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.

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 Al${}_2$O${}_3$ 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.

This study theoretically analyzed the optical properties and electric field enhancement of gold nanospheres. Based on numerical analysis, the gold nanospheres were coated experimentally with diallyldimethylammonium chloride (C₈H₁₆ClN) for targeted drug delivery. Numerically, a resonance peak for 10 nm nanospheres was observed at 510 nm. As the radius increased from 10 nm to 100 nm, the resonance peak shifted from 510 nm to 605 nm. The nanosphere radius also affected the extinction cross-section. The resonance peaks showed a red shift as the radius of the nanosphere increased. For experiment analysis, gold nanospheres were synthesized using a seed-mediated technique and then coated with different concentrations of C₈H₁₆ClN. The UV absorbance by the nanospheres increased with an increase in the concentration of C₈H₁₆ClN from 10 mg ml⁻¹ to 20 mg ml^–1. UV–vis spectrum confirmed a rise in resonance peaks with increasing coating concentration. The coated gold nanospheres were used to deliver the doxorubicin-HCl (DOX-HCl) drug. Maximum drug release was observed when the temperature was set at 50 °C. It was concluded that the nanospheres, coated with 20 mg ml^–1 of C₈H₁₆ClN, are excellent candidates for drug delivery applications. The gold nanospheres with a radius of 50 nm were best for target drug delivery, and the particles above 50 nm were best for thermal therapies for cancer treatment.