NANOCHEMISTRY

Nanochemistry



Nanochemistry

Part 4: Synthesis of Ag and Au Nanoparticles

In cancer research field, GNPs can be used simultaneously for imaging and killing tumor cells. The cancer cells tagged with the GNPs (using cancer cell specific ligands or antibodies) are imaged by dark-field microscopy, TPL microscopy or SERS. Irradiation of the imaged area by near-IR laser results in local heat emission and the death of GNP tagged cells by photothermal ablation (PTA). The viability of this approach was demonstrated with spherical, rod, cube, shell, and hollow (spheres or cages) GNPs. The recently developed hollow gold nanospheres seem to be one of the best candidates for PTA due to their size and shape (ideal for delivery) and absorption (strong and narrow bandwidth in NIR region). PTA of tumors was also evaluated in animal models with encouraging results.

The development of rapid and ecofriendly processes for the synthesis of silver (Ag) and gold (Au) nanoparticles is of great importance in the field of nanotechnology. One example of the Synthesis of Ag And Au Nanoparticles is that the nano era demands the synthesis of new nanostructured materials, if possible by simplified techniques, with remarkable properties and versatile applications(De, 2010: 121-128). Here, we demonstrate a new single-step reproducible melt-quench methodology to fabricate core-shell bimetallic (Au0 Ag0) nanoparticles (28 89 nm) embedded glasses (dielectrics) by the use of a new reducing glass matrix, K2O B2O3 Sb2O3 (KBS) without applying any external reducing agent or multiple processing steps. The surface plasmon resonance (SPR) band of these nanocomposites embedded in KBS glass is tunable in the range 554-681 nm. More remarkably, taking advantage of the selective reduction capability of Sb2O3, this single-step methodology is used to fabricate inter-metallic: rare-earth ions co-embedded (Au Ag:Sm3+) dielectric (glass)-based-dnanocomposites and study the effect of enhanced local field on the red upconversion fluorescence of Sm3+ ions at 636 nm. The enhancement is found to be about 2 folds. This single-step in-situ selective reduction approach can be used to fabricate a variety of hybrid-nanocomposite devices for laser based applications.

In recent years, small semiconductor nanocrystals, or quantum dots (QDs), have emerged as promising alternatives to chemical fluorophores and visible fluorescent proteins (VFPs) in the area of fluorescence microscopy. However, during our recent application of commercial QDs to the investigation of signal transduction in mammalian cells.

Nanoparticles and Plasmonics are increasingly finding wide applications in many areas related to environmental, medical diagnostics and homeland defense due to their unique electromagnetic, physical and chemical properties. Practical applications would require nanoparticles to be conjugated to biomolecules. Therefore a universal approach for conjugation of silver colloidal nanoparticles to biomolecules has been developed in our group. Surface functionalized silver colloids were labeled with a Raman-active dye and bio-receptor molecule and used as labels for cellular imaging. These silver nanoparticles can easily be transferred to chloroform containing the cationic surfactant octadecylamine by an electrostatic complexation process (Hu, 2009: 102 106). The now hydrophobic silver nanoparticles may be spread on the surface of water and assembled into highly ordered, linear superstructures that could be transferred as ...