ABSTRACT
Nanoslits have various applications, including localized surface plasmon resonance (LSPR)-based nanodevices, optical biosensors, superfocusing, high-efficiency refractive index sensors and chip-based protein detection. In this study, the effect of substrates on the optical properties of gold nanoslits placed in free space is discussed; for this purpose, glass BK7 and Al2O3 are used as substrates and the wavelength of incident light is supposed to be 650 nm. The optical properties, power flow and electric field enhancement for gold nanoslits are investigated by using the finite element method (FEM) in COMSOL Multiphysics software. The effect of polarization of an incident electromagnetic wave as it propagates from a gold nanoslit is also analyzed. As special case, the effect of glass and alumina substrate on magnetic field, power flow and electric field enhancement is discussed. The goal of this research is to investigate the phenomenon of power flow and electric field enhancement. The study of power flow in gold nanoslits provides valuable insights into the behavior of light at the nanoscale and offers opportunities for developing novel applications in the field of nanophotonics and plasmonics. The consequences of this study show the significance of gold nanoslits as optical nanosensors.
ABSTRACT
Hyperthermia (HT) is a technique for treating malignancies by raising the temperature of the defected tissues. This technique has been used as a treatment to raise tumor area temperatures between 42 °C to 48 °C. Hyperthermia penetrates deeper malignant cells by heating the region of interest when magnetic nanoparticles (MNPs) are exposed to an externally induced magnetic field of the incident wave. In this work, numerical analysis was used to examine the temporal and spatial temperature distributions within a tumor. The temperature field was analyzed using the mass transfer and diffusion theories in the interstitial tissue. A bio-heating module in COMSOL Multi-Physics was used for different types of gold nanoparticles (AuNPs) including nanorods, nanospheres, and nano-ellipsoids with different shapes. The objective of this study is to analyze the use of AuNPs for hyperthermia. The results show that AuNPs achieve a maximum temperature for Au nanorods as compared to nano ellipsoids and nanospheres. The Au NPs achieve thermal equilibrium after 0.5 µs and are effective for hyperthermia treatment. The results describe the effect of nanoparticle shape and surface coating on thermal absorption around the nanoparticle in hyperthermia. The significance of Au NPs for hyperthermia is explained. It is expected that this study will be helpful in the future for hyperthermia treatment.
ABSTRACT
The optical properties and electric field enhancement of gold nanorods for different cases were investigated in this study. The numerical analysis was carried out to understand the functionality and working of gold nanorods, while the experimental portion of the work was focused on the efficiency of gold nanorods for targeted drug delivery. COMSOL Multiphysics was used for numerical analysis. The theoretical results suggest the use of gold nanorods (AuNRs) for anticancer applications. The resonance peaks for gold nanorods of 10 nm diameter were observed at 560 nm. The resonance peaks shifted towards longer wavelengths with an increase in nanorod size. The resonance peaks showed a shift of 140 nm with a change in nanorod length from 25 to 45 nm. On the experimental side, 22 nm, 35 nm and 47 nm long gold nanorods were produced using the seed-mediated growth method. The surface morphology of the nanorods, as well as their optical characteristics, were characterized. Later, gold nanorods were applied to the targeted delivery of the doxorubicin drug. Gold nanorods showed better efficiency for doxorubicin drug loading time, release time, loading temperature, and release temperature. These results reveal that AuNRs@DA possess good ability to load and deliver the drug directly to the tumorous cells since these cells show high temperature and acidity.
ABSTRACT
The finite element analysis technique was used to investigate the suitability of silver nanorods, spheres, ellipsoids and core−shell structures for the hyperthermia treatment of cancer. The temperature of the silver nanostructures was raised from 42 to 46 °C, in order to kill the cancerous cells. The time taken by the nanostructures to attain this temperature, with external source heating, was also estimated. The heat transfer module in COMSOL Multiphysics was used for the finite element analysis of hyperthermia, based on silver nanostructures. The thermal response of different shapes of silver nanostructures was evaluated by placing them inside the spherical domain of the tumor tissue. The proposed geometries were heated at different time intervals. Optimization of the geometries was performed to achieve the best treatment temperature. It was observed that silver nanorods quickly attain the desired temperature, as compared to other shapes. The silver nanorods achieved the highest temperature of 44.3 °C among all the analyzed geometries. Moreover, the central volume, used to identify the thermal response, was the maximum for the silver nano-ellipsoids. Thermal equilibrium in the treatment region was attained after 0.5 µs of heating, which made these structures suitable for hyperthermia treatment.
