Adsorption and Polymer Film Formation on Metal Nanoclusters

Abstract

We examine experimentally and theoretically the effect of polymer adsorption layers on the stability of metal nanoclusters. We find that, somewhat contrary to expectation in this low volume fraction limit, the thickness of the adsorbed layer does not increase linearly with the number of repeating units in the chain (i.e., molecular weight), N. Rather, in the range we examine experimentally it decreases with molecular weight, in agreement with our model predictions. The number of contacts between the polymer chain and the cluster surface, i.e., polymer anchoring points, increases significantly with N, as does the polymer volume fraction in the adsorbed layer. As a result, although a large fraction of active surface sites remains available, particles stabilized by long chains resist flocculation, while particles stabilized by short chains do not.

Cross Section Investigations of Compositions and Sub‐Structures of Tips Obtained by Focused Electron Beam Induced Deposition

“…This ligand material might act like the PMMA units in co-polymers, protecting the nano-crystals against agglomeration. [25] In the same paper, decomposition of cobalt carbonyl taking place already at temperatures as low as 40 C is reported. Larger clusters (20 nm) had been obtained by decomposition of cobalt carbonyl in pure toluene.…”

“…For the remaining lower beam currents nonrealistic small thermal conductivities below 10 ±6 ...10 ±4 W/cmK would result. However, as shown in [25] the cobalt grain formation inside a polymer-like nano-composite deposit could also take place at around 40 C. Summarizing, the model of electron beam heating can account at least semi-quantitatively for the proposed picture of FEB deposition: the initial low-metal-containing nano-composite due to bulk dissipation of heat (except for high current 3 lA), higher cobalt contents and increasing Co-grain size with increasing tip length and increasing beam current, better structural and compositional uniformity of low current deposits, and the composition fluctuations due to thermal decomposition inset and corresponding change in tip heat conductivity. In the same framework the appearance of the thermodynamically more stable hexagonal Co-phase could be explained.…”

Nanostructured Materials Preparation via Condensation Ways

“…Thermolysis of metal carbonyls in block-copolymers in the synthesis, for example, Cr 2 O 3 , Fe 2 O 3 , and Co 2 O 3 nanoparticles in polystyrene-b-poly(methyl-methacrylate) diblock copolymer (PS-PMMA) as a model system is studied in detail [488][489][490][491][492]. Results showed that the rates for reactions performed in a diblock copolymer solution are much faster than the rates of the same reactions performed in a homopolymer solution.…”

Use of Lead (II) Sulfide Nanoparticles as Stabilizer for PMMA Exposed to Gamma Irradiation

“…These results mean that the predicted interactions between PMMA and PbS-NP have indeed taken place. Thus, the adsorption of PbS-NP on PMMA molecules occurs near to carbonyl group 30,31 , probably between the Pb atom in PbS-NP and the oxygen atom in PMMA molecule.…”

“…Thus, the PbS nanoparticles act as a plasticizer in the PMMA molecule. Since interactions between PMMA matrix and PbS-NP were found in the FT-IR and viscosity analysis, these interactions can cause increase of mobility of the polymers molecules giving them the plasticizing effect 30,33 . The changes in properties of irradiated samples may be attributed to the radiation-induced oxidative degradation of the PMMA molecules.…”