Substrate Channeling in Compartmentalized Nanoreactors
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Pickering Emulsions of Self-Assembled Lead Sulfide Quantum Dots with Janus-Ligand Shells as Nanoreactors for Photocatalytic Reactions
Not Available
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Zr‐Porphyrin Metal–Organic Framework as nanoreactor for boosting the formation of hydrogen clathrates
Abstract We report the first experimental evidence for rapid formation of hydrogen clathrates under mild pressure and temperature conditions within the cavities of a zirconium‐metalloporphyrin framework, specifically PCN‐222. PCN‐222 has been selected for its 1D mesoporous channels, high water‐stability, and proper hydrophilic behavior. Firstly, we optimize a microwave (MW)‐assisted method for the synthesis of nanosized PCN‐222 particles with precise structure control (exceptional homogeneity in morphology and crystalline phase purity), taking advantage of MW in terms of rapid/homogeneous heating, time and energy savings, as well as potential scalability of the synthetic method. Second, we explore the relevance of the large mesoporous 1D open channels within the PCN‐222 to promote the nucleation and growth of confined hydrogen clathrates. Experimental results show that PCN‐222 drives the nucleation process at a lower pressure than the bulk system (1.35 kbar vs 2 kbar), with fast kinetics (minutes), using pure water, and with a nearly complete water‐to‐hydrate conversion. Unfortunately, PCN‐222 cannot withstand these high pressures, which lead to a significant alteration of the mesoporous structure while the microporous network remains mainly unchanged.
Carrillo‐Carrión, Carolina↗
Zr‐Porphyrin Metal–Organic Framework as nanoreactor for boosting the formation of hydrogen clathrates
Abstract We report the first experimental evidence for rapid formation of hydrogen clathrates under mild pressure and temperature conditions within the cavities of a zirconium‐metalloporphyrin framework, specifically PCN‐222. PCN‐222 has been selected for its 1D mesoporous channels, high water‐stability, and proper hydrophilic behavior. Firstly, we optimize a microwave (MW)‐assisted method for the synthesis of nanosized PCN‐222 particles with precise structure control (exceptional homogeneity in morphology and crystalline phase purity), taking advantage of MW in terms of rapid/homogeneous heating, time and energy savings, as well as potential scalability of the synthetic method. Second, we explore the relevance of the large mesoporous 1D open channels within the PCN‐222 to promote the nucleation and growth of confined hydrogen clathrates. Experimental results show that PCN‐222 drives the nucleation process at a lower pressure than the bulk system (1.35 kbar vs 2 kbar), with fast kinetics (minutes), using pure water, and with a nearly complete water‐to‐hydrate conversion. Unfortunately, PCN‐222 cannot withstand these high pressures, which lead to a significant alteration of the mesoporous structure while the microporous network remains mainly unchanged.
Carrillo‐Carrión, Carolina↗
Multiscale Modeling Approach for the Aldol Addition Reaction in Multicompartment Micelle-Based Nanoreactor
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Site-Isolated Upconversion Nanoparticle Arrays Synthesized in Polyol Nanoreactors
Not provided.
Chemistry↗
Photoresponsive Azobenzene-Functionalized Shell Cross-Linked Micelles for Selective Asymmetric Transfer Hydrogenation
We describe the substrate-selective asymmetric transfer hydrogenation of aromatic ketones using rhodium complexes immobilized on a photoresponsive nanoreactor. The nanoreactor is based on multifunctional amphiphilic poly(2-oxazoline)s that are covalently cross-linked with functionalized azobenzene after micelle formation in water. The nanoreactor switches its morphology upon light irradiation in a wavelength-selective manner as confirmed by dynamic light scattering. Kinetic studies show that the gated behavior induced by the phototriggered reversible isomerization of trans- azobenzene to cis- azobenzene in the cross-linking layer is key to discriminate among substrates and reagents during catalysis. Under UV light irradiation, the diffusion of larger substrates into the core is slower in comparison to smaller substrates. The nanoreactor displays substrate selectivity, converting smaller ketone-substrates faster to the corresponding secondary alcohols.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
First principles reaction discovery: from the Schrodinger equation to experimental prediction for methane pyrolysis
Our recent success in exploiting graphical processing units (GPUs) to accelerate quantum chemistry computations led to the development of the ab initio nanoreactor, a computational framework for automatic reaction discovery and kinetic model construction. In this work, we apply the ab initio nanoreactor to methane pyrolysis, from automatic reaction discovery to path refinement and kinetic modeling. Elementary reactions occurring during methane pyrolysis are revealed using GPU-accelerated ab initio molecular dynamics simulations. Subsequently, these reaction paths are refined at a higher level of theory with optimized reactant, product, and transition state geometries. Reaction rate coefficients are calculated by transition state theory based on the optimized reaction paths. The discovered reactions lead to a kinetic model with 53 species and 134 reactions, which is validated against experimental data and simulations using literature kinetic models. We highlight the advantage of leveraging local brute force and Monte Carlo sensitivity analysis approaches for efficient identification of important reactions. Both sensitivity approaches can further improve the accuracy of the methane pyrolysis kinetic model. The results in this work demonstrate the power of the ab initio nanoreactor framework for computationally affordable systematic reaction discovery and accurate kinetic modeling.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Higher-Order VLP-Based Protein Macromolecular Framework Structures Assembled via Coiled-Coil Interactions
Hierarchical organization is one of the fundamental features observed in biological systems that allows for efficient and effective functioning. Virus-like particles (VLPs) are elegant examples of a hierarchically organized supramolecular structure, where many subunits are self-assembled to generate the functional cage-like architecture. Utilizing VLPs as building blocks to construct two- and three-dimensional (3D) higher-order structures is an emerging research area in developing functional biomimetic materials. VLPs derived from P22 bacteriophages can be repurposed as nanoreactors by encapsulating enzymes and modular units to build higher-order catalytic materials via several techniques. In this study, we have used coiled-coil peptide interactions to mediate the P22 interparticle assembly into a highly stable, amorphous protein macromolecular framework (PMF) material, where the assembly does not depend on the VLP morphology, a limitation observed in previously reported P22 PMF assemblies. Many encapsulated enzymes lose their optimum functionalities under the harsh conditions that are required for the P22 VLP morphology transitions. Therefore, the coiled-coil-based PMF provides a fitting and versatile platform for constructing functional higher-order catalytic materials compatible with sensitive enzymes. Finally, we have characterized the material properties of the PMF and utilized the disordered PMF to construct a biocatalytic 3D material performing single- and multistep catalysis.
