scholarly journals Investigation of thermal conductivity property of plasmonic nanofluids based on gold nanorods prepared by seed-mediated growth method

2019 ◽  
Vol 2 (22) ◽  
pp. 119-133
Author(s):  
Mahsa Mohammadzadeh ◽  
Mohsen Ashjari ◽  
Davoud Zare
Keyword(s):  
Thermal Conductivity ◽  
Aspect Ratio ◽  
Gold Nanorods ◽  
Thermal Conductivity Coefficient ◽  
Volume Fraction ◽  
Effect Of Temperature ◽  
Basic Fluid ◽  
Vis Spectroscopy ◽  
Growth Method ◽  
Seed Mediated

In this paper, nanofluids were prepared based on gold nanorods in basic fluid, water, by single-stage chemical reduction and in different volume fractions and the used gold nanorods were synthesized by seed-mediated growth method in different dimensional ratios. The properties of the prepared nanoparticles, including crystalline size, aspect ratio, surface properties, nanoparticle purity, shape and morphology of nanostructures were investigated using x-ray diffraction, UV-vis spectroscopy, FT-IR, and transmitted electron microscopy. The effect of changing parameters of Nano rod dimensions, changes in Nano rod volume fraction in water and also the effect of temperature on the nanofluid thermal conductivity coefficient were investigated using transient hot wire method. The results showed that reducing the aspect ratio, increasing the volume fraction and increasing the temperature increase the thermal conductivity. In fact, results show that an increase in the nanorods aspect ratio with a constant volume fraction of 1:50 of gold in water nanorod and at room temperature leads to a decrease in the thermal conductivity of the nanofluid. Also, increasing the two parameters of volume fraction and temperature significantly increases the thermal conductivity coefficient.

Effect of aspect ratio on the chirality of gold nanorods prepared through conventional seed-mediated growth method

2021 ◽  
Vol 1152 ◽  
pp. 338277
Author(s):  
Xiaojuan Zhou ◽  
Qiang Liu ◽  
Xiaoyu Shi ◽  
Chunli Xu ◽  
Baoxin Li
Keyword(s):  
Aspect Ratio ◽  
Gold Nanorods ◽  
Growth Method ◽  
Seed Mediated

Effects of Variable Viscosity and Thermal Conductivity of CuO-Water Nanofluid on Heat Transfer Enhancement in Natural Convection: Mathematical Model and Simulation

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Eiyad Abu-Nada
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Cylinder Surface ◽  
Transfer Enhancement

Heat transfer enhancement in horizontal annuli using variable thermal conductivity and variable viscosity of CuO-water nanofluid is investigated numerically. The base case of simulation used thermal conductivity and viscosity data that consider temperature property dependence and nanoparticle size. It was observed that for Ra≥104, the average Nusselt number was deteriorated by increasing the volume fraction of nanoparticles. However, for Ra=103, the average Nusselt number enhancement depends on aspect ratio of the annulus as well as volume fraction of nanoparticles. Also, for Ra=103, the average Nusselt number was less sensitive to volume fraction of nanoparticles at high aspect ratio and the average Nusselt number increased by increasing the volume fraction of nanoaprticles for aspect ratios ≤0.4. For Ra≥104, the Nusselt number was deteriorated everywhere around the cylinder surface especially at high aspect ratio. However, this reduction is only restricted to certain regions around the cylinder surface for Ra=103. For Ra≥104, the Maxwell–Garnett and the Chon et al. conductivity models demonstrated similar results. But, there was a deviation in the prediction at Ra=103 and this deviation becomes more significant at high volume fraction of nanoparticles. The Nguyen et al. data and the Brinkman model give completely different predictions for Ra≥104, where the difference in prediction of the Nusselt number reached 50%. However, this difference was less than 10% at Ra=103.

scholarly journals Investigation on the Effect of Centrifugation Speed on the Shape Separation of Gold Nanorods

2018 ◽  
Vol 7 (4.30) ◽  
pp. 330 ◽  
Author(s):  
Caessandra Addine Minun ◽  
Nur Zehan An’Nisa ◽  
Marlia Morsin ◽  
Nur Liyana Razali ◽  
Suratun Nafisah ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Gold Nanorods ◽  
Localized Surface Plasmon Resonance ◽  
Crystal Orientation ◽  
Surface Density ◽  
Morphological Analysis ◽  
Localized Surface Plasmon ◽  
Plasmon Peak ◽  
Sensing Material ◽  
Growth Method

High-quality gold nanorods (AuNRs) with a uniform aspect ratio and sizes are crucial for applications in biomedical or sensor industry. AuNRs is implementing Localized Surface Plasmon Resonance (LSPR) as sensing method which is highly dependent on the size, separation of nanoparticles, aspect ratio and the shape of the nanoparticles. Thus, in this process, the shape, surface density and aspect ratio of AuNRs were investigated to be used further as LSPR sensing material. The AuNRs was prepared using Seed Mediated Growth Method (SMGM) and the growth solution of the AuNRs was centrifuged with the speed ranging from 2500 rpm to 5000 rpm to separate the particles shaper prior to deposition as thin film. The XRD result shows the peak at 2θ = 38º which shows the (111) crystal orientation of the AuNRs. There are also two distinct peaks formed at the absorption spectra graph obtained from the UV-Vis result which associated with transverse plasmon peak (t-LSPR) and longitudinal plasmon peak (l-LSPR). The t-LSPR peak is significantly smaller than the l-LSPR and located in the wavelength ranges from 500 nm to 560 nm whereas the l-LSPR of the AuNRs shows a stronger and a higher peak which is located in the wavelength ranges from 700 nm to 780 nm. The morphological analysis using FESEM shows that the higher centrifugation speed separates the AuNRs with higher aspect ratio and higher surface density.

