X‐ray and UV photoelectron spectroscopy of Ag nanoclusters

Abstract

The main purpose of the present work is to analyze a series of Ag nanoparticles (NPs) with different size or ligand functionalization by using X‐ray photoelectron spectroscopy (XPS) and to identify the differences in the band‐shape and energy peak position of photoemission spectra due to the particle dimension. A transmission electron microscopy characterization was performed, to verify the consistency of the results. Three types of samples were prepared starting from AgNO3 water solution and adding different capping agents. In the first two cases, the formation of NPs was promoted by the reduction of silver ions Ag+1 to metallic Ag0 through the addition of sodium borohydride, whereas in the last case, it was triggered by the exposure to UV light. Depending on the size of the NPs, a different physical behavior can be recognized. NPs with diameter of about 5 nm are characterized by the phenomenon of localized surface plasmon resonance (LSPR). The other type of samples having a diameter of about 1.5 nm presents discrete energy levels instead of electronic bands, and in this case, a typical fluorescence phenomenon can be observed. In the latter case, we can refer to such systems as nanoclusters. The XPS analyses were focused on the Ag 3D spectra looking for the possible shifts of the Ag doublet as a function of the particles size. The ultraviolet photoelectron spectroscopy with He II source was used for the investigation of possible changes in the valence band.

Silver Single‐Atom Catalyst for Efficient Electrochemical CO2 Reduction Synthesized from Thermal Transformation and Surface Reconstruction

“…This was due to the binding between O Latt and Ag atoms with higher electronegativity (1.93) when compared to Mn atoms with lower electronegativity (1.55). The increase in bonding energy also suggested a decrease in size of Ag NPs of Ag NP /MnO 2 [19] . Note that elevated surface Ag content as high as 7.72 % (Table S1) and the ca.…”

“…Thei ncrease in bonding energy also suggested adecrease in size of Ag NPs of Ag NP /MnO 2 . [19] Note that elevated surface Ag content as high as 7.72 % (Table S1) and the ca. 4o xygen atoms around 1A ga tom (Table S2), suggested the coordination of O Latt in Ag 1 /MnO 2 with the surface Ag atoms.T his may restrict the mobility of surface oxygen species and cause the reduction of adsorbed oxygen in XPS ( Figure S4c and Table S1) and vanishment of labile oxygen species in O-K XAS spectra ( Figure S5).…”

Evaluation of Long–Lasting Antibacterial Properties and Cytotoxic Behavior of Functionalized Silver-Nanocellulose Composite

“…To better identify the silver oxidation state, the Auger parameter α′ was calculated given by the sum of the binding energy of the core level peak (Ag 3d 5/2 ) and the kinetic energy of the photoinduced Auger signal (Ag MNN). The obtained value α′ = 725.9 eV, indicates the presence of Ag only in its metallic oxidation state [ 42 ]. Thus, the XPS measurements testifies the presence of Ag NPs in the cellulosic structure of the Ag-ONCs [ 43 ].…”

Hydroxyapatite Functionalized Calcium Carbonate Composites with Ag Nanoparticles: An Integrated Characterization Study

“…The composites of Ag nanoparticles dispersed in hydroxyapatite HA-FCC were synthesized by using different methods and characterized by XRD, TEM, REELS, and XPS The determination of Ag oxidation state by using the Auger parameter for identification of metallic Ag and consequently of the NPs formation is fast and reliable. This method has already been used successfully for other types of compounds with Ag nanoparticles in solution [18,19].…”

“…This phenomenon is characteristic for some metals, also including silver [ 16 ]. The noticeable shift of photoemission peaks could be also caused by the reduced size of NPs, as it has been demonstrated for Ag and Au [ 17 , 18 , 19 , 20 , 21 , 22 ]. This shift, which is called size-shift, occurs when the metallic nanoparticles are of the dimension less than ≈5 nm and has been also predicted in previous theoretical works [ 23 , 24 ].…”