The work reported in this dissertation describes the design and synthesis of different gold nanoshells with strong absorption coefficients at the near-infrared region (NIR) of the spectrum, and includes preliminary studies of their use for the photo-induced heating of pancreatic cancer cells and ex vivo tissues. As the emphasis was on gold nanoshells with maximum extinctions located at 800 nm, the methods explored for their synthesis led us to the preparation of silica-core and hollow gold nanoshells of improved stability, with maximum extinctions at or beyond the targeted within the near-infrared window. The synthesis of silica-core gold nanoshells was investigated first given its relevance as one of the pioneering methods to produce gold nanostructures with strong absorption and scattering coefficients in the visible and the near-infrared regions of the spectrum. By using a classical method of synthesis, we explored the aging of the precursor materials and the effect of using higher concentrations than the customary for the reduction of gold during the shell growth. We found that the aging for one week of the as-prepared or purified precursors, namely, the gold cluster suspensions, and the seeded silica particles, along with higher concentrations of gold in the plating solution, produced fully coated nanoshells of 120 nm in size with smooth surfaces and maximum extinctions around 800 nm. Additional work carried out to reduce the time and steps in the synthesis of silica-core gold nanoshells, led us to improve the seeding step by increasing the ionic strength of the cluster suspension, and also to explore the growth of gold on tin-seeded silica nanoparticles. The synthesis of hollow gold nanoshells (HGS) of with maximum extinctions at the NIR via the galvanic replacement of silver nanoparticles for gold in solution was explored next. A first method explored led us to obtain HGS with maximum extinctions between 650 and 800 nm and sizes between 30 and 80 nm from silver nanoparticles, which were grown by the addition of silver nitrate and a mild reducer. We developed a second method that led us to obtain HGS with maximum extinctions between 750 and 950 nm by adjusting the pH of the precursor solution of the silver particles without much effort or additional steps. The last part of this work consisted in demonstrating the photo-induced heating of two biological systems containing HGS. Photothermal therapy studies of immobilized PANC1 pancreas cancer cells in well-plates were carried out with functionalized HGS. We found that cells exposed to HGS remained viable after incubation. Moreover, the cells incubated with HGS modified with mercaptoundecanoic acid and folic acid turned non-viable after being irradiated with a laser at 800 nm. The other study consisted in the laser-induced heating between 750 and 1000 nm of ex vivo tissues of chicken and pork with nanoshells injected. In comparison with non-injected tissues, it was found that the temperature at the irradiated areas with HGS increased more than 10 °C. Moreover, the extent of the heated area was broader when the laser was used at wavelengths beyond 900 nm, suggesting that the heating was due to the radiation absorbed and transformed into heat primarily by the HGS and at a lesser extent by the water in the tissue.

The structure and properties of chemical vapor deposited zinc sulfide (CVD ZnS) were assessed before and after heat treatments, involving different annealing and hot isostatic pressing (HIPing) profiles. Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder x-ray diffraction, x-ray chemical microanalysis, photoluminescence, ultraviolet through longwave infrared transmission, and mechanical testing. Before heat treatment, CVD ZnS consists of lamellar twinned structures in 10 to 100 nm layers aggregated into domains which compose grains typically 5 to 10 μm in diameter with an overall crystallographic texture on the {100} planes. The scattering behavior of CVD ZnS was investigated and described by a surface scattering model based on internal surface roughness and refractive index variations due to onedimensional stacking disorder. The two to five percent hexagonality measured by x-ray diffraction is believed to form due to oxygen impurities at the twin boundaries which cause nanostructural polytypism and result in differential refractive index and scattering. CVD ZnS variants in low temperature deposited red ZnS and sulfur precursor elemental ZnS are examined as well. Color in CVD ZnS is believed to be due to band edge position, probably due to oxygen content, and not directly related to the hydride absorption at 6 μm. After annealing or hot isostatic pressing above 850 °C for sufficient time, CVD ZnS recrystallizes and becomes strongly textured on the {111} planes. This recrystallization is required to remove stacking disorder, resulting in a structure with less than half a percent hexagonality and low visible scattering. The recrystallization is believed to proceed by diffusing the oxygen at the nano-twin boundaries back into the lattice, thus unpinning the boundaries and allowing them to move and grow into the tabular recrystallized morphology by polytype induced exaggerated grain growth. The presence of active metals like platinum, silver, copper, or nickel during hot isostatic pressing causes a reaction with sulfur and lowers the temperature required for recrystallization. The optical scattering model is consistent in describing standard CVD ZnS, elemental ZnS, and multispectral recrystallized ZnS as having successively lower birefringence at internal surfaces.