Search results for "Kulta"

Kannattava ja eettinen kultakaivostoiminta Sierra Leonessa

2012

Tällä tutkimuksella on haluttu selvittää länsimaalaisten ja sierraleonelaisten toimijoiden käsitysten pohjalta, kuinka eettistä Sierra Leonessa harjoitettu, omistajilleen lisäarvoa tuottava, ja kannattava kultakaivostoiminta on suhteessa liiketoiminnan eri sidosryhmiin. Liiketoiminnan kannattavuutta tarkastellaan kannattavuusteorioiden avulla, sekä kannattavuuslaskelmien perusteella. Kultakaivostoiminta on omistajilleen riskisijoittamista, johon liittyy suuret liiketoiminnalliset riskit, mutta myös suuret tuotto-odotukset. Kultakaivostoiminnan vaikutuksia eri sidosryhmiin tarkastellaan sidosryhmäteorian perusteella valittujen tärkeimpien sidosryhmien näkökulmasta. Vaikutusten …

Isomer dynamics of the [Au6(NHC-S)4]2+ nanocluster

2022

The use of metal nanoclusters is strongly reliant on their size and configuration; hence, studying the potential isomers of a cluster is extremely beneficial in understanding their performance. In general, the prediction and identification of isomer structures and their properties can be challenging and computationally expensive. Our work describes an investigation to find local isomers for the previously experimentally characterized small gold cluster [Au6(NHC-S)4]2+ protected by bidentate mixed carbene-thiolate ligands. We employ the molecular dynamics simulation method where the interatomic forces are calculated from density functional theory. We find several isomers that are more stable…

Dynamic Stabilization of the Ligand-Metal Interface in Atomically Precise Gold Nanoclusters Au68 and Au144 Protected by meta-Mercaptobenzoic Acid

2017

Ligand-stabilized, atomically precise gold nanoclusters with a metal core of a uniform size of just 1-3 nm constitute an interesting class of nanomaterials with versatile possibilities for applications due to their size-dependent properties and modifiable ligand layers. The key to extending the usability of the clusters in applications is to understand the chemical bonding in the ligand layer as a function of cluster size and ligand structure. Previously, it has been shown that monodispersed gold nanoclusters, stabilized by meta-mercaptobenzoic acid (m-MBA or 3-MBA) ligands and with sizes of 68-144 gold atoms, show ambient stability. Here we show that a combination of nuclear magnetic reson…

Dynamics of weak interactions in the ligand layer of meta-mercaptobenzoic acid protected gold nanoclusters Au68(m-MBA)32 and Au144(m-MBA)40

2020

Atomically precise metal nanoclusters, stabilized and functionalized by organic ligands, are emerging nanomaterials with potential applications in plasmonics, nano-electronics, bio-imaging, nanocatalysis, and as therapeutic agents or drug carriers in nanomedicine. The ligand layer has an important role in modifying the physico-chemical properties of the clusters and in defining the interactions between the clusters and the environment. While this role is well recognized from a great deal of experimental studies, there is very little theoretical information on dynamical processes within the layer itself. Here, we have performed extensive molecular dynamics simulations, with forces calculated…

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.

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…

Käytettävyys ja estetiikka www-sovellusten luottamusta herättävinä tekijöinä

2003

Elucidating the ligand shell structure and dynamics of Au683MBA32 gold nanocluster using molecular dynamics simulations

2017

Synthesising novel gold nanoparticles and -clusters can be often easier than characterising them, and after experimental analysis many options for the possible molecular formula of the cluster may remain as equally valid options. These options may be investigated by quantum computational means, such as density functional theory, but since DFT includes the electronic interactions, this might take time and excessive effort if the amount of options is large. In this thesis a new way of easing the computational task is introduced by a novel method, that combines a guessing algorithm and molecular dynamics simulations. The algorithm produces possible structures by utilising existing structures o…

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…

Oligopeptidipäällysteiset kultananopartikkelit lääketieteellisissä sovelluksissa

2016

Pro Gradu -tutkielmassa käsitellään oligopeptidipäällysteisten kultananopartikkeleiden sovelluksia lääketieteessä. Tutkielmassa käydään läpi kultananopartikkeleiden yleisiä ominaisuuksia sekä niiden soveltuvuutta biologisiin ja lääketieteellisiin sovelluksiin. Lisäksi esitellään yleisimmät kultananopartikkeleiden päällystyksessä käytettävät oligopeptidit ja kuvataan erityyppisille oligopeptidipäällysteisille kultananopartikkeleille kehiteltyjä lääketieteellisiä sovelluksia, joihin lukeutuvat muun muassa syöpähoito, biologinen kuvantaminen, kolorimetriset biomolekyylianalyysit ja lääkeaineiden kohdennettu kuljetus. Kokeellisessa osassa pyrittiin valmistamaan tiolifunktionalisoitu oligopeptid…