Photochemical Synthesis of Water-Soluble Gold Nanorods: The Role of Silver Ions in Assisting Anisotropic Growth
The role of Ag+ ions in the ultraviolet-driven photochemical synthesis of Au nanorods (NRs) in aqueous surfactant mixtures has been investigated in order to elucidate the mechanism that drives anisotropic nanoparticle growth. The samples, grown in the presence of varying amounts of Ag+ ions for scheduled irradiation times, have been characterized by ultraviolet−visible−near infrared (UV−vis−NIR) absorption spectroscopy, analytical transmission electron microscopy (ATEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and extended X-ray absorption fine structure (EXAFS) measurements. Moreover, the time evolution of size and shape distribution has been investigated by stat…
Photobleaching and Recovery Kinetics of a Palette of Carbon Nanodots Probed by In Situ Optical Spectroscopy
Carbon dots (CDs) are a family of fluorescent nanoparticles displaying a wide range of interesting properties, which make them attractive for potential applications in different fields like bioimaging, photocatalysis, and many others. However, despite many years of dedicated studies, wide variations exist in the literature concerning the reported photostability of CDs, and even the photoluminescence mechanism is still unclear. Furthermore, an increasing number of recent studies have highlighted the photobleaching (PB) of CDs under intense UV or visible light beams. PB phenomena need to be fully addressed to optimize practical uses of CDs and can also provide information on the fundamental m…
The fate of silver ions in the photochemical synthesis of gold nanorods: an Extended X-ray Absorption Fine Structure analysis
Water-soluble gold nanorods (Au NRs) were synthesized using a silver-ion mediated photochemical route under UV irradiation. Extended X-ray Absorption Fine Structure (EXAFS) measurements on the Ag K-edge were performed on samples obtained at different Ag/Au ratios and at increasing irradiation times in order to investigate the fate of silver ions during the growth of Au NRs. EXAFS measurements allowed to probe the chemical state and the local environment of silver in the final product. Experimental data suggest that Ag atoms are placed on top of the Au particles as metallic Ag(0), while no significant contribution to the EXAFS spectra comes from AgBr or other Ag(+) based species. The reporte…