scholarly journals Impact of Metals on (Star)Dust Chemistry: A Laboratory Astrophysics Approach

2021 ◽  
Vol 8 ◽  
Author(s):  
Rémi Bérard ◽  
Kremena Makasheva ◽  
Karine Demyk ◽  
Aude Simon ◽  
Dianailys Nuñez Reyes ◽  
...  
Keyword(s):  
Metallic Nanoparticles ◽  
Density Functional ◽  
Plasma Reactor ◽  
Laboratory Astrophysics ◽  
Laser Vaporization ◽  
Metallic Silver ◽  
Laser Mass Spectrometry ◽  
Research Fields ◽  
Complex Chemistry ◽  
Silver Atoms

Laboratory experiments are essential in exploring the mechanisms involved in stardust formation. One key question is how a metal is incorporated into dust for an environment rich in elements involved in stardust formation (C, H, O, Si). To address experimentally this question we have used a radiofrequency cold plasma reactor in which cyclic organosilicon dust formation is observed. Metallic (silver) atoms were injected in the plasma during the dust nucleation phase to study their incorporation in the dust. The experiments show formation of silver nanoparticles (~15 nm) under conditions in which organosilicon dust of size 200 nm or less is grown. The presence of AgSiO bonds, revealed by infrared spectroscopy, suggests the presence of junctions between the metallic nanoparticles and the organosilicon dust. Even after annealing we could not conclude on the formation of silver silicates, emphasizing that most of silver is included in the metallic nanoparticles. The molecular analysis performed by laser mass spectrometry exhibits a complex chemistry leading to a variety of molecules including large hydrocarbons and organometallic species. In order to gain insights into the involved chemical molecular pathways, the reactivity of silver atoms/ions with acetylene was studied in a laser vaporization source. Key organometallic species, AgnC2Hm (n = 1–3; m = 0–2), were identified and their structures and energetic data computed using density functional theory. This allows us to propose that molecular Ag–C seeds promote the formation of Ag clusters but also catalyze hydrocarbon growth. Throughout the article, we show how the developed methodology can be used to characterize the incorporation of metal atoms both in the molecular and dust phases. The presence of silver species in the plasma was motivated by objectives finding their application in other research fields than astrochemistry. Still, the reported methodology is a demonstration laying down the ground for future studies on metals of astrophysical interest, such as iron.

Plasmonic resonances of nanoparticles from large-scale quantum mechanical simulations

2017 ◽  
Vol 31 (24) ◽  
pp. 1740003 ◽  
Author(s):  
Xu Zhang ◽  
Hongping Xiang ◽  
Mingliang Zhang ◽  
Gang Lu
Keyword(s):  
Density Functional Theory ◽  
Metallic Nanoparticles ◽  
Density Functional ◽  
Large Scale ◽  
Incident Light ◽  
Time Dependent ◽  
Coherent Motion ◽  
Quantum Mechanical ◽  
Functional Theory ◽  
Conduction Electrons

Plasmonic resonance of metallic nanoparticles results from coherent motion of its conduction electrons, driven by incident light. For the nanoparticles less than 10 nm in diameter, localized surface plasmonic resonances become sensitive to the quantum nature of the conduction electrons. Unfortunately, quantum mechanical simulations based on time-dependent Kohn–Sham density functional theory are computationally too expensive to tackle metal particles larger than 2 nm. Herein, we introduce the recently developed time-dependent orbital-free density functional theory (TD-OFDFT) approach which enables large-scale quantum mechanical simulations of plasmonic responses of metallic nanostructures. Using TD-OFDFT, we have performed quantum mechanical simulations to understand size-dependent plasmonic response of Na nanoparticles and plasmonic responses in Na nanoparticle dimers and trimers. An outlook of future development of the TD-OFDFT method is also presented.

scholarly journals Recent Advances in the Design and Photocatalytic Enhanced Performance of Gold Plasmonic Nanostructures Decorated with Non-Titania Based Semiconductor Hetero-Nanoarchitectures

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1459
Author(s):  
Jose I. Garcia-Peiro ◽  
Javier Bonet-Aleta ◽  
Carlos J. Bueno-Alejo ◽  
Jose L. Hueso
Keyword(s):  
Metallic Nanoparticles ◽  
Near Infrared ◽  
Environmental Chemistry ◽  
Gold Nanostructures ◽  
Plasmonic Nanostructures ◽  
Strong Impact ◽  
Metal Chalcogenides ◽  
Research Fields ◽  
Recent Advances ◽  
Crystallographic Facets

