Tailoring shape,size and optical properties of gold and silver nanostructures for biomedical applications

Abstract

Nanostructures of gold and silver (nanospheres, nanorods, and core-shell nanostructures) are considered to be the workhorse of next generation nanomedicine. They can be synthesized in different shapes and sizes with controlled dispersity and easy functionalization with specific antibodies and targeting agents. Faraday studied colloidal gold and the optical properties of metal NPs. Since then many studies were made that leads to improvements in classical wet chemistry methods for synthesis of noble metal NPs. They are found as atomic clusters in the colloidal suspension and exhibit different optical properties depending on their size and structure. The different parameters that influence the size, growth, and dispersion of gold and silver NPs are studied. The optical and electromagnetic field enhancement of these nanostructures can be tailored by fine-tuning their shape and size. This master project aims at the development of multifunctional nano-platform of gold and silver nanostructures targeting potential applications in medical imaging and therapy. To fine-tune the shape, size and optical properties of gold and silver nanostructures, we plan to synthesize metallic NPs and modify their surface with small organic molecule providing different chemical properties (charge, affinities etc.). The conventional Frens-Turkevich synthesis method was used with some modifications. These nanohybrids were characterized via analytical methods such as DLS, UV-vis and electron microscopy to develop, optimize and control biocompatible synthesis. Experiments were made by changing one parameter at a time like the metal precursor concentration and the citrate concentration followed by the spectroscopic characterization to optimize the synthesis. Nanostructures of gold and silver such as Au NRs and Ag-Au alloy NPs were also synthesized to cover the spectra from visible to NIR region. The correlation between the optical properties and the different parameters involved in the synthesis was explored. The optical properties of each nanostructure were studied by analyzing their absorption spectra. DLS, UV-vis spectra, EDS, TEM, STEM, HRTEM and SAED images were used to determine the size, shape, dispersion, optical property, elemental composition and crystallographic analysis of the colloid NPs.