Limits...
Ultrasonic-aided fabrication of gold nanofluids.

Chen HJ, Wen D - Nanoscale Res Lett (2011)

Bottom Line: The ultrasonication technique is found to be a very powerful tool in engineering the size and shape of GNPs.Subsequent property measurement shows that both particle size and particle shape play significant roles in determining the effective thermal conductivity.A large increase in effective thermal conductivity can be achieved (approximately 65%) for gold nanofluids using plate-shaped particles under low particle concentrations (i.e.764 μM/L).

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Engineering and Materials Science, Queen Mary University of London, London, UK. d.wen@qmul.ac.uk.

ABSTRACT
A novel ultrasonic-aided one-step method for the fabrication of gold nanofluids is proposed in this study. Both spherical- and plate-shaped gold nanoparticles (GNPs) in the size range of 10-300 nm are synthesized. Subsequent purification produces well-controlled nanofluids with known solid and liquid contents. The morphology and properties of the nanoparticle and nanofluids are characterized by transmission electron microscopy, scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffraction spectroscopy, and dynamic light scattering, as well as effective thermal conductivities. The ultrasonication technique is found to be a very powerful tool in engineering the size and shape of GNPs. Subsequent property measurement shows that both particle size and particle shape play significant roles in determining the effective thermal conductivity. A large increase in effective thermal conductivity can be achieved (approximately 65%) for gold nanofluids using plate-shaped particles under low particle concentrations (i.e.764 μM/L).

No MeSH data available.


The thermal conductivities of the gold nanomaterials (250, 60, and 15 nm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211254&req=5

Figure 8: The thermal conductivities of the gold nanomaterials (250, 60, and 15 nm).

Mentions: Figure 8 shows the effective thermal conductivity of gold nanofluids in different concentrations of 1.1, 11.1, 33.31, 330, and 764 μM/L, respectively. The uncertainty of the thermal conductivity measurement is calibrated before use, which has an uncertainty of 8.4% within the experimental range. With the increase of particle concentrations, the effective thermal conductivities of gold nanofluids increase, exhibiting a non-linear trend, i.e., the increase is small at low concentrations but becomes significantly at over 33.31 μM/l. Figure 8 also shows that the effective thermal conductivity, keff, is significantly affected by particle size. As the specific surface area increases with the decrease of particle size, it is expected that keff would be higher at low particle dimensions. This is true when we compare the gold nanofluids containing 10-nm spherical nanoparticles with that of 60-nm gold nanoplates. For instance, at a concentration of 33.3 μM/L, keff is 30% higher than the base fluid for 10-nm spherical nanoparticles whereas a 17% enhancement is observed for 60-nm gold nanoplates. In a similar study using chemical synthesized GNPs, Paul et al. [22] obtained 48% increase in the effective thermal conductivity for 0.00026 vol.% concentration with an average particle size of 21 nm. Such a trend should be maintained until the thermal conductivity of the solid particle becomes significantly size-dependent. It is well-known from physics that the thermal conductivity of a solid particle becomes smaller at lower dimensions because of the confinement of the phonon dynamics by the interface. Consequently, further increase in the specific surface area is penalized by a decrease in the particle thermal conductivities. Qualitatively, there would have an optimum particle size where a maximum increase in the effective thermal conductivity is reached. The exact optimum size is difficult to quantify as it depends on an accurate prediction of size-dependent thermal conductivity, which alone is still an active research topic, as well as the interfacial resistance between the particle and suspending liquid that will be discussed below.


Ultrasonic-aided fabrication of gold nanofluids.

Chen HJ, Wen D - Nanoscale Res Lett (2011)

The thermal conductivities of the gold nanomaterials (250, 60, and 15 nm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211254&req=5

Figure 8: The thermal conductivities of the gold nanomaterials (250, 60, and 15 nm).
Mentions: Figure 8 shows the effective thermal conductivity of gold nanofluids in different concentrations of 1.1, 11.1, 33.31, 330, and 764 μM/L, respectively. The uncertainty of the thermal conductivity measurement is calibrated before use, which has an uncertainty of 8.4% within the experimental range. With the increase of particle concentrations, the effective thermal conductivities of gold nanofluids increase, exhibiting a non-linear trend, i.e., the increase is small at low concentrations but becomes significantly at over 33.31 μM/l. Figure 8 also shows that the effective thermal conductivity, keff, is significantly affected by particle size. As the specific surface area increases with the decrease of particle size, it is expected that keff would be higher at low particle dimensions. This is true when we compare the gold nanofluids containing 10-nm spherical nanoparticles with that of 60-nm gold nanoplates. For instance, at a concentration of 33.3 μM/L, keff is 30% higher than the base fluid for 10-nm spherical nanoparticles whereas a 17% enhancement is observed for 60-nm gold nanoplates. In a similar study using chemical synthesized GNPs, Paul et al. [22] obtained 48% increase in the effective thermal conductivity for 0.00026 vol.% concentration with an average particle size of 21 nm. Such a trend should be maintained until the thermal conductivity of the solid particle becomes significantly size-dependent. It is well-known from physics that the thermal conductivity of a solid particle becomes smaller at lower dimensions because of the confinement of the phonon dynamics by the interface. Consequently, further increase in the specific surface area is penalized by a decrease in the particle thermal conductivities. Qualitatively, there would have an optimum particle size where a maximum increase in the effective thermal conductivity is reached. The exact optimum size is difficult to quantify as it depends on an accurate prediction of size-dependent thermal conductivity, which alone is still an active research topic, as well as the interfacial resistance between the particle and suspending liquid that will be discussed below.

Bottom Line: The ultrasonication technique is found to be a very powerful tool in engineering the size and shape of GNPs.Subsequent property measurement shows that both particle size and particle shape play significant roles in determining the effective thermal conductivity.A large increase in effective thermal conductivity can be achieved (approximately 65%) for gold nanofluids using plate-shaped particles under low particle concentrations (i.e.764 μM/L).

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Engineering and Materials Science, Queen Mary University of London, London, UK. d.wen@qmul.ac.uk.

ABSTRACT
A novel ultrasonic-aided one-step method for the fabrication of gold nanofluids is proposed in this study. Both spherical- and plate-shaped gold nanoparticles (GNPs) in the size range of 10-300 nm are synthesized. Subsequent purification produces well-controlled nanofluids with known solid and liquid contents. The morphology and properties of the nanoparticle and nanofluids are characterized by transmission electron microscopy, scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffraction spectroscopy, and dynamic light scattering, as well as effective thermal conductivities. The ultrasonication technique is found to be a very powerful tool in engineering the size and shape of GNPs. Subsequent property measurement shows that both particle size and particle shape play significant roles in determining the effective thermal conductivity. A large increase in effective thermal conductivity can be achieved (approximately 65%) for gold nanofluids using plate-shaped particles under low particle concentrations (i.e.764 μM/L).

No MeSH data available.