. An innovative approach of using crude glycerol for sustained growth and tolerance of bacteria as source of carbon and energy makes this study more significant. In addition to this, a mixed culture concept introduced here is expected to make impact in process economics for industrial scale synthesis for direct transformation of glycerol into C3 and specifically, C4 diols.

Cascade Reductive Etherification of Bioderived Aldehydes over Zr-Based Catalysts.

An efficient one-pot catalytic cascade sequence has been developed for the production of value-added ethers from bioderived aldehydes. Etherification of 5-(hydroxymethyl)furfural with different aliphatic alcohols over acidic Zr-montmorillonite (Zr-Mont) catalyst produced a mixture of 5-(alkoxymethyl)furfural and 2-(dialkoxymethyl)-5-(alkoxymethyl)furan. The latter was selectively converted back into 5-(alkoxymethyl)furfural by treating it with water over the same catalyst. The synthesis of 2,5-bis(alkoxymethyl)furan was achieved through a cascade sequence involving etherification, transfer hydrogenation, and re-etherification over a combination of acidic Zr-Mont and the charge-transfer hydrogenation catalyst [ZrO(OH)2 ]. This catalyst combination was further explored for the cascade conversion of 2-furfuraldehyde into 2-(alkoxymethyl)furan. The scope of this strategy was then extended for the reductive etherification of lignin-derived arylaldehydes to obtain the respective benzyl ethers in >80 % yield. Additionally, the mixture of Zr-Mont and ZrO(OH)2 does not undergo mutual destruction, which was proved by recycling experiments and XRD analysis. Both the catalysts were thoroughly characterized using BET, temperature-programmed desorption of NH3 and CO2 , pyridine-FTIR, XRD, inductively coupled plasma optical emission spectroscopy, and X-ray photoelectron spectroscopy techniques.

Heterogeneously Catalyzed Domino Synthesis of 3-Indolylquinones Involving Direct Oxidative C-C Coupling of Hydroquinones and Indoles.

A domino synthesis of 3-indolylquinones was achieved successfully via direct oxidative C-C coupling of hydroquinones with indoles over Ag2O and Fe3O4/povidone-phosphotungstic acid (PVP-PWA) catalysts using H2O2 in tetrahydrofuran at room temperature. Ag2O catalyzed the in situ oxidation of hydroquinone and 3-indolylhydroquinone intermediates, whereas ferrite solid acid, Fe3O4/PVP-PWA, with a 1:4:1 ratio of Fe3O4, PVP, and PWA, catalyzed the activation of quinones. The efficiency of this catalytic domino approach was established by a broad scope of substrates involving a variety of hydroquinones and quinones to give high yields (81-97%) of 3-indolylquinones. Fe3O4/PVP-PWA was separated magnetically, whereas simple filtration could separate Ag2O, both of which could be recycled several times without losing their activities.

CO2 Laser Direct Written MOF-Based Metal-Decorated and Heteroatom-Doped Porous Graphene for Flexible All-Solid-State Microsupercapacitor with Extremely High Cycling Stability.

Over the past decade, flexible and wearable microelectronic devices and systems have gained significant importance. Because portable power source is an essential need of such wearable devices, currently there is considerable research emphasis on the development of planar interdigitated micro energy -torage devices by employing diverse precursor materials to obtain functional materials (functional carbon, oxides, etc.) with the desirable set of properties. Herein we report for the first time the use of metal organic framework (MOF) and zeolitic imidazolate framework (ZIF-67) for high-wavelength photothermal laser direct writing of metal-decorated, heteroatom-doped, porous few-layer graphene electrodes for microsupercapacitor application. We argue that the specific attributes of MOF as a precursor and the high-wavelength laser writing approach (which creates extremely high localized and transient temperature (>2500 °C) due to strong absorption by lattice vibrations) are together responsible for the peculiar interesting properties of the carbon material thus synthesized, thereby rendering extremely high cycling stability to the corresponding microsupercapacitor device. Our device exhibits near 100% retention after 200 000 cycles as well as stability under 150° bending.

Reduced Graphene Oxide Composite with Oxidizable Manganese/Cobalt Mixed Oxide for p-Cresol Oxidation by Using Molecular Oxygen.

A composite of graphene oxide (GO) with mixed oxide (MnCo) was prepared by using a solvothermal method. During the synthesis, both the reduction of GO and growth of metal oxides took place simultaneously. The as-prepared composite material was highly selective for the liquid-phase oxidation of p-cresol to form p-hydroxybenzaldehyde in 71 % yield within 1 h. The composite material was characterised by SEM, X-ray photoelectron spectroscopy, high-resolution TEM and cyclic voltammetry (CV). A CV study revealed that the increase in the redox potential of the mixed oxide after being supported on GO, led to its higher activity of the catalyst for the oxidation reaction. The stability of the catalyst under the reaction conditions was studied by its successful reuse in three cycles.

Hierarchically nanoperforated graphene as a high performance electrode material for ultracapacitors.

