Search results for "Kulta"
showing 10 items of 67 documents
Solubility-Driven Isolation of a Metastable Nonagold Cluster with Body-Centered Cubic Structure.
2020
The conventional synthetic methodology of atomically precise gold nanoclusters using reduction in solutions offers only thermodynamically most stable nanoclusters. We report herein a solubility‐driven isolation strategy to access the synthesis of a metastable gold cluster. The cluster, with the composition of [Au 9 (PPh 3 ) 8 ] + ( 1 ), displays an unusual, nearly perfect body‐centered‐cubic (bcc) structure. As revealed by ESI‐MS and UV/Vis measurement, the cluster is metastable in solution and converts to the well‐known [Au 11 (PPh 3 ) 8 Cl 2 ] + ( 2 ) within just 90 min. DFT calculations revealed that while both 1 and 2 are eight‐electron superatoms, there is a driving force to convert 1 …
Nanodevices by DNA based gold nanostructures
2017
In this thesis DNA based structures were utilized to create gold nanostructures for nanosensing and nanoelectronic applications. In the past, both of these fields have been dominated by the conventional lithography methods, e.g., electron beam lithography and UV-lithography, but more recently scaling down the components by these techniques has become increasingly more complex and costly. Especially in the micro- and nanoelectronics, the increase in the component density and thus computational power would require fabrication of sub-10-nm components, which is challenging for the top-down approaches. Aforementioned developments have led researchers to seek alternative methods to fabricate these…
What Contributes to the Measured Chiral Optical Response of the Glutathione-Protected Au25 Nanocluster?
2023
The water-soluble glutathione-protected [Au25(GSH)18]−1 nanocluster was investigated by integrating several methodologies such as molecular dynamics simulations, essential dynamics analysis, and state-of-the-art time-dependent density functional theory calculations. Fundamental aspects such as conformational, weak interactions and solvent effects, especially hydrogen-bonds, were included and found to play a fundamental role in assessing the optical response of this system. Our analysis demonstrated not only that the electronic circular dichroism is extremely sensitive to the solvent presence but also that the solvent itself plays an active role in the optical activity of such system, formin…
Bi-, Tetra-, and Hexanuclear AuI and Binuclear AgI Complexes and AgI Coordination Polymers Containing Phenylaminobis(phosphonite), PhN{P(OC6H4OMe-o)2…
2008
The reactions of phenylaminobis(phosphonite), PhN{P(OC6H4OMe-o)2}2 (1) (PNP), with [AuCl(SMe2)] in appropriate ratios, afford the bi- and mononuclear complexes, [(AuCl)2(µ-PNP)] (2) and [(AuCl)(PNP)]2 (3) in good yield. Treatment of 2 with 2 equiv of AgX (X = OTf or ClO4) followed by the addition of 1 or 2,2′-bipyridine affords [Au2(µ-PNP)2](OTf)2 (4) and [Au2(C10H8N2)2(µ-PNP)](ClO4)2 (5), respectively. Similarly, the macrocycles [Au4(C4H4N2)2(µ-PNP)2](ClO4)4 (6), [Au4(C10H8N2)2(µ-PNP)2](ClO4)4 (7), and [Au6(C3H3N3)2(µ-PNP)3](ClO4)6 (8) are obtained by treating 2 with pyrazine, 4,4′-bipyridine, or 1,3,5-triazine in the presence of AgClO4. The reaction of 1 with AgOTf in a 1:2 molar ratio pr…
Computational Experiments with the Roots of Fibonacci-like Polynomials as a Window to Mathematics Research
2022
Fibonacci-like polynomials, the roots of which are responsible for a cyclic behavior of orbits of a second-order two-parametric difference equation, are considered. Using Maple and Wolfram Alpha, the location of the largest and the smallest roots responsible for the cycles of period p among the roots responsible for the cycles of periods 2kp (period-doubling) and kp (period-multiplying) has been determined. These purely computational results of experimental mathematics, made possible by the use of modern digital tools, can be used as a motivation for confirmation through not-yet-developed methods of formal mathematics. peerReviewed
Growth of two-dimensional Au patches in graphene pores : a density-functional study
2016
Grafeenin löytämisen myötä kaksiulotteisten (2D) materiaalien tutkimus on edennyt huomattavasti viimeisen vuosikymmenen aikana. Myös 2D-metalleja on tutkittu, ja esimerkiksi atominpaksuinen rautakerros on onnistuttu kokeellisesti luomaan grafeenin reunalle. Metalleista erityisesti kullan on havaittu käyttäytyvän hyvin eri tavalla nanomittakaavassa. Tässä Pro gradu -tutkielmassa on simuloitu kaksiulotteisten kultasaarekkeiden kasvua grafeenin reunalle tiheysfunktionaaliteoriaa (DFT) käyttämällä. Tavoitteena oli selvittää, kuinka kulta-atomit kulkeutuvat grafeenin pintaa pitkin lopulta reunalle, ja asettuvatko kulta-atomit kaksiulotteisesti samaan tasoon grafeenin kanssa. Tulosten perusteella…
Oxidative Dehydrogenation of Ethanol on Gold : Combination of Kinetic Experiments and Computation Approach to Unravel the Reaction Mechanism
2021
Abstract Selective alcohol dehydrogenation on heterogeneous catalysts is a key industrial reaction for production of aldehydes, ketones, and carboxylic compounds. Design of catalysts with improved activity and selectivity requires understanding of the reaction mechanism and kinetics. Herein, experiments, density functional theory (DFT) and kinetic modelling were combined to elucidate the mechanism and kinetics of ethanol oxidative dehydrogenation to acetaldehyde on gold catalysts. Catalytic experiments clearly emphasized the role of oxygen in this reaction. Ethanol conversion was rather independent on the gold cluster size. Formation of minor products, acetic acid and ethyl acetate was stru…
Identification of sub-μs isomeric states in the odd-odd nucleus 178Au
2021
The neutron-deficient gold (Z=79) isotopes in the vicinity of the neutron midshell N=104 provide prolific examples of shape coexistence and isomerism at low excitation energy. They can be probed via a number of different experimental techniques. In this study, two new isomeric states with half-lives of 294(7) and 373(9) ns have been observed in the neutron-deficient odd-odd nuclide 178Au (N=99) in an experiment at the RITU gas-filled separator at JYFL, Jyväskylä. This result was achieved due to the use of a segmented planar germanium detector with a high efficiency at low energies. By applying the recoil-decay tagging technique, they were assigned to decay to two different long-lived α-deca…
Oxidative dehydrogenation of alcohols on gold : An experimental and computational study on the role of water and the alcohol chain length
2023
The oxidative dehydrogenation of primary alcohols promoted by gold nanoparticles was investigated from an experimental and computational viewpoint to derive a plausible reaction mechanism and to understand the role of water and alcohol chain length in the elementary steps. The influence of water in reaction kinetics and product distribution was determined in a laboratory-scale microreactor adding water to the reaction mixture in different amounts. DFT calculations revealed that the presence of water on the catalyst surface is beneficial to assist the key step in alcohol oxidation i.e., oxygen activation by protonation. The calculations were performed for primary alcohols ranging from methan…
Computational studies of gold-absorbate complexes on modified oxides
2016
While bulk gold is known for its chemical inertness, nanosized gold clusters are active catalysts for a variety of important reactions. For some practical applications gold clusters are supported and the cluster-support interaction can modify the cluster's properties. The knowledge of this interaction can be vital for obtaining desired cluster properties. In this thesis, the adsorption of Au atoms and clusters on modified oxide surfaces is studied using density functional theory (DFT) calculations. The support effects are considered by direct analysis of the adsorbed Au and using other coadsorbates as reactivity probes. Doping the CaO(001) surface by replacing a cation with a high valence d…