| 1. |
- Babenkov, Sergey V., et al.
(författare)
-
Hybrid organic-inorganic systems formed by self-assembled gold nanoparticles in CuPcF4 molecular crystal
- 2016
-
Ingår i: Organic Electronics. - : Elsevier BV. - 1566-1199. ; 32, s. 228-236
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we have fabricated and studied hybrid organic-inorganic nanocomposite system formed by gold nanoparticles self-assembled in organic semiconductor thin film - copper tetrafluorophthalocyanine (CuPcF4). By means of Photoelectron Spectroscopy and Transmission Electron Microscopy (TEM) the evolution of the morphology and electronic structure of the system as a function of nominal gold content have been investigated. The gold atoms, deposited onto the CuPcF4 surface, diffuse into the organic matrix and self-assemble to nanoparticles in a well-defined manner with a narrow size distribution, which depends on the amount of deposited gold. Using High-Resolution TEM, we were able to observe the atomic planes of single gold nanoparticles and their coalescence processes. Photoelectron spectroscopy has not revealed any detectable chemical reaction between gold and organic. However, the strong upward band bending, induced by gold nanoparticles in the organic film, takes place.
|
|
| 2. |
- Hautala, Lauri, et al.
(författare)
-
Probing RbBr solvation in freestanding sub-2 nm water clusters
- 2017
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 19:36, s. 25158-25167
-
Tidskriftsartikel (refereegranskat)abstract
- Concentration dependent solvation of RbBr in freestanding sub-2 nm water clusters was studied using core level photoelectron spectroscopy with synchrotron radiation. Spectral features recorded from dilute to saturated clusters indicate that either solvent shared or contact ion pairs are present in increasing amount when the concentration exceeds 2 mol kg-1. For comparison, spectra from anhydrous RbBr clusters are also presented.
|
|
| 3. |
- Hautala, Lauri, et al.
(författare)
-
Surface site coordination dependent responses resolved in free clusters: applications for neutral sub-nanometer cluster studies
- 2015
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:10, s. 7012-7022
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we demonstrate how surface site specific experimental information can be obtained from free low nanometer scale clusters using photoelectron spectroscopy utilising synchrotron radiation. In addition, we show how it can be used to gain insight into the geometry and surface structure of the clusters. The present experiments were conducted on alkali metal halides, RbCl and CsCl, which were chosen as advantageous test cases due to their simple electronic and geometric structures. These heavy alkali metal salts provide additional clarity since the surface and bulk responses can be separated, which is not the case for clusters of lighter alkali metal salts. Computational chemical shift calculations and simple alkali halide cluster size modelling were used to interpret the experimental results.
|
|
| 4. |
- Pokapanich, Wandared, et al.
(författare)
-
Core level photoelectron spectroscopy probed heterogeneous xenon/neon clusters
- 2017
-
Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 135, s. 45-48
-
Tidskriftsartikel (refereegranskat)abstract
- Binary rare gas clusters; xenon and neon which have a significant contrariety between sizes, produced by a co-expansion set up and have been studied using synchrotron radiation based x-ray photoelectron spectroscopy. Concentration ratios of the heterogeneous clusters; 1%, 3%, 5% and 10% were controlled. The core level spectra were used to determine structure of the mixed cluster and analyzed by considering screening mechanisms. Furthermore, electron binding energy shift calculations demonstrated cluster aggregation models which may occur in such process. The results showed that in the case of low mixing ratios of 3% and 5% of xenon in neon, the geometric structures exhibit xenon in the center and xenon/neon interfaced in the outer shells. However, neon cluster vanished when the concentration of xenon was increased to 10%.
|
|
| 5. |
- Tchaplyguine, Maxim, et al.
