Facile synthesis of nanostructured Ni/NiO/N-doped graphene electrocatalysts for enhanced oxygen evolution reaction.

Electrocatalysts containing a Ni/NiO/N-doped graphene interface have been synthesised using the ligand-assisted chemical vapor deposition technique. NiO nanoparticles were used as the substrate to grow N-doped graphene by decomposing vapours of benzene and N-containing ligands. The method was demonstrated with two nitrogen-containing ligands, namely dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (L) and melamine (M). The structure and composition of the as-synthesized composites were characterized by XRD, Raman spectroscopy, SEM, TEM and XPS. The composite prepared using the ligand L had NiO sandwiched between Ni and N-doped graphene and showed an overpotential of 292 mV at 10 mA cm-2 and a Tafel slope of 45.41 mV dec-1 for the OER, which is comparable to the existing noble metal catalysts. The composite prepared using the ligand M had Ni encapsulated by N-doped graphene without NiO. It showed an overpotential of 390 mV at 10 mA cm-2 and a Tafel slope of 78.9 mV dec-1. The ligand-assisted CVD route demonstrates a facile route to control the microstructure of the electrocatalysts.

Iron-based nanocatalyst for the acceptorless dehydrogenation reactions.

Development of sustainable catalytic systems for fundamentally important synthetic transformations and energy storage applications is an intellectually stimulating challenge. Catalytic dehydrogenation of feedstock chemicals, such as alcohols and amines to value-added products with the concomitant generation of dihydrogen is of much interest in the context of hydrogen economy and is an effective alternative to the classical oxidation reactions. Despite a number of homogeneous catalysts being identified for the acceptorless dehydrogenation, the use of high price and limited availability of precious metals and poor recovery of the catalyst have spurred interest in catalysis with more earth-abundant alternatives, especially iron. However, no report has described a reusable iron-based heterogeneous catalyst for oxidant-free and acceptorless dehydrogenation reactions. Here we replace expensive noble metal catalysts with an inexpensive, benign, and sustainable nanoscale iron catalyst for the efficient acceptorless dehydrogenation of N-heterocycles and alcohols with liberation of hydrogen gas.

Room-Temperature Activation of CO2 by Dual Defect-Stabilized Nanoscale Hematite (Fe2-δO3-v ): Concurrent Role of Fe and O Vacancies.

We demonstrate that synthetically controlled concurrent stabilization of Fe and O vacancy defects on the surface of interbraided nanoscale hematite (Fe2-δO3-v ) renders an interesting surface chemistry which can reduce CO2 to CO at room temperature (RT). Importantly, we realized a highly enhanced output of 410 µmol h-1 g-1 at RT, as compared to that of 10 µmol h-1 g-1 for bulk hematite. It is argued based on the activity degradation under cycling and first principles density functional theory calculations that the excess chemical energy embedded in the defect-stabilized surface is expended in this high-energy conversion process, which leads to progressive filling up of oxygen vacancies.

Earth Abundant Iron-Rich N-Doped Graphene Based Spacer and Cavity Materials for Surface Plasmon-Coupled Emission Enhancements.

We demonstrate for the first time the use of Fe-based nanoparticles on N-doped graphene as spacer and cavity materials and study their plasmonic effect on the spontaneous emission of a radiating dipole. Fe-C-MF was produced by pyrolizing FeOOH and melamine formaldehyde precursor on graphene, while Fe-C-PH was produced by pyrolizing the Fe-phenanthroline complex on graphene. The use of the Fe-C-MF composite consisting of Fe-rich crystalline phases supported on N-doped graphene presented a spacer material with 116-fold fluorescence enhancements. On the other hand, the Fe-C-PH/Ag based cavity resulted in an 82-fold enhancement in Surface Plasmon-Coupled Emission (SPCE), with high directionality and polarization of Rhodamine 6G (Rh6G) emission owing to Casimir and Purcell effects. The use of a mobile phone as a cost-effective fluorescence detection device in the present work opens up a flexible perspective for the study of different nanomaterials as tunable substrates in cavity mode and spacer applications.

ATP driven clathrin dependent entry of carbon nanospheres prefer cells with glucose receptors.

BACKGROUND: Intrinsically fluorescent glucose derived carbon nanospheres (CSP) efficiently enter mammalian cells and also cross the blood brain barrier (BBB). However, the mechanistic details of CSP entry inside mammalian cells and its specificity are not known. RESULTS: In this report, the biochemical and cellular mechanism of CSP entry into the living cell have been investigated. By employing confocal imaging we show that CSP entry into the mammalian cells is an ATP-dependent clathrin mediated endocytosis process. Zeta potential studies suggest that it has a strong preference for cells which possess high levels of glucose transporters such as the glial cells, thereby enabling it to target individual organs/tissues such as the brain with increased specificity. CONCLUSION: The endocytosis of Glucose derived CSP into mammalian cells is an ATP dependent process mediated by clathrin coated pits. CSPs utilize the surface functional groups to target cells containing glucose transporters on its membrane thereby implicating a potential application for specific targeting of the brain or cancer cells.

Microfluidic study of fast gas-liquid reactions.

We present a new concept for studies of the kinetics of fast gas-liquid reactions. The strategy relies on the microfluidic generation of highly monodisperse gas bubbles in the liquid reaction medium and subsequent analysis of time-dependent changes in bubble dimensions. Using reactions of CO(2) with secondary amines as an exemplary system, we demonstrate that the method enables rapid determination of reaction rate constant and conversion, and comparison of various binding agents. The proposed approach addresses two challenges in studies of gas-liquid reactions: a mass-transfer limitation and a poorly defined gas-liquid interface. The proposed strategy offers new possibilities in studies of the fundamental aspects of rapid multiphase reactions, and can be combined with throughput optimization of reaction conditions.