Plasmonic photocatalysts combining metallic nanoparticles and semiconductors have been aimed as versatile alternatives to drive light-assisted catalytic chemical reactions beyond the ultraviolet (UV) regions, and overcome one of the major drawbacks of the most exploited photocatalysts (TiO2 or ZnO). The strong size and morphology dependence of metallic nanostructures to tune their visible to near-infrared (vis-NIR) light harvesting capabilities has been combined with the design of a wide variety of architectures for the semiconductor supports to promote the selective activity of specific crystallographic facets. The search for efficient heterojunctions has been subjected to numerous studies, especially those involving gold nanostructures and titania semiconductors. In the present review, we paid special attention to the most recent advances in the design of gold-semiconductor hetero-nanostructures including emerging metal oxides such as cerium oxide or copper oxide (CeO2 or Cu2O) or metal chalcogenides such as copper sulfide or cadmium sulfides (CuS or CdS). These alternative hybrid materials were thoroughly built in past years to target research fields of strong impact, such as solar energy conversion, water splitting, environmental chemistry, or nanomedicine. Herein, we evaluate the influence of tuning the morphologies of the plasmonic gold nanostructures or the semiconductor interacting structures, and how these variations in geometry, either individual or combined, have a significant influence on the final photocatalytic performance.

New Coordination Architectures of Dithioether Ligand with Silver Salts: Effect of Anions on Complex Structures

2006 ◽  
Vol 59 (1) ◽  
pp. 34 ◽  
Author(s):  
Ya-Bo Xie ◽  
Jian-Rong Li ◽  
Xian-He Bu
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Chain Structure ◽  
X Ray Crystallography ◽  
Silver Salts ◽  
1D Chain ◽  
The Difference ◽  
A Chain ◽  
Dithioether Ligand ◽  
Silver Atoms

Reactions of a flexible dithioether ligand, 2,3-bis(5-methyl-1,3,4-thiadiazole-2-thiomethyl)quinoxaline (L), with AgX (X = ClO4ˉ or PF6ˉ) lead to the formation of two new one-dimensional (1D) silver(i) complexes: {[AgL](ClO4)}∞ 1 and {[Ag2L(CH3OH)](PF6)2(CH3OH)}∞ 2, which have been characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. Although 1 and 2 are synthesized under the same conditions, they take different structures due to the difference in anions in the silver salts. In 1, each ligand supplies three N-donors to bridge two silver atoms to result in a chain structure, and all silver atoms in the chain possess the same coordination geometry. In 2, each ligand gives six N-donors to coordinate to two silver atoms of different geometries, forming a 1D chain. The changes in counteranions affect the coordination mode of the ligand and the geometry of the Ag(i) centre, and consequently give rise to complexes with different structures. The coordination features of the ligand have also been primarily investigated through density functional theory calculations.

The Thermal Decomposition of Silver(I) Oxide

1960 ◽  
Vol 13 (4) ◽  
pp. 431 ◽  
Author(s):  
JA Allen
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Lattice Parameter ◽  
Activation Energies ◽  
Metallic Silver ◽  
Cent Oxygen ◽  
Total Oxygen ◽  
The Third ◽  
Limiting Value ◽  
Silver Atoms

The thermal decomposition of precipitated silver(I) oxide in a vacuum has been studied over the range 100-350 �C. Three regions are identified : in the fist, 100-200 �C, the activation energy is 30 kcal, 5 per cent. of the total oxygen is evolved, and the lattice parameter increases to a limiting value ; in the second, 200-300 �C, the activation energy is 50 kcal, and a further 1-2 per cent. oxygen is evolved; in the third, above 300 �C, metallic silver crystallizes, the oxide lattice contracts to a constant value, and the activation energy becomes 36 kcal. The activation energies in the three regions are interpreted as being associated, respectively, with (i) the diffusion of silver into the oxide lattice, (ii) the formation of aggregates of silver " atoms " not conforming to the normal silver lattice in an oxide lattice saturated with silver, and (iii) the reaction at the interface between metallic silver and the oxide.