59 BASIC BIOLOGICAL SCIENCES↗
Ti‐Modified Imogolite Nanotubes as Promising Photocatalyst 1D Nanostructures for H 2 Production
Imogolite nanotubes (INTs) are predicted as a unique 1D material with spatial separation of conduction and valence band edges but their large band gaps have inhibited their use as photocatalysts. The first step toward using these NTs in photocatalysis and exploiting the polarization-promoted charge separation across their walls is to reduce their band gap. Here, the modification of double-walled aluminogermanate INTs by incorporation of titanium into the NT walls is explored. The precursor ratio x = [Ti]/([Ge]+[Ti]) is modulated between 0 and 1. Structural and optical properties are determined at different scales and the photocatalytic performance is evaluated for H 2 production. Although the incorporation of Ti atoms into the structure remains limited, the optimal condition is found around x = 0.4 for which the resulting NTs reveal a remarkable hydrogen production of ≈1500 µmol g −1 after 5 h for a noble metal-free photocatalyst, a 65-fold increase relative to a commercial TiO 2 -P25. This is correlated to a lowering of the recombination rate of photogenerated charge carriers for the most active structures. These results confirm the theoretical predictions regarding the potential of modified INTs as photoactive nanoreactors and pave the way for investigating and exploiting their polarization properties for energy applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Hairy nanoparticles by atom transfer radical polymerization in miniemulsion
Polymer nanoparticles with various architectures and functionalities are promising materials in numerous fields. Miniemulsion polymerization is one of the suitable pathways to prepare polymer nanoparticles since each droplet could act as a “nanoreactor”. A “smart” atom transfer radical polymerization (ATRP) catalytic system comprising Cu-TPMA/DS – (TPMA = tris(2-pyridylmethyl)amine, DS – = dodecyl sulfate anion) ion pair catalyst was efficiently applied in miniemulsion ATRP at low catalyst concentrations. Herein, hairy nanoparticles consisting of hydrophobic poly(n-butyl methacrylate) (P(BMA/EGDMA), EGDMA = ethylene glycol dimethacrylate) network “core” and hydrophilic oligo(ethylene oxide) methyl ether methacrylate (OEOMA) chains as “hair” were prepared by miniemulsion ATRP and a successive chain extension by aqueous ATRP from the particle surface. The addition of an inimer, 2-(α-bromoisobutyryloxy)ethyl methacrylate (HEMA-iBBr) to the P(BMA/EGDMA) network introduced more ATRP initiation sites for ATRP of OEOMA, enabling adjustment of the particle size from >400 nm to <150 nm. The miniemulsion system remained stable after the one pot synthesis of P(BMA/EGDMA)-g-POEOMA and P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA, and the resulting polymer nanoparticles were re-dispersed in water for further modification. A zwitterionic monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was grafted from P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA. The resulting hairy nanoparticles provide an avenue for the design and preparation of novel nanostructured materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Stimulus-Responsive Modulation of Solvation Environments in Solid Catalysts
Liquid environments play a crucial role in the biological processes occurring in living organisms as well as in many human-made processes involving electrochemistry, photo-, and thermocatalysis. In the majority of these systems, aqueous phases are ubiquitous due to water’s natural abundance. Water molecules, however, can exert large changes in the chemical environment of catalytically active sites, altering the reaction rates, selectivity, and catalyst stability. These solvation effects induced by water molecules near catalytic sites can drastically change the energy landscape and unlock unique reaction pathways with far more favorable kinetics. In nature, living organisms couple these complex interactions with detection, communication, and actuation mechanisms to induce self-regulatory behavior, ensuring stability of the system and thus long-term durability. Extrapolating this behavior to heterogeneous catalysis is desirable because the resulting “smart materials” can potentially unlock new chemical conversion processes with higher atom efficiency, rates, and stability. The combination of polymer chemistry and heterogeneous catalysis has introduced versatile approaches for creating materials that can respond to cues in the reaction medium that alter the accessibility, intrinsic activity, and selectivity of the catalyst. To achieve this, one could combine stimulus-responsive polymers, which undergo a large volumetric phase transition in response to an external stimulus, with a solid catalyst. This chemo-mechanical response has been employed to create a variety of nanoreactor vessels with stimulus-responsive character that turn on- and off- depending on the reaction conditions. In this Account, we focus on the impact of these polymer coatings on the solvation environment around the active site and the implications of these effects on the reaction energy landscape, molecular arrangement of the solvent, electric fields at the catalyst–liquid interface, binding energy, and mobility of surface reaction intermediates. These seemingly subtle changes in solvent molecules induced by the presence of polymers can have a tremendous impact on the development of bioinspired heterogeneous catalysts, reliable chemical clocks, micro/nanoreactors, and robots. The large library of polymer chemistries offers a plethora of combinations of stimulus-responsive mechanisms (e.g., temperature, pH, light, magnetic field, solvent composition), providing the possibility of creating homeostatic catalysts à la carte.