Microgels for the encapsulation and stimulus-responsive release of molecules with distinct polarities.

A microfluidic strategy for the encapsulation and stimulus-responsive release of molecules with distinct polarities from the interior of microgels is reported. The approach relies on (i) the generation of a primary O/W emulsion by the ultrasonication method, (ii) MF emulsification of the primary emulsion, and (iii) photopolymerization of the monomer present in the aqueous phase of the droplets, thereby transforming them into microgels. Non-polar molecules are dissolved in oil droplets embedded in the microgels. Polar molecules are physically associated with the hydrogel network. Upon heating, the microgels contract and release polar and non-polar cargo molecules. The approach paves the way for stimuli-responsive vehicles for multiple drug delivery.

Microbubbles loaded with nanoparticles: a route to multiple imaging modalities.

We report a single-step approach to producing small and stable bubbles functionalized with nanoparticles. The strategy includes the following events occurring in sequence: (i) a microfluidic generation of bubbles from a mixture of CO(2) and a minute amount of gases with low solubility in water, in an aqueous solution of a protein, a polysaccharide, and anionic nanoparticles; (ii) rapid dissolution of CO(2) leading to the shrinkage of bubbles and an increase in acidity of the medium in the vicinity of the bubbles; and (iii) co-deposition of the biopolymers and nanoparticles at the bubble-liquid interface. The proposed approach yielded microbubbles with a narrow size distribution, long-term stability, and multiple functions originating from the attachment of metal oxide, metal, or semiconductor nanoparticles onto the bubble surface. We show the potential applications of these bubbles in ultrasound and magnetic resonance imaging.

pH-Sensitive breathing of clay within the polyelectrolyte matrix.

Stimuli-responsive organic-inorganic hybrid spheres were synthesized by coating the colloidal polystyrene spheres with polyelectrolyte-protected aminoclay, Mg phyllo(organo)silicate layers in a layer-by-layer method. The clay layers are sandwiched between the polyelectrolyte layers. The aminoclay swells in water due to protonation of amino groups, and the degree of swelling depends on the pH of the medium. As a result, the hybrid spheres undergo a size change up to 60% as the pH is changed from 9 to 4. The stimuli-responsive property of the hybrid spheres was used for the release of ibuprofen and eosin at different pH.

Functionalized carbon nanomaterials derived from carbohydrates.

A tremendous growth in the field of carbon nanomaterials has led to the emergence of carbon nanotubes, fullerenes, mesoporous carbon and more recently graphene. Some of these materials have found applications in electronics, sensors, catalysis, drug delivery, composites, and so forth. The high temperatures and hydrocarbon precursors involved in their synthesis usually yield highly inert graphitic surfaces. As some of the applications require functionalization of their inert graphitic surface with groups like -COOH, -OH, and -NH(2), treatment of these materials in oxidizing agents and concentrated acids become inevitable. More recent works have involved using precursors like carbohydrates to produce carbon nanostructures rich in functional groups in a single-step under hydrothermal conditions. These carbon nanostructures have already found many applications in composites, drug delivery, materials synthesis, and Li ion batteries. The review aims to highlight some of the recent developments in the application of carbohydrate derived carbon nanostructures and also provide an outlook of their future prospects.

Investigations of the conversion of inorganic carbonates to methane.

Inorganic carbonates, which occur abundantly on earth, constitute an inexpensive natural source of carbon. Therefore, the direct conversion of these carbonates into methane is of considerable importance. Thermal decomposition of transition metal carbonates with the composition MCa(CO(3))(2) (where M=Co, Ni, or Fe, and M/Ca is 1:1) and M(1)M(2)Ca(CO(3))(3) (where M(1)M(2)=CoNi, NiFe, or FeCo, and M(1)/M(2)/Ca is 1:1:2) shows that the reduced transition metals in combination with metal oxide nanoparticles (e.g., Co/CoO/CaO) act as catalysts for the conversion of CO(2) (produced from the carbonates) into methane. The favorable decomposition conditions include heating at 550 degrees C in an H(2) atmosphere for 5-6 h. These catalysts are found to be excellent for the methanation of CaCO(3), exhibiting high efficiency in the utilization of H(2) with 100 % conversion and 100 % selectivity. The best catalyst for conversion of CaCO(3) into CH(4) is Co/CoO/CaO. There are also indications that similar catalysts based on Fe may yield higher hydrocarbons.

Intrinsically fluorescent carbon nanospheres as a nuclear targeting vector: delivery of membrane-impermeable molecule to modulate gene expression in vivo.

In this report, we demonstrate glucose-derived carbon nanospheres to be an emerging class of intracellular carriers. The surfaces of these spheres are highly functionalized and do not need any further modification. Besides, the intrinsic fluorescence property of carbon nanospheres helps in tracking their cellular localization without any additional fluorescent tags. The spheres are found to target the nucleus of the mammalian cells, causing no toxicity. Interestingly, the in vivo experiments show that these nanospheres have an important ability to cross the blood-brain barrier and localize in the brain besides getting localized in the liver and the spleen. There is also evidence to show that they are continuously being removed from these tissues over time. Furthermore, these nanospheres were used as a carrier for the membrane-impermeable molecule CTPB (N-(4-chloro-3-trifluoromethylphenyl)-2-ethoxybenzamide), the only known small-molecule activator of histone acetyltransferase (HAT) p300. Biochemical analyses such as Western blotting, immunohistochemistry, and gene expression analysis show the induction of the hyperacetylation of histone acetyltransferase (HAT) p300 (autoacetylation) as well as histones both in vitro and in vivo and the activation of HAT-dependent transcription upon CTPB delivery. These results establish an alternative path for the activation of gene expression mediated by the induction of HAT activity instead of histone deacetylase (HDAC) inhibition.