Optical anisotropy and sign reversal in layer-by-layer assembled films from chiral nanoparticles

2016 ◽  
Vol 191 ◽  
pp. 141-157 ◽  
Author(s):  
Zhumei Liang ◽  
Kalil Bernardino ◽  
Jishu Han ◽  
Yunlong Zhou ◽  
Kai Sun ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
Metallic Nanoparticles ◽  
Density Functional ◽  
Structural Changes ◽  
Building Blocks ◽  
Layer By Layer ◽  
Semiconductor Films ◽  
Surface Ligands ◽  
Circular Dichroïsm

Chiral anisotropy and related optical effects at the nanoscale represent some of the most dynamic areas of nanomaterials today. Translation of optical activity of chiral semiconductor and metallic nanoparticles (NPs) into optoelectronic devices requires preparation of thin films from chiral NPs on both flat and curved surfaces. In this paper we demonstrate that chiral NP films can be made via layer-by-layer assembly (LBL) using negatively charged chiral CdS NPs, stabilized by d- and l-cysteine and positively charged polyelectrolytes, as building blocks. LBL coatings from NPs combine simplicity of preparation and strong optical activity. Circular extinction measurements using circular dichroism instruments indicate that the film possess four chiroptical bands at 280, 320, 350, and 390 nm. The latter two bands at 390 and 350 nm are associated with the band gap transitions (chiral excitons), while the former two are attributed to transitions involving surface ligands. When NPs are assembled in LBL films, the rotatory activity and the sign for circular extinction associated with the electronic transition in the inorganic core of the NPs is conserved. However, this is not true for circular extinction bands at short wavelengths: the sign of the rotatory optical activity is reversed. This effect is attributed to the change of the conformation of surface ligands in the polyelectrolyte matrix, which was confirmed both by semi-empirical and density functional (DFT) quantum mechanical calculations. Circular dichroism spectra calculated using a DFT algorithm closely match the experimental spectra of CdS NPs. These findings indicate that the spectroscopic methods sensitive to chirality of the surface ligands can be used to investigate fine structural changes in the surface layer of nanocolloids. Strong rotatory optical activity of nanostructured semiconductor films opens the possibilities for new polarization-based optical devices.

scholarly journals A Facile Strategy to Prepare Small Water Clusters via Interacting with Functional Molecules

2021 ◽  
Vol 22 (15) ◽  
pp. 8250
Author(s):  
Shanmeiyu Zhang ◽  
Yanyan Zhang ◽  
Chongchong Wu ◽  
Hui Yang ◽  
Qiqi Zhang ◽  
...  
Keyword(s):  
Density Functional ◽  
Md Simulation ◽  
Water Clusters ◽  
Sodium Dodecyl ◽  
Water System ◽  
Functional Theory ◽  
Small Water ◽  
Research Fields ◽  
Simulation Calculation ◽  
Oilfield Development

Although small water clusters (SWCs) are important in many research fields, efficient methods of preparing SWCs are still rarely reported, which is mainly due to the lack of related materials and understanding of the molecular interaction mechanisms. In this study, a series of functional molecules were added in water to obtain small water cluster systems. The decreasing rate of the half-peak width in a sodium dodecyl sulfate (SDS)–water system reaches ≈20% at 0.05 mM from 17O nuclear magnetic resonance (NMR) results. Based on density functional theory (DFT) and molecular dynamics (MD) simulation calculation, it can be concluded that functional molecules with stronger negative electrostatic potential (ESP) and higher hydrophilicity have a stronger ability to destroy big water clusters. Notably, the concentrations of our selected molecule systems are one to two magnitudes lower than that of previous reports. This study provides a promising way to optimize aqueous systems in various fields such as oilfield development, protein stability, and metal anti-corrosion.

scholarly journals Radiolytic Synthesis of Colloidal Silver Nanoparticles for Antibacterial Wound Dressings

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Pimpon Uttayarat ◽  
Jarurattana Eamsiri ◽  
Theeranan Tangthong ◽  
Phiriyatorn Suwanmala
Keyword(s):  
Silver Nanoparticles ◽  
Gamma Radiation ◽  
Metallic Nanoparticles ◽  
Antibacterial Properties ◽  
Wound Dressings ◽  
Poly Vinyl Alcohol ◽  
Metallic Silver ◽  
Colloidal Silver ◽  
Colloidal Silver Nanoparticles ◽  
Radiolytic Synthesis

Radiolytic synthesis provides a convenient and environmentally-friendly approach to prepare metallic nanoparticles in large scale with narrow size distribution. In this report, colloidal silver nanoparticles (AgNPs) were synthesized by gamma radiation using poly(vinyl alcohol) (PVA) or silk fibroin (SF) as stabilizers and were evaluated for their antibacterial properties. The conversion of metallic silver ions to silver atoms depended on irradiation dose and stabilizer concentration as determined by UV-Vis spectrophotometry and transmission electron microscopy. The uniformly dispersed AgNPs with diameter 32.3 ± 4.40 nm were evaluated as antiseptic agents in films composed of chitosan, SF, and PVA that were processed by irradiation-induced crosslinking. Using disc diffusion assay, the films containing 432 ppm AgNPs could effectively inhibit the growth of bothStaphylococcus aureusandPseudomonas aeruginosa. Therefore, we have demonstrated in our present study that gamma radiation technique can potentially be applied in the mass production of antibacterial wound dressings.

scholarly journals Oscillation in Excited State Lifetimes with Size of Sub-Nanometer Neutral (TiO2)n Clusters Observed with Ultrafast Pump-Probe Spectroscopy

2021 ◽  
Author(s):  
Jacob Garcia ◽  
Lauren Heald ◽  
ryan shaffer ◽  
Scott Sayres
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Laser Vaporization ◽  
Carrier Recombination ◽  
Electron Hole Pair ◽  
Excited State Lifetimes ◽  
Probe Spectroscopy

<div>Neutral titanium oxide clusters of up to 1 nm in diameter (TiO<sub>2</sub>)<sub>n</sub>, with n < 10, are produced in a laser vaporization source and subsequently ionized by a sequence of femtosecond laser pulses. Using 400 nm pump, 800 nm probe lasers, the excited state lifetimes of neutral (TiO<sub>2</sub>)<sub>n</sub> clusters are measured. All clusters exhibit a rapid relaxation lifetime of ~30 fs, followed by a sub-picosecond lifetime that we attribute to carrier recombination. The excited state lifetimes oscillate with size, with even numbered clusters possessing longer lifetimes. Density functional theory calculations show the excited state lifetimes are correlated with electron-hole pair localization or polaron-like formation in the excited states of neutral clusters. Thus, structural rigidity is suggested as a feature for extending excited state lifetimes in titania materials.</div>

scholarly journals Periodic DFT Calculations—Review of Applications in the Pharmaceutical Sciences

Pharmaceutics ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 415 ◽  
Author(s):  
Anna Helena Mazurek ◽  
Łukasz Szeleszczuk ◽  
Dariusz Maciej Pisklak
Keyword(s):  
Dft Calculations ◽  
Structure Prediction ◽  
Density Functional ◽  
Drug Analysis ◽  
Pharmaceutical Sciences ◽  
Pharmaceutical Ingredients ◽  
Complex Chemistry ◽  
Periodic Dft Calculations ◽  
Periodic Calculations ◽  
Periodic Dft

In the introduction to this review the complex chemistry of solid-state pharmaceutical compounds is summarized. It is also explained why the density functional theory (DFT) periodic calculations became recently so popular in studying the solid APIs (active pharmaceutical ingredients). Further, the most popular programs enabling DFT periodic calculations are presented and compared. Subsequently, on the large number of examples, the applications of such calculations in pharmaceutical sciences are discussed. The mentioned topics include, among others, validation of the experimentally obtained crystal structures and crystal structure prediction, insight into crystallization and solvation processes, development of new polymorph synthesis ways, and formulation techniques as well as application of the periodic DFT calculations in the drug analysis.

Degradation of Assembled Silicon Nanostructured Thin Films: a Theoretical and Experimental Study

2005 ◽  
Vol 887 ◽  
Author(s):  
Valeria Bertani ◽  
Luisa D'Urso ◽  
Alfio Alessandro Scalisi ◽  
Giuseppe Compagnini ◽  
Orazio Puglisi
Keyword(s):  
Density Functional ◽  
Silicon Nanoparticles ◽  
Near Infrared ◽  
Correlation Energy ◽  
Solid Phase ◽  
Laser Vaporization ◽  
Silicon Nanoclusters ◽  
Silicon Clusters ◽  
Flight Mass Spectrometry ◽  
Raman And Infrared Spectroscopy

ABSTRACTThe study of the structures and properties of small elemental clusters has been an extremely active area of current research, due to the peculiar behavior of these species halfway between that of single atoms and of the bulk phase. In this work silicon nanoclusters are generated by ablation of a high purity polycrystalline rod with a pulsed laser vaporization source and then deposited on a support. Their structure is studied both in the gas phase by means of Time of Flight Mass Spectrometry and in the solid phase through in situ Raman and Infrared Spectroscopy. The spectra reveal that the as deposited clusters are hydrogenated with negligible amount of oxide. Degradation of silicon nanoclusters has been studied after gas exposure. In the gas of air a consistent modification was observed, leading to a near-infrared luminescent silicon nanoparticles. In the second part of the work, density functional theory is applied to investigate the geometrical structure of silicon clusters and their interaction, in term of structure and energy, with different gases. The calculations were performed with the Gaussian 03 program suite, adopting the B3LYP functional to calculate the exchange and correlation energy. Si8 has been chosen as model cluster to study the degradation of silicon clusters both kinetically and thermodynamically, in order to explain the experimental evidences. Experimental and calculated infrared spectra are compared.

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