Publications by authors named "Easan Sivaniah"

Quantum dots, which won the Nobel Prize in Chemistry, have recently gained significant attention in precision medicine due to their unique properties, such as size-tunable emission, high photostability, efficient light absorption, and vibrant luminescence. Consequently, there is a growing demand to identify new types of quantum dots from various sources and explore their potential applications as stimuli-responsive biosensors, biomolecular imaging probes, and targeted drug delivery agents. Biomass-waste-derived carbon quantum dots (CQDs) are an attractive alternative to conventional QDs, which often require expensive and toxic precursors, as they offer several merits in eco-friendly synthesis, preparation from renewable sources, and cost-effective production.

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Graphene oxide (GO) with its unique two-dimensional structure offers an emerging platform for designing advanced gas separation membranes that allow for highly selective transport of hydrogen molecules. Nevertheless, further tuning of the interlayer spacing of GO laminates and its effect on membrane separation efficiency remains to be explored. Here, positively charged fullerene C derivatives are electrostatically bonded to the surface of GO sheets in order to manipulate the interlayer spacing between GO nanolaminates.

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As a ubiquitous family of enzymes with high performance in converting carbon dioxide (CO) into bicarbonate, carbonic anhydrases (CAs) sparked enormous attention for carbon capture. Nevertheless, the high cost and operational instability of CAs hamper their practical relevance, and the utility of CAs is mainly limited to aqueous applications where CO-to-bicarbonate conversion is possible. Taking advantage of the chemical motif that endows CA-like active sites (metal-coordinated histidine), here we introduce a new line of high-performance gas separation membranes with CO-philic behavior.

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Advances in microfluidic technology towards flexibility, transparency, functionality, wearability, scale reduction or complexity enhancement are currently limited by choices in materials and assembly methods. Organized microfibrillation is a method for optically printing well-defined porosity into thin polymer films with ultrahigh resolution. Here we demonstrate this method to create self-enclosed microfluidic devices with a few simple steps, in a number of flexible and transparent formats.

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Article Synopsis
  • * The study highlights how thermodynamic issues and the size of side groups affect the PUs' morphology and overall properties.
  • * Increased 1,2-vinyl content results in better phase mixing and smaller microdomains, which leads to more complex pathways for gas molecules, ultimately reducing gas permeability in the membranes.
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The conversion of CO into functional materials under ambient conditions is a major challenge to realize a carbon-neutral society. Metal-organic frameworks (MOFs) have been extensively studied as designable porous materials. Despite the fact that CO is an attractive renewable resource, the synthesis of MOFs from CO remains unexplored.

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Borohydride (BH)-containing coordination polymers converted CO into HCO or [BH(OCHO)], whose reaction routes were affected by the electronegativity of metal ions and the coordination mode of BH. The reactions were investigated using thermal gravimetric analysis under CO gas flow, infrared spectroscopy, and NMR experiments.

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Article Synopsis
  • Membranes combining TiCT MXene nanosheets with Pebax-1657 demonstrate outstanding CO separation efficiency, exceeding typical performance limits.
  • Characterization shows that strong hydrogen bonds between the materials create pathways for efficient CO transport.
  • The new membranes are not only easy to fabricate but also economically viable for energy-efficient CO capture at a cost of $29 per ton.
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  • The study explored how different organic ligands influence the performance of zirconium-based metal-organic framework (Zr-MOF) membranes for gas separation.
  • Various Zr-MOF membranes were created using a specific synthesis method, resulting in thin layers that retained the original structure and size.
  • The membranes demonstrated high selectivity for hydrogen gas due to their unique pore structure; while larger gas molecules were hindered, hydrogen's movement was largely unaffected, achieving impressive separation factors for different gas mixtures.
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Control of the reactivity of hydride (H) in crystal structures has been a challenge because of its strong electron-donating ability and reactivity with protic species. For metal borohydrides, the dehydrogenation activity and air stability are in a trade-off, and control of the reactivity of BH has been demanded. For this purpose, we synthesize a series of BH -based coordination polymers/metal-organic frameworks.

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Porous coordination polymers (PCPs) were synthesized by using CO and metal borohydrides as precursors. Borohydrides converted CO into bridging ligands such as formate (HCO) or formylhydroborate ([BH(OCHO)]) which are available to construct porous architectures; one of them shows 380 m g surface area.

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Article Synopsis
  • * Researchers have found a way to control this microfibrillation by using standing-wave optics to create a periodic stress field, allowing for the intentional development of layered structures within the polymer films.
  • * This innovative technique not only produces vibrant multi-layered structures with tunable colours but also enables an inkless, high-resolution printing method, achieving up to 14,000 dots per inch on various flexible and transparent materials.
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Polyimide-based materials provide attractive chemistries for the development of gas-separation membranes. Modification of inter- and intra-chain interactions is a route to improve the separation performance. In this work, copolyimides with Tröger's base (TB) monomers are designed and synthesized.

