Browsing by Subject "catalysis"

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  • Mattinen, Miika; Leskelä, Markku; Ritala, Mikko (2021)
    2D transition metal dichalcogenides (TMDCs) are among the most exciting materials of today. Their layered crystal structures result in unique and useful electronic, optical, catalytic, and quantum properties. To realize the technological potential of TMDCs, methods depositing uniform films of controlled thickness at low temperatures in a highly controllable, scalable, and repeatable manner are needed. Atomic layer deposition (ALD) is a chemical gas-phase thin film deposition method capable of meeting these challenges. In this review, the applications evaluated for ALD TMDCs are systematically examined, including electronics and optoelectonics, electrocatalysis and photocatalysis, energy storage, lubrication, plasmonics, solar cells, and photonics. This review focuses on understanding the interplay between ALD precursors and deposition conditions, the resulting film characteristics such as thickness, crystallinity, and morphology, and ultimately device performance. Through rational choice of precursors and conditions, ALD is observed to exhibit potential to meet the varying requirements of widely different applications. Beyond the current state of ALD TMDCs, the future prospects, opportunities, and challenges in different applications are discussed. The authors hope that the review aids in bringing together experts in the fields of ALD, TMDCs, and various applications to eventually realize industrial applications of ALD TMDCs.
  • Lorion, Melanie M.; Koch, Vanessa; Nieger, Martin; Chen, Hi-Yung; Lei, Aiwen; Bräse, Stefan; Cossy, Janine (2020)
    A cobalt-catalyzed cross-coupling of alpha-bromo alpha-fluoro beta-lactams with diarylzinc or diallylzinc reagents is herein disclosed. The protocol proved to be general, chemoselective and operationally simple allowing the C4 functionalization of beta-lactams. The substrate scope was expanded to alpha-bromo lactams and amides, alpha-bromo lactones and esters as well asN- and O-containing heterocycles.
  • Mkrtchyan, Satenik; Jakubczyk, Michal; Lanka, Suneel; Pittelkow, Michael; Iaroshenko, Viktor O. (2021)
    We describe a mechanism-guided discovery of a synthetic methodology that enables the preparation of aromatic amides from 2-bromo-2,2-difluoroacetamides utilizing a copper-catalyzed direct arylation. Readily available and structurally simple aryl precursors such as aryl boronic acids, aryl trialkoxysilanes and dimethyl-aryl-sulfonium salts were used as the source for the aryl substituents. The scope of the reactions was tested, and the reactions were insensitive to the electronic nature of the aryl groups, as both electron-rich and electron-deficient aryls were successfully introduced. A wide range of 2-bromo-2,2-difluoroacetamides as either aliphatic or aromatic secondary or tertiary amides were also reactive under the developed conditions. The described synthetic protocols displayed excellent efficiency and were successfully utilized for the expeditious preparation of diverse aromatic amides in good-to-excellent yields. The reactions were scaled up to gram quantities.
  • Heczko, Vilma (Helsingin yliopisto, 2021)
    Plasmonic catalysis utilises light energy to drive chemical reactions. Compared to conventional catalytic processes, which are run by high temperatures and pressures, light-driven processes can lower energy consumption and increase selectivity. Conventional plasmonic nanoparticles (Ag, Au) are relatively scarce and expensive, and therefore the use of materials with earth-abundant elements in plasmonic catalysis is widely pursued. Despite their good optical properties, plasmonic nanoparticles are often unsuitable catalysts. Hybrid catalysts, structures consisting of a light-harvesting plasmonic part and a catalytical centre of different material, have emerged as an opportunity to address these challenges and obtain desired properties. This thesis consists of two parts: In the first part, properties of plasmonic materials are described, and previous studies of hybrid catalysts with earth-abundant plasmonic materials are reviewed. Experimental work on plasmonic-catalytic nanohybrids, with TiN as the plasmonic part and Pd as the catalytic entity, is described in the second part. In this context, a Pd/TiN (Pd nanoparticles supported into TiN) catalyst was synthesised, characterised and applied to test catalytical reactions. Contrary to the hypothesis, light-induced rate enhancement was not observed in our current catalytical studies. These results call for further optimisation of synthesis and reaction conditions to prepare an earth-abundant, light-active catalyst.
  • Kankala, Ranjith Kumar; Zhang, Hongbo; Liu, Chen-Guang; Kanubaddi, Kiran Reddy; Chia-Hung Lee, Chia-Hung Lee; Wang, Shi-Bin; Cui, Wenguo; Santos, Hélder A.; Lin, KaiLi; Chen, Ai-Zheng (2019)
    Despite their advantageous morphological attributes and attractive physicochemical properties, mesoporous silica nanoparticles (MSNs) are merely supported as carriers or vectors for a reason. Incorporating various metal species in the confined nanospaces of MSNs (M‐MSNs) significantly enriches their mesoporous architecture and diverse functionalities, bringing exciting potentials to this burgeoning field of research. These incorporated guest species offer enormous benefits to the MSN hosts concerning the reduction of their eventual size and the enhancement of their performance and stability, among other benefits. Substantially, the guest species act through contributing to reduced aggregation, augmented durability, ease of long‐term storage, and reduced toxicity, attributes that are of particular interest in diverse fields of biomedicine. In this review, the first aim is to discuss the current advancements and latest breakthroughs in the fabrication of M‐MSNs, emphasizing the pros and cons, the confinement of various metal species in the nanospaces of MSNs, and various factors influencing the encapsulation of metal species in MSNs. Further, an emphasis on potential applications of M‐MSNs in various fields, including in adsorption, catalysis, photoluminescence, and biomedicine, among others, along with a set of examples is provided. Finally, the advances in M‐MSNs with perspectives are summarized.