Search results for "Note"

Surface Nanophysics: Macro-, Meso-, Micro- and Nano-approaches

2017

The surface factor is very important for manipulating objects at a nanoscale. Thermodynamic behaviour is observed from the classical point of view, and conditional division into macro-, meso-, micro- and nano-approaches is presented. Processes of physical and chemical adsorption on the surface are presented from the energy and structure aspects. The occurrence of electronic states of the surface is presented from the classical point of view in comparison with molecular electronic states. One of the most important non-invasive optical methods to investigate nanoparticles is the surface plasmon resonance (SPR), which is quite useful for practical detection of nanoparticles in the surrounding …

Electrical Transport and Confocal Raman Studies of Electrochemically Modified Individual Carbon Nanotubes

2003

Towards Controlled Synthesis of Water-Soluble Gold Nanoclusters : Synthesis and Analysis

2019

Water-soluble gold nanoclusters with well-defined molecular structures and stability possess particular biophysical properties making them excellent candidates for biological applications as well as for fundamental spectroscopic studies. The currently existing synthetic protocols for atomically monodisperse thiolate-protected gold nanoclusters (AuMPCs) have been widely expanded with organothiolates, yet the direct synthesis reports for water-soluble AuMPCs are still deficient. Here, we demonstrate a wet-chemistry pH-controlled synthesis of two large water-soluble nanoclusters utilizing p-mercaptobenzoic acid (pMBA), affording different sizes of plasmonic AuMPCs on the preparative scale (∼7 …

A route to simple nonionic surfactants

2016

AbstractA method for the synthesis of nonionic surfactants – N-alkyl-O-(2-hydroxyethyl) carbamates is proposed by acylation of fatty amines with ethylene carbonate without any solvent or catalyst. The surface tension of the prepared surfactants was measured, toxicity and biodegradability were determined for the surfactant with n-dodecyl as a hydrophobic group and N-monosubstituted amide and hydroxyl groups for their hydrophilic part.

Dyes of a Shadow Theatre: Investigating Tholu Bommalu Indian Puppets through a Highly Sensitive Multi-Spectroscopic Approach

2021

Tholu Bommalu are typical leather puppets of the traditional Indian shadow theatre. Two of these objects are part of a collection in the International Puppets Museum “Antonio Pasqualino” (Palermo, Sicily, Italy), which can count on one hundred-seventy-three of artifacts. These Indian puppets were investigated to obtain information related to the use of dyes for their manufacturing through a multi-technical approach exploiting the combination of highly sensitive spectroscopic techniques. Wet cotton stubbons were used to entrap small particles of dyes on the fibers from the art objects for the consequent analyses. Visible Light Micro-Reflectance spectroscopy was employed for the preliminary i…

High speed microfluidic prototyping by programmable proximity aperture MeV ion beam lithography

2013

Abstract Microfluidics refers to the science and technology for controlling and manipulating fluids that flow along microchannels. For the development of complex prototypes, many microfluidic test structures are required first. Normally, these devices are fabricated via photolithography. This technique requires a photomask for transferring a pattern to photoresists by exposing with UV light. However, this method can be slow when a new structure is required to change. This is because a series of photomasks are needed, which is time consuming and costly. Here, we present a programmable proximity aperture lithography (PPAL) technique for the development of microfluidic prototype in poly(methyl…

Isophorone on Au/MgO/Ag(001) : Physisorption with Electrostatic Site Selection

2017

We report a computational study of isophorone C9H14O adsorption on a Ag(001)-supported ultrathin MgO film with Au adatoms and clusters employing density functional theory calculations. The calculations show that the keto form of isophorone is more stable than the enol tautomers both in gas phase and on the MgO/Ag(001) surface. The interaction between the keto isophorone and step and terrace sites of MgO/Ag(001) displays long interaction distances, relatively weakly exothermic adsorption energies, lack of charge transfer, and minor changes in the density of states, all of which indicate that the molecule merely physisorbs on the surface. The step sites are energetically preferred adsorption …

Jahn–Teller effects in Au25(SR)18

2016

The relationship between oxidation state, structure, and magnetism in many molecules is well described by first-order Jahn–Teller distortions. This relationship is not yet well defined for ligated nanoclusters and nanoparticles, especially the nano-technologically relevant gold-thiolate protected metal clusters. Here we interrogate the relationships between structure, magnetism, and oxidation state for the three stable oxidation states, −1, 0 and +1 of the thiolate protected nanocluster Au25(SR)18. We present the single crystal X-ray structures of the previously undetermined charge state Au25(SR)18+1, as well as a higher quality single crystal structure of the neutral compound Au25(SR)180. …

A Unified AMBER-Compatible Molecular Mechanics Force Field for Thiolate-Protected Gold Nanoclusters.

2016

We present transferable AMBER-compatible force field parameters for thiolate-protected gold nanoclusters. Five different sized clusters containing both organo-soluble and water-soluble thiolate ligands served as test systems in MD simulations, and parameters were validated against DFT and experimental results. The cluster geometries remain intact during the MD simulations in various solvents, and structural fluctuations and energetics showed agreement with DFT calculations. Experimental diffusion coefficients and crystal structures were also reproduced with sufficient accuracy. The presented parameter set contains the minimum number of cluster-specific parameters enabling the use of these p…

Symmetry breaking in ligand-protected gold clusters probed by nonlinear optics

2016

The first hyperpolarizabilities of [Au25(SR)18](-1/0) and Au38(SR)24 clusters were determined by Hyper-Rayleigh Scattering. A strong dependence on the molecular symmetry was observed, and we explore two strategies to destroy the center of inversion in [Au25(SR)18](-1/0), protection by chiral ligands and alloying of the cluster with silver. This may open new avenues to applications of Au : SR clusters in second-order nonlinear optics.