Surface chemical states of gold nanoparticles prepared using the solution‐plasma method in a CsCl aqueous solution

Abstract

In this study, gold nanoparticles (AuNPs) prepared in a 5 mM CsCl aqueous solution using the solution‐plasma method are characterized via transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy with synchrotron radiation (SR‐XPS). The particle diameter is measured over the process time via TEM. During the solution‐plasma process, small particles of 2.1 to 2.2‐nm diameter are generated in the CsCl aqueous solution; these particles then enlarge via Ostwald ripening over time until they reach an equilibrium size of ~13 nm after 36 days. In addition, the surface chemical states of the AuNPs are characterized at different depths via SR‐XPS. The SR‐XPS measurements obtained using incident X‐ray energy (hν) of 945.0 eV revealed that Cs─Au, Cl─Au, and Cs─Cl─Au bonds are present 1.2 nm below the surface. The measurements obtained at an incident X‐ray energy of 2515.0 eV showed that Cs─Cl─Au bonding is also present 2.5 nm below the surface, indicating that Cs and Cl strongly interact with Au. The TEM and SR‐XPS measurements revealed that 2 processes occur cyclically during the growth process via Ostwald ripening: (i) the Cs and Cl in the aqueous solution adsorb on the AuNP surface and (ii) Au atoms subsequently bond to the AuNPs surface.

Gold-Supported Nanostructured NiFeCoPr Hydroxide as a High-Performance Supercapacitor Electrode and Electrocatalyst toward the Oxygen Evolution Reaction

“…The fitting results showed the existence of two predominant Ni species, i.e., Ni 2+ (855.6 eV) and Ni 3+ (857.2 eV) in the Ni 2p spectrum, suggesting two valence states for Ni in the material. − Peak fitting analysis for Fe 2p (Figure c) identified two distinct iron species, which were assigned to Fe 2+ (710.5 eV) and Fe 3+ (712.6 eV). − The Fe 3+ has been known to improve the OER activities by enhancing the binding energy of intermediates (e.g., · OH and · OOH) on the Ni and Co sites. , The Co 2p (Figure d) was identified as Co 3+ (780.9 eV) and Co 2+ (784.1 eV). − The peaks in the Pr 3d spectrum (Figure e) located at ∼930 eV and ∼955 eV were ascribed to Pr (3d 5/2 ) and Pr (3d 3/2 ) levels. The peak fitting showed two predominant Pr valence state of Pr 3+ (929.1 eV) and Pr 4+ (932.6 eV). , The presence of Au(0) was confirmed in the Au 4f spectrum (Figure f), , and the peaks at 531.3 and 529.4 eV in the O 1s spectrum (Figure g) were assigned to the hydroxide/oxyhydroxide group (−OOH or – OH) and lattice oxygen bonds (O–M), , respectively. The EDS results for the average atomic ratios of Ni:Fe:Co:Pr:Au:O in NiFeCoPrO-Au/NF obtained from spot analysis at five different points, turned out to be 14:9:11:1:5:60.…”

“…The peak fitting showed two predominant Pr valence state of Pr 3+ (929.1 eV) and Pr 4+ (932.6 eV). 60,61 The presence of Au(0) was confirmed in the Au 4f spectrum (Figure 3f), 62,63 and the peaks at 531.3 and 529.4 eV in the O 1s spectrum (Figure 3g) were assigned to the hydroxide/oxyhydroxide group (−OOH or − OH) and lattice oxygen bonds (O−M), 64,65 respectively. The EDS results for the average atomic ratios of Ni:Fe:Co:Pr:Au:O in NiFeCoPrO-Au/NF obtained from spot analysis at five different points, turned out to be 14:9:11:1:5:60.…”

Surface modification and Ag nanoparticles support of graphene nanoplates via plasma in liquid

“…In the modification of GNP via AgNO 3 aqueous solution, it is expected that Ag nanoparticles are physisorbed to GNP, due to metal ions are reduced by electrons or hydrogen radicals. [32][33][34][35] While Ag nanoparticles synthesis itself via PLP had been already reported, 34) this study conducts synthesis of Ag nanoparticles and their physisorption to GNP simultaneously without dispersant.…”