Algorithm based on the Thomson problem for determination of equilibrium structures of metal nanoclusters

2017 ◽  
Vol 146 (24) ◽  
pp. 244107 ◽  
Author(s):  
E. Arias ◽  
E. Florez ◽  
J. F. Pérez–Torres
Keyword(s):  
Metal Nanoclusters ◽  
Equilibrium Structures ◽  
Thomson Problem

scholarly journals How accurate is the determination of equilibrium structures for van der Waals complexes? The dimer N2O⋯CO as an example

2021 ◽  
Vol 154 (19) ◽  
pp. 194302
Author(s):  
Jean Demaison ◽  
Natalja Vogt ◽  
Yan Jin ◽  
Rizalina Tama Saragi ◽  
Marcos Juanes ◽  
...  
Keyword(s):  
Van Der Waals ◽  
Van Der Waals Complexes ◽  
Equilibrium Structures

scholarly journals Effect of Nobel Metal Ions on the Synthesis of Metal Nanoclusters for Selective Detection of Various Heavy Metals

2020 ◽  
Author(s):  
AMIT NAIN
Keyword(s):  
Metal Ions ◽  
Photoelectron Spectroscopy ◽  
Sea Water ◽  
Metal Nanoclusters ◽  
Average Life ◽  
Metal Core ◽  
X Ray ◽  
Metal Metal ◽  
Pl Quenching

In this study, effect of noble metal ions (Au, Ag and Cu) on the synthesis of metal nanoclusters (MNCs) have been investigated. Through heating at 70ºC, TSA/BSA–Au, –Ag and –Cu NCs were separately prepared from Au3+, Ag+ and Cu2+ respectively in the presence of bovine serum albumin (BSA) and thiosalicylic acid (TSA). They exhibit photoluminescence (PL) at 700, 624 and 430 nm, with an average life times of 1500, 100 and 11.71 ns, respectively, when excited at 350 nm. X–ray photoelectron spectroscopy (XPS) data support the presence of metal core (M0) and metal–thiolate shell (Mn–SRm) in each of the TSA/BSA–Metal nanoclusters (MNCs). Spectroscopic measurements reveal the formation of Au32–SR, Ag9–SR and (Cu4–Cu13)–SR species in the TSA/BSA–Au, –Ag and –Cu NCs respectively. Through PL quenching of the TSA/BSA–Au, –Ag and –Cu NCs, they have been used separately for quantitation of Hg2+, As3+ and Cr6+ , with linear ranges of 1400, 418, and 40400 nM and limits of detection (LODs) of 0.25, 2.34 and 3.54 nM, respectively. The PL quenching is mainly due to aggregation of the MNCs via metal–metal or metal–thiol interaction. The stable TSA/BSA–Au, –Ag and –Cu NCs have been employed separately for the determination of the concentrations of Hg2+, As3+ and Cr6+ ions in the spiked sea water samples, showing advantages of simplicity, rapidity, high selectivity, and sensitivity.

Rapid Determination of H2S Poisoning in a Forensic Study Using a Novel Fluorescence Assay Based on Zn/Cu@BSA Nanoclusters

2018 ◽  
Vol 71 (3) ◽  
pp. 142 ◽  
Author(s):  
Lagabaiyila Zha ◽  
Weicheng Duan ◽  
Di Wen ◽  
Yadong Guo ◽  
Jie Yan ◽  
...  
Keyword(s):  
Quantitative Determination ◽  
Limit Of Detection ◽  
Rapid Determination ◽  
Forensic Analysis ◽  
Gas Chromatography Mass Spectrometry ◽  
Metal Nanoclusters ◽  
Fluorescence Sensing ◽  
Blood Samples ◽  
H2s Poisoning