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The development of thin film composite (TFC) membranes offers an opportunity to achieve the permeability/selectivity requirements for optimum CO separation performance. However, the durability and performance of thin film gas separation membranes are mostly challenged by weak mechanical properties and high CO plasticization. Here, we designed new polyurethane (PU) structures with bulky aromatic chain extenders that afford preferred mechanical properties for ultra-thin-film formation.

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Microporous polyimides (PIM-PIs, KAUST-PIs) and polymers containing Tröger's base (TB) derivatives with improved permeability and selectivity have great importance for separation of environmental gas pairs. Despite the tremendous progress in this field, facile synthesis of microporous polymers at the industrial scale designing new monomers is still lacking. In this study, a new potential approach for large scale synthesis of spirobisindane diamine (DAS) (3) has been reported from commercially available 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI) and 3,4-difluoronitrobenzene.

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The authors show that quiescent (Q-Cell) Escherichia coli cultures can maintain metabolic activity in the absence of growth for up to 24 h, leading to four times greater specific productivity of a model metabolite, 3-hydroxybutyrate (3HB), than a control. Q-cells can be created by using the proton ionophore indole to halt cell division of an hns mutant strain. This uncouples metabolism from cell growth and allows for more efficient use of carbon feedstocks because less metabolic effort is diverted to surplus biomass production.

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We developed a method for the immobilization of multiple active enzymes, allowing the production of chiral products from nonchiral substrates with recycling of expensive cofactors. Using a rapid, two-step process under nondenaturing conditions, we could preserve enzyme activity by separating the production of an immobilization scaffold from the attachment of the enzymes. The technique is applicable to a wide range of enzymes and will facilitate simple, cost-effective enzyme immobilization for research and industrial purposes.

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The prevalence of the condensed phase, interpenetration, and fragility of mesoporous coordination polymers (meso-PCPs) featuring dense open metal sites (OMSs) place strict limitations on their preparation, as revealed by experimental and theoretical reticular chemistry investigations. Herein, we propose a rational design of stabilized high-porosity meso-PCPs, employing a low-symmetry ligand in combination with the shortest linker, formic acid. The resulting dimeric clusters (PCP-31 and PCP-32) exhibit high surface areas, ultrahigh porosities, and high OMS densities (3.

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Cubic and highly porous [Mn(2-methylimidazolate)] (Mn-ZIF-8) was synthesized from [Mn(BH)·3THF]·NaBH under an Ar atmosphere. The structure contains rare Mn-4N tetrahedral geometry and has larger cell parameters, resulting in 20% larger amounts of gas uptake compared with [Zn(2-methylimidazolate)]. A kinetically favored reaction using a reactive metal borohydride precursor is key for the construction of new metal-organic framework systems.

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The formation of two-dimensional (2D) oriented porous organic cage crystals (consisting of imine-based tetrahedral molecules) on various substrates (such as silicon wafers and glass) by solution-processing is reported. Insight into the crystallinity, preferred orientation, and cage crystal growth was obtained by experimental and computational techniques. For the first time, structural defects in porous molecular materials were observed directly and the defect concentration could be correlated with crystal growth rate.

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Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation.

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Organic open frameworks with well-defined micropore (pore dimensions below 2 nm) structure are attractive next-generation materials for gas sorption, storage, catalysis and molecular level separations. Polymers of intrinsic microporosity (PIMs) represent a paradigm shift in conceptualizing molecular sieves from conventional ordered frameworks to disordered frameworks with heterogeneous distributions of microporosity. PIMs contain interconnected regions of micropores with high gas permeability but with a level of heterogeneity that compromises their molecular selectivity.

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In biopolyester synthesis, polyhydroxyalkanoate (PHA) synthase (PhaC) catalyzes the polymerization of PHA in bacterial cells, followed by a chain transfer (CT) reaction in which the PHA polymer chain is transferred from PhaC to a CT agent. Accordingly, the frequency of CT reaction determines PHA molecular weight. Previous studies have shown that exogenous alcohols are effective CT agents.

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High-performance membranes are attractive for molecular-level separations in industrial-scale chemical, energy and environmental processes. The next-generation membranes for these processes are based on molecular sieving materials to simultaneously achieve high throughput and selectivity. Membranes made from polymeric molecular sieves such as polymers of intrinsic microporosity (pore size<2 nm) are especially interesting in being solution processable and highly permeable but currently have modest selectivity.

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The type I polyhydroxyalkanoate synthase from Cupriavidus necator was heterologously expressed in Escherichia coli with simultaneous overexpression of chaperone proteins. Compared to expression of synthase alone (14.55 mg liter(-1)), coexpression with chaperones resulted in the production of larger total quantities of enzyme, including a larger proportion in the soluble fraction.

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