High performance is reported for a symmetric ultracapacitor (UC) cell made up of hierarchically perforated graphene nanosheets (HPGN) as an electrode material with excellent values of energy density (68.43 Wh kg⁻¹) and power density (36.31 kW kg⁻¹). Perforations are incorporated in the graphite oxide (GO) and graphene system at room temperature by using silica nanoparticles as template. The symmetric HPGN-based UC cell exhibits excellent specific capacitance (Cs) of 492 F g⁻¹ at 0.1 A g⁻¹ and 200 F g⁻¹ at 20 A g⁻¹ in 1 M H2SO4 electrolyte. This performance is further highlighted by galvanostatic charge-discharge study at 2 A g⁻¹ over a large number (1000) of cycles exhibiting 93% retention of the initial Cs. These property features are far superior as compared to those of symmetric UC cells made up of only graphene nanosheets (GNs), i.e. graphene sheets without perforations. The latter exhibit Cs of only 158 F g⁻¹ at 0.1 A g⁻¹ and the cells is not stable at high current density.

Highly Efficient Povidone-Phosphotungstic Acid Catalyst for the Tandem Acetalization of Aldehydes to Bis- and Tris(indolyl)methanes.

A novel, nonleachable hybrid of heteropoly acid and polyvinylpyrrolidone (or povidone) catalyzes the acetalization of aldehydes in methanol at room temperature followed by reaction with indole to give bis(indolyl)methanes (BIMs) and tris(indolyl)methanes (TIMs) in quantitative yields (90-97 %). The catalyst was shown by pyridine FTIR spectroscopy to possess Brønsted acidity, and the hybrid formation was confirmed by XRD and 31 P NMR studies. Friedel-Crafts alkylation of indole as well as the tandem synthesis of BIMs and TIMs were established with several types of carbonyl and indole substrates to give the corresponding products quantitatively. The catalyst was recycled efficiently for three successive runs without losing its original activity.

Mixed Co-Mn Oxide-Catalysed Selective Aerobic Oxidation of Vanillyl Alcohol to Vanillin in Base-Free Conditions.

Manganese-doped cobalt mixed oxide (MnCo-MO) catalyst was prepared by a solvothermal method. The as-prepared catalyst was characterised by X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, O2 temperature-programmed oxidation and XRD. This catalyst gave 62 % conversion with 83 % selectivity to vanillin in 2 hours for the liquid-phase air oxidation of vanillyl alcohol without using base. Three different types of metal oxides were observed in the prepared catalyst, which could be identified as Co3 O4 , Mn3 O4 and CoMn2 O4 . Among these, the tetragonal phase of CoMn2 O4 was found to be more active and selective for vanillyl alcohol oxidation than Co3 O4 and Mn3 O4 . High-resolution TEM characterisation revealed the morphology of MnCo-MO nanorods with a particle size of 10 nm. Successful recycling of the catalyst was also established in this oxidation reaction.

Reductive dechlorination of gamma-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles.

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane (gamma-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5mg/L of lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m(2)/g), manyfold greater that of commercial grade micro- or milli-scale iron particles (approximately 1.6m(2)/g); and, (2) increased catalytic reactivity due to the presence of Pd on the surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity.

Effect of surface chemistry of Fe-Ni nanoparticles on mechanistic pathways of azo dye degradation.

The degradation of Orange G, a monoazo dye, in aqueous solutions was investigated using as-synthesized and stored Fe-Ni bimetallic nanoparticles. Batch experiments with a nanocatalyst loading of 3 g/L showed complete dye degradation (150 mg/L) after 10 min of reaction time. HPLC-MS analysis of the degradation products showed that as-synthesized nanoparticles reductively cleaved the azo linkage to produce aniline as the major degradation product. However, 1-year-stored nanoparticles showed an oxidative degradation of Orange G through a hydroxyl-radical induced coupling of parent and/or product molecules. XPS analysis in corroboration with HPLC-MS data showed that the surface chemistry between Fe and Ni in as-synthesized and stored nanoparticles play a crucial role in directing the mode of degradation. Reductive dye degradation using as-synthesized nanoparticles proceeded through hydride transfer from nickel, whereas formation of a Fe2+ -Ni(0) galvanic cell in stored nanoparticles generated hydroxyl radicals from water in a nonFenton type reaction. The latter were responsible for the generation of radical centers on the dye molecule, which led to a coupling-mediated oxidative degradation of Orange G. The generation of hydroxyl radicals is further substantiated with radical quenching experiments using ascorbic acid indicating that stored nanoparticles degrade Orange G through a predominantly oxidative mechanism. HPLC-MS and XPS analysis of dye degradation using as-synthesized nanoparticles exposed to air and water confirmed that the reductive or oxidative degradation capability of Fe-Ni nanoparticles is decided by the time and type of catalyst aging process.

Catalytic ring hydrogenation of phenol under supercritical carbon dioxide.

A charcoal-supported rhodium catalyst was highly active for the ring hydrogenation of phenol and cresols under supercritical carbon dioxide.