Thiolate–Protected Gold Nanoparticles Via Physical Approach: Unusual Structural and Photophysical Characteristics

Abstract

Here we report a novel physical approach for thiolate–protected fluorescent gold nanoparticles with a controlled size of the order of a few nanometers. This approach is based on a sputtering of gold into a liquid matrix containing thiolate ligand as a stabilizer at various concentrations, thus no reductant was used. The size of the gold nanoparticles was successfully controlled to range from 1.6 to 7.4 nm by adjusting the thiol concentrations. Surface plasmon absorption was observed in larger nanoparticles, but it was not observed in smaller ones. Such smaller nanoparticles fluoresced at around 670 nm with a small spectral shift according to their size, however, the diameter (1.6–2.7 nm) was very strange to show such red emission compared with photophysical characteristics of reported gold cluster or nanoparticles synthesized by chemical method. By detailed investigations using TEM, HAADF-STEM, XPS, and TGA, and size fractionation by size exclusion chromatography, we finally arrived at the plausible mechanism for the origin of unusual fluorescence property; the obtained gold nanoparticles are not single-crystal and are composed of aggregates of very small components such as multinuclear gold clusters or complexes.

Ultrafast angle-resolved photoemission spectroscopy of quantum materials

“…2(b)] [35,40], which is confined to binding energies less than 70 meV. In addition, the pump induces a marked change in band velocity [35,40]. This is particularly visible in Fig.…”

“…2(a), middle panel] [29], as well as an increase in ARPES linewidth [ Fig. 2(b)] [35,40], which is confined to binding energies less than 70 meV. In addition, the pump induces a marked change in band velocity [35,40].…”

“…More recently, we and others have improved significantly on the energy and momentum resolution of these initial works. By pumping at lower fluence values than those previously explored, a number of studies using 1.5 eV pump/6 eV probe time-resolved ARPES have shown that it is possible to explore a wide variety of phenomena associated not just with metallic-state dynamics, but also with dynamics associated with the superconducting ground state of cuprates [29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Evidence for the electron-boson coupling interaction within this low-fluence, low-temperature regime can be observed in time-resolved ARPES spectra of cuprate superconductors through a variety of features.…”

Nanostructured Hematite Decorated with Gold Nanoparticles for Functionalization and Biocompatibility

“…In Figure b, the Au 4f peaks at 84.7 and 88.3 eV are at a relatively higher binding energy than zero valent Au0 (87.7 and 84.0 eV). Positive and negative shifts of Au 4 f peaks have been detected for AuNPs in some conditions . The positive shift of AuNP BE is related to the interaction of the nanoparticles with hematite surface and gold oxidation states.…”

Synthesis and characterization of fluorescent gold nanoclusters

“…This can be explained due to the nature of the MuA molecules (pKa = 6.5), the AuNCs have the tendency to aggregate over time in the dispersing medium. [20,21]…”