Search results for "hiukkaset"

Ligand assisted hydrogenation of levulinic acid on Pt(111) from first principles calculations

2021

In this study, we investigate the hydrogenation reaction of levulinic acid to 4-hydroxypentanoic acid on ligand-modified Pt(111) using DFT. Modifying nanoparticle surfaces with ligands can have beneficial effects on the desired reaction such as improved selectivity or lower activation energies. The N3,N3-dimethyl-N2-(quinolin-2-yl)propane-1,2-diamine (AQ) ligand was selected to modify the surface, since it combines good surface adsorption properties with functional groups that can influence the reaction. The adsorption geometry of the AQ ligand was studied as well as the co-adsorption of a second AQ ligand for the possibility of self-assembly. We found that dissociated hydrogen from the Pt(…

Rare beta decays and the spectrum-shape method

2017

This is a thesis consisting of seven publications and an introductory part on theoretical studies on rare single beta decays. Firstly, the theoretical framework is applied to the computation of partial half-lives for few selected cases of rare single beta-decay transitions. This includes the study on a possible ultra-low-Q-value decay branch of 115Cd as well as the highly forbidden beta decays of 48Ca and 50V. The double magic 48Ca is one of the few experimentally verified nuclei that decay via the two-neutrino mode of double beta decay. A theoretical study on the single beta-decay branches was used to inspect the competition between the single and double beta-decay channels. In the case of…

Toxicity of silver nanoparticles to Lumbriculus variegatus is a function of dissolved silver and promoted by low sediment pH

2018

Toxicity of silver nanoparticles (AgNPs) to benthic organisms is a major concern. The use of AgNPs in industry and consumer products leads to increasing release of AgNPs into the aquatic environment—sediments being the major sink. Effects of sediment pH on the toxicity of AgNPs to benthic oligochaeta Lumbriculus variegatus were studied in a 23‐d toxicity test. Artificially prepared sediments (pH 5 and 7) were spiked with varying concentrations of uncoated AgNP, polyvinylpyrrolidone (PVP)‐coated AgNP, and silver nitrate (AgNO3) as dissolved Ag reference. Number of individuals and biomass change were used as endpoints for the toxicity. The toxic effects were related to the bioaccessible conce…

Behaviour of sediment-associated silver nanoparticles and their toxicity to Lumbriculus variegatus

2017

The increasing use of silver nanoparticles (AgNPs) in industry and consumer products results in the increasing environmental concentrations of AgNPs. In the aquatic environment, sediment is the major sink for the AgNPs. The behaviour and toxicity of AgNPs in sediments is largely unknown, and therefore the potential risk to the benthic ecosystems is difficult to predict. The aim of this thesis was to study the toxicity and uptake of uncoated AgNPs (uc-AgNPs) and polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs) to Lumbriculus variegatus in sediment exposures. Also, the association of AgNP-originated dissolved Ag with sediment components was studied using a sequential extraction method. Studies w…

Application of 3D printed scavengers for improving the accuracy of single-particle inductively coupled plasma mass spectrometry analyses of silver na…

2023

The determination of silver nanoparticles (Ag NPs) with single-particle inductively coupled plasma mass spectrometry can be severely interfered with coexisting dissolved silver causing high background signals, which can lead to inaccurate quantification of NP size and particle concentration. In this paper, chemically active and reusable 3D printed scavengers are applied for highly efficient dissolved silver removal in Ag NP dispersions, allowing more accurate determination of particle concentration and size. Selective laser sintering was used for constructing the porous 3D scavengers constituting of polystyrene used as a supporting material and ion-exchange material SiliaBond Tosic acid (TA…

Encapsulation of AgNPs in a Lignin Isocyanate Film : Characterization and Antimicrobial Properties

2023

Lignin isolated from agricultural residues is a promising alternative for petroleum-based polymers as feedstocks in development of antimicrobial materials. A polymer blend based on silver nanoparticles and lignin–toluene diisocyanate film (AgNPs–Lg–TDIs) was generated from organosolv lignin and silver nanoparticles (AgNPs). Lignin was isolated from Parthenium hysterophorus using acidified methanol and used to synthesize lignin capped silver nanoparticles. Lignin–toluene diisocyanate film (Lg–TDI) was prepared by treating lignin (Lg) with toluene diisocyanate (TDI) followed by solvent casting to form films. Functional groups present and thermal properties of the films were evaluated using Fo…

Synthesis, characterization, and reactivity of heavier group 13 and 14 metallylenes and metalloid clusters : small molecule activation and more

2015

Enhancing silicon solar cell efficiency with metal nanoparticles

2009

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…

¹²C-ionien energiajättö vedessä

2015

Tässä tutkimuksessa käsiteltiin varatuista raskaista hiukkasista koostuvan säteilyn yleistä käyttäytymistä sen vuorovaikuttaessa materiaalin kanssa, sekä tutustuttiin lyhyesti erilaisiin tapoihin mitata säteilyn energiajättöä. Lisäksi MCP-pohjaisiin lentoaikailmaisimiin perustuvalla mittausasetelmalla määritettiin kokeellisesti C-12-ioneista koostuvan säteilyn energiajättöä eripaksuisissa vesikohtioissa. Kohtioiden paksuudet olivat 0,39 mm, 0,57 mm ja 0,93 mm. Motivaationa mittauksille toimi suihkujen käyttö hadroniterapiassa, sillä varattujen raskaiden hiukkasten energiajätön käyttäytyminen materiassa toimii syvällä kudoksissa olevien kasvainten hoitoon erityisen hyvin. Lopulliset tulokset…