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961.
Gabor A. Somorjai Prof. Jeong Y. Park Dr. 《Angewandte Chemie (International ed. in English)》2008,47(48):9212-9228
Selectivity—the production of one molecule out of many other thermodynamically feasible product molecules—is the key concept in developing clean processes that do not produce by‐products (green chemistry). Small differences in the potential‐energy barriers of single reaction steps control which reaction channel is more likely to yield the desired product molecule (selectivity), while the overall activation energy of the reaction controls the turnover rates (activity). Recent studies have demonstrated that tailoring parameters at the atomic or molecular level—such as the surface structures of active sites—gives turnover rates and reaction selectivities that depend on the nanoparticle size and shape. Here, we highlight seven molecular components that influence the selectivity of heterogeneous catalyst reactions on single‐crystal model surfaces and colloid nanoparticles: surface structure, adsorbate‐induced restructuring, adsorbate mobility, reaction intermediates, surface composition, charge transport, and oxidation states. We show the importance of the single factors by means of examples and describe in situ analyses that permit their roles in surface reactions to be investigated. 相似文献
962.
963.
Lee SH Son JK Jeong BS Jeong TC Chang HW Lee ES Jahng Y 《Molecules (Basel, Switzerland)》2008,13(2):272-300
Rutaecarpine is an indolopyridoquinazolinone alkaloid isolated from Evodia rutaecarpa and related herbs, which has shown a variety of intriguing biological properties such as anti-thrombotic, anticancer, anti-inflammatory and analgesic, anti-obesity and thermoregulatory, vasorelaxing activity, as well as effects on the cardiovascular and endocrine systems. Recent progress in the studies on the isolation, synthesis, structure-activity relationship studies, biological activities and metabolism of rutaecarpine are reviewed. 相似文献
964.
Wasylycia JR Sapelnikova S Jeong H Dragoljic J Marcus SL Harrison DJ 《Lab on a chip》2008,8(6):979-982
We report fuel generation systems for molecular motors based on pyruvate kinase, or for the first time, mitochondria, implemented within microfluidic devices. Intact organelles acted as bio-nanopower supplies for molecular motors, using isolated mitochondria to convert chemical energy from succinate to ATP, harnessing nature's enzymatic transformation cascades directly. Motors were activated essentially equally by ATP produced by pyruvate kinase, mitochondria, or direct addition of ATP. 相似文献
965.
Melfi PJ Camiolo S Lee JT Ali MF McDevitt JT Lynch VM Sessler JL 《Dalton transactions (Cambridge, England : 2003)》2008,(12):1538-1540
The synthesis of an isoamethyrin derivative containing two CH(2)CH(2)CO(2)CH(3) moieties in the beta-pyrrolic positions and its use in the colorimetric detection of the uranyl cation after immobilization onto a solid support is reported. 相似文献
966.
We experimentally studied a nematic liquid crystal whose molecules form twisted head-to-head H-bonded dimers. We observed that when the material transformed from the isotropic to nematic phase, it formed droplets with chiral propeller textures. We carried out a computer simulation to investigate the liquid crystal director configuration inside the droplets and to study the effects of elastic constants and chirality on the droplet texture. Results of our study show it is likely that the material in the droplets had nonzero chirality due to spontaneous chiral phase separation. 相似文献
967.
The production of nanofibrous PLA/HA composite scaffolds is described. The morphological, mechanical, surface, and thermal properties of the composites were extensively investigated. The results show that the mixture of PLA and HA formed smooth nanofibers without lumps. The incorporation of HA increased the mechanical strength of the nanofibers and changed the morphology, increasing the mean fiber diameter and pore size. Surface and internal properties confirmed that HA was homogeneously distributed inside the nanofibers and oriented towards their surface. The nanofiber composites allowed the adhesion and proliferation of pre-osteoblasts for up to 3 weeks. 相似文献
968.
Jingnan Wu Zhaoheng Ling Leandro R. Franco Sang Young Jeong Zewdneh Genene Josué Mena Si Chen Cailing Chen Prof. C. Moyses Araujo Prof. Cleber F. N. Marchiori Joost Kimpel Xiaoming Chang Furkan H. Isikgor Qiaonan Chen Hendrik Faber Prof. Yu Han Frédéric Laquai Prof. Maojie Zhang Prof. Han Young Woo Prof. Donghong Yu Prof. Thomas D. Anthopoulos Prof. Ergang Wang 《Angewandte Chemie (International ed. in English)》2023,62(45):e202302888
The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive “conformational lock” mechanism, arising from the intensified intramolecular π–π interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs. 相似文献
969.
Dr. Jianfeng Li Dr. Zhicai Chen Junwei Wang Sang Young Jeong Dr. Kun Yang Dr. Kui Feng Jie Yang Dr. Bin Liu Prof. Dr. Han Young Woo Prof. Dr. Xugang Guo 《Angewandte Chemie (International ed. in English)》2023,62(38):e202307647
Developing high-performance but low-cost n-type polymers remains a significant challenge in the commercialization of organic field-effect transistors (OFETs). To achieve this objective, it is essential to design the key electron-deficient units with simple structures and facile preparation processes, which can facilitate the production of low-cost n-type polymers. Herein, by sequentially introducing fluorine and cyano functionalities onto trans-1,3-butadiene, we developed a series of structurally simple but highly electron-deficient building blocks, namely 1,4-dicyano-butadiene ( CNDE ), 3-fluoro-1,4-dicyano-butadiene ( CNFDE ), and 2,3-difluoro-1,4-dicyano-butadiene ( CNDFDE ), featuring a highly coplanar backbone and deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels (−3.03–4.33 eV), which render them highly attractive for developing n-type semiconducting polymers. Notably, all these electron-deficient units can be easily accessed by a two-step high-yield synthetic procedure from low-cost raw materials, thus rendering them highly promising candidates for commercial applications. Upon polymerization with diketopyrrolopyrrole ( DPP ), three copolymers were developed that demonstrated unipolar n-type transport characteristics in OFETs with the highest electron mobility of >1 cm2 V−1 s−1. Hence, CNDE , CNFDE , and CNDFDE represent a class of novel, simple, and efficient electron-deficient units for constructing low-cost n-type polymers, thereby providing valuable insight for OFET applications. 相似文献
970.
Prof. Dr. Joonghan Kim Dakyeung Oh Eunji Park Jeongmin Park Jungyoon Kim Prof. Dr. Jeong Sik Lim 《Chemphyschem》2023,24(13):e202300048
The photochemical reaction mechanism underlying the intramolecular H-transfer of the H2C3O+⋅ radical cation to the H2CCCO+⋅ methylene ketene cation was elucidated using time-dependent density functional theory and high-level ab initio methods. Once the D1 state of H2C3O+⋅ is populated, the reaction proceeds to form an intermediate (IM) in the D1 state (IM4D1). The molecular structure of the conical intersection (CI) was optimized using a multiconfigurational ab initio method. The CI is readily accessible because it lies slightly above the IM4D1 in energy. In addition, the gradient difference vector of the CI is almost parallel to the intramolecular H-transfer reaction coordinate. Once the vibration mode of IM4D1 which is parallel to the reaction coordinate is populated, the degeneracy of the CI is readily lifted and H2CCCO+⋅ was formed via a relaxation pathway in the D0 state. Our calculated results clearly describe the photochemical intramolecular H transfer reaction reported in a recent study. 相似文献