Search results for "Kulta"
showing 10 items of 67 documents
Modeling the atomic and electronic structure of nanoparticle-ligand interfaces
2013
Timantit työssään : kulta- ja kelloalan myyjien käsityksiä puheviestintäosaamisestaan asiakaspalvelutilanteissa
2007
The Role of Donor and Acceptor Substituents on the Nonlinear Optical Properties of Gold Nanoclusters
2018
In recent years, a large number of monolayer-protected clusters (MPCs) have been studied by means of single crystal structure characterization. A central aspect of research on MPCs is the correlation of their interesting optical properties with structural features and the formulation of a theoretical framework that allows interpretation of their unique properties. For this, superatom and jellium models have been proven successful. Little attention, however, has been paid to the influence of the protecting ligands. Here, we investigate the effect of changes in [Au25(SR)18-x(SR′)x]−, where SR′ represents a para-substituted thiophenolate derivative (SPh-4-X). We computed the first hyperpolariz…
Electronic, structural and chemical properties of gold clusters on ultra-thin oxide films
2009
Two decades ago, it was found that gold is catalytically active as clusters although it is known to be inert as bulk material. In the work presented in this thesis, density functional theory calculations have been applied to show that the properties of gold clusters and small molecules, namely O2 and NO2, are di erent on oxide thin lms supported by metal carriers than on single crystal oxide surfaces. Collectively, these di erences are called thin- lm e ects. The e ects and the mechanisms behind them have been studied with atomistic calculations and rationalized with simple physical models. The signi cance of the thin- lm e ects for heterogeneous catalysis is discussed. It has been found th…
Size dependent swift heavy ion induced Au nanoparticle elongation in SiO2 matrix
2022
The elongation of spherical Au nanoparticles embedded in SiO2 under swift heavy ion (SHI) irradiation is an extensively studied phenomenon. The use of a TEM grid as a substrate facilitates the identification of the same nanoparticle before and after the irradiation. Since the underdensification of SiO2 inside the ion track plays a key role, the elongation is sensitive to the matrix material properties. Therefore, we studied the elongation process of SHI irradiated Au spherical nanoparticles of various diameters (5–80 nm) embedded either in atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD) SiO2. The results show that a different elongation ratio is achieved d…
Effect of Gold(I) on the Room-Temperature Phosphorescence of Ethynylphenanthrene.
2020
The synthesis of two series of gold(I) complexes containing the general formulae PR 3 ‐Au‐C≡C‐phenanthrene (PR 3 = PPh 3 ( 1a / 2a ), PMe 3 ( 1b / 2b ), PNaph 3 ( 1c / 2c )) or (diphos)(Au‐C≡C‐phenanthrene) 2 (diphos = 1,1‐ bis (diphenylphosphino)methane, dppm ( 1d / 2d ); 1,4‐ bis (diphenylphosphino)butane, dppb ( 1e / 2e )) have been synthesized. The two series differ on the position of the alkynyl substituent on the phenanthrene chromophore, being at the 9‐position (9‐ethynylphenanthrene) for the L1 ‐series and at the 2‐position (2‐ethynylphenanthrene) for the L2 ‐series. The compounds have been fully characterized by 1 H and 31 P NMR and IR spectroscopy, mass spectrometry and single cry…
New collective structures in 179Au and their implications for the triaxial deformation of the 178Pt core
2022
The extremely neutron-deficient isotope 179Au has been studied by a combination of in-beam γ-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/2−, T1/2=328 ns isomer. A new rotational band, associated with the unfavored signature band of the 1h9/2⊕2f7/2 proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and T1/2=2.16(8)µs was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the 1i13/2 proton-intruder configuration. Calculations based on the particle-pl…
Fakultatīvo migrantu ziemošanas vietu pārmaiņas Latvijā gredzenotajiem putniem
2017
Šajā bakalaura darbā aplūkota piecu fakultatīvo migrantu putnu sugu – sarkanrīklītes Erithacus rubecula, dziedātājstrazda Turdus philomelos, pelēkā strazda Turdus pilaris, melnā meža strazda Turdus merula un lielās zīlītes Parus major – iespējamās ziemošanas vietu izmaiņas Latvijā gredzenotajiem putniem, periodā sākot no 1931. /1932. gada līdz 2014. /2015. gada ziemai. Tika izmantoti gredzenoto un pēc tam kontrolēto putnu dati no Latvijas Gredzenošanas centra arhīva.Veicot datu statistisko analīzi, konstatēts, ka nevienai no piecām apskatītajām sugām nav statistiski būtiski izmanījies migrācijas attālums. Divām sugām – dziedātājstrazdam Turdus philomelos (r2=0,012, p=0,429, n=64) u…
Arheoloģija Baltijā 21. gs. sākumā: jaunākie pētījumi, aktuālās diskusijas un mūsdienu izaicinājumi: referātu kopsavilkumi, 2022. gada 18. februārī L…
2022
Jau divas desmitgades Latvijas Universitātes (LU) starptautiskās zinātniskās konferences ietvaros katru otro gadu norisinās Arheoloģijas sekcija, ko rīko LU Vēstures un filozofijas fakultāte. Pirmoreiz šāda sekcija tika rīkota LU 61. zinātniskajā konferencē 2003. gada 10. februārī. Turpinot iesākto tradīciju, arī 2022. gada 18. februārī LU 80. starptautiskās konferences ietvaros Vēstures un filozofijas fakultātes Vēstures un arheoloģijas nodaļa organizēja arheoloģijas problemātikai veltītu sekciju, kurā tika aplūkotas daudzveidīgās un aktuālās mūsdienu arheoloģijas attīstības tendences Latvijā un Eiropā. Daļa konferences referātu pievērsās dabaszinātņu un tās pētniecisko metožu lomai arheol…
Electronic and vibrational spectroscopic studies of gold-nanoclusters
2016
Gold nanoclusters are a peculiar new material with properties between that of bulk metal and single atoms. They show size-dependent evolution of optical and electronic properties sensitive to the change of single atom or single electron in the system. Understanding the relationship between structure and properties is important to both fundamental scientific question of the role of the quantum size effects in small metal-clusters, and to application of nanoclusters in e.g. photonics, nanoelectronics, and heterogeneous catalysis. In this thesis four spectroscopic studies of monolayer-protected gold-nanoclusters are presented. The optical gap of the Au144(PET)60 and (Au/Ag)144(PET)60 (PET: pheny…