scholarly journals A universal signature in the melting of metallic nanoparticles

Nanoscale ◽  
2021 ◽  
Author(s):  
Laia Delgado-Callico ◽  
Kevin Rossi ◽  
Raphael Pinto-Miles ◽  
Pascal Salzbrenner ◽  
Francesca Baletto

We unveil a universal feature in the distribution of the atomic-pair distances that characterizes the melting of monometallic nanoparticles, in vacuum or in a strongly interacting environment, regardless of their size, shape, and composition.

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 146
Author(s):  
Daria V. Mamonova ◽  
Anna A. Vasileva ◽  
Yuri V. Petrov ◽  
Alexandra V. Koroleva ◽  
Denis V. Danilov ◽  
...  

Multimetallic plasmonic systems usually have distinct advantages over monometallic nanoparticles due to the peculiarity of the electronic structure appearing in advanced functionality systems, which is of great importance in a variety of applications including catalysis and sensing. Despite several reported techniques, the controllable synthesis of multimetallic plasmonic nanoparticles in soft conditions is still a challenge. Here, mono-, bi- and tri-metallic nanoparticles were successfully obtained as a result of a single step laser-induced deposition approach from monometallic commercially available precursors. The process of nanoparticles formation is starting with photodecomposition of the metal precursor resulting in nucleation and the following growth of the metal phase. The deposited nanoparticles were studied comprehensively with various experimental techniques such as SEM, TEM, EDX, XPS, and UV-VIS absorption spectroscopy. The size of monometallic nanoparticles is strongly dependent on the type of metal: 140–200 nm for Au, 40–60 nm for Ag, 2–3 nm for Pt. Bi- and trimetallic nanoparticles were core-shell structures representing monometallic crystallites surrounded by an alloy of respective metals. The formation of an alloy phase took place between monometallic nanocrystallites of different metals in course of their growth and agglomeration stage.


2020 ◽  
Vol 76 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Soham Banerjee ◽  
Chia-Hao Liu ◽  
Kirsten M. Ø. Jensen ◽  
Pavol Juhás ◽  
Jennifer D. Lee ◽  
...  

A novel approach for finding and evaluating structural models of small metallic nanoparticles is presented. Rather than fitting a single model with many degrees of freedom, libraries of clusters from multiple structural motifs are built algorithmically and individually refined against experimental pair distribution functions. Each cluster fit is highly constrained. The approach, called cluster-mining, returns all candidate structure models that are consistent with the data as measured by a goodness of fit. It is highly automated, easy to use, and yields models that are more physically realistic and result in better agreement to the data than models based on cubic close-packed crystallographic cores, often reported in the literature for metallic nanoparticles.


2020 ◽  
Vol 92 (2) ◽  
pp. 20101
Author(s):  
Behnam Kheyraddini Mousavi ◽  
Morteza Rezaei Talarposhti ◽  
Farshid Karbassian ◽  
Arash Kheyraddini Mousavi

Metal-assisted chemical etching (MACE) is applied for fabrication of silicon nanowires (SiNWs). We have shown the effect of amorphous sheath of SiNWs by treating the nanowires with SF6 and the resulting reduction of absorption bandwidth, i.e. making SiNWs semi-transparent in near-infrared (IR). For the first time, by treating the fabricated SiNWs with copper containing HF∕H2O2∕H2O solution, we have generated crystalline nanowires with broader light absorption spectrum, up to λ = 1 μm. Both the absorption and photo-luminescence (PL) of the SiNWs are observed from visible to IR wavelengths. It is found that the SiNWs have PL at visible and near Infrared wavelengths, which may infer presence of mechanisms such as forbidden gap transitions other can involvement of plasmonic resonances. Non-radiative recombination of excitons is one of the reasons behind absorption of SiNWs. Also, on the dielectric metal interface, the absorption mechanism can be due to plasmonic dissipation or plasmon-assisted generation of excitons in the indirect band-gap material. Comparison between nanowires with and without metallic nanoparticles has revealed the effect of nanoparticles on absorption enhancement. The broader near IR absorption, paves the way for applications like hyperthermia of cancer while the optical transition in near IR also facilitates harvesting electromagnetic energy at a broad spectrum from visible to IR.


2012 ◽  
Vol 9 (2) ◽  
pp. 1
Author(s):  
Asra Hosseini

From earliest cities to the present, spatial division into residential zones and neighbourhoods is the universal feature of urban areas. This study explored issue of measuring neighbourhoods through spatial autocorrelation method based on Moran's I index in respect of achieving to best neighbourhoods' model for forming cities smarter. The research carried out by selection of 35 neighbourhoods only within central part of traditional city of Kerman in Iran. The results illustrate, 75% of neighbourhoods' area in the inner city of Kerman had clustered pattern, and it shows reduction in Moran's index is associated with disproportional distribution of density and increasing in Moran's I and Z-score have monotonic relation with more dense areas and clustered pattern. It may be more efficient for urban planner to focus on spatial autocorrelation to foster neighbourhood cohesion rather than emphasis on suburban area. It is recommended characteristics of historic neighbourhoods can be successfully linked to redevelopment plans toward making city smarter, and also people's quality of life can be related to the way that neighbourhoods' patterns are defined. 


2012 ◽  
Vol 9 (2) ◽  
pp. 1
Author(s):  
Asra Hosseini

From earliest cities to the present, spatial division into residential zones and neighbourhoods is the universal feature ofurban areas. This study explored issue ofmeasuring neighbourhoods through spatial autocorrelation method based on Moran's I index in respect of achieving to best neighbourhoods' model for forming cities smarter. The research carried out by selection of 35 neighbourhoods only within central part of traditional city of Kerman in Iran. The results illustrate, 75% ofneighbourhoods, area in the inner city of Kerman had clustered pattern, and it shows reduction in Moran's index is associated with disproportional distribution of density and increasing in Moran's I and Z-score have monotonic relation with more dense areas and clustered pattern. It may be more efficient for urban planner to focus on spatial autocorrelation to foster neighbourhood cohesion rather than emphasis on suburban area. It is recommended characteristics of historic neighbourhoods can be successfully linked to redevelopment plans toward making city smarter, and also people's quality of life can be related to the way that neighbourhoods' patterns are defined.


2017 ◽  
Vol 13 (2) ◽  
pp. 4671-4677 ◽  
Author(s):  
A. M. Abdelghany ◽  
A.H. Oraby ◽  
Awatif A Hindi ◽  
Doaa M El-Nagar ◽  
Fathia S Alhakami

Bimetallic nanoparticles of silver (Ag) and gold (Au) were synthesized at room temperature using Curcumin. Reduction process of silver and gold ions with different molar ratios leads to production of different nanostructures including alloys and core-shells. Produced nanoparticles were characterized simultaneously with FTIR, UV/vis. spectroscopy, transmission electron microscopy (TEM), and Energy-dispersive X-ray (EDAX). UV/vis. optical absorption spectra of as synthesized nanoparticles reveals presence of surface palsmon resonance (SPR) of both silver at (425 nm) and gold at (540 nm) with small shift and broadness of gold band after mixing with resucing and capping agent in natural extract which suggest presence of bimetallic nano structure (Au/Ag). FTIR and EDAX data approve the presence of bimetallic nano structure combined with curcumin extract. TEM micrographs shows that silver and gold can be synthesized separately in the form of nano particles using curcumin extract. Synthesis of gold nano particles in presence of silver effectively enhance and control formation of bi-metallic structure.


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