Speaker: Fuhai Zhou, Chemistry Ph.D. student supervised by Professor Sanjay Rastogi

The non-crystalline region and its influence on crystal plasticity in semi-crystalline synthetic polymers

Abstract

Synthetic polymers, having high modulus and high tensile strength, are semi-crystalline materials having chains traversing between the crystalline and non-crystalline regions. While the three dimensional crystallographic order exists in the crystalline region, the differences in chain topology persists in the non-crystalline region. The variations in the chain topology can be tuned by controlling the polymerization conditions. In this seminar I will demonstrate the influence of chain topology on deformation of the crystalline regions in solid-state. The crystal deformation, under compression, can be so pronounced that cohesion between the nascent particles as obtained during polymerization can be achieved to an extent that the macroscopic forces can be translated to molecular length scale leading to ultimate properties in the uniaxial and biaxial drawn films. These concepts are translated in overcoming the persistent problem in sintering of UHMWPE used in prostheses, providing a novel route to enhance the life expectancy of the prostheses by reducing oxygen permeability and adhesive as well as fatigue wear while increasing impact strength even after irradiation.

Bio

Fuhai is a PhD candidate under the supervision of Professor Sanjay Rastogi. He obtained his master’s degree from Xi’an Jiaotong University in China and joined KAUST in 2021.  As part of his PhD study, his research is to understand crystal plasticity in ultra-high molecular weight polyethylene and develop grain boundary free prostheses with enhanced mechanical properties.

Speaker: Xiting Yuan, Chemistry Ph.D. student supervised by Professor Mohamed Eddaoudi

A Water-Soluble N‑Heterocyclic Carbene-Stabilized Au₁₃ Cluster: Synthesis, Characterization, Application in Cell Imaging and Fabrication of Metal-organic Frameworks (MOFs)

Abstract

Here report the first synthesis of a carboxyl-capped carbene-stabilized single-crystal Au₁₃ cluster (Au₁₃-c), namely Au₁₃(bi-NHC carboxyl)₅Cl₂. The synthesized Au₁₃-c cluster is water-soluble and exhibits a strong emission at 710 nm in H₂O (QY=2.65%). DFT calculations revealed that this cluster is an electronically stable eight-electron super-atom, deciphering also its optical transitions in the UV-Vis range. On the on hand, the Au₁₃-c cluster of ultra-small size reveals excellent thermal and chemical stability, especially under biological conditions. These excellent features have enabled its utilization in cell imaging applications, which was successfully demonstrated on both cancer and noncancer cells. On the other hand, functionalization with carboxyl groups not only enables the clusters to be applied in biochemistry but also paves the way for their use as building units in the fabrication of metal–organic frameworks (MOFs) via their coordination with other metals, which could lead to new topologies.

Bio

Xiting is currently in her fourth year of PhD under the supervision of Professor Mohamed Eddaoudi at KAUST AMPM center. She obtained her BSc in Chemistry, from Northeast Normal University (China) in 2017 and master degree in Chemistry from Xiamen University (China) in 2020. Her research focuses on the design and synthesis of hybrid materials combined with Metal-Organic Frameworks (MOFs) and Nanoclusters for applications. 

Speaker: Yan Wang, Chemistry Ph.D. Candidate supervised by Professor Javier Ruiz-Martínez

Unveiling the Evolution of N2O Species over Atomically Dispersed Mn species supported on the TiO2in NH3Selective Catalytic Reduction of NO

Abstract

Nitrogen oxides have emerged as one of the main sources of air pollution from stationary and mobile sources, which can cause serious damage to the environment and human health. Selective catalytic reduction (SCR) of NO with NH3has been the predominant technology for deNOx in industry. [1] To date, manganese oxides are reported to be one of the most promising catalysts for mobile source emissions at low temperatures. However, a large amount of N2O could be produced on the MnOx in the NH3-SCR reaction, which is the main byproduct and has a strong greenhouse effect as well as severe hazards towards human health. How to further suppress the formation of N2O remains a challenge. Based on our previous work, we hypothesized that using Ce to space the MnOx active sites on the TiO2could produce less N2O. [2] On the other hand, single-atom catalyst (SAC) has been widely used in heterogeneous catalysis due to its high dispersion and maximized atom utilization efficiency. Hence, one of the efficient approaches for clarifying N2O species formation on MnOx-TiO2is to prepare single Mn-atom catalysts which by definition results in a complete dispersion and spacing of the metal over the support.In this talk, the N2O formation species over single atoms will be comprehensively unravelled via catalytic performance study as well as advanced characterizations(X-ray Absorption Spectroscopy (XAS), Scanning Transmission Electron Microscopy (STEM), and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), etc.)

Bio

YanWang is currently in his4th year of Ph. D program under the supervision of Professor Javier Ruiz-Martínez at KAUST Catalysis Center. His Ph.D. research focuses on understanding the performance of Mn single Atoms, clusters, and nanoparticles in NH3Selective Catalytic Reduction of NO.

References

[1] Han, L.; Cai, S.; Gao, M.; Hasegawa, J.-y.; Wang, P.; Zhang, J.; Shi, L.; Zhang, D. Chemical Reviews 2019, 119, 10916-10976.

[2] Gevers, L. E.; Enakonda, L. R.; Shahid, A.; Ould-Chikh, S.; Silva, C. I. Q.; Paalanen, P. P.; Aguilar-Tapia, A.; Hazemann, J.-L.; Hedhili, M. N.; Wen, F.; Ruiz-Martínez, J. Nature Communications 2022, 13, 2960.