Search results for "Nanoclusters"
showing 10 items of 164 documents
Structural and Theoretical Basis for Ligand Exchange on Thiolate Monolayer Protected Gold Nanoclusters
2012
Ligand exchange reactions are widely used for imparting new functionality on or integrating nanoparticles into devices. Thiolate-for-thiolate ligand exchange in monolayer protected gold nanoclusters has been used for over a decade; however, a firm structural basis of this reaction has been lacking. Herein, we present the first single-crystal X-ray structure of a partially exchanged Au(102)(p-MBA)(40)(p-BBT)(4) (p-MBA = para-mercaptobenzoic acid, p-BBT = para-bromobenzene thiol) with p-BBT as the incoming ligand. The crystal structure shows that 2 of the 22 symmetry-unique p-MBA ligand sites are partially exchanged to p-BBT under the initial fast kinetics in a 5 min timescale exchange reacti…
All-thiol-stabilized Ag44 and Au12Ag32 nanoparticles with single-crystal structures
2013
Noble metal nanoparticles stabilized by organic ligands are important for applications in assembly, site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, molecular recognition and molecular electronics, and catalysis. Here we report crystal structures and theoretical analysis of three Ag44(SR)30 and three Au12Ag32(SR)30 intermetallic nanoclusters stabilized with fluorinated arylthiols (SR=SPhF, SPhF2 or SPhCF3). The nanocluster forms a Keplerate solid of concentric icosahedral and dodecahedral atom shells, protected by six Ag2(SR)5 units. Positive counterions in the crystal indicate a high negative charge of 4(-) per nanoparticle, and density functional theory…
Metal Doping of Au25(SR)18- Clusters : Insights and Hindsights
2019
The structure, properties, and applications of atomically precise gold nanoclusters are the object of active research worldwide. Over the last few years, research has been also focusing on selective doping of metal nanoclusters through introduction of foreign-metal atoms. Doping has been studied for several clusters, especially the atomically precise Au25(SR)18. Doping has been carried out with noble metals, such as platinum, and less noble metals, such as cadmium and mercury, also because of the ease by which monodoping can be achieved with these metals. Previous studies, which relied extensively on the use of mass spectrometry and single crystal X-ray crystallography, led to assign the sp…
Nanostructuring thin Au films on transparent conductive oxide substrates
2013
Fabrication processes of Au nanostructures on indium-tin-oxide (ITO) surface by simple, versatile, and low-cost bottom-up methodologies are investigated in this work. A first methodology exploits the patterning effects induced by nanosecond laser irradiations on thin Au films deposited on ITO surface. We show that after the laser irradiations, the Au film break-up into nanoclusters whose mean size and surface density are tunable by the laser fluence. A second methodology exploits, instead, the patterning effects of standard furnace thermal processes on the Au film deposited on the ITO. We observe, in this case, a peculiar shape evolution from pre-formed nanoclusters during the Au deposition…
Role of Ge nanoclusters in the performance of photodetectors compatible with Si technology
2013
In this work, we investigate the spectral response of metal-oxide- semiconductor photodetectors based on Ge nanoclusters (NCs) embedded in a silicon dioxide (SiO2) matrix. The role of Ge NC size and density on the spectral response was evaluated by comparing the performance of PDs based on either densely packed arrays of 2 nm-diameter NCs or a more sparse array of 8 nm-diameter Ge NCs. Our Ge NC photodetectors exhibit a high spectral responsivity in the 500-1000 nm range with internal quantum efficiency of ~ 700% at - 10 V, and with NC array parameters such as NC density and size playing a crucial role in the photoconductive gain and response time. We find that the configuration with a more…
One‐Pot Synthesis of Superparamagnetic CoO‐MCM‐41 Nanocomposites with Uniform and Highly Dispersed Magnetic Nanoclusters
2004
Superparamagnetic CoO-MCM-41 mesoporous nanocomposites, with variable cobalt amounts, in the form of well-dispersed CoO-like clusters, were prepared in a large compositional range by a one-step reproducible procedure employing co-hydrolysis and co-condensation of the inorganic precursors in a water/triethanolamine medium. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Ligand-Protected Gold Nanoclusters as Superatoms—Insights from Theory and Computations
2012
Abstract Gold clusters and nanoparticles, stabilized by various ligands, exhibit a rich array of interesting and important electronic, optical, chemical and catalytic properties. Many particles can now be synthesized by wet chemistry, and they can be handled as normal chemicals: stored, modified and functionalized for applications in medical therapy, biolabelling, sensing, nanoelectronics and catalysis. In recent years, understanding of the stability, surface chemistry and functionalization of these interesting building blocks of nano-matter has taken a quantum leap. This is facilitated by simultaneous breakthroughs in experimental and theoretical fronts concerning accurate structural deter…
Room-temperature efficient light detection by amorphous Ge quantum wells
2013
In this work, ultrathin amorphous Ge films (2 to 30 nm in thickness) embedded in SiO2 layers were grown by magnetron sputtering and employed as proficient light sensitizer in photodetector devices. A noteworthy modification of the visible photon absorption is evidenced due to quantum confinement effects which cause both a blueshift (from 0.8 to 1.8 eV) in the bandgap and an enhancement (up to three times) in the optical oscillator strength of confined carriers. The reported quantum confinement effects have been exploited to enhance light detection by Ge quantum wells, as demonstrated by photodetectors with an internal quantum efficiency of 70%. © 2013 Cosentino et al.
Surface Coordination of Multiple Ligands Endows N‐Heterocyclic Carbene‐Stabilized Gold Nanoclusters with High Robustness and Surface Reactivity
2020
Deciphering the molecular pictures of the multi-component and non-periodic organic-inorganic interlayer is a grand technical challenge. Here we show that the atomic arrangement of hybrid surface ligands on metal nanoparticles can be precisely quantified through comprehensive characterization of a novel gold cluster, Au 44 ( i Pr 2 -bimy) 9 (PA) 6 Br 8 , which features three types of ligands, namely, carbene (1,3-diisopropylbenzimidazolin-2-ylidene, i Pr 2 -bimy), alkynyl (phenylacetylide, PA), and halide (Br), respectively. The delicately balanced stereochemical effects and bonding capabilities of the three ligands give rise to peculiar geometrical and electronic structures. Remarkably, des…
CNT Arrays Grown upon Catalytic Nickel Particles as Applied in the Nanoelectronic Devices: Ab Initio Simulation of Growth Mechanism
2012
Carbon nanotubes, due to their exceptional and unique properties, have aroused a lot of research interest making them promising candidates as interconnects for future high-speed nanoelectronics. To predict a growth mechanism for carbon nanotubes (CNTs) upon a metal particle as synthesized in the porous membrane block then incorporated in the nanoelectronic device, we have performed a series of large-scale DFT-LCAO calculations using the CRYSTAL-06 code. Carbon adatoms can appear upon the densely-packed Ni(111) catalyst surface due to dissociation of hydrocarbon molecules (e.g., CH4) when applying the CVD method for the nanotube growth. We have started with adsorption properties of carbon at…