Exploration of the Interaction of Electromagnetic Fields with Nanoscale Materials.
Abstract
Nanoscale materials usually present strikingly different properties in comparison with their bulk
counterparts, such as quantum size effects, surface plasmon resonance (SPR). To explore new
properties as well as for novel applications, nanomaterials are being extensively investigated.
This project investigates the interactions of electromagnetic fields with nanoscale materials,
particularly gold nanoparticles (GNPs), over a wide range of frequency bands, including static
field, 261 kHz, 13.56 MHz, 2.45 GHz, millimetre wave, THz, and the visible light. Especially,
the efforts have been devoted to the study of heating effect of GNPs in association with potential
biomedical applications. To explain the electromagnetic heating of GNPs, dielectric properties of
GNP dispersions has been studied from 100 MHz to 20 GHz, as well as in the millimetre wave
and THz ranges. The static field induced effects on the size distribution of GNPs has also been
examined using ultra-violet spectroscopy and correlated to SPR.
It has been revealed that purified GNPs cannot increase the specific absorption rate substantially
at whichever frequency points of 261 kHz, 13.56 MHz, or 2.45 GHz. However, a greater
temperature rise has been observed in the impurified GNP dispersions compared to deionisedwater,
after 10 min RF treatment at 13.56 MHz. The measurements on dielectric properties show
that impurified samples have much higher effective conductivity than that of deionised-water,
while the conductivity change of purified ones is very small and not detectable within the
measurement accuracy. This observation supports that the heating effect of GNP dispersions is
mostly contributed by the impurities and disproves that GNPs can increase the specific
absorption rate significantly. The magnetic field heating at 261 kHz suggests that GNPs have
very weak magnetic properties. It has been found that a static field can change the size
distribution of GNPs. Up to 2 THz, it is measured that the dielectric properties of GNP
dispersions have no convincing change compared to deionised-water, implying that the
electromagnetic heating of GNP below 2 THz may be insignificant. In addition, it is confirmed
that GNPs have strong absorption in the visible light range due to SPR.
Authors
Liu, XiaomingCollections
- Theses [3706]