catalysts↗
Can Li: A Career in Catalysis
Prof. Can Li is distinguished for his seminal achievements in fundamental and applied researches in catalysis, especially in advancing the characterization of catalysts and catalytic reactions related to solar energy conversion and fine chemical synthesis. The scope of his research is wide ranging, and he is leading some of the fields. This account highlights his major scientific achievements in advancing the fundamental sciences of characterizing catalysts and understanding the mechanisms of catalytic reactions by developing in situ spectroscopic techniques (e.g., infrared (IR), ultraviolet (UV), Raman, space- and time-resolved spectroscopies and photoelectric imaging), and applying the obtained knowledge in the rational design and synthesis of catalysts for practical applications in photocatalytic, electrocatalytic and photoelectrocatalytic water splitting and CO 2 reduction, chiral synthesis in nanoreactors and ultradeep desulfurization of fuels, and fine chemical synthesis. In particular, his demonstration of the kiloton scale solar fuel production project will be introduced as a successful model for converting fundamental science into practical and impactful applications to convert CO 2 and water into solar fuels. This account also highlights his services to the catalysis communities and international collaborations for promoting catalysis science worldwide.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Vertex protein PduN tunes encapsulated pathway performance by dictating bacterial metabolosome morphology
Engineering subcellular organization in microbes shows great promise in addressing bottlenecks in metabolic engineering efforts; however, rules guiding selection of an organization strategy or platform are lacking. Here, we study compartment morphology as a factor in mediating encapsulated pathway performance. Using the 1,2-propanediol utilization microcompartment (Pdu MCP) system from Salmonella enterica serovar Typhimurium LT2, we find that we can shift the morphology of this protein nanoreactor from polyhedral to tubular by removing vertex protein PduN. Analysis of the metabolic function between these Pdu microtubes (MTs) shows that they provide a diffusional barrier capable of shielding the cytosol from a toxic pathway intermediate, similar to native MCPs. However, kinetic modeling suggests that the different surface area to volume ratios of MCP and MT structures alters encapsulated pathway performance. Finally, we report a microscopy-based assay that permits rapid assessment of Pdu MT formation to enable future engineering efforts on these structures.
59 BASIC BIOLOGICAL SCIENCES↗
Rapid and efficient hydrogen clathrate hydrate formation in confined nanospace
Clathrate hydrates are crystalline solids characterized by their ability to accommodate large quantities of guest molecules. Although CH 4 and CO 2 are the traditional guests found in natural systems, incorporating smaller molecules (e.g., H 2 ) is challenging due to the need to apply higher pressures to stabilize the hydrogen-bonded network. Another critical limitation of hydrates is the slow nucleation and growth kinetics. Here, we show that specially designed activated carbon materials can surpass these obstacles by acting as nanoreactors promoting the nucleation and growth of H 2 hydrates. The confinement effects in the inner cavities promote the massive growth of hydrogen hydrates at moderate temperatures, using pure water, with extremely fast kinetics and much lower pressures than the bulk system.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Nanopore Device for Reversible Ion and Molecule Sensing or Migration
Disclosed are methods and devices for detection of ion migration and binding, utilizing a nanopipette adapted for use in an electrochemical sensing circuit. The nanopipette may be functionalized on its interior bore with metal chelators for binding and sensing metal ions or other specific binding molecules such as boronic acid for binding and sensing glucose. Such a functionalized nanopipette is comprised in an electrical sensor that detects when the nanopipette selectively and reversibly binds ions or small molecules. Also disclosed is a nanoreactor, comprising a nanopipette, for controlling precipitation in aqueous solutions by voltage-directed ion migration, wherein ions may be directed out of the interior bore by a repulsing charge in the bore.
Pourmand, Nader↗