Search results for "kulta"
showing 10 items of 67 documents
Carbon nanotube field-effect devices with asymmetric electrode configuration by contact geometry
2014
We have studied experimentally the conductive properties of single walled carbon nanotube (SWNT) based field-effect type devices, with different contact geometries at the connecting electrode. The device designs are asymmetric with one end of the SWNT having the metal electrode deposited on top and immersing it, while at the other end, the SWNT is on top of the electrode. The devices were made with either gold or palladium as electrode materials, of which the latter resulted in different behavior of the different contact types. This is argued to be caused by the existence of a thin insulating layer of surface adsorbents on the palladium, possibly Pd5O4, the effect of which is enhanced by th…
Kultakmeņi Latvijas teritorijā kā arheoloģiskās izpētes objekts: funkcionalitāte un izmantošanas hronoloģija
2022
Pētījumā, izmantojot triangulācijas pieeju, akmeņu folklora salīdzināta ar arheoloģisko materiālu, rakstiskajos avotos rodamo informāciju un ikonogrāfisko materiālu, identificējot vairākas kultakmeņu funkcijas, kas var pārklāties laikā. Ziedošana uzskatāma par sekundāru funkciju kultakmeņiem, kuru primārā funkcija saistīta ar apbedīšanas rituāliem vai depozītu sargāšanu. Savukārt krustakmeņiem, kuru primārā funkcija saistīta ar kristīgās telpas robežu iezīmēšanu ainavā, sekundārā funkcija saistīta ar upurēšanu. Kultakmeņu funkcijas korelē ar dabas objektu situējumu ainavā. Kultakmeņi situēti tiešā kopienas apdzīvotās teritorijas tuvumā vai ir tās ainavas sastāvdaļa. Veicot Grīžu Velna beņķa…
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…
Cubic aromaticity in ligand-stabilized doped Au superatoms
2021
The magnetic response of valence electrons in doped gold-based [M@Au8L8]q superatoms (M = Pd, Pt, Ag, Au, Cd, Hg, Ir, and Rh; L = PPh3; and q = 0, +1, +2) is studied by calculating the gauge including magnetically induced currents (GIMIC) in the framework of the auxiliary density functional theory. The studied systems include 24 different combinations of the dopant, total cluster charge, and cluster structure (cubic-like or oblate). The magnetically induced currents (both diatropic and paratropic) are shown to be sensitive to the atomic structure of clusters, the number of superatomic electrons, and the chemical nature of the dopant metal. Among the cubic-like structures, the strongest arom…
Kultakmeņi Daugavas lejtecē: identifikācija un izmantošanas hronoloģija
2019
Līdz šim lielākoties notikusi kultakmeņu apzināšana un tipoloģizēšana pēc to vizuālajām pazīmēm. Kulta vietu arheoloģiskajā izpētē iegūtais arheoloģiskais materiāls ir mazskaitlīgs un vienveidīgs, un līdz šim ne vienmēr ļāvis identificēt un datēt kultakmeņus. Bakaulara darbā, analizējot ar kultakmeņu identifikāciju un izmantošanas hronoloģiju saistīto problemātiku, identificēti Daugavas kultakmeņu marķieri. Lai pārbaudītu 3D vizualizācijas iespējas Daugavas kultakmeņu interpretācijā un identifikācijā, kas līdz šim nav darīts, veikta Mārtiņsalas akmens elku 3D vizuālizācija. Lai precizētu kultakmeņu izmantošanas hronoloģiju, veikta kultakmeņu un iespējamo kultakmeņu situēšana ar senvietām, i…
Introducing Golden Section in the Mathematics Class to Develop Critical Thinking from the STEAM Perspective
2021
The Golden Section is a mathematical concept that is one of the most famous examples of connections between mathematics and the arts. Despite its widespread references in various areas of nature, art, architecture, literature, music, or aesthetics, discussions of the golden ratio often turn out to be false or misleading. Most of the incorrect statements are based on approximations or stem from the lack of checking the facts, making scientific mistakes in verifying the original scientific, historical, cultural context, or performing arbitrary operations in the measurements. This article offers geometric data and measurements, which allow the students to explore the golden ratio in various co…
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…
Heterometallic Au(I)–Cu(I) Clusters : Luminescence Studies and 1O2 Production
2023
Two different organometallic gold(I) compounds containing naphthalene and phenanthrene as fluorophores and 2-pyridyldiphenylphosphane as the ancillary ligand were synthesized (compounds 1 with naphthalene and 2 with phenanthrene). They were reacted with three different copper(I) salts with different counterions (PF6–, OTf–, and BF4–; OTf = triflate) to obtain six Au(I)/Cu(I) heterometallic clusters (compounds 1a–c for naphthalene derivatives and 2a–c for phenanthrene derivatives). The heterometallic compounds present red pure room-temperature phosphorescence in both solution, the solid state, and air-equilibrated samples, as a difference with the dual emission recorded for the gold(I) precu…
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…
Kaliksareeneilla päällystetyt kultananopartikkelit
2011
Pro gradu -tutkielmassa kerrotaan, mitä tällä hetkellä tiedetään kaliksareeneilla päällystettyjen kultananopartikkeleiden rakenteesta. Lisäksi käsitellään partikkelien valmistusta joko suorilla menetelmillä tai valmiisiin kultananopartikkeleihin tehdyllä ligandinvaihdolla ja kerrotaan valmistettujen partikkelien karakterisointimenetelmistä. Tutkielmassa perehdytään myös kaliksareeneilla päällystettyjen kultananopartikkelien sovelluksiin materiaalitieteissä, tunnistuksessa ja havaitsemisessa, katalyysissä ja sitoutumisessa biologisiin rakenteisiin. Kokeellisessa osassa pyrittiin valmistamaan resorsinareeneja, pyrogallareeneja ja kultananopartikkeleita ligandinvaihtoa varten.