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Clusters—between Atoms and Nanoparticles

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Nanochemistry".

Deadline for manuscript submissions: 30 November 2024 | Viewed by 1679

Special Issue Editor


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Guest Editor
Faculty of Non-Ferrous Metals, AGH University of Krakow, Al. A. Mickiewicza 30, 30-059 Krakow, Poland
Interests: nanoparticles; nanomaterielas; clusters; metalorganic; complexes; kinetics; catalyst; metal determination; separation
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Special Issue Information

Dear Colleagues,

In recent years, alongside metallic nanoparticles, a new trend related to the application of metal clusters has been observed. The growing interest in nanoclusters, and in particular, gold nanoclusters (AuNCs), is related to their unique molecule-like properties and the biocompatibility of AuNCs. The term “cluster” is defined as a small object consisting of several to 100 gold atoms with a total diameter below 2 nm. Contrary to particles with a larger size (>2 nm), AuNCs have no plasmon resonance effect. Moreover, AuNCs can be considered molecules due to the effects of quantum confinement, in which the conduction band is significantly quantized. Gold clusters containing a core size comparable to the Fermi wavelength of an electron, i.e., 5 Å, are characterized by fluorescence. This effect is observed as a result of light being absorbed of a certain energy, which excites electrons and causes them to move to higher energy levels. The consequence of this process is an energy release in the form of light, but with a lower energy than the length of light that causes excitation. Taking this into account, AuNCs absorb light in the wavelength range of 650 to 900 nm (this range is also called a therapeutic window of tissues), and they find application in, for example, cancer diagnostics. Despite the increasing number of publications on this topic, most of them focus on the application of gold nanoclusters in the context of fluorescence properties rather than kinetics and the mechanism of their formation. However, this basic knowledge can help us to comprehend in further detail the process of nanoparticle formation in complex forms, including clusters and small and larger particles.

Taking into account the above-mentioned aspects, this Special Issue welcome papers related to any aspect of metallic clusters, including those addressing the process of their formation, kinetic and mechanism studies, properties, and applications.

Dr. Magdalena Luty-Błocho
Guest Editor

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Keywords

  • metallic clusters
  • kinetic
  • mechanism of cluster formation
  • properties
  • applications

Published Papers (2 papers)

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17 pages, 5695 KiB  
Article
Synthesis of Gold Clusters and Nanoparticles Using Cinnamon Extract—A Mechanism and Kinetics Study
by Magdalena Luty-Błocho, Jowita Cyndrowska, Bogdan Rutkowski and Volker Hessel
Molecules 2024, 29(7), 1426; https://doi.org/10.3390/molecules29071426 - 22 Mar 2024
Viewed by 696
Abstract
In this work, UV-Vis spectrophotometry, High Resolution Scanning Transmission Electron Microscopes and selected experimental conditions were used to screen the colloidal system. The obtained results complement the established knowledge regarding the mechanism of nanoparticle formation. The process of gold nanoparticles formation involves a [...] Read more.
In this work, UV-Vis spectrophotometry, High Resolution Scanning Transmission Electron Microscopes and selected experimental conditions were used to screen the colloidal system. The obtained results complement the established knowledge regarding the mechanism of nanoparticle formation. The process of gold nanoparticles formation involves a two-step reduction of Au ions to Au(0); atom association and metastable cluster formation; autocatalytic cluster growth; ultra-small particle formation (1–2 nm, in diameter); particle growth and larger particles formation; and further autocatalytic crystal growth (D > 100 nm). As a reductant of Au(III) ions, a cinnamon extract was used. It was confirmed that eugenol as one of the cinnamon extract compounds is responsible for fast Au(III) ion reduction, whereas cinnamaldehyde acts as a gold-particle stabilizer. Spectrophotometry studies were carried out to track kinetic traces of gold nanoparticle (D > 2 nm) formation in the colloidal solution. Using the Watzky—Finke model, the rate constants of nucleation and autocatalytic growth were determined. Moreover, the values of energy, enthalpy and entropy of activation for stages related to the process of nanoparticle formation (Index 1 relates to nucleation, and Index 2 relates to the growth) were determined and found to be E1 = 70.6 kJ, E2 = 19.6 kJ, ΔH1 = 67.9 kJ/mol, ΔH2 = 17 kJ/mol, ΔS1 = −76.2 J/(K·mol), ΔS2 = −204.2 J/(K·mol), respectively. In this work the limitation of each technique (spectrophotometry vs. HRSTEM) as a complex tool to understand the dynamic of the colloidal system was discussed. Full article
(This article belongs to the Special Issue Clusters—between Atoms and Nanoparticles)
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11 pages, 3600 KiB  
Article
Au30(PiPr2nBu)12Cl6—An Open Cluster Provides Insight into the Influence of the Sterical Demand of the Phosphine Ligand in the Formation of Metalloid Gold Clusters
by Markus Strienz and Andreas Schnepf
Molecules 2024, 29(2), 286; https://doi.org/10.3390/molecules29020286 - 5 Jan 2024
Viewed by 776
Abstract
Phosphine-stabilized gold clusters are an important subgroup of metalloid gold cluster compounds and are important model compounds for nanoparticles. Although there are numerous gold clusters with different phosphine ligands, the effect of phosphine on cluster formation and structure remains unclear. While the linear [...] Read more.
Phosphine-stabilized gold clusters are an important subgroup of metalloid gold cluster compounds and are important model compounds for nanoparticles. Although there are numerous gold clusters with different phosphine ligands, the effect of phosphine on cluster formation and structure remains unclear. While the linear alkyl-substituted phosphine gold chlorides result in a Au32 cluster, the bulky tBu3P leads to a Au20 cluster. The reduction of (iPr2nBuP)AuCl, with the steric demand of the phosphine ligand between the mentioned phosphines, results in the successful synthesis and crystallization of a new metalloid gold cluster, Au30(PiPr2nBu)12Cl6. Its structure is similar to the Au32 cluster but with two missing AuCl units. The UV/Vis studies and quantum chemical calculations show the similarities between the two clusters and the influence of the phosphine ligand in the synthesis of metalloid gold clusters. Full article
(This article belongs to the Special Issue Clusters—between Atoms and Nanoparticles)
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