scholarly journals Two-step synthesis of high aspect ratio gold nanorods

2006 ◽  
Vol 4 (1) ◽  
pp. 160-165 ◽  
Author(s):  
Tom Mortier ◽  
André Persoons ◽  
Thierry Verbiest
Keyword(s):  
Aspect Ratio ◽  
Gold Nanorods ◽  
High Aspect Ratio ◽  
Cetyltrimethylammonium Bromide ◽  
Surfactant Concentration ◽  
Synthetic Method ◽  
Aspect Ratios ◽  
Seed Mediated

AbstractWe describe a very simple, two-step synthetic method to prepare gold nanorods with extremely high aspect ratios (> 20) and average lengths of more than 1000 nm. The method is based on a seed-mediated growth in presence of the surfactant cetyltrimethylammonium bromide. The length and aspect ratios of the nanorods can be manipulated by varying the surfactant concentration.

A Numerical Technique for Computing Effective Thermal Conductivity of Fluid-Particle Mixtures

2004 ◽  
Author(s):  
Satish Kumar ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Aspect Ratio ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Numerical Technique ◽  
Fluid Particle ◽  
Finite Volume Scheme ◽  
Ratio Distribution ◽  
Periodic Arrays

Periodic arrays of particles, foams, and other structures impregnated with a static fluid play an important role in heat transfer enhancement. In this paper, we develop a numerical method for computing conduction heat transfer in periodic beds by exploiting the periodicity of heat flux and the resulting linear variation of mean temperature. The numerical technique is developed within the framework of an unstructured finite volume scheme in order to enable the computation of effective thermal conductivity for complex fluid-particle arrangements. The method is applied to the computation of effective thermal conductivity of ordered as well as random beds of spheres and rods. The effect of varying surface area, aspect ratio, volume fraction, orientation, and distribution is studied for various solid-to-fluid conductivity ratios. Unlike classical theories which predict only a dependence on volume fraction, these direct simulations show that aspect ratio, distribution, and alignment of particles have an important influence on the effective thermal conductivity of the bed.

scholarly journals Seed-Mediated Growth of Gold Nanorods: Limits of Length to Diameter Ratio Control

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Christopher J. Ward ◽  
Robert Tronndorf ◽  
Alicia S. Eustes ◽  
Maria L. Auad ◽  
Edward W. Davis
Keyword(s):  
Ascorbic Acid ◽  
Aspect Ratio ◽  
Gold Nanorods ◽  
Reducing Agent ◽  
Gold Content ◽  
Reaction Conditions ◽  
Growth Solution ◽  
Transmission Electron ◽  
Seed Mediated

The effects of the seed reaction conditions on the two-step seed-mediated growth of gold nanorods and the effect of gold and reducing agent content in the growth solution were evaluated. Results indicate that the reaction conditions used to produce the seeds have a significant impact on the aspect ratio of the gold nanorods produced. Increasing the concentration of gold or the reaction temperature in the seed production step results in lower length to diameter (aspect ratio) gold rods. In addition, the amount of prepared seed added to the growth solution impacts the rod aspect ratio, with increasing amounts of seed reducing the aspect ratio. The effects of reducing agent, ascorbic acid (AA), and gold content of the growth solution on the aspect ratio of the produced rods are strongly interrelated. There exists a minimum ascorbic acid to gold concentration below which rods will not form; however, increasing the ratio above this minimum results in shorter rods being formed. Characterization of nanorod growth is performed by UV-vis-NIR spectrophotometry and transmission electron microscopy (TEM).

Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method

2003 ◽  
Vol 15 (10) ◽  
pp. 1957-1962 ◽  
Author(s):  
Babak Nikoobakht ◽  
Mostafa A. El-Sayed
Keyword(s):  
Growth Mechanism ◽  
Gold Nanorods ◽  
Growth Method ◽  
Seed Mediated

Investigation on Thermal Conductivity of Low Concentration AlN/EG Nanofluids

2013 ◽  
Vol 546 ◽  
pp. 112-116
Author(s):  
Yan Jiao Li ◽  
Chang Jiang Liu ◽  
Zhi Qing Guo ◽  
Qiu Juan Lv ◽  
Fang Xie
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Maxwell Model ◽  
Experimental Results ◽  
Effect Of Temperature ◽  
Transient Hot Wire ◽  
Hot Wire ◽  
Wire Method ◽  
Nanoparticles Volume Fraction

The thermal conductivity of AlN/EG nanofluids was investigated by transient hot-wire method. Experimental results indicated that the thermal conductivity of AlN/EG nanofluids increase nearly linear with the increase of nanoparticles volume fraction, and the results can’t be predicted by conditional Maxwell model. The effect of temperature on effective thermal conductivity of AlN/EG nanofluids was investigated. Result indicated that the thermal conductivity of AlN/EG nanofluids increased with the increase of temperature.

Synthesis of Chitosan-Stabilized Gold Nanorod Using Tripolyphosphate

2013 ◽  
Vol 652-654 ◽  
pp. 250-253
Author(s):  
Hua Nan Guan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gold Nanoparticles ◽  
Chemical Synthesis ◽  
Gold Nanorods ◽  
Gold Nanorod ◽  
Gold Salt ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Seed Mediated

An improvement in the previously reported seed-mediated chemical synthesis of gold nanorods (GNRs) is reported. Gold nanoparticles were prepared by reducing gold salt with a polysaccharide, chitosan, in the presence of tripolyphosphate (TPP). The obtained gold nanoparticles were characterized with UV-vis spectroscopy and transmission electron microscopy. The study shows that TPP plays an important role in the formation of GNRs.

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