Superstructures and SERS Properties of Gold Nanocrystals with Different Shapes

2011 ◽  
Vol 50 (7) ◽  
pp. 1593-1596 ◽  
Author(s):  
Zhening Zhu ◽  
Haifeng Meng ◽  
Wenjing Liu ◽  
Xinfeng Liu ◽  
Jianxiao Gong ◽  
...  
Keyword(s):  
Gold Nanocrystals ◽  
Different Shapes

scholarly journals Covalently capped seed-mediated growth: a unique approach toward hierarchical growth of gold nanocrystals

Nanoscale ◽  
2014 ◽  
Vol 6 (12) ◽  
pp. 6478-6481 ◽  
Author(s):  
Youju Huang ◽  
Anirban Dandapat ◽  
Dong-Hwan Kim
Keyword(s):  
Gold Nanostructures ◽  
Gold Nanocrystals ◽  
Unique Approach ◽  
Different Shapes ◽  
Seed Mediated ◽  
Growth Approach

A new 600 dpi in TIF format)??>method is proposed for synthesizing hierarchical gold nanostructures in different shapes using the covalently capped seed-mediated growth approach.

Superstructures and SERS Properties of Gold Nanocrystals with Different Shapes

2011 ◽  
Vol 123 (7) ◽  
pp. 1631-1634 ◽  
Author(s):  
Zhening Zhu ◽  
Haifeng Meng ◽  
Wenjing Liu ◽  
Xinfeng Liu ◽  
Jianxiao Gong ◽  
...  
Keyword(s):  
Gold Nanocrystals ◽  
Different Shapes

In Situ Synthesis of Shape-Selective Gold Nanocrystals Using Oligopeptide Template: Effect of Various Reaction Parameters

2008 ◽  
Vol 8 (11) ◽  
pp. 5934-5941 ◽  
Author(s):  
Satyabrata Si ◽  
Enakshi Dinda ◽  
Tarun K. Mandal
Keyword(s):  
Tryptophan Residue ◽  
Amino Group ◽  
X Ray Diffraction ◽  
Gold Nanocrystals ◽  
C Terminus ◽  
Transmission Electron ◽  
Redox Active ◽  
Shape Selective ◽  
Different Shapes

An oligopeptide with a free amino group at the N-terminus and a redox active tryptophan residue at the C-terminus was used to synthesize gold nanocrystals of different shapes. The concentration ratio of peptide to HAuCl4 has a significant effect on the shape of the formed nanocrystals and the polyhedral gold nanocrystals are mainly formed at higher such ratio. The effect of medium pH and reaction temperature on the shape of the formed gold nanocrystals has also been investigated. However, an oligopeptide with blocked amino group with tert-butyloxycarbonyl group resulted only spherical gold nanocrystals along with some aggregated structures. A probable mechanism for the formation of polyhedral gold nanocrystals has been described, which indicate the presence of multiple anchoring sites in the peptide molecules is mainly responsible for this type of crystal growth. The formed nanocrystals were well characterized by various experimental techniques like, UV-visible spectroscopy, transmission electron microscopy, and X-ray diffraction.

Structural phenomena in the growth of carbon nanotubes

1993 ◽  
Vol 51 ◽  
pp. 750-751
Author(s):  
Jun Jiao
Keyword(s):  
Carbon Nanotubes ◽  
Growth Mechanism ◽  
Carbonaceous Material ◽  
Cluster Growth ◽  
Structural Elements ◽  
Rich Variety ◽  
Different Shapes ◽  
Point To Point

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.

Elucidating the Weakly Reversible Cs-Pb-Br Perovskite Nanocrystal Reaction Network with High-Throughput Maps and Transformations

2020 ◽  
Author(s):  
Jakob Dahl ◽  
Xingzhi Wang ◽  
Xiao Huang ◽  
Emory Chan ◽  
Paul Alivisatos
Keyword(s):  
High Throughput ◽  
Dynamic Equilibrium ◽  
Reaction Network ◽  
Substantial Impact ◽  
Equilibrium Behavior ◽  
Automated Method ◽  
Lead Bromide ◽  
Different Shapes ◽  
Complex Chemistry ◽  
Lead Halide

<p>Advances in automation and data analytics can aid exploration of the complex chemistry of nanoparticles. Lead halide perovskite colloidal nanocrystals provide an interesting proving ground: there are reports of many different phases and transformations, which has made it hard to form a coherent conceptual framework for their controlled formation through traditional methods. In this work, we systematically explore the portion of Cs-Pb-Br synthesis space in which many optically distinguishable species are formed using high-throughput robotic synthesis to understand their formation reactions. We deploy an automated method that allows us to determine the relative amount of absorbance that can be attributed to each species in order to create maps of the synthetic space. These in turn facilitate improved understanding of the interplay between kinetic and thermodynamic factors that underlie which combination of species are likely to be prevalent under a given set of conditions. Based on these maps, we test potential transformation routes between perovskite nanocrystals of different shapes and phases. We find that shape is determined kinetically, but many reactions between different phases show equilibrium behavior. We demonstrate a dynamic equilibrium between complexes, monolayers and nanocrystals of lead bromide, with substantial impact on the reaction outcomes. This allows us to construct a chemical reaction network that qualitatively explains our results as well as previous reports and can serve as a guide for those seeking to prepare a particular composition and shape. </p>

The Formability and Elongation of Aluminum Alloys AA5083 and AA3003 for Micro-Truss Sandwiches Manufacturing

2020 ◽  
Vol 38 (9A) ◽  
pp. 1396-1405
Author(s):  
Arwa F. Tawfeeq ◽  
Matthew R. Barnett
Keyword(s):  
Aluminum Alloy ◽  
Strain Rate ◽  
Cost Effective ◽  
Tensile Tests ◽  
Truss Structures ◽  
High Quality ◽  
Trade Off ◽  
Clad Layer ◽  
Higher Temperature ◽  
Different Shapes

The development in the manufacturing of micro-truss structures has demonstrated the effectiveness of brazing for assembling these sandwiches, which opens new opportunities for cost-effective and high-quality truss manufacturing. An evolving idea in micro-truss manufacturing is the possibility of forming these structures in different shapes with the aid of elevated temperature. This work investigates the formability and elongation of aluminum alloy sheets typically used for micro-truss manufacturing, namely AA5083 and AA3003. Tensile tests were performed at a temperature in the range of 25-500 ○C and strain rate in the range of 2x10-4 -10-2 s-1. The results showed that the clad layer in AA3003 exhibited an insignificant effect on the formability and elongation of AA3003. The formability of the two alloys was improved significantly with values of m as high as 0.4 and 0.13 for AA5083 and AA3003 at 500 °C. While the elongation of both AA5083 and AA3003 was improved at a higher temperature, the elongation of AA5083 was inversely related to strain rate. It was concluded that the higher the temperature is the better the formability and elongation of the two alloys but at the expense of work hardening. This suggests a trade-off situation between formability and strength. 

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