X-ray photoelectron spectroscopy study on gold nanoparticles supported on diamond

Boyen, Hans‐Gerd; Herzog, Thomas; Kästle, G.; Weigl, F.; Ziemann, P.; Spatz, Joachim P.; Möller, Martin; Wahrenberg, R.; Garnier, M. G.; Oelhafen, P.

doi:10.1103/physrevb.65.075412

Cited by 56 publications

(48 citation statements)

References 22 publications

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“…While the complete removal of ligands using hydrogen and oxygen plasma has been documented before, [15][16][17][18][19] our results reveal that it is also possible to clean the layers of organic residues using nitrogen as a plasma medium.…”

Section: Ligand Removalmentioning

confidence: 72%

“…Nevertheless, several approaches to solve this problem were successfully tested using different procedures, such as thermolysis, [12][13][14] treatment with ozone [14] or the exposure to mild oxygen and/or hydrogen plasmas. [15][16][17][18][19] In this article, we focus on plasma treatment as a cleaning method and its structural and, in particular, chemical impact on the particle layers, paying attention to both the particles themselves as well as their lateral arrangement in the layers. Both reducing and oxidizing plasma media were used to remove the organic shell from the as-deposited particle layers through a combination of sputtering, electron-induced reactions, and etching with free radicals.…”

Section: Introductionmentioning

confidence: 99%

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Structural and Chemical Effects of Plasma Treatment on Close‐Packed Colloidal Nanoparticle Layers

Gehl¹,

Frömsdorf²,

Aleksandrovic³

et al. 2008

Adv Funct Materials

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The interaction of nitrogen, oxygen, and hydrogen plasmas with spin‐coated arrays of colloidal cobalt–platinum particles was investigated with a large variety of microscopic and spectroscopic techniques. It could be demonstrated that the organic ligands of the nanoparticles can be completely removed. Yet, due to the short (∼1.6 nm) interparticle distances within the layers, strong degradation and sintering effects are observed after hydrogen and nitrogen plasma treatments. In the case of oxygen plasma, the shape and size of the individual particles are unaffected and can be preserved, even if a short hydrogen plasma is subsequently applied to reduce the particles back to their metallic state. Nevertheless, the mesoscopic order of the particle arrays is slightly decreased as observed by the breakup of larger ordered areas into smaller domains forming island–trench structures. Probing the surface chemistry of the particles with temperature programmed desorption, a rather complex surface chemistry is found to result from the plasma treatments. The first TPD spectrum after the cleaning process with oxygen and subsequent hydrogen plasmas reveals that the particles are loaded with adsorbed and implanted hydrogen. After removal of this hydrogen, subsequent TPD spectra using CO as a probe molecule, show broad signals between 190 and 360 K pointing to nonmetallic surface properties. While the platinum was found to be completely reduced, XPS measurements reveal a remaining fraction of oxidic cobalt species which are enriched at the surface. Thus, although the structure of the close‐packed Co–Pt nanoparticle arrays can be qualitatively preserved during plasma‐based ligand removal, the treatment leads to a complex materials system the chemical properties of which are influenced by the particle components, the substrate, and the plasma media.

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Section: Ligand Removalmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Structural and Chemical Effects of Plasma Treatment on Close‐Packed Colloidal Nanoparticle Layers

Gehl¹,

Frömsdorf²,

Aleksandrovic³

et al. 2008

Adv Funct Materials

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show abstract

“…Indeed, previous work has demonstrated that this is possible by ªburning offº the polymer matrix of the metalloaded micelles in an oxygen plasma [26] resulting in a complete removal of the polymer. [27] It even turns out that the exposure to an oxygen plasma leads to the reduction of metal salts bound to the micellar cores. Thus, starting with a layer of micelles on top of a substrate, each loaded with a metal salt, the oxygen plasma treatment results in an ordered array of ªnakedº metal nanoislands.…”

Section: Introductionmentioning

confidence: 99%

A Micellar Route to Ordered Arrays of Magnetic Nanoparticles: From Size‐Selected Pure Cobalt Dots to Cobalt–Cobalt Oxide Core–Shell Systems

Boyen¹,

Kästle

Zürn

et al. 2003

Adv Funct Materials

Self Cite

118

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Starting with Co‐salt‐loaded inverse micelles, which form if the diblock copolymer polystyrene‐block‐poly(2‐vinylpyridine) is dissolved in a selective solvent like toluene and CoCl2 is added to the solution, monomicellar arrays of such micelles exhibiting a significant hexagonal order can be prepared on top of various substrates with tailored intermicellar distances and structure heights. In order to remove the polymer matrix and to finally obtain arrays of pure Co nanoparticles, the micelles are first exposed to an oxygen plasma, followed by a treatment in a hydrogen plasma. Applying in‐situ X‐ray photoelectron spectroscopy, it is demonstrated that: 1) The oxygen plasma completely removes the polymer, though conserving the original order of the micellar array. Furthermore, the resulting nanoparticles are entirely oxidized with a chemical shift of the Co 2p3/2 line pointing to the formation of Co3O4. 2) By the subsequent hydrogen plasma treatment the nanoparticles are fully reduced to metallic Co. 3) By exposing the pure Co nanoparticles for 100 s to various oxygen partial pressures p, a stepwise oxidation is observed with a still metallic Co core surrounded by an oxide shell. The data allow the extraction of the thickness of the oxide shell as a function of the total exposure to oxygen (p × time), thus giving the opportunity to control the ferromagnetic–antiferromagnetic composition of an exchange‐biased magnetic system.

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“…The increase in the core-level binding energy in small particles was also attributed to the poor screening of the core-hole and hence a manifestation of the size-induced metalenonmetal transition that happens at particle sizes in the range of 1e2 nm diameter consisting of 300 AE 100 atoms [504]. However, the metaleinsulator transition for Au nanoparticles deposited on diamond is excluded based on an XPS observation and the occurrence of the band offset was assigned to the range of cluster sizes [567]. (vi) Yang and Wu [568] investigated the core-level shifts in sparse Au clusters on oxides, Au/ MgO(001) and Au/TiO 2 (110), with a varying coverage and in the presence of surface oxygen vacancies, by using the DFT full-potential-linearized augmented plane-wave method.…”

Section: Outstanding Modelsmentioning

confidence: 99%

Size dependence of nanostructures: Impact of bond order deficiency

Sun

2007

Progress in Solid State Chemistry

821

717

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X-ray photoelectron spectroscopy study on gold nanoparticles supported on diamond

Cited by 56 publications

References 22 publications

Structural and Chemical Effects of Plasma Treatment on Close‐Packed Colloidal Nanoparticle Layers

Structural and Chemical Effects of Plasma Treatment on Close‐Packed Colloidal Nanoparticle Layers

A Micellar Route to Ordered Arrays of Magnetic Nanoparticles: From Size‐Selected Pure Cobalt Dots to Cobalt–Cobalt Oxide Core–Shell Systems

Size dependence of nanostructures: Impact of bond order deficiency

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