The quantitative determination of H2S in the blood can provide valid evidence for H2S poisoning through occupational exposure. However, known traditional methods for the detection of H2S in blood are time consuming, require complicated pretreatments, and have low sensitivity. In this paper, a new fluorescence sensing assay is proposed for the rapid detection of H2S poisoning in forensic cases based on bovine serum albumin (BSA)-stabilised zinc/copper (Zn/Cu) bi-metal nanoclusters (Zn/Cu@BSA NCs). The as-prepared Zn/Cu@BSA NCs probes have been characterised by UV-vis absorption and fluorescence spectroscopy. The fluorescence of Zn/Cu@BSA NCs can be quenched through specific interactions between HS−/S2− and the Zn2+/Cu2+ bi-metal ions. Under optimised conditions, the fluorescence sensing method was linear in the concentration range of 2.5 nM to 30 mM with 0.69 nM as the limit of detection. Moreover, the practical feasibility of this fluorescence sensing method has also been demonstrated by the analysis of mice blood samples containing different levels of sulfide and human blood samples from forensic cases of H2S poisoning. Compared with gas chromatography/mass spectrometry (GC/MS), this fluorescence sensing method is quite simple, straightforward, and can be accurate for the quantitative determination of H2S poisoning in a few minutes for forensic analysis. Overall, this is the first report of a bi-metal fluorescence sensing assay for detecting H2S poisoning directly in blood. This research may provide a new approach for forensic toxicologists to monitor poisoning by H2S using a fluorescence-sensing method.

scholarly journals Local Environment and Dynamic Behavior of Fluoride Anions in Silicogermanate Zeolites: A Computational Study of the AST Framework

2018 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Local Environment ◽  
Distribution Functions ◽  
Suitable Model ◽  
General Behaviour ◽  
Functional Theory ◽  
Molecular Dynamics Calculations ◽  
Equilibrium Structures

<p>In silicogermanate zeolites containing double four-ring (<i>d4r</i>) building units, the germanium atoms preferentially occupy the corners of these cube-like units. While this general behaviour is well known, the absence of long-range order precludes a determination of the preferred arrangements of Si and Ge atoms at the corners of <i>d4r</i> cages by means of crystallographic methods. If fluoride anions are present during the synthesis, these are incorporated into the <i>d4r</i> cages. Due to the sensitivity of the <sup>19</sup>F chemical shift to the local environment, NMR experiments can provide indirect insights into the predominant (Si,Ge) arrangements. However, conflicting interpretations have been reported, both with regard to the preference for, or avoidance of, Ge-O-Ge linkages, and concerning the equilibrium position of fluorine inside the cage, where fluorine might either occupy the cage centre or participate in a partly covalent Ge-F bond. In order to shed light on the energetically preferred local arrangements, periodic electronic structure calculations in the framework of dispersion-corrected density functional theory (DFT) were performed. The AST framework was used as a suitable model system, as this zeolite is synthetically accessible across the range of (Si<sub>1-n</sub>,Ge<sub>n</sub>)O<sub>2</sub> compositions (0 ≤ <i>n</i> ≤ 1). DFT structure optimisations for (Si,Ge)-AST systems containing fluoride anions and organic cations revealed that arrangements of Si and Ge at the cage vertices which maximise the number of Ge-O-Ge linkages are energetically preferred, and that fluorine tends to form relatively short (~2.2 to 2.4 Å) bonds to Ge atoms that are surrounded by Ge-O-Ge linkages. The preference for Ge-O-Ge linkages disappears in the absence of fluorine, pointing to a “templating” effect of the anions. In addition to the prediction of equilibrium structures, DFT-based Molecular Dynamics calculations were performed for selected AST models in order to analyse the dynamics of fluoride anions confined to <i>d4r</i> cages. These calculations showed that the freedom of movement of fluorine varies markedly depending on the local environment, and that it correlates with the average Ge-F distance (short Ge-F bonds = restricted motion). An analysis of the Ge-F radial distribution functions provided no evidence for a coexistence of separate local energy minima at the cage centre and in the proximity of a germanium atom for any of the systems considered. The computational approach pursued in this work provides important new insights into the local structure of silicogermanate zeolites with <i>d4r</i> units, enhancing the atomic-level understanding of these materials. In particular, the findings presented here constitute valuable complementary information that can aid the interpretation of experimental data.<i></i></p>

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