scholarly journals PdO self-assembly on zeolite SSZ-13 with rows of O3Al(IV)OH selectively incorporated in PdO(101) facets for moisture-resistant methane oxidation

2021 ◽  
Author(s):  
Libor Kovarik ◽  
Nicholas Jaegers ◽  
Janos Szanyi ◽  
Miroslaw Derewinski ◽  
Yong Wang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Methane Oxidation ◽  
Self Assembly ◽  
Bond Activation ◽  
Methane Combustion ◽  
Water Dissociation ◽  
Structure Property ◽  
New Strategy ◽  
Selective Incorporation ◽  
Catalytic Methane Oxidation

We describe an efficient way to prepare moisture-tolerant methane (hydrocarbon) combustion catalysts based on PdO nanoparticles supported on siliceous SSZ-13 zeolite. Only zeolites with high Si/Al ratios >15 are hydrophobic enough to exclude the Pd from the micropores while forming well-faceted PdO nanoparticles. Simultaneously, during self-assembly mobile Al hydroxo species get incorporated into the as-formed PdO nanoparticles. For the first time, we reveal selective incorporation of rows of O3Al(IV)-OHbridging aluminum hydroxo-species into the (101) facets of PdO nanoparticles that form during thermal self-assembly in Pd/SSZ-13 using state-of-the-art atomically-resolved HAADF-STEM imaging, solid-state NMR, DFT calculations and reactivity measurements. The Al+3-OH moieties form atom-thin rows in place of tri-coordinate Pd ions Pd+2 in Pd1O3 on (101) facets: these tri-coordinate Pd1+2O3 are responsible for C-H bond dissociation of methane and hydrocarbons during catalytic methane oxidation. However, on unmodified or non-zeolite supported PdO nanoparticles in the presence of water vapor from engine exhaust, water competes with methane by forming a deactivated Pdtetra(OH)(H2O)Pdtetra site with two water molecules on contiguous 3-coordinate Pd, which is not active for C-H bond activation. When Al-OH moieties are present in place of some tri-coordinate Pd1O3 sites, water dissociation becomes kinetically unfavorable due to disruption of Pdtetra(OH)(H2O)Pdtetra species formation. Consequently, our catalytic measurements reveal a significantly more stable performance of such catalysts in methane combustion in the presence of water vapor. Our findings provide an unprecedented atomic-level insight into structure-property relationships for supported PdO materials in catalytic methane oxidation and offer a new strategy to prepare moisture-tolerant Pd-containing methane combustion catalysts for green-house gas mitigation by selectively doping atomically thin rows of non-precious metal into specific facets of PdO.

Carbon Dioxide-Mediated C(sp2)–H Arylation of Primary and Secondary Benzylamines

2018 ◽  
Author(s):  
Mohit Kapoor ◽  
Pratibha Chand-Thakuri ◽  
Michael Young
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Bond Activation ◽  
Bond Formation ◽  
Carbon Bond ◽  
Chelate Effect ◽  
Free Amine ◽  
Carbon Carbon Bond ◽  
New Strategy ◽  
Metal Catalyzed

Carbon-carbon bond formation by transition metal-catalyzed C–H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of <i>ortho</i>-arylbenzylamines, however, effective <i>ortho</i>-C–C bond formation from C–H bond activation of free primary and secondary benzylamines using Pd<sup>II</sup> remains an outstanding challenge. Presented herein is a new strategy for constructing <i>ortho</i>-arylated primary and secondary benzylamines mediated by carbon dioxide (CO<sub>2</sub>). The use of CO<sub>2</sub> is critical to allowing this transformation to proceed under milder conditions than previously reported, and that are necessary to furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, a chelate effect is demonstrated to facilitate selective monoarylation.

scholarly journals Photoacoustics for listening to Metal Nanoparticles Super-Aggregates

2021 ◽  
Author(s):  
Roberto Li Voti ◽  
Grigore Leahu ◽  
Concita Sibilia ◽  
Roberto Matassa ◽  
Giuseppe Familiari ◽  
...  
Keyword(s):  
Metal Nanoparticles ◽  
Size Distribution ◽  
Packing Density ◽  
Self Assembly ◽  
Détection Signal ◽  
Photoacoustic Detection ◽  
New Strategy ◽  
Aggregate Packing ◽  
Detection Signal

Photoacoustic detection signal has been used to build a new strategy to determine the mesoscale self-assembly of metal nanoparticles in terms of size distribution and aggregate packing density (metal nanoparticles...

scholarly journals Self-assembly induced luminescence of Eu3+-complexes and application in bioimaging

2021 ◽  
Author(s):  
Ping-Ru Su ◽  
Tao Wang ◽  
Pan-Pan Zhou ◽  
Xiao-Xi Yang ◽  
Xiao-Xia Feng ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Rare Earth ◽  
Luminescence Intensity ◽  
Self Assembly ◽  
Room Temperature ◽  
Molecular Motion ◽  
Proof Of Concept ◽  
Room Temperature Phosphorescence ◽  
New Strategy ◽  
Size Controlled

Abstract Design and engineering of highly efficient emitting materials with assembly-induced luminescence, such as room temperature phosphorescence (RTP) and aggregation-induced emission (AIE), have stimulated extensive efforts. Here, we propose a new strategy to obtain size-controlled Eu3+-complex nanoparticles (Eu-NPs) with self-assembly induced luminescence (SAIL) characteristics without encapsulation or hybridization. Compared with previous RTP or AIE materials, the SAIL phenomena of increased luminescence intensity and lifetime in aqueous solution for the proposed Eu-NPs are due to the combined effect of self-assembly in confining the molecular motion and shielding the water quenching. As a proof of concept, we also show that this system can be further applied in bioimaging, temperature measurement and HClO sensing. The SAIL activity of the rare-earth (RE) system proposed here offers a further step forward on the roadmap for the development of RE light conversion systems and their integration in bioimaging and therapy applications.

scholarly journals Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4705
Author(s):  
Boer Liu ◽  
Xi Chen ◽  
Glenn A. Spiering ◽  
Robert B. Moore ◽  
Timothy E. Long
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Microphase Separation ◽  
Triblock Copolymers ◽  
Random Copolymer ◽  
Thermomechanical Properties ◽  
Structure Property ◽  
Scanning Calorimetry ◽  
Central Block ◽  
Quadruple Hydrogen Bonding

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.

scholarly journals Predicting carbon nanotube forest attributes and mechanical properties using simulated images and deep learning

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Taher Hajilounezhad ◽  
Rina Bao ◽  
Kannappan Palaniappan ◽  
Filiz Bunyak ◽  
Prasad Calyam ◽  
...  
Keyword(s):  
Machine Learning ◽  
Deep Learning ◽  
Carbon Nanotube ◽  
High Throughput ◽  
Self Assembly ◽  
Mechanical Performance ◽  
Physical Parameters ◽  
Structure Property ◽  
Processing Parameter ◽  
Physics Based Simulation

AbstractUnderstanding and controlling the self-assembly of vertically oriented carbon nanotube (CNT) forests is essential for realizing their potential in myriad applications. The governing process–structure–property mechanisms are poorly understood, and the processing parameter space is far too vast to exhaustively explore experimentally. We overcome these limitations by using a physics-based simulation as a high-throughput virtual laboratory and image-based machine learning to relate CNT forest synthesis attributes to their mechanical performance. Using CNTNet, our image-based deep learning classifier module trained with synthetic imagery, combinations of CNT diameter, density, and population growth rate classes were labeled with an accuracy of >91%. The CNTNet regression module predicted CNT forest stiffness and buckling load properties with a lower root-mean-square error than that of a regression predictor based on CNT physical parameters. These results demonstrate that image-based machine learning trained using only simulated imagery can distinguish subtle CNT forest morphological features to predict physical material properties with high accuracy. CNTNet paves the way to incorporate scanning electron microscope imagery for high-throughput material discovery.

Regulation of melanoma cell growth by a miR-21 loaded targeted delivery system based on microparticles and nanoparticles targeting phosphatase and tensin homolog (PTEN)

2021 ◽  
Vol 11 (11) ◽  
pp. 1766-1773
Author(s):  
Lei Jin ◽  
Tong Yang
Keyword(s):  
Delivery System ◽  
Self Assembly ◽  
Targeted Delivery ◽  
Melanoma Cells ◽  
Phosphatase And Tensin Homolog ◽  
Tensin Homolog ◽  
Assembly Method ◽  
New Strategy ◽  
Low Levels ◽  
Phosphatase And Tensin Homologue

The modulatory effect of miR-21 on the proliferation of melanoma cells through stimulation of PTEN (Phosphatase and tensin homologue deleted on chromosome 10) expression was investigated in the current study. PTEN, as a tumor suppressor, is expressed in low levels in melanoma tissues and cell lines. Nevertheless, miR-21 can stimulate cancer development and suppress cell apoptosis. Overexpression of PTEN substantially impaired the proliferation of miR-21-treated melanoma cells. In addition, miR-21 and PTEN were observed to exhibit a combinatorial effect, whereas miR-21 could negatively regulate the expression of PTEN. In conclusion, these findings demonstrate that miR-21 affects melanoma development by targeting PTEN, establishing a new strategy for treating malignant melanoma. Furthermore, in this study, microparticles and nanoparticles were employed as carriers to construct, through the self-assembly method, nanocapsules carrying miR-21 in order to develop an efficient nanocapsule delivery system of miR-21 against melanoma cells.

Complete methane oxidation over Ba modified Pd/Al2O3: The effect of water vapor

2018 ◽  
Vol 231 ◽  
pp. 242-250 ◽  
Author(s):  
Ida Friberg ◽  
Nadezda Sadokhina ◽  
Louise Olsson
Keyword(s):  
Water Vapor ◽  
Methane Oxidation ◽  
Effect Of Water

Synthesis of 6-hydroxy-N-(6-methylpyridin-2-yl) naphthalene-2- carboxamide and its alkoxy analogues

2017 ◽  
Vol 1 (3) ◽  
Author(s):  
Braja G. Bag ◽  
Subrata Ghorai ◽  
Saikat K. Panja ◽  
Shaishab K. Dinda ◽  
Koushik Paul
Keyword(s):  
Self Assembly ◽  
Alkyl Chains ◽  
Replication Studies ◽  
Naphthoic Acid ◽  
New Strategy ◽  
Donor Acceptor ◽  
High Yields ◽  
Self Replication

6-hydroxy-N-(6-methylpyridin-2-yl)naphthalene-2- carboxamide and its alkoxy analogues bearing long alkyl chains have been synthesized using 6-hydroxy-2-naphthoic acid and 2-amino-6-picoline. The facile synthetic scheme reported here using conventional laboratory reagents opens up a new strategy for the generation of libraries of such compounds in high yields. The H-bond donor acceptor groups along with the reactive 2-naphthol moiety present in the target compounds make them useful for their use in self-assembly and self-replication studies.

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