(författare)
-
Ag-Cu oxide nanoparticles with high oxidation states : towards new high T-c materials
- 2018
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 47:46, s. 16660-16667
-
Tidskriftsartikel (refereegranskat)abstract
- In Ag-Cu oxides possible to fabricate so far, superconductivity has not been detected, but high conductivity was. In the quest for superconductivity the demand is to create a high and peculiar copper-oxygen coordination. Such coordination makes it non-trivial to determine Cu oxidation states, which may be several and co-existing. Another reason for uncertainty is in oxygen deficiency typical for superconducting crystals. Finally, Cu oxidation is influenced by the other metals in the substance. For chemical fabrication the difficulty is to tune the relative abundances of elements in a fine way. Ag-Cu oxides have been also produced by reactive co-sputtering of Cu and Ag, but the composition with high Cu oxidation states necessary for high conductivity has not been realized. In the present work we have fabricated Ag-Cu-oxide nanoparticles containing Cu and Ag in high oxidation states actual for superconductivity. The fabrication includes reactive sputtering of Ag and Cu metals, their vapour oxidation and aggregation into nanoparticles. The ability to create different and high oxidation states, also co-existing, is demonstrated. The fabrication approach also allows overcoming the poor miscibility of Cu and Ag. The nanoparticle composition and the oxidation states could be determined due to an experimental arrangement in which photoelectron spectroscopy is applied to free nanoparticles in a beam in vacuum, what allows avoiding any contact of the particles to a substrate or atmosphere. The combination of the fabrication and characterization methods has proven to be a powerful approach when fine composition tuning and control are desirable.
|
|
| 6. |
- Tchaplyguine, Maxim, et al.
(författare)
-
Gold Oxide Nanoparticles with Variable Gold Oxidation State
- 2015
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:16, s. 8937-8943
-
Tidskriftsartikel (refereegranskat)abstract
- Gold-oxide-containing nanoparticles have been produced in a range of partial to full oxidation conditions, where the nanoparticle electronic structure and stoichiometry have been characterized. Our results indicate that with the increase of the oxidation degree in these nanoparticles the gold oxidation state possibly changes from lower oxides with monoor divalent metal to the higher oxide with the trivalent gold. At intermediate oxidation conditions our observations are consistent with a radially segregated structure of such nanopaiticles-with the core containing mainly oxide and the surface covered with few monolayers of metallic gold. These results have been possible to obtain combining the vapor aggregation method for the nanoparticle fabrication and synchrotron-based photoelectron spectroscopy for their characterization. The deposition of the oxidized nanoparticles has showed that the species assigned as containing lower oxide could be preserved in the landing and then studied on a substrate for a limited time. The possible lower oxide formation in nanoparticles is discussed in connection to the enhanced catalytic activity of gold nanoparticles.
|
|
| 7. |
- Wright, Charles, et al.
(författare)
-
Tin Oxides : Insights into Chemical States from a Nanoparticle Study
- 2017
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:35, s. 19414-19419
-
Tidskriftsartikel (refereegranskat)abstract
- Tin oxides are semiconductor materials currently attracting close attention in electronics, photovoltaics, gas sensing, and catalysis. Depending on the tin oxidation state-Sn(IV), Sn(II), or intermediate-the corresponding oxide has either n- or p-type natural conductivity, ascribed to oxygen or metal deficiency in the lattice. Such crystalline imperfections severely complicate the task of establishing tin oxidation state, especially at nanoscale. In spite of the striking differences between SnO2 and SnO in their most fundamental properties, there have been enduring problems in identifying the oxide type. These problems were to a great extent caused by the controversy around the characteristic chemical shift, that is, the difference in electron binding energy of a certain core level in an oxide and its parent metal. Using in situ fabricated bare tin oxide nanoparticles, we have been able to resolve the controversy: Our photoelectron spectroscopic study on tin oxide nanoparticles shows that, in contrast to a common opinion of a close chemical shift for SnO2 and SnO, the shift value for tin(IV) oxide is, in fact, 3 times larger than that for tin(II) oxide. Moreover, our investigation of the nanoparticle valence electronic structure clarifies the question of why previously the identification of oxidation states encountered problems